Experimental study of the anaerobic urban wastewater treatment in a submerged hollow-fiber membrane bioreactor at semi-industrial scale

The aim of this study was to assess the effect of several operational variables on both biological and separation process performance in a submerged anaerobic membrane bioreactor pilot plant that treats urban wastewater. The pilot plant is equipped with two industrial hollow-fiber ultrafiltration membrane modules (PURON ® Koch Membrane Systems, 30 m 2 of filtration surface each). It was operated under mesophilic conditions (at 33 oC), 70 days of SRT, and variable HRT ranging from 20 to 6 hours. The effects of the influent COD/SO4-S ratio (ranging from 2 to 12) and the MLTS concentration (ranging from 6 to 22 g·L -1 ) were also analysed. The main performance results were about 87% of COD removal, effluent VFA below 20 mg L -1 and biogas methane concentrations over 55% v/v. Methane yield was strongly affected by the influent COD/SO4-S ratio. No irreversible fouling problems were detected, even for MLTS concentrations above 22 g·L -1 .