Aquatic environmental risk assessment of a tank truck cleaning effluent discharged in the lower part of the river "Schijn"
Faculty of Sciences. Biology
S.l. , 2010
University of Antwerp
The presented study considers the risk assessment of a wastewater discharged by a tank truck cleaning company. The biological quality of the receiving surface water is found to be very low (Belgian Biotic Index (BBI) = 2). It is however not feasible to connect the deteriorated water quality directly to the studied discharge given the presence of other possible sources of environmental stress. Whole effluent toxicity testing was performed on a series of effluent samples providing a more direct means for effluent risk assessment. Acute ecotoxicological test procedures used included 4 different test species representative for a number of basic and interconnected ecosystem processes (Pseudokirchneriella subcapitata, primary production; nitrifying sludge, nitrification; Vibrio fisheri, decomposition; Daphnia magna, primary consumption). The effluent was found to be highly toxic for the unicellular algae Pseudokirchneriella subcapitata (average 1652 acute toxic units, TUa). Three different risk assessment methods were used to assess the environmental impact of the studied effluent based on the most sensitive test species data. All 3 methods concluded that toxicity in the effluent is high enough to cause acute toxicity in the receiving water. In addition, two short-term assays were evaluated for their ability to reproduce the data obtained from standard toxicity tests with algae and daphnids. An enzymatic inhibition test using Daphnia magna (1.15h) was found able to consistently reproduce the 48h Daphnia magna immobilization test results. Alternative short-term tests with Pseudokirchneriella subcapitata (4.5h) however could not reproduce the high toxicity values, measured with the 72h Pseudokirchneriella subcapitata growth inhibition assay.