Abstract: A process for treating wastewater including: feeding organic wastewater to a first aerobic tank and an anoxic tank; nitrifying and denitrifying the organic wastewater by bacteria supported on carriers in the first aerobic tank followed by discharging primary treated water; denitrifying the organic wastewater and the primary treated water by bacteria in an activated sludge in the anoxic tank followed by discharging secondary treated water; nitrifying the secondary treated water by bacteria in an activated sludge in the second aerobic tank followed by discharging tertiary treated water; and separating the sludge from the tertiary treated water in the solid-liquid separator followed by discharging final treated water while returning the sludge to the anoxic tank. According to this process, a load in a latter anoxic tank can be reduced, the anoxic tank can be downsized compared with the prior process and treated water with good water quality is stably provided.

Abstract: To provide an inexpensive wastewater treatment method which facilitates downsizing of tanks and requires less withdrawal of an excessive sludge, the use is made of an aeration tank 1 in which wastewater is contacted with a particulate carrier under an aerobic condition, and a total oxidization tank 3 in which the volume of a sludge generated in the aeration tank 1 is reduced under an aerobic condition, a coefficient of self-oxidization of the sludge flowing into the total oxidization tank 3 is set to 0.05 (per day), and the method includes a step of adding a coagulant to the total oxidization tank 3 for the purpose of improving the solid-liquid separating characteristic of the sludge within the total oxidization tank.

Abstract: To provide an inexpensive wastewater treatment method which facilitates downsizing of tanks and requires less withdrawal of an excessive sludge, the use is made of an aeration tank 1 in which wastewater is contacted with a particulate carrier under an aerobic condition, and a total oxidization tank 3 in which the volume of a sludge generated in the aeration tank 1 is reduced under an aerobic condition, a coefficient of self-oxidization of the sludge flowing into the total oxidization tank 3 is set to 0.05 (per day), and the method includes a step of adding a coagulant to the total oxidization tank 3 for the purpose of improving the solid-liquid separating characteristic of the sludge within the total oxidization tank.

Abstract: A method of wastewater treatment that reduced equipment cost and running cost and realizes high efficiency implementation and further tank miniaturization, and that reduces excess sludge withdrawal. There is provided a method of wastewater treatment with excess sludge withdrawal reduced, characterized in that there are installed an aeration tank wherein wastewater is brought into contact with carrier particles under aerobic conditions, a total oxidization tank and a sedimentation tank, and that operation is made while maintaining the BOD sludge load in the total oxidization tank at 0.08 kg-BOD/Kg-MLSS*day or smaller, and that a coagulant is charged in the complete oxidization tank in order to improve the setting in the sedimentation tank.

Abstract: A method of wastewater treatment that reduced equipment cost and running cost and realizes high efficiency implementation and further tank miniaturization, and that reduces excess sludge withdrawal. There is provided a method of wastewater treatment with excess sludge withdrawal reduced, characterized in that there are installed an aeration tank wherein wastewater is brought into contact with carrier particles under aerobic conditions, a total oxidization tank and a sedimentation tank, and that operation is made while maintaining the BOD sludge load in the total oxidization tank at 0.08 kg-BOD/Kg-MLSS*day or smaller, and that a coagulant is charged in the complete oxidization tank in order to improve the setting in the sedimentation tank.