A method and device for continuously adding composite denitrifying bacteria

Abstract

The present invention specifically relates to a method and device for continuously adding composite denitrifying bacteria, wherein the method comprises the following steps: placing slow-release granules of anaerobic and aerobic denitrifying bacteria into a primary anoxic tank and an aerobic tank, respectively, and introducing a primary nutrient solution to expand and multiply the released anaerobic / aerobic denitrifying bacteria; and then placing slow-release granules of anaerobic denitrifying bacteria and carbon source granules into a secondary anoxic tank to perform a deep treatment of nitrate nitrogen in the overflow bacterial liquid of the primary anoxic tank and the aerobic tank, thereby continuously replenishing composite denitrifying bacteria for the biochemical system. Among them, the preparation of slow-release granules of anaerobic / aerobic denitrifying bacteria can slowly release anaerobic / aerobic denitrifying bacteria for a long time, thereby avoiding excessive loss of bacterial strains; and the preparation of slow-release granules of carbon source can release fast-acting carbon sources for a long time to rapidly degrade total nitrogen, and the carbon source is not easily lost. The above method can significantly increase the concentration of denitrifying bacteria in the biochemical system and maintain a stable concentration, thereby increasing the total nitrogen degradation efficiency of the biochemical system and reducing the operating cost of sewage treatment.

Description

Technical Field

[0001] The present invention relates to the field of environmentally friendly microorganisms, and in particular to a method and device for continuously adding composite denitrifying bacteria. Background Art

[0002] Currently, wastewater treatment primarily relies on biological denitrification. This involves converting organic nitrogen into ammoniacal nitrogen through ammonification under anaerobic conditions, then converting ammoniacal nitrogen into nitrate nitrogen through nitrification under aerobic conditions, and finally converting nitrate nitrogen into ammonia gas through denitrification under anoxic conditions. The activated sludge process is one of the mainstream processes for degrading total nitrogen in traditional wastewater treatment, but it has several drawbacks. First, the activated sludge requires a long period of acclimatization during the biochemical system startup process. Second, the large amount of carbon source required is often required. During wastewater treatment operations, when the carbon-nitrogen ratio is imbalanced and total nitrogen concentrations are high, large amounts of carbon source are often required to achieve denitrification. However, activated sludge is a composite of bacteria, and not all bacterial species are capable of denitrification. Many inefficient bacterial species use carbon sources for growth, resulting in carbon source waste and high sludge production. Third, due to fluctuations in total nitrogen concentration in the raw water during wastewater treatment operations, the treated effluent is also unstable. To this end, the present invention proposes a method and device for continuously adding composite denitrifying bacteria to continuously supplement denitrifying bacteria to the biochemical system to overcome the above problems. Summary of the Invention

[0003] The purpose of the present invention is to provide a method and device for continuously adding composite denitrifying bacteria in order to solve the above-mentioned deficiencies in the prior art.

[0004] The purpose of the present invention is achieved by the following technical solution: A method for continuously adding composite denitrifying bacteria comprises the following steps:

[0005] S1. Prepare anaerobic denitrifying bacteria slow-release granules, aerobic denitrifying bacteria slow-release granules and carbon source slow-release granules for standby use;

[0006] S2. Putting anaerobic denitrifying bacteria slow-release granules into the primary anoxic tank, and putting aerobic denitrifying bacteria slow-release granules into the aerobic tank, and then introducing the primary nutrient solution into the primary anoxic tank and the aerobic tank for anoxic culture and aerobic culture respectively;

[0007] S3, adding anaerobic denitrifying bacteria slow-release particles and carbon source slow-release particles into the secondary anoxic tank, passing the primary nutrient solution into the tank for anoxic culture, and then passing the bacterial solution produced in the primary anoxic tank and the aerobic tank in step S2 into the secondary anoxic tank for secondary anoxic culture;

[0008] S4. After starting the culture for a certain period of time, the supernatant of the secondary sedimentation tank of the biochemical system and the secondary nutrient solution are continuously added to the primary anoxic tank and the aerobic tank respectively for expansion and proliferation, and the composite denitrifying bacteria solution produced by the secondary anoxic culture is introduced into the biochemical system to continuously replenish the composite denitrifying bacteria.

[0009] In the present invention, anaerobic denitrifying bacteria slow-release granules are first added to the primary anoxic tank, and aerobic denitrifying bacteria slow-release granules are added to the aerobic tank, respectively, to release and expand the anaerobic and aerobic denitrifying bacteria. The bacterial liquid overflowing from the primary anoxic tank and the aerobic tank enters the secondary anoxic tank, where anaerobic denitrifying bacteria slow-release granules and carbon source slow-release granules are added to maintain a stable concentration of anaerobic denitrifying bacteria in the secondary anoxic tank, preventing insufficient or fluctuating denitrifying bacteria concentration. The anoxic denitrifying bacteria in the secondary anoxic tank, under conditions rich in carbon source, thoroughly treat the nitrate nitrogen in the bacterial liquid, preventing the nitrate nitrogen from entering the biochemical system.

[0010] Furthermore, in step S2, the input amount of the anaerobic denitrifying bacteria slow-release granules and the aerobic denitrifying bacteria slow-release granules is 15 to 30% of the volume of the primary anoxic tank and the aerobic tank, respectively; in step S3, the total input amount of the anaerobic denitrifying bacteria slow-release granules and the carbon source slow-release granules is 15 to 30% of the volume of the secondary anoxic tank, and the weight ratio of the anaerobic denitrifying bacteria slow-release granules to the carbon source slow-release granules is 1:1 to 1.2.

[0011] Furthermore, the preparation of the anaerobic denitrifying bacteria slow-release granules or aerobic denitrifying bacteria slow-release granules comprises the following steps:

[0012] (1) mixing anaerobic denitrifying bacteria or aerobic denitrifying bacteria with a sodium alginate solution to obtain a mixed solution, and then immersing a polyurethane sponge block in the mixed solution and mixing thoroughly to obtain a blended solution;

[0013] (2) adding the blended liquid into the vegetable oil and stirring, adding the inorganic salt solution after the particles are formed and continuing to stir to obtain shaped particles, taking out the shaped particles and soaking them in the inorganic salt solution again to obtain anaerobic denitrifying bacteria slow-release particles or aerobic denitrifying bacteria slow-release particles.

[0014] Furthermore, the mass ratio of the anaerobic denitrifying bacteria or aerobic denitrifying bacteria to the sodium alginate solution is 1:400-600, the inorganic salt solution is preferably a calcium chloride solution, and the concentration of the calcium chloride solution is 0.5%-2%wt.

[0015] In the present invention, the above steps are prepared into anaerobic denitrifying bacteria slow-release particles and aerobic denitrifying bacteria slow-release particles. The slow-release particles can slowly release bacteria, provide anaerobic denitrifying bacteria and aerobic denitrifying bacteria growth sources in the primary anoxic tank and the aerobic tank for a long time, and then continuously supplement the composite denitrifying bacteria for the biochemical system, thereby improving the denitrifying bacteria concentration of the biochemical system; and reduce the number of artificial additions of bacteria, making the daily operation and management of the sewage treatment process simpler. In the above step (2), the mixed liquid is stirred in vegetable oil to disperse the mixed liquid into non-adhesive dispersed droplets, and calcium chloride solution is added to react with sodium alginate to produce calcium alginate on the surface of the droplets to obtain shaped spherical particles. After stopping stirring, the spheres will no longer adhere, and the dispersion is good. By using a polyurethane sponge block as a skeleton to load anaerobic denitrifying bacteria or aerobic denitrifying bacteria, the structural strength of the denitrifying bacteria slow-release particles is increased, the particles are prevented from disintegrating during use, and the release time of the denitrifying bacteria is extended.

[0016] Furthermore, the primary nutrient solution and the secondary nutrient solution both include a carbon source, a nitrogen source, a phosphorus source and trace elements, wherein the carbon source is at least one of glucose, sodium acetate, methanol, maltose and sucrose, and the carbon source concentration is controlled to be 1-10 g / L; the nitrogen source is at least one of sodium nitrate, sodium nitrate, sodium nitrite or potassium nitrite, and the nitrogen source concentration is controlled to be 0.1-2 g / L; the phosphorus source is at least one of dipotassium hydrogen phosphate, potassium dihydrogen phosphate or sodium dihydrogen phosphate, and the phosphorus source concentration is controlled to be 10-100 mg / L; the trace elements include 1-5 mg / L CaCl2, 1-5 mg / L MgCl2, 0.1-1 mg / L CuSO4, 1-30 mg / L MnSO4 and 0.1-1 mg / L ZnSO4.

[0017] Furthermore, the carbon source slow-release particles include the following raw materials in weight percentage: 30-90% polylactic acid, 20-50% starch, 1-10% water-absorbing material and 5-20% inorganic material.

[0018] Furthermore, the water-absorbing material is at least one of xanthan gum, chitosan and carrageenan, and the inorganic material is at least one of perlite powder, diatomaceous earth, activated carbon, vermiculite powder and zeolite powder.

[0019] Furthermore, the preparation of the carbon source slow-release particles includes the following steps: heating the polylactic acid material to a molten state, adding starch, a water-absorbing material and an inorganic material thereto and mixing them thoroughly to obtain a blend, injecting the blend into a screw extruder, extruding and molding it, and then pelletizing it.

[0020] In the present invention, the carbon source slow-release particles are prepared by using polylactic acid as a carrier, starch as a fast-acting carbon source, and a water-absorbing material and an inorganic material. After the carbon source is gradually decomposed, the remaining polylactic acid serves as a porous skeleton particle. The inorganic material in the polylactic acid can improve the roughness of the surface of the polylactic acid skeleton, which is conducive to the formation of a biofilm. During the release process, the carbon source slow-release particles gradually complete the biofilm formation of denitrifying bacteria. After all the fast-acting carbon sources in the carbon source slow-release particles are released, the polylactic acid skeleton can be put into the biochemical system to further improve the denitrification capacity of the biochemical system. Polylactic acid can also be slowly decomposed to release the carbon source required for the denitrification process. Therefore, the carbon source slow-release particles of the present invention can release the fast-acting carbon source for a long time, quickly degrade total nitrogen, and the fast-acting carbon source is not easy to lose; compared with the traditional direct addition of the fast-acting carbon source, it saves more workload in operation. In addition, the carbon source slow-release particles can be used as a carrier for bacterial biofilm formation, which helps to maintain the stability of the bacterial content in the secondary anoxic tank.

[0021] The present invention also provides a composite denitrifying bacteria continuous dosing device, which is used to implement the above-mentioned composite denitrifying bacteria continuous dosing method. The device includes a primary anoxic tank and an aerobic tank, the water inlet ends of the primary anoxic tank and the aerobic tank are both connected to a water inlet pump and a feed pump, the water outlet ends of the primary anoxic tank and the aerobic tank are both connected to a secondary anoxic tank, the top of the secondary anoxic tank is provided with a drain port, the drain port is connected to an external biochemical system through a pipeline, and the bottom of the secondary anoxic tank is provided with an emptying port.

[0022] Furthermore, an aeration device is provided in the aerobic tank, an overflow port is provided at the top of the aerobic tank, and a stirring device is provided in both the first-level anoxic tank and the second-level anoxic tank.

[0023] Furthermore, the first-level anoxic tank contains a number of anaerobic denitrifying bacteria slow-release particles, the aerobic tank contains a number of aerobic denitrifying bacteria slow-release particles, and the second-level anoxic tank contains a number of anaerobic denitrifying bacteria slow-release particles and a number of carbon source slow-release particles.

[0024] The above-mentioned device of the present invention realizes the release and amplification of anaerobic denitrifying bacteria and aerobic denitrifying bacteria by setting up a primary anoxic tank and an aerobic tank, and deeply treats the nitrate nitrogen of the bacterial liquid overflowing from the primary anoxic tank and the aerobic tank through the secondary anoxic tank, thereby continuously replenishing denitrifying bacteria for the biochemical system, improving the denitrifying bacteria concentration of the biochemical system, and maintaining the stability of the denitrifying bacteria concentration.

[0025] The beneficial effects of the present invention are:

[0026] (1) The method for continuously adding denitrifying bacteria of the present invention can continuously add denitrifying bacteria to the biochemical system, thereby improving the competitiveness of denitrifying bacteria in the biochemical system for carbon source utilization, allowing more carbon sources to be used for the degradation of total nitrogen, and preventing the carbon source from being absorbed in large quantities by other invalid or inefficient bacteria, resulting in a decrease in the utilization rate of the carbon source. In addition, the method for supplementing denitrifying bacteria to the biochemical system can improve the total nitrogen degradation efficiency of the biochemical system, and significantly reduce the operating cost of sewage treatment.

[0027] (2) The present invention prepares anaerobic denitrifying bacteria slow-release granules and aerobic denitrifying bacteria slow-release granules, which can slowly release anaerobic denitrifying bacteria and aerobic denitrifying bacteria over a long period of time, thereby avoiding excessive loss of bacteria, and continuously replenishing the composite denitrifying bacteria for the biochemical system, thereby increasing the concentration of denitrifying bacteria in the biochemical system and maintaining a stable concentration; and reducing the number of times the bacteria are manually added, making the daily operation and management of the sewage treatment process simpler.

[0028] (3) The present invention, by preparing carbon source slow-release granules, can release a fast-acting carbon source over a long period of time to rapidly degrade total nitrogen, and the fast-acting carbon source is not easily lost; compared to the traditional method of directly adding a fast-acting carbon source, the operation is more labor-saving. In addition, the carbon source slow-release granules can serve as a carrier for bacterial biofilm formation, helping to maintain the stability of the bacterial content in the secondary anoxic tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 1 is a schematic top view of the continuous dosing device for composite denitrifying bacteria according to the present invention;

[0030] Figure 2 This is a front view schematic diagram of the composite denitrifying bacteria continuous dosing device of the present invention;

[0031] Figure 3 This is a comparison chart of COD treatment effects of the biochemical system in Example 3 of the present invention;

[0032] Figure 4 This is a comparison diagram of the TN treatment effect of the biochemical system in Example 3 of the present invention;

[0033] Figure 5 This is a comparison chart of bacterial liquid concentrations produced by the device in Example 4 of the present invention;

[0034] Figure 6 This is a comparison chart of the TN treatment effects of the bacterial liquid produced by the device in Example 5 of the present invention.

[0035] Figure numerals: 1. Primary anoxic tank; 2. Aerobic tank; 3. Water inlet pump; 4. Feed pump; 5. Secondary anoxic tank; 6. Drain port; 7. Emptying port; 8. Aeration device; 9. Stirring device; 10. Anaerobic denitrifying bacteria slow-release granules; 11. Aerobic denitrifying bacteria slow-release granules; 12. Carbon source slow-release granules. DETAILED DESCRIPTION

[0036] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to examples and drawings. The contents mentioned in the embodiments are not intended to limit the present invention.

[0037] As a typical embodiment of the present invention, a method for continuously adding composite denitrifying bacteria includes the following steps:

[0038] S1. Prepare anaerobic denitrifying bacteria slow-release granules, aerobic denitrifying bacteria slow-release granules and carbon source slow-release granules for standby use;

[0039] S2. Putting anaerobic denitrifying bacteria slow-release granules into the primary anoxic tank, and putting aerobic denitrifying bacteria slow-release granules into the aerobic tank, and then introducing the primary nutrient solution into the primary anoxic tank and the aerobic tank for anoxic culture and aerobic culture respectively;

[0040] S3, adding anaerobic denitrifying bacteria slow-release particles and carbon source slow-release particles into the secondary anoxic tank, passing the primary nutrient solution into the tank for anoxic culture, and then passing the bacterial solution produced in the primary anoxic tank and the aerobic tank in step S2 into the secondary anoxic tank for secondary anoxic culture;

[0041] S4. After starting the culture for a certain period of time, the supernatant of the secondary sedimentation tank of the biochemical system and the secondary nutrient solution are continuously added to the primary anoxic tank and the aerobic tank respectively for expansion and proliferation, and the composite denitrifying bacteria solution produced by the secondary anoxic culture is introduced into the biochemical system to continuously replenish the composite denitrifying bacteria.

[0042] Furthermore, in step S2, the input amount of the anaerobic denitrifying bacteria slow-release granules and the aerobic denitrifying bacteria slow-release granules is 15 to 30% of the volume of the primary anoxic tank and the aerobic tank, respectively; in step S3, the total input amount of the anaerobic denitrifying bacteria slow-release granules and the carbon source slow-release granules is 15 to 30% of the volume of the secondary anoxic tank, and the weight ratio of the anaerobic denitrifying bacteria slow-release granules to the carbon source slow-release granules is 1:1 to 1.2.

[0043] Furthermore, the preparation of the anaerobic denitrifying bacteria slow-release granules or aerobic denitrifying bacteria slow-release granules comprises the following steps:

[0044] (1) mixing anaerobic denitrifying bacteria or aerobic denitrifying bacteria with a sodium alginate solution to obtain a mixed solution, and then immersing a polyurethane sponge block in the mixed solution and mixing thoroughly to obtain a blended solution;

[0045] (2) adding the blended liquid into the vegetable oil and stirring, adding the inorganic salt solution after the particles are formed and continuing to stir to obtain shaped particles, taking out the shaped particles and soaking them in the inorganic salt solution again to obtain anaerobic denitrifying bacteria slow-release particles or aerobic denitrifying bacteria slow-release particles.

[0046] Furthermore, the mass ratio of the anaerobic denitrifying bacteria or aerobic denitrifying bacteria to the sodium alginate solution is 1:400-600.

[0047] Furthermore, the primary nutrient solution and the secondary nutrient solution both include a carbon source, a nitrogen source, a phosphorus source and trace elements, wherein the carbon source is at least one of glucose, sodium acetate, methanol, maltose and sucrose, and the carbon source concentration is controlled to be 1-10 g / L; the nitrogen source is at least one of sodium nitrate, sodium nitrate, sodium nitrite or potassium nitrite, and the nitrogen source concentration is controlled to be 0.1-2 g / L; the phosphorus source is at least one of dipotassium hydrogen phosphate, potassium dihydrogen phosphate or sodium dihydrogen phosphate, and the phosphorus source concentration is controlled to be 10-100 mg / L; the trace elements include 1-5 mg / L CaCl2, 1-5 mg / L MgCl2, 0.1-1 mg / L CuSO4, 1-30 mg / L MnSO4 and 0.1-1 mg / L ZnSO4.

[0048] Furthermore, the carbon source slow-release particles include the following raw materials in weight percentage: 30-90% polylactic acid, 20-50% starch, 1-10% water-absorbing material and 5-20% inorganic material.

[0049] Furthermore, the water-absorbing material is at least one of xanthan gum, chitosan and carrageenan, and the inorganic material is at least one of perlite powder, diatomaceous earth, activated carbon, vermiculite powder and zeolite powder.

[0050] Furthermore, the preparation of the carbon source slow-release granules includes the following steps: heating a polylactic acid material to a molten state, adding starch, a water-absorbing material, and an inorganic material thereto and thoroughly mixing to obtain a blend, injecting the blend into a screw extruder for extrusion molding, and then pelletizing. The polylactic acid material has a number average molecular weight of 10,000 to 50,000.

[0051] As a typical embodiment of the present invention, a composite denitrifying bacteria continuous dosing device is also provided. Figure 1-2 As shown, it includes a primary anoxic tank 1 and an aerobic tank 2. The water inlets of the primary anoxic tank 1 and the aerobic tank 2 are connected to a water inlet pump 3 and a feed pump 4. The water outlets of the primary anoxic tank 1 and the aerobic tank 2 are connected to a secondary anoxic tank 5. A drain port 6 is provided at the top of the secondary anoxic tank 5. The drain port 6 is connected to the external biochemical system through a pipeline. An emptying port is provided at the bottom of the secondary anoxic tank 5.

[0052] Furthermore, the aerobic tank 2 is provided with an aeration device 8, and an overflow port is provided at the top of the aerobic tank 2. Both the primary anoxic tank 1 and the secondary anoxic tank 5 are provided with a stirring device 9. The aeration device 8 provides sufficient oxygen, increases dissolved oxygen in the water, promotes the growth of aerobic denitrifying bacteria, and aids in biodegradation. The stirring device 9 prevents sediment deposition in the primary anoxic tank 1 and the secondary anoxic tank 5.

[0053] Furthermore, the primary anoxic tank 1 contains a number of anaerobic denitrifying bacteria slow-release particles 10, the aerobic tank 2 contains a number of aerobic denitrifying bacteria slow-release particles 11, and the secondary anoxic tank 5 contains a number of anaerobic denitrifying bacteria slow-release particles 10 and a number of carbon source slow-release particles 12.

[0054] Example 1

[0055] This embodiment provides a method for continuously adding composite denitrifying bacteria, comprising the following steps:

[0056] S1. Prepare anaerobic denitrifying bacteria slow-release granules, aerobic denitrifying bacteria slow-release granules and carbon source slow-release granules for standby use;

[0057] S2. Put 100L of anaerobic denitrifying bacteria slow-release granules into a primary anoxic tank, and put 100L of aerobic denitrifying bacteria slow-release granules into an aerobic tank. The volumes of the primary anoxic tank and the aerobic tank are both 500L. Then, 350L of primary nutrient solution are introduced into the primary anoxic tank and the aerobic tank, respectively, for anoxic and aerobic cultivation.

[0058] S3, adding anaerobic denitrifying bacteria slow-release granules and carbon source slow-release granules into a secondary anoxic tank with a volume of 1000L, and passing 500L of primary nutrient solution, and then passing the bacterial liquid produced in the primary anoxic tank and the aerobic tank in step S2 into the secondary anoxic tank for secondary anoxic culture;

[0059] S4. After 2 days of culture, the supernatant of the secondary sedimentation tank of the biochemical system is added to the primary anoxic tank and the aerobic tank through the water inlet pump at a rate of 40 L / h; the secondary nutrient solution is added to the primary anoxic tank and the aerobic tank through the feed pump at a rate of 2 L / h. By continuously adding water and replenishing the nutrient solution, the anaerobic denitrifying bacteria and anoxic denitrifying bacteria cultured in the primary anoxic tank and the aerobic tank are introduced into the secondary anoxic tank, and the composite denitrifying bacteria liquid is obtained from the secondary anoxic tank through the secondary anoxic culture, and introduced into the biochemical system, thereby realizing the continuous addition of the composite denitrifying bacteria of the biochemical system.

[0060] Furthermore, the preparation of the anaerobic denitrifying bacteria slow-release granules or aerobic denitrifying bacteria slow-release granules comprises the following steps:

[0061] (1) mixing anaerobic denitrifying bacteria or aerobic denitrifying bacteria with a 2% sodium alginate solution at a mass ratio of 1:500 to obtain a mixed solution, and then immersing a polyurethane sponge block in the mixed solution and mixing thoroughly to obtain a blended solution;

[0062] (2) adding the blended liquid into vegetable oil and stirring, wherein the volume of the vegetable oil is 3 times the volume of the blended liquid; after forming particles with a diameter of 3 to 5 mm in the vegetable oil, adding a 1% calcium chloride solution, wherein the volume of the added calcium chloride solution is 1 times the volume of the blended liquid; continuing stirring for 10 minutes to obtain shaped particles; taking out the shaped particles and placing them in a 1% calcium chloride solution for immersion for 1 hour; wherein the volume of the calcium chloride solution is 3 times the volume of the blended liquid; filtering and drying to obtain the anaerobic denitrifying bacteria slow-release particles or the aerobic denitrifying bacteria slow-release particles.

[0063] In step (1), the polyurethane sponge block is a cube with a side length of 3 mm, the volume ratio of the mixed liquid to the polyurethane sponge block is 1:0.8, and the density of the polyurethane sponge block is 10 to 30 ppi. The anaerobic denitrifying bacteria is Castellaniella FN7-1, and the aerobic denitrifying bacteria is Arthrobacter mysorens FN10.

[0064] Furthermore, the primary nutrient solution includes the following raw material components: 2g / L glucose, 3g / L CH3COONa, 0.5g / LKNO3, 0.5g / L NaNO3, 20mg / L CaCl2, 20mg / L MgCl2, 0.1mg / L CuSO4, 5mg / L MnSO4 and 0.2mg / L ZnSO4.

[0065] Furthermore, the secondary nutrient solution includes the following raw material components: 60 g / L glucose, 40 g / L CH3COONa, 20 g / LNaNO3, 50 mg / L CaCl2, 50 mg / L MgCl2, 1 mg / L CuSO4, 50 mg / L MnSO4 and 1 mg / L ZnSO4.

[0066] Furthermore, the carbon source slow-release particles include the following raw materials in weight percentage: 60% polylactic acid, 28% starch, 2% water-absorbing material and 10% inorganic material, wherein the water-absorbing material is composed of 1% carrageenan and 1% xanthan gum, and the inorganic material is composed of 5% diatomaceous earth and 5% activated carbon.

[0067] Furthermore, the preparation of the carbon source slow-release particles includes the following steps: heating the polylactic acid material to a molten state at 220°C, adding starch, water-absorbing material and inorganic material thereto according to the above weight percentages and fully mixing them to obtain a blend, injecting the blend into a screw extruder and extruding it into a rod with a diameter of 4 mm, the processing temperature of the screw extruder is 220-250°C, and then supercooling the obtained rod into particles with a length of 4 mm.

[0068] Example 2

[0069] like Figures 1-2 As shown, this embodiment provides a composite denitrifying bacteria continuous dosing device, including a primary anoxic tank 1 and an aerobic tank 2, the water inlet ends of the primary anoxic tank 1 and the aerobic tank 2 are connected to a water inlet pump 3 and a feed pump 4, the water outlet ends of the primary anoxic tank 1 and the aerobic tank 2 are connected to a secondary anoxic tank 5, the top of the secondary anoxic tank 5 is provided with a drain port 6, the drain port 6 is connected to the external biochemical system through a pipeline, and the bottom of the secondary anoxic tank 5 is provided with an emptying port.

[0070] Furthermore, an aeration device 8 is provided in the aerobic tank 2 , an overflow port is provided at the top of the aerobic tank 2 , and a stirring device 9 is provided in both the primary anoxic tank 1 and the secondary anoxic tank 5 .

[0071] Furthermore, the primary anoxic tank 1 contains a number of anaerobic denitrifying bacteria slow-release particles 10, the aerobic tank 2 contains a number of aerobic denitrifying bacteria slow-release particles 11, and the secondary anoxic tank 5 contains a number of anaerobic denitrifying bacteria slow-release particles 10 and a number of carbon source slow-release particles 12.

[0072] Example 3

[0073] The composite denitrifying bacteria solution obtained in Example 1 was introduced into the biochemical system to treat domestic sewage, and the average COD concentration and TN of the domestic sewage treated in 12 months of the year were calculated. The equipment group was named, and its COD treatment effect and TN (total nitrogen) treatment effect were as follows: Figures 3-4 The raw water group refers to untreated domestic sewage, the blank group refers to sewage that has passed through the biochemical system but without the addition of denitrifying bacteria, and the single-bacteria-dosing group refers to the direct addition of anaerobic denitrifying bacteria and aerobic denitrifying bacteria to the biochemical system. The bacterial species and dosage are the same as those in Example 1.

[0074] In this embodiment, the biochemical system processes 800-1000 t / h of water, adopts A / O process, has anoxic residence time of 4-6 h, aerobic residence time of 10-12 h, water temperature of 20-30°C, pH of 7-8.0, anoxic Do is less than 0.5 mg / L, and aerobic Do is 2-5 mg / L.

[0075] Depend on Figure 3 It can be seen that the COD concentration of domestic sewage raw water is basically between 200 and 300 mg / L throughout the year. The utilization rate of COD in the blank group, single-time bacterial injection group and equipment group is basically the same, and the COD concentration is maintained at around 50 mg / L.

[0076] Depend on Figure 4 It can be seen that the total nitrogen concentration of the effluent of the domestic sewage raw water group basically fluctuates within the range of 70 to 90 mg / L. The TN removal effect of the blank group is poor, and the average TN concentration is about 30 mg / L. The single-bacteria group has a good TN removal effect after the initial bacteria addition, but the TN removal effect is unstable and shows a significant decrease after long-term operation. The equipment group of the present invention uses the composite denitrifying bacteria solution obtained in Example 1 to continuously add it to the biochemical system to treat domestic sewage, and the total nitrogen concentration of the effluent can be maintained below 20 mg / L during long-term operation. Figure 3 It can be seen that the trend is basically consistent with the COD degradation trend. After continuous addition of composite denitrifying bacteria in the equipment group, the TN removal effect can be significantly improved without changing the COD concentration.

[0077] Example 4

[0078] Free denitrifying bacteria were added into the biochemical system equipment as a free group. The denitrifying bacteria were the same as those in Example 1. The bacteria were added once per culture cycle. Each culture cycle was 1-2 months. The slow-release granules prepared according to the preparation method of anaerobic denitrifying bacteria slow-release granules / aerobic denitrifying bacteria slow-release granules in Example 1 were added into the biochemical system equipment as a slow-release group. After culture using the same equipment and conditions, the bacterial concentration of the equipment was monitored. The results were as follows: Figure 5 shown.

[0079] Depend on Figure 5 It can be seen that the bacterial concentration of the sustained-release group in the equipment can remain stable at a higher concentration, while the bacterial concentration of the free group decreases significantly as the culture time prolongs due to the rapid loss of bacterial species.

[0080] Example 5

[0081] By adding a free carbon source as a free carbon source group into the biochemical system equipment, the free carbon source here refers to starch; the carbon source slow-release granules prepared according to the preparation method of carbon source slow-release granules in Example 1 are added into the biochemical system equipment as a slow-release carbon source group, and the TN concentration of the bacterial liquid discharged from the biochemical system is monitored. The results are as follows Figure 6 shown.

[0082] Depend on Figure 6It can be seen that the TN concentration of the bacterial solution discharged from the equipment in the carbon source slow-release group remained stable at a lower concentration (below 10 mg / L), while the TN concentration of the bacterial solution discharged from the equipment in the free carbon source group was much higher than that in the carbon source slow-release group due to the rapid loss of free carbon source and inaccurate addition, and the concentration fluctuated greatly.

[0083] The above specific embodiments are further explanations of the technical solutions and beneficial effects of the present invention, and are not intended to limit the implementation methods. For those skilled in the art, any obvious substitutions that do not depart from the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A method for continuously adding composite denitrifying bacteria, characterized in that: The steps include: S1. Prepare anaerobic denitrifying bacteria slow-release granules, aerobic denitrifying bacteria slow-release granules and carbon source slow-release granules for standby use; S2. Putting anaerobic denitrifying bacteria slow-release granules into the primary anoxic tank, and putting aerobic denitrifying bacteria slow-release granules into the aerobic tank, and then introducing the primary nutrient solution into the primary anoxic tank and the aerobic tank for anoxic culture and aerobic culture respectively; S3, adding anaerobic denitrifying bacteria slow-release particles and carbon source slow-release particles into the secondary anoxic tank, passing the primary nutrient solution into the tank for anoxic culture, and then passing the bacterial solution produced in the primary anoxic tank and the aerobic tank in step S2 into the secondary anoxic tank for secondary anoxic culture; S4. After starting the culture for a certain period of time, the supernatant of the secondary sedimentation tank of the biochemical system and the secondary nutrient solution are continuously added to the primary anoxic tank and the aerobic tank respectively to expand the culture and multiply the bacteria, and the composite denitrifying bacteria solution produced by the secondary anoxic culture is introduced into the biochemical system to continuously replenish the composite denitrifying bacteria; The preparation of the anaerobic denitrifying bacteria slow-release granules or the aerobic denitrifying bacteria slow-release granules comprises the following steps: (1) Mixing anaerobic denitrifying bacteria or aerobic denitrifying bacteria with a sodium alginate solution to obtain a mixed solution, and then immersing a polyurethane sponge block in the mixed solution and mixing thoroughly to obtain a blended solution; (2) adding the blended liquid into the vegetable oil and stirring, adding the inorganic salt solution after the particles are formed and continuing to stir to obtain shaped particles, taking out the shaped particles and soaking them in the inorganic salt solution again to obtain anaerobic denitrifying bacteria slow-release particles or aerobic denitrifying bacteria slow-release particles; The inorganic salt solution is a calcium chloride solution.

2. The method for continuously adding composite denitrifying bacteria according to claim 1, wherein: The mass ratio of the anaerobic denitrifying bacteria or aerobic denitrifying bacteria to the sodium alginate solution is 1:400-600.

3. The method for continuously adding composite denitrifying bacteria according to claim 1, wherein: The primary nutrient solution and the secondary nutrient solution both include a carbon source, a nitrogen source, a phosphorus source and trace elements, wherein the carbon source is at least one of glucose, sodium acetate, methanol, maltose and sucrose, the nitrogen source is at least one of sodium nitrate, sodium nitrite or potassium nitrite, the phosphorus source is at least one of dipotassium hydrogen phosphate, potassium dihydrogen phosphate or sodium dihydrogen phosphate, and the trace elements include 1~5mg / L CaCl2, 1~5mg / L MgCl2, 0.1~1mg / L CuSO4, 1~30mg / L MnSO4 and 0.1~1mg / L ZnSO4.

4. The method for continuously adding composite denitrifying bacteria according to claim 1, wherein: The carbon source slow-release particles include the following raw materials in weight percentage: 30-90% polylactic acid, 20-50% starch, 1-10% water-absorbing material and 5-20% inorganic material.

5. The method for continuously adding composite denitrifying bacteria according to claim 4, wherein: The water-absorbing material is at least one of xanthan gum, chitosan and carrageenan.

6. The method for continuously adding composite denitrifying bacteria according to claim 4, wherein: The inorganic material is at least one of pearlite powder, diatomaceous earth, activated carbon, vermiculite powder and zeolite powder.

7. The method for continuously adding composite denitrifying bacteria according to claim 4, characterized in that: The preparation of the carbon source slow-release particles comprises the following steps: heating a polylactic acid material to a molten state, adding starch, a water-absorbing material and an inorganic material thereto and fully mixing them to obtain a blend, injecting the blend into a screw extruder, extruding and molding the blend, and then pelletizing the blend.

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