Impacts of monochloramine as an antifouling agent during nanofiltration (NF) of portable water

Abstract

In this study, we investigated the potential applicability of monochloramine (MCA) for the control of membrane biofouling using a pilot-scale nanofiltration (NF) process in an advanced drinking water treatment process. It was found that membrane fouling was significantly mitigated and the increase of trans-membrane pressure was retarded more than three folds by the addition of 5 mg/L MCA. The analysis of membrane foulants after the autopsy revealed that the organic content was significantly decreased from 63.1% to 49.1% and most of the microorganisms were inactivated by the addition of MCA. Interestingly, the addition of MCA caused a dramatic decrease in protein compounds in extracellular polymeric substances extracted from biofilms, which hindered the development of dense biofilm structure. The addition of MCA also induced a significant change in the microbial community structures in the biofilm. In the presence of MCA, Alphaproteobacteria became the dominant class accounting for 59.8%, while Betaproteobacteria, which is the major bacterial community forming the biofilm in the membrane process, was decreased by 31.8%. Based on this study, the addition of MCA was effective in retarding the formation of biofilm on NF membrane surfaces by inactivating microorganisms and weakening the strength of biofilm structures.