Strategy for flux enhancement in biofilm ceramic membrane bioreactor applying prepolymerized and non-prepolymerized inorganic coagulants

Abstract

Considering new legislative and economic restrictions caused by the water crisis, this work focuses on a more efficient wastewater treatment process, which combines biological treatment in a moving bed biofilm system with a membrane bioreactor (BF-MBR) and coagulation, particularly addressing fouling alleviation in the separation stage. The study justifies the positive impact of coagulantdosinginBF-MBRregardingmembranefluxandfoulingrate. Statisticaltechniquesconnect the results of coagulation and membrane separation experiments with properties of mixed liquor, obtainedafterbiotreatmentintherepresentativepilotplantandcharacteristicsofprepolymerizedand non-prepolymerized inorganic coagulants. Research results substantiate the need for a pH-controlled coagulation of mixed liquor in BF-MBR depending on coagulant type, which influences charge, hydrophobicity and size of flocs and organic content of the system. It is suggested, that the adsorption/charge neutralization mechanism dominates in flux enhancement in BF-MBR, giving the best results in the case of prepolymerized aluminium coagulants. Together with high quality of permeate, the application of prepolymerized aluminium chloride of medium basicity entails a tenfold increase in filtration time of the membrane separation cycle and increases net membrane flux by 30–56%. The results of the study are practically significant for the development of an automated controlsystemforBF-MBR,optimizingtreatmentratestogetherwithmembraneseparationefficiency.