Permeability of chloramine species by RO membrane and its impacts on downstream UV based process in potable reuse trains

The use of membranes for wastewater filtration necessitates chloramine addition as a disinfectant to mitigate membrane biofouling. However, the speciation of chloramine (i.e., monochloramine and dichloramine) in potable reuse process trains has not been studied in depth. This study investigated the permeability of mono- and dichloramine across RO membranes t lab and pilot scale, he oxidative effects of mono- and dichloramine on polyamide RO membranes, and the implications for downstream UV treatment. The permeability of chloramine species was lower in the pilot-scale system (system recovery = 58.3%) as compared to that of the lab-scale system (system recovery <1%), suggesting that increases in system recovery associated with series treatment trains leads to higher permeabilities due to overall higher concentration polarization. When exposing polyamide membranes to monochloramine (19,934 ppm h), the flux increased by 131%. On the contrary, when exposing polyamide membranes to dichloramine (18,636 ppm h), the flux decreased by 36%. Dichloramine exhibited stronger oxidative degradation of membranes as compared with monochloramine, as observed by attenuated total reflection Fourier transform infrared (ATR-FTIR) analysis. Real wastewater samples containing mono- and dichloramine were separated using RO membranes. The change in the RO permeate’s UV transmittance (UVT) was used to indicate the impacts of monochloramine and dichloramine permeability on downstream UV based processes in potable reuse trains.