Water and Wasterwater Treatment

The photocatalytic degradation of Toluidine Blue dye (TB) in aqueous solution was investigated under UV light in the presence of magnesium oxide (MgO) as a photocatalyst at different operating parameters. The operating
conditions were photocatalyst dose, initial dye concentration and the pH of the solution. Increasing of photocatalyst dose from 10 to 70 mg enhanced the degradation rate of TB dye. However, the increasing of TB dye concentration from 2 to 8 mg/L negatively affected the degradation rate. It was found that the percent of dye
removal reached the maximum value at high acidic medium. In dark condition, 15 % of dye was adsorbed by MgO. Furthermore, the kinetics involved in the degradation of TB dye was examined and the degradation was found to follow pseudo first order kinetic model.

This review paper is aimed to find out the role of plant based water treatment and its insecticides effects on the use of Moringa seeds powder, based on the previous research attempts and in comparison with some trials that are summed up in this review article. Consequently, the objective of the paper is to show different experiences and to understand how to access the activity of Moringa oleifera on the removal of physio chemical and biological impurities, present in turbid waters of tropical countries like India, and to expose their ideonity to help in the fight against diarrhea and other diseases, provoked by biotic and abiotic elements of waste waters.

The use of wastewater in agricultural irrigation has the potential for positive and negative environmental impacts.With careful planning and management, the use of wastewater can be beneficial to the environment. Constructedwetlands are usedworldwideforwastewater treatment, and this study discussesthe resultsofthesewetlandsincold and moderateregions ofthe world.Results show a remarkable BOD5 removal efficiency (58.8–99.84% of the influent BOD5 concentration( , even though only 62% of these wetlands were constructed following the U.S. EPA guidelines. The constructed wetlands can help remove TSS up to a level that is compatible with the quality standards for most reuse application in irrigation of crops. These wetlands cannot provide a water reclamation solution from a microbiological quality perspective that can meet reuse quality standards for irrigation.In terms of acidity, the effluent from constructed wetlands in cold climate is appropriate for irrigation of all crops. As a result, for reusing constructed wetland effluent in irrigation, combined systems like WSP-CW system require complying with the standard effluent for reuse water

Keywords:
Constructed wetlands, feasibility, irrigation, removal efficiency, reuse water

Pencemaran air adalah suatu perubahan keadaan di suatu tempat penampungan air seperti danau, sungai, lautan dan air tanah akibat aktivitas manusia. Danau, sungai, lautan dan air tanah adalah bagian penting dalam siklus kehidupan manusia dan merupakan salah satu bagian dari siklus hidrologi. Selain mengalirkan air juga mengalirkan sedimen dan polutan. Berbagai macam fungsinya sangat membantu kehidupan manusia. Pemanfaatan terbesar danau, sungai, dan air tanah adalah untuk irigasi pertanian, bahan baku air minum, dan kegiatan produksi lainnya, selain sebagai penampungan air baku, badan air juga sebagai saluran pembuangan air hujan dan air limbah, bahkan sebenarnya berpotensi sebagai objek wisata.

A strategy for adaptive control and energetic optimization of aerobic fermentors was implemented, with both air flow and agitation speed as manipulated variables. This strategy is separable in its components: control, optimization, estimation. We optimized parameter’s estimation (from the usual KLa correlation) using sinusoidal excitation of air flow and agitation speed. We have implemented parameter’s estimation trough recursive least squares algorithm with forgetting factor. We carried separate essays on control, optimization and estimation algorithms. We carried our essays using an original computational simulation environment, with noise and delay generating facilities for data sampling and filtering.

Our results show the convergence and robustness of the estimation algorithm used, improved with use of both forgetting factor and KLa dead-band facilities. Control algorithm used in our work compares favorably with PID using the integrated area criteria for deviation between oxygen molarity and critical molarity (set point). Optimization algorithm clearly reduces energetic consumption, respecting critical molarity. Integration of control, optimization and adaptive algorithms was implemented, but future work is needed for stability. Methods were defined and implemented for stability improvement. We have implemented data acquisition and computer manipulation of air flow and agitation speed for actual fermentors.

Nos últimos anos a urbanização ganhou cada vez mais forças, tornando-se um fenômeno global. De acordo com o Censo de 2010 da SEADE (Fundação Sistema Estadual de Análise de Dados), no Estado de São Paulo, o grau de urbanização já era de 88,64% em 1980, chegando a 95,94% em 2010. No município de Santo André, em particular, esse grau de urbanização é de 100% desde a década de 80. Esses números mostram como a população urbana passa a dominar o cenário na maioria das cidades, gerando novas demandas, necessidades e problemas a serem solucionados.
Uma boa alternativa para lidar com esse novo modelo de população e com as características da vida urbana - economia instável, alta densidade demográfica, deslocamentos pelo espaço, entre tantas outras – foi o uso de cenários prospectivos também na área do planejamento urbano.
A construção de cenários inicialmente é mais forte no planejamento militar e econômico. Porém, os centros urbanos, na segunda metade do século XX, passam a ser menos previsíveis, vivem em constantes crises e afundados em problemas, o que indica a necessidade de mudar a forma de planejar.
O futuro sempre foi uma preocupação das grandes civilizações, e a projeção de cenários criou uma situação mais confortável em relação a essas expectativas. Porém, descrever cenários de desenvolvimento urbano não é uma tarefa simples, pois suas variáveis relacionam-se com incertezas, comportamentos e a velocidade da comunicação.
Uma das etapas mais difundidas na projeção de cenários, entre os estudiosos, é o estudo demográfico. O IBGE, maior órgão de estudo demográfico e estatístico do país, divulga todos os anos censos que analisam mais de 500 fatores apenas para conclusões demográficas. Além de outros estudos sobre a população que podem auxiliar na complexa teia de informações que serve de base à construção de cenários.

Palavras-chave: Planejamento, urbanização, futuro, desenvolvimento, população.

Natural disaster such as earthquakes cause severe damage to water and wastewater facilities, other water and wastewater infrastructure in a city or small community and or industrial complex. There are numerous statistics and reports from around the world about the severe damage caused by accidents on the lifelines of various facilities, including water, wastewater and gas, electricity and telecommunications after a highintensity earthquake including severe damages and threats to public health and well-being in the kobe of Japan, Sommanra and Indonesia earthquakes and similar cases. In this article, we have tried to find ways to reduce the damage to the vital Lines.

Keywords: vital Lines, water, wastewater, crisis management

The population growth, added to the urbanization and the economic development, are indubitable causes of the increasing generation of waste, and in Brazil, its mismanagement highlights difficulties as to inadequate disposal, informal collection and insufficiency regarding the public collection system. Sewage sludge, which is waste, refers to an inevitable product of the wastewater treatment, with its inadequate disposal being an existing problem all around the world. To the national scenario, there is a lack of official information concerning the sewage sludge disposal. However, many authors have been searching for alternative ways to utilize and reutilize those biosolids. The purpose of this research was to map, using the Mapping Study methodology, the main trends of the use and disposal of sewage sludge in Brazil, based upon the technical and scientific work published from 2004 to 2014. The electronic publications were searched for on the SciELO database, CAPES, and the Google Scholar website. According to the scientometric data analysis proposed by this study, Brazilian reality as for the disposal of sewage sludge is either the vegetable production or the restoration of degraded lands, present in 91,7% of the publications found, drawing attention to agricultural application (82,1%), especially the corn production (19,9%). However, even lessened in numbers, lines of research on the use of biosolids for production of ceramic artifacts, civil construction and energy generation (8,3%), have swimmingly come into view. The State of São Paulo is the largest federal unit with technical and scientific production in the research area, reaching 61.8% of all articles found.

Proyecto de Tecnologías Apropiadas II, Manual de un Sistema de Recolección y Filtrado de Aguas grises Precedentes de Lavadoras.
Ve más con respecto a nuestro trabajo en el siguiente video de YouTube : https://youtu.be/DZKBHRUVjMU
Y para ver más sobre nuestro trabajo y el manual completo siguenos en nuestra cuenta de Instagram: @Coronafiltro

A batch leaching test was performed to measure the leached concentrations of
chromium (Cr), lead (Pb), arsenic (As), nickel (Ni), copper (Cu), cadmium (Cd), and zinc (Zn)
from dredged sediment samples from the Leeds & Liverpool canal/ Liverpool section. The
obtained results confirmed that the leached concentrations of the studied heavy metals were
less than the toxicity levels and followed the order: Zn > Cu > Ni > Pb > Cr > As > Cd. The
highest concentration was of Zn (about 0.28 mg/L), followed by Cu at a concentration of 0.17
mg/L, while the lowest concentration was of Cd at 0.009 mg/L. Therefore, the dredged
sediments from this canal can be safely relocated in dumping sites such as landfills, or reused
such as by spreading on agricultural fields.

The soil quality of a municipal solid waste dumpsite in Onitsha-Owerri road, Onitsha southeastern Nigeria was investigated for possible pollution impacts. Soil samples were collected from three sampling points each located within the dumpsite and a control away from the dumpsite at 0–15, 15–30 and 30–45cm depth profiles. Toxic metals were analyzed with the Atomic Absorption Spectrophotometer. Mean Ni, Fe, Pb, Mn, Zn, Cr and Cd concentrations were 2.04 ± 0.53, 287.14 ± 69.76, 16.12 ± 4.16, 90 ± 18.12, 91.11±19.88, 16.52 ± 4.01 and 9.54± 1.49 mg/kg. The one-way analysis of variance (ANOVA) test revealed that the levels of the ANALYSIS ARTICLE Page42 ANALYSIS edaphic parameters differed significantly across the soil depths [F(11.24) >Fcrit(3.97)] at P<0.05. A post-hoc means plots that utilized the middle soil profile (30-45cm soil depth) as predictor variable revealed that at the top (0-15cm depth) and bottom (30-45cm depth) soil profiles, Mn (160.20mg/kg), Zn (191.00mg/kg) and Fe (600.20mg/kg) contributed mostly to the observed differences. The edaphic variables measured in this study revealed very significant interactions. All the variables correlated significant with the heavy metals at P<0.01. The wastes at the dumpsite impacted on the overlying soil pedons as well as the high porous sand compositions and high toxic metal levels could make groundwater aquifer of the area vulnerable to pollution from surface point source.

Groundwater contamination with arsenic, a geo environmental hazard, is reported throughout the globe. The scale and spread of the contamination has reached at an alarming level. The recommended maximum concentration limit for arsenic is 10 μg/L in drinking water. However, much higher concentration of arsenic in groundwater is reported in several countries including India. The arsenic source is geological, specifically through leaching of arsenic bearing minerals. The ground water with high arsenic content has high iron, manganese, bicarbonate and low fluoride, sulphate and chloride content. A continuous and long term exposure of arsenic contaminated water shows significant impact on living organisms, effecting human health ailment through food chain. Such health damage as is irreversible the only solution left is to avoid arsenic free water. The adsorptive removal is the most popular technique considering the operational simplicity, applicability in wide range of solution condition and repetitive use of adsorbent via recycling. However, biopolymer, due to its degradable character and easy availability in nature, becomes a popular choice for preparation of new generation adsorbents. Cellulose being the most abundant biopolymer in nature, on modification with transition metal e.g. cerium, iron or aluminum is used for arsenic removal from laboratory samples. The adsorbent was characterized by FTIR, FESEM, EDS and EPR studies. The adsorption kinetics was established by Pseudo 1st order kinetic model. The process was applied for removal of arsenic from some real samples.

ABSTRACT: The increased rate of industrialization coupled with rapid urbanization in Pakistan has given rise to serious water pollution and environmental problems. A vast range of industries has been established in the country during the last twenty five years, including tanneries, fertilizers, textiles, refineries, chemicals, vegetable oils, paper and pulp, sugar and food industries. Little attention however, has paid towards a large scale release of wastewater from these industries. Presently, wastewater produced from these industries has been consider- ed a serious problem and research is being conducted to solve its associated problems. Recently, it has been realized that there is a significant threat of water-borne diseases, degradation of freshwater quality, environmental depletion and soil deterioration from the effluent and toxic emission of industries. Being a developing country and having limited resources, it is hard to install treatment plants on the industrial effluent with every industry before discharging them into streams. In this paper, an effort has been made to solve wastewater problems by implementing statistical tools on data of Karachi industrial state.

This research study was focused on treating domestic wastewater by electrocoagulation using iron and aluminum electrodes. The routine Physico chemical characteristics viz., COD, BOD5, Nitrate, Phosphate, Electrical conductivity, TDS and pH were considered to evaluate the treatment efficiencies. A glass reactor of capacity 1.3 L with a working volume of 1 L into which electrodes were immersed was used. Reactor operating conditions was contact period and potential applied across the electrode (5, 10, 15V). Two Electrode configurations with Fe-Al and four electrode configuration with Fe-Al-Fe-Al were considered. The promising results were obtained in removal of considered parameters with increase in number of electrodes. For 4 electrode configuration with 30min contact period, removal efficiency of PO4, NO3 and COD were 94%, 86% and 98% respectively. BOD5 removal was higher than 80% for both 2 and 4 electrode configuration employed.

Nowadays with concern of water resources reduction, it is more common to use other resources such as filtered sewage using in irrigation and agriculture. Although this solution is the sub tree of a stable management of water resources, but with the researches that have been made by the scientists, it has a bad influence and would cause the poisoning of the soil with the heavy elements because of the wastewater. Due to the results of the long time research, phytoremediation usage would increase the stability of this solution. This way is much cheaper than filtering the additional wastes which are used. The main problem for doing any activity due to filtering of metal pollution, is finding the kind of pollutant metals, so in regarded to that we could use hyper accumulator plants. In this research, we examine classified heavy metals with the producer factories. Among the whole three hundred thousand kinds of vascular plants, about 418 of them are metal hyper accumulator plants. Since most of the researches have been done some work on plants compatible with European or American climate so only a few of these known hyper accumulator plants are able to live in the climate of Iran. The experiments which have been done in Iran are like treatment experiments and there are no additional to the whole hyper accumulator plants so far. In this paper, we examine separately the hyper accumulator plants which are recognized in Iran and the whole experimented hyper accumulator plants in climates of some countries similar to Iran condition. All of the heavy metals have examined due to their majority.

Der Vortrag beschäftigt sich mit der Frage, wie man im pharaonischen Ägypten mit der Ressource Wasser umging. Zum einen wird die Bewässerung diskutiert, zum anderen die Entwässerung, also die die Ableitung von gebrauchtem Wasser sowie ferner von Regenwasser. Diese Praxis wurde bisher erst den Römern zuge¬schrieben, doch sind die tatsächlich älte¬sten Entwässerungstechniken in Ägypten belegt. Bereits im Alten Reich, also zur Zeit der Pyramiden, setzte man Techniken ein, die auch heute noch Anwendung finden, darüber war man sehr erfindungsreich und kreativ.   
Ableitungssysteme für Oberflächenwasser sind z.B. in der Festung Buhen am 2. Katarakt überliefert, aber auch in der Planstadt Illahun aus dem Mittleren Reich. Die Ableitung von Gebrauchtwasser ist in den Häusern der Könige und Wohlhabenden belegt, existier¬ten doch dort Bäder wie z.B. im Palast von Medinet Habu und in Amarna. Das Badezimmer von Pharao Ramses III. ist heute noch in seinem Palast in Medinet Habu zugänglich. Die von Heidi Köpp-Junk derzeitige Untersuchung der Tempelanlage von Athribis/Ägypten ermöglicht gänzlich neue Erkenntnisse über die Nutzung von Wasser in einem griechisch-römischen Tempel.
Der Vortrag eröffnet neue Einsichten in die Bereiche Wohnkultur, Baukunst, Siedlungsarchäologie, Wasserbautechnik und Hygiene.

Expanded granular sludge bed (EGSB) reactors were rarely applied for complete ammonium removal over nitrite. In this study, a high ammonium loading rate of 3677 mg N/L/d was achieved in an EGSB reactor. Approximately 5.5-8.5% of influent ammonium was converted to nitrous oxide (N 2 O) that is a potent greenhouse gas. Moreover, the percentage increased linearly with the increase in ammonium load. A model well matched the reactor dynamics. The model indicated that hydroxylamine (NH 2 OH) oxidation contributed to over 40% of produced N 2 O, and denitrification by ammonium oxidizing bacteria contributed to N 2 O emission significantly. Furthermore, the model suggests that a low oxygen concentration can result in a low N 2 O emission at the cost of a slightly low ammonium removal rate while influent organic matter play a minor role in reducing N 2 O emission. This study shows that EGSB reactors are effective in ammonium removal. In addition, the emission of N 2 O is significant.

The study was conducted at Ashuganj-Polash agro-irrigation project (APAIP), Brahmanbaria, aim to determine the chemical properties of power plant disposal water and to assess its suitability for irrigation. Initial soil samples (before irrigating crop field) and final soil samples (after crop harvesting) were collected. During irrigation ten water samples (six from crop field and four from irrigation canals) were collected for analysis. All soil samples were analyzed in Humboldt soil testing laboratory and water samples in biochemistry laboratory of Bangladesh Agricultural University and compared to FAO irrigation standard. Results show that the sodium absorption-1 ratio (SAR) (0.53 to 0.88), residual sodium bi-carbonate (0.8 to 1.3meq L), Kelly's ratio (0.31 to 0.6) and total hardness (85 to 150) found in normal range and largely suitable for irrigation. Soluble sodium percentage values found in satisfactory (20.26 to 41.1) level and magnesium absorption (57.1 to 76.4) found unsuitable for irrigation. Statistically similar value of pH, EC, total nitrogen, organic carbon, calcium, magnesium and phosphorus in initial and final soil sample were observed. But potassium and sulfur value reduced in final soil sample from initial soil. The water samples fall within the permissible limit and found suitable for crop production.

Sustainable development plays a key role in the survival of mankind. This is reflected in the management of resources as well as harmonizing of the human and other materials available to man. Waste water management and treatment technology is vital in achieving both goal 7 of the Millennium Development Goals that is, environmental sustainability and the Sustainable Development Goals 6 which dwells on access to adequate and equitable sanitation and hygiene for all. Waste water treatment is essential in environmental management. Waste water treatment can be defined as the proportion of wastewater that is treated, in order to reduce pollutants before being discharged to the environment, by level of treatment. This work tries to explain the role of sustainable development in waste water treatment management. The major focus is to analyze Don Parker General Enterprise Limited, their effluent treatment facility. Don Parker General Enterprise Limited is based in Warri-Yowonron college road, opposite yowonron college , Delta State, Nigeria, which is one of the developing countries of the world. Don Parker General Limited uses integrated activated carbon sludge process for their effluent treatment. This work will discuss briefly process technology involved in waste water treatment as practiced by Don Parker General Limited the outcome of the laboratory sample taken on the 4 th July, 2014 and analyzed between 4 th July-15 th July, 2014 and overall link it with sustainable development.

Traditional batik industrial wastewater is not well treated so far. The waste is simply dumped into the surrounding water bodies. Raw wastewater quality characteristics of batik small and medium enterprises (SMEs) included pH (6.05), turbidity (1306 NTU/Nephelometric Turbidity Unit), TSS/Total Suspended Solid (1248 mg/l) and COD/Chemical Oxygen Demand (3712.5 mg/l).
M. oleifera seed powder coagulant addition and deposition length as well as their interactions in batik effluent treatment significantly (0.01) affected turbidity decrease.  Interaction of M. oleifera seed powder coagulant addition (4000 mg/l) and deposition length (180 minutes) showed the lowest turbidity decline namely 59.25 NTU (95.5% reduction).
M. oleifera seed powder coagulant addition significantly (0.01) affected TSS reduction.  Deposition length and the interaction between the coagulant addition and deposition length did not significantly affect the TSS.  Treatment of 5000 mg/l M. oleifera seed coagulant and 60 minutes precipitation gave the best results with the lowest TSS of 156.00 mg/l (87.5% reduction).
In general, the best treatment combination was shown by treatment of 5000 mg/l coagulant addition and 180 minutes long deposition which eventually produced turbidity of 61 NTU and TSS of 170 mg/l.  However further investigation need to be carried out to treat the remaining high COD.

Reuse of wastewater in aquaculture provides a scope to enhance water productivity of the system. Quantification of nutrient inputs
incorporated through treated domestic sewage with varying dosages viz. 79.3 · 105 l ha1 and 67.7 · 105 l ha1 and water productivity in
a controlled carp culture system were assessed in comparison to those involved in a fertilized based one, with a view to correlate among
physical, chemical and biological processes involved in fish yield under the systems. The net water productivities were measured on the
basis of net return values (in Indian rupees; INR) from the carp production systems at a stocking density @ 5000 per ha with four species
combination. Selected relevant water parameters such as dissolved oxygen, total alkalinity, biochemical oxygen demand (BOD5) in sewage
effluent and fertilizer based systems were monitored along with certain biological parameters viz. gross primary productivity, fish
production and water productivity. The nutrient inputs in terms of total ammonia–nitrogen (TAN) in effluents, total nitrogen (TN)
in fertilizers and phosphorus (P2O5) in both effluents and fertilizers were found significantly correlated with biological production.
The results of the experiment revealed that the sewage incorporation at 79.3 · 105 l ha1 yielded similar gross fish production as recorded
from fertilizer based system, whereas net water productivity using sewage as nutrient source was found 64% higher than that of a fertilizer
based system.

Per-and Polyfluoroalkyl substances (PFAS) are a group of durable and stable chemicals, which have been used in non-stick cookware, fire retardant materials and stain resistant carpets and have found their ways to Nation's drinking water stream through landfill leachate. Clark Technology's LeachBuster system was used to remove these contaminants from leachate streams for over 4 years. This article is a summary of the results of this study. Concentration of these substances ranged from around 0.5 Nano grams/liter (ng/l) to around 500 ng/l. The system remove all of these compounds from the leachate to under 2 ng/l which is well below the required discharge limits for most of the regulatory bodies.. Introduction:

What are the major factors able to increase the capacity of suppliers in outsourcing processes? To answer this research question, a three-round Delphi survey was administered to an expert panel composed of 50 industrial experts of the Water and Wastewater Company (WWC) in Iran. The administered questionnaire – based on 50 items categorized into 4 groups: judicial-legal, contract, management, and financial – was developed based on prior literature and experts’ answers. Respondents have been asked to evaluate each item with regard to the capacity of suppliers in outsourcing processes on a 5-point Likert scale. Factor analysis, one-sample t-test and the Friedman test were used for data analysis. Results show that the factor categories able to increase the capacity of suppliers in outsourcing processes at WWC are the following, in order of importance: financial, judicial-legal, contracts, and management. The findings help to focus on the shortcomings and deficiencies of current outsourcing processes.

The Jordanian chabazite-phillipsite tuff and faujasite-phillipsite tuff have suitable mineralogical and technical properties that enable them to be used for ion-exchange processes. These include suitable grain size and total cation exchange capacity, acceptable zeolite content, good attrition resistance and high packed-bed density. The chabazite-phillipsite tuff (ZE1 and ZE2) has an excellent efficiency to remove Pb and an acceptable efficiency to remove Fe, Cu, Zn and Ni from effluent wastewater of a battery factory and other industries. The faujasite-phillipsite tuff (ZE3) is 6.97 times more efficient than the ZE1 and ZE2. A bed of ZE3 (1,000 kg) loaded in a 1.17-m 3 column is capable of cleaning about 2,456 m 3 of the effluent from the factory at a cost of US $200/ton. The wastewater is contaminated with 20 ppm Pb in the presence of competing ions including Ca (210 ppm), Na (1,950 ppm) and Fe (169 ppm). This quantity of wastewater is equivalent to 120 working days of effluent discharge from the factory at a flow rate of 20 m 3 /day.

Solar distillation is based on the use of solar radiation to heat water in a basin. The water evaporates and condenses on the inner surface of an inclined glass plate. The condensate flows down and is collected. Solar distillation removes bacteria, arsenic, fluoride, nitrate, salinity, total dissolved solids, and hardness. The running cost is negligible. However, the yield of distilled water per unit area of the collector varies widely depending on the weather. The aim of the present work is to examine the use a solar still for (i) distillation of water containing excess fluoride, total dissolved solids, and hardness, (ii) harvesting rainwater, and (iii) disposal of spent zirconium-SPADNS solution. Defluoridation was done by using solar distillation for water having a high concentration cF of fluoride (F−) (cF = 10 - 2000 mg/L), and the values of cF in the distillates were well below the desirable limit of 1 mg/L. I visited Hebbagodi village twice, in June 2010 and July 2011, and Lakkihalli village in July 2011, and collected water samples from different locations. The samples had high values of water quality parameters such as cF, total dissolved solids, total hardness, calcium hardness, and magnesium hardness. They were distilled using solar stills. For the distillates, the values of all the parameters were well below the desirable limits. In view of the above results, solar distillation can be used to treat water having high levels of F−, dissolved solids, and hardness. The cost of the still for an area of 1 m2 was about Rs. 4500. Rainwater was collected using a glass beaker in 2010 and using the upper surface of solar still placed on the terrace of our department in 2011. The water quality parameters were estimated and found to be below the desirable limits for all parameters, except that the pH of some of the rainwater samples was slightly below the desirable lower limit of 6.5. Hence rainwater can be used for drinking in areas where the usual source of water has high levels of F−, dissolved solids, and hardness, if a pH that is slightly lower than the desirable limit can be tolerated. One of the standard methods used for the estimation of fluoride F− in water is a spectrophotometric method based on a coloured zirconium-SPADNS solution. The spent solution was distilled in a solar still to obtain a colourless distillate. However the pH of distillate was very low, i.e., the distillate was acidic. The pH of the feed was changed to an alkaline pH using about 10 volume % of 8 N NaOH solution. On distilling it using a stainless steel solar still, a colourless distillate having a pH of range 6.12 - 7.23 was obtained, which can be disposed in the sewer.

Therefore, solar stills can be used for treatment of drinking water, rainwater harvesting, and disposal of spent zirconium-SPADNS solution.