Mathematical modeling assisted investigation of forward osmosis as pretreatment for microbial desalination cells to achieve continuous water desalination and wastewater treatment

Abstract

Coupling forward osmosis (FO) with microbial desalination cells (MDCs) can lead to some synergistic benefits, i.e. simultaneous water recovery, desalination and removal of COD (chemical oxygen demand). Herein, an FO-MDC system was developed and examined in a continuously-operated mode. It achieved 70.6% COD removal from a synthetic wastewater and 94.0% conductivity decrease in a salt solution containing 35gL-1 NaCl. The flow rates of both wastewater and salt water exerted strong effects on the system performance. At a draw flow rate of 0.02mLmin-1, the effluent TDS (total dissolved solids) reached 315mgL-1, lower than the maximum contaminant levels of the National Secondary Drinking Water Regulations. A mathematical model was developed for the first time through integrating FO model with MDC model. This model could well predict the key performance parameters such as current generation and desalination effectiveness and rate. When further tested with actual domestic wastewater amended with glucose and NaHCO3, the FO-MDC system generated a desalinated effluent containing 1130mgTDSL-1. The results of this study suggest that proper coordination of the treatment capacity of the two membrane-based treatment processes could create a potentially effective system for wastewater reuse and seawater desalination.