Assessment of complex industrial effluents in the Netherlands using a whole effluent toxicity (or wet) approach

The assessment of Dutch waste water discharges or effluents is focused on t he reduction of specific pollutants or substances. Many effluents in the Ne therlands are of a complex nature though. Because of several limitations, a n assessment of complex effluents is not possible by merely using a chemica l specific approach. Examples are lack of analytical techniques, lack of ec otoxicological data and unknown combination processes. Therefore an additio nal approach is needed. The Whole Effluent Toxicity or WET approach has bee n introduced to overcome the mentioned limitations. It focuses on acute tox icity. In 1994 a pilot study was initiated in order to try out, adjust and evaluate the WET approach. The aims were to gain more insight in the occurr ence of acute toxicity in complex effluents, and to try and prove the addit ional value of the approach. The study was performed with 17 different indu strial effluents, consisting of 6 industrial branches. All effluents were t ested with four different organisms. The results showed acute toxicity for at least one organism in 15 out of 17 effluents. In 8 cases the toxicity of the effluents could not be explained by using physical and chemical data. The results clearly show that the use of acute toxicity tests produces valu able, and especially additional, information. (C) 1999 Published by Elsevie r Science Ltd on behalf of the IAWQ. All rights reserved.