Abstract: In this investigation,the individual submerged membrane bioreactor(MBR),the biological activated carbon(BAC),and the hybrid BAC+MBR process are operated in parallel and investigated in terms of their effectiveness for coping with ammonium shock loading in drinking water sources.Experimental results show that the individual MBR exhibits excellent capacity in dealing with the sudden high-ammonium pollution,as demonstrated by the fact that even when the NH3-N concentration of 8-10 mg/L is presented in raw water,the corresponding MBR effluent concentration is only(0.36±0.15) mg/L,and the effluent NO₂^--N accumulation is observed only when the influent NH₃-N concentration is as high as 9.74 mg/L.Due to the limited availability of dissolved oxygen in BAC,the efficiency of BAC for ammonium removal during ammonium shock loading is lower.On the other hand,excellent NH₃-N removal can also be achieved using the hybrid BAC+MBR process during the sudden high-ammonium period(8-10 mg/L),with a effluent NH₃-N concentration of as low as(0.39±0.19) mg/L.However,longer duration of NO₂^--N accumulation is detected in the hybrid BAC+MBR effluent as compared with that in individual MBR effluent.Nonetheless,the hybrid BAC+MBR process is able to remove more organic pollutants from the water through two stages of biodegradation.Thus,the suitable biological treatment process is supposed to choose according to the raw water qualities.