Experimental test to evaluate performance of an anaerobic reactor providedwith an external membrane unit

The coupling of a wastewater treatment anaerobic reactor with a microfiltra tion or ultrafiltration membrane is particularly attractive: lower sludge p roduction than in an aerobic reactor, methane production and dissociation o f the mean residence times of the different phases. However, the industrial development of such a process is hampered by membrane fouling which can be a result of many causes and require a comprehensive study especially fouli ng by anaerobic suspensions. In order to simplify the study, the different phases of anaerobic oxidation were separated and this work is focused on th e filtration of an anaerobic suspension fed with acetic acid as the sole ca rbon source at 2 g/l TOC. The effluent quality was excellent without sludge production in spite of large variation of the liquid phase space time. The tested filtration elements were tubular Carbosep membranes. The M14 membra ne showed the greatest flux of 120 l/m(2) h at 0.5 bar and 25 Pa shear stre ss and the flux increased to 180 l/m(2) h when a baffle was introduced. The main fouling mechanism appears to be the particle deposition on the membra ne surface as no flux decline was observed at higher cross-flow velocity. ( C) 1998 Published by Elsevier Science Ltd. All rights reserved.