Sludge aggregation and biofouling mitigation in A/O-MBR treating anaerobically digested swine slurry with PAC/PAM flocculation pretreatmen

Abstract

Sludge aggregation and biofouling mitigation in anoxic/oxic membrane bioreactor (A/O-MBR) treating anaerobically digested swine slurry with PAC/PAM flocculation pretreatment were studied in this study. Two laboratory A/O-MBRs were set-up and operated with anaerobically digested leachate with and without PAC/PAM flocculation pretreatment, respectively, for over 150 days. Zeta potential, average size, soluble microbial products (SMP), extracellular polymeric substances (EPS), microscope, relative hydrophobicity (RH), etc. of sludge characteristics were detected in this study. Flocculation pretreatment with 1600 mg PAC/L wastewater and 50 mg PAM/L wastewater effectively optimized the anaerobically digested swine slurry with the obvious CODCr and TP removal for further biological treatment. Meanwhile, PAC/PAM pretreatment caused approximate 55–74 mg/L Al flowing into A/O-MBR, leading to sludge aggregation and high density of biomass. PAC/PAM pretreatment also caused SMP decrease and RH increase, and bridged polysaccharides to enhance gelation. EPS decrease further contributed to the decrease of the membrane mass transfer coefficient. PAC/PAM flocculation pretreatment effectively led to the sludge aggregation and further caused biofouling mitigation.