Fouling Causes and Control Strategies for Membrane Bioreactors In Municipal Wastewater Treatment

This paper summarizes the extensive experimental results over last six years using large-scale membrane bioreactor pilot plants to treat municipal wastewater.  First, the causes of membrane fouling were identified by monitoring the fouling rate under different operating conditions and characterizing the fouling materials deposited on the membrane surface.  Different mechanisms were demonstrated between short-term physicochemical and long-term irreversible membrane fouling.  Colloidal particles represented by cTOC were identified as a fraction of mixed liquor controlling the critical flux and short-term membrane fouling, whereas the irreversible fouling was initiated by depositing the proteins directly on membrane wall, followed by the accumulation of carbohydrates to hold bacteria tightly.  Secondly, new fouling control strategies will be discussed, with emphasis on their effectiveness and energy consumption.  Finally, selected case studies will be used to illustrate the applications of these fouling strategies in practice.