| In this paper, the imitated wastewater was treated using the recirculated membrane bioreactor (MBR) . Experiments were carried out to investigate the operation efficiency and Mass balance relationships. Kinetic models of microorganism multiplication and organic pollutants removal were established based on mass balance in a membrane bioreactor.The start up of the membrane bioreactor could be finished in 10 days, when the operating conditions were: the influent flux 10 L/d, the .HRT 48h, the influent COD 251.4～409.4 mg/L, the volume loading 0.13～0.20 kgCOD/(m3·d),the influent temperature 18.6～25.3°C .When the operating conditions was the influent COD 422.8～885.4 mg/L, the influent flux were increased gradually from 10 L/d to 70.8 L/d, the volume loading was increased from 0.20 kgCOD/ (m3·d) to 2.96 kgCOD/(m3·d), the average COD removal efficiency was 93.7%. The change of volume loading and sludge loading had not obvious effect on COD removal rates. The impact loading were come into being due to change of influent quality in the 23st and the32st, the 47stdays, volume loading rose to 3.60 kgCOD/(m3·d), 4.46 kgCOD/(m3·d) and 5.00 kgCOD/(m3·d), COD removal efficiency were 96.9%, 98.4% and 97.8%. The operation effect of membrane bioreactor were not influenced.During the course of all-operation, sludge appearance has been changed, that color was changed from dust color to snuff color, moreover, MLSS increase from 2436 mg/L to 12380 mg/L, whereas the ratio of MLVSS/MLSS was decreased. In the phases of steadily operation, the rotifer that belongs to metazoa was found in course of observed the microbe phase of sludge mixed liquid by microscope. Thus it can be seen that the membrane bioreactor had many outstanding advantages, such as shorter start up period, higher organic contamination removal rates, quicker change of volume loading, more stability operation, stronger anti-impact loading capability, and operation status of the membrane bioreactor were estimated by the means that the microbe phase of sludge mixed liquid were observed by microscope.Mass balance relationships were investigated in the SMBR for treating two-phase anaerobic digest effluent. Kinetic models of microorganism multiplication and organic pollutants removal were established based on mass balance in a recirculated membrane bioreactor. Kinetic constants of Vmax , Ks and the relationship of Y with Kd, were solved in this study. The study of mass balance in the membrane bioreactor showed that COD removal was mainly obtained by the metabolism of microorganism. The ISS increased in the percent of metabolism microorganism, and increased with the increasing of SRT and the shortening of HRT.
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