Inactivation of Chironomid larvae with chlorine dioxide

In this paper, comparative experiments on the inactivation of Chironomid larvae by chlorine dioxide and chlorine were conducted. In addition, batch experiments were performed in order to analyze the influence of pH value, organic precursor concentration and temperature on the inactivation efficiency of Chironomid larvae with chlorine dioxide. Based on it, removal effect of different pre-oxidation followed by coagulation process on Chironomid larvae in raw water was evaluated. The results showed that chlorine dioxide possessed better inactivation performance than chlorine, and complete inactivation of Chironomid larvae was obtained at CT value of 37.5 mg min/L (dose of 1.5 mg/L and exposure time of 25 min). The pH in the range of 6-8 did not affect the inactivation efficiency of chlorine dioxide, whereas pH 10 resulted in around 10% decrease in inactivation rate. Meanwhile, the organic precursor had negative effects on inactivation, indicated by the decreased inactivation rate from 100% at TOC concentration of 0 mg/L to 62.2% at 8 mg/L when the CT value was 45 mg min/L. With regard to the temperature, the inactivation efficiency of Chironomid larvae was significantly improved with the temperature increasing within the range investigated of 10-25 degrees C. The inactivation rate was reduced by 68.9% when temperature reduced from 25 degrees C to 10 degrees C. The coagulation jar test showed that Chironomid larvae in the raw water could be completely removed by chlorine dioxide pre-oxidation in combination with the coagulation process at CT value of 24.8 mg min/L. (c) 2006 Elsevier B.V. All rights reserved.