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Advanced treatment for actual hydrolyzed polyacrylamide-containing wastewater in a biofilm/activated sludge membrane bioreactor system: Biodegradation and interception

Zhao, Lanmei, Zhang, Congcong, Bao, Mutai, Lu, Jinren
Biochemical engineering journal 2019 v.141 pp. 120-130
activated sludge, ammonification, biodegradation, biofilm, biotransformation, chemical oxygen demand, cleaning, denitrification, fouling, hydrolysis, membrane bioreactors, membrane permeability, microfiltration, microorganisms, nitrification, nitrogen, nitrogen content, oil fields, polyacrylamide, scanning electron microscopy, tryptophan, tyrosine, viscosity, wastewater, water reuse
This study deeply investigated the overall performance, nitrogen transformation, membrane fouling and cleaning, extracelluar polymeric substances (EPS) and microbial function in a biofilm/activated sludge membrane bioreactor (BF-AS-MBR) for treating actual hydrolyzed polyacrylamide (HPAM)-containing oilfield wastewater. The removal efficiencies of HPAM, COD, viscosity, TOC and TN achieved 97.5%, 98.5%, 74.8%, 98.5% and 96.2%, respectively. Nitrogen transformation revealed nitratation became the main reaction in the process of aerobic amide group bioconversion and surpassed denitrification, nitritation and ammonification in BF-AS-MBR system. Scanning electron microscopy (SEM) showed the morphology of new, contaminated and washed membranes. The membrane permeability was recovered to 92% and 87% after the first and second cleaning, respectively. Tryptophan protein-like, aromatic protein-like, simple aromatic protein-like and fulvic acid-like organics presented in loosely bound EPS (LB-EPS) of sludge. Polysaccharide-like and tyrosine protein-like organics presented in tightly bound EPS (TB-EPS) of sludge. Tryptophan protein-like organics existed solely in TB-EPS of cake sludge, and played an essential role in membrane fouling. HPAM-degrading microorganisms and nitrifiers were deeply discussed to explore its correlations with HPAM removal, EPS and membrane fouling. The viscosities of HPAM solution re-prepared with different effluent were compared, and the order was: supernatant after biodegradation < effluent after membrane filtration ≈ clean water. This study offered a technical support and theoretical foundation for treating actual HPAM-containing oilfield wastewater, and improved water reuse.