Biostability characterization in a full-scale hybrid NF/RO treatment system

When a drinking water distribution system experiences bacterial growth, it can result in problems including reduced water quality, pipe corrosion, and possibly an increased incidence of bacteriological diseases. Assimilable organic carbon (AOC) has been correlated with such bacterial growth in drinking water distribution systems. When AOC is not removed from the water supply, disinfectants must be added to the water to decrease the potential for bacterial growth. Nanofiltration (NF) has proved effective at producing high-quality finished water. The objective of this study was to quantify the biostability potential across an NF treatment process to show the effects of treatment on AOC. The results indicate that the interactions between feedwater chemistry and a membrane surface can adversly affect the produced effluent. A reverse osmosis system is not capable of removing the majority of AOC when adverse solution chemistry-membrane interactions exist and thus produces biologically unstable water. Greater focus must be placed on feedwater quality in a reverse osmosis process in order to maximize efficiency. - SH.