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

Many human pathogenic micro-organisms can be transmitted by waters contamin ated by wastewater effluents. Wastewater disinfection helps prevent the spr ead of these pathogens in aquatic environments. Chlorination is the most wi dely used method for the disinfection of wastewater, but can cause the form ation 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 altern ative to chlorine, such as chlorine dioxide, ozone, peracetic acid and UV r adiation, on the formation of mutagenic and toxic compounds in wastewater. Wastewater samples were collected before and after disinfection in summer a nd in winter and then adsorbed using silica C-18 cartridges. Concentrates w ere tested For mutagenicity using the Ames rest. For toxicity test, a biolu minescence assay using Vibrio fischeri photobacteria was employed. To detec t DNA damage activity non-concentrated water samples were tested using two genotoxicity plant tests (Allium test and Tradescantia/micronuclei test). A ll disinfectant treatments produced bacterial mutagenicity, particularly af ter treatment with ClO2 or ozone. The Allium cepa test gave positive result s only for PAA-treated wastewater sampled in winter and the Tradescantia/MC N test always gave negative results. Raw wastewater, ClO2- and PAA-disinfec ted waters showed toxic effects in the marine bacteria test. (C) 2000 Elsev ier Science Ltd. All rights reserved.