Improved low-carbon-consuming fouling control in long-term membrane-based sewage pre-concentration: The role of enhanced coagulation process and air backflushing in sustainable sewage treatment

Membrane-based sewage pre-concentration is considered as a promising approach for sustainable wastewater treatment, however it suffers from fast cake layer fouling and unsatisfied concentration efficiency before implementation. This study proposed an enhanced membrane coagulation reactor (E-MCR), which combines microfiltration with enhanced coagulation process (ECP) and air-backflushing (AB), to solve the fouling control and carbon-consumption conflict. ECP was demonstrated to mainly contribute to the reduction of total resistance, cake layer resistance and irreversible resistance proportion, along with elevated cake layer filterability. Moreover, the high amount of loosely bound extracellular polymeric substances (EPS) in raw sewage was found to contribute most to the ineffectiveness of conventional aeration in sewage pre-concentration membrane fouling control. AB pressure was found as the key parameter in keeping the filtration sustainability. In long-term performance evaluation, the scenario with AB pressure of 200 kPa, AB ratio of 30 s:5 min30 s and concentrate retention time (CRT) of id achieved optimized filtration and maximized concentration efficiency with a concentrate of 9700 mg COD/L and 94% recovery, yielding carbon and phosphorus free permeate promising for low level reclamation or simple further treatment. With good anaerobic biodegradability of the concentrate (optimized value of 56.9%, similar to blackwater), E-MCR could get a net energy production (at least 0.0315 kWh/m(3)) when coupled with anaerobic digestion, showing the promise of a carbon-neutral membrane-based sewage treatment process.