Ecotoxicological effects of disinfection of treated wastewater

Katarzyna Affek, Adam Muszyński, Nina Doskocz, Monika Załęska-Radziwiłł

Treated wastewater may provide an effective alternative for meeting agriculture’s demands and increase freshwater resources for other needs. Disinfection of treated wastewater protects the receivers; nevertheless, hazards of handling disinfectants, and the fact that some of them do not remove certain pathogenic and opportunistic organisms, are two main reasons for undertaking research in this field. Ecotoxicity of effluent from a full-scale wastewater treatment plant, subjected to disinfection by chlorination, ozonation and UV irradiation, was investigated under laboratory conditions. The efficiency of bacterial inactivation was examined: microorganisms were sensitive to chlorine and UV disinfection, however, they were more resistant to ozonation. Ecotoxicity was evaluated on samples before disinfection and on disinfected samples in which the bacterial inactivation level was similar. Immobilization, growth and enzymatic ecotoxicological tests were performed using consumers, producers and decomposers, respectively. UV irradiation had the least negative impact on the tested bioindicators. Although some studies have shown opposite trends, it has been proved that ozonation and chlorination increase the toxicity of treated wastewater. This study suggests that the wide application of disinfectants to wastewater should be reviewed because, under the experimental conditions tested, they were able to cause harmful effects on one or more of the species tested and they could adv ersely affect biodiversity in the environment.

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