Influence of aeration intensity on the performance of A/0-type sequencing batch MBR system treating azo dye wastewater

Among the numerous parameters affecting the membrane bioreactor(MBR)performance,the aeration intensity is one of the most important factors.In the present investigation,an anoxic/aerobic-type(A/O-type)sequencing batch MBR system,added anoxic process as a pretreatment to improve the biodegradability of azo dye wastewater,was investigated under different aeration intensities and the impact of the aeration intensity on effluent quantity,sludge properties,extracellular polymeric substances(EPS)amount generated as well as the change of permeation flux were examined.Neither lower nor higher aeration intensities could improve A/O-type sequencing batch MBR performances.The results showed 0.15 m^(3)·h^(-1)aeration intensity was promising for treatment of azo dye wastewater under the conditions examined.Under this aeration intensity,chemical oxygen demand(COD),ammonium nitrogen and color removal as well as membrane flux amounted to 97.8%,96.5%,98.7%and 6.21 L·m^(-2)·h^(-1),respectively.The effluent quality,with 25.0 mg·L^(-1)COD,0.84 mg·L^(-1)ammonium nitrogen and 8 chroma,could directly meet the reuse standard in China.In the meantime,the sludge relative hydrophobicity,the bound EPS,soluble EPS and EPS amounts contained in the membrane fouling layer were 70.3%,52.0 mg·g^(-1)VSS,38.8 mg·g^(-1)VSS and 90.8 mg·g^(-1)VSS,respectively,which showed close relationships to both pollutant removals and membrane flux.

Effects of operative conditions on membrane fouling of jet loop membrane bioreactor

The orthogonal experiments, which involves three factors： aeration intensity, suction time and suction suspended time, were designed to research membrane fouling of jet loop membrane bioreactor （JLMBR）. Experimental results indicate that increasing aeration intensity, reducing suction time and increasing suction suspended time all could mitigate membrane fouling effectively. However excessive aeration intensity, too short suction time and excessive suction suspended time were bad for bioreactor running. The optimal aeration intensity, suction time and suction suspended time were 0.75 1.00 m3/（m2.h）, 8 -10 min and 4 -5 min, respectively. The three factors all had effect on membrane pollution rate, while the suction time was the most important one and followed by aeration intensity and suction suspended time. It also indicates that, comparing with traditional submerged membrane bioreactors, JLMBR had lower membrane pollution rate.