The influence of different disinfectants on mutagenicity and toxicity of urban wastewater

Many human pathogenic micro-organisms can be transmitted by waters contaminated by wastewater effluents. Wastewater disinfection helps prevent the spread of these pathogens in aquatic environments. Chlorination is the most widely used method for the disinfection of wastewater, but can cause the formation of mutagenic/carcinogenic and toxic by-products which are potentially harmful to human and aquatic organisms. The aim of this research was to study the influence of disinfectants alternative to chlorine, such as chlorine dioxide, ozone, peracetic acid and UV radiation, on the formation of mutagenic and toxic compounds in wastewater. Wastewater samples were collected before and after disinfection in summer and in winter and then adsorbed using silica C18 cartridges. Concentrates were tested for mutagenicity using the Ames test. For toxicity test, a bioluminescence assay using Vibrio fischeri photobacteria was employed. To detect DNA damage activity non-concentrated water samples were tested using two genotoxicity plant tests (Allium test and Tradescantia/micronuclei test). All disinfectant treatments produced bacterial mutagenicity, particularly after treatment with ClO2 or ozone. The Allium cepa test gave positive results only for PAA-treated wastewater sampled in winter and the Tradescantia/MCN test always gave negative results. Raw wastewater, ClO2- and PAA-disinfected waters showed toxic effects in the marine bacteria test.