Performance comparison of reverse osmosis (RO) with integrated nanofiltration (NF) and reverse osmosis process for desalination of MBR effluent

Membrane bioreactor (MBR) effluents of industrial wastewaters generally include high amounts of salinity, nitrate and hardness. Although MBR process can be applied for the production of low and/or medium quality water, nanofiltration (NF) or reverse osmosis (RO) processes are needed for removal of excess salinity from MBR effluent. Since the fouling is a unique problem for membrane systems, pre-treatment operations are gaining importance. Main objective of this study is to investigate the effect of NF system as pre-treatment before RO system in wastewater treatment. Feed solutions with two different conductivities were fed to the RO system for this purpose. In addition, change in the permeate quality was monitored and permeate quality increase was noticed in the NF pre-treatment study. Average normalized permeate fluxes of RO system were 32.3 L/m(2).h and 28.7 L/m(2).h for the study with NF pre-treatment and with only RO study, respectively. Treated wastewaters were also evaluated for the suitability of their reuse in cooling, steam generation as process water and agricultural irrigation. Experiments were performed in wastewater treatment plant of ITOB-Industrial Organized Zone (ITOB-OSB) Tekeli-Menderes, Izmir, Turkey.