A AAAOF sewage treatment system and process

Abstract

The present invention relates to an AAAOF sewage treatment system and process, and belongs to the field of water, wastewater, sewage or sludge treatment. The sewage treatment system includes a biochemical tank, a secondary sedimentation tank and a sludge concentration tank; the biochemical tank is composed of a pre-anoxic tank, an anaerobic tank, an anoxic tank, an aerobic tank, an aerobic tank and an anaerobic tank connected in sequence; the pre-anoxic tank, the anaerobic tank, the aerobic tank and the anaerobic tank are all connected to the water inlet; the effluent of the biochemical tank is connected to the secondary sedimentation tank, and after the sludge is precipitated in the secondary sedimentation tank, a part of the sludge flows back to the pre-anoxic tank, and the other part of the sludge enters the sludge concentration tank, and the supernatant obtained by the treatment of the sludge concentration tank flows back to the anoxic tank. The sewage treatment system can further improve the efficiency of biological nitrogen removal and phosphorus removal on dry days, and has the sewage treatment capacity of overload treatment of more than 2 times the dry day design flow on rainy days, thereby greatly reducing the overflow pollution of the urban drainage system.

Description

Technical Field

[0001] The present invention relates to the field of water, wastewater, sewage or sludge treatment, and in particular to an AAAOF sewage treatment system and process. Background Art

[0002] Due to the imperfect drainage network, incomplete separation of rainwater and sewage, and damage and leakage of the network, a large amount of external water can easily enter the sewage network. On the one hand, the influent concentration of the sewage treatment plant on rainy days is low, only 50%-60% of the concentration on dry days, resulting in insufficient carbon source for sewage and low efficiency of nitrogen and phosphorus removal. On the other hand, due to the limited treatment capacity of the sewage treatment plant, a large amount of overflow sewage on rainy days flows directly into the river, causing serious rainy day overflow pollution.

[0003] At present, the actual influent concentration of most sewage treatment plants on rainy days is only 30%-50% of the designed influent concentration, which makes the biochemical system have the potential to operate beyond the designed load on rainy days. However, when the actual treated water volume exceeds the designed scale, the existing sewage treatment process will shorten the hydraulic retention time of the biochemical pool, reduce the efficiency of biological nitrogen and phosphorus removal, and cause the biochemical pool to reduce the efficiency of pollutant removal, resulting in N, P and other indicators not meeting the standards. Therefore, how to improve the removal efficiency of the biochemical pool for organic matter and N, P without expanding the biochemical pool, and ensure that the effluent of the sewage treatment plant is stable and meets the standards, is the most effective way to achieve the improvement of the capacity of the sewage treatment plant on rainy days.

[0004] The current mainstream sewage treatment process is the anaerobic / anoxic / aerobic process with nitrogen and phosphorus removal functions, which is commonly known as the AAO process. In the traditional AAO process, the return sludge contains a high level of nitrate, which causes a denitrification reaction in the anaerobic tank, so that the limited carbon source is used by denitrifying bacteria, inhibiting the phosphorus release reaction of polyphosphate bacteria and reducing the biological phosphorus removal efficiency of the AAO process. For this reason, people have improved the traditional AAO process by adding a pre-anoxic tank before the anaerobic tank, so that the return sludge first undergoes a denitrification reaction with part of the sewage in the pre-anoxic tank to eliminate the nitrate concentration entering the anaerobic tank, thereby improving the nitrogen and phosphorus removal efficiency of the AAO process system. Although the improved AAO process has a high nitrogen and phosphorus removal efficiency, the required hydraulic retention time is relatively long, generally 14-23h.

[0005] In addition, activated sludge has a strong flocculation and adsorption function. Based on this, people have developed an adsorption-regeneration process, that is, sludge is activated by aeration to make the microorganisms in the sludge extremely hungry; then the activated sludge is mixed with sewage in the reaction tank to react, so that the microorganisms adsorb a large amount of pollutants; then the mixed liquid enters the sedimentation tank for mud and water separation. Part of the precipitated sludge is returned to the sludge activation tank to continue to participate in the next stage of reaction, and the other part is discharged as residual sludge. This process only requires 3.5-4h of hydraulic retention time, COD removal rate can reach about 70%, SS removal rate can reach about 80%, TP removal rate can reach about 40%, and nitrogen removal rate is relatively low, generally 10%-20%. The advantage of this process is that it can achieve a good pollutant removal effect at a very short hydraulic retention time. The disadvantage is that the N and P removal rates are low, which cannot meet the requirements of the Class A or Class B emission standards of the "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB 18918-2002). Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides an AAAOF sewage treatment system and process, which solves the technical problems of low utilization rate of carbon sources in sewage, low efficiency of nitrogen and phosphorus removal, and limited ability to increase production capacity on rainy days in traditional AAO sewage treatment process.

[0008] (II) Technical solution

[0009] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0010] In a first aspect, the present invention provides an AAAOF sewage treatment system including a biochemical tank, a secondary sedimentation tank and a sludge concentration tank;

[0011] The biochemical pool is composed of a pre-anoxic pool, an anaerobic pool, an anoxic pool, an aerobic pool 1, an aerobic pool 2 and an anaerobic pool connected in sequence;

[0012] The pre-anoxic tank, the anaerobic tank, the second aerobic tank and the facultative anoxic tank are all connected to the water inlet;

[0013] The effluent from the biochemical pool is connected to the secondary sedimentation tank. After the sludge is separated from the water in the secondary sedimentation tank, part of the sludge flows back to the pre-anoxic pool, and the other part of the sludge enters the sludge thickening pool. The supernatant obtained by the sludge thickening pool flows back to the anoxic pool.

[0014] Optionally, an aeration system is also included, which includes an aerobic tank blower and a facultative aerobic tank blower, the aerobic tank blower is connected to the aerobic tank one and the aerobic tank two, the aerobic tank one and the aerobic tank two are provided with an aeration device, the facultative aerobic tank blower is connected to the facultative aerobic tank, and the facultative aerobic tank is provided with an aeration device.

[0015] Optionally, it further comprises a water inlet pipeline, through which the inlet water is respectively connected to the pre-anoxic tank, the anaerobic tank, the second aerobic tank and the facultative anoxic tank.

[0016] Optionally, a water inlet main valve and a water inlet total flow meter are provided on the water inlet pipeline.

[0017] Optionally, a water inlet valve and a water inlet flowmeter are also provided on the water inlet pipeline connected to the pre-anoxic pool;

[0018] An anaerobic tank water inlet valve and an anaerobic tank water inlet flowmeter are also provided on the water inlet pipeline connected to the anaerobic tank;

[0019] The water inlet pipe connected to the aerobic second tank is also provided with an aerobic second tank water inlet valve and an aerobic second tank water inlet flowmeter;

[0020] The water inlet pipe connected to the anoxic pool is also provided with an anoxic pool water inlet valve and an anoxic pool water inlet flowmeter. Through the total water inlet valve and the total water inlet flowmeter, the pre-anoxic pool water inlet valve and the pre-anoxic pool water inlet flowmeter, the anaerobic pool water inlet valve and the anaerobic pool water inlet flowmeter, the aerobic second pool water inlet valve and the aerobic second pool water inlet flowmeter, the anoxic pool water inlet valve and the anoxic pool water inlet flowmeter, etc., the conduction or cutoff of each water inlet passage and the water inlet distribution ratio can be accurately regulated according to factors such as weather conditions and the C / N ratio in the influent.

[0021] Optionally, the terminal mixed liquid of the anoxic tank is refluxed to the anoxic tank through a nitrification liquid reflux pump; the secondary sedimentation tank is connected to the pre-anoxic tank through a sludge reflux pipe, and the sludge reflux pipe is provided with a reflux sludge pump and a reflux sludge flowmeter, and a residual sludge pump is provided on the pipeline connecting the secondary sedimentation tank and the sludge thickening tank; the supernatant of the sludge thickening tank is refluxed to the anoxic tank through a supernatant reflux pump.

[0022] Optionally, a suspended filler is provided in the anoxic tank.

[0023] Optionally, the suspended filler is MBBR filler, or other forms of suspended filler.

[0024] Optionally, the aerobic tank 1 is provided with an online sludge concentration detector, the aerobic tank 2 is provided with an online dissolved oxygen meter for the aerobic tank 2, the facultative tank is provided with an online dissolved oxygen meter for the facultative tank, and the water outlet of the biochemical tank is provided with an online ammonia nitrogen detector and an online total nitrogen detector.

[0025] In a second aspect, the present invention provides an AAAOF sewage treatment process, which utilizes the sewage treatment system; including a dry day operation mode and a rainy day operation mode, assuming that the dry day design water inflow flow is Q:

[0026] When the water flow in the water inlet pipe is ≤1.3Q, the sewage treatment system operates in the dry weather operation mode, including:

[0027] Open the water inlet valve of the pre-anoxic tank to allow 0.2-0.3Q of water to enter the pre-anoxic tank; adjust the return sludge pump to allow 0.5-0.6Q of sludge to flow back to the pre-anoxic tank;

[0028] Adjust the water inlet valve of the anaerobic tank to allow 0.6-0.9Q of water to enter the anaerobic tank;

[0029] The water inlet valve of the aerobic pool 2 is closed, and the air supply of the aerobic pool blower is adjusted to control the dissolved oxygen in the aerobic pool 1 and the aerobic pool 2 to be 1.5-2 mg / L;

[0030] Adjust the water inlet valve of the oxygen tank to allow 0.1-0.2Q of water to enter the oxygen tank, and adjust the air supply of the blower of the oxygen tank to control the dissolved oxygen in the oxygen tank to 0.2-1.0 mg / L;

[0031] Adjust the flow rate of the nitrification liquid reflux pump so that the reflux rate of the nitrification liquid in the aerobic tank is controlled at 1.0-2.0Q;

[0032] Adjust the flow rate of the supernatant reflux pump so that the supernatant reflux rate of the sludge thickening tank is controlled at 0.03-0.04Q;

[0033] When the water flow in the water inlet pipe is greater than 1.3Q and less than or equal to 2.4Q, the sewage treatment system operates in the rainy day operation mode, including:

[0034] Close the pre-anoxic tank inlet valve, and adjust the anaerobic tank inlet valve to allow 1.0-1.1Q of influent to enter the anaerobic tank through the anaerobic tank inlet valve;

[0035] Open the water inlet valve of the second aerobic pool and the water inlet valve of the facultative anoxic pool, the water inlet amount of the second aerobic pool is 0-0.7Q, and the water inlet amount of the facultative anoxic pool is 0-0.7Q;

[0036] Adjust the flow rate of the return sludge pump to increase the return sludge volume to 1.0-1.1Q; adjust the flow rate of the nitrification liquid return pump to increase the nitrification liquid return volume to 2Q-3Q;

[0037] Increasing the air supply of the aerobic pool blower to increase the dissolved oxygen concentration in the aerobic pool 1 and the aerobic pool 2 to 2-3 mg / L;

[0038] The aeration tank is continuously aerated, and the air supply of the aeration tank blower is adjusted to control the dissolved oxygen concentration at the outlet of the biochemical tank to be 0.2-1.0 mg / L;

[0039] The flow rate of the supernatant liquid reflux pump is adjusted so that the supernatant liquid reflux rate of the sludge thickening tank is controlled at 0.06-0.08Q.

[0040] Optionally, in the dry weather operation mode, the hydraulic retention time of each treatment tank is: 1-2h for the pre-anoxic tank, 2-3h for the anaerobic tank, 2-3h for the anoxic tank, 4-5h for the aerobic tank 1, 2-3h for the aerobic tank 2, and 1-2h for the facultative aerobic tank;

[0041] In the rainy day operation mode, the hydraulic retention time of each treatment pool is: 1-2 hours for the anaerobic pool, 2-3 hours for the anoxic pool, 4-5 hours for the aerobic pool 1; 1-1.5 hours for the aerobic pool 2, and 0.5-1 hour for the facultative aerobic pool.

[0042] Optionally, by monitoring the ammonia nitrogen concentration of the biochemical pool effluent detected by the online ammonia nitrogen detector and the total nitrogen concentration of the biochemical pool detected by the online total nitrogen detector, the water inlet valve of the aerobic second pool and the water inlet valve of the facultative aerobic pool are adjusted in real time to control the water inflow of the aerobic second pool and the facultative aerobic pool, specifically including:

[0043] Set the ammonia nitrogen concentration of the biochemical pool effluent to a and the total nitrogen concentration to b;

[0044] When the ammonia nitrogen concentration of the biochemical pool effluent detected by the online ammonia nitrogen detector is higher than a, and the total nitrogen concentration of the biochemical pool detected by the online total nitrogen detector is lower than b, the water inlet valve of the aerobic pool II is adjusted to increase the water inlet volume of the aerobic pool II; the water inlet valve of the facultative aerobic pool is adjusted to reduce the water inlet volume of the facultative aerobic pool, and at the same time, the air supply of the blower of the facultative aerobic pool is increased to increase the dissolved oxygen concentration of the facultative aerobic pool to 0.8-1.0 mg / L;

[0045] When the ammonia nitrogen concentration of the biochemical pool effluent detected by the online ammonia nitrogen detector is lower than a, and the total nitrogen concentration of the biochemical pool detected by the online total nitrogen detector is higher than b, the air supply of the blower of the anoxic pool is reduced to reduce the dissolved oxygen concentration of the anoxic pool to below 0.5 mg / L; at the same time, the flow rate of the nitrification liquid reflux pump is increased to 3-4Q;

[0046] When the ammonia nitrogen concentration of the biochemical pool effluent detected by the online ammonia nitrogen detector is higher than a, and the total nitrogen concentration of the biochemical pool detected by the online total nitrogen detector is higher than b, adjust the water inlet valve of the aerobic second pool and the water inlet valve of the facultative anoxic pool to reduce the water inlet volume of the aerobic second pool and the water inlet volume of the facultative anoxic pool.

[0047] (III) Beneficial effects

[0048] The present invention combines the characteristics of the improved AAO process and couples the flocculation and adsorption functions of activated sludge to provide an AAAOF sewage treatment system and process. Without increasing the volume of the biochemical pool and the hydraulic retention time (the hydraulic retention time of the present invention is 12-18 hours on dry days and 8-9 hours on rainy days), the treatment capacity of the biochemical pool is greatly improved by adjusting the water inlet method, aeration method, sludge return ratio, nitrification liquid return ratio and the like, so that the dry-day biochemical pool can have better biological denitrification and phosphorus removal efficiency, and on rainy days it has the overload treatment capacity of sewage treatment exceeding twice the dry-day design flow, thereby greatly reducing overflow pollution of urban drainage systems.

[0049] In the sewage treatment system of the present invention, the anaerobic tank has direct water inflow in the dry day mode. In the rainy day operation mode, the anaerobic tank, the second aerobic tank and the anaerobic tank all have direct water inflow; the pre-anoxic tank does not have water inflow, and is used for denitrification and denitrification of the return sludge. The residual sludge of the sewage treatment system of the present invention will undergo anaerobic hydrolysis reaction in the sludge thickening tank, so that the organic matter adsorbed by the activated sludge is converted into a carbon source rich in organic acids, and the supernatant of the sludge thickening tank is returned to the anoxic tank to provide the anoxic tank with the carbon source required for denitrification and denitrification; thereby, the AAAOF sewage treatment system provided by the present invention can effectively improve the production capacity on rainy days, improve the utilization rate of the carbon source brought by the incoming water, and improve the denitrification and dephosphorization effects.

[0050] In the sewage treatment process of the present invention, when operating in a dry day operation mode, the simultaneous nitrification and denitrification functions of the anoxic tank can be utilized to improve the efficiency of biological nitrogen removal and phosphorus removal, and when operating in a rainy day operation mode, the biological flocculation and adsorption functions of the anoxic tank can be utilized to enable the biochemical pool to have a sewage treatment capacity of more than twice the dry day flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a schematic diagram of an AAAOF sewage treatment system of the present invention.

[0052] [Description of Reference Numerals]

[0053] 1: pre-anoxic tank inlet valve; 2: anaerobic tank inlet valve; 3: aerobic tank 2 inlet valve; 4: anoxic tank inlet valve; 5: return sludge pump; 6: residual sludge pump; 7: nitrification liquid return pump; 8: aerobic tank blower; 9: anoxic tank blower; 10: water inlet main valve; 11: water inlet total flow meter; 12: anaerobic tank inlet flow meter; 13: aerobic tank 2 inlet flow meter; 14: anoxic tank inlet flow meter; 15: return sludge flow meter; 16: aerobic tank 2 online dissolved oxygen meter; 17: anoxic tank online dissolved oxygen meter; 18: online ammonia nitrogen monitor; 19: online total nitrogen monitor; 20: online sludge concentration monitor; 21: pre-anoxic tank inlet flow meter; 22: supernatant return pump. DETAILED DESCRIPTION

[0054] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0055] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0056] The present invention provides a pre-anoxic / anaerobic / anoxic / aerobic / facultative anoxic (AAAOF) sewage treatment system, such as Figure 1 The system includes a biochemical tank, a secondary sedimentation tank, a sludge thickening tank, an aeration system and a control system.

[0057] Among them, the biochemical pool is composed of a pre-anoxic pool, an anaerobic pool, an anoxic pool, an aerobic pool 1, an aerobic pool 2 and an anaerobic pool connected in sequence. The biochemical pool is designed according to the dry day design scale Q. When the inlet flow rate is Q, the total hydraulic retention time is 12-13h. The hydraulic retention time of each treatment pool is: pre-anoxic pool 1h, anaerobic pool 2h, anoxic pool 2h, aerobic pool 1 4-5h, aerobic pool 2h, facultative pool 1h, and suspended fillers (MBBR fillers, filling volume ratio is 30-35%) are arranged in the facultative pool.

[0058] The sewage is passed through the biochemical pool to remove organic matter and achieve biological denitrification and phosphorus removal; then it flows into the secondary sedimentation tank for sedimentation to separate mud and water. The clean water from the secondary sedimentation tank is directly discharged or enters the deep treatment unit of the sewage treatment plant for treatment; part of the sludge in the secondary sedimentation tank is directly returned to the anaerobic tank, and the other part is discharged into the sludge concentration tank. In order to make full use of the carbon source adsorbed in the sludge, the supernatant of the sludge concentration tank is returned to the anoxic tank and used as a carbon source for denitrification and denitrification, and the concentrated sludge is transported to the sludge dewatering room.

[0059] Sewage enters the biochemical pool in multiple ways: water enters the pre-anoxic pool, and the flow rate into the pre-anoxic pool is controlled by the pre-anoxic pool water inlet valve 1; water enters the anaerobic pool, and the flow rate into the anaerobic pool is controlled by the anaerobic pool water inlet valve 2; water enters the aerobic second pool, and the flow rate into the aerobic second pool is controlled by the aerobic second pool water inlet valve 3; water enters the facultative pool, and the flow rate into the facultative pool is controlled by the facultative pool water inlet valve 4; the total water inflow of the biochemical pool can be controlled and adjusted by the main inlet valve 10.

[0060] Sludge return: Part of the sludge coming out of the secondary sedimentation tank is returned to the pre-anoxic tank through the return sludge pump 5, and the return ratio is 0.5Q-1.1Q; the other part is discharged to the sludge thickening tank through the residual sludge pump 6.

[0061] Return of supernatant from sludge thickening tank: The residence time of sludge in the sludge thickening tank is 14-18 hours. Anaerobic hydrolysis reaction occurs in the sludge thickening tank. The supernatant contains rich carbon source. The supernatant is returned to the anoxic tank through the supernatant return pump 22 as a carbon source for denitrification.

[0062] In order to monitor and conveniently adjust the inflow of the pre-anoxic tank, anaerobic tank, aerobic tank and anoxic tank, a total inflow flow meter 11 is set on the biochemical tank inlet main pipe, a pre-anoxic tank inlet flow meter 21 is set on the pre-anoxic tank inlet pipe; an anaerobic tank inlet flow meter 12 is set on the anaerobic tank inlet pipe, an aerobic tank inlet flow meter 13 is set on the aerobic tank inlet pipe, and an oxic tank inlet flow meter 14 is set on the oxic tank inlet pipe. In order to conveniently adjust the return sludge volume, a return sludge flow meter 15 is set on the return sludge pipe.

[0063] Nitration liquid reflux: The mixed liquid at the end of the anoxic tank is refluxed to the anoxic tank through the nitration liquid reflux pump 7 at the bottom of the anoxic tank, and the reflux rate is 1Q-3Q.

[0064] Aeration system: aeration of aerobic pool 1 and aerobic pool 2 is supplied by aerobic pool blower 8, and the dissolved oxygen concentration is 1.5-3 mg / L; aeration of facultative aerobic pool is supplied by facultative aerobic pool blower 9, and the dissolved oxygen concentration is 0.2-1.0 mg / L.

[0065] Control system: an online sludge concentration detector 20 is installed at the end of the aerobic tank 1, an online dissolved oxygen meter 16 is installed at the end of the aerobic tank 2; an online dissolved oxygen meter 17 is installed at the end of the facultative aerobic tank; an online ammonia nitrogen monitor 18 and a total nitrogen online detector 19 are installed at the outlet of the biochemical tank.

[0066] The sewage treatment system of the present invention can be operated in a dry day operation mode and a rainy day operation mode. In the dry day mode, the sewage volume can be treated at 1.3 times the design scale (Q); when the water flow of the pipe network is greater than or equal to 1.3Q, the sewage volume can be treated at most 2.4Q in the rainy day operation mode.

[0067] Without adding suspended biological fillers to the aerobic tank, the system can handle a maximum sewage volume of more than 2.0Q in rainy day operation mode.

[0068] The process of treating sewage using the AAAOF sewage treatment system of the present invention includes: a dry day operation mode and a rainy day operation mode.

[0069] Switch between dry day operation mode and rainy day operation mode according to weather conditions, and set the dry day design flow rate as Q;

[0070] (1) When the water flow in the water inlet pipe is less than or equal to 1.3Q, the sewage treatment system operates in the dry weather operation mode:

[0071] Open the pre-anoxic tank inlet valve 1 to allow 0.3Q of inlet water to enter the pre-anoxic tank; adjust the return sludge pump 5 to allow 0.5Q of sludge to flow back to the pre-anoxic tank; the inlet water and the return sludge are mixed in the pre-anoxic tank, and the carbon source in the inlet water and the nitrate in the return sludge are used to complete the denitrification reaction, providing a nitrate-free anaerobic environment for the anaerobic tank.

[0072] Adjust the anaerobic tank inlet valve 2 to allow 0.6-0.9Q of inlet water to enter the anaerobic tank. The polyphosphate bacteria in the anaerobic tank utilize the carbon source in the sewage to fully release phosphorus and absorb the organic carbon source.

[0073] Close the water inlet valve 3 of the aerobic pool 2, and stop the aerobic pool 2 from entering. Adjust the air supply of the aerobic pool blower 8 to control the dissolved oxygen in the aerobic pool 1 and the aerobic pool 2 at 1.5-2 mg / L.

[0074] Adjust the water inlet valve 4 of the aerobic tank to allow 0.1-0.2Q of influent to enter the aerobic tank, and adjust the air supply of the aerobic tank blower 9 to control the dissolved oxygen in the aerobic tank at 0.2-1.0 mg / L, so that the aerobic tank is in an aerobic state; at this time, the microorganisms outside the activated sludge and outside the biofilm are in an aerobic state, and the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the aerobic tank can undergo both nitrification and synchronous denitrification.

[0075] Adjust the flow rate of the nitrification liquid reflux pump 7 so that the nitrification liquid reflux rate of the aeration tank is controlled at 1.0-2.0Q.

[0076] The flow rate of the supernatant liquid return pump 22 is adjusted so that the return rate of the supernatant liquid in the sludge thickening tank is controlled at 0.03-0.04Q.

[0077] In the dry weather operation mode, the hydraulic retention time of each treatment pool is: 1-2 hours for the pre-anoxic pool, 2-3 hours for the anaerobic pool, 2-3 hours for the anoxic pool, 4-5 hours for the aerobic pool 1, 2-3 hours for the aerobic pool 2, and 1-2 hours for the facultative aerobic pool. The hydraulic retention time refers to the retention time of all the water entering a treatment pool.

[0078] (2) When the water flow in the water inlet pipe is greater than 1.3Q and less than or equal to 2.4Q, the sewage treatment system operates in the rainy day operation mode:

[0079] Close the pre-anoxic tank inlet valve 1 to stop the water from entering the pre-anoxic tank; adjust the anaerobic tank inlet valve 2 to allow 1.0Q of water to enter the anaerobic tank through the anaerobic tank inlet valve 2.

[0080] Open the aerobic pool inlet valve 3 and the facultative aerobic pool inlet valve 4, and the inlet water with a flow rate of q1 enters the aerobic pool through the aerobic pool inlet valve 3, and the inlet water with a flow rate of q2 enters the facultative aerobic pool through the facultative aerobic pool inlet valve 4; at the beginning, q1=q2, but q1 and q2 can be adjusted according to the water quality of the biochemical pool effluent, the adjustment range of q1 is 0-0.7Q, and the adjustment range of q2 is 0-0.7Q.

[0081] Adjust the flow rate of the return sludge pump 5 to increase the return sludge volume to 1.0Q to increase the biochemical system microbial biomass. Increase the flow rate of the nitrification liquid return pump 7 to increase the nitrification liquid return volume to 2Q-3Q.

[0082] Increase the air supply of the aerobic tank blower 8 to increase the dissolved oxygen concentration in the aerobic tank 1 and the aerobic tank 2 to 2-3 mg / L, so that the microorganisms can increase the decomposition and nitrification reaction rates of organic matter in a high dissolved oxygen environment, reduce the ammonia nitrogen concentration of the mixed solution, and put the microorganisms in a hungry state, so that the activated sludge has better adsorption capacity in the anoxic tank.

[0083] The facultative aerobic tank is changed to continuous aeration, and the air supply of the facultative aerobic tank blower 9 is adjusted to control the dissolved oxygen concentration at the outlet of the biochemical tank to 0.2-1.0 mg / L, so that the facultative aerobic tank is in an facultative aerobic state; at this time, the microorganisms outside the activated sludge and outside the biofilm are in an aerobic state, and the microorganisms inside are in an anoxic state due to insufficient oxygen supply, so that the facultative aerobic tank can undergo both nitrification and synchronous denitrification.

[0084] The flow rate of the supernatant liquid return pump 22 is adjusted so that the return rate of the supernatant liquid in the sludge thickening tank is controlled at 0.06-0.08Q.

[0085] In the rainy day operation mode, the hydraulic retention time of each treatment pool is: 1-2 hours for the anaerobic pool, 2-3 hours for the anoxic pool, 4-5 hours for the aerobic pool 1, 1-1.5 hours for the aerobic pool 2, and 0.5-1 hour for the facultative aerobic pool. The hydraulic retention time refers to the retention time of all water entering a treatment pool.

[0086] In the rainy day operation mode, 1.0Q of influent enters from the anaerobic tank and undergoes a complete anaerobic / anoxic / aerobic reaction, that is, 1.0 times of influent undergoes a complete biological denitrification and phosphorus removal process, which can achieve a higher denitrification and phosphorus removal effect. In addition, 0.3-1.4Q of influent is purified through the aerobic tank and the facultative anoxic tank: the influent entering from the aerobic tank mainly removes ammonia nitrogen and organic matter through nitrification and oxidation in the aerobic tank; the influent entering from the facultative anoxic tank has a residence time of 30-60min in the facultative anoxic tank, and mainly removes organic matter and phosphorus in the water through biological adsorption. Moreover, since the microorganisms outside the activated sludge and the outside of the biofilm in the facultative anoxic tank are in an aerobic state, the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the facultative anoxic tank can undergo both nitrification and synchronous denitrification, further removing ammonia nitrogen and total nitrogen.

[0087] In the rainy day operation mode, due to the low dissolved oxygen in the facultative oxygen tank, the activated sludge adsorbs a higher concentration of carbon source, resulting in a higher carbon source in the return sludge, excess sludge and sludge returned with the nitrification solution. Therefore, the carbon source returned with the nitrification solution can improve the denitrification efficiency of the anoxic tank; the return sludge contains a higher carbon source, and the return sludge can continue to fully denitrify in the pre-anoxic tank, thereby reducing the nitrate concentration in the pre-anoxic tank and creating a good anaerobic environment for the phosphorus release reaction of polyphosphate bacteria in the anaerobic tank; the carbon source adsorbed by the excess sludge will undergo an anaerobic hydrolysis reaction in the sludge thickening tank, so that the supernatant contains a higher carbon source. The return of the supernatant to the anoxic tank is equivalent to supplementing the carbon source for the denitrification reaction in the anoxic tank, thereby improving the denitrification efficiency.

[0088] The present invention can also ensure the removal efficiency of ammonia nitrogen and TN in the biochemical pool by adjusting the water volume ratio and dissolved oxygen concentration of the aerobic second pool and the anoxic pool. The details are as follows:

[0089] According to the equation relationship of "ammonia nitrogen + nitrate nitrogen ≈ total nitrogen" in the sewage treatment system, the concentration control standards of ammonia nitrogen and nitrate nitrogen in the effluent of the biochemical pool are set as a value and b value respectively:

[0090] If the effluent ammonia nitrogen concentration of the biochemical pool is higher than the set value a, and the total nitrogen is lower than the value b, it means that the nitrification reaction is insufficient. Adjust the water inlet valve 3 of the aerobic pool 2 to increase the water inlet volume q1 of the aerobic pool 2; adjust the water inlet valve 4 of the facultative aerobic pool to reduce the water inlet volume q2 of the facultative aerobic pool. At the same time, increase the air supply of the blower 9 of the facultative aerobic pool to increase the dissolved oxygen concentration of the facultative aerobic pool to 0.8-1.0 mg / L to strengthen the nitrification reaction of the system and thereby reduce the effluent ammonia nitrogen concentration.

[0091] If the ammonia nitrogen in the effluent of the biochemical pool is lower than the value a, but the total nitrogen is higher than the value b, it means that the system is insufficient in denitrification. In this case, the air supply of the blower 9 of the anaerobic pool should be reduced to reduce the dissolved oxygen concentration in the anaerobic pool to below 0.5 mg / L, so that the anaerobic pool is transformed into an anaerobic pool to promote denitrification and denitrification. At the same time, the flow rate of the nitrification liquid return pump 7 should be increased to 3-4Q to increase the nitrification liquid return ratio and further strengthen the denitrification of the anoxic pool. The above measures can enhance the denitrification and denitrification function of the system, and thus ensure that the effluent TN meets the standard.

[0092] If the effluent ammonia nitrogen is higher than value a and the nitrate nitrogen is also higher than value b, it means that the system's nitrification and denitrification capabilities are insufficient. In this case, the aerobic tank inlet valve 3 and the anaerobic tank inlet valve 4 should be adjusted to reduce the aerobic tank inlet volume q1 and the anaerobic tank inlet volume q2 to ensure that the ammonia nitrogen and total nitrogen in the biochemical pool meet the standards.

[0093] Embodiment 1:

[0094] A simulation experiment was conducted using the water quality of a sewage treatment plant in Hunan Province. The design flow rate on dry days was Q = 10m 3 / h, when the water flow is 1.0Q, it operates in dry weather mode.

[0095] Open the pre-anoxic tank inlet valve 1, and 0.3Q of sewage enters the pre-anoxic tank; adjust the return sludge pump 5, and 0.5Q of sludge flows back to the pre-anoxic tank; the sewage and the return sludge are mixed in the pre-anoxic tank, and the carbon source in the sewage and the nitrate in the return sludge are used to complete the denitrification reaction, providing a nitrate-free anaerobic environment for the anaerobic tank.

[0096] Adjust the anaerobic tank inlet valve 2, and 0.6Q sewage will enter the anaerobic tank. The polyphosphate bacteria in the anaerobic tank will use the carbon source in the sewage to fully release phosphorus and absorb organic carbon source.

[0097] Close the water inlet valve 4 of the aerobic pool 2, and stop the aerobic pool 2 from entering. Adjust the air supply of the aerobic pool blower 8 to control the dissolved oxygen in the aerobic pool 1 and the aerobic pool 2 at 1.5-2 mg / L.

[0098] Adjust the water inlet valve 5 of the aerobic tank, 0.1Q of sewage enters the aerobic tank, and adjust the air supply of the aerobic tank blower 9 to control the dissolved oxygen in the aerobic tank at 0.2-1.0 mg / L. At this time, the microorganisms outside the activated sludge and the biofilm of the suspended filler are in an aerobic state, while the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that both nitrification and synchronous denitrification can occur in the aerobic tank.

[0099] Adjust the flow rate of the nitrification liquid reflux pump 7, and the nitrification liquid reflux rate of the aeration tank is 1.0Q.

[0100] The remaining sludge is sent to the sludge thickening tank through the remaining sludge pump 6, and the sludge undergoes anaerobic hydrolysis reaction in the sludge thickening tank to release the carbon source into the supernatant. The flow rate of the supernatant return pump 22 is adjusted so that the flow rate of the supernatant returning to the anoxic tank is controlled at 0.03Q, which serves as the denitrification carbon source in the anoxic tank.

[0101] Through the above process, the pollutant removal effect is as follows:

[0102] index COD BOD TN <![CDATA[NH3-N]]> TP Influent (mg / L) 300 150 35 30 3 Outlet water (mg / L 21.39 3.21 13.65 1.44 0.22 Removal rate 92.87％ 97.86％ 61.00％ 95.20％ 92.67％

[0103] All indicators are better than Class A standards.

[0104] Embodiment 2:

[0105] A simulation experiment was conducted using the water quality of a sewage treatment plant in Hunan Province. The design flow rate on dry days was Q = 10m 3 / h, when the water flow is 1.3Q, it operates in drought mode.

[0106] Open the pre-anoxic tank inlet valve 1, and 0.3Q of sewage enters the pre-anoxic tank; adjust the return sludge pump 5, and 0.5Q of sludge flows back to the pre-anoxic tank; the sewage and the return sludge are mixed in the pre-anoxic tank, and the carbon source in the sewage and the nitrate in the return sludge are used to complete the denitrification reaction, providing a nitrate-free anaerobic environment for the anaerobic tank.

[0107] Adjust the anaerobic tank inlet valve 2, and 0.9Q sewage will enter the anaerobic tank. The polyphosphate bacteria in the anaerobic tank will use the carbon source in the sewage to fully release phosphorus and absorb organic carbon source.

[0108] Close the water inlet valve 3 of the aerobic pool 2, and stop the aerobic pool 2 from entering. Adjust the air supply of the aerobic pool blower 8 to control the dissolved oxygen in the aerobic pool 1 and the aerobic pool 2 at 1.5-2 mg / L.

[0109] Adjust the water inlet valve 4 of the aerobic tank, 0.1Q of sewage enters the aerobic tank, and adjust the air supply of the aerobic tank blower 9 to control the dissolved oxygen in the aerobic tank at 0.2-1.0 mg / L. At this time, the microorganisms outside the activated sludge and the biofilm of the suspended filler are in an aerobic state, while the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the aerobic tank can undergo both nitrification and synchronous denitrification.

[0110] Adjust the flow rate of the nitrification liquid reflux pump 7, and control the nitrification liquid reflux rate of the aeration tank at 1.0-2.0Q.

[0111] The remaining sludge is sent to the sludge thickening tank through the remaining sludge pump 6, and the sludge undergoes anaerobic hydrolysis reaction in the sludge thickening tank to release the carbon source into the supernatant. The flow rate of the supernatant return pump 22 is adjusted so that the flow rate of the supernatant returning to the anoxic tank is controlled at 0.04Q, which serves as the denitrification carbon source in the anoxic tank.

[0112] Through the above process, the pollutant removal effect is as follows:

[0113] index COD BOD TN <![CDATA[NH3-N]]> TP Influent (mg / L) 220 100 35 30 3 Outlet water (mg / L 16.18 2.65 7.24 4.92 0.8 Removal rate 92.65％ 97.35％ 79.31％ 83.60％ 73.33％

[0114] Except for TP, all other indicators are better than Level A standards.

[0115] Embodiment 3:

[0116] A simulation experiment was conducted using the water quality of a sewage treatment plant in Hunan Province. The design flow rate on dry days was Q = 10m 3 / h, when the water flow is 2Q, it operates in rainy day mode.

[0117] Close the pre-anoxic tank inlet valve 1 to stop the sewage from entering the pre-anoxic tank; adjust the anaerobic tank inlet valve 2 to allow 1.0Q sewage to enter the anaerobic tank through the anaerobic tank inlet valve 2.

[0118] Open the water inlet valve 3 of the aerobic tank 2 and the water inlet valve 4 of the anoxic tank 2. 0.5Q of sewage enters the aerobic tank 2 through the water inlet valve 3 of the aerobic tank 2, and 0.5Q of sewage enters the anoxic tank through the water inlet valve 4 of the anoxic tank.

[0119] Adjust the flow rate of the return sludge pump 5 to increase the return sludge volume to 1.0Q to increase the biochemical system microbial biomass. Increase the flow rate of the nitrification liquid return pump 7 to increase the nitrification liquid return volume to 2Q-3Q.

[0120] Increase the air supply of the aerobic tank blower 8 to increase the dissolved oxygen concentration in the aerobic tank 1 and the aerobic tank 2 to 2-3 mg / L, so that the microorganisms can increase the decomposition and nitrification reaction rates of organic matter in a high dissolved oxygen environment, reduce the ammonia nitrogen concentration of the mixed solution, and put the microorganisms in a hungry state, so that the activated sludge has better adsorption capacity in the anoxic tank.

[0121] The facultative aerobic tank is changed to continuous aeration, and the air supply of the facultative aerobic tank blower 9 is adjusted to reduce the dissolved oxygen concentration at the outlet of the biochemical tank to 0.2-1.0 mg / L, so that the facultative aerobic tank is in an facultative aerobic state; at this time, the microorganisms outside the activated sludge and the outside of the biofilm are in an aerobic state, and the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the facultative aerobic tank can undergo both nitrification and synchronous denitrification.

[0122] In the rainy day operation mode, 1.0Q of sewage enters from the anaerobic tank and undergoes a complete anaerobic / anoxic / aerobic reaction, that is, 1.0 times of sewage undergoes a relatively complete biological denitrification and phosphorus removal process, which can achieve a higher denitrification and phosphorus removal effect. In addition, 1.0Q of sewage is purified through the aerobic tank and the facultative anoxic tank: the sewage entering from the aerobic tank mainly removes ammonia nitrogen and organic matter through nitrification and oxidation in the aerobic tank; the retention time in the facultative anoxic tank is about 30 minutes, and the organic matter and phosphorus in the water are mainly removed through biological adsorption. Moreover, since the microorganisms outside the activated sludge and the outside of the biofilm in the facultative anoxic tank are in an aerobic state, the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the facultative anoxic tank can undergo both nitrification and synchronous denitrification, further removing ammonia nitrogen and total nitrogen.

[0123] Another advantage of the rainy day operation mode is that since the dissolved oxygen in the facultative oxygen tank is lower and the activated sludge adsorbs a higher concentration of carbon source, the denitrification efficiency of the anoxic tank can be improved; the return sludge contains a higher carbon source, and the return sludge can continue to undergo sufficient denitrification and nitrogen removal in the pre-anoxic tank, thereby reducing the nitrate concentration in the pre-anoxic tank and creating a good anaerobic environment for the phosphorus release reaction of polyphosphate bacteria in the anaerobic tank.

[0124] The remaining sludge is sent to the sludge thickening tank through the remaining sludge pump 6, and the sludge undergoes anaerobic hydrolysis reaction in the sludge thickening tank to release the carbon source into the supernatant. The flow rate of the supernatant return pump 22 is adjusted so that the flow rate of the supernatant returning to the anoxic tank is controlled at 0.06Q, which serves as the denitrification carbon source in the anoxic tank.

[0125] Through the above process, the pollutant removal effect is as follows:

[0126] index COD BOD TN <![CDATA[NH3-N]]> TP Influent (mg / L) 153 73 16.9 11.2 1.6 Outlet water (mg / L 20.02 4.11 7.89 0.97 0.82 Removal rate 86.92％ 94.37％ 53.31％ 91.34％ 48.75％

[0127] Except for TP, all other indicators are better than Level A standards.

[0128] Embodiment 4:

[0129] A simulation experiment was conducted using the water quality of a sewage treatment plant in Hunan Province. The design flow rate on dry days was Q = 10m 3 / h, when the water flow is 2.4Q, it operates in rainy day mode.

[0130] Close the pre-anoxic tank inlet valve 1 to stop the sewage from entering the pre-anoxic tank; adjust the anaerobic tank inlet valve 2 to allow 1.0Q sewage to enter the anaerobic tank through the anaerobic tank inlet valve 2.

[0131] Open the water inlet valve 3 of the aerobic tank 2 and the water inlet valve 4 of the anoxic tank 2. 0.5Q of sewage enters the aerobic tank 2 through the water inlet valve 3 of the aerobic tank 2, and 0.5Q of sewage enters the anoxic tank through the water inlet valve 4 of the anoxic tank.

[0132] Adjust the flow rate of the return sludge pump 5 to increase the return sludge volume to 1.0Q to increase the biochemical system microbial biomass. Increase the flow rate of the nitrification liquid return pump 7 to increase the nitrification liquid return volume to 2Q-3Q.

[0133] Increase the air supply of the aerobic tank blower 8 to increase the dissolved oxygen concentration in the aerobic tank 1 and the aerobic tank 2 to 2-3 mg / L, so that the microorganisms can increase the decomposition and nitrification reaction rates of organic matter in a high dissolved oxygen environment, reduce the ammonia nitrogen concentration of the mixed solution, and put the microorganisms in a hungry state, so that the activated sludge has better adsorption capacity in the anoxic tank.

[0134] The facultative aerobic tank is changed to continuous aeration, and the air supply of the facultative aerobic tank blower 9 is adjusted to reduce the dissolved oxygen concentration at the outlet of the biochemical tank to 0.2-1.0 mg / L, so that the facultative aerobic tank is in an facultative aerobic state; at this time, the microorganisms outside the activated sludge and the outside of the biofilm are in an aerobic state, and the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the facultative aerobic tank can undergo both nitrification and synchronous denitrification.

[0135] In the rainy day operation mode, 1.0Q of sewage enters from the anaerobic tank and undergoes a complete anaerobic / anoxic / aerobic reaction, that is, 1.0 times of sewage undergoes a relatively complete biological denitrification and phosphorus removal process, which can achieve a higher denitrification and phosphorus removal effect. In addition, 1.0Q of sewage is purified through the aerobic tank and the facultative anoxic tank: the sewage entering from the aerobic tank mainly removes ammonia nitrogen and organic matter through nitrification and oxidation in the aerobic tank; the retention time in the facultative anoxic tank is about 30 minutes, and the organic matter and phosphorus in the water are mainly removed through biological adsorption. Moreover, since the microorganisms outside the activated sludge and the outside of the biofilm in the facultative anoxic tank are in an aerobic state, the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the facultative anoxic tank can undergo both nitrification and synchronous denitrification, further removing ammonia nitrogen and total nitrogen.

[0136] Another advantage of the rainy day operation mode is that since the dissolved oxygen in the facultative oxygen tank is lower and the activated sludge adsorbs a higher concentration of carbon source, the denitrification efficiency of the anoxic tank can be improved; the return sludge contains a higher carbon source, and the return sludge can continue to undergo sufficient denitrification and nitrogen removal in the pre-anoxic tank, thereby reducing the nitrate concentration in the pre-anoxic tank and creating a good anaerobic environment for the phosphorus release reaction of polyphosphate bacteria in the anaerobic tank.

[0137] The remaining sludge is sent to the sludge thickening tank through the remaining sludge pump 6, and the sludge undergoes anaerobic hydrolysis reaction in the sludge thickening tank to release the carbon source into the supernatant. The flow rate of the supernatant return pump 22 is adjusted so that the flow rate of the supernatant returning to the anoxic tank is controlled at 0.08Q, which serves as the denitrification carbon source in the anoxic tank.

[0138] Through the above process, the pollutant removal effect is as follows:

[0139] index COD BOD <![CDATA[NH3-N]]> TN TP Influent (mg / L) 106 45.3 14.1 16.6 1.3 Outlet water (mg / L 14.95 3.57 1.09 9.32 0.75 Removal rate 85.90％ 92.12％ 92.27％ 43.86％ 42.31％

[0140] Except for TP, all other indicators are better than Level A standards.

[0141] Embodiment 5:

[0142] The difference between this embodiment and embodiment 3 is that the aerobic tank is no longer equipped with suspended biological fillers, and other conditions are the same. A simulation experiment was conducted using the water quality of a sewage treatment plant in Hunan Province. The design flow rate on a dry day is Q = 10m 3 / h, when the water flow is 2.0Q, it operates in rainy day mode.

[0143] Close the pre-anoxic tank inlet valve 1 to stop the sewage from entering the pre-anoxic tank; adjust the anaerobic tank inlet valve 2 to allow 1.0Q sewage to enter the anaerobic tank through the anaerobic tank inlet valve 2.

[0144] Open the water inlet valve 3 of the aerobic tank 2 and the water inlet valve 4 of the anoxic tank 2. 0.5Q of sewage enters the aerobic tank 2 through the water inlet valve 3 of the aerobic tank 2, and 0.5Q of sewage enters the anoxic tank through the water inlet valve 4 of the anoxic tank.

[0145] Adjust the flow rate of the return sludge pump 5 to increase the return sludge volume to 1.0Q to increase the biochemical system microbial biomass. Increase the flow rate of the nitrification liquid return pump 7 to increase the nitrification liquid return volume to 2Q-3Q.

[0146] Increase the air supply of the aerobic tank blower 8 to increase the dissolved oxygen concentration in the aerobic tank 1 and the aerobic tank 2 to 2-3 mg / L, so that the microorganisms can increase the decomposition and nitrification reaction rates of organic matter in a high dissolved oxygen environment, reduce the ammonia nitrogen concentration of the mixed solution, and put the microorganisms in a hungry state, so that the activated sludge has better adsorption capacity in the anoxic tank.

[0147] The facultative aerobic tank is changed to continuous aeration, and the air supply of the facultative aerobic tank blower 9 is adjusted to reduce the dissolved oxygen concentration at the outlet of the biochemical tank to 0.2-1.0 mg / L, so that the facultative aerobic tank is in an facultative aerobic state; at this time, the microorganisms outside the activated sludge and the outside of the biofilm are in an aerobic state, and the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the facultative aerobic tank can undergo both nitrification and synchronous denitrification.

[0148] In the rainy day operation mode, 1.0Q of sewage enters from the anaerobic tank and undergoes a complete anaerobic / anoxic / aerobic reaction, that is, 1.0 times of sewage undergoes a relatively complete biological denitrification and phosphorus removal process, which can achieve a higher denitrification and phosphorus removal effect. In addition, 1.0Q of sewage is purified through the aerobic tank and the facultative anoxic tank: the sewage entering from the aerobic tank mainly removes ammonia nitrogen and organic matter through nitrification and oxidation in the aerobic tank; the retention time in the facultative anoxic tank is about 30 minutes, and the organic matter and phosphorus in the water are mainly removed through biological adsorption. Moreover, since the microorganisms outside the activated sludge and the outside of the biofilm in the facultative anoxic tank are in an aerobic state, the microorganisms inside are in an anoxic state with insufficient oxygen supply, so that the facultative anoxic tank can undergo both nitrification and synchronous denitrification, further removing ammonia nitrogen and total nitrogen.

[0149] Another advantage of the rainy day operation mode is that since the dissolved oxygen in the facultative oxygen tank is lower and the activated sludge adsorbs a higher concentration of carbon source, the denitrification efficiency of the anoxic tank can be improved; the return sludge contains a higher carbon source, and the return sludge can continue to undergo sufficient denitrification and nitrogen removal in the pre-anoxic tank, thereby reducing the nitrate concentration in the pre-anoxic tank and creating a good anaerobic environment for the phosphorus release reaction of polyphosphate bacteria in the anaerobic tank.

[0150] The remaining sludge is sent to the sludge thickening tank through the remaining sludge pump 6. The sludge undergoes anaerobic hydrolysis in the sludge thickening tank to release carbon source into the supernatant. The flow rate of the supernatant return pump 22 is adjusted so that the flow rate of the supernatant returning to the anoxic tank is controlled at 0.06Q to serve as the denitrification carbon source in the anoxic tank.

[0151] Through the above process, the pollutant removal effect is as follows:

[0152] index COD BOD <![CDATA[NH3-N]]> TN TP Influent (mg / L) 108.5 45.8 15.5 18.8 1.5 Outlet water (mg / L 14.92 3.4 0.9 10.97 0.95 Removal rate 86.25％ 92.58％ 94.19％ 41.65％ 36.67％

[0153] Except for TP, all other indicators are better than Level A standards.

[0154] The results of Examples 1-5 of the present invention show that the AAAOF sewage treatment system of the present invention can significantly improve the rainy day production capacity of the sewage treatment plant, and the effluent water quality is good, and can effectively remove pollutants such as COD, BOD, NH3-N, TN and TP in the sewage.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An AAAOF sewage treatment process, characterized in that: It includes utilizing a pre-anoxic / anaerobic / anoxic / aerobic / facultative anaerobic sewage treatment system to perform sewage treatment in a dry day operation mode or a rainy day operation mode; The pre-anoxic / anaerobic / anoxic / aerobic / facultative anaerobic sewage treatment system comprises a biochemical tank, a secondary sedimentation tank, a sludge concentration tank and an aeration system; the biochemical tank is composed of a pre-anoxic tank, an anaerobic tank, an anoxic tank, an aerobic tank 1, an aerobic tank 2 and a facultative anaerobic tank connected in sequence; the aeration system comprises an aerobic tank blower (8) and a facultative anaerobic tank blower (9), the aerobic tank blower (8) is connected to the aerobic tank 1 and the aerobic tank 2 respectively; the facultative anaerobic tank blower (9) is connected to the aerobic tank 1 and the aerobic tank 2 respectively; the facultative anaerobic tank blower (9) is connected to the The water inlet pipeline is connected to the pre-anoxic pool, the anaerobic pool, the second aerobic pool and the facultative anoxic pool respectively; the water inlet pipeline connected to the pre-anoxic pool is also provided with a pre-anoxic pool water inlet valve (1); the water inlet pipeline connected to the anaerobic pool is also provided with an anaerobic pool water inlet valve (2); the water inlet pipeline connected to the second aerobic pool is also provided with an aerobic pool water inlet valve (3); the water inlet pipeline connected to the facultative anoxic pool is also provided with a facultative anoxic pool water inlet valve (4); The terminal mixed liquid of the anoxic tank is returned to the anoxic tank through the nitrification liquid return pump (7); the effluent of the biochemical tank is connected to the secondary sedimentation tank, and after the sludge is separated from the water in the secondary sedimentation tank, a part of the sludge is returned to the pre-anoxic tank through the return sludge pump (5), and the other part of the sludge enters the sludge concentration tank, and the supernatant obtained by the treatment in the sludge concentration tank is returned to the anoxic tank through the supernatant return pump (22); Wherein, when the pre-anoxic / anaerobic / anoxic / aerobic / facultative anaerobic sewage treatment system is used for sewage treatment, the design water inflow flow rate on a dry day is assumed to be Q: When the water flow in the water inlet pipe is ≤1.3Q, the sewage treatment system operates in the dry weather operation mode, including: Open the water inlet valve (1) of the pre-anoxic tank to allow 0.2-0.3Q of water to enter the pre-anoxic tank; adjust the return sludge pump (5) to allow 0.4-0.5Q of sludge to flow back to the pre-anoxic tank; Adjust the anaerobic tank water inlet valve (2) to allow 0.6-0.9Q of water to enter the anaerobic tank; The water inlet valve (3) of the aerobic tank 2 is closed, and the air supply of the aerobic tank blower (8) is adjusted to control the dissolved oxygen in the aerobic tank 1 and the aerobic tank 2 to be 1.5-2 mg / L; Adjust the water inlet valve (4) of the oxygen pool to allow 0.1-0.2Q of water to enter the oxygen pool, and adjust the air supply of the oxygen pool blower (9) to control the dissolved oxygen in the oxygen pool to 0.2-1.0 mg / L; Adjusting the flow rate of the nitrification liquid reflux pump (7) so that the reflux rate of the nitrification liquid in the aerobic tank is controlled at 1.0-2.0Q; Adjusting the flow rate of the supernatant liquid return pump (22) so that the return rate of the supernatant liquid in the sludge thickening tank is controlled at 0.03-0.04Q; When the water flow in the water inlet pipe is greater than 1.3Q and less than or equal to 2.4Q, the sewage treatment system operates in the rainy day operation mode, including: The pre-anoxic tank water inlet valve (1) is closed, and the anaerobic tank water inlet valve (2) is adjusted to allow 1.0-1.1Q of influent to enter the anaerobic tank through the anaerobic tank water inlet valve (2); Open the water inlet valve (3) of the second aerobic pool and the water inlet valve (4) of the facultative anoxic pool, the water inlet amount of the second aerobic pool is 0-0.7Q, and the water inlet amount of the facultative anoxic pool is 0-0.7Q; The flow rate of the return sludge pump (5) is adjusted to increase the return sludge volume to 1.0-1.1Q; the flow rate of the nitrification liquid return pump (7) is adjusted to increase the nitrification liquid return volume to 2Q-3Q; Increasing the air supply of the aerobic pool blower (8) to increase the dissolved oxygen concentration in the aerobic pool 1 and the aerobic pool 2 to 2-3 mg / L; The aeration tank is continuously aerated, and the air supply of the aeration tank blower (9) is adjusted to control the dissolved oxygen concentration at the outlet of the biochemical tank to be 0.2-1.0 mg / L; The flow rate of the supernatant liquid return pump (22) is adjusted so that the return rate of the supernatant liquid in the sludge thickening tank is controlled at 0.06-0.08Q.

2. The AAAOF sewage treatment process according to claim 1, characterized in that: The first aerobic pool and the second aerobic pool are provided with an aeration device, and the facultative aerobic pool is provided with an aeration device.

3. The AAAOF sewage treatment process according to claim 1, characterized in that: The water inlet pipeline is provided with a water inlet main valve (10) and a water inlet main flow meter (11).

4. The AAAOF sewage treatment process according to claim 3, characterized in that: A water inlet flowmeter (21) for the pre-anoxic tank is also provided on the water inlet pipeline connected to the pre-anoxic tank; An anaerobic tank water inlet flowmeter (12) is also provided on the water inlet pipeline connected to the anaerobic tank; A water inlet flowmeter (13) for the aerobic second tank is also provided on the water inlet pipeline connected to the aerobic second tank; A water inlet flowmeter (14) for the anoxic pool is also provided on the water inlet pipeline connected to the anoxic pool.

5. The AAAOF sewage treatment process according to claim 1, characterized in that: The secondary sedimentation tank is connected to the pre-anoxic tank via a sludge return pipeline, and the sludge return pipeline is provided with the return sludge pump (5) and the return sludge flowmeter (15). A residual sludge pump (6) is provided on the pipeline connecting the secondary sedimentation tank and the sludge thickening tank; the supernatant of the sludge thickening tank is returned to the anoxic tank via a supernatant return pump (22).

6. The AAAOF wastewater treatment process according to claim 1, characterized in that: A suspended filler is arranged in the anoxic pool.

7. The AAAOF sewage treatment process according to claim 1, characterized in that: The aerobic tank 1 is provided with an online sludge concentration detector (20), the aerobic tank 2 is provided with an online dissolved oxygen meter (16), the anoxic tank is provided with an online dissolved oxygen meter (17), and the biochemical tank outlet is provided with an online ammonia nitrogen detector (18) and an online total nitrogen detector (19).

8. The AAAOF sewage treatment process according to claim 1, characterized in that: In the dry weather operation mode, the hydraulic retention time of each treatment tank is: 1-2 hours for the pre-anoxic tank, 2-3 hours for the anaerobic tank, 2-3 hours for the anoxic tank, 4-5 hours for the aerobic tank 1, 2-3 hours for the aerobic tank 2, and 1-2 hours for the facultative aerobic tank; In the rainy day operation mode, the hydraulic retention time of each treatment pool is: 1-2 hours for the anaerobic pool, 2-3 hours for the anoxic pool, 4-5 hours for the aerobic pool 1, 1-1.5 hours for the aerobic pool 2, and 0.5-1 hour for the facultative aerobic pool.

9. The AAAOF wastewater treatment process according to claim 1, characterized in that: An online ammonia nitrogen detector (18) and an online total nitrogen detector (19) are provided at the water outlet of the biochemical pool; by monitoring the ammonia nitrogen concentration of the biochemical pool outlet water detected by the online ammonia nitrogen detector (18) and the total nitrogen concentration of the biochemical pool detected by the online total nitrogen detector (19), the water inlet valve (3) of the aerobic second pool and the water inlet valve (4) of the facultative aerobic pool are adjusted in real time to control the water inflow of the aerobic second pool and the facultative aerobic pool, specifically comprising: Set the ammonia nitrogen concentration of the biochemical pool effluent to a and the total nitrogen concentration to b; When the ammonia nitrogen concentration of the biochemical pool effluent detected by the online ammonia nitrogen detector (18) is higher than a, and the total nitrogen concentration of the biochemical pool detected by the online total nitrogen detector (19) is lower than b, the water inlet valve (3) of the aerobic second pool is adjusted to increase the water inlet volume of the aerobic second pool; the water inlet valve (4) of the facultative aerobic pool is adjusted to reduce the water inlet volume of the facultative aerobic pool, and at the same time, the air supply of the facultative aerobic pool blower (9) is increased to increase the dissolved oxygen concentration of the facultative aerobic pool to 0.8-1.0 mg / L; When the ammonia nitrogen concentration of the biochemical pool effluent detected by the online ammonia nitrogen detector (18) is lower than a, and the total nitrogen concentration of the biochemical pool detected by the online total nitrogen detector (19) is higher than b, the air supply of the aerobic pool blower (9) is reduced to reduce the dissolved oxygen concentration of the aerobic pool to below 0.5 mg / L; at the same time, the flow rate of the nitrification liquid reflux pump (7) is increased to 3-4Q; When the ammonia nitrogen concentration of the biochemical pool effluent detected by the online ammonia nitrogen detector (18) is higher than a, and the total nitrogen concentration of the biochemical pool detected by the online total nitrogen detector (19) is higher than b, the aerobic second pool water inlet valve (3) and the facultative anoxic pool water inlet valve (4) are adjusted to reduce the water inlet volume of the aerobic second pool and the water inlet volume of the facultative anoxic pool.

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