This study investigated the chlorination of Microcystis aeruginosa extracellular organic matter(EOM) solutions under different conditions, to determine how the metabolites produced by these organisms affect water safety and the formation of assimilable organic carbon(AOC). The effects of chlorine dosages, coagulant dosage, reaction time and temperature on the formation of AOC were investigated during the disinfection of M.aeruginosa metabolite solutions. The concentration of AOC followed a decreasing and then increasing pattern with increasing temperature and reaction time. The concentration of AOC decreased and then increased with increasing chlorination dosage, followed by a slight decrease at the highest level of chlorination. However, the concentration of AOC decreased continuously with increasing coagulant dosage. The formation of AOC can be suppressed under appropriate conditions. In this study, chlorination at 4 mg/L, combined with a coagulant dose of 40 mg/L at 20°C over a reaction time of 12 hr, produced the minimum AOC.
Chironomid larvae propagated excessively in eutrophic water body and c ould not be effectively inactivated by the conventional disinfection process lik e chlorination due to its stronger resistance to oxidation. In this paper, a pil ot-scale study of chlorine dioxide preoxidation cooperating with routine clarifi cation process for Chironomid larvae removal was conducted in Shenzhen Waterwork s in Guangdong Province, China. The experimental results were compared with that of the existing prechlorination process in several aspects, including the Chiro nomid larvae removal efficiencies of water samples taken from the outlets of sed imentation tank, sand filter, the security of drinking water and so on. The resu lts showed that chlorine dioxide might be more effective to inactivate Chironomi d larvae than chlorine and Chironomid larvae could be thoroughly removed from wa ter by pre-dosing chlorine dioxide process. The GC-MS examination and Ames test further showed that the sort and amount of organic substance in the treated wate r by chlorine dioxide preoxidation were evidently less than that of prechlorinat ion and the mutagenicity of drinking water treated by pre-dosing chlorine dioxid e was substantially reduced compared with prechlorination.
SUN Xing-binCUI Fu-yiZHANG Jin-songGUO Zhao-haiZHAO KaiLIU Li-junLV Wei-min
