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

Two biofilm annular reactors(BAR) in series were investigated to compare the relative efficacy of chlorine and chlorite in nitrification by analyzing residue chlorine,NH₄⁺-N,NO₂^--N,NO₃^--N,DO,HPC and AOB.The results showed that the concentration of NH₄⁺-N was dropped and those of NO₂^--N and NO₃^--N were increased during the stage of adding chlorine.However,that was not happened by adding chlorite because of enhancing the effluent concentration of residue chlorine and DO.Consequently,the chlorite was more effective than chlorine in mitigating nitrification.Compared with equivalent chorine(0.6 mg/L),the suspended and attached HPC of the first BAR reduced 2.58 log and 2.86 log,respectively,both suspended and attached AOB declined 1 log using the chlorite.Therefore,the effect of chlorite is better than chorine combined with chloramine in mitigating nitrification in distribution systems.