Device and method for strengthening Fammox denitrification efficiency based on extracellular electron transfer regulation and control strategy

Abstract

The invention discloses a device and a method for strengthening the denitrification efficiency of Fammox based on an extracellular electron transfer regulation and control strategy. The device comprises a CSTR (continuous stirred tank reactor) main body, a water inlet and outlet system, a stirring and constant temperature device, an aeration and anaerobic maintenance device and an EET (ethylene terephthalate) enhanced feeding device, the temperature, the stirring speed and the inlet water iron ion concentration in the Fammox reactor are accurately regulated and controlled, and the L-cysteine and the corn straw biochar are added, so that the electron transfer efficiency and the iron matrix utilization rate in the reaction are effectively improved, and the nitrogen removal efficiency and the Fe (III) utilization and reduction rate are remarkably improved. The L-cysteine and the corn straw biochar adopted by the invention have relatively good economical efficiency and environmental protection property, the denitrification efficiency of Fammox can be remarkably improved, and the utilization and reduction capability of ferric iron (Fe (III)) is effectively enhanced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment and resource utilization technology, and in particular to a device and method for enhancing Feammox denitrification efficiency based on an extracellular electron transport regulation strategy. Background Technology

[0002] With the increasing demand for low-carbon and resource-efficient wastewater treatment, traditional nitrification-denitrification processes generally face problems such as high external carbon source requirements, high energy consumption, and greenhouse gas emissions. In contrast, anaerobic iron ammonia oxidation (Feammox), as an autotrophic nitrogen removal pathway, utilizes Fe(III) as a terminal electron acceptor and can effectively remove nitrogen and couple iron cycling under low C / N ratio conditions, showing promising application prospects.

[0003] However, the Feammox system is often limited in its engineering applications by insufficient extracellular electron transport efficiency. On the one hand, electrons generated by ammonia oxidation metabolism need to be exported through the transmembrane electron transport chain; on the other hand, there is still significant resistance to the transfer of electrons from the microbial surface to the iron matrix (such as dissolved Fe(III) or solid iron minerals), which leads to low utilization efficiency of the iron matrix and insufficient Fe(III) / Fe(II) cycling, thus affecting the denitrification rate and stability. Therefore, it is urgent to optimize the electron transport process to improve the efficiency of the Feammox reaction. Summary of the Invention

[0004] This invention provides an apparatus and method for enhancing the nitrogen removal efficiency of Feammox based on an extracellular electron transport regulation strategy. By regulating the temperature, stirring, and iron ion concentration in the reactor, and combining this with the addition of L-cysteine ​​and corn straw biochar, the electron transport efficiency in the Feammox reaction is improved, thereby enhancing the nitrogen removal efficiency. The specific technical solution is as follows:

[0005] A device for enhancing the denitrification efficiency of Feammox based on an extracellular electron transfer regulation strategy mainly includes a Feammox CSTR reactor installation structure, which includes an inlet and outlet water system, a reactor main structure, a stirring and mixing device, a constant temperature control device, an aeration and anaerobic maintenance device, and an EET enhancement dosing device.

[0006] The water inlet and outlet system consists of an inlet, an outlet, an inlet tank, an outlet tank, a diaphragm pump, and pipelines.

[0007] The diaphragm pump is an Aldos V series pump used to control the continuous inlet flow rate;

[0008] The water inlet tank is connected to the water inlet port of the diaphragm pump via a pipeline, and the water outlet port of the diaphragm pump is connected to the water inlet of the main reactor.

[0009] The water outlet tank is connected to the water outlet of the main reactor. The reactor adopts a continuous water inlet-continuous water outlet operation mode, with the water flow being bottom inlet and top outlet.

[0010] The main structure of the CSTR reactor consists of a top cover, a bottom cover, an effective reaction zone, and a three-phase separator. The sampling port and sludge discharge port are located on the main structure of the reactor. The main material of the main structure of the CSTR reactor is plexiglass.

[0011] The mixing device consists of a motor at the top of the reactor, a stirring paddle, and a speed regulator; the stirring paddle is driven by the top motor to mix the mud and water, and the stirring speed is controlled by the speed regulator to 110 r / min.

[0012] The constant temperature control device consists of a water bath jacket and a super constant temperature water bath.

[0013] The water bath jacket is wrapped around the outside of the effective reaction zone of the CSTR reactor and is connected to the super constant temperature water bath through pipelines. Warm water circulates from bottom to top in the super constant temperature water bath to control the temperature. The temperature is controlled at 32±1℃ by the constant temperature water bath device.

[0014] The aeration and anaerobic maintenance device consists of a nitrogen cylinder, a nitrogen cylinder pressure control valve, an aeration disc, a gas collection bag, and a gas washing bottle.

[0015] The nitrogen cylinder regulates the nitrogen flow rate through a pressure control valve and introduces nitrogen into the water inlet tank and aeration disc through pipelines for inert gas replacement.

[0016] The gas washing bottle is connected to the water inlet tank. After the non-inert gas is discharged, the bottle is closed. The remaining nitrogen is stored in the gas collection bag to ensure that when the gas pressure in the water inlet tank decreases, the nitrogen in the gas collection bag can be replenished to maintain the anaerobic environment.

[0017] The EET enhanced dosing device consists of a dosing port, a storage bottle and a metering pump. The added L-cysteine ​​or corn straw biochar is stored in the storage bottle and connected to the reactor through the outlet of the metering pump for intermittent dosing.

[0018] A method for enhancing the denitrification efficiency of Feammox based on an extracellular electron transport regulation strategy is proposed. The method mainly consists of two parts: Feammox system startup and enhancement of Feammox based on EET.

[0019] The Feammox system startup and operation method is as follows: Anaerobic granular sludge is selected as seed sludge. After removing the supernatant by static sedimentation, the settled sludge is collected. The sludge inoculation amount is 40% (v / v) of the effective volume of the reactor, i.e., 2 L of anaerobic granular sludge is inoculated. The reactor is a CSTR reactor (effective reaction volume is 5L). After inoculation, the stirring device and temperature control device are turned on simultaneously. The stirring speed is controlled at 110 r / min and the temperature is controlled at 32 ± 1 ℃. The reactor adopts a continuous influent-continuous effluent operation mode. The influent is controlled by a diaphragm pump. The initial HRT is set to 10 hours. During operation, the anaerobic environment is maintained.

[0020] The EET-based enhancement method for Feammox is as follows: Stable Feammox sludge is selected as inoculum, with an inoculum volume of 40% (v / v) of the reactor's effective volume, i.e., 1 L of stable Feammox sludge. The reactor is a small-scale CSTR reactor with an effective reaction volume of 2.5 L. After inoculation, the stirring and temperature control devices are simultaneously activated, with the stirring speed controlled at 110 r / min and the temperature controlled at 32 ± 1 ℃. The reactor operates in a continuous influent-continuous effluent mode, with the influent controlled by a diaphragm pump. The initial HRT is set to 10 hours, and an anaerobic environment is maintained during operation. L-cysteine ​​and corn straw biochar are both added to the reactor using an enhanced dosing device.

[0021] The operation and enhancement process of the Feammox system is mainly divided into the following three stages:

[0022] Phase I, days 1–30, is the adaptation and establishment period for the Feammox reaction: During this phase, a low-disturbance continuous flow operation mode is used to establish the sludge basic metabolism and iron-nitrogen coupling reaction capacity, and gradually establish the basic Feammox reaction conditions. The influent Fe(III) concentration is gradually increased from 5 mg / L to 10 mg / L, and the ammonia nitrogen concentration is gradually increased from 5 mg / L to 25 mg / L.

[0023] Phase II, days 31-95, is the stabilization period of the Feammox reaction: In this phase, the continuous flow operation mode and basic operating conditions are maintained in the same manner as in Phase I (temperature 32±1℃, stirring 110 r / min, HRT 10 h). By steadily increasing the supply of Fe(III) electron acceptors and controlling the influent load, the system forms a more stable Fe(III) / Fe(II) cycle characteristic. During this phase, the influent Fe(III) concentration is stabilized at around 30 mg / L, and the ammonia nitrogen concentration is stabilized at 40 mg / L.

[0024] Phase III: Days 96-160 are the EET enhancement period for the Feammox reaction: In this phase, to overcome the electron transport bottleneck in the Feammox system and establish a complete "transmembrane electron transport and extracellular mediated transport" EET chain, under the same basic influent and operating conditions as in Phase II, two parallel reactors are selected to independently implement the following strategy for enhancement:

[0025] Strategy A is direct EET enhancement: L-cysteine ​​is added to the reactor as an EET regulator to promote the synthesis and expression of cytochrome c in functional bacterial communities. The addition method is intermittent: add one day and stop for two days, while maintaining the same influent conditions as the previous stage.

[0026] Strategy B is electron shuttle (EET) enhancement: Corn straw biochar is added to the reactor as an electron shuttle, which mediates extracellular electron transfer through its conductive network and surface functional groups, reduces electron transfer resistance and promotes Fe(III) / Fe(II) cycle; the biochar is added to the reactor in a one-time addition and supplemented later, and is effectively retained by a three-phase separator structure to prevent large amounts of loss with the effluent.

[0027] Beneficial effects:

[0028] This invention significantly improves the electron transfer efficiency and denitrification performance of the Feammox reaction system through an extracellular electron transfer regulation strategy. By precisely controlling the reactor temperature, stirring speed, and influent iron ion concentration, and combining this with the addition of L-cysteine ​​and corn straw biochar, efficient electron transfer between the iron matrix (Fe(III)) and microorganisms is promoted, thereby improving nitrogen removal efficiency and enhancing the utilization and conversion rate of Fe(III). The use of a CSTR reactor ensures thorough mixing of activated sludge and influent, guaranteeing the stability and efficiency of the reaction process. By gradually increasing the Fe(III) concentration, the inhibitory effect of high-concentration Fe(III) on microorganisms is avoided, effectively improving the denitrification rate and stability of the reactor. Furthermore, the use of low-cost sludge sources and environmentally friendly electron transfer enhancers gives this invention significant advantages in terms of economy and environmental friendliness. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the Feammox reactor.

[0030] Figure 2 A graph showing the change in nitrogen content in the Feammox reactor before and after the addition of L-cysteine;

[0031] Figure 3 A graph showing the change in iron ion content in the Feammox reactor before and after the addition of L-cysteine;

[0032] Figure 4 A graph showing the changes in nitrogen content in the Feammox reactor before and after the addition of corn straw biochar.

[0033] Figure 5 The graph shows the change in iron ion content in the Feammox reactor before and after the addition of corn stalk biochar.

[0034] In the diagram: 1. Nitrogen cylinder; 2. Nitrogen cylinder pressure control valve; 3. Water inlet tank; 4. Aeration disc; 5. Gas collection bag; 6. Gas washing bottle; 7. Water inlet pump; 8. Agitator; 9. Three-phase separator; 10. Motor; 11. Speed ​​controller; 12. Water outlet tank; 13. Water bath jacket; 14. Super constant temperature water bath; 15. CSTR reactor; 16. Water inlet; 17. Sludge discharge port; 18. Sampling port; 19. Water outlet; 20. Chemical dosing port; 21. Chemical dosing metering pump; 22. Chemical storage bottle; 23. Bottom cover; 24. Top cover; 25. Effective reaction zone. Detailed Implementation

[0035] The invention will be further described below with reference to the accompanying drawings, but it should not be construed that the scope of the invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practice in the art without departing from the spirit of the invention should be included within the scope of protection of the invention.

[0036] like Figure 1-5 As shown, a device for enhancing the denitrification efficiency of Feammox based on an extracellular electron transfer regulation strategy includes a Feammox CSTR reactor installation structure, which includes an inlet and outlet water system, a reactor main structure, a stirring and mixing device, a constant temperature control device, an aeration and anaerobic maintenance device, and an EET enhancement dosing device.

[0037] The water inlet and outlet system consists of an inlet 16, an outlet 19, an inlet tank 3, an outlet tank 12, a diaphragm pump 7, and pipelines.

[0038] The diaphragm pump 7 is an Aldos V series pump used to control the continuous inlet flow rate;

[0039] The water inlet tank 3 is connected to the water inlet port of the diaphragm pump 7 via a pipeline, and the water outlet port of the diaphragm pump is connected to the water inlet 16 of the main reactor.

[0040] The water outlet tank 12 is connected to the water outlet 19 of the main reactor. The reactor adopts a continuous water inlet-continuous water outlet operation mode, with the water flow being bottom inlet and top outlet.

[0041] The main structure of the CSTR reactor consists of a top cover 24, a bottom cover 23, an effective reaction zone 25, and a three-phase separator 9, and the main material is plexiglass.

[0042] The stirring and mixing device consists of a top motor 10, a stirring paddle 8, and a speed regulator 11. The stirring paddle 8 is driven by the top motor 10 to mix and stir the mud and water. The stirring speed is controlled by the speed regulator 11 to 110 r / min.

[0043] The constant temperature control device consists of a water bath jacket 13 and a super constant temperature water bath 14.

[0044] The water bath jacket 13 is wrapped around the outside of the effective reaction zone 25 of the CSTR reactor and is connected to the super constant temperature water bath 14 through a pipeline. Warm water circulates from bottom to top in the super constant temperature water bath 14 to control the temperature. The temperature is controlled at 32±1℃ by the constant temperature water bath device.

[0045] The aeration and anaerobic maintenance device consists of a nitrogen cylinder 1, a nitrogen cylinder pressure control valve 2, an aeration disc 4, a gas collection bag 5, and a gas washing bottle 6.

[0046] The nitrogen cylinder 1 regulates the nitrogen flow rate through the pressure control valve 2, and introduces the nitrogen into the water inlet tank 3 and aeration disc 4 through the pipeline for inert gas replacement.

[0047] The gas washing bottle 6 is connected to the water inlet tank 3. After the non-inert gas is discharged, it is closed. The remaining nitrogen is stored in the gas collection bag 5 to ensure that when the gas pressure in the water inlet tank 3 decreases, the nitrogen in the gas collection bag 5 can be replenished to maintain the anaerobic environment.

[0048] The EET enhanced dosing device consists of a dosing port 20, a storage bottle 22 and a metering pump 21. The added L-cysteine ​​or corn straw biochar is stored in the storage bottle 22 and connected to the reactor through the outlet of the metering pump 21 for intermittent dosing.

[0049] A method for enhancing the denitrification efficiency of Feammox based on an extracellular electron transport regulation strategy is proposed. The method mainly consists of two parts: Feammox system startup and enhancement of Feammox based on EET.

[0050] The Feammox system startup and operation method is as follows: Anaerobic granular sludge is selected as seed sludge. After removing the supernatant by static sedimentation, the settled sludge is collected. The sludge inoculation amount is 40% (v / v) of the effective volume of the reactor, i.e., 2 L of anaerobic granular sludge is inoculated. The reactor is a CSTR reactor with an effective reaction volume of 5 L. After inoculation, the stirring device and temperature control device are turned on simultaneously. The stirring speed is controlled at 110 r / min and the temperature is controlled at 32 ± 1 ℃. The reactor adopts a continuous influent-continuous effluent operation mode. The influent is controlled by diaphragm pump 7. The initial HRT is set to 10 hours. During operation, the anaerobic environment is maintained.

[0051] The EET-based enhancement method for Feammox is as follows: Stable Feammox sludge is selected as inoculum, with an inoculum volume of 40% (v / v) of the reactor's effective volume, i.e., 1 L of stable Feammox sludge. The reactor is a small-scale CSTR reactor with an effective reaction volume of 2.5 L. After inoculation, the stirring and temperature control devices are simultaneously activated, with the stirring speed controlled at 110 r / min and the temperature controlled at 32 ± 1 ℃. The reactor operates in a continuous influent-continuous effluent mode, with the influent controlled by a diaphragm pump 7. The initial HRT is set to 10 hours, and an anaerobic environment is maintained during operation. L-cysteine ​​and corn straw biochar are both added to the reactor using an enhanced dosing device.

[0052] The operation and enhancement process of the Feammox system is mainly divided into the following three stages:

[0053] Phase I, days 1-30, is the adaptation and establishment period for the Feammox reaction: During this phase, a low-disturbance continuous flow operation mode is used to establish the sludge basic metabolism and iron-nitrogen coupling reaction capacity, and gradually establish the basic Feammox reaction conditions. The influent Fe(III) concentration is gradually increased from 5 mg / L to 10 mg / L, and the ammonia nitrogen concentration is gradually increased from 5 mg / L to 25 mg / L.

[0054] Phase II, days 31-95, is the stabilization period of the Feammox reaction: In this phase, the continuous flow operation mode and basic operating conditions are maintained in the same manner as in Phase I (temperature 32±1℃, stirring 110 r / min, HRT 10 h). By steadily increasing the supply of Fe(III) electron acceptors and controlling the influent load, the system forms a more stable Fe(III) / Fe(II) cycle characteristic. During this phase, the influent Fe(III) concentration is stabilized at around 30 mg / L, and the ammonia nitrogen concentration is stabilized at 40 mg / L.

[0055] Phase III: Days 96-160 are the EET enhancement period for the Feammox reaction: In this phase, to overcome the electron transport bottleneck in the Feammox system and establish a complete "transmembrane electron transport and extracellular mediated transport" EET chain, under the same basic influent and operating conditions as in Phase II, two parallel reactors are selected to independently implement the following strategy for enhancement:

[0056] Strategy A is direct EET enhancement: L-cysteine ​​is added to the reactor as an EET regulator to promote the synthesis and expression of cytochrome c in functional bacterial communities. The addition method is intermittent: add one day and stop for two days, while maintaining the same influent conditions as the previous stage.

[0057] Strategy B is electron shuttle (EET) enhancement: Corn straw biochar is added to the reactor as an electron shuttle, which mediates extracellular electron transfer through its conductive network and surface functional groups, reduces electron transfer resistance and promotes Fe(III) / Fe(II) cycle; the biochar is added to the reactor in a one-time addition and supplemented later, and is effectively retained by a three-phase separator structure to prevent large amounts of loss with the effluent.

[0058] Example 1

[0059] Direct EET enhancement (L-cysteine ​​addition)

[0060] In this embodiment, L-cysteine ​​was selected as an electron transport regulator to enhance the electron transport efficiency in the Feammox reaction. The addition time was chosen after 95 days of Feammox operation, with an L-cysteine ​​dosage of 0.6 g / L, and an intermittent addition method was adopted – adding for one day and stopping for two days.

[0061] Figure 2 The changes in nitrogen trioxides after the addition of L-cysteine ​​are shown, and the changes in ammonia nitrogen (NH4) are also shown. + -N), nitrite nitrogen (NO2) - -N) and nitrate nitrogen (NO3) - The concentration of L-cysteine ​​(N) changed during reactor operation. After the addition of L-cysteine, i.e., Phase III (days 96-160), the reactor's denitrification efficiency significantly improved, with the average ammonia nitrogen removal rate increasing from 25.29% to 29.34%; the highest ammonia nitrogen removal rate increased from 38.39% to 39.48%, reaching its highest level after enhancement. NH4 + The nitrogen concentration (-N) was 19.21 mg / L. This indicates that the addition of L-cysteine ​​significantly improved the nitrogen removal efficiency of the Feammox reactor, successfully enhancing the nitrogen removal efficiency in the Feammox reaction.

[0062] Figure 3 The changes in the concentrations of Fe(III) and Fe(II) in the Feammox reactor after the addition of L-cysteine ​​are shown. With the addition of L-cysteine, the reduction of Fe(III) became more complete, with the average Fe(III) reduction rate increasing from 13.7% to 40.59%. The highest Fe(III) reduction rate after enhancement reached 66.81%, and the effluent Fe(II) concentration gradually increased to 29.15 mg / L, indicating a significant improvement in electron transfer efficiency. This demonstrates that the addition of L-cysteine ​​enhances the electron transfer efficiency in the Feammox reaction and promotes the reduction of Fe(III) to Fe(II).

[0063] Example 2

[0064] Electron shuttle (EET) enhancement (corn stalk biochar addition)

[0065] In this embodiment, corn straw biochar was selected as the electron shuttle to promote the EET mechanism in the Feammox reaction through its conductive network and surface functional groups. The addition time was chosen to be 95 days after Feammox operation, with a corn straw biochar dosage of 5 g / L, and a one-time addition followed by supplementary addition was adopted to ensure its effective retention in the reactor.

[0066] Figure 4 The ammonia nitrogen (NH4) levels in the influent and effluent of the Feammox reactor before and after the addition of corn straw biochar were demonstrated. + -N), nitrite nitrogen (NO2) - -N) and nitrate nitrogen (NO3) - Changes in ammonia nitrogen (N-N) concentration. After the addition of corn straw biochar, i.e., Phase III (days 96-160), the reactor's nitrogen removal efficiency significantly improved, with the average ammonia nitrogen removal rate increasing from 25.29% to 34.40%; the highest ammonia nitrogen removal rate increased from 38.39% to 49.25%, reaching its highest value after enhancement. NH4 + -N was 24.58 mg / L. This indicates that the addition of corn straw biochar significantly improved the nitrogen removal efficiency of the Feammox reactor.

[0067] Figure 5 The changes in Fe(III) and Fe(II) concentrations in the Feammox reactor after the addition of corn straw biochar are shown. With the addition of corn straw biochar, the reduction of Fe(III) became more complete, with the average Fe(III) reduction rate increasing from 13.7% to 45.27%. The highest Fe(III) reduction rate after enhancement reached 75.11%, and the effluent Fe(II) concentration gradually increased to 30.71 mg / L. This indicates that corn straw biochar effectively acts as an electron shuttle, promoting the reduction of Fe(III) and Fe(II). 3+ The reduction reaction converts it into Fe. 2+ This further enhances the electron transfer efficiency in the Feammox reaction.

Claims

1. A device for enhancing Feammox denitrification efficiency based on an extracellular electron transport regulation strategy, characterized in that: The installation structure includes Feammox's CSTR reactor, which includes an inlet and outlet water system, a reactor body structure, a mixing device, a temperature control device, an aeration and anaerobic maintenance device, and an EET enhancement dosing device. The water inlet and outlet system consists of an inlet, an outlet, an inlet tank, an outlet tank, a diaphragm pump, and pipelines. The diaphragm pump is an Aldos V series pump used to control the continuous inlet flow rate. The inlet tank is connected to the inlet port of the diaphragm pump via pipelines, and the outlet port of the diaphragm pump is connected to the inlet of the main reactor. The outlet tank is connected to the outlet of the main reactor. The main structure of the reactor includes a top cover, a bottom cover, an effective reaction zone, and a three-phase separator; The effective reaction zone is located between the top cover and the bottom cover, and the three-phase separator is located above the effective reaction zone; the sampling port and the sludge discharge port are located on the main structure of the reactor. The mixing device includes a motor, a stirring paddle, and a speed regulator, all mounted on the top cover. The stirring paddle is driven by the motor to mix the mud and water, and the stirring speed is controlled by the speed regulator. The stirring paddle extends into the effective reaction zone. The constant temperature control device consists of a water bath jacket and a super constant temperature water bath. The water bath jacket is wrapped around the outside of the effective reaction zone of the CSTR reactor and is connected to the super constant temperature water bath through pipelines. The super constant temperature water bath is used to control the temperature by circulating warm water from bottom to top in the water bath jacket. The aeration and anaerobic maintenance device consists of a nitrogen cylinder, a nitrogen cylinder pressure control valve, an aeration disc, a gas collection bag, and a gas washing bottle. The nitrogen cylinder regulates the nitrogen flow rate through the pressure control valve and introduces nitrogen into the aeration disc inside the water inlet tank through a pipeline for inert gas replacement. The gas washing bottle is connected to the water inlet tank and is used to close after discharging non-inert gases. The gas collection bag is connected to the water inlet tank and is used to store residual nitrogen and replenish nitrogen when the gas pressure in the water inlet tank decreases to maintain the anaerobic environment. The EET enhancement dosing device consists of a dosing port, a storage bottle, and a metering pump. The EET enhancement agent is stored in the storage bottle, which is connected to the inlet of the metering pump, and the outlet is connected to the dosing port through a pipeline for intermittent dosing.

2. The device for enhancing Feammox denitrification efficiency based on an extracellular electron transport regulation strategy according to claim 1, characterized in that: The main material of the reactor's main structure is plexiglass.

3. The device for enhancing Feammox denitrification efficiency based on an extracellular electron transport regulation strategy according to claim 1, characterized in that: The diaphragm pump is an Aldos V-series diaphragm pump.

4. A method for enhancing Feammox denitrification efficiency based on an extracellular electron transport regulation strategy according to any one of claims 1-3, characterized in that: This method is divided into two parts: the startup and operation of the Feammox system and the enhancement of Feammox based on EET. Feammox system startup and operation: Anaerobic granular sludge was selected as the seed sludge, and the sludge inoculation amount was 40% (v / v) of the effective volume of the reactor, that is, 2 L of anaerobic granular sludge was inoculated; the reactor was a CSTR reactor with an effective reaction volume of 5 L. After inoculating with sludge, the stirring device and the constant temperature control device are turned on simultaneously, and the stirring speed is controlled at 110 r / min and the temperature is controlled at 32 ± 1 ℃. Start the inlet and outlet water system and operate in a continuous inlet-continuous outlet mode. The inlet water is controlled by a diaphragm pump. The initial HRT is set to 10 hours. During operation, the anaerobic environment in the reactor is maintained by aeration and anaerobic maintenance devices. The enhancement method for Feammox based on EET is as follows: Select stable Feammox sludge as inoculum sludge, and the sludge inoculum amount is 40% (v / v) of the effective volume of the reactor, that is, 1 L of stable Feammox sludge is inoculated; the reactor is a small CSTR reactor with an effective reaction volume of 2.5L. After inoculation, the stirring device and temperature control device are turned on at the same time, and the stirring speed is controlled at 110 r / min and the temperature is controlled at 32 ± 1 ℃. The reactor operates in a continuous influent-continuous effluent mode. The influent is controlled by a diaphragm pump, and the initial HRT is set to 10 hours. An anaerobic environment is maintained during operation. L-cysteine ​​and corn straw biochar are added to the reactor by an enhanced dosing device. The Feammox system operation and enhancement process can be mainly divided into the following three stages: Phase I, the adaptation and establishment period of the Feammox reaction: In this phase, the sludge basic metabolism and iron-nitrogen coupling reaction capacity are established by using a low-disturbance continuous flow operation mode, and the basic Feammox reaction conditions are gradually established. The influent Fe(III) concentration is gradually increased from 5 mg / L to 10 mg / L, and the ammonia nitrogen concentration is gradually increased from 5 mg / L to 25 mg / L. Phase II, the stabilization period of the Feammox reaction: In this phase, the continuous flow operation mode and basic operating conditions are maintained in the same manner as in Phase I (temperature 32±1℃, stirring 110r / min, HRT 10h). By steadily increasing the supply of Fe(III) electron acceptors and controlling the influent load, the system forms a more stable Fe(III) / Fe(II) cycle characteristic. In this phase, the influent Fe(III) concentration is stabilized at around 30mg / L, and the ammonia nitrogen concentration is stabilized at 40mg / L. Phase III, EET Enhancement of the Feammox Reaction: In this phase, to overcome the electron transport bottleneck in the Feammox system and establish a complete EET chain of "transmembrane electron transport - extracellular mediated transport," two parallel reactors were selected to implement the process independently, while maintaining the same basic feed water conditions and operating conditions as in Phase II. At least one of the following strategies was employed for EET enhancement: Strategy A is direct EET enhancement: L-cysteine ​​is added to the reactor as an EET regulator to promote the synthesis and expression of cytochrome c in functional bacterial communities. The addition method is intermittent: add one day and stop for two days, while maintaining the same influent conditions as the previous stage. Strategy B is to enhance the electron shuttle (EET): corn straw biochar is added to the reactor as an electron shuttle. Through its conductive network and surface functional groups, extracellular electron transfer is mediated, reducing electron transfer resistance and promoting the Fe(III) / Fe(II) cycle. The biochar is added in a one-time addition to the reactor and then supplemented later. It is effectively retained by the three-phase separator (9) structure to prevent a large amount of loss with the effluent.

5. The method for enhancing Feammox denitrification efficiency based on an extracellular electron transport regulation strategy according to claim 4, characterized in that: During the startup and operation of the Feammox system, the anaerobic granular sludge undergoes static sedimentation to remove the supernatant before inoculation.

6. The method for enhancing Feammox denitrification efficiency based on an extracellular electron transport regulation strategy according to claim 4, characterized in that: Phase I, the adaptation and establishment period of the Feammox reaction, corresponds to days 1 to 30; Phase II, the stabilization period of the Feammox reaction, corresponds to days 31 to 95; and Phase III, the EET enhancement period of the Feammox reaction, corresponds to days 96 to 160.

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