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Recent Developments in Oxygenation of the Tidal Thames
Abstract
Increased polluting loads are discharged to the tidal Thames at times of heavy rainfall. This can lead to a rapid decline in dissolved-oxygen (DO) concentrations, which, on occasions, has resulted in fish mortality. The problem is caused by the cumulative effect of surface runoff, increased flows from sewage-treatment works, and storm-sewage discharges from the combined drainage of Inner London.
An experimental system of in-river oxygenation has been operated by Thames Water in order to alleviate the problem. This scheme demonstrated that the river oxygenation concept is viable. There was, however, a need to increase the operating reliability of the plant and to provide extra oxygenation capacity. Thames Water carried out a detailed investigation into the various options prior to the acquisition of a new, purpose-built, self-propelled, oxygenation vessel, which was delivered to the River Thames in October 1988.
... km 2 , which equates to ~1.2-2.4 km in horizontal stream distance . When hypoxic events are spatially and temporally variable, oxygenation plants constructed on vessels such as the 'Thames Bubbler' could be employed to ameliorate small-scale events, and also potentially create oxygen refugia if hypoxia occurred over a wider area (Lloyd and Whiteland, 1990). ...
Not all estuaries are equally susceptible to anthropogenic perturbation. Microtidal estuaries with long residence times are intrinsically less robust than well-flushed macrotidal estuaries, facilitating the accumulation of contaminants. This promotes development of blooms of non-toxic and toxic phytoplankton, and hypoxia and anoxia may occur in deeper sections of the typically stratified water column. In Mediterranean and arid climates, high temperatures and low and/or seasonal rainfall can result in marked hypersalinity. Thus, any increase in an-thropogenic perturbation will further decrease the health of a system in which the biota already experiences natural stress. Microtidal estuaries are also more susceptible to climate change, the detrimental longer-term effects of which are becoming manifestly obvious. Numerous attempts have been made to develop novel solutions to problems caused by eutrophication, phytoplankton blooms, hypoxia and hypersalinity, which have met with various levels of success, but the need for such measures and effective legislation is increasingly critical.
... Fine bubbles are formed which readily dissolve under pressure and the oxygen-rich liquor is returned to the water body via a twin nozzle sparge system. The system was successful in elevating DO concentrations in the MSC, in common with other polluted waterbodies such as the River Thames (Lloyd & Whiteland 1990). A near continuous supply (>85%) of oxygen injection is required in the MSC during the summer, based on the frequency of DO concentrations falling to less than 4 mg L –1 at temperatures of over 16 o C as measured at Trafford Road Bridge (APEM 1990b). ...
Introduction The upper reaches of the Manchester Ship Canal (MSC) and associated dock basins have been polluted by operational discharges, surface water runoff as well as upstream inputs from the River Irwell. The resulting poor water quality has been exacerbated by the deep (7 m) water column and limited water exchange. In this chapter, we describe the water quality management strategies put in place since the late 1980s to address poor water quality, specifically oxygenation of the water column of the MSC and isolation of the docks from the canal followed by destratification of the water column and habitat diversification. We then examine the effectiveness of these strategies in improving water quality, increasing biodiversity and enhancing the recreational potential of the enclosed dock basins and the MSC.
Written for researchers and practitioners in environmental pollution, management and ecology, this interdisciplinary account explores the ecological issues associated with industrial pollution to provide a complete picture of this important environmental problem from cause to effect to solution. Bringing together diverse viewpoints from academia and environmental agencies and regulators, the contributors cover such topics as biological resources of mining areas, biomonitoring of freshwater and marine ecosystems and risk assessment of contaminated land in order to explore important questions such as: What are the effects of pollutants on functional ecology and ecosystems? Do current monitoring techniques accurately signal the extent of industrial pollution? Does existing policy provide a coherent and practicable approach? Case studies from throughout the world illustrate major themes and provide valuable insights into the positive and negative effects of industrial pollution, the provision of appropriate monitoring schemes and the design of remediation and restoration strategies.
Written for researchers and practitioners in environmental pollution, management and ecology, this interdisciplinary account explores the ecological issues associated with industrial pollution to provide a complete picture of this important environmental problem from cause to effect to solution. Bringing together diverse viewpoints from academia and environmental agencies and regulators, the contributors cover such topics as biological resources of mining areas, biomonitoring of freshwater and marine ecosystems and risk assessment of contaminated land in order to explore important questions such as: What are the effects of pollutants on functional ecology and ecosystems? Do current monitoring techniques accurately signal the extent of industrial pollution? Does existing policy provide a coherent and practicable approach? Case studies from throughout the world illustrate major themes and provide valuable insights into the positive and negative effects of industrial pollution, the provision of appropriate monitoring schemes and the design of remediation and restoration strategies.
Written for researchers and practitioners in environmental pollution, management and ecology, this interdisciplinary account explores the ecological issues associated with industrial pollution to provide a complete picture of this important environmental problem from cause to effect to solution. Bringing together diverse viewpoints from academia and environmental agencies and regulators, the contributors cover such topics as biological resources of mining areas, biomonitoring of freshwater and marine ecosystems and risk assessment of contaminated land in order to explore important questions such as: What are the effects of pollutants on functional ecology and ecosystems? Do current monitoring techniques accurately signal the extent of industrial pollution? Does existing policy provide a coherent and practicable approach? Case studies from throughout the world illustrate major themes and provide valuable insights into the positive and negative effects of industrial pollution, the provision of appropriate monitoring schemes and the design of remediation and restoration strategies.
Written for researchers and practitioners in environmental pollution, management and ecology, this interdisciplinary account explores the ecological issues associated with industrial pollution to provide a complete picture of this important environmental problem from cause to effect to solution. Bringing together diverse viewpoints from academia and environmental agencies and regulators, the contributors cover such topics as biological resources of mining areas, biomonitoring of freshwater and marine ecosystems and risk assessment of contaminated land in order to explore important questions such as: What are the effects of pollutants on functional ecology and ecosystems? Do current monitoring techniques accurately signal the extent of industrial pollution? Does existing policy provide a coherent and practicable approach? Case studies from throughout the world illustrate major themes and provide valuable insights into the positive and negative effects of industrial pollution, the provision of appropriate monitoring schemes and the design of remediation and restoration strategies.
Written for researchers and practitioners in environmental pollution, management and ecology, this interdisciplinary account explores the ecological issues associated with industrial pollution to provide a complete picture of this important environmental problem from cause to effect to solution. Bringing together diverse viewpoints from academia and environmental agencies and regulators, the contributors cover such topics as biological resources of mining areas, biomonitoring of freshwater and marine ecosystems and risk assessment of contaminated land in order to explore important questions such as: What are the effects of pollutants on functional ecology and ecosystems? Do current monitoring techniques accurately signal the extent of industrial pollution? Does existing policy provide a coherent and practicable approach? Case studies from throughout the world illustrate major themes and provide valuable insights into the positive and negative effects of industrial pollution, the provision of appropriate monitoring schemes and the design of remediation and restoration strategies.
Dissolved and pariculate arsenic species have been determined in the Thames Estuary and Plume. During February 1989 only dissolved inorganic arsenic was detected in the estuary (mean concentration 97.8 ± 5.7 nM) and the plume (mean concentration 43.7 ± 12.0 nM). In July 1990, the mean concentration of dissolved inorganic arsenic in the plume was 28.2 ± 14.0 nM and about 8% of the total dissolved arsenic concentrations comprised the methylated species monomethylarsenic (mean 0.52 ± 0.22 nM) and dimethylarsenic (mean 1.85 ± 1.70 nM). Concentrations of arsenic in suspended particulate matter were 89 ± 39 nmol g−1 in February and 61 ± 12 nmol g−1 in July. Partition coefficients (KDs) for arsenic were about 103 litre kg−1 and were an order of magnitude lower than those for the Humber Plume. Fluxes of dissolved inorganic arsenic form the estuary based on zero salinity end member concentrations were 22 kg d−1 in February and 7 kg d−1 in July. The concentrations of dissolved inorganic arsenic in sediment porewaters were five times higher than those in the water column indicating diffusional fluxes from the sediments amounting to 1.2–2.6 kg d−l over the whole plume. The results were synthesised as an annual arsenic budget for the Thames Plume, which showed that cycling of arsenic by phytoplankton was the dominant process.
Over the last quarter century, some £400 million has been spent to change the tidal River Thames from a 'dead' river and estuary to one which now is capable of supporting a diversity of fish and other fauna. For historic reasons, London's drainage is mainly on the 'combined' system and, once in five years, storm sewage overflows coinciding with specific tidal conditions may result in severe dissolved oxygen depletions and fish mortalities. Of the different methods for remedying this situation, the only practicable solution appears to be in injection of 'pure' oxygen using a pressure swing adsorption unit applied from a Vitox system on a barge following the minimum of the oxygen sag curve as it moves down river.
Mobile oxygenation in the Thames estuary
- GRIFFITHS I. M.