Operation of Different Reverse Osmosis (RO) Membrane Modules for the Treatment of High-Strength Wastewater to Enhance the Recovery of Clean Water—A Case Study in Bac Ninh, Vietnam

In this study, a wastewater treatment plant (WWTP) in Vietnam receiving high-strength wastewater with COD of about 30,000 mg/L and various heavy metals from industries was treated by different RO membrane modules in order to meet the stringent national discharge standard and recover wastewater for reuse. The Fenton and coagulation pre-treatments were employed based on optimal conditions, which were experimentally pre-determined. For the RO membrane system, the two-stage treatment employed a plate frame RO (PFRO) followed by spiral wound RO (SPRO) to obtain high-quality permeate, while the high-pressure PFRO (HP PFRO) module was employed for the recovery of concentrated streams from the PFRO unit. As a result, a significant COD removal efficiency of 99.62% was achieved in the SPRO module. The heavy metal concentrations (i.e., Cu, Fe, Zn, Mn, Cr) measured in the output mostly met the standards for discharge levels. A significant decrease in electrical conductivity (EC) to below 250 µS/cm was achieved. In addition, high rates of water recovery were achieved from the RO modules (i.e., PFRO 63%, HP PFRO 9–12%, SPRO > 80–90%). The high-quality treated wastewater was thus suitable for reuse purposes. This study highlights the feasibility of RO membranes for practical treatment of high-strength wastewater and provides valuable data for the WWTP operator.