An integrated MDC–FO membrane configuration for simultaneous desalination, wastewater treatment and energy recovery

A novel microbial desalination cell (MDC) configuration was developed by introducing a forward osmosis (FO) membrane, separating the cathode chamber from a fourth extra chamber. Wastewater is treated using a sequential anode–cathode feed. The new chamber then serves as a FO draw chamber, where a saline solution is used to recover freshwater from the adjacent cathode chamber. The diluted saline solution then goes to the MDC middle chamber for further desalination. Three identical cells were constructed and operated in cyclic-batch-flow mode at different initial wastewater and saline solution concentrations. Up to 84.8 ± 1.7% of the wastewater was recovered as freshwater. Freshwater recovery decreases at lower salt concentrations and higher wastewater COD concentrations due to the lower osmotic pressure difference. Salinity of saline water was decreased by up to 69.57 ± 3.85% at the highest initial salinity. COD removal up to 94.42 ± 4.15% was reached. COD removal rates were higher at higher COD concentrations. Polarization curves show the effect of COD on the internal resistance, where cells operated at lower COD experienced higher internal resistance. Scanning electron microscopy (SEM) images revealed the extent of fouling on the ion exchange membrane and biofilm formation on the FO membranes and the electrodes.