Evaluation of Whole Effluent Bioassays for Assessment of Hydrocarbon Ecotoxicity – Phase III Stream Study

Report no. 7/15: Toxicity predictions based on laboratory- based Whole Effluent Toxicity (WET) tests have been assessed by dosing outdoor stream mesocosms with unmodified and fortified refinery effluents. The tests performed allowed the process effluents to be classified on the basis of their toxicity to a range of aquatic organisms and endpoints.

Duplicate stream channels were exposed to three different profiles of hydrocarbon contamination: an unfortified effluent (A) containing low levels of mono aromatics and naphthenic mono aromatics, 10mM of Potential Bioaccumulative Substances (PBS) and low levels of biodegradable substances; effluent (B) fortified with kerosene and containing very high levels of hydrocarbon contamination (mainly normal and iso
paraffins, mono and di-naphthenes and mono aromatics) with very high PBS levels (≈700 mM); and effluent (C) fortified with diesel and containing high levels of hydrocarbon contamination (mainly normal and iso paraffins and mono naphthenes) with high PBS levels (≈300 mM).