The role of forward osmosis and microfiltration in an integrated osmotic-microfiltration membrane bioreactor system

• By integrating MF with OMBR, salinity build-up in the bioreactor could be controlled.
• Hydrophobic and readily biodegradable TrOCs were well removed (>90%) by O/MF-MBR.
• OMBR offered better treatment than MF-MBR for hydrophilic/persistent TrOCs.
• Resistant TrOCs retained by forward osmosis leaked through MF channel of the O/MF-MBR.

This study investigates the performance of an integrated osmotic and microfiltration membrane bioreactor (O/MF-MBR) system for wastewater treatment and reclamation. The O/MF-MBR system simultaneously used microfiltration (MF) and forward osmosis (FO) membranes to extract water from the mixed liquor of an aerobic bioreactor. The MF membrane facilitated the bleeding of dissolved inorganic salts and thus prevented the build-up of salinity in the bioreactor. As a result, sludge production and microbial activity were relatively stable over 60 days of operation. Compared to MF, the FO process produced a better permeate quality in terms of nutrients, total organic carbon, as well as hydrophilic and biologically persistent trace organic chemicals (TrOCs). The high rejection by the FO membrane also led to accumulation of hydrophilic and biologically persistent TrOCs in the bioreactor, consequently increasing their concentration in the MF permeate. On the other hand, hydrophobic and readily biodegradable TrOCs were minimally detected in both MF and FO permeates, with no clear difference in the removal efficiencies between two processes.