Sewage treatment system and method for nitrogen removal and phosphorus recovery

Abstract

The invention provides a nitrogen removal and phosphorus recovery sewage treatment system which comprises a pretreatment system, a biological treatment system, an advanced treatment system, a sludge treatment system and a phosphorus recovery system which are connected in sequence, and the pretreatment system comprises a coarse screen, a fine screen, an aerated grit chamber and a fine screen tank which are connected in sequence; the biological treatment system comprises an AO treatment unit and a secondary sedimentation tank unit which are connected in sequence; the deep treatment system comprises a denitrification filter tank, an air floatation tank and a contact disinfection tank which are connected in sequence; the sludge treatment system comprises a sludge thickening tank unit, a sludge conditioning tank and a sludge dewatering machine room which are connected in sequence; the phosphorus recovery system comprises a phosphorus slag stirring tank, a phosphorus slag concentration tank and a phosphorus slag dehydration workshop which are connected in sequence. According to the sewage treatment system, the technological process is simple, all functional sections are reasonably arranged, the pretreatment system removes large suspended solids and inorganic sand grains, the biological treatment system strengthens removal of total nitrogen and organic matter, and the deep treatment system further removes TN and TP.

Description

technical field [0001] The invention relates to the technical field of sewage treatment, in particular to a sewage treatment system and method for denitrification and phosphorus recovery. Background technique [0002] At present, the discharge standards of domestic sewage plants usually have relatively strict nitrogen and phosphorus effluent indicators, so the AAO process with simultaneous denitrification and phosphorus removal and its deformation process are usually used in the design as the main biochemical treatment process of sewage treatment plants; AAO process is a process with simultaneous denitrification The phosphorus removal process is mainly composed of anaerobic section, anoxic section and aerobic section; the principle of the phosphorus removal process is to release phosphorus through anaerobic, aerobic excess phosphorus absorption, and discharge excess phosphorus absorption sludge to achieve removal The purpose of phosphorus in water; however, according to the ...

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Problems solved by technology

[0002] At present, the discharge standards of domestic sewage plants usually have relatively strict nitrogen and phosphorus effluent indicators, so the AAO process with simultaneous denitrification and phosphorus removal and its deformation process are usually used in the design as the main biochemical treatment process of sewage treatment plants; AAO process is a process with simultaneous denitrification The phosphorus removal process is mainly composed of anaerobic section, anoxic section and aerobic section; the principle of the phosphorus removal process is to release phosphorus through anaerobic, aerobic excess phosphorus absorption, and discharge excess phosphorus absorption sludge to achieve removal The purpose of phosphorus in water; however, according to the "Survey Plan for Upgrading Urban Sewage Treatment Plants Based on New Local Standards" and the evaluation report on the operation of sewage treatment plants made by our unit, the anaerobic section of most sewage treatment plants is due to the drop of influent oxygen and The content of nitrate nitrogen is high, it is difficult to form an obvious anaerobic environment, and the lack of obvious anaerobic phosphorus release process causes the anaerobic pond to fail to perform the function of biological phosphorus removal but to operate as an anoxic pond, making it difficult to form effective biological phosphorus removal process, resulting in high TP content in the effluent of the secondary sedimentation tank. During the operation, excessive chemical phosphorus removal agents are often added to the end of the biological tank or into the secondary sedimentation tank to ensure the TP of the effluent water. Entering the anaerobic tank, further inhibiting the activity of phosphorus-accumulating microorganisms

[0003] On the other hand, after adding chemical phosphorus removal agents at the end of the aerobic tank, the sewage sludge mixture enters the secondary settling tank for mud-water separation, and part of the separated sludge is discharged to the sludge as residual sludge at the bottom of the secondary settling tank The thickening tank is concentrated; the sludge thickening tank is an anaerobic environment, which will produce a large amount of anaerobic phosphorus release phenomenon, and as the concentration process proceeds, it is necessary to continuously remove the supernatant rich in phosphate, and the supernatant usually enters The sewage pipe network in the factory area is aggregated to the front end of the entire treatment process and mixed with the influent water again, which increases the burden of biological phosphorus removal

[0004] According to the above introduction, in the traditional sewage system, the phosphorus element entering the sewage plant will eventually become part of the dried sludge and be transported to the outside of the plant for disposal. It is difficult to extract phosphate from the dried sludge mixed with a large amount of phosphate. The usual way out is incineration or landfill, resulting in a great waste of phosphorus

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