High-efficiency concentrated capture of carbon and phosphorus from real urban sewage via an ultrafiltration-forward osmosis (UF-FO) hybrid system

Urban wastewater contains abundant recoverable energy, primarily distributed in particulate and soluble organic matter. It is estimated that anaerobic treatment combined with biogas recovery technology can provide sufficient electricity to achieve energy self-sufficiency in wastewater treatment plants. Therefore, strengthening wastewater pretreatment to separate and concentrate organic matter not only enhances the anaerobic stability of both solids and liquid streams but also provides additional resources for subsequent energy recovery. This study proposes an innovative treatment method that integrates ultrafiltration (UF) and forward osmosis (FO) systems. The results demonstrate that the UF system achieved a chemical oxygen demand (COD) capture efficiency of 78.6 %, effectively retaining 68.3 % of organic matter in the sidestream, thus offering abundant resources for subsequent bioenergy recovery. Meanwhile, the FO system retained over 90 % of PO 4 3- -P, significantly increasing phosphorus concentration, with concentration multiples of 6.30 for PO 4 3- -P and 6.37 for total phosphorus (TP), facilitating efficient phosphorus recovery. Compared to conventional methods, the integrated UF-FO system reduced sludge production by over 50 % and increased net electricity generation by 39.2 %, demonstrating significant environmental benefits. This combined system provides a sustainable solution for fully enclosed wastewater treatment, achieving the triple objectives of resource recovery, energy production, and environmental protection.