Anaerobic membrane bioreactor treatment of domestic wastewater in Tunisia Ahlem Saddoud, Mariem Ellouze, Abdelhafidh Dhouib, Sami Sayadi* Laboratoire des Bioprocédés, Centre de Biotechnologie de Sfax, BP «K», 3038 Sfax, Tunisia Tel./fax: +216 (74) 440 452; email: sami.sayadi@cbs.rnrt.tn Received 27 December 2005; Accepted 27 August 2006 Abstract An anaerobic cross-flow ultrafiltration membrane bioreactor was investigated for municipal wastewater treatment at 37°C. The removal of the total suspended solid, the soluble chemical oxygen demand and the biochemical oxygen demand were respectively 100%, 90% and 88%. Less than 85 mg l !1 of soluble chemical oxygen demand in the effluent was obtained by ranging the organic loading rate from 0.23 to 2 g COD l !1 d !1 . The biomass accumulated in the reactor reached 4.3 to 4.9 g l !1 in terms of MLVSS in the last month of the treatment. The biogas production increased with the increase of the loading rate to reach an average of 28 l after 140 days. The average content of the biogas in methane was practically constant at 70%. The treated wastewater could be considered non phytotoxic since the germination index of Lepidium sativum ranged between 60 and 87%. The quality of the treated wastewater fits largely with Tunisian norm NT 106.03 and World Health Organization Guidelines for the microbiological quality of treated wastewater used in agriculture. However, this treated wastewater should undergo further processes to reduce its contents in residual nitrogen and phosphate and thus to conform with the Tunisian standards NT 106.02, a requirement for acceptance in hydraulic public domain. Keywords: Domestic wastewater; Anaerobic digestion; Membrane bioreactor; Cross-flow; Ultrafiltration 1. Introduction The overexploitation of water resources in arid countries is a serious cause of water shortage and degradation of its quality. Indeed, agriculture, industry and households compete for the rare *Corresponding author. existing water resources [1]. There is an urgent need to recycle and reuse wastewaters in agri- culture. Research has been particularly interested in treating and recycling domestic wastewater [2,3]. The biological treatment of wastewater is the oldest process since the conscious use of microorganisms started in the 1920s with the development of the activated sludge process in Desalination 207 (2007) 205–215 0011-9164/07/$– See front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.desal.2006.08.005