[Inactivation and removal of chlorine dioxide on cyclops of zooplankton]

Comparative experiments on the inactivation of cyclops by chlorine dioxide and chlorine were conducted. Batch experiments were performed in order to analyze the influence of pH value, organic precursor concentration on the rate of inactivation of cyclops with chlorine dioxide. In addition, the synergistic effect of different pre-oxidation followed by coagulation process on removal of cyclops in raw water was evaluated. It was found that chlorine dioxide possessed better inactivation effect than chlorine. Cyclops can be completely inactivated after 30 min of contact time by low dosage of chlorine dioxide (1.0 mg/L). The rate of inactivation was essentially the same at pH 5.7 and 8.0, and pH 9.8 resulted in the 10% of decrease in inactivation rate of cyclops than pH 5.7 - 8.0 in same contact time. The organic precursor concentration had negative effects on inactivation, and the higher the organic precursor concentration was, the lower inactivation rate of cyclops was achieved. The coagulation jar test showed that cyclops in the raw water could be completely removed by synergistic effect of chlorine dioxide pre-oxidation followed by coagulation process at chlorine dioxide dosage of 0.9 mg/L.