Research On The Performance And The Membrane Fouling Of Aerobic Granules Membrane Bioreactor

In this study,an aerobic granules membrane bioreactor(AGMBR) was built up,which combined aerobic granulars technology with membrane bioreactor technology.The performance of AGMBR and the impact on the membrane fouling of aerobic granules were investigated.An aerobic sludge membrane bioreactor(ASMBR) was operated under the same conditions to compare with the AGMBR.This study included two parts.Firstly,to improve the stability of conventional aerobic granules,aerobic nitrifying granules were successfully cultivated under stepwise increased substrate NH₄⁺-N concentrations in an sequencing batch airlift reactor(SBAR).Aerobic nitrifying granules,which were dominated by both heterotrophs and nitrifying bacteria,had excellent stability and simultaneous removal of COD,N and P in wastewaters.The stability, physical characteristic and removal efficiency were all investigated.Secondly,the AGMBR was built up by setting the membrane module in the SBAR.The stability and removal efficiency of AGMBR and the cultivation,morphology,removal efficiency,stability of aerobic nitrifying granules in the AGMBR were investigated.Meanwhile,the ASMBR was operated under identical conditions with the AGMBR,to compare their fouling behaviors and membrane fouling mechanisms.The results showed that aerobic granules had an excellent membrane permeability.The main conclusions were as followed:(1) The aerobic nitrifying granules,which had excellent performance,were successfully cultivated.The nitrifying granules were compact on day 180.The value of sludge volume index(SVI) was below 30 ml/g and the mean granules size was about 1.6 mm.(2) The AGMBR showed excellent organics removal and simultaneous nitrification and denitrification(SND) performances during 102 days operation.COD,NH₄⁺-N and TN average removal efficiencies of AGMBR remained at 86%,94%and 45%,when influent concentrations of COD and NH₄⁺-N were 500 mg/L and 200 mg/L respectively.(3) The AGMBR had an excellent membrane permeability and the period of cleaning membrane was extended.In the AGMBR,pore blocking resistance is the predominant factor of the membrane fouling,which is 64.81%of the membrane total resistance.And the cake resistance of the AGMBR is 2.1×10¹² m^-1,which is much smaller than 16.07×10¹² m^-1 in the ASMBR.The period of cleaning membrane was at least 2.43 times longer as that in the ASMBR.New aerobic granule was produced and grown gradually during experiment operation,which ensure the stabilization of performance and operation in the AGMBR.The excellent membrane permeability of aerobic granules was due to the larger granule size,the compact structure and low compressibility,and better settling ability.So it was hard to form fouling cake layer on the membrane module surface in AGMBR and the cake resistance was reduced.Therefore,the pore blocking resistance is the predominant factor of the membrane fouling in the AGMBR.