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(T/EH055) Wastewater fractionation by solid phase (Oasis) extraction and screening for toxicity and genotoxicity. Schultz, Eija1, Pessala, Piia1, Herve, Sirpa2, 1 2 ABSTRACT- The aim of the study was to identify toxic compounds from different wastewater effluents, using the U.S.EPA toxicity identification evaluation (TIE) protocol and small-scale toxicity tests. We also aimed to improve the TIE protocols solid phase extraction method which is used for fractionation and concentration of organic compounds. Composite samples (24 h) of treated industrial and municipal wastewater effluents were fractionated and screened for acute toxicity with the reverse electron transport (RET) mitochondria test. Solid phase extraction was performed with OasisTM cartridges, which are stabile at a wide pH range and which usually have a high recovery percentage. Before extraction the effluents were divided into subsamples and their pH values were adjusted to pH 3, 7.5 and 11. The cartridges were eluated with methanol and after evaporation the residues were screened for toxicity and genotoxicity. The genotoxic potential was tested with a novel VitotoxTM (Labsystems) assay based on the induction of the SOS response in the genetically modified luminescent Salmonella typhimurium TA104 recN2-4 strain by genotoxic compounds. The acute toxicities of the effluent samples to the RET assay were often so low, that IC50 values could not be measured. Although the toxicity of whole effluents was low, the cause of the toxicity could be tracked down to mainly organic compounds with a relatively low pKa value. Interestingly, an effluent with low acute toxicity (IC20=34 % effluent) showed a distinct genotoxic effect in the organic fraction. The methods used enabled chemical characterisation and identification of harmful substances, which appear in low concentrations in effluents and may be persistent and bioaccumulative. Key words: toxicity identification evaluation, genotoxicity, small-scale toxicity tests, solid phase extraction |
