N Fallah - Department of Chemical Engineering, Amirkabir University of Technology, P.O.Box۱۵۸۷۵-۴۴۱۳., Tehran, Iran
B Bonakdarpour - Department of Chemical Engineering, Amirkabir University of Technology, P.O.Box۱۵۸۷۵-۴۴۱۳., Tehran, Iran-Food Process Engineering and Biotechnology Research Centre, Amirkabir University of Technology, Tehran, Iran
B Nasernejad - Department of Chemical Engineering, Amirkabir University of Technology, P.O.Box۱۵۸۷۵-۴۴۱۳., Tehran, Iran-Food Process Engineering and Biotechnology Research Centre, Amirkabir University of Technology, Tehran, Iran
M Alavimoghaddam - Department of Civil Engineering, Amirkabir University of Technology, P.O.Box۱۵۸۷۵-۴۴۱۳., Tehran, Iran

In this study, the potential of a Membrane Bioreactor (MBR) for treating Styrene contaminated wastewater was evaluated. Synthetic wastewater with COD and styrene concentrations of 1500 mg/L and 50 mg/l respectively was fed into the MBR. The MBR was operated for a period in excess of 100 days; HRT was set of 24 hours during the initial 50 days and thereafter was decreased to 18 hours. At both HRTs, the removal efficiency of COD and Styrene was consistently higher than 99%. More significantly, no Styrene was detected in the exhaust air, which meant that, at both HRTs, the mechanism of styrene removal in the MBR was exclusively through biodegradation. TMP profile showed fairly low and constant TMPs up to day 70, whereas after this period the TMP started to rise. A change in the morphology of the sludge, from floccular to dispersed, was observed when HRT was decreased. This was attributed to decrease in EPS concentration, probably as a result of increase in styrene loading rate. As a consequence, the particle size distribution of the activated sludge shifted to lower mean particle sizes and the increase in the percentage of smaller particles resulted in increase in the rate of membrane fouling.

Activated Sludge, Biodegradation, Immersed Membrane Bioreactor, Styrene