NOVELTY - A driving assistance device (20) of sewage works comprises aeration gas volume display part (23) which displays aeration gas volume required when processing with water treatment plant (10) by activated sludge method provided with aeration apparatus (16) connected to diffuser (17) installed in reaction tank (12), flowmeter (41) which measures water quantity of sewage or water quantity of treated water flowing into reaction tank, and chemical oxygen demand (COD) concentration meter (42) or biological oxygen demand (BOD) densitometer which measures organic substance component concentration.    USE - A driving assistance device of sewage works (claimed).    ADVANTAGE - Favorably treated water quality can be kept stable, and aeration gas volume and electric energy required by aeration are reduced.    DETAILED DESCRIPTION - A driving assistance device (20) of sewage works comprises aeration gas volume display part (23) which displays aeration gas volume required when processing with water treatment plant (10) by activated sludge method provided with aeration apparatus (16) connected to diffuser (17) installed in reaction tank (12), flowmeter (41) which measures water quantity of sewage or water quantity of treated water flowing into reaction tank, chemical oxygen demand (COD) concentration meter (42) or biological oxygen demand (BOD) densitometer which measures organic substance component concentration of sewage flowing into reaction tank, ammonia nitrogen densitometer (43, 47) or total-nitrogen densitometer which measures nitrogen component concentration of sewage flowing into reaction tank, and mixed liquor suspended solid (MLSS) densitometer (45) which measures MLSS concentration of reaction tank. Ammonia nitrogen densitometer and/or nitrate-nitrogen densitometer (46) is provided in reaction tank terminal or final sedimentation tank (15). From the value which multiplies BOD removal rate in reaction tank to BOD loading volume computed based on measured value of flowmeter and COD concentration meter or BOD densitometer, amount of BOD is computed based on measured value of nitrate-nitrogen densitometer and is reduced when nitrate-nitrogen densitometer is installed in reaction tank terminal or final sedimentation tank. When nitrate-nitrogen densitometer is not installed, amount of BOD which is computed based on nitrate-nitrogen concentration computed according to inflow Kjeldahl nitrogen amount, surplus-sludge generation amount, and denitrifying conditions is reduced. Amount of BOD oxidized with activated sludge is computed by reaction tank. A 1st calculation unit computes oxygen amount required for oxidation of BOD from amount of BOD. Kjeldahl nitrogen removal amount by surplus sludge is reduced when ammonia nitrogen densitometer is installed in reaction tank terminal or final sedimentation tank from Kjeldahl nitrogen amount computed based on measured value of flowmeter and ammonia nitrogen densitometer or total-nitrogen densitometer. Amount of ammonia nitrogen flowing out of reaction tank computed from value reduces target value of reaction tank terminal or ammonia nitrogen concentration of final sedimentation tank from measured value of ammonia nitrogen densitometer of final sedimentation tank. When ammonia nitrogen densitometer is not installed, Kjeldahl nitrogen amount, which reduces amount of ammonia nitrogen flowing out of reaction tank computed from target value of ammonia nitrogen concentration of reaction tank terminal and is oxidized by activated sludge by reaction tank, is computed. A 2nd calculation unit computes oxygen amount required for nitrification reaction from Kjeldahl nitrogen amount, and a 3rd calculation unit computes oxygen amount required for endogenous respiration based on measured value of MLSS densitometer. Oxygen amount required for oxidation of BOD is computed using 1st calculation unit. A 4th calculation unit computes oxygen required to remove BOD and Kjeldahl nitrogen in sewage flowing into reaction tank by totaling oxygen amount required for nitrification reaction and oxygen amount required for endogenous respiration. A 5th calculation unit computes required aeration gas volume based on required oxygen amount computed by 4th calculation unit, performance curve of diffuser is provided, and required aeration gas volume computed by 5th calculation unit is displayed on aeration gas volume display part. An INDEPENDENT CLAIM is included for driving assistance method of sewage works.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of a driving assistance device of sewage works. (Drawing includes non-English language text).    Water treatment plant (10)    Reaction tank (12)    Aeration apparatus (16)    Diffuser (17)    Driving assistance device (20)