Preparation and application of autotrophic denitrifying bacteria immobilized packing based on carbon dioxide capture

Abstract

The application discloses a kind of preparation and application of autotrophic denitrification bacteria immobilized packing based on carbon dioxide capture, belong to environmental engineering technical field.The exhaust emitted by funeral parlor is utilized as resource, as the inorganic carbon source of sulfur autotrophic denitrification process, and the denitrification capacity of autotrophic denitrification bacteria group is strengthened.Meanwhile, the autotrophic denitrification bacteria liquid obtained by domestication is immobilized, and is prepared into granular denitrification functional bacteria agent, and the denitrification capacity of bacteria group is strengthened.Finally, the tolerance of granular denitrification functional bacteria agent to environmental factors temperature, pH and different concentrations of nitrate nitrogen is investigated, and the foundation for bacteria group to resist various adverse conditions in practical application is laid.The granular denitrification functional bacteria agent prepared in the application can achieve 99.87% nitrate nitrogen removal rate after 15% CO2 concentration is input, and the carrier plays a buffering protection role for autotrophic denitrification bacteria group, so that the tolerance of granular denitrification functional bacteria agent to extreme temperature, weak acid and high concentration nitrate nitrogen is obviously improved compared with free bacteria group.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, specifically relating to the preparation and application of an autotrophic denitrifying bacteria immobilization packing material based on carbon dioxide capture. Background Technology

[0002] To meet the material demands of human societal development, large quantities of ammonia are synthesized and used industrially, severely disrupting the Earth's original nitrogen balance. The most serious impact comes from the excessive application of nitrogen fertilizers. While industrial nitrogen fertilizer production has solved the problem of food yield, it has also led to the ocean system bearing nearly twice the nitrogen input. In addition, the chemical industry's consumption of fossil fuels and nitric acid has also resulted in significant nitrogen emissions. - -N is the highest valence form of nitrogen in the biological cycle, and it accumulates more easily in aquatic ecosystems, being a significant factor contributing to eutrophication. With the increasing nitrogen emissions from humans each year, NO3- in water bodies... - The accumulation of -N is becoming increasingly severe, NO3 - -N pollution has become a serious environmental problem that urgently needs to be addressed.

[0003] Currently, NO3 - NO3- pollution treatment technologies can be divided into three main categories based on their reaction principles: physical technologies, chemical technologies, and biological technologies. Physical technologies only address NO3-... - Simple separation and concentration of -N is essentially a transfer of pollutants rather than their removal; chemical treatment technologies, however, will generate secondary pollutants (NO2). - -N and NH4 + Nitrogen removal is expensive and requires significant investment. Therefore, biological treatment technologies are preferred for nitrogen removal in practical engineering applications. Among these, sulfur autotrophic denitrification technology is widely used due to its advantages such as no need for external carbon sources, reduced operating costs, high nitrogen removal load, no burden of excessive residual sludge treatment, and simple operation and maintenance. Its reaction principle is based on sulfur-oxidizing bacteria using inorganic carbon sources as electron donors to oxidize sulfur from reduced sulfides (S₂O₃) under anoxic or anaerobic conditions. 0 S 2- SO3 2- S4O6 2- S2O3 2- (etc.) to obtain energy and electrons, and to convert NO3 - -N acts as an electron acceptor, reducing it to N2. Therefore, screening for sulfur-autotrophic denitrifying bacteria with high denitrification capacity is of practical significance for improving the efficiency of biological denitrification in wastewater. Summary of the Invention

[0004] [Technical Issues]

[0005] In response to the global climate crisis, the demand for wastewater and industrial wastewater treatment technologies based on carbon reduction is growing rapidly. Sulfate autotrophic denitrification (SOD) technology has emerged as a new total nitrogen reduction technology. Since autotrophic microorganisms utilize inorganic carbon sources to build their cell structures, adding CO2-rich waste gas (such as combustion flue gas) to the SOD process not only helps to enrich the SOD bacteria community and enhance the process's nitrogen removal performance, but also serves as a novel carbon capture and utilization (CUU) technology to achieve CO2 fixation and resource recovery, thus promoting pollution reduction and carbon reduction in wastewater treatment. Therefore, there is an urgent need for a method that combines carbon capture and SOD technologies.

[0006] [Technical Solution]

[0007] Based on the properties of sulfur autotrophic denitrification process, this invention introduces CO2-rich combustion flue gas into a culture medium to obtain a dominant autotrophic denitrifying bacterial community enhanced by exogenous CO2. By adding carrier sodium alginate, polyvinyl alcohol, and cyanobacterial-based biochar, the bacterial solution is prepared into a granular denitrifying functional bacterial agent to match existing process structures and enhance the removal capacity of nitrogen-containing pollutants. At the same time, the system also has the advantages of simple operation and reduced maintenance difficulty.

[0008] This invention provides a method for preparing immobilized packing material for autotrophic denitrifying bacteria cultured in a carbon dioxide environment, comprising the following steps:

[0009] (1) Preparation of culture medium, comprising the following components: sulfur elemental filler, KNO3, K2HPO4, Ca(OH)2, NaHCO3, MgSO4·7H2O, and trace element solution, wherein the trace element solution comprises FeCl2·2H2O, CoCl2·6H2O, MnCl2·4H2O, CuCl2·2H2O, ZnCl2, HBO3, and (NH4)6Mo7O. 24 ·4H2O, Na2SeO3, NiCl2 ·6H2O, EDTA;

[0010] (2) Take activated sludge from the anoxic pool of the sewage treatment plant, dilute it with water to obtain a sludge-water mixture, place it in a culture vessel, add culture medium, and culture sulfur autotrophic denitrifying bacteria at a constant temperature.

[0011] (3) After a period of incubation, the culture medium in the incubator was taken to measure NO3. - -N concentration, taking NO3 - The culture medium with the lowest -N concentration was inoculated into fresh culture medium, and CO2 gas was injected. The medium was then cultured at a constant temperature to obtain a denitrifying bacterial culture.

[0012] (4) Dissolve sodium alginate, polyvinyl alcohol and cyanobacterial biochar in water, then add the denitrifying bacterial solution obtained in step (3) and stir to form a mixture. Add the mixture to a saturated boric acid solution of calcium chloride to solidify it. Take it out and let it stand. After washing with physiological saline, the immobilized filler is obtained.

[0013] Furthermore, the culture medium in step (1) contains 10g of sulfur-containing filler, 12mg of KNO3, 0.16g of K2HPO4, 0.8mg of Ca(OH)2, 0.16g of NaHCO3, 16mg of MgSO4·7H2O, and 2mL of trace element solution per 80mL. The specific components of the trace element solution are: FeCl2·2H2O 1.2g / L, CoCl2·6H2O 1.2g / L, MnCl2·4H2O 0.3g / L, CuCl2·2H2O 0.018g / L, ZnCl2 0.03g / L, HBO3 0.03g / L, and (NH4)6Mo7O. 24 ·4H2O 0.054g / L, Na2SeO3 0.04g / L, NiCl2·6H2O 0.03g / L, EDTA 0.6g / L.

[0014] Furthermore, the NO3 in the culture medium in step (1) - -N concentration is 19-25 mg / L.

[0015] Furthermore, in step (2), the volume ratio of activated sludge to water in the anoxic tank is 1:(8-10), specifically 1:9.

[0016] Furthermore, in step (2), the volume ratio of the mud-water mixture to the culture medium is 1:(3-5), specifically 1:4.

[0017] Furthermore, the culture temperature in step (2) is 30±5℃.

[0018] Furthermore, in step (2), the sulfur autotrophic denitrifying bacteria are cultured in the dark.

[0019] Furthermore, in step (3) NO3 - The volume ratio of the culture medium with the lowest -N concentration to fresh culture medium is 1:(3-6). Specifically, 1:4 can be selected.

[0020] Furthermore, the gas containing CO2 in step (3) is pure CO2 or waste gas containing 10% to 50% CO2.

[0021] Preferably, the gas containing CO2 in step (3) is pure CO2 or cremation flue gas or incineration exhaust gas containing 10% to 50% CO2.

[0022] Specifically, the gas containing CO2 in step (3) can be pure CO2 or the exhaust gas emitted by the funeral home, with the main components being 10% to 20% CO2 and 100 mg / m³. 3 SO2 and 100mg / m 3 NO x And fluorides and chlorides.

[0023] Furthermore, after injecting CO2-containing gas in step (3), the CO2 concentration (v / v) in the bottle is 1-30%. Specifically, it can be 15%.

[0024] Furthermore, the culture temperature in step (3) is 30±5℃.

[0025] Furthermore, in step (4), the mass ratio of sodium alginate to polyvinyl alcohol is 1:(1-3), specifically 1:2.

[0026] Furthermore, in step (4), the mass ratio of sodium alginate to cyanobacterial biochar is 1:(0.1-0.5), specifically 1:0.2.

[0027] Furthermore, in step (4), the mass-to-volume ratio of sodium alginate to water is 1g:(80-120)mL, specifically 1g:100mL.

[0028] Furthermore, in step (4), the volume ratio of the denitrifying bacterial solution to water is 1:(2-3), specifically 1:2.5.

[0029] Furthermore, in step (4), the concentration of calcium chloride in the saturated boric acid solution of calcium chloride is 1-3%, specifically 2%.

[0030] Furthermore, in step (4), the resting time is to place the food in a refrigerator at 4°C for 24 hours.

[0031] This invention provides an immobilized packing material for autotrophic denitrifying bacteria cultured in a carbon dioxide environment, prepared according to the above method.

[0032] The application of the autotrophic denitrifying bacteria immobilized packing material cultured under carbon dioxide environment provided by this invention in the fields of wastewater treatment and environmental protection.

[0033] [Beneficial Effects]

[0034] 1. This invention utilizes cremation flue gas emitted from funeral homes as an inorganic carbon source for a sulfur autotrophic denitrification process, enhancing the nitrogen removal capacity of autotrophic denitrifying bacteria. Currently, there is no research on the resource utilization of cremation flue gas. This invention innovatively combines cremation flue gas with the cultivation of autotrophic denitrifying bacteria, achieving the recovery and reuse of waste gas and providing a new approach for future pollution control, emission reduction, and environmental protection.

[0035] 2. This invention immobilizes the obtained autotrophic denitrifying bacterial solution and adds sodium alginate, polyvinyl alcohol, and cyanobacterial-based biochar. While preparing granular denitrifying functional bacterial agents to enhance the denitrification capacity of the bacterial community, it also realizes the resource reuse of Taihu Lake cyanobacteria. Furthermore, it was found that Taihu Lake cyanobacterial biochar, compared with other biochars and porous microparticles, enables the prepared immobilized packing material to have a better denitrification effect.

[0036] 3. The granular denitrifying functional bacterial agent prepared in this invention can achieve a nitrate nitrogen removal rate of 99.87% after introducing 15% CO2. Simultaneously, the tolerance of the granular denitrifying functional bacterial agent to environmental factors such as temperature, pH, and different concentrations of nitrate nitrogen was investigated. It was found that the immobilized carrier plays a buffering and protective role for the autotrophic denitrifying bacterial community, significantly improving the tolerance of the granular denitrifying functional bacterial agent to extreme temperatures, weak acids, and high concentrations of nitrate nitrogen compared to free bacterial communities. This lays the foundation for the bacterial community to resist various adverse conditions in practical applications. Attached Figure Description

[0037] Figure 1 The effect of blank immobilized carrier on the growth of autotrophic denitrifying bacteria.

[0038] Figure 2 The effect of different temperatures on the denitrification efficiency.

[0039] Figure 3 The effect of different pH values ​​on denitrification efficiency.

[0040] Figure 4 For particulate denitrifying bacterial agents, the effects on different concentrations of NO3 - -N processing power.

[0041] Figure 5 To investigate the effect of different amounts of sludge inoculation on nitrogen removal efficiency. Detailed Implementation

[0042] Source of raw materials

[0043] The sulfur filler is derived from 4-8mm hemispherical industrial-grade sulfur produced by Sinopec; KNO3, K2HPO4, Ca(OH)2, NaHCO3, MgSO4·7H2O, FeCl2·2H2O, CoCl2·6H2O, MnCl2·4H2O, CuCl2·2H2O, ZnCl2, HBO3, (NH4)6Mo7O 24The reagents, including 4H2O, Na2SeO3, NiCl2·6H2O, EDTA, CaCl, and sodium alginate, were all purchased from Sinopharm Group; the sludge used for inoculation came from the anoxic pond of a sewage treatment plant in Wuxi; the cyanobacteria-based biochar was obtained by pulverizing dried Taihu cyanobacteria, impregnating them with a 0.3 mol / L sodium hydroxide solution, pyrolyzing them in a muffle furnace at 500℃ for 1 hour, cooling, washing, drying, and grinding; the flue gas refers to the exhaust gas emitted by the funeral home, mainly composed of 10%–20% CO2 and 100 mg / m³ of oxygen. 3 SO2 and 100mg / m 3 NO x And fluorides and chlorides.

[0044] Example 1

[0045] (1) Prepare the culture medium. Each 80 mL of culture medium contains the following components: 10 g of sulfur element filler, 12 mg of KNO3, 0.16 g of K2HPO4, 0.8 mg of Ca(OH)2, 0.16 g of NaHCO3, 16 mg of MgSO4·7H2O, and 2 mL of trace element solution. The specific components of the trace element solution are: 1.2 g / L FeCl2·2H2O, 1.2 g / L CoCl2·6H2O, 0.3 g / L MnCl2·4H2O, 0.018 g / L CuCl2·2H2O, 0.03 g / L ZnCl2, 0.03 g / L HBO3, and (NH4)6Mo7O. 24 ·4H2O 0.054g / L, Na2SeO3 0.04g / L, NiCl2·6H2O 0.03g / L, EDTA 0.6g / L.

[0046] (2) Take 25 mL of activated sludge from the anoxic tank of the wastewater treatment plant, add 225 mL of deionized water, shake to mix, and take 20 mL of the sludge-water mixture into six sterilized and deoxygenated Erlenmeyer flasks, and add NO3. - 80 mL of culture medium with a nitrogen concentration of 20 mg / L was prepared. The Erlenmeyer flask was placed in a constant-temperature shaker at 30 ± 5 °C and 150 rpm in the dark to culture sulfur-autotrophic denitrifying bacteria. After 5 days of culture, NO3 was measured every 8 hours from the culture flask. - -N concentration.

[0047] (3) Take 8 mL of NO3 - The culture medium from the culture bottle with the lowest -N concentration and 32 mL of fresh culture medium were inoculated into a new culture bottle. Flue gas was introduced to make the CO2 concentration (v / v) in the bottle reach 15%. The culture was then incubated in a biochemical incubator at 30±5℃ to obtain a denitrifying bacterial solution.

[0048] Comparative Example 1

[0049] The amount of sludge inoculum determines the growth rate of the microbial community in the system. A larger inoculum can shorten the time it takes for the denitrifying bacteria to reach peak reproduction after inoculation, quickly start the system, and reduce competitive inhibition caused by the growth of other microorganisms. However, an excessively large inoculum will cause competition among the acclimated microorganisms, while an excessively small inoculum will affect the denitrification effect or lead to an excessively long cultivation period. Therefore, it is necessary to compare the effects of different sludge inoculum amounts on the denitrification effect. Sludge inoculum amounts of 1%, 2%, 3%, 4%, 5%, and 6% were selected, and the system was cultivated for 15 days to investigate the effect of different inoculum amounts on the denitrification effect.

[0050] Depend on Figure 5 It can be seen that when the sludge inoculum amount is 1%, the average denitrification rate is 20.75%. When the sludge inoculum amount is 2%-6%, the average denitrification rates are 39.75%, 34.52%, 32.87%, 28.87%, and 26.40%, respectively, indicating an improvement in denitrification efficiency. Specifically, when the sludge inoculum amount is 2%, NO3... - -N removal rate was the highest. Based on the experimental results, 2% was selected as the initial sludge inoculation amount.

[0051] Comparative Example 2

[0052] Take 8 mL of NO3 from step (2) of Example 1 - The culture medium with the lowest CO2 concentration and 32 mL of fresh culture medium were inoculated into 24 new acclimatization culture bottles. The 24 bottles were labeled, and there were 6 experimental groups, with 4 replicates in each group. Bottles 1-4 served as blank samples, while bottles 5-24 were injected with different amounts of flue gas using a syringe to achieve CO2 concentrations (v / v) of 5%, 10%, 15%, 20%, and 25%, respectively. The bottles were cultured for 25 days, and NO3 was measured at the same time each day. - -N concentration changes.

[0053] The experimental results are shown in Table 1. The NO3 content in the experimental group 5-24 injected with flue gas... - The NO3- removal rate was generally higher than that of the control group by 1-4, demonstrating that exogenous CO2 can serve as an inorganic carbon source to construct the cellular structure of autotrophic denitrifying bacteria, thereby enhancing the nitrate removal capacity of the autotrophic denitrifying bacteria. When the injected CO2 concentration was 5%-15%, NO3- - -N removal rate is positively correlated with injected CO2; when the injected CO2 concentration is 20%-25%, NO3 removal rate is higher. - -N removal rate is negatively correlated with injected CO2. The 15% CO2 concentration group showed the best denitrification effect, with virtually no NO3 in the effluent. - -N.

[0054] Table 1. Effect of CO2 concentration on the nitrogen removal capacity of autotrophic denitrifying bacteria.

[0055]

[0056] Example 2

[0057] This example illustrates the preparation process of sodium alginate filler.

[0058] Weigh 5g of sodium alginate and dissolve it in 100mL of pure water. Heat and stir continuously until completely dissolved, then cool to 30±5℃ for later use. Take 8mL of the denitrifying bacterial solution obtained in step (3) of Example 1 and mix it with 20mL of sodium alginate solution. Use a syringe to drip the mixture into 2% calcium chloride solution for fixation. Place the mixture in a refrigerator at 4℃ for crosslinking for 24h, and then wash it with 0.9% physiological saline for later use.

[0059] Example 3

[0060] This example illustrates the preparation process of sodium alginate + cyanobacteria-based biochar powder filler.

[0061] Weigh 5g of sodium alginate and 2g of cyanobacterial biochar powder and place them in 100mL of pure water. Heat and stir continuously until completely dissolved, then cool to 30±5℃ for later use. Take 8mL of the denitrifying bacterial solution obtained in step (3) of Example 1 and mix it with 20mL of sodium alginate + cyanobacterial biochar solution. Use a syringe to drip the mixture into a 2% calcium chloride solution for fixation. Place the mixture in a 4℃ refrigerator for crosslinking for 24h, and then wash it with 0.9% physiological saline for later use.

[0062] Example 4

[0063] This example illustrates the preparation process of sodium alginate + polyvinyl alcohol filler.

[0064] Weigh 5g of sodium alginate and 10g of polyvinyl alcohol and place them in 100mL of pure water. Heat and stir continuously until completely dissolved, then cool to 30±5℃ for later use. Take 8mL of the denitrifying bacterial solution obtained in step (3) of Example 1 and mix it with 20mL of sodium alginate + polyvinyl alcohol solution. Use a syringe to drip the mixture into a 2% calcium chloride saturated boric acid solution for fixation. Place the solution in a 4℃ refrigerator for crosslinking for 24h, and then wash it with 0.9% physiological saline for later use.

[0065] Example 5

[0066] This example illustrates the preparation process of sodium alginate + polyvinyl alcohol + cyanobacteria-based biochar filler.

[0067] Weigh 5g sodium alginate, 10g polyvinyl alcohol, and 1g cyanobacterial biochar and place them in 100mL of pure water. Heat and stir continuously until completely dissolved, then cool to 30±5℃ for later use. Take 8mL of the denitrifying bacterial solution obtained in step (3) of Example 1 and mix it with 20mL of sodium alginate + polyvinyl alcohol + cyanobacterial biochar solution. Fix the mixture by dripping it into a 2% calcium chloride saturated boric acid solution using a syringe. Place the mixture in a 4℃ refrigerator for crosslinking for 24h, and then wash it with 0.9% physiological saline for later use.

[0068] Example 6

[0069] This example illustrates the preparation process of a blank filler.

[0070] Blank sodium alginate filler: Weigh 5g of sodium alginate and dissolve it in 100mL of pure water. Heat and stir continuously until completely dissolved. Cool and then use a syringe to drip it into a 2% calcium chloride solution for fixation. Place it in a 4℃ refrigerator for crosslinking for 24h, and then wash it with 0.9% physiological saline for later use.

[0071] Blank sodium alginate + cyanobacterial biochar filler: Weigh 5g sodium alginate and 2g cyanobacterial biochar powder into 100mL pure water, heat and stir continuously until completely dissolved, cool, and fix by dripping into 2% calcium chloride solution with a syringe. Place in a 4℃ refrigerator for crosslinking for 24h, and then wash with 0.9% physiological saline for later use.

[0072] Blank sodium alginate + polyvinyl alcohol filler: Weigh 5g sodium alginate and 10g polyvinyl alcohol into 100mL pure water, heat and stir continuously until completely dissolved, cool, and fix by dripping into a 2% calcium chloride saturated boric acid solution with a syringe. Place in a 4℃ refrigerator for crosslinking for 24h, and then wash with 0.9% physiological saline for later use.

[0073] Blank sodium alginate + polyvinyl alcohol + cyanobacterial biochar filler: Weigh 5g sodium alginate, 10g polyvinyl alcohol and 1g cyanobacterial biochar and place them in 100mL pure water. Heat and stir continuously until completely dissolved. Cool and fix with a syringe by dripping into a 2% calcium chloride saturated boric acid solution. Place in a 4℃ refrigerator for crosslinking for 24h, and then wash with 0.9% physiological saline for later use.

[0074] Example 7

[0075] This example is a performance evaluation of the immobilized packing materials prepared in Examples 2-5.

[0076] (1) Determination of mechanical strength

[0077] The four immobilized packings prepared in Examples 2-5 were placed in a shaker and shaken for 48 hours. The presence of cracks or expansion was observed. The experiment showed that the four immobilized packings all had a certain mechanical strength and could resist external impacts.

[0078] (2) Determination of denitrification effect

[0079] Weigh 28g of each of the four immobilized packing materials prepared in Examples 2-5, 8g of each of the four blank immobilized carriers prepared in Example 6, and 8mL of free bacterial solution, i.e., the denitrifying bacterial solution obtained in step (3) of Example 1. Inoculate each of these into 100mL of culture medium, inject pure CO2 to make the CO2 concentration (v / v) in the bottle reach 15%, seal, and incubate for 60h. OD is measured every 4h. 600 Value and finally calculate NO3 - -N removal rate.

[0080] Depend on Figure 1 It can be seen that the OD in culture flasks containing only free bacterial culture is different. 600 Compared to the values ​​in the culture flasks containing blank immobilized carrier + denitrified bacterial culture in the first 12 hours of the experiment, the OD values ​​were significantly higher. 600 The values ​​decreased for the blank sodium alginate group, the blank sodium alginate + cyanobacteria-based biochar group, and the blank sodium alginate + polyvinyl alcohol group, respectively. 600 The decrease may be due to steric hindrance or diffusion resistance created after the bacterial culture passed through the immobilized carrier. With increasing time, the OD of the blank immobilized carrier + denitrified bacterial culture group... 600 The OD values ​​gradually increased compared to the free bacterial culture group, and the OD values ​​of each group were higher. 600 The OD values ​​reached their maximum at 32 hours of the experiment. The OD values ​​for the free bacterial culture group, the blank sodium alginate group, the blank sodium alginate + cyanobacterial biochar group, the blank sodium alginate + polyvinyl alcohol group, and the blank sodium alginate + polyvinyl alcohol + cyanobacterial biochar group at 32 hours were: 600 The values ​​were 1.35, 1.30, 1.34, 1.38, and 1.49, respectively, with the OD values ​​of the blank sodium alginate + polyvinyl alcohol + cyanobacteria-based biochar group being the highest. 600 The OD values ​​were significantly higher than those of other groups, indicating that the packing material composed of sodium alginate + polyvinyl alcohol + cyanobacterial biochar had high porosity and good mass transfer performance. Furthermore, the OD values ​​of the blank immobilized carrier + denitrifying bacterial solution group were significantly higher than those of other groups. 600 The trend of the value over time is consistent with that of the group that only introduced free bacterial solution, indicating that the blank immobilized carrier has no adverse effect on the growth of autotrophic denitrifying bacteria and is suitable for the growth of autotrophic denitrifying bacteria.

[0081] Free bacterial suspension and four prepared immobilized packing materials were quantitatively added to culture media, and four blank immobilized carrier culture media were prepared. Pure CO2 was injected into each medium to achieve a CO2 concentration (v / v) of 15%. The media were then sealed and incubated in a biochemical incubator at 30±5℃ for 12 hours. NO3 was then measured. - -N removal rate, the results are shown in Table 2.

[0082] Table 2 shows that in groups 2, 4, 6, and 8, only blank immobilized carriers without bacteria were added, and their NO3 content was... - -N removal rates were all below 16%. However, after immobilizing autotrophic denitrifying bacteria, NO3 removal rates were significantly lower. - -N removal rate increased significantly in group 4. - The removal rates of NO3- were all above 90%, with groups 3, 5, 7, and 9 achieving removal rates of 90.45%, 91.87%, 94.21%, and 99.87%, respectively, significantly higher than those of free bacterial suspension (NO3-). - -N removal rate was 85.87%. The above results indicate that the blank immobilized carrier effectively removes NO3-. - The removal of -N was not affected; denitrification was mainly accomplished by autotrophic denitrifying bacteria. Furthermore, preparing the bacterial solution into granular denitrification functional agents reduced the impact of external conditions on denitrification, thereby enhancing denitrification. It was found that the sodium alginate + polyvinyl alcohol + cyanobacteria-based biochar packing material performed best.

[0083] Table 2 Comparison of denitrification effects of free bacterial suspension, blank immobilized carrier, and immobilized bacterial population

[0084]

[0085] Note: Groups 1-9 are respectively free bacterial solution, blank sodium alginate packing, immobilized sodium alginate packing, blank sodium alginate + cyanobacterial biochar packing, immobilized sodium alginate + cyanobacterial biochar packing, blank sodium alginate + polyvinyl alcohol packing, immobilized sodium alginate + polyvinyl alcohol packing, blank sodium alginate + polyvinyl alcohol + cyanobacterial biochar packing, and immobilized sodium alginate + polyvinyl alcohol + cyanobacterial biochar packing.

[0086] (3) Determination of tolerance to temperature, pH and different concentrations of nitrate nitrogen

[0087] Sodium alginate + polyvinyl alcohol + cyanobacterial biochar filler was added to the culture medium, and the temperature, pH and nitrate nitrogen concentration were adjusted to investigate the tolerance of the immobilized filler.

[0088] Temperature and pH are easily variable factors in the environment; both excessively high and low temperatures can significantly affect enzyme activity. Therefore, it is necessary to investigate the tolerance of particulate denitrifying bacterial agents to temperature and pH. 8 mL of free bacterial solution (i.e., the denitrifying bacterial solution obtained in step (3) of Example 1) and 28 g of sodium alginate + polyvinyl alcohol + cyanobacterial biochar filler were added to 100 mL of culture medium, respectively, and cultured in a shaker for 48 h. The temperature or pH was adjusted individually to examine the tolerance of the immobilized filler. The culture medium containing the free bacterial solution was used as a control group. The results are as follows: Figure 2 and 3 As shown.

[0089] Simultaneously, it is necessary to investigate the tolerance of granular denitrifying bacterial agents to different concentrations of nitrate nitrogen in order to facilitate practical application. Free bacterial solutions and sodium alginate + polyvinyl alcohol + cyanobacterial biochar filler were respectively added to 10 culture substrates, and the amount of KNO3 in the culture substrates was adjusted to achieve NO3... - Nitrate nitrogen concentrations of 20 mg / L, 40 mg / L, 60 mg / L, 80 mg / L, and 100 mg / L were added to a constant-temperature shaker and cultured for 12 h in the dark at 30 ± 5 °C and 150 rpm. The tolerance of the immobilized packing material to different concentrations of nitrate nitrogen was investigated. A culture medium with added free bacterial solution was used as a control group. The results are as follows: Figure 4 As shown.

[0090] Depend on Figure 2 It can be seen that when the temperatures are 5℃, 10℃, 15℃, and 20℃, the NO3 content of both free bacterial solution and particulate denitrifying functional bacterial agent is [data missing]. - The removal rates of NO3- were both very low, indicating that lower temperatures inhibit the enzyme activity of microorganisms. When the temperature was adjusted to 25℃, the NO3- removal rates of both were significantly lower. - -N removal rate increased significantly, including NO3 removal from immobilized microorganisms. - -N removal rate is higher than that of free bacterial solution; at a temperature of 30℃, the NO3 removal rate of free bacterial solution is higher. - -N removal rate was 89.74%, NO3 removal rate of immobilized microorganisms - -N removal rate was 99.05%; when the temperature rose to 35℃, the NO3- of both decreased. - -N removal rates all decreased slightly. These results indicate that particulate denitrifying bacterial agents have better environmental adaptability than free bacterial solutions.

[0091] Figure 3 This study investigated the effect of different pH values ​​on denitrification efficiency. Specifically, it examined the NO3 concentrations in free bacterial solution and particulate denitrification functional bacterial agent at pH = 5. - Both NO3- removal rates were very low, and the structure of the immobilized packing material changed from spherical to pasty, resulting in a weakened protective effect on microorganisms. The microorganisms were inhibited by the acidity, leading to a decrease in their denitrification capacity. When the pH was adjusted to 6, the NO3- removal rates of both decreased. - -N removal rate increased significantly, with granular denitrifying bacterial agents showing stronger denitrification ability. At pH 7, 8, and 9, the NO3 removal rate of granular denitrifying bacterial agents... - -N removal rates consistently exceeded 90%, reaching 94.38%, 99.07%, and 97.68%, respectively. In summary, compared to free bacterial suspensions, the immobilized granular denitrifying bacterial agent can adapt to a wider pH range, indicating that the carrier effectively immobilizes and protects the autotrophic denitrifying bacterial community.

[0092] Depend on Figure 4It can be seen that the denitrification capacity of particulate denitrifying bacterial agents is always higher than that of free bacterial solutions, and the denitrification capacity is affected by NO3. - The effect of -N concentration is relatively small when treating low concentrations of NO3. - At -N (20 mg / L), the removal rates of both free bacterial solution and particulate denitrifying bacterial agent were higher than 90%, and the removal rates were similar, at 94.12% and 100%, respectively. When NO3... - When the NO3- concentration was increased to 40 mg / L, the removal rates of both decreased slightly, to 89.58% and 97.35%, respectively. - When the NO3- concentration was increased to 60 mg / L, the removal rate of the free bacterial solution group dropped significantly to 65.98%, while the particulate denitrifying bacterial agent could still maintain more than 80% of NO3 removal. - -N removal rate. When NO3 - After increasing the NO3 concentration to 80 mg / L, the removal rate of the free bacterial solution was only 42.97%, but the NO3 removal rate of the particulate denitrifying bacterial agent was significantly higher. - -N removal rate was still 79.87%, compared to the treatment rate of 60 mg / L NO3. - The removal rates at -N levels are extremely close, indicating that the particulate denitrifying bacterial agent is adapting to high concentrations of NO3. - -N environment. When NO3 - After increasing the NO3- concentration to 100 mg / L, the removal rate of the free bacterial solution was only 29.87%, but the NO3- removal rate of the particulate denitrifying bacterial agent was significantly higher. - The NO3- removal rate actually increased to 82.68%, indicating that the autotrophic denitrifying bacteria have adapted to the environment and can withstand high nitrate nitrogen loads. In conclusion, compared with free bacterial solutions, the immobilized granular denitrifying bacterial agent exhibits enhanced denitrification capacity and is more suitable for treating nitrogen-containing environments with high NO3- concentrations. - -N polluted water bodies.

[0093] Comparative Example 3

[0094] This comparative example shows a comparison between cyanobacteria-based biochar immobilization carriers and other immobilization carriers.

[0095] Preparation processes of other immobilized carriers:

[0096] (1) Sodium alginate + polyvinyl alcohol + rice husk immobilization filler: Weigh 5g sodium alginate, 10g polyvinyl alcohol and 1g rice husk and place them in 100mL pure water and mix well. Take 8mL of dominant denitrifying bacteria solution and mix it with 20mL of sodium alginate + polyvinyl alcohol + rice husk solution. Use a syringe to drip the mixture into a 2% calcium chloride saturated boric acid solution to solidify it into spheres. Place them in a refrigerator at 4℃ for crosslinking for 24h, and then wash them with 0.9% physiological saline for later use.

[0097] (2) Sodium alginate + polyvinyl alcohol + wheat straw immobilization filler: Weigh 5g sodium alginate, 10g polyvinyl alcohol and 1g wheat straw and place them in 100mL pure water and mix well. Take 8mL of dominant denitrifying bacteria solution and mix it with 20mL of sodium alginate + polyvinyl alcohol + wheat straw solution. Use a syringe to drip the mixture into a 2% calcium chloride saturated boric acid solution to solidify it into spheres. Place them in a refrigerator at 4℃ for cross-linking for 24h, and then wash them with 0.9% physiological saline for later use.

[0098] (3) Sodium alginate + polyvinyl alcohol + ceramsite immobilization filler: Weigh 5g sodium alginate, 10g polyvinyl alcohol and 1g ceramsite and place them in 100mL pure water, mix well. Take 8mL of dominant denitrifying bacteria solution and mix it with 20mL of sodium alginate + polyvinyl alcohol + ceramsite solution, use a syringe to drip it into 2% calcium chloride saturated boric acid solution to solidify it into spheres, place it in a 4℃ refrigerator for crosslinking for 24h, and then wash it with 0.9% physiological saline for later use.

[0099] (4) Sodium alginate + polyvinyl alcohol + loofah sponge immobilization filler: Weigh 5g sodium alginate, 10g polyvinyl alcohol and 1g loofah sponge and place them in 100mL pure water and mix well. Take 8mL of dominant denitrifying bacteria solution and mix it with 20mL of sodium alginate + polyvinyl alcohol + loofah sponge solution. Use a syringe to drip the mixture into a 2% calcium chloride saturated boric acid solution to solidify it into spheres. Place them in a refrigerator at 4℃ for crosslinking for 24h, and then wash them with 0.9% physiological saline for later use.

[0100] Performance comparison:

[0101] Five types of immobilized packing materials were selected: sodium alginate + polyvinyl alcohol + rice husk, sodium alginate + polyvinyl alcohol + wheat straw, sodium alginate + polyvinyl alcohol + ceramsite, sodium alginate + polyvinyl alcohol + loofah sponge, and sodium alginate + polyvinyl alcohol + cyanobacteria-based biochar. Each group was tested in duplicate. 4g of each material was added to two 100mL Erlenmeyer flasks (each flask was labeled) to ensure consistent volume. 46mL of artificially prepared water with a nitrate nitrogen content of 20mg / L was added to each flask, ensuring a top volume of 50mL. Then, combustion flue gas was injected using a syringe to achieve a CO2 concentration (v / v) of 15% in each flask. The flasks were then sealed, and placed in a constant-temperature shaker at 30±5℃ and 150rpm for 6 hours in the dark to investigate the effect of the immobilized carrier on the nitrogen removal performance of autotrophic denitrifying bacteria.

[0102] Table 3 shows that the average nitrate nitrogen removal rate of the sodium alginate + polyvinyl alcohol + rice husk immobilized packing was 97.23%, the average nitrate nitrogen removal rate of the sodium alginate + polyvinyl alcohol + wheat straw immobilized packing was 98.05%, the average nitrate nitrogen removal rate of the sodium alginate + polyvinyl alcohol + ceramsite immobilized packing was 96.73%, the average nitrate nitrogen removal rate of the sodium alginate + polyvinyl alcohol + loofah sponge immobilized packing was 98.93%, and the average nitrate nitrogen removal rate of the sodium alginate + polyvinyl alcohol + cyanobacteria-based biochar packing was 99.94%. Among them, the sodium alginate + polyvinyl alcohol + ceramsite immobilized packing had the worst denitrification effect, while the sodium alginate + polyvinyl alcohol + cyanobacteria-based biochar packing had the best denitrification effect, with virtually no nitrate nitrogen in the effluent.

[0103] Table 3 Comparison of denitrification effects of different particulate denitrifying agents

[0104]

[0105] Note: Groups 1-10 are respectively sodium alginate + polyvinyl alcohol + rice husk immobilized packing, sodium alginate + polyvinyl alcohol + wheat straw immobilized packing, sodium alginate + polyvinyl alcohol + ceramsite immobilized packing, sodium alginate + polyvinyl alcohol + loofah sponge immobilized packing, and sodium alginate + polyvinyl alcohol + cyanobacteria-based biochar packing.

[0106] Example 8

[0107] Add 4g each of sodium alginate, polyvinyl alcohol, and cyanobacteria-based biochar packing material to nine 100mL Erlenmeyer flasks (labeled 1, 2, 3, 4, 5, 6, 7, 8, and 9). Then add 46mL of artificially prepared water with a nitrate nitrogen content of 100mg / L to each flask, ensuring a top volume of 50mL. Next, do not inject CO2 flue gas into flasks 1, 2, and 3; inject pure CO2 into flasks 4, 5, and 6 using a syringe to achieve a CO2 concentration (v / v) of 15%, and then stopper them; inject cremation flue gas into flasks 7, 8, and 9 using a syringe to achieve a CO2 concentration (v / v) of 15%, and then stopper them to ensure a sealed space. Nine conical flasks were placed in a constant temperature shaker and cultured in the dark at 30±5℃ and 150 rpm for 12 h to investigate the effects of pure CO2 and flue gas on the denitrification performance of autotrophic denitrifying bacteria.

[0108] Table 4 shows that the nitrate removal rate in the control group remained around 85%, while the groups injected with pure CO2 and flue gas achieved nitrate removal rates exceeding 99%. This indicates that injecting pure CO2 or flue gas can enhance the denitrification capacity of autotrophic denitrifying bacteria, achieving high nitrate removal rates. Among these, groups 7-9, injected with flue gas, showed stronger denitrification effects than those injected with pure CO2. After 9 hours of reaction, the nitrate content in the effluent of groups 7-9 had decreased to approximately 0.1 mg / L, while the nitrate content in the effluent of groups 4-6 remained around 7 mg / L. However, after 12 hours of reaction, the nitrate content in the effluent of groups 4-6 also decreased to approximately 0.1 mg / L. In conclusion, autotrophic denitrifying bacteria exhibit excellent denitrification effects after the introduction of pure CO2 and combustion flue gas. However, the introduction of combustion flue gas is preferred because it allows for the resource utilization of waste and reduces costs, laying the foundation for further research on capturing CO2 from the air to enhance autotrophic denitrification.

[0109] Table 4 Comparison of the effects of pure CO2 and flue gas on the nitrogen removal performance of autotrophic denitrifying bacteria

[0110]

[0111] Note: - indicates that the instrument cannot detect nitrate nitrogen in the water sample.

[0112] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing immobilized packing material based on autotrophic denitrifying bacteria cultured under carbon dioxide environment, characterized in that, Includes the following steps: (1) Preparation of culture medium, comprising the following components: sulfur element filler, KNO3, K2HPO4, Ca(OH)2, NaHCO3, MgSO4•7H2O and trace element solution, wherein the trace element solution comprises FeCl2·2H2O, CoCl2·6H2O, MnCl2·4H2O, CuCl2·2H2O, ZnCl2, HBO3, (NH4)6Mo7O 24 ·4H2O, Na2SeO3, NiCl2 ·6H2O, EDTA; (2) Take activated sludge from the anoxic tank of the sewage treatment plant, dilute it with water to obtain a sludge-water mixture, place it in a culture vessel, add culture medium, and culture sulfur autotrophic denitrifying bacteria at a constant temperature. (3) After culturing for a period of time, the culture medium in the incubator was taken to determine NO3. - -N concentration, taking NO3 - The culture medium with the lowest CO2 concentration was inoculated into fresh culture medium, and then infused with combustion flue gas. The mixture was then cultured at a constant temperature to obtain a denitrifying bacterial solution. After the combustion flue gas was injected, the CO2 volume concentration inside the flask was 15%. (4) Dissolve sodium alginate, polyvinyl alcohol and cyanobacterial biochar in water, then add the denitrifying bacterial solution obtained in step (3) and stir to form a mixture. Add the mixture to a saturated boric acid solution of calcium chloride to solidify it. Take it out and let it stand. After washing with physiological saline, the immobilized filler is obtained. The mass ratio of sodium alginate to polyvinyl alcohol is 1:1~3; the mass ratio of sodium alginate to cyanobacterial biochar is 1:0.1~0.5; the mass-volume ratio of sodium alginate to water is 1g:80~120mL; the volume ratio of denitrifying bacterial solution to water is 1:2~3.

2. The method according to claim 1, characterized in that, The culture medium in step (1) contains 10 g of sulfur-containing filler, 12 mg of KNO3, 0.16 g of K2HPO4, 0.8 mg of Ca(OH)2, 0.16 g of NaHCO3, 16 mg of MgSO4•7H2O, and 2 mL of trace element solution per 80 mL. The specific components of the trace element solution are: 1.2 g / L FeCl2·2H2O, 1.2 g / L CoCl2·6H2O, 0.3 g / L MnCl2·4H2O, 0.018 g / L CuCl2·2H2O, 0.03 g / L ZnCl2, 0.03 g / L HBO3, and (NH4)6Mo7O. 24 ·4H2O 0.054 g / L, Na2SeO3 0.04 g / L, NiCl2·6H2O 0.03 g / L, EDTA0.6 g / L.

3. The method according to claim 1, characterized in that, In step (2), the volume ratio of activated sludge to water in the anoxic tank is 1:8~10; in step (2), the volume ratio of sludge-water mixture to culture medium is 1:3~5.

4. The method according to claim 1, characterized in that, NO3 in step (3) - The volume ratio of the culture medium with the lowest -N concentration to fresh culture medium is 1:3~6.

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