To investigate the operational efficiency of the combined process of contact oxidation and ultrafiltration for the pollutants removal of groundwater, which contained high concentration of Mn(II), Fe(II) and ammonia, a pilot-scale system was conducted and operated in Harbin. Moreover, membrane fouling potential was also investigated under different fluxes. The concentrations of total iron, Fe²⁺, Mn²⁺ and NH₄⁺-N in the feed water were approximately 14.67, 11.23, 0.83, and 2.22 mg/L, respectively. Experimental results showed that the effluent water quality of the combined process met Chinese Drinking Water Standard (GB5749—2006), with an average concentration of iron, manganese and ammonia in the effluent of 0.06, 0.04 and 0.44 mg/L, respectively. Furthermore, the turbidity of UF effluent was lower than 0.10 NTU, and with a bacteria removal efficiency of approximately 100%. SEM-EDS results demonstrated a low flux would be beneficial to alleviate the membrane fouling.