Recent Patents on Biotechnology 2010, 4, 65-80 65 1872-2083/10 $100.00+.00 © 2010 Bentham Science Publishers Ltd. Membrane Bio Reactors (MBR) in Waste Water Treatment: A Review of the Recent Patents A. Hussain 1 , Aiman Eid Al-Rawajfeh 1,2, * and Hassan Alsaraierh 3 1 Doosan Desalination R&D Centre, Doosan Heavy Industries and Construction, Dubai, United Arab Emirates, 2 Tafila Technical University, Department of Chemical Engineering, P. O. Box 179, 66110 Tafila, Jordan, 3 Tafila Technical University, Department of Chemistry, P. O. Box 179, 66110 Tafila, Jordan Received: August 4, 2009; Accepted: September 28, 2009; Revised: October 30, 2009 Abstract: Effluent standards have become more and more stringent due to an increase in awareness about environmental impacts on both continuous and intermittent polluting discharge. For that, a high efficient waste water treatment plants are needed to be designed. Membrane bioreactor (MBR) can be good solution to cope with such issues. MBR systems respects the conventional activated sludge process which use microorganisms for degradation of organic pollutants and requires aeration as well as reduced foot print and sludge production through maintaining a high biomass concentration in the bio reactor. The present work elucidates the recent patents and critically reviews the advancement in MBR process, which can be helpful to designer. It was found that the behavior of aeration device, mixed liquor suspended solids (MLSS) concentration, flux enhancer and handling of sludge plays an important role in the performance of MBR process. Keywords: Membrane, MBR, flux enhancer, activated sludge, municipal and industrial waste. 1. INTRODUCTION Waste water reclamation is gaining popularity world wide as a mean of conserving natural resources used for drinking water supply. The use of MBR technology, which combines conventional activated sludge treatment with low pressure membrane filtration, has been proven to be a feasible and efficient method of producing reclaimed water. The membrane component of the MBR process eliminates the need for a clarifier and is performed using low pressure membranes such as microfiltration (MF), ultrafiltration (UF) or nanofiltration (NF). MBR technology offers several advantages over the conventional waste water treatment including reduced foot print, and consistent, as well as, superior effluent water quality with ease of operation. For many areas, it is necessary to further treat reclaimed waste water to reduce its inherent salinity, which makes it useable for irrigation and industrial use. The superior effluent quality of the MBR process makes it suitable for further treatment by reverse osmosis (RO) and nanofiltration (NF) as a final polishing step in reducing the salinity of reclaimed water [1]. The original process of MBR was introduced by Dorr-Oliver Inc. and combines the use of an activated sludge bioreactor with cross flow membrane filtration loop [2]. The major break through for the MBR technology came in 1989 with the idea of Prof. Yamamoto to submerge membranes in the bio reactor [3]. Before that, MBRs were designed in which there are separation device located external to the reactor and relied on high transmembrane pressure (TMP) to maintain filtration. The other key steps in the recent MBR develop- ment were the acceptance of modest fluxes and the use of two phase bubbly flow to control fouling [4]. *Address correspondence to this author at Tafila Technical University (TTU), Department of Chemical Engineering, P. O. Box 179, 66110 Tafila, Jordan; Tel: 00962 3 22 50 034; Fax: 00962 3 22 50 431; E-mail: aimanr@yahoo.com The treatment of sewage or waste water is mostly done first in primary clarification tanks, where the settled solids are removed. The partially treated waste water is then fed to a secondary treatment plant for "biological treatment", where microorganism degrade and stabilize the organic waste water to bio mass, water and gas. The microorganism that grow on the substrate in the waste water are separated from the water by further settling of the reacted waste water in the biological tanks, in which carbon substrates are measured as biochemical oxygen demand (BOD) or chemical oxygen demand (COD), leaving a relatively clean effluent as the treated effluent. The latter will then be discharged into open water or sent for further tertiary treatment or for reuse. This biological treatment by far is the most common treatment process for municipal and industrial waste waters. Most biological treatment plants now use the conventional activated sludge process (CAS). CAS has proved useful for the treatment of many organic wastes which were at one time thought to be toxic to biological systems or species. This process is a treatment technique in which waste water and reused biological sludge full of living microorganisms is mixed and aerated. The mixture formed of waste water and biological sludge is designated as mixed liquor. After the mixed liquor has been formed in the aeration tank of an activated sludge process, excess mixed liquor is discharged into settling tanks and the treated supernatant is run off to undergo further treatment before discharge. Some of the settled material, the sludge, is returned back to the head of the aeration system to re-seed the new sewage or waste water entering the tank. “Excess sludge” which eventually accumulates beyond the returned sludge is removed from the treatment process to keep the ratio of biomass feed to sewage or wastewater, food to microorganism (F/M) in balance. However, activated sludge process has a large foot print due to the need for large aeration tanks and clarifier tanks. The CAS wastewater treatment process also generates large