Two pilot-scale membrane bioreactors with different running processes were studied in treating domestic wastewater under the same conditions.The results showed that both systems had good ability for CODCr and ammonia nitrogen removal.Membrane sequencing batch reactor (MSBR) showed higher removal efficiency than aerobic membrane bioreactor (AMBR) for total nitrogen.But the high dissolved oxygen (DO)

low C/N and lack of mechanical agitation of MSBR limited further increase of the TN removal efficiency.The membrane fouling of AMBR was more serious than that of MSBR.The increase rates of TMP versus CODCr rejected by unit membrane area were 0.065 kPa·g-1·m2 and 0.037 kPa·g-1·m2 respectively for MSBR and AMBR.Detailed analysis was made to explain this phenomenon.