Biological pretreatment coupled gravity-driven membrane filtration for purifying decentralized domestic wastewater toward resource reuse

Abstract

Membrane bioreactor (MBR) is an effective technology for the decentralized wastewater treatment; however, its high energy consumption and complex operation & maintenance limit its intensive application. This study introduced an innovative membrane-based process, gravity-driven membrane (GDM) filtration, to treat the decentralized wastewater without any cleaning procedures, and different biological pretreatments were constructed, including (I) tubular filler (TF-8), (II) tubular filler (TF-4), (III) fiber bundle filler (FBF), and (IV) sole aeration (control) to improve the filtration performance. The results indicated that the flux of GDM control can be maintained during long-term filtration in treating the real decentralized wastewater, and introducing the biological pretreatment processes could improve the stabilized flux of GDM without any influence on its stability. The average flux of TF-8/GDM was 3.69 ± 0.89 L m−2 h−1 during long-term filtration. Furthermore, coupling pre-treatment to GDM can effectively improve permeability quality and withstand the shock of water quality fluctuations. The average removal rates of chemical oxygen demand (COD) and dissolved organic carbon (DOC) by TF-8 were 59.7% and 48.3%, respectively. Besides, the organic contaminants could be further removed by the following GDM process owing to the biodegradation function of the self-formed biofilm on the membrane surface, and the DOC concentration in the GDM effluent can be reduced to as low as 4.5 mg L−1. Additionally, the elements of nitrogen (N) and phosphorus (P) could be effectively retention through the coupling process, with a retention rate of 84.3%–94.6% for total nitrogen (TN) and 99.8%–104.8% for total phosphorus (TP), respectively. Therefore, these findings can benefit to develop of new strategies to provide stable effluent quality, resource recovery, and energy consumption reduction in the membrane-based decentralized domestic wastewater treatment.