Method of wastewater treatment with excess sludge withdrawal reduced

Abstract

A method of wastewater treatment that reduces 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 complete oxidation tank and a sedimentation tank, and that operation is made while maintaining the BOD sludge load in the complete oxidation tank at = 0.08 kg-BOD / kg-MLSS day, and that a coagulant is charged in the complete oxidation tank in order to improve the settling in the sedimentation tank.

Description

technical field [0001] The present invention relates to a wastewater treatment method with a small extraction amount of excess sludge. Background technique [0002] In the past, in the drainage treatment method using the activated sludge method, in the aeration tank, the drainage was brought into contact with the activated sludge under aerobic conditions, the sludge was allowed to settle in the sedimentation tank, and a part was returned to the aeration tank , the other part is extracted as excess sludge, thus, the BOD volume load is 0.3-0.8kg / m 3 · Under daily conditions, normal operation can be performed (for example, refer to Non-Patent Document 1). On the other hand, people are developing a carrier that can hold microorganisms at a high concentration. If this carrier is used, 2 to 5 kg / m can be applied 3 · The higher BOD volume load per day can reduce the overall size of the aeration tank (for example, refer to Non-Patent Document 2). [0003] In the past activated sl...

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Problems solved by technology

In addition, by not pumping out the sludge and forming a fully oxidized state in which the growth rate of the sludge is balanced with the rate of oxidation of the sludge itself, a system that does not generate excess sludge can be constructed theoretically. If the state of full oxidation is formed in the mud tank, the MLSS in the aeration tank is very high, so there is a disadvantage that a very large activated sludge tank must be installed

In addition, in this case, there is also a problem that the sludge is finely divided, and the sludge cannot be separated by natural sedimentation.

Generally, in order to temporarily treat the sludge in the settling tank, the operation of adding a flocculant to settle the sludge is performed. However, if the flocculant is added to the aeration tank, the sludge will settle, and the aeration in the aeration tank will cause the sludge to settle. Gas is not sufficiently carried out, and a large amount of sludge settled in the settling tank is discharged out of the system as excess sludge, thus, no coagulant is used in the full oxidation tank for reducing excess sludge capacity

[0007] Although the present inventors have proposed a treatment device and a drainage treatment method that do not generate excess sludge by combining an aeration tank and a total oxidation tank using a microbial immobilization carrier with a separation membrane, but, due to the suitable separation membrane The pore size is less than 0.1 micron, so there is a problem that the transmitted flux is very small, the membrane filtration device is large, and the equipment cost and operating cost are very large (see Patent Document 2)

Also, no mention of nitrogen removal

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