Effect of carriers on sludge characteristics and mitigation of membrane fouling in attached-growth membrane bioreactor

This study aims to investigate the effect of carriers on membrane fouling. Three sets of submerged membrane bioreactors (MBRs), including one suspended-growth MBR, called SMBR, and two attached-growth MBRs (one called AMBR, and another with baffles called AMBRb) were operated at various media volume fractions. The results indicated that the membrane-fouling rates of AMBR and AMBRb were lower than that of SMBR. Moreover, the operation times of AMBR and AMBRb were 4.2 and 3.5 times longer, respectively, than that of SMBR at an optimum media volume fraction of 30%. The biochemical effects of carriers on sludge suspension significantly affected membrane fouling, unlike the physical effects of carriers. Further studies on sludge characteristics indicated that particle size, soluble microbial product (SMP), sludge volume index (SVI) and filament index (FI) did not remarkably affect membrane fouling, whereas the protein in bound EPS primarily contributed to membrane fouling.

► A new set of MBR was designed to study carriers’ effects on membrane fouling.
► Carriers had greatly positive effects on mitigation of membrane fouling.
► The optimum media volume fraction for membrane performance was 30%.
► Carriers’ biochemical effects primarily affected membrane fouling.
► The protein in bound EPS primarily contributed to membrane fouling.