Studies on the fouling behavior and cleaning method of pervaporation desalination membranes for reclamation of reverse osmosis concentrated water

Schematic diagram of two stages of membrane fouling. [Display omitted] •Desalination performance of PV membrane to industrial reverse osmosis concentrate is first reported.•The produced water meets the discharge standard.•Chemical softening pretreatment is necessary to mitigate fouling.•Membrane flux is recovered 98% after chemical washing. Pervaporation (PV), as a cost-efficient concentrating process, has been studied for Zero Liquid Discharge (ZLD) of desalination. Although high water flux and excellent salt rejection have been reported for many PV membranes. The desalination performance, fouling behavior, and cleaning protocol for treating real reverse osmosis concentrate (ROC) generated from industrial plants have never been studied. Meanwhile, understanding the fouling behavior and cleaning method in the treating process is crucial for the development of suitable PV desalination membranes. In this study, we used a lab-made PV membrane to treat industrial ROC with a high chemical oxygen demand (COD) value and high salt concentrations. The results showed that conductivity and COD of the produced water were below 20 μs/cm and 70 mg/L, respectively, which fulfilled the discharge standard. However, the membrane fouling problem was not trivial. To address the fouling issue, a chemical softening method was adopted to remove the calcium salts of the ROC, and a membrane cleaning method was developed to regenerate the water flux. As a result, a long-term water flux of 31.27 kg/m2·h with a flux recovery rate of 98% were realized. This highlights the potential of PV desalination technology for ROC reclamation.