The volume of sewage increases as the population grows and the standard of living rises, and also varies in direct proportion to the volume of available water supply. Present1y(at the end of 1998), the sewage treatment ratio is 60%, and 85 facilities are woiking for sewage treatment While sewage treatment plant has been constructed in large cities and heavily industrialized cities, the most treatment plant employ one type of process, i.e. activated sludge process, which may not be desirable for some cities in economical point of view and also in terms of process optimization. Moreover, poor sewer systems resulted in lower strength influet than the designed strength.
In this study, to develop a proper process for treating low strength sewage several existing sewage treatment plants were diagnosed. A continuously contacted sequencing batch reactor composed of pre-anoxic contact zone and intermittently aerated zone was operated for biological nitrogen removal. The removal efficiencies of organic matter (SCOD) and total nitrogen (T-N) were 89% and about 60% at the TCOD/T-N ratio as low as 6.0, respectively.