Analysis of Filterability of Mixed Liquor Under Variant Aeration Intensities in Membrane Bioreactor

The influence of aeration intensity on the filterability of mixed liquor in membrane bioreactors(MBRs)has been studied.Two lab-scale MBRs with aeration intensities of 500 L/h and 100 L/h,respectively,were operated for 60 d with a constant permeating flux,and the filtration tests for mixed liquor have been conducted to confirm the mixed sludge filterability.Experimental results show that excessive aeration intensity has negative impact on the filterability of the mixed sludge in MBR and increases the rate of membrane fouling.The increase of aeration intensity results in the increase of soluble microbial products(SMPs)with relative molecular weight over 10 000 in the supernatant,which significantly obstructs the filtration of the mixed sludge.Small particles with the size of 1～10 μm and EPS in flocs also increase when the aeration intensity is over 500 L/h.