Comparing the performance of various nanofiltration membranes in advanced oxidation-nanofiltration treatment of reverse osmosis concentrates.

Reverse osmosis (RO) technique plays an important role in the treatment of secondary biochemical effluent. However, the reverse osmosis concentrate (ROC) with high salinity and organic pollutants generated from this process remains a challenge to be tackled. The O3-assisted UV-Fenton advanced oxidation process (AOP) as a pretreatment for the nanofiltration (NF) was used to treat the ROC of industrial wastewater. The optimal removal rates of COD and UV254 were 80.4 and 77.4%, respectively. In the NF process, four types of commercial NF membranes (NF90 (Dow, USA), DK (GE, USA), NT101, and NT103 (NADIR, Germany)) were used to treat the AOP effluent. The effects of operating pressure and feed temperature on ion rejection were investigated. The results show that NF90 and NT103 membranes had better rejections to monovalent ions, while DK and NT101 membranes could effectively separate monovalent and divalent ions and their ion rejections decreased with the increase of feed temperature. With the NF90 membrane, the highest TDS removal rate of 89.65% was obtained at the operating pressure of 1.2 MPa.