A sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater advanced denitrification system and method

Abstract

The application relates to the technical field of sewage treatment, in particular to a sulfur autotrophy-anaerobic ammonia oxidation coupled sewage advanced denitrification system and method. + ‑ The application regulates the NH4 + ‑ ratio in the influent by mixing raw water and tail water in an anaerobic tank; nanometer zero-valent iron is embedded into NaY molecular sieve to obtain NaY-nZVI composite materials, which are then loaded onto PVDC fibers to obtain modified PVDC fibers; the modified PVDC fibers are used to prepare a three-dimensional network PVDC carrier fixed biofilm to realize efficient cooperation of sulfur autotrophy / heterotrophic short-cut denitrification and anaerobic ammonia oxidation denitrification. The system has high denitrification efficiency, does not need external carbon source, greatly reduces the operation cost, and after backwashing, the activity recovery rate of the biofilm is as high as more than 90%.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, specifically to a sulfur autotrophic-anaerobic ammonia oxidation coupled deep denitrification system and method for wastewater. Background Technology

[0002] Anaerobic ammonia oxidation (AMO) is recognized as one of the most economical nitrogen removal technologies. AMO is a biological reaction under anaerobic conditions, using ammonia as an electron donor and nitrite as an electron acceptor to produce nitrogen and nitrate. It includes two processes: first, catabolic metabolism, where ammonia acts as the electron donor and nitrite as the electron acceptor, reacting in a 1:1.32 ratio to produce nitrogen and storing the energy as ATP; second, anabolism, where nitrite acts as the electron acceptor, providing reducing power, and utilizing carbon dioxide and ATP from catabolic metabolism to synthesize cellular substances, producing nitrate in the process.

[0003] Chinese patent application CN111661924A discloses a system and application of sulfur autotrophic short-cut denitrification coupled with anaerobic ammonia oxidation for nitrogen removal. Wastewater undergoes anaerobic reaction and anaerobic-aerobic reaction in an anaerobic reactor and a nitrification reactor, respectively. After aerobic nitrification, the wastewater is placed in a sulfur autotrophic short-cut denitrification reactor, where nitrate nitrogen is reduced to nitrite nitrogen, resulting in nitrite nitrogen accumulation. The wastewater after short-cut denitrification and the ammonia-rich wastewater after anaerobic treatment are then introduced into an anaerobic ammonia oxidation reactor to remove nitrogen.

[0004] However, the aforementioned literature and existing technologies all suffer from the same problem: stable short-cut nitrification is difficult to control. The main method to achieve short-cut nitrification is to enhance the growth of AOB while inhibiting the growth of NOB to achieve higher NO2. - Accumulation rates can be achieved through adjustments to environmental factors such as temperature, pH, and dissolved oxygen, as well as through proper sludge removal. However, in practical engineering applications, these control measures are often difficult to implement due to the large daily processing volume. Furthermore, anaerobic ammonia oxidation (ANAO) is continuously being phased out due to a lack of substrate. Therefore, coupling ANAO with sulfur autotrophic short-cut denitrification can achieve higher nitrite ion accumulation, thereby providing a substrate to enhance the growth of ANAO bacteria. In addition, the ANAO process is highly sensitive to temperature changes, which affect the activity of related enzymes during the reaction. The optimal growth temperature for ANAO bacteria is 30-35℃. However, when the temperature is below 11℃ or above 45℃, the activity of ANAO bacteria is completely inhibited. Biofilm attachment can increase the amount of microorganisms; therefore, there is a need for an enrichment device and method for ANAO bacteria that can achieve heterotrophic short-cut denitrification coupled with sulfur autotrophic short-cut denitrification. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a sulfur autotrophic-anaerobic ammonia oxidation coupled deep denitrification system and method for wastewater. This system effectively enriches anaerobic ammonia oxidizing bacteria, increases the amount of microorganisms through a self-made biofilm, and eliminates the need for an external carbon source, thus reducing operating costs and demonstrating promising application prospects.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system, including an influent mixing unit, an upflow reaction tower, and a backwashing unit. The influent mixing unit and the backwashing unit are respectively connected to the bottom of the upflow reaction tower. The upflow reaction tower is provided with a multi-layer PVDC three-dimensional mesh filter media layer. The multi-layer PVDC three-dimensional mesh filter media layer includes a three-dimensional mesh PVDC carrier and sulfur autotrophic particles, anaerobic ammonia oxidizing bacteria, and sulfur autotrophic bacteria disposed in the PVDC carrier.

[0008] Preferably, the PVDC three-dimensional mesh filter layer has a thickness of 30-50 mm, a porosity of ≥95%, and a tensile strength of ≥15 MPa.

[0009] Preferably, the three-dimensional mesh PVDC carrier is formed by bonding several modified PVDC fibers and has a "micropore-macropore" gradient structure, with a surface pore diameter of 1-1.5 mm and an internal pore diameter of 2-2.2 mm.

[0010] Preferably, the modified PVDC fiber is obtained by mixing and reacting PVDC fiber with NaY-nZVI composite material modified with coupling agent KH550 after acid treatment and surface modification with coupling agent KH560 in toluene.

[0011] Preferably, the method for preparing the modified PVDC fiber includes the following steps:

[0012] Step 1:

[0013] S1: NaY-type molecular sieves were vacuum dried at 105-110℃ to constant weight. After cooling, the dried NaY-type molecular sieves were added to an acidic ferrous sulfate solution under nitrogen protection. After ultrasonic dispersion for 1-2 hours, the solid was collected by filtration and washed with deionized water. The solid was then dispersed in deionized water, and sodium borohydride solution was added and stirred for 30-60 minutes. The mixture was then filtered, washed with water, and freeze-dried under vacuum to obtain the NaY-nZVI composite material. The content of nano-zero valent iron in the NaY-nZVI composite material was 7-10 wt.%.

[0014] S2: By weight, 1-2 parts of NaY-nZVI composite material, 96-98 parts of toluene, and 1-2 parts of coupling agent KH560 are mixed, ultrasonically dispersed for 30-60 min, and reacted at 80-85℃ for 6-8 h. After filtration, washing, and drying, epoxy-grafted NaY-nZVI composite material is obtained.

[0015] Step 2:

[0016] PVDC fibers with a diameter of 1-2 mm were extracted by soaking in acetone for 48 hours, then removed and acidified in concentrated nitric acid at 60-70℃ for 2-3 hours, and washed with water until neutral to obtain pretreated PVDC fibers; the pretreated PVDC fibers were soaked in an ethanol solution of 3 wt.% coupling agent KH550 and refluxed under nitrogen for 2-3 hours to obtain amino-grafted PVDC fibers.

[0017] Step 3:

[0018] Amino-grafted PVDC fibers and epoxy-grafted NaY-nZVI composites were dispersed in toluene, refluxed for 8-10 h, cooled, filtered, washed with anhydrous ethanol, and vacuum dried to obtain modified PVDC fibers; wherein the mass ratio of NaY-nZVI composites to PVDC fibers was (1-3):100.

[0019] Preferably, the particle size of the sulfur autotrophic particles is 3-5 mm.

[0020] Preferably, the method for preparing the sulfur autotrophic particles is as follows: pyrite powder, magnetite powder, calcite powder, sulfur powder, and catalyst are mixed and granulated in a mass ratio of (1-12):(1-3):(1-3):3:(1-3).

[0021] Secondly, this application provides a deep denitrification method for wastewater coupled with sulfur autotrophy and anaerobic ammonia oxidation, which is based on the above-mentioned deep denitrification system for wastewater. The raw water and effluent from the anoxic tank are mixed and fed into the influent mixing unit. The influent from the influent mixing unit is sent into the upflow reaction tower for denitrification treatment. The multi-layer PVDC three-dimensional mesh filter media layer in the upflow reaction tower is flushed by the backwashing unit.

[0022] Preferably, the NH4 in the influent... + / NO3 - The molar ratio is 0.8-1.2; among which, the ammonia nitrogen content in the raw water of the anoxic pool is 20-30 mg / L and the nitrate nitrogen content is 15-20 mg / L.

[0023] Preferably, the hydraulic load of the upflow reaction tower is 0.6-1.2m. 3 / (m 2The hydraulic residence time of the empty tower of the upflow reactor is 2-3 hours, and the operating temperature of the upflow reactor is 10-35℃.

[0024] Preferably, the backwashing unit employs a combined water and steam backwash, with a water flushing intensity of 8-10 L / (m²). 2 ·s), air impact intensity 15-20L / (m 2 ·s), the rinsing cycle is 7-10 days.

[0025] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0026] (1) This application discloses a sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system and method, which achieves precise control of the substrate ratio by mixing the raw water and effluent in the anoxic tank, thereby matching the stoichiometric ratio (NH4+) in the anaerobic ammonia oxidation reaction. + NO2 - =1:1.32). After coupling, sulfur autotrophic denitrification can accumulate nitrite for anaerobic ammonia oxidation, avoiding insufficient nitrite concentration.

[0027] (2) This application mixes pyrite powder, magnetite powder, calcite powder, sulfur powder, and catalyst in a certain proportion and granulates them to prepare sulfur autotrophic particles. On the one hand, iron, as an essential nutrient element for the growth and metabolism of anaerobic ammonia-oxidizing bacteria, can significantly improve the activity of anaerobic ammonia-oxidizing bacteria; Fe released from pyrite... 2+ With PO4 3- Fe3(PO4)2 precipitate is generated, achieving a total phosphorus removal rate of ≥85% in water. Furthermore, this application also controls the component ratios during the preparation of sulfur autotrophic particles to avoid SO4 precipitate formation. 2- Excessive content inhibits the growth of anaerobic ammonia-oxidizing bacteria. In sulfur-autotrophic particulate matter, magnetite and pyrite can also produce a synergistic effect, Fe... 2+ It promotes heme synthesis in anaerobic ammonia oxidizing bacteria, while sulfur autotrophic denitrification inhibits sulfate production, thus avoiding excessive sulfate content that inhibits the growth of anaerobic ammonia oxidizing bacteria.

[0028] (3) This application also includes a PVDC three-dimensional mesh filter layer, which is made of several modified PVDC fibers bonded together. It has a gradient structure of "micropores-macropores" (surface pore size is 1 mm, internal pore size is 2 mm), making it easier for bacteria to adhere to the PVDC three-dimensional mesh filter layer. Furthermore, in preparing the PVDC three-dimensional mesh filter layer, this application first embeds nano-zero-valent iron into NaY molecular sieves, then modifies the NaY-nZVI composite material with coupling agent KH560, introducing epoxy groups onto its surface. Simultaneously, it uses coupling agent KH550 to modify the PVDC fibers, introducing amino groups onto their surface. The reaction between epoxy groups and amino groups modifies the NaY-nZVI composite material onto the PVDC fibers, resulting in modified PVDC fibers. The NaY-nZVI composite material effectively overcomes the disadvantages of nano-zero-valent iron's easy agglomeration and passivation, while retaining the strong reducing properties of zero-valent iron. Under aerobic conditions, the presence of highly reducing zero-valent iron reacts with dissolved oxygen in the water, thus consuming the dissolved oxygen around the modified PVDC fibers. This creates an anoxic zone within the internal pores of the PVDC three-dimensional mesh filter media layer in a shorter time, providing favorable environmental conditions for the reproduction of anaerobic microorganisms. This further enhances the adhesion of bacteria to the PVDC three-dimensional mesh filter media layer, achieving a bacterial density ≥10⁹ CFU / g. Simultaneously, it accelerates the formation of biofilm on the PVDC three-dimensional mesh filter media layer, with biofilm activity recovering to over 90% within 24 hours after backwashing. Biofilm formation effectively maintains a high quantity of active microorganisms, laying the foundation for efficient nitrogen removal in the coupled system. Attached Figure Description

[0029] Figure 1 This is a physical image of the PVDC three-dimensional mesh filter media layer in an upflow reaction tower. Detailed Implementation

[0030] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0031] In this application, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0032] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0033] Furthermore, the terms "first" and "second" appearing in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] Example 1:

[0035] A sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system, the system comprising an influent mixing unit, an upflow reaction tower and a backwashing unit; the influent mixing unit and the backwashing unit are respectively connected to the bottom end of the upflow reaction tower.

[0036] The upflow reaction tower is equipped with multiple layers of PVDC three-dimensional mesh filter media (such as...). Figure 1 As shown in the figure, the PVDC three-dimensional mesh filter layer includes a three-dimensional mesh PVDC carrier and sulfur autotrophic particles, anaerobic ammonia oxidizing bacteria and sulfur autotrophic bacteria disposed in the PVDC carrier.

[0037] The PVDC three-dimensional mesh filter layer has a thickness of 50 mm, a porosity of 95%, and a tensile strength of 15 MPa.

[0038] The three-dimensional mesh PVDC carrier is formed by bonding several modified PVDC fibers and has a "micropore-macropore" gradient structure with a surface pore diameter of 1 mm and an internal pore diameter of 2 mm.

[0039] The method for preparing the modified PVDC fiber includes the following steps:

[0040] Step 1:

[0041] S1: NaY-type molecular sieves were vacuum dried at 105℃ to constant weight. After cooling, the dried NaY-type molecular sieves were added to an acidic ferrous sulfate solution under nitrogen protection. After ultrasonic dispersion for 1 hour, the solid was collected by filtration and washed with deionized water. The solid was then dispersed in deionized water, and sodium borohydride solution was added and stirred for 30 minutes. The mixture was then filtered, washed with water, and freeze-dried under vacuum to obtain the NaY-nZVI composite material. The content of nano-zero valent iron in the NaY-nZVI composite material was 8.5 wt.%.

[0042] S2: Mix 2g of NaY-nZVI composite material, 96g of toluene and 2g of coupling agent KH560, disperse ultrasonically for 30min, react at 80℃ for 6h, filter, wash and dry to obtain epoxy-grafted NaY-nZVI composite material.

[0043] Step 2:

[0044] PVDC fibers with a diameter of 1 mm were extracted by soaking in acetone for 48 h, and then placed in concentrated nitric acid at 60 °C for 2 h. After washing with water until neutral, pretreated PVDC fibers were obtained. The pretreated PVDC fibers were then soaked in an ethanol solution of 3 wt.% coupling agent KH550 and refluxed under nitrogen for 2 h to obtain amino-grafted PVDC fibers.

[0045] Step 3:

[0046] Amino-grafted PVDC fibers and epoxy-grafted NaY-nZVI composites were dispersed in toluene, refluxed for 8 hours, cooled, filtered, washed with anhydrous ethanol, and vacuum dried to obtain modified PVDC fibers; wherein the mass ratio of NaY-nZVI composites to PVDC fibers was 1:100.

[0047] The method for preparing the sulfur autotrophic particles is as follows: pyrite powder, magnetite powder, calcite powder, sulfur powder, and catalyst are mixed and granulated in a mass ratio of 1:1:1:3:1, with a particle size of 3 mm.

[0048] When performing deep denitrification treatment on wastewater, the system mixes the raw water and effluent from the anoxic tank into the influent mixing unit. The influent from the influent mixing unit is then sent into the upflow reaction tower for denitrification treatment. The multi-layer PVDC three-dimensional mesh filter media layer in the upflow reaction tower is flushed through the backwashing unit.

[0049] In the influent water distribution unit of this system, NH4 in the influent water + / NO3 - The molar ratio is 1.1; the ammonia nitrogen content in the raw water of the anoxic pool is 25 mg / L, and the nitrate nitrogen content is 15 mg / L.

[0050] The hydraulic load of the upflow reactor in this system is 1.2m. 3 / (m 2 ·h).

[0051] The hydraulic residence time of the empty tower of the flow reactor in this system is 2 hours.

[0052] The operating temperature of the flow reaction tower in this system is 10℃.

[0053] The system's backwashing unit employs a combined water and steam backwash, with a water flushing intensity of 8 L / (m²). 2 ·s), air impact intensity 15L / (m 2 ·s), the rinsing cycle is 7 days.

[0054] Example 2:

[0055] A sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system, the system comprising an influent mixing unit, an upflow reaction tower and a backwashing unit; the influent mixing unit and the backwashing unit are respectively connected to the bottom end of the upflow reaction tower.

[0056] The upflow reaction tower is equipped with a multi-layer PVDC three-dimensional mesh filter media layer, which includes a three-dimensional mesh PVDC carrier and sulfur autotrophic particles, anaerobic ammonia oxidizing bacteria and sulfur autotrophic bacteria disposed in the PVDC carrier.

[0057] The PVDC three-dimensional mesh filter layer has a thickness of 50 mm, a porosity of 95%, and a tensile strength of 15 MPa.

[0058] The three-dimensional mesh PVDC carrier is formed by bonding several modified PVDC fibers and has a "micropore-macropore" gradient structure with a surface pore diameter of 1 mm and an internal pore diameter of 2 mm.

[0059] The method for preparing the modified PVDC fiber includes the following steps:

[0060] Step 1:

[0061] S1: NaY-type molecular sieves were vacuum dried at 110℃ to constant weight. After cooling, the dried NaY-type molecular sieves were added to an acidic ferrous sulfate solution under nitrogen protection. After ultrasonic dispersion for 1.5 h, the solid was collected by filtration and washed with deionized water. The solid was then dispersed in deionized water, and sodium borohydride solution was added and stirred for 45 min. The mixture was then filtered, washed with water, and freeze-dried under vacuum to obtain the NaY-nZVI composite material. The content of nano-zero valent iron in the NaY-nZVI composite material was 8.5 wt.%.

[0062] S2: Mix 2g of NaY-nZVI composite material, 96g of toluene and 2g of coupling agent KH560, disperse ultrasonically for 50min, react at 85℃ for 7h, filter, wash and dry to obtain epoxy-grafted NaY-nZVI composite material.

[0063] Step 2:

[0064] PVDC fibers with a diameter of 1.3 mm were extracted by soaking in acetone for 48 h, and then placed in concentrated nitric acid at 65 °C for 2.5 h. After washing with water until neutral, pretreated PVDC fibers were obtained. The pretreated PVDC fibers were then soaked in an ethanol solution of 3 wt.% coupling agent KH550 and refluxed under nitrogen for 2.5 h to obtain amino-grafted PVDC fibers.

[0065] Step 3:

[0066] Amino-grafted PVDC fibers and epoxy-grafted NaY-nZVI composites were dispersed in toluene, refluxed for 9 hours, cooled, filtered, washed with anhydrous ethanol, and vacuum dried to obtain modified PVDC fibers; wherein the mass ratio of NaY-nZVI composites to PVDC fibers was 1.8:100.

[0067] The method for preparing the sulfur autotrophic particles is as follows: pyrite powder, magnetite powder, calcite powder, sulfur powder, and catalyst are mixed and granulated in a mass ratio of 7:2.4:2:3:1.6, and the particle size is 3 mm.

[0068] When performing deep denitrification treatment on wastewater, the system mixes the raw water and effluent from the anoxic tank into the influent mixing unit. The influent from the influent mixing unit is then sent into the upflow reaction tower for denitrification treatment. The multi-layer PVDC three-dimensional mesh filter media layer in the upflow reaction tower is flushed through the backwashing unit.

[0069] In the influent water distribution unit of this system, NH4 in the influent water + / NO3 - The molar ratio is 1.1; the ammonia nitrogen content in the raw water of the anoxic pool is 25 mg / L, and the nitrate nitrogen content is 15 mg / L.

[0070] The hydraulic load of the upflow reactor in this system is 1.2m. 3 / (m 2 ·h).

[0071] The hydraulic residence time of the empty tower of the flow reactor in this system is 2 hours.

[0072] The operating temperature of the flow reaction tower in this system is 10℃.

[0073] The system's backwashing unit employs a combined water and steam backwash, with a water flushing intensity of 8 L / (m²). 2 ·s), air impact intensity 15L / (m 2 ·s), the rinsing cycle is 7 days.

[0074] Example 3:

[0075] A sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system, the system comprising an influent mixing unit, an upflow reaction tower and a backwashing unit; the influent mixing unit and the backwashing unit are respectively connected to the bottom end of the upflow reaction tower.

[0076] The upflow reaction tower is equipped with a multi-layer PVDC three-dimensional mesh filter media layer, which includes a three-dimensional mesh PVDC carrier and sulfur autotrophic particles, anaerobic ammonia oxidizing bacteria and sulfur autotrophic bacteria disposed in the PVDC carrier.

[0077] The PVDC three-dimensional mesh filter layer has a thickness of 50 mm, a porosity of 95%, and a tensile strength of 15 MPa.

[0078] The three-dimensional mesh PVDC carrier is formed by bonding several modified PVDC fibers and has a "micropore-macropore" gradient structure with a surface pore diameter of 1 mm and an internal pore diameter of 2 mm.

[0079] The method for preparing the modified PVDC fiber includes the following steps:

[0080] Step 1:

[0081] S1: NaY-type molecular sieves were vacuum dried at 110℃ to constant weight. After cooling, the dried NaY-type molecular sieves were added to an acidic ferrous sulfate solution under nitrogen protection. After ultrasonic dispersion for 2 hours, the solid was collected by filtration and washed with deionized water. The solid was then dispersed in deionized water, and sodium borohydride solution was added and stirred for 60 minutes. The mixture was then filtered, washed with water, and freeze-dried under vacuum to obtain the NaY-nZVI composite material. The content of nano-zero valent iron in the NaY-nZVI composite material was 8.5 wt.%.

[0082] S2: Mix 2g of NaY-nZVI composite material, 96g of toluene and 2g of coupling agent KH560, disperse ultrasonically for 60min, react at 85℃ for 8h, filter, wash and dry to obtain epoxy-grafted NaY-nZVI composite material.

[0083] Step 2:

[0084] PVDC fibers with a diameter of 2 mm were extracted by soaking in acetone for 48 h, and then placed in concentrated nitric acid at 70 °C for 3 h. After washing with water until neutral, pretreated PVDC fibers were obtained. The pretreated PVDC fibers were then soaked in an ethanol solution of 3 wt.% coupling agent KH550 and refluxed under nitrogen for 3 h to obtain amino-grafted PVDC fibers.

[0085] Step 3:

[0086] Amino-grafted PVDC fibers and epoxy-grafted NaY-nZVI composites were dispersed in toluene, refluxed for 10 h, cooled, filtered, washed with anhydrous ethanol, and vacuum dried to obtain modified PVDC fibers; wherein the mass ratio of NaY-nZVI composites to PVDC fibers was 3:100.

[0087] The method for preparing the sulfur autotrophic particles is as follows: pyrite powder, magnetite powder, calcite powder, sulfur powder, and catalyst are mixed and granulated in a mass ratio of 12:2:3:3:2, with a particle size of 3 mm.

[0088] When performing deep denitrification treatment on wastewater, the system mixes the raw water and effluent from the anoxic tank into the influent mixing unit. The influent from the influent mixing unit is then sent into the upflow reaction tower for denitrification treatment. The multi-layer PVDC three-dimensional mesh filter media layer in the upflow reaction tower is flushed through the backwashing unit.

[0089] In the influent water distribution unit of this system, NH4 in the influent water + / NO3 - The molar ratio is 1.1; the ammonia nitrogen content in the raw water of the anoxic pool is 25 mg / L, and the nitrate nitrogen content is 15 mg / L.

[0090] The hydraulic load of the upflow reactor in this system is 1.2m. 3 / (m 2 ·h).

[0091] The hydraulic residence time of the empty tower of the flow reactor in this system is 2 hours.

[0092] The operating temperature of the flow reaction tower in this system is 10℃.

[0093] The system's backwashing unit employs a combined water and steam backwash, with a water flushing intensity of 8 L / (m²). 2 ·s), air impact intensity 15L / (m 2 ·s), the rinsing cycle is 7 days.

[0094] Comparative Example 1:

[0095] Denitrification is performed using the traditional MBBR process.

[0096] The MBBR biological packing balls are made of PVDC material, with polyurethane sponge as the internal filler. Methanol is used as the external carbon source, and the sulfur autotrophic particles from Example 1 are inserted into the polyurethane spherical biological packing. After microorganisms attach to the surface of the polyurethane spherical biological packing and form a biofilm, oxygen cannot enter the packing under the action of the biofilm, providing an anaerobic environment for denitrification inside the balls.

[0097] Comparative Example 2:

[0098] PVDC fibers with unloaded NaY-nZVI composite material were used, and the remaining parameters were the same as in Example 1.

[0099] A sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system, the system comprising an influent mixing unit, an upflow reaction tower and a backwashing unit; the influent mixing unit and the backwashing unit are respectively connected to the bottom end of the upflow reaction tower.

[0100] The upflow reaction tower is equipped with a multi-layer PVDC three-dimensional mesh filter media layer, which includes a three-dimensional mesh PVDC carrier and sulfur autotrophic particles, anaerobic ammonia oxidizing bacteria and sulfur autotrophic bacteria disposed in the PVDC carrier.

[0101] The PVDC three-dimensional mesh filter layer has a thickness of 50 mm, a porosity of 95%, and a tensile strength of 15 MPa.

[0102] The three-dimensional mesh PVDC carrier is formed by bonding several modified PVDC fibers and has a "micropore-macropore" gradient structure with a surface pore diameter of 1 mm and an internal pore diameter of 2 mm.

[0103] The method for preparing the sulfur autotrophic particles is as follows: pyrite powder, magnetite powder, calcite powder, sulfur powder, and catalyst are mixed and granulated in a mass ratio of 7:2.4:2:3:1.6, and the particle size is 3 mm.

[0104] When performing deep denitrification treatment on wastewater, the system mixes the raw water and effluent from the anoxic tank into the influent mixing unit. The influent from the influent mixing unit is then sent into the upflow reaction tower for denitrification treatment. The multi-layer PVDC three-dimensional mesh filter media layer in the upflow reaction tower is flushed through the backwashing unit.

[0105] In the influent water distribution unit of this system, NH4 in the influent water + / NO3 - The molar ratio is 1.1; the ammonia nitrogen content in the raw water of the anoxic pool is 25 mg / L, and the nitrate nitrogen content is 15 mg / L.

[0106] The hydraulic load of the upflow reactor in this system is 1.2m. 3 / (m 2 ·h).

[0107] The hydraulic residence time of the empty tower of the flow reactor in this system is 2 hours.

[0108] The operating temperature of the flow reaction tower in this system is 10℃.

[0109] The system's backwashing unit employs a combined water and steam backwash, with a water flushing intensity of 8 L / (m²). 2 ·s), air impact intensity 15L / (m 2 ·s), the rinsing cycle is 7 days.

[0110] Comparative Example 3:

[0111] PVDC fibers with surface-loaded NaY molecular sieves were used, and the remaining parameters were the same as in Example 1.

[0112] A sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system, the system comprising an influent mixing unit, an upflow reaction tower and a backwashing unit; the influent mixing unit and the backwashing unit are respectively connected to the bottom end of the upflow reaction tower.

[0113] The upflow reaction tower is equipped with a multi-layer PVDC three-dimensional mesh filter media layer, which includes a three-dimensional mesh PVDC carrier and sulfur autotrophic particles, anaerobic ammonia oxidizing bacteria and sulfur autotrophic bacteria disposed in the PVDC carrier.

[0114] The three-dimensional mesh PVDC carrier is formed by bonding several modified PVDC fibers and has a "micropore-macropore" gradient structure with a surface pore diameter of 1 mm and an internal pore diameter of 2 mm.

[0115] The method for preparing the modified PVDC fiber includes the following steps:

[0116] Step 1:

[0117] 2g of NaY molecular sieve, 96g of toluene and 2g of coupling agent KH560 were mixed, ultrasonically dispersed for 30min, and reacted at 80℃ for 6h. After filtration, washing and drying, epoxy-grafted NaY molecular sieve was obtained.

[0118] Step 2:

[0119] PVDC fibers with a diameter of 1 mm were extracted by soaking in acetone for 48 h, and then placed in concentrated nitric acid at 60 °C for 2 h. After washing with water until neutral, pretreated PVDC fibers were obtained. The pretreated PVDC fibers were then soaked in an ethanol solution of 3 wt.% coupling agent KH550 and refluxed under nitrogen for 2 h to obtain amino-grafted PVDC fibers.

[0120] Step 3:

[0121] Amino-grafted PVDC fibers and epoxy-grafted NaY molecular sieves were dispersed in toluene, refluxed for 8 hours, cooled, filtered, washed with anhydrous ethanol, and vacuum dried to obtain modified PVDC fibers; wherein the mass ratio of NaY-nZVI composite material to PVDC fibers was 1:100.

[0122] The method for preparing the sulfur autotrophic particles is as follows: pyrite powder, magnetite powder, calcite powder, sulfur powder, and catalyst are mixed and granulated in a mass ratio of 1:1:1:3:1, with a particle size of 3 mm.

[0123] When performing deep denitrification treatment on wastewater, the system mixes the raw water and effluent from the anoxic tank into the influent mixing unit. The influent from the influent mixing unit is then sent into the upflow reaction tower for denitrification treatment. The multi-layer PVDC three-dimensional mesh filter media layer in the upflow reaction tower is flushed through the backwashing unit.

[0124] In the influent water distribution unit of this system, NH4 in the influent water + / NO3 - The molar ratio is 1.1; the ammonia nitrogen content in the raw water of the anoxic pool is 25 mg / L, and the nitrate nitrogen content is 15 mg / L.

[0125] The hydraulic load of the upflow reactor in this system is 1.2m. 3 / (m 2 ·h).

[0126] The hydraulic residence time of the empty tower of the flow reactor in this system is 2 hours.

[0127] The operating temperature of the flow reaction tower in this system is 10℃.

[0128] The system's backwashing unit employs a combined water and steam backwash, with a water flushing intensity of 8 L / (m²). 2 ·s), air impact intensity 15L / (m 2 ·s), the rinsing cycle is 7 days.

[0129] The systems from Examples 1-3 and Comparative Examples 1-3 were applied to the effluent of a wastewater treatment plant. Table 1 shows the parameters of various indicators in the effluent of the wastewater treatment plant, and the results after treatment are shown in Table 2 below.

[0130] Among them, NO3-N is tested using ultraviolet spectrophotometry according to the reference standard HJ / T 346-2007; NH4 + -N is tested using Nessler's reagent spectrophotometry according to standard HJ 535-2009; TN is tested using ultraviolet spectrophotometry according to standard HJ / T 346-2007; TP is tested using molybdenum antimony spectrophotometry according to standard HJ 632-2011; and COD is tested using rapid digestion spectrophotometry according to standard HJ / T 399-2007.

[0131] Table 1. Parameters of various indicators in wastewater effluent from wastewater treatment plants

[0132] project content <![CDATA[NH4 + -N]]> 8mg / L <![CDATA[NO3 - -N]]> 25mg / L TN 30mg / L TP 1.2 mg / L COD 50mg / L

[0133] Table 2. Parameters of various indicators of wastewater effluent after treatment at wastewater treatment plants

[0134]

[0135] Compared with Comparative Example 1, Example 1 incorporated a PVDC three-dimensional mesh filter layer. This PVDC three-dimensional mesh filter layer was made of several modified PVDC fibers bonded together, possessing a gradient structure of "micropores-macropores" (surface pore size 1 mm, internal pore size 2 mm), making it easier for microorganisms to adhere to the PVDC three-dimensional mesh filter layer. Compared with traditional process systems, this resulted in lower operating energy consumption, lower carbon source costs, and lower sludge production.

[0136] Compared with Comparative Example 2, Example 1 first embedded nano-zero-valent iron into NaY molecular sieves, then modified the NaY-nZVI composite material with coupling agent KH560 to introduce epoxy groups on its surface. Simultaneously, PVDC fibers were modified with coupling agent KH550 to introduce amino groups on their surface. The reaction between epoxy and amino groups was then used to modify the NaY-nZVI composite material onto the PVDC fibers, resulting in modified PVDC fibers. The NaY-nZVI composite material effectively overcomes the disadvantages of nano-zero-valent iron's easy agglomeration and passivation, while retaining the strong reducing properties of zero-valent iron. Under conditions where there is a small amount of dissolved oxygen in the water, the presence of strongly reducing zero-valent iron will react with it, thus creating an anoxic region within the internal voids of the PVDC three-dimensional mesh filter layer in a shorter time. This provides favorable environmental conditions for the reproduction of anaerobic microorganisms and accelerates the formation of biofilm on the PVDC three-dimensional mesh filter layer. Therefore, the denitrification effect in Example 1 is superior to that in Comparative Example 2.

[0137] Data from Example 1 and Comparative Example 3 show that simply loading NaY molecular sieves onto the surface of PVDC fibers cannot achieve the desired effect of this application: that is, to create an internal environment conducive to bacterial growth in the middle of the filter media layer. Therefore, this control group indicates that the effective component in this application is actually the nano-zero-valent iron in the NaY-nZVI composite material. In addition, it should be noted that NaY molecular sieves also have certain adsorption properties. Based on the experimental results of Comparative Examples 2 and 3, it can be seen that the presence of NaY improves the denitrification rate of the system to a certain extent, but the improvement is not significant.

[0138] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0139] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system, comprising an influent mixing unit, an upflow reaction tower, and a backwashing unit, wherein the influent mixing unit and the backwashing unit are respectively connected to the bottom end of the upflow reaction tower, characterized in that: The upflow reaction tower is equipped with a multi-layer PVDC three-dimensional mesh filter material layer, which includes a three-dimensional mesh PVDC carrier and sulfur autotrophic particles, anaerobic ammonia oxidizing bacteria and sulfur autotrophic bacteria disposed in the PVDC carrier; the three-dimensional mesh PVDC carrier is formed by bonding several modified PVDC fibers, with a surface pore size of 1-1.5 mm and an internal pore size of 2-2.2 mm; the modified PVDC fibers are obtained by mixing and reacting PVDC fibers with NaY-nZVI composite material modified by coupling agent KH560 after acid treatment and surface modification with coupling agent KH550 in toluene; the sulfur autotrophic particles are prepared by mixing and granulating pyrite powder, magnetite powder, calcite powder, sulfur powder and catalyst in a mass ratio of (1-12):(1-3):(1-3):3:(1-3).

2. The sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system according to claim 1, characterized in that: The PVDC three-dimensional mesh filter media layer has a thickness of 30-50mm, a porosity of ≥95%, and a tensile strength of ≥15MPa.

3. The sulfur autotrophic-anaerobic ammonia oxidation coupled wastewater deep denitrification system according to claim 1, characterized in that: The particle size of the sulfur autotrophic particles is 3-5 mm.

4. A method for deep denitrification of wastewater coupled with sulfur autotrophic-anaerobic ammonia oxidation, implemented based on the deep denitrification system of any one of claims 1 to 3, characterized in that: The raw water and effluent from the anoxic tank are mixed and fed into the influent mixing unit. The influent from the influent mixing unit is then sent into the upflow reactor for denitrification treatment. The multi-layer PVDC three-dimensional mesh filter media layer in the upflow reactor is flushed by the backwashing unit.

5. The deep nitrogen removal method for wastewater coupled with sulfur autotrophic-anaerobic ammonia oxidation according to claim 4, characterized in that: The influent contains NH4 + / NO3 ⁻ The molar ratio is 0.8-1.2; among which, the ammonia nitrogen content in the raw water of the anoxic pool is 20-30 mg / L, and the nitrate nitrogen content is 15-20 mg / L.

6. The deep nitrogen removal method for wastewater coupled with sulfur autotrophic-anaerobic ammonia oxidation according to claim 4, characterized in that: The hydraulic load of the upflow reactor is 0.6-1.2m. 3 / (m 2 The hydraulic residence time of the empty tower of the upflow reactor is 2-3 hours, and the operating temperature of the upflow reactor is 10-35℃.

7. The deep nitrogen removal method for wastewater coupled with sulfur autotrophic-anaerobic ammonia oxidation according to claim 4, characterized in that: The backwashing unit adopts a combined water and air backwash, with a water flushing intensity of 8-10 L / (m²·s) and an air flushing intensity of 15-20 L / (m²·s), and a flushing cycle of 7-10 days.

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