A method for enhancing the low-temperature denitrification performance of anaerobic ammonium-oxidizing bacteria

Abstract

A method for enhancing the low-temperature denitrification performance of anaerobic ammonium oxidizing (ANAMMOX) bacteria comprises obtaining an initial ANAMMOX inoculum cultured at an initial culture temperature above 20°C; reducing the culture temperature to 15°C and incubating for 1 to 5 days; reducing the culture temperature to 3 to 6°C and incubating for 1 to 5 days; increasing the culture temperature to 10 to 15°C and incubating for 1 to 3 days; and repeating the above steps at least once. In sewage treatment systems, the method of the present invention can significantly improve the activity and denitrification stability of the inoculated ANAMMOX sludge, significantly enhancing the engineering applicability and low-temperature adaptability of ANAMMOX.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbial water treatment, and in particular relates to a method for enhancing the low-temperature denitrification performance of anaerobic ammonia-oxidizing bacteria. Background Art

[0002] Environmental problems caused by environmental pollution have attracted great attention from all parties. Nitrogen, as a microbial nutrient, accumulates in water bodies, leading to eutrophication and endangering traditional aquatic organisms. The current field of sewage denitrification still relies mainly on traditional microbial denitrification methods, mainly relying on nitrification and denitrification technology. This traditional technology has slow processing speed and high processing cost, and it is difficult to meet the higher water treatment requirements of today's society. Anaerobic ammonium oxidation (ANAMMOX), as a shortcut reaction, breaks through the basic theory of traditional nitrification-denitrification and shortens the reaction path. However, its reaction process requires ammonia nitrogen and nitrite nitrogen as nitrogen sources, and has high requirements for ambient temperature. Changes in ambient temperature will greatly affect the activity of anaerobic ammonia-oxidizing bacteria themselves.

[0003] Due to the microbial characteristics of anaerobic ammonium oxidizing bacteria, their most suitable operating temperature is above 30°C. As the water temperature decreases, their activity will continue to decline. When the temperature is below 12°C, the activity is almost completely lost. Therefore, in northern my country, and even parts of southern China, anaerobic ammonium oxidizing bacteria will almost lose their activity in winter, greatly affecting the operating temperature of denitrification based on this autotrophic process. Therefore, how to obtain an efficient, low-temperature stable anaerobic ammonium oxidation process to ensure stable denitrification operation in winter has become a top priority for the large-scale application of this process. Therefore, researchers from all parties are seeking to develop a new method for cultivating anaerobic ammonium oxidizing bacteria suitable for working at low temperatures to ensure the stability of the process in low-temperature conditions.

[0004] Therefore, if a new cultivation method can be developed to cultivate anaerobic ammonia oxidation bacteria with strong adaptability to low temperatures, and after large-scale enrichment, they can still have good survival activity in a low-temperature environment, it will be possible to better ensure the progress of the short-term nitrification-anaerobic ammonia oxidation process, provide new ideas for low-carbon and high-efficiency denitrification of sewage in a low-temperature environment, and solve the main technical difficulties in the short-term nitrification-anaerobic ammonia oxidation process, which is difficult to operate stably in winter. Summary of the Invention

[0005] In order to solve the deficiencies in the prior art, the purpose of the present invention is to achieve high activity of anaerobic ammonia-oxidizing bacteria at low temperatures and to provide a method for enhancing the low-temperature denitrification performance of anaerobic ammonia-oxidizing bacteria.

[0006] The present invention provides a method for enhancing the low-temperature denitrification performance of anaerobic ammonia-oxidizing bacteria, comprising:

[0007] A) obtaining an anaerobic ammonium oxidizing original inoculum cultured at an initial culture temperature, wherein the relative abundance of anaerobic ammonium oxidizing bacteria in the anaerobic ammonium oxidizing original inoculum reaches 10% or more, and the initial culture temperature is above 20° C.;

[0008] B) lowering the incubation temperature to 15°C and incubating for 1 to 5 days;

[0009] C) lowering the incubation temperature to 3-6°C and incubating for 1-5 days;

[0010] D) raising the incubation temperature to 10-15° C. and incubating for 1-3 days;

[0011] E) Repeat steps B) to D) at least once.

[0012] Optionally, in step B), before lowering the incubation temperature to 15° C. and incubating for 1 to 5 days, the step further comprises:

[0013] If the initial incubation temperature is greater than or equal to 32°C, the incubation temperature is lowered to 20-25°C and incubation is continued for 1-5 days.

[0014] Optionally, it also includes:

[0015] When the incubation temperature is between 20 and 25°C, sodium acetate or glucose is added to the incubation medium to make the COD equivalent in the incubation medium be 50 to 150 mg / L.

[0016] Optionally, the step B) further comprises:

[0017] After the cultivation temperature drops to 15°C, sodium acetate or glucose is added to the cultivation medium to make the COD equivalent in the cultivation medium 50-150 mg / L.

[0018] Optionally, in step C), before lowering the incubation temperature to 3-6° C. and incubating for 1-5 days, the step further comprises:

[0019] When the cultivation temperature of the anaerobic ammonia oxidizing bacteria drops to 10° C., a nitrate solution is added to the cultivation substrate to assist the cultivation, so that the nitrate concentration in the cultivation substrate is 30 to 300 mg / L in terms of nitrogen.

[0020] Optionally, in step C), before lowering the incubation temperature to 3-6° C. and incubating for 1-5 days, the step further comprises:

[0021] When the cultivation temperature of the anaerobic ammonia oxidizing bacteria drops to 7° C., a nitrate solution is added to the cultivation substrate to assist in the cultivation, so that the nitrate concentration in the cultivation substrate is 100 to 500 mg / L in terms of nitrogen.

[0022] Optionally, the nitrate is one or more of sodium nitrate, potassium nitrate and calcium nitrate.

[0023] Optionally, the step D) further comprises:

[0024] When the cultivation temperature rises to above 10°C, ensure that the nitrate concentration in the cultivation medium is below 30 mg / L in terms of nitrogen.

[0025] Optionally, the step D) further comprises:

[0026] When the cultivation temperature rises to above 10°C, ensure that the ammonia nitrogen concentration and nitrite nitrogen concentration in the cultivation medium are within 30-100 mg / L.

[0027] Optionally, the step A) further comprises enriching the original anaerobic ammonium-oxidizing bacteria on a fixed biofilm.

[0028] The beneficial effect of the present invention is that, compared with the existing technology, it solves the problems of low activity and difficulty in starting anaerobic ammonium oxidizing bacteria at low temperatures, allowing anaerobic ammonium oxidizing bacteria to break through the low temperature operating limit of 12 to 15°C, ensuring that they can still maintain high activity at 10°C to complete the removal of nitrogen from water. Implementation of the method of the present invention can significantly increase the denitrification activity of anaerobic ammonium oxidizing bacteria at temperatures of 8 to 15°C, thereby improving their denitrification capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram showing the change in ammonia nitrogen concentration over time in the inlet and outlet water of an anaerobic ammonium oxidation zone provided in an embodiment of the present invention;

[0030] Figure 2 A schematic diagram showing the change in nitrite nitrogen concentration over time in the inlet and outlet water of an anaerobic ammonium oxidation zone provided in an embodiment of the present invention;

[0031] Figure 3 A schematic diagram showing the change in nitrate nitrogen concentration over time in the inlet and outlet water of an anaerobic ammonium oxidation zone provided in an embodiment of the present invention;

[0032] Figure 4 A schematic diagram showing the change in total nitrogen concentration over time in the inlet and outlet water of an anaerobic ammonium oxidation zone provided in an embodiment of the present invention;

[0033] Figure 5 Schematic diagram of the biofilm state in the anaerobic ammonium oxidation zone provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0035] Anaerobic ammonium oxidizing (ANAMMOX) bacteria are autotrophic denitrifying microorganisms that use nitrite as an electron acceptor and ammonia as an electron donor, converting nitrite and ammonia in water into nitrogen gas. ANAMMOX bacteria have a long cultivation cycle and are highly temperature-dependent, typically losing activity below 15°C, significantly impacting the stability of the denitrification process at low temperatures. The present invention provides a method for enhancing the low-temperature denitrification performance of ANAMMOX bacteria, comprising steps A) through E).

[0036] A) obtaining an anaerobic ammonium oxidizing original seed bacteria cultured at an initial culture temperature, wherein the relative abundance of anaerobic ammonium oxidizing bacteria in the anaerobic ammonium oxidizing original seed bacteria reaches above 10%, and the initial culture temperature is above 20°C.

[0037] After obtaining the original anaerobic ammonium oxidizing bacteria, the original anaerobic ammonium oxidizing bacteria can be pre-enriched on the fixed biofilm, and then a subsequent low-temperature cultivation and strengthening process is carried out to ensure that the cultivated and strengthened anaerobic ammonium oxidizing bacteria and fixed organisms can be directly added to the reactor to be operated.

[0038] B) Lower the incubation temperature to 15°C and incubate for 1 to 5 days.

[0039] In the embodiments of the present invention, the initial incubation temperature is first determined. If the initial incubation temperature is between 20°C and 32°C, the incubation temperature can be directly lowered to 15°C and incubated for 1 to 5 days. In some preferred embodiments, after the incubation temperature is lowered to 15°C, a certain amount of sodium acetate or glucose is added to the incubation medium to achieve a COD equivalent of 50 to 150 mg / L in the incubation medium.

[0040] In order to better enhance the denitrification performance of anaerobic ammonia oxidizing bacteria, if the initial incubation temperature is above 32°C, the incubation temperature can be first lowered to 20-25°C and incubated for 1-5 days, and then the incubation temperature can be further lowered to 15°C and incubated for 1-5 days. In some preferred embodiments, when the incubation temperature is between 20 and 25°C, sodium acetate or glucose can be added to the incubation matrix so that the COD equivalent in the incubation matrix is 50-150 mg / L. After incubating at 20-25°C for 1-5 days, when the incubation temperature is further lowered to 15°C, a certain amount of sodium acetate or glucose can be added again to ensure that the COD equivalent in the incubation matrix is maintained at 50-150 mg / L.

[0041] C) Lower the incubation temperature to 3-6°C and incubate for 1-5 days.

[0042] In some preferred embodiments, before further lowering the incubation temperature to 3-6°C and incubating for 1-5 days, the method further includes adding a nitrate solution to the incubation medium to assist in the incubation after the incubation temperature of the anaerobic ammonium oxidizing bacteria has dropped to 10°C, so that the nitrate concentration in the incubation medium is 30-300 mg / L, calculated as nitrogen. When the incubation temperature of the anaerobic ammonium oxidizing bacteria has dropped further to 7°C, a nitrate solution may be further added to the incubation medium to assist in the incubation, so that the nitrate concentration in the incubation medium is 100-500 mg / L, calculated as nitrogen.

[0043] The nitrate solution used in the embodiment of the present invention is one or more of a sodium nitrate solution, a potassium nitrate solution and a calcium nitrate solution, which is not specifically limited in the embodiment of the present invention.

[0044] D) Raise the incubation temperature to 10-15°C and incubate for 1-3 days.

[0045] After the anaerobic ammonium oxidizing bacteria are incubated at 3-6°C, the incubation temperature is raised to 10-15°C and incubated for 1-3 days. In some preferred embodiments, before the incubation temperature is raised to above 10°C, it is necessary to ensure that the nitrate concentration (as nitrogen) in the incubation medium is below 30 mg / L, and that the ammonia nitrogen concentration and nitrite nitrogen concentration (as nitrogen) in the incubation medium are within the range of 30-100 mg / L.

[0046] E) Repeat steps B) to D) at least once.

[0047] To further improve the activity of anaerobic ammonium oxidizing bacteria at low temperatures, the embodiment of the present application repeats steps B) to D) once or more than once.

[0048] Illustratively, when the initial incubation temperature is greater than or equal to 32°C, the cycle is repeated at least once: lowering the incubation temperature to 20-25°C and continuing incubation for 1-5 days, further lowering the incubation temperature to 15°C and incubating for 1-5 days, further lowering the incubation temperature to 3-6°C and incubating for 1-5 days, and increasing the incubation temperature to 10-15°C and incubating for 1-3 days.

[0049] Illustratively, when the initial incubation temperature is between 20 and 32° C., the cycle of lowering the incubation temperature to 15° C. and incubating for 1 to 5 days, further lowering the incubation temperature to 3 to 6° C. and incubating for 1 to 5 days, and raising the incubation temperature to 10 to 15° C. and incubating for 1 to 3 days is repeated at least once.

[0050] The following examples will further illustrate the present invention.

[0051] Example 1

[0052] The anaerobic ammonia-oxidizing bacteria cultured at an initial culture temperature of 35°C were pre-enriched on the fixed biofilm, and the ambient temperature, i.e., the culture temperature, was lowered to 22°C and cultured for 2 days. During this period, sodium acetate was added to the matrix to make the COD equivalent in the matrix 70 mg / L.

[0053] The incubation temperature was further lowered to 15°C and incubated for 2 days, during which sodium acetate was added again to ensure that the COD equivalent in the substrate was maintained at 70-80 mg / L.

[0054] The cultivation temperature was further lowered to 5°C and cultivated for 5 days. Prior to this, when the cultivation temperature was lowered to 10°C, sodium nitrate solution was added to the substrate to assist the cultivation, so that the concentration of sodium nitrate in the substrate was 200 mg / L in terms of nitrogen.

[0055] Raise the incubation temperature to 12°C and incubate for 3 days. When the incubation temperature rises above 10°C, ensure that the nitrate concentration (in terms of nitrogen) in the substrate is below 30 mg / L, and ensure that the ammonia nitrogen concentration and nitrite nitrogen concentration (in terms of nitrogen) in the substrate are within 60 mg / L. If the concentration is not within the control range, it can be regulated by adding water or nitrite and nitrate.

[0056] After repeating the above process twice, enhanced anaerobic ammonia-oxidizing bacteria were obtained.

[0057] Application effect of embodiment 1

[0058] See also Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5 , based on the anaerobic ammonia-oxidizing bacteria cultivated in Example 1, a rapid start-up under low temperature conditions can be completed, and the anaerobic ammonia-oxidizing process can still be completed well under the working condition where the ambient temperature is lower than 15°C for a long time. The anaerobic ammonia-oxidizing bacteria and fixed biofilm cultivated and strengthened in Example 1 are added to the reactor to be operated, and almost all ammonia nitrogen is completely removed in the anaerobic ammonia-oxidizing zone (of course, when the ammonia nitrogen concentration in the influent is high, the nitrite nitrogen in the system will also be consumed first). This situation shows that the biological activity of the anaerobic ammonia-oxidizing zone is good, and the ammonia nitrogen and nitrite nitrogen under the current load can be well removed. Even when the temperature is lower than 12°C and the hydraulic retention time is shortened to 3.7 hours, the removal of ammonia nitrogen and nitrite nitrogen can still be completed well. The denitrification volumetric load of the anaerobic ammonium oxidation reactor started by this method can reach 0.9kg / (m3·d). For the same batch of sludge, its volumetric load at 25°C is only 1.45kg / (m3·d). Compared with the load in the incubation stage under the same sludge volume, the load reduction rate at 25°C does not exceed 38%, which is much better than the traditional literature report that anaerobic ammonium oxidation is almost inactivated at 15°C.

[0059] Comparison of total nitrogen revealed that a significant amount of nitrogen was processed through the anaerobic ammonium oxidation process and left the wastewater in the form of nitrogen gas. This indicates that the low-temperature enhanced anaerobic ammonium oxidizing bacteria used in the system still exhibited good denitrification effectiveness even at a water temperature of 10°C. The continuous generation of large amounts of bubbles indicates that the anaerobic ammonium oxidizing bacteria are active, and that ammonia nitrogen and nitrite nitrogen in the wastewater can be quickly and effectively converted into nitrogen gas.

[0060] The beneficial effect of the present invention is that, compared with the existing technology, it solves the problems of low activity and difficulty in starting anaerobic ammonium oxidizing bacteria at low temperatures, allowing anaerobic ammonium oxidizing bacteria to break through the low temperature operating limit of 12 to 15°C, ensuring that they can still maintain high activity at 10°C to complete the removal of nitrogen from water. Implementation of the method of the present invention can significantly increase the denitrification activity of anaerobic ammonium oxidizing bacteria at temperatures of 8 to 15°C, thereby improving their denitrification capacity.

[0061] The applicant of the present invention has made a detailed explanation and description of the implementation examples of the present invention in conjunction with the drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred implementation plans of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, and is not a limitation on the scope of protection of the present invention. On the contrary, any improvements or modifications based on the inventive spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for enhancing the low-temperature denitrification performance of anaerobic ammonia-oxidizing bacteria, characterized in that: include: A) obtaining an anaerobic ammonium oxidizing original seed bacteria cultured at an initial culture temperature, wherein the relative abundance of anaerobic ammonium oxidizing bacteria in the anaerobic ammonium oxidizing original seed bacteria reaches 10% or more, and the initial culture temperature is above 20° C.; B) Lower the incubation temperature to 15°C and incubate for 1-5 days; In step B), before lowering the incubation temperature to 15°C and incubating for 1-5 days, the method further includes: if the initial incubation temperature is greater than or equal to 32°C, lowering the incubation temperature to 20-25°C and continuing the incubation for 1-5 days; while the incubation temperature is between 20-25°C, adding sodium acetate or glucose to the incubation medium to adjust the COD equivalent in the incubation medium to 50-150 mg / L; C) Lower the incubation temperature to 3-6°C and incubate for 1-5 days; In the step C), before lowering the incubation temperature to 3-6°C and incubating for 1-5 days, the method further comprises: when the incubation temperature of the anaerobic ammonia oxidizing bacteria is lowered to 10°C, adding a nitrate solution to the incubation medium to assist in the incubation, so that the nitrate concentration in the incubation medium is 30-300 mg / L in terms of nitrogen; D) Increase the incubation temperature to 10-15°C and incubate for 1-3 days; E) Repeat steps B) to D) at least once; The nitrate is one or more of sodium nitrate, potassium nitrate and calcium nitrate.

2. The method for enhancing the low-temperature denitrification performance of anaerobic ammonium-oxidizing bacteria according to claim 1, characterized in that: The step B) further comprises: After the incubation temperature drops to 15°C, add sodium acetate or glucose to the incubation medium to make the COD equivalent in the incubation medium 50~150 mg / L.

3. The method for enhancing the low-temperature denitrification performance of anaerobic ammonium oxidizing bacteria according to claim 1, characterized in that: In the step C), before lowering the incubation temperature to 3-6° C. and incubating for 1-5 days, the step further comprises: When the cultivation temperature of the anaerobic ammonia oxidizing bacteria drops to 7°C, a nitrate solution is added to the cultivation medium to assist the cultivation, so that the nitrate concentration in the cultivation medium is 100-500 mg / L in terms of nitrogen.

4. The method for enhancing the low-temperature denitrification performance of anaerobic ammonium oxidizing bacteria according to claim 1, characterized in that: The step D) further comprises: When the cultivation temperature rises to above 10°C, ensure that the nitrate concentration in the cultivation medium is below 30 mg / L in terms of nitrogen.

5. The method for enhancing the low-temperature denitrification performance of anaerobic ammonium-oxidizing bacteria according to claim 1, characterized in that: The step D) further comprises: When the cultivation temperature rises to above 10°C, ensure that the ammonia nitrogen concentration and nitrite nitrogen concentration in the cultivation medium are within 30~100 mg / L.

6. The method for enhancing the low-temperature denitrification performance of anaerobic ammonium-oxidizing bacteria according to claim 1, characterized in that: The step A) further comprises enriching the original anaerobic ammonium-oxidizing bacteria on the fixed biofilm.

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