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).
