NOVELTY - System comprises an aeration tank, a concentrating tank, a fermentation tank, a marsh gas purifier, a marsh gas generator and a dryer, which are orderly connected. The marsh gas generator at the same time is connected with the aeration tank and the fermentation tank. The concentrating tank is connected with a sedimentation tank and a deodorizing device. The concentrating tank and fermentation tank are provided with a filter. The filter is connected with the concentrating tank and the fermentation tank.    USE - The system is useful for reducing sludge in sewage treatment plant (claimed).    ADVANTAGE - The system: saves energy (claimed); reduces sewage operation cost; does not generate secondary pollution; effectively utilizes the sludge resource; and reduces sludge treatment cost.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for reducing the sludge in sewage treatment plant, comprising (a) aerating the sludge in the aeration tank for 1-4 days, depositing the sludge (balance amount) into the sedimentation tank, discharging the precipitated sludge into the concentrating tank for concentrating, removing the concentrated odor of supernatant through the deodorizing device, adding the sludge based on the favorable and unfavorable conditions, filtering the concentrated sludge by filter press, passing the filtered sludge into the fermentation tank to ferment for 27-33 days, collecting the marsh gas produced by the fermentation tank into the storage tank, and finally delivering into the marsh gas generator, purifying the marsh gas through the marsh gas purifier, and compressing through the compression blower; (b) supplying power to the drier, and drying the fermented sludge by the drier; (c) supplying power to the fan, blowing air into the aeration tank of the aeration device through the fan to support the aeration tank for aeration; and (d) supplying power to the water heater, providing hot water to the fermentation tank, and supplying heat.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the system for reducing sludge in sewage treatment plant (Drawing includes non-English language text).