Genotoxicity of influents and effluents of the wastewater treatment plant

Abstract

Wastewaters are treated through different processes of wastewater treatment procedures. Nevertheless they often contain mutagens especially when the proportion of industrial wastewater in comparison to municipal wastewater is high. In this study we evaluated mutagenic potential of influents and effluents from a wastewater treatment plant that is processing both industrial and domestic wastewater. The mutagenicity of XAD-2 extracts of influent and effluent was evaluated by means of Ames test using S. typhimurium strains TA100 and TA98 in the presence and in the absence of metabolic activation. Extracts that were mutagenic to strain TA98 without metabolic activation were suspected to contain nitropolyaromatic hydrocarbons (nitro-PAHs). To confirm this hypothesis they were tested with nitroreductase (TA98NR) and O-acetiltransferase (TA98/1,8DNP6) deficient derivatives of strain TA98, that are resistant to nitropolyaromatic hydrocarbons. The nitroreductase deficient strain TA98NR was less sensitive to the mutagenic extracts of influent than the parent strain TA98. The O-acetiltransferase deficient strain TA98/1,8DNP6 was resistant to the mutagenic extracts of influent. The mutagenic extracts of the effluent were nearly equally mutagenic to the parent strain TA98 and both deficient strains TA98NR and TA98/1,8DNP6. On the basis of the responses of nitroreductase deficient strains on the influent and effluent it was concluded that the influent contained nitro-PAHs. These were not removed or inactivated during the biological treatment of the wastewater, but activated to the final nucleophylic form able to induce mutations strain TA98 and in its nitroreductase deficient derivatives TA98NR and TA98/1,8DNP6.