Using single-species toxicity tests, community-level responses, and toxicity identification evaluators to investigate effluent impacts

A 4-stage procedure is described to investigate the toxicity and biological impact of a point source discharge and to identify the major toxicants using whole effluent toxicity (WET) tests. Stage 1 employed standard WET tests to determine effluent toxicity, followed by assessment of the receiving water toxicity with indigenous (Gammarus pulex) and standard (Daphnia magna) test species (stage 2). Stage 3 investigated the impact of discharges on the structure and functioning of the benthic macroinvertebrate community. In stage 4, toxicity identification evaluations (TIE) were used to identify toxic components in the effluent. Receiving-water toxicity and ecological impacts detected downstream of the discharge were consistent with the results of WET tests performed on the effluent. Downstream a reduction in D. magna survival, in G. pulex survival and feeding rate, in detritus processing and in biotic indices was found. Chlorine was the principle toxicant found in the effluent. There are 31 references.