Chlorine Dioxide Disinfection Process Optimization And Security Control

The objectives of this project are to study chlorine dioxide persistence and chlorite formation throughout treatment plants and distribution system and set up relevant criterion of dosage applied on drinking water and residual disinfector of finish water.It was showed that chlorine dioxide and chlorine decayed quickly in the beginning in samples, then the consumption was constant in first order-model. 39.7%~57.9% and 48.0%~70.0% of chlorine dioxide consumption converted to chlorite with the combinations of chlorine dioxide and chlorine and chlorine dioxide respectively. The most common methods for the generation of chlorine dioxide for drinking water treatment in china is that sodium chlorate is reacted with hydrochloric acid. The disinfector includes chlorine dioxide, chlorine, chlorite and chlorate. As the study has showed, chlorite and chlorate have no effect on bacteria and coliform, chlorine dioxide and chlorine have simlar effect on bacteria and coliform. So residual disinfector of finish water should be defined as the sum of residual chlorine dioxide and chlorine.In one water treatment plant which was applied pre-oxidation process, the dosage applied on drinking water should be 0.5mg/L, residual disinfector of finish water should be above 0.3mg/L. In another water treatment plant which was not applied pre-oxidation process, the dosage applied on drinking water should be above 1 .0mg/L, residual disinfector of finish water should be above 0.4mg/L. Forthermoer, if the the dosage applied on drinking water exceeds 0.5mg/L, chlorite concentration may exceed 0.2mg/L which approached the maximum contaminant level (MCL) (0.2mg/L) and some process should be applied to reduce chlorite concentration.