Structurally-reinforced modified sulfur autotrophic microbial agent capsule as well as preparation method and application thereof

Abstract

The invention relates to a structure-reinforced modified sulfur autotrophic microbial agent capsule and a preparation method and application thereof. The preparation method comprises the following steps: carrying out thiolation modification on alginate, and then mixing with polyvinyl alcohol to obtain a gel solution; adding waterborne polyurethane into the gel solution to prepare porous modified gel; adding powdered sulfur and the iron-rich sludge biochar, stirring and mixing to obtain modified reinforced gel which has a reinforced network structure and contains an inorganic electron donor; and mixing with sulfur autotrophic bacteria liquid, and carrying out cross-linking immobilization to obtain the composite capsule. According to the capsule, on the basis of strengthening the mechanical and mass transfer performance of hydrogel, the bioavailability of sulfur is improved, and the denitrification effect is improved through immobilized active microorganisms. The removal effect on nitrate nitrogen and nitrite nitrogen in sewage can be obviously optimized, and the sewage treatment agent has reusability and anti-impact stability.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and particularly relates to a modified sulfur autotrophic bacteria agent capsule with a reinforced structure, and a preparation method and application thereof. Background Art

[0002] Sulfur autotrophic denitrification (SAD) is a process in which sulfur oxidizing bacteria (SOB) use inorganic sulfur compounds as electron donors to reduce nitrates. This process has excellent denitrification effect, does not require organic carbon, has low sludge production and operating costs, and has low greenhouse gas emissions. It is expected to achieve carbon neutrality in wastewater treatment plants. However, the SAD denitrification load is usually 0.5~2.5 kg N / m 3 / d, which is much lower than the heterotrophic denitrification process (3.0~6.0 kg N / m 3 / d), the main reasons are: ① the SAD process cannot retain enough SOB biomass; ② the uptake rate of solid sulfur by microorganisms is slow.

[0003] Considering the slow growth rate of SOB (0.04-0.27 h–1), immobilizing it to form biofilm or particles is an effective way to enrich biomass and increase the electron transfer rate.

[0004] At present, the embedding method is the main means of microbial immobilization technology, which is simple to operate and has little effect on microbial activity. Commonly used microbial embedding materials are mainly sodium alginate (SA) and polyvinyl alcohol (PVA). SA has abundant hydroxyl and carboxyl groups on its molecular skeleton, which is easy to form gel particles, but its mechanical strength is low and its biodegradability is poor; and PVA-derived carriers generally have three main problems: ① The generated gel particles are easy to agglomerate; ② The cross-linking speed is slow, and the survival rate of immobilized microorganisms drops sharply under strong acidity (pH <4); ③ The generated PVA carrier lacks sufficient pore structure, which affects the mass transfer of nutrients in sewage and the excretion of microbial metabolites, and is prone to swelling and breaking after long-term use.

[0005] In addition, when SA is used as an embedding material, increasing the SA content will increase the viscosity of the capsule and make it difficult to form a ball, and excessive SA will affect the activity of microorganisms; when PVA is used as an embedding material, increasing the PVA content will increase the mechanical strength of the capsule, but at the same time it will also reduce the porosity and mass transfer performance. On the other hand, there is currently a lack of research on the long-term performance of bacterial capsules and the bioavailability of sulfur, and large-scale applications may face limitations.

[0006] Therefore, modifying the PVA / SA carrier, strengthening the mechanical strength and mass transfer performance of the carrier, increasing the types and quantity of activated groups, and improving the bioavailability of sulfur can further promote the large-scale application of the SAD process. Summary of the invention

[0007] The primary purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a structurally reinforced modified sulfur autotrophic bacterial agent capsule and a preparation method thereof. By effectively fixing SOB biomass in particles with high mechanical strength and excellent mass transfer performance, the bioavailability of sulfur is improved, thereby improving the denitrification effect of the sulfur autotrophic denitrification process.

[0008] Another object of the present invention is to provide application of the structurally reinforced modified sulfur autotrophic agent capsule.

[0009] The purpose of the present invention is achieved through the following technical solutions: The first aspect of the present invention provides a method for preparing a structure-enhanced modified sulfur autotrophic agent capsule, comprising the following steps: S1. Dissolve polyvinyl alcohol and thiolated alginate in water at 90° C. to obtain a gel solution, wherein the polyvinyl alcohol content is 6-10 wt % and the thiolated alginate content is 0.5-2 wt %.

[0010] The thiolated alginate can be prepared by thiolation of common alginates such as thiolated sodium alginate, thiolated calcium alginate, thiolated potassium alginate, etc.

[0011] Preferably, the thiolated alginate is activated by reacting an alginate solution with 1-ethyl-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC·HCl) and N-hydroxysuccinimide at room temperature; then, adding cysteine, adjusting the pH to about 4.0, and reacting at room temperature with stirring; then, raising the pH to 6.0, and reacting at room temperature with stirring for 0.5 to 2 hours; finally, dialysis purification of the obtained reaction solution, and freeze drying.

[0012] In a preferred embodiment, the thiolated alginate is thiolated sodium alginate. Specifically, the preparation method of thiolated sodium alginate includes: preparing a 0.5-1wt% sodium alginate (SA) solution, adding 1-ethyl-(3-dimethylaminopropyl)-carbodiimide hydrochloride and 100 mmol / L N-hydroxysuccinimide at a final concentration of 50 mmol / L, respectively, and reacting at room temperature for 30-60 minutes to convert the activated sodium alginate carboxyl group into an active ester product; then, adding cysteine ​​twice the weight of the sodium alginate, adjusting the pH to about 4.0, and reacting at room temperature for 2 hours; then, raising the pH to 6.0, and reacting at room temperature for 1 hour; dialyzing the obtained reaction solution to purify the thiolated sodium alginate, and collecting the sample by freeze drying.

[0013] S2. After the gel solution is cooled to room temperature, 1 to 5 wt % of anionic aqueous polyurethane having a solid content of 30% is added and stirred to obtain a porous modified gel.

[0014] S3. Add 10-20 wt % sulfur powder and 1-5 wt % iron-rich sludge biochar to the porous modified gel, stir and mix, and obtain a modified and reinforced gel.

[0015] Preferably, the particle size of the sulfur powder and sludge biochar is 200-300 mesh.

[0016] Preferably, the iron-rich sludge biochar is produced by anoxic thermal decomposition of iron-rich sludge at 500-700°C, wherein the iron content of the iron-rich sludge is 20wt%-40wt%, and the organic matter content is 20wt%-30wt% (all dry weight). The iron-rich sludge can be derived from excess sludge using an inorganic iron salt flocculant or excess sludge from advanced oxidation processes (AOPs) involving iron catalysts.

[0017] S4. Add 30-40 wt % sulfur autotrophic bacteria solution to the modified and strengthened gel, stir and mix evenly to obtain a gel-bacteria solution mixture, and then drop the gel-bacteria solution mixture into the cross-linking liquid to obtain the structurally strengthened modified sulfur autotrophic bacteria capsule.

[0018] Preferably, the total number of viable bacteria in the sulfur autotrophic bacterial liquid is ≥ 2×10 8 CFU / g, and the sulfur autotrophic bacterial liquid is denitrifying Thiobacillus and / or Thiomonas bacterial liquid.

[0019] Preferably, the cross-linking liquid is a 2-4 wt% calcium chloride solution.

[0020] Alginate has good biocompatibility, biodegradability and non-toxicity. Its performance can be further improved by chemical modification or physical blending. The present application uses cysteine ​​to functionalize alginate to form thiolated alginate, which is then mixed with PVA. As the functional groups (carboxyl, hydroxyl, thiol and amide) of alginate increase and disulfide bonds are formed, the conversion of solid sulfur to soluble sulfur can be accelerated: for example, hydrophilic groups (such as carboxyl) make sulfur particles more easily absorbed into bacterial cells, accelerating the transport of sulfur at the solid phase interface; disulfide bonds and thiol groups can open the SS single bonds in elemental sulfur through nucleophilic attacks.

[0021] Adding waterborne polyurethane can promote the formation of pores and pores on the surface of the carrier and expand the internal three-dimensional network structure. The honeycomb pore structure can provide abundant attachment sites for microorganisms, protecting them from external toxicity, and the dense external and loose internal pore structure can ensure the transport of nutrients and metabolites and prevent the loss of immobilized microorganisms.

[0022] The iron-based sludge biochar was introduced into the polymer network structure of the carrier by physical blending. Its main functions are: ① improving the mechanical strength of the carrier. Its unique structure is firmly combined with the polymer molecules to form a hybrid material, which gradually reduces the water swelling performance of the capsule and significantly improves the mechanical strength; ② generating S-Fe co-electron donors in the system through the Fe (II) / Fe (III) cycle; ③ removing phosphorus to a certain extent. Due to thermal decomposition, the iron contained in the iron-based sludge biochar mainly exists in the form of Fe (III). Although Fe (III) cannot directly participate in the denitrification process as an electron donor, the Fe (II) / Fe (III) cycle can be generated through microbial action, that is, under anoxic conditions, Fe (III) acts as the final electron acceptor of iron-reducing bacteria, while Fe (II) acts as an electron donor for iron-oxidizing bacteria. Different forms of Fe can promote the performance of SAD denitrification. The hydrogel obtained has a reinforced network structure and contains inorganic electron donors, which is beneficial to nitrification.

[0023] The second aspect of the present invention also provides a modified and enhanced sulfur autotrophic composite bacterial agent capsule prepared by the preparation method. The sulfur autotrophic bacterial agent capsule is based on strengthening the mechanical and mass transfer properties of the hydrogel and improving the bioavailability of sulfur, and improves the denitrification effect through immobilized active microorganisms. Under suitable working conditions, the composite bacterial agent capsule can significantly optimize the removal effect of nitrate nitrogen and nitrite nitrogen in sewage, and has certain reusability and impact stability.

[0024] The third aspect of the present invention also provides the use of the modified and enhanced sulfur autotrophic composite bacterial agent capsule in water treatment, such as for treating domestic sewage containing nitrate nitrogen and nitrite nitrogen, aquaculture tail water, industrial tail water, surface water and groundwater.

[0025] In some embodiments, a circulating biological fluidized bed reactor is used, and the filling ratio of the composite bacterial agent capsules of the present invention is 40-60% (v / v). The composite bacterial agent capsules are suspended and fluidized through an external circulation water circuit or by filling with inert gas, which can increase the contact frequency between the bacterial agent and the flowing water and enhance the absorption and utilization of pollutants in the sewage.

[0026] In some embodiments, a column reactor with fixed bed filler is used, and the composite bacterial agent capsule of the present invention can be used as a filler or supplementary material and added all at once or in batches to enhance the removal efficiency of pollutants.

[0027] The fourth aspect of the present invention provides a water treatment agent, comprising the modified and enhanced sulfur autotrophic composite bacterial agent capsule.

[0028] Compared with the prior art, the present invention has the following beneficial effects: The present invention is to modify alginate by thiolation, and then mix it with polyvinyl alcohol to obtain a gel solution; add waterborne polyurethane to the gel solution to obtain a porous modified gel; add sulfur powder and iron-rich sludge biochar and stir and mix to obtain a modified and reinforced gel with a reinforced network structure and containing an inorganic electron donor; and then mix it with a sulfur autotrophic bacteria liquid, and perform cross-linking and fixation to obtain a composite capsule. The capsule improves the bioavailability of sulfur based on the mechanical and mass transfer properties of the reinforced hydrogel, and improves the denitrification effect through immobilized active microorganisms. It can significantly optimize the removal effect of nitrate nitrogen and nitrite nitrogen in sewage, and has certain reusability and impact stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The appearance characteristics of the sulfur autotrophic agent capsule prepared in this example; Figure 2 The mass transfer efficiency comparison curve of the sulfur autotrophic bacteria capsules prepared in the embodiment and comparative examples 1 to 3; Figure 3 The change trend of nitrate nitrogen and nitrite nitrogen concentrations in the inlet and outlet water after the sulfur autotrophic bacteria capsules prepared in Examples and Comparative Examples 1 to 3 are loaded into the fluidized bed reactor; Figure 4 This is a comparison chart of the removal effects of nitrate nitrogen in sewage after the sulfur autotrophic bacteria capsules prepared in Example and Comparative Example 4 were loaded into an upflow denitrification packed bed. DETAILED DESCRIPTION

[0030] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0031] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0032] Example S1. Add 8 g of polyvinyl alcohol and 1 g of thiolated sodium alginate into 100 ml of distilled water, and stir in a 90°C water bath until completely dissolved to obtain a gel solution.

[0033] The preparation of thiolated alginate comprises the following steps: S11. Add 1 g of sodium alginate powder to 100 ml of distilled water and stir in a 90°C water bath until completely dissolved; S12. After cooling to room temperature, 1-ethyl-(3-dimethylaminopropyl)-carbodiimide hydrochloride and 100 mmol / L N-hydroxysuccinimide were added to the solution at a final concentration of 50 mmol / L, and the mixture was stirred at room temperature for 60 min. S13. 2 times the weight of sodium alginate was added to the reaction mixture, cysteine ​​was adjusted to about 4.0, and the reaction was stirred at room temperature for 2h; S14. The pH of the reaction was raised to 6.0 and the reaction was stirred at room temperature for 1 h; S15. The reaction solution was dialyzed against 1 mmol / L hydrochloric acid solution, dialyzed twice against 1% NaCl in 1 mmol / L HCl solution, and dialyzed again thoroughly against 1 mmol / L HCl aqueous solution for purification. The sample was freeze-dried at -40°C and stored at 4°C until use.

[0034] S2. After the gel solution obtained in S1 was cooled to room temperature, 1 wt % of anionic aqueous polyurethane with a solid content of 30% was added and stirred for 5 min to obtain a porous modified gel.

[0035] S3. Add 15 wt % sulfur powder and 2.5 wt % iron-rich sludge biochar to the porous modified gel obtained in S2, and stir to mix, to obtain a modified reinforced gel having a reinforced network structure and containing an inorganic electron donor.

[0036] The preparation of iron-rich sludge biochar includes the following steps: S31. The sludge from the water treatment plant was dried at 105°C to obtain dried sludge, wherein the iron content was 20wt%~40wt% and the organic matter content was 20wt%~30wt% (all dry weight); S32. Under anoxic conditions, the dried sludge was thermally decomposed at 700℃ for 4h, and then ground into 200-300 mesh after cooling to obtain iron-rich sludge biochar.

[0037] S4. Add 30 wt% sulfur autotrophic bacterial solution to the modified and strengthened gel obtained in S3, stir evenly, and obtain a gel-bacteria solution mixture. The sulfur autotrophic bacterial solution contains a mixed bacterial solution of denitrifying Thiobacillus and Thiomonas, and the total number of viable bacteria is 3.50×10 8 CFU / g.

[0038] S5. Completely dissolve 4 g of calcium chloride in 200 ml of distilled water to prepare a 2 wt % calcium chloride crosslinking solution.

[0039] S6. Use a pear-shaped separatory funnel or a perforated plate to drop the gel-bacteria mixture obtained in S4 into 2 wt% calcium chloride cross-linking solution for fixation, and then cross-link at 4°C for 12 hours to obtain composite capsules with a diameter of 3~4 mm.

[0040] Comparative Example 1 The difference from the embodiment is that, in the comparative example 1, when preparing the bacterial agent capsule, sodium alginate is used instead of thiolated sodium alginate, and no aqueous polyurethane or iron-rich sludge biochar is added; the details are as follows: S1. Add 8 g polyvinyl alcohol and 1 g sodium alginate to 100 ml distilled water, and stir in a 90°C water bath until completely dissolved to obtain a gel solution; S2. After the gel solution was cooled to room temperature, 30wt% sulfur autotrophic bacteria solution was added and stirred evenly; S3. 4g of calcium chloride was completely dissolved in 200ml of distilled water to obtain a 2 wt% calcium chloride cross-linking solution; S4. Use a pear-shaped separatory funnel or a perforated plate to drop the mixture into the cross-linking solution for fixation, and then cross-link at 4°C for 12 hours to obtain composite capsules with a diameter of 3~4 mm.

[0041] Comparative Example 2 The preparation method of this comparative example is similar to that of the embodiment, except that no waterborne polyurethane modification is added.

[0042] Comparative Example 3 The preparation method of this comparative example is similar to that of the embodiment, except that no iron-rich sludge biochar is added.

[0043] Comparative Example 4 The preparation method of this comparative example is similar to that of the embodiment, except that no sulfur autotrophic bacteria liquid is added.

[0044] Performance Testing: The appearance characteristics of the sulfur autotrophic agent capsules of the morphology embodiment are as follows Figure 1 As shown, the capsule is spherical and does not show tailing or aggregation.

[0045] 2. Mechanical properties Randomly select quantitative examples and comparative examples of bacterial capsules, place them on a balance, press them slowly with a flat plate, and record the reading when they are broken as the compressive strength index. Another quantitative capsule is placed in 40 mL of distilled water, stirred at room temperature at 500 rpm / min for 120 minutes, and its unbroken retention rate is measured as a mechanical strength index. According to the experimental results, the physical properties of comparative example 1 without adding water-based polyurethane and sludge biochar are the worst, and comparative example 2 directly using biochar as the adsorption matrix does not significantly improve the mechanical strength of the capsule. Comparative example 3 modified with water-based polyurethane has a three-dimensional network structure inside the capsule, and the capsule retention rate after high-speed stirring reaches 70%. Furthermore, the embodiment reduces the water swelling performance of the capsule through biochar, significantly improves the mechanical strength of the material, the compressive strength reaches 252.35g, and the capsule retention rate is 82%.

[0046] Table 1 Physical properties of bacterial capsules

[0047] 3. Mass transfer efficiency A certain amount of the bacterial capsules of the embodiment and the comparative example were placed in a 0.01% methylene blue solution, and the change in absorbance at 660 nm at the sampling time was detected to reflect the carrier mass transfer efficiency. Figure 2 By comparison, it can be seen that the Example and Comparative Example 3 with the addition of waterborne polyurethane have better effects, with the maximum mass transfer efficiency reaching about 93%, while the maximum mass transfer efficiencies of Comparative Examples 1 and 2 are 31.79% and 31.12%, respectively. Waterborne polyurethane is conducive to forming a porous structure in the capsule, improving mass transfer efficiency and swelling performance. On the other hand, although the addition of iron-rich sludge biochar increases the mass transfer equilibrium time of the capsule from 1.5h to 4h to a certain extent, it does not ultimately affect the mutual exchange between the capsule and the simulated nutrients.

[0048] Application example: Experiment on treating simulated sewage with sulfur autotrophic bacteria capsules The composite bacterial agent capsules prepared in Example and Comparative Examples 1 to 3 were respectively loaded into 4 identical fluidized bed reactors, and the particles were fluidized by providing a water flow rate of 5 L / min through an external circulating water circuit, and the HRT was adjusted to 2.5 h. 0.5 g / L sodium bicarbonate was added to the sewage to supplement the alkalinity, and the pH value was about 7.60, and potassium nitrate was added to supplement the nitrate nitrogen, with a concentration of about 35 mg / L.

[0049] Depend on Figure 3 It can be seen that the startup time of the embodiment is short, and it has an excellent denitrification effect after the start of operation. The immobilized microorganisms grow rapidly, the denitrification performance of the system gradually improves, and the nitrate concentration of the effluent is stably lower than 8 mg / L during stable operation, and there is no nitrite nitrogen accumulation. In contrast, the nitrate concentration of the effluent of Comparative Example 1 is close to 20 mg / L, and the nitrite nitrogen concentration reaches a maximum of 2.69 mg / L. Under the combined action of thiolated sodium alginate, aqueous polyurethane and iron-rich sludge biochar, the composite bacterial agent capsule significantly enhances the denitrification process.

[0050] In particular, the effect of Comparative Example 3 was better than that of Comparative Example 1 and Comparative Example 2 at the beginning of operation, and then the denitrification performance declined, and the average effluent nitrate nitrogen concentration (16.23 mg / L) was higher than that of Comparative Example 2 (13.87 mg / L). The above observations show that the introduction of aqueous polyurethane into the gel can expand the microbial load, but the lack of iron-rich sludge biochar to supplement the electron donor leads to incomplete denitrification. The accumulation of low nitrite nitrogen (the average effluent concentration in the stable period is 0.37 mg / L) in Comparative Example 3 can be attributed to the following reasons: ① The iron-rich sludge biochar system is more conducive to the growth of iron-reducing bacteria, promoting the reduction of Fe (III) to Fe (II); ② Fe (II) can react with nitrate nitrogen under the action of microorganisms, enriching the electron donor combination in the system.

[0051] 10Fe 2+ +2NO3 -+24H2O→N2+10Fe(OH)3+22H + The composite bacterial agent capsules prepared in Example 1 and Comparative Example 4 were respectively added into two upflow packed filter beds with the same structure, and the addition amount was 10% of the filter volume. The reactors were all started up and in a steady state, and the nitrate nitrogen in the effluent was about 8.79 mg / L. Figure 4 As shown, the composite bacterial agent capsule prepared in the present application can be directly used to enhance the denitrification effect of the sulfur autotrophic fixed bed. Specifically, the embodiment greatly accelerates the denitrification rate due to the fixation of a large number of active microorganisms in the system, and the nitrate nitrogen concentration in the effluent can be lower than 1 mg / L; while although the comparative example 4 does not embed active microorganisms, it can increase the bioavailability of sulfur through the modified gel, and improve the electron donor deficiency of amorphous iron in the iron-rich sludge biochar, so that the nitrate nitrogen in the effluent can be reduced by about 40%.

[0052] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a structure-enhanced modified sulfur autotrophic agent capsule, characterized in that: The following steps are involved: S1. dissolving polyvinyl alcohol and thiolated alginate in water at 90° C. to obtain a gel solution, wherein the polyvinyl alcohol content is 6 to 10 wt % and the thiolated alginate content is 0.5 to 2 wt %; S2. After the gel solution was cooled to room temperature, 1 to 5 wt% of anionic aqueous polyurethane having a solid content of 30% was added and stirred to obtain a porous modified gel; S3. Adding 10 to 20 wt% sulfur powder and 1 to 5 wt% iron-rich sludge biochar to the porous modified gel, stirring and mixing to obtain a modified reinforced gel; S4. Add 30-40 wt % sulfur autotrophic bacteria solution to the modified and strengthened gel, stir and mix evenly to obtain a gel-bacteria solution mixture, and then drop the gel-bacteria solution mixture into the cross-linking liquid to obtain the structurally strengthened modified sulfur autotrophic bacteria capsule.

2. The preparation method according to claim 1, characterized in that: The thiolated alginate is thiolated sodium alginate, thiolated calcium alginate or thiolated potassium alginate.

3. The preparation method according to claim 1, characterized in that: The thiolated alginate is activated by reacting an alginate solution with 1-ethyl-3-dimethylaminopropyl-carbodiimide hydrochloride and N-hydroxysuccinimide at room temperature; then, cysteine ​​is added, the pH is adjusted to about 4.0, and the reaction is stirred at room temperature; then, the pH is raised to 6.0, and the reaction is stirred at room temperature for 0.5 to 2 hours; finally, the obtained reaction solution is dialyzed for purification and freeze-dried.

4. The preparation method according to claim 1, characterized in that: The particle sizes of the sulfur powder and iron-rich sludge biochar are 200-300 meshes.

5. The preparation method according to claim 1, characterized in that: The iron-rich sludge biochar is prepared by anaerobic thermal decomposition of iron-rich sludge at 500-700° C.; calculated by dry weight, the iron content of the iron-rich sludge is 20wt%-40wt%, and the organic matter content is 20wt%-30wt%.

6. The preparation method according to claim 1, characterized in that: The total number of live bacteria in the sulfur autotrophic bacterial liquid is ≥2×10 8 CFU / g, and the sulfur autotrophic bacterial liquid is denitrifying Thiobacillus and / or Thiomonas bacterial liquid.

7. The preparation method according to claim 1, characterized in that: The cross-linking liquid is a 2-4 wt% calcium chloride solution.

8. The modified and enhanced sulfur autotrophic composite bacterial agent capsule prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the modified and enhanced sulfur autotrophic composite bacterial agent capsule according to claim 8 in water treatment.

10. A water treatment agent, characterized in that: It comprises the modified and enhanced sulfur autotrophic composite bacterial agent capsule as described in claim 8.

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