[Analysis of characteristics of microbial communities in membrane bioreactor and conventional activated sludge...

A submerged MBR and CAS were used for municipal wastewater treatment to investigate their performance and the microbial community. The effluent COD concentrations of MBR and CAS were 39.6 mg/L and 62.9 mg/L on average, respectively. The effluent concentrations of NH4+-N in MBR and CAS were 6.8 mg/L and 14.5 mg/L on average, respectively. MBR demonstrated a more stable and excellent effluent quality than CAS. The microbial community in the MBR and CAS indicate a clear difference in despite of same inoculation due to operation conditions of the MBR with the lower F/M ratio, accumulation of inert substance and strong shear force in aeration. The results of DGGE indicate that the quantity of the bacteria and the change of the similarities coefficient of the microbial community in MBR are more than those in the CAS. The result of DGGE showed that the quantity of bacteria in MBR is always larger than that in CAS, on 15, 124, 186 and 230 d, the quantity of lanes are 22, 25, 24 and 20 in MBR and 19, 14, 17 and 20 in CAS, respectively. The Dice similarity index are 54.1%, 63.7%, 63.9% and 66.8% in MBR and 71.8%, 61.4%, 9.1% and 65.9% in CAS, respectively. These phenomena show that the discharge of the excess sludge from CAS results in a loss of some no-selective bacteria, and the microbial community in the MBR has higher capability acclimatized the environment variable than that in the CAS. According to the Dice coefficient of the microbial community was higher and higher during the whole operation, it was influenced by the changes of environments, e.g. influent concentration, temperature and so on.