Application of MBR to an easily installed municipal wastewater treatment plant

An easily installed wastewater treatment plant was developed using an MBR p rocess. The plant consists of inlet pumps, automatic fine screen, a main re actor in which aerator-mixer and MF membrane separators are installed and a control board. The main reactor is a sheeted pond which is easily construc ted on-site by an excavation. As a result, the installation of this plant i s easy and inexpensive, operation is easy, yet the effluent quality is high . The 50 m(3)/d pilot plant was constructed in our experimental facility in Ibaraki Pref., and operated from January 1997 to April 1998 to evaluate pe rformance, stability and the ease of separation and installation of each un it. The results were satisfactory in all areas, except the durability of me mbrane permeability in the latter half of the experiment. For both hollow f ibre type and plate type, membrane permeability immediately decreased due t o the deposit of concentrated sludge cake on the surface, even though conti nuous 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.