Composite denitrification accelerant and preparation method thereof

Abstract

The invention discloses a composite denitrification accelerant and a preparation method thereof, and belongs to the technical field of sewage treatment. The carbon source composite material is prepared from the following raw materials in parts by weight: 30-50% of a carbon source, 2-5% of vitamins, 2-5% of amino acids, 1-3% of a biological stimulant, 1-2% of signal molecules, 1-5% of metal elements, 3-5% of a pH regulator and 25-60% of water. Through metabolites such as vitamins, amino acids and biological stimulants, growth and reproduction of denitrifying bacteria are promoted, and functions of related enzymes in the denitrification process are improved. The signal molecule optimizes the metabolic activity of bacteria by regulating and controlling the expression of genes, related to the denitrification process, of the denitrifying bacteria. The metal ions can enhance the activity of the denitrifying enzyme, so that the efficiency of denitrification treatment is improved. According to the denitrification accelerant, the denitrification process is promoted through the synergistic effect of three aspects of growth and reproduction of denitrifying bacteria, expression of denitrification genes and improvement of activity of denitrification-related enzymes.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a composite denitrification promoter and a preparation method thereof. Background Art

[0002] With the continuous acceleration of the industrialization and urbanization processes, the discharge of high-nitrogen sewage is increasing continuously. High-nitrogen sewage contains a large amount of organic nitrogen and ammonia nitrogen. Since nitrogen is the main nutrient element for the growth of algae, excessive nitrogen will cause a large number of algae to reproduce, leading to water eutrophication. Eutrophication will cause hypoxia in the water, affecting the survival of aquatic organisms and destroying the ecological balance. It has great harm to the environment. Therefore, how to efficiently treat high-nitrogen sewage is an important issue.

[0003] The existing nitrogen-containing sewage treatment processes mainly rely on biological denitrification. The traditional biological denitrification technology mainly oxidizes ammonia nitrogen in sewage to nitrate through nitrification, and then reduces nitrate to nitrogen through denitrification. The traditional biological denitrification technology is mature and the denitrification effect is stable. The existing new biological denitrification technologies mainly include the short-cut nitrification-denitrification method and the anaerobic ammonium oxidation method. The short-cut nitrification-denitrification method oxidizes ammonia nitrogen to nitrite nitrogen and then reduces it to nitrogen. This method can save carbon sources and energy compared with the traditional biological denitrification technology, but there are problems of strict control conditions and poor operation stability. The anaerobic ammonium oxidation method mainly directly reacts ammonia nitrogen with nitrite to generate nitrogen under anaerobic conditions, but this method has problems of long start-up time and high requirements for water quality.

[0004] The existing biological denitrification technologies mostly rely on the nitrification-denitrification of nitrifying bacteria. Therefore, improving the nitrification-denitrification efficiency of nitrifying bacteria can directly affect the treatment efficiency of high-nitrogen sewage. The invention patent CN110040846B discloses a carbon source denitrification promoter, which is a composite carbon source. By providing the nutrients and trace elements required for the growth of denitrifying bacteria, it accelerates the reproduction of denitrifying bacteria, and improves the efficiency of the denitrification process by rapidly increasing the content of denitrifying bacteria in sewage. However, this promoter replaces the traditional carbon source, and a large dosage is required in the treatment process of high-concentration and high-water-volume sewage, greatly increasing the cost of the carbon source required for sewage treatment. In addition, this promoter adds biological enzymes. Since the activity of biological enzymes is affected by various factors such as temperature, pH, and heavy metal ions, the requirements for storage conditions and use conditions are relatively high. After the enzyme is inactivated, the efficiency of this promoter will be greatly affected. In addition, the life activities of denitrifying bacteria, including growth and reproduction, are all controlled by corresponding genes. Simply adding carbon sources, enzymes, and trace elements required by bacteria has limited effects on the life activities of bacteria.

[0005] In summary, by regulating the gene expression of denitrifying bacteria, the enzyme treatment efficiency, and life activities including growth and reproduction, the efficiency of the nitrification-denitrification process in sewage treatment can be controlled. Summary of the Invention

[0006] In view of the fact that the existing process can only regulate macroscopic factors such as temperature, pH, and concentration, and ignores the regulation of microscopic factors such as the gene expression of denitrifying bacteria, the enzyme treatment efficiency, and life activities including growth and reproduction. The present invention provides a composite denitrification promoter, which can improve the nitrification-denitrification efficiency of nitrifying bacteria, accelerate the growth and reproduction rate of denitrifying bacteria, and accelerate the film-forming rate of denitrifying bacteria on the packing.

[0007] The specific technical solution of the present invention is: it is made of the following components by mass percentage: carbon source 30-50%, bacterial metabolites 5-13%, signal molecules 1-2%, metal elements 1-5%, pH regulator 3-5%, water 25-60%.

[0008] The composite denitrification promoter of the present invention supports the metabolic activities of denitrifying bacteria through the vitamin B complex and amino acids in the bacterial metabolites, promotes the growth and reproduction of denitrifying bacteria, improves the function of enzymes related to denitrification in denitrifying bacteria, and ultimately increases the rate of denitrification. The biostimulants in the bacterial metabolites can improve the activity of denitrifying bacteria, improve the growth environment of bacteria, and enhance the metabolic capacity of denitrifying bacteria. At the same time, signal molecules can regulate the reproduction of denitrifying bacteria and the expression of genes related to denitrification, and accelerate the reproduction of denitrifying bacteria when the number of denitrifying bacteria is small and the denitrification efficiency is low, thereby improving the efficiency of denitrification treatment. Metal elements and pH have a great influence on the activity of enzymes related to the denitrification process. By metal elements and controlling the acidic environment, the activity of enzymes related to the denitrification process is ensured to improve the efficiency of denitrification treatment. In summary, the denitrification promoter of the present invention accelerates the denitrification process by accelerating the growth and reproduction of denitrifying bacteria, regulating the expression of genes related to denitrifying bacteria, and increasing the activity of enzymes related to denitrification.

[0009] Preferably, the carbon source includes one or more of ethanol, sodium acetate, glucose, and glycerol.

[0010] The above carbon source is non-toxic and pollution-free, has no negative impact on sewage treatment, the raw materials are simple and easy to obtain, and can better provide the energy required for denitrifying bacteria to maintain life activities and promote the synthesis of denitrifying enzymes.

[0011] The bacterial metabolites include vitamin B complex, amino acids, and biostimulants.

[0012] Preferably, the B-vitamin mixture is a mixture of vitamin B1, vitamin B2, and vitamin B6, and the amino acids include one or more of glutamic acid and aspartic acid.

[0013] Denitrifying bacteria require specific vitamins and amino acids to support their metabolic activities. B-vitamins, glutamic acid, and aspartic acid can promote the growth of denitrifying bacteria and improve the function of the enzyme system.

[0014] The biostimulant includes one or more of humic acid and fulvic acid.

[0015] The above biostimulant can stimulate the activity of denitrifying bacteria, improve the bacterial growth environment, and enhance its metabolic capacity.

[0016] Preferably, the signal molecule includes one or more of acyl-homoserine lactone, oligopeptide signal molecules, autoinducer-2, and diffusible signal factor. More preferably, the signal molecule is acyl-homoserine lactone.

[0017] The above signal molecules enable bacteria to sense the number of similar bacteria in the surrounding environment and coordinate the behavior of the population, including the denitrification process. Signal molecules can regulate the expression of denitrification-related genes, optimize the metabolic activity of bacteria, and thus improve the denitrification efficiency.

[0018] Preferably, the metal element includes one or more of iron, copper, zinc, and molybdenum. More preferably, the metal element is iron.

[0019] The above metal elements are cofactors of denitrifying enzymes, which can enhance the activity of denitrifying enzymes and improve the denitrification efficiency.

[0020] Preferably, the pH regulator includes one or more of acetic acid, carbonic acid, citric acid, sodium acetate, and sodium citrate. More preferably, the pH regulator is acetic acid.

[0021] The preparation method of the composite denitrification promoter is as follows: 1) The B-vitamin mixture is obtained by inoculating, culturing, centrifuging, ultrasonically disrupting, separating and purifying, and freeze-drying yeast. 2) Humic acid is obtained by crushing, pickling, extracting, aerating, centrifuging, acid-precipitating, and freeze-drying natural raw materials. 3) Dissolve the carbon source in water at room temperature, add the pH regulator, metal element, bacterial metabolite, and signal molecule in sequence, mix evenly, and store at room temperature in a cool place.

[0022] Preferably, in step 1), the dissolved oxygen content needs to be controlled above 30% during the aeration process.

[0023] When the dissolved oxygen content in the fermentation broth is higher than 30%, the fermentation product of yeast is a mixture of B vitamins.

[0024] Preferably, in the step 2), the extraction process is to keep the temperature at 50 - 70 °C and extract for 1 - 2 h.

[0025] Beneficial effects:

[0026] The composite denitrification promoter of the present invention maintains a weakly acidic environment of the promoter through a pH regulator to ensure the stable existence of amino acids, metal elements, and bacterial metabolites in the promoter. It promotes the growth of denitrifying bacteria and improves the function of the enzyme system through vitamins and amino acids. It improves the activity of denitrifying bacteria, improves the growth environment of bacteria, and enhances their metabolic capacity through a biostimulant. It regulates the expression of denitrification-related genes through signal molecules. It enhances the activity of denitrifying enzymes through metal elements. Through the synergistic action of the above substances, the efficiency of the denitrification process is improved. Specific embodiments

[0027] To better illustrate the technical effects of the present invention, the following specific examples and comparative examples are analyzed.

[0028] General example:

[0029] A composite denitrification promoter is made of the following components in mass percentages: carbon source 30 - 50%, bacterial metabolite 5 - 13%, signal molecule 1 - 2%, metal element 1 - 5%, pH regulator 3 - 5%, and water 25 - 60%.

[0030] A preparation method of a composite denitrification promoter includes: 1) Inoculate baker's yeast into a YPD slant medium containing 1% yeast extract, 2% peptone, 2% glucose, and 2% agar, adjust the pH to 5.5 - 6.5, the temperature to 28 - 30 °C, aerate the medium, control the dissolved oxygen content to be higher than 30%, and culture for 24 - 48 h. Glucose is added in batches during the culture process. Then centrifuge and separate at a speed of 4000 rpm for 15 min to obtain baker's yeast. After ultrasonic fragmentation treatment, it is separated and purified by activated carbon adsorption and ion exchange chromatography, and stored in the dark at low temperature after freeze-drying to obtain a mixture of B vitamins. 2) Crush raw materials such as peat, lignite, and weathered coal to 80 - 100 mesh, wash with dilute hydrochloric acid, and then dry at a low temperature below 60°C. Extract with 0.5 mol / L sodium hydroxide solution at 50 - 70°C for 1 - 2 h, while performing low-speed stirring and aeration, and centrifuge at 3000 rpm for 15 min. Take the supernatant, adjust the pH to 1.5 - 2 with 1 mol / L hydrochloric acid, refrigerate at 4°C for 12 h, and centrifuge at 4000 rpm for 10 min. Take the precipitate, wash it 2 - 3 times with 0.1 mol / L dilute hydrochloric acid, then dissolve it with 0.1 mol / L sodium hydroxide, repeat acid precipitation 1 - 2 times, and then freeze-dry to obtain humic acid. 3) Dissolve the carbon source in water at room temperature, add the pH regulator, metal elements, vitamin B complex mixture, humic acid, amino acids, and signaling molecules in sequence, mix evenly, and store at room temperature in a cool place.

[0031] Example 1

[0032] A composite denitrification promoter is made of the following components in mass percentage: sodium acetate 40%, vitamin B complex mixture 3.5%, glutamic acid 3.5%, humic acid 2%, acyl-homoserine lactone 1.5%, ferric chloride 3%, acetic acid 4%, water 42.5%.

[0033] A preparation method of a composite denitrification promoter includes: 1) Inoculate baker's yeast into a YPD slant medium containing 1% yeast extract, 2% peptone, 2% glucose, and 2% agar, adjust the pH to 5.5 - 6.5, the temperature to 28 - 30°C, aerate the medium, control the dissolved oxygen content to be higher than 30%, and culture for 24 - 48 h. During the culture process, add glucose in batches. Then centrifuge at 5000 rpm for 10 min to obtain baker's yeast. After ultrasonic fragmentation treatment, separate and purify by activated carbon adsorption and ion exchange chromatography, and store in the dark at low temperature after freeze-drying to obtain the vitamin B complex mixture. 2) Crush raw materials such as peat, lignite, and weathered coal to 80 - 100 mesh, wash with dilute hydrochloric acid, and then dry at a low temperature below 60°C. Extract with 0.5 mol / L sodium hydroxide solution at 50 - 70°C for 1 - 2 h, while performing low-speed stirring and aeration, and centrifuge at 3000 rpm for 15 min. Take the supernatant, adjust the pH to 1.5 - 2 with 1 mol / L hydrochloric acid, refrigerate at 4°C for 12 h, and centrifuge at 4000 rpm for 10 min. Take the precipitate, wash it 2 - 3 times with 0.1 mol / L dilute hydrochloric acid, then dissolve it with 0.1 mol / L sodium hydroxide, repeat acid precipitation 1 - 2 times, and then freeze-dry to obtain humic acid. 3) Dissolve the carbon source in water at room temperature, and sequentially add a pH regulator, ferric chloride, a mixture of vitamin B, humic acid, amino acids, and acyl-homoserine lactone. After mixing evenly, store it at room temperature in a cool place.

[0034] Example 2

[0035] A composite denitrification promoter is made of the following components by mass percentage: sodium acetate 30%, mixture of vitamin B 2%, glutamic acid 2%, humic acid 1%, acyl-homoserine lactone 1%, ferric chloride 1%, acetic acid 3%, water 60%.

[0036] A preparation method of a composite denitrification promoter includes: 1) Inoculate baker's yeast into a YPD slant medium containing 1% yeast extract, 2% peptone, 2% glucose, and 2% agar, adjust the pH to 5.5 - 6.5, the temperature to 28 - 30 °C, aerate the medium, control the dissolved oxygen content to be higher than 30%, and culture for 24 - 48 h. During the culture process, supplement glucose in batches. Then centrifuge at a speed of 5000 rpm for 10 min to obtain baker's yeast. After ultrasonic fragmentation treatment, separate and purify it by activated carbon adsorption and ion exchange chromatography, and store it in the dark at low temperature after freeze-drying to obtain a mixture of vitamin B. 2) Crush raw materials such as peat, lignite, and weathered coal to 80 - 100 mesh, wash them with dilute hydrochloric acid, and then dry them at a low temperature below 60 °C. Extract with 0.5 mol / L sodium hydroxide solution at 50 - 70 °C for 1 - 2 h, while stirring and aerating at a low speed, and centrifuge at a speed of 3000 rpm for 15 min. Take the supernatant, adjust the pH to 1.5 - 2 with 1 mol / L hydrochloric acid, refrigerate at 4 °C for 12 h, and centrifuge at a speed of 4000 rpm for 10 min. Take the precipitate, wash it 2 - 3 times with 0.1 mol / L dilute hydrochloric acid, and then dissolve it with 0.1 mol / L sodium hydroxide. Repeat acid precipitation 1 - 2 times and then freeze-dry to obtain humic acid. 3) Dissolve the carbon source in water at room temperature, and sequentially add a pH regulator, ferric chloride, a mixture of vitamin B, humic acid, amino acids, and acyl-homoserine lactone. After mixing evenly, store it at room temperature in a cool place.

[0037] Example 3

[0038] A composite denitrification promoter is made of the following components by mass percentage: sodium acetate 50%, mixture of vitamin B 5%, glutamic acid 5%, humic acid 3%, acyl-homoserine lactone 2%, ferric chloride 5%, acetic acid 5%, water 25%.

[0039] A preparation method of a composite denitrification promoter includes: 1) Inoculate baker's yeast into a YPD slant medium containing 1% yeast extract, 2% peptone, 2% glucose, and 2% agar. Adjust the pH to 5.5 - 6.5, the temperature to 28 - 30 °C, aerate the medium, control the dissolved oxygen content to be higher than 30%, and culture for 24 - 48 h. During the culture process, add glucose in batches. Then centrifuge at a speed of 5000 rpm for 10 min to obtain baker's yeast. After ultrasonic disruption treatment, separate and purify it by activated carbon adsorption and ion exchange chromatography, and store it in the dark at low temperature after freeze-drying to obtain a vitamin B complex mixture. 2) Crush raw materials such as peat, lignite, and weathered coal to 80 - 100 mesh, wash them with dilute hydrochloric acid, and then dry them at a low temperature below 60 °C. Extract with 0.5 mol / L sodium hydroxide solution at 50 - 70 °C for 1 - 2 h, while performing low-speed stirring and aeration, and centrifuge at a speed of 3000 rpm for 15 min. Take the supernatant, adjust the pH to 1.5 - 2 with 1 mol / L hydrochloric acid, refrigerate at 4 °C for 12 h, and centrifuge at a speed of 4000 rpm for 10 min. Take the precipitate, wash it 2 - 3 times with 0.1 mol / L dilute hydrochloric acid, and then dissolve it with 0.1 mol / L sodium hydroxide. Repeat acid precipitation 1 - 2 times and then freeze-dry to obtain humic acid. 3) Dissolve the carbon source in water at room temperature, and sequentially add a pH regulator, ferric chloride, vitamin B complex mixture, humic acid, amino acids, acyl-homoserine lactone. After mixing evenly, store it at room temperature in a cool place.

[0040] Example 4

[0041] A composite denitrification promoter is made of the following components by mass percentage: sodium acetate 40%, glutamic acid 3.5%, humic acid 2%, acyl-homoserine lactone 1.5%, ferric chloride 3%, acetic acid 4%, water 46%.

[0042] A preparation method of a composite denitrification promoter includes: 1) Crush raw materials such as peat, lignite, and weathered coal to 80 - 100 mesh, wash them with dilute hydrochloric acid, and then dry them at a low temperature below 60 °C. Extract with 0.5 mol / L sodium hydroxide solution at 50 - 70 °C for 1 - 2 h, while performing low-speed stirring and aeration, and centrifuge at a speed of 3000 rpm for 15 min. Take the supernatant, adjust the pH to 1.5 - 2 with 1 mol / L hydrochloric acid, refrigerate at 4 °C for 12 h, and centrifuge at a speed of 4000 rpm for 10 min. Take the precipitate, wash it 2 - 3 times with 0.1 mol / L dilute hydrochloric acid, and then dissolve it with 0.1 mol / L sodium hydroxide. Repeat acid precipitation 1 - 2 times and then freeze-dry to obtain humic acid. 2) Dissolve the carbon source in water at room temperature, add the pH regulator, ferric chloride, vitamin B complex mixture, humic acid, amino acid, and acyl-homoserine lactone in sequence. After mixing evenly, store it at room temperature in a cool place.

[0043] Example 5

[0044] A composite denitrification promoter is made of the following components by mass percentage: sodium acetate 40%, vitamin B complex mixture 3.5%, humic acid 2%, acyl-homoserine lactone 1.5%, ferric chloride 3%, acetic acid 4%, and water 46%.

[0045] A preparation method of a composite denitrification promoter includes: 1) Inoculate baker's yeast into a YPD slant medium containing 1% yeast extract, 2% peptone, 2% glucose, and 2% agar. Adjust the pH to 5.5 - 6.5 and the temperature to 28 - 30 °C. Aerate the medium and control the dissolved oxygen content to be higher than 30%. Incubate for 24 - 48 h, and add glucose in batches during the incubation process. Then centrifuge at a speed of 5000 rpm for 10 min to obtain baker's yeast. After ultrasonic disruption treatment, separate and purify it by activated carbon adsorption and ion exchange chromatography, and store it in the dark at low temperature after freeze-drying to obtain the vitamin B complex mixture. 2) Crush raw materials such as peat, lignite, and weathered coal to 80 - 100 mesh, wash them with dilute hydrochloric acid, and then dry them at a low temperature below 60 °C. Extract with 0.5 mol / L sodium hydroxide solution at 50 - 70 °C for 1 - 2 h, while stirring and aerating at a low speed, and centrifuge at a speed of 3000 rpm for 15 min. Take the supernatant, adjust the pH to 1.5 - 2 with 1 mol / L hydrochloric acid, refrigerate at 4 °C for 12 h, and centrifuge at a speed of 4000 rpm for 10 min. Take the precipitate, wash it 2 - 3 times with 0.1 mol / L dilute hydrochloric acid, and then dissolve it with 0.1 mol / L sodium hydroxide. Repeat acid precipitation 1 - 2 times and then freeze-dry to obtain humic acid. 3) Dissolve the carbon source in water at room temperature, add the pH regulator, ferric chloride, vitamin B complex mixture, humic acid, amino acid, and acyl-homoserine lactone in sequence. After mixing evenly, store it at room temperature in a cool place.

[0046] Example 6

[0047] A composite denitrification promoter is made of the following components by mass percentage: sodium acetate 40%, vitamin B complex mixture 3.5%, glutamic acid 3.5%, acyl-homoserine lactone 1.5%, ferric chloride 3%, acetic acid 4%, and water 44.5%.

[0048] A preparation method of a composite denitrification promoter includes: 1) Inoculate baker's yeast into YPD slant medium containing 1% yeast extract, 2% peptone, 2% glucose, and 2% agar. Adjust the pH to 5.5 - 6.5 and the temperature to 28 - 30 °C. Aerate the medium and control the dissolved oxygen content to be higher than 30%. Incubate for 24 - 48 h, and supplement glucose in batches during the incubation process. Then centrifuge at 5000 rpm for 10 min to obtain baker's yeast. After ultrasonic disruption treatment, separate and purify it by activated carbon adsorption and ion exchange chromatography, and store it in the dark at low temperature after freeze-drying to obtain a vitamin B complex mixture. 2) Dissolve the carbon source in water at room temperature, and sequentially add a pH regulator, ferric chloride, vitamin B complex mixture, humic acid, amino acids, and acyl homoserine lactone. Mix evenly and store at room temperature in a cool place.

[0049] Example 7

[0050] A composite denitrification promoter is made of the following components by mass percentage: sodium acetate 40%, vitamin B complex mixture 3.5%, glutamic acid 3.5%, humic acid 2%, ferric chloride 3%, acetic acid 4%, and water 44%.

[0051] A preparation method of a composite denitrification promoter includes: 1) Inoculate baker's yeast into YPD slant medium containing 1% yeast extract, 2% peptone, 2% glucose, and 2% agar. Adjust the pH to 5.5 - 6.5 and the temperature to 28 - 30 °C. Aerate the medium and control the dissolved oxygen content to be higher than 30%. Incubate for 24 - 48 h, and supplement glucose in batches during the incubation process. Then centrifuge at 5000 rpm for 10 min to obtain baker's yeast. After ultrasonic disruption treatment, separate and purify it by activated carbon adsorption and ion exchange chromatography, and store it in the dark at low temperature after freeze-drying to obtain a vitamin B complex mixture. 2) Crush raw materials such as peat, lignite, and weathered coal to 80 - 100 mesh, wash them with dilute hydrochloric acid, and then dry them at a low temperature below 60 °C. Extract with 0.5 mol / L sodium hydroxide solution at 50 - 70 °C for 1 - 2 h, while stirring and aerating at a low speed, and centrifuge at 3000 rpm for 15 min. Take the supernatant, adjust the pH to 1.5 - 2 with 1 mol / L hydrochloric acid, refrigerate at 4 °C for 12 h, and centrifuge at 4000 rpm for 10 min. Take the precipitate, wash it 2 - 3 times with 0.1 mol / L dilute hydrochloric acid, and then dissolve it with 0.1 mol / L sodium hydroxide. Repeat acid precipitation 1 - 2 times and then freeze-dry to obtain humic acid. 3) Dissolve the carbon source in water at room temperature, and sequentially add a pH regulator, ferric chloride, vitamin B complex mixture, humic acid, amino acids, and acyl homoserine lactone. Mix evenly and store at room temperature in a cool place.

[0052] Example 8

[0053] A composite denitrification promoter is made of components with the following mass percentages: sodium acetate 40%, vitamin B complex mixture 3.5%, glutamic acid 3.5%, humic acid 2%, acyl-homoserine lactone 1.5%, acetic acid 4%, and water 45.5%.

[0054] A preparation method of a composite denitrification promoter includes: 1) Inoculate baker's yeast into a YPD slant medium containing 1% yeast extract, 2% peptone, 2% glucose, and 2% agar, adjust the pH to 5.5 - 6.5, the temperature to 28 - 30 °C, aerate the medium, control the dissolved oxygen content to be higher than 30%, culture for 24 - 48 h, and add glucose in batches during the culture process. Then centrifuge at a speed of 5000 rpm for 10 min to obtain baker's yeast. After ultrasonic disruption treatment, separate and purify by activated carbon adsorption and ion exchange chromatography, and store in the dark at low temperature after freeze-drying to obtain the vitamin B complex mixture. 2) Crush raw materials such as peat, lignite, and weathered coal to 80 - 100 mesh, wash with dilute hydrochloric acid, and then dry at a low temperature below 60 °C. Extract with 0.5 mol / L sodium hydroxide solution at 50 - 70 °C for 1 - 2 h, while performing low-speed stirring and aeration, and centrifuge at a speed of 3000 rpm for 15 min. Take the supernatant, adjust the pH to 1.5 - 2 with 1 mol / L hydrochloric acid, refrigerate at 4 °C for 12 h, and centrifuge at a speed of 4000 rpm for 10 min. Take the precipitate, wash it 2 - 3 times with 0.1 mol / L dilute hydrochloric acid, and then dissolve it with 0.1 mol / L sodium hydroxide. Repeat acid precipitation 1 - 2 times and then freeze-dry to obtain humic acid. 3) Dissolve the carbon source in water at room temperature, add a pH regulator, ferric chloride, vitamin B complex mixture, humic acid, amino acid, and acyl-homoserine lactone in sequence, mix evenly, and store at room temperature in a cool place.

[0055] Comparative Example 1

[0056] This comparative example is a denitrification system without a denitrification promoter.

[0057] Comparative Example 2

[0058] This comparative example is a conventional carbon source type denitrification promoter. The specific carbon source is methanol.

[0059] Comparative Example 3

[0060] This comparative example is a conventional electron donor type denitrification promoter. The specific electron donor is sodium sulfide

[0061] Comparative Example 4

[0062] This comparative example is a conventional trace element type denitrification promoter. The specific trace element is iron ion.

[0063] Comparative Example 5

[0064] This comparative example is a conventional biostimulation type denitrification promoter. The specific biostimulant is glutamic acid.

[0065] Denitrification efficiency, safety and stability tests were carried out on Examples 1-8 and Comparative Examples 1-5. The specific test methods are as follows:

[0066] Nitrate removal rate test:

[0067] Add 4L of nitrate solution with a concentration of 100mg / L to the SBR reactor, adjust the PH to 7-8, the dissolved oxygen concentration is less than 0.5mg / L, add the denitrification promoter to the SBR reactor, measure the nitrate concentration, and calculate the nitrate removal rate.

[0068] Safety test:

[0069] The half-effect concentration was measured using the luminescent bacteria method

[0070] Stability test:

[0071] Continuous dosing was carried out for 10 cycles, each cycle was 48h, and the efficiency decay was observed.

[0072] Comparing the data of Examples 1-5, it can be seen that the B vitamin mixture and glutamic acid have obvious effects on the denitrification of denitrifying bacteria. In Example 4 without the B vitamin mixture, the nitrate removal rate at 6h decreased by about 20%. In Example 5 without glutamic acid, the nitrate removal rate at 6h decreased by about 20%. This is because both the B vitamin mixture and glutamic acid can support the metabolic activities of denitrifying bacteria, promote the growth of denitrifying bacteria, and improve the function of denitrification-related enzymes, thereby improving the efficiency of the denitrification process.

[0073] Comparing the data of Example 1 and Example 6, it can be seen that humic acid has an obvious positive effect on the denitrification process. The nitrate removal rate at 6h of Example 6 without humic acid is about 25% lower than that of Example 1. This is because humic acid can stimulate the activity of denitrifying bacteria, improve the growth environment of denitrifying bacteria, enhance its metabolic ability, and thereby improve the efficiency of the denitrification process.

[0074] Comparing the data of Comparative Example 1, Example 7 and Example 8, it can be seen that acyl-homoserine lactone and iron ions have a certain influence on the denitrification process. This is because acyl-homoserine lactone is a signal molecule of denitrifying bacteria. Signal molecules enable bacteria to sense the number of similar bacteria in the surrounding environment, coordinate the behavior of the population, and can also regulate the expression of genes related to denitrification in denitrifying bacteria, optimize the metabolic activity of bacteria, thereby improving the denitrification efficiency. In this example, there is already a synergistic regulation of the metabolic activities of denitrifying bacteria by the vitamin B complex, glutamic acid, and humic acid. Therefore, the nitrate removal rate at 6 h in Example 7 remains at a relatively high level. Metal ions are cofactors of denitrifying enzymes, which can enhance the activity of denitrifying enzymes and improve the denitrification efficiency. Due to the presence of the vitamin B complex, glutamic acid, and humic acid, the influence of metal ions on the nitrate removal rate at 6 h is relatively weakened.

[0075] From the data of Comparative Examples 1-5, it can be seen that the improvement of the nitrate removal rate at 6 h by conventional denitrification promoters is limited. This is because the action mechanisms of these denitrification promoters are single, and they only improve the efficiency of the denitrification process from the perspectives of a single carbon source, electron donor, trace element, and biostimulant, ignoring various factors affecting the denitrification efficiency.

[0076] The raw materials and equipment used in the present invention are all common raw materials and equipment in the art unless otherwise specified; the methods used in the present invention are all conventional methods in the art unless otherwise specified.

[0077] The above are only preferred embodiments of the present invention and do not impose any limitation on the present invention. Any simple modification, change, and equivalent transformation made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A composite denitrification promoter, characterized in that, The composite denitrification promoter is made of the following components by mass percentage: carbon source 30-50%, bacterial metabolites 5-13%, signal molecules 1-2%, metal elements 1-5%, pH regulator 3-5%, and water 25-60%.

2. The composite denitrification promoter according to claim 1, characterized in that The carbon source includes one or more of ethanol, sodium acetate, glucose, and glycerol.

3. The composite denitrification promoter according to claim 1, wherein The bacterial metabolites are vitamin B complex mixture 2-5%, amino acids 2-5%, and biostimulants 1-3%.

4. The composite denitrification promoter according to any one of claims 1 or 3, characterized in that, The vitamin B complex mixture is a mixture of vitamin B1, vitamin B2, and vitamin B6.

5. The composite denitrification promoter according to any one of claims 1 or 3, characterized in that, The amino acids include one or more of glutamic acid and aspartic acid.

6. The composite denitrification promoter according to any one of claims 1 or 3, characterized in that The biostimulants include one or more of humic acid and fulvic acid.

7. The composite denitrification promoter according to claim 1, characterized in that, The signal molecules include one or more of acyl homoserine lactone, oligopeptide signal molecules, autoinducer-2, and diffusible signal factor.

8. A preparation method of the composite denitrification promoter according to any one of claims 1-6, comprising: 1) Obtaining the vitamin B complex mixture after inoculating, culturing, centrifugally separating, ultrasonically disrupting, separating and purifying, and freeze-drying yeast. 2) Obtaining humic acid after crushing, pickling, extracting, aerating, centrifuging, acid-precipitating, and freeze-drying natural raw materials. 3) Dissolving the carbon source in water at room temperature, adding the pH regulator, metal elements, bacterial metabolites, and signal molecules in sequence, mixing evenly, and storing at room temperature in a cool place.

9. The preparation method of the composite denitrification promoter according to claim 8, characterized in that, In step 1), the dissolved oxygen content in the aeration link needs to be controlled above 30%.

10. The preparation method of the composite denitrification promoter according to any one of claims 8 or 9, characterized in that, In step 2), the extraction process is to maintain the temperature at 50-70°C and extract for 1-2 hours.

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