Activated sludge treatment of small-scale wastewater by a plunging liquid jet bioreactor with cross-flow filtration

Abstract A new energy-saving membrane bioreactor was developed and applied to biological treatment of wastewater. The reactor used air entrainment by a plunging liquid jet for aeration and membrane filtration for solid-liquid separation. The major feature of the bioreactor was that the membrane module was incorporated into the liquid circulation line for the formation of the liquid jet so that the operations of aeration and membrane separation could both be accomplished using only one pump. Air entrainment and oxygen transfer characteristics of the reactor were investigated. Wastewater treatment by the bioreactor was carried out successfully with the TOC removal efficiency above 97%. The TOC removal efficiency of the cake layer deposit on the ceramic microfilter was comparable to that of the suspended microorganisms in the aeration tank. The role of the cake layer was evaluated in terms of facility of operation. The results obtained show that the bioreactor system has considerable potential for the biological treatment of small-scale agricultural or domestic wastewater discharged in rural or sparsely populated areas.