Iron-loaded biomass charcoal reinforced PN-Anammox integrated denitrification method

Abstract

The invention discloses an iron-loaded biomass charcoal reinforced PN-Anammox integrated nitrogen removal method and a preparation method thereof. The preparation method comprises the following steps: firstly, selecting a proper biomass material, drying the biomass material, soaking the biomass material in an iron salt solution, and performing post-treatment to obtain biomass charcoal particles Fe / BC loaded with micro-nano iron; then inoculating the Fe / BC and anaerobic ammonia oxidation sludge into an anaerobic reactor for culturing, and regulating and controlling process parameters to form Fe / BC-Anammox composite anaerobic sludge particles; and then inoculating into a reactor containing domesticated and matured short-cut nitrification sludge, regulating and controlling reaction conditions to construct an integrated denitrification system, monitoring the effect, and enabling the denitrification system to stably operate within a certain dissolved oxygen fluctuation range. The method has a wide prospect in the field of ammonia nitrogen wastewater treatment, and a new method is provided for solving the problem of poor stability of related PN-Anammox integrated denitrification.

Description

Technical Field

[0001] The invention relates to the fields of functional materials and environmental engineering, in particular to biological treatment technologies related to nitrogen removal, and specifically to an iron-loaded biochar-enhanced PN-Anammox integrated denitrification method. Background Art

[0002] With the rapid development of industry and cities, rare earths are widely used because of their excellent optical, electrical and magnetic properties. At present, the main mining process of rare earth mines is the in-situ leaching process with ammonium sulfate as the leaching agent, which leaves a large amount of ammonium salts in the soil after leaching. Under rainwater irrigation conditions, ammonium salts easily migrate downward, settle to surface water or infiltrate into groundwater, causing ammonia nitrogen enrichment in the deep mine, acidification of surface water in the mining area, and excessive ammonia nitrogen, resulting in eutrophication of water bodies. It causes serious harm to the surrounding environment and affects people's living conditions and physical and mental health. Therefore, it is urgent to remove the residual ammonium salts in rare earth tailings. Traditional nitrogen removal methods, such as nitrification and denitrification processes, usually require a lot of energy consumption, especially the supply of dissolved oxygen (DO). The short-range nitrification-anaerobic ammonia oxidation (PN-Anammox) integrated reaction system has gradually become a research hotspot in the field of ammonia nitrogen pollution control due to its high efficiency and energy-saving characteristics. The internal part of the integrated PN-Anammox microbial particles is mainly AnAOB bacteria, which requires an anaerobic environment, and the external part is AOB bacteria, which requires an aerobic environment. Therefore, the difference in dissolved oxygen demand of integrated microbial particles becomes a technical bottleneck problem for integrated PN-Anammox denitrification.

[0003] However, the stable operation of the PN-Anammox integrated system faces multiple challenges. The system startup is difficult, and the functional bacteria in the PN-Anammox sludge grow slowly, making it difficult for the system to quickly achieve the ideal denitrification effect. In addition, the biochemical reaction conditions of the system are also relatively harsh. Factors such as temperature, pH, and ammonia nitrogen concentration have a great influence on the reaction process, and the slightest carelessness may cause the system to operate unstable. Among them, the main controlling factor for the stable operation of integrated denitrification is dissolved oxygen. Excessive dissolved oxygen will inhibit the Anammox reaction, thereby affecting the nitrogen removal efficiency. At the same time, there are differences in the optimal environmental conditions required for AOB and AnAOB, especially in the control of dissolved oxygen concentration. Therefore, how to accurately control the dissolved oxygen in the reactor has become the key to improving the system operation efficiency and removal performance.

[0004] Biochar, as a material with high specific surface area and good adsorption performance, has been widely used in environmental pollution control. Iron, as an important metal element, is a cofactor of various enzymes in microbial cells, a carrier of redox, and an important component of the electron transport chain. The use of iron to modify biochar can significantly improve its adsorption performance. This can not only enhance the activity of anaerobic ammonia-oxidizing bacteria, but also use its redox properties as a buffering wrapping material to effectively control the dissolved oxygen in the system. A stable environment is formed in the reactor to promote the synergistic effect of AOB and AnAOB in the same reactor, thereby improving the denitrification efficiency of the short-range nitrification-anaerobic ammonia oxidation integrated system. The application of such composite materials provides new ideas and possibilities for optimizing ammonia nitrogen removal technology and improving system energy efficiency. Therefore, the application of iron-loaded biochar in the PN-Anammox integrated reactor, especially its role in dissolved oxygen control and system stability, has important ecological and engineering significance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for regulating dissolved oxygen in a PN-Anammox integrated denitrification system by using iron-loaded biochar, so as to solve the problems of unstable dissolved oxygen concentration and low anaerobic ammonia oxidation efficiency during the PN-Anammox integrated cultivation process, thereby improving nitrogen removal efficiency and system operation stability. The present invention is easy to operate, green and environmentally friendly, and provides a technical idea for solving the problem of dissolved oxygen control in a PN-Anammox integrated system.

[0006] In order to achieve the above object, the present invention provides an iron-loaded biochar-enhanced PN-Anammox integrated denitrification method, characterized in that it comprises the following steps: S1) Selecting a suitable biomass material, drying it under certain temperature conditions to remove the moisture therein, and then carbonizing it to obtain an unmodified biomass carbon material BC, impregnating the BC in an iron salt solution, and then reducing it to obtain iron-loaded micro-nano biomass carbon particles; S2) inoculating mature anaerobic ammonium oxidation sludge and iron-loaded micro-nano biochar particles in an anaerobic reactor, and adjusting the process parameters in the reactor to achieve a stable denitrification effect of the system to form Fe / BC-Anammox composite anaerobic sludge particles; S3) The Fe / BC-Anammox composite anaerobic sludge particles in step S2) are inoculated into a reactor containing domesticated mature short-term nitrification sludge, in which the reaction conditions are adjusted to promote the interaction between short-term nitrification and anaerobic ammonium oxidizing bacteria, construct an integrated denitrification system, and monitor the denitrification effect of the integrated short-term nitrification-anaerobic ammonium oxidation. Furthermore, the biomass in step S1) includes but is not limited to common straw or sawdust biomass materials, and its main components include one or more of cellulose, hemicellulose, lignin and sugars.

[0007] Further, the iron salt is FeCl 3 •6H 2 O, FeSO 4 •6H 2 O; the immersion temperature is 20~30℃, and the immersion time is 2~24h.

[0008] Furthermore, it is characterized in that the iron in the iron-loaded biochar prepared in step S1) is Fe 0 , FeO or Fe 3 O 4 One or more of the .

[0009] Furthermore, it is characterized in that the process parameters are the temperature, pH, aeration rate, n(NH 4 + -N): n(NO 2 - -N), stirring rate. By adjusting the temperature, pH, aeration volume, n(NH 4 + -N): n(NO 2 - -N), stirring rate and other process parameters to obtain the ideal nitrogen removal efficiency and nitrogen treatment load, and continue to operate until the system achieves a stable denitrification effect and forms Fe / BC-Anammox composite anaerobic sludge particles; Furthermore, it is characterized in that the reaction conditions are temperature, pH value, dissolved oxygen concentration, and ammonia nitrogen concentration. The reaction conditions, such as temperature, pH value, dissolved oxygen concentration, and ammonia nitrogen concentration, are regulated to cultivate the interaction between short-range nitrification and anaerobic ammonia oxidizing bacteria, construct an integrated denitrification system, and monitor the denitrification effect of the short-range nitrification-anaerobic ammonia oxidizing integrated system.

[0010] Further, it is characterized in that the amount of the iron-loaded biochar material inoculated into the anaerobic reactor in step S2) relative to the ammonia nitrogen wastewater is 0.5~5.0wt%; the volume percentage of the anaerobic ammonia oxidation sludge relative to the ammonia nitrogen wastewater is 0.5~2.0v; the ammonia nitrogen concentration is 50~400 mg / L; the temperature is 25~35°C, and the pH is 7~10.

[0011] Furthermore, it is characterized in that the ratio of nitrite concentration to ammonia nitrogen concentration in the effluent is 1 to 1.5.

[0012] Furthermore, it is characterized in that the temperature is adjusted to 20-40°C, the pH is adjusted to 7-10, and the dissolved oxygen is adjusted to 0-1.5 mg / L by adopting intermittent aeration.

[0013] Furthermore, the reduction treatment method in step S1) can be reduction by adding a soluble organic / inorganic substance reducing agent or pyrolysis reduction; the pyrolysis reduction temperature is 350-700° C. and the time is 1-4 h.

[0014] During the operation of the integrated system, the ideal control range of dissolved oxygen (DO) is set according to the needs of the denitrification reaction. By installing dissolved oxygen sensors or probes at key locations in the system (such as the inlet and outlet of the reaction tank), real-time monitoring of dissolved oxygen concentration is achieved. This allows timely evaluation of the denitrification efficiency and stability of the denitrification system under aeration fluctuation conditions.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1) Regulate the dissolved oxygen concentration in the PN / A integrated system to improve the denitrification stability of the system The iron salt modified biochar used in the present invention has a high specific surface area and good adsorption performance as a composite material, and the introduction of iron elements not only improves the adsorption capacity of biochar, but also improves the redox environment of the system. The iron-loaded biochar is used as a buffer material to effectively regulate the dissolved oxygen concentration in the reactor. In traditional nitrogen removal systems, excessive dissolved oxygen inhibits the anaerobic ammonia oxidation reaction, resulting in low denitrification efficiency. The present invention optimizes the control of dissolved oxygen through the redox characteristics of iron-loaded biochar, so that in the same reactor, short-range nitrification and anaerobic ammonia oxidation denitrification reactions can be coordinated and operated within an ideal dissolved oxygen range, avoiding the problem of affecting the denitrification effect due to bacterial competition or incompatibility in traditional systems, thereby improving the denitrification efficiency and long-term stability of the system.

[0016] 2) Green and environmentally friendly, easy to operate and implement The invention is easy to operate and environmentally friendly. The preparation method of the iron-loaded biochar material uses common biomass materials and iron salt modification. The whole process does not involve complex chemicals or high energy consumption operations, meets environmental protection requirements, and the materials in the preparation process can be recycled, reducing the generation of waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work. In the drawings: FIG1 is a schematic diagram of the structure of the present invention.

[0018] Figure 2 shows the sugarcane bagasse biochar material without iron loading and the magnetic Fe loading 3 O 4 Scanning electron microscope image of bagasse biochar material.

[0019] Figure 3 shows the addition of magnetic Fe 3 O 4 Effect of bagasse biochar versus no added loading on nitrogen removal in an integrated system.

[0020] Figure 4 To add magnetic Fe 3 O 4 Effect of bagasse biochar versus no added loading on dissolved oxygen in an integrated system. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0022] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections.

[0023] In order to simplify the drawings, only the parts related to the present invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0024] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0025] In the embodiments shown in the drawings, the indications of directions (such as up, down, left, right, front and back) used to explain the structure and movement of the various components of the present invention are not absolute but relative. These descriptions are appropriate when these components are in the positions shown in the drawings. If the descriptions of the positions of these components change, the indications of these directions also change accordingly.

[0026] In addition, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation of the present invention will be described below with reference to the accompanying drawings.

[0028] Example 1 A method for removing ammonia nitrogen from rare earth mine wastewater by iron-loaded biochar-enhanced PN-Anammox integration comprises the following steps: 1) Preparation of unmodified biochar material (BC) Select sugarcane bagasse biomass as the raw material, wash away the sugar and place it in an 80°C oven to dry. Then put the dried sugarcane bagasse into a porcelain boat, wrap it with tin foil and place it in a muffle furnace and heat it to 550°C at a rate of 10°C / min for 1 hour. After the pyrolysis process is completed, the obtained biochar is naturally cooled to ambient temperature to obtain unmodified sugarcane bagasse biochar material for use. (The method for preparing unmodified biochar in the following examples is the same and will not be repeated here) 2) Preparation of magnetic Fe 3 O 4 Bagasse biochar materials (Fe 3 O 4 / BC) The material was prepared by coprecipitation. 300 mL of secondary water was placed in a 500 mL three-necked flask, nitrogen was passed through the flask at room temperature for 30 min to exhaust the air in the flask, and then 2.25 g of FeCl was added to the three-necked flask. 3 6H 2 O and 1.15 g of FeSO 4 6H 2 O, mechanically stir at room temperature for 20 minutes, the solution is orange-red. Weigh 0.69g of BC in the above mixed solution and mechanically stir at room temperature for 3h. Add 35mL of concentrated ammonia water to the mixed solution, a black precipitate is generated, and anhydrous ethanol is quickly added to the mixed solution to prevent the precipitate from aggregating, and measure the pH of the mixed solution to make its value 10. Heat in a 60℃ water bath and continue mechanical stirring for 4h, cool to room temperature, and the whole process is carried out in a nitrogen atmosphere. The product is separated with a magnet, washed three times with deionized water, washed three times with anhydrous ethanol, and then placed in a 70℃ oven to dry for 20h. Finally, an iron-carbon composite material with an iron-carbon ratio of 1:1 is generated for use.

[0029] 3) Prepare simulated ammonia nitrogen wastewater for culturing anaerobic ammonia-oxidizing bacteria. The specific composition is as follows: 50~100 mg / L NH 4 + -N, 65~132mg / L NO 2 --N, 1000 mg / L NaHCO 3 , 1000 mg / L KHCO 3 , 27 mg / L KH 2 PO 4 , 136 mg / LCaCl 2 , 20 mg / L MgSO 4 , 1.0 mL / L trace element solution I, 1.2 mL / L trace element solution II. The components of trace element solution I are: 5.0 g / L EDTA and 5.0 g / L FeSO 4 7H 2 O. The composition of trace element solution II is: 5.0 g / L EDTA, 0.22 g / L NaMoO 4 ·2H 2 O, 0.19 g / LNiCl 2 6H 2 O, 0.25 g / LCuSO 4 ·5H 2 O, 0.24 g / LCoCl 2 6H 2 O, 0.43 g / L ZnSO 4 7H 2 O, and 0.99 g / L MnCl 2 ·4H 2 O. (the simulated ammonia nitrogen wastewater composition in the following examples is the same and will not be repeated); inoculate the anaerobic ammonium oxidation sludge into the reactor, add Fe 3 O 4 / BC material, set the temperature to 30 °C, the hydraulic retention time to 22 h, and replace the influent water regularly every day. After the influent is completed, N2 is passed through the reactor for 5 min. 2 To maintain the oxygen-free environment of the system, take the inlet and outlet water regularly every day to measure the NH in the reactor. 4 + -N, NO 2 - -N, NO 3 - -N concentration changes until the denitrification performance of the anaerobic ammonium oxidation system is stable; 4) Add the denitrification performance of step 3) to the short-range nitrification reactor in stable operation and load Fe 3 O 4 / BC material anaerobic ammonia oxidation sludge, to construct a short-cut nitrification-anaerobic ammonia oxidation integrated denitrification system. The amount of anaerobic ammonia oxidation sludge is 2% of the mass of ammonia nitrogen wastewater; the amount of short-cut nitrification sludge is 2% of the volume of ammonia nitrogen wastewater. Intermittent aeration is adopted, and the aeration mode is selected as 30min aeration and 30min stop aeration alternately. The dissolved oxygen in the system is controlled to be lower than 1.2mg / L by a glass rotor flowmeter. The initial concentration of ammonia nitrogen in the influent is 150mg / L, and the pH value of the ammonia nitrogen wastewater is adjusted to 8.0; then after 10 days of denitrification treatment at a temperature of 30℃ and a speed of 150r / min, the average effluent ammonia nitrogen concentration in the system is measured to be 7.24mg / L, the average ammonia nitrogen removal rate is 95.17%, the average effluent nitrate nitrogen is 2.14mg / L, the average nitrite nitrogen is 0.03 mg / L, and the solution oxygen in the system is 0.3~0.5mg / L.

[0030] Comparative Example 1 A method for constructing a short-range nitrification-anaerobic ammonium oxidation integrated system of biochar without iron loading, comprising the following steps: 1) Prepare simulated ammonia nitrogen wastewater for culturing anaerobic ammonium oxidizing bacteria, inoculate anaerobic ammonium oxidizing sludge into the reactor, do not add any additional materials, set the temperature to 30℃, the hydraulic retention time to 22h, replace the influent water regularly every day, and pass N2 into the reactor for 5min after the influent is completed. 2 To maintain the oxygen-free environment of the system, take the inlet and outlet water regularly every day to measure the NH in the reactor. 4 + -N, NO 2 - -N, NO 3 - -N concentration changes until the denitrification performance of the anaerobic ammonium oxidation system is stable; 2) Add the anaerobic ammonium oxidation sludge with stable denitrification performance in step 1) of this example to the stably operating short-cut nitrification reactor to construct a short-cut nitrification-anaerobic ammonium oxidation integrated denitrification system. The amount of anaerobic ammonium oxidation sludge is 2% of the mass of the ammonia nitrogen wastewater; the amount of short-cut nitrification sludge is 2% of the volume of the ammonia nitrogen wastewater. Intermittent aeration is adopted, and the aeration mode is selected as 30 minutes of aeration and 30 minutes of non-aeration alternation. A glass rotor flowmeter is used to control the dissolved oxygen in the system to be lower than 1.2 mg / L. The initial influent ammonia nitrogen concentration was 150 mg / L, and the pH value of the ammonia nitrogen wastewater was adjusted to 8.0; then after 10 days of denitrification treatment at a temperature of 30°C and a rotation speed of 150 r / min, the average effluent ammonia nitrogen concentration in the system was measured to be 47.4 mg / L, the average ammonia nitrogen removal rate was 68.4%, the average effluent nitrate nitrogen was 73.52 mg / L, the average nitrite nitrogen was 17.11 mg / L, and the solution oxygen in the system was 1~1.2 mg / L.

[0031] Comparative Example 2 A method for constructing a short-range nitrification-anaerobic ammonium oxidation integrated system with unmodified biochar, comprising the following steps: 1) Prepare simulated ammonia nitrogen wastewater for culturing anaerobic ammonium oxidizing bacteria, inoculate anaerobic ammonium oxidizing sludge into the reactor, add unmodified biomass carbon material, set the temperature to 30 °C, the hydraulic retention time to 22 h, replace the influent water regularly every day, and pass N into the reactor for 5 min after the influent is completed. 2 To maintain the oxygen-free environment of the system, take the inlet and outlet water regularly every day to measure the NH in the reactor. 4 + -N, NO 2 - -N, NO 3 - -N concentration changes until the denitrification performance of the anaerobic ammonium oxidation system is stable; 2) Add the anaerobic ammonium oxidation sludge with stable denitrification performance in step 1) of this example to the stably operating short-cut nitrification reactor to construct a short-cut nitrification-anaerobic ammonium oxidation integrated denitrification system. The amount of anaerobic ammonium oxidation sludge is 2% of the mass of the ammonia nitrogen wastewater; the amount of short-cut nitrification sludge is 2% of the volume of the ammonia nitrogen wastewater. Intermittent aeration is adopted, and the aeration mode is selected as 30 minutes of aeration and 30 minutes of non-aeration alternation. A glass rotor flowmeter is used to control the dissolved oxygen in the system to be lower than 1.2 mg / L. The initial influent ammonia nitrogen concentration was 150 mg / L, and the pH value of the ammonia nitrogen wastewater was adjusted to 8.0; then after 10 days of denitrification treatment at a temperature of 30°C and a rotation speed of 150 r / min, the average effluent ammonia nitrogen concentration in the system was measured to be 35.69 mg / L, the average ammonia nitrogen removal rate was 76.21%, the average effluent nitrate nitrogen was 51.56 mg / L, the average nitrite nitrogen was 32.18 mg / L, and the solution oxygen in the system was 0.7~0.9 mg / L.

[0032] Example 2 A method for removing ammonia nitrogen from rare earth mine wastewater by iron-loaded biochar-enhanced PN-Anammox integration comprises the following steps: 1) Preparation of zero-valent iron-loaded bagasse biochar material (Fe 0 / BC) Prepared by liquid phase reduction method. Weigh 2.78g of FeSO 4 •6H 2 O was added to anhydrous ethanol / water solution (V (anhydrous ethanol): (water) = 30:70) to fully dissolve, and the solution was transferred to a three-necked flask, and a certain amount of unmodified biochar was added to make the mass ratio of BC and nano zero-valent iron in the composite material 2:1. Then nitrogen was introduced and mechanical stirring was performed. After ventilation for 20 minutes, 100 ml of sodium borohydride (NaBH) with a pH of 8 and a concentration of 0.04 mol / L was added.4 ) solution was dripped into the three-necked flask from the constant pressure funnel at a rate of 2 drops / s, and the mechanical stirring was continued vigorously for 50 minutes. After the reduction reaction was completed, nitrogen was continued to be introduced until no obvious hydrogen was generated in the reactor. The mixed solution was poured out and transferred to a nitrogen-filled glove box. After filtration, it was washed with anhydrous ethanol and centrifuged. After repeating 3 times, part of the supernatant was poured out and the remaining solid was saturated with N 2 Dry in an oven under protection and store in a sealed container for later use.

[0033] 2) Prepare simulated ammonia nitrogen wastewater for culturing anaerobic ammonium oxidizing bacteria, inoculate the anaerobic ammonium oxidizing sludge into the reactor, and add the Fe prepared in step 1) of this example. 0 / BC, set the temperature to 30 °C, the hydraulic retention time to 22 h, and replace the influent water regularly every day. After the influent is completed, N2 is passed through the reactor for 5 min. 2 To maintain the oxygen-free environment of the system, take the inlet and outlet water regularly every day to measure the NH in the reactor. 4 + -N, NO 2 - -N, NO 3 - -N concentration changes until the denitrification performance of the anaerobic ammonium oxidation system is stable; 3) Add the anaerobic ammonium oxidation sludge with stable denitrification performance and loaded with Fe0 / BC materials in step 2) to the stably operating short-cut nitrification reactor to construct a short-cut nitrification-anaerobic ammonium oxidation integrated denitrification system. The amount of anaerobic ammonium oxidation sludge is 2% of the mass of the ammonia nitrogen wastewater; the amount of short-cut nitrification sludge is 2% of the volume of the ammonia nitrogen wastewater. Intermittent aeration is adopted, and the aeration mode is selected as 30 minutes of aeration and 30 minutes of non-aeration alternation. The dissolved oxygen in the system is controlled to be lower than 1.2 mg / L by a glass rotor flowmeter. The initial influent ammonia nitrogen concentration was 150 mg / L, and the pH value of the ammonia nitrogen wastewater was adjusted to 8.0; then after 10 days of denitrification treatment at a temperature of 30°C and a rotation speed of 150 r / min, the average effluent ammonia nitrogen concentration in the system was measured to be 5.64 mg / L, the average ammonia nitrogen removal rate was 96.24%, the average effluent nitrate nitrogen was 3.2 mg / L, the average nitrite nitrogen was 0 mg / L, and the solution oxygen in the system was 0.2~0.4 mg / L.

[0034] Example 3 A method for removing ammonia nitrogen from rare earth mine wastewater by iron-loaded biochar-enhanced PN-Anammox integration comprises the following steps: 1) Preparation of iron-loaded bagasse biochar materials (Fe 2+ / BC) Take 2.5g of unmodified biochar material and 50mL of different concentrations of FeCl 3 6H 2O and Na 2 S·9H 2 O mixed solution (iron-sulfur molar ratio of 20:1) was immersed and stirred for 3 hours. After the stirred mixture was separated from the solid and liquid and dried, it was pyrolyzed in an anaerobic environment for 3 hours. The fully stirred mixture was poured into a centrifuge tube for solid-liquid separation, and the separated sludge was dried at 60°C for 12 hours. The dried precursor was placed in a tubular furnace and pyrolyzed and carbonized in an anaerobic environment. The temperature was raised to 500°C and maintained for 2 hours. After cooling to room temperature, it was taken out, ground into powder, and collected through an 80-mesh sieve to prepare the obtained ferrous sulfide-biochar composite material (Fe 2+ / BC).

[0035] 2) Prepare simulated ammonia nitrogen wastewater for culturing anaerobic ammonium oxidizing bacteria, inoculate the anaerobic ammonium oxidizing sludge into the reactor, and add the Fe prepared in step 1) of this example. 2+ / BC, set the temperature to 30 °C, the hydraulic retention time to 22 h, and replace the influent water regularly every day. After the influent is completed, N2 is passed through the reactor for 5 min. 2 To maintain the oxygen-free environment of the system, take the inlet and outlet water regularly every day to measure the NH in the reactor. 4 + -N, NO 2 - -N, NO 3 - -N concentration changes until the denitrification performance of the anaerobic ammonium oxidation system is stable; 3) Add the denitrification performance of step 2) to the short-range nitrification reactor in stable operation and load Fe 2+ / BC material anaerobic ammonia oxidation sludge, to construct a short-cut nitrification-anaerobic ammonia oxidation integrated denitrification system. The amount of anaerobic ammonia oxidation sludge is 2% of the mass of ammonia nitrogen wastewater; the amount of short-cut nitrification sludge is 2% of the volume of ammonia nitrogen wastewater. Intermittent aeration is adopted, and the aeration mode is selected as 30min aeration and 30min stop aeration alternately. The dissolved oxygen in the system is controlled to be lower than 1.2mg / L by a glass rotor flowmeter. The initial concentration of ammonia nitrogen in the influent is 150mg / L, and the pH value of the ammonia nitrogen wastewater is adjusted to 8.0; then after 10 days of denitrification treatment at a temperature of 30℃ and a speed of 150r / min, the average effluent ammonia nitrogen concentration in the system is measured to be 14.28 mg / L, the average ammonia nitrogen removal rate is 90.48%, the average effluent nitrate nitrogen is 4.55mg / L, the average nitrite nitrogen is 2.02 mg / L, and the solution oxygen in the system is 0.5~0.7mg / L.

[0036] Figure 1It is a schematic diagram of the structure of the present invention. The present invention prepares an iron-loaded biochar composite material by introducing loaded iron on the basis of unmodified biochar. The composite material has an excellent porous structure, which can provide more attachment sites for anaerobic ammonia-oxidizing bacteria, and its reducibility helps to reduce external environmental fluctuations, especially the adverse effects of dissolved oxygen on the activity of anaerobic ammonia-oxidizing bacteria. Fe / BC-Anammox composite anaerobic sludge particles are formed by anaerobic culture, and then inoculated in a short-range nitrification-anaerobic ammonia oxidation integrated system. The inner layer of the structure provides a suitable anaerobic environment for anaerobic ammonia-oxidizing bacteria, and aerobic ammonia-oxidizing bacteria grow in the outer layer in full contact with oxygen, which can effectively solve the problems of low denitrification efficiency and difficulty in starting due to the difficulty in controlling dissolved oxygen in the short-range nitrification-anaerobic ammonia oxidation system.

[0037] Figure 2 The left picture of Example 1 shows the unmodified biochar material (BC) and the right picture shows the magnetic Fe 3 O 4 Bagasse biochar materials (Fe 3 O 4 / BC) scanning electron microscope (SEM) image. As can be seen from the figure, the unmodified biochar is mainly a flaky structure with a smooth surface and less pores. 3 O 4 In contrast, the surface structure of bagasse biochar material has changed significantly. Specifically, Fe 3 O 4 More tiny pores appeared on the surface of BC, forming a more evenly distributed pore structure. Its surface was rougher and its specific surface area increased significantly. This is because nZVI, which is spherical in shape and small in diameter, was successfully loaded on the surface of BC. The rich specific surface area and uniform pore structure provide an ideal support platform for the attachment, reproduction and growth of microorganisms. Its excellent pore structure can also regulate the dissolved oxygen (DO) concentration in the integrated system, reduce the adverse factors of the denitrification process, and thus improve the denitrification efficiency.

[0038] Figure 3 and Figure 4 The changes in the concentration of nitrogen in the effluent water and the average dissolved oxygen concentration in the system in Example 1 and Comparative Example 1 are shown respectively. Figure 4 It can be observed that under the same reaction conditions, the Fe 3 O 4 The average dissolved oxygen concentration of the integrated system with biochar loaded with BC (0.3-0.5 mg / L) is lower than that of the ordinary integrated system without any materials (1-1.2 mg / L). Existing studies have shown that the dissolved oxygen concentration of 0.3-0.5 mg / L is sufficient to ensure the smooth progress of the short-range nitrification process, and this concentration range is also conducive to the smooth flow of Fe 3 O4 / BC loaded biochar inner layer forms a nearly anaerobic environment, which effectively promotes the anaerobic ammonia oxidation denitrification process and improves the denitrification performance of the integrated system. Figure 3 It was further verified that Fe 3 O 4 The concentration of nitrogen in the effluent of the integrated system with biochar / BC was significantly lower than that of the ordinary integrated system, and the ammonia nitrogen removal rate reached 95.17%, which was 26.77% higher than that of the ordinary integrated system. The main reason for this improvement is that in a short period of time, the dynamic environment created by sufficient aeration in the system 3 O 4 / BC-loaded biochar is reducing and can react with excess oxygen in the system; its porous structure can also absorb some oxygen, providing a buffer for the anaerobic ammonia-oxidizing bacteria in the inner layer, placing them in a nearly anaerobic environment, thereby ensuring the efficient denitrification reaction. In contrast, in ordinary integrated systems that do not contain any materials, anaerobic ammonia-oxidizing bacteria are directly exposed to oxygen. Although the ammonia oxidation process can effectively remove some ammonia nitrogen, in this environment, nitrite oxidizing bacteria (NOB) are not effectively inhibited, resulting in a high concentration of nitrate nitrogen in the system. In addition, higher dissolved oxygen concentrations also inhibit the activity of anaerobic ammonia-oxidizing bacteria, thereby affecting the overall denitrification effect of the system.

[0039] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. An iron-loaded biochar-enhanced PN-Anammox integrated denitrification method, characterized in that: The following steps are involved: S1) Selecting a suitable biomass material, drying it under certain temperature conditions to remove the moisture therein, and then carbonizing it to obtain an unmodified biomass carbon material BC, impregnating the BC in an iron salt solution, and then reducing it to obtain iron-loaded micro-nano biomass carbon particles; S2) inoculating mature anaerobic ammonium oxidation sludge and iron-loaded micro-nano biochar particles in an anaerobic reactor, and adjusting the process parameters in the reactor to achieve a stable denitrification effect of the system to form Fe / BC-Anammox composite anaerobic sludge particles; S3) The Fe / BC-Anammox composite anaerobic sludge particles in step S2) are inoculated into a reactor containing domesticated mature short-term nitrification sludge, in which the reaction conditions are adjusted to promote the interaction between short-term nitrification and anaerobic ammonium oxidizing bacteria, construct an integrated denitrification system, and monitor the denitrification effect of the integrated short-term nitrification-anaerobic ammonium oxidation.

2. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 1, characterized in that: Step S1) The biomass includes but is not limited to common straw or sawdust biomass materials, and its main components include one or more of cellulose, hemicellulose, lignin and sugars.

3. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 1, characterized in that: The iron salt is one or two of FeCl3•6H2O and FeSO4•6H2O; the immersion temperature is 20-30°C, and the immersion time is 2-24h.

4. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 1, characterized in that: Step S1) The iron in the iron-loaded biochar prepared is Fe 0 , FeO or Fe3O4 or a combination of several thereof.

5. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 1, characterized in that: The process parameters are the temperature, pH, aeration rate, n(NH4 + -N): n (NO2 - -N), stirring rate.

6. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 1, characterized in that: The reaction conditions are temperature, pH value, dissolved oxygen concentration, and ammonia nitrogen concentration.

7. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 1, characterized in that: The amount of the iron-loaded biochar material inoculated into the anaerobic reactor in step S2) relative to the ammonia nitrogen wastewater is 0.5-5.0wt%; the volume percentage of the anaerobic ammonia oxidation sludge relative to the ammonia nitrogen wastewater is 0.5-2.0v; the ammonia nitrogen concentration is 50-400 mg / L; the temperature is 25-35°C, and the pH is 7-10.

8. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 5, characterized in that: The ratio of effluent nitrite concentration to ammonia nitrogen concentration is 1~1.

5.

9. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 6, characterized in that: By adopting intermittent aeration, the temperature is adjusted to 20~40℃, the pH is 7~10, and the dissolved oxygen concentration is 0~1.5mg / L.

10. The iron-loaded biochar-enhanced PN-Anammox integrated denitrification method according to claim 6, characterized in that: Step S1) The reduction treatment method may be to add a soluble organic / inorganic substance reducing agent for reduction or to perform pyrolysis reduction; the pyrolysis reduction temperature is 350-700°C and the time is 1-4 h.

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