Short-cut nitrification-iron coupling sulfur cycle biological denitrification method

Abstract

The invention discloses a short-cut nitrification-iron coupling sulfur cycle biological denitrification method, and belongs to the technical field of nitrogen-containing wastewater treatment. According to the method, ammonia nitrogen in the wastewater is converted into nitrite by utilizing a domesticated nitrosobacteria agent; then, sulfate reducing bacteria and thiobacillus denitrificans are inoculated into a culture medium containing iron ions or ferrous ions together for domestication to obtain a complex microbial inoculant, and nitrite and nitrate in the wastewater are further removed through the complex microbial inoculant. In a sulfur circulating microorganism system, Fe < 2 + > can promote the activity of a biological denitrification key enzyme in a biological system by forming an iron carrier in the form of FeS, S < 2-> is fixed in the system and prevented from escaping, and when electron donors in the system are insufficient, the Fe < 2 + > can be used as a substitute electron donor for biological denitrification, so that the requirement on an external organic carbon source is reduced, and the energy consumption is reduced. And meanwhile, the impact load resistance of the system can be enhanced. Through sulfate reduction and sulfur autotrophic denitrification and iron coupling, sulfate in wastewater is converted into electron donors, a carbon-nitrogen-sulfur-iron biological co-reaction system is formed, the defects of a single-strain denitrification system are overcome, the denitrification effect is enhanced, and energy consumption and cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nitrogen-containing wastewater treatment, and in particular to a short-range nitrification-iron coupled sulfur cycle biological denitrification method. Background Art

[0002] With the development of the national economy and the improvement of people's living standards, the discharge of nitrogen-containing wastewater has increased dramatically, especially low-carbon nitrogen-containing wastewater. Among them, there are many problems in the removal of ammonia nitrogen in sewage. For the removal of ammonia nitrogen, traditional biological denitrification processes such as sequencing batch activated sludge and anaerobic / anoxic / aerobic processes are mature, stable and effective, but the operation is complicated and the energy consumption is high. New biological denitrification processes such as anaerobic ammonia oxidation, simultaneous nitrification and denitrification, and short-range nitrification-denitrification processes have the advantages of higher efficiency and low energy consumption, but they also face challenges due to environmental sensitivity and high operating requirements. Therefore, the process selection needs to be combined with actual needs.

[0003] In practical applications, the short-term nitrification process has the problem of unstable nitrite accumulation in the short-term nitrification stage. Compared with heterotrophic denitrification, biological autotrophic denitrification has the application advantage of low sludge production, which can reduce the operating costs caused by subsequent sludge disposal. Common autotrophic denitrification electron donors include hydrogen, iron and sulfur. Autotrophic denitrification can greatly reduce the cost of adding organic carbon sources. Sulfur autotrophic denitrification (SAD) is the current mainstream autotrophic denitrification process. It refers to the biological process in which sulfur-oxidizing bacteria reduce nitrite by oxidizing reduced sulfur under anoxic or anaerobic conditions, using sulfur as an electron donor, so it has significant carbon reduction benefits. At the same time, SAD also has certain disadvantages, such as: S 2- Easy to lose in the system, etc. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for short-range nitrification-iron coupled sulfur cycle biological denitrification. In the short-range nitrification process, nitrite bacteria first convert ammonia nitrogen into nitrite. In the sulfur cycle microbial system, Fe 2+ By forming iron carriers in the form of FeS, sulfide can be effectively fixed in the system to prevent it from escaping. When the electron donor in the system is insufficient, it can serve as an alternative electron donor for biological denitrification to reduce the demand for external organic carbon sources. Sodium sulfate, as a sulfur source for sulfur autotrophic denitrification, converts sulfate pollutants in wastewater into electron donors through the combination of sulfate reduction and sulfur autotrophic denitrification, forming a carbon-nitrogen-sulfur biological co-reaction system, overcoming the defects of a single bacterial species denitrification system. Iron carriers in the form of FeS can also promote the activity of key enzymes of biological denitrification in the biological system, enhance the system's ability to resist shock loads, and thus enhance denitrification stability.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a method for short-range nitrification-iron coupled sulfur cycle biological denitrification, which first uses a domesticated nitrosating bacterial agent to convert ammonia nitrogen in wastewater into nitrite; then sulfate-reducing bacteria and denitrifying Thiobacillus are inoculated together into a culture medium containing iron ions or ferrous ions to further remove nitrite and nitrate from the wastewater.

[0006] The culture medium formula for acclimating the nitrosating bacteria agent is: 0.2-2g / L NH4Cl, 0.5-2g / L NaHCO3; the acclimation conditions are DO≤0.5mg / L, 15-40°C, 80-200rpm, and the acclimation time is 7-20 days; the pH in the culture medium is 7-9, and the pH is adjusted by sodium bicarbonate or sodium carbonate. The preferred dosage of sodium bicarbonate is 1g / L.

[0007] The iron ion is selected from at least one of ferric sulfate, ferric nitrate and ferric chloride; the ferrous ion is selected from at least one of ferrous sulfate, ferrous chloride, ferrous sulfate and ferrous nitrate.

[0008] The culture medium containing ferrous ions is formulated as follows: 0.4-2 g / L C6H 12 O6, 0.2-3g / L NaNO2, 0.1-0.5g / L Na2SO4, 0.04-0.1g / L KH2PO4, 0.1-0.3g / L FeSO4; the culture medium formula containing iron ions is prepared by replacing 0.1-0.3g / L FeSO4 in the culture medium formula containing ferrous ions with 0.1-0.4g / L Fe2(SO4)3.

[0009] The acclimation conditions for acclimating sulfate-reducing bacteria and denitrifying thiobacillus are 15-40°C, 80-200rpm, anaerobic darkness, and acclimation time of 3-5 days; the pH in the culture medium is 6-9, and the pH is adjusted by sulfuric acid solution and sodium hydroxide solution. Preferably, 1 mol / L sulfuric acid solution and 1 mol / L sodium hydroxide solution are used.

[0010] Further,

[0011] The inoculation volume ratio of sulfate-reducing bacteria and denitrifying Thiobacillus during acclimation was 1-5; the concentration range of sulfate-reducing bacteria and denitrifying Thiobacillus in the inoculum after acclimation was 10 4 ~10 5 cfu / mL.

[0012] The concentration range of nitrite-producing bacteria after domestication is 10 3 ~10 5 cfu / mL.

[0013] The domesticated nitrite-containing bacteria are inoculated into nitrogen-containing wastewater, with the volume ratio of wastewater to bacteria being 0.5-5. An inorganic carbon source is added until the inorganic C / N is 0.3-1.5. Under low dissolved oxygen conditions of DO ≤ 0.5 mg / L, 15-40°C, 80-200 rpm, and pH 8-9, ammonia nitrogen in the wastewater is converted into nitrite; the conversion time is 6-24 hours.

[0014] The composite bacterial agent acclimated with iron ions or ferrous ions is inoculated into nitrogen-containing wastewater, the volume ratio of wastewater to composite bacterial agent is 0.5-5, an organic carbon source is added to COD / N of 1.6-3.7, and culture is carried out under anaerobic dark conditions at 15-40°C, 80-200rpm, and pH 6-9 to remove nitrite nitrogen and nitrate nitrogen in the wastewater.

[0015] The denitrification time is 6 to 24 hours.

[0016] The concentrations of nitrite nitrogen and nitrate nitrogen in nitrogen-containing wastewater are controlled at 50-1000 mg / L.

[0017] The inorganic carbon source is selected from at least one of sodium bicarbonate and sodium carbonate,

[0018] The organic carbon source is selected from at least one of glucose, sucrose and xylose.

[0019] The method of the invention is used for treating wastewater containing ammonia nitrogen, nitrate and nitrite.

[0020] Sulfate reduction: Under anaerobic conditions, sulfate-reducing bacteria in the inoculant use the electrons provided by the organic carbon source to reduce sulfate to H2S and HS - and S 2- Sulfides such as sulfide provide electron donors for sulfur autotrophic denitrification.

[0021] Sulfur autotrophic denitrification: Under anaerobic conditions, the denitrifying Thiobacillus in the bacterial agent uses the sulfide generated by sulfate reduction as an electron donor to provide electrons to the nitrite nitrogen in the water sample, and the nitrite nitrogen is converted into nitrogen gas, and the sulfide is converted back into sulfate. Using sulfide as an electron donor solves the problem of poor mass transfer efficiency in traditional sulfur autotrophic denitrification.

[0022] Iron carrier strengthening: Fe 2+ By forming an iron carrier in the form of FeS, S 2- It is fixed in the system to prevent it from escaping, and when the electron donor in the system is insufficient, it can serve as an alternative electron donor for biological denitrification, reducing the demand for external organic carbon sources and enhancing the system's ability to resist shock loads. Iron carriers in the form of FeS can also promote the activity of key enzymes in biological denitrification in biological systems.

[0023] Compared with the prior art, the present invention provides a short-range nitrification-iron coupled sulfur cycle biological denitrification method, which has the following effects:

[0024] (1) The present invention makes full use of the water quality characteristics of common low-carbon nitrogen-containing wastewater. This type of wastewater contains pollutants such as sulfate. Nitrosifying bacteria first convert ammonia nitrogen into nitrite, and the iron carrier-enhanced sulfur cycle biological denitrification agent then uses sulfate-reducing bacteria to reduce sulfate into H2S and HS. - and S 2- Sulfides such as ferrous iron can provide electron donors for sulfur autotrophic denitrification. Denitrifying Thiobacillus can use sulfides in water to achieve autotrophic denitrification and remove nitrite from water, while ferrous iron can react with S 2- Form FeS precipitates, effectively converting S 2- It is fixed in the system to prevent it from escaping. When trivalent iron is added to the system, it can also be converted into divalent iron. When the electron donor is insufficient in the system, it can be used as an alternative electron donor for biological denitrification. Iron carriers in the form of FeS can also promote the activity of key enzymes of biological denitrification in the biological system. At the same time, it can also enhance the flocculation effect of microorganisms and the system's ability to resist shock loads, thereby enhancing the system's denitrification stability.

[0025] (2) The nitrite-degrading bacteria have a high oxidation rate for ammonia nitrogen. Under the conditions of inorganic C / N of 0.3-1.5 and low dissolved oxygen, the maximum accumulation of nitrite in the culture medium with ammonia nitrogen as the only nitrogen source reached 230 mg / L, which shows that short-range nitrifying bacteria have great application potential in degrading ammonia nitrogen in wastewater;

[0026] (3) Both nitrite-oxidizing bacteria and iron-coupled sulfur cycle biological systems have a certain degree of salt tolerance and can be used to transform ammonia nitrogen in saline wastewater.

[0027] (4) The iron-coupled sulfur cycle microbial system of the present invention has high-efficiency low-carbon denitrification performance and is suitable for denitrification treatment of low-carbon wastewater. At 15-40°C and when COD / N is 2.6-3.7, the nitrite nitrogen removal rate reaches 100%, which shows that the iron-coupled sulfur cycle biological system has great application potential for degrading nitrite nitrogen in wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The nitrite accumulation of the short-range nitrifying microbial denitrifying agent under different inorganic C / N ratios in Example 1;

[0029] Figure 2 The nitrate accumulation of the short-range nitrifying microbial denitrifying agent under different inorganic C / N ratios in Example 1;

[0030] Figure 3 The nitrite accumulation of the short-range nitrifying microbial denitrifying agent under different sulfate concentrations in Example 1;

[0031] Figure 4 The nitrate accumulation of the short-range nitrifying microbial denitrifying agent under different sulfate concentrations in Example 1;

[0032] Figure 5 The nitrite accumulation of the short-range nitrifying microbial denitrifying agent under different chloride concentrations in Example 1;

[0033] Figure 6 The nitrate accumulation of the short-range nitrifying microbial denitrifying agent under different chloride concentrations in Example 1;

[0034] Figure 7 This is a diagram showing the nitrite removal effect of the sulfur cycle microbial denitrification agent under different carbon-nitrogen ratios in Example 3;

[0035] Figure 8 This is a diagram showing the nitrate removal effect of the sulfur cycle microbial denitrification agent under different carbon-nitrogen ratios in Example 3;

[0036] Fig. 9 This is a diagram showing the nitrite removal effect of the iron carrier enhanced sulfur cycle microbial denitrification agent under different carbon-nitrogen ratios in Example 3;

[0037] Fig.10 This is a diagram showing the nitrate removal effect of the iron carrier enhanced sulfur cycle microbial denitrification agent under different carbon-nitrogen ratio conditions in Example 3;

[0038] Fig.11 It is a comparison diagram of the NAR / NIR enzyme activities of the iron carrier enhanced sulfur cycle microbial denitrification agent and the sulfur cycle microbial denitrification agent in Example 6;

[0039] Fig.12 This is a scanning electron micrograph of the iron carrier enhanced sulfur cycle microbial denitrification agent in Example 7;

[0040] Fig.13 This is a scanning electron microscope image of the sulfur cycle microbial denitrification agent in Example 7;

[0041] Fig.14 This is a comparison chart of X-ray diffraction analysis (XRD) of the iron carrier enhanced sulfur cycle microbial denitrification agent and the sulfur cycle microbial denitrification agent in Example 8. DETAILED DESCRIPTION

[0042] Example 1

[0043] (1) Nitrosating bacteria were purchased from the “China Microbial Strain Query Network” platform, and the nitrosating bacteria platform number is bio-67412.

[0044] Domestication of the nitrosating bacteria agent of the present invention: inoculating nitrosating bacteria into a culture medium for domestication to obtain a nitrosating denitrifying bacteria agent, wherein the culture medium contains 0.5 g / L NH4Cl and 1 g / L NaHCO3;

[0045] The acclimation conditions were DO ≤ 0.5 mg / L, 30°C, 130 rpm, and the acclimation time was 12 days. The pH of the culture medium was 8, and sodium bicarbonate was used to adjust the pH. The concentration range of nitrite-forming bacteria in the inoculum after acclimation was 10 3 ~10 5 cfu / mL.

[0046] The nitrite-degrading bacteria were used in the ammonia nitrogen degradation experiment, in which the ammonia nitrogen concentration was 60±3 mg / L, the nitrogen source added to the wastewater was NH4Cl (i.e. ammonia nitrogen), the inorganic carbon source was NaHCO3, and the concentration of the biological bacteria was 10 3 ~10 5 cfu / mL, the ratio with wastewater was 1:1, and the degradation conditions were: temperature 30℃, time 6h, pH 8.

[0047] The short-range nitrification biological agent prepared in Example 1 was applied to the ammonia nitrogen degradation experiment. Figure 1 and Figure 2 are the nitrite accumulation and nitrate accumulation of short-range nitrifying microbial denitrification agents under different inorganic C / N ratios. Figure 1 It can be seen that when the inorganic C / N is 0.9-1.3, the nitrite accumulation is relatively high. When the inorganic C / N is 1.2-1.3, the nitrite accumulation reaches 30 mg / L. Figure 3 and Figure 4 They are respectively the accumulation of nitrite and nitrate under different sulfate concentrations when the inorganic carbon-nitrogen ratio of the short-range nitrifying microbial denitrifying agent is 1. Figure 3 It can be seen that when the sulfate concentration is 0-8g / L, the nitrite accumulation is the highest when the sulfate concentration is 3.2g / L, and the nitrite accumulation reaches 31mg / L; Figure 5 and Figure 6 The accumulation of nitrite and nitrate under different chloride concentrations when the inorganic carbon-nitrogen ratio of the short-range nitrifying microbial denitrifying agent is 1. Figure 5 It can be seen that the nitrite accumulation is similar when the chloride concentration is 0 and 1.6 g / L, and the nitrite accumulation reaches 30 mg / L, indicating that the nitrite bacteria has a certain salt tolerance. Figure 2 , Figure 4 and Figure 6It can be seen that the nitrate accumulation is all below 4 mg / L. Table 1 shows the nitrite accumulation effect of long-term operation of short-range nitrifying microbial agents. When the initial concentration of ammonia nitrogen is 289.5 mg / L, the maximum accumulation of nitrite can reach 232.3 mg / L after 48 hours of reaction, and the maximum accumulation of nitrate can reach 44.2 mg / L. The efficiency of converting ammonia nitrogen into nitrite is relatively high.

[0048] Table 1 Nitrite accumulation effect of short-term nitrification microbial agents after long-term operation

[0049]

[0050] Example 2: Domestication of iron carrier-enhanced sulfur cycle microbial denitrification agent

[0051] The sulfate-reducing bacteria and denitrifying Thiobacillus in this example were purchased from the "China Microbial Strain Query Network" platform. The platform number of the sulfate-reducing bacteria is bio-00232, and the platform number of the denitrifying Thiobacillus is bio-72703.

[0052] The iron carrier enhanced sulfur cycle composite bacterial agent of the present invention is domesticated by inoculating sulfate reducing bacteria and denitrifying Thiobacillus in a culture medium at a volume of 1:1 to obtain an iron carrier enhanced sulfur cycle microbial denitrifying bacterial agent, wherein the culture medium contains 0.5 g / L C6H 12 O6, 1g / L NaNO2, 0.1g / L Na2SO4, 0.06g / L KH2PO4, 0.1g / L FeSO4;

[0053] The acclimation conditions were 30°C, 130rpm, anaerobic darkness, and acclimation time was 7 days; the pH in the culture medium was 7, and the pH was adjusted using 1 mol / L sulfuric acid solution and 1 mol / L sodium hydroxide solution. The concentration range of sulfate-reducing bacteria and denitrifying Thiobacillus in the inoculum after acclimation was 10 4 ~10 5 cfu / mL.

[0054] At the same time, a sulfur cycle composite bacterial agent was prepared as a control. The difference between the preparation of this bacterial agent and the preparation of the iron carrier enhanced sulfur cycle composite bacterial agent is that FeSO4 is not added to the culture medium, and the other culture and acclimatization steps are the same.

[0055] Example 3: Improvement of denitrification capacity of iron carrier enhanced sulfur cycle composite bacterial agent compared with sulfur cycle composite bacterial agent under different carbon-nitrogen ratio conditions

[0056] The iron carrier enhanced sulfur cycle composite bacterial agent and the sulfur cycle composite bacterial agent prepared in Example 2 were added to the simulated nitrogen-containing wastewater, respectively, and the volume ratio of wastewater to composite bacterial agent was 3:1, and NO2 - -N concentration was 60±3 mg / L, and the organic carbon source added to the simulated nitrogen-containing wastewater was C6H12 O6, the sulfur source is Na2SO4, the nitrogen source is NaNO2 (i.e. nitrite nitrogen), organic carbon source and nitrogen source are added until COD / N is 1.6, 2.1, 2.6, 3.2, 3.7 respectively, and the reaction is carried out under anaerobic darkness, 30°C, 120rpm, pH 7. The removal capacity of sulfur cycle compound bacteria agent and iron carrier enhanced sulfur cycle compound bacteria agent on nitrite after 6 hours of reaction is measured. The results are as follows Figure 7 and Fig. 9 As shown in Figure 2, the sulfur cycle compound bacteria agent and iron carrier enhanced the removal ability of the sulfur cycle compound bacteria agent on nitrite. Figure 8 and Fig.10 As shown, the iron carrier enhanced sulfur cycle composite bacteria agent can achieve a nitrite removal rate of more than 80% when the COD / N is 2.1, and can achieve a nitrite removal rate of more than 92% when the COD / N is 2.6-3.2, and the nitrite removal rate is 100% when the COD / N is 3.2-3.7. The nitrite removal rate of the sulfur cycle composite bacteria agent is 69% when the COD / N is 2.1, and although it can achieve a nitrite removal rate of more than 89% when the COD / N is 2.6-3.2, the nitrite removal rate is 96% when the COD / N is 3.2-3.7. After 6 hours of reaction, the nitrate concentration of the iron carrier enhanced sulfur cycle composite bacteria agent is below 1 mg / L, indicating that the iron carrier enhanced sulfur cycle composite bacteria agent has a higher denitrification efficiency than the sulfur cycle composite bacteria agent under low carbon-nitrogen ratio conditions, can reduce the use of organic carbon sources, and has good economic benefits.

[0057] Example 4: Improvement of denitrification capacity of the iron carrier-enhanced sulfur cycle composite bacterial agent acclimated with ferrous iron compared with the sulfur cycle composite bacterial agent with added ferrous iron

[0058] The difference between Example 4 and Example 3 is that the COD / N is 2.6, the influent nitrite nitrogen concentration is 200±5 mg / L, and 1 mM ferrous ions are added to the sulfur cycle composite bacteria wastewater. It can be seen from Table 2 that compared with the sulfur cycle composite bacteria with added ferrous ions, the iron carrier enhanced sulfur cycle composite bacteria after long-term ferrous domestication has a higher nitrite nitrogen degradation efficiency, and the nitrite concentration is reduced from 200.74 mg / L to 0.07 mg / L within 24 hours, and the degradation efficiency reaches 99.97%. The nitrate concentration is reduced from 18.08 mg / L to 0.02 mg / L, and the degradation efficiency reaches 99.88%. The nitrite removal rate of the sulfur cycle composite bacteria in 24 hours is 81.17%, and the nitrate removal rate is 78.74%, indicating that the iron carrier enhanced sulfur cycle composite bacteria has a better denitrification effect after long-term domestication.

[0059] Table 2 Denitrification effect of the iron carrier enhanced sulfur cycle composite bacteria agent after long-term ferrous iron acclimation and the sulfur cycle composite bacteria agent with added ferrous iron

[0060]

[0061] Example 5: Improvement of denitrification capacity of iron carrier enhanced sulfur cycle composite bacterial agent compared with sulfur cycle composite bacterial agent under high concentration nitrite wastewater load

[0062] The difference between Example 5 and Example 3 is that the COD / N is 2.6, and the influent nitrite nitrogen concentration is 180-227 mg / L. It can be seen from Tables 3 and 4 that compared with the sulfur cycle composite bacterial agent, the iron carrier enhanced sulfur cycle composite bacterial agent has a nitrite removal rate of more than 99% after reacting for 24 hours under different nitrite wastewater loads, and a nitrate removal rate of more than 95%. However, the sulfur cycle composite bacterial agent still has nitrite accumulation after reacting for 24 hours under different nitrite loads, and the nitrite removal rate is between 80%-90%, and the nitrate removal rate is between 70%-90%. As the nitrite concentration increases, the nitrite removal rate gradually decreases. It shows that the iron carrier enhanced sulfur cycle composite bacterial agent can enhance the shock load resistance to water quality fluctuations and improve the denitrification efficiency under different nitrite wastewater loads.

[0063] Table 3 Denitrification effect of iron carrier enhanced sulfur cycle composite bacterial agent under high concentration nitrite wastewater load

[0064]

[0065] Table 4 Denitrification effect of sulfur cycle composite bacterial agent under high concentration nitrite wastewater load

[0066]

[0067] Example 6: Improvement of the activity of key denitrification enzymes by using iron carrier-enhanced sulfur cycle composite bacterial agent compared with sulfur cycle composite bacterial agent

[0068] The sulfur cycle composite bacterial agent (Iron-0) and the iron carrier enhanced sulfur cycle composite bacterial agent (Iron-1) were centrifuged at 4000rpm, 4℃, 10min, and then washed twice with 0.1M PBS buffer. This step was repeated three times, and the last time they were resuspended with 0.1M PBS buffer, and then ultrasonically broken at 20kHz, 5min, 4℃, and centrifuged at 10000g, 4℃, 10min to extract the supernatant. The supernatant was the crude enzyme solution, which was used to determine the activity of the key denitrification enzymes. The activities of nitrate reductase (NAR) and nitrite reductase (NIR) in the crude enzyme solutions of different groups were determined. Fig.11 As shown, compared with the sulfur cycle composite bacteria agent, the sulfur cycle composite bacteria agent enhanced by iron carrier increased the activities of two key enzymes under the condition of COD / N of 2.1 and promoted the removal of nitrite, indicating that the sulfur cycle composite bacteria agent enhanced by iron carrier accelerated the removal rate of nitrite and nitrate by enhancing the activity of key denitrification enzymes.

[0069] Example 7: Comparison of SEM and EDS of iron carrier enhanced sulfur cycle composite bacterial agent and sulfur cycle composite bacterial agent

[0070] SEM images of iron carrier enhanced sulfur cycle composite bacterial agent and sulfur cycle composite bacterial agent Fig.12 and Fig.13 As shown. Fig.13 It can be seen that the surface of the sulfur cycle composite bacterial agent is smooth and there are certain gaps between the bacteria. Fig.12 Dense and fine-sized precipitates appeared on the surface of the iron carrier-enhanced sulfur cycle composite agent. These precipitates almost filled the gaps between the bacteria, making the sludge surface structure more compact. The formed precipitates allowed the microorganisms to condense into bacterial flocs, making the flocculation effect of the microorganisms better. It can be seen from Tables 5 and 6 that the iron carrier-enhanced sulfur cycle composite agent has an increased mass of Fe compared to the sulfur cycle composite agent, generating precipitate FeS. This iron carrier in the form of FeS can effectively transfer S 2- It is fixed in the system to prevent it from escaping, and when the electron donor is insufficient in the system, it can serve as an alternative electron donor for biological denitrification, reducing the demand for external organic carbon sources and enhancing the denitrification stability of the system.

[0071] Table 5 Element weight and atomic percentage corresponding to the EDS spectrum of the iron carrier enhanced sulfur cycle composite bacterial agent

[0072] element Weight Percent Atomic Percent carbon 70.5％ 90.3％ sulfur 7.4％ 3.6％ iron 22.1％ 6.1％ total 100％ 100％

[0073] Table 6 Element weight and atomic percentage corresponding to the EDS spectrum of sulfur cycle composite bacterial agent

[0074] element Weight Percent Atomic Percent carbon 72.42％ 91.8％ nitrogen 3.39％ 1.61％ sulfur 24.19％ 6.59％ total 100％ 100％

[0075] Example 8: XRD comparison between iron carrier enhanced sulfur cycle composite bacterial agent and sulfur cycle composite bacterial agent

[0076] X-ray diffraction analysis (XRD) revealed the crystal structure changes of the iron carrier enhanced sulfur cycle composite agent and the sulfur cycle composite agent. Iron-0 and iron-1 represent the XRD analysis diagrams of the sulfur cycle composite agent and the iron carrier enhanced sulfur cycle composite agent, respectively. Fig.14As shown. No relevant characteristic peaks appeared in the sulfur cycle composite bacterial agent that was not acclimated with iron, while the iron carrier enhanced sulfur cycle composite bacterial agent showed peaks related to sulfur and iron at 27.6°, 21.1°, 52.2° and 43.9°. By comparing the PDF#49-1632 card, it was determined that the substance was ferrous sulfide (FeS), which was consistent with the previous SEM and EDS analysis. Therefore, it can be determined that the precipitate formed on the sludge surface is FeS. Ferrous sulfide, as the main component of natural pyrrhotite, has a flaky structure similar to graphite and belongs to the hexagonal crystal system. Thiobacillus can use it for denitrification reaction, and the Fe and S in it can be used as electron donors for denitrification. The FeS produced can improve the denitrification performance of the biological system and enhance the denitrification stability of the system.

[0077] Example 9: Short-term nitrification nitrite accumulation effect and iron carrier enhanced sulfur cycle composite bacterial agent denitrification performance

[0078] The nitrite-degrading bacteria agent in Example 1 was applied to the ammonia nitrogen degradation experiment, and the concentration of the biological bacteria agent was 10 3 ~10 5 cfu / mL, the ratio of the wastewater to the wastewater was 1:1, the ammonia nitrogen concentration was 60.33 mg / L, the inorganic C / N was 1, the degradation conditions were a temperature of 30°C, a reaction time of 6 h, and a pH of 8. The short-range nitrification effluent was treated with the iron carrier enhanced sulfur cycle composite bacterial agent prepared in Example 2. The volume ratio of the short-range nitrification effluent to the iron carrier enhanced sulfur cycle composite bacterial agent was 3:1, and NO2 - -N concentration was 23.51 mg / L, organic carbon source was added until COD / N was 2.6, and the reaction was carried out under anaerobic darkness, 30°C, 120rpm, and pH 7. The removal capacity of the iron carrier-enhanced sulfur cycle composite agent for nitrite in the short-range nitrification effluent was determined after 3 hours of reaction. As shown in Table 7, the nitrite accumulation of the short-range nitrification microbial denitrification agent reached 29.81 mg / L after 6 hours of reaction. The effluent was then treated with the iron carrier-enhanced sulfur cycle composite agent. After 3 hours of reaction, the residual nitrite concentration was 0.17 mg / L, and the removal rate reached 99%. As shown in Table 7, the residual nitrate concentration after 3 hours of reaction was 1.98 mg / L, indicating that the iron carrier-enhanced sulfur cycle composite agent can also achieve a high nitrite removal rate for the effluent from the short-range nitrification stage.

[0079] Table 7 Short-term nitrification nitrite accumulation effect and iron carrier enhanced sulfur cycle composite bacterial agent denitrification performance

[0080]

[0081]

[0082] Therefore, the present invention adopts the above-mentioned short-range nitrification-iron coupled sulfur cycle biological denitrification bacterial agent preparation method and application, which can not only remove ammonia nitrogen, nitrite nitrogen and nitrate nitrogen under low-carbon conditions, but also adapt to the complex wastewater generated in the actual process operation. This method has good application prospects for removing ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in low-carbon wastewater.

[0083] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for short-range nitrification-iron coupled sulfur cycle biological denitrification, characterized in that: The following steps are involved: First, the ammonia nitrogen in the wastewater is converted into nitrite using the domesticated nitrite-degrading bacteria; then sulfate-reducing bacteria and denitrifying Thiobacillus are inoculated together into a culture medium containing iron ions or ferrous ions to obtain a composite bacterial agent to further remove nitrite and nitrate from the wastewater.

2. The method according to claim 1, characterized in that: The iron ion is selected from at least one of ferric sulfate, ferric nitrate and ferric chloride; the ferrous ion is selected from at least one of ferrous sulfate, ferrous chloride, ferrous sulfate and ferrous nitrate.

3. The method according to claim 1 or 2, characterized in that: The culture medium formula for acclimating and culturing nitrite-containing bacteria is: 0.2-2 g / L NH4Cl, 0.5-2 g / L NaHCO3; the acclimation conditions are DO≤0.5 mg / L, 15-40°C, 80-200 rpm, and the acclimation time is 7-20 days; The pH of the culture medium is 7 to 9, and sodium bicarbonate or sodium carbonate is used to adjust the pH; The culture medium containing ferrous ions is formulated as follows: 0.4-2 g / L C6H 12 O6, 0.2-3g / L NaNO2, 0.1-0.5g / L Na2SO4, 0.04-0.1g / L KH2PO4, 0.1-0.3g / L FeSO4; the culture medium formula containing iron ions is obtained by replacing 0.1-0.3g / L FeSO4 in the culture medium formula containing ferrous ions with 0.1-0.4g / L Fe2(SO4)3; The acclimation conditions for acclimating sulfate-reducing bacteria and denitrifying Thiobacillus are 15-40° C., 80-200 rpm, anaerobic darkness, and the acclimation time is 3-5 days; the pH in the culture medium is 6-9, and the pH is adjusted using sulfuric acid solution and sodium hydroxide solution.

4. The method according to any one of claims 1 to 3, characterized in that: The inoculation volume ratio of sulfate-reducing bacteria and denitrifying Thiobacillus during acclimation was 1-5, and the concentration range of sulfate-reducing bacteria and denitrifying Thiobacillus in the inoculum after acclimation was 10 4 ~10 5 cfu / mL; the concentration range of nitrite-containing bacteria after domestication is 10 3 ~10 5 cfu / mL.

5. The method according to any one of claims 1 to 4, characterized in that: The domesticated nitrite-containing bacteria are inoculated into nitrogen-containing wastewater, with the volume ratio of wastewater to bacteria being 0.5-5. An inorganic carbon source is added until the inorganic C / N is 0.3-1.

5. Under low dissolved oxygen conditions of DO ≤ 0.5 mg / L, 15-40°C, 80-200 rpm, and pH 8-9, ammonia nitrogen in the wastewater is converted into nitrite; the conversion time is 6-24 hours.

6. The method according to any one of claims 1 to 4, characterized in that: The composite bacterial agent acclimated with iron ions or ferrous ions is inoculated into nitrogen-containing wastewater, the volume ratio of wastewater to composite bacterial agent is 0.5-5, and an organic carbon source is added to COD / N of 1.6-3.

7. Under anaerobic dark conditions, the culture is carried out at 15-40°C, 80-200rpm, and pH 6-9 to further remove nitrite nitrogen and nitrate nitrogen in the wastewater.

7. The method according to claim 1 or 6, characterized in that: The denitrification time is 6 to 24 hours.

8. The method according to claim 1, 5 or 6, characterized in that: The concentrations of nitrite nitrogen and nitrate nitrogen in nitrogen-containing wastewater are controlled at 50-1000 mg / L.

9. The method according to claim 1, 5 or 6, characterized in that: The inorganic carbon source is selected from at least one of sodium bicarbonate and sodium carbonate, and the organic carbon source is selected from at least one of glucose, sucrose and xylose.

10. The method according to claim 1, characterized in that Used to treat wastewater containing ammonia nitrogen, nitrate and nitrite.

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