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(349) Combining toxicity identification and toxicity backtracking to evaluate public wastewater treatment plants receiving mixed influents . Indeherberg, M.1, Witters, H.2, Jansen, C.3, Van Sprang, P.3, Vandenbroele, M.3, 1 2 3 ABSTRACT- Currently, in Flanders, public wastewater treatment plants generally receive both domestic and industrial wastewater. The quality of the treatment plant's effluent is monitored from a physico-chemical perspective but ecotoxicological evaluation is missing. The Flemish Environmental Institute (VMM) initiated a study aimed at evaluating the efficiency of the public waste water treatment plants in reducing ecotoxicity of the receiving water. 8 Treatment plants, receiving complex chemical mixtures, were evaluated applying Direct Toxicity Assessment procedures (DTA) (acute Daphnia magna and rainbow trout-, alga growth inhibition-, microtox-test). Toxicity identification (TIE) and toxicity backtracking procedures, identifying respectively cause and source of remaining toxicity, are initiated on occasion of poor removal of ecotoxicity by specific treatment plants. In respect of TIE, a modified phase I approach has been applied giving special attention to salts (mock tests) and organic compounds of different polarity and size. Toxicity backtracking includes ecotoxicological evaluation of waste waters discharged to the public treatment plant of concern. This case-by case ecotoxicological evaluation took place both on raw (industrial) effluents and right after a waste water treatment procedure similar to the one applied for the public treatment plant itself. The project will contribute in developing a regulatory instrument to improve the ecological quality of specific urban and industrial impoverished river basins. The combination of TIE, toxicity backtracking and laboratory wastewater treatment applications must allow for more scientifically sound conclusions concerning cause - effect relationships. The given methodology will allow prioritising the chemical group of concern. Only in second place, the single chemical approach comes in. Key words: Wastewater treatment plant, DTA, TIE, toxicity backtracking |
