Sustainable integrated membrane contactor process for water reclamation, sodium sulfate salt and energy recovery from industrial effluent

The combined global impacts of water shortage and energy provide strong impetus to use innovative combinations of technologies to supply sustainably produced high quality water. Recent innovations have focused on the integration of membrane processes with other chemical separation unit processes and various stand-alone membrane processes. Coupling well-developed pressure driven membrane processes (such as nanofiltration (NF) and reverse osmosis (RO) with low energy demand membrane processes which allow the utilization of low-grade energy, industrial waste heat or renewable energy (such as membrane distillation (MD)) brings the promise of new sustainable technical solutions. In this work, two case studies will be reviewed and discussed — 1) integrated NF and MD-Crystallizer for resource recovery; and 2) the potential application of MD-Crystallizer for the concentration of RO brine (secondary reject from industrial wastewater treatment plant) towards a zero liquid discharge (ZLD) process. In Case I, MD flux of 15–20 Lm−2 h−1 with a water recovery of 80% was achieved (at a feed temperature (TF) of 60 °C and permeate temperature (TP) of 20 °C). In Case II, average MD flux of 4 Lm−2 h−1 with overall water recovery of 95% was achieved when operating with RO brine (TF = 45 °C; TP = 25 °C).

Research highlights
► Integrated membrane contactor process based on two case studies will be discussed.
► Case 1: Recovery of Na2SO4 from industrial effluent using MF-NF-MD-Crystallization.
► Case 2: RO-MD for brine concentration from an industrial waste water treatment plant.
► NF-MDC and RO-MDC give high recovery and potential zero liquid discharge process.