Experimental study of the anaerobic urban wastewater treatment in a submerged hollow-fibre membrane bioreactor at pilot 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-fibre ultrafiltration membrane modules (PURON® Koch Membrane Systems, 30 m2 of filtration surface each). It was operated under mesophilic conditions (at 33 °C), 70 days of SRT, and variable HRT ranging from 20 to 6 h. 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.