With high concentrations of chemical oxygen demand (COD) and ammonium while low ratio of COD to total nitrogen (TN), digested piggery wastewater is difficult to treat using conventional biological methods. In this study, a biofilm membrane bioreactor (BF-MBR) and a traditional type of membrane bioreactor (MBR) were parallel operated to treat digested piggery wastewater, and the pollutant removal performance were compared at influent COD/TN ratios of 1. 0 ± 0. 2 and 2. 3 ± 0. 4, respectively. The results showed that the effluent quality in both reactors was poor and unstable when the influent COD/TN ratio was 1. 0 ± 0. 2. The effluent quality and stability were greatly improved as the influent COD/TN ratio was increased to 2. 3 ± 0. 4. The removal rates of COD and ammonium were respectively 92. 3% ± 2. 4% and 97. 5% ± 4. 1% in BF-MBR, slightly higher than 91. 9% ± 1. 5% and 91. 2% ± 14. 0% in MBR. Benefited from the biofilm, 36. 7% ± 19. 5% of TN and 54. 0% ± 18. 9% of TP were removed by BF-MBR, significantly higher than the respective values of 19. 2% ± 12. 4% and 29. 0% ± 18. 1% by MBR. Moreover, BF-MBR consumed less than 40% of the alkaline chemicals as MBR. BF-MBR was considered more suitable for treatment of digested piggery wastewater due to its better pollutant removal performance and low consumption of alkaline.