A method for improving anaerobic ammonium oxidation denitrification efficiency based on variable temperature control

Abstract

This invention discloses a method for improving the efficiency of anaerobic ammonium oxidation (ANAMMOX) denitrification by temperature regulation. This method maintains the water temperature at 28-34°C during reactor operation and, after completion, subjects the ANAMMOX granular sludge to a 14-17°C environment. Compared to maintaining a continuously mesophilic environment, this method saves approximately 30% of energy and consumption, significantly improving the activity of ANAMMOX bacteria and nitrogen removal efficiency. At its peak, the total nitrogen removal rate can be increased by 5.16 times, achieving true energy efficiency and high efficiency, and possessing promising application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of urban sewage treatment and regeneration, and specifically relates to a method for improving the denitrification efficiency of anaerobic ammonia oxidation based on variable temperature control. Background Art

[0002] Sewage denitrification has always been the focus and difficulty in the field of sewage treatment. Among them, nitrification and denitrification process has become a mature sewage denitrification process. Nitrification reaction is the process in which ammonia oxidizing bacteria convert NH4 + -N is converted to NO2 - -N is eventually converted into NO3 - -N process, denitrification reaction refers to the process in which denitrifying bacteria convert NO3 - -N and NO2 - The process of reducing -N to N2 is a long, complex and energy-intensive denitrification pathway, which runs counter to the dual carbon goals. The discovery of anaerobic ammonium oxidation broke this path and directly converted NH4 + -N and NO2 - -N is converted to NO3 - -N and N2, compared to traditional nitrification and denitrification processes, it can save about 60% of aeration energy and 100% of carbon sources. Due to its low energy consumption and low cost, the anaerobic ammonium oxidation process has been widely studied by scholars at home and abroad. However, in contrast, the anaerobic ammonium oxidation process has not been widely used in the field of water treatment engineering. Temperature is the biggest obstacle to the promotion of anaerobic ammonium oxidation engineering applications. In winter, the temperature drops and the influent temperature of sewage treatment plants is low. However, anaerobic ammonium oxidizing bacteria are mesophilic bacteria. Low temperatures pose a challenge to the efficient and stable operation of anaerobic ammonium oxidation. Anaerobic ammonium oxidation can be started and the reaction can be operated in a low-temperature environment, but the load is generally low. Technicians usually intervene by using measures such as heating or cold acclimation to maintain a high load.

[0003] Temperature is an important environmental factor that affects microbial activity. Low temperatures pose several challenges to the survival of microorganisms, such as reduced enzyme activity, changes in protein structure, and reduced membrane fluidity, which have a wide range of effects on microbial functions, including cell metabolism disorders, reduced gene copy number, weakened nutrient absorption, blocked energy cycles, and slowed growth rates. If there is an environment where multiple microorganisms work together, low temperatures may also affect the communication mechanism between different microorganisms and destroy the stable reaction system. Anaerobic ammonium oxidizing bacteria are extremely sensitive to environmental changes and have a long growth cycle. As a mesophilic bacterium, its living environment has high temperature requirements. A large number of studies have shown that the optimal temperature range for anaerobic ammonium oxidation is 30-35°C. Most technologies related to anaerobic ammonium oxidation operate in the medium temperature range of 30-35°C. In order to maintain the medium temperature environment, factories often need to consume a lot of energy, which significantly increases economic costs and the difficulty of process control. In addition, nitrite nitrogen is an important substrate for anaerobic ammonium oxidation reactions. Maintaining the dominant position of anaerobic ammonium oxidation in the denitrification function requires ensuring a stable source of nitrite nitrogen. However, nitrite nitrogen is also a bridge for nitrification and denitrification reactions. Anaerobic ammonium oxidizing bacteria are usually at a disadvantage when competing with nitrifying bacteria and denitrifying bacteria for nitrite nitrogen, and their living space is squeezed. How to ensure the living space of anaerobic ammonium oxidizing bacteria is the key to stable engineering operation. Therefore, it is of great significance to develop a method that does not require long-term maintenance of medium temperature conditions, reduces temperature maintenance energy consumption, and maintains or enhances anaerobic ammonium oxidation activity. Summary of the Invention

[0004] To address the problem of low efficiency and high consumption of anaerobic ammonium oxidation (ANAMMOX) in low-temperature environments, the present invention aims to provide a method for enhancing the activity of ANAMMOX bacteria and improving denitrification efficiency through variable temperature regulation. This invention utilizes a variable temperature regulation strategy to improve ANAMMOX denitrification efficiency by reducing gene competition, optimizing material transport, and maintaining intracellular stability. A low temperature environment (14-17°C) is maintained during the reaction stop phase, and a moderate temperature environment (28-34°C) is restored during the reaction. First, the inhibitory factors nxrB and nirS genes of the anaerobic ammonium oxidation system are related to nitrite nitrogen metabolism. Their abundance (in terms of copy number) is significantly reduced at low temperatures, and the competition for nitrite nitrogen is reduced, which is conducive to maintaining the dominant position of anaerobic ammonium oxidation denitrification. Secondly, anaerobic ammonium oxidizing bacteria can secrete a large amount of extracellular polymers (EPS) composed of proteins and polysaccharides. A large amount of EPS hinders the effective transfer of substrates such as ammonia nitrogen and nitrite nitrogen. The low temperature environment reduces the secretion of EPS and improves the efficiency of substrate transfer. Finally, the cold shock proteins (CSPs) and molecular chaperone proteins possessed by anaerobic ammonium oxidizing bacteria can stabilize the secondary structure of RNA and DNA under low temperature conditions, maintaining efficient transcription, translation and DNA replication. Therefore, the present invention utilizes variable temperature regulation to give play to the uniqueness of anaerobic ammonium oxidizing bacteria, better maintain activity in a low temperature environment, reduce cell damage, and thus maintain a more superior denitrification performance.

[0005] Compared with other methods for maintaining the activity of anaerobic ammonia oxidation, the present invention has the following advantages: First, compared with conventional optimum temperature operation, the denitrification rate (NRR) of this variable temperature control strategy can be increased by about 5 times, and the particle structure is better maintained. Secondly, the temperature-variable strategy does not need to control the dissolved oxygen during actual operation, which simplifies the difficulty of implementation. Finally, the temperature-variable strategy does not need to maintain a temperature above 30°C all the time, reducing energy consumption. The implementation of the temperature-variable strategy can reduce energy consumption by about 30% compared to maintaining a medium temperature environment all the time (assuming that the reactor needs to maintain a water temperature of 30°C in a 15°C environment), realizing a truly energy-saving and environmentally friendly water treatment process.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for improving anaerobic ammonium oxidation denitrification efficiency by temperature control, specifically comprising:

[0008] For the anaerobic ammonium oxidation granular sludge reactor, the water temperature is maintained at 28-34°C during operation. After the operation, the 28-34°C water is discharged, and the remaining anaerobic ammonium oxidation granular sludge is placed in an environment of 14-17°C for 5-10 hours. The low temperature environment is used to reduce the copy number of other related metabolic genes that compete with anaerobic ammonium oxidation bacteria for nitrite nitrogen, reduce the activity of related enzymes, and avoid the obstruction of EPS to mass transfer. The water temperature is maintained at 28-34°C in the next operation cycle, thereby achieving an improvement in the total nitrogen removal rate and removal rate of the anaerobic ammonium oxidation granular sludge in the next operation cycle.

[0009] Preferably, in the anaerobic ammonium oxidation granular sludge reactor, the sludge concentration MLSS (mixed liquor suspended solids concentration) is 1723-3450.2 mg / L. The sludge concentration MLSS refers to the suspended solids content of the mixed liquor after the sewage and activated sludge are mixed.

[0010] Preferably, in the anaerobic ammonium oxidation granular sludge reactor, the influent matrix of the sludge wastewater contains 70-92 mg / LNH4 + -N, 105-130mg / L NO2 - -N, pH is 7.62-8.2, and DO is 0.49-1.6 mg / L.

[0011] Preferably, the stirring operation time of one operation cycle of the anaerobic ammonium oxidation granular sludge reactor is 2.25-10 hours.

[0012] Preferably, the anaerobic ammonium oxidation granular sludge reactor is an anaerobic ammonium oxidation granular sludge sequencing batch reactor (SBR).

[0013] Preferably, the influent of the anaerobic ammonium oxidation granular sludge reactor is artificial simulated water or actual wastewater.

[0014] Preferably, the number of operating cycles is ≥5, and the total nitrogen removal rate begins to increase from the sixth cycle.

[0015] After the present invention implements the variable temperature control strategy, the total nitrogen removal rate is significantly improved compared with the traditional method of maintaining a medium temperature environment, with the maximum improvement being 5.16 times.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] (1) The present invention can enhance the activity of anaerobic ammonia-oxidizing bacteria without intervening in dissolved oxygen and maintaining a medium temperature environment for a long time, thereby strengthening the anaerobic ammonia oxidation effect and achieving a better denitrification effect in the reactor.

[0018] (2) The variable temperature control strategy implemented in the present invention can enhance the denitrification activity of the anaerobic ammonium oxidation granular sludge and better maintain the particle structure and color of the granular sludge.

[0019] (3) The variable temperature control strategy implemented in the present invention can reduce energy consumption by about 30% compared with maintaining a medium temperature environment (assuming that the reactor needs to maintain a water temperature of 30°C in an environment of 15°C). BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The morphology of granular sludge is compared after the temperature-variable control strategy is implemented in Example 1 of the present invention and the medium-temperature environment reactor is maintained in Comparative Example 1 for 68 days.

[0021] Figure 2 The percentage of total nitrogen removal rate improvement when the temperature-variable control strategy is implemented in Example 1 of the present invention and the reactor is maintained in a medium temperature environment for 68 days (102 cycles) compared with the comparative example 1 is maintained. The percentage of total nitrogen removal rate improvement (%) = (total nitrogen removal rate of the temperature-variable control group - total nitrogen removal rate of the medium temperature environment group) / total nitrogen removal rate of the medium temperature environment group * 100%.

[0022] Figure 3 The nxrB gene copy number of the reactor (V) in Example 1 of the present invention, which implements the variable temperature control strategy, and the reactor (C) in Comparative Example 1, which always maintains the medium temperature environment.

[0023] Figure 4 The nirS gene copy number of the reactor (V) in Example 1 of the present invention, which implements the variable temperature control strategy, and the reactor (C) in Comparative Example 1, which always maintains the medium temperature environment.

[0024] Figure 5 The EPS content of the reactor (V) in Example 1 of the present invention, which implements the variable temperature control strategy, and the reactor (C) in Comparative Example 1, which always maintains a medium temperature environment, is shown in FIG. 1 , where PN is protein and PS is polysaccharide.

[0025] Figure 6 The inlet ammonia nitrogen concentration and nitrite nitrogen concentration of the reactor (V) implementing the variable temperature control strategy in Example 1 of the present invention during the operation cycle, where Inf. and eff. refer to the inlet and outlet water, respectively.

[0026] Figure 7 The sludge concentration MLSS of the reactor (V) during the operation cycle is obtained by implementing the variable temperature control strategy in Example 1 of the present invention.

[0027] Figure 8 The pH value of the system of the reactor (V) during the operation cycle of the variable temperature control strategy implemented in Example 1 of the present invention is shown in FIG. 1, where Inf. and eff. refer to the inlet and outlet water, respectively.

[0028] Figure 9 This is the DO value of the system during the operation cycle of the reactor (V) implementing the variable temperature control strategy in Example 1 of the present invention, where Inf. and eff. refer to the inlet and outlet water, respectively. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail below with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

[0030] In the examples of the present invention, if the specific conditions are not specified, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. All raw materials and reagents used without specifying the manufacturer are conventional products that can be purchased from the market.

[0031] The reactor used in the Examples and Comparative Examples of the present invention was a sequencing batch reactor (SBR) with an effective volume of 5 L and a sludge concentration (MLSS) of 1723-3450.2 mg / L. A stirring device was installed above the reactor to ensure uniform mixing of the sludge and water. The effluent was pumped out via a peristaltic pump. The influent ammonia nitrogen concentration was 70-92 mg / L, the nitrite nitrogen concentration was 105-128 mg / L, the pH was 7.62-8.2, and the DO was 0.49-1.6 mg / L. The pH was adjusted using sodium bicarbonate.

[0032] Example 1

[0033] When the reactor is in operation, the water temperature is maintained at 31°C, and the operation cycle is stirred for 10 hours. After 10 hours, the stirring device is turned off. After the operation is completed, the 31°C water is discharged, and the remaining anaerobic ammonia oxidation granular sludge is placed in an ambient temperature of 15°C for 10 hours. When the next operation cycle begins, take out the reactor and place it in a room temperature environment. The operating temperature is restored to 30°C and stirred for 10 hours. Repeat the above operation cycle (maintain the water temperature at 30°C and stir for 2.25-10 hours during a single cycle. After the end, place it in an ambient temperature of 15°C, and the single placement time is 5-10 hours). The experiment lasted 68 days, for a total of 102 cycles.

[0034] Figure 3-4 The results showed that with the increase of the number of operation cycles, the gene copy numbers of other metabolic genes related to nitrite nitrogen competition with anaerobic ammonium oxidation, such as nxrB and nirS, were 2.13×10 8 and 5.32×10 9 copies / g, which was reduced by about 74% and 58% compared with the reactor with the same operating period in which the operating temperature and the reactor environment temperature were maintained at 30°C (Comparative Example 1). Figure 5 The results show that the PN and PS contents of EPS are 193.69 and 39.16 mg / g, respectively, which are reduced by about 19% and 13% compared with the reactor with the same operating cycle in which the operating temperature and the ambient temperature of the reactor are maintained at 30°C (Comparative Example 1), effectively reducing the EPS's resistance to ammonia nitrogen and nitrous oxide mass transfer. Figure 2 The results show that compared with the reactor with the same operating cycle in which the operating temperature and the ambient temperature of the reactor were maintained at 30°C (Comparative Example 1), the total nitrogen removal rate increased from an initial 0.01-fold increase to 5.16-fold (102nd operating cycle). The number of nitrite nitrogen metabolism gene copies and EPS content decreased, anaerobic ammonium oxidation competed for nitrite nitrogen in an advantageous position, and the mass transfer barrier was reduced, successfully improving the denitrification effect of anaerobic ammonium oxidation granular sludge. Compared with the reactor that always maintained a medium temperature environment, the energy consumption can be reduced by about 30% (assuming that the reactor needs to maintain a water temperature of 30°C in a 15°C environment). At the same time, the sludge basically maintains the granular form and appears light brown in color.

[0035] Comparative Example 1

[0036] When the reactor is in operation, the water temperature is maintained at 31°C, and the operation cycle is stirred for 10 hours, and the stirring device is turned off after 10 hours. After the operation is completed, the 31°C water is discharged, and the remaining anaerobic ammonia oxidation granular sludge is placed in an ambient temperature of 30°C for 10 hours. When the next operation cycle begins, take out the reactor and place it in a room temperature environment. The operating temperature continues to be maintained at 30°C and stirred for 10 hours. Repeat the above operation cycle (during single cycle operation, the water temperature is maintained at 30°C and stirred for 2.25-10 hours. The operation time of the same repeated cycle is exactly the same as that of Example 1. After the end, it is placed in an ambient temperature of 30°C. The placement time of the same cycle is exactly the same as that of Example 1). The experiment was carried out for 68 days, for a total of 102 cycles.

[0037] Compared with the reactor placed at 15°C ambient temperature after the operation was stopped in Example 1, Figure 3-4 It shows that with the increase of the number of running cycles, the gene copy numbers of nxrB and nirS in the later stage of this comparative example are 8.11×10 8 and 1.26×10 10 copies / g, which increased by about 2.3 times and 1.38 times compared with the reactor implementing the variable temperature strategy. Figure 5 The results showed that the PN and PS contents of EPS were 239.69 and 45.10 mg / g, respectively, which were increased by 24% and 15% compared with the reactor implementing the variable temperature strategy. However, the total nitrogen removal rate was only 0.16 times that of the reactor implementing the variable temperature strategy ( Figure 2 ), and more serious particle disintegration occurred, and the color appeared dark brown and black, indicating that the activity of anaerobic ammonium oxidation particles was poor.

[0038] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control, characterized in that: Specifically: For the anaerobic ammonium oxidation granular sludge reactor, the water temperature is maintained at 28-34°C during operation. After the operation, the 28-34°C water is discharged, and the remaining anaerobic ammonium oxidation granular sludge is placed in an environment of 14-17°C for 5-10 hours. The low temperature environment is used to reduce the copy number of other related metabolic genes that compete with anaerobic ammonium oxidation bacteria for nitrite nitrogen, reduce the activity of related enzymes, and avoid the obstruction of EPS to mass transfer. The water temperature is maintained at 28-34°C in the next operation cycle, thereby achieving an improvement in the total nitrogen removal rate and removal rate of the anaerobic ammonium oxidation granular sludge in the next operation cycle.

2. The method of improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1, characterized in that: In the anaerobic ammonium oxidation granular sludge reactor, the influent matrix of the sludge wastewater contains 70-92 mg / L NH4 + -N, 105-130mg / L NO2 - -N.

3. The method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1 or 2, characterized in that: The stirring operation time of one operation cycle of the anaerobic ammonium oxidation granular sludge reactor is 2.25-10 hours.

4. The method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1 or 2, characterized in that: In the anaerobic ammonium oxidation granular sludge reactor, the sludge concentration MLSS is 1723-3450.2 mg / L.

5. The method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1 or 2, characterized in that: In the anaerobic ammonium oxidation granular sludge reactor, the influent matrix pH of the sludge wastewater is 7.62-8.

2.

6. The method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1 or 2, characterized in that: In the anaerobic ammonium oxidation granular sludge reactor, the influent matrix DO of the sludge wastewater is 0.49-1.6 mg / L.

7. The method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1 or 2, characterized in that: The influent of the anaerobic ammonium oxidation granular sludge reactor is artificial simulated water or actual wastewater.

8. The method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1 or 2, characterized in that: The anaerobic ammonium oxidation granular sludge reactor is an anaerobic ammonium oxidation granular sludge sequencing batch reactor.

9. The method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1 or 2, characterized in that: The water temperature is maintained at 30-31°C during the operation.

10. The method for improving the efficiency of anaerobic ammonium oxidation denitrification by temperature control according to claim 1 or 2, characterized in that: The number of operating cycles is ≥5.

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