Journal of Environmental Science and Health Part A (2007) 42, 895–901 Copyright C  Taylor & Francis Group, LLC ISSN: 1093-4529 (Print); 1532-4117 (Online) DOI: 10.1080/10934520701369941 Particulates and bacteria removal by ceramic microfiltration, UV photolysis, and their combination AHMED AIDAN 1 ,MEHRAB MEHRVAR 2∗ , TALEB HASSAN IBRAHIM 1 , and VALENTIN NENOV 3 1 Department of Chemical Engineering, American University of Sharjah, Sharjah, United Arab Emirates 2 Department of Chemical Engineering, Ryerson University, Toronto, Ontario, Canada M5B 2K3 3 Department of Water Treatment Technology, Bourgas University, Bourgas 8010, Bulgaria Membrane microfiltration (MF) or ultrafiltration (UF) systems of activated sludge is crucial part of a bioreactor process used in municipal wastewater treatment. In this study, both cylindrical and flat sheet ceramic membranes were used to treat municipal wastewaters. The effects of removing water turbidity and coliform bacteria from an artificial wastewater were studied by performing batch experiments by MF and ultraviolet (UV) photolysis of 254 nm wavelength. It was shown that the microfiltration had a high effect of suspended solid removal. However, the effect of bacteria removal was limited so that the rate of cfu removal was approximately 61%. Combined consecutive processes in the treatment (MF/UV and UV/MF) confirmed that a specific porosity of the ceramic filter for bacteria removal was required. The continuous membrane bioreactor (MBR) tests performed by using a MF membrane with the pore size of 0.2 μm showed that particulate matter and microorganisms found in municipal wastewater could be effectively removed. Turbidity was decreased from 4.50 to 0.05 NTU, with a removal efficiency of greater than 98%. The permeate total suspended solid (TSS) content for the whole run was below 5 mgL −1 . The density of total coliforms was decreased more than four orders of magnitude (from around 1×10 5 mL −1 to less than 5 mL −1 in the effluent). Keywords: Membrane bioreactors, combined processes, ceramic filters, UV photolysis, municipal wastewater. Introduction Currently, treated municipal wastewater is discharged to the environment and generally it is considered as a waste. However, municipal wastewater effluent should be regarded as a resource from which high quality water for reuse can be produced. An added benefit is that water reuse reduces the discharge of municipal wastewater to the environment and, thus, it offers a degree of source water protection. In recent years, applications of membrane separation techniques in wastewater treatment have drawn worldwide attention to researchers and engineers. The membrane bioreactor (MBR) process, which consists of an activated sludge bioreactor and a microfiltration membrane, is an emerging biotreatment technology that has demonstrated a great promise in water reuse. It has the advantage of the rapid development in membrane manufacturing and the potential to fundamentally advance biological treatment Address correspondence to Mehrab Mehrvar, Department of Chemical Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B 2K3; E-mail: mmehrvar@ ryerson.ca Received October 16, 2006. processes. Possessing advantages such as excellent effluent quality, a high biomass concentration without any concern for sludge settling problems, a simple flow configuration and small footprint demand, MBRs have been successfully used in biological wastewater treatment and the reclama- tion of treated effluents. [1] For the treatment of domestic wastewater, a sludge con- centration from 3,000 to 10,000 mgL −1 or higher in mixed liquor suspended solid (MLSS) can be maintained in an MBR with a hydraulic retention time (HRT) of 10–20 h. [2,3] This allows large macromolecules to be in contact with biomass for longer period than that within a conventional activated sludge process and therefore, this leads to achieve a chemical oxygen demand (COD) or a biological oxygen demand (BOD 5 ) removal of more than 98%. One particular element of interest is the MBR efficiency for the removal of pathogens in the treated water. The effect of disinfection can be reached by different methods. There are many ap- proaches that are used for the disinfection of water. The ad- vantages and disadvantages of each method are described in the literature. [4] Production of disinfected water with con- stant high quality by use of membrane technology is a good alternative for the conventional treatment techniques, as the conventional methods of water treatment have their own