Study On The Improvement Of Membrane Bioreactor

On the base of the aeration modes, the jet aeration was used in the recirculated membrane bioreactor in our research. Comparison of the oxygen supply ability between blast aeration and jet aeration through the tap water experiment, the latter was better further. At the same time the oxygen supply ability is studied and several performance parameter was determined at different Circular flux. Q₄(2.51m³/h) was determined as the circular flux in due form phase. removal efficiency of pollutantsOxygen transferring rate and utilization efficiency was improved highly using jet aeration and dissolved oxygen(DO) was enough(the average DO is 6.26mg/L). Sludge grain was broke into pieces by jet aeration and shear action of circular pump, improving highly biological efficiency. On the other hand, imperceptible sludge grain easily led to membrane fouling. During the whole operation period of the bioreactor removal effect of COD,NH₃-N and NTU is very good, and average removal rate of COD,NH₃-N and NTU reached at 96.01%,99.1% and 99.83%. But removal effect of TN and phosphorus is not good, and average removal rate of TN,TP and PO₄^3- was 37.9%,17.16% and 3.11%.Effect of different SRT(20d, 40d, 80d) on removal efficiency of pollutants was researched in this paper. Y and K_d of system was 0.1755 and 0.05 d^-1. Effect of the volume-loading rate of COD on removal efficiency of pollutants was researched in every SRT, and the best volume-loading rate of COD was 3.13 kgCOD/(m^·3·d) in this paper. Removal effect of influent COD in system is very good, and it depended on biological interaction mostly. It was very important for the rejection of membrane and it keeped effluent COD at about 50mg/L.It appeared membrane fouling after the system running a period of time. Then it taked chemical cleaning method(0.4%NaClO+0.4%NaOH) which combined with physical chemical method for membrane fouling. Resume rate of membrane flux for three cleaning of membrane was 99.1%,78.2%,65.5%, and it showed that it appears irreversible membrane fouling. We should find better cleaning methods.