Effects of salinity on the removal of trace organic contaminants by membrane bioreactor treatment for water reuse
This study investigated the effects of salinity on the performance of a membrane bioreactor (MBR) system with a specific focus on the removal of trace organic contaminants. Eight trace organic contaminants were selected for this investigation. The obtained results indicated that changes in salinity in the range of 1-12 g/L have small impact on the removal of carbonaceous organic matter and total nitrogen (TN) by the MBR. The permeate water quality in terms of total organic carbon and TN slightly decreased when the system was exposed to higher salt concentration. A decrease in sludge production in saline mixed liquor was observed at salt concentration of 4 g/L, and then, microbial could adapt to the saline condition as evidenced in a gradual increase in biomass throughout this study. At a low salinity level, removal efficiencies of the selected trace organics are consistent with values previously reported in the literature. There was no significant impact of salinity on removal of the eight selected trace organic contaminants with bisphenol A being the only exception. However, severe membrane fouling was observed, when the salinity of the mixed liquor increased beyond 4 g/L. This could be explained by the increase in protein concentration in the supernatant which was probably released by the microbial population in response to the increase in salinity.