Deformable improved AO system suitable for high-hardness and low-COD degradation-resistant sewage and operation method of deformable improved AO system

Abstract

A deformable improved AO system suitable for degradation-resistant sewage with high hardness and low COD comprises a biological tank, a secondary sedimentation tank and a backflow and excess sludge pump room, the biological tank comprises an anoxic tank and an aerobic tank, the anoxic tank comprises a first anoxic tank and a second anoxic tank which are sequentially connected, and the aerobic tank comprises a second anoxic tank and a third anoxic tank which are sequentially connected. The aerobic tank comprises a first aerobic tank, a second aerobic tank, a third aerobic tank and a rear aerobic tank which are sequentially connected, the second anoxic tank is sequentially connected with the first aerobic tank, the rear aerobic tank is sequentially connected with the secondary sedimentation tank, and the secondary sedimentation tank is sequentially connected with the reflux and excess sludge pump room. The oxygen elimination tank is sequentially connected with the first anoxic tank, and the reflux system is a sludge reflux system arranged between the reflux and excess sludge pump room and the first oxygen elimination tank. The system is suitable for treatment of high-hardness and low-COD degradation-resistant sewage, and has the advantages of good nitrogen and phosphorus removal effect, strong dissolved oxygen change adaptability, excellent effluent quality, high carbon source utilization efficiency, energy conservation and consumption reduction.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to a deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage and an operation method thereof. Background Art

[0002] The composition of municipal sewage in the current sewage treatment field is becoming increasingly complex, and mixed water of domestic sewage and industrial wastewater is very common. Domestic sewage contains a certain amount of organic matter and nutrients, and industrial wastewater may contain high concentrations of difficult-to-degrade organic matter, heavy metals, high salinity and other pollutants due to its different production processes and raw materials. After these two types of sewage are mixed, they may have high hardness, low COD and difficult-to-degrade characteristics. Effective technical measures must still be taken to ensure that the water quality meets the discharge standards, which brings new challenges to sewage treatment.

[0003] On the one hand, this type of sewage usually contains high concentrations of metal ions such as calcium and magnesium. Although a hardness removal sedimentation tank is often set up in the pretreatment stage, the hardness of the effluent is still often high. These ions react with organic matter in the water to form precipitation, which is prone to blockage and hardening of the biological pool filler, affecting the normal operation of the system. Therefore, whether or not the pre-oxidation treatment outside the plant is carried out, it is often necessary to choose to carry out pre-ozone treatment in the plant according to the water quality. This leads to the downstream sewage being in a high dissolved oxygen state sometimes and a low dissolved oxygen state sometimes, depending on whether it has been pre-ozone treated, that is, the dissolved oxygen in the biological pool inlet water may vary greatly. At the same time, in the high dissolved oxygen state, the aerator is not selected reasonably, and the small and loose bacterial flocs are easily overexposed and die, which leads to poor denitrification effect. On the other hand, low COD difficult-to-degrade sewage is difficult to control in terms of treatment cost, microbial activity and treatment stability. The traditional AO process is difficult to solve the above problems well, which affects the stable compliance and energy saving of urban sewage treatment plants with high emission standards. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing AO process for high-hardness, low-COD difficult-to-degrade sewage, and provide a deformable improved AO system suitable for the treatment of high-hardness, low-COD difficult-to-degrade sewage. The system is suitable for the treatment of high-hardness, low-COD difficult-to-degrade sewage, and has the advantages of good nitrogen and phosphorus removal effects, strong adaptability to dissolved oxygen changes, excellent effluent water quality, high carbon source utilization efficiency, and energy saving and consumption reduction.

[0005] Another object of the present invention is to provide an operating method of the above-mentioned deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage.

[0006] As conceived above, the technical solution of the present invention is: a deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage, including a biological pool, a secondary sedimentation tank and a return and residual sludge pump room, the biological pool includes an anoxic pool and an aerobic pool, the anoxic pool includes a first anoxic pool and a second anoxic pool connected in sequence, the aerobic pool includes a first aerobic pool, a second aerobic pool, a third aerobic pool and a post-aerobic pool connected in sequence, the second anoxic pool is connected to the first aerobic pool, the post-aerobic pool is connected to the secondary sedimentation tank, the secondary sedimentation tank is connected to the return and residual sludge pump room, characterized in that: the system also includes an oxygen removal tank and a return system, the oxygen removal tank is connected to the first anoxic tank, and the return system is a sludge return system arranged between the return and residual sludge pump room and the first oxygen removal tank.

[0007] Preferably, the deoxidation tank comprises a first deoxidation tank and a second deoxidation tank which are connected in sequence, and the second deoxidation tank is connected in sequence to the first anoxic tank.

[0008] Preferably, the present system further comprises a deformable communication system, which comprises a deformable communication system arranged between the second oxygen elimination tank and the first anoxic tank, a deformable communication system arranged between the second oxygen elimination tank and the third aerobic tank, a deformable communication system arranged between the second anoxic tank and the first aerobic tank, a deformable communication system arranged between the second anoxic tank and the post-aerobic tank, a deformable communication system arranged between the first aerobic tank and the first anoxic tank, and a deformable communication system arranged between the third aerobic tank and the post-aerobic tank.

[0009] Preferably, a mixed liquor reflux system is provided between the post-aerobic tank and the first anoxic tank.

[0010] Preferably, the deformation communication system is in the form of a partition wall with a gate or a pipeline with a valve.

[0011] Preferably, the first deoxidation tank and the second deoxidation tank are connected in series in two compartments, and a stirrer is provided in each compartment.

[0012] Preferably, the aerators used in the first aerobic tank, the second aerobic tank and the third aerobic tank are medium-pore cyclone aerators.

[0013] Preferably, guide walls and propellers are provided in the first aerobic pool and the third aerobic pool, and the propellers are equipped with frequency converters.

[0014] The operating method of the deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage is characterized by comprising the following steps:

[0015] a) The pretreated sewage influent enters the first deoxidation tank together with the sludge returned from the return and excess sludge pump room, and then enters the second deoxidation tank downstream, where it stays for 0.5-1 hour under stirring conditions, undergoes biochemical reactions under the stirring of the agitator and the action of microorganisms, consumes the dissolved oxygen brought by the return sludge and the influent pretreated by the pre-ozonation process, and hydrolyzes the organic matter in the influent;

[0016] b) the mixed liquor of the oxygen elimination tank obtained in step a) enters the first anoxic tank together with the mixed liquor returned from the post-aerobic tank, and then enters the second anoxic tank downstream, stays for 4-6 hours under anoxic stirring conditions, and performs denitrification and denitrification reaction under the action of microorganisms;

[0017] c) the anoxic pool mixed liquid obtained in step b) enters the first aerobic pool, the second aerobic pool, the third aerobic pool, and the post-aerobic pool in sequence, stays under aerobic conditions for 7-8 hours, and undergoes nitrification reaction, aerobic phosphorus absorption reaction, and organic matter oxidation reaction under the action of microorganisms;

[0018] d) the mixed liquor from the aerobic tank obtained in step c) is refluxed to the first anoxic tank as the reflux mixed liquor, and the remaining part enters the secondary sedimentation tank for sedimentation, the effluent enters the subsequent treatment structure, and the sludge enters the reflux and excess sludge pump room;

[0019] e) In step d), part of the sludge discharged from the return and excess sludge pump room enters the first deoxidation tank as return sludge, and part of it is discharged to the sludge treatment system as excess sludge.

[0020] Preferably, the return amount of the returned sludge in step a) is 0.5-1 times the inlet flow rate, the return amount of the mixed liquor returned to the post-oxidation tank in step b) is 2-3 times the inlet flow rate, and the DO concentration of the first aerobic tank, the second aerobic tank, the third aerobic tank and the post-aerobic tank in step c) is controlled at 1-3 mg / L.

[0021] The operating method of the deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage is characterized by comprising the following steps:

[0022] a) The sewage influent that has been pretreated including the pre-ozonation process enters the first deoxidation tank together with the sludge returned from the return and excess sludge pump room, and then enters the second deoxidation tank downstream, where it stays for 0.5-1 hour under stirring conditions, undergoes biochemical reactions under the stirring of the stirrer and the action of microorganisms, consumes the dissolved oxygen brought by the returned sludge and the influent that has been pretreated with the pre-ozonation process, and hydrolyzes the organic matter in the influent;

[0023] b) the mixed liquor of the deoxidation tank obtained in step a) enters the third aerobic tank through the deformed communication system between the second deoxidation tank and the third aerobic tank, and then enters the second aerobic tank and the first aerobic tank in sequence, stays for 6.5-7.2 hours under aerobic conditions, and performs nitrification reaction, aerobic phosphorus absorption reaction and organic matter oxidation reaction under the action of microorganisms;

[0024] c) the mixed liquor of the aerobic pool obtained in step b) finally enters the first anoxic pool and the second anoxic pool in sequence from the first aerobic pool through the deformed communication system between the first aerobic pool and the first anoxic pool, stays for 4-6 hours under anoxic stirring conditions, and performs denitrification reaction and denitrification phosphorus removal reaction under the action of microorganisms;

[0025] d) the anoxic pool mixed liquid obtained in step c) finally enters the post-aerobic pool from the second anoxic pool through the deformed communication system between the second anoxic pool and the post-aerobic pool, stays under aerobic conditions for 0.5-0.8 hours, and undergoes nitrification reaction, aerobic phosphorus absorption reaction and organic matter oxidation reaction under the action of microorganisms;

[0026] e) the mixed liquor from the aerobic tank obtained in step d) enters the secondary sedimentation tank for precipitation, the effluent enters the subsequent treatment structure, and the sludge enters the return flow and excess sludge pump room;

[0027] f) In step d), part of the sludge discharged from the return and excess sludge pump room enters the first deoxidation tank as return sludge, and part of it is discharged to the sludge treatment system as excess sludge.

[0028] Preferably, the return flow rate of the return sludge in step a) is 0.5-1 times the inlet flow rate, the DO concentrations of the first aerobic tank, the second aerobic tank and the third aerobic tank in step b) are controlled at 1-3 mg / L, and the DO concentration of the post aerobic tank in step d) is controlled at 1-3 mg / L.

[0029] The present invention has the following advantages and positive effects:

[0030] 1. The present invention organically integrates the deoxidation tank with the existing AO process system, and sets a deformation communication system between parts of the tank body to form an improved AO process, which is suitable for the treatment of high-hardness, low-COD difficult-to-degrade sewage.

[0031] 2. The present invention can flexibly transform the process according to the change of influent water quality, and can flexibly switch through the deformation connection system between specific tank bodies to form two process deformations, which are respectively specifically aimed at whether to carry out oxidation pre-treatment outside the factory and whether to operate the pre-ozone tank in the pretreatment stage inside the factory, so as to flexibly handle different working conditions such as excessively high or low dissolved oxygen in sewage.

[0032] 3. The present invention can maintain low oxygen transfer efficiency and avoid overexposure when generating stirring effect by matching reasonable mesoporous cyclone aerator and aerobic pool propeller selection, thereby ensuring the activity of bacterial flocs and the denitrification capacity of the pool body and realizing reliable treatment of sewage.

[0033] 4. The present invention has the advantages of good nitrogen and phosphorus removal effect, strong adaptability to dissolved oxygen changes, excellent effluent quality, high carbon source utilization efficiency, energy saving and consumption reduction

[0034] 5. The present invention is highly targeted and operable, and can solve the shortcomings of the existing AO process system in treating specific domestic industrial mixed municipal sewage with high hardness and low COD. It can provide new ideas for the engineering design and operation management of urban sewage treatment plants with high emission standards in my country, and has important practical significance for the stable compliance with standards and energy conservation and consumption reduction of sewage treatment plants with high emission standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a process flow chart of the present invention;

[0036] Figure 2 is a general plan view of the present invention;

[0037] Figure 3 is a plan view of the biological pond of the present invention;

[0038] Figure 4 This is a schematic diagram of the operation principle of the present invention when the pre-ozone tank is not in operation during pre-treatment in a sewage plant;

[0039] Figure 5 This is an operation process flow chart of the present invention when the pre-ozone tank is not operated in the sewage treatment plant pretreatment;

[0040] Figure 6 This is a schematic diagram of the operation principle of the present invention when the pre-ozone tank is operated in the pre-treatment of a sewage plant;

[0041] Figure 7 It is an operation process flow chart of the present invention when a pre-ozone tank is operated in a sewage plant for pretreatment. DETAILED DESCRIPTION

[0042] Referring to the accompanying drawings, the present invention provides a deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage, including a biological pool, a secondary sedimentation tank, and a return and excess sludge pump house. The biological pool includes a first oxygen elimination tank, a second oxygen elimination tank, a first anoxic tank, a second anoxic tank, a first aerobic tank, a second aerobic tank, a third aerobic tank and a post-aerobic tank, wherein: the first oxygen elimination tank is connected to the second oxygen elimination tank, the second oxygen elimination tank is connected to the first anoxic tank, the first anoxic tank is connected to the second anoxic tank, the second anoxic tank is connected to the first aerobic tank, the first aerobic tank is connected to the second aerobic tank, the second aerobic tank is connected to the third aerobic tank, the third aerobic tank is connected to the post-aerobic tank, the post-aerobic tank is connected to the secondary sedimentation tank, and the secondary sedimentation tank is connected to the return and excess sludge pump house.

[0043] The system also includes a reflux and deformation connection system, which are respectively a sludge reflux system ① arranged between the reflux and excess sludge pump room (1) and the first aerobic tank, a deformation connection system ② arranged between the second aerobic tank and the first anoxic tank, a deformation connection system ③ arranged between the second aerobic tank and the third aerobic tank, a deformation connection system ④ arranged between the second anoxic tank and the first aerobic tank, a deformation connection system ⑤ arranged between the second anoxic tank and the post-aerobic tank, a deformation connection system ⑥ arranged between the first aerobic tank and the first anoxic tank, a deformation connection system ⑦ arranged between the third aerobic tank and the post-aerobic tank, and a mixed liquor reflux system ⑧ arranged between the post-aerobic tank and the first anoxic tank.

[0044] Preferably, the second oxygen elimination tank is connected to the third aerobic tank, the first anoxic tank is connected to the first aerobic tank, and the second anoxic tank is connected to the third aerobic tank.

[0045] Preferably, the deformation communication system is in the form of a partition wall with a gate or a pipeline with a valve.

[0046] Preferably, the first deoxidation tank and the second deoxidation tank are connected in series in two compartments, and a stirrer is provided in each compartment.

[0047] Preferably, the aerators used in the first aerobic tank, the second aerobic tank and the third aerobic tank are medium-pore cyclone aerators.

[0048] Preferably, guide walls and propellers are provided in the first aerobic tank and the third aerobic tank. The propellers are equipped with frequency converters and can be transformed into MBBR process sections by adding suspended fillers.

[0049] The present invention discloses a method for a deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage, which can be deformed and switched between two process routes.

[0050] 1. If the pre-ozone tank is not used in the sewage treatment plant, and the dissolved oxygen in the sewage is low, the following process route is adopted:

[0051] a) The pre-treated sewage influent a, together with the sludge e returned from the return and excess sludge pump room, enters the first deoxidation tank and then flows downstream into the second deoxidation tank, where it stays for 0.5-1 hour under stirring conditions. Under the stirring of the agitator and the action of microorganisms (MLSS is 2-3g / L), a biochemical reaction is carried out to consume the dissolved oxygen brought by the returned sludge e and the influent a that may contain pre-ozone process pretreatment, and to hydrolyze the organic matter in the influent a to a certain extent; the return flow of the returned sludge e is 0.5-1 times the flow of the influent a;

[0052] b) the mixed liquor of the deoxidation tank obtained in step a) enters the first anoxic tank together with the mixed liquor d returned from the post-aerobic tank, and then flows downstream into the second anoxic tank, where it stays for 4-6 hours under anoxic stirring conditions, and undergoes denitrification and denitrification reaction under the action of microorganisms (MLSS is 2-3g / L); wherein the return amount of the mixed liquor d returned from the post-oxidation tank is 2-3 times the flow rate of the inlet water a;

[0053] c) the anoxic pool mixed solution obtained in step b) enters the first aerobic pool, the second aerobic pool, the third aerobic pool, and the post-aerobic pool in a downstream direction in sequence, stays for 7-8 hours under aerobic conditions, and performs nitrification reaction, aerobic phosphorus absorption reaction, and organic matter oxidation reaction under the action of microorganisms (MLSS is 2-3g / L), and at the same time, the DO concentrations of the first aerobic pool, the second aerobic pool, the third aerobic pool, and the post-aerobic pool are controlled at 1-3mg / L as much as possible;

[0054] d) the mixed liquor of the aerobic tank obtained in step c) is returned to the first anoxic tank ( as the return mixed liquor d, the remaining part enters the secondary sedimentation tank for precipitation, the effluent b enters the subsequent treatment structure, and the sludge c enters the return and excess sludge pump room;

[0055] e) In step d), part of the sludge c is discharged as return sludge e into the first deoxidation tank in the return and excess sludge pump room, and part of it is discharged as excess sludge f into the sludge treatment system.

[0056] In this process route, the opening and closing relationships of the reflux and deformation connection systems are as follows:

[0057]

[0058]

[0059] 2. If the sewage plant operates a pre-ozonation tank, and the dissolved oxygen content is still too high after passing through the biological tank and deoxygenation tank, resulting in poor denitrification effect in the anoxic tank, use the following method: Figure 6 Figure 7 Process route:

[0060] a) The sewage influent a, which has been pretreated including the pre-ozonation process, enters the first deoxidation tank together with the sludge e returned from the return and excess sludge pump room, and then flows downstream into the second deoxidation tank, where it stays for 0.5-1 hour under stirring conditions. Under the stirring of the agitator and the action of microorganisms (MLSS is 2-3g / L), a biochemical reaction is carried out to consume the dissolved oxygen brought by the returned sludge e and the influent a that may contain the pre-ozonation process, and the organic matter in the influent a is hydrolyzed to a certain extent; the return flow of the returned sludge e is 0.5-1 times the flow of the influent a;

[0061] b) the mixed liquor of the aerobic tank obtained in step a) enters the third aerobic tank through the deformed communication system between the second aerobic tank and the third aerobic tank, and then enters the second aerobic tank and the first aerobic tank in sequence, stays for 6.5-7.2 hours under aerobic conditions, and performs nitrification reaction, aerobic phosphorus absorption reaction and organic matter oxidation reaction under the action of microorganisms (MLSS is 2-3g / L), and at the same time, the DO concentrations of the first aerobic tank, the second aerobic tank and the third aerobic tank are controlled at 1-3mg / L as much as possible;

[0062] c) the mixed liquor of the aerobic pool obtained in step b) finally enters the first anoxic pool and the second anoxic pool in sequence from the first aerobic pool through the deformed communication system between the first aerobic pool and the first anoxic pool, stays for 4-6 hours under anoxic stirring conditions, and performs denitrification reaction and denitrification phosphorus removal reaction under the action of microorganisms (MLSS is 2-3g / L);

[0063] d) the mixed liquor in the anoxic tank obtained in step c) finally enters the post-aerobic tank from the second anoxic tank through the deformed communication system between the second anoxic tank and the post-aerobic tank, stays for 0.5-0.8 hours under aerobic conditions, and undergoes nitrification reaction, aerobic phosphorus absorption reaction and organic matter oxidation reaction under the action of microorganisms (MLSS is 2-3 g / L), and the DO concentration in the post-aerobic tank is controlled at 1-3 mg / L as much as possible;

[0064] e) the mixed liquor from the aerobic tank obtained in step d) enters the secondary sedimentation tank for precipitation, the effluent enters the subsequent treatment structure, and the sludge enters the return flow and excess sludge pump room;

[0065] f) In step d), part of the sludge c is discharged as return sludge e into the first deoxidation tank in the return and excess sludge pump room, and part of it is discharged as excess sludge f into the sludge treatment system.

[0066] In this process, the opening and closing relationships of the reflux and deformation connection systems are as follows:

[0067] Serial number Name of reflux and deformation connection system Open and closed state 1 Sludge return system between the return and excess sludge pump room (10) and the first deoxidation tank (1) Open 2 A deformable communication system between the second oxygen elimination tank (2) and the first anoxic tank (3) closure 3 A deformable communication system between the second oxygen elimination tank (2) and the third aerobic tank (7) Open 4 A deformable communication system between the second anoxic pool (4) and the first aerobic pool (5) closure 5 A deformable communication system between the second anoxic tank (4) and the post-aerobic tank (8) Open 6 A deformable communication system between the first aerobic tank (5) and the first anoxic tank (3) Open 7 Deformed communication system between the third aerobic tank (7) and the post-aerobic tank (8) closure 8 Mixed liquid reflux system between the post-aerobic tank (8) and the first anoxic tank (3) closure

[0068] 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 and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage, comprising a biological pool, a secondary sedimentation tank, and a return and excess sludge pump house, wherein the biological pool comprises an anoxic pool and an aerobic pool, wherein the anoxic pool comprises a first anoxic pool and a second anoxic pool connected in sequence, wherein the aerobic pool comprises a first aerobic pool, a second aerobic pool, a third aerobic pool, and a post-aerobic pool connected in sequence, wherein the second anoxic pool is connected in sequence to the first aerobic pool, wherein the post-aerobic pool is connected in sequence to the secondary sedimentation tank, wherein the secondary sedimentation tank is connected in sequence to the return and excess sludge pump house, wherein: The system also includes an oxygen removal tank and a reflow system. The oxygen removal tank is connected to the first anoxic tank in sequence. The reflow system is a sludge reflow system arranged between the reflow and excess sludge pump room and the first oxygen removal tank.

2. The deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1 is characterized by: The deoxidation tank comprises a first deoxidation tank and a second deoxidation tank connected in sequence, and the second deoxidation tank is connected in sequence to the first anoxic tank.

3. The deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1 is characterized by: The system also includes a deformable communication system, which includes a deformable communication system arranged between the second oxygen elimination tank and the first anoxic tank, a deformable communication system arranged between the second oxygen elimination tank and the third aerobic tank, a deformable communication system arranged between the second anoxic tank and the first aerobic tank, a deformable communication system arranged between the second anoxic tank and the post-aerobic tank, a deformable communication system arranged between the first aerobic tank and the first anoxic tank, and a deformable communication system arranged between the third aerobic tank and the post-aerobic tank.

4. The deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1 is characterized by: A mixed liquid reflux system is arranged between the post-aerobic tank and the first anoxic tank.

5. The deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1 is characterized in that: Features: The deformation communication system adopts the form of a partition wall with a gate or a pipeline with a valve.

6. The deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1 is characterized by: The first deoxidation tank and the second deoxidation tank are connected in series in two compartments, and each compartment is provided with a stirrer.

7. The deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1 is characterized by: The aerators used in the first aerobic tank, the second aerobic tank and the third aerobic tank are medium-pore cyclone aerators.

8. The deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1 is characterized by: The first aerobic pool and the third aerobic pool are provided with guide walls and propellers, and the propellers are equipped with frequency converters.

9. An operating method of a deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1, characterized in that: The steps include: a) The pretreated sewage influent enters the first deoxidation tank together with the sludge returned from the return and excess sludge pump room, and then enters the second deoxidation tank downstream, where it stays for 0.5-1 hour under stirring conditions, undergoes biochemical reactions under the stirring of the agitator and the action of microorganisms, consumes the dissolved oxygen brought by the return sludge and the influent pretreated by the pre-ozonation process, and hydrolyzes the organic matter in the influent; b) the mixed liquor of the oxygen elimination tank obtained in step a) enters the first anoxic tank together with the mixed liquor returned from the post-aerobic tank, and then enters the second anoxic tank downstream, stays for 4-6 hours under anoxic stirring conditions, and performs denitrification and denitrification reaction under the action of microorganisms; c) the anoxic pool mixed liquid obtained in step b) enters the first aerobic pool, the second aerobic pool, the third aerobic pool, and the post-aerobic pool in sequence, stays under aerobic conditions for 7-8 hours, and undergoes nitrification reaction, aerobic phosphorus absorption reaction, and organic matter oxidation reaction under the action of microorganisms; d) the mixed liquor from the aerobic tank obtained in step c) is refluxed to the first anoxic tank as the reflux mixed liquor, and the remaining part enters the secondary sedimentation tank for sedimentation, the effluent enters the subsequent treatment structure, and the sludge enters the reflux and excess sludge pump room; e) In step d), part of the sludge discharged from the return and excess sludge pump room enters the first deoxidation tank as return sludge, and part of it is discharged to the sludge treatment system as excess sludge.

10. The operating method of the deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 9, characterized in that: The return amount of the returned sludge in step a) is 0.5-1 times of the influent flow rate, the return amount of the mixed liquor returned to the post-oxidation tank in step b) is 2-3 times of the influent flow rate, and the DO concentration of the first aerobic tank, the second aerobic tank, the third aerobic tank and the post-aerobic tank in step c) is controlled at 1-3 mg / L.

11. An operating method of a deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 1, characterized in that: The steps include: a) The sewage influent that has been pretreated including the pre-ozonation process enters the first deoxidation tank together with the sludge returned from the return and excess sludge pump room, and then enters the second deoxidation tank downstream, where it stays for 0.5-1 hour under stirring conditions, undergoes biochemical reactions under the stirring of the stirrer and the action of microorganisms, consumes the dissolved oxygen brought by the returned sludge and the influent that has been pretreated with the pre-ozonation process, and hydrolyzes the organic matter in the influent; b) the mixed liquor of the deoxidation tank obtained in step a) enters the third aerobic tank through the deformed communication system between the second deoxidation tank and the third aerobic tank, and then enters the second aerobic tank and the first aerobic tank in sequence, stays for 6.5-7.2 hours under aerobic conditions, and performs nitrification reaction, aerobic phosphorus absorption reaction and organic matter oxidation reaction under the action of microorganisms; c) the mixed liquor of the aerobic pool obtained in step b) finally enters the first anoxic pool and the second anoxic pool in sequence from the first aerobic pool through the deformed communication system between the first aerobic pool and the first anoxic pool, stays for 4-6 hours under anoxic stirring conditions, and performs denitrification reaction and denitrification phosphorus removal reaction under the action of microorganisms; d) the anoxic pool mixed liquid obtained in step c) finally enters the post-aerobic pool from the second anoxic pool through the deformed communication system between the second anoxic pool and the post-aerobic pool, stays under aerobic conditions for 0.5-0.8 hours, and undergoes nitrification reaction, aerobic phosphorus absorption reaction and organic matter oxidation reaction under the action of microorganisms; e) the mixed liquor from the aerobic tank obtained in step d) enters the secondary sedimentation tank for precipitation, the effluent enters the subsequent treatment structure, and the sludge enters the return flow and excess sludge pump room; f) In step d), part of the sludge discharged from the return and excess sludge pump room enters the first deoxidation tank as return sludge, and part of it is discharged to the sludge treatment system as excess sludge.

12. The method for operating the deformable improved AO system suitable for high-hardness, low-COD difficult-to-degrade sewage according to claim 11, characterized in that: In step a), the return amount of the returned sludge is 0.5-1 times of the influent flow rate, in step b), the DO concentrations of the first aerobic tank, the second aerobic tank and the third aerobic tank are controlled at 1-3 mg / L, and in step d), the DO concentration of the post aerobic tank is controlled at 1-3 mg / L.

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