Enhanced removal of natural organic matter by hybrid process of electrocoagulation and dead-end microfiltration

• There is a critical need to optimize NOM removal by membrane filtration.
• EC pretreatment significantly improved NOM removal rates and may dramatically mitigates fouling, in MF.
• The differences between improved NOM removal mechanism and fouling mitigation mechanism were discussed.
• The effects of solution pH, electrodes type and EC operation times were investigated.
• The filtration performance of hybrid EC&MF were supreme to UF, demonstrating its potential as efficient NOM removal method.

The significant role played by natural organic matter (NOM) in aquatic environments and water purification processes motivates the critical need to optimize its removal by membrane filtration. This work studied the performances of hybrid process that combines electrocoagulation (EC) and dead-end microfiltration (MF) to remove NOM. Both iron and aluminum were used as the anode materials under experimental conditions of pH 6, 7 and 8. Filtration performance was characterized by NOM removal rates and the time needed to filter 750 mL of solution. The results revealed that both iron- and aluminum-based electrocoagulation pretreatment can mitigate NOM fouling and improve NOM removal rates. Still, improved NOM removal due to EC pretreatment was not necessarily followed by fouling mitigation and, in some conditions, a severe fouling effect coupled with improved removal rates was observed. In general, the positive effect of EC on fouling was observed both at the initial stage and during the late stages of filtration. Both fouling mitigation intensity and improved removal rates were strongly dependent on initial pH value, EC operation time and type of electrode. The most significant improvement in MF performance due to iron- or aluminum-based EC was observed at pH 6. At higher pHs (7 and 8), the iron electrode was favored over the aluminum electrode.At optimal conditions, a 36-fold shorter filtration time and a 20% increase in NOM removal rates were observed with the EC-MF hybrid process as compared to 100 kDa ultrafiltration alone. These observations emphasize the high potential to incorporate an EC-MF hybrid process into NOM removal methods, due to its ability to facilitate high fluxes, low fouling, and high colloidal/NOM removal.