Oily Wastewater Treatment by Forward Osmosis and Nanofiltration Membranes

Abstract

Membrane technologies have been widely applied in water purification and wastewater treatment. This work describes and demonstrates two different membrane flat sheet modes, which are forward osmosis (FO-HTI Cartridge and Pouch) and nanofiltration (NF-90 and thin film NF-DL) for the treatment of oily wastewater (OWW). These membranes’ performance efficiency and reliability for reuse were investigated, especially when operated for a period under initial load conditions. Experiments were conducted in FO and NF mode to determine the water flux, the reverse salt flux, membrane wettability, and oil rejection. It was found that about 100% oil rejection could be achieved for oily treatment by FO at a pH of 6.7 to 7.3. The water flux was found to change slightly at feed initial concentration up to 30 mg L-1, indicating that the basic separation properties and the structure of the FO membrane have not been were unaffected. A less stable permeate flux was obtained for oil content ranging from 30 to 300 mg L-1. The average water fluxes for the FO-HTI Cartridge and Pouch membrane were ~ 8.5 and ~ 5 L.m-2 h-1, respectively, using 0.5 M NaCl as a draw solution. It was observed that this flux decreased rapidly with increasing oil-content concentration of the feed solution due to concentration polarization. The hydrophilicity and wetting behavior of NF membrane with average contact angles of a range (49.6° to 52.7°) were slightly higher hydrophilic than that of FO membranes with a range of contact angles approximately (64.82° to 67.27°).