Fractionation and toxicity evaluation of waste waters

Several toxicity-based procedures have been proposed for waste water risk assessment but the toxic agents could never be identified in these very complex mixtures. A procedure was adopted using disposable solid-phase extraction cartridges to extract organic chemicals and preparative HPLC to fractionate them in relation of their hydrophobicity. Acute toxicity of whole samples and their fractions was measured on Daphnia magna, using a commercially available biokit. The procedure was applied to leachate from an industrial landfill and a textile effluent. In both cases the toxic effects due to xenobiotics were highest in the most hydrophobic HPLC fraction. The compounds responsible for the observed toxicity were identified and quantified by GC–MS. Reconstructed mixtures were analysed to assess their fitting with GC profiles and tested for toxicity to compare the responses of individual chemicals and mixtures.