Disinfectant Efficacy of Chlorine and Chlorine Dioxide in Nitrification Control in Water Distribution Systems

Two biofilm annular reactors (BAR) in series were adopted in the study, and the effects of chlorine and chlorine dioxide disinfection on nitrification were compared by analyzing residue chlorine, NH₄⁺-N, NO₂^--N, NO₃^--N, DO, HPC and AOB.The results showed that chlorine dioxide was more effective than chlorine in enhancing the effluent concentration of residue chlorine and DO.The concentration of NH₄⁺-N was droped while NO₂^--N and NO₃^--N were increased during the stage of chlorine, but not happening during the stage of chlorine dioxide.Compared with equivalent chorine (0.6mg/L) , the chlorine dioxide was more effective in removing suspended and boifilm HPC with 2.54 log and 1.63 log reductions, respectively, and both suspended and biofilm AOB with 1 log reduction.Chlorine was ineffective in controlling AOB.Therefore, the effect of chorine dioxide combined with chloramine was better than chorine combined with chloramine in mitigating nitrification in distribution systems.