Simultaneous removal of iron, manganese, and ammonia enhanced by preloaded MnO2 on low-pressure ultrafiltration membrane

Low-pressure ultrafiltration membrane (LPM) is an ideal technology for decentralized water supply. However, the applicability for removing ferrous iron (Fe 2+ ), manganese (Mn 2+ ), and ammonia (NH 4 + ) in the source water and related mechanisms remained unknown. To fill this major knowledge gap, we systematically compared the pristine (pr-LPM) and MnO 2 -preloaded membrane (Mn-LPM). Mn-LPM allowed higher water flux while enhancing the removal of Fe 2+ , Mn 2+ , and NH 4 + . The removal efficiency of Mn 2+ immediately reached 99.6% on the first day. The preloading of MnO 2 also enhanced the removal capacity of NH 4 + . A series of instrument characterizations suggest that a higher NH 4 + concentration resulted in a thicker bio-cake layer, correlating to the higher pollutant removal efficiency and the decrease in the stable flux. Under high NH 4 + concentrations, Anaerobic Ammonia Oxidation likely contributes to NH 4 + removal. These findings significantly improve the understanding and help the design of LPM systems for cost-effective decentralized water supply in remote areas.