Optimization of the enhanced membrane coagulation reactor for sewage concentration efficiency and energy recovery

The application of an enhanced membrane coagulation reactor (E-MCR) for sewage concentration and energy recovery through anaerobic digestion (AD) was investigated. The results show that the addition of powder-activated carbon (PAC) and polyaluminum chloride (PACl) enhanced the sewage concentration efficiency and minimized the membrane fouling. The reactor was operated for 100 d with 70 d without severe fouling. The flux of 6 L/(m² h) with sludge retention time of 2 d recorded a long-term stable performance and recovered concentrates with about 6000-9800 mg/L of chemical oxygen demand (COD) values. The concentrate was used as feed for AD using a continuous stirred tank reactor. The results show that at a thermophilic temperature of 35°C, a high biogas yield was achieved at 20 and 30 d hydraulic retention time (HRT). Meanwhile, biogas yields of 10, 220, and 295 mL/(gCOD) were achieved at 10, 20, and 30 d HRT, respectively. The addition of PAC/PACl and the low flux condition enhanced the concentration efficiency and minimized the membrane fouling during the long-term operation. Thus, with the optimization of the operation, E-MCR becomes a promising option for sewage concentration and energy recovery.