Intensifying low-pressure membrane performance based on bio-cake layers coupled with pre-loading layers

Abstract

Low-pressure ultrafiltration membranes (LPM) are a promising technology for the decentralized water supply. However, currently available ultrafiltration membranes cannot easily achieve the simultaneous removal of ferrous iron (Fe2+), manganese (Mn2+), and ammonia (NH4+). In this study, LPM coupled with three pre-loading layers consisting of manganese dioxide (MnO2) powder, powdered activated carbon (PAC), and zeolite powder, labeled M-LPM, C-LPM, and Z-LPM, respectively, in order to improve the effluent quality and shorten the ripening time without reducing the stable flux. The results show that the stable flux of M-LPM and C-LPM increased, while decreased for Z-LPM due to the viscosity of the pre-loading layer material. The ripening time of the three LPM systems was shortened, with M-LPM showing excellent Mn2+ removal throughout filtration, while Z-LPM exhibited notable adsorption of Mn2+ and NH4+. CLSM analysis revealed that the biological reactions occurred intensely in the upper area of the bio-cake layer. Based on the analysis of key enzyme genes, the microbial pollutant removal pathways were constructed. In addition, the optimal loading curve of the M-LPM pre-loading layer was established. Overall, the enhanced performance highlights the feasibility and potential of applying the LPM strategy in decentralized water supplies.