Roles of sponge sizes and membrane types in a single stage sponge-submerged membrane bioreactor for improving nutrient removal from wastewater for reuse

Sponge not only can reduce membrane fouling by means of mechanical cleaning and maintain a balance of suspended-attached microorganisms in submerged membrane bioreactor (SMBR), but also can enhance dissolved organic matter and nutrient removal. This study investigated the performance of three different sizes of sponge (S28–30/45R, S28–30/60R and S28–30/90R) associated with continuous aerated SMBR. A laboratory-scale single stage sponge-SMBR (SSMBR) showed high performance for removing dissolved organic matter (>96%) and PO4–P (>98.8), while coarse sponges such as S28–30/45R, S28–30/60R could achieve more than 99% removal of NH4–N. When three-size sponges (S28–30/45R, S28–30/60R and S28–30/90R) were mixed at a ratio of 1:1:1 and in conjunction with two kinds of membranes (0.1 µm hollow fiber and 2 µm nonwoven), the SSMBR system has proved its generic merits of superior treated effluent quality and less membrane fouling. The NH4–N and PO4–P removal were found excellent, which were more than 99.8% and over 99% respectively. Molecular weight distribution also indicated that major fractions of organic matter could be successfully removed by SSMBR.