Applying a dynamic membrane filtration (DMF) process for domestic wastewater preconcentration: Organics recovery and bioenergy production potential analysis

Abstract

Wastewater is increasingly recognized as a valuable resource rather than as a waste, motivating a shift in the perspective of wastewater treatment from pollution control to resource recovery. This study proposes the recovery of organic matter from domestic wastewater for the production of bioenergy through a novel process of wastewater preconcentration based on dynamic membrane filtration (DMF). The selection of a dynamic membrane (DM) supporting material, the preconcentration performance of organics, and the biomethane production potential (BMP) of the organic concentrate were investigated. The process optimization results indicated that a DM module with a supporting material of a 25 μm stainless steel mesh with a three-layer structure, assisted by internal suspended particles derived from raw wastewater, enabled the rapid DM layer formation within 1 h. The DMF process operated under a constant high flux of 30–60 L/m2 h at a trans-membrane pressure (TMP) of less than 40 kPa. During the continuous DMF operation, the average chemical oxygen demand (COD) of the influent, effluent and concentrate was 305, 113 and 2000–2500 mg/L, respectively, while the removal performance of other pollutants(such as nitrogen and phosphorus) varied, indicating differential retention effects for the various pollutants by the DM layer. Air back-flushing can effectively regenerate the DM layer and maintain long-term stable operation, but higher rates of TMP increase were observed for later filtration cycles, probably due to the accumulation of physically irremovable fouling. The BMP of the DMF concentrate was 0.20 L CH4/g COD, which was comparable to the ordinary biogas yield from municipal wastewater by anaerobic digestion. The DMF process integrated with anaerobic digestion can be a promising alternative for energy-sufficient wastewater treatment.