A control method for reducing nitrous oxide emissions from aerobic pools in urban sewage treatment plants and the application of AHLs

Abstract

The present invention belongs to the technical field of biological treatment of sewage, and specifically relates to a control method for reducing nitrous oxide emissions in aerobic pools of urban sewage treatment plants and the application of AHLs. The present invention adds a certain concentration of signal molecules such as N-acyl homoserine lactone, which enter the A / A / O reactor with the influent. The signal molecules regulate the composition and content of sludge extracellular polymers (EPS), and at the same time change the electron transfer activity, which is conducive to the enrichment of nitrifying bacteria, thereby changing the microbial metabolic pathway, increasing the sludge particle size, and finally achieving the regulation of N2O generation and release, thereby reducing the emission of N2O in the aerobic unit of the sewage treatment plant.

Description

Technical Field

[0001] The invention belongs to the technical field of biological sewage treatment, and in particular relates to a control method for reducing nitrous oxide emission in an aerobic pool of a municipal sewage treatment plant and the application of AHLs. Background Art

[0002] Greenhouse gas emissions have attracted attention, and the reduction of nitrous oxide (N2O) emissions in aerobic pools of sewage treatment plants faces new challenges. As a major non-CO2 greenhouse gas, N2O has a greenhouse effect equivalent to 298 times that of CO2, with a significant greenhouse effect. It will also damage the ozone layer and may form acid rain, which will have a significant negative impact on the environmental ecosystem. Aerobic treatment units are the main source of N2O emissions from sewage treatment plants. The A / A / O process is the most widely used simultaneous nitrogen and phosphorus removal sewage treatment process in my country. During the operation of the A / A / O process, the aeration process often leads to higher N2O emissions.

[0003] Quorum sensing technology (QS) has been introduced into the field of sewage treatment. Studies have shown that signal molecules affect the release of N2O during sewage treatment by changing the characteristics of activated sludge. In addition, quorum sensing technology can also affect the production and release of N2O by changing the structure of microbial communities and the metabolic activities of microorganisms involved in sewage treatment.

[0004] Nitrifying bacteria and denitrifying bacteria that affect denitrification and N2O emissions have quorum sensing characteristics. By selecting appropriate types and concentrations of exogenous signal molecules, quorum sensing will affect the composition, function, and growth rate of microorganisms, thereby reducing N2O emissions from aerobic units in sewage treatment plants. Therefore, the control method for reducing N2O emissions in aerobic treatment units of urban sewage treatment plants is a very important technical development direction. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, the present invention provides a control method for reducing nitrous oxide emissions from aerobic pools in urban sewage treatment plants and the application of AHLs (N-acyl homoserine lactones). The present invention adds a certain concentration of signal molecules, which enter the A / A / O reactor with the influent. The signal molecules regulate the composition and content of sludge extracellular polymers (EPS), while changing the electron transfer activity, which is beneficial to the enrichment of nitrifying bacteria, thereby changing the microbial metabolic pathway, increasing the sludge particle size, and finally achieving the regulation of N2O generation and release, thereby reducing the emission of N2O from the aerobic unit of the sewage treatment plant.

[0006] The technical solution provided by the present invention is as follows:

[0007] An application of AHLs for reducing the N2O emission of an anaerobic tank, an anoxic tank and / or an aerobic tank in an A / A / O system, wherein the AHLs is C12-HSL.

[0008] Based on the above technical solution, the addition of C12-HSL minimizes the daily N2O emission of the system, which can significantly reduce the daily N2O emission of anaerobic tanks, anoxic tanks and aerobic tanks, and has a significant inhibitory effect on the release of N2O in aerobic tanks.

[0009] The present invention also provides an application of AHLs for reducing the total content of EPS in an aerobic pool in an A / A / O system, wherein the AHLs are C8-HSL or C12-HSL, and the EPS include S-EPS, LB-EPS and TB-EPS.

[0010] Based on the above technical solution, C8-HSL and C12-HSL can reduce the total content of EPS (the total amount of S-EPS, LB-EPS and TB-EPS).

[0011] The present invention also provides an application of AHLs for increasing the particle size of activated sludge in an aerobic tank in an A / A / O system, wherein the AHLs are C8-HSL, C12-HSL or C6-HSL.

[0012] Based on the above technical solutions, C8-HSL, C12-HSL and C6-HSL can promote the aggregation of organisms in the mixture and maintain its complete sludge floc structure, thereby maintaining the stability of the sludge.

[0013] Preferably, the AHLs is C12-HSL. C12-HSL is more likely to promote the aggregation of microorganisms in the mixture, thereby maintaining the sedimentation performance and stability of the mixture.

[0014] The present invention also provides an application of AHLs for strengthening the ammonium-producing dissimilatory nitrate reduction process in an aerobic pool in an A / A / O system, wherein the AHLs is C12-HSL.

[0015] Based on the above technical solution, C12-HSL can enhance the dissimilatory nitrate reduction process of ammonium production and reduce the release of N2O.

[0016] The present invention also provides an application of AHLs for increasing the abundance of nirK enzyme and norB enzyme in an aerobic pool in an A / A / O system, wherein the AHLs is C8-HSL, C12-HSL or C6-HSL.

[0017] Based on the above technical solutions, C8-HSL, C12-HSL and C6-HSL can all increase the abundance of nirK and norB.

[0018] The present invention also provides an application of AHLs for increasing the activity abundance of nitrous oxide reductase in an aerobic pool in an A / A / O system to increase the conversion rate of N2O to N2, wherein the AHLs is C12-HSL.

[0019] Based on the above technical scheme, C12-HSL has a stronger promoting effect on the activity abundance of nitrous oxide reductase (EC:1.7.2.4) than other signal molecule treatments. Therefore, more N2O produced under the condition of adding C12-HSL is converted into N2, thereby reducing the emission of N2O in the aerobic treatment unit of the sewage treatment plant.

[0020] In the above technical solution, the N-acyl homoserine lactone is N-hexanoyl-L-homoserine lactone (C6-HSL), octanoyl-L-homoserine lactone (C8-HSL), and dodecanoyl-L-homoserine lactone (C12-HSL).

[0021] The present invention also provides a control method for reducing nitrous oxide emissions from an aerobic pool in a municipal sewage treatment plant, which is characterized by comprising the following steps:

[0022] Step 1: Perform water quality tests on COD, total nitrogen, total phosphorus, and pH of urban sewage, then add reagents to regulate the pH and C / N ratio of the influent, and add a certain concentration of signal molecules into the anaerobic tank in the A / A / O system;

[0023] Step 2: Control the dissolved oxygen concentration and internal recirculation ratio of the anoxic zone according to the dissolved oxygen detector in the anoxic zone, the dissolved oxygen detector at the end of the aerobic zone, and the nitrate concentration detection data;

[0024] Step 3: Evaluate the denitrification performance of the aerobic treatment unit of the sewage treatment plant through the data detected by the aerobic zone dissolved oxygen detector and pH detector, as well as the measured nitrate concentration and N2O emission, so as to determine the type and dosage of signal molecules to be added;

[0025] Step 4: Add the determined signal molecule type and dosage into the aerobic tank of the urban sewage treatment plant to reduce the emission of nitrous oxide, wherein the signal molecule is C8-HSL, C12-HSL or C6-HSL, and the concentration is 20-30nmol / L.

[0026] Specifically, in step one:

[0027] The water quality characteristics of urban sewage are tested by COD, total nitrogen, total phosphorus and pH, and the amount of carbon source added is determined by analyzing the total nitrogen concentration to meet the carbon source required for denitrification;

[0028] By measuring the activated sludge concentration during operation, the return ratio of the external return pipeline is adjusted to maintain the sludge concentration at about 3500 mg / L;

[0029] Analyze the test data of the pH detector and control the inlet pH between 6.0 and 8.0 by fine-tuning the dosage of acid or alkali chemical reagents to meet the pH range required for denitrification;

[0030] The C / N ratio is regulated by controlling the dosage of the carbon source, wherein the carbon source includes but is not limited to methanol, sodium acetate and glucose.

[0031] Specifically, in step 2:

[0032] When the dissolved oxygen concentration in the anoxic zone exceeds 0.5 mg / L as measured by the dissolved oxygen detector, the aeration volume of the aerobic treatment unit is reduced by adjusting the air supply, thereby reducing its dissolved oxygen concentration, and controlling the dissolved oxygen concentration of the mixed liquid after the sludge in the aerobic zone is returned to the anoxic zone to be within 0.5 mg / L;

[0033] According to the detection of nitrate concentration in the effluent from the end of the aerobic unit, when the effluent nitrate concentration is higher than 15 mg / L, the internal reflux ratio of the reflux nitrification liquid to the anoxic zone is increased to ensure the denitrification effect of the A / A / O process.

[0034] Specifically, in step three:

[0035] When the nitrite concentration in the aerobic treatment unit is higher than 15 mg / L, the aeration is adjusted to increase the air supply in the aerobic zone, thereby increasing the dissolved oxygen concentration in the aerobic zone and promoting nitrification.

[0036] According to the dissolved oxygen concentration in the aerobic zone detected by the dissolved oxygen detector, the dissolved oxygen in the pool is maintained within the range of 2-3 mg / L to avoid excessive aeration and increase in energy consumption;

[0037] The pH of the aerobic zone is tested using a pH detector, and the pH of the aerobic zone is maintained within the range of 6.0 to 8.0 by adjusting the dosage of acid / base chemical reagents to ensure that the pH of the aerobic zone is within the appropriate range for nitrification;

[0038] The N2O emission in the aerobic zone was detected by gas chromatography, and the appropriate type and concentration of signal molecules were determined by comparing with the working condition without adding signal molecules.

[0039] Beneficial effects of the present invention:

[0040] 1. The present invention does not change the operating parameters of the sewage treatment plant. By adding signal molecules to the influent, the complex interactions and influences between the operating parameters of the sewage treatment plant are avoided, and the operating parameters are maintained in a range suitable for denitrification.

[0041] 2. The present invention reduces the emission of N2O from the aerobic treatment unit of the sewage treatment plant by adding signal molecules, without the need to upgrade the sewage treatment plant process or to invest in additional large-scale facilities, thereby reducing construction costs.

[0042] 3. The present invention reduces the manpower and time costs of nitrifying strain screening. In the A / A / O process, N2O mainly comes from the metabolic processes of denitrifying bacteria and ammonia oxidizing bacteria, nitrite oxidizing bacteria, aerobic denitrifying bacteria and other microorganisms in the nitrification process. However, the screening of nitrifying strains consumes a lot of manpower and time costs, and there is a phenomenon that the strains are difficult to survive in the actual complex water environment. These practical problems can be well solved by regulating the microbial nitrogen metabolic pathway through the regulation of quorum sensing by signal molecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of A / A / O reactor.

[0044] Figure 2 The changes in daily N2O emissions from the A / A / O reactor under different operating conditions.

[0045] Figure 3 The changes in EPS component content in the aerobic unit under different working conditions.

[0046] Figure 4 The changes in particle size of activated sludge in the aerobic unit under different working conditions. DETAILED DESCRIPTION

[0047] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0048] Unless otherwise specified, the test methods used in the embodiments of the present invention are conventional methods; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0049] Example

[0050] like Figure 1 The figure shows a schematic diagram of an A / A / O reactor. It includes a water inlet bucket, a peristaltic pump, an anaerobic tank, an anoxic tank, an aerobic tank and a secondary sedimentation tank which are connected in sequence. The aerobic tank is connected to the anoxic tank through a nitrification liquid return pipe. The secondary sedimentation tank is connected to the anaerobic tank through a sludge return pipe. The main body of the A / A / O reactor device is made of transparent organic glass. The A / A / O reactor was used for testing.

[0051] The inlet water quality of A / A / O reactor is as follows:

[0052] In the present invention, artificial simulated domestic sewage is selected as the influent of the A / A / O system. Typical urban pollutant water quality (i.e., low carbon source water quality) is simulated, and the indicators are shown in Table 1. In order to meet the nutrient components required for microbial reproduction, a carbon source composed of CH3COONa, starch and glucose is added to improve the accuracy and reliability of the simulation.

[0053] Table 1 Composition of simulated wastewater

[0054]

[0055] Appropriate activated sludge was obtained from the secondary sedimentation tank of a sewage treatment plant in Wuhan. The effective volumes of the anaerobic tank, anoxic tank, aerobic tank and secondary sedimentation tank are 2.5, 2.5, 7.5 and 10L respectively. The inlet flow rate is 1L / h, and the dissolved oxygen (DO) concentration is about 2-3mg / L. The hydraulic retention time (HRT) of the first three reaction tanks is 2.5, 2.5 and 7.5h respectively. To ensure the effective operation of the A / A / O system, the return sludge ratio is adjusted to 70%, and the reflux ratio R in the nitrification liquid is set to 300%. The remaining sludge is discharged from the bottom of the secondary sedimentation tank to ensure that the sludge age SRT of the A / A / O system reaches 15d.

[0056] Signal molecule processing conditions, the specific information is as follows:

[0057] Table 2 Signal molecule dosing parameters under different operating conditions

[0058]

[0059] Signal molecule addition method. Detailed information is as follows:

[0060] In view of the fact that AHLs (signal molecules) are soluble in water and easily hydrolyzed, in order to preserve AHLs for a long time, they were dissolved in methanol (purity higher than 99%) and prepared into a 0.1 mg / mL solution, which was refrigerated at -20°C for later use. During the experiment, a certain amount of AHLs solution was added to the inlet water and pumped into the reactor by a peristaltic pump.

[0061] In order to illustrate the effect of adding signal molecules on N2O emission reduction in the aerobic treatment unit of sewage treatment, different working conditions in Table 2 were set and run. In addition, sludge samples were taken after the sludge culture was completed, and the differences in microbial communities and metabolic-related enzyme functional genes were determined using 16S and qPCR technology. At the same time, the differences in N2O release under different working conditions were determined by gas chromatography.

[0062] Effect Example 1

[0063] like Figure 2As shown in the figure, the N2O release of the A / A / O system under different working conditions was monitored. Under condition I, the daily N2O emission of the aerobic tank was 1.23 mg, which was higher than that of the anaerobic tank and the anoxic tank. Under conditions II-V, the daily N2O emissions of the aerobic tank were 1.30 mg, 0.62 mg, 1.76 mg and 1.31 mg, respectively. The results showed that the addition of C6-HSL and C8-HSL promoted the daily N2O emissions, which increased by 5.69% and 43.23%, respectively; C12-HSL inhibited N2O emissions, and the daily emissions decreased by 49.46%. Among them, after adding C8-HSL, the proportion of N2O release in the aerobic tank to the total A / A / O release decreased from 43.03% to 38.73%. The results showed that C8-HSL mainly promoted the release of N2O in anaerobic and anoxic tanks, mainly promoting denitrification, and the increase in the abundance of aerobic denitrifying bacteria in aerobic tanks further confirmed this result, as shown in Table 3. In contrast, the addition of C12-HSL resulted in the lowest daily N2O emission in the system, with daily emissions of 0.49 mg / d, 0.55 mg / d and 0.62 mg / d in the anoxic tank, anaerobic tank and aerobic tank, respectively. Compared with condition I, they decreased by 32.53%, 39.36% and 49.46%, respectively, indicating that C12-HSL had the strongest inhibitory effect on N2O release in aerobic tanks (49.46%).

[0064] Table 3 Relative abundance of functional bacteria in aerobic pools

[0065]

[0066] Effect Example 2

[0067] The EPS content in the aerobic pool of the A / A / O system under different working conditions was monitored in Table 2. The polysaccharide and protein contents of total EPS, SEPS, LB-EPS, TB-EPS and the PN / PS ratio of total EPS under different working conditions are shown in Table 2. Figure 3(a), (b), (c) and (d) in the experiment. Since no matter what type of signal molecule is added, it can greatly promote the secretion of EPS polysaccharide content, that is, QS upregulates the biosynthesis and secretion of polysaccharides. Polysaccharides are the key structure of cell aggregation, and the positive regulation of QS on the expression of related genes has also been confirmed. The difference lies mainly in the effect of C12-HSL on EPS protein. In the experiment of the present invention, exogenous C12-HSL did promote the increase of LB-EPS and TB-EPS protein content in the early stage, but as the operation time increases, C12-HSL has an inhibitory effect on protein secretion. C8-HSL, C12-HSL and C6-HSL can promote the conversion of LB-EPS to S-EPS. Finally, in terms of the total amount of EPS, compared with condition I, C8-HSL and C12-HSL reduced the total content of EPS (the total amount of S-EPS, LB-EPS and TB-EPS), while C6-HSL increased the total content of EPS.

[0068] Effect Example 3

[0069] Changes in particle size of activated sludge in aerobic units under different working conditions Figure 4 As shown. Exogenous signal molecules have a significant effect on the particle size of the mixture in the aerobic treatment unit. Under condition I, particles with a size greater than 200 μm accounted for 39.42% of the particle size distribution. Under conditions II and III, this proportion increased to 68.11% and 71.08%, respectively. The median particle size d under conditions I, II, III, and IV 0.5 The d values ​​of C8-HSL, C12-HSL and C6-HSL were 89.63, 147.14, 162.52 and 137.52 μm respectively. The results showed that C8-HSL, C12-HSL and C6-HSL could promote the aggregation of organisms in the mixture and maintain the complete sludge floc structure, thus maintaining the stability of the sludge. 0.5 The maximum value indicates that C12-HSL is more likely to promote the aggregation of microorganisms in the mixture, thereby maintaining the sedimentation performance and stability of the mixture. 0.5 The size of the flocs was 143.25 μm. Therefore, it was not necessary to add signal molecules for a long time to maintain the stability of the flocs.

[0070] Effect Example 4

[0071] Nitrate reduction includes assimilative nitrate reduction and dissimilative nitrate reduction. Assimilative nitrate reduction refers to the process in which nitrate is reduced to nitrite and ammonium, and ammonium is used to enter the body and become biomass. Many bacteria, fungi and algae have the ability to absorb nitrate reduction. The enzyme involved in this reaction process is nirA enzyme (EC:1.7.7.1). In this process, the abundance of this type of enzyme was the highest when C8-HSL was added, followed by C12-HSL and C6-HSL. This shows that under II conditions, more microorganisms can reduce nitrate to ammonium and complete their life processes. Dissimilative nitrate reduction can be divided into ammonium-producing dissimilative nitrate reduction and denitrification. The first step of the ammonium-producing dissimilative nitrate reduction reaction is the reduction of nitrate to nitrite and the generation of energy; the second step is the reduction of nitrite to ammonium under the action of NADH reductase. The enzymes involved in this process are nitrate reductase (EC: 1.7.99.4), ferredoxin nitrate reductase (EC: 1.7.7.2) and nitrite reductase (cytochrome; ammonia production) (EC: 1.7.2.2). It can be seen from Table 4 that the abundance of these three enzymes is the highest in the condition of adding C12-HSL, and there is a competitive relationship between the ammonium-producing dissimilatory nitrate reduction process and the denitrification process. To a certain extent, when the ammonium-producing dissimilatory nitrate reduction pathway is dominant, the denitrification pathway is in a weak position. More nitrate is reduced to ammonium instead of producing nitrogen gas through denitrification, thus avoiding the production of N2O during the denitrification process. Therefore, one of the reasons for the reduction in N2O release after adding C12-HSL is that the ammonium-producing dissimilatory nitrate reduction process in the aerobic tank is strengthened.

[0072] During the denitrification process, N2O in the aerobic pool is reduced to NO by the nirK enzyme (EC: 1.7.2.1), NO is reduced to N2O by the nitric oxide reductase norB (EC: 1.7.2.5), and N2O is reduced to nitrogen by the nitrous oxide reductase (EC: 1.7.2.4). Then, the generated nitrogen is converted into ammonia by the action of nitrogenase (EC: 1.18.6.1) for use by microorganisms to complete the nitrogen fixation process. As shown in Table 4, C8-HSL, C12-HSL and C6-HSL can all increase the abundance of nirK and norB. The promotion effect of C12-HSL on the activity abundance of nitrous oxide reductase (EC: 1.7.2.4) is stronger than that of other signal molecules. Therefore, more N2O produced under the condition of adding C12-HSL is converted into N2, thereby reducing the emission of N2O in the aerobic treatment unit of the sewage treatment plant. Another reason is that the denitrification process in the aerobic pool is strengthened to achieve complete denitrification.

[0073] Table 4 Abundance of enzyme genes related to carbon metabolism and nitrogen metabolism

[0074]

[0075]

[0076]

[0077] According to effect examples 1-4, we can see that:

[0078] The mechanism by which signal molecules regulate the generation and release of N2O is as follows: signal molecules such as C12-HSL regulate the composition and content of sludge extracellular polymers (EPS) through quorum sensing (QS), increasing the sludge particle size, which is beneficial to the enrichment of nitrifying bacteria, while changing the electron transfer activity, thereby changing the microbial metabolic pathway, and ultimately achieving the regulation of N2O generation and release, thereby reducing N2O emissions from aerobic treatment units in sewage treatment plants.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An application of AHLs, characterized in that: Used to reduce the nitrous oxide emission of anaerobic tanks, anoxic tanks and / or aerobic tanks in an A / A / O system, the AHLs are C12-HSL, the addition concentration of the AHLs is 20-30nmol / L, and the A / A / O system includes an anaerobic tank, anoxic tank and aerobic tank connected in sequence.

2. A control method for reducing nitrous oxide emissions from aerobic pools in urban sewage treatment plants, characterized in that: The following steps are involved: Step 1, performing water quality tests on COD, total nitrogen, total phosphorus and pH of municipal sewage, then adding reagents to regulate the pH and C / N ratio of the influent, and adding a certain concentration of signal molecules into the anaerobic tank in the A / A / O system, wherein the A / A / O system includes an anaerobic tank, an anoxic tank and an aerobic tank connected in sequence, and the signal molecules are C8-HSL, C6-HSL or C12-HSL; Step 2: Control the dissolved oxygen concentration and internal recirculation ratio of the anoxic tank according to the dissolved oxygen detector in the anoxic tank, the dissolved oxygen detector at the end of the aerobic tank, and the nitrate concentration detection data at the end of the aerobic tank; Step 3: Evaluate the denitrification performance of the aerobic pool of the sewage treatment plant through the data detected by the aerobic pool dissolved oxygen detector and pH detector, as well as the measured nitrate concentration and nitrous oxide emission, so as to determine that the type of signal molecule added is C12-HSL, and the addition concentration is 20-30nmol / L; Step 4: Add the determined signal molecule type and dosage into the aerobic tank of the urban sewage treatment plant to reduce the emission of nitrous oxide.

3. The control method according to claim 2, characterized in that: In step one: The water quality characteristics of urban sewage are tested by detecting COD, total nitrogen, total phosphorus and pH, and the amount of carbon source added is determined by analyzing the total nitrogen concentration to meet the carbon source required for denitrification; By measuring the activated sludge concentration during operation, the return ratio of the external return pipeline was adjusted to maintain the sludge concentration at 3500 mg / L; Analyze the test data of the pH detector and control the inlet pH between 6.0 and 8.0 by fine-tuning the dosage of acidic or alkaline chemical reagents to meet the pH range required for denitrification; The C / N ratio was regulated by controlling the dosage of carbon sources, including methanol, sodium acetate and glucose.

4. The control method according to claim 2, characterized in that: In step 2: When the dissolved oxygen concentration in the anoxic tank exceeds 0.5 mg / L as measured by the dissolved oxygen detector, the aeration volume of the aerobic tank is reduced by adjusting the air supply, thereby reducing its dissolved oxygen concentration, and controlling the dissolved oxygen concentration of the mixed liquid after the nitrified liquid in the aerobic tank is returned to the anoxic tank to be within 0.5 mg / L; According to the detection of nitrate concentration in the effluent from the end of the aerobic tank, when the effluent nitrate concentration is higher than 15 mg / L, the internal reflow ratio of the reflux nitrification liquid to the anoxic tank is increased to ensure the denitrification effect of the A / A / O process.

5. The control method according to claim 2, characterized in that: In step three: When the nitrite concentration in the aerobic pool is higher than 15 mg / L, the aeration supply in the aerobic pool is increased by adjusting aeration to increase the dissolved oxygen concentration in the aerobic pool and promote nitrification. According to the detection of dissolved oxygen concentration in the aerobic pool by the dissolved oxygen detector, the dissolved oxygen in the aerobic pool is maintained within the range of 2-3 mg / L to avoid excessive aeration and increase in energy consumption; The pH of the aerobic pool is tested using a pH tester, and the pH of the aerobic pool is maintained within the range of 6.0 to 8.0 by adjusting the dosage of acidic or alkaline chemical reagents to ensure that the pH of the aerobic pool is within the appropriate range for nitrification; The nitrous oxide emissions from the aerobic pool were tested using a gas chromatograph, and the appropriate type and concentration of signal molecules were determined by comparing with the operating conditions without adding signal molecules.

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