An easily installed wastewater treatment plant was developed using an MBR process. The plant consists of inlet pumps, automatic fine screen, a main reactor in which aerator-mixer and MF membrane separators are installed and a control board. The main reactor is a sheeted pond which is easily constructed on-site by an excavation. As a result, the installation of this plant is easy and inexpensive, operation is easy, yet the effluent quality is high. The 50 m3/d pilot plant was constructed in our experimental facility in Ibaraki Pref., and operated from January 1997 to April 1998 to evaluate performance, stability and the ease of separation and installation of each unit. The results were satisfactory in all areas, except the durability of membrane permeability in the latter half of the experiment. For both hollow fibre type and plate type, membrane permeability immediately decreased due to the deposit of concentrated sludge cake on the surface, even though continuous bubble washing had been made. Hence,drastic improvement is needed in the way of sludge deposit control on the membrane surface. This is the key for the developed system to become a practical one.

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