BACKGROUND: The effects of sludge retention time, organic loading rate, specific aeration demand per membrane area (SAD m ) and exploiting poly(vinyl chloride)/polycarbonate/modified silver nanoparticles (PVC/PC/MAg) nanocomposite membrane in membrane fouling and removal performance of submerged membrane bioreactors (SMBRs) were compared. A reference membrane bioreactor (R-SMBR) having a pure PVC/PC hollow fiber membrane module and no operational condition improvement was used as a reference for comparison. RESULTS: The results revealed that all of the parameters had a considerable influence on improving membrane fouling, among which optimizing SADm and installing nanocomposite membranes in the SMBRs had comparable performances. Although the nanocomposite membrane had excellent potential to boost the membrane flux up to 62% in comparison with the R-SMBR, it did not play any noticeable roles in rectifying the removal efficiency of the SMBR. On the other hand, not only did SAD m increase the membrane flux up to 55%, but it also increased about 5% of COD and 3% of NH4+ -N removal. CONCLUSIONS: Sludge characteristics were not affected by membrane modification since the concentration of extracellular polymeric substances, soluble microbial products and mean particle size were 110 ± 1 mg g−1 VSS, 54 ± 1 mg L−1 and 50 ∼m, respectively, for both the R-SMBR and the SMBR in which the modified membrane was installed. However, the opera- tional parameters could also modify the treatment performance of the SMBRs by positively impacting on sludge characteristics besides mitigating membrane fouling.
