MEMBRANE BIOREACTOR (MBR) TECHNOLOGY FOR WASTEWATER RECLAMATION AND REUSE

Abstract

Water scarcity in Pakistan is a very serious issue particularly in Islamabad where per gallon cost of water is higher than any other city of Pakistan. One of the options to meet rising water demand is water reclamation and reuse for non-portable purposes. The effluent from conventional technologies cannot meet water reuse standards. Therefore, membrane bioreactor (MBR) or membrane based treatment technologies can be the technology of choice in Pakistan for water reuse. One of the primary disadvantages of MBR is membrane fouling. New biological method to control membrane bio-fouling is to monitor and control the concentration of acyl-homoserine lactone (AHLs) in the environment, which is known as quorum quenching (QQ). Furthermore, backwashing has been incorporated in most of the MBR systems as one of the standard operating strategies to mitigate fouling. Most of the studies done to evaluate fouling are based on lab scales MBR setups. A very limited knowledge is available about pilot-scale MBR setups and transition stage of achieving unsteady to steady state operation. Therefore, this study aims at (a) Parallel studies to determine influence of the QQ and filtration cycle (filtration/backwashing/relaxation) through bench-scale MBR using real wastewater. (b) Establishment, commissioning and performance evaluation of pilot-scale membrane bioreactor (MBR) plant. (c) Process optimization of the pilot-scale MBR plant from unsteady to steady state. This study was performed in two phases. In phase-A two bench scale MBR plant were operated in parallel Whereas in phase-B, a pilot-scale membrane bioreactor (MBR) plant with 50 m3/day capacity installed to treat real wastewater of university campus at NUST, Islamabad-Pakistan. Phase-A, it was revealed the presence of CEBs prolonged the filtration cycle of membrane in QQ-MBR by reducing the bio-fouling, due to decrease in concentration of AHLs and consequently reduction in soluble EPS concentration. Whereas backwashing help to retard the TMP jump by inhabiting pore narrowing and pore blocking. In Phase -B, High SRT favors high treatment performance, high concentration of biomass, but poor sludge characteristics. In case of lower SRT, treatment performance suffers a bit along with less biomass but sludge characteristics are good with high MLVSS/MLSS ratio. TMP goes high with time because of EPS production. Higher jumps in TMP occur when flux is increased. Higher flux and shorter SRT leads to rapid membrane fouling.