Effects of Fine Particles on Performance of Enhanced Backwash for Fouling Reduction in Anaerobic Membrane Bioreactors

Anaerobic membrane bioreactor (AnMBR) can produce high-quality effluents through effective solid-liquid separation using microfiltration. During the operation of the membrane bioreactor system, membrane fouling is one of the main problems. Several models have been proposed to understand the mechanisms of fouling of the membrane. Usually, cake formation and pore blocking are found to be the main mechanisms. Many factors such as hydrodynamic conditions, membrane materials, and sludge properties are involved in fouling. Particle size distributions and extracellular polymeric substance concentrations in sludge properties have been suggested as being key parameters in determining the degree of fouling in an AnMBR. To control membrane fouling, numerous methods are used during operation, such as bubbling of biogas produced in the AnMBR, backwash with permeate, and enhanced backwash, in which a chemical reagent is introduced to dissolve foulants adsorbed to the membrane surfaces. Enhanced backwash is effective in recovering flux from high-strength organic feed solutions; however, little research has been conducted on the effects of sludge properties on the efficiency of enhanced backwash in an AnMBR.