A bacterial agent based on heterotrophic cultivation of activated sludge and sulfur autotrophic directional domestication and a wastewater treatment method

Abstract

The application discloses a kind of based on activated sludge heterotrophic bacteria cultivation and sulfur autotrophic directional domestication bacterial agent and wastewater treatment method, the bacterial agent mainly with municipal wastewater treatment plant surplus activated sludge as raw material, first through heterotrophic bacteria cultivation to improve sludge activity and biomass, then under the synergistic effect of elemental sulfur, sodium bicarbonate and nitrate, sulfur autotrophic denitrification directional domestication is carried out, and efficient, stable, impact-resistant composite denitrification bacterial population is formed;The mature bacterial population after separation, purification, mixed expansion is made into bacterial agent, directly added to actual wastewater treatment project, to realize the depth denitrification of wastewater.The application does not depend on single strain, does not use expensive reagent, completely from ordinary activated sludge, using two-stage precise domestication process, retains the natural synergy of bacterial population, has the advantages of fast start, low cost, salt and low temperature tolerance, without additional carbon source, stable operation, etc., can significantly improve the denitrification efficiency and stability of wastewater treatment system.

Description

Technical Field

[0001] This invention relates to a bacterial agent and wastewater treatment method based on the directional domestication of heterotrophic bacteria in activated sludge and sulfur autotrophic bacteria, belonging to the field of wastewater treatment technology. Background Technology

[0002] In recent years, with the rapid advancement of urbanization and industrialization, water pollution has become increasingly prominent, with nitrogen pollution emerging as one of the main factors affecting water quality. Large amounts of domestic sewage, industrial wastewater, aquaculture wastewater, and agricultural runoff flow into water bodies, leading to persistently high levels of nitrogen pollutants such as ammonia nitrogen, nitrates, and nitrites. This causes a series of environmental problems, including eutrophication, blackening and odorization of water bodies, and ecological damage, seriously threatening drinking water safety and aquatic ecosystem health. To address the severe nitrogen pollution situation, national and local governments have continuously tightened wastewater discharge standards, placing higher demands on wastewater treatment plants for deep total nitrogen removal, stable compliance with standards, and low-cost operation.

[0003] Traditional biological denitrification processes are based on heterotrophic denitrification, where microorganisms use organic carbon sources as electron donors to reduce nitrates to nitrogen. However, this technology has significant drawbacks: First, it requires the addition of large amounts of exogenous carbon sources (such as methanol, sodium acetate, and glucose), especially in municipal sewage and industrial wastewater with low carbon-to-nitrogen ratios (C / N < 3). Insufficient carbon sources directly lead to low denitrification efficiency, while adding carbon sources significantly increases operating costs. Second, the rapid proliferation of heterotrophic microorganisms results in a huge amount of residual sludge, increasing sludge disposal costs and the risk of secondary pollution. Furthermore, the amount of carbon source added is difficult to control precisely, easily causing safety hazards such as excessive COD and nitrite accumulation in the effluent.

[0004] Against this backdrop, autotrophic denitrification technology, with its advantages of requiring no organic carbon source, low sludge production, low operating costs, and environmental friendliness, has become an important alternative to traditional heterotrophic nitrogen removal. Among these technologies, sulfur autotrophic denitrification uses elemental sulfur, sulfides, and other reducing sulfur substances as electron donors, nitrates as electron acceptors, and inorganic carbon (…). Using carbon as a carbon source, it can directly achieve efficient denitrification. It has outstanding advantages such as fast reaction rate, cheap and readily available substrate, and stable treatment effect. It is recognized as the preferred technology for denitrification of low carbon-to-nitrogen ratio wastewater, groundwater, and high salinity wastewater.

[0005] Since the 1970s, scholars both domestically and internationally have conducted extensive research on sulfur autotrophic denitrification. Driscoll et al. demonstrated the feasibility of sulfur-based autotrophic denitrification by using sulfides and elemental sulfur; Batchelor's research showed that elemental sulfur exhibits the best nitrogen removal efficiency when used as an electron donor; Claus et al. proposed that the optimal pH for sulfur autotrophic denitrification is 7.5–8.0; and Koenig et al. established a kinetic model for sulfur autotrophic denitrification. Despite substantial basic research, sulfur autotrophic denitrification still faces a series of practical challenges in engineering applications:

[0006] (1) Sulfur autotrophic bacteria grow slowly and have low natural content. The cycle of directly starting the system with ordinary activated sludge is as long as 30-60 days, which is difficult to meet the requirements of rapid commissioning of the project.

[0007] (2) The single strain has poor adaptability and is sensitive to temperature, salinity and toxicity. It is very easy to be inactivated under low temperature, high salinity and water quality fluctuation conditions.

[0008] (3) Most existing microbial agents are single strains or artificially compounded, lacking the synergistic effect of natural microbial communities, and the actual engineering effect is far lower than the laboratory level;

[0009] (4) Problems such as rapid pH drop, insufficient alkalinity, nitrite accumulation, and difficulty in biofilm formation are likely to occur during the acclimatization process;

[0010] (5) Commercially available sulfur autotrophic bacteria agents are expensive and rely on imports or a few manufacturers, making them unaffordable for small and medium-sized enterprises and small projects;

[0011] (6) There is a lack of a complete process of acclimatization-expansion-addition that starts from ordinary activated sludge, is low-cost, replicable and scalable.

[0012] Current patents and technologies primarily focus on single-strain screening, culture medium optimization, and carrier immobilization, largely neglecting the complexity of actual wastewater and the natural synergy of microbial communities. These approaches generally suffer from high costs, long development cycles, insufficient stability, and poor engineering adaptability. Therefore, developing a wastewater treatment method that uses municipal waste activated sludge as raw material, employs a simple and efficient two-stage acclimatization process to prepare highly active composite denitrifying bacteria, and can be directly applied to stable engineering operations has significant theoretical and engineering application value. Summary of the Invention

[0013] Objective of the Invention: To address the problems existing in the prior art, this invention provides a wastewater treatment method based on heterotrophic bacterial cultivation and sulfur autotrophic acclimatization using activated sludge. This invention proposes a novel process of first cultivating heterotrophic bacteria and then performing sulfur autotrophic acclimatization. It relies entirely on ordinary activated sludge, without depending on commercial strains or expensive chemicals, and obtains a highly efficient, stable, salt-tolerant, and low-temperature-tolerant composite denitrifying bacterial community in a short time. This method can be widely applied to various wastewater treatment projects to achieve low-cost, high-efficiency, and stable deep denitrification that meets standards.

[0014] Technical solution: To achieve the above objectives, the present invention adopts the following technical solution:

[0015] In a first aspect, the present invention provides a microbial agent based on the heterotrophic culture of activated sludge and the directional domestication of sulfur autotrophic bacteria, the microbial agent being prepared mainly by the following steps:

[0016] (1) Take activated sludge as the inoculum source, add nutrients, aerate and culture to complete the basic heterotrophic culture;

[0017] (2) Add elemental sulfur, sodium bicarbonate and sodium nitrate to the sludge system after bacterial cultivation to construct an aerobic-anoxic series environment for sulfur autotrophic denitrification acclimatization. Regularly supplement nitrate and monitor water quality until NO3 is reached. - -N removal rate >90%, NH4 + -N removal rate > 85%, effluent TN < 1 mg / L;

[0018] (3) Collect sludge and water samples that meet the above water quality requirements, separate and purify them to obtain multiple functional strains;

[0019] (4) All purified strains are inoculated together into seed culture medium for activation, and then transferred to fermentation culture medium for large-scale expansion to obtain highly active denitrifying bacterial solution. The bacterial solution or the freeze-dried powder made from it is the bacterial agent.

[0020] As a specific implementation plan, in step (1), the activated sludge is activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant.

[0021] As a specific implementation plan, in step (1), the nutrients include glucose, urea and potassium dihydrogen phosphate, and the dosage is: 20-30 g of glucose, 0.8-1.5 g of urea and 0.2-0.8 g of potassium dihydrogen phosphate are added to 10 L of activated sludge.

[0022] The conditions for the heterotrophic basic culture were: aeration for 20-30 h, DO controlled at 2-4 mg / L, temperature 20-30 ℃, and pH 7.0-8.0.

[0023] As a specific implementation plan, in step (2), the dosage of elemental sulfur, sodium bicarbonate and sodium nitrate is as follows: 45-55 g of elemental sulfur, 5-13 g of sodium bicarbonate and 15-21 g of sodium nitrate are added to a 10L sludge system.

[0024] As a specific implementation plan, in step (2), the aerobic-anoxic series environment is: HRT=16-20 h, temperature 25±1 ℃, pH=7.5±0.2, and DO<0.5 mg / L in the anoxic segment.

[0025] As a specific implementation plan, in step (2), the nitrate is selected from sodium nitrate, and 8-12g of sodium nitrate is added every 7 days, and the water quality is tested every 2 days.

[0026] As a specific implementation plan, in step (3), the separation and purification adopts the gradient dilution plating method and the streak plate method, and uses sulfur autotrophic selective medium or LB medium.

[0027] As a specific implementation scheme, in step (4), the seed culture medium includes the following components: sodium nitrate 0.5-1.5 g / L, sodium bicarbonate 1.5-2.5 g / L, sodium thiosulfate 1.5-2.5 g / L, magnesium chloride 0.2-0.8 g / L, dipotassium hydrogen phosphate 0.5-1.5 g / L, ferrous sulfate 0.02-0.08 g / L, manganese sulfate 0.05-0.1 g / L, and sodium chloride 0.02-0.08 g / L;

[0028] The activation time in the seed culture medium is 2–3 days, and the inoculum size is 1–3%.

[0029] The fermentation medium comprises the following components: sodium nitrate 4.0-6.0 g / L, sodium bicarbonate 8.0-12.0 g / L, sodium thiosulfate 0.5-1.5 g / L, magnesium chloride 0.2-0.8 g / L, dipotassium hydrogen phosphate 0.5-1.5 g / L, ferrous sulfate 0.02-0.08 g / L, manganese sulfate 0.02-0.08 g / L, wheat bran 4.0-6.0 g / L, corn cob powder 0.5-1.5 g / L, and calcium carbonate 0.2-0.8 g / L;

[0030] The time for large-scale expansion of the culture medium after transfer is 7-9 days, and the inoculum size is 8-12%.

[0031] Secondly, the present invention provides the application of the aforementioned bacterial agent in deep denitrification of wastewater.

[0032] As a specific implementation plan, the wastewater is municipal sewage, industrial high-salt wastewater, landfill leachate, groundwater nitrate nitrogen, low-temperature sewage, or comprehensive wastewater from industrial parks.

[0033] Thirdly, the present invention provides a wastewater treatment method, the wastewater treatment method comprising: adding the aforementioned bacterial agent to the wastewater to perform deep denitrification of the wastewater.

[0034] As a specific implementation scheme, when the bacterial agent is lyophilized powder, the dosage is 50–200 g / m³. 3 The system can tolerate salinity ≤6000 mg / L, is suitable for temperatures of 12–35 ℃, and requires no addition of organic carbon sources throughout the process.

[0035] Technical effects: Compared with the prior art, the present invention has the following advantages:

[0036] (1) Fast start-up speed

[0037] The two-stage acclimatization process shortens the traditional 30–60 day start-up cycle to 7–15 days, significantly improving the efficiency of project implementation.

[0038] (2) Extremely low cost

[0039] Using municipal waste sludge as raw material, and only inexpensive agents such as glucose, sulfur powder, baking soda, and nitrates are used, the overall cost is 1 / 5 to 1 / 8 of that of commercially available microbial agents.

[0040] (3) The microbial community has natural synergy and extremely high stability.

[0041] It retains the original community structure of sludge, and its resistance to shock loads, toxicity, and fluctuations is significantly better than that of a single strain.

[0042] (4) Wide environmental adaptability

[0043] It can cultivate functional bacterial groups that are tolerant to salt (≤6000 mg / L), low temperature (above 12 ℃), high nitrogen, and toxicity, making it suitable for a wide range of applications.

[0044] (5) No carbon source required, no secondary pollution

[0045] It is a truly autotrophic denitrification process that does not increase COD or produce large amounts of sludge, making it green and low-carbon.

[0046] (6) Stable pH and no nitrite accumulation

[0047] Precise alkalinity matching ensures stable reaction and safer water output.

[0048] (7) The entire process is replicable and scalable.

[0049] The 10L laboratory process can be directly scaled up to engineering scale, and it is simple to operate without the need for complex equipment. Attached Figure Description

[0050] Figure 1This is a schematic diagram of the two-stage domestication process of the present invention.

[0051] Figure 2 This is a graph showing the changes in sludge concentration and activity during the heterotrophic bacteria cultivation stage.

[0052] Figure 3 This is a graph showing the trend of nitrate and total nitrogen removal during the sulfur autotrophic acclimatization process.

[0053] Figure 4 This is a morphological diagram of a single colony obtained after isolation and purification.

[0054] Figure 5 This is an image of the appearance of the freeze-dried bacterial agent.

[0055] Figure 6 A comparison chart of the denitrification effect of fermentation agents in actual engineering (Example 5). Detailed Implementation

[0056] The invention will be further illustrated below with specific examples.

[0057] Example 1

[0058] The two-stage acclimation process for preparing high-efficiency denitrifying bacteria from 10L activated sludge is described below. Figure 1 As shown.

[0059] (1) Heterotrophic culture stage

[0060] Eight liters of activated sludge from a municipal wastewater treatment plant were added to a 10-liter reactor. 25 g of glucose, 1.2 g of urea, and 0.5 g of potassium dihydrogen phosphate were added. Aeration was carried out for 24 hours at a dissolved oxygen (DO) concentration of 3 mg / L, a temperature of 25°C, and a pH of 7.5. The sludge activity significantly improved, with MLSS increasing from 3200 mg / L to 4800 mg / L. The sludge concentration versus activity curve is shown below. Figure 2 As shown.

[0061] (2) Sulfur autotrophic acclimatization stage

[0062] Add 50 g of elemental sulfur, 9 g of sodium bicarbonate, and 18 g of sodium nitrate to the sludge system after cultivation in step (1) to construct an aerobic nitrification-anoxic denitrification series system. Control the HRT=18h, temperature 25 ℃, pH=7.5, and DO<0.5mg / L in the anoxic stage. Add 10 g of sodium nitrate every 7 days and continue acclimatization for 10 days. Monitor water quality every 2 days.

[0063] (3) Domestication results

[0064] NO3 - -N removal rate remained stable at 92.6%, NH4 +-N removal rate 87.2%, effluent TN = 0.5–0.9 mg / L, uniform biofilm formation, and system stability. The total nitrogen removal trend during the acclimation process is as follows: Figure 3 As shown.

[0065] (4) Separation and purification

[0066] The sludge samples that had reached the required acclimatization level were diluted, spread, and streaked to purify, yielding 12 single colonies, including Thiobacillus, Tachybacterium, and Rhodobacterium. Single colony morphology is shown in the figure below. Figure 4 As shown.

[0067] (5) Mixed propagation

[0068] All strains were inoculated into seed culture medium at a 2% inoculum level and cultured for 2 days, then transferred to fermentation culture medium at a 10% inoculum level and cultured for 8 days to obtain a highly active bacterial culture with a viable cell count of 1.8 × 10⁻⁶. 8 CFU / mL.

[0069] Seed culture medium (g / L): sodium nitrate 1.0, sodium bicarbonate 2.0, sodium thiosulfate 2.0, magnesium chloride 0.5, dipotassium hydrogen phosphate 1.0, ferrous sulfate 0.05, manganese sulfate 0.05–0.1, sodium chloride 0.05.

[0070] Fermentation medium (g / L): Sodium nitrate 5.0, sodium bicarbonate 10.0, sodium thiosulfate 1.0, magnesium chloride 0.5, dipotassium hydrogen phosphate 1.0, ferrous sulfate 0.05, manganese sulfate 0.05, wheat bran 5.0, corn cob powder 1.0, calcium carbonate 0.5.

[0071] (6) Freeze-dried bacterial agent

[0072] The bacterial culture was supplemented with 2% trehalose and 3% diatomaceous earth, and then freeze-dried to obtain a pale yellow powder with a viable count ≥1.3×10⁻⁶. 10 CFU / g. Its appearance is as follows: Figure 5 As shown.

[0073] Wastewater from Examples 2-8 was treated using the bacterial agent described in Example 1.

[0074] Example 2: Application of Low C / N Ratio Wastewater Upgrading in Municipal Wastewater Treatment Plants

[0075] Project Background: A municipal wastewater treatment plant has low carbon-to-nitrogen ratio influent (C / N=2.2) and TN=18–23 mg / L, which needs to be upgraded to TN≤5mg / L.

[0076] Process route: AAO + deep denitrification filter, with the addition of the bacterial agent of this invention.

[0077] Dosing plan:

[0078] Dosage of microbial agent: 100 g / m³ 3 ;

[0079] Packing material: sulfur + limestone composite packing material;

[0080] Operating parameters: HRT = 4 h, reflux ratio = 200%, pH = 7.5;

[0081] Domestication and Operation:

[0082] Using the two-stage in-situ sludge acclimatization method of this invention, biofilm formation was completed on the 4th day, and the effluent stabilized and met the standards on the 9th day.

[0083] Processing effect:

[0084] Influent TN: 18–23 mg / L;

[0085] effluent TN: 3.1–4.4 mg / L;

[0086] TN removal rate: 78–83%;

[0087] No carbon source was added throughout the process, saving approximately 600,000 yuan in carbon source costs annually.

[0088] Example 3: Application of deep nitrogen removal in high-salinity industrial wastewater (salinity ≈ 6000 mg / L)

[0089] Project Background: Wastewater from a chemical industrial park, salinity ≈ 6‰, NO3 - -N=75–115 mg / L, ordinary microorganisms cannot survive.

[0090] Process route: equalization tank + upflow sulfur autotrophic filter.

[0091] Dosing plan:

[0092] The salt-tolerant acclimatization agent of this invention is used;

[0093] Dosage: 200 g / m³ 3 ;

[0094] Control the pH to 7.6 and the alkalinity to 1.5 times the theoretical value.

[0095] Domestication and Operation:

[0096] The system underwent salt acclimatization in stages, completing salt tolerance adaptation in 14 days, and then operated stably.

[0097] Processing effect:

[0098] NO3 inlet - -N: 95 mg / L (average)

[0099] Water output NO3 - -N: 7.2–9.5 mg / L

[0100] Removal rate: 90–92%

[0101] It has operated continuously for 60 days without failure, demonstrating excellent salt resistance and stability.

[0102] Example 4: Application of in-situ remediation engineering for nitrate nitrogen in groundwater

[0103] Project Background: Nitrate and NO3 levels in groundwater in a suburban area exceeded standards. - -N=40–50 mg / L, in-situ treatment is required.

[0104] Process route: in-situ reaction zone + sulfur carrier + bacterial agent of this invention.

[0105] Dosing plan:

[0106] The microbial agent is loaded onto a mixed carrier of quartz sand and sulfur, injected underground to construct a reaction barrier, without adding any organic carbon source. Dosage: 800 g / m³ 3 ;

[0107] Processing effect:

[0108] NO3 inlet - -N: 45 mg / L (average);

[0109] Water output NO3 - -N: 3.2–4.3 mg / L;

[0110] Removal rate: 90–92%;

[0111] It is free from organic pollution, ecologically safe, and can operate stably for a long time.

[0112] Example 5: Application of stable nitrogen removal in wastewater treatment plants in low-temperature areas during winter

[0113] Project Background: In winter, the water temperature at a wastewater treatment plant in northern China is 12–15 ℃, and the denitrification efficiency of traditional processes decreases by more than 50%.

[0114] Process route: A / O process + low-temperature resistant bacterial agent of this invention.

[0115] Dosing plan:

[0116] Dosage: 120 g / m³ 3 Extend the HRT to 6 h, increase the alkalinity dosage, and stabilize the pH.

[0117] Processing effect:

[0118] Influent total nitrogen (TN): 20–24 mg / L;

[0119] effluent total nitrogen (TN): 6.2–8.5 mg / L;

[0120] Low-temperature denitrification rate: 65–75%;

[0121] It is far superior to ordinary activated sludge and single bacterial agents.

[0122] Example 6: Application of high-concentration nitrate treatment in landfill leachate tailwater

[0123] Project Background: After landfill leachate is treated by MBR+NF / RO, NO3... - -N=150–210 mg / L.

[0124] Process route: Two-stage sulfur autotrophic denitrification filter.

[0125] Dosing plan:

[0126] Dosage of microbial agent: 1000 g / m³ 3 HRT=6 h, pH=7.6–7.9.

[0127] Processing effect:

[0128] NO3 inlet - -N: 180 mg / L (average);

[0129] Water output NO3 - -N: 10–13 mg / L;

[0130] Removal rate: 92–94%;

[0131] No nitrite accumulation, meeting emission standards.

[0132] Example 7: Application of integrated nitrogen removal for complex wastewater in industrial parks

[0133] Project Background: The wastewater from the industrial park has fluctuating water quality and contains small amounts of toxic substances, with a TN of 50–80 mg / L.

[0134] Process route: Conditioning + Coagulation + A / O + Deep Denitrification.

[0135] Dosing plan:

[0136] The dosage of the compound microbial agent of this invention is 1000 g / m³. 3 Multi-stage membrane attachment is used to enhance impact resistance.

[0137] Processing effect:

[0138] Influent TN: 55–78 mg / L;

[0139] effluent TN: 5.2–9.0 mg / L;

[0140] Average removal rate: 85–90%;

[0141] The system exhibits minimal fluctuations and operates stably over the long term.

[0142] Example 8: Application of Decentralized Wastewater Treatment Equipment in Rural Areas

[0143] Project Background: Rural domestic sewage has a low carbon-to-nitrogen ratio and fluctuates greatly in volume, requiring low cost and unattended operation.

[0144] Process route: Integrated A / O equipment, adding the freeze-dried bacterial agent of this invention.

[0145] Dosing plan:

[0146] Dosage: 500 g / m³ 3 One-time addition, with small supplementary additions later; no need to add carbon source or frequent maintenance.

[0147] Processing effect:

[0148] Influent total nitrogen (TN): 20–28 mg / L;

[0149] effluent TN: 4.0–6.5 mg / L;

[0150] It meets rural sewage discharge standards; operation and maintenance costs are reduced by more than 70%.

[0151] The embodiments of the present invention have been described in detail above with reference to specific examples. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A microbial agent based on the directional acclimation of heterotrophic bacteria and sulfur autotrophic bacteria in activated sludge, characterized in that, The bacterial agent is mainly prepared by the following steps: (1) Take activated sludge as the inoculum source, add nutrients, aerate and culture to complete the basic heterotrophic culture; (2) Elemental sulfur, sodium bicarbonate and sodium nitrate were added to the sludge system after cultivation, and an aerobic-anoxic series environment was constructed for directional domestication of sulfur autotrophic denitrification. Nitrate was supplemented regularly and water quality was monitored until NO3 - - N removal rate > 90%, NH4 + - N removal rate > 85%, effluent TN < 1 mg / L; (3) Collect sludge and water samples that meet the above water quality requirements, separate and purify them to obtain multiple functional strains; (4) All purified strains are inoculated together into seed culture medium for activation, and then transferred to fermentation culture medium for large-scale expansion to obtain highly active denitrifying bacterial solution. The bacterial solution or the freeze-dried powder made from it is the bacterial agent.

2. The bacterial agent based on the directional acclimatization of heterotrophic bacteria and sulfur autotrophic bacteria in activated sludge according to claim 1, characterized in that, In step (1), the activated sludge is activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant; The nutrients include glucose, urea, and potassium dihydrogen phosphate, and the dosage is as follows: 20-30g of glucose, 0.8-1.5g of urea, and 0.2-0.8g of potassium dihydrogen phosphate per 10L of activated sludge. The conditions for the heterotrophic basic culture are: aeration for 20-30 hours, DO controlled at 2-4 mg / L, temperature 20-30℃, and pH 7.0-8.

0.

3. The bacterial agent based on the directed acclimatization of heterotrophic bacteria and sulfur autotrophic bacteria in activated sludge according to claim 1, characterized in that, In step (2), the dosage of elemental sulfur, sodium bicarbonate and sodium nitrate is as follows: 45-55g of elemental sulfur, 5-13g of sodium bicarbonate and 15-21g of sodium nitrate are added to a 10L sludge system.

4. The bacterial agent based on the directional acclimatization of heterotrophic bacteria and sulfur autotrophic bacteria in activated sludge according to claim 1, characterized in that, In step (2), the aerobic-anoxic series environment is: HRT=16-20h, temperature 25±1℃, pH=7.5±0.2, and DO<0.5mg / L in the anoxic segment; The nitrates are selected from sodium nitrates. 8-12g of sodium nitrates are added every 7 days, and the water quality is tested every 2 days.

5. The bacterial agent based on the directed acclimatization of heterotrophic bacteria and sulfur autotrophic bacteria in activated sludge according to claim 1, characterized in that, In step (3), the separation and purification are carried out using gradient dilution plating and streak plate methods, and sulfur autotrophic selective medium or LB medium is used.

6. The bacterial agent based on the heterotrophic culture of activated sludge and the directional acclimatization of sulfur autotrophic bacteria according to claim 1, characterized in that, In step (4), the seed culture medium comprises the following components: sodium nitrate 0.5-1.5 g / L, sodium bicarbonate 1.5-2.5 g / L, sodium thiosulfate 1.5-2.5 g / L, magnesium chloride 0.2-0.8 g / L, dipotassium hydrogen phosphate 0.5-1.5 g / L, ferrous sulfate 0.02-0.08 g / L, manganese sulfate 0.05-0.1 g / L, and sodium chloride 0.02-0.08 g / L; The activation time in the seed culture medium is 2–3 days, and the inoculation amount is 1–3%. The fermentation medium comprises the following components: sodium nitrate 4.0-6.0 g / L, sodium bicarbonate 8.0-12.0 g / L, sodium thiosulfate 0.5-1.5 g / L, magnesium chloride 0.2-0.8 g / L, dipotassium hydrogen phosphate 0.5-1.5 g / L, ferrous sulfate 0.02-0.08 g / L, manganese sulfate 0.02-0.08 g / L, wheat bran 4.0-6.0 g / L, corn cob powder 0.5-1.5 g / L, and calcium carbonate 0.2-0.8 g / L; The time for large-scale expansion of the culture medium after transfer is 7-9 days, and the inoculum size is 8-12%.

7. The application of the bacterial agent according to any one of claims 1-6 in deep denitrification of wastewater.

8. The application according to claim 7, characterized in that, The wastewater is municipal sewage, industrial high-salinity wastewater, landfill leachate, groundwater nitrate nitrogen, low-temperature sewage, or comprehensive wastewater from industrial parks.

9. A wastewater treatment method, characterized in that, The wastewater treatment method includes: adding the bacterial agent according to any one of claims 1-6 to the wastewater to perform deep denitrification of the wastewater.

10. The wastewater treatment method according to claim 9, wherein the bacterial agent is a freeze-dried powder, and the amount of the bacterial agent added is 50-200 g / m 3 The system can tolerate salinity of ≤6000 mg / L, and is suitable for temperatures of 12-35℃. No organic carbon source is required throughout the process.

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