Membrane as Solid∕Liquid Separator and Air Diffuser in Bioreactor

A bench-scale pilot plant was operated to evaluate the potential of using microfiltration hollow fiber membrane modules as an air diffuser and solid∕liquid separator in an alternate cycle within a bioreactor treating domestic wastewater. Two modules capable of air backwashing were immersed in a bioreactor. Compressed air backwashing and filtration by suction were effected alternatively. The experimental results reveal that application of the air backwashing technique to submerged membrane modules is capable of not only declogging the membranes but also of aerating the mixed liquor. Thus, better filtration flux rate and aeration without a separate aeration device were attained simultaneously. It was also noted that the introduction of an anoxic zone enhanced the removal of nitrogen. In addition, operation at low hydraulic retention time with high sludge concentration and the absence of a sedimentation tank indicate considerable savings on the plant area.