Improved type A<2>/O or invert A<2>/O technique

Abstract

The invention provides an improved A<2>/O or inverted A<2>/O process, which belongs to the technical field of sewage treatment. The process is designed to be an oxidation ditch which comprises an outer ditch, a middle ditch, an inner ditch and a central island area. The central island area is designed with a secondary sedimentation tank; a space between the outer wall of the secondary sedimentation tank and the inner wall of the inner ditch is designed to be a sludge return area; sewage first enters an anoxic/anaerobic tank of the inner ditch, and then enters an anaerobic/anoxic tank of the middle ditch and an aerobic tank of the outer ditch in turn, and finally enters the secondary sedimentation tank to be discharged; and part of sludge in the secondary sedimentation tank cyclically enters the anoxic/anaerobic tank of the inner ditch through the sludge return area. The process has excellent phosphorus and nitrogen removal effect on the treatment of the municipal sewage with low or even ultra-low concentration. In addition, as the secondary sedimentation tank is designed to be in the central island area, the process has the advantages of compact equipment, small occupied area, low investment cost and operating cost conservation. To the process using only one set of equipment, the process still has the characteristics of appropriate proportion, perfect and convenient arrangement.

Description

technical field [0001] The invention belongs to the technical field of sewage treatment, in particular to an improved A 2 / O or invert A 2 / O process. Background technique [0002] The denitrification and dephosphorization treatment process of urban sewage is generally divided into A 2 / O method, oxidation ditch method and SBR method, with A 2 The / O method is the mainstream. Traditional A 2 The / O method consists of three stages: anaerobic, anoxic, and aerobic. Generally speaking, urban sewage has a large amount of water and low concentration. It is very common in the south of the Yangtze River in my country with low concentration or even ultra-low concentration urban sewage. This kind of sewage is treated with traditional A 2 / O method, the following problems generally exist: [0003] 1. The mixed liquid backflow method is not easy to deal with in engineering, and the power consumption will be high if the pump is used for backflow. In order to ensure a certain deni...

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Problems solved by technology

[0003] 1. The mixed liquid backflow method is not easy to deal with in engineering, and the power consumption will be high if the pump backflow is used

In order to ensure a certain denitrification efficiency, the reflux ratio of the mixed solution is often very large, which requires a reflux of the mixed solution equivalent to 1-4 times the quantum of influent water. Although the head is very low (generally between 0.5-2m), if the scale of the sewage plant Larger, the power consumption of the mixed liquid reflux is astonishing. In addition, the mixed liquid reflux brings inconvenience to the daily production and operation of the sewage plant, the structural layout of the biochemical tank and the layout of the aeration pipeline

[0004] 2. The nitrate rich in return sludge is unfavorable for biological phosphorus removal

The return sludge contains a large amount of nitrate, which will affect the anaerobic environment when returning to the anaerobic tank. The denitrification of nitrogen and anaerobic phosphorus release compete with each other, which is not good for phosphorus removal.

[0005] 3. Insufficient carbon source leads to low nitrogen removal rate

However, due to the process realized by this equipment, the residence time in the aerobic zone of the inner ditch is short, and the time in the anaerobic zone of the outer ditch is longer, which is different from that of A 2 The residence time of each stage of / O is not coordinated, and the purpose of phosphorus and nitrogen removal cannot be better completed

Although a group of oxidation ditches can be used in some urban sewage and industrial sewage to solve the problems of excessive investment and large land occupation, but in actual use A 2 / O and inverted A 2 There is still a gap between the technology and theory of / O nitrogen and phosphorus removal

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