Enhanced removal of Chironomus kiiensis larvae in conventional water treatment process by pre-oxidation

Chironomus kiiensis larvae, which cannot be exterminated by conventional disinfection processes, propagate prolifically in eutrophic water bodies, therefore posing a potential problem for drinking water quality. In this work, quantitative experimental studies were carried out on inactivation of Chironomus kiiensis larvae using conventional oxidants of chlorine (Cl₂), chlorine dioxide (ClO₂) and ozone under conditions of different oxidant dosages, organic precursor concentration and pH values. The results showed that three oxidants used could inactivate Chironomus kiiensis larvae to some extent. Chlorine and chlorine dioxide were proved to be the least and most efficient oxidant for inactivating Chironomus kiiensis larvae, respectively. In addition, the synergic removal effects with pre-oxidation followed by conventional water treatment processes were also evaluated. The results showed that pre-oxidation could lead to enhanced removal of the inactivated organism by the subsequent coagulation process while lowering the dosage of oxidant. In view of the need to secure drinking water quality, it is necessary to combine oxidant inactivation with conventional processes for removing Chironomus kiiensis larvae from micro-polluted water sources.