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(327) Copper speciation, consents and environmental aquatic standards. Gardner, Michael1, Comber, Sean1, van Veen, Eleanor1, Burton, Nicola2, 1 2 ABSTRACT- The UK water industry is coming under increasing regulatory pressure to reduce the concentration of copper in sewage effluent, through the introduction of lower Environmental Quality Standards, European Directives and tighter consents on the discharge of effluent. This is set against a background of increasing copper concentrations entering sewage treatment works from copper leached from household plumbing in new housing developments. Although utilities can limit loads of copper from point sources (largely industrial discharges), domestic and diffuse inputs are effectively beyond their control. Although the current Environmental Quality Standard (EQS) for copper in freshwaters recognises that copper complexed by natural ligands, is significantly less toxic than inorganic copper, this is rarely considered when setting consents. In view of this, tests were performed to assess the copper complexation characteristics of sewage treatment works final effluents, and its effect on the toxicity of copper to the freshwater invertebrate Daphnia magna. Overall, although a wide range of different receiving waters were sampled, a relatively narrow range of dissolved copper concentrations was measured, than in the effluents, reflecting the varied nature of the effluents. In all final effluents the complexation capacity exceeded that of the receiving water, often by over an order of magnitude. In most cases the proportion of inorganic copper constituted only a minor proportion of the total, with free Cu2+ concentrations being negligible. The type of sewage treatment (activated sludge or filtration) did not affect the complexation capacity of the final effluent. Toxicity tests with Daphnia showed that the copper complexation capacity of the final effluent reduced the toxicity of copper significantly. Of all the measures of copper species, the inorganic fraction determined by voltammetry provided the best estimate of EC50, although it still tended to overestimate the proportion of metal that was bio-available and toxic to the organism. Key words: copper, speciation, effluents, daphnia |
