Integrated electroflocculation-membrane process for pre-concentration of domestic wastewater: Filtration performance, organics recovery and membrane fouling characteristics

Abstract

A novel electroflocculation-membrane (EFM) reactor for pre-concentrating domestic wastewater (DWW) is proposed in this study, using a conventional direct membrane filtration (DMF) reactor as a control. The results showed that under the operating conditions of a current density of 5 A/m2, an electrolysis time of 2.5 h and an inter-electrode distance of 25 mm, an obviously higher organics recovery efficiency of 72.92 % can be achieved in EFM, while only 55.14 % was obtained in DMF. Concentrate with chemical oxygen demand (COD) concentration of 4391.50 mg/L and 3322.88 mg/L was finally got by EFM and DMF, respectively. The higher retention effect of the dissolved organics remained key to the enhanced organics recovery capability of the EFM. Membrane fouling was also mitigated with EFM in continuous operation, with transmembrane pressure (TMP) increasing rate of 0.15 kPa/h (1.27 kPa/h for DMF). The loose and porous floc structure and small size distribution of the supernatant in EFM were the main contributors for reducing the resistance of the cake layer to mitigate membrane fouling. This study provides a new perspective on future wastewater resource recovery.