COMPARING PERFORMANCE AND FOULING BEHAVIOR OF MEMBRANE BIOREACTORS (MBRs) FOR DOMESTIC WASTEWATER TREATMENT

Abstract

Water scarcity and water pollution pose a critical challenge in many developing countries including Pakistan. One way to cope with the existing water scarcity is to reuse wastewater after suitable level of treatment. Membrane bioreactor (MBR) is a newly developed technology for wastewater treatment, which combines biological treatment with membrane filtration. MBR enjoys its advantages of small area requirement, better treatment efficiency and less treatment time as compared with conventional wastewater treatment techniques. In this study, three differently configured lab-scale Membrane Bio Reactors (MBRs) were operated in parallel under same conditions at IESE-NUST. Conventional MBR (C-MBR) was simply a submerged membrane bioreactor. In Moving Biofilm MBR (MB-MBR), biofilm carriers (Kaldnes) were introduced. A third reactor Anoxic/Oxic MBR (A/O-MBR) was designed, installed and operated as a hybrid MBR, with anoxic/oxic conditions and biofilm carriers. MBRs were operated under two phases. MBRs treatment performance and their fouling behavior were compared. All MBRs removed almost 95 % Chemical Oxygen Demand from domestic wastewater. Addition of biofilm carrier (Kaldnes) was effective in removal of total nitrogen and total phosphorus while A/O-MBR with kaldnes and anoxic/Oxic conditions exhibited best treatment performance among all. Comparison of membrane fouling in MBRs also revealed that anoxic/oxic conditions and biofilm carriers were helpful in fouling control. C-MBR fouled earlier followed by MB-MBR, while A/OMBR fouled after a longer span. Membrane fouling factors were analyzed by continuous examination of sludge characteristics like Specific Oxygen Uptake Rate (SOUR), Extra Polymeric Substances (EPS), Particle Size Distribution (PSD), and Specific Cake Resistance (SCR).