Effects of SRT and HRT on MBR Fouling Performance

INTRODUCTION

Membrane bioreactor ( MBR ) has gained considerable interest as one of the most promising treatment process concerning wastewater treatment, and water reclamation. Fouling has been identified to be the major drawback for MBR future operation, expansion and upgrading. Membrane fouling leads to the membrane flux decrease, operational pressure increase and frequent membrane cleaning or replacement. It is recognized that the hydraulic performance of MBRs may be improved by the optimization of the operating  conditions.

All the parameters involved in the design and operational conditions of MBR processes have an influence on membrane fouling. The factors are depending on the feed and biomass characteristics, operating conditions such as hydraulic retention time (HRT), solids retention time ( SRT) and the type of membrane. The effects of biomass charateristics are very complicated due to the fact that the mixture of activated sludge comprises of fine particles, solute, colloidal, flocs and microorganisms.

Many investigators have reported that the biological constituents of activated sludge have a contribution to membrane fouling. A number of studies for mitigation of membrane fouling have been carried out, such as the improvement of membrane materials  and modules, the modification of sludge characteristics and the optimization of operational parameters including flux, fluid dynamics, membrane flux enhancer, vibration, chemical cleaning, ultrasonication.