Environmental Protection Agency
Establishment
The Environmental Protection Agency Act,
1992, was enacted on 23 April, 1992, and
under this legislation the Agency was formally established on 26 July, 1993.
Responsibilities
The Agency has a wide range of statutory
duties and powers under the Act. The main
responsibilities of the Agency include the
following:
- the licensing and regulation of
large/complex industrial and other
processes with significant polluting
potential, on the basis of integrated pollution control (IPC) and the application
of best available technologies for this
purpose;
- the monitoring of environmental quality,
including the establishment of databases
to which the public will have access,
and the publication of periodic reports
on the state of the environment;
- advising public authorities in respect of
environmental functions and assisting
local authorities in the performance of
their environmental protection functions;
- the promotion of environmentally sound
practices through, for example, the
encouragement of the use of environmental audits, the setting of environmental
quality objectives and the issuing of
codes of practice on matters affecting
the environment;
- the promotion and co-ordination of environmental research;
- the licensing and regulation of all
significant waste disposal and recovery
activities, including landfills and the
preparation and periodic updating of a
national hazardous waste management
plan for implementation by other bodies;
- implementing a system of permitting for
the control of VOC emissions resulting
from the storage of significant quantities
of petrol at terminals;
- implementing and enforcing the GMO
Regulations for the contained use and
deliberate release of GMOs into the
environment;
- preparation and implementation of a
national hydrometric programme for the
collection, analysis and publication of
information on the levels, volumes and
flows of water in rivers, lakes and
groundwaters; and
- generally overseeing the performance by
local authorities of their statutory environmental protection functions.
Status
The Agency is an independent public body.
Its sponsor in Government is the
Department of the Environment and Local
Government. Independence is assured
through the selection procedures for the
Director General and Directors and the freedom, as provided in the legislation, to act
on its own initiative. The assignment, under
the legislation, of direct responsibility for a
wide range of functions underpins this
independence. Under the legislation, it is a
specific offence to attempt to influence the
Agency, or anyone acting on its behalf, in
an improper manner.
Organisation
The Agency's headquarters is located in
Wexford and it operates five regional
inspectorates, located in Dublin, Cork,
Kilkenny, Castlebar and Monaghan.
Management
The Agency is managed by a full-time
Executive Board consisting of a Director
General and four Directors. The Executive
Board is appointed by the Government
following detailed procedures laid down in
the Act.
Advisory Committee
The Agency is assisted by an Advisory
Committee of twelve members. The members are appointed by the Minister for the
Environment and Local Government and
are selected mainly from those nominated
by organisations with an interest in environmental and developmental matters. The
Committee has been given a wide range of
advisory functions under the Act, both in
relation to the Agency and to the Minister.
© Environmental Protection Agency 2001
All or part of this publication may be reproduced without
further permission, provided the source is acknowledged.
PARAMETERS OF WATER QUALITY
Interpretation and Standards
Published by the Environmental Protection Agency, Ireland.
Although every effort has been made to ensure the accuracy of the material
contained in this publication) complete accuracy cannot be guaranteed. The
Environmental Protection Agency cannot accept any responsibility
whatsoever for loss or damage occasioned or claimed to have been
occasioned, in part or in full, as a consequence of any person acting, or
refraining from acting, as a result of a matter contained in this publication.
The definitive sources of the water quality standards quoted in this
publication are the relevant European Union Directives and the national
Statutory Instruments which contain the corresponding Regulations.
ISBN 1-84096-015-3
Price: Ir £ 10.00
Ä12.70
Parameters of Water Quality : Interpretation and Standards
CONTENTS
List of Abbreviations
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Glossary of Terms
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Units of Expression
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Principal Relevant Atomic Weights …
A Note on Sources
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Standards of Water Quality
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EU Water Quality Directives and Associated Regulations
Provisions of the Main Directives and Regulations
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Surface Water Directive (75/440 EEC)
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Bathing Water Directive (76/160/EEC)
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THE PRINCIPAL PARAMETERS OF WATER QUALITY
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INTRODUCTION
Dangerous Substances Directive (76/464/EEC)
Freshwater Fish Directive (78/659/EEC)
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Shellfish Directive (79/923/EEC)
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Ground Water Directive (80/68/EEC)
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Drinking Water Directive (80/778/EEC)
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Drinking Water Directive (98/83/EC)
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A Brief Overview of the Above Directives
Parameters Covered in the Present Volume
PRESENTATION OF THE DATA
Acidity
Acrylamide
Alkalinity
Aluminium
Ammonia
Antimony
Arsenic
Barium
Benzene
Benzo(a)pyrene
Beryllium
Boron
Bromate
Cadmium
Calcium
Carbon Dioxide (Free)
Chloride
Chlorine, Residual
Chlorophyll
Chromium
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Parameters of Water Quality : Interpretation and Standards
Contents : Continued
THE PRINCIPAL PARAMETERS OF WATER QUALITY [Continued]
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
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40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
Clostridium perfringens (including spores)
Cobalt
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Coliforms, Faecal& Total
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Colony Counts
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Colour
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Conductivity
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Copper
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Cryptosporidium
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Cyanide
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1,2-Dichloroethane
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Enterococci ...
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Enteropathogenic Viruses
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Epichlorohydrin
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Fluoride
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Giardia
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Hardness ...
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Heavy Metals
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Hydrocarbons, Dissolved & Emulsified
Iron
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Lead
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Magnesium...
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Manganese ...
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Mercury
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Methylene Blue-Active Substances
Molybdenum
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Nickel
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Nitrate
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Nitrite
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Nitrogen, Kjeldahl
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Odour
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Organic Carbon, Total …
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Organo-Halogenated Substances …
Oxidisability
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Oxygen Demand, Biochemical
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Oxygen Demand, Chemical
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Oxygen, Dissolved
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Pathogenic Staphylococci
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Pesticides (Individual & Total)
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pH
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Phenols
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Phosphates ...
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Phosphorus, Total
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Polychlorinated Biphenyls & Terphenyls
Polycyclic Aromatic Hydrocarbons…
Potassium ...
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Pseudomonas aeruginosa
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Salinity
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Salmonella ...
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Selenium ...
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Silica
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43
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52
53
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60
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62
63
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70
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75
77
79
81
82
83
85
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89
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91
92
93
93
94
95
Parameters of Water Quality : Interpretation and Standards
Contents : Continued
THE PRINCIPAL PARAMETERS OF WATER QUALITY [Continued]
71. Silicon, Toxic or Persistent Organic Compounds
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72. Silver
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73. Sodium
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74. Solids, Settleable
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75. Solids, Suspended
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76. Solids, Total
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77. Solids, Total Dissolved
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78. Substances Affecting Taste
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79. Substances Extractable in Chloroform
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80. Substances which Possess Carcinogenic, Mutagenic or Teratogenic Properties
81. Sulphate
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82. Sulphide
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83. Tarry Residues and Floating Matter
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84. Taste
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85. Tellurium
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86. Temperature
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87. Tetrachloroethylene …
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88. Thallium
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89. Tin
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90. Tin,Organo-Compounds
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91. Titanium
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92. Total Indicative Dose [Radioactivity]
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93. Transparency
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94. Trichloroethylene
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95. Trihalomethanes
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96. Tritium
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97. Turbidity
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98. Uranium
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99. Vanadium
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100. Vinyl Chloride
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101. Zinc
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96
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98
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102
103
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110
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112
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114
114
116
116
117
118
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119
APPENDICES
Appendix 1 :
Appendix 2 :
Appendix 3 :
Appendix 4 :
Appendix 5 :
Appendix 6 :
Appendix 7 :
Appendix 8 :
Appendix 9 :
Variations in Water Quality in Space and Time
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Units of Analysis
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Concentrations in Milligrams/Litre of Total Ammonia in Fresh Water which
contain an Un-ionised Ammonia Concentration of 0.02 mg/l NH4
Saturation Index/Langelier Index/Calcium Carbonate Saturation Index
Supplementary List of EU Directives and Associated Regulations
Dangerous Substances Directive - List I and List II Substances
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Ground Water Directive - List I and List II Substances
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World Health Organisation: Guidelines for Bacteriological Quality
World Health Organisation: Recommended Treatments
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7
121
122
125
126
127
129
130
131
132
Parameters of Water Quality - Interpretation and Standards
LIST OF ABBREVIATIONS
[A] / [B] / [C] / [D]
Indicate (in increasing order) four arbitrary classifications of complexity of
analytical techniques. Thus, [A] indicates a basic technique which is found
in virtually any laboratory; [D] denotes a technique of high sophistication
which will be available in only specialised laboratories. Further, the use of
more than one classification - e.g. [B]/[C] - indicates that there are two
techniques commonly used for the particular determination, one more
complex than the other.
(S)
(C)
Salmonid waters - Freshwater Fish Directive/Salmonid Water Regulations
Cyprinid waters - Freshwater Fish Directive
G [value]
I [value]
MAC
Guide [advisory] value in EU Directives
Mandatory [imperative] value in EU Directives
Maximum admissible concentration - 1980 Drinking Water Directive/ 1988
Regulations
Minimum required concentration - 1980 Drinking Water Directive/1988 Regulations
MRC
NLV
National Limit Value - fixed in accordance with Directives/corresponding
Regulations
n/a
Not applicable
GLOSSARY OF TERMS
A1 waters |
A2 waters | --------A3 waters |
Cyprinid waters
Salmonid waters
96-hour LC50
Organoleptic tests/
properties
The water categories in the 1975 Surface Water Directive/1989 Regulations.
Waters of a quality sufficient to support coarse but not game fish.
Waters of a quality sufficient to support game fish.
The concentration of a toxic material which will bring about the death of 50
per cent of the species under test in 96 hours.
Tests for and characteristics of parameters which depend on or affect the
senses of smell and taste.
UNITS OF EXPRESSION
µg/l x
mg/l x
ng/l x
micrograms per litre of substance x, expressed as x
milligrams per litre of substance x, expressed as x
nanograms per litre of substance x, expressed as x.
PRINCIPAL RELEVANT ATOMIC WEIGHTS
Calcium (Ca)
Carbon (C)
Chlorine (Cl)
Hydrogen (H)
40
12
35.5
1
Nitrogen (N)
Oxygen (O)
Phosphorus (P)
Sulphur (S)
8
14
16
31
32.
Parameters of Water Quality - Interpretation and Standards
ACKNOWLEDGEMENTS
The valuable assistance of Gerry O'Flaherty and
the late Marie Allen is gratefully acknowledged.
IMPORTANT NOTICE
Readers are advised that this document, as posted on the
Environmental Protection Agency website, is a slightly reformatted
version of the published volume of the same name, which was issued by
the E.P.A. in 2001. The content of this present version is identical to that
of the latter and has not been updated or revised. Therefore, readers
should be aware that additional Regulations may now be in force and, if
so, they should be taken into account when considering the subject matter
of this document.
9
Parameters of Water Quality - Interpretation and Standards
A Note on Sources
The most relevant sources for the present volume are unquestionably the various
Directives relating to water which have been adopted by the Council of the European
Union over a period of some 25 years. All the standards which are cited herein originate in
the respective Directives, although in many cases successive Ministers for the
Environment (and Local Government) have made national Regulations which transpose
the provisions of the corresponding Directives into Irish law. In making the Regulations,
the respective Ministers have generally adopted the same limit values for the individual
parameters as are given in the original Directives. However, there are some important
exceptions where a Minister has fixed a standard which is stricter than in the Directive.
In this volume, Regulations (where they have been made) are cited as they have
precedence over the underlying Directive, the latter being quoted only where necessary.
This scheme is necessary in the case of the Freshwater Fish Directive (78/659/EEC) which
specifies parallel standards for salmonid and cyprinid waters, respectively. There are
Ministerial Regulations covering the former only, and, accordingly, the coverage of the
latter below is based on the Directive. The EU Directives which are quoted extensively in
this handbook are listed in detail in the text below. The texts of the respective Directives
have been published in the Official Journal of the European Communities and the
appropriate references are cited. A supplementary list of Directives is set out in Appendix
5, again with Journal references.
The reader of previous editions of this book will note that in the present version the
tables containing the standards cover EU-related legislation only, and that references to
American EPA or World Health Organisation [WHO] sources have been omitted. This
change has been made for two reasons. Firstly, the information presented was advisory or
for guidance and had no legal force and, further, some of it was either out of date or of
little current relevance. Secondly, with the future adoption by the EU of the Framework
Directive in the Field of Water Policy, systems will be put in place for the incorporation of
standards for any substances for which it is considered they are required. It is the
intention of the EU Commission that a list of priority dangerous substances will be drawn
up, with appropriate environmental quality standards [EQSs], and incorporated in the
Framework Directive, and, further, that there will be future additions to the Directive as
circumstances warrant.
It is important to stress, however, that one of the most important sources of all is the
invaluable WHO publication Guidelines for drinking-water quality.1 This is an essential
reference work which should be in the hands of all concerned with the quality of drinking
water. The reader should note that the only definitive sources of water quality standards
in Ireland are the respective EU Directives and/or the corresponding National Regulations
made in connection therewith. This volume is not a legal document.
_________________
The WHO Guidelines for Drinking-water quality at present comprises four volumes, as under. Of these,
the first two are essential for those concerned with drinking water quality, the remaining two being strongly
recommended. [1] Guidelines for Drinking-water Quality Volume I : Recommendations, Second Edition,
Paperback 188 pages (1993), ISBN 92 4 154460 0; [2] Guidelines for Drinking-water Quality Addendum to
Volume I : Recommendations. Paperback - 36 pages (1998), ISBN 92 4 154514 3; [3] Guidelines for Drinkingwater Quality Volume 2: Health Criteria and Other Supporting Information, Second Edition, Hardcover - 973
pages (1996), ISBN 92 4 154480 5; [4] Guidelines for Drinking-water Quality Volume 3: Surveillance and
Control of Community Water Supplies, Second Edition, Paperback -238 pages (1997), ISBN 92 4 154503 8.
1
10
INTRODUCTION
The present volume is a completely new edition of the handbook originally published
by the Environmental Research Unit in early 1989. The latter, in turn, was based on a
manual produced in October 1986 as the sixth in a series of publications for the Water
Supply Distribution Training Programme of An Foras Forbartha. As with its predecessors,
the present aim is to present in an immediately accessible, compact form all the relevant
data and informative comment useful to the environmentalist faced with problems caused
by a wide variety of water pollutants, and who may be called upon to take immediate
remedial action.
In this context, the term environmentalist is used bearing in mind particularly those
personnel - administrators, chemists, engineers or technicians - who are immediately
charged with the implementation of national and EU legislation concerning water
pollution. The present book is therefore addressed to monitoring agencies, in particular,
but it is the hope that others with an active concern for or professional involvement in the
field of water pollution control will find it of some value.
The aim of the handbook is to distil the principal facts and figures on a total of some
100 individual or group pollutants - information which is otherwise available, but in a
wide variety of sources - into a single volume, in which the parameters are treated
individually, in a generally uniform format. While there is a very large (and growing)
body of scientific and technical literature in the field of water and wastewater analyses
and their interpretation and significance, many publications, because of the thoroughness
with which they deal with perhaps a very specialised aspect, do not contain in succinct
"capsule" form those facts which are of most practical value.
Among the most relevant facts concerning each parameter are, of course, the limits
(advisory or mandatory) which either scientific or medical opinion or legislative bodies
consider applicable. Hence, there is a comprehensive presentation of all concentration
levels specified either nationally or in the legislation of the EU. It is considered that the
present compendium of guide and mandatory levels as set out in the relevant EU
Directives, and the associated national Regulations made by the respective Ministers for
the Environment (and Local Government) - and which is as comprehensive as possible at
the time of writing - should prove a convenient reference source.
One major reason for the publication of the present handbook is the fact that the
variety of analytical techniques and their complexity is growing, necessitating the
presence of an increasingly high degree of specialisation in the laboratory. There is often
an accordingly wide gap between those who perform a set of analyses and those who will
be responsible for the interpretation of the results and the taking of any consequent
action. It is the intention that this manual will help to bridge this gap.
STANDARDS OF WATER QUALITY
There are many sources of water quality criteria and standards - they may originate
in the Member States of the European Union, or may be adopted by the Council or
Parliament of the EU, or by individual countries, or they may be issued by international
bodies.
11
Parameters of Water Quality - Interpretation and Standards
Further, these various levels specified will take cognisance of the differing uses for
which water quality must be maintained. The requirements, as regards suitability, of
water for industrial use, for drinking, for boilers and so on, may differ widely and each
may be quite demanding. The ultimate objective of the imposition of standards (which may
necessitate extensive treatment prior to use) is the protection of the end uses, be these by
humans, animals, agriculture or industry. In the present context, however, the main
considerations are in regard to safeguarding public health and the protection of the whole
aquatic environment. Both have very high quality requirements which complement each
other to a great extent. For example, in general terms, if a river or lake water meets the
most stringent fishery requirements it will meet all or virtually all other environmental
quality objectives [EQOs). In fact, the EU Framework Directive in the field of Water
Policy1 defines a single EQO - achieving and maintaining "good ecological status." 2
In Ireland the origins of the vast majority of water quality standards imposed to date
are the various EU Directives which since 1975 have specified the quality required of
waters for different uses. Under the most important Directives, however, the actual
standards which are in legal force are enshrined in the corresponding Ministerial
Regulations. These give effect in Irish law to the quality and other requirements of the
Directives. It is important to bear in mind that the Minister for the Environment and
Local Government has (and exercises) the power to require that national standards may
be more strict than the levels laid down in the Directives. It should also be understood
that, in cases where Regulations have been made in connection with a Directive, it is the
Regulations which must be adhered to.
Both Directives and Regulations are aimed primarily at the safeguarding of human
health by protecting both waters and fish (as part of the food chain), as well, of course, as
the aquatic environment at large. Because of the importance of these Directives and
Regulations and their complexity (including the interrelationship between different
Directives) their main provisions are for convenience summarised below insofar as they
deal with quality standards. However, sampling and analytical aspects of the Directives
are not covered here. The adoption of the Framework Directive will mean that the
standards enshrined in the individual water Directives will (over a period of time) be
subsumed into the former and that the latter enactments will be repealed.
EU WATER QUALITY DIRECTIVES AND ASSOCIATED REGULATIONS
In the period since 1975 a total of eight "primary" Directives,3 which are particularly
relevant to the quality of water for various uses, have been adopted by the EU. Further,
National Regulations have been made in connection virtually all these Directives. In the
table below and, where appropriate, throughout this volume the Directives are listed in
chronological order of adoption. Each Directive has an official reference number and also
an official title which is in some cases quite lengthy. Familiar usage in this country and
elsewhere has resulted in informal short titles being given to the Directives and it is by
these designations that the Directives (and the corresponding Regulations) are generally
known.
__________
1
This is referred to from now on simply as the Framework Directive.
This is defined in very great detail in the Directive.
3
The total of eight includes Directive 98/83/EC of 3 November 1998 - a new Drinking Water Directive which will replace the original Directive 80/778/EEC by 01 January 2004, at the latest.
2
12
Parameters of Water Quality - Interpretation and Standards
For convenience Table 1 below sets out the reference numbers and the full and short titles.
The respective dates of publication of these Directives are given in footnotes to Table 1.
A supplementary list of Directives appears in Appendix 5. These are aimed mainly at
the prohibition of discharges of specific compounds or compound classes, often from
particular industries. Their provisions are most important in their implications and the
inclusion of these Directives in an Appendix to the main text of the present volume is not
intended to diminish in any way their relevance. It simply reflects the fact that the bulk of
the principal water quality standards and limit values are dealt with by Directives other
than these.
Table 1
EU WATER QUALITY DIRECTIVES
____________________________________________________________________________________
No
Official Ref No
Full Title Of Directive
Short Title
____________________________________________________________________________________
1 75/440/EEC*
Council Directive of 16 June 1975 concerning the quality
required of surface water intended for the abstraction of
drinking water in the Member States. 4
Surface Water
2 76/160/EEC*
Council Directive of 8 December 1975 concerning the quality
of bathing water. 5
Bathing Water
3 76/464/EEC
Council Directive of 4 May 1976 on pollution caused by certain
dangerous substances discharged into the aquatic environment
of the Community .6
Dangerous
Substances
4 78/659/EEC*
Council Directive of 18 July 1978 on the quality of fresh waters
needing protection or improvement in order to support fish life.7
Freshwater Fish
5 79/923/EEC*
Council Directive of 30 October 1979 on the quality required of
shellfish waters. 8
Shellfish
6 80/68/EEC*
Council Directive of 17 December 1979 on the protection of
groundwater against pollution caused by certain dangerous
substances. 9
Ground Water
7 80/778/EEC*
Council Directive of 15 July 1980 relating to the quality of water
intended for human consumption. 10
Drinking Water
8 98/83/EC
Council Directive of 3 November 1998 relating to the quality of
water intended for human consumption. 11
Drinking Water
____________________________________________________________________________________
*
The Minister for the Environment has made Regulations incorporating the requirements of the
Directive; these are discussed in detail below insofar as they deal with water quality standards.
________________
Official Journal of the European Communities
Official Journal of the European Communities
Official Journal of the European Communities
Official Journal of the European Communities
Official Journal of the European Communities
Official Journal of the European Communities
Official Journal of the European Communities
Official Journal of the European Communities
No L 194,
No L 31,
No L 129,
No L 222,
No L 281,
No L 20,
No L 229,
No L 330,
13
pp 26-31, 25 July 1975.
pp 1-7, 05 February 1976
pp 23-29, 18 May 1976.
pp 1-10, 14 August 1978.
pp 47-52, 10 October 1979.
pp 43-48, 26 January 1980.
pp 11-29, 30 August 1980.
pp 32-54, 05 December 1998.
Parameters of Water Quality - Interpretation and Standards
PROVISIONS OF THE MAIN DIRECTIVES AND REGULATIONS
The principal provisions of the listed Directives and/or the associated Regulations are
summarised below for convenience. It is most important to bear in mind when considering
the Directives and Regulations, and when examining the standards and limits set out in
the main body of this volume, that in many (but not all) cases there is a required
percentage compliance in terms of numbers of samples analysed. That is, there is
a degree of flexibility so that a single excessive value obtained in a sampling programme of
adequate intensity would not mean that the water in question was in breach of the
requirements. The individual required compliance percentages are specified below for the
respective Directives or Regulations.
It must be emphasised that the interpretation of the Directives is a complex matter
requiring .no little concentration, and it may be noted that, in addition to defining national
quality standards, the Regulations also seek to clarify the general requirements of the
Directives. It is therefore considered useful to give only a very broad outline of the
provisions of this highly important body of legislation in the following paragraphs. The
reader is accordingly urged to refer to the original texts of the Directives or, more
importantly, where they have been made, to the associated Regulations.
Another important factor to be remembered in the consideration of levels and
standards is that in several Directives/Regulations departures from the stated limits may
be granted by the Minister for the Environment and Local Government where the
parameters concerned are likely to be influenced by exceptional climatological or geological
conditions. It must be understood that such departures constitute approved waivers of the
relevant Directive(s) for the individual parameters referred to. There are no blanket
waivers of Directive provisions, nor are there waivers in the case of any parameter which
has any connotation for the health of the public.
Surface Water (75/440/EEC)
This Directive - adopted on 16 June 1976 - was the first of the series relating
principally to water quality to come into force. It must be remembered that the informal
title given almost universally to the Directive - the "Surface Water Directive" - is actually
a misnomer in that it can convey the impression that it covers the quality of surface
waters in general. In fact, as is quite unambiguous in the full title (cf Table 1), it covers
the quality only of surface water which is used as a source of water for human
consumption - drinking water - with appropriate treatment following abstraction. The
Directive really deals with so-called "raw water" (i.e. water intended for distribution after
the appropriate treatment processes).
The important topics of the extent and frequency of sampling and analysis required
for implementation were not covered by the Directive, and the EU subsequently adopted a
separate Directive on sampling and analysis in connection with the Surface Water
Directive. It may be noted for completeness that the so-called "Methods of Analysis and
Frequency of Sampling" 12 Directive (which is not dealt with in the present volume
because of its detailed, operational content) was adopted on 9 October 1979, with reference
number 79/869/EEC.
__________
12
Official Journal of the European Communities
No L271, pp 44-53, 29 October 1979.
14
Parameters of Water Quality - Interpretation and Standards
The European Communities (Quality of Surface Water Intended for the Abstraction
of Drinking Water) Regulations, 1989, were signed by the Minister for the Environment on
10 November 1989 and took effect from 1 December 1989. These Regulations,13 though
concise, incorporate the requirements of both the Surface Water and Methods of Analysis
Directives, thereby simplifying very considerably the task of interpretation. In the
discussion of the individual parameters of water quality below, the limit values specified
are those laid down by the Regulations.
The Regulations categorise surface waters from which water for public supply will be
taken as Al, A2 or A3, depending on the (increasing) degree of treatment which will be
applied, and they set out quality standards for a total of 39 parameters. There is a
requirement that 95% of samples taken comply with the standards and, further, that, in
the case of the 5% of samples not complying, (i) the water does not deviate from the
standards in question by more than 50%, with the exception of the standards for
temperature, pH, dissolved oxygen and the microbiological parameters, (ii) there is no
resultant danger to public health, and (iii) no two consecutive samples deviate from the
quality standards. The topic of analytical methods is covered in depth by the Regulations,
but is not discussed in the present volume.
Bathing Water (76/160/EEC)
The Bathing Water Directive has been given effect in Irish law by the European
Communities (Quality of Bathing Water) Regulations, 1988, signed by the Minister for the
Environment on 4 May 1988.14 These Regulations laid down quality requirements for all
fresh and sea waters which were defined as bathing areas. Specific bathing areas were
designated for monitoring in accordance with the provisions of the Directive, and
monitoring has been carried out on a regular basis since 1978-79 by the sanitary
authorities concerned.
The Bathing Water Regulations specified quality standards for the various relevant
parameters and they also dealt in detail with the matter of percentage compliance of
samples with the prescribed limit values. This was done both in the Regulations on a
parameter by parameter basis. The principal point of note is that the national limit values
for total and faecal coliforms were 50% lower than the mandatory values in the Directive,
although at a lower compliance percentage.
The European Communities (Quality of Bathing Water) (Revocation) Regulations,
1992,15 formally revoked both the 1988 and 198916 Regulations and made way for the
adoption of the Quality of Bathing Waters Regulations, 1992.17 The latter, which are not
considered comprehensively in the present context (and which should be referred to), reenact all the provisions of the 1988 and 1989 Regulations and expand their coverage. The
change most relevant to the present volume was the addition of the total and faecal
coliform standards in the original Directive to those adopted in the 1988 Regulations. As a
result, there is now a more comprehensive coliform standard in the current Regulations
than is contained in either of the original sources on its own.
________________
13
14
15
16
17
Statutory Instrument
S.I. No 294 of 1989.
Statutory Instrument
S.I. No 84 of 1988.
Statutory Instrument
S.I. No 154 of 1992.
These Regulations [Statutory Instrument S.I. No 99 of 1989] had designated further bathing areas only.
Statutory Instrument
S.I. No 155 of 1992.
15
Parameters of Water Quality - Interpretation and Standards
Dangerous Substances (76/464/EEC)
This framework18 Directive is potentially very wide-ranging in its scope. In its
original coverage the Directive applied to inland surface water, territorial waters, internal
coastal waters and groundwater. However, the last-mentioned category has subsequently
been dealt with by another Directive (see below). The Dangerous Substances Directive
requires Member States to take:
appropriate steps to eliminate pollution of [these waters] by the dangerous substances in the families and groups of substances in List I of the Annex and to reduce pollution of the said waters by
the dangerous substances in the families and groups of substances in List II of the Annex.
It notes that the provisions "represent only a first step towards this goal." Details of the
contents of Lists I and II are given in Appendix 6. The substances specified by the
Directive in List I (the "black list") and in List II (the "grey list") represent a very wide
range of materials and the thrust of the Directive is towards emission control rather than
environmental monitoring. The main provisions of the Directive are as under:• List I discharges must be authorised, such authorisation laying down emission standards for
discharges to waters and, where necessary, to sewers [see Directive for further details}.
• The Council of the European Communities, on a proposal from the Commission, may lay
down limit values for said emission standards, and may also lay down quality objectives.
• List II discharges shall also be subject to authorisation, again with emission standards based
on quality objectives (where the latter have been defined).
• Member States are required to establish programmes in order to reduce pollution by List II
substances, such programmes to include quality objectives and so on.
• "The competent authority shall draw up an inventory of the discharges ... which may contain
substances within List I to which emission standards are applicable."
It will be noted from reference to the Lists that the coverage of the Directive is, as
mentioned, very wide indeed, and that it is accordingly totally impractical to approach the
implementation of the provisions from a general monitoring point of view. As stated, the
emphasis is on control of emissions but, of course, it follows that where such controls are
imposed specific monitoring for the pollutants under restriction is both feasible and
necessary. Such monitoring may be very complex and demanding on resources.
Among the further Directives listed in Appendix 5 are so-called "daughter" Directives
based on the Dangerous Substances Directive; these relate to discharges of cadmium and
mercury, for example, as well as selected pesticides. Ministerial Regulations have been
made in connection with some of these further Directives and in certain circumstances
water quality standards which must be observed are laid down. However, because of the
specific nature of the quality standards and monitoring requirements and the rather
intricate way in which they are related to the quantities being discharged of the pollutants
in question, neither the daughter Directives nor the associated Regulations are
commented upon in the present context. The reader is therefore recommended to consult
the original sources.
_________________
It is important that Directive 76/464/EEC not be confused with the year 2000 Water Framework
Directive. Although described often as a "framework" Directive, perhaps a better term for the former would
have been "umbrella" Directive as it was envisaged that 76/464/EEC would form the blanket under which
further, "daughter" Directives (dealing separately or in groups with specific dangerous substances) would be
adopted.
In fact, several such subsidiary Directives were adopted, as shown in Appendix 5. The new Framework
Directive in contrast establishes a complex structure within which much environmental protection activity
may be developed without further legislation.
18
16
Parameters of Water Quality - Interpretation and Standards
Freshwater Fish (78/659/EEC)
The Freshwater Fish Directive is, in practical terms, one of the most important of all
the earlier Directives in that its quality requirements have been applied widely in various
contexts, notably in Water Quality Management Plans. This was because, effectively, if
the quality standards for fish (especially salmonid fish) are met by a water, then that
water will be of sufficiently high quality for a variety of EQOs including that of serving as
a source of raw water for public supply. Because of this wide use of its quality standards
there is great familiarity with this Directive so that its provisions are only briefly
summarised here.
The Directive classifies fresh waters as either salmonid (S) or cyprinid (C), the
former being of such quality as to support game fish and the latter being of a lesser quality
but satisfactory for coarse fish. Accordingly, there is a dual range of standards, those for
salmonid waters obviously being rather stricter than the quality requirements for cyprinid
waters. The standards apply "to those waters designated by the Member States as needing
protection or improvement in order to support fish life." A range of Irish waters has been
designated under the terms of the Directive and in each case the waters have been
classified as salmonid, requiring the higher quality standards. On 18 November 1988, in
order to incorporate fully in Irish law the requirements of the Directive for salmonid
waters and the designations of waters thus far made, the then Minister for the
Environment signed the European Communities (Quality of Salmonid Waters)
Regulations.19
Article 6 of the Directive specifies that 95% of samples for key parameters (e.g. pH
and non-ionised ammonia), based on an effective monthly sampling frequency, shall
conform to the specified values. Because of the wording used, in which conformity with
both G (guide) and I (mandatory) values is referred to (necessitating careful
interpretation) it is important to consult the text of the Directive if cyprinid waters are
under consideration. In the case of salmonid waters the Regulations are comprehensive,
giving details of compliance required on an individual parameter basis, where appropriate.
Shellfish (79/923/EEC)
The Directive "concerns the quality of shellfish waters and applies to those coastal
and brackish waters designated by Member States as needing protection or improvement
in order to support shellfish.. .life and growth..." Both G and I values are set out in the
Directive.
In cases of discharges containing the parameters metals and
organohalogenated substances, in addition to the quality objectives specified by the
present Directive any emission standards laid down by Member States under the
Dangerous Substances Directive (76/464/EEC, q.v.) shall also be applied. 20
Under the Shellfish Directive, Member States are required to make initial
designations of shellfish waters within two years following the notification of the Directive
and also to establish programmes "in order to reduce pollution and to ensure that
designated waters conform, within six years of designation, [with the values specified]."
________________
Statutory Instrument S.I. No 293 of 1988. Note that to date there are no corresponding Regulations for
cyprinid waters.
20 In fact, emission standards exist in "daughter" Directives of Directive (76/464/EEC) and not in the latter
itself. More importantly, such standards will be enshrined in the Framework Directive, in due course.
19
17
Parameters of Wafer Quality - Interpretation and Standards
Minimum sampling frequencies are laid down in the Annex but, as is the case with
other Directives, monitoring may be reduced or suspended in the absence of pollution. The
required compliances vary from 100% for organohalogenated substances and metals to
95% for salinity and dissolved oxygen to 75% for remaining parameters (cf original source).
The Quality of Shellfish Waters Regulations were made in 1994 21; they designated specific
shellfishery waters.
Groundwater (80/68/EEC)
The Groundwater Directive is a follow-up ("daughter") Directive within the
framework of the Dangerous Substances Directive (76/464/EEC, q.v.) and its formulation
was envisaged in the latter. Its principal provisions are as follows:
•
Its purpose is to prevent the pollution of ground water by substances belonging to
"substances in Lists I or II." [cf Annexes to this Directive and Directive (76/464/EEC), and
Appendices 6 and 7 below; these are not quite identical but are very similar in their scope],
•
The provisions do not apply to the following:- (a) discharges of domestic effluents from
isolated dwellings not connected to a sewerage system and situated outside areas protected
for the abstraction of water for human consumption; (b) discharges which are found by the
competent authority of the Member State concerned to contain substances in Lists I or II in
a quantity and concentration so small as to obviate any present or future danger of
deterioration in the quality of receiving ground water; and (c) discharges of matter
containing radioactive substances.
•
Member States are required to prevent the introduction into ground water of substances in
List I and limit the introduction into ground water of substances in List II so as to avoid
pollution of this water by these substances. The general prohibition on direct discharges
containing List I substances does not apply in the case of ground, waters which are found
on investigation to be permanently unsuitable for other uses, especially domestic or
agricultural. Authorisations are required for any such discharges to these waters.
•
Accordingly. Member States shall prohibit all direct discharge of substances in List I, shall
"subject to prior investigation any disposal or tipping for the purpose of disposal of these
substances which might lead to indirect discharge" and shall "take all appropriate
measures they deem necessary to prevent any indirect discharge of substances in list I due
to activities on or in the ground other than those mentioned just [above]."
•
Member States must also "make subject to prior investigation all discharges of substances
in list II, so as to limit such discharges" and similarly "the disposal or tipping for the
purpose of disposal of these substances which might lead to indirect discharge." In addition,
they are required to "take the appropriate measures they shall deem necessary to limit ail
indirect discharge of substances in list II, due to activities on or in the ground other than
those mentioned [above]. "
For further essential detail about the requirements of this Directive (especially as
regards the "prior investigations" mentioned, the authorisation of discharges and the
content of such authorisations) it is most important that the original text be referred to.
Finally, it should be noted that the Local Government (Water Pollution) Regulations,
1992,22 set a limit of zero for discharges of List I substances to ground water.
________________
21
22
Statutory Instrument
Statutory Instrument
S.I. No 200 of 1994.
S.I. No 271 of 1992.
18
Parameters of Water Quality - Interpretation and Standards
Drinking Water (80/778/EEC)
According to the 1988 Regulations which give effect in Irish law to the requirements
of the Directive, all water used for human consumption, whether "in its original state or
after treatment, regardless of origin," is covered, as is water used in the food industry.
However, natural mineral waters and medicinal waters do not fall under its provisions.
The Regulations [European Communities (Quality of Water Intended for Human
Consumption) Regulations, 1988]23 were signed by the Minister for the Environment on 29
April 1988 and took effect on 1 June 1988. Maximum admissible concentrations (MAC
values) are fixed for over fifty parameters. In some cases - as was also the case in some of
the other Directives commented upon earlier - departures from the values specified may be
granted by the Minister because of climatological or geological factors which may make the
standards impossible to attain.
A handbook on the implementation of the Drinking Water Regulations was prepared
by the Environmental Research Unit and issued in autumn 1989. Although intended
primarily for the information and guidance of those responsible for the implementation of
the Regulations - the sanitary authorities - the handbook proved to be of interest to a
wider readership. A new edition will be published on the formal introduction of the
provisions of the new Drinking Water Directive 98/83/EC.
Drinking Water (98/83/EC)
The new Drinking Water Directive was adopted by the EU Council on 3 November
1998 and came into force on 25 December 1998 (after the passing of the specified 20 days
from its publication in the Official Journal). Accordingly, the final deadline for the
technical adoption24 by the Member States of this Directive (and for the simultaneous
repeal of Directive 80/778/EEC) is 25 December 2003. However, any necessary
administrative or legislative provisions must be in place by 25 December 2000.
The corollary of the new Directive is that the provisions of both the 1980 and the
1988 Regulations will be rescinded and replaced by the markedly different requirements
enshrined in the 1998 Directive. The Minister for the Environment and Local Government
will make Regulations in due course, and these will be the applicable legislation in
Ireland. Because the content of a new edition of the 1989 handbook for sanitary
authorities will depend very much on the provisions made by the Minister for the
Environment and Local Government in any new Regulations, some time must necessarily
elapse before the publication is available. Likewise, it would, of course, be impossible to
anticipate the provisions of such Regulations in this present volume, which, in any event,
is not an appropriate context. Nonetheless, it may be noted that the new Directive differs
very greatly from its predecessor and a wholly new approach to sampling and analysis will
be required on the part of the sanitary authorities. What are appropriate and particularly
relevant to the present publication, are the list of parameters and the applicable limit
values contained in Directive 98/83/EC which will constitute a key element of new
Regulations.
________________
23
24
Statutory Instrument S.I. No 81 of 1988.
The application of the limit values, termed "parametric values" in the Directive.
19
Parameters of Water Quality - Interpretation and Standards
One prominent change in terminology concerns the limit values - the old term MAC
("maximum admissible concentration") has been abolished and the standard term for limit
value in Directive 98/83/EC is "parametric value" [PV]. 25 Other major changes concern
the old C1-C4 and A-E parameter classifications which have been replaced by a new
scheme. Further, the actual limit values for several parameters have been revised
(downwards) for some key parameters. All these matters, which are of prime concern to
the sanitary authorities, will demand detailed consideration in the new handbook.
A BRIEF OVERVIEW OF THE ABOVE DIRECTIVES
It is noteworthy that most of the above Directives (all except the Dangerous
Substances and Ground Water Directives) are based on the so-called "Environmental
Quality Objective" [EQO] approach, in which standards [EQSs] are laid down for various
types of water in which contaminants may be found, and the concentrations of which are
more or less strictly limited. Monitoring under these Directives/Regulations will detect
and, if adequate in its scope, quantify the extent to which any pollutants are present.
(These observations are more appropriate, however, to Directives other than the Drinking
Water Directive, where the extensive range of limits is naturally aimed at the protection of
public health.) The two exceptions are emission control Directives, under which pollution
of the aquatic environment and/or ground water in particular should be limited by the
issue of and policing of discharge authorisations.
As mentioned above, most of these individual Directives will give way to the Water
Framework Directive (over several years), but the latter will straightaway incorporate
Article 6 of the Dangerous Substances Directive 76/464/EEC which provides that the EU
Council (on a proposal from the Commission) may specify EQSs for specified substances on
a list which will form one of its Annexes. The key aim of the Framework Directive is, as
stated, to achieve and maintain good ecological status throughout the aquatic
environment. One of the principal means of reaching this goal is the strict control of
dangerous substances using procedures which originated in the Dangerous Substances
Directive 76/464/EEC.
_________________
The very rarely referred to MRC ("minimum required concentration") does not appear in Directive
(98/83/EC).
25
20
Parameters of Water Quality - Interpretation and Standards
PARAMETERS COVERED IN THE PRESENT VOLUME
The list of parameters in the first edition of the present publication has been revised
thoroughly, with some parameters of minor significance being omitted, and a range of
additional determinands (largely organic micropollutants) added. In the present volume,
the following approach has been adopted.
Firstly, all parameters which appeared in previous editions have been retained, as
they may well be of practical (if not statutory) interest to readers. Secondly, all "new"
parameters - those listed in Directive 98/83/EC and in "daughter" Directives to Directive
76/464/EEC - have been included and are treated in the standard format used throughout.
Thirdly, the MAC values specified in Directive 80/778/EEC have been excluded from
the list of standards as they are being replaced by the PVs [parametric values] of Directive
98/83/EC. Fourthly, these PVs are presented throughout the present text, although it must
be remembered that the Minister for the Environment and Local Government, when
making Regulations in connection with Directive 98/83/EC, may decide to set stricter
limits than the Directive for certain parameters.
21
Parameters of Water Quality - Interpretation and Standards
PRESENTATION OF THE DATA
For convenience in reference each parameter included in this volume is covered in a
standard format consisting of a numbered template in which important explanatory and
background information is summarised. This is followed by a standardised tabular format
in which the limit figures specified by the various sources are quoted clearly. The
parameters are dealt with in one alphabetical series and, in general, the text and tables
relating to a given parameter are complete in themselves. However, because of the close
relationship between some parameters full cross-references are provided. The elements of
the template are as follows, in the order in which they appear:
•
Chemical Symbol or Formula: These are in the conventional chemical notation,
e.g. Antimony is Sb, Silver is Ag, Silica is SiO2, and so on. In many cases the entry
is "Not Applicable" as there is either no chemical formula at all, as for
microbiological parameters, or else the parameter, although chemical, is a bulk one,
e.g. Pesticides, so that the use of formulae is precluded on practical grounds.
•
Units used for Analytical Results: The complex subject of units of analysis is
dealt with in detail in Appendix 2 of this volume. It may simply be noted here that
for several key parameters the results of analysis may be reported in terms other
than those of the chemical formulae of the entities being determined. Examples are
nitrate, NO3–, reported often as N, and phosphate, PO4– – – commonly reported as P.
•
Normal Methods of Analysis: Although analytical methodology is not covered by
the present volume, brief mention is made of the methods most commonly employed
for the determination of the various parameters. It must be stressed, however, that
in many cases there are additional or alternative techniques which may be used
satisfactorily. As a guide, letters [A], [B], [C] and [D] have been used throughout to
indicate, respectively, an increasing degree of sophistication of the technique
and/or of the equipment used. Thus, [A] indicates a method suitable for use in a
more basic water laboratory, [B] implies a method more demanding of staff
expertise or equipment, [C] implies an elaborate laboratory set-up, with advanced
instrumentation, and [D] denotes a specialist laboratory with state-of-the-art
equipment. A dual designation, e.g. [B/C], is used for those methods which may be
practicable at different levels of instrumentation or expertise. It may be noted that
these designations are quite in for mat and are offered for guidance only. In reality,
there may often be no clear gradations between the capabilities of different
laboratories.
•
Occurrence/Origin: A brief indication is given as to whether substances covered
by the parameter occur in rock, are constituents of sewage or industrial wastes, or
are synthetic materials. It is assumed throughout that substances attributed to
industrial wastes could equally well arise from tiphead leachates, this is not always
specified.
•
Health/Sanitary Significance: Brief reference is made to known toxic or
physiological effects - or the lack of them - of each parameter. It must be stressed
that such references are not in any way exhaustive, but are merely indicative. This
volume does not purport in any way to deal with medical matters or with any
material connection between a given parameter and the health of the user/consumer
of a water containing it.
22
Parameters of Water Quality - Interpretation and Standards
•
Background Information: This section contains adequate detail to set the
significance of each parameter in perspective. In some important cases, notably
"Oxygen Demand, Biochemical," "Hardness" and "Oxygen, Dissolved," the entries
are fairly lengthy, but this is in line with one of the primary aims of this volume,
namely to act as a "free-standing" reference for the engineer, environmentalist or
scientist.
•
Comments: Where appropriate, further amplifying information on the parameter
is given under this heading.
Important Note As regards analytical methods, it may be added that it is assumed
throughout this treatment of the results of analysis that such results are the end product of
a properly designed and competently executed programme of sampling and analysis in
which all precautions necessary to ensure meaningful data have been taken. While the
present volume does not deal with such operational matters, it is important that the
opportunity be taken to stress that the taking of samples, which might at first glance
appear to be a fairly simple procedure, may in fact be anything but, depending on the
parameters to be determined. Unless the proper procedures are followed strictly the
validity of the sample may be compromised, and the resulting analytical data of little value.
Layout of the Tables
In the tabular format mentioned, the "Recommended or
Mandatory Limit Values" for the respective parameters are presented as follows. The table
first gives the values contained in the EU Directives summarised above. However, where
Regulations have been made by the Minister for the Environment which contain national
quality standards, the values quoted are generally those in the Regulations, not the
Directive corresponding to such Regulations. National values are, clearly, mandatory
standards which must be complied with to the extent laid down in the appropriate
Regulations.
This is in contrast to the Directives (whose values are quoted here if no Regulations
have been made to date) which contain either recommended or "guide" values, designated
as G values, or mandatory figures, designated I values (imperatif). The latter are
standards which must be adhered to; they are legal requirements of the EU. References
under the Surface Water Regulations to "A1, A2 and A3" waters indicate the different
water categories specified in the Regulations. As mentioned above, under the Freshwater
Fish Directive, "(S)" and "(C)" denote salmonid and cyprinid waters, respectively.
To avoid unnecessary blank spaces, references to Directives or other sources
containing no data on a given parameter have been omitted from the respective 'tables as
appropriate. It follows, therefore, that if a Directive or the corresponding Regulations are
not referred to under a given heading then neither the Directive nor the Regulations
expressly refer to the parameter in question. However, the term "No
reference/recommendation" in a table does not imply that the parameter is not or may not
be of relevance to the intended readership. Where necessary, notes are used to present
detail which cannot be summarised in a table or to explain some of the complexities which
arise in certain cases. To simplify presentation the notes are numbered separately for
each parameter rather than in one large overall series.
Analytical Units The potential for confusion arising from the multiplicity of units
employed (in particular in the different Directives) is unfortunately rather great and,
accordingly, it is essential that in studying standards attention be paid both to the limit
value and to the units in which such value is expressed. A detailed note on units forms
Appendix 2.
23
The
Principal Parameters
of
Water Quality
[in alphabetical order]
24
Parameters of Water Quality - Interpretation and Standards
1. ACIDITY
Not Applicable [Bulk parameter]
Chemical Symbol or Formula:
mg/l CaCO3.
Units Used for Analytical Results:
Titration with Sodium Hydroxide [A]
Normal Method(s) of Analysis:
Occurrence/Origin:
Arises from the presence of weak or strong acids and/or certain
inorganic salts. The presence of dissolved carbon dioxide is usually the main acidity factor in
unpolluted surface waters (it forms the weak acid H2CO3 - carbonic acid).
Health/Sanitary Significance:
No
considerations in excessively acid waters.
particular
implications
apart
from
palatability
Background Information: The determination is arbitrary to a degree in that the end-point pH
values [colour changes] will depend on the choice of indicator reagents made by the analyst.
Commonly, methyl orange or bromophenol blue are used in the first stage as indicator (colour
change around pH 4.5), with phenolphthalein in the second stage (colour change around pH 8.3).
Hence the various terms methyl orange acidity (alternatively, mineral acidity), and
phenolphthalein acidity (or total acidity).
Comments: The acidity of a water will affect its corrosiveness and also the speciation1 of some of
its other constituents.
Acidity : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
2. ACRYLAMIDE
Chemical Symbol or Formula:
C3H5NO.
Units Used for Analytical Results:
µg/l compound.
Normal Method(s) of Analysis:
Chromatography [C/D]
Occurrence/Origin: Synthetic chemical which is the monomer from which polyacrylamide is
derived.
Health/Sanitary Significance: Highly toxic, acrylamide is a carcinogenic substance. It can also
be absorbed readily through unbroken skin and it affects the central nervous system.
Background Information: Polyacrylamide is used as a flocculant aid in water treatment and
the polymeric substance inevitably contains traces of acrylamide monomer.
Comments:
The WHO Guidelines note that "the most important source of drinking-water
contamination by acrylamide is the use of polyacrylamide flocculants that contain residual,
acrylamide monomer" and adds that "concentrations in drinking-water can be controlled by
product and dose specification."
_________
1
i.e. The precise form in which the parameter will exist in the water [cf "Ammonia"].
25
Parameters of Water Quality - Interpretation and Standards
Acrylamide : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l compound n/a
0.10
[1]
_______________________________________________________________________________________
Notes
[1]
The Directive states that "The parametric value refers to the residual monomer concentration in the
water as calculated according to specifications of the maximum release from the corresponding
polymer in contact with the water."
3. ALKALINITY
Chemical Symbol or Formula:
Not Applicable [Bulk parameter]
Units Used for Analytical Results:
mg/l CaCO3.
Normal Method(s) of Analysis:
Titration with Sulphuric Acid [A]
Occurrence/Origin: The alkalinity of a natural water is generally due to the presence of
bicarbonates formed in reactions in the soils through which the water percolates. It is a measure of
the capacity of the water to neutralise acids and it reflects its so-called buffer capacity (its inherent
resistance to pH change). A poorly-buffered water will have a low or very low alkalinity and will be
susceptible to pH reduction by, for example, "acid rain." At times, however, river alkalinity values
of up to 400 mg/l CaCO3 may be found; they are without significance in the context of the quality of
the water.
Health/Sanitary Significance:
There is little known sanitary significance attaching to
alkalinity (even up to 400 mg/l CaCO3), though unpalatability may result in highly alkaline
waters.
Background Information: Alkalinity in natural waters may also be attributable to carbonates
and hydroxides. Sometimes analysis is carried out to distinguish between the alkalinity elements
and this is done by using different indicators in the titration procedure and by making appropriate
calculations. The indicators most commonly employed are phenolphthalein (colour change around
pH8.3) and methyl orange (colour change around pH4.5), resulting in the additional terms
phenolphthalein alkalinity and methyl orange alkalinity; the latter is synonymous with total
alkalinity.
Alkalinity is involved in the consequential effects of eutrophication [over-enrichment] of
waters. Where a high degree of photosynthesis occurs, as discussed below under "Oxygen,
Dissolved" (q.v.), there is a high consumption of carbon dioxide by algae. As any free carbon dioxide
initially available is consumed, more is produced in a series of related chemical equilibrium
⇔
H2CO3 [H2O + CO2]
reactions, as follows: 1.
H+ + HCO3 –
⇔
HCO3 –
2.
H+ + CO3 – –
3.
H2O
⇔
H+ + OH–.
As the carbon dioxide is consumed by photosynthesis, more is produced (reaction 1, left to
right) by the action of bicarbonate ions, present as alkalinity, and hydrogen ions to give
undissociated carbonic acid (carbon dioxide and water). Any carbonate ions present will then react
with more hydrogen ions to replace the bicarbonate consumed (reaction 2, again left to right). Both
these reactions consume hydrogen ions, more of which are produced as in reaction 3 (equilibrium
again to the right). A net overall effect is the production of hydroxyl ions and an increase in the
pH. It is not uncommon for extreme photosynthetic activity to produce pH levels high enough to
cause serious damage (even death) to fish.
26
Parameters of Water Quality - Interpretation and Standards
Comments: The parameter is of interest to water engineers in that it is a factor concerned in the
computation of the so-called Langelier "Saturation Index" which relates to the corrosion of or
deposition of scale in distribution networks (see Appendix 4). Alkalinity is sometimes designated
alkali level.
Alkalinity : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
4. ALUMINIUM
Chemical Symbol or Formula:
Al.
Units Used for Analytical Results:
mg/l Al.
Normal Method(s) of Analysis:
Colorimetry [B]; Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Aluminium is one of the most abundant elements in the earth's crust. A
salt, aluminium sulphate, is very widely used for colour- and colloid-removal in the treatment of
waters for drinking.
Health/Sanitary Significance: Not originally considered to be a significant health hazard in
drinking waters, aluminium has more recently been shown to pose a danger to persons suffering
from kidney disorders. It causes neurological problems and has been cited as a contributory factor
to Alzheimer disease. However, the WHO Guidelines for Drinking-Water Quality2 states that:
There is a need for further studies, but the balance of epidemiological and physiological evidence at
present does not support a causal role for aluminium in Alzheimer disease. Therefore, no health-based
guideline value is recommended.
Background Information: The compound aluminium sulphate ("alum") is very widely used in
water treatment to remove colour and non-filtrable matter in raw waters. The alum is hydrolysed
and is converted to a flocculent hydroxide which, being dense and insoluble, precipitates bringing
with it the offending colour and turbidity particles. With careful plant control it is possible to
ensure that residual aluminium levels are acceptable (i.e. 0.2 mg/l Al or less, above which
discoloration may occur).
Comments: Aluminium levels are limited under the Drinking Water Directive 198/83/EC].
Aluminium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l Al
n/a
200
_______________________________________________________________________________________
__________
2 Second Edition. 1993.
27
Parameters of Water Quality - Interpretation and Standards
5. AMMONIA
Chemical Symbol or Formula:
NH3.
Units Used for Analytical Results:
mg/l N.
Normal Method(s) of Analysis:
Colorimetric (Manual; Nessler's Reagent) [A/B];
Colorimetric (Automated; Berthelot Reaction) [B/C].
Occurrence/Origin: Ammonia is generally present in natural waters, though in very small
amounts, as a result of microbiological activity which causes the reduction of nitrogen-containing
compounds. When present in levels above 0.1 mg/l N, sewage or industrial contamination may be
indicated.
Health/Sanitary Significance:
From the viewpoint of human health the significance of
ammonia is marked because it indicates the possibility of sewage pollution and the consequent
possible presence of pathogenic micro-organisms.
Background Information: The form of the ammonia - whether it is "free" (as NH3) or "saline"
(as NH4+) in slightly acid waters - depends on the pH and these forms are not distinguished from
one another during analysis. The different terms commonly applied to the forms of ammonia are as
total ammonium (NH3 & NH4+)
follows:
total ammonia (NH3 & NH4+)
free and saline ammonia (NH3 & NH4+)
free ammonia (NH3)
ionised ammonia (NH4+)
and
un-ionised ammonia (NH3).
The different forms arise from the pH/temperature related equilibrium reactions:
1.
2.
NH3 + H2O
NH3.H2O
⇔
⇔
NH3.H2O
NH4+ + OH–.
The ammonia tolerances for fishery waters are narrow and have been considered and
reported on by the European Inland Fisheries Advisory Commission. Research has shown that it is
the un-ionised species of ammonia which is most harmful to freshwater aquatic life and to game
fish, in particular. Arising from the complex relationship between total ammonia concentration,
pH and temperature there emerges a level for total ammonia of around 0.3 mg/l NH3 which is
considered to be that which would contain the limiting amount of un-ionised ammonia (see
Appendix 3 for full details). Because of the ease of natural interconversion from one form to
another - this could be brought about by pH changes caused by algal activity, for example - the
total ammonia levels should be very low.
Comments: Before the advent of microbiological techniques for assessing the potability of a water
the analysis for ammonia was used as an indication of sewage contamination, often in conjunction
with chloride, because both are present in significant quantities in sewage. High ammonia levels
interfere with chlorination processes in water treatment, an aspect which is discussed in detail
below (see "Chlorine"). The formation of chloramine compounds (which are much less potent
disinfectants than free chlorine) by reaction between the added chlorine and the ammonia present
in the water necessitates an increased use of chlorine if disinfection efficiencies are to be
maintained.
Ammonia : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
n/a
0.2
[1]
A1 waters
mg/l NH4
n/a
1.5
[1]
A2 waters
mg/l NH4
n/a
4
[1,2]
A3 waters
mg/l NH4
_______________________________________________________________________________________
Surface Water Regulations [1989]
28
Parameters of Water Quality - Interpretation and Standards
Ammonia : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value
Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
Dangerous Substances Directive [76/464/EEC]
Freshwater Fish Directive [78/659/EEC]
(S)
(C)
(S)
(C)
Salmonid Waters Regulations [1988]
-
[3]
List II substance
[4]
mg/l NH3
< 0.005 < 0.025
[5]
[5]
mg/l NH3
< 0.005 < 0.025
< 0.04 < 1
[6]
mg/l NH4
<1
[6]
mg/l NH4
< 0.2
mg/l NH3
n/a
< .02
[5,7]
n/a
<1
[6,8]
mg/l NH3
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
mg/l NH4
n/a
0.5
[9]
_______________________________________________________________________________________
Notes
[1]
Designation is "Ammonia."
[2]
Departure from standard may be granted by Minister "where exceptional meteorological or
geographical conditions have arisen."
[3]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters ... or, in the case of... ammonia, that there is a
tendency towards eutrophication."
[4]
List II specifies "Substances which have an adverse effect on the oxygen balance, particularly
ammonia, nitrites."
[5]
Limits are for "Non-ionised Ammonia."
[6]
Limits are for "Total Ammonium."
[7]
Standard may be exceeded in the form of minor peaks in daytime and, subject to this, be conformed
with by 95% of samples over a period of 12 months where sampling is carried out at least once per month;
where sampling is less frequent the standard shall be conformed with by all samples.
[8]
Standard is < 1 "subject to conforming with. the standard for non-ionised ammonia." Standard to be
conformed with by 95% of samples over a period of 12 months where sampling is carried out at least once per
month; where sampling is less frequent the standard shall be conformed with by all samples.
[9]
Parameter designated "Ammonium."
6. ANTIMONY
Chemical Symbol or Formula:
Sb.
Units Used for Analytical Results:
mg/l Sb.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C]
Occurrence/Origin: Naturally occurring trace element used in metal industry and in flame
retardant materials. Antimony can occur naturally in water from weathering of rocks but is more
likely to arise from effluents.
Health/Sanitary Significance: Although the health effects of antimony have not been
established definitively, there is evidence of actual or potential carcinogenicity of some antimony
compounds. Accordingly, concentrations are limited in drinking water.
29
Parameters of Water Quality - Interpretation and Standards
Background Information:
µg/l.
Comments:
Antimony levels in freshwater streams in the US can be around 1
Antimony levels are limited under Drinking Water Directive [98/83/EC].
Antimony : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
µg/l Sb
n/a
5
_______________________________________________________________________________________
7. ARSENIC
Chemical Symbol or Formula:
As.
Units Used for Analytical Results:
mg/l As.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [C/D]
Occurrence/Origin:
This element is very widely distributed throughout the earth's crust,
according to the WHO Guidelines, which state that "it is introduced into water through the
dissolution of minerals and ores, from industrial effluents, and from atmospheric deposition:
concentrations in ground water in some areas are sometimes elevated as a result of erosion from
natural sources. The average daily intake of inorganic arsenic in water is estimated to be similar
to that from food; intake from air is negligible." Arsenic is used in the glass and semiconductor
industries and as a fungicide in timber processing. A major US emission source is coal-fired power
plant.
Health/Sanitary Significance:
Very toxic to humans, some arsenical compounds are
carcinogens, hence much of the concern regarding them, but there are a variety of other effects on
health. The WHO states that inorganic arsenic is a documented human carcinogen, and that a
relatively high incidence of skin and possibly other cancers that increase with dose and age has
been observed in populations ingesting water containing high concentrations of arsenic.
Background Information: Found in air and in all living organisms.
Comments: Parameter is extensively covered by Directives and Regulations (see below).
Arsenic : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l As
n/a
0.05
A2 waters
mg/l As
n/a
0.05
A3 waters
mg/l As
n/a
0.10
_______________________________________________________________________________________
30
Parameters of Water Quality - Interpretation and Standards
Arsenic : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
mg/l As
[1]
Dangerous Substances Directive [76/464/EEC]
List II substance
Shellfish Directive [79/923/EEC]
mg/l As
[2]
[3]
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
µg/l As
n/a
10
_______________________________________________________________________________________
Notes
[1] Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..."
[3]
"The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with .article 1 [of the Directive], to the high quality of shellfish products."
[3] "The concentration of [this] substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of [this and
other specified] metals must be taken into consideration."
8. BARIUM
Chemical Symbol or Formula:
Ba.
Units Used for Analytical Results:
mg/l Ba.
Normal Method(s) of Analysis: Turbidimetric [A/B]; Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Naturally occurring mineral (e.g. in barytes), which has in the past been
mined in several places in Ireland, including Benbulben in County Sligo. According to the WHO
Guidelines, while food is the main source of barium intake by humans, where barium occurs in
drinking water supplies the latter can contribute a significant proportion of total intake.
Health/Sanitary Significance: Excessive amounts of barium can cause muscular, cardiovascular
and renal damage. Although not markedly toxic, barium in excess quantities is clearly undesirable.
Background Information: In normal surface waters levels are likely to be low as traces of
barium will react with sulphate present to form the highly insoluble barium sulphate.
Comments: The WHO 1993 Guidelines set a guideline value of 0.7 mg/l but Directive [98/83/EC]
neither sets a parametric value nor refers to the metal, in contrast to Directive [80/778/EEC].
Barium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l Ba
mg/l Ba
mg/l Ba
n/a
n/a
n/a
0.10
1.0
1.0
_______________________________________________________________________________________
31
Parameters of Water Quality - Interpretation and Standards
Barium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
No reference/parametric value
_______________________________________________________________________________________
9. BENZENE
Chemical Symbol or Formula:
C6H6.
Units Used for Analytical Results:
µg/l compound.
Normal Method(s) of Analysis:
Gas Chromatography [C].
Occurrence/Origin: Constituent of some petroleum products; industrial raw material; solvent.
Health/Sanitary Significance:
system adversely.
Carcinogenic substance which also affects the central nervous
Background Information: Emissions from motor vehicles account for most of the benzene in
the air, which can in due course reach the aquatic environment. Pollution from industrial sources
can also introduce benzene to water.
Comments: Benzene is not a naturally-occurring constituent of water.
Benzene : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l compound
n/a
1.0
_______________________________________________________________________________________
BENZO(b)FLUORANTHENE
(See Poly cyclic Aromatic Hydrocarbons)
BENZO(k)FLUORANTHENE
(See Polycyclic Aromatic Hydrocarbons)
BENZO(ghi)PERYLENE
(See Polycyclic Aromatic Hydrocarbons)
32
Parameters of Water Quality - Interpretation and Standards
10. BENZO(a)PYRENE 3
Chemical Symbol or Formula:
C20H12.
Units Used for Analytical Results:
µg/l compound
Normal Method(s) of Analysis:
High-Pressure Liquid Chromatography [C]
Occurrence/Origin:
Synthetic complex aromatic organic compound formed by pyrolysis or
combustion of organic materials. See discussion of “Polycychc Aromatic Hydrocarbons” below.
Health/Sanitary Significance:
Benzo(a)pyrene is a carcinogenic and mutagenic substance
which is considered to be highly undesirable in drinking water, even though the WHO Guidelines
indicate that food is the main source of human exposure to this type of substance.
Background Information: See “Polycyclic Aromatic Hydrocarbons” below.
Comments: The undesirability of the presence of, and the need to restrict the concentrations of,
benzo(a)pyrene is indicated clearly by its designation as a discrete parameter in Drinking Water
Directive [98/83/EC], in contrast to its former inclusion as a constituent of the group parameter
“Polycyclic Aromatic Hydrocarbons” (q.v.).
Benzo(a)pyrene : Recommended or Mandatory Limit Values
______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l compound
n/a
0.010
_______________________________________________________________________________________
11. BERYLLIUM
Chemical Symbol or Formula:
Be.
Units Used for Analytical Results:
mg/I Be.
Normal Method(s) of Analysis: Colorimetric (Aluminon) [B]; Atomic Absorption Spectrometry
[B/C]
Occurrence/Origin:
The major source is combustion of fossil fuels, the metal reaching
waterthrough atmospheric fall- or wash-out. Weathering of rocks and soils, as well as discharges,
also contributes.
Health/Sanitary Significance: The metal and its compounds, if inhaled for example, are very
toxic and can lead to a variety of respiratory and other diseases. The picture regarding the toxicity
of beryllium and compounds in water and food is, however, very unclear and there is no compelling
evidence in favour of restriction, hence the lack of standards.
Background Information: It is used in brass and other alloys and also in the aircraft and space
industries.
Comments: It is significant that WHO refers to the low level of exposure risk. The parameter is
listed in both the Surface Water and Drinking Water Directives - though without any limit values
being quoted, hence its omission from the corresponding Regulations.
__________
3
Alternatively named 3,4-Benzopyrene.
33
Parameters of Water Quality - Interpretation and Standards
Beryllium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
BIOCHEMICAL OXYGEN DEMAND
(See "Oxygen Demand, Biochemical")
BOD
(See "Oxygen Demand, Biochemical")
12. BORON
Chemical Symbol or Formula:
B.
Units Used for Analytical Results:
mg/l B.
Normal Method(s) of Analysis:
Spectrometry [B/C]
Occurrence/Origin:
alloys.
Colorimetric
(Curcumin)
[B];
Atomic
Absorption
Naturally occurring trace element. Used in cleaning compounds and in
Health/Sanitary Significance:
Although excessive amounts of boron can cause nervous
problems, the element is not considered a problem in drinking water. It has been identified as a
danger to crops when present in irrigation water at the 1 - 2 mg/l concentration range.
Background Information: Present in seawater around 5 mg/l.
Comments: The Surface Water and Drinking Water Regulations specify limits.
Boron : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l B
n/a
2.0
A2 waters
mg/l B
n/a
2.0
A3 waters
mg/l B
n/a
2.0
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
mg/l B
n/a
1.0
_______________________________________________________________________________________
34
Parameters of Water Quality - Interpretation and Standards
13. BROMATE
Chemical Symbol or Formula:
BrO3 –.
Units Used for Analytical Results:
µg/l BrO3 –.
Normal Method(s) of Analysis:
Ion Chromatography [C]
Occurrence/Origin: Occurs when bromide ions [Br–] present in water are oxidised by ozone and
some other oxidising agents (including, it is believed, chlorine).
Health/Sanitary Significance: Both carcinogenic and mutagenic.
Background Information: Has come into prominence along with trihalomethanes [THM; q.v.],
both being formed by the action of chlorine on constituents in water before it is distributed.
Comments:
[80/778/EEC].
Bromate was not a determinand in the earlier Drinking Water Directive
Bromate : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l BrO3 – n/a
10
[1]
_______________________________________________________________________________________
Notes
[1] The Directive states that "Where possible, without compromising disinfection, Member States should strive for a
lower value.
For the water referred to in Article 6(1)(a), (b) and (d), the value must be met, at. the latest, 10 calendar
years after the entry into force of the Directive. The parametric value for bromate from five years after the entry into
force of this Directive until 10 years after its entry into force is 25 µg/l."
BROMODICHLOROMETHANE
(See "Trihalomethanes")
BROMOFORM
(See "Trihalomethanes")
14. CADMIUM
Chemical Symbol or Formula:
Cd.
Units Used for Analytical Results:
µg/l Cd.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C]
Occurrence/Origin: In ores, including those of zinc. Cadmium in water is due nearly exclusively
to industrial discharges (e.g. from electroplating, paint-making, manufacture of plastics etc) and
landfill leachates.
35
Parameters of Water Quality - Interpretation and Standards
Health/Sanitary Significance:
concentrations in waters.
Very highly toxic, hence severe restrictions on its
Background Information: The metal is very strongly adsorbed on muds, humus and organic
matter, leading to the possibility 'of entry to the food chain via fish and fish food, and subsequent
accumulation in tissue.
Comments: The principal physiological effects of cadmium are bone damage, chronic kidney
disease, cancer and hypertension. The metal is also highly toxic to aquatic life.
Cadmium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l Cd
n/a
0.005
A2 waters
mg/l Cd
n/a
0.005
A3 waters
mg/l Cd
n/a
0.005
Bathing Water Regulations [1989-1998]
mg/l Cd
[1]
Dangerous Substances Directive [76/464/EEC]
List I substance [2]
Shellfish Directive [79/923/EEC]
mg/l Cd
[3]
[4]
Ground Water Directive [80/68/EEC]
List I substance
Drinking Water Directive [98/83/EC]
µg/l Cd
n/a
5.0
[2]
_______________________________________________________________________________________
Notes
[1]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing
that there has been: a deterioration, in the quality of waters..."
[2]
Designation is "Cadmium and its compounds."
f3]
"The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
[4] "The concentration of [this] substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of [this and
other specified] metals must be taken into consideration."
CAE
(See "Substances Extractable in Chloroform")
15. CALCIUM
Chemical Symbol or Formula:
Ca.
Units Used for Analytical Results:
mg/l Ca.
Normal Method(s) of Analysis:
Spectrometry [B].
Occurrence/Origin:
Titration (Calcium Hardness) [A]; Atomic Absorption
Occurs in rocks, bones, shells etc. Very abundant.
36
Parameters of Water Quality - Interpretation and Standards
Health/Sanitary Significance: High levels may be beneficial (see below) and waters which are
rich in calcium (and hence are very hard) are very palatable.
Background Information: This element is the most important and abundant in the human
body and an adequate intake is essential for normal growth and health. The maximum daily
requirement is of the order of 1 - 2 grams and comes especially from dairy products. There is some
evidence to show that the incidence of heart disease is reduced in areas served by a public water
supply with a high degree of hardness, the primary constituent of which is calcium, so that the
presence of the element in a water supply is beneficial to health.
Comments:
Despite the potential health benefits of calcium abundance there are problems
associated with hardness, as discussed below (q.v.).
Calcium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
No reference/parametric value
_______________________________________________________________________________________
CARBON-ALCOHOL EXTRACT
(See "Substances Extractable in Chloroform")
CARBON-CHLOROFORM EXTRACT
(See "Substances Extractable in Chloroform")
16. CARBON DIOXIDE (FREE)
Chemical Symbol or Formula:
CO2
Units Used for Analytical Results:
mg/l CO2.
Normal Method(s) of Analysis: Titration with Sodium Carbonate [A; field test]; Nomograph
[Alkalinity/Total Dissolved Solids] [B]
Occurrence/Origin: From air, algal respiration, organic breakdown.
Health/Sanitary Significance: None.
Background Information:
The chemical equations given for "Alkalinity" (q.v.) show the
interrelationship between carbon dioxide, bicarbonate and carbonate. The primary interest in free
carbon dioxide concentrations arises in connection with the behaviour of waters in distribution
systems - whether they will be corrosive or whether they will tend to deposit insoluble calcium
carbonate as scale. The Langelier Index was devised to characterise waters on the basis of such
tendencies (see Appendix 4).
Comments: High levels of free carbon dioxide may also enhance the effects of deoxygenation and
of high ammonia concentrations. Excessive levels of carbon dioxide may have adverse effects on
aquatic life.
37
Parameters of Water Quality - Interpretation and Standards
Carbon Dioxide (Free) : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
CCE
(See "Substances Extractable in Chloroform")
CHEMICAL OXYGEN DEMAND
(See "Oxygen Demand, Chemical")
17. CHLORIDE
Chemical Symbol or Formula:
Cl–
Units Used for Analytical Results:
mg/l Cl.
Normal Method (s) of Analysis: Titration (Mohr Method: Silver Nitrate) [A]
Occurrence/Origin:
Chloride exists in all natural waters, the concentrations varying very
widely and reaching a maximum in sea water (up to 35,000 mg/l Cl). In fresh waters the sources
include soil and rock formations, sea spray and waste discharges. Sewage contains large amounts
of chloride, as do some industrial effluents.
Health/Sanitary Significance: Chloride does not pose a health hazard to humans and the
principal consideration is in relation to palatability.
Background Information: At levels above 250 mg/l Cl water will begin to taste salty and will
become increasingly objectionable as the concentration rises further. However, external
circumstances govern acceptability and in some arid areas waters containing up to 2,000 mg/l Cl
are consumed, though not by people unfamiliar with such concentrations. High chloride levels may
similarly render freshwater unsuitable for agricultural irrigation.
Comments: Because sewage is such a rich source of chloride, a high result may indicate pollution
of a water by a sewage effluent. Natural levels in rivers and other fresh waters are usually in the
range 15-35 mg/l Cl - much below drinking water standards. What is normally important to note in
a series of results from a river, for example, is not the absolute level, but rather the relative levels
from one sampling point to another.
An increase of even 5 mg/l at one station may give rise to suspicions of a sewage discharge,
especially if the free ammonia levels (q.v.) are also elevated. In coastal areas, however, elevated
chloride values may be due to sea spray, or sea water infiltration, and not necessarily to
discharges. Normal raw water treatment processes do not remove chloride.
38
Parameters of Water Quality - Interpretation and Standards
Chloride : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l Cl
n/a
250
mg/l Cl
n/a
250
mg/l Cl
n/a
250
Drinking Water Directive [98/83/EC]
mg/l Cl
n/a
250
_______________________________________________________________________________________
18. CHLORINE, RESIDUAL
Chemical Symbol or Formula:
Cl2.
Units Used for Analytical Results:
mg/l Cl.
Normal Method(s) of Analysis:
Colorimetric (DPD) [A; in-situ test].
Occurrence/Origin: Water treatment processes, industrial effluents, chlorinated sewage and
other effluents.
Health/Sanitary Significance: No direct significance at the relatively tiny levels used in water
treatment processes.
Background Information:
Water supplies are disinfected to destroy or deactivate
microorganisms which can produce diseases such as cholera, typhoid and so on, and the process is
the most important in water treatment. Disinfection maybe achieved in various ways but the vast
majority of supplies are treated with chlorine which is a powerful oxidising agent and an extremely
efficient disinfectant. It is relatively easy to handle and is also cost-effective, hence its almost
universal use. Chlorine is very reactive and will only remain, as discussed below, in treated
waters of high quality. It is not a constituent of unpolluted natural waters.
The primary effects of chlorination are extremely beneficial and for many minor water
supplies the process may be the only treatment deemed necessary. Quite low levels are effective for
disinfection in normal circumstances, but should the ammonia or organic content of the water be
high then the water may have an appreciable "chlorine demand" and a higher chlorine input may
be needed to achieve a given degree of protection.
As in many cases the treatment works for a public water supply may be a considerable
distance from the ultimate consumers, it is essential that continuing protection be afforded along
the distribution system, particularly if it is old and prone to leaks and/ or infiltration of extraneous
matter. The philosophy underlying chlorination is therefore to ensure that there is a chlorine
residual which will protect against recontamination. Dosage, contact time and other factors in the
chlorinattion process will be adjusted so that a concentration of 0.1-0.3 mg/l Cl remains after 30
minutes' contact.
Chlorine reacts with water to form hypochlorous acid (HOCl) and hydrochloric acid (HCl).
The former is a weak acid which dissociates to give hypochlorite ions (OCl–) and there is a chemical
equilibrium between the dissociated and the undissociated forms (the latter actually effects the
disinfection) but it is very common to add the chlorine as hypochlorite solution. The free chlorine
residual is taken to include chlorine, hypochlorous acid and hypochlorite, irrespective of form.
39
Parameters of Water Quality - Interpretation and Standards
Because of the reactivity with reducing agents and organic matter these free residual forms
may not persist and there may not therefore be continuing protection. Ammonia will also react
with chlorine forms to give mono-chloramine (NH2Cl), di-chloramine (NHCl2) and tri-chloramine
(NCl3), depending on relative concentrations and pH. The mono- and di-chloramines have
significant disinfection power which persists. Because of this it is sometimes the practice to add
ammonia in the chlorination stage to give a combined residual rather than a free residual. The
results of a complete analysis will therefore show from the relative proportions of free and
combined residuals the extent to which disinfection can be maintained during distribution of a
supply. Free chlorine is a more efficient disinfection agent than the chloramines but, being more
reactive, it is more likely to disappear fairly quickly from solution; the combined chlorine, on the
other hand, gives longer-lasting protection.
Two further points should be noted about the use of chlorine. First, if a water is polluted by
phenols or by trace organic compounds released from decaying algal growths, chlorination can give
rise to very severe taste and odour problems, rendering the water unfit to drink. Second, it should
also be noted about chlorination that where a water contains even small amounts of organic
(humic) colouring matter, the reaction between it and the added chlorine will give rise to
undesirable chlorinated by-products [e.g. trihalomethanes; q.v.] which are also subject to
restriction.
Comments: Although chlorine is a poisonous gas, its toxicity to humans is not a consideration in
drinking water supplies as a water would be unacceptable on organoleptic grounds long before the
onset of directly toxic effects. There are, however, strict limits on its concentration in fishery
waters as its toxicity to aquatic life forms is much more marked.
Chlorine : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Freshwater Fish Directive [78/659/EEC]
(S)
(C)
mg/l HOCl < .005 [1]
mg/l HOCl < .005 [1]
Salmonid Waters Regulations [1988]
mg/l HOCl n/a
< .005 [2]
Drinking Water Directive [98/83/EC]
[3]
_______________________________________________________________________________________
Notes
[1] Designation is "Total residual chlorine." "The I values correspond to pH = 6. Higher concentrations of
total chlorine can. be accepted if the pH is higher." Most Irish rivers would be covered by the latter provision;
however, no further values are quoted.
[2] Standard to be conformed with by 95 % of samples over a period of 12 months where sampling is carried
out at least once per month; where sampling is less frequent the standard shall be conformed with by all
samples.
[3] According to Article 7 of the Directive, "Member States shall take all measures necessary to ensure
that, where disinfection forms part of the preparation or distribution of water intended for human
consumption, the efficiency of the disinfection treatment applied is verified, and that any contamination
from disinfection by-products is kept as low as possible without compromising the disinfection." However,
residual chlorine per se is not mentioned as a parameter.
CHLORODIBROMOMETHANE
(See "Trihalomethanes")
CHLOROFORM
(See "Trihalomethanes")
40
Parameters of Water Quality - Interpretation and Standards
19. CHLOROPHYLL
Chemical Symbol or Formula:
[Complex chemical structure; rarely used]
Units Used for Analytical Results:
µg/l or mg/m3 chlorophyll (total) 4
Normal Method(s) of Analysis: Solvent extraction/Colorimetry [B]
Occurrence/Origin:
vegetation.
Naturally-occurring green pigment in algae, cyanobacteria, plants,
Health/Sanitary Significance: No direct implications for health or sanitation.
Background Information: Chlorophyll is perhaps the single most important parameter in the
assessment of the water quality of lakes, particularly in regard to their trophic quality (i.e.
whether or not, or to what degree, they are enriched due to the presence of nutrients such as
phosphorus and - to a much lesser extent - nitrogen in the form of nitrate}. Excessive nutrient
presence in lakes promotes the growth of algae which in overabundance cause serious
environmental problems.
In over-enriched - eutrophic - lakes "algal blooms" can occur. These are surface
accumulations of cyanobacteria (formerly classified as blue-green algae), i.e. dense masses of algae
which can be swept by the winds into bays or along the lake shore (where they can decay, causing
further problems), and which can seriously disrupt the dissolved oxygen regime. In day time, when
conditions are bright or sunny, the algae will carry out photosynthesis, consuming carbon dioxide
and releasing oxygen to the waterbody (see "Oxygen, Dissolved"). In darkness, however, the algae
respire, consuming dissolved oxygen the levels of which may become critically low - low enough,
infact, to cause fish mortality.
Cyanobacterial and algal material can release trace organic components which can cause
severe problems on two main accounts. Firstly, the compounds released by cyanobacteria can prove
toxic to animals ingesting the water in which they are present. It has been necessary in some
instances for local authorities to warn the public not to walk dogs along affected lakeshores or to
allow them access to the water. Secondly, in cases where algae are present they can give rise to
taste and odour problems if the water is used as drinking water source. One characteristic of
waters affected by algal presence is a musty taste or odour. The tastes and odours are much more
pronounced if the water is chlorinated prior to distribution as drinking water. In some instances
the severity of the taste and odour has been such that temporary closure of the supply was needed.
There are no mandatory standards for chlorophyll concentrations in water, nor are there
references to the parameter in the various EU Directives relating to water quality. However, the
Organisation for Economic Cooperation and Development [OECD] in 1982 proposed a trophic
classification scheme for lake waters which has been adopted (with modifications) in Ireland by the
EPA, and which forms the basis for the reporting of quality status in lakes. This scheme is shown
in the table below and alongside it is a summation of the corresponding environmental
characteristics.
___________________________________________________________________________________________
________________________________________________________________________________________________________
LAKE CLASSIFICATION SCHEME
Trophic category of
Lake water
Annual Maximum
Chlorophyll mg/m3
__________________________________________________________________________________________
Oligotrophic [O]
Mesotrophic [M]
Eutrophic - Moderately [m-E]
Eutrophic - Strongly [s-E]
Eutrophic-Highly [h-E]
Hypertrophic [H]
<8
8 - 25
25 - 35
35 - 55
55 - 75
> 75
__________________________________________________________________________________________
4
CATEGORY DESCRIPTORS
Alga
Growth
Deoxygen. in Level of
Hypolimnion Pollution
Impairment of
Use of Lake
_______________________________________________________________________________________________________
Low
Moderate
Substantial
High
High
Very high
Low
Moderate
May be high
High
Prob. total
Prob. total
Very low
Low
Significant
Strong
High
Very high
Prob. none
Very little
May be appr.
Appreciable
High
Very high
______________________________________________________________________________________________________
Results are the same numerically as the units quoted are exact equivalents.
41
Parameters of Water Quality - Interpretation and Standards
Comments: While not mandatory, the modified OECD classification is an invaluable tool in the
categorisation of Irish lake waters.
Chlorophyll : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
20. CHROMIUM
Chemical Symbol or Formula:
Cr.
Units Used for Analytical Results:
mg/l Cr.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Natural occurrence is in ore, but chromium arises in surface waters from
discharges from electroplating, tanning, textile, paint and dyeing plants.
Health/Sanitary Significance: Chromium is toxic, to a degree which varies with the form in
which it occurs, whether as the trivalent CrIII or the hexavalent CrVI form. The latter is considered
the more hazardous but because it is difficult to distinguish by analysis the figures quoted below
refer mainly to the total chromium concentrations.
Background Information:
The element is an essential dietary requirement - in limited
amounts - and a deficiency can lead to disruption of glucose metabolism. Indeed, it has been
reported that chromium deficiency is of greater nutritional concern than overexposure. However, it
is considered that the element is carcinogenic (at high concentrations), though much more evidence
of this is needed, and it can act as a skin irritant. Hence its limitation in domestic water supplies.
The deaths of livestock resulting from watering in chromium-contaminated water have been
reported from time to time.
Comments: There is an extensive list of criteria/standards/recommendations for this element.
Chromium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l Cr
n/a
0.05
[1]
A2 waters
mg/l Cr
n/a
0.05
[1]
A3 waters
mg/l Cr
n/a
0.05
[1]
[2]
Bathing Water Regulations [1989-1998]
mg/l CrVI
Dangerous Substances Directive [76/464/EEC]
List II substance
Shellfish Directive [79/923/EEC]
[3]
[4]
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
µg/l Cr
n/a
50
_______________________________________________________________________________________
42
Parameters of Water Quality - Interpretation and Standards
Chromium: Notes
[1]
Total chromium.
[2]
Parameter is "Heavy metals such as ... chrome VI..." Sampling to be earned out "where an
investigation ... shows, or there are other grounds for believing, that there has been a deterioration in the
quality of waters..."
[3]
"The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
[4]
"The concentration of [this] substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of [this and
other specified] metals must be taken into consideration."
21. CLOSTRIDIUM PERFRINGENS (Including Spores)
Chemical Symbol or Formula:
Not Applicable [Microbiological Parameter].
Units Used for Analytical Results:
Normal Method(s) of Analysis:
Membrane Filtration Method [B].
Number of organisms/100 ml sample.
Most Probable Number (MPN; Multiple Tube Method) [B];
Occurrence/Origin: Human and animal wastes and/or soil.
Health/Sanitary Significance: Some species are pathogenic, but health effects - as in the case of
the disease of botulism - are also caused by toxins from Clostridium species instead of direct
infection.
Background Information; Some Clostridium species have the property of reducing sulphite to
sulphide, this characteristic forming the basis of test procedures. They may be used as indicators of
faecal pollution and this likely to become a widespread practice. Clostridium perfringens is a
specific and characteristic member of the group.
Comments:
Clostridia are anaerobic, spore-forming organisms, largely but not solely of
intestinal origin. They exist in much smaller numbers than E. Coli. Their spores can survive in
water much longer than organisms of the coliform group and they are more resistant to
disinfection. The WHO Guidelines note that "Their presence in disinfected waters may ... indicate
deficiencies in treatment and that disinfection-resistant pathogens could have survived
treatment," and adds the observation that they are indicative of intermittent or remote
contamination, with the caution that "Because they tend to survive and accumulate, they may be
detected long after and far from the pollution and thus give rise to false alarms." A limit appears
in Drinking Water Directive [98/83/EC] only.
Clostridium perfringens : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
no/100 ml
n/a
0
[1]
_______________________________________________________________________________________
Notes
[1]
This parameter need not be measured unless the water originates from or is influenced by surface
water. In the event of non-compliance with this parametric value, the Member State concerned must
investigate the supply to ensure that there is no potential danger to human health arising from the presence
of pathogenic micro-organisms, e.g. cryptosporidium. Member States must include the results of all such
investigations in the reports they must submit under Article 13(2).
43
Parameters of Water Quality - Interpretation and Standards
CLOSTRIDIA, SULPHITE-REDUCING
(See "Clostridium Perfringens (Including Spores")
22. COBALT
Chemical Symbol or Formula:
Co.
Units Used for Analytical Results:
mg/l Co.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Occurs in ores. Presence in water due to discharges.
Health/Sanitary Significance: Little significance in water due to low level of occurrence. The
metal and its compounds are hazardous as solids or strong solutions.
Background Information: Cobalt is contained in the Vitamin B12 molecule and as such is an
important dietary requirement, being provided by green vegetables, in particular. It is rarely
found in natural waters and, accordingly, there are few recommendations as to its limitation.
Comments:
The lack of standards for drinking water reflects the minimal risk.
Cobalt : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
COD
(See "Oxygen Demand, Chemical")
23. COLIFORMS, FAECAL & TOTAL
Chemical Symbol or Formula:
Not Applicable [Microbiological parameter].
Units Used for Analytical Results:
Number of organisms/100 ml sample.
Normal Method (s) of Analysis:
Membrane Filtration Method [B].
Most Probable Number (MPN: Multiple Tube Method) [B];
Occurrence/Origin: Faecal coliforms originate in human and animal waste. Total coliforms
include faecal and also other bacteria with similar properties which originate in soil and are nonfaecal.
Health/Sanitary Significance:
[see detailed discussion below].
Indicators of possible presence of pathogenic micro-organisms
Background Information:
The risk to consumers of infection from drinking polluted waters
will vary very widely from instance to instance because the numbers of pathogenic organisms (i.e.
the actual disease-causing organisms) in contaminated waters will show great variations. The
number of pathogens in a sewage contaminated water is a function of the number of persons (so44
Parameters of Water Quality - Interpretation and Standards
called "carriers") who excrete such organisms. As the latter is an unknown quantity, and as the
positive identification of specific bacteria may be a very difficult task (and not one suited to the
routine bacteriological screening of a water on public health grounds) an indirect approach is
universally adopted.
To ensure a high factor of safety, the practice has been to monitor indicator organisms which, by
definition, should be (i) easily detected and identified, (ii) of the same origin as the pathogens (i.e.
from the human or animal intestine), (iii) present in far greater numbers than the pathogens, and
(iv) present whenever the pathogens are likely to be present. In addition, they should show the
same or better survival characteristics than the pathogens and, of course, they must not be in
themselves pathogenic. To date the universal indicator organisms have been the coliforms,
specifically Escherichia coli.5 These bacteria are of definite faecal origin (human and animal) and
they are excreted in vast numbers. Their presence in a water supply is proof that faecal
contamination has occurred and it is therefore a definite indication of the risk that pathogens may
be present. The absence of these faecal coliforms indicates strongly the probability that pathogens
are absent.
Because not all coliform organisms (or organisms which show the same test behaviour as
coliforms) are of faecal origin, some types being able to grow in soil, a second analysis is carried out
for the presence of total coliforms, giving an indication of the general level of microbiological
contamination of a water. Each microbiological test procedure is designed around some distinctive,
characteristic property of the group of organisms under study. In the case of the coliforms this is
the ability to grow aerobically on an agar/bile-salt medium and to ferment lactose, producing acid
and gas, within 48 hours at 37°C. E. coli are distinguished by further individual properties.
As indicated above, two distinct analytical procedures are used routinely. The first is a
multiple tube technique in which several replicates of each of three different dilutions of sample
are incubated in test-tubes containing the appropriate medium. After incubation the number of
positive results is noted, i.e. the number of tubes at each dilution in which the production of gas
etc. is observed, and the result - the Most Probable Number of organisms in 100 ml of sample,
commonly known as the MPN - is obtained from probability tables. It is presumed that each
"positive" indication is due to the presence of coliforms and the test is known as the "presumptive
coliform test." [Confirmatory tests may then be carried out as required.] Concurrent Most
Probable Number determinations are made for faecal and total coliforms (at different incubation
temperatures) and the results reported separately.
In the MPN technique actual numbers of coliforms are not being determined, as they are in
the second commonly used procedure - Membrane Filtration. Here, measured amounts of sample
are passed through sterilised filter membranes. The micro-organisms present are retained on the
membranes which are transferred to a suitable medium for culturing separately at the appropriate
temperatures. The numbers of resulting colonies are counted to give presumptive E. coli and total
coliform counts. The term presumptive is applied as additional tests would be required to verify
that the organisms showed all the reactions characteristic of the coliform group. However, if these
extra tests are omitted and waters assessed on the basis of presumptive tests only there is an even
greater margin of safety, as a "worst-case" situation is assumed to apply.
The philosophy which has been adopted universally is to use the coliforms as definite
indicators of sewage (faecal) pollution and to apply strict limits on their presence in water sources
and supplies. The interpretation of the results of analysis may be summarised as follows:
Where E. coli are present in large numbers the inference is that heavy, recent pollution by human or
animal wastes has occurred; if the B. coli numbers are low it is inferred that pollution from the same
source(s) is either less recent or less severe. If coliforms not including E. coli are observed the indication is that either the pollution is recent and non-faecal in origin or of remote, faecal origin such that
the intestinal conforms have not survived.
___________________
5
This part of the discussion deals specifically with the organisms E. coli Type I (classified on the basis of test responses)
which are the classic indicators of faecal contamination. The quite distinct - and in particular circumstances - highly
toxic E. coli Type 0.157 is not germane to the present discussion.
45
Parameters of Water Quality - Interpretation and Standards
However, if any coliforms at all are found in a treated drinking water supply, following chlorination, it
should be concluded that either inadequate treatment is being applied or else that contamination has
been introduced during distribution of the water, or in the sampling or handling of the sample(s). Any
indication at all of contamination, however apparently mild, must be regarded as a matter of gravity
and the circumstances investigated promptly.
Comments: The whole philosophy behind the use of the coliforms as indicators is to give a very
high margin of safety. While the exact safety factor would, of course, depend on the ratio of
coliforms to pathogens, in practice this is never quantified. Experience has shown this approach to
be satisfactory.
Recommended or Mandatory Limit Values
FAECAL COLIFORMS
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
Bathing Water Regulations [1989-1998]
no/100 ml
n/a
1,000
no/100 ml
n/a
5,000
no/100 ml
n/a
40,000
no/100 ml
n/a
< 1,000
[1]
no/100 ml
n/a
< 2,000
[2]
Shellfish Directive [79/923/EEC]
no/100 ml
< 300 [3]
Drinking Water Directive [98/83/EC]
no/100 ml
n/a
0
[4,5,6]
no/250 ml
n/a
0
[4,5,7]
_______________________________________________________________________________________
Notes
[1]
To be conformed with by 80% or more of samples and not to be exceeded by any two consecutive
samples in any case.
[2]
To be conformed with by 95% or more of samples and not to be exceeded by any two consecutive
samples in any case.
[3]
Value applies "in the shellfish flesh and intervalvular liquid," but, pending the adoption of another
Directive on the protection of the consumers of shellfish products, "it is essential that this value be observed
in waters in which live shell fish directly edible by man."
[4]
The parameter is designated “Escherichia coli (E. coli)” and not as faecal coliforms (which it is, in fact).
[5]
Analysis by membrane filtration procedure.
[6]
This parametric value applies to all drinking water other than that offered for sale in bottles or
containers.
[7]
This parametric value applies to water offered for sale in bottles or containers.
TOTAL COLIFORMS
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
Bathing Water Regulations [1989-1998]
no/100 ml
n/a
5,000
[1]
no/100 ml
n/a
25,000
[1]
no/100 ml
n/a
100,000
[1]
[2]
no/100 ml
n/a
< 5,000
[3]
no/100 ml
n/a
< 10,000
Drinking Water Directive [98/83/EC]
no/100 ml
n/a
0
[4,5,]
_______________________________________________________________________________________
46
Parameters of Water Quality - Interpretation and Standards
Total Coliforms : Notes
[1]
Incubation temperature 37 "C.
[2]
To be conformed with by 80% or more of samples and not to be exceeded by any two consecutive
samples in any case.
[3]
To be conformed with by 95% or more of samples and not to be exceeded by any two consecutive
samples in any case.
[4]
The parameter is designated "Coliform bacteria" and not as total coliforms (which it is, in fact).
[5]
Analysis by membrane filtration procedure.
24. COLONY COUNT(S)
Chemical Symbol or Formula:
Not Applicable [Microbiological parameter].
Units Used for Analytical Results:
temperature of incubation [22ºC and 37°C].
Number of organisms/ml sample at the stated
Normal Method(s) of Analysis: Incubation on appropriate media plates [B/C].
Occurrence/Origin: Natural or artificial colonisation of water.
Health/Sanitary Significance: None specific - general indicator of the microbiological purity.
Background Information:
This is an empirical measurement of aerobic and facultative
anaerobic bacteria as a group which is made to assess the overall microbiological quality of a water
for human consumption. EU Drinking Water Directive [98/83/EC] uses the parameter designation
Colony Count (at stated temperature); alternative designations Standard Plate Count, Total
Bacteria (Count) and Total Plate Count (at a stated temperature) are also used.
Comments: Because bacteria will have differing properties and hence will not all respond in like
manner to the conditions chosen in the test procedure it is clear that the parameter is a rather
arbitrary one which nonetheless is useful as a general purity indicator.
Colony Counts: Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
-
n/a No abnormal
[1]
change
no/1 ml
n/a
100
[2]
no/1 ml
n/a
20
[3]
_______________________________________________________________________________________
Notes
[1]
Indicator parameter. Incubation temperature 22°C. Applies to water other than that offered for
sale in bottles or containers.
[2]
Microbiological parameter. Incubation temperature 22°C.
Applies to water offered for sale in
bottles or containers.
[3]
Microbiological parameter. Incubation temperature 37°C.
Applies to water offered for sale in
bottles or containers.
25. COLOUR
Chemical Symbol or Formula:
Not Applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l Pt/Co [mg/l Hazen].
47
Parameters of Water Quality - Interpretation and Standards
Normal Method(s) of Analysis: Colorimetric [A/C]
Occurrence/Origin: Natural colour reflects the presence of complex organic molecules derived
from vegetable (humic) matter such as peat, leaves, branches and soon. Its effect can be enhanced
by the presence of suspended matter but this is normally eliminated in the analysis by filtration.
Obviously, the more vegetable matter in the water the greater is the colour. Exceptionally, natural
colour may arise from the presence of colloidal iron/manganese in a water but organic matter is
almost always the cause.
Health/Sanitary Significance: Objections to high colour are generally on aesthetic grounds
rather than on the basis of a health hazard. Consumers are reluctant to drink water, however safe,
which has a yellowish-brown colour not unlike that of urine, and because of this revulsion any
marked colour is very undesirable. So strong may be the objection to colour in water that
occasional cases have been noted of people turning from coloured but otherwise safe waters to
alternative supplies without coloration, and of a much lower bacteriological quality. However, the
1998 EU Drinking Water Directive - in contrast to its 1980 predecessor - does not set a
quantitative standard for colour, effectively leaving the matter to the reactions of consumers.
Nonetheless, it must be noted that the presence of colour on a persistent basis (i.e. with
short-term seasonal peak values discounted) in a water which is then disinfected by chlorination is
highly undesirable. This because of the readiness with which the colour-causing substances
reacted with the added chlorine giving rise to the presence of trihalomethanes (THM; q.v.). The
latter compounds are a potential hazard to public health.
Background Information: Because of its origins in vegetable matter the degree of colour in a
water will vary very widely in space and in time. The highest colour levels in rivers occur in floods,
especially the first flood after a dry season when accumulated deposits of decaying leaves and
debris are swept up into the heavy flow releasing highly colouring matter. Because of this
variability (which could perhaps be ten-fold) it is essential that many determinations are made to
establish the true range of colour in a river, particularly if the water is to be used after treatment
for public supply.
Comments: In the present context - and, indeed, in general usage - the term "colour" refers to
the natural coloration occurring in waters and not to any induced colouring resulting from wastes.
Colour : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l Pt/Co
mg/l Pt/Co
mg/l Pt/Co
mg/l Pt/Co
mg/l Pt/Co
Bathing Water Regulations [1989-1998]
Shellfish Directive [79/923/EEC]
Drinking Water Directive [98/83/EC]
-
n/a
n/a
n/a
n/a
-
20
100
150
-
[1,2]
[1,2]
[1,2]
[3]
[4]
-
Acceptable to
consumers and
no abnormal change
_______________________________________________________________________________________
Notes
[1]
Parameter is "Colouration (sic) [after simple filtration]."
[2]
Departure may be granted by the Minister "where exceptional climatic or geographical conditions have
arisen."
48
Parameters of Water Quality - Interpretation and Standards
Colour : Notes (continued)
[3]
The standard in the Regulations is "No abnormal change in colour." It is specified that the standard
"be conformed with in 95% of inspections of bathing water. No two consecutive inspections to fail standard."
[4]
Parameter is "Coloration [after Filtration]" [through a 0.45µm membrane]. "A discharge affecting
shellfish waters must not cause the colour of the waters after filtration to deviate by more than 10 mg Pt/l
(sic) from the colour of the waters not so affected."
26. CONDUCTIVITY
Chemical Symbol or Formula:
Not Applicable [Physical parameter].
Units Used for Analytical Results:
µS/cm.6
Normal Method(s) of Analysis:
Electrometric [A].
Occurrence/Origin:
Reflects mineral salt content of water.
Health/Sanitary Significance: No direct significance.
Background Information: Also referred to as electrical conductivity and, not wholly accurately,
as specific conductance, the conductivity of a water is an expression of its ability to conduct an
electric current. As this property is related to the ionic content of the sample which is in turn a
function of the dissolved (ionisable) solids concentration, the relevance of easily performed
conductivity measurements is apparent. In itself conductivity is a property of little interest to a
water analyst but it is an invaluable indicator of the range into which hardness and alkalinity
values are likely to fall, and also of the order of the dissolved solids content of the water. While a
certain proportion of the dissolved solids (for example, those which are of vegetable origin) will not
be ionised (and hence will not be reflected in the conductivity figures) for many surface waters the
following approximation will apply: Conductivity (µS/cm) x 2/3 = Total Dissolved Solids (mg/l).
In samples from a source which is regularly tested a rapid conductivity analysis may be an
adequate replacement for other, longer determinations.
Comments: It is important to note that there is an interrelationship between conductivity and
temperature, the former increasing with temperature at a rate of some 2 per cent per degree C
rise. There is a regrettable lack of uniformity in the terms in which conductivity is reported. Some
UK methods manuals report the results at 20°C while the standard US reference manual uses
25°C. A difference of 10 percent can therefore arise depending on how the results are quoted. An
error of this magnitude could not be tolerated, especially where conductivity readings are being
used to estimate salinity.
Conductivity : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
µS/cm
n/a
1,000
[1]
µS/cm
n/a
1,000
[1]
µS/cm
n/a
1,000
[1]
Drinking Water Directive [98/83/EC]
µS/cm
n/a
2,500
[1,2]
_______________________________________________________________________________________
Notes
[1]
Measured at 20 °C.
[2]
"The water should not be aggressive."
__________
6
The unit is micro-Siemens/centimetre.
49
Parameters of Water Quality - Interpretation and Standards
27. COPPER
Chemical Symbol or Formula:
Cu.
Units Used for Analytical Results:
mg/l Cu.
Normal Method(s) of Analysis: Atomic Absorption Spectrometry [B/C]
Occurrence/Origin: Ores; industrial wastes.
Health/Sanitary Significance: Copper is not particularly toxic to humans (indeed, it is an
essential dietary requirement) and medicinal doses up to 20 mg/l are not unknown. However,
astringent tastes in water can be caused by levels above 1 mg/l Cu.
Background Information: This element is present naturally in metalliferous areas but more
often its presence in waters is due to attack on copper piping. Rarely, its occurrence may be due to
its use as an algicide. Unless used with great care for algal control there is a grave risk of fish kills,
as it is as a toxicant to fish that copper is of greatest interest. In recent years there has been at
least one major fish kill attributed to the improper use of copper as an algal toxicant. Copper is an
element the toxicity of which to fish varies widely with the hardness of the water.
Comments:
tanks.
A problem associated with high levels of copper in water is galvanic corrosion of
Copper : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
Dangerous Substances Directive [76/464/EEC]
Freshwater Fish Directive [78/659/EEC]
(S)
(C)
Salmonid Waters Regulations [1988]
mg/l Cu
mg/l Cu
mg/l Cu
n/a
0.05
[1]
n/a
0.1
[1]
n/a
1.0
[1]
List II substance
[2]
mg/l Cu < 0.04
mg/l Cu < 0.04
[2]
mg/l Cu
n/a
< 0.005
[3,7]
[4,7]
mg/l Cu
n/a
< 0.022
[5,7]
mg/l Cu
n/a
< 0.04
[6,7]
mg/l Cu
n/a
< 0.112
Shellfish Directive [79/923/EEC]
mg/l Cu
[8]
[9]
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
mg/l Cu
n/a
2.0
[10]
_______________________________________________________________________________________
Notes
[1]
Departure may be granted "where exceptional climatic or geographical conditions have arisen."
[2]
Parameter is "Dissolved copper." The G values given are with reference to a hardness value of 100 mg/
CaCO3. Relevant values for other hardness levels are as follows:
_______________________________________________________________________________
Hardness
10
50
100
500
mg/ CaCO3
_______________________________________________________________________________
Copper
(S)
0.005
0.022
0.04
0.112
mg/l Cu
(C)
0.005
0.022
0.04
0.112
mg/l Cu
_______________________________________________________________________________
50
Parameters of Water Quality - Interpretation and Standards
Copper : Notes (Continued)
[3]
Standard applies to water of hardness 10 mg/l CaCO3.
[4]
Standard applies to water of hardness 50 mg/l CaCO3.
[5]
Standard applies to water of hardness 100 mg/l CaCO3.
[6]
Standard applies to water of hardness 300 mg/l CaCO3.
[7]
Standard to be conformed with by 95% of samples over a period of 12 months where sampling is
carried out at least once per month; where sampling is less frequent the standard shall be conformed with by
all samples.
[8]
"The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
[9]
"The concentration of [this] substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of this and
other specified] metals must be taken into consideration."
[10] "The value applies to a sample of water intended for human consumption obtained by an adequate
sampling method ..... at the tap and taken so as to be representative of a weekly average value ingested by
consumers. Where appropriate the sampling and monitoring methods must be applied in a harmonised
fashion to be drawn up in accordance with Article 7(4). Member States must take account of the occurrence
of peak levels that may cause adverse effects on human health."
28. CRYPTOSPORIDIUM
Chemical Symbol or Formula:
Not Applicable [Microbiological parameter]
Units Used for Analytical Results:
Number of cysts/100 litres.
Normal Method(s) of Analysis:
Advanced Microbiological Techniques [C/D]
Occurrence/Origin:
Present in human and animal wastes.
Health/Sanitary Significance: Cryptosporidium is a small (microscopic) parasite present in
faecal material. It has pathogenic effects in both children and adults, when it enters the
gastrointestinal tract and causes an infection termed cryptosporidiosis. The effects of the latter
include fever, stomach upsets, weight loss and diarrhoea. While healthy adults will normally
recover within three days, the effects on both old and young, and those with weakened immune
systems, are much more serious and can lead to death.
The Cryptosporidium organism - a protozoan - is protected by an outer shell (termed a cyst)
which affords it protection and permits it to survive for long periods outside the body. It can occur
in drinking water supplies which are contaminated by human or animal waste and is considered
by the WHO to be a pathogen of high health significance.
Background Information:
A problem associated with Cryptosporidium is that it is very
resistant to destruction by chlorine and other disinfectants. It may survive the disinfection process
unless specific additional treatment is applied.
Comments: If the quality of a drinking water is suspect, the water should be brought to the boil
before consumption. This will destroy the micro-organisms present.
Cryptosporidium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
[1]
_______________________________________________________________________________________
51
Parameters of Water Quality - Interpretation and Standards
Cryptosporidium: Notes
[1]
While the Directive does not include Cryptosporidium in. any of its lists of parameters, Article 4
stipulates that: "For the purposes of the minimum requirements of this Directive, water intended for human
consumption shall be clean and wholesome if it: ...is free from any micro-organisms and parasites and from
any substances which, in numbers or concentrations, constitute a potential danger to public health."
29. CYANIDE
Chemical Symbol or Formula:
CN–
Units Used for Analytical Results:
mg/l CN.
Normal Method(s) of Analysis: Colorimetric (after distillation) (B]; Specific Ion Electrode (after
distillation) [B].
Occurrence/Origin: Industrial effluents (principally electroplating).
Health/Sanitary Significance: Cyanide is a reactive, highly toxic entity which in excessive
amount will cause mortality rapidly to humans and to fish.
Background Information: It is a common constituent of industrial wastes, especially from
metal plating processes and electronic components manufacture.
Comments: Due to its reactivity cyanide does not persist in the environment.
Cyanide : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l CN
n/a
0.05
A2 waters
mg/l CN
n/a
0.05
A3 waters
mg/l CN
n/a
0.05
Bathing Water Regulations [1989-1998]
mg/l CN
[1]
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
µg/l CN
n/a
50
_______________________________________________________________________________________
Notes
[1] Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..."
30. 1,2-DICHLOROETHANE
Chemical Symbol or Formula:
C2H4Cl2.
Units Used for Analytical Results:
µg/l C2H4Cl2.
Normal Method(s) of Analysis:
Gas Chromatography [C].
52
Parameters of Water Quality - Interpretation and Standards
Occurrence/Origin: Synthetic organic solvent used in various industries.
Health/Sanitary Significance: Toxic substance which causes a variety of ill-effects in humans,
including eye damage, dermatitis, narcotic effects etc.
Background Information: The compound is alternatively known as ethylene dichloride. It is
used as a solvent for a variety of materials, especially rubber.
Comments: This only limit for this substance occurs in Drinking Water Directive [98/83/EC].
1,2-Dichloroethane : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l
n/a
3.0
_______________________________________________________________________________________
E. coli
(See "Coliforms, Faecal and Total")
31. ENTEROCOCCI
Chemical Symbol or Formula:
Not Applicable [Microbiological parameter].
Units Used for Analytical Results:
Number of organisms/100 ml sample.
Normal Method(s) of Analysis:
Filtration procedure [B].
Occurrence/Origin:
Most Probable Number (MPN) technique [B]; Membrane
Sewage and similar wastes.
Health/Sanitary Significance: Some members of the group "enterococci" have pathogenic
properties.
Background Information:
These organisms originate in faeces, both animal and human.
Despite their having some pathogenic properties, their main use is as an indicator of faecal
pollution and, as they can be reliably and easily determined, their estimation is useful in clarifying
the position in waters which show no E. coli but large numbers of coliform bacteria as a group. In
the earlier Drinking Water Directive [80/778/EEC] the relevant parameter was "Faecal
Streptococci" but this has been replaced by the present broader term. One of the more relevant
members of this group is Streptococcus faecalis.
Comments: While the measurement of faecal streptococci has been recommended as a source of
valuable supplementary information on surface water quality, particularly in combination with
data from faecal coliform assays, it should be remembered that a limitation on the use of faecal
streptococci is their shorter survival time in the aquatic environment.
Enterococci : Recommended or Mandatory Limit Values
___________________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
___________________________________________________________________________________________
Surface Water Regulations [1989]
no./100 ml
no./100 ml
no./100 ml
A1 waters
A2 waters
A3 waters
n/a
n/a
n/a
200
2,000
10,000
_________________________________________________________________________________________________________________________________________________________________________________________________________
53
Parameters of Water Quality - Interpretation and Standards
Enterococci : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
Drinking Water Directive [98/83/EC]
no./100 ml
n/a
< 300
[1]
no./100 ml
n/a
0
[2,3]
no./250 ml
n/a
0
[2,4]
_______________________________________________________________________________________
Notes
[1]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..." Standard to be conformed with by 95% of
samples and not to be exceeded by any two consecutive samples,
[2]
Parameter is designated "Enterococci."
[3]
This parametric value applies to drinking water other than that offered for sale in bottles or
containers.
[4]
This parametric value applies to "water offered for sale in bottles or containers,"
32. ENTEROPATHOGENIC VIRUSES
Chemical Symbol or Formula:
Not Applicable [Microbiological parameter].
Units Used for Analytical Results:
Normal Method(s) of Analysis:
PFU / 10 litres.
[Specialised microbiological techniques] [D]
Occurrence/Origin: Human and animal wastes.
Health/Sanitary Significance: Viruses are pathogens with highly specific reactions, causing
several well-known major diseases in man, as discussed below.
Background Information: Those viruses of concern in water supply can pass through the
stomach and into the intestine where they multiply and from which they are excreted. Among the
diseases which are viral in origin and are water-borne are poliomyelitis, gastro-enteritis and
infectious hepatitis. Because the detection of viruses is a complicated analytical procedure and
cannot be done quickly, the analysis is not carried out as a routine and reliance is placed instead
on the coliforms as indicators of faecal pollution (see "Coliforms, Faecal & Total" above).
However, caution must be exercised as the viruses are not as susceptible to chlorination as
bacteria and it does not necessarily follow that a complete bacterial kill will be matched by the
absence of all viruses. It is critically important, therefore, that adequate care is taken in
chlorination and that proper chlorine residuals are maintained in water supplies.
Comments: Deficiencies in analytical and epidemiological techniques mean that it is not possible
to assert that a water is free of viruses, hence the absence of limit values or guideline levels in
most of the sources cited, including the 1993 WHO Guidelines. However, this invaluable WHO
publication contains a table of recommended treatments for different sources aimed at producing
water with a negligible virus risk. Details are quoted in Appendix 9 below. The relevance of the
low turbidity requirement mentioned in the Appendix (which must be met before the water is
disinfected) arises because the colloidal solid matter giving rise to turbidity may otherwise act as a
shield for any viruses present, possibly preventing fully efficient disinfection.
54
Parameters of Water Quality - Interpretation and Standards
Enteropathogenic Viruses : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
PFU/10 litres
0
[1,2]
Drinking Water Directive [98/83/EC]
[3]
_______________________________________________________________________________________
Notes
[1]
Units are plaque-forming units [PFU]/10 litres.
[2]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..." A 95% compliance is required.
[3]
Article 4(1) of the Directive states, inter alia, that: "For the purposes of the minimum requirements of
this Directive, water intended for human consumption shall be wholesome and clean if it... is free from any
micro-organisms and parasites and from any substances which, in numbers or concentrations, constitute a
potential danger to human health......."; Article 7(6) requires that "Member States shall ensure that
additional monitoring is carried out on a case-by-case basis of substances and micro-organisms for which no
parametric value has been set in accordance with Article 5, if there is reason to suspect that they may be
present in amounts or numbers which constitute a potential danger to human health."
33. EPICHLOROHYDRIN
Chemical Symbol or Formula:
C3H5ClO.
Units Used for Analytical Results:
µg/l C3H5ClO.
Normal Method(s) of Analysis:
Gas Chromatography [C].
Occurrence/Origin:
Synthetic chlorinated solvent.
Health/Sanitary Significance: Toxic substance which is a strong skin irritant and which can
cause kidney and other damage.
Background Information: Solvent for resins, gums, enamels, cellulose, lacquers etc.
Comments: This is another of the series of chlorinated solvents the concentration of which in
drinking water is subject to strict controls.
Epichlorohydrin : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l
n/a
0.10
[1]
_______________________________________________________________________________________
Notes
[1]
The Directive states that: The parametric value refers to the residual monomer concentration in the
water as calculated according to specifications of the maximum release from the corresponding polymer in
contact with the water.
55
Parameters of Water Quality - Interpretation and Standards
ESCHERICHIA COLI
(See "Coliforms, Faecal and Total")
ETHYLENE DICHLORIDE
(See "1,2-Dichloroethane")
FAECAL COLIFORMS
(See "Coliforms, Faecal and Total")
34. FLUORIDE
Chemical Symbol or Formula:
F –.
Units Used for Analytical Results:
mg/I F.
Normal Method(s) of Analysis: Colorimetric (after distillation) [B]; Specific Ion Electrode [B].
Occurrence/Origin: Occurs naturally in quite rare instances; arises almost exclusively from
fluoridation of public water supplies and from industrial discharges.
Health/Sanitary Significance: Health studies have shown that the addition of fluoride to water
supplies in levels above 0.6 mg/l F leads to a reduction in tooth decay in growing children and that
the optimum beneficial effect occurs around 1.0 mg/l.
Background Information:
At levels markedly over 1.5 mg/l an inverse effect occurs and
mottling of teeth (or severe damage at gross levels) will arise. For this reason there is a constraint
on fluoride levels, the effects of which vary with temperature.
Comments: It should be noted that fluoride levels in fluoridated public water supplies in Ireland
are legally restricted to the range 0.8-1.0 mg/l F. The same legislation specifies the distillation
procedure for fluoride analysis. In making the 1988 Drinking Water Regulations the then Minister
for the Environment fixed 1.0 mg/l F [1,000 µg/1 F] as the MAC. Thus the limit value for fluoride
in Ireland is one-third less than that which applies elsewhere in the EU.
Fluoride : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l F
mg/l F
mg/l F
n/a
n/a
n/a
1.0
1.7
1.7
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
mg/l F
n/a
1.5
_______________________________________________________________________________________
56
Parameters of Water Quality - Interpretation and Standards
FREE CARBON DIOXIDE
(See "Carbon Dioxide, Free")
35. GIARDIA
Chemical Symbol or Formula:
Not Applicable [Microbiological parameter]
Units Used for Analytical Results: Number of cysts/100 litres.
Normal Method(s) of Analysis: Advanced Microbiological Techniques [C/D]
Occurrence/Origin: Present in human and animal wastes.
Health/Sanitary Significance: Giardia is a small (microscopic) parasite present in human and
animal wastes which has pathogenic effects m both children and adults. If ingested in water,
Giardia can cause fever, stomach upsets (often very severe) and diarrhoea; however, it is rarely
fatal. The organism is protected by an outer shell (termed a cyst) which affords it protection and
permits it to survive for long periods outside the body.
Background Information: A problem associated with Giardia is that the cysts are not very
amenable to destruction by chlorine. Unless an enhanced chlorine dosage and extended contact
time are used Giardia may survive the disinfection process.
Comments: If the quality of a drinking water is suspect, the water should be brought to the boil
before consumption. This will destroy the Giardia and other micro-organisms present.
Giardia : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
[1]
_______________________________________________________________________________________
Notes
[1]
While the Directive does not include Giardia in any of its lists of parameters Article 4 stipulates that:
"For the purposes of the minimum requirements of this Directive, water intended for human consumption
shall be clean and wholesome if it...is free from any micro-organisms and parasites and from any substances
which, in numbers or concentrations, constitute a potential danger to public health."
HALOFORMS
(See "Trihalomethanes")
36. HARDNESS
Chemical Symbol or Formula:
Not Applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l CaCO3.
Normal Method(s) of Analysis:
Titration with EDTA [A].
Occurrence/Origin:
Rock formations - limestone etc.
57
Parameters of Water Quality - Interpretation and Standards
Health/Sanitary Significance:
Hardness is a natural characteristic of water which can
enhance its palatability and consumer acceptability for drinking purposes. Health studies in
several countries in recent years indicate that mortality rates from heart diseases are lower in
areas with hard water.
Background Information: Originally taken to be the capacity of a water to destroy the lather of
soap, hardness was determined formerly by titration with soap solution. Nowadays, the analysis
comprises the determination of calcium and magnesium which are the main constituents of
hardness. Although barium, strontium and iron can also contribute to hardness, their
concentrations are normally so low in this context that they can be ignored. Thus, total hardness is
taken to comprise the calcium and magnesium concentrations expressed as mg/l CaCO3. The
widespread abundance of these metals in rock formations leads often to very considerable
hardness levels in surface and ground waters.
The following is one of several such arbitrary classifications of waters by hardness7:
Soft
Moderately Soft
Slightly Hard
up to 50 mg/l CaCO3
51-100 mg/l CaCO3
101 - 150 mg/l CaCO3
Moderately Hard 151-250 mg/l CaCO3
Hard
251-350 mg/l CaCO3
Excessively Hard over 350 mg/l CaCO3.
A variety of additional terms is used to describe different aspects of hardness. These are frequently
encountered and are summarised briefly below:
Calcium Hardness is the expression of the results of the measurement of calcium only, as mg/l CaCO3.
Carbonate Hardness is the hardness derived from the solubilisation of calcium or magnesium carbonate (by
conversion of the carbonate to bicarbonate). This hardness is removed by heating (see below).
Magnesium Hardness The difference between total hardness and calcium hardness is taken as the magnesium
hardness (all figures as mg/l CaCO3.).
Non-carbonate Hardness is the hardness due to the solution of calcium chloride or magnesium sulphate, for
example.
Permanent Hardness This is equivalent to non-carbonate hardness in that it cannot be reduced or removed by
heating.
Temporary Hardness The same as carbonate hardness, this form may be removed by heating the waters, when
chemical reactions occur as follows:
2HCO3 –
CO3 – – + Ca++
→
→
H2O + CO2 + CO3 – –
CaCO3
Calcium Carbonate (insoluble)
This is in fact what happens in most cases when the temporary hardness is deposited as scale in boilers, etc.
Total Hardness is the expression of the results of direct measurement (principally of calcium and
magnesium) expressed as mg/l CaCO3.
Comments: As has been pointed out earlier (cf. "Copper") hardness levels have a bearing on the
toxicity of some metals. In general, these toxic effects are markedly less in waters with a
significant degree of hardness. The chief disadvantages of hard waters are that they neutralise
the lathering power of soap (though not modern detergent formulations) and, more important, that
they can cause blockage of pipes and severely reduced boiler efficiency because of scale formation.
These effects will increase as the hardness rises to and beyond 200 mg/l CaCO3.
Hardness: Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Freshwater Fish Directive [78/659/EEC]
(S)
(C)
-
-
-
[1]
[1]
__________
The boundaries between the top of one hardness band and the bottom of the following one are nowhere
near as exact as the presentation convention used apparently implies. Indeed, there is no rigidity about the
classification, which should be used sensibly as a handy measure.
7
58
Parameters of Water Quality - Interpretation and Standards
Hardness: Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Salmonid Waters Regulations [1988]
[2]
Drinking Water Directive [98/83/EC]
[3]
_______________________________________________________________________________________
Notes
[1]
There are no limits for hardness as such in this Directive, but Annex II contains data on the
relationship between hardness and the acceptable levels of dissolved copper and total zinc in salmonid and
cyprinid waters.
[2]
There are no limits for hardness as such in the Regulations, but the Second Schedule contains data on
the relationship between hardness and the permissible levels of dissolved copper and total zinc in salmonid
waters.
[3] There is no reference to hardness in this Directive.
37. HEAVY METALS
Chemical Symbol or Formula:
Varies with each metal.
Units Used for Analytical Results:
Normal Method(s) of Analysis:
Occurrence/Origin:
geological formations.
µg/l or mg/l metal.
Atomic Absorption Spectrometry8 [B/C/D]
Principally from effluent discharges, or from distribution piping, or from
Health/Sanitary Significance: Toxic to humans (to a degree varying greatly from metal to
metal) and to fish (the hazard levels for which are generally very much lower). Easily accumulable
in fish and other tissue and hence liable to enter food chain.
Background Information: The parameters in this very important category comprise principally
those listed below. Arsenic, though non-metallic, is included for convenience as it is toxic and is
generally referred to as a constituent of this group. All the elements listed below are discussed
under separate paragraphs in this volume but the general class "Heavy Metals" has been included
for completeness as references to the group are very common indeed. The term "heavy metals" is
rather inaccurate and, indeed, could be misleading. It arises from the high atomic weights of
several metals in the broad group, although other metals regarded as in the same group have low
atomic weights. Nonetheless, the term both is widely current and a useful descriptor. The following
is a listing of the more commonly referred to metals in this class:
Antimony
Cobalt
Nickel
Tin
Arsenic
Copper
Selenium
Titanium
Beryllium
Lead
Silver
Uranium
Cadmium
Mercury
Tellurium
Vanadium
Chromium
Molybdenum
Thallium
Zinc.
The individual substances are all more or less toxic to either man or fish or both, and their
presence is highly undesirable in raw or finished public waters or in fishery waters, salmonid or
cyprinid.
__________
8
And related techniques, including ICP [inductively-coupled plasma] spectroscopy.
59
Parameters of Water Quality - Interpretation and Standards
Comments: It should be noted that in the case of some of these metals complexes can be formed
with organic materials (so-called "organometallics"), the resultant compounds being very toxic
indeed, perhaps far more so than the un-complexed elements. Examples of such noxious materials
are methylmercury and tributyltin.
38. HYDROCARBONS, DISSOLVED & EMULSIFIED
Chemical Symbol or Formula:
Not Applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l material.
Normal Method(s) of Analysis: Gravimetric [B/C] or Gas Chromatographic [C].
Occurrence/Origin: Effluent discharges, oil spillages etc.
Health/Sanitary Significance: The main implications are organoleptic in the context of this
parameter as covered by the Directives and Regulations (see below), but many complex
hydrocarbon materials are carcinogenic (e.g. polycyclic aromatic hydrocarbons, q.v.).
Background Information: This heading includes petroleum, oil, grease and related materials.
Problems caused by these substances include interference with such vital processes as the mass
transfer of oxygen from air to water (essential in river reaeration, for example), blockage of pipes,
fouling of plant and animal life, odour and taste problems, and the like.
Comments: It is worth reiterating that this parameter as herein defined is an overall aggregate
(or bulk) parameter which is nonetheless limited in its scope by the generalised nature of the
relevvan analytical methods. A large number of specific (and potentially undesirable) hydrocarbon
compounds are thus excluded from its coverage.
Hydrocarbons : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
Bathing Water Regulations [1989-1998]
Dangerous Substances Directive [76/464/EEC]
Freshwater Fish Directive [78/659/EEC]
(S)
(C)
Salmonid Waters Regulations [1988]
Shellfish Directive [79/923/EEC]
Ground Water Directive [80/68/EEC]
Drinking Water Directive [98/83/EC]
mg/l
mg/l
mg/l
mg/l
-
n/a
0.01
n/a
0.2
n/a
1
Lists I & II substances
List I substances
-
[1]
[1]
[1]
[2,3]
[4,5]
[6,7]
[6,7]
[6,7]
[6,8]
[9]
[10]
_______________________________________________________________________________________
60
Parameters of Water Quality - Interpretation and Standards
Notes
[1]
Parameter is designated as "Dissolved or emulsified hydrocarbons [after extraction by petroleum
ether]."
[2]
Parameter is described as "Mineral oils."
[3]
Standard is "No film visible on the surface of bathing water and no odour. To be conformed with in
95% of inspections of bathing water. No two consecutive inspections to fail standard."
[4]
Parameter is described as "Persistent mineral oils and hydrocarbons of petroleum origin" in List I.
[5]
Parameter is described as "Non-persistent mineral oils/hydrocarbons of petroleum origin" in List II.
[6]
Parameter is described as "Petroleum hydrocarbons."
[7]
No units are quoted nor is any limit value, but the Directive and Regulations state [in Annex I,
footnote 3, and in the Second Schedule, respectively]: "Petroleum products must not be present [in water] in
such quantities that they: - form a visible film on the surface of the water or form coatings on the beds of
water-courses and lakes - impart a detectable 'hydrocarbon' taste to fish - produce harmful effects in fish."
[8]
No units are quoted nor is any limit value, but the Directive states as the I value: "Hydrocarbons must
not be present in the shellfish water in such quantities as to: - produce a visible film on the surface of the
water and/or a deposit on the shellfish - have harmful effects on the shellfish."
[9]
Parameter is described as "Mineral oils and hydrocarbons."
[10] The 1998 Drinking Water Directive contains no references to "hydrocarbons" per se as a generic
parameter. The parametric values quoted in the Directive apply to specific compounds or to particular
compound groups.
INDENO(l,2,3-c,d)PYRENE
(See "Polycyclic Aromatic Hydrocarbons)
39. IRON
Chemical Symbol or Formula:
Fe.
Units Used for Analytical Results:
mg/l Fe.
Normal Method(s) of Analysis:
Spectrometry [B/C].
Colorimetric (o-PhenanthroIine) [B]; Atomic Absorption
Occurrence/Origin: Geological formations (especially under reducing conditions); acid drainage;
effluent discharges.
Health/Sanitary Significance: The objections to iron are primarily organoleptic, but there has
been recent medical concern about high levels in drinking water.
Background Information: Iron is present in significant amounts in soils and rocks, principally
in insoluble forms. However, many complex reactions which occur naturally in ground formations
can give rise to more soluble forms of iron which will therefore be present in water passing through
such formations. Appreciable amounts of iron may therefore be present in ground waters. Severe
problems can be caused in drinking water supplies by the presence of iron although there is
normally no harmful effect on persons consuming waters with significant amounts of iron. Rather,
the problems are primarily aesthetic, as the soluble (reduced) ferrous (Fe++) iron is oxidised in air
to the insoluble ferric (Fei+++) form, resulting in colour or turbidity (or, in severe cases, precipitate
formation). Laundry becomes stained if washed in water with excessive iron, and vegetables
likewise become discoloured on cooking. Taste problems may also occur. When waters rich in iron
are used to make tea (in which tannins are present) there may be a reaction giving rise to offcolours which may in severe cases resemble that of ink. Problems have been reported also with the
addition of such waters to whiskey.
Comments: The metal is quite harmful to aquatic life, as evidenced by laboratory studies, but in
nature the degree of toxicity may be lessened by the interaction of the iron with other constituents
of a water. Should the metal be converted to an insoluble form then the iron deposits will interfere
with fish food and with spawning.
61
Parameters of Water Quality - Interpretation and Standards
Iron : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l Fe
n/a
0.2
[1,2]
mg/l Fe
n/a
2.0
[1,2]
mg/l Fe
n/a
2.0
[1,2]
Drinking Water Directive [98/83/EC]
µg/l Fe
n/a
200
[3]
_______________________________________________________________________________________
Notes
[1]
Parameter is described as "Dissolved iron."
[2]
Departure may be granted by the Minister "in. the case of surface water in shallow lakes or virtually
stagnant surface water."
[3]
Parameter is described as "Iron."
40. LEAD
Chemical Symbol or Formula:
Pb.
Units Used for Analytical Results:
mg/l Pb.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry s [B/C/D]
Occurrence/Origin: Leaching from ores; effluent discharges; attack on water pipes.
Health/Sanitary Significance: Toxic cumulative poison.
Background Information:
Lead is one of the most commonly determined heavy metals.
Because it accumulates in body tissue it follows that strict limits on its presence in raw and
finished drinking waters must be imposed. Particular attention is paid to this element as in many
older houses extensive use is made of lead piping and there is a danger of lead being brought into
solution ("plumbosolvency"). Levels may be quite marked in samples taken first thing in the
morning when the initial yield will be of water which has been standing in such pipes for perhaps
twelve hours. Hence the recommendation that drinking water pipes be flushed briefly in the
morning before the water is consumed.
Comments:
The comments accompanying the standard in the Drinking Water Regulations
reflect the fact that some waters which are in prolonged contact with old lead pipes are liable to
dissolve possibly significant amounts of the metal. However, in Ireland there are no perceived
risks from the normal daytime use of such water/plumbing combinations when throughput is likely
to be high. In the EU as a whole, however, there is heightened concern about lead in drinking
water, as is shown clearly in the notes below pertaining to Drinking Water Directive [98/83/EC].
Lead : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l Fe
n/a
0.05
A2 waters
mg/l Fe
n/a
0.05
A3 waters
mg/l Fe
n/a
0.05
_______________________________________________________________________________________
62
Parameters of Water Quality - Interpretation and Standards
Lead : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
mg/l Pb
[1]
Dangerous Substances Directive [76/464/EEC]
List II substance
Shellfish Directive [79/923/EEC]
mg/l Pb
[2]
[3]
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
µg/l Pb
n/a
10
[4,5]
_______________________________________________________________________________________
Notes
[1]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in. the quality of waters..."
[2]
"The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
[3]
"The concentration of [this] substance in the shellfish, water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of [this and
other specified] metals must be taken into consideration."
[4] The value applies to a sample of water intended for human consumption obtained by an adequate
sampling method ...... at the tap and taken so as to he representative of a weekly average value ingested by
consumers. Where appropriate the sampling and monitoring methods must be applied in a harmonised
fashion to be drawn up in accordance with Article 7(4). Member States must take account of the occurrence
of peak levels that may cause adverse effects on human health.
[5] For water referred to in Article 6(l)(a), (b) and (d), the value must be met, at the latest, 15 calendar
years after the entry into force of this Directive. The parametric value for lead from five years after the
entry into force of this Directive until 15 years after its entry into force is 25 µg/l.
Member States must ensure that all appropriate measures are taken to reduce the concentration of lead in
water intended for human consumption as much as possible during the period needed to achieve compliance
with the parametric value.
When implementing the measures to achieve compliance with that value Member States must progressively
give priority where lead concentrations in water intended for human consumption are highest.
41. MAGNESIUM
Chemical Symbol or Formula:
Mg.
Units Used for Analytical Results:
mg/l Mg.
Normal Method(s) of Analysis:
[B/C].
Titration with EDTA [A]; Atomic Absorption Spectrometry
Occurrence/Origin: Major constituent of geological formations.
Health/Sanitary Significance: Indirect (in conjunction with Sulphate, q.v.).
Background Information: Like calcium (q.v.), magnesium is abundant and a major dietary
requirement for humans (0.3-0.5 g/day). It is the second major constituent of hardness (see above)
and it generally comprises 15-20 per cent of the total hardness expressed as CaCO3. Its
concentration is very significant when considered in conjunction with that of sulphate (q.v.).
Comments: Magnesium sulphate is used medicinally as "Epsom Salts," a laxative.
63
Parameters of Water Quality - Interpretation and Standards
Magnesium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
[1]
_______________________________________________________________________________________
Notes
[1] The MAC specified in the 1980 Drinking Water Directive is not carried forward to the corresponding
1998 Directive, which makes no reference to magnesium or other elements of water hardness.
42. MANGANESE
Chemical Symbol or Formula:
Mn.
Units Used for Analytical Results:
Normal Method(s) of
Spectrometry [B/C].
Analvsis:
mg/l Mn.
Colorimetric (Persulphate) [B];
Atomic Absorption
Occurrence/Origin: Widely distributed constituent of ores and rocks.
Health/Sanitary Significance:
No particular toxicological connotations; the objections to
manganese - like iron - are aesthetic.
Background Information: As with iron, manganese is found widely in soils and is a constituent
of many ground waters. It, too, may be brought into solution in reducing conditions and the excess
metal will be later deposited as the water is reaerated. The general remarks for iron (q.v.) apply to
manganese but the staining problems with this metal may be even more severe, hence the quite
stringent limits.
A second effect of the presence of manganese much above the limits is an
unacceptable taste problem.
Comments: Toxicity is not a factor, as waters with high levels of manganese will be rejected by
the consumer long before any danger threshold is reached.
Manganese : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l Mn
n/a
0.05
[1]
mg/l Mn
n/a
0.3
[1]
mg/l Mn
n/a
1.0
[1]
Drinking Water Directive [98/83/EC]
µg/l Mn
n/a
50
_______________________________________________________________________________________
Notes
[1] Departure may be granted by the Minister "in the case of surface water in shallow lakes or virtually
stagnant surface water."
64
Parameters of Water Quality - Interpretation and Standards
MBAS
(See "Methylene Blue-Active Substances")
43. MERCURY
Chemical Symbol or Formula:
Hg.
Units Used for Analytical Results:
µg/l Hg.
Normal Method(s) of Analysis:
Flameless Atomic Absorption Spectrometry [C]; or
ICP [inductively-coupled plasma] Spectroscopy [D].
Occurrence/Origin:
Normally from industrial waste discharges.
Health/Sanitary Significance:
methyl-mercury).
Very toxic, especially in organo-mercury compounds (e.g.
Background Information: This is a very toxic element, the hazards of which are magnified by
the accumulation of organo-mercury compounds in fish. It is generally industrial in origin (dental
amalgams, anti-fouling paints, plastics manufacture, Hgttery-making, paper-making and so on)
though some comes from the natural environment.
Comments: There have been some major pollution incidents (notably in Japan) where both death
and severe damage to health has been caused to many people consuming fish and shellfish
contaminated by heavy industrial discharges of mercury.
Mercury : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l Hg
mg/l Hg
mg/l Hg
n/a
n/a
n/a
0.001
0.001
0.001
Bathing Water Regulations [1989-1998]
mg/l Hg
[1]
Dangerous Substances Directive [76/464/EEC]
List I substance
Shellfish Directive [79/923/EEC]
mg/l Hg
[2]
[3]
Ground Water Directive [80/68/EEC]
List I substance
Drinking Water Directive [98/83/EC]
µg/l Hg
n/a
1.0
_______________________________________________________________________________________
Notes
[1]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..."
[2]
“The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
(3]
"The concentration of [this] substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of [this and
other specified] metals must be taken into consideration."
65
Parameters of Water Quality - Interpretation and Standards
44. METHYLENE BLUE-ACTIVE SUBSTANCES
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results: mg/l reference material (Lauryl sulphate; Manoxol OT etc.).
Normal Method(s) of Analysis:
Methylene Blue/Solvent Extraction [B]
Occurrence/Origin: Synthetic materials in domestic and industrial wastes.
Health/Sanitary Significance: No immediate implications as other problems (see below) will
prevent consumption of waters with these materials present.
Background Information:
Often abbreviated to MBAS, the designation of this parameter is
the chemically correct term for the group of compounds commonly known as anionic detergents. To
cloud the issue further, the non-specific terms surf octants (surface active agents) and sy ndets
(synthetic detergents) are also used on occasion, the former more frequently. Synthetic detergents
fall into three groups - anionic, cationic and non-ionic. The last-mentioned are all substituted
polymers of ethylene oxide which do not ionise in water. They are more expensive than the anionic
type but are coming into greater use. The cationic types are salts of quaternary ammonium
hydroxide and are known for their properties of disinfection. The major group comprises the
anionic detergents which are all sodium salts of organic sulphates or sulphonates. Such entities
form ion pairs with the reagent methylene blue, a property which forms the basis of their
estimation. The results are quoted as mg/l standard reference material. Some authorities specify
lauryl sulphate which is used increasingly as a standard. However, UK practice has been to use a
chemically similar but distinct material, Manoxol OT (sodium di-octyl sulphosuccinate), and it is
therefore important to note which terms are used to express the results.
It is worth noting that other terms have been used in connection with synthetic detergents.
"Hard" and "soft" detergents are those which are biodegraded with difficulty and with ease,
respectively. The designations have nothing to do with the hardness of the waters in which they
are used. Some of the original anionic detergents were very hard; structurally they were of the
"ABS" (alkylbenzenesulphonate) type. Later, there was a move towards the much more
biodegradable ("soft") linear alkylate sulphate/sulphonate ("LAS") detergents. This was to help
eliminate the major problem of foaming. In the US very severe foaming problems were
encountered in the days of first use of synthetic detergents. Other disadvantages associated with
them include interference with the reaeration of water which is low in dissolved oxygen, and the
synergistic foaming effects which can arise when waters containing sub-foaming concentrations of
different types of detergents are mixed. Most detergent preparations contain around 20 per cent
surface active agent (which is all that is determined in this test): the rest of the formulation
consists of so-called "builders" which enhance the properties of the active constituent. Chief among
these are phosphates which are of major environmental significance (see below).
Comments: It should be noted that, as there may be some extraneous matter which will also
react with methylene blue, the analysis is more correctly designated as "methylene blue active
substances" than as anionic detergents, even though the latter may in fact represent 100 per cent
of levels found.
Methylene Blue - Active Substances : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l LAS
mg/l LAS
mg/l LAS
n/a
n/a
n/a
0.2
0.2
0.2
[1,2]
[1,2]
[1,2]
_______________________________________________________________________________________
66
Parameters of Water Quality - Interpretation and Standards
Methylene Blue - Active Substances : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
mg/l LAS
[2,3,4]
Drinking Water Directive [98/83/EC]
[5]
_______________________________________________________________________________________
Notes
[1]
Parameter is described as "Surfactants (reacting with methylene blue)."
[2]
Unit of analysis is mg/l lauryl sulphate [LAS-type surfactant].
[3]
Parameter is described as "Surface active substances reacting with methylene blue."
[4]
Standard is "No lasting foam." Standard to be conformed with in 95% of inspections of bathing water.
No two consecutive inspections to fail standard.
[5]
The MAC specified in the 1980 Drinking Water Directive is not carried forward to the corresponding
1998 Directive, which makes no reference to MBAS or surfactant materials.
45. MOLYBDENUM
Chemical Symbol or Formula:
Mo.
Units Used for Analytical Results:
mg/l Mo.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C]
Occurrence/Origin: Industrial effluents, but low occurrence rate.
Health/Sanitary Significance: None.
Background Information: Natural molybdenum levels in waters likely to be used as sources of
public supply are very low and, in any event, human toxicity caused by this metal is very rare.
However, the sensitivity of livestock to the element has been found to be significant although no
specific limits for water have apparently been set for animal drinking water
Comments: There are no applicable standards for this element.
Molybdenum : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
46. NICKEL
Chemical Symbol or Formula:
Ni.
Units Used for Analytical Results:
Normal Method(s) of Analysis:
mg/l Ni.
Atomic Absorption Spectrometry [B/C]
67
Parameters of Water Quality - Interpretation and Standards
Occurrence/Origin: Principal sources are minerals and industrial wastes.
Health/Sanitary Significance: Very limited.
Background Information:
This is another metallic element which is of moderate concern
because of possible carcinogenicity as far as humans are concerned; it also has variable harmful
effects on aquatic life. It is toxic to plant life, too, and is a hazard to fish (generally in the mg/l
concentration range).
Comments: None.
Nickel : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Shellfish Directive [79/923/EEC]
mg/l Ni
[1]
[2]
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
µg/l Ni
n/a
20
[3]
_______________________________________________________________________________________
Notes
[1]
"The concentration. of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shell fish products."
[2]
"The concentration of [this] substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of [this and
other specified] metals must be taken into consideration."
[3] The Directive states that "The value applies to a sample of water intended for human consumption
obtained by an adequate sampling method ...... at the tap and taken so as to he representative of a weekly
average value ingested by consumers. Where appropriate the sampling and monitoring methods must be
applied in a harmonised fashion to be drawn up in accordance with Article 7(4). Member States must take
account of the occurrence of peak levels that may cause adverse effects on human health."
47. NITRATE
Chemical Symbol or Formula:
NO3–
Units Used for Analytical Results:
mg/l N or mg/l NO3–.
Normal Methods of Analysis: Manual/Automated Colorimetry [A/B]; Specific Ion Electrode [B].
Occurrence/Origin: Oxidation of ammonia: agricultural fertiliser run-off.
Health/Sanitary Significance: Hazard to infants above 11 mg/l N [50 mg/l NO3].
Background Information: Relatively little of the nitrate found in natural waters is of mineral
origin, most coming from organic and inorganic sources, the former including waste discharges and
the latter comprising chiefly artificial fertilisers. However, bacterial oxidation and fixing of
nitrogen by plants can both produce nitrate. Interest is centred on nitrate concentrations for
various reasons. Most importantly, high nitrate levels in waters to be used for drinking will render
them hazardous to infants as they induce the "blue baby" syndrome (methaemoglobinaemia). The
nitrate itself is not a direct toxicant but is a health hazard because of its conversion to nitrite [see
also below] which reacts with blood haemoglobin to cause methaemoglobinaemia.
68
Parameters of Water Quality - Interpretation and Standards
Of increasing importance is the degree to which fertiliser run-off can contribute to
eutrophication problems in lakes. Sewage is rich in nitrogenous matter which through bacterial
action may ultimately appear in the aquatic environment as nitrate. Hence, the presence of nitrate
in ground waters, for example, is cause for suspicion of past sewage pollution or of excess levels of
fertilisers or manure slurries spread on land. (High nitrite levels would indicate more recent
pollution as nitrite is an intermediate stage in the ammonia-to-nitrate oxidation). In rivers high
levels of nitrate are more likely to indicate significant run-off from agricultural land than anything
else and the parameter is not of primary importance per se. However, it should be noted that there
is a general tendency for nitrate concentrations in rivers to increase as a result of enhanced
nutrient run-off; this may ultimately lessen their utility as potential sources of public water
supply. Nitrite concentrations in rivers are rarely more than 1 - 2 per cent of the nitrate level so
that it may therefore be acceptable to carry out the analytically convenient determination of
nitrate + nitrite at the same time. This determination is correctly referred to as total oxidised
nitrogen.
Comments: Although the topic of the units in which analytical results are expressed is dealt
with in detail in Appendix 2, it should be noted here that very often nitrate results as expressed as
NO3 rather than as N and that there is over a four-fold difference between the applicable limit
values, the former being the higher.
Nitrate : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value
Value
_______________________________________________________________________________________
n/a
50
[1]
A1 waters
mg/l NO3
n/a
50
[1]
A2 waters
mg/l NO3
n/a
50
[1]
A3 waters
mg/l NO3
[2]
Bathing Water Regulations [1989-1998]
mg/l NO3
n/a
50
[3]
Drinking Water Directive [98/83/EC]
mg/l NO3
_______________________________________________________________________________________
Surface Water Regulations [1989]
Note
[1]
Departure from standard may be granted by Minister "in the case of surface water in shallow lakes or
virtually stagnant surface water" or "where exceptional meteorological or geographical conditions have
arisen."
[2]
Sampling to be carried out "where an investigation .... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..."
[3]
The Directive specifies that "Member States must ensure that the condition that [nitrate]/50 +
[nitrite]/3 < 1, the square brackets signifying the concentrations in mg/l for nitrate (NO3) and nitrite (NO2),
is complied with and that the value of 0.10 mg/l for nitrites is complied ex water treatment works."
48. NITRITE
Chemical Symbol or Formula:
NO2–
Units Used for Analytical Results:
mg/l NO2–.
Normal Methods of Analysis:
Occurrence/Origin:
Manual or Automated Colorimetry [A/B]
Generally from untreated or partially treated wastes.
Health/Sanitary Significance: Methaemoglobinaemia-causing agent [cf. Nitrate].
Background Information: Nitrite exists normally in very low concentrations and even in waste
treatment plant effluents levels are relatively low, principally because the nitrogen will tend to
exist in the more reduced (ammonia; NH3) or more oxidised (nitrate; NO3 ) forms.
69
Parameters of Water Quality - Interpretation and Standards
Because nitrite is an intermediate in the oxidisation of ammonia to nitrate, because such
oxidation can proceed in soil, and because sewage is a rich source of ammonia nitrogen, waters
which show any appreciable amounts of nitrite are regarded as being of highly questionable
quality. Levels in unpolluted waters are normally low, below 0.03 mg/l NC)2. Values greater than
this may indicate sewage pollution.
Comments: The significance of nitrite (at the low levels often found in surface waters) is mainly
as an indicator of possible sewage pollution rather than as a hazard itself although, as mentioned
above under "Nitrate" (q.v.), it is nitrite rather than nitrate which is the direct toxicant. There is,
accordingly, a stricter limit for nitrite in drinking waters. In addition, nitrites can give rise to the
presence of nitrosamines by reaction with organic compounds and there may be carcinogenic
effects.
Nitrite : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
[1]
Freshwater Fish Directive [78/659/EEC]
(S)
mg/l NO2 < 0.01
(C)
mg/l NO2 < 0.03
[2]
n/a
< 0.05
Salmonid Waters Regulations [1988]
mg/l NO2
Ground Water Directive [80/68/EEC]
List II substance
n/a
0.50
[3,4]
Drinking Water Directive [98/83/EC]
mg/l NO2
_______________________________________________________________________________________
Notes
[1]
"Substances which have an adverse effect on the oxygen balance, particularly: ammonia, nitrites."
[2]
Standard to be conformed with by 95°/o of samples over a period of 12 months where sampling is
carried out at least once per month; where sampling is less frequent the standard shall be conformed with by
all samples.
[3]
The Directive requires that "Member States must ensure that the condition that [nitrate]/50 +
[nitrite]/3 < 1, the square brackets signifying the concentrations in mg/l for nitrate (NO3) and nitrite (NO2),
is complied with and that the value of 0.10 mg/l for nitrites is complied ex water treatment works."
[4]
The latter requirement in note [3] appears inconsistent with the parametric value of 0.50 mg/l NO2.
49. NITROGEN, KJELDAHL
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l N.
Normal Method(s) of Analysis:
Digestion, Distillation, Colorimetry [B/C].
Occurrence/Origin: Principally from organic matter naturally present (e.g. from peat, falling
leaves etc.) or added in discharges.
Health/Sanitary Significance:
overall purity of a water.
No direct significance but parameter is an indication of the
Background Information: This determination is for organically-bound nitrogen and, under the
normal test conditions (without ammonia removal), it includes ammonia. However, the results do
not include oxidised nitrogen. The sum of the organically-bound nitrogen and ammonia figures is
the "Kjeldahl nitrogen" value; if the ammonia has been excluded the result is "organic nitrogen."
The term "total nitrogen" refers to the sum of the Kjeldahl and total oxidised nitrogen figures.
70
Parameters of Water Quality • Interpretation and Standards
In past years much reliance was placed on the so-called albuminoid nitrogen determination
which was frequently carried out in conjunction with the manual distillation technique for
measuring ammonia. In this test the ammonia-free residue from the initial distillation is treated
with alkaline potassium permanganate and then distilled again to give a further quantity of
ammonia which is derived from proteinaceous matter and is a reflection of the organic content.
Although alternative procedures have superseded the albuminoid nitrogen determination, it may
still be found useful especially in assessing water with possible sewage contamination. While high
values are themselves indicative of pollution, the albuminoid nitrogen results are most often
considered in conjunction with the figures for ammonia. This is because in natural waters the ratio
of free/saline ammonia nitrogen to albuminoid nitrogen is normally significantly less than unity
(frequently of the order of 0.2-0.4), being a reflection of the fact that albuminoid nitrogen sources
(principally vegetable) occur with a natural frequency. When the ratio approaches or exceeds unity
an extraneous source of free ammonia is indicated and in many cases this is a sewage discharge.
Thus, by scrutinising this nitrogen ratio the analyst can get an early indication of possible sewage
contamination of a water, an indication which may be reinforced by elevated chloride values (q.v.).
Comments:
In the Kjeldahl nitrogen determination the sample is subjected to quite severe
digestion conditions which break down proteins and other organic matter and convert the nitrogen
to ammonia, in which form it is actually measured.
Nitrogen, Kjeldahl : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value
Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l N
n/a
1
[1]
A2 waters
mg/l N
n/a
2
[1]
A3 waters
mg/l N
n/a
3
[1]
Bathing Water Regulations [1989-1998]
[2]
Drinking Water Directive [98/83/EC]
[3]
_______________________________________________________________________________________
Notes
[1]
Parameter listed as "Nitrogen by Kjeldahl method (except in NO2 and NO3)."
[2]
Parameter designated as: "Nitrogen Kjeldahl." Sampling to be carried out "where an investigation ...
shows, or there are other grounds for believing, that there has been a deterioration in the quality of waters
... or, in the case of Nitrogen Kjeldahl..., that there is a tendency towards eutrophication."
[3]
The MAC specified in the 1980 Drinking Water Directive is not carried forward to the corresponding
1998 Directive, which makes no reference to Kjeldahl nitrogen or to organic nitrogen.
NITROGEN, TOTAL
(See "Nitrogen, Kjeldahl")
50. ODOUR
Chemical Symbol or Formula:
Not applicable [Organoleptic parameter].
Units Used for Analytical Results:
Description.
Normal Method(s) of Analysis:
Dilution Factor [@ stated temperature] /Qualitative
Subjective personal assessment [A]; Odour Panel [D].
71
Parameters of Water Quality - Interpretation, and Standards
Occurrence/Origin: Due to presence of inorganic or organic contaminants in water, possibly
greatly exacerbated by chlorination.
Health/Sanitary Significance: Organoleptic considerations only.
Background Information: Related to taste, a strong odour from a water for consumption will
obviously cause revulsion or rejection on the part of the consumer. Its cause is normally dissolved
volatile organic compounds small concentrations of which may have great organoleptic effects.
However, in polluted rivers a very common cause is the presence of hydrogen sulphide gas
produced from the reduction of sulphates in the anaerobic conditions which can prevail after a
heavy organic discharge to the water. Likewise, the formation of a putrescible sludge on the bed of
a river by deposition of settleable organic solids can give rise to sulphide odours.
Comments:
In the case of such sludge formation the odour may emanate from the bottom
deposits or from sludge particles brought to the surface with gas bubbles even though the water
column above may not be anaerobic.
Odour : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value
Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
Bathing Water Regulations [1989-1998]
Drinking Water Directive [98/83/EC]
DF/25 ºC
DF/25 ºC
DF/25 ºC
n/a
n/a
n/a
-
-
5
10
20
[1]
-
[2]
[1]
[1]
Acceptable to
consumers and no
abnormal change
_______________________________________________________________________________________
Notes
[1] Unit of analysis is dilution factor [DF] at 25 °C.
[2] The standard for Mineral oils [cf. "Hydrocarbons" above] is "No film visible on the surface of
bathing water and no odour." Assessment is visual and olfactory.
51. ORGANIC CARBON, TOTAL
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units used for Analytical Results:
mg/l C.
Normal Method(s) of Analysis:
Instrumental (Various techniques) [C]
Occurrence/Origin: Natural or added organic matter in water.
Health/Sanitary Significance: No direct significance, but an indicator of overall purity of water.
Background Information:
The determination of total organic carbon [or TOC] is
complementary to the oxygen demand analyses (biochemical and chemical) discussed below and, in
strict terms, it is a better indicator of organic content in that it is a direct measurement of the key
element. Also, it is theoretically independent of the form in which the carbon exists (i.e. the
structure of the organic compounds) in the water and the analyses should therefore be comparable
for a wide range of organically polluted waters.
72
Parameters of Water Quality - Interpretation and Standards
The parameter is one which is relevant in the treatment of water for drinking, especially in
the case of large supplies where it may be necessary to use water of A3 (or, possibly, A2) quality
[cf. Surface Water Regulations] as a source. The capital costs of the instrumentation needed may
well be justified in terms of the quality control benefits which would accrue during treatment.
Comments: Because of the relative infrequency of instrumental organic carbon measurements
(the classic combustion methods do not lend themselves to routine use) there is little or no
background information on naturally occurring levels in surface waters and there is accordingly no
datum against which mild organic pollution may be assessed by this parameter. Many rivers are
highly coloured, especially in flood, indicating a high content of humic matter and hence the
background concentrations may be quite considerable in waters which receive no pollutional
discharges.
Organic Carbon, Total : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value
Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
-
-
No abnormal
change
_______________________________________________________________________________________
Notes
[1]
The Directive states that "This parameter need not be measured for supplies of less than 10,000 m3 a
day."
52. ORGANO-HALOGENATED SUBSTANCES
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
Normal Method(s) of Analysis:
Occurrence/Origin:
mg/l Cl or mg/l compound(g).
Chromatographic techniques (GLC/HPLC) [C]
Synthetic materials arising from discharges, run-off etc.
Health/Sanitary Significance: Many are carcinogenic; all are undesirable.
Background Information: This bulk parameter includes all organic compounds containing
halogens [bromine, chlorine, fluorine and iodine].
These range from structurally simple
compounds like chloroform (CHCl3) or methylene chloride (CH2Cl2) to extremely complex molecules
such as are present in pesticide or PCB mixtures. The latter classes of compounds are discussed
separately below. Haloforms (or Trihalomethanes; THM) have the general formula CHX3, where X
represents a halogen atom, and they are considered to be possible carcinogens and hence are
undesirable in drinking water. One of the group, chloroform, has been detected increasingly in
treated water supplies, being among the by-products of the chlorination step in water treatment.
See "Trihalomethanes" below.
Comments:
Because of the complexity of this whole subject and its interrelationship with
pesticides (q.v.) the reader is referred to the original sources for the fullest available discussion.
The 1998 Drinking Water Directive adopts a specific compound approach which is both welcome
and helpful to the analyst and to the water quality regulator. Thus, it covers a series of specific
organo-chlorine compounds and eschews the use of generalised parameter titles such as that under
discussion.
73
Parameters of Water Quality - Interpretation and Standards
Organo-Halogenated Substances : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l Cl
[1]
A2 waters
mg/l Cl
[1]
A3 waters
mg/l Cl
[1]
Bathing Water Regulations [1989-1998]
[2,3]
Dangerous Substances Directive [76/464/EEC]
List I substance
[4]
Shellfish Directive [79/923/EEC]
[5]
[6]
Ground Water Directive [80/68/EEC]
List I substance
[4]
Drinking Water Directive [98/83/EC]
[7]
_______________________________________________________________________________________
Notes
[1]
The Regulations refer to the parameter: "Total pesticides [parathion, BHC, dieldrin]," which falls
under the heading of “Organo-Halogenated Substances." Pesticides are treated separately below (q.v.).
[2]
The parameter is designated "Pesticides [parathion, HCH, dieldrin]."
[3]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..."
[4]
List I refers to "Organohalogen compounds and substances which may form such compounds in the
aquatic environment."
[5]
"The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
[6]
"The concentration of [this] substance in the shellfish water or in shellfish flesh must not reach or
exceed a level which has harmful effects on the shellfish and larvae.
[7] Drinking Water Directive [98/83/EC] includes the two parameters designated respectively "Pesticides"
and "Pesticides - Total". See parameter "Pesticides" below.
53. OXIDISABILITY
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l O2.
Normal Method(s) of Analysis:
Various Wet Oxidation techniques [B]
Occurrence/Origin: Measure of organic (and other oxidisable) matter present in a water,
naturally or from added wastes.
Health/Sanitary Significance:
water.
No direct significance but a reflection of overall purity of a
Background Information: All parameters covered by this heading are a measure of the organic
content of a water (and of those inorganic constituents which are amenable to oxidation). They are
determined by estimating the oxygen consumption from heated acid potassium permanganate
solution. The European test procedures use boiling temperature and a short time but this has not
been the common past practice in Ireland and the United Kingdom where analysis has been of the
oxygen absorbed from acid permanganate solution in 4 hours at 27°C. The former method is
specified by Directive [98/83/EC].
74
Parameters of Water Quality - Interpretation and Standards
The result of the 4-hour/27°C test is the so-called permanganate value (PV) and it gives a
useful, even if partial, picture of the organic content of a water. As with any test using a specific
oxidant the results will reflect preferentially the presence of those compounds which are
susceptible to the action of that oxidant, in this case acid potassium permanganate, and not those
compounds which are largely unaffected by the reagent. For example, a highly coloured water
which contains significant organic (humic) matter will have a very high permanganate value.
Accordingly, there is generally a good correlation between permanganate value and colour. But as
this humic matter is biologically inert it will not be assessed in a bioassay procedure such as the
biochemical oxygen demand test (q.v.). Because of the variations in response of different types of
water and waste water to the action of permanganate and, not least, because of the tedious nature
of this rather arbitrary test procedure modern preferences are for the organic carbon
determination in surface waters, and for the chemical oxygen demand (see below) for wastewaters,
in addition, of course, to the biochemical oxygen demand test.
Comment: The topic of oxidisability is discussed further below - see "Oxygen Demand, Chemical."
Oxidisability : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
n/a
5.0
[1]
Drinking Water Directive [98/83/EC]
mg/l O2
_______________________________________________________________________________________
Notes
[1]
Parameter is designated "Oxidisability" and is the subject of two notes. The first states that "This
parameter need not be measured if the parameter TOC is measured" and the second requires that
"Oxidation should be carried out for 10 minutes at 100 °C under acid conditions using permanganate." The
results of analysis are therefore not comparable with those of the so-called "Permanganate Value" which also
uses potassium permanganate [KMnO4] as oxidant, but with incubation at 27°C for 4 hours.
54. OXYGEN DEMAND, BIOCHEMICAL
Chemical Symbol or Formula:
Not applicable [Bulk parameter]
Units Used for Analytical Results:
mg/l O2.
Normal Method(s) of Analysis:
Method or by Oxygen Meter [A).
Occurrence/Origin:
Incubation technique with oxygen determinations by Winkler
Natural or introduced organic matter in water.
Health/Sanitary Significance:
overall water quality.
No direct health implications, but an important indicator of
Background Information: When organic matter is discharged into a watercourse it serves as a
food source for the bacteria present there. These will sooner or later commence the breakdown of
this matter to less complex organic substances and ultimately to simple compounds such as carbon
dioxide and water. If previously unpolluted, the receiving water will be saturated with dissolved
oxygen (DO), or nearly so, and the bacteria present in the water will be aerobic types. Thus the
bacterial breakdown of the organic matter added will be an aerobic process - the bacteria will
multiply, degrading the waste and utilising the DO as they do so. If the quantity of waste present
is sufficiently large, the rate of bacterial uptake of oxygen will outstrip that at which the DO is
replenished from the atmosphere and from photosynthesis, and ultimately the receiving water will
become anaerobic.
75
Parameters of Water Quality - Interpretation and Standards
Bacterial degradation of the waste will continue but now the products will be offensive in
nature -for example, hydrogen sulphide. Even if the uptake of oxygen is not sufficient to result in
anaerobic conditions there will be other undesirable effects as the DO level falls, notably damage
to fisheries and, ultimately, fish deaths. Where levels are around 50 per cent saturation for
significant periods there may be adverse, though non-lethal, effects on game fish. Coarse fish will
be likewise affected if levels are regularly around 30 per cent saturation.
Because of the potential danger to the oxygen levels in receiving waters from waste
discharges considerable emphasis is placed in the laboratory on the estimation of the oxygen
demand of wastes: i.e. the amount of oxygen which will be required in their breakdown. This is
done chemically and biologically, by a variety of tests which are also employed to assess the actual
effects of waste discharges on receiving water, as discussed below. As in most cases the oxygen
demand of a waste on the DO level of a receiving water results from biological action, it follows
that the most important analytical method should also depend on a biological process, to measure
the biochemical oxygen demand or BOD. The principle of this test, which was devised some 85
years ago, is straightforward. The (five-day) BOD of a water is the amount of dissolved oxygen
taken up by bacteria in degrading oxidisable matter in the sample, measured after 5 days
incubation in the dark at 20°C. The BOD is simply the amount by which the DO level has dropped
during the incubation period. This technique is the basis of BOD analyses for all types of sample
even though considerable extensions of procedure are necessary in dealing with wastewaters and
polluted surface waters.
The Eighth Report of the Royal Commission on Sewage Disposal (1912) contained a
classification of river waters based on BOD levels which has been very widely quoted in the
ensuing years. In some respects the classification was too precise in that it tried to distinguish
between clean waters, very clean waters and so on. Current scientific opinion is that such a rigid
approach is unjustified and that waters with a BOD failing within the range of 0 - 4 mg/l O2 are of
satisfactory quality for salmonid fish and thus for other beneficial uses. If an upper limit for BOD
of 4 mg/l O2 is adopted as a criterion of satisfactory quality then it is possible to assess the degree
to which waters are polluted by reference to this datum. It is most important to remember,
however.. that a BOD figure for a receiving water indicates the maximum extent to which the
oxygen level may be depleted by the organic matter present. In reality, no appreciable
deoxygenation may occur because of factors such as low temperatures, reaeration at weirs or
shallows, dilution by tributaries and so on. Conversely, in some waters which do not have high
BOD levels, but which are eutrophic, there may be severe night-time DO depletions caused by
algal respiration (see below). Notwithstanding the many often contradictory considerations which
govern the interpretation of BOD data the analysis is one of the most important elements in river
quality surveillance and it seems unlikely to be superseded for a long time yet.
Somewhat different considerations apply to the BOD analysis of effluents. BOD data are
normally required for one of two purposes. Firstly, it is necessary to know the strength of a waste
which is to be treated by biological means, as in an oxidation ditch or percolating filter. This is
essential so that adequate treatment capacity may be provided for in the design of the plant.
Secondly.. where wastes are being discharged to receiving waters a knowledge of their strength
and the magnitude of the river discharge will permit the dilution to be calculated and hence the
maximum potential change in the river BOD at the boundary of the mixing zone. A factor which
must be borne in mind in obtaining and in assessing BOD results is nitrification. This is the
oxidation of ammonia to nitrate by suitable micro-organisms and if the process is occurring under
test conditions high oxygen uptake values will be recorded. For normal river waters the onset of
nitrification under BOD test conditions does not occur within the 5-day period of the analysis but
in the case of waters or wastewaters containing nitrifying organisms this phenomenon will take
place much more promptly. Unless suitable precautions are taken the result is an apparently very
high BOD level which, if the analysis is being used to check the performance of a waste treatment
works (with respect to the removal of organic matter), for example, may lead to serious errors in
the interpretation and use of the data.
76
Parameters of Water Quality - Interpretation and Standards
The recommendations of the Royal Commission referred to above also dealt with the quality
of sewage effluents and they included the so-called "20/30" effluent standard (i.e. an effluent of
BOD value 20 mg/l O2 and suspended solids 30 mg/l) which has been widely used and misused
since. It is often forgotten that the standards were based on the premise that in no case would the
BOD value of the river receiving the discharge be increased to more than 4 mg/l O2. The "20/30"
standard was suggested as one which would, even in cases of limited available dilution, ensure
that the resultant river BOD would be less than 4 mg/l O2. It was in no way advocated as the
ultimate goal of all treatment processes, the thinking being that it was more important to specify a
limit for the river after receiving a discharge than to fix general effluent standards.
Comments: The DO level of a receiving water may also be depleted by some inorganic waste
discharges. A waste containing sulphite, for example, can have serious effects. These will include
the direct chemical uptake of oxygen during the BOD incubation period, the extent of which
uptake will contribute to the apparent BOD value of the sample. It is arguable, however, that in
such cases while a percentage of the oxygen depletion may be caused by chemical rather than
biochemical reaction, the results will still reflect the maximum possible oxygen depletion effects in
the receiving water. See also the comments on "Oxygen Demand, Chemical."
Oxygen Demand, Biochemical : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
n/a
5
[1,2]
A1 waters
mg/l O2
n/a
5
[1,2]
A2 waters
mg/l O2
A3 waters
mg/l O2
n/a
7
[1,2]
<3
Freshwater Fish Directive [78/659/EEC]
(S)
mg/l O2
[3]
[3]
<6
(C)
mg/l O2
[4]
n/a
<5
Salmonid Waters Regulations [1988]
mg/l O2
_______________________________________________________________________________________
Surface Water Regulations [1989]
Notes
[1]
Parameter is described as "Biochemical oxygen demand [BOD5] [at 20°C without nitrification]." A
nitrification inhibitor should therefore he used in the analytical procedure.
[2]
Departure may he granted by the Minister "in the case of surface water in shallow lakes or virtually
stagnant surface water."
[3]
Nitrification [cf. Note 1 immediately above] should not be inhibited.
[4]
"Where weed or sewage fungus growths are excessive appropriate measures for control should be
taken. Standard to he conformed with by 95% of samples over a period of 12 months where sampling is
carried out at least once per month; where sampling is less frequent the standard shall be conformed with by
all samples."
55. OXYGEN DEMAND, CHEMICAL
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l O2.
Normal Method(s) of Analysis:
Microdigestion and Colorimetry [A]; Titrimetric following
Reflux Distillation with Acid Potassium Dichromate [B].
Occurrence/Origin: Natural or, more probably, added organic matter.
77
Parameters of Water Quality - Interpretation and Standards
Health/Sanitary Significance:
water quality.
No direct hazard implications; COD is an indicator of overall
Background Information: Except in special cases, the five-day BOD analysis gives a measure
of the oxygen demand of biodegradable carbonaceous matter in a sample. The oxidation is not
complete and the five-day BOD value in a properly conducted test usually amounts to some 65
percent of the total carbonaceous oxygen demand. To measure the latter in the BOD test would
take some four times as long and would involve special measures to counter the side-effects of
oxidation of nitrogenous matter, the nitrification referred to above (cf. "Oxygen Demand,
Biochemical").
The ideal approach is to obtain a rapid, accurate measurement of the total carbonaceous
oxygen demand and, in an attempt to reach this goal, chemical methods have been devised. The
first point to consider is that in any such method the only organic compounds affected will be those
amenable to oxidation by the particular chemical agent used. (This point has been touched on
above under the parameter "Oxidisability"; q.v.). There is a wide variety of chemical oxidants and
hence there will be a correspondingly wide range of effects.
Potassium permanganate has been widely used to measure the oxygen demand of river
waters but there may be little or no correlation with BOD figures. As mentioned above, peaty
waters of low BOD often have very high permanganate values, reflecting the intense colour caused
by the presence of biologically inert but chemically oxidisable vegetable matter. However, for any
one type of sample the permanganate values may be useful (in indicating changes in the
performance of a treatment plant, for example), and it may be possible to correlate the figures with
those for BOD after a sufficiently large number of analyses have been carried out.
The reagent favoured in U.S. methods is potassium dichromate and although the term
chemical oxygen demand (COD) is a general one, which should be qualified by the mention of the
actual oxidant used, in practice the abbreviation COD refers specifically to the test in which
potassium dichromate is used to carry out the oxidation. A drawback is that the standard test
procedure is in practice applicable only to very heavily polluted waters or to effluents, though its
use for the latter makes it a most valuable method. Comparisons have been made between the
permanganate value test and the COD and have indicated the variability of the former as a
general oxidant.
The COD test procedure involves the use of additional reagents to catalyse the oxidation of
organic matter and to suppress the effects of interfering substances such as chloride, and, as a
result, in many cases the oxidation achieved is at or very near the maximum level. As pointed out
earlier, for biodegradable compounds the five-day BOD level corresponds to some 65 per cent
oxidation of the total organic matter present so that, if for such compounds the chemical oxidation
is fully efficient, the COD/BOD ratio should be 100:65 or 1.54: 1. This is the case for domestic
sewage for which COD values around 480-500 mg/l and BOD figures in the region of 310 mg/l give
a good correspondence with the ratio. It is possible to work out the applicable ratio for wastes
which do not change their composition but which are only partially affected in either oxygen
demand test. Application of the COD/BOD ratio to the results of a quickly performed COD test is
very useful for the analyst and for the plant manager.
Comments: It has been mentioned that the COD test is applicable to heavily polluted waters and
to wastewaters. This is because the sensitivity of the normal test procedure is not adequate for
waters with an oxygen demand of only a few mg/l O2. There is a "low level" test but this is best
applied to waters with an oxygen demand in the vicinity of 25 mg/l O2 which is rather larger than
one would hope to find in clean waters. It may be noted that the original (U.S.) standard method
for COD used quite large volumes of sample and reagents. As the latter contain toxic and/or
expensive additives (mercury and silver salts are used in relatively large amounts to suppress
interference and catalyse the oxidation, respectively), and as the reaction mixture comprises 50 per
cent sulphuric acid, it is highly desirable on grounds of both safety and economy that quantities
should be scaled down. The use of "miniature" digestion apparatus is therefore recommended
strongly.
78
Parameters of Water Quality - Interpretation and Standards
Oxygen Demand, Chemical : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l O2
n/a
[1]
n/a
[1]
A2 waters
mg/l O2
n/a
40
[1]
A3 waters
mg/l O2
_______________________________________________________________________________________
Notes
[1]
Value specified in Regulations for A3 water only,
56. OXYGEN, DISSOLVED
Chemical Symbol or Formula:
O2.
Units Used for Analytical Results:
mg/l O2.
Normal Method(s) of Analysis:
Electrometric [DO Meter] [A/B]; Winkler Titration [A/B].
Occurrence/Origin: Natural characteristic of clean waters.
Health/Sanitary Significance:
fish.
Slight organoleptic significance only, but critical for survival of
Background Information: The importance of dissolved oxygen [DO] has already been touched
upon in the discussion of BOD above. The prime requirements for DO arise in connection with fish
life and it is generally true that if water quality is suitable for fish it will also meet the criteria for
most if not all other beneficial uses and be of good ecological status, as required by the Water
Framework Directive. The cardinal point about the solubility of oxygen in water is that it has an
inverse relationship with temperature, as shown in the table below. The consequence is that the
actual concentrations of DO in a river will be lowest in summertime when it is usually the case
that the risk of damage to a water supply source or of environmental pollution is greatest,
especially in areas developed as tourist centres or where such farming operations as silage-making
are carried on.
SOLUBILITY OF OXYGEN IN WATER IN CONTACT
WITH WATER-SATURATED AIR AT 760 MM Hg
OXYGEN CONCENTRATIONS IN mg/litre CORRESPONDING TO 100% SATURATION
______________________________________________________________________________
Temp DO
Temp DO
Temp DO
Temp DO
Temp DO
°C mg/l
°C mg/l
°C mg/l
°C mg/l
°C mg/l
______________________________________________________________________________
0
14.6
5
12.8
10 11.3
15 10.2
20 9.2
1
14.2
6
12.5
11 11.1
16 10.0
21 9.0
2
13.8
7
12.2
12 10.8
17 9.7
22 8.8
3
13.5
8
11.9
13 10.6
18 9.5
23 8.7
4
13.1
9
11.6
14 10.4
19 9.4
24 8.5
______________________________________________________________________________
79
Parameters of Water Quality - Interpretation and Standards
The saturation concentration of 9.2 mg/l O2 at 20°C (around the normal Irish summer
temperature) is not a large quantity and, although it is fully adequate to support the fauna and
flora of an unpolluted river, it will be depleted very rapidly (even after allowing for natural
reaeration over weirs, rocks and so on) by the bacterial degradation of even a small amount of
organic matter. See also the discussion under "Oxygen Demand, Biochemical."
Because such biological activity takes place in receiving waters it is essential that DO levels
are measured in situ by instrumental means, or at least that chemical reagents are added at once
to the samples to "fix" the DO for a reliable subsequent laboratory analysis. Delayed DO values
obtained from analysis of unfixed samples are meaningless and are potentially grossly misleading.
As indicated above (under "Oxygen Demand, Biochemical"), salmonid fish will begin to be affected
as DO levels drop to around 50 per cent saturation; cyprinid fish are likewise affected at levels in
the vicinity of 30 per cent. In many instances of fish kills the mortality is directly due to
asphyxiation as the DO levels fall massively because of organic pollution. Should levels around
zero persist then anaerobic (or septic) conditions will set in and any remaining organic matter will
undergo anaerobic decomposition to yield products such as methane and ammonia. Coupled with
this will be the reduction of sulphates present to sulphide and the consequent emission of offensive
odours. Restoration of aerobic conditions will cure the last mentioned problem.
The effects of eutrophication are closely related to the DO regime in both rivers and lakes.
Where there are dense growths of phytoplankton, photosynthesis will take place during the
extended daylight periods of summertime, resulting in the production of oxygen which may lead to
water DO levels far in excess of 100 per cent saturation. An excess of DO is not a problem in itself
but it indicates that the daytime conditions may be mirrored by an equally large undersaturation
of oxygen at night-time when photosynthesis ceases and plant respiration supervenes with the
consumption of oxygen. The DO concentrations may, therefore, follow something like a "sine wave"
pattern with the troughs occurring in the early hours of the morning, just before dawn. Where the
amplitude of this "sine wave" is great the DO minimum may be such as to cause fish kills. It
should be remembered that the magnitude of this so-called diurnal variation will be greatest
where there are both eutrophication and organic pollution effects. But while a high day-time DO
may not (in the absence of organic pollution) be matched by a critically low night-time level it is
indicative nonetheless of less than satisfactory conditions.
Comments: The importance of DO is underlined by the comprehensive requirements of the
Freshwater Fish Directive and Salmonid Waters Regulations. The values specified below, along
with the accompanying notes, are worthy of study,
Oxygen, Dissolved : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value
Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
Bathing Water Regulations [1989-1998]
Freshwater Fish Directive [78/659/EEC]
% sat’n O2
% sat’n O2
% sat’n O2
% sat’n O2
n/a
n/a
n/a
> 60%
> 50%
> 30%
[1]
[1]
[1]
n/a > 70 and < 120 [2]
[3]
50% > 9 50% > 9
mg/l O2
mg/l O2 100% > 7
50% > 8 50% > 7
[4]
(C)
mg/l O2
mg/l O2 100% > 5
[5]
Salmonid Waters Regulations [1988]
pH units
n/a > 6 and < 9
> 70
[6,7]
Shellfish Directive [79/923/EEC]
% sat’n O2
> 80
_______________________________________________________________________________________
(S)
80
Parameters of Water Quality - Interpretation and Standards
Oxygen, Dissolved : Notes
[1]
Parameter is "Dissolved oxygen saturation rate." Departure from the standard may be granted by the
Minister "in the case of surface water in shallow lakes or virtually stagnant surface water."
[2]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing..
that there has been a deterioration in the quality of waters..." Standard to be conformed with by 95% of
samples. No two consecutive samples to fall outside range,
[3]
The I value for salmonid water contains the provision: "When the oxygen concentration falls below 6
mg/l, Member States shall implement the provisions of Article 7 [3] [of the Directive]. The competent
authority must prove that this situation will have no harmful consequences for the balanced development of
the fish population."
[4]
The I value for cyprinid water contains the provision: "When the oxygen concentration falls below 4
mg/l, Member States shall implement the provisions of Article 7 [3] [of the Directive]. The competent
authority must prove that this situation will have no harmful consequences for the balanced development of
the fish population."
[5]
The Regulations specify: 50% > 9 mg/l O2. "When the oxygen content falls below 6 mg/litre the local
authority must prove that there will he no harmful consequences for the balanced development of the fish
population."
[6]
The I value quoted is an average value; there are also the following provisions: "Should an individual
measurement indicate a value lower than 70%, measurements shall he repeated. An individual
measurement may not indicate a value of less than 60% unless there are no harmful consequences for the
development of shellfish colonies."
[7]
The sampling frequency is given as "monthly, with a minimum of one sample representative of low
oxygen conditions on the day of sampling... Where major daily variations are suspected, a minimum of two
samples in one day shall be taken."
57. PATHOGENIC STAPHYLOCOCCI
Chemical Symbol or Formula:
Not applicable [Microbiological Parameter].
Units Used for Analytical Results:
Number of organisms/100 ml water.
Normal Method(s) of Analysis:
Membrane Filtration Technique [B].
Occurrence/Origin: Sewage discharges.
Health/Sanitary Significance: Pathogenic micro-organisms (causing food poisoning and related
illnesses).
Background Information:
Staphylococci are likely to be present in sewage-contaminated
waters and in bathing waters. However, their determination is not carried out routinely, the main
emphasis being put on the detection of total and faecal coliforms. By relying on the use of
indicator organisms rather than the estimation of the staphylococci directly, the approach is very
conservative, making for a high degree of protection.
Comments: See also "Coliforms, Faecal and Total" above.
Pathogenic Staphylococci : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
No reference / parametric value
[1]
_______________________________________________________________________________________
81
Parameters of Water Quality - Interpretation and Standards
Notes
[1] Directive [98/83/EC] makes no reference to staphylococci, but incorporates the following relevant
provisions: Article 4(1) Without prejudice to their obligations under other Community provisions, Member
States shall take the measures necessary to ensure that water intended for human consumption is
wholesome and clean. For the purposes of the minimum requirements of this Directive, water intended for
human consumption shall be wholesome and clean if it; (a) is free from any micro-organisms and parasites
and from any substances which, in numbers or concentrations, constitute a potential danger to human
health.
Article 7(6) Member States shall ensure that additional monitoring is carried out on a case-by-case
basis of substances and micro-organisms for which no parametric value has been set in accordance with
Article 5, if there is reason to suspect that they may be present in amounts or numbers which constitute a
potential danger to human health.
PCBs & PCTs
(See "Polychlorinated Biphenyls")
PERCHLOROETHYLENE
(See "Tetrachloroethylene")
58. PESTICIDES (INDIVIDUAL & TOTAL)
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
µg/l specific compound(s).
Normal Method(s) of Analysis:
Chromatographic techniques (GLC & HPLC) [B/C)
Occurrence/Origin:
Synthetic compounds - agricultural discharges, spillages or runoff,
industrial waste discharges.
Health/Sanitary Significance: Compounds of great acute or chronic toxicity.
Background Information: This broad designation is used in EU Directives to encompass a
large group of compounds with either related uses or similar chemical composition. The substances
covered comprise insecticides (organo-chlorine and organo-phosphorus), herbicides, fungicides,
PCBs (polychlorinated biphenyls) and PCTs (polychlorinated terphenyls). Compounds such as
pesticides are among those which cause mortality or severe reproductive or genetic problems in
fauna and which also qualify for inclusion under the broad heading of substances which possess
carcinogenic, mutagenic or teratogenic properties (see below). As such, they are highly undesirable
in waters of virtually any type. Even if levels in, say, a river water are very low there is the
probability of bioaccumulation in fish or other living tissue and, to compound the matter, of
retention on the in-situ sediments.
Comments:
PCBs and PCTs are dealt with jointly in this volume under the heading
"Polychlorinated Biphenyls."
Pesticides : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value
Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l
n/a
0.0005
[1]
A2 waters
mg/l
n/a
0.0025
[1]
A3 waters
mg/l
n/a
0.005
[1]
_______________________________________________________________________________________
82
Parameters of Water Quality - Interpretation and Standards
Pesticides : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
Dangerous Substances Directive [76/464/EEC]
Shellfish Directive [79/923/EEC]
Ground Water Directive [80/68/EEC]
Drinking Water Directive [98/83/EC]
mg/l
[2,3]
List I substance
[4]
[5]
[6]
[7]
List I substance
[4]
µg/l
n/a
0.10
[8,9]
µg/l
n/a
0.10
[8,10]
_______________________________________________________________________________________
Notes
[1]
Parameter is described as '"Total pesticides [parathion, BHC, dieldrin]." Note that this is a misleading
definition [which, however, is taken from the Directive, although virtually meaningless] and that the
number of compounds covered is a tiny fraction of the real total [which will, in any event, grow as new
compounds are developed].
[2]
The definition is "Pesticides (parathion, HCH [BHC], dieldrin)."
[3]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..."
[4]
List I includes "organohalogen compounds and substances which may form such compounds in the
aquatic environment" and "organophosphorus compounds." Both compound groups include many pesticides.
[5]
"The concentration of each substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
[6]
"The concentration of each substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae."
[7]
Parameter quoted as "Organohalogenated substances." Although this parameter is dealt with
separately and its definition would imply a potentially wide range of compounds, in practice it is usually
taken to mean organohalogen pesticides.
[8] "Pesticides" means:
- organic insecticides,
- organic herbicides,
- organic fungicides,
- organic nematocides,
- organic acaricides,
- organic algicides,
- organic rodenticides
- organic slimicides,
- related products (inter alia, growth regulators)
and their relevant metabolites, degradation and reaction products.
Only those pesticides which are likely to be present in a given supply need be monitored.
[9] The parametric value applies to each individual pesticide. In the case of aldrin, dieldrin, heptachlor
and heptachlor epoxide the parametric value is 0.030 µg/l.
[10] "Pesticides - Total" means the sum of all individual pesticides detected and quantified in the monitoring
procedure.
59. pH
Chemical Symbol:
Not applicable [Physical parameter].
Units Used for Analytical Results:
pH units.
Normal Method(s) of Analysis:
Electrometry [pH electrode] [A/B]
Occurrence/Origin:
Physical characteristic of all waters/solutions.
83
Parameters of Water Quality - Interpretation and Standards
Health/Sanitary Significance:
None - except that extreme values will show excessive
acidity/alkalinity, with organoleptic consequences.
Background Information: By definition pH is the negative logarithm of the hydrogen ion
concentration of a solution and it is thus a measure of whether the liquid is acid or alkaline. The
pH scale (derived from the ionisation constant of water) ranges from 0 (very acid) to 14 (very
alkaline). The range of natural pH in fresh waters extends from around 4.5, for acid, peaty upland
waters, to over 10.0 in waters where there is intense photosynthetic activity by algae. However,
the most frequently encountered range is 6.5-8.0.
In waters with low dissolved solids, which consequently have a low buffering capacity (i.e.
low internal resistance to pH change), changes in pH induced by external causes may be quite
dramatic. Extremes of pH can affect the palatability of a water but the corrosive effect on
distribution systems is a more urgent problem (see Appendix 4). The effect of pH on fish is also an
important consideration and values which depart increasingly from the normally found levels will
have a more and more marked effect on fish, leading ultimately to mortality. The range of pH
suitable for fisheries is considered to be 5.0-9.0, though 6.5-8.5 is preferable.
Comments: Apart from the aspects just mentioned, pH values govern the behaviour of several
other important parameters of water quality. Ammonia toxicity, chlorine disinfection efficiency,
and metal solubility are all influenced by pH, for example.
pH : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
pH units
n/a
5.5-8.5
A2 waters
pH units
n/a
5.5-9.0
A3 waters
pH units
n/a
5.5-9.0
Bathing Water Regulations [1989-1998]
pH units
n/a > 6 and < 9
Freshwater Fish Directive [78/659/EEC]
(S)
pH units
n/a > 6.0 and < 9.0
(C)
pH units
n/a > 6.0 and < 9.0
Salmonid Waters Regulations [1988]
pH units
n/a > 6 and < 9
Shellfish Directive [79/923/EEC]
pH units
n/a 7.0-9.0
Drinking Water Directive [98/83/EC]
pH units
n/a > 6.5 and < 9.5
_______________________________________________________________________________________
[1]
[2,3]
[2,3]
[2,4]
[5]
Notes
[1]
Sampling to be carried out "where an investigation, ..shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..." No two consecutive samples to fall outside the
range.
[2]
"Artificial pH variations with respect to the unaffected values shall not exceed ± 0.5 of a pH unit
within the limits 6 and 9 provided that these variations do not increase the harmfulness of other substances
present in the water,"
[3]
Derogations possible "because of exceptional weather or special geographical conditions."
[4]
Standard to he conformed with by 95% of samples over a period of 12 months where sampling is
carried out at least once per month; where sampling is less frequent the standard shall be conformed with by
all samples.
[5]
Parameter is designated: "Hydrogen ion concentration," with the comments: "The water should not be
aggressive," and "For still water put into bottles or containers, the minimum value may be reduced to 4.5 pH
units. For water put into bottles or containers which is naturally rich in or artificially enriched with carbon
dioxide, the minimum value may be lower."
84
Parameters of Water Quality - Interpretation and Standards
60. PHENOLS
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l C6H5OH [Phenol].
Normal Method(s) of Analysis:
Chloroform/4-Aminoantipyrene Extraction Method [B/C];
Instrumental Chromatographic Techniques [C].
Occurrence/Origin: Polluted surface waters (roads/roadworks run-off); industrial effluents.
Health/Sanitary Significance: Many phenolic compounds are corrosive and toxic to a marked
extent, but their primary significance in waters is organoleptic.
Background Information: Phenol itself (carbolic acid; C6H5OH) is used as a reference material
for this determination, which includes many related compounds, including some natural phenolic
types, although the last-mentioned are not normally problem-causing. The main difficulties which
arise (even in waters with minute traces of phenols) are of taste and odour which are magnified
greatly when the water is chlorinated. Severe problems are caused and rejection of supplies by
consumers is likely.
Comments: The compounds originate in industrial processes and can reach water sources from
discharges or they can be leached from road covering materials. Instances of severe contamination
of wells have been reported consequent on the tarmacadaming of nearby yards or areas.
Phenols : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l C6H5OH n/a
0.0005
[1]
A2 waters
mg/l C6H5OH
n/a
0.005
[1]
n/a
0.1
[1]
A3 waters
mg/l C6H5OH
[2]
Bathing Water Regulations [1989-1998]
mg/l C6H5OH
Freshwater Fish Directive [78/659/EEC]
(S)
mg/l C6H5OH
[3]
[3]
(C)
mg/l C6H5OH
Salmonid Waters Regulations [1988]
[4]
Drinking Water Directive [98/83/EC]
[5]
_______________________________________________________________________________________
Notes
[1]
Parameter appears in the Regulations as "Phenols [phenol index] paranitraniline 4-aminoantipyrene."
This is potentially confusing to the non-chemist as the latter two words are the names of re agents used in
different analytical procedures for phenols.
[2]
Parameter is "Phenols [phenol indices]." Standard is < 0.05 mg/l and no specific odour. Standard to
be conformed with by 95% samples and not to be exceeded by any two consecutive samples. No sample to
exceed 0.075 mg/l [C6H5OH]. [Note that the Regulations erroneously give the units as mg/l C4H3OH].
[3]
Parameter is "Phenolic compounds" which "must not be present in such concentrations that they
adversely affect fish flavour."
[4]
Regulations specify that "Phenolic compounds must not be present in such quantities that they
adversely affect fish flavour."
[5]
There is no reference to phenols in this Directive.
85
Parameters of Water Quality - Interpretation and Standards
61. PHOSPHATES
Chemical Symbol or Formula:
PO4– – –.
Units Used for Analytical Results:
mg/l P.
Normal Method (s) of Analysis:
Manual or Automated Colorimetry [B/C].
Occurrence/Origin:
Phosphorus occurs widely in nature in plants, in micro-organisms, in
animal wastes and so on. It is widely used as an agricultural fertiliser and as a major constituent
of detergents, particularly those for domestic use. Run-off and sewage discharges are thus
important contributors of phosphorus to surface waters.
Health/Sanitary Significance:
None.
Background Information:
The significance of phosphorus is principally in regard to the
phenomenon of eutrophication (over-enrichment) of lakes and, to a lesser extent, rivers.
Phosphorus gaining access to such water bodies, along with nitrogen as nitrate, promotes the
growth of algae and other plants leading to blooms, littoral slimes, diurnal dissolved oxygen
variations of great magnitude and related problems, as discussed elsewhere in this volume.
There is considerable debate as to the availability of the various forms of phosphorus
(orthophosphate, polyphosphate, organic phosphate and so on) for the growth of algae although it
is considered that orthophosphate is the most readily used form. Phosphorus may be in true
solution, in colloidal suspension or adsorbed onto particulate matter, and it is very difficult to
differentiate between the various fractions by separation (e.g. filtration) or analysis. A useful
parameter is orthosphosphate (strictly, total filtrable and non-filtrable orthophosphate) which is
the phosphate responding to the analytical procedure without any pre-treatment such as
hydrolysis or oxidative digestion. Caution must be exercised in considering the results of
phosphorus analysis as the element exists in bound and unbound forms which are very difficult to
separate totally in analysis. There is always the likelihood, for example, of some of the bound
polyphosphate forms being changed by hydrolysis to orthophosphate under the actual analytical
conditions. However, the determination of orthophosphate as specified is of great use in
highlighting the presence of one of the most important nutrients and the results are of special
interest in waters receiving sewage discharges.
The importance of controlling phosphorus levels in the Irish aquatic environment is
highlighted by the publication (in May 1997) by the Minister for the Environment and Local
Government of a 10-year strategy paper entitled Managing Ireland's Rivers and Lakes - A
Catchment-Ba-sed Strategy Against Eutrophication. This document deals with the topic of
phosphorus levels (expressed as mg/l median Molybdate-Reactive Phosphate [MRP] 9) and it sets
out interim statutory standards, in terms of MRP, for the year 2007 for water in several quality
classes, rivers and lakes being treated separately.
Comments: These statutory standards are presented below, following the details of phosphorus
standards in other legislation.
Phosphates : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l P2O5
mg/l P2O5
mg/l P2O5
n/a
n/a
n/a
0.5
0.7
0.7
[1]
[1]
[1]
____________________
This precisely-defined unit is broadly equivalent to "orthophosphate" as determined using the ascorbic
acid/molybdate colorimetric procedure.
9
86
Parameters of Water Quality - Interpretation and Standards
Phosphates : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
[2]
Dangerous Substances Directive [761464/EEC]
List II substance
[3]
Ground Water Directive [80168/EEC]
List II substance
[3]
Drinking Water Directive [98/83/EC]
[4]
_______________________________________________________________________________________
Phosphorus : INTERIM STATUTORY STANDARDS FOR RIVERS
___________________________________________________________________________________________
Phosphorus
Parameter
Environmental ExistingBiolWaters
ogical Quality
[Q] Rating
EQS [as annual
Corresponding
median value as
Minimum Target
MRP [mg/l P]
Q Rating
for year 2007
___________________________________________________________________________________________
Molybdate- Reactive Rivers
Phosphate [MRP]
[mg/I P]
5]
0.015
5
4 - 5] Unpolluted 0.020
4-5
4]
0.030
4
----------------------------------------------------------------------------------3-4
Slightly
0.080
4
polluted
----------------------------------------------------------------------------------3]
Moderately 0.050
3 - 4*
2 - 3 ] polluted
0.070
3*
----------------------------------------------------------------------------------<2
Seriously
0.070
3*
polluted
___________________________________________________________________________________________
Phosphorus : INTERIM STATUTORY STANDARDS FOR LAKES
___________________________________________________________________________________________
Phosphorus
Parameter
Environmental Existing
Target
EQS [as annual
Waters
Trophic Status Trophic Status
average Total P
[Q] Rating
for year 2007
(µg/l P)] in 2007
___________________________________________________________________________________________
Total Phosphorus
[µg/l P]
Clear Water
Lakes
UltraUltraOligotrophic
Oligotrophic
<5
Oligotrophic
Oligotrophic
5 - 10
Mesotrophic
Mesotrophic [or
10 - 20
[satisfactory]
Oligotrophic**]
[5 - 10]
------------------------------------------------------------------------------Eutrophic
Mesotrophic
10 - 20
Hypertrophic
Eutrophic
20 - 50
[unsatisfactory]
___________________________________________________________________________________________
87
Parameters of Water Quality - Interpretation and Standards
Phosphorus : INTERIM STATUTORY STANDARDS FOR LAKES
___________________________________________________________________________________________
Phosphorus
Parameter
Environmental Existing
Target
EQS [as annual
Waters
Trophic Status Trophic Status
average Total P
[Q] Rating
for year 2007
(µg/l P)] in 2007
___________________________________________________________________________________________
Total Phosphorus
[µg/l P]
Other Lakes
Oligotrophic
Oligotrcphic
< 10
Mesotrophic
Mesotrophic [or
10 - 35
[satisfactory]
Oligotrophic**]
[< 10]
------------------------------------------------------------------------------Eutrophic
Mesotrophic
10 - 35*
Hypertrophic
Eutrophic
35 - 100*
[unsatisfactory]
___________________________________________________________________________________________
* Proposed interim EQSs.
** In the case of lakes which were originally of this quality
___________________________________________________________________________________________
Notes
[1]
Departure may be granted by the Minister “in the case of surface water in shallow lakes or virtually
stagnant surface water.”
[2]
Parameter is designated: “Phosphates” Sampling to be carried out ‘where an investigation shows, or
there are other grounds for believing, that there has been a deterioration in the quality of waters
[3]
List II refers to “Inorganic compounds of phosphorus and elemental phosphorus.”
[4]
There is no reference to phosphate or phosphorus in this Directive.
62. PHOSPHORUS, TOTAL
Chemical Symbol or Formula;
Not applicable [Bulk parameter).
Units Used for Analytical Results:
mg/l P.
Normal Method(s) of Analysis:
orthophosphate (see above) [B/C]
Digestion, followed by determination of the resultant
Occurrence/Origin: Natural or added organic matter (wastes, vegetation etc.).
Health/Sanitary Significance: Indirect - indicates overall water quality.
Background Information: This is the most complete determination of the element phosphorus,
irrespective of the compounds in which it is actually present in the water. All forms of phosphorus
are converted to soluble orthophosphate which is the species detected by the chemical reaction
used in the analysis.
It has been the practice in lake investigations to determine total phosphorus as one of the
most meaningful parameters in the assessment of eutrophication but there is a difficulty in that
not all the phosphorus measured under test conditions may be effectively available in the
environment to promote algal growth. Orthophosphate is thus determined frequently as well.
Comments: An advantage of this parameter is that it is a total one: it is thus subject to less
ambiguity of interpretation than other phosphorus parameters.
88
Parameters of Water Quality - Interpretation and Standards
Phosphorus, Total : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Freshwater Fish Directive [78/659/EEC]
(S)
mg/l P
[1]
(C)
mg/l P
[1]
_______________________________________________________________________________________
Notes
[1]
No figures whatever are quoted but there is the following comment: "In the case of lakes of average
depth between 18 and 300 m, the following formula could be applied:
Z/Tw
L
where
<
10
( 1 + Tw – 2)
L = loading expressed as mg P/square metre lake surface/year
Z = mean depth of lake in metres
Tw = theoretical renewal time of lake water in years.
In other cases limit values of 0.2 mg/l for salmonid and of 0.4 mg/l for cyprinid waters, expressed PO4
[corresponding to 0.062 and 0.124 mg/l as P, respectively], may be regarded as indicative in order to reduce
eutrophication." The parameter is not included in the Regulations for salmonid waters.
POLYAROMATIC HYDROCARBONS
(See "Polycyclic Aromatic Hydrocarbons")
63. POLYCHLORINATED BIPHENYLS & TERPHENYLS
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
µg/l reference PCB/PCT (mixture) used.
Normal Method(s) of Analysis:
Gas-Liquid Chromatography (GLC) [G].
Occurrence/Origin:
Synthetic components of transformer coolant oils which gain access to
water by spillages or industrial discharges.
Health/Sanitary Significance:
potential carcinogens.
Compounds of marked chronic toxicity; they are actual or
Background Information: Commonly termed PCBs/PCTs, this parameter covers those chlorinated compounds which have been used as mixtures in transformer coolant oils. The mixtures are
normally designated by a proprietary name, for example "Aroclor," to which is suffixed a number,
e.g. 1254 or 1260. The first two digits represent the number of carbon atoms in the molecule and
the second two the percentage by weight of chlorine. The basic molecules present are biphenyl,
which is C12H10 and comprises two benzene rings joined together, or terphenyl (C18H14, consisting
of three fused benzene rings).
When these are chlorinated a whole range of polychlorinated compounds is produced and the
mixtures are of such complexity that no effort is made to identify the individual components. The
mixtures are dense and extremely stable, resisting biodegradation and conventional incineration
procedures.
89
Parameters of Water Quality - Interpretation and Standards
[The best process currently available for their destruction is very high temperature "flash"
incineration. It is not without significance that, according to current estimates, about 90% of the
total world production of these materials since the 1940s, when they were introduced, is still
extant].
PCBs/PCTs are toxic, causing genetic effects and mortality to fauna. They are accumulated to
a very great extent by fauna and there are many literature references to concentration factors of
over 100,000 - in other words, an infinitesimal concentration in a water may be matched by
100,000 times that amount in the tissue of fish or animals normally resident in that water. When
these toxicants enter the food chain, through consumption of fish for example, there is a health
risk to man.
Comments: Minor spillages of PCBs are not uncommon and in order to minimise their effects on
the environment it is essential that specialist expertise be used in both disposal of these materials
and cleaning up after any spillage has occurred.
Polychlorinated Biphenyls & Terphenyls : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
[1]
_______________________________________________________________________________________
Notes
[1]
In contrast to Directive 80/778/EEC, the 1998 Drinking Water Directive makes no express reference to
PCBs or PCTs.
64. POLYCYCLIC AROMATIC HYDROCARBONS
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l PAH [or specific PAH compound(s)].
Normal Method(s) of Analysis:
High Pressure Liquid Chromatography (HPLC) [C].
Occurrence/Origin: Synthetic compounds occurring in soot, tar, vehicle exhausts, combustion
products of hydrocarbon fuels.
Health/Sanitary Significance: Carcinogens of greater or lesser potency.
Background Information: This term, while strictly applicable to very many substances, has
been defined as applying to six specific compounds:
Fluoranthene
11,12-benzofluoranthene [benzo(k)fluoranthene]
1,12-benzoperylene [benzo(ghi)perylene}
3,4-benzofluoranthene [benzo(b)fluoranthene]
3,4-benzopyrene [benzo(a)pyrene]
indeno(l,2,3-cd)pyrene
but in the 1998 Drinking Water Directive fluoranthene has been omitted, while benzo(a)pyrene
[3,4-benzopyrene] has been listed as a separate parameter, leaving the four remaining compounds
(shown in italics) to constitute the group designated: "Polycyclic Aromatic Hydrocarbons."
It may be useful to comment on the nomenclature of these compounds and related materials.
They are so-called aromatic compounds, the term being used for those substances containing the
"aromatic ring" (i.e. the cyclic molecular structure of benzene) a basic element of their composition.
As the substances contain more than one such ring, they are termed polycyclic (or sometimes, polyaromatic compounds). The compounds are hydrocarbons - i.e. they consist of the elements carbon
and hydrogen only.
90
Parameters of Water Quality - Interpretation and Standards
The alternative often-used designation - "polynuclear aromatic hydrocarbons" • arises from the
(inaccurate) use by organic chemists of the word "nucleus" to refer to the benzene ring structure.
As there is more than one such ring in these compounds they are termed "polynuclear."
All of these materials are complex organic molecules which originate typically in the
combustion of organic compounds. Their analysis, like that of many other so-called
micropollutants, is difficult, but the procedures are justified because of the potential health
hazards posed by the PAH. The listed compounds can be determined relatively easily, albeit with
advanced instrumental techniques, and their presence is also taken as indicative of the possible
occurrence of other undesirable aromatic compounds. While all have been regarded previously as
carcinogens, the six listed compounds comprising the most widely found such group in the
environment, by far the most hazardous compound among them is benzo(a)pyrene [3,4benzopyrene], which, as mentioned, has been highlighted in Drinking Water Directive [98/83/EC].
Comments: The compounds covered by the Surface Water Regulations are the six originally
identified by the WHO, although this is implicit rather than stated. The 1998 Drinking Water
Directive treats benzo(a)pyrene separately and the remaining substances (other than the omitted
fluoranthene) as a group parameter.
Polycyclic Aromatic Hydrocarbons : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
mg/l
n/a
0.0002
[1]
mg/l
n/a
0.0002
[1]
mg/l
n/a
0.001
[1]
Drinking Water Directive [98/83/EC]
µg/l
n/a
0.10
[2,3]
_______________________________________________________________________________________
Notes
[1]
The parameter is termed "Polycyclic aromatic hydrocarbons" without any qualification.
[2]
The parameter is termed "Polycyclic aromatic hydrocarbons," with a statement that "The specified
compounds are: benzo(b)fluoranthene; benzo(k)fluoranthene; benzo(ghi)perylene; indeno(l,2,3-cd)pyrene." It
should be noted that the variations in nomenclature arise from the use of different naming conventions by
the EU and the WHO.
[3]
The Directive notes that the parametric value applies to the "Sum of concentrations of specified
compounds."
POLYNUCLEAR AROMATIC HYDROCARBONS
(See "Polycyclic Aromatic Hydrocarbons")
65. POTASSIUM
Chemical Symbol or Formula:
K.
Units Used for Analytical Results:
mg/l K.
Normal Method(s) of Analysis: Flame Photometry [B/C], Atomic Absorption Spectrometry [B/C].
Occurrence/Origin:
Geological formations.
Health/Sanitary Significance: None, except at gross levels.
91
Parameters of Water Quality - Interpretation and Standards
Background Information:
Potassium is an essential constituent of many artificial fertiliser
formulations, and hence its determination is often carried out on lake waters when an assessment
is being made of nutrient input. However, potassium tends to be "fixed" in soils and is not that
easily leached out. There are no implications of toxicity.
Comments: Very often potassium is measured on samples solely to permmit the calculation of an
"ion balance" for the verification of the analysis.
Potassium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
[1]
_______________________________________________________________________________________
Notes
[1]
The limit value for potassium in the earlier Directive has not been carried forward to Directive
[98/83/EC] in which there is no reference to this element.
66. PSEUDOMONAS AERUGINOSA
Chemical Symbol or Formula:
Not applicable [Microbiological parameter].
Units Used for Analytical Results:
No of organisms/250 ml sample.
Normal Method(s) of Analysis:
[B]; Membrane Filtration Method [B].
Most Probable Number (MPN; Multiple Tube Method)
Occurrence/Origin:
Pseudomonas bacteria are ubiquitous in the environment and can
metabolise most types of organic matter in a variety of conditions. The specific organism
Pseudomonas aeruginosa is the only one of the group which is pathogenic to man; it is abundant in
sewage.
Health/Sanitary Significance:
infections.
Pseudomonas aeruginosa is associated with eye and ear
Background Information:
The presence of Pseudomonas aeruginosa is undesirable in
recreational waters - in swimming pools and at bathing beaches.
Comments:
The only current limit value applies to bottled drinking water.
Pseudomonas aeruginosa : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
no/250 ml n/a
0
[1]
_______________________________________________________________________________________
[1]
Notes
The limit value "applies to water offered for sale in bottles or containers."
92
Parameters of Water Quality - Interpretation and Standards
RESIDUAL CHLORINE
(See "Chlorine, Residual")
67. SALINITY
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
‰ [parts per thousand].
Normal Method(s) of Analysis:
Electrometric (Salinity/Conductivity Meter) [A/B].
Occurrence/Origin:
Natural property of seawater.
Health/Sanitary Significance: Organoleptic considerations only.
Background Information: This specific parameter is of interest only in tidal waters or in other
surface waters where there may be infiltration of seawater. The presence of a high salt content
(the greater constituent of which is chloride, q.v.) may render a water unsuitable for domestic,
agricultural or industrial use, or may affect its suitability for shellfish.
Comments: Full seawater is 35 parts per thousand salinity, about 35,000 mg/l Cl.
Salinity: Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Shellfish Directive [79/923/EEC]
‰
12-38
< 40
[1,2]
_______________________________________________________________________________________
Notes
[1]
Unit of analysis is parts per thousand (‰).
[2]
The following qualification applies to the I value: "[A] discharge affecting shellfish waters must not
cause their salinity to exceed by more than 10% the salinity of waters not so affected."
68. SALMONELLA
Chemical Symbol or Formula:
Not applicable [Microbiological parameter].
Units Used for Analytical Results:
Number of organisms/specified volume of water.
Normal Method(s) of Analysis:
Membrane Filtration technique [B].
Occurrence/Origin: Sewage and similar wastes.
Health/Sanitary Significance:
fever, paratyphoid fever etc.
Pathogenic micro-organisms causing diseases such as typhoid
Background Information:
The most commonly occurring pathogenic micro-organisms in
polluted water include salmonella types, for example Salmonella typhi and Salmonella paratyphi,
which are causes of enteric diseases of greater or lesser severity.
There are also milder forms of
93
Parameters of Water Quality - Interpretation and Standards
gastric illnesses caused by other bacteria of the salmonella type. The analysis for these organisms
is not always carried out, in contrast to the tests for total and faecal conforms [see under that
heading for a fuller discussion of pathogens], but salmonella are determined more frequently than
are staphylococci.
Comments:
As with pathogenic staphylococci (q.v.) the non-determination of the specific
pathogens in a routine analysis does not at all imply a reduced level of concern over their presence
or absence. Instead, the policy of reliance on the test for the far more abundant coliform organisms
(q.v.), used as indicators of the possible presence of pathogens, makes for a rather greater safety
margin.
Salmonella : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
no/500 ml
n/a
0
A2 waters
no/100 ml
n/a
0
A3 waters
[1]
Bathing Water Regulations [1989-1998]
no/1000 ml n/a
0
[2]
Drinking Water Directive [98/83/EC]
[3]
_______________________________________________________________________________________
Notes
[1]
No standard specified for A3 waters.
[2]
Sampling to be carried out "where an investigation ... shows, or there are other grounds for believing,
that there has been a deterioration in the quality of waters..." Standard to be conformed with by 95% of
samples. Not to be exceeded by any two consecutive samples.
[3] Article 4(1) of the Directive states, inter alia, that; "For the purposes of the minimum requirements of
this Directive, water intended for human consumption shall be wholesome and clean if it ...is free from any
microorganisms and parasites and from any substances which, in numbers or concentrations, constitute a
potential danger to human health......."; Article 7(6) requires that "Member States shall ensure that
additional monitoring is carried out on a case-by-case basis of substances and micro-organisms for which no
parametric value has been set in accordance with Article 5, if there is reason to suspect that they may be
present in amounts or numbers which constitute a potential danger to human health." There is no express
reference to salmonella.
SEC
(See "Substances Extractable in Chloroform")
69. SELENIUM
Chemical Symbol or Formula:
Se.
Units Used for Analytical Results:
µg/l Se.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [C]
Occurrence/Origin: Weathering of rocks/soils, but major environmental sources are man-made.
Health/Sanitary Significance: Toxic element except in trace concentrations.
94
Parameters of Water Quality - Interpretation and Standards
Background Information: Although it is an essential biological requirement for both man and
animals, selenium in more than very small amounts is toxic, causing a variety of illnesses. There
have been conflicting reports as to whether or not the element is carcinogenic.
Comments: Where selenium is found it is probably of industrial origin. It is used as a chemical
catalyst, in photographic equipment and processes, in electrical components and so on.
Selenium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l Se
n/a
0.01
A2 waters
mg/l Se
n/a
0.01
A3 waters
mg/l Se
n/a
0.01
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
µg/l Se
10
_______________________________________________________________________________________
70. SILICA
Chemical Symbol or Formula:
SiO2.
Units Used for Analytical Results:
mg/l SiO2.
Normal Method(s) of Analysis: Manual/Automated Colorimetric technique (Molybdate/ Aminonaphtholsulphonic Acid) [B/C].
Occurrence/Origin:
Rocks and geological formations.
Health/Sanitary Significance: No definite health implications in water.
Background Information: Silicon (as silica) is the most abundant element found in rocks and it
will always be present in natural waters. The element is a major component of the structure of
diatoms (Bacillariophyta), one of the main divisions of the algae, and when algal growth takes
place in a water there will be a dramatic drop in the silica levels as the diatom population rises.
The subsequent replenishment of silica is principally from run-off.
Comments: It is in connection with the diatom population that silica is determined as there are
no apparent connotations for the purity of the water or its suitability for consumption.
Silica : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
95
Parameters of Water Quality - Interpretation and Standards
71. SILICON, TOXIC OR PERSISTENT ORGANIC COMPOUNDS
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l Si [or compound(s) detected].
Normal Method(s) of Analysis:
[Specialised analytical techniques] [C/D]
Occurrence/Origin: Industrial wastes, tip-head leachates.
Health/Sanitary Significance: Toxic materials.
Background Information:
There are no specified limits or identified compounds and the
parameter is a general "catch-all" for hazardous, silicon-containing organic materials.
Comments: It is worthy of note that the parameter is mentioned only in the two Directives [Dangerous Substances and Groundwater] which seek to prevent rather than detect discharges.
Silicon, Toxic/Persistent Organic Compounds : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance [1]
Ground Water Directive [80/68/EEC]
List II substance [1]
_______________________________________________________________________________________
Notes
[1]
List II refers to "Toxic or persistent organic compounds of silicon, and substances which may give rise
to such compounds in water, excluding those which are biologically harmless or are rapidly converted in
water to harmless substances."
72. SILVER
Chemical Symbol or Formula:
Ag.
Units Used for Analytical Results:
mg/l Ag.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C]
Occurrence/Origin: Ores, industrial wastes (e.g. photographic effluents).
Health/Sanitary Significance: Metal of varying toxicity.
Background Information: This metal is toxic, especially to micro-organisms, and its soluble
salts are excellent disinfectants. It is not considered particularly toxic to humans and, as it is
likely to be found only in very low levels (such that it would be practically impossible to reach
hazardous levels through consumption of water and food), few limits have been set. However, it
has been reported that restrictions on its use were introduced to discourage the use of silver as a
disinfectant because of possible health effects if used unduly liberally.
Comments: Nowadays, economic considerations are likely to restrict the discharge of silver.
96
Parameters of Water Quality - Interpretation and Standards
Silver : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Shellfish Directive [79/923/EEC]
mg/l Ag
[1]
[2]
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
[3]
_______________________________________________________________________________________
Notes
[1]
"The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
[2]
"The concentration of [this] substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of [this and
other specified] metals must be taken into consideration."
[3]
The limit value for silver in the earlier Directive has not been carried forward to Directive [98/83/EC]
in which there is no reference to this element.
73. SODIUM
Chemical Symbol or Formula:
Na.
Units Used for Analytical Results:
mg/l Na.
Normal Method(s) of Analysis: Flame Photometry [B/C]; Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Abundant constituent of rocks and soils.
Health/Sanitary Significance: Causes hypertension if taken in excess.
Background Information: Sodium is always present in natural waters. It is also an essential
dietary requirement and the normal intake is as common salt (sodium chloride) in food; daily
consumption may amount to 5 grams or more. The main reason for limiting it is the joint effect
which it exercises with sulphate (see below) but too excessive an intake (the latter normally being
2-3 times the dietary threshold) can cause hypertension, as mentioned.
Comments: Sodium sulphate is used medicinally as a laxative ["Glauber Salts"].
Sodium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
mg/l Na
n/a
200
_______________________________________________________________________________________
97
Parameters of Water Quality - Interpretation and Standards
74. SOLIDS, SETTLEABLE
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
millilitres/litre [ml/l] solids.
Normal Method(s) of Analysis: Settlement in lmhoffCone [A]
Occurrence/Origin: Not a normal determinand in analysis of water unless it is grossly polluted.
Health/Sanitary Significance: No direct implications, but in water is an indicator of gross
pollution.
Background Information: This parameter is not normally determined in water analysis where
reliance is placed on suspended solids (see below), but is one of those measured in the analysis of
sewage effluents. Its main use is in the assessment of treatment plant performance.
Comments: There is an obvious relationship to the parameter "Solids, Suspended" (q.v.). Both
are therefore of concern in fishery waters where high deposition of solids can interfere with fish
and with spawning grounds.
Solids, Settleable : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
75. SOLIDS, SUSPENDED
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l solids (Dried at stated temperature).
Normal Method(s) of Analysis: Gravimetric (Filtration, with drying at stated temperature) [A].
Occurrence/Origin: Natural deposition in or discharges to water.
Health/Sanitary Significance: No direct significance.
Background Information: Matter which is suspended in quiescent water consists of finely
divided light solids which may never settle or do so only very slowly. Indeed, the net effect may be
one of apparent turbidity without any discernible solids. In flowing water, on the other hand, the
solids which are kept in suspension by the turbulence may be settleable if the water is let stand.
While the latter would be determinable as "Solids, Settleable," and the former could possibly be
assessed as "Turbidity," there will be those solids of intermediate grading which also require
estimation. To determine as much as possible of the solids present (not in solution), the
determination of "suspended" solids is carried out.
The procedure consists of filtering the sample through a defined medium (a common
specification is through a 0.45 µm membrane) and drying at a specified temperature (commonly
105°C) with gravimetric estimation of the concentration. Failing the use of a membrane fitter,
glass-fibre paper (grade GF/C) may be used although its porosity is much greater than the former.
It is important that the temperature of the drying be adhered to and also quoted with the results.
It is clear that the term "suspended solids" is in fact defined by the filtration conditions.
98
Parameters of Water Quality - Interpretation and Standards
The significance of suspended solids in water is great, on a number of grounds. The solids
may in fact consist of algal growths and hence be indicative of severely eutrophic conditions; they
may indicate the discharge of washings from sandpits, quarries or mines; they will reduce light
penetration in surface waters and interfere with aquatic plant life; they will seriously damage
fishery waters and may affect fish life; they may form deposits on the bed of rivers and lakes which
will in turn give rise to septic and offensive conditions; and they may indicate the presence of
unsatisfactory sewage effluent discharges.
Comments: The Royal Commission on Sewage Disposal (Eighth Report, 1912), referred to under
"BOD" above, recommended that suspended solids be limited in effluents, and the second element
in the "20/30" effluent previously discussed is a level of 30 mg/l suspended solids.
It is in the context of effluent analysis that suspended solids measurements are most
relevant as they are good indicators of both the pollution potential of an effluent and the
performance efficiency of treatment plant.
Solids, Suspended : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
mg/l
n/a
50
[1]
A2 waters
mg/l
n/a
[1]
A3 waters
mg/l
n/a
[1]
Freshwater Fish Directive [78/659/EEC]
(S)
mg/l
< 25
[2]
(C)
mg/l
< 25
[2]
[3]
Salmonid Waters Regulations [1988]
mg/l
n/a
< 25
Shellfish Directive [79/923/EEC]
mg/l
[4]
_______________________________________________________________________________________
Notes
[1]
Parameter is "Total suspended solids." Standard specified for A1 waters only.
[2]
"The values shown are average concentrations and do Not apply to suspended solids with harmful
chemical properties. Floods are liable to cause particularly high concentrations." Departures are possible
"because of exceptional weather or special geographical conditions."
[3]
"The standard is expressed as an average concentration over a period of 12 months and does Not apply
to suspended solids with harmful chemical properties."
[4]
The I value quoted is: "A discharge affecting shellfish waters must not cause the suspended solid
content of the waters to exceed by more than 50% the content of waters not so affected."
76. SOLIDS, TOTAL
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l solids (Dried at stated temperature).
Normal Method(s) of Analysis:
Gravimetric (Dried at stated temperature) [A]
Occurrence/Origin:
Natural and added solids present in water.
Health/Sanitary Significance:
Primarily of organoleptic concern.
99
Parameters of Water Quality - Interpretation and Standards
Background Information:
This parameter comprises the total solids present in the whole
sample which is analysed directly without filtration. It is referred to also as Dry Residue(s) or Total
Residue(s). The drying temperature must he quoted with the results. There are two commonly
used drying temperatures - 105°C and 180°C, the latter being favoured in some continental
European standards.
At 105°C the residue may retain some water even after an hour's drying. There will be some
conversion of bicarbonates to carbonates by loss of carbon dioxide but loss of organic matter will be
minimal. At 180°C virtually all the water will be lost, as will some organic matter. In addition to
loss of carbon dioxide in bicarbonates, some further loss may occur in carbonates. Because of these
differences in behaviour the temperature must be quoted to obtain the most meaningful picture
from the results.
At times the residue from the total solids determination is analysed further by igniting it for
an hour in a furnace at 550-600°C. Under this drastic heat, organic matter will be volatilised and
there will be some further loss in weight by destruction of some inorganic compounds. The weight
lost represents the Volatile Solids and the ultimate residue is the so-called Fixed Residue or NonVolatile Solids, present in the sample.
Comments: While there is no direct correlation between loss in weight on ignition of a sample
and its organic content, in certain circumstances (as, for example, an investigation of the extent to
which organic sludge is deposited over an area of river bed), the determination of volatile solids
will give a useful trace of the levels of organic matter.
Solids, Total : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
77. SOLIDS, TOTAL DISSOLVED
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l solids (Dried at stated temperature).
Normal Method (s) o f Analysis: Gravimetric (Dried at stated temperature after filtration) [A].
Occurrence/Origin: Natural or added solutes present in a water.
Health/Sanitary Significance: Principally organoleptic implications.
Background Information: The parameter is determined as for total solids except that the
sample is filtered through a defined medium (membrane or glass fibre paper; cf. "Solids,
Suspended") beforehand. The term Total Filtrable Solids is also used. It is often convenient and
acceptable to use the very rapid determination of conductivity (q.v.) to give an estimation of the
total dissolved solids.
Comments: As discussed earlier, the total dissolved solids, or TDS, includes ionised and nonionised matter but only the former is reflected in the conductivity. Where TDS are high the water
may be "saline" and the applicable parameter "Salinity."
100
Parameters of Water Quality - Interpretation and Standards
Solids, Total Dissolved : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
SS
(See "Solids, Suspended")
SUSPENDED SOLIDS
(See "Solids, Suspended")
TDS
(See "Solids, Total Dissolved")
TOTAL DISSOLVED SOLIDS
(See "Solids, Total Dissolved")
STANDARD PLATE COUNT(S)
(See "Colony Counts")
STREPTOCOCCI, FAECAL
(See "Enterococci")
78. SUBSTANCES AFFECTING TASTE
Chemical Symbol or Formula:
Not applicable [Organoleptic parameter].
Units Used for Analytical Results:
mg/l compound(s) identified/detected.
Normal Method(s) of Analysis:
[Specific techniques as appropriate] [C]
Occurrence/Origin: Naturally occurring or added solutes.
Health/Sanitary Significance: Primarily organoleptic effects.
Background Information:
This is a somewhat ill-defined parameter in that there are
potentially so many of these substances that their control, while most desirable (particularly for
fishery and shellfish waters, and for drinking water sources), is virtually impossible to achieve.
The only practicable approach is to monitor and regulate the presence of selected pollutants
(phenols, metals and so on) which are known to have deleterious effects.
101
Parameters of Water Quality - Interpretation and Standards
Comments:
The parameter is closely related to Tainting Substances, and for all practical
purposes the two may be taken as one.
Substances Affecting Taste : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
[1]
Shellfish Directive [79/923/EEC]
[2]
Ground Water Directive [80/68/EEC]
List II substance
[3]
_______________________________________________________________________________________
Notes
[1]
List II includes "Substances which, have a deleterious effect on the taste and/or smell of the products
for human consumption derived from the aquatic environment."
[2]
Parameter is "Substances affecting the taste of the shellfish." The I value is a "Concentration lower
than that liable to impair the taste of the shellfish."
[3]
List II includes "Substances which have a deleterious effect on the taste and/or odour of groundwater,
and compounds liable to cause the formation of such substances in such water and to render it unfit for
human consumption."
79. SUBSTANCES EXTRACTABLE IN CHLOROFORM
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l SEC.
Normal Method(s) of Analysis:
Extraction, Drying & Gravimetry [B/C]
Occurrence/Origin: Principally from waste discharges of all types.
Health/Sanitary Significance: General indicator of organic content of water.
Background Information: Commonly abbreviated to SEC, this is a bulk parameter which
encompasses many organic contaminants in water. In one respect it is selective as it relates to a
single solvent, admittedly a powerful one, which is used for the direct extraction of organic matter
from a water sample. A related parameter is the Carbon-Chloroform Extract (CCE), in which the
sample is passed through a column of activated carbon to permit removal of the organics by
adsorption: subsequent recovery is .effected by extraction of the carbon with chloroform. There is a
third, related test the Carbon-Alcohol Extract (CAE) - in which alcohol replaces chloroform as the
recovery solvent.
Comments:
Chloroform and alcohol are both powerful solvents and their use in these
determinations is intended to ensure as near quantitative extraction (or recovery from carbon) of
organics as possible. As such, the tests are complementary to total organic carbon determinations
(see above) in that each will give a general overall indication of organic content which may not be
reflected completely or at all in oxygen demand or oxidisability analyses.
It should be noted that the SEC analysis has fallen out of favour for two main reasons. First,
the relative crudity of the analytical procedure does not match the comparative stringency of the
limits for surface waters, in particular A1 waters. A high degree of analytical skill is required if
errors are to be avoided. Second, and of much greater importance, is the health hazard to analysts
carrying out extractions with chloroform, which is considered to be carcinogenic. The use of
chloroform is increasingly being ruled out for laboratory use on health and safety grounds.
102
Parameters of Water Quality - Interpretation and Standards
Substances Extractable in Chloroform : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
mg/l SEC
n/a
0.2
mg/l SEC
n/a
0.4
mg/l SEC
n/a
1.0
_______________________________________________________________________________________
Surface Water Regulations [1989]
80.
A1 waters
A2 waters
A3 waters
SUBSTANCES WHICH POSSESS CARCINOGENIC,
MUTAGENIC OR TERATOGENIC PROPERTIES
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l compound(s) identified/detected.
Normal Method (s) of Analysis: [Appropriate specific analytical techniques] [C/D]
Occurrence/Origin: Wastes, effluents, leachates etc.
Health/Sanitary Significance: Apparent from designation of parameter.
Background Information: While the significance of this parameter is immediately obvious, it is
also clear that because of its great scope there is no way in which specific analysis can be carried
out under this heading. Instead, limits have been and will continue to be placed on individual
substances which are known to be cancer causing or which cause mutagenic or genetic disorders of
any kind, and control will be exercised by limiting the individual chemicals or groups of substances
as they become known.
Comments: This another of the essentially preventative rather than detection parameters which
arise mainly under the Dangerous Substances and Ground Water Directives. While its desirability
is clear, its practicality from the control point of view is questionable.
Substances which Possess...Properties : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List I substance
[1]
Ground Water Directive [80/68/EEC]
List I substance
[2]
_______________________________________________________________________________________
Notes
[1]
List I refers to "Substances in respect of which it has been. proved that they possess carcinogenic
properties in or via the aquatic environment."
[2]
List I refers to "Substances which possess carcinogenic, mutagenic or teratogenic properties in or via
the aquatic environment."
103
Parameters of Water Quality - Interpretation and Standards
81. SULPHATE
Chemical Symbol or Formula:
SO4
Units Used for Analytical Results:
– –.
mg/l SO4
Normal Method(s) of Analysis: Turbidimetric (Barium Sulphate) [B/G]; Ion Chromatography
[C].
Occurrence/Origin: Rocks, geological formations, discharges and so on .
Health/Sanitary Significance: Excess sulphate has a laxative effect, especially in combination
with magnesium and/or sodium.
Background Information: Sulphates exist in nearly all natural waters, the concentrations
varying according to the nature of the terrain through which they flow. They are often derived
from the sulphides of heavy metals (iron, nickel, copper and lead). Iron sulphides are present in
sedimentary rocks from which they can be oxidised to sulphate in humid climates; the latter may
then leach into watercourses so that ground waters are often excessively high in sulphates. As
magnesium and sodium are present in many waters their combination with sulphate will have an
enhanced laxative effect of greater or lesser magnitude depending on concentration. The utility of a
water for domestic purposes will therefore be severely limited by high sulphate concentrations,
hence the limit of 250 mg/l SO4.
Comments:
Other problems are associated with sulphate. In polluted waters in which the
dissolved oxygen i.e. zero, sulphate is very readily reduced to sulphide causing noxious odours.
Waters containing sulphates in excess will also attack the fabric of concrete sewer pipes.
Sulphate : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
mg/l SO4
n/a
200
mg/l SO4
n/a
200
[1]
mg/l SO4
n/a
200
[1]
Drinking Water Directive [98/83/EC]
mg/l SO4
n/a
250
[2]
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
Notes
[1]
Departure may be granted by the Minister "where exceptional meteorological or geographical
conditions have arisen." [A2 and A3 water only.]
[2]
"The water must not he aggressive."
82. SULPHIDE
Chemical Symbol or Formula:
S– – .
Units Used for Analytical Results:
mg/l S.
Normal Method(s) of Analysis: Lead Acetate Paper (Qualitative) [A]; Specific Ion Electrode [B].
Occurrence/Origin: From anaerobic decomposition of organic matter in water or in waste, and
from bacterial reduction of sulphate.
104
Parameters of Water Quality - Interpretation and Standards
Health/Sanitary Significance: Toxic effects on man and aquatic life (see discussion below).
Background Information: The principal interest in sulphide arises because of its toxicity, and
also the odour problems associated with the presence of undissociated hydrogen sulphide (H2S)
which is produced by anaerobic reduction of sulphate. There is an equilibrium relationship
between the dissociated and undissociated H2S forms which is dependent on pH. If the latter is
above 8 there will be no odour problems but as the pH drops to under 7 any H2S present will give
rise to offensive odours. This is because the chemical equilibria:
H2S
⇔
H+ + HS
–
⇔
H+ + S
––
will shift to the left, favouring the presence of undissociated hydrogen sulphide, which is a highly
toxic substance. It is the H2S species which particularly affects aquatic life and which has caused
fatalities to persons working in sewers.
Comments: A problem associated with sulphide is the so-called "crown corrosion" of concrete
sewers. If these are not well ventilated the H2S present can be converted by aerobic bacteria
resident on the sewer walls above the level of the wastewater to sulphuric acid which will then
attack the sewer.
Sulphide : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
No reference/recommendation
_______________________________________________________________________________________
SUSPENDED SOLIDS
(See "Solids, Suspended")
TAINTING SUBSTANCES
(See "Substances Affecting Taste")
83. TARRY RESIDUES AND FLOATING MATTER
Chemical Symbol or Formula:
Not applicable [General bulk parameter].
Units Used for Analytical Results:
General description of environment.
Normal Method(s) of Analysis:
Visual [A].
Occurrence/Origin: Jetsam, littering, discharges.
Health/Sanitary Significance: None with litter; hazard with sewage solids and the like.
Background Information:
The environmental relevance of the parameter - which is fully
defined in Note [3] on page 106 - is obvious.
Comments: River surveys in Ireland have shown on occasion that alleged pollution of a river has
in fact been despoliation of the river banks and surface by littering.
105
Parameters of Water Quality - Interpretation and Standards
Tarry Residues and Floating Matter; Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
n/a
[1,2]
Dangerous Substances Directive [76/464/EEC]
List I substance
[3]
_______________________________________________________________________________________
Notes
[1]
Parameter is described as "Tarry residues. Floating matter such as wood, plastic articles...bottles,
containers of glass, plastic, rubber and other substances. Waste or splinters."
[2]
Standard is "No offensive presence." Standard to be conformed with in 95% of inspections of bathing
water. No two consecutive inspections to fail standard.
[3]
List I refers to "Persistent synthetic substances which may float, remain in suspension or sink, and
which may interfere with any use of the waters."
84. TASTE
Chemical Symbol or Formula:
Not applicable [Organoleptic parameter].
Units Used for Analytical Results:
Dilution Factor at Stated Temperature [D].
Normal Method(s) of Analysis: Taste Panel in Controlled Conditions (see "Comments" below).
Occurrence/Origin: Presence of offensive solutes, natural or added.
Health/Sanitary Significance: Principally organoleptic.
Background Information: As with odour (q.v.), taste is a parameter which can lead to severe
consumer reaction which may necessitate the condemnation of a water supply. While astringent
tastes can be caused by the presence of excessive amounts of metals or dissolved salts, there are
often other more serious problems which arise in such cases (e.g. physiological effects). Purely
organoleptic taste problems arise most commonly from algae and from phenols after chlorination.
Decaying algal masses can release to the water trace organic compounds (including phenolic types)
which produce offensive tastes after chlorination during treatment.
Comments: It should be noted that, in practice, in the great majority of cases, taste is assessed
by an individual analyst and is described subjectively. The use of a taste pane! is a very complex
and expensive matter if the specified procedures are adhered to correctly.
Taste : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Freshwater Fish Directive [78/659/EEC]
(S)
(C)
[1]
[1]
Salmonid Waters Regulations [1988]
[1]
Shellfish Directive [79/923/EEC]
[2]
_______________________________________________________________________________________
106
Parameters of Water Quality - Interpretation and Standards
Taste : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
-
-
Acceptable to
consumers and
no abnormal change
_______________________________________________________________________________________
Notes
[1]
[2]
No specific mention in parameter list but references under "Hydrocarbons" and "Phenols" [q.v.].
See "Substances affecting taste" above.
TDS
(See "Solids, Total Dissolved")
85. TELLURIUM
Chemical Symbol or Formula:
Te.
Units Used for Analytical Results:
mg/l Te.
Normal Method(s) of Analysis: Atomic Absorption Spectrometry [B/C]
Occurrence/Origin: Minerals and wastes (porcelain, enamel, glass, electronic).
Health/Sanitary Significance: Toxic metal.
Background Information: Among the effects of ingestion of tellurium are nausea, vomiting and
depression, but these are rarely found because of the comparatively low exposure risk.
Comments:
The lack of reference in the Directives (apart from Dangerous Substances and
Ground Water) indicates an absence of immediate concern over tellurium.
Tellurium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
86. TEMPERATURE
Chemical Symbol or Formula:
Not applicable [Physical parameter]
Units Used for Analytical Results:
Degrees Celsius [°C].
107
Parameters of Water Quality - Interpretation and Standards
Normal Method(s) of Analysis: Thermometry [A] or Thermistor [as in DO probe] [A/B], with
measurement in the field (usually in association with the DO measurement: q.v.).
Occurrence/Origin: Generally climatologically influenced (in the absence of thermal discharges).
Health/Sanitary Significance: None.
Background Information: The natural variation in temperature found in Irish surface waters
is of the order of 25°C - from freezing point to a summer maximum of around 25°C in occasional
years. Thermal pollution would, of course, alter the position, possibly very significantly. The effect
of temperature, and especially changes in temperature, on living organisms can be critical and the
subject is a very wide and complex one. Where biochemical reactions are concerned, as in the
uptake of oxygen by bacteria, a rise of 10°C in temperature leads to an approximate doubling of the
rate of reaction. Conversely, such reactions are retarded by cooling, hence the recommendation
often made that waters be cooled to 4°C in the interval between sampling and analysis.
Another most important factor is that some key constituents of a water either change their
form (as in the ionisation of ammonia) or alter their concentration (as with dissolved oxygen) when
temperature changes. In fact, the primary interest in the temperature of surface waters is due to
the inverse relationship between it and oxygen solubility (See "Oxygen, Dissolved"). However,
elevated temperatures and, more importantly, steep temperature gradients can have directly
harmful effects on fish. It is for the latter reason that changes in temperature are subject to limits.
The table comprising Appendix 3 shows the complex relationship between temperature, pH value
and the concentration in water of the toxic equilibrium species of ammonia. A table showing the
oxygen solubility/temperature relationship appears under the parameter "Oxygen, Dissolved."
Comments: The most comprehensive provisions concerning temperature arise under the
Freshwater Fish Directive and Salmonid Waters Regulations.
Temperature : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
[1]
[1]
[1]
[2,3]
Freshwater Fish Directive [78/659/EEC]
(S)
(C)
[2,3]
Salmonid Waters Regulations [1988]
mg/l Zn
n/a
[4]
Shellfish Directive [79/923/EEC]
mg/l Zn
[5]
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
ºC
ºC
ºC
ºC
ºC
n/a
n/a
n/a
25
25
25
Notes
[1]
Departure may be granted by the Minister "where exceptional meteorological or geographical
conditions have arisen.."
[2]
I value is: "... Temperature measured downstream of a point of thermal discharge [at the edge of the
mixing zone] must not exceed the unaffected temperature by more than: "1.5°C" in salmonid waters and
"3.0"C" in cyprinid waters. "Derogations limited in geographical scope may be decided by Member States in
particular conditions if the competent authority can prove that there are no harmful consequences for the
balanced development of the fish population."
[3]
"Thermal discharges must not cause the temperature downstream of the point of thermal discharge [at
the edge of the mixing zone] to exceed the following: 21.5°C¶/10°C" in salmonid waters and 28°C¶/10°C in
cyprinid waters.
108
Parameters of Water Quality - Interpretation and Standards
"The 10°C temperature limit applies only to breeding periods of species which need cold water for reproduction and only to waters which may contain such species." Temperature limits may, however, be exceeded for
2% of the time.
[4]
Standard laid down in Regulations is: "Temperature measured downstream of a point of thermal
discharge [at the edge of the mixing zone as determined by the local authority] must not [a] exceed the unaffected temperature by more than. 1.5°C
[b] exceed [i] 21.5°C, or [ii] 10°C during the period from I November to 30 April where species
which need cold water for reproduction are present.
A thermal discharge must not cause sudden variations m temperature." "[Temperature limits to be conformed with for 98% of the time.]"
[5]
G value is; "A discharge affecting shellfish waters must not cause the temperature of the waters to
exceed by more than 2°C the temperature of water not so affected."
TETRACHLOROETHENE
(See "Tetrachloroethylene")
87. TETRACHLOROETHYLENE
Chemical Symbol or Formula:
C2Cl4.
Units Used for Analytical Results:
µg/l C2Cl4.
Normal Method(s) of Analysis:
Gas Chromatography [B/C].
Occurrence/Origin: Synthetic solvent used extensively in dry-cleaning industry; also used to a
significant extent for degreasing metals.
Health/Sanitary Significance:
Toxic solvent which can cause narcosis, dermatitis and
ultimately fatal intoxication. However, when handled according to proper procedures and with
adequate ventilation, tetrachloroethylene may be used without problems.
Background Information: Synonyms for tetrachloroethylene are tetrachloroethene and
perchloroethylene. It is the most commonly used dry-cleaning solvent.
Comments: As with all chlorinated solvents, this substance should be handled with care, and in
well-ventilated areas.
Tetrachloroethylene: Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l
n/a
10
[1]
_______________________________________________________________________________________
Notes
[1]
The parameter is designated "Tetrachloroethene and trichloroethene" and the parametric
value is the "Sum of concentrations of specified parameters."
________________
¶ : Departures possible "because of exceptional weather or special geographical conditioas."
109
Parameters of Water Quality - Interpretation and Standards
88. THALLIUM
Chemical Symbol or Formula:
Tl.
Units Used for Analytical Results:
mg/l Tl.
Normal Method(s) of Analysis: Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Minerals, but more often from discharges.
Health/Sanitary Significance:
pain and, ultimately, death.
Causes a wide variety of effects including nausea, vomiting,
Background Information: The metal is used at 2-3% concentration in rodent poisons, and is
also used in the electrical components industry.
Comments: As with tellurium there is a low risk of exposure.
Thallium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
THM
(See "Trihalomethanes")
89. TIN
Chemical Symbol or Formula:
Sn.
Units Used for Analytical Results:
mg/l Sn.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Ores, effluents from tin-plating and alloy manufacture.
Health/Sanitary Significance: Little concern regarding tin itself and its inorganic compounds,
but see next parameter below.
Background Information: Tin has only rarely been found in water - and then only in trace concentrations. The level of exposure from foods, natural as well as canned, is rather higher than
would be expected to result from consumption of a water supply.
Comments: No specific standards have been laid down for (inorganic) tin.
110
Parameters of Water Quality - Interpretation and Standards
Tin : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
90. TIN, ORGANO-COMPOUNDS
Chemical Symbol or Formula:
Not applicable [Bulk parameter].
Units Used for Analytical Results:
mg/l Sn [or specific compound(s)].
Normal Method(s) of Analysis:
Chromatography [C].
Atomic
Absorption
Spectrometry/Gas
Liquid
Occurrence/Origin: Principally synthetic substances used for pest control.
Health/Sanitary Significance: High to very high toxicity, depending on the compound structure.
Background Information: This parameter comprises another group of specific organometallic
substances, all of which, as mentioned, are toxic and highly undesirable in the environment.
Compounds such as tributyltin and triphenyltin are present in antifouling marine paints and have
become a problem particularly in enclosed marina areas and in some shellfishery waters.
Consequently, their use has been prohibited in Ireland.
Comments: There is a problem for analysts in that for some of the organotin compounds of
concern there are as yet no satisfactory methods of determination.
Tin, Organo-Compounds : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List I substance
Ground Water Directive [80/68/EEC]
List I substance
_______________________________________________________________________________________
91. TITANIUM
Chemical Symbol or Formula:
Ti.
Units Used for Analytical Results:
mg/l Ti.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [C]
Occurrence/Origin: Minerals and industrial wastes; found rarely.
Health/Sanitary Significance:
No practical significance.
111
Parameters of Water Quality - Interpretation and Standards
Background Information:
greatly its tensile strength.
Comments:
The metal is used in some bronze alloys and in steel to increase
No quality criteria or standards specified.
Titanium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
TOC
(See "Organic Carbon, Total")
TOTAL BACTERIA COUNT(S)
(See "Colony Counts")
TOTAL COLIFORMS
(See "Coliforms, Faecal & Total")
TOTAL COLONY COUNT(S)
(See "Colony Counts")
TOTAL DISSOLVED SOLIDS
(See "Solids, Total Dissolved")
TOTAL HARDNESS
(See "Hardness")
92. TOTAL INDICATIVE DOSE [RADIOACTIVITY] 10
________________
This parameter is included as it is among those covered by Drinking Water Directive [98/83/EC].
However, there are as yet no definitive requirements in the Directive, which states the following:
10
[Note 9]
Excluding tritium, potassium-40, radon and radon decay products; monitoring frequencies,
monitoring methods and the most relevant locations for monitoring points to be set later in Annex II.
[Note 10]
1. The proposals required by Note 8 on monitoring frequencies, and Note 9 on monitoring
frequencies, monitoring methods and the most relevant locations for monitoring points in Annex II shall be
adopted in accordance with the procedure laid down in Article 12. When elaborating these proposals the
Commission shall take into account inter alia the relevant provisions under existing legislation or appropriate
monitoring programmes including monitoring results as derived from them. The Commission shall submit these
proposals at the latest within 18 months following the date referred to in Article 18 of the Directive.
2. A Member State is not required to monitor drinking water for tritium or radioactivity to
establish total indicative dose where it is satisfied that, on the basis of other monitoring carried out, the levels of
tritium of the calculated total indicative dose are well below the parametric value. In that case, it shall
communicate the grounds for its decision to the Commission, including the results of this other monitoring carried
out.
112
Parameters of Water Quality - Interpretation and Standards
TOTAL NITROGEN
(See "Nitrogen, Kjeldahl")
TOTAL ORGANIC CARBON
(See "Organic Carbon, Total")
TOTAL PLATE COUNT(S)
(See "Colony Counts")
TOTAL SOLIDS
(See "Solids, Total")
93. TRANSPARENCY
Chemical Symbol or Formula:
Not applicable [Physical parameter].
Units Used for Analytical Results:
metres Secchi.
Normal Method(s) of Analysis:
Visual observation with Secchi Disc [A].
Occurrence/Origin: Physical property of water.
Health/Sanitary Significance: None, except as indicator of possible loss of quality.
Background Information: This parameter gives an indication of the presence or absence of
suspended matter, living or inert, and hence it is a reflection of the overall quality of a water.
However, it must be remembered that the presence of any undesirable substances in solution will
not be indicated by transparency. It is expressed as the maximum depth in metres at which it is
possible to distinguish the markings of a Secchi disc, and it is widely used in studies on lakes to
assess the abundance of algae.
The parameter is also determined in bathing waters as a check on aesthetic suitability.
Comments: Transparency is related to "Turbidity" (q.v.).
Transparency : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Bathing Water Regulations [1989-1998]
metres/depth
>1
[1]
_______________________________________________________________________________________
Notes
[1]
Standard "to be conformed with in 95% of inspections of bathing water. No two consecutive
inspections to fail standard. Transparency never to be less than 0.5." [Units are equivalent to metres
Secchi].
113
Parameters of Water Quality - Interpretation and Standards
TRIBUTYLTIN
(See "Tin, Organo-Compounds")
TRICHLOROETHENE
(See "Trichloroethylene")
94. TRICHLOROETHYLENE
Chemical Symbol or Formula:
C2HCl3.
Units Used for Analytical Results:
µg/l C2HCl3.
Normal Method(s) of Analysis:
Gas Chromatography [B/C].
Occurrence/Origin: Synthetic solvent used in various industrial and manufacturing processes
(e.g. solvent for paints, varnishes, resins etc); used in dry-cleaning and in metals degreasing.
Health/Sanitary Significance: Potential carcinogen. Causes narcosis and effects similar to
alcohol inebriation. See also "Tetrachloroethylene," which is a very similar compound.
Background Information: Trichloroethylene is used in the manufacture of organic chemicals
and pharmaceuticals, and it also has some medical uses.
Comments: See observations under "Tetrachloroethylene."
Trichloroethylene : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l
n/a
10
[1]
_______________________________________________________________________________________
Notes
[1]
The parameter is designated “Tetrachloroethene and trichloroethene” and the parametric value is the
"Sum of concentrations of specified parameters."
95. TRIHALOMETHANES
Chemical Symbol or Formula:
atoms.
Units Used for Analytical Results:
CHX3 [where X indicates chlorine (Cl) and/or bromine (Br)
[µg/l compound(s).
Normal Method(s) of Analysis: Gas Chromatography [C].
Occurrence/Origin: Synthetic constituents of some chlorinated drinking waters.
Health/Sanitary Significance: Some of the compounds are actual or potential carcinogens and
have also been held responsible for other physiological ill-effects.
114
Parameters of Water Quality - Interpretation and Standards
Background Information: Trihalomethanes, as the name indicates, are derivatives of the
simplest organic compound - methane, CH4 - in which three of the hydrogen atoms are substituted
by halogen atoms. The principal halogens are fluorine (F2), chlorine (Cl2), bromine (Br2) and iodine
(I2), but, while many combinations are theoretically possible, the term trihalomethanes is applied
to four specific compounds containing only chlorine and/or bromine as the halogen elements. The
four
compounds
are:
chloroform
[CHCl3]
bromodichloromethane
[CHBrCl2]
As two of the four substances are
dibromochloromethane (CHBr2Cl) - bromoform (CHBr3).
chloroform and bromoform, the alternative designation haloforms is quite frequently applied to the
group, which, however, is most often referred to simply as THMs.
THMs are unwelcome by-products of the disinfection by chlorination of water containing
organic matter. The most common source of such matter is the natural colour of many raw waters
which are abstracted from surface water sources, principally rivers and streams. While very many
of the larger public water supplies derived from such sources will involve multi-stage treatment,
including flocculation (coagulation) which is aimed specifically at colour removal, the opposite is
the case with very many smaller supplies where the sole stage of treatment is disinfection,
invariably chlorination.
As a powerful oxidising agent, chlorine breaks down the complex - and inert - organic
molecules which are the colouring agents, forming smaller, reactive entities which react with
chlorine (and with bromine derived from the oxidation by chlorine of bromide naturally present) to
form the THM compounds, the most abundant of which is chloroform. There is thus a fairly
straightforward relationship between the degree of colour in the water prior to chlorination and
the quantities of THMs present following chlorination. If colour is present at the point of
chlorination, THMs will be formed. They will also be formed if the multi- stage treatment of a
coloured raw water includes a pre-chlorination process, where chlorine is added at the outset to
reduce the complexity of organic materials present in order to make them more amenable to
subsequent treatment stages. The latter will not remove any THMs formed at the initial stage and
they will pass through to the final water. It may be noted that, in sharp contrast, the chlorination
of ground waters - which are essentially uncoloured - will give rise to negligible, if any, THM
concentrations.
Comments:
While the presence of THMs in drinking water is a relatively widespread
phenomenon, and one which is a matter for concern, as reflected in the provisions of Drinking
Water Directive [98/83/EC] - see below - it must be remembered that the compounds are not "new"
or recent pollutants. In fact, their presence - though unknown and undetected - will have declined
steadily over the century since chlorination was first introduced. This is because water treatment
processes have been developed, improved and extended over the years, with the result that colour
levels nowadays are much lower than they were in earlier decades. Nonetheless, as the Directive
indicates, the need for conformity with acceptable limits is a matter of priority. Another by-product
of chlorination (which is a matter for equal if not greater concern) is bromate (q.v.).
Trihalomethanes : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l
n/a
100
[1,2]
_______________________________________________________________________________________
Notes
[1] The parameter is designated "Trihalomethanes - Total" and the parametric value applies to the "Sum
of concentrations of specified compounds."
[2]
The Directive contains the following important Note:
Where possible, without compromising disinfection, Member States should strive for a lower value,
The specified compounds are: chloroform, bromoform, dibromochloromethane, bromodichloromethane.
115
Parameters of Water Quality - Interpretation and Standards
For the water referred to in Article 6(l)(a), (h) and (d), the value must be met, at the latest, 10 cal
endar years after the entry into force of this Directive. The parametric value for total THMs from five years
after the entry into force of this Directive until 10 years after its entry into force is 150 µg/l.
Member States must ensure that all appropriate measures are taken to reduce the concentration of
THMs in water intended for human consumption as much as possible during the period needed to achieve
compliance with the parametric value.
When implementing the measures to achieve this value, Member States must progressively give
priority to those areas where THM concentrations in water intended for human consumption are highest.
TRIPHENYLTIN
(See "Tin, Organo-Compounds)
96. TRITIUM 11
H or T
Chemical Symbol or Formula:
3
Units Used for Analytical Results:
Bq/l. [Becquerels/litre]
Comments:
See footnote below.
1
Tritium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
Bq/l
n/a
100
_______________________________________________________________________________________
97. TURBIDITY
Chemical Symbol or Formula:
Not applicable [Bulk physical parameter].
Units Used for Analytical Results:
Formazin Turbidity Units [FTU]; Jackson Turbidity
Unit [JTU]; Nephelometric Turbidity Units [NTU]; Silica Units [SiO2].
Normal Method(s) of Analysis: Turbidimeter orNephelometer [B/C]
Occurrence/Origin: Clay particles, sewage solids, silt and sand washings, organic and biological
sludges etc.
________________
This parameter is included as it is among those covered by Drinking Water Directive [98/83/EC].
However, there are as yet no definitive requirements in the Directive, which states the following:
11
[Note 8]
Monitoring frequencies to be set later in Annex II.
[Note 10]
1. The proposals required by Note 8 on monitoring frequencies, and Note 9 on monitoring
frequencies, monitoring methods and the most relevant locations for monitoring points in Annex II shall be
adopted in accordance with the procedure laid down in Article 12. When elaborating these proposals the
Commission shall take into account inter alia the relevant provisions under existing legislation or appropriate
monitoring programmes including monitoring results as derived from them. The Commission shall submit these
proposals at the latest within 18 months following the date referred to in Article 18 of the Directive.
2. A Member State is not required to monitor drinking water for tritium or radioactivity to
establish total indicative dose where it is satisfied that, on the basis of other monitoring carried out, the levels of
tritium of the calculated total indicative dose are well below the parametric value. In that case, it shall
communicate the grounds for its decision to the Commission, including the results of this other monitoring carried
out.
116
Parameters of Water Quality - Interpretation and Standards
Health/Sanitary Significance: Direct health effects depend on the precise composition of the
turbidity-causing materials, but there are other implications, as discussed below.
Background Information: Turbidity in water arises from the presence of very finely divided
solids (which are not filtrable by routine methods). The existence of turbidity in water will affect
its acceptability to consumers and it will also affect markedly its utility in certain industries. The
particles forming the turbidity may also interfere with the treatability of waters and in the case of
the disinfection process the consequences could be grave. As turbidity can be caused by sewage
matter in a water there is a risk that pathogenic organisms could be shielded by the turbidity
particles and hence escape the action of the disinfectant.
Comments: As indicated above, there is a relative multiplicity of units for turbidity in water, a
fact which has caused a marked degree of confusion at times. However, the position is rather
simpler than at first appears, as FTU (formazin), JTU (Jackson) and NTU (nephelometric) are
virtually equivalent and are used interchangeably. Silica units differ. The 1980 Drinking Water
Directive showed the following "parallel" MAC values for turbidity (from which the relationship
may be inferred): Jackson units [JTU/FTU/NTU] - MAC 4; Silica units - MAC 10 mg/l SiO2. It will
be noted below that Drinking Water Directive [98/83/EC] adverts to nephelometric units [NTU].
Turbidity : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value
Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
-
-
Acceptable
[1]
to consumers and
no abnormal change
_______________________________________________________________________________________
Notes
[1]
The Directive states that. "In the case of surface water treatment, Member States should strive for a
parametric value not exceeding 1.0 NTU (nephelometric turbidity units) in. the water ex treatment works."
98. URANIUM
Chemical Symbol or Formula:
U.
Units Used for Analytical Results:
mg/l U.
Normal Method(s) of Analysis: Radiometric or Fluorometric techniques [D]
Occurrence/Origin: Rare natural occurrence; equally rare in effluents.
Health/Sanitary Significance: Highly toxic, with a variety of effects leading ultimately to death.
Background Information: This radioactive element is used in the nuclear industry and is thus
far from being universally encountered. There is no general concern in the context of drinking
water quality. The EU controls arise in the Dangerous Substances and Ground Water Directives
which seek to limit discharges.
Comments: There are atomic absorption spectrometric procedures for uranium analysis but (ICP
analysis excepted) their sensitivity is generally inadequate for very low levels.
117
Parameters of Water Quality - Interpretation and Standards
Uranium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
99. VANADIUM
Chemical Symbol or Formula:
V.
Units Used for Analytical Results:
mg/l V.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Widespread in rocks and minerals.
Health/Sanitary Significance:
Some undesirable physiological effects (e.g. ear, nose, throat
irritation) but not a hazard of significance in water.
Background Information: This element is naturally quite abundant and in addition relatively
large amounts enter the environment from industrial and related activities.
Comments: Levels for other than human life are quite low.
Vanadium : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
List II substance
Ground Water Directive [80/68/EEC]
List II substance
_______________________________________________________________________________________
100. VINYL CHLORIDE
Chemical Symbol or Formula:
C2H3Cl.
Units Used for Analytical Results:
µg/l C2H3Cl.
Normal Method(s) of Analysis:
Gas Chromatography [C].
Occurrence/Origin: Synthetic gaseous compound which polymerises very readily and is an
important raw material in the manufacture of plastics. It is also used as a refrigerant.
118
Parameters of Water Quality - Interpretation and Standards
Health/Sanitary Significance: Being very volatile it can caused local frostbite, if spilled on
skin, as it evaporates. More importantly, it is a suspected causative agent of liver cancer.
Background Information: Although a very reactive monomer which forms plastic polymers
very easily, it is almost inevitable that in some cases the resultant polymer - the most common of
which is polyvinyl chloride or PVC - will contain vestigial amounts of vinyl chloride itself. Thus, in
the first use, in particular, of vessels made of PVC there is the possibility of residual monomer
gaining access to water. The note in Drinking Water Directive [98/83/EC] is appended with this in
mind (q.v.).
Comments: Vinyl chloride was not a parameter in Directive [80/778/EEC].
Vinyl Chloride : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Drinking Water Directive [98/83/EC]
µg/l
n/a
0.50
[1]
_______________________________________________________________________________________
Notes
[1] Note 1 states that “The parametric value refers to the residual monomer concentration in the water as
calculated according to specifications of the maximum release from the corresponding polymer in contact
with the water.”
101. ZINC
Chemical Symbol or Formula:
Zn.
Units Used for Analytical Results:
mg/l Zn.
Normal Method(s) of Analysis:
Atomic Absorption Spectrometry [B/C].
Occurrence/Origin: Natural geological occurrence and from wastes.
Health/Sanitary Significance: Inhalation of zinc-containing fumes can cause a variety of
physiological effects, but principal significance of excessive amounts in water is that emetic effects
occur.
Background Information: Zinc is essential to man but if ingested in gross amounts it has an
emetic effect. However, the concern in water supply arises in regard to taste not toxicity, and quite
high levels are permissible. In fishery water, in contrast, the toxic action is much more important
and very much lower limits have been imposed.
Comments: The toxicity of zinc to aquatic life is (as with copper) dependent on the hardness of
the water: it decreases with rising hardness.
Zinc : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
mg/l Zn
n/a
3.0
mg/l Zn
n/a
5.0
mg/l Zn
n/a
5.0
_______________________________________________________________________________________
Surface Water Regulations [1989]
A1 waters
A2 waters
A3 waters
119
Parameters of Water Quality - Interpretation and Standards
Zinc : Recommended or Mandatory Limit Values
_______________________________________________________________________________________
EU Directive or National
Units of
G
I/PV
Note(s)
[Ministerial] Regulations
Analysis
Value Value
_______________________________________________________________________________________
Dangerous Substances Directive [76/464/EEC]
Freshwater Fish Directive [78/659/EEC]
(S)
(C)
Salmonid Waters Regulations [1988]
List II substance
mg/l Zn
n/a
< 0.3
[1]
mg/l Zn
n/a
< 1.0
[1]
[2,6]
mg/l Zn
n/a
< 0.03
[3,6]
mg/l Zn
n/a
< 0.2
[4,6]
mg/l Zn
n/a
< 0.3
mg/l Zn
n/a
< 0.5
[5,6]
Shellfish Directive [79/923/EEC]
mg/l Zn
[7]
[8]
Ground Water Directive [80/68/EEC]
List II substance
Drinking Water Directive [98/83/EC]
[9]
_______________________________________________________________________________________
Notes
[1]
Parameter is "Total zinc." The I values given are with reference to a hardness value of 100 mg/l
CaCO3 .
Relevant values for other hardness levels are as follows;
_______________________________________________________________
Hardness
10
50
100 500 mg/l CaCO3
_______________________________________________________________
Zinc (S) [salmonid]
0.03 0.2 0.3 0.5 mg/l Zn
(C) [cyprinid]
0.3 0.7 1.0 2.0 mg/l Zn
_______________________________________________________________
[2] Standard applies to water of hardness
10 mg/l
CaCO3
[3]
Standard applies to water of hardness
50 mg/l
CaCO3
[4]
Standard applies to water of hardness
100 mg/l
CaCO3
[5]
Standard applies to water of hardness
500 mg/l
CaCO3
[6]
Standard to be conformed with by 95% of samples over a period of 12 months where sampling is
carried out at least once per month; where sampling is less frequent the standard shall be conformed with by
all samples.
[7]
"The concentration of [this] substance in shellfish flesh must be so limited that it contributes, in
accordance with Article 1 [of the Directive], to the high quality of shellfish products."
[8]
"The concentration of [this] substance in the shellfish water or in the shellfish flesh must not exceed a
level which gives rise to harmful effects on the shellfish and their larvae. The synergic effects of [this and
other specified] metals must be taken into consideration."
[9] The MAC values specified in Directive [80/778/EEC] have not been carried forward to Directive
[98/83/EC], and the latter makes no reference to zinc.
120
Parameters of Water Quality - Interpretation and Standards
APPENDICES
Appendix 1
VARIATIONS IN WATER QUALITY IN SPACE AND TIME
___________________________________________________________________________________________
---------------------------------------------
Effects of
Note
River
Lake
x
Raw
x
x
TYPE OF WATER
Drinking
x
x
Bathing
x
x
---------------------------------Fishing
Shellfish
Ground
x
___________________________________________________________________________________________
Variations in Space
Geological formations
Bogs (worked or not)
Discharges from towns
Other point-source dischrgs
Diffuse discharges
Tributary streams
Tides
Distribution systems
x
x
x
x
x
x
x
-
x
x
x
x
x
x
-
x
x
x
x
x
x
-
x
x
x
x
x
-
x
x
x
x
x
x
-
x
x
x
x
-
x
x
x
x
-
1
2
3
3
4
5
6
7
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
-
x
x
x
x
x
x
x
x
x
x
-
x
x
x
8
9
10
11
12
Variations in Time
Variations in discharges
Eutrophic’n/Photosynthesis
Flooding/Rainstorms
Changes in land use
Agriculture/Climate
___________________________________________________________________________________________
NOTES
1.
The principal effect is on the hardness of the water although in ore-bearing areas the metals content
will be affected. This may lead to direct or indirect consequences for drinking water sources and fishery
waters, the former being the toxicity of some metals and the latter the effects of hardness. If hardness is
very high the water may need softening before use in large supplies. However, the toxic effect of metals is
less pronounced in hard than in soft waters.
2.
Peaty waters are characteristically of high colour which may render them unacceptable for drinking or
bathing on aesthetic grounds. They may also be acid and therefore unsuitable for fish or for acceptance into a
distribution system on the grounds of corrosion. In worked bog areas there is a likelihood of high suspended
solids which will damage fishery waters both by direct interference with fish and by settling on the bed with
consequent damage to spawning.
3.
The effects of discharges from point sources (sewage works, industries, intensive agriculture etc) are
physical, chemical and microbiological, depending on the precise nature of the pollutants being released.
Accordingly, waters of all types may be affected. Details of the effects are discussed fully under the headings
of the individual parameters in the main text.
4.
Diffuse discharges can also affect all waters, though the consequences are chronic rather than acute
and consist principally of eutrophication aspects (weed growths etc.).
5.
Depending on the quality of a tributary stream the receiving water body may be improved or become
more polluted below the confluence. The general characteristics of the receiving water may also be affected if
there are significant differences between it and the tributary in such parameters as hardness, colour etc.
121
Parameters of Water Quality - Interpretation and Standards
Appendix 1 : Variations in Water Quality in Space And Time : Continued
6.
The overriding tidal effect is of salinity, an increase in which will rule out a water as a source of public
or domestic supply. However, large variations in salinity in an estuary, for example, will affect shellfish
development. A consequential tidal effect in some estuaries is that a segment or "plug" of water containing a
pollution discharge may be subject to tidal movements and, instead of being dispersed promptly to sea, may
move up and down the estuary for a considerable time.
7.
These effects include the dissolution of metals from the distribution system, a well known case being
the attack of some waters on lead piping in houses: the loss of disinfection protection by absorption of
residual chlorine by organic matter in fouled mains; and the risk of bacterial recontamination in cracked or
leaking mains.
8.
Water quality may vary greatly because of changes in the composition of discharges over both short
and extended periods. Sewage discharges, for example, vary significantly from night to day and also within
the day. Some industrial discharges may be seasonal in nature and for many months of the year there may
be no effect on water quality.
9.
Eutrophication effects are seasonal and occur principally in the period of maximum sunlight, in
summertime. There are also in-day changes as a consequence of eutrophication. In daytime, when it is light,
algae will carry out photosynthesis, producing oxygen and possibly leading to supersaturation of dissolved
oxygen. At night, respiration predominates, with oxygen being consumed and dissolved oxygen levels falling.
The magnitude of this fall may have serious (even fatal) consequences for fish. In addition, the physical
presence of heavy algal growths affects the value of various types of water.
10. Changes caused as a result of floods include a lowering of the dissolved salts (by straightforward
dilution), an increase - often dramatic - in the colour of the water because of the stirring up of decaying
vegetable matter, and often, arising from the same cause, a large rise in suspended solids and biochemical
oxygen demand levels, which may consequently put the dissolved oxygen values at risk.
11. These long-term effects arise mainly from the intensification of animal-rearing, with the consequent
concentration of previously weaker or well dispersed wastes, and the making of silage on a large scale. The
resultant pollution will in many cases be point-source although in others (for example, the use of artificial
fertilisers and, in many instances, where animal slurries are spread on land) the effects are diffuse.
12. There is a close interrelationship between agricultural land use and climate, especially with regard to
such operations as the spreading of artificial fertilisers, the land-disposal of animal slurries, and the siting of
silage pits and soakaways. The adoption of incorrect procedures will lead to excessive runoff of nutrients and
organic matter in times of heavy rainfall.
Appendix 2
UNITS OF ANALYSIS
For very many parameters the results of analysis are expressed in terms of the weight of the
determinand per unit volume of water. For example, the expression 0.07 mg/l Mn represents a concentration
of 0.07 milligrams of manganese, expressed as Mn (i.e. as metal only, not in any of its compounds), per litre
of water. There is a significant number of other parameters, however, which are or may be described in
various terms, and it is essential that the usage of these be understood fully if serious errors of
interpretation are to be avoided. For convenience, the parameters covered in the present volume are grouped
below:
Individual Parameters expressed as themselves - Weight per unit Volume (w/v)
Acrylamide
Aluminium
Antimony
Arsenic
Barium
Benzene
_________________
1
µg/l compound
mg/l Al 1
mg/l Sb
mg/l As
mg/l Ba
µg/l compound
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(ghi)perylene
Benzo(k)fluoranthene
Beryllium
Boron
Or as µg/l Al, ng/l Al etc, as appropriate
122
µg/l compound
µg/l compound
µg/l compound
µg/l compound
mg/l Be
mg/l B
Parameters of Water Quality - Interpretation and Standards
Appendix 2 : Units of Analysis : Continued
Individual Parameters expressed as themselves - Weight per unit Volume (w/v) : Continued
Bromate
Cadmium
Calcium
Carbon Dioxide
Chloride
Chlorine
Chlorophyll
Chromium
Cobalt
Copper
Cyanide
1,2-Dichloroethane
Epichlorohydrin
Fluoride
lndeno(l,2,3-c,d)pyrene
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
mg/l BrO3
mg/lCd
mg/l Ca
mg/l CO2
mg/l Cl
mg/l Cl2
µg/l compound
mg/l Cr
mg/l Co
mg/l Cu
mg/l CN
µg/l compound
µg/l compound
mg/l F
µg/l compound
mg/l Fe
mg/l Pb
mg/l Mg
mg/l Mn
mg/l Hg
mg/l Mo
Nickel
mg/l Ni
Nitrogen, Kjeldahl
mg/l N
Oxygen, Dissolved
mg/l O2
Pesticides (Individual) µg/l individ compds
Potassium
mg/l K
Selenium
mg/l Se
Silver
mg/l Ag
Sodium
mg/l Na
Sulphate
mg/l SO4
Sulphide
mg/l S
Tellurium
mg/l Te
Tetrachloroethylene
µg/l compound
Thallium
mg/l Tl
Tin
mg/l Sn
Titanium
mg/l Ti
Trichloroethylene
µg/l compound
Uranium
mg/l U
Vanadium
mg/l V
Vinyl chloride
µg/l compound
Zinc
mg/l Zn
Bulk Parameters expressed as a single unit - Weight per unit Volume (w/v)
Acidity
Alkalinity
Hardness
Hydrocarbons, Dissolved and Emulsified
Methylene Blue Active Substances (MBAS)
Organic Carbon, Total
Organo-Halogenated Substances
Oxidisability
Oxygen Demand, Biochemical
Oxygen Demand, Chemical
Pesticides
Phenols
Polychlorinated Biphenyls & Terphenyls (PCBs & PCTs)
Polynuclear Aromatic Hydrocarbons (PAH)
Silicon, Toxic or Persistent Organic Compounds
Solids, Settleable
Solids, Suspended
Solids, Total
Solids, Total Dissolved
Substances affecting Taste
Substances Extractable in Chloroform
Substances which possess Carcinogenic, Mutagenic
or Teratogenic Properties
Tarry Residues and Floating Matter
Tin, Organo-Compounds
Trihalomethanes
____________________
mg/l CaCO3
mg/l CaCO3
mg/l CaCO3
mg/l dry weight
mg/l lauryl sulphate (see text)
mg/l C
mg/l halogen
mg/l O2
mg/l O2
mg/l O2
mg/l reference compounds 2
mg/l C6H5OH 3
mg/l reference material 4
mg/l reference compounds 2
mg/l Si
mg/l residue at given temperature
mg/l residue at given temperature
mg/l residue at given temperature
mg/l residue at given temperature
mg/l specific substances (see text)
mg/l dry residue
mg/l specific substances .(see text)
[descriptive assessment only]
mg/l Sn
µg/l total trihalomethanes 5
2
These, while apparently bulk parameters, are not strictly so, as each constituent in the mixture must be
expressed in w/v terms on its own.
3
It should also be noted that, in some cases, e.g. Phenols, the result for a group parameter is given in terms of a
single compound, in this case Phenol itself, C6H5OH
4
Because of the complexity of PCB/PCT mixtures it is impractical to report individual compound concentrations.
5
The individual concentrations of the four THM compounds are reported as µg/l of the respective compounds.
123
Parameters of Water Quality - Interpretation and Standards
Appendix 2 : Units of Analysis : Continued
Parameters expressed as units other than Weight per unit Volume
Clostridium perfringens (including spores)
Coliforms, Faecal [E. coli (Type 1)]
Coliforms, Total
Colony counts [22 °C & 37 °C]
Colour
Conductivity
Cryptosporidium
Enterococci
Enteropathogenic Viruses
Giardia
Odour
Pathogenic Staphyllococci
pH
Salinity
Salmonella
Taste
Temperature
Transparency
Turbidity
number/20 ml
number/100 ml
number/100 ml
number/ml at respective temperatures
mg/l Pt/Co [Hazen units]
µS/cm at stated temperature
number of cysts/100 litres
number/100 ml
PFU (Plaque-forming units) /10 litres
number of cysts/100 litres
dilution rate at stated temperature
number/100 ml
pH units
‰ (parts per thousand)
number/litre
dilution rate at stated temperature
degrees C/ ºC [Celsius]
metres (Secchi)
FTU (Formazin Turbidity Units) or NTU (Nephelometric Turbidity Units) or JTU (Jackson Turbidity
Units) or mg/l Silica (SiO2).6, 7
Individual Parameters commonly expressed in more than one unit (w/v)
Ammonia
Chlorine, Residual
Nitrate
Nitrite
Nitrogen, Kjeldahl
Phosphates
Phosphorus, Total
Silica
mg/l N
mg/l Cl
mg/l N
mg/l N
mg/l N
mg/l P
mg/l P
mg/l Si
mg/l NH4
mg/l PO4
-
mg/l NH3
mg/l HOCl
mg/l NO3
mg/l NO2
mg/l NH3
mg/l P2O5
mg/l PO4
mg/l SiO2.
The multiplicity of units generally arises from the chemical relationships between the different forms of
a parameter and/or from the nature of the analytical methodology used in its determination. In the case of
total phosphorus, for example, the most meaningful (and obvious) unit for the parameter is mg/l P.
However, the actual determination process involves the conversion of all the phosphorus forms in the sample
to orthophosphate (PO4) in which form it is measured and in terms of which it may not unreasonably be
expressed. A similar reasoning can be applied to ammonia, by which the unit mg/l N is most frequently
adopted in order to give a commonality of reporting with other forms of nitrogen. The term mg/l NH3 reflects
the form in which the species is determined, while mg/l NH4 arises from the chemical equilibrium between
different ammonia species.
Example:
Nitrate (NO3) may be reported as µg or mg/l NO3 or as µg or mg/l N. As the units of expression are in
direct relation to the atomic/molecular weights of the species in terms of which the results are quoted there
is in this example a four-fold difference in numerical terms between, the two expressions:
1
Nitrate as NO3
x
14
+
3
x
ATOMIC WT.
OF NITROGEN
1
Nitrate as N
x
16
=
ATOMIC WT.
OF OXYGEN
14
=
ATOMIC WT.
OF NITROGEN
NO3
:
N
=
7
14
ATOMIC WT.
OF NITROGEN
62
:
14
________________
6
62
MOLECULAR WT.
OF NITRATE
See suitable analytical text for further details of procedures, units etc.
Note that not all the commonly used units for turbidity are equivalent.
124
=
4.43 :
1
Parameters of Water Quality - Interpretation and Standards
Appendix 2 : Units of Analysis : Continued
General Observations
The following additional points should also be noted concerning the expression of analytical results.
Firstly, the most common expression is as "milligrams/litre" (mg/l), i.e. an expression of weight per unit
volume [w/v]. The term "parts per million" (ppm) implies a relationship of either volume with volume [v/v] or
weight with weight [w/w]. However, as the density of water is almost exactly unity, 1 ml weighing 1 gram,
the terms "parts per million" (v/v) and "milligrams/litre" (w/v) are in effect synonymous and are widely
regarded as such. Preferred usage, however, is mg/l rather than ppm. One reason for the avoidance of the
expression "parts per million" is that it can easily lead to the term "parts per billion" when dealing with
micropollutants, for example. An ambiguity could possibly arise because of the 1000-fold difference between
the American "billion" and the established (though currently changing) English meaning of the word.
Secondly, in the case of micropollutants which are present normally in water in infinitesimal amounts,
common practice is to use such terms as microgram per litre (ng/l) or even nanograms per litre (ng/l). The
relationship between them is:
1 milligram/litre
1 microgram/litre
1 milligram/litre
=
=
=
1,000
1,000
1,000,000
micrograms/litre
nanograms/litre
nanograms/litre.
Occasionally, hardness and alkalinity values, in particular, are quoted in terms of milliequivalents per
litre (meq/l). The normal expression of these determinands is as concentrations of CaCO3, the molecular
weight of which is 100 and the equivalent weight 50. The conversion to meq/l is therefore:
X mg/l CaCO3 =
X / 50 meq/l CaCO3.
Appendix 3
CONCENTRATIONS IN MILLIGRAMS/LITRE OF TOTAL AMMONIA IN FRESH WATER
WHICH CONTAIN AN UN-IONISED AMMONIA CONCENTRATION OF 0.02 mg/l NH3
____________________________________________________________________________________________________
pH
6.0
6.5
7.0
7.5
8.0
8.9
9.0*
9.5*
Temp (° C)
____________________________________________________________________________________________________
5
160.
51.
16.
5.1
1.6
0.53
0.18
0.071
10
110.
34.
11.
3.4
1.1
0.36
0.13
0.054
15
73.
23.
7.3
2.3
0.75
0.25
0.09
0.043
20
50.
16.
5.1
1.6
0.52
0.18
0.07
0.036
25
35.
11.
3.5
1.1
0.37
0.13
0.055
0.031
30
25.
7.9
2.5
0.8
0.27
0.10
0.045
0.028
____________________________________________________________________________________________________
* Criteria may be unduly low if there is low free carbon dioxide in the water.
[NOTE that the value of 0.02 mg/l NH3 is a long-term toxic effect level for fish,
both salmonid and cyprinid. Lethal levels are about ten times greater].
____________________________________________________________________________________________________
References
European Inland Fisheries Advisory Commission, 1970. Water Quality Criteria for European Freshwater Fish, Report
on Ammonia and Inland Fisheries. EIFAC Technical Paper No 11.
Thurston, R.V., et al., 1974. Aqueous Ammonia Equilibrium Calculations. Fisheries Bioassay Laboratory Technical
Report No. 74 - 1, Montana State University.
125
Parameters of Water Quality - Interpretation and Standards
Appendix 4
SATURATION INDEX - LANGELIER INDEX - CALCIUM CARBONATE SATURATION INDEX
Background
A water with a pH value under 7 may dissolve metals to an extent which, if not causing deterioration
of storage tanks or distribution mains, may nonetheless give rise to undesirable metal concentrations. Such
waters are also unlikely to deposit calcium carbonate as a protective scale in pipes. The interrelationship
between pH, hardness and alkalinity was studied by Langelier who in 1936 proposed a means of calculating
the corrosivity or scale-forming tendencies of a water.
Significance
Langelier took account of calcium concentration, alkalinity, pH, temperature and total dissolved solids
[TDS] concentration in postulating the saturation pH or pHs. This is the pH value at which the water would
be just saturated with respect to calcium carbonate.
The Langelier Index is:
pH
actual pH
-
pHs
saturation pH [calculated].
A value of zero indicates a stable water. If the value of the Index is negative the water will tend to dissolve
calcium carbonate and, by inference, be corrosive. A positive Index indicates scale-forming propensities.
Calculation Method
There is no direct analysis involved. Instead, the Index is calculated from the values observed for the
relevant parameters, in conjunction with constants from the tables given below. It should be noted that the
following is a modified equation (by Larson):
pHs
=
A
+
B – log [Ca++]
–
log [alkalinity]
where A and B are constants as functions of temperature and TDS, respectively, and [ ] indicates concentrations as mg/litre CaCO3.
Interpretation of Index
It must be remembered that the Index gives an indication of how a water may behave with respect to
corrosion of or deposition of scale on distribution mains. A water with a positive Index may not, in fact,
deposit scale, perhaps because of the presence of polyphosphates which act as sequestering agents, or it may
do so erratically and not give a protective shell.
Table 1
____________________
Table 2
___________________
Table 3
___________________________________________
Temp. of Constant
Sample
A
deg C
____________________
TDS of
Constant
Sample
B
mg/l
___________________
[Ca++] or
[Ca++] or
[alkalinity]
Log.
[alkalinity] Log.
mg/l CaCO3
mg/l CaCO3
___________________________________________
0
2.60
4
2.50
8
2.40
12
2.30
16
2.20
20
2.10
____________________
0
9.70
100
9.77
200
9.83
400
9.86
800
9.89
1000
9.90
___________________
10
1.00
200
2.30
20
1.30
300
2.48
30
1.48
400
2.60
40
1.60
500
2.70
50
1.70
600
2.78
60
1.78
700
2.84
70
1.84
800
2.90
80
1.90
900
2.95
100
2.00
1000
3.00
___________________________________________
126
Parameters of Water Quality - Interpretation and Standards
Appendix 5
A : SUPPLEMENTARY LIST OF EU DIRECTIVES CONCERNING
THE AQUATIC ENVIRONMENT 1
____________________________________________________________________________________________________
Formal Title [with date adopted & O.J.2 reference]
Informal Title
____________________________________________________________________________________________________
Council Directive 82/176/EEC of 22 March 1982 on limit values and quality
objectives for mercury discharges by the chlor-alkali electrolysis industry.
[O.J., L 81, 27 March 1982]
Mercury from ChlorAlkali industry
Council Directive 83/513/EEC of 26 September 1983 on limit values and quality
objectives for cadmium discharges. [O.J., L 291, 24 October 1983]
Cadmium
Council Directive 84/156/EEC of 8 March 1984 on limit values and quality
Objectives for mercury discharges by sectors other than the chlor-alkali
electrolysis industry. [O.J., L 74, 17 March 1984]
Mercury from other
than Chlor-Alkali
industry
Council Directive 84/491/EEC of 9 October 1984 on limit values and quality
objectives for discharges of hexachlorocyclohexane. [O.J., L 274, 17 October 1984]
Hexachlorocyclohexane
Council Directive 85/337/EEC of 27 June 1985 on the assessment of the effects
of certain public and private projects on the environment.
[O.J., L 175, 05 July 1985]
Environmental Impact
Council Directive 86/278/EEC of 12 June 1986 on the protection of the
Environment and in particular of the soil when sewage sludge is used in
agriculture. [O.J., L 181, 8 July 1986]
Sewage Sludge
Council Directive 86/280/EEC of 12 June 1986 on limit values and quality
objectives for discharges of certain dangerous substances included in List I of
the Annex to Directive 76/464/EEC. [O.J., L 181, 8 July 1986]
List I Substances
["Standard Articles"]
Council Directive 88/347/EEC of 16 June 1988 amending Annex II to Directive
86/280/EEC. [O.J., L 158, 25 June 1988]
[Chlorinated
Compounds]
Council Directive 90/415/EEC of 27 July 1990 amending Annex II to Directive
86/280/EEC. [O.J., L 219, 14 August 1990]
EDC/TRI/PER/TCB 3
Council Directive 91/271/EEC of 21 May 1991 concerning urban wastewater
treatment, [O.J., L135, 30 May 1991]
Urban Waste Water
Council Directive 91/414/EEC of 15 July 1991 concerning the placing of plant
protection products on the market. [O.J., L 206, 22 July 1992]
Plant Protection
Council Directive 91/676/EEC of 12 December 1991 concerning the protection
of waters against pollution caused by nitrates from agricultural sources.
[O.J., L375,31 December 1991]
Nitrates
Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural
habitats and of wild flora and fauna. {O.J., L 206, 22 July 1992]
Habitats
Council Directive 96/6 I/EC of 24 September 1996 concerning integrated pollution prevention and control. {O.J., L 257, 10 October 1996]
IPPC
Council Directive 96/82/EC of 9 December 1996 on the control of major-accident
hazards involving dangerous substances. [O.J., L 10, 14 January 1997]
_________________________
Seveso
1
In addition to these Directives there is an important related EU document which is relevant in the context of the
present volume although it will be supplanted by an Annex of the Water Framework Directive (with a similar purpose) :
Communication from the Commission to the Council on dangerous substances which might be included in List I of
Council Directive 76/464/EEC. [O.J., C 176. 14 July 1982]. (The so-called “List of 129 Substances”).
2
O. J. denotes the Official Journal of the European Communities in which Directives etc are published
3
EDC: 1,2-Dichloroethane: TRI: Trichloroethylene: PER: Perchloroethylene; TCB: Trichlorobenzene.
127
Parameters of Water Quality - Interpretation and Standards
B : SUPPLEMENTARY LIST OF NATIONAL REGULATIONS CONCERNING
THE AQUATIC ENVIRONMENT 3
____________________________________________________________________________________________________
Title [with Statutory Instrument (S.I.) reference]
____________________________________________________________________________________________________
Local Government (Water Pollution) (Control of Cadmium Discharges) Regulations, 1985. [S.I. No 294 of
1985.]
Local Government (Water Pollution) Act, 1977 (Control of Hexachlorocyclohexane and Mercury Discharges)
Regulations, 1986. [S.I. No 55 of 1986.]
European Communities (Quality of Water Intended for Human Consumption) Regulations, 1988. [S.I. No 81
of 1988. 4]
European Communities (Quality of Salmonid Waters) Regulations, 1988. [S.I. No 293 of 1988.]
European Communities (Quality of Surface Water Intended for the Abstraction of Drinking Water)
Regulations, 1989. [S.I. No 294 of 1989. 5]
Quality of Bathing Water Regulations, 1992. [S.I. No 155 of 1992.]
Local Government (Water Pollution) Regulations, 1992. [S.I. No 271 of 1992.]
Local Government (Water Pollution) Acts, 1977 and 1990 (Control of Aldrin, Dieldrin, Endrin, Isodrin, HCB,
HCBD and CHCl3 Discharges), Regulations, 1993. [S.I. No 348 of 1993.S]
Quality of Shellfish Waters Regulations, 1994. [S.I. No 200 of 1994.]
Local Government (Water Pollution) Acts, 1977 and 1990 (Control of Carbon tetrachloride, DDT and
Pentachlorophenol Discharges), Regulations, 1994. [S.I. No 43 of 1994.]
Local Government (Water Pollution) Acts, 1977 and 1990 (Control of EDO, TRI, PER and TCB Discharges),
Regulations, 1994. [S.I. No 245 of 1994.5 ]
Environmental Protection Agency Act, 1992, [Urban Waste Water Treatment] Regulations, 1994. [S.I. No
419 of 1994.]
Quality of Bathing Water Regulations, 1996. [S.I. No 230 of 1996.]
Local Government (Water Pollution) (Nutrient Management Planning Consultation) Regulations, 1998.
[S.I. No 257 of 1998.]
Local Government (Water Pollution) Act, 1977 (Water Quality Standards for Phosphorus) Regulations, 1998.
[S.I. No 258 of 1998.]
Protection of Groundwater Regulations, 1999. [S.I. No 41 of 1999.]
________________
3
For the sake of completeness details of the Regulations (where adopted) corresponding to the
Directives listed in Part A are presented below.
4
These Regulations are the topic of a publication "A Handbook on Implementation for Sanitary Authorities."
There are separate handbooks for the Drinking Water and Surface Water Regulations. The latter is out of print but a
new edition of the Drinking Water Handbook has been published by the EPA.
5
CHCl3 Chloroform; HCB; Hexachlorobenzene; HCBD; Hexachlorobutadiene.
6
See footnote 3 on page 127.
128
Parameters of Water Quality - Interpretation and Standards
Appendix 6
DANGEROUS SUBSTANCES DIRECTIVE 76/464/EEC
LIST I & LIST II SUBSTANCES
LIST I OF FAMILIES AND GROUPS OF SUBSTANCES
List I contains certain individual substances which belong to the following families and groups of substances,
selected mainly on the basis of their toxicity, persistence and bioaccumulation with the exception of those
which are biologically harmless or which are rapidly converted into substances which are biologically
harmless.
1.
Organohalogen compounds and substances which may form such compounds in the aquatic
environment
2.
Organophosphorus compounds
3.
Organotin compounds
4.
Substances in respect of which it has been proved that they possess carcinogenic properties
in or via the aquatic environment 1
5.
Mercury and its compounds
6.
Cadmium and its compounds
7.
Persistent mineral oils and hydrocarbons of petroleum origin
And for the purpose of implementing Articles 2, 8, 9 and 14 of this Directive:
8.
Persistent synthetic substances which may float, remain in suspension or sink and which
may interfere with any use of the waters.
LIST II OF FAMILIES AND GROUPS OF SUBSTANCES
List II contains:
Substances belonging to the families and groups of substances in List I for which the limit
values referred to in Article 6 of the Directive have not been determined
Certain individual substances and categories of substances belonging to the families and
groups of substances listed below
and which have a deleterious effect on the aquatic environment, which can, however, be confined to a given
area and which depend on the characteristics and location of the water into which they are discharged.
Families and groups of substances referred to in the second indent:
1.
The following metalloids and their compounds:
1 Zinc
6 Selenium
11 Tin
16 Vanadium
2 Copper
7 Arsenic
12 Barium
17 Cobalt
3 Nickel
8 Antimony
13 Beryllium
18 Thallium
4 Chromium
9 Molybdenum 14 Boron
19 .Tellurium
5 Lead
10 Titanium
15 Uranium
20 Silver.
2.
Biocides and their derivatives not appearing in List I
3.
Substances which have a deleterious effect on the taste and/or smell of the products for human
consumption derived from the aquatic environment, and compounds liable to give rise to such
substances in water
4.
Toxic or persistent organic compounds of silicon and substances which may give rise to such
compounds in water, excluding those which are biologically harmless or are rapidly converted
in water into harmless substances
5.
Inorganic compounds of phosphorus and elemental phosphorus
6.
Non-persistent mineral oils and hydrocarbons of petroleum origin
7.
Cyanides, fluorides
8.
Substances which have an adverse effect on the oxygen balance, particularly:
ammonia, nitrites.
________________
1
Where certain substances in List II are carcinogenic they are included in category 4 of this list.
129
Parameters of Water Quality - Interpretation and Standards
Appendix 7
GROUNDWATER DIRECTIVE 80/68/EEC
LIST I & LIST II SUBSTANCES
LIST I OF FAMILIES AND GROUPS OF SUBSTANCES
List I contains the individual substances which belong to the families and groups of substances
enumerated below, with the exception of those which are considered inappropriate to List I on the basis of a
low
risk of toxicity, persistence and bioaccumulation.
Such substances which with regard to toxicity, persistence and bioaccumulation are appropriate to List
II are to be classed in List II.
1.
2.
3.
4.
5.
6.
7.
8.
Organohalogen compounds and substances which may form such compounds in the aquatic
environment
Organophosphorus compounds
Organotin compounds
Substances which possess carcinogenic, mutagenic or teratogenic properties in or via the
aquatic environment 1
Mercury and its compounds
Cadmium and its compounds
Mineral oils and hydrocarbons
Cyanides.
LIST II OF FAMILIES AND GROUPS OF SUBSTANCES
List II contains the individual substances and the categories of substances belonging to the families
and groups of substances listed below which could have a harmful effect on groundwater.
1.
2.
3.
4.
5.
6.
7.
The following metalloids and metals and their compounds:
1 Zinc
6 Selenium
11 Tin
16 Vanadium
2 Copper
7 Arsenic
12 Barium
17 Cobalt
3 Nickel
8 Antimony
13 Beryllium
18 Thallium
4 Chrome
9 Molybdenum
14 Boron
19 Tellurium
5 Lead
10 Titanium
15 Uranium
20 Silver.
Biocides and their derivatives not appearing in List I
Substances which have a deleterious effect on the taste and/or odour of groundwater and
compounds liable to cause the formation of such substances in such water and to render
it unfit for human consumption
Toxic or persistent organic compounds of silicon, and substances which may cause the formation of such compounds in water, excluding those which are biologically harmless or are
rapidly converted in water into harmless substances
Inorganic compounds of phosphorus and elemental phosphorus
Fluorides
Ammonia and nitrites.
________________
1
Where certain substances in List II are carcinogenic, mutagenic or teratogenic, they are included in category 4 of
this list.
130
Parameters of Water Quality - Interpretation and Standards
Appendix 8
WORLD HEALTH ORGANISATION GUIDELINES [1993] FOR THE
Bacteriological Quality of Drinking-water a
____________________________________________________________________________________________________
Organisms
Guideline value
____________________________________________________________________________________________________
All water intended for drinking
E. coli or thermotolerant coliform bacteria b
Must not be detectable in any 100-ml sample
Treated water entering the distribution system
E. coli or thermotolerant coliform bacteria b
Total coliform bacteria
Must not be detectable in any 100-ml sample
Must not be detectable in any 100-ml sample
Treated water in the distribution system
E. coli or thermotolerant coliform bacteria b
Must not be detectable in any 100-ml sample
Total coliform bacteria
Must not be detectable in any 100-ml sample. In the
case of large supplies, where sufficient samples are
examined, must not be present in 95% of samples
taken throughout any 12-month period
____________________________________________________________________________________________________
a
Immediate investigative action must be taken if either E. coli or total coliform bacteria are
detected. The minimum action in the case of total coliform bacteria is repeat sampling; if these bacteria are
detected in the repeat sample, the cause must be determined by immediate further investigation.
b
Although E. coli is the more precise indicator of faecal pollution, the count of thermotolerant
coliform bacteria is an acceptable alternative. If necessary, proper confirmatory tests must be carried out.
Total coliform bacteria are not acceptable indicators of the sanitary quality of rural water supplies,
particularly in tropical areas where many bacteria of no sanitary significance occur in almost all untreated
supplies.
____________________________________________________________________________________________________
Source: Guidelines for drinking-water quality, Second Edition, World Health Organisation, Geneva. 1993.
131
Parameters of Water Quality - Interpretation and Standards
Appendix 9
WORLD HEALTH ORGANISATION RECOMMENDED TREATMENTS
FOR DIFFERENT WATER SOURCES TO PRODUCE
WATER WITH NEGLIGIBLE VIRUS RISK a
____________________________________________________________________________________________________
Type of Source
Recommended Treatment
____________________________________________________________________________________________________
GROUND WATER
Protected, deep wells: essentially free of faecal contamination
Disinfection b
Unprotected, shallow wells; faecally contaminated
Filtration and disinfection
SURFACE WATER
Protected, impounded upland water; essentially free of faecal
contamination
Disinfection
Unprotected impounded water or upland river; faecal
contamination
Filtration and disinfection
Unprotected lowland rivers; faecal contamination
Pre-disinfection or storage, filtration,
disinfection
Unprotected watershed; heavy faecal contamination
Pre-disinfection or storage, filtration,
additional treatment and disinfection
Unprotected watershed; gross faecal contamination
Not recommended for drinking-water
supply
____________________________________________________________________________________________________
a
For all sources, the median value of turbidity before terminal disinfection must not exceed 1
nephelometric turbidity unit (NTU) and must not exceed 5 NTU in single samples.
Terminal disinfection must produce a residual concentration of free chlorine of > 0.5 mg/litre after
at least 30 minutes of contact in water at pH < 8.0, or must be shown to be an equivalent disinfection
process in terms of the degree of enterovirus inactivation (> 99.99%).
Filtration must be either slow sand filtration or rapid filtration (sand, dual, or mixed media) pre
ceded by adequate coagulation-flocculation (with sedimentation or flotation). Diatomaceous earth filtration or a filtration process demonstrated to be equivalent for virus reduction can also be used. The
degree of virus reduction must be > 90%.
Additional treatment may consist of slow sand filtration, ozonation with granular activated carbon
adsorption, or any other process demonstrated to achieve > 99°/o enterovirus reduction.
Disinfection should be used if monitoring has shown the presence of E. coli or thermotolerant
coliform bacteria.
____________________________________________________________________________________________________
b
Source: Guidelines for drinking-water quality, Second Edition, World Health Organisation, Geneva. 1993.
132