Microbial complexing agent and application thereof in efficient sewage odor decomposition treatment process

Abstract

The invention relates to the technical field of sewage treatment, in particular to a microbial complexing agent and application thereof in a sewage stink efficient decomposition treatment process. The problems that in the prior art, a microbial complexing agent is poor in stability and low in sewage decomposition efficiency are solved. The preparation method comprises the following steps: co-culturing saccharomycetes and bacillus to obtain a culture solution I; co-culturing nitrifying bacteria and denitrifying bacteria to obtain a culture solution II; docosahexaenoic acid modified chitosan, nano aluminum oxide and modified chitosan are used for modification to obtain a composite carrier, purple sulfur bacteria, lactobacillus plantarum, a culture solution I and a culture solution II are inoculated to the composite carrier, and the microbial complexing agent is obtained through freeze drying. The prepared microbial complexing agent is applied to a sewage decomposition treatment process, the separation efficiency of the complexing agent is improved by utilizing the synergistic effect of multiple microorganisms, and the stability of the microbial complexing agent is improved by utilizing the synergistic effect of composite carriers.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, in particular to a microbial composite agent and an application thereof in a process for efficiently decomposing and treating sewage odor. Background Art

[0002] With the rapid development of industrialization and urbanization, the problem of sewage discharge is becoming increasingly serious. Sewage treatment is not only related to the sustainable use of water resources, but also a key link in protecting the ecological environment. Sewage that has not been effectively treated contains a large amount of harmful substances. If it is directly discharged into the natural environment, it will cause serious pollution to water bodies, soil and air, destroy the ecological balance, and threaten biodiversity.

[0003] In the sewage treatment process, sewage odor is a problem that cannot be ignored. The odorous gas emitted by sewage has complex components, mainly including volatile organic compounds such as hydrogen sulfide, ammonia, and methyl mercaptan. These odorous gases can cause serious harm to the human body. In addition, sewage odor will also have a negative impact on surrounding commercial activities, tourism, etc., hindering the sustainable development of the city.

[0004] Traditional sewage deodorization methods usually use physical adsorption and chemical oxidation methods. Although they can alleviate the odor problem to a certain extent, they have limitations such as high cost and easy secondary pollution. In the existing technology, due to the advantages of wide sources, low cost, and no secondary pollution, microbial complex agents have gradually become a new type of sewage treatment material, providing a new solution for sewage odor treatment. By utilizing the synergistic effect of multiple microorganisms in the microbial complex agent, the odorous substances in the sewage can be decomposed into harmless substances, thereby achieving efficient decomposition and treatment of sewage odor, which has important practical significance and broad application prospects.

[0005] However, most of the current microbial technologies use functional bacteria to cultivate and propagate, and then apply them to polluted environments. These bacteria have uncertainties in the process of sewage treatment. They cannot achieve the desired effect due to environmental inadaptability or are overly rampant and uncontrollable, thus bringing hidden dangers to treatment. In the existing technology, there are still problems with the low stability of microbial complex agents in sewage treatment and the low separation efficiency in the sewage treatment process.

[0006] Therefore, a microbial composite agent and its application in the efficient decomposition and treatment process of sewage odor were proposed. Summary of the invention

[0007] The present invention aims to provide a microbial composite agent and its application in a sewage odor efficient decomposition treatment process, wherein a culture solution 1 is obtained by co-culturing Candida and Bacillus subtilis, a culture solution 2 is obtained by co-culturing nitrifying bacteria and denitrifying bacteria, chitosan is modified by docosahexaenoic acid, a composite carrier of the microbial composite agent is obtained by preparing nano-alumina with a high surface area and modifying the modified chitosan, purple sulfur bacteria and plant lactobacillus are introduced, the culture solution 1 and the culture solution 2 are inoculated on the composite carrier, and the microbial composite agent is obtained by freeze drying; the prepared microbial composite agent is applied to the sewage decomposition treatment process, the synergistic effect of multiple microorganisms is used to improve the separation efficiency of the composite agent, and the synergistic effect between the composite carriers is used to improve the stability of the microbial composite agent.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The present invention provides a microbial composite agent, which comprises 8-20 parts of purple sulfur bacteria, 20-35 parts of culture solution 1, 25-35 parts of culture solution 2, 90-120 parts of composite carriers, and 10-20 parts of lactic acid bacteria;

[0010] Wherein the culture medium 1 includes Candida and Bacillus;

[0011] Culture medium 2 includes Nitrosomonas, Nitrobacter eutropha, and Pseudomonas stutzeri;

[0012] The composite carrier includes nano-alumina and modified chitosan, wherein the mass ratio of modified chitosan to nano-alumina is 1:2-5;

[0013] The lactic acid bacteria is selected from one of Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus casei.

[0014] Preferably, the Bacillus is selected from one of Bacillus subtilis, Clostridium sporogenes and Bacillus licheniformis.

[0015] Preferably, the preparation of culture solution 1 comprises the following steps:

[0016] 20 g / L glucose, 10 g / L yeast extract, 20 g / L tryptone, and 15 g / L agar are added to adjust the pH of the culture medium to 6.0-7.0, and the medium is sterilized under high pressure at 121°C for 20 minutes, and cooled to room temperature for use; Candida and Bacillus subtilis strains are taken out from glycerol cryopreservation tubes, and are inoculated into test tubes containing 5 mL of liquid culture medium respectively, and activated and cultured to obtain Candida liquid and Bacillus subtilis liquid; the Candida liquid and Bacillus subtilis liquid are inoculated into a 250 mL conical flask containing culture medium; the conical flask is placed in a shaking incubator, and cultured at 20-50°C for 30 hours to obtain culture solution 1.

[0017] Preferably, the volume ratio of Candida albicans to Bacillus subtilis is 1-3:1-3.

[0018] Preferably, the preparation of the culture medium 2 comprises the following steps:

[0019] 1 g / L ammonium chloride, 1 g / L potassium nitrate, 1 g / L potassium dihydrogen phosphate, 0.4 g / L magnesium sulfate, 0.2 g / L calcium chloride, and 2 mL / L trace element solution were added, the pH was adjusted to 7.0-8.0, and the mixture was sterilized under high pressure at 121°C for 20 min. The mixture was cooled to room temperature and then used for later use. The freeze-dried powders of Nitrosomonas eutropha, Nitrobacter vedoti, and Pseudomonas strewingii were respectively dissolved with sterile water, inoculated into glass bottles on a sterile operating table, and then the narrow-mouthed glass bottles were placed in an airlift bioreactor, sterile air was introduced, the gas flow rate was controlled to be 0.6 / min, and the temperature was 20-40°C for 60 h to obtain culture solution II.

[0020] Preferably, the volume ratio of Nitrosomonas, Nitrobacter vedotinus and Pseudomonas stutzeri is 1-2:1-2:1-3.

[0021] Preferably, the preparation of the composite carrier comprises the following steps:

[0022] Chitosan is added into an acetic acid solution and stirred until completely dissolved to obtain a chitosan solution; Docosahexaenoic acid is slowly added into the chitosan solution and reacted at 50°C for 2 hours to obtain a modified chitosan; nano-alumina is slowly dropped into the modified chitosan under stirring conditions, and after the dropwise addition is completed, the stirring reaction is continued for 2 hours to obtain a mixed solution; the mixed solution is aged at 50-80°C for 3-8 hours to obtain a reactant; the reactant is separated and centrifuged, washed with deionized water, and dried at 80°C for 2 hours to obtain a composite carrier.

[0023] Preferably, the preparation of the microbial composite comprises the following method:

[0024] Purple sulfur bacteria and plant lactobacillus are inoculated into a composite carrier, and cultured at 28°C for 24 hours to obtain a preculture; culture solution one is inoculated into the preculture, and cultured on a shaking table for 12 hours to obtain a culture; culture solution two is inoculated into the culture, and cultured on a shaking table for 12 hours to obtain a microbial complex; the microbial complex is freeze-dried to obtain a microbial composite agent; the pre-freezing temperature of freeze-drying is -30°C, and the pre-freezing time is 3-5 hours; the sublimation drying pressure is 40-80Pa; the sublimation drying temperature is 20°C, and the sublimation drying time is 36 hours; the analytical drying temperature is 25-40°C; and the analytical drying time is 3-5 hours.

[0025] Preferably, the density of the bacterial liquid in the pre-culture is 5×10 8 CFU / mL; the bacterial density in culture medium 1 is 3×10 8 CFU / mL; the bacterial density in culture medium 2 is 3×108 CFU / mL.

[0026] The present invention also provides an application of the above microbial composite agent in a process for efficiently decomposing and treating sewage odor.

[0027] Preferably, the initial indicators of the sewage used in the present invention are COD measurement value of 7268 mg / L; BOD 5 The measured value was 2265 mg / L; the measured value of ammonia nitrogen compounds was 1682 mg / L; and the measured value of sulfur-containing gas was 1625 mg / L.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention uses a co-culture method to co-culture Candida and Bacillus subtilis to obtain a culture solution, controls the culture temperature and culture pH to improve the compatibility of yeast and Bacillus, and uses the two to complement each other in the degradation of different organic matter. The metabolic products of yeast can reduce the pH value, which is helpful for the reproduction of Bacillus in a suitable environment. The synergistic effect improves the degradation rate of organic matter in sewage and more efficiently reduces COD and BOD. 5 At the same time, purple sulfur bacteria are introduced as photosynthetic bacteria, which can utilize simple organic compounds in sewage under light conditions, thereby reducing the content of organic pollutants in the water and improving the separation efficiency of organic matter in sewage by microbial complexes.

[0030] 2. The present invention co-cultivates Nitrosomonas, Nitrobacter vedoti and Pseudomonas strechingensis to obtain culture solution 2 by using a co-cultivation method, controls the culture temperature and culture pH to improve the compatibility of yeast and Bacillus, utilizes nitrifying bacteria to convert ammonia nitrogen into nitrate through aerobic action, and denitrifying bacteria reduce nitrate to nitrogen gas under hypoxic conditions. The combination of the two can significantly improve the removal efficiency of ammonia nitrogen in sewage. Under the synergistic effect, nitrifying bacteria provide sufficient nitrate source for denitrifying bacteria, and denitrifying bacteria convert it into gaseous nitrogen under anaerobic conditions, further reducing the pollution of ammonia nitrogen to water bodies, and at the same time cooperates with purple sulfur bacteria to oxidize sulfur-containing malodorous gases in sewage, thereby improving the decomposition efficiency of malodorous gases in sewage.

[0031] 3. Chitosan modified with docosahexaenoic acid is modified by preparing nano-alumina with high surface area and modifying the modified chitosan to obtain a composite carrier of the microbial complex. The synergistic effect of modified chitosan and nano-alumina is used to increase the microbial attachment sites. At the same time, chitosan can form a protective film on the surface of microorganisms to slow down the damage of cell membranes caused by low temperature. At the same time, docosahexaenoic acid cooperates with chitosan to improve the fluidity of microbial cell membranes, increase the decomposition efficiency of the microbial complex to sewage under low temperature conditions, and improve low-temperature stability.

[0032] 4. By using Lactobacillus plantarum, which has strong adaptability and can survive in the complex environment of alkaline sewage, it can ferment and produce acid using organic substances such as sugars in sewage, thereby lowering the pH value of sewage and inhibiting the growth of harmful microorganisms. At the same time, its metabolites can provide nutrition and a suitable pH environment for other microorganisms. By freeze-drying the microbial complex, the separation efficiency of the microbial complex for sewage can be improved, and the residual odorous gas can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The COD and BOD values ​​of the microbial composites obtained in Examples 1-5 and Comparative Examples 1-3 after wastewater treatment are shown in Table 1. 5 Schematic representation of the measured values. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The present invention comprises Candida albicans, ATCC 2001; Bacillus subtilis, ATCC 19659; Bacillus licheniformis, ATCC11946; Clostridium sporogenes, ATCC 19404; Lactobacillus plantarum, ATCC 14917; Lactobacillus acidophilus, ATCC 4356; Lactobacillus casei, ATCC 393; Purple sulfur bacteria, ATCC 17899; Nitrobacter vedotinus, ATCC 25391; Pseudomonas stutzeri, ATCC17588; and Nitrosomonas eutropha, ATCC 19718.

[0036] See also Figure 1 The present invention provides a microbial composite agent and its application in a highly efficient decomposition and treatment process for sewage odor. The technical scheme is as follows:

[0037] Example 1

[0038] 10 parts of polyvinyl alcohol are added to 20 ml of 95% ethanol, and stirred at 200 rpm for 10 minutes to fully dissolve the polyvinyl alcohol to obtain a solution; citric acid is added to the solution, the pH is adjusted to 3.5, and the solution is mixed evenly to obtain an acidic solution; 40 parts of aluminum isopropoxide are added to the acidic solution, and the solution is placed in an ultrasonic cleaning apparatus to fully dissolve the solution to obtain a sol; the sol is dried, ground into powder, and after grinding, placed in a box-type resistance furnace, heated to 400°C, calcined at a constant temperature for 6 hours, and cooled to room temperature to obtain nano alumina;

[0039] Dissolve 10 parts of chitosan in 2 ml of acetic acid solution and stir until completely dissolved to obtain a chitosan solution; slowly add 2 parts of docosahexaenoic acid to the chitosan solution and react at 50°C for 2 hours to obtain modified chitosan; slowly drop 24 parts of nano-alumina into 6 parts of modified chitosan under stirring conditions to allow the nano-alumina particles to fully contact and interact with the chitosan molecules. After the dropwise addition is completed, continue to stir and react for 2 hours to obtain a mixed solution; age the mixed solution at 60°C for 5 hours to allow chitosan to be adsorbed and modified on the surface of the nano-alumina, and obtain a composite carrier by separation and centrifugation, deionized water washing, and 80°C vacuum drying for 2 hours.

[0040] 20g / L glucose, 10g / L yeast extract, 20g / L tryptone, 15g / L agar, adjust the pH of the culture medium to 6.0-7.0, sterilize at 121℃ for 20min, cool to room temperature and set aside; take out Candida and Bacillus subtilis strains from glycerol cryopreservation tubes, pick appropriate amount of bacterial lawns with inoculation loops on a sterile operating table, inoculate into test tubes containing 5mL liquid culture medium, and perform activation culture. The activation culture conditions are 30℃, 15 0r / min, culture for 10h to obtain Candida liquid and Bacillus subtilis liquid respectively; select a 5L fully automatic constant temperature shaking incubator, take 10mL of the activated Candida liquid and Bacillus subtilis liquid respectively (5% of the total volume, taking 200mL of culture medium as an example), and inoculate them into a 250mL conical flask filled with culture medium according to a volume ratio of 1:1; put the conical flask into a shaking incubator, and culture for 30h at 30°C and 150r / min to obtain culture solution 1;

[0041] 1g / L ammonium chloride, 1g / L potassium nitrate, 1g / L potassium dihydrogen phosphate, 0.4g / L magnesium sulfate, 0.2g / L calcium chloride, and 2mL / L trace element solution were added, the pH was adjusted to 7.0-8.0, and the mixture was sterilized at 121°C for 20min under high pressure, and then cooled to room temperature for use; the freeze-dried powders of Nitrosomonas eutropha, Nitrobacter vedoti, and Pseudomonas strechingensis were dissolved in sterile water, respectively, and inoculated into a 1000mL narrow-necked glass bottle containing 800mL mixed culture medium in a sterile operating table at a volume ratio of 1:1:2, and the inoculation amount was 5% of the total volume. The narrow-necked glass bottle was placed in an airlift bioreactor, sterile air was introduced, the gas flow rate was controlled to be 0.6 / min, the temperature was 30°C, the pH was 7.0-8.0, and the culture solution 2 was obtained under the condition of 100r / min for 60h.

[0042] 15 parts of purple sulfur bacteria and 18 parts of plant lactobacillus were inoculated into the composite carrier and cultured for 24 hours under the conditions of light intensity of 5000 lux and temperature of 28°C to obtain a pre-culture, wherein the bacterial liquid density was 5×10 8CFU / mL; inoculate 25 portions of culture fluid one into the pre-culture, and culture in a shaker at 30°C and 120r / min for 12 hours to obtain a culture; inoculate 30 portions of culture fluid two into the culture, and culture in a shaker at 35°C and 120r / min for 12 hours to obtain a microbial complex; freeze-dry the microbial complex, the pre-freezing temperature of freeze-drying is -30°C, and the pre-freezing time is 4 hours; the sublimation drying pressure is 60Pa; the sublimation drying temperature is 20°C, and the sublimation drying time is 36 hours; the analytical drying temperature is 30°C; and the analytical drying time is 5 hours.

[0043] Examples 2-8 refer to the preparation methods and parameter conditions of Example 1, with the differences shown in Table 1.

[0044] Table 1 Component dosage of Examples 1-8

[0045]

[0046] Comparative Example 1 refers to Example 1, except that purple sulfur bacteria are not added.

[0047] Comparative Example 2 refers to Example 1, except that no co-culture solution 1 is added.

[0048] Comparative Example 3 refers to Example 1, except that Candida and Bacillus subtilis are not co-cultured.

[0049] Comparative Example 4 refers to Example 1, except that Candida is not added.

[0050] Comparative Example 5 refers to Example 1, except that Bacillus subtilis was not added.

[0051] Comparative Example 6 refers to Example 1, except that Clostridium sporogenes is added instead of Bacillus subtilis.

[0052] Comparative Example 7 refers to Example 1, except that Bacillus licheniformis is added instead of Bacillus subtilis.

[0053] Example 9 Chemical Oxygen Demand Test

[0054] The sewage used in the present invention is leachate from a domestic waste landfill, and the water quality index is mainly tested according to "Water and Wastewater Detection and Analysis Methods (Fourth Edition)" and "Standard Detection Methods for Drinking Water" (GB / T 5750.1-12-2006). The microbial composite agents prepared in Examples 1-8 and Comparative Examples 1-7 are respectively added to 10L of sewage at a usage amount of 35g / L, and are continuously stirred for 72h, aerated once every 2h, and the treatment temperature is 25°C. The chemical oxygen demand COD and biochemical oxygen demand BOD are respectively measured by potassium dichromate method and dilution multiple method. 5The test results are shown in Table 2; COD values ​​and BOD values ​​of wastewater treated with the microbial composite agent obtained in Examples 1-5 and Comparative Examples 1-3 5 The measured value is Figure 1 shown.

[0055] Table 2 Test results of Examples 1-8 and Comparative Examples 1-7

[0056] Example COD reduction rate / % <![CDATA[BOD 5 Decline rate / %]]> Example 1 92.8 88.5 Example 2 91.6 87.2 Example 3 92.5 88.1 Example 4 92.2 87.9 Example 5 92.6 88.3 Example 6 92.7 88.4 Example 7 92.8 88.4 Example 8 92.6 88.2 Comparative Example 1 70.8 65.2 Comparative Example 2 65.2 60.4 Comparative Example 3 80.8 78.6 Comparative Example 4 75.2 71.8 Comparative Example 5 74.6 70.9 Comparative Example 6 76.5 72.5 Comparative Example 7 90.8 86.2

[0057] Through Table 2, Figure 1As a result, it can be seen that the microbial composite agent prepared without adding purple sulfur bacteria in comparative example 1 has a significant adverse effect on the reduction of chemical oxygen demand and biochemical oxygen demand in sewage, and shows a significantly reduced reduction rate relative to Examples 1-8. Because purple sulfur bacteria can use simple organic compounds in sewage as a carbon source for its growth under light conditions, and convert them into cellular substances or harmless substances through photosynthesis and metabolic pathways, thereby reducing the content of organic pollutants in water, and releasing oxygen in the process, improving the redox conditions of sewage, and providing a more favorable environment for other microorganisms to degrade organic matter. At the same time, through photosynthesis and metabolism, the concentration of biodegradable organic matter in sewage is reduced, thereby reducing the BOD value; As can be seen from the results of comparative examples 2-5, the microbial composite agent obtained by using a single yeast or spore-forming bacteria has no obvious reduction in chemical oxygen demand and biochemical oxygen demand. The microbial composite agent obtained without co-cultivation has a significantly improved reduction effect compared with a single bacterium, but compared with Examples 1-8 There is still a significant reduction; during the sewage treatment process, yeast decomposes organic matter in sewage, especially soluble or easily decomposable organic matter, by fermentation or redox reaction, releasing carbon dioxide and water, thereby reducing the content of organic pollutants in water and reducing biochemical oxygen demand. In addition, yeast can combine with suspended matter and organic matter in water to form larger biological flocs, enhance precipitation, and thus reduce soluble organic matter and particulate matter in water; the addition of Bacillus can decompose complex organic compounds, while secreting a variety of hydrolases to decompose organic pollutants and convert them into simple inorganic matter or smaller organic matter, thereby reducing COD; in Comparative Examples 6-7, by changing the type of Bacillus, the use of anaerobic Bacillus has no obvious synergistic effect on reducing oxygen demand due to the difference in the living environment with yeast, and the selection of aerobic Bacillus can cooperate with yeast to improve the sewage treatment capacity of the microbial composite agent; the results of Example 5 show that too high a culture temperature will lead to the inactivation of microorganisms, thereby indirectly reducing the decomposition efficiency. From the results in Table 2 and Table 1, it can be seen that the culture solution formed by yeast and Bacillus can improve the compatibility between microorganisms, and at the same time, the two can complement each other in the degradation of different organic matter. The metabolic products of yeast can lower the pH value, which helps Bacillus to reproduce in a suitable environment. The synergistic effect improves the degradation rate of organic matter in sewage and reduces COD and BOD5 more efficiently.

[0058] Examples 10-17 were prepared according to the same method and parameters as in Example 1, with the differences shown in Table 3.

[0059] Table 3 Parameter changes of Examples 10-17

[0060]

[0061] Comparative Example 8 was prepared according to the preparation method and parameter conditions of Example 1, except that no culture medium 2 was added.

[0062] Comparative Example 9 refers to Example 1, except that Nitrobacter versicaninum is not added to the culture solution 2.

[0063] Comparative Example 10 refers to Example 1, except that Pseudomonas stretzschlowskii is not added to the culture solution 2.

[0064] Comparative Example 11 refers to Example 1, except that no culture is performed, and Nitrosomonas eutropha, Nitrobacter vedoti and Pseudomonas stutzeri are directly inoculated on the composite carrier.

[0065] Comparative Example 12 refers to Example 1, except that culture solution 2 is inoculated first and then culture solution 1 is inoculated.

[0066] Comparative Example 13 refers to Example 1, except that culture solution 1 and culture solution 2 are inoculated into the composite carrier at the same time.

[0067] Example 18 Malodorous Gas Detection

[0068] The microbial composites prepared in Examples 10-17 and Comparative Examples 8-13 were added to 10L of sewage at a usage amount of 35g / L, and were continuously stirred for 72h, aerated once every 2h, and the treatment temperature was 25°C. Nessler's reagent photometry and lead chloride spectrophotometry were used for ammonia nitrogen compounds and sulfur-containing odorous gases, respectively. The test results are shown in Table 4.

[0069] Table 4 Malodorous gas detection of Examples 10-17 and Comparative Examples 8-13

[0070] Example Ammonia nitrogen reduction rate / % Sulfur gas reduction rate / % Example 10 88.2 87.6 Embodiment 11 87.8 87.2 Example 12 86.6 85.9 Embodiment 13 88.5 87.5 Embodiment 14 85.9 85.2 Embodiment 15 86.5 86.5 Example 16 87.2 86.5 Embodiment 17 88.3 87.2 Comparative Example 8 65.8 62.5 Comparative Example 9 70.5 69.8 Comparative Example 10 72.5 68.5 Comparative Example 11 80.5 77.8 Comparative Example 12 82.5 80.2 Comparative Example 13 83.2 82.4

[0071] From the results in Table 4, it can be seen that the ammonia nitrogen reduction rate and hydrogen sulfide reduction rate of the microbial composite agent obtained in Comparative Example 8 without adding the culture solution 2 are significantly lower than those in Examples 10-17. Since the Nitrosomonas and Nitrobacter vedotinus in the culture solution 2 can convert ammonia nitrogen into nitrite and nitrate, Pseudomonas strechingensis can reduce nitrate to nitrogen gas in a low-oxygen environment to achieve nitrogen removal. At the same time, Pseudomonas strechingensis obtains energy by oxidizing hydrogen sulfide, converting hydrogen sulfide into sulfur, sulfate or other sulfur compounds, thereby removing hydrogen sulfide in the environment and reducing the source of odor in sewage. In ratios 9-11, by reducing the types of bacteria in the culture solution 2 and not obtaining the culture solution 2 through cultivation, the sewage odor treatment effect of the obtained microbial composite agent is significantly reduced. The co-cultivation process can increase the biocompatibility of nitrifying bacteria and denitrifying bacteria, avoid competitive growth caused by the simultaneous addition process, and at the same time, use Nitrosomonas, Nitrobacter vedoti and Pseudomonas stutzeri to play a synergistic role in the sewage treatment process. Nitrifying bacteria convert ammonia nitrogen into nitrates through aerobic action, and the latter reduces nitrates to nitrogen gas under hypoxic conditions. The combination of the two can significantly improve the removal efficiency of ammonia nitrogen in sewage. The nitrifying bacteria provide sufficient nitrate source for the denitrifying bacteria, and the denitrifying bacteria convert it into gaseous nitrogen under anoxic conditions, further reducing the pollution of ammonia nitrogen to the water body, and at the same time oxidizing the hydrogen sulfide gas in the sewage; in comparative examples 12-13, the order of adding culture solution 1 and culture solution 2 is changed, which has an adverse effect on the decomposition ability of the microbial composite agent. Since nitrifying bacteria usually require sufficient oxygen, while denitrifying bacteria rely on a low oxygen environment, the co-culture of the two can ensure that the nitrification process occurs in an oxygenated environment and the denitrification process occurs in an anaerobic environment by properly regulating the environmental conditions. The combination effectively improves the nitrogen removal efficiency. However, the growth of purple sulfur bacteria in the system caused by the addition of culture medium first and the high oxygen concentration in the composite agent will affect the growth of denitrifying bacteria, thereby inhibiting the growth of denitrifying bacteria and reducing the degree of reduction of hydrogen sulfide gas and nitrate. In summary, nitrifying bacteria convert ammonia nitrogen into nitrate, providing sufficient substrate for denitrifying bacteria. Denitrifying bacteria generate nitrogen by reducing nitrate under low oxygen conditions, maintain energy balance, and reduce the concentration of harmful gases such as hydrogen sulfide. The efficient decomposition of malodorous gases by the microbial composite agent is improved through co-culture and bacterial synergy.

[0072] Examples 19-25 refer to the preparation methods and parameter conditions of Example 1, with the differences shown in Table 5.

[0073] Table 5 Parameter changes of Examples 19-25

[0074]

[0075] Comparative Example 14 refers to Example 1, except that nano-alumina is used as the carrier.

[0076] Comparative Example 15 refers to Example 1, except that chitosan is used as the carrier.

[0077] Comparative Example 16 refers to Example 1, except that no docosahexaenoic acid modification is added.

[0078] Comparative Example 17 refers to Example 1, except that the alumina is not subjected to calcination treatment.

[0079] Example 26 Low temperature stability test

[0080] The microbial composites prepared in Examples 19-25 and Comparative Examples 14-17 were added to 10L of sewage at a usage amount of 35g / L, and were continuously stirred for 72h, aerated once every 2h, and the treatment temperature was 5°C. The chemical oxygen demand (COD) and ammonia nitrogen compound tests were carried out using potassium dichromate method and Nessler's reagent photometry, respectively. The test results are shown in Table 6.

[0081] Table 6 Stability test of Examples 19-25 and Comparative Examples 14-17

[0082] Example COD reduction rate / % Ammonia nitrogen reduction rate / % Embodiment 19 92.8 88.2 Embodiment 20 90.2 85.1 Embodiment 21 90.8 85.8 Embodiment 22 91.2 87.3 Embodiment 23 91.3 86.2 Embodiment 24 90.5 85.6 Embodiment 25 91.5 86.3 Comparative Example 14 70.2 68.2 Comparative Example 15 70.6 70.5 Comparative Example 16 71.2 62.5 Comparative Example 17 80.5 78.8

[0083] The results in Table 6 show that in Comparative Examples 14-15 and 17, by using a single carrier as the carrier of the microbial composite, the low-temperature decomposition effect of the prepared microbial composite is poor, and the reduction rate of chemical oxygen demand and ammonia nitrogen compounds is significantly reduced. Due to the good biocompatibility of chitosan, it can provide a protective environment for microorganisms. Under low temperature conditions, chitosan forms a protective film and increases the adaptability of microorganisms to maintain the low-temperature activity of microorganisms. At the same time, nano-alumina is treated with polyvinyl alcohol template calcination to form a pore structure with a high specific surface area, which can provide an ideal attachment surface for microorganisms. The surface energy of nano-alumina interacts with chitosan to form a relatively stable composite material. The stability of the material helps to maintain the function of microorganisms in a low-temperature environment. Unsaturated docosahexaenoic acid is introduced in Comparative Example 16, which can cooperate with the composite carrier to improve the low-temperature stability of microorganisms under low temperature conditions. Qualitatively, unsaturated fatty acids contain multiple double bonds in lipid molecules, which makes it impossible for fatty acid chains to be completely arranged and the interaction between lipid molecules is weak, thereby increasing the fluidity of the membrane. At the same time, unsaturated fatty acids can reduce the phase transition temperature of membrane lipids, improve the fluidity of the membrane, and enable the microbial cell membrane to maintain a certain fluidity and flexibility at low temperatures, ensuring the normal operation of the cells, thereby improving the low-temperature stability of the microorganisms. From the results in Table 6, it can be seen that by utilizing the synergistic effect of chitosan and nano-alumina, nano-alumina provides a high specific surface area, increases the microbial attachment sites, and improves the stability of the microorganisms. At the same time, chitosan can form a protective film on the surface of microorganisms to slow down the damage of low temperature to the cell membrane. In addition, unsaturated fatty acids cooperate with chitosan to improve the fluidity of microbial cell membranes, thereby improving the activity of microorganisms under low temperature conditions and increasing the decomposition efficiency of the microbial complex under low temperature conditions.

[0084] Examples 27-33 refer to the preparation methods and parameter conditions of Example 1, with the differences shown in Table 7.

[0085] Table 7 Parameter changes of Examples 27-33

[0086]

[0087] Comparative Example 18 refers to Example 1, except that lactic acid bacteria are not added.

[0088] Comparative Example 19 refers to Example 1, except that Lactobacillus acidophilus is added as lactic acid bacteria.

[0089] Comparative Example 20 refers to Example 1, except that Lactobacillus casei was added as lactic acid bacteria.

[0090] Comparative Example 21 refers to Example 1, except that the prepared microbial complex is not freeze-dried.

[0091] Example 34 pH stability test

[0092] The microbial composites prepared in Examples 27-33 and Comparative Examples 18-21 were added to 10L of sewage at a usage amount of 35g / L, and were continuously stirred for 72h, aerated once every 2h, the treatment temperature was 25°C, the sewage pH was 8.0-11.5, the pH value of the treated sewage was measured by a pHS-25 acidity meter, and the chemical oxygen demand COD and ammonia nitrogen compound tests were carried out by potassium dichromate method and Nessler's reagent photometry, respectively. The test results are shown in Table 8.

[0093] Table 8 Stability test of Examples 27-33 and Comparative Examples 18-21

[0094]

[0095]

[0096] As shown in the results of Table 8, the pH regulating ability of the microbial composites prepared by not adding lactic acid bacteria or adding other lactic acid bacteria in Comparative Examples 18-20 is significantly worse than that of Examples 27-33. Since lactic acid bacteria convert sugars into lactic acid through fermentation during metabolism, the pH of the culture medium can be reduced, thereby affecting the growth and metabolism of other microorganisms in the microbial composite. The other microorganisms in the composite have a certain acid resistance and can grow under weak acid conditions. The addition of lactic acid bacteria can adjust the pH of sewage to maintain the growth and metabolism of other microorganisms, and improve the efficient decomposition of sewage by the microbial composite under synergistic effects. In addition, lactic acid bacteria can help maintain pH stability, reduce the impact of acidic metabolites on the environment, and reduce the growth inhibitory effect of alkaline sewage on microorganisms. Compared with Lactobacillus acidophilus and Lactobacillus casei, Lactobacillus plantarum has a stronger adaptability and can survive in the complex environment of alkaline sewage. It uses organic substances such as sugars in sewage to ferment and produce acid, reduces the pH value of sewage, and inhibits the growth of harmful microorganisms. At the same time, its metabolites can provide nutrition and suitable pH for other microorganisms. H environment, which helps to build a stable microbial community, and can also produce antibacterial substances such as bacteriocins, which have an inhibitory effect on some pathogens in sewage and reduce the potential harm of pathogens to the environment and human health; the microbial composite obtained without freeze-drying in Example 21 has little effect on pH, but the activity of the microbial composite is reduced. During the freeze-drying process, the microorganisms are in a low temperature and low moisture environment, their metabolic activities are almost stopped, and their physiological activities are in a dormant state, which helps to reduce the biochemical reactions in the microbial cells and avoid the loss of energy and nutrients due to metabolic consumption, so that the microorganisms can maintain their original activity for a longer period of time. At the same time, it reduces the risk of decreased activity or even death of microorganisms due to excessive reproduction or unsuitable growth conditions, which is beneficial to maintaining the activity and stability of the microorganisms; From the results in Table 8, it can be seen that the use of plant lactobacillus in conjunction with other microorganisms can improve the decomposition efficiency of the microbial composite in alkaline sewage, improve the pH stability of the microbial composite, and at the same time, freeze-dry the microbial composite to improve the separation efficiency of the microbial composite for sewage and reduce the residue of odorous gases.

[0097] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A microbial composite agent, characterized in that: The microbial composite agent comprises 8-20 parts of purple sulfur bacteria, 20-35 parts of culture solution 1, 25-35 parts of culture solution 2, 90-120 parts of composite carrier, and 10-20 parts of lactic acid bacteria; wherein the culture solution 1 comprises Candida and Bacillus; The second culture solution includes Nitrosomonas, Nitrobacter eutropha and Pseudomonas stutzeri; The composite carrier comprises nano-alumina and modified chitosan; wherein the mass ratio of the modified chitosan to the nano-alumina is 1:2-5; The lactic acid bacteria is selected from one of Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus casei.

2. A microbial composite agent according to claim 1, characterized in that: The bacillus is selected from one of Bacillus subtilis, Clostridium sporogenes and Bacillus licheniformis.

3. A microbial composite agent according to claim 1, characterized in that: The preparation of the culture solution 1 comprises the following steps: 20 g / L glucose, 10 g / L yeast extract, 20 g / L tryptone, and 15 g / L agar are added to adjust the pH of the culture medium to 6.0-7.0, and the medium is sterilized at 121° C. for 20 min under high pressure, and cooled to room temperature for use; the Candida and Bacillus subtilis strains are taken out from the glycerol cryopreservation tubes, and are inoculated into test tubes containing 5 mL of liquid culture medium, respectively, and activated and cultured to obtain Candida liquid and Bacillus subtilis liquid; the Candida liquid and the Bacillus subtilis liquid are inoculated into a 250 mL conical flask containing culture medium; the conical flask is placed in a shaking incubator, and cultured at 20-50° C. for 30 hours to obtain the culture solution 1.

4. A microbial composite agent according to claim 3, characterized in that: The volume ratio of the Candida albicans to the Bacillus subtilis is 1-3:1-3.

5. The microbial composite agent according to claim 1, characterized in that: The preparation of the culture solution 2 comprises the following steps: 1 g / L of ammonium chloride, 1 g / L of potassium nitrate, 1 g / L of potassium dihydrogen phosphate, 0.4 g / L of magnesium sulfate, 0.2 g / L of calcium chloride, and 2 mL / L of trace element solution were added, the pH value was adjusted to 7.0-8.0, and the mixture was sterilized under high pressure at 121° C. for 20 min, and cooled to room temperature for use; the freeze-dried powders of the Nitrosomonas eutropha, the Nitrobacter vedotinus, and the Pseudomonas strechingensis were respectively dissolved with sterile water, inoculated into glass bottles on a sterile operating table, and then the narrow-mouthed glass bottles were placed in an airlift bioreactor, sterile air was introduced, the gas flow rate was controlled to be 0.6 L / min, and the temperature was 20-40° C. and cultured for 60 h to obtain the culture solution II.

6. A microbial composite agent according to claim 5, characterized in that: The volume ratio of the Nitrosomonas, the Nitrobacter vedotinus and the Pseudomonas stutzeri is 1-2:1-2:1-3.

7. The microbial composite agent according to claim 1, characterized in that: The preparation of the composite carrier comprises the following steps: Chitosan is added to an acetic acid solution and stirred until completely dissolved to obtain a chitosan solution; docosahexaenoic acid is slowly added to the chitosan solution, and the reaction is carried out at 50° C. for 2 hours to obtain a modified chitosan; the nano-alumina is slowly dropped into the modified chitosan under stirring conditions, and after the dropwise addition is completed, the stirring reaction is continued for 2 hours to obtain a mixed solution; the mixed solution is aged at 50-80° C. for 3-8 hours to obtain a reactant; the reactant is separated and centrifuged, washed with deionized water, and dried at 80° C. for 2 hours to obtain the composite carrier.

8. The microbial composite agent according to claim 1, characterized in that: The preparation of the microbial composite agent comprises the following method: The purple sulfur bacteria and the plant lactobacillus are inoculated into the composite carrier, and cultured at 28°C for 24 hours to obtain a preculture; the culture solution 1 is inoculated into the preculture, and cultured on a shaking table for 12 hours to obtain a culture; the culture solution 2 is inoculated into the culture, and cultured on a shaking table for 12 hours to obtain a microbial complex; the microbial complex is freeze-dried to obtain the microbial composite agent; the pre-freezing temperature of the freeze-drying is -30°C, and the pre-freezing time is 3-5 hours; the sublimation drying pressure is 40-80Pa; the sublimation drying temperature is 20°C, and the sublimation drying time is 36 hours; the analytical drying temperature is 25-40°C; and the analytical drying time is 3-5 hours.

9. Use of the microbial composite agent as claimed in claim 1 in a process for efficiently decomposing and treating malodor in sewage.

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