Data for water quality surveys of effluent from sewage treatment works (STWs) in the rural Kennet... more Data for water quality surveys of effluent from sewage treatment works (STWs) in the rural Kennet/Dun sub-catchments of the upper Thames Basin are presented to characterize treated sewage effluent. Water quality determinand relationships with boron (B) are presented to provide information that can be used, with stream water quality information, to assess the relative inputs of treated sewage effluent pollutants
Changes in the relationship between soluble reactive phosphorus (SRP) concentration and river flo... more Changes in the relationship between soluble reactive phosphorus (SRP) concentration and river flow between 1966 and 2006 were assessed for the River Frome, UK using the recently developed Load Apportionment Model. The resulting source load estimates gave good agreement with known changes within the catchment. The model indicated an increase in point source contribution to the total river load from
Science of The Total Environment - SCI TOTAL ENVIR, 2010
Phosphorus concentrations in the upper River Thames Basin (southeastern England) are described an... more Phosphorus concentrations in the upper River Thames Basin (southeastern England) are described and linked to sewage effluent sources. Weekly surveys between 1997 and 2007 of the Thames and two of its major tributaries, the Thame and the Kennet indicated that phosphorus was mainly in soluble reactive (SRP) form. Baseflow concentrations in the Thames reduced from 1584μg/l in 1998 to 376μg/l in 2006 and from 2655 to 715μg/l for the Thame. Flow response, flux and endmember mixing analysis indicated that these declines resulted from SRP reductions in sewage treatment works (STW) effluent following phosphorus stripping for the major STWs in the region. This was confirmed by comparing our analysis with direct measurements of SRP in the effluents based on Environment Agency data. A within-river loss under baseflow of ~64% (range 56–78%) of the SRP-effluent input was estimated for the Thames, with a near balance for the Thame. SRP concentrations in the Kennet were an order of magnitude lower...
This paper presents new information on the hydrology and water quality of the eroding peatland he... more This paper presents new information on the hydrology and water quality of the eroding peatland headwaters of the River Severn in mid-Wales and links it to the impact of plantation conifer forestry further down the catchment. The Upper Hafren is dominated by low-growing peatland vegetation, with an average annual precipitation of around 2650 mm with around 250 mm evaporation. With low catchment permeability, stream response to rainfall is "flashy" with the rising limb to peak stormflow typically under an hour. The water quality is characteristically "dilute"; stormflow is acidic and enriched in aluminium and iron from the acid organic soil inputs. Baseflow is circum-neutral and calcium and bicarbonate bearing due to the inputs of groundwater enriched from weathering of the underlying rocks. Annual cycling is observed for the nutrients reflecting uptake and decomposition processes linked to the vegetation and for arsenic implying seasonal water-logging within the peat soils and underlying glacial drift. Over the decadal scale, sulphate and nitrate concentrations have declined while Gran alkalinity, dissolved organic carbon and iron have increased, indicating a reduction in stream acidification. Within the forested areas the water quality is slightly more concentrated and acidic, transgressing the boundary for acid neutralisation capacity as a threshold for biological damage. Annual sulphate and aluminium concentrations are double those observed in the Upper Hafren, reflecting the influence of forestry and the greater ability of trees to scavenge pollutant inputs from gaseous and mist/cloud-water sources compared to short vegetation. Acidification is decreasing more rapidly in the forest compared to the eroding peatland possibly due to the progressive harvesting of the mature forest reducing the scavenging of acidifying inputs. For the Lower Hafren, long-term average annual precipitation is slightly lower, with lower average altitude, at around 2520mm and evaporation is around double that of the Upper Hafren.
The relationship between calcium carbonate saturation and phosphorus concentrations for seven sit... more The relationship between calcium carbonate saturation and phosphorus concentrations for seven sites on the upper reaches of the River Kennet are examined. The findings are related to issues of groundwater supplies and the introduction of phosphorus treatment of effluent from the Marlborough sewage treatment works (STW) at part of the way along the study reach. Being supplied from a Cretaceous Chalk aquifer, the Kennet is mainly of a calcium-bicarbonate type and has a relatively constant composition of many major water quality determinands. Typically, the waters average a pH of approximately eight (range approx. 7.5-8.5) during the day with the lowest values occurring at the upstream site. Dissolved carbon dioxide varies from approximately 5 to 35 times atmospheric pressure during the late morning with the highest values occurring at the upstream site. However, in-stream biological activity gives rise to marked diurnal fluctuations in pH and dissolved carbon dioxide concentrations and during the summer months, by mid to late afternoon, pH is at its maximum and dissolved carbon dioxide is at its lowest: this is shown by continuous measurements at one of the river sites. Alkalinity and calcium concentrations remain relatively constant at approximately 4,700 microEq/l (range 3,500-6,000 microEq/l) and 120 mg/l (range 85-150 mg/l), respectively, and the waters are oversaturated with respect to calcium carbonate (calcite) typically by a factor of six (range 2-25). Along the reach, soluble reactive phosphate (SRP) increases from the first to the second site with the introduction of sewage supplies from the Marlborough STW, and then declines further downstream as sewage dilution and uptake by the river bed/aquatic plants increases. The differences in concentration decrease after phosphorus removal from Marlborough STW. Despite this change, there is no clear indication of any calcite solubility control except perhaps at times of extreme baseflow during the growing season when within-stream photosynthesis is maximal and within-stream residence times are longer. A comparison of river and groundwater data shows that the groundwaters have similar alkalinities and calcium concentrations. However, the groundwaters have (a) higher carbon dioxide saturations (a factor of 2-5 times the value for the river), (b) lower pHs (0.5-1.5 units), (c) lower SRP concentrations (a quarter or less of the river values) and (d) waters near calcite saturation (unlike the surface waters which are oversaturated). The findings indicate a river system dominated by the input carbon dioxide laden groundwaters in approximate equilibrium with calcite attenuated by within-channel biological and physical processes. Within the river: (a) the waters degas carbon dioxide increasing the pH, producing oversaturated conditions; and (b) oscillating pH-dissolved carbon dioxide levels occur between day and night due to changing balances between photosynthesis and respiration. It seems that lowering the phosphorus levels have not resulted in calcite precipitation within the water column and that no significant within-stream self-cleansing mechanisms are occurring that might be predicted from theory: other components in the water such as dissolved organic carbon may inhibit calcite nucleation. However, the low SRP levels in the groundwater coupled with calcite saturation, may well indicate that phosphorous concentrations within the groundwater are regulated by such processes: the number of calcite nucleating sites are orders of magnitude higher and the calcite inhibitors may be less prevalent.
This paper examines the nutrient chemistry and biological quality indices [Mean Trophic Rank (MTR... more This paper examines the nutrient chemistry and biological quality indices [Mean Trophic Rank (MTR) and Trophic Diatom Index (TDI)] for rivers within the upper Thames basin. The predominant sources of nitrogen within the rivers monitored were diffuse and agricultural in nature. However, phosphorus showed both diffuse and point source signals. MTR surveys undertaken both upstream and downstream of major STWs indicate that these rivers are 'at risk' of eutrophication or 'badly damaged'. MTR surveys also indicate increased trophic status downstream of STWs, whereas TDI does not indicate such a consistent pattern. Phosphorus treatment at selected major sewage treatment works in the upper Thames basin resulted in significant reductions in in-stream P concentrations and reductions in fluxes by a half to two thirds. However, the effects of P-reduction on in-stream ecology (measured as MTR and TDI) were more difficult to ascribe, owing to: (1) the high variability in river flow rates experienced since P-reduction was introduced; (2) lag effects related to P stores in river bed sediments; and (3) diffuse and smaller point source inputs upstream. The results of this study indicate that control of upstream sources of phosphorus may prove critical in improving the biological quality status of UK lowland rivers, including ecological responses to P-source controls on the major sewage treatment works downstream. Upstream sources include both diffuse (agricultural) sources and small point source inputs which, at present, are not classified as 'qualifying discharges' under the Urban Wastewater Treatment Directive (UWWTD) and are thus not subject to phosphorus control measures. These results are of relevance for integrated, sustainable management and protection of European freshwater resources, particularly in terms of new ecological targets for water quality management under the new Water Framework Directive.
Data for water quality surveys of effluent from sewage treatment works (STWs) in the rural Kennet... more Data for water quality surveys of effluent from sewage treatment works (STWs) in the rural Kennet/Dun sub-catchments of the upper Thames Basin are presented to characterize treated sewage effluent. Water quality determinand relationships with boron (B) are presented to provide information that can be used, with stream water quality information, to assess the relative inputs of treated sewage effluent pollutants
Changes in the relationship between soluble reactive phosphorus (SRP) concentration and river flo... more Changes in the relationship between soluble reactive phosphorus (SRP) concentration and river flow between 1966 and 2006 were assessed for the River Frome, UK using the recently developed Load Apportionment Model. The resulting source load estimates gave good agreement with known changes within the catchment. The model indicated an increase in point source contribution to the total river load from
Science of The Total Environment - SCI TOTAL ENVIR, 2010
Phosphorus concentrations in the upper River Thames Basin (southeastern England) are described an... more Phosphorus concentrations in the upper River Thames Basin (southeastern England) are described and linked to sewage effluent sources. Weekly surveys between 1997 and 2007 of the Thames and two of its major tributaries, the Thame and the Kennet indicated that phosphorus was mainly in soluble reactive (SRP) form. Baseflow concentrations in the Thames reduced from 1584μg/l in 1998 to 376μg/l in 2006 and from 2655 to 715μg/l for the Thame. Flow response, flux and endmember mixing analysis indicated that these declines resulted from SRP reductions in sewage treatment works (STW) effluent following phosphorus stripping for the major STWs in the region. This was confirmed by comparing our analysis with direct measurements of SRP in the effluents based on Environment Agency data. A within-river loss under baseflow of ~64% (range 56–78%) of the SRP-effluent input was estimated for the Thames, with a near balance for the Thame. SRP concentrations in the Kennet were an order of magnitude lower...
This paper presents new information on the hydrology and water quality of the eroding peatland he... more This paper presents new information on the hydrology and water quality of the eroding peatland headwaters of the River Severn in mid-Wales and links it to the impact of plantation conifer forestry further down the catchment. The Upper Hafren is dominated by low-growing peatland vegetation, with an average annual precipitation of around 2650 mm with around 250 mm evaporation. With low catchment permeability, stream response to rainfall is "flashy" with the rising limb to peak stormflow typically under an hour. The water quality is characteristically "dilute"; stormflow is acidic and enriched in aluminium and iron from the acid organic soil inputs. Baseflow is circum-neutral and calcium and bicarbonate bearing due to the inputs of groundwater enriched from weathering of the underlying rocks. Annual cycling is observed for the nutrients reflecting uptake and decomposition processes linked to the vegetation and for arsenic implying seasonal water-logging within the peat soils and underlying glacial drift. Over the decadal scale, sulphate and nitrate concentrations have declined while Gran alkalinity, dissolved organic carbon and iron have increased, indicating a reduction in stream acidification. Within the forested areas the water quality is slightly more concentrated and acidic, transgressing the boundary for acid neutralisation capacity as a threshold for biological damage. Annual sulphate and aluminium concentrations are double those observed in the Upper Hafren, reflecting the influence of forestry and the greater ability of trees to scavenge pollutant inputs from gaseous and mist/cloud-water sources compared to short vegetation. Acidification is decreasing more rapidly in the forest compared to the eroding peatland possibly due to the progressive harvesting of the mature forest reducing the scavenging of acidifying inputs. For the Lower Hafren, long-term average annual precipitation is slightly lower, with lower average altitude, at around 2520mm and evaporation is around double that of the Upper Hafren.
The relationship between calcium carbonate saturation and phosphorus concentrations for seven sit... more The relationship between calcium carbonate saturation and phosphorus concentrations for seven sites on the upper reaches of the River Kennet are examined. The findings are related to issues of groundwater supplies and the introduction of phosphorus treatment of effluent from the Marlborough sewage treatment works (STW) at part of the way along the study reach. Being supplied from a Cretaceous Chalk aquifer, the Kennet is mainly of a calcium-bicarbonate type and has a relatively constant composition of many major water quality determinands. Typically, the waters average a pH of approximately eight (range approx. 7.5-8.5) during the day with the lowest values occurring at the upstream site. Dissolved carbon dioxide varies from approximately 5 to 35 times atmospheric pressure during the late morning with the highest values occurring at the upstream site. However, in-stream biological activity gives rise to marked diurnal fluctuations in pH and dissolved carbon dioxide concentrations and during the summer months, by mid to late afternoon, pH is at its maximum and dissolved carbon dioxide is at its lowest: this is shown by continuous measurements at one of the river sites. Alkalinity and calcium concentrations remain relatively constant at approximately 4,700 microEq/l (range 3,500-6,000 microEq/l) and 120 mg/l (range 85-150 mg/l), respectively, and the waters are oversaturated with respect to calcium carbonate (calcite) typically by a factor of six (range 2-25). Along the reach, soluble reactive phosphate (SRP) increases from the first to the second site with the introduction of sewage supplies from the Marlborough STW, and then declines further downstream as sewage dilution and uptake by the river bed/aquatic plants increases. The differences in concentration decrease after phosphorus removal from Marlborough STW. Despite this change, there is no clear indication of any calcite solubility control except perhaps at times of extreme baseflow during the growing season when within-stream photosynthesis is maximal and within-stream residence times are longer. A comparison of river and groundwater data shows that the groundwaters have similar alkalinities and calcium concentrations. However, the groundwaters have (a) higher carbon dioxide saturations (a factor of 2-5 times the value for the river), (b) lower pHs (0.5-1.5 units), (c) lower SRP concentrations (a quarter or less of the river values) and (d) waters near calcite saturation (unlike the surface waters which are oversaturated). The findings indicate a river system dominated by the input carbon dioxide laden groundwaters in approximate equilibrium with calcite attenuated by within-channel biological and physical processes. Within the river: (a) the waters degas carbon dioxide increasing the pH, producing oversaturated conditions; and (b) oscillating pH-dissolved carbon dioxide levels occur between day and night due to changing balances between photosynthesis and respiration. It seems that lowering the phosphorus levels have not resulted in calcite precipitation within the water column and that no significant within-stream self-cleansing mechanisms are occurring that might be predicted from theory: other components in the water such as dissolved organic carbon may inhibit calcite nucleation. However, the low SRP levels in the groundwater coupled with calcite saturation, may well indicate that phosphorous concentrations within the groundwater are regulated by such processes: the number of calcite nucleating sites are orders of magnitude higher and the calcite inhibitors may be less prevalent.
This paper examines the nutrient chemistry and biological quality indices [Mean Trophic Rank (MTR... more This paper examines the nutrient chemistry and biological quality indices [Mean Trophic Rank (MTR) and Trophic Diatom Index (TDI)] for rivers within the upper Thames basin. The predominant sources of nitrogen within the rivers monitored were diffuse and agricultural in nature. However, phosphorus showed both diffuse and point source signals. MTR surveys undertaken both upstream and downstream of major STWs indicate that these rivers are 'at risk' of eutrophication or 'badly damaged'. MTR surveys also indicate increased trophic status downstream of STWs, whereas TDI does not indicate such a consistent pattern. Phosphorus treatment at selected major sewage treatment works in the upper Thames basin resulted in significant reductions in in-stream P concentrations and reductions in fluxes by a half to two thirds. However, the effects of P-reduction on in-stream ecology (measured as MTR and TDI) were more difficult to ascribe, owing to: (1) the high variability in river flow rates experienced since P-reduction was introduced; (2) lag effects related to P stores in river bed sediments; and (3) diffuse and smaller point source inputs upstream. The results of this study indicate that control of upstream sources of phosphorus may prove critical in improving the biological quality status of UK lowland rivers, including ecological responses to P-source controls on the major sewage treatment works downstream. Upstream sources include both diffuse (agricultural) sources and small point source inputs which, at present, are not classified as 'qualifying discharges' under the Urban Wastewater Treatment Directive (UWWTD) and are thus not subject to phosphorus control measures. These results are of relevance for integrated, sustainable management and protection of European freshwater resources, particularly in terms of new ecological targets for water quality management under the new Water Framework Directive.
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