The permeate flux remained relatively stable at around 5.67 LMH after 50 days; a decrease by 43% from the initial water flux of 9.90 LMH. This decline in permeate flux could be due to the elevated salinity in the bioreactor which resulted from the accumulation of salts within the bioreactor. The increase in the salinity of the bioreactor not only reduces the effective osmotic driving force and affects the FO process performance, but may also cause adverse impact on the biological activities in the bioreactor