Improved AAO (anaerobic-anoxic-oxic) sewage treatment system and method for enabling total nitrogen in effluent of improved AAO sewage treatment system to reach surface IV water standard

Abstract

The invention discloses an improved AAO (anaerobic-anoxic-oxic) sewage treatment system and a method for enabling total nitrogen in effluent of the improved AAO sewage treatment system to reach surface IV water standards. The improved AAO sewage treatment system comprises a pre-anoxic section, an anaerobic section, an anoxic section, an aerobic section and a degassing section, the pre-anoxic section, the anaerobic section, the anoxic section, the aerobic section and the degassing section jointly form the biological sewage treatment tank, the pre-anoxic section is additionally arranged in front of the anaerobic section in a multi-point water inlet mode, most inlet water enters the anaerobic section, a small part of inlet water and external return sludge enter the pre-anoxic section, and the anaerobic section and the external return sludge enter the degassing section. Nitrate nitrogen brought into the external return sludge is removed by utilizing a biological nitrogen removal effect, so that the anaerobic phosphorus release effect of the anaerobic section is not influenced by the nitrate nitrogen, and the biological phosphorus removal effect is enhanced. In the anoxic section, microorganisms utilize a carbon source from the anaerobic section to convert into an intracellular carbon source, so that a large amount of productivity of aerobic metabolism is avoided, denitrification is carried out, nitrate nitrogen brought in by internal reflux is oxidized, and the aim of denitrification is achieved. In the aerobic section, microorganisms oxidize organic matters and ammonia nitrogen, so that the concentration of the organic matters and the concentration of the ammonia nitrogen in water are reduced. Compared with a traditional AAO process, the AAO process has the advantages that the aeration rate is small, the energy consumption is low, meanwhile, a degassing section is arranged, nitrate nitrogen provides chemical oxygen for microorganisms in a molecular oxygen competition state, the total nitrogen effluent index is good, and the effluent total nitrogen reaches the earth surface IV water standard.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to an improved AAO sewage treatment system and a method for achieving surface IV water standard for total nitrogen in effluent thereof. Background Art

[0002] my country's ecological civilization construction has entered a critical period with carbon reduction as the key strategic direction, promoting the synergy of pollution reduction and carbon reduction, promoting the comprehensive green transformation of economic and social development, and realizing the improvement of ecological environment quality from quantitative change to qualitative change. Sewage treatment is not only an important starting point for deepening the battle against pollution, but also an important field for promoting greenhouse gas emission reduction. In recent years, my country's sewage collection and treatment facilities have been continuously improved. As of now, my country has built nearly 5,000 urban and county sewage treatment plants with a total treatment capacity of more than 250 million cubic meters per day, and the urban sewage treatment rate exceeds 98%. However, the sewage collection efficiency is low, the carbon source is insufficient, and the denitrification efficiency is low in the sewage treatment process. The standard remains at the Class A standard of the Pollutant Emission Standard for Urban Sewage Treatment Plants (GB18918-20020).

[0003] The traditional A / A / O method is to add an anoxic zone after the anaerobic zone and before the aerobic zone of the A / O process. The raw sewage enters the anaerobic reaction tank, and the phosphorus-containing return sludge discharged from the sedimentation tank also enters simultaneously. Its main function is to release phosphorus, and at the same time, some organic matter is ammonified. The sewage enters the anoxic reaction tank through the first anaerobic reaction tank. The primary function is to remove nitrogen. Nitrate nitrogen is sent from the aerobic reaction tank through internal circulation. The mixed liquid enters the aerobic reaction tank from the anoxic reaction tank to remove BOD, nitrify and absorb phosphorus. Under the action of different microbial flora, the organic matter, nitrogen and phosphorus in the sewage are removed, achieving the purpose of simultaneous biological phosphorus removal and biological nitrogen removal. However, there is an adverse effect of nitrate nitrogen in the return sludge on the release of phosphorus in the anaerobic tank, and the carbon source utilization efficiency is not high, resulting in low efficiency of phosphorus removal.

[0004] Therefore, the present invention proposes an improved AAO sewage treatment system and a method for achieving the total nitrogen in the effluent thereof to meet the surface IV water standard to solve the problems existing in the prior art. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to propose an improved AAO sewage treatment system and a method for achieving the total nitrogen in its effluent to meet the surface IV water standard, so as to solve the problems of the total nitrogen removal efficiency of the existing sewage treatment system and the difficulty in meeting the surface IV water standard.

[0006] In order to achieve the purpose of the present invention, the present invention is implemented by the following technical solutions:

[0007] An improved AAO sewage treatment system and a method for achieving surface IV water standard for total nitrogen in effluent thereof, comprising a pre-anoxic section, an anaerobic section, an anoxic section, an aerobic first section, an aerobic second section, a degassing section, and a double-layer sedimentation tank. A selection zone is added before the anaerobic section, and an external return pipe and a water inlet pipe are provided; a multi-point water inlet pipe is provided above the anaerobic section; a mixed liquor return pipe is provided in the anoxic section; a mixed liquor return pump 019 is connected to the rear end of the aerobic second section, an aeration pipe is provided at the bottom of the aerobic first section and the aerobic second section, the degassing section flows from the side away from the aerobic second section to the double-layer sedimentation tank by gravity, the pre-anoxic section, the anaerobic section, and the anoxic section are all provided with flow pushers 015, 016, and 017, a plant external return pipe is provided in the middle of the double-layer sedimentation tank near the degassing section to discharge to the pre-anoxic section, and a residual sludge discharge pipe is provided in the middle of the side away from the degassing section of the double-layer sedimentation tank.

[0008] A further improvement is that: the pre-anoxic section is connected with a water inlet pipe and an external reflux, with 30% water inlet and 100% external reflux.

[0009] A further improvement is that the anaerobic section is connected to multiple water inlet points of 70%.

[0010] A further improvement is that the pre-anoxic section, anaerobic section, anoxic section, aerobic section and degassing section are connected in series and together constitute a biological pool, the average sludge concentration in the biological pool is 5-6g / L, and the sludge settling ratio SV30 is not higher than 70%.

[0011] A further improvement is that the dissolved oxygen in the aerobic first stage is maintained above 0.5-1.0 mg / L, and the dissolved oxygen in the aerobic second stage is maintained within 1.0-2.0 mg / L.

[0012] A further improvement is that the mixed liquid reflux pipe refluxes the nitrification liquid in the aerobic section to the anoxic zone, and the nitrification liquid reflux ratio is 100-200%. The external reflux ratio is 50%-100%.

[0013] The beneficial effects of the present invention are as follows: the present invention forms a sewage biological treatment pool through a pre-anoxic section, an anaerobic section, an anoxic section, an aerobic section and a degassing section, thereby avoiding the adverse effects of nitrate in the return sludge on the anaerobic zone, and at the same time, by controlling the dissolved oxygen return ratio and the carbon source, ensuring the dissolved oxygen environment for denitrification, ensuring a sufficient return ratio to ensure the denitrification effect, ensuring that the microorganisms convert the external carbon source into an intracellular carbon source, and effectively utilizing the carbon source for denitrification. Compared with the traditional AAO process, the aeration volume is small, the energy consumption is low, the carbon source demand is small, and a degassing section is set at the same time to reduce the external return dissolved oxygen, and the nitrified nitrogen is removed in the anoxic section, thereby achieving the improvement of the removal efficiency of the total nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the existing technical solutions, the drawings required for describing the embodiments or the existing technologies are briefly introduced below.

[0015] Figure 1 is a system schematic diagram of the present invention;

[0016] Among them: 001, water inlet pipe; 002, multi-point water inlet pipe; 003, pre-anoxic section; 004, anaerobic section; 005, anoxic section; 006, aerobic section one; 007, aerobic section two; 008, degassing section; 009, double-layer sedimentation tank; 010, external return pipe; 011, carbon source pipe; 012, aeration pipe; 013, residual sludge discharge pipe; 014, mixed liquor return pipe; 015, pre-anoxic section flowmaker; 016, anaerobic section flowmaker; 017, anoxic section flowmaker; 018, water distribution gate; 019, mixed liquor return pump. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] See also Figure 1 The present embodiment provides an improved AAO sewage treatment system and a method for achieving surface IV water standard total nitrogen in its effluent, comprising a pre-anoxic section 003, an anaerobic section 004, an anoxic section 005, an aerobic first section 006, an aerobic second section 007, a degassing section 008 and a double-layer sedimentation tank 009; the anoxic section 005 is located between the anaerobic zone 004 and the aerobic first section 006, the aerobic second section 007 is located between the aerobic first section 007 and the degassing section 008, the upper part of the anaerobic zone 004 away from the anoxic zone 005 is provided with a sewage inlet pipe 002, and the upper part of the anoxic zone 005 is connected with a mixed liquid return pipe 006. Flow pipe 014, one end of the mixed liquor return pipe 014 away from the aerobic first section 007 is located in the aerobic second section and is connected to a mixed liquor return pump 019, a water distribution gate 018 is provided on the side of the deaeration section 006 away from the aerobic second section 007, an aeration pipe 012 is provided in both the aerobic first section 006 and the aerobic first section 007, a flow pusher 015 is provided in the pre-anoxic section 003, a flow pusher 016 is provided in the anaerobic section 004, a flow pusher 017 is provided in the anoxic section 005, an external return pipe 010 and a residual sludge discharge pipe 013 are provided in the double-layer sedimentation tank 009 away from the deaeration section 009.

[0019] The pre-anoxic section is connected to a partial inlet pipe 001 and an external return pipe 010, the anaerobic section 004 is connected to a multi-point inlet pipe 002, and the anoxic section 005 is connected to a mixed liquor return pipe 014. The sewage enters the anaerobic section and the pre-anoxic section at different points, and the carbon source is reasonably distributed according to the actual influent water quality, so that both areas can obtain appropriate nutrients, the rationality of carbon source distribution is greatly improved, and the carbon source required for denitrification can be guaranteed, creating favorable conditions for achieving denitrification standards; the returned sludge first enters the pre-anoxic section, which increases the sludge denitrification effect, eliminates the adverse effects of nitrate nitrogen in the returned sludge on phosphorus release in the anaerobic section, further enhances the phosphorus removal effect, and ensures the effluent water quality.

[0020] The pre-anoxic section 003 is connected to the anaerobic section 004 through the baffle wall, the anaerobic section 004 is connected to the anoxic section 005 through the baffle wall, the anoxic section 005 is connected to the aerobic first section 006 through the baffle wall, the aerobic first section 006 is connected to the aerobic second section 007 through the baffle wall, the aerobic second section 007 is connected to the degassing section 008 through the baffle wall, and the degassing section 008 is connected to the double-layer sedimentation tank 009 through the water distribution gate.

[0021] The pre-anoxic section 003, the anaerobic section 004, the anoxic section 005, the aerobic section 1 006, the aerobic section 2 007 and the degassing section 008 are connected in series and together constitute a biological pool. The average sludge concentration in the biological pool is 5-6 g / L, and the sludge settling ratio SV30 is not higher than 70%.

[0022] The dissolved oxygen in the pre-anoxic section 003 is maintained below 0.2-0.5 mg / L, the dissolved oxygen in the anaerobic section 004 is maintained at 0 mg / L, the dissolved oxygen in the anoxic section 005 is maintained at 0.2-0.5 mg / L, the dissolved oxygen in the aerobic section 1 is maintained above 0.5 mg / L, and the dissolved oxygen in the aerobic section 2 is maintained within 1.0-2.0 mg / L.

[0023] The end of the degassing section 008 is connected to a double-layer sedimentation tank 009 through a water distribution gate 018, and the external reflux ratio is 50%-100%. The mixed liquid reflux pump 019 refluxes the nitrification liquid in the aerobic second section 007 to the anoxic zone 005, and the nitrification liquid reflux ratio is 100-200%.

[0024] When in use, the sewage to be treated first enters the pre-anoxic zone 003 through the sewage inlet pipe 001, the double-layer sedimentation tank 009, and the sludge return pipe 010. At the same time, the carbon source pipe 011 is added according to the situation. At this time, the flow pusher 015 is turned on for stirring and mixing, which increases the sludge denitrification effect, eliminates the adverse effect of nitrate nitrogen in the return sludge on the phosphorus release in the anaerobic section, and further enhances the phosphorus removal effect; the multi-point inlet pipe 002 is included in the anaerobic section 004, and the flow pusher 016 is turned on for stirring and mixing, anaerobic phosphorus release and synthesis of PHB energy; then the sewage and mixed liquid return pipe 014 enter the anoxic section 005 for denitrification reaction, and the rationality of carbon source distribution is greatly improved, which can ensure the carbon source required for denitrification. , creating favorable conditions for achieving denitrification standards; the effluent from the anoxic section 005 then enters the aerobic section 1 006 and the aerobic section 2 007. At this time, the aeration pipe 012 is opened to use polyphosphate bacteria to aerobic phosphorus absorption and nitrifying bacteria to convert ammonia nitrogen into nitrate nitrogen to complete the nitrification reaction; at the end of the aerobic section 2 007, a mixed liquid reflux pump 019 is used to return the mixed liquid containing nitrate nitrogen to the anoxic zone 005; the effluent from the aerobic section 2 007 enters the degassing section 008 to consume part of the dissolved oxygen; finally, the sewage is discharged from the terminal water distribution gate 018 into the double-layer sedimentation tank and mud and water are separated; in actual operation, the entire system can adjust various operating parameters according to the actual influent water quality, and make the denitrification efficiency of the entire sewage treatment system reach the surface IV water standard.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An improved AAO sewage treatment system and a method for the effluent total nitrogen to reach the surface IV water standard, characterized in that: The present invention comprises a pre-anoxic section 003, an anaerobic section 004, an anoxic section 005, an aerobic first section 006, an aerobic second section 007, a degassing section 008 and a double-layer sedimentation tank 009. The anoxic section 005 is located between the anaerobic section 004 and the aerobic first section 006. The aerobic first section 006 is located between the anoxic section 005 and the aerobic second section 007. A sewage inlet pipe 001 and a sludge return pipe 010 are provided at the bottom of the pre-anoxic section 003 away from the anaerobic section 004. A multi-point inlet pipe 002 is connected to the bottom of the anaerobic section 004. A mixed liquor return pipe 014 is connected to the upper part of the anoxic section 003. The aerobic second section 006 is provided with a sludge return pipe 014. A mixed liquor reflux pipe 014 is arranged at the rear end of 07, an aeration pipe 012 and a mixed liquor reflux pump 019 are arranged at the bottom of the aerobic first section 006 and the aerobic second section 007, the deaeration section 008 flows by gravity to the double-layer sedimentation tank 009 on the side away from the aerobic second section 007, flow pushers 015, 016, 017 are arranged in the pre-anoxic section 003, the anaerobic section 004 and the anoxic section 005, a plant sludge external reflux pipe to the pre-anoxic section 003 is arranged in the middle of the double-layer sedimentation tank 009 on the side close to the deaeration section 008, and a plant residual sludge discharge pipe 013 is arranged in the middle of the double-layer sedimentation tank 009 on the side away from the deaeration section 008.

2. The improved AAO sewage treatment system and the method for the effluent total nitrogen to reach IV water standard according to claim 1, characterized in that: The pre-anoxic section 003 is connected to a part of the water inlet 001 and an external reflux 010 .

3. The improved AAO sewage treatment system and the method for the effluent total nitrogen reaching the surface IV water standard according to claim 1, characterized in that: The pre-anoxic section 003 is connected to the anaerobic section 004 through a baffle wall, the anaerobic section 004 is connected to the anoxic section 005 through a baffle wall, the anoxic section 005 is connected to the aerobic first section 006 through a baffle wall, the aerobic first section 006 is connected to the aerobic second section 007 through a baffle wall, the aerobic second section 007 is connected to the degassing section 008 through a baffle wall, and the degassing section 008 is connected to the double-layer sedimentation tank 009 through a water distribution gate 018.

4. The improved AAO sewage treatment system and the method for the effluent total nitrogen to reach IV water standard according to claim 1, characterized in that: The pre-anoxic section 003, the anaerobic section 004, the anoxic section 005, the aerobic first section 006, the aerobic second section 007 and the degassing section 008 are connected in series and together constitute a biological pool.

5. The improved AAO sewage treatment system and the method for the effluent total nitrogen to reach IV water standard according to claim 1, characterized in that: The end of the degassing section 008 is connected to a double-layer secondary sedimentation tank 009 through an end water distribution gate 018 .

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