DEVELOPMENT OF A SEWAGE EQUALIZATION SYSTEM TO REGULATE BUILDING SEWAGE FLOW AND CONTROL ODOR

In Japan's large cities, many large buildings are constructed on building sites of limited size. Without appropriate mitigation, sewage flow from these buildings would exceed the existing public sewer capacity. In response, Tokyo Metropolitan Government has advised that large buildings must have a chamber installed for the temporary storage of sewage during peak production times. These excess-flow regulating chambers store excess flow during the day and drain it to the public sewer at night when there is capacity in the sewerage system. However, storage of sewage for long periods of time generates hydrogen sulfide, resulting in the emission of offensive odors. We conducted a survey of buildings producing large sewage volumes and confirmed that the sewage flow rate displays large fluctuations over short periods of time. We therefore developed a sewage equalization system that stores sewage temporarily when the flow rate exceeds the prescribed flow rate and discharges it as soon as the flow subsides, thereby shortening the storage time and reducing the build-up of offensive odor. Verification tests carried out on an existing building confirmed that the sewage equalization system is capable of lowering the peak discharge rate from large buildings and preventing hydrogen sulfide production. It was confirmed that the system can be smaller and the initial and running costs lower than for a conventional excess-flow regulating chamber.