Display omitted •Mass flows of C and N were redesigned by AnMBR-PN/A.•Removal efficiencies of COD and TN were 90.3%-95.1% and 75.0%-81.7%, respectively.•48.4%-63.1% of C was captured as CH4 and 26.7%-39.7% of C was captured as sludge.•8.5%-16.1% of N was entrapped by membrane and 45.3%-58.1% of N was removed by PN/A.•AnMBR and PN/A mutually complement each other ensured excellent system performance. A pilot-scale anaerobic membrane bioreactor (AnMBR) integrated with a one-stage partial nitritation-anammox (PN/A) reactor was operated for the treatment of municipal wastewater (MWW) at seasonal temperatures of 15–25 °C. The removal efficiencies of COD and total nitrogen (TN) were always > 90% and > 75% respectively. The methanogenesis and PN/A were identified as the primary removal pathways of COD and TN, respectively, and were suppressed at low temperatures. With the temperature dropped from 25 °C to 20 °C to 15 °C, the methane-accounted COD decreased from 63.1% to 59.6% to 48.4%, and the PN/A-accounted TN decreased from 58.1% to 51.7% to 45.3%. The AnMBR and PN/A mutually complement each other in this combined process, as the AnMBR removed 8.5%-16.1% of TN by sludge entrainment and the PN/A reactor removed 2.6%-3.4% of COD by denitrification and aerobic oxidation. These results highlighted the strong feasibility of applying the AnMBR-PN/A process to the treatment of MWW in temperate climate.