A magnetically enhanced sewage treatment system and treatment process

Abstract

The present invention relates to a magnetically enhanced sewage treatment system and treatment process. The magnetically enhanced sewage treatment system includes a biochemical tank, a reoxygenation tank, a secondary sedimentation tank, a sludge hydrolysis / activation tank, and a magnetic powder dosing device, which are connected in sequence. The biochemical tank includes a pre-anoxic tank, an anaerobic tank, an anoxic tank, an aerobic tank, and a facultative aerobic tank, which are connected in sequence. The nitrified liquid in the aerobic tank is partially returned to the anoxic tank, and the facultative aerobic tank is connected to the reoxygenation tank. The sludge hydrolysis / activation tank hydrolyzes sludge on sunny days and activates sludge on rainy days. The treated sludge is returned to the facultative aerobic tank. The magnetic powder dosing device adds magnetic powder to the facultative aerobic tank on rainy days. Part of the sludge obtained at the bottom of the secondary sedimentation tank is returned to the pre-anoxic tank, part is returned to the sludge hydrolysis / activation tank, and the remaining part is dehydrated. The present invention effectively suppresses excessive anaerobic denitrification of sludge in the secondary sedimentation tank through the reoxygenation tank, and increases the sludge settling rate in the secondary sedimentation tank by adding magnetic powder to the facultative aerobic tank, thereby increasing the amount of water treated in the rainy season. The present invention also achieves dynamic optimization of carbon source utilization efficiency and biological denitrification and phosphorus removal capacity through the sludge hydrolysis / activation tank, and synergistically ensures stable operation under different working conditions on sunny and rainy days.

Description

Technical Field

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

[0002] my country's urban sewage treatment facilities are now universally available, and significant progress has been made in water environment management. However, the current situation of urban water pollution remains severe, particularly with the temporary black and odorous discharge of water bodies caused by overflow from drainage pipe networks on rainy days. Causes of drainage pipe overflow during rainy days include inadequate rainwater and sewage diversion, severe pipe leakage, and insufficient rainy-day treatment capacity at sewage treatment plants. Therefore, sewage treatment processes with low development, construction, and operating costs, and the ability to improve rainy-day sewage treatment capacity, are crucial for reducing overflow pollution from urban drainage systems and eliminating the black and odorous discharge of urban water bodies during rainy days.

[0003] A 3 The AAO process is also commonly known as the improved AAO process. It is based on the AAO process and adds a pre-anoxic tank. In the pre-anoxic tank, the return sludge is mixed with a small amount of sewage to be treated. In the anoxic state, the denitrifying bacteria use the carbon source in the water to be treated to convert the nitrate nitrogen brought by the return sludge into N2 and discharge it, thereby reducing the nitrate nitrogen concentration in the subsequent anaerobic tank, which is beneficial to the release of phosphorus and absorption of organic carbon sources by the phosphate-accumulating bacteria in the anaerobic tank, thereby improving the denitrification and phosphorus removal efficiency of the entire biochemical tank. Therefore, AAO is a very important biochemical process for the treatment of nitrate nitrogen in the anaerobic tank. 3 O process is a kind of wastewater treatment process for nitrogen and phosphorus removal that has been widely used in recent years. 3 The O process has the disadvantages of long hydraulic retention time, large pool volume, large aeration volume, and high construction and operating costs.

[0004] The adsorption regeneration aeration wastewater treatment process primarily consists of a sludge activation tank, an adsorption tank, and a sedimentation tank. The wastewater to be treated and the activated sludge enter the adsorption tank. After thorough mixing, the sludge's flocculation and adsorption properties remove organic matter from the wastewater. The mixed solution then enters the sedimentation tank, where the sludge and water are separated. The clean water is discharged, and a portion of the sludge enters the sludge activation tank, while the remaining portion is discharged as residual sludge. Aeration in the sludge activation tank oxidizes the adsorbed organic matter and starves the microorganisms, enhancing the sludge's adsorption properties in the adsorption tank. While the adsorption regeneration process has a high organic matter removal rate, it is less effective at removing nitrogen and phosphorus, and is therefore rarely used in municipal wastewater treatment.

[0005] The invention patent with application number 202410054522.3 discloses an AAAOF sewage treatment system and process. Although this process utilizes the adsorption effect of sludge in the F section, it is difficult to further increase the amount of water treated on rainy days. In addition, the effluent of the AAAOF process is in the facultative oxygen section. The too low dissolved oxygen in the facultative oxygen section may cause excessive anaerobic reaction of the sludge in the secondary sedimentation tank, thereby reducing the sedimentation effect of the sludge and causing the water quality of the effluent from the secondary sedimentation tank to deteriorate. Therefore, it is necessary to further increase the amount of water treated on rainy days and avoid the problem of deterioration of the water quality of the effluent from the secondary sedimentation tank due to excessive anaerobic reaction of the sludge in the secondary sedimentation tank. Summary of the Invention

[0006] (1) Technical issues to be resolved

[0007] In order to solve the problems in the existing technology that the treatment capacity of sewage treatment processes on rainy days cannot be further improved, and that sludge may undergo excessive anaerobic reaction in the secondary sedimentation tank, resulting in deterioration of the water quality of the secondary sedimentation tank effluent, the present invention provides a magnetically enhanced sewage treatment system and treatment process.

[0008] (2) Technical solution

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

[0010] The present invention provides a magnetically enhanced sewage treatment system, comprising a biochemical tank, a reoxygenation tank, a secondary sedimentation tank and a sludge hydrolysis / activation tank connected in sequence, and a magnetic powder dosing device;

[0011] The biochemical pool includes a pre-anoxic pool, an anaerobic pool, an anoxic pool, an aerobic pool and an anaerobic pool connected in sequence; the nitrification liquid at the end of the aerobic pool partially flows back to the anoxic pool;

[0012] The aeration tank is connected to the reoxygenation tank;

[0013] The sludge hydrolysis / activation tank hydrolyzes the sludge on sunny days and activates the sludge on rainy days; the sludge that has been hydrolyzed or activated is returned to the aeration tank;

[0014] The magnetic powder adding device is used to add magnetic powder to the aeration tank on rainy days;

[0015] Part of the sludge obtained at the bottom of the secondary sedimentation tank is returned to the pre-anoxic tank, part is returned to the sludge hydrolysis / activation tank, and the remaining part is dehydrated;

[0016] The magnetically enhanced sewage treatment system further includes water inlet pipes connected to the pre-anoxic tank, the anaerobic tank and the facultative aerobic tank respectively, and sewage enters the pre-anoxic tank, the anaerobic tank and the facultative aerobic tank respectively through the water inlet pipes.

[0017] The magnetically enhanced sewage treatment system as described above preferably further comprises a magnetic powder recovery device connected to the aerobic tank, and the sludge portion is transported to the magnetic powder recovery device;

[0018] The amount of magnetic powder added by the magnetic powder dosing device to the aeration tank is 0.5-2g / L;

[0019] The magnetic powder is Fe3O4 nano magnetic powder with a particle size of 20-200nm.

[0020] The magnetically enhanced sewage treatment system as described above preferably further comprises water inlet pipes connected to the pre-anoxic tank, the anaerobic tank and the facultative aerobic tank respectively, and sewage enters the pre-anoxic tank, the anaerobic tank and the facultative aerobic tank respectively through the water inlet pipes;

[0021] The water inlet pipe is provided with a water inlet main valve and a water inlet total flow meter;

[0022] A pre-anoxic pool water inlet valve and a pre-anoxic pool water inlet flowmeter are also provided on the water inlet pipeline connected to the pre-anoxic pool;

[0023] An anaerobic tank water inlet valve and an anaerobic tank water inlet flow meter are also provided on the water inlet pipe connected to the anaerobic tank;

[0024] The water inlet pipe connected to the aeration tank is also provided with an aeration tank water inlet valve and an aeration tank water inlet flowmeter;

[0025] The pre-anoxic tank is also provided with a pre-anoxic tank return sludge flowmeter, and the facultative aerobic tank is also provided with a facultative aerobic tank return sludge flowmeter.

[0026] In the magnetically enhanced sewage treatment system as described above, preferably, a pre-anoxic tank mixer is provided in the pre-anoxic tank, an anaerobic tank mixer is provided in the anaerobic tank, and an anoxic tank mixer is provided in the anoxic tank;

[0027] The aerobic tank is provided with an aerobic tank online dissolved oxygen meter, an aerobic tank online ammonia nitrogen monitor and an online sludge concentration monitor;

[0028] The aerobic tank is provided with an online ammonia nitrogen monitor for the aerobic tank, an online dissolved oxygen meter for the aerobic tank and a stirrer for the aerobic tank;

[0029] An online dissolved oxygen meter for the reoxygenation tank is provided in the reoxygenation tank;

[0030] The sludge hydrolysis / activation tank is provided with a sludge hydrolysis / activation tank online dissolved oxygen meter and a sludge hydrolysis / activation tank agitator.

[0031] The magnetically enhanced sewage treatment system as described above preferably further comprises a return excess sludge pumping station, into which the sludge obtained from the bottom of the secondary sedimentation tank enters; the return excess sludge pumping station is provided with a first sludge return pump, a second sludge return pump and an excess sludge pump;

[0032] Part of the sludge is returned to the pre-anoxic tank through the first sludge return pump, part is returned to the sludge hydrolysis / activation tank through the second sludge return pump, part is transported to the magnetic powder recovery device through the residual sludge pump, and the other part is transported to the sludge dewatering system through the residual sludge pump for dewatering treatment.

[0033] The magnetically enhanced sewage treatment system as described above preferably further comprises an aeration device, wherein the aeration device comprises an aeration pipe assembly and a blower assembly;

[0034] The aeration pipe assembly includes aeration pipes respectively arranged at the bottom of the aerobic tank, the facultative aerobic tank, the reoxygenation tank and the sludge hydrolysis / activation tank;

[0035] The blower assembly includes an aerobic tank blower, a facultative aerobic tank blower, and a sludge hydrolysis / activation tank blower. The aerobic tank blower is connected to the aeration pipe at the bottom of the aerobic tank, the facultative aerobic tank blower is connected to the aeration pipe at the bottom of the facultative aerobic tank and the aeration pipe at the bottom of the reoxygenation tank, and the sludge hydrolysis / activation tank blower is connected to the aeration pipe at the bottom of the sludge hydrolysis / activation tank.

[0036] The aeration pipe at the bottom of the aeration tank and the aeration pipe at the bottom of the reoxygenation tank are respectively provided with an aeration tank air valve and a reoxygenation tank air valve.

[0037] The present invention also provides a sewage treatment process using the magnetically enhanced sewage treatment system, wherein the magnetically enhanced sewage treatment system includes a sunny day mode and a rainy day mode;

[0038] Assuming that the design inflow volume on a sunny day is Q, when the inflow volume is less than 1.3Q, the magnetic enhanced sewage treatment system operates in sunny day mode; when the inflow volume is greater than or equal to 1.3Q, the magnetic enhanced sewage treatment system operates in rainy day mode;

[0039] When the magnetically enhanced sewage treatment system is operated in sunny weather mode, the sewage treatment process includes the following steps:

[0040] S1: The sewage to be treated enters the pre-anoxic tank, anaerobic tank and facultative aerobic tank respectively;

[0041] S2: The sewage in the pre-anoxic tank is mixed with the returned sludge to undergo denitrification, and the effluent enters the anaerobic tank;

[0042] S3: The water undergoes phosphorus desorption reaction in the anaerobic tank, and the effluent enters the anoxic tank;

[0043] S4: The influent of the anoxic tank and the nitrified liquid returned from the aerobic tank undergo denitrification and denitrification reactions, and the effluent enters the aerobic tank;

[0044] S5: Nitrification and phosphorus absorption reactions take place in the aerobic tank, with part of the terminal nitrification liquid returning to the anoxic tank and part entering the facultative aerobic tank;

[0045] S6: The sewage in the facultative aerobic tank, the nitrification liquid from the aerobic tank and the hydrolyzed sludge are mixed to simultaneously carry out nitrification, denitrification and simultaneous nitrification, denitrification and phosphorus removal reactions;

[0046] S7: The effluent from the aeration tank enters the reoxygenation tank for treatment;

[0047] S8: The effluent from the reoxygenation tank is separated into mud and water in the secondary sedimentation tank, the supernatant is discharged, and the bottom sludge is discharged into the return residual sludge pump station;

[0048] S9: Part of the sludge from the return excess sludge pumping station is returned to the pre-anoxic tank, part is returned to the sludge hydrolysis / activation tank, and the remaining part is dehydrated;

[0049] S10: The sludge is hydrolyzed in the sludge hydrolysis / activation tank under anoxic conditions and then returned to the facultative aerobic tank;

[0050] When the magnetically enhanced sewage treatment system is operated in rainy weather mode, the sewage treatment process includes the following steps:

[0051] A1: The sewage to be treated enters the pre-anoxic tank, anaerobic tank and facultative aerobic tank respectively;

[0052] A2: The sewage in the pre-anoxic tank is mixed with the returned sludge to undergo denitrification, and the effluent enters the anaerobic tank;

[0053] A3: The water undergoes phosphorus desorption reaction in the anaerobic tank, and the effluent enters the anoxic tank;

[0054] A4: The influent of the anoxic tank and the nitrified liquid returned from the aerobic tank undergo denitrification and denitrification reactions, and the effluent enters the aerobic tank;

[0055] A5: Nitrification and phosphorus absorption reactions occur in the aerobic tank, with part of the terminal nitrification liquid returning to the anoxic tank and part entering the facultative aerobic tank;

[0056] A6: Magnetic powder is added to the aerobic tank through a magnetic powder dosing device. The sewage in the aerobic tank, the nitrification liquid from the aerobic tank, the activated sludge and the magnetic powder are mixed, and nitrification reaction, magnetic enhanced denitrification reaction and simultaneous nitrification, denitrification and phosphorus removal reaction are carried out simultaneously;

[0057] A7: The effluent from the aeration tank enters the reoxygenation tank for treatment;

[0058] A8: The effluent from the reoxygenation tank is separated into mud and water in the secondary sedimentation tank, the supernatant is discharged, and the bottom sludge is discharged into the return residual sludge pump station;

[0059] A9: Part of the sludge from the return excess sludge pumping station is returned to the pre-anoxic tank, part is returned to the sludge hydrolysis / activation tank, and the remaining part is transported to the magnetic powder recovery device to recover the magnetic powder. The recovered magnetic powder is added to the aeration tank, and the remaining sludge is dehydrated;

[0060] A10: The sludge is activated in the sludge hydrolysis / activation tank and then returned to the aeration tank.

[0061] In the sewage treatment process described above, preferably, when the magnetically enhanced sewage treatment system is operated in sunny day mode, in step S1, the water inflow of the pre-anoxic tank is 0.1Q-0.3Q; the water inflow of the anaerobic tank is 0.6Q-0.8Q; and the water inflow of the facultative aerobic tank is 0.1Q-0.4Q;

[0062] In step S5, the reflux flow rate of the terminal nitrification liquid portion returning to the anoxic tank is 1.0 to 2.0 times the inlet flow rate of the pre-anoxic tank;

[0063] In step S9, the sludge return rate of the pre-anoxic tank is 0.4Q-0.7Q;

[0064] In step S10, the sludge return rate of the aerobic tank is 0.1Q-0.2Q;

[0065] When the magnetic enhanced sewage treatment system operates in rainy day mode, the water treatment volume of the magnetic enhanced sewage treatment system is 1.3Q-3.0Q;

[0066] In step A1, the water inflow of the pre-anoxic tank is 0.2Q-0.3Q; the water inflow of the anaerobic tank is 0.7Q-0.8Q; the water inflow of the facultative aerobic tank is 0.3Q-2.0Q;

[0067] In step A5, the reflux ratio of the terminal nitrification liquid portion back to the anoxic tank is 1.0Q-2.0Q;

[0068] In step A9, the sludge return rate of the pre-anoxic tank is 0.4Q-0.5Q;

[0069] In step A10, the sludge return rate of the aerobic tank is 0.2Q-0.5Q.

[0070] In the sewage treatment process described above, preferably, when the magnetically enhanced sewage treatment system is operated in sunny mode or rainy mode, the dissolved oxygen concentration in the aerobic tank is 2.0 mg / L-3.0 mg / L, the dissolved oxygen concentration in the facultative aerobic tank is 0.5 mg / L-1.5 mg / L, and the dissolved oxygen concentration in the reoxygenation tank is 2.0 mg / L-3.0 mg / L;

[0071] In step A6, the magnetic powder adding device adds magnetic powder to the aeration tank at a dosage of 0.5-2 g / L;

[0072] In step A10, when the sludge is activated in the sludge hydrolysis / activation tank, the dissolved oxygen concentration in the sludge hydrolysis / activation tank is 2.0 mg / L-3.0 mg / L;

[0073] When the magnetically enhanced sewage treatment system is operated in sunny day mode, the hydraulic retention time in the pre-anoxic tank is 0.5h-1.0h, the hydraulic retention time in the anaerobic tank is 1.0h-2.0h, the hydraulic retention time in the anoxic tank is 2.0h-3.0h, the hydraulic retention time in the aerobic tank is 4.0h-7.0h, the hydraulic retention time in the facultative aerobic tank is 1.5h-3.0h, the hydraulic retention time in the reoxygenation tank is 5min-10min, and the total hydraulic retention time is 9.0h-16.0h;

[0074] When the magnetic enhanced sewage treatment system is operated in sunny mode, the hydraulic retention time of sludge hydrolysis in the sludge hydrolysis / activation tank is 2h-4h, and the sludge ratio returned from the return excess sludge pumping station to the sludge hydrolysis / activation tank is 20%-50%;

[0075] When the magnetically enhanced sewage treatment system is operated in rainy day mode, the hydraulic retention time in the pre-anoxic tank is 0.5h-1.0h, the hydraulic retention time in the anaerobic tank is 1.0h-2.0h, the hydraulic retention time in the anoxic tank is 2.0h-3.0h, the hydraulic retention time in the aerobic tank is 4.0h-7.0h, the hydraulic retention time in the facultative aerobic tank is 0.5h-1.0h, the hydraulic retention time in the reoxygenation tank is 2min-4min, and the total hydraulic retention time is 8.0h-14.0h;

[0076] When the magnetically enhanced sewage treatment system operates in rainy day mode, the hydraulic retention time of sludge activation in the sludge hydrolysis / activation tank is 1.5h-2h, and the sludge ratio returned from the return residual sludge pumping station to the sludge hydrolysis / activation tank is 20%-50%.

[0077] (3) Beneficial effects

[0078] First, the present invention provides a magnetic powder dosing device for adding magnetic powder to the aerobic tank. Adding magnetic powder to the aerobic tank on rainy days can form magnetically enhanced activated sludge flocs with the magnetic powder as the core. The exterior of the magnetically enhanced activated sludge flocs is in an aerobic state, while the interior is in an anoxic state, creating an aerobic-anoxic environment at the microscopic level. The magnetic powder's micromagnetic field can enhance microbial activity, thereby improving the denitrification and phosphorus removal efficiency of the microorganisms. The density of the magnetically enhanced activated sludge is significantly increased, which can increase the sludge settling rate in the secondary sedimentation tank by more than three times, thereby resolving the problem of insufficient treated water during the rainy season and increasing the treated water volume by three times.

[0079] Secondly, the present invention also sets up a sludge hydrolysis / activation tank in the magnetically enhanced sewage treatment system, which realizes the dynamic optimization of carbon source utilization efficiency and biological denitrification and phosphorus removal capacity, and synergistically ensures stable operation under different working conditions on sunny and rainy days. The sludge hydrolysis / activation tank hydrolyzes the sludge on sunny days, hydrolyzes the difficult-to-degrade organic matter adsorbed by the sludge into small molecular organic matter, provides more carbon sources for denitrification for the anoxic tank and the facultative anoxic tank, and improves the utilization rate of the carbon source. Sludge hydrolysis can also enable the nitrate nitrogen remaining in the sludge to complete the denitrification reaction, reduce the concentration of nitrate nitrogen returned to the facultative anoxic tank, facilitate phosphorus removal, and also improve the denitrification efficiency of the biochemical tank. On rainy days, the sludge hydrolysis / activation tank is used to activate the sludge, converting the ammonia nitrogen and oxygen remaining in the sludge into nitrate nitrogen. In the sludge after activation treatment, the metabolism of microorganisms is accelerated, and the sludge is in a hungry state, and the flocculation and adsorption capacity of the sludge is enhanced.

[0080] Thirdly, the present invention also oxygenates the effluent from the aerobic tank by setting up a reoxygenation tank, thereby increasing the concentration of dissolved oxygen in the effluent from the aerobic tank, which can effectively inhibit excessive anaerobic denitrification of sludge in the secondary sedimentation tank and avoid affecting the sedimentation effect and the effluent quality of the secondary sedimentation tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 It is a structural schematic diagram of the magnetically enhanced sewage treatment system in the present invention.

[0082] [Description of Reference Numerals]

[0083] 1: Pre-anoxic tank; 2: Anaerobic tank; 3: Anoxic tank; 4: Aerobic tank; 5: Facultative aerobic tank; 6: Reaeration tank; 7: Secondary sedimentation tank; 8: Return residual sludge pump station; 9: Sludge hydrolysis / activation tank; 10: Main water inlet valve; 11: Pre-anoxic tank inlet valve; 12: Anaerobic tank inlet valve; 13: Facultative aerobic tank inlet valve; 14: Nitrification solution return pump; 15: First sludge return pump; 16: Second sludge return pump; 17: Residual sludge pump; 18: Aerobic tank blower; 19: Facultative aerobic tank blower; 20: Sludge hydrolysis / activation tank blower; 21: Facultative aerobic tank air valve; 22: Reaeration tank air valve; 23: Total water inlet flow meter; 24: Pre-anoxic tank inlet flow meter ; 25: Anaerobic tank inlet flow meter; 26: Facultative aerobic tank inlet flow meter; 27: Pre-anoxic tank return sludge flow meter; 28: Facultative aerobic tank return sludge flow meter; 29: Aerobic tank online dissolved oxygen meter; 30: Aerobic tank online ammonia nitrogen monitor; 31: Online sludge concentration monitor; 32: Facultative ammonia nitrogen monitor; 33: Facultative aerobic tank online dissolved oxygen meter; 34: Reaeration tank online dissolved oxygen meter; 35: Sludge hydrolysis / activation tank online dissolved oxygen meter; 36: Pre-anoxic tank mixer; 37: Anaerobic tank mixer; 38: Anoxic tank mixer; 39: Facultative aerobic tank mixer; 40: Sludge hydrolysis / activation tank mixer; 41: Magnetic powder dosing device; 42: Magnetic powder recovery device. DETAILED DESCRIPTION

[0084] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with specific embodiments.

[0085] like Figure 1 As shown, the present invention provides a magnetically enhanced sewage treatment system, comprising a biochemical tank, a reoxygenation tank 6, a secondary sedimentation tank 7 and a sludge hydrolysis / activation tank 9, which are connected in sequence, and a magnetic powder dosing device 41.

[0086] The biochemical pool includes a pre-anoxic pool 1, an anaerobic pool 2, an anoxic pool 3, an aerobic pool 4, and an anaerobic pool 5, which are connected in sequence. The nitrification liquid at the end of the aerobic pool 4 flows back to the anoxic pool 3, and the anaerobic pool 5 is connected to the reoxygenation pool 6.

[0087] The sludge hydrolysis / activation tank 9 performs hydrolysis treatment on the sludge on sunny days and activation treatment on the sludge on rainy days. The sludge that has been hydrolyzed or activated is returned to the aeration tank 5 .

[0088] The magnetic powder adding device 41 is used to add magnetic powder to the aeration tank 5 on rainy days.

[0089] Part of the sludge obtained at the bottom of the secondary sedimentation tank 7 is returned to the pre-anoxic tank 1, part is returned to the sludge hydrolysis / activation tank 9, and the remaining part enters the sludge dewatering system for dewatering treatment.

[0090] The present invention oxygenates the effluent from the facultative aerobic tank by providing a reoxygenation tank, thereby increasing the concentration of dissolved oxygen in the effluent from the facultative aerobic tank, and can effectively inhibit excessive anaerobic denitrification of sludge in the secondary sedimentation tank, thereby avoiding affecting the sedimentation effect and the effluent quality of the secondary sedimentation tank.

[0091] The present invention also includes a magnetic powder dosing device for adding magnetic powder to the aerobic tank. During rainy days, adding magnetic powder to the aerobic tank forms magnetically enhanced activated sludge flocs centered around the magnetic powder. The exterior of the magnetically enhanced activated sludge flocs is aerobic, while the interior is anoxic, creating a microscopic aerobic-anoxic environment. The magnetic powder's micromagnetic field enhances microbial activity, thereby increasing their denitrification and phosphorus removal efficiency. This significantly increases the density of the magnetically enhanced activated sludge, increasing the sludge settling rate in the secondary sedimentation tank by more than three times. This addresses the issue of insufficient treated water during the rainy season and can triple the treated water volume.

[0092] The sludge hydrolysis / activation tank of the present invention achieves dynamic optimization of carbon source utilization efficiency and biological denitrification and phosphorus removal capacity, synergistically ensuring stable operation under different working conditions on sunny and rainy days. The sludge hydrolysis / activation tank hydrolyzes the sludge on sunny days, hydrolyzing the difficult-to-degrade organic matter adsorbed by the sludge into small-molecule organic matter, providing more carbon sources for denitrification in the anoxic and facultative oxic tanks, thereby improving carbon source utilization. Sludge hydrolysis also allows the nitrate nitrogen remaining in the sludge to complete the denitrification reaction, reducing the concentration of nitrate nitrogen returned to the facultative oxic tank, facilitating phosphorus removal, and also improving the denitrification efficiency of the biochemical tank. Although the existing AAAOF wastewater treatment process utilizes the adsorption effect of sludge in stage F, long-term research by researchers of the present invention has found that the microorganisms in the return sludge are still "satisfied", and the flocculation and adsorption capacity of the return sludge is limited. Therefore, the amount of water treated on rainy days is limited, with a maximum upper limit of only 2.4 times the amount of water on sunny days. Based on this problem, the present invention uses a sludge hydrolysis / activation tank to activate the sludge on rainy days, converting the residual ammonia nitrogen and oxygen in the sludge into nitrate nitrogen. In the activated sludge, the metabolism of microorganisms is accelerated and they are in a hungry state. The flocculation and adsorption capacity of the sludge is enhanced, and the treated water volume can reach three times that of a sunny day.

[0093] Preferably, the magnetically enhanced wastewater treatment system further includes a magnetic powder recovery device 42 connected to the aeration tank 5, to which the sludge is transported. The magnetic powder dosing device 41 adds 0.5-2 g / L of magnetic powder to the aeration tank 5. The magnetic powder is preferably Fe3O4 nanoparticles with a particle size of 20-200 nm, but other magnetic powder carrier materials may also be used.

[0094] Magnetic powder has two functions: First, it creates a micromagnetic field, which increases microbial activity and enhances biological nitrogen and phosphorus removal. Second, it enhances flocculation, forming magnetically enhanced activated sludge, which significantly increases sludge density and can more than triple the sedimentation rate in secondary sedimentation tanks, thereby addressing the problem of insufficient secondary sedimentation tank capacity during the rainy season.

[0095] Preferably, the magnetically enhanced sewage treatment system further includes water inlet pipes connected to the pre-anoxic tank 1, the anaerobic tank 2, and the facultative aerobic tank 5, respectively. The sewage inlet can be divided into three routes, and enters the pre-anoxic tank 1, the anaerobic tank 2, and the facultative aerobic tank 5 respectively through the water inlet pipes. A main water inlet valve 10 and a main water inlet flowmeter 23 are provided on the water inlet pipe. A pre-anoxic tank inlet valve 11 and a pre-anoxic tank inlet flowmeter 24 are also provided on the water inlet pipe connected to the pre-anoxic tank 1. An anaerobic tank inlet valve 12 and an anaerobic tank inlet flowmeter 25 are also provided on the water inlet pipe connected to the anaerobic tank 2. An facultative aerobic tank inlet valve 13 and a facultative aerobic tank inlet flowmeter 26 are also provided on the water inlet pipe connected to the facultative aerobic tank 5. A pre-anoxic tank return sludge flowmeter 27 is also provided in the pre-anoxic tank 1, and a facultative aerobic tank return sludge flowmeter 28 is also provided in the facultative aerobic tank 5.

[0096] Preferably, a pre-anoxic tank mixer 36 is provided in the pre-anoxic tank 1, an anaerobic tank mixer 37 is provided in the anaerobic tank 2, and an anoxic tank mixer 38 is provided in the anoxic tank 3. The aerobic tank 4 is provided with an aerobic tank online dissolved oxygen meter 29, an aerobic tank online ammonia nitrogen monitor 30, and an online sludge concentration monitor 31. The facultative aerobic tank 5 is provided with an facultative ammonia nitrogen monitor 32, an facultative aerobic tank online dissolved oxygen meter 33, and a facultative aerobic tank mixer 39. The reoxygenation tank 6 is provided with an online reoxygenation tank dissolved oxygen meter 34. The sludge hydrolysis / activation tank 9 is provided with an online sludge hydrolysis / activation tank dissolved oxygen meter 35 and a sludge hydrolysis / activation tank mixer 40. The function of each of the above mixers is to uniformly mix the sludge with the sewage to prevent sludge sedimentation.

[0097] Preferably, the magnetically enhanced sewage treatment system further includes a return excess sludge pumping station 8. The sludge obtained from the bottom of the secondary sedimentation tank 7 enters the return excess sludge pumping station 8. The return excess sludge pumping station 8 is provided with a first sludge return pump 15, a second sludge return pump 16, and an excess sludge pump 17. Part of the sludge is returned to the pre-anoxic tank 1 through the first sludge return pump 15, part is returned to the sludge hydrolysis / activation tank 9 through the second sludge return pump 16, part is transported to the magnetic powder recovery device 42 through the excess sludge pump 17, and the remaining part is transported to the sludge dewatering system for dewatering treatment through the excess sludge pump 17.

[0098] Preferably, the magnetically enhanced sewage treatment system further includes an aeration device, comprising an aeration pipe assembly and a blower assembly. The aeration pipe assembly includes aeration pipes disposed at the bottom of the aerobic tank 4, the facultative aerobic tank 5, the reoxygenation tank 6, and the sludge hydrolysis / activation tank 9, respectively. The blower assembly includes an aerobic tank blower 18, a facultative aerobic tank blower 19, and a sludge hydrolysis / activation tank blower 20. The aerobic tank blower 18 is connected to the aeration pipe at the bottom of the aerobic tank 4, the facultative aerobic tank blower 19 is connected to the aeration pipes at the bottom of the facultative aerobic tank 5 and the reoxygenation tank 6, and the sludge hydrolysis / activation tank blower 20 is connected to the aeration pipe at the bottom of the sludge hydrolysis / activation tank 9. The aeration pipes at the bottom of the facultative aerobic tank 5 and the reoxygenation tank 6 are also provided with a facultative aerobic tank air valve 21 and a reoxygenation tank air valve 22, respectively.

[0099] The aeration volume of each pool can be adjusted by the automatic control system sending instructions to the blower based on the dissolved oxygen concentration of the aerobic pool, facultative aerobic pool, reoxygenation pool, and sludge hydrolysis / activation pool.

[0100] The present invention also provides a sewage treatment process using the magnetically enhanced sewage treatment system. The magnetically enhanced sewage treatment system includes a sunny day mode and a rainy day mode.

[0101] Assuming that the design water inflow on a sunny day is Q, when the water inflow is less than 1.3Q, the magnetically enhanced sewage treatment system operates in sunny day mode; when the water inflow is greater than or equal to 1.3Q, the magnetically enhanced sewage treatment system operates in rainy day mode.

[0102] When the magnetically enhanced sewage treatment system is operated in sunny weather mode, the sewage treatment process includes the following steps:

[0103] S1: The sewage to be treated enters the pre-anoxic tank 1, the anaerobic tank 2 and the facultative aerobic tank 5 respectively.

[0104] S2: The sewage in the pre-anoxic tank 1 is mixed with the returned sludge. The denitrifying bacteria use the carbon source in the sewage to convert the remaining nitrate in the returned sludge into nitrogen gas, undergoing a denitrification reaction. The effluent enters the anaerobic tank 2.

[0105] S3: The anaerobic tank 2 is used for water dephosphorization reaction. Microorganisms in the anaerobic tank absorb organic carbon sources in the sewage, accumulate phosphorus and release phosphorus. The effluent enters the anoxic tank 3.

[0106] S4: The influent of the anoxic tank 3 and the nitrified liquid returned from the aerobic tank 4 undergo denitrification and denitrification reactions. The denitrifying bacteria utilize the carbon source absorbed in the anaerobic tank to perform denitrification and denitrification reactions in the anoxic tank. Nitrate nitrogen is converted into nitrogen gas, and the effluent enters the aerobic tank 4.

[0107] S5: Nitrification reaction and phosphorus absorption reaction are carried out in the aerobic tank 4. Nitrifying bacteria oxidize ammonia nitrogen into nitrate nitrogen under sufficient dissolved oxygen conditions, and polyphosphate bacteria absorb phosphorus, thereby removing ammonia nitrogen and phosphorus. The terminal nitrification liquid is partially returned to the anoxic tank 3 through the nitrification liquid reflux pump 14, and partially enters the facultative aerobic tank 5.

[0108] S6: The sewage from the facultative aerobic tank 5, the nitrified liquid from the aerobic tank 4, and the hydrolyzed sludge are mixed, and nitrification, denitrification, and simultaneous nitrification, denitrification, and phosphorus removal reactions are carried out simultaneously. During the nitrification reaction, nitrifying bacteria continue to convert ammonia nitrogen into nitrate nitrogen. During the denitrification reaction, the microorganisms within the activated sludge mass are in an anoxic state. The denitrifying bacteria use the carbon source introduced from the facultative aerobic influent to convert nitrate into nitrogen gas. During the simultaneous nitrification and denitrification reaction, in the facultative aerobic zone, under low dissolved oxygen conditions, the simultaneous nitrifying and denitrifying bacteria in the activated sludge are more active. They directly utilize ammonia nitrogen and nitrite to undergo simultaneous nitrification, denitrification, and phosphorus removal, converting ammonia nitrogen and nitrite nitrogen into nitrogen gas and absorbing phosphorus, thereby completing the simultaneous removal of ammonia nitrogen, total nitrogen, and total phosphorus.

[0109] S7: The effluent from the aeration tank 5 enters the reoxygenation tank 6 for treatment.

[0110] S8: The effluent from the reoxygenation tank 6 is separated into mud and water by the secondary sedimentation tank 7, the supernatant is discharged, and the bottom sludge is discharged into the return residual sludge pump station 8.

[0111] S9: Part of the sludge from the return residual sludge pumping station 8 is returned to the pre-anoxic tank 1, part is returned to the sludge hydrolysis / activation tank 9, and the remaining part is dehydrated.

[0112] S10: The sludge is hydrolyzed in the sludge hydrolysis / activation tank 9 under anoxic conditions, that is, without turning on the blower for aeration, and then returned to the aerobic tank 5. The return of sludge from the aerobic tank can increase the biomass of the aerobic tank and provide part of the carbon source to the aerobic tank, thereby improving the treatment efficiency.

[0113] When the magnetically enhanced sewage treatment system is operated in rainy weather mode, the sewage treatment process includes the following steps:

[0114] A1: The sewage to be treated enters the pre-anoxic tank 1, the anaerobic tank 2 and the facultative aerobic tank 5 respectively.

[0115] A2: The sewage in the pre-anoxic tank 1 is mixed with the returned sludge to undergo denitrification. The denitrifying bacteria use the carbon source in the sewage to convert the remaining nitrate in the returned sludge into nitrogen gas, and the effluent enters the anaerobic tank 2.

[0116] A3: The anaerobic tank 2 undergoes a water dephosphorization reaction. Microorganisms in the anaerobic tank absorb organic carbon sources in the sewage, accumulate phosphorus and release phosphorus. The effluent enters the anoxic tank 3.

[0117] A4: The influent of the anoxic tank 3 and the nitrified liquid returned from the aerobic tank 4 undergo denitrification and denitrification reactions. The denitrifying bacteria utilize the carbon source absorbed in the anaerobic tank to carry out denitrification and denitrification reactions in the anoxic tank, converting nitrate nitrogen into nitrogen gas. The effluent enters the aerobic tank 4.

[0118] A5: Nitrification reaction and phosphorus absorption reaction take place in the aerobic tank 4. Nitrifying bacteria oxidize ammonia nitrogen into nitrate nitrogen under sufficient dissolved oxygen conditions, and polyphosphate bacteria absorb phosphorus, thereby removing ammonia nitrogen and phosphorus. Part of the terminal nitrification liquid flows back to the anoxic tank 3, and part enters the facultative aerobic tank 5.

[0119] A6: Magnetic powder is added to the aerobic tank 5 via the magnetic powder dosing device 41. The raw sewage in the aerobic tank 5, the nitrified liquid from the aerobic tank 4, the activated sludge, and the magnetic powder are mixed, leading to simultaneous nitrification, magnetically enhanced denitrification, and simultaneous nitrification, denitrification, and phosphorus removal reactions. Fe₃O₄ nanoparticles have excellent flocculation properties and enhance the function of the activated sludge biofloculation and adsorption tank. Their excellent adsorption properties effectively remove organic pollutants, suspended solids, and TP from wastewater entering the aerobic tank. After the addition of magnetic powder, magnetically enhanced activated sludge flocs with the magnetic powder as their core rapidly form in the aerobic tank. The outer surface of the magnetically enhanced activated sludge flocs is aerobic, while the inner surface is anoxic, creating a microscopic aerobic-anoxic environment. The magnetic powder's micromagnetic field enhances microbial activity, thereby improving the efficiency of microbial nitrogen and phosphorus removal. The higher density of the magnetically enhanced activated sludge can increase the settling rate of the secondary sedimentation tank by three times or more, thereby addressing the issue of insufficient secondary sedimentation tank capacity during the rainy season.

[0120] The facultative aerobic tank can simultaneously complete nitrification, denitrification and simultaneous nitrification, denitrification and phosphorus removal reactions: in the nitrification reaction, nitrifying bacteria continue to convert ammonia nitrogen into nitrate nitrogen. In the denitrification reaction, the microorganisms inside the magnetically enhanced activated sludge group are in an anoxic state. The denitrifying bacteria use the carbon source brought in from the facultative aerobic section to convert nitrate into nitrogen gas. In the simultaneous nitrification and denitrification reaction, in the facultative aerobic zone, under low dissolved oxygen conditions, the simultaneous nitrification and denitrification bacteria in the magnetically enhanced activated sludge will be more active, directly using ammonia nitrogen and nitrite to undergo simultaneous nitrification, denitrification and phosphorus removal, converting ammonia nitrogen and nitrite nitrogen into nitrogen gas and absorbing phosphorus, thereby completing the simultaneous removal of ammonia nitrogen, total nitrogen and total phosphorus.

[0121] A7: The effluent from the aeration tank 5 enters the reoxygenation tank 6 for treatment.

[0122] A8: The effluent from the reoxygenation tank 6 is separated into mud and water by the secondary sedimentation tank 7, the supernatant is discharged, and the bottom sludge is discharged into the return residual sludge pump station 8.

[0123] A9: Part of the sludge from the return residual sludge pumping station 8 is returned to the pre-anoxic tank 1, part is returned to the sludge hydrolysis / activation tank 9, and the remaining part is transported to the magnetic powder recovery device 42 to recover the magnetic powder. The recovered magnetic powder is added to the anoxic tank 5, and the remaining sludge is dehydrated.

[0124] A10: The sludge is activated in the sludge hydrolysis / activation tank 9 and then returned to the aeration tank 5.

[0125] Preferably, when the magnetically enhanced sewage treatment system operates in sunny weather mode, in step S1, the water inflow to the pre-anoxic tank 1 is 0.1Q-0.3Q; the water inflow to the anaerobic tank 2 is 0.6Q-0.8Q; and the water inflow to the facultative aerobic tank 5 is 0.1Q-0.4Q. In step S5, the return flow rate of the terminal nitrified liquid portion back to the anoxic tank 3 is 1.0-2.0 times the return flow rate of the pre-anoxic tank 1. In step S9, the sludge return flow rate of the pre-anoxic tank 1 is 0.4Q-0.7Q, and in step S10, the sludge return flow rate of the facultative aerobic tank 5 is 0.1Q-0.2Q.

[0126] When the magnetically enhanced sewage treatment system operates in rainy day mode, the treated water volume of the magnetically enhanced sewage treatment system is 1.3Q-3.0Q. In step A1, the water inflow of the pre-anoxic tank 1 is 0.2Q-0.3Q; the water inflow of the anaerobic tank 2 is 0.7Q-0.8Q; the water inflow of the facultative aerobic tank 5 is 0.3Q-2.0Q. In step A5, the reflux ratio of the terminal nitrification liquid part back to the anoxic tank 3 is 1.0Q-2.0Q. In step A9, the sludge return volume of the pre-anoxic tank 1 is 0.4Q-0.5Q. In step A10, the sludge return volume of the facultative aerobic tank 5 is 0.2Q-0.5Q.

[0127] When the magnetically enhanced sewage treatment system operates in sunny day mode or rainy day mode, the dissolved oxygen concentration in the aerobic tank 4 is 2.0 mg / L-3.0 mg / L, the dissolved oxygen concentration in the facultative aerobic tank 5 is 0.5 mg / L-1.5 mg / L, and the dissolved oxygen concentration in the reoxygenation tank 6 is 2.0 mg / L-3.0 mg / L.

[0128] In step A6, the magnetic powder dosing device 41 adds magnetic powder to the aeration tank 5 at a dosage of 0.5-2 g / L. In step A10, when the sludge is activated in the sludge hydrolysis / activation tank 9, the dissolved oxygen concentration in the sludge hydrolysis / activation tank 9 is 2.0 mg / L-3.0 mg / L.

[0129] When the magnetically enhanced sewage treatment system operates in sunny weather mode, the hydraulic retention time in the pre-anoxic tank 1 is 0.5-1.0 hours, the hydraulic retention time in the anaerobic tank 2 is 1.0-2.0 hours, the hydraulic retention time in the anoxic tank 3 is 2.0-3.0 hours, the hydraulic retention time in the aerobic tank 4 is 4.0-7.0 hours, the hydraulic retention time in the facultative aerobic tank 5 is 1.5-3.0 hours, and the hydraulic retention time in the reoxygenation tank 6 is 5-10 minutes, for a total hydraulic retention time of 9.0-16.0 hours. The total hydraulic retention time is the sum of the residence time of the sewage in the pre-anoxic tank 1, anaerobic tank 2, anoxic tank 3, aerobic tank 4, facultative aerobic tank 5, and reoxygenation tank 6.

[0130] When the magnetically enhanced sewage treatment system operates in sunny day mode, the hydraulic retention time of sludge hydrolysis in the sludge hydrolysis / activation tank 9 is 2h-4h, and the sludge ratio returned from the return residual sludge pump station 8 to the sludge hydrolysis / activation tank 9 is 20%-50%.

[0131] When the magnetically enhanced sewage treatment system of the sewage treatment system operates in rainy day mode, the hydraulic retention time in the pre-anoxic tank 1 is 0.5h-1.0h, the hydraulic retention time in the anaerobic tank 2 is 1.0h-2.0h, the hydraulic retention time in the anoxic tank 3 is 2.0h-3.0h, the hydraulic retention time in the aerobic tank 4 is 4.0h-7.0h, the hydraulic retention time in the facultative aerobic tank 5 is 0.5h-1.0h, the hydraulic retention time in the reoxygenation tank 6 is 2min-4min, and the total hydraulic retention time is 8.0h-14.0h.

[0132] When the magnetically enhanced sewage treatment system operates in rainy day mode, the hydraulic retention time of sludge activation in the sludge hydrolysis / activation tank 9 is 1.5h-2h, and the sludge ratio returned from the return residual sludge pump station 8 to the sludge hydrolysis / activation tank 9 is 20%-50%.

[0133] In order to further clarify the solution of the present invention and its technical advancement, the following is an explanation with reference to specific embodiments and technical effects.

[0134] Example 1

[0135] This embodiment provides a sewage treatment process, and a simulation experiment is conducted using the water quality of a sewage treatment plant, with a design flow rate of Q = 60L / d. The total residence time of the water in the biochemical tank and the reoxygenation tank is 12.6h, of which the residence time of the pre-anoxic tank is 0.5h, the residence time of the anaerobic tank is 1h, the hydraulic retention time of the anoxic tank is 2.5h, the hydraulic retention time of the aerobic tank is 6h, the hydraulic retention time of the facultative aerobic tank is 2.5h, the hydraulic retention time of the reoxygenation tank is 0.1h, and the hydraulic retention time of the sludge hydrolysis tank is 2.0h. The hydraulic retention time in the secondary sedimentation tank is 4h. The system operates in sunny day mode:

[0136] Adjust the valve of the pre-anoxic tank, 0.1Q sewage enters the pre-anoxic tank, the sewage mixes and reacts with the return sludge, and the effluent from the pre-anoxic tank enters the anaerobic tank.

[0137] Adjust the water inlet valve of the anaerobic tank, 0.7Q sewage enters the anaerobic tank and is fully mixed with the mixed liquid entering the pre-anoxic tank, and the effluent from the anaerobic tank enters the anoxic tank.

[0138] In the anoxic tank, the effluent from the anaerobic tank is mixed with the nitrified liquid returned from the aerobic tank. Denitrifying bacteria use the carbon source in the sewage to complete the denitrification reaction and remove TN. The effluent from the anoxic tank enters the aerobic tank.

[0139] Adjust the air supply of the aerobic pool blower to control the dissolved oxygen in the aerobic pool at 2.0mg / L-3.0mg / L. Nitrifying bacteria use the dissolved oxygen in the aerobic pool to undergo nitrification reaction, oxidizing ammonia nitrogen into nitrate nitrogen. Adjust the flow rate of the nitrification liquid reflux pump. 1.0Q of nitrification liquid from the aerobic pool will flow back to the anoxic pool, and the rest of the nitrification liquid will flow to the facultative aerobic pool.

[0140] Adjust the inlet valve of the aeration tank to allow 0.2Q of wastewater to enter the aeration tank, where it mixes with the nitrification solution from the aerobic tank and 0.1Q of sludge from the sludge hydrolysis tank. Adjust the air supply from the aeration tank blower to keep the dissolved oxygen level in the aeration tank between 0.5mg / L and 1.5mg / L. Nitrification, denitrification, and simultaneous nitrification, denitrification, and phosphorus removal reactions are simultaneously completed in the aeration tank.

[0141] The effluent from the aeration tank enters the reoxygenation tank, where the dissolved oxygen concentration of the mixed liquor is increased to 2.0mg-3.0mg / L, and the effluent is discharged to the secondary sedimentation tank.

[0142] In the secondary sedimentation tank, after the sedimentation sludge and water are separated, the supernatant is discharged and the sludge is discharged to the return residual sludge pumping station.

[0143] The sludge return pump in the return residual sludge pumping station transports part of the sludge to the pre-anoxic tank through the first sludge return pump, with a sludge return rate of 0.5Q; part of the sludge is transported to the sludge hydrolysis / activation tank through the second sludge return pump, with a return rate of 0.1Q; the remaining sludge is discharged to the sludge dewatering system through the residual sludge pump.

[0144] In sunny day mode, the sludge hydrolysis / activation tank operates as a sludge hydrolysis tank, and the hydrolyzed sludge is returned to the aeration tank.

[0145] In this embodiment, the pollutant removal effect is shown in Table 1:

[0146] Table 1 Statistics of pollutants and their removal effects in Example 1

[0147] index COD <![CDATA[BOD5]]> <![CDATA[NH3-N]]> TN TP SS Influent (mg / L) 220 102 26 31 2.2 202 Outlet water (mg / L) 14.54 2.16 1.84 13.63 0.46 15.8 Removal rate 93.39％ 97.88％ 92.92％ 56.03％ 79.09％ 92.18％

[0148] In the effluent of Example 1, except for SS, the other pollutant indicators are all better than the Class A standard.

[0149] Comparative Example 1

[0150] This embodiment provides a traditional A 3 A wastewater treatment process for O was simulated using water from a sewage treatment plant. The design flow rate, Q, was 60 L / d. The total retention time in the biochemical tank was 12.6 hours, including 0.6 hours in the pre-anoxic tank, 1 hour in the anaerobic tank, 2.5 hours in the anoxic tank, and 8.5 hours in the aerobic tank. The hydraulic retention time in the secondary clarifier was 4 hours.

[0151] Adjust the water inlet valve of the pre-anoxic tank so that 0.3 times the sewage enters the pre-anoxic tank and mixes with 0.6Q of return sludge.

[0152] Adjust the water inlet valve of the anaerobic tank so that 0.7Q sewage enters the anaerobic tank and mixes with the effluent from the pre-anoxic tank.

[0153] The effluent from the anaerobic tank enters the anoxic tank and mixes with the nitrified liquid returned from the aerobic tank. In the anoxic tank, the denitrifying bacteria use the carbon source in the sewage to complete the denitrification reaction and remove TN. The effluent from the anoxic tank enters the aerobic tank.

[0154] Adjust the air supply of the aerobic tank blower to control the dissolved oxygen in the aerobic tank at 2.0mg / L~3.0mg / L. Part of the mixed liquid in the aerobic tank is discharged to the secondary sedimentation tank, and the other part is returned to the anoxic tank with a return flow of 2.0Q.

[0155] The effluent from the aerobic tank is separated into mud and water in the secondary sedimentation tank, the supernatant is discharged, and the sludge is discharged to the return residual sludge pump station.

[0156] At the return residual sludge pumping station, a portion of the sludge with a mass of 0.6Q is returned to the pre-anoxic tank through the sludge return pump, and the remaining sludge is discharged to the sludge dewatering system.

[0157] In this embodiment, the pollutant removal effect is shown in Table 2:

[0158] Table 2 Statistics of pollutants and their removal effects in comparative example 1

[0159] index COD <![CDATA[BOD5]]> <![CDATA[NH3-N]]> TN TP SS Influent (mg / L) 220 102 26 31 2.2 202 Outlet water (mg / L) 15.57 2.33 1.08 15.59 0.56 16.6 Removal rate 92.92％ 97.72％ 95.85％ 49.71％ 74.55％ 91.78％

[0160] It can be seen from Table 2 that TN, TP and SS of Comparative Example 1 can meet the Class B emission standard, and the remaining pollutants can meet the Class A emission standard.

[0161] Comparing the treatment effects of Example 1 and Comparative Example 1, it can be seen that the treatment process of the present invention is operated in sunny mode, and the effluent water quality is better than that of the traditional A 3 O process is good.

[0162] Example 2

[0163] This embodiment provides a sewage treatment process. A simulation experiment was conducted using the water quality of a sewage treatment plant. The design flow rate Q was 60 L / d on sunny days, and the treatment capacity was 180 L / d on rainy days. The total retention time in the biochemical tank was 10.7 hours, including a 0.5-hour retention time in the pre-anoxic tank, a 1-hour retention time in the anaerobic tank, a 2.5-hour hydraulic retention time in the anoxic tank, a 6-hour hydraulic retention time in the aerobic tank, a 0.7-hour hydraulic retention time in the facultative aerobic tank, a 3-minute hydraulic retention time in the reoxygenation tank, and a 2.0-hour hydraulic retention time in the sludge activation tank. The hydraulic retention time in the secondary sedimentation tank was 1.33 hours. The system operated in rainy-day mode.

[0164] Adjust the valve of the pre-anoxic tank, 0.3Q sewage enters the pre-anoxic tank, the sewage mixes and reacts with the return sludge, and the effluent from the pre-anoxic tank enters the anaerobic tank.

[0165] Adjust the water inlet valve of the anaerobic tank, 0.7Q sewage enters the anaerobic tank and is fully mixed with the mixed liquid entering the pre-anoxic tank, and the effluent from the anaerobic tank enters the anoxic tank.

[0166] In the anoxic tank, the effluent from the anaerobic tank is mixed with the nitrified liquid returned from the aerobic tank. Denitrifying bacteria use the carbon source in the sewage to complete the denitrification reaction and remove TN. The effluent from the anoxic tank enters the aerobic tank.

[0167] Adjust the air supply of the aerobic pool blower to keep the dissolved oxygen in the aerobic pool at 2.0mg / L to 3.0mg / L. Adjust the flow rate of the nitrification liquid return pump so that 1.0Q of nitrification liquid from the aerobic pool is returned to the anoxic pool, and the remaining nitrification liquid flows to the facultative aerobic pool.

[0168] Start the magnetic powder dosing device at a dosage of 1g / L. The magnetic powder is Fe₃O₄ nanoparticles with an average particle size of 20nm. Adjust the water inlet valve of the aeration tank to allow 2.0Q of sewage to enter the aeration tank, where it mixes with the nitrification solution from the aerobic tank, 0.5Q of sludge from the sludge hydrolysis tank, and the magnetic powder. Adjust the air supply of the aeration tank blower to keep the dissolved oxygen level in the aeration tank between 0.5mg / L and 1.5mg / L.

[0169] The effluent from the aeration tank enters the reoxygenation tank, where the dissolved oxygen concentration of the mixed liquor is increased to 2.0mg~3.0mg / L, and the effluent is discharged to the secondary sedimentation tank.

[0170] The supernatant from the secondary sedimentation tank is discharged, and the sludge is discharged to the return excess sludge pump station. The first sludge return pump in the return excess sludge pump station transports part of the sludge to the pre-anoxic tank with a sludge return rate of 0.5Q. Part of the sludge is transported to the sludge hydrolysis / activation tank via the second sludge return pump with a return rate of 0.5Q. Another part of the sludge is discharged to the magnetic powder recovery device via the excess sludge pump. The magnetic powder recovered by the magnetic powder recovery device is transported to the facultative aeration tank for recycling, and the remaining sludge is sent to the sludge dewatering system.

[0171] The sludge hydrolysis / activation tank is operated as a sludge activation tank. The sludge activation tank blower is turned on for aeration. The dissolved oxygen is controlled at 2.0mg / L-3.0mg / L. The sludge regenerated in the sludge activation tank is returned to the aeration tank.

[0172] In this embodiment, the pollutant removal effect is shown in Table 3:

[0173] Table 3 Statistics of pollutants and their removal effects in Example 2

[0174] index COD <![CDATA[BOD5]]> <![CDATA[NH3-N]]> TN TP SS Influent (mg / L) 89.6 45.5 12.1 15.5 1.12 109.2 Outlet water (mg / L) 18.86 7.26 4.16 10.06 0.45 13.54 Removal rate 78.95％ 84.04％ 65.62％ 35.10％ 59.82％ 87.60％

[0175] As shown in Table 3, except for SS, all other indicators of the effluent of Example 2 are better than the Class A standard.

[0176] Example 3

[0177] This embodiment provides a sewage treatment process. This differs from Example 2 in that the system operates in rainy-day mode, with a total biochemical tank residence time of 12 hours and a treated water volume 2.6 times that of a sunny day. The pre-anoxic tank residence time is 1 hour, the anaerobic tank residence time is 2 hours, the anoxic tank hydraulic retention time is 2 hours, the aerobic tank hydraulic retention time is 6 hours, the facultative aerobic tank hydraulic retention time is 1.0 hour, the reoxygenation tank hydraulic retention time is 5 minutes, and the sludge activation tank hydraulic retention time is 2 hours. The hydraulic retention time in the secondary sedimentation tank is 1.6 hours.

[0178] Adjust the valve of the pre-anoxic tank, 0.2Q sewage enters the pre-anoxic tank, the sewage mixes and reacts with the return sludge, and the effluent from the pre-anoxic tank enters the anaerobic tank.

[0179] Adjust the water inlet valve of the anaerobic tank, 0.8Q sewage enters the anaerobic tank and is fully mixed with the mixed liquid entering the pre-anoxic tank, and the effluent from the anaerobic tank enters the anoxic tank.

[0180] Adjust the air supply of the aerobic pool blower to keep the dissolved oxygen in the aerobic pool at 2.0mg / L to 3.0mg / L. Adjust the flow rate of the nitrification liquid return pump so that 2.0Q of nitrification liquid from the aerobic pool is returned to the anoxic pool, and the remaining nitrification liquid flows to the facultative aerobic pool.

[0181] Start the magnetic powder dosing device, the magnetic powder dosage is 0.5g / L, the magnetic powder is Fe3O4 nano magnetic powder with an average particle size of 50nm; adjust the water inlet valve of the aerobic tank, 1.6Q sewage enters the aerobic tank and is mixed with the nitrification liquid from the aerobic tank, 0.5Q sludge from the sludge hydrolysis tank and magnetic powder.

[0182] In this embodiment, the pollutant removal effect is shown in Table 4:

[0183] Table 4 Statistics of pollutants and their removal effects in Example 3

[0184]

[0185]

[0186] It can be seen from Table 4 that, in the effluent of Example 3, except for SS, all other indicators are better than the Class A standard.

[0187] Example 4

[0188] This embodiment provides a sewage treatment process. This embodiment differs from Embodiment 2 in that the total retention time in the biochemical tank is 11.1 hours, the treated water volume is 2.8 times that of a sunny day, the retention time in the pre-anoxic tank is 0.8 hours, the retention time in the anaerobic tank is 1.5 hours, the hydraulic retention time in the anoxic tank is 3 hours, the hydraulic retention time in the aerobic tank is 5 hours, the hydraulic retention time in the facultative aerobic tank is 0.8 hours, the hydraulic retention time in the reoxygenation tank is 4 minutes, and the hydraulic retention time in the sludge activation tank is 1.6 hours. The system operates in rainy day mode.

[0189] Adjust the valve in the pre-anoxic tank to allow 0.25Q of wastewater to enter the pre-anoxic tank. This wastewater mixes with the return sludge, and the effluent from the pre-anoxic tank enters the anaerobic tank. Adjust the inlet valve in the anaerobic tank to allow 0.75Q of wastewater to enter the anaerobic tank, where it mixes thoroughly with the mixed liquid entering the pre-anoxic tank. The effluent from the anaerobic tank enters the anoxic tank. The magnetic powder dosage is 2g / L, and the magnetic powder is Fe3O4 nanoparticles with an average particle size of 200nm.

[0190] In this embodiment, the pollutant removal effect is shown in Table 5:

[0191] Table 5 Statistics of pollutants and their removal effects in Example 4

[0192] index COD <![CDATA[BOD5]]> <![CDATA[NH3-N]]> TN TP SS Influent (mg / L) 126 63.3 13.1 16.4 1.43 126 Outlet water (mg / L) 19.52 8.24 4.38 10.38 0.43 15.54 Removal rate 84.51％ 86.98％ 66.56％ 36.71％ 69.93％ 87.67％

[0193] As shown in Table 5, in the effluent of Example 4, except for SS, all indicators are better than the Class A standard.

[0194] In Examples 2 to 4, due to the addition of magnetic powder, the setting of a reoxygenation tank, and the activation treatment of the sludge, a magnetically enhanced activated sludge system was formed, which greatly improved the denitrification and phosphorus removal effects of the aerobic tank and also improved the sedimentation effect of the secondary sedimentation tank. Therefore, the treatment capacity in the rainy season reached 3 times the design scale in the dry season. Compared with the AAAOF treatment process in the prior art, the treated water volume can be increased by 25%, and the effluent water quality has also been further improved compared with the AAAOF process in the prior art. All indicators, especially TP, have reached the Class A emission standard.

[0195] Comparative Example 2

[0196] This comparative example provides a sewage treatment process. A simulation experiment was conducted using the water quality of a sewage treatment plant. The design flow rate Q was 60 L / d on sunny days, and the treatment capacity was 120 L / d on rainy days. The total retention time in the biochemical and reoxygenation tanks was 12.6 hours. The retention time in the pre-anoxic tank was 0.5 hours; the anaerobic tank was 1 hour; the anoxic tank was 2.5 hours; the aerobic tank was 6 hours; the facultative aerobic tank was 2.5 hours; the reoxygenation tank was 0.1 hours; and the sludge activation tank was 2.0 hours. The secondary sedimentation tank was 2 hours. The system operated in rainy-day mode.

[0197] Adjust the valve of the pre-anoxic tank, 0.3Q sewage enters the pre-anoxic tank, the sewage mixes and reacts with the return sludge, and the effluent from the pre-anoxic tank enters the anaerobic tank.

[0198] Adjust the water inlet valve of the anaerobic tank, 0.7Q sewage enters the anaerobic tank and is fully mixed with the mixed liquid entering the pre-anoxic tank, and the effluent from the anaerobic tank enters the anoxic tank.

[0199] In the anoxic tank, the effluent from the anaerobic tank is mixed with the nitrified liquid returned from the aerobic tank. Denitrifying bacteria use the carbon source in the sewage to complete the denitrification reaction and remove TN. The effluent from the anoxic tank enters the aerobic tank.

[0200] Adjust the air supply from the aerobic tank blower to keep the dissolved oxygen level in the aerobic tank between 2.0mg / L and 3.0mg / L. Nitrifying bacteria utilize the dissolved oxygen in the aerobic tank to nitrify and oxidize ammonia nitrogen into nitrate nitrogen. Adjust the flow rate of the nitrification liquid return pump so that 1.0Q of the nitrification liquid from the aerobic tank is returned to the anoxic tank, and the remaining nitrification liquid flows to the facultative aerobic tank.

[0201] Adjust the water inlet valve of the aeration tank so that 1.0Q sewage enters the aeration tank and mixes with the nitrification liquid from the aerobic tank and 0.5Q sludge from the sludge hydrolysis tank; adjust the air supply of the blower in the aeration tank to control the dissolved oxygen in the aeration tank at 0.5mg / L-1.5mg / L.

[0202] The effluent from the aeration tank enters the reoxygenation tank, where the dissolved oxygen concentration of the mixed liquor is increased to 2.0mg~3.0mg / L, and the effluent is discharged to the secondary sedimentation tank.

[0203] In the secondary sedimentation tank, after the sedimentation mud and water are separated, the supernatant is discharged; the sludge is discharged to the return residual sludge pump station.

[0204] The No. 1 sludge return pump in the return residual sludge pumping station transports part of the sludge to the pre-anoxic tank, with a sludge return volume of 0.5Q; part of the sludge is transported to the sludge hydrolysis / activation tank through the No. 2 sludge return pump, with a return volume of 0.5Q; the remaining sludge is discharged to the sludge dewatering system through the residual sludge pump.

[0205] In rainy day mode, the sludge hydrolysis / activation tank operates as a sludge activation tank. That is, the sludge activation tank blower is turned on for aeration, and the dissolved oxygen level is controlled at 2.0mg / L-3.0mg / L. The residual ammonia nitrogen in the sludge is oxidized into nitrate nitrogen. Simultaneously, the metabolism of microorganisms accelerates under aerobic conditions, ultimately starving the microorganisms and enhancing the flocculation and adsorption capacity of the sludge. This process is known as sludge regeneration. The regenerated sludge in the sludge activation tank is then returned to the aerobic tank.

[0206] In this comparative example, the pollutant removal effect is shown in Table 6:

[0207] Table 6 Statistics of pollutants and their removal effects in comparative example 2

[0208] index COD <![CDATA[BOD5]]> <![CDATA[NH3-N]]> TN TP SS Influent (mg / L) 153 73 15.2 20.3 1.8 156 Outlet water (mg / L) 20.88 8.18 4.43 11.16 0.81 19.2 Removal rate 86.35％ 88.79％ 70.86％ 45.02％ 55.28％ 87.69％

[0209] Table 6 shows that when comparative example 2 is operated in rainy season mode, TP and SS can only reach the Class B standard, while the other indicators are better than the Class A standard.

[0210] The rainy day treatment capacity of Comparative Example 2 can only reach twice that of the sunny day mode and cannot be further improved. Except for SS, the TP of its effluent quality can only reach the Class B emission standard. Overall, the effluent water quality cannot fully meet the Class A emission standard as in Examples 2-4.

[0211] In addition, under the condition that the difference in influent water quality is not large, in the process of treating sewage for two consecutive months in Examples 2-4, there was no problem of deterioration of the effluent water quality in the secondary sedimentation tank. However, the AAAOF treatment process in the prior art had a total of three deterioration problems in the effluent water quality of the secondary sedimentation tank during the two consecutive months of operation. Specifically, on the 15th day, the 38th day and the 55th day, the sludge in the secondary sedimentation tank floated, the effluent was turbid, and the TP content was >0.8 mg / L. After the water quality deteriorated, it needed to be adjusted or stopped, and the sewage treatment capacity was reduced or lost during this period.

[0212] 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above 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. A magnetically enhanced sewage treatment system, characterized in that: It includes a biochemical tank, a reoxygenation tank (6), a secondary sedimentation tank (7), and a sludge hydrolysis / activation tank (9), and a magnetic powder dosing device (41) connected in sequence; The biochemical pool comprises a pre-anoxic pool (1), an anaerobic pool (2), an anoxic pool (3), an aerobic pool (4) and an anaerobic pool (5) which are connected in sequence; the nitrification liquid at the end of the aerobic pool (4) partially flows back to the anoxic pool (3); The aeration tank (5) is connected to the reoxygenation tank (6); The sludge hydrolysis / activation tank (9) performs hydrolysis treatment on the sludge on sunny days and performs activation treatment on the sludge on rainy days; the sludge that has undergone hydrolysis treatment or activation treatment is returned to the aeration tank (5); The magnetic powder adding device (41) is used to add magnetic powder to the aerobic tank (5) on rainy days; Part of the sludge obtained at the bottom of the secondary sedimentation tank (7) is returned to the pre-anoxic tank (1), part is returned to the sludge hydrolysis / activation tank (9), and the remaining part is dehydrated; The magnetically enhanced sewage treatment system further comprises water inlet pipes respectively connected to the pre-anoxic tank (1), the anaerobic tank (2) and the facultative aerobic tank (5), and sewage inlet respectively enters the pre-anoxic tank (1), the anaerobic tank (2) and the facultative aerobic tank (5) through the water inlet pipes.

2. The magnetic enhanced sewage treatment system according to claim 1, characterized in that: It also includes a magnetic powder recovery device (42) connected to the aerobic tank (5), and the sludge portion is transported to the magnetic powder recovery device (42); The magnetic powder adding device (41) adds 0.5-2 g / L of magnetic powder to the oxygenation tank (5); The magnetic powder is Fe3O4 nano magnetic powder with a particle size of 20-200nm.

3. The magnetic enhanced sewage treatment system according to claim 1, characterized in that: The water inlet pipeline is provided with a water inlet main valve (10) and a water inlet total flow meter (23); A pre-anoxic tank water inlet valve (11) and a pre-anoxic tank water inlet flowmeter (24) are also provided on the water inlet pipeline connected to the pre-anoxic tank (1); An anaerobic tank water inlet valve (12) and an anaerobic tank water inlet flowmeter (25) are also provided on the water inlet pipeline connected to the anaerobic tank (2); The water inlet pipe connected to the aeration tank (5) is also provided with an aeration tank water inlet valve (13) and an aeration tank water inlet flowmeter (26); The pre-anoxic tank (1) is further provided with a pre-anoxic tank return sludge flowmeter (27), and the facultative aerobic tank (5) is further provided with a facultative aerobic tank return sludge flowmeter (28).

4. The magnetic enhanced sewage treatment system according to claim 1, characterized in that: The pre-anoxic tank (1) is provided with a pre-anoxic tank stirrer (36), the anaerobic tank (2) is provided with an anaerobic tank stirrer (37), and the anoxic tank (3) is provided with an anoxic tank stirrer (38); The aerobic tank (4) is provided with an aerobic tank online dissolved oxygen meter (29), an aerobic tank online ammonia nitrogen monitor (30) and an online sludge concentration monitor (31); The aerobic tank (5) is provided with an online ammonia nitrogen monitor (32), an online dissolved oxygen meter (33) and an aerobic tank agitator (39); The reoxygenation tank (6) is provided with a reoxygenation tank online dissolved oxygen meter (34); The sludge hydrolysis / activation tank (9) is provided with a sludge hydrolysis / activation tank online dissolved oxygen meter (35) and a sludge hydrolysis / activation tank agitator (40).

5. The magnetic enhanced sewage treatment system according to claim 2, characterized in that: It also includes a return excess sludge pump station (8), wherein the sludge obtained from the bottom of the secondary sedimentation tank (7) enters the return excess sludge pump station (8); the return excess sludge pump station (8) is provided with a first sludge return pump (15), a second sludge return pump (16) and an excess sludge pump (17); Part of the sludge is returned to the pre-anoxic tank (1) through the first sludge return pump (15), part of it is returned to the sludge hydrolysis / activation tank (9) through the second sludge return pump (16), part of it is transported to the magnetic powder recovery device (42) through the residual sludge pump (17), and the other part of it is transported to the sludge dewatering system through the residual sludge pump (17) for dewatering treatment.

6. The magnetic enhanced sewage treatment system according to claim 1, characterized in that: Also included is an aeration device, which includes an aeration tube assembly and a blower assembly; The aeration pipe assembly includes aeration pipes respectively arranged at the bottom of the aerobic tank (4), the facultative aerobic tank (5), the reoxygenation tank (6) and the sludge hydrolysis / activation tank (9); The blower assembly comprises an aerobic tank blower (18), a facultative aerobic tank blower (19) and a sludge hydrolysis / activation tank blower (20), wherein the aerobic tank blower (18) is connected to the aeration pipe at the bottom of the aerobic tank (4), the facultative aerobic tank blower (19) is connected to the aeration pipe at the bottom of the facultative aerobic tank (5) and the aeration pipe at the bottom of the reoxygenation tank (6), and the sludge hydrolysis / activation tank blower (20) is connected to the aeration pipe at the bottom of the sludge hydrolysis / activation tank (9); The aeration pipe at the bottom of the aeration tank (5) and the aeration pipe at the bottom of the reoxygenation tank (6) are also provided with an aeration tank air valve (21) and a reoxygenation tank air valve (22) respectively.

7. A sewage treatment process using the magnetically enhanced sewage treatment system according to any one of claims 1 to 6, characterized in that: The magnetically enhanced sewage treatment system includes sunny day mode and rainy day mode; Assuming that the design inflow volume on a sunny day is Q, when the inflow volume is less than 1.3Q, the magnetic enhanced sewage treatment system operates in sunny day mode; when the inflow volume is greater than or equal to 1.3Q, the magnetic enhanced sewage treatment system operates in rainy day mode; When the magnetically enhanced sewage treatment system is operated in sunny weather mode, the sewage treatment process includes the following steps: S1: The sewage to be treated enters the pre-anoxic tank (1), anaerobic tank (2) and facultative aerobic tank (5) respectively; S2: The sewage in the pre-anoxic tank (1) is mixed with the returned sludge to undergo denitrification, and the effluent enters the anaerobic tank (2); S3: The anaerobic tank (2) undergoes water-phosphorus separation reaction, and the effluent enters the anoxic tank (3); S4: The influent of the anoxic tank (3) and the nitrified liquid returned from the aerobic tank (4) undergo denitrification and denitrification reactions, and the effluent enters the aerobic tank (4); S5: Nitrification and phosphorus absorption reactions are carried out in the aerobic tank (4), and part of the terminal nitrification liquid flows back to the anoxic tank (3), and part enters the facultative aerobic tank (5); S6: The sewage in the aerobic tank (5), the nitrification liquid from the aerobic tank (4) and the hydrolyzed sludge are mixed to simultaneously carry out nitrification, denitrification and simultaneous nitrification, denitrification and phosphorus removal reactions; S7: The effluent from the aeration tank (5) enters the reoxygenation tank (6) for treatment; S8: The effluent from the reoxygenation tank (6) is separated into mud and water by the secondary sedimentation tank (7), the supernatant is discharged, and the bottom sludge is discharged into the return residual sludge pump station (8); S9: Part of the sludge from the return excess sludge pumping station (8) is returned to the pre-anoxic tank (1), part is returned to the sludge hydrolysis / activation tank (9), and the remaining part is dehydrated; S10: The sludge is hydrolyzed in the sludge hydrolysis / activation tank (9) under anoxic conditions and then returned to the facultative aerobic tank (5); When the magnetically enhanced sewage treatment system is operated in rainy weather mode, the sewage treatment process includes the following steps: A1: The sewage to be treated enters the pre-anoxic tank (1), anaerobic tank (2) and facultative aerobic tank (5) respectively; A2: The sewage in the pre-anoxic tank (1) is mixed with the returned sludge to undergo denitrification, and the effluent enters the anaerobic tank (2); A3: The anaerobic tank (2) undergoes water-phosphorus separation, and the effluent enters the anoxic tank (3); A4: The influent of the anoxic tank (3) and the nitrified liquid returned from the aerobic tank (4) undergo denitrification and denitrification reactions, and the effluent enters the aerobic tank (4); A5: Nitrification and phosphorus absorption reactions are carried out in the aerobic tank (4). Part of the terminal nitrification liquid flows back to the anoxic tank (3), and part enters the facultative aerobic tank (5); A6: Magnetic powder is added to the aerobic tank (5) through the magnetic powder adding device (41), and the sewage in the aerobic tank (5), the nitrification liquid from the aerobic tank (4), the activated sludge and the magnetic powder are mixed to simultaneously carry out nitrification reaction, magnetic enhanced denitrification reaction and simultaneous nitrification, denitrification and phosphorus removal reaction; A7: The effluent from the aeration tank (5) enters the reoxygenation tank (6) for treatment; A8: The effluent from the reoxygenation tank (6) is separated into mud and water by the secondary sedimentation tank (7), the supernatant is discharged, and the bottom sludge is discharged into the return residual sludge pump station (8); A9: Part of the sludge from the return excess sludge pump station (8) is returned to the pre-anoxic tank (1), part is returned to the sludge hydrolysis / activation tank (9), and the remaining part is transported to the magnetic powder recovery device (42) to recover the magnetic powder. The recovered magnetic powder is added to the facultative aerobic tank (5), and the remaining sludge is dehydrated; A10: The sludge is activated in the sludge hydrolysis / activation tank (9) and then returned to the aeration tank (5).

8. The sewage treatment process according to claim 7, characterized in that: When the magnetic enhanced sewage treatment system is operated in sunny day mode, in step S1, the water inflow of the pre-anoxic tank (1) is 0.1Q-0.3Q; the water inflow of the anaerobic tank (2) is 0.6Q-0.8Q; and the water inflow of the facultative aerobic tank (5) is 0.1Q-0.4Q; In step S5, the reflux flow rate of the terminal nitrification liquid portion returning to the anoxic tank (3) is 1.0 to 2.0 times the inlet flow rate of the pre-anoxic tank (1); In step S9, the sludge return rate of the pre-anoxic tank (1) is 0.4Q-0.7Q; In step S10, the sludge return rate of the aerobic tank (5) is 0.1Q-0.2Q; When the magnetic enhanced sewage treatment system operates in rainy day mode, the water treatment volume of the magnetic enhanced sewage treatment system is 1.3Q-3.0Q; In step A1, the water inflow of the pre-anoxic tank (1) is 0.2Q-0.3Q; the water inflow of the anaerobic tank (2) is 0.7Q-0.8Q; the water inflow of the facultative aerobic tank (5) is 0.3Q-2.0Q; In step A5, the reflux ratio of the terminal nitrification liquid portion back to the anoxic tank (3) is 1.0Q-2.0Q; In step A9, the sludge return rate of the pre-anoxic tank (1) is 0.4Q-0.5Q; In step A10, the sludge return rate of the aerobic tank (5) is 0.2Q-0.5Q.

9. The sewage treatment process according to claim 7, characterized in that: When the magnetically enhanced sewage treatment system is operated in sunny day mode or rainy day mode, the dissolved oxygen concentration in the aerobic tank (4) is 2.0 mg / L-3.0 mg / L, the dissolved oxygen concentration in the facultative oxygen tank (5) is 0.5 mg / L-1.5 mg / L, and the dissolved oxygen concentration in the reoxygenation tank (6) is 2.0 mg / L-3.0 mg / L; In step A6, the magnetic powder adding device (41) adds magnetic powder to the oxygenation tank (5) at a dosage of 0.5-2 g / L. In step A10, when the sludge is activated in the sludge hydrolysis / activation tank (9), the dissolved oxygen concentration in the sludge hydrolysis / activation tank (9) is 2.0 mg / L-3.0 mg / L; When the magnetically enhanced sewage treatment system is operated in sunny day mode, the hydraulic retention time in the pre-anoxic tank (1) is 0.5h-1.0h, the hydraulic retention time in the anaerobic tank (2) is 1.0h-2.0h, the hydraulic retention time in the anoxic tank (3) is 2.0h-3.0h, the hydraulic retention time in the aerobic tank (4) is 4.0h-7.0h, the hydraulic retention time in the facultative aerobic tank (5) is 1.5h-3.0h, the hydraulic retention time in the reoxygenation tank (6) is 5min-10min, and the total hydraulic retention time is 9.0h-16.0h; When the magnetically enhanced sewage treatment system is operated in sunny mode, the hydraulic retention time of sludge hydrolysis in the sludge hydrolysis / activation tank (9) is 2 hours to 4 hours, and the sludge ratio returned from the return excess sludge pump station (8) to the sludge hydrolysis / activation tank (9) is 20% to 50%; When the magnetically enhanced sewage treatment system of the sewage treatment system is operated in rainy day mode, the hydraulic retention time in the pre-anoxic tank (1) is 0.5h-1.0h, the hydraulic retention time in the anaerobic tank (2) is 1.0h-2.0h, the hydraulic retention time in the anoxic tank (3) is 2.0h-3.0h, the hydraulic retention time in the aerobic tank (4) is 4.0h-7.0h, the hydraulic retention time in the facultative aerobic tank (5) is 0.5h-1.0h, the hydraulic retention time in the reoxygenation tank (6) is 2min-4min, and the total hydraulic retention time is 8.0h-14.0h; When the magnetically enhanced sewage treatment system is operated in rainy day mode, the hydraulic retention time of sludge activation in the sludge hydrolysis / activation tank (9) is 1.5h-2h, and the sludge ratio returned from the return residual sludge pump station (8) to the sludge hydrolysis / activation tank (9) is 20%-50%.

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