Genotoxicity of the disinfection by-products resulting from peracetic acid- or hypochlorite-disinfected sewage wastewater

Wastewater disinfection is routinely carried out to prevent the spread of human pathogens present in wastewater
effluents. To this aim, chemical and physical treatments are applied to the effluents before their emission in water
bodies. In this study, the influence of two widely used disinfectants, peracetic acid (PAA) and sodium hypochlorite
(NaClO), on the formation of mutagenic by-products was investigated. Wastewater samples were collected before and
after disinfection, in winter and in summer, at a pilot plant installed in a municipal wastewater-treatment plant. Samples
were adsorbed usingsilica C18 cartridges and the concentrates were tested for mutagenicity in the Salmonella
typhimurium reversion test with strains TA98 and TA100. Non-concentrated water samples were tested with two plant
genotoxicity assays (the Allium cepa root anaphase aberration test and the Tradescantia/micronucleus test).
Mutagenicity assays in bacteria and in Tradescantia showed borderline mutagenicity in some of the wastewater
samples, independent of the disinfection procedure applied. Negative results were obtained in the A. cepa anaphase
aberration test. These results indicate that, in the conditions applied, wastewater disinfection with PAA and NaClO
does not lead to the formation of significant amounts of genotoxic by-products.