Toxicity-based criteria for the evaluation of textile wastewater treatment efficiency

Brazilian textile mills import wastewater treatment technologies, performances of which are generally evaluated only on a physicochemical basis. Thus, a battery of bioassays was used to evaluate the performance of an ozonation system to treat textile effluents. Comparative toxicological profiles for bacteria (Vibrio fischeri), algae (Scenedesmus subspicatus), daphnia (Daphnia magna), fish (Poecilia reticulata), and plants (soybean--Glycine max, rice--Oryza sativa, and wheat--Triticum aestivum), as well as genotoxic effects (Vicia faba micronucleus assay), are presented for both raw and ozonated textile effluents. The relative sensitivity of bioassays (or end points) to textile effluents found in this study in decreasing order was plant enzymes > bacteria > algae daphnids approximately = plant biomass approximately = germination rate > fish. No significant genotoxic effect was found. We have concluded that ozonation was relatively effective in reducing toxicity of textile effluents. Bioassays used in this study proved to be sensitive and reliable tools for determining the toxicity of industrial effluents, and thus they can be used to evaluate emerging technology efficiency.