Genotoxicity of disinfection by-products (DBPs) upon chlorination of nine different freshwater algal species at variable reaction time

Nine local dominant freshwater algal species, including green algae (Chlorella sp., Chlamydomonas sp. and Scenedesmus quadricauda), diatom (Navicula pelliculosa, Nitzschia palea Grunow and Synedra sp.), blue-green algae (Microcystis sp., Chroococcus sp. and Gloeocapsa sp.) were isolated from source water reservoirs and cultivated in the laboratory. The algal biomass was chlorinated (20 °C, pH 7, residual chlorine 2 mg L⁻¹). Yields of chloroform, dichloroacetic acid, trichloroacetic acid, dichloroacetonitrile and trichloroacetonitrile and genotoxicity of the chlorinated solutions at eight chlorination intervals (0.5, 1, 2, 5, 10, 30, 60 and 120 min) were determined via SOS-ChromoTest and Comet assay. The results showed that green algae and diatom were more effective disinfection by-products (DBPs) precursors than blue-green algae. Genotoxicity was shown to be chlorination time-dependent, in agreement with our previous findings, suggesting that intermediate DBPs rather than trihalomethanes or haloacetic acids were major contributors to the genotoxicity of chlorinated solutions.