Pervaporation-assisted desalination of seawater reverse osmosis brine

In this work, pervaporation (PV) was employed to desalinate seawater reverse osmosis (SWRO) brine. Synthetic brines were used to examine the influence of operating conditions (e.g., feed salt content, temperature, permeate pressure and feed pH) on the PV performance. A flux of 6.6 kg/(m2 h) with a salt rejection of 99.9% was achieved for a feed salt content of 50 g/L at a temperature of 50 °C and permeate pressure of 0.5 kPa. Water flux was increased with an increase in temperature and/or a decrease in permeate pressure, whereas the feed pH had little impact. The fouling behavior of the PV membrane was examined using a real SWRO brine at different volume concentration factors (VCFs). When the VCF increased from 1.0 to 3.0, the corresponding TDS in the feed solution increased from 55 to 165 g/L, and the water flux decreased from 6.2 to 3.0 kg/(m2 h). The PV and membrane distillation (MD) processes were compared under the same operating conditions. After 110 h, the water fluxes of the PV and MD membranes were reduced by 21.8% and 52.1%, respectively. The MD membrane suffered more severe fouling than the PV membrane, and the fouled PV membrane could be cleaned more easily with a simple water rinse. These results demonstrated that PV is advantageous over MD in terms of fouling resistance, membrane cleaning and flux recovery.