Genotoxicity of substances in the nightsoil and its biologically treated water

Genotoxicity was evaluated in the performance of nightsoil treatment plants, because the human feces and urine would contain some genotoxic compounds. A newly developed assay, Salmonella typhimurium NM strains in umu test, were applied to the samples to detect highly sensitive activities induced by nitroarenes and aromatic amines. Strong genotoxicity could be observed in the influent of a nightsoil treatment plant and the effluent from biological reactor by both of parent strain and new strains. The quantitative analysis using the genotoxic intensity, that is, the slopes of dose-response was conducted to compare the genotoxicity on a group of some compounds included in complex samples such as nightsoil. The genotoxicity on aromatic amines was converted to the potency by aminofluorene represented as mg aminofluorene/mg dry weight. The genotoxicity could not be removed by biological treatment process and ultra filtration, and reduced around 90% by coagulation-sedimentation process. While the potency on nitroarenes which was converted to 1-nitropyrene, mg nitropyrene/mg dry weight, could not be removed sufficiently through the treatment process.