Effect of Hydraulic Retention Time on Sludge Properties,Cake Layer Structure,and Membrane Fouling in a Thermophilic Submerged Aerobic Membrane Bioreactor

Sludge properties, cake layer structure, and membrane fouling in a membrane bioreactor were studied under various hydraulic retention times (HRT). A decrease in HRT resulted in an increase in extracellular polymeric substance production in bulk sludge and changes in cake layer structure from gel layer to one or two cake layers. Particle size distribution in cake sludge changed with respect to HRT. An evolution in cake layer thickness and porosity was observed with trans-membrane pressure (TMP) jump. The change in cake layer structure might bear more responsibility for the TMP jump than the quantity of cake layer.