A method for calculating greenhouse gas emission flux from sewage biochemical treatment processes

Abstract

The present invention provides a method for calculating greenhouse gas emission fluxes in a sewage biochemical treatment process, which can quickly and accurately calculate the greenhouse gas emissions of a biological pool, thereby providing basic data for the low-carbon transformation of the biochemical process and effect evaluation before and after the transformation.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to a method for calculating greenhouse gas emission flux in a sewage biochemical treatment process. Background Art

[0002] While the wastewater treatment industry accounts for a relatively small portion of the economy, it is energy-intensive. Studies have shown that while electricity consumption in the wastewater treatment industry accounts for approximately 1% of total electricity consumption, its carbon emissions contribute approximately 2%-3% of total carbon emissions. Therefore, carbon emissions from wastewater treatment are not negligible. Unlike other sectors such as energy, industry, construction, and transportation, the wastewater treatment process not only produces indirect emissions from energy consumption, but also produces non-CO2 greenhouse gases such as CH4 and N2O. Over a 100-year period, the global warming potential (GWP) of CH4 and N2O is 25 times and 298 times that of CO2, respectively. my country's wastewater treatment industry faces numerous challenges in achieving synergistic and effective pollution and carbon reduction.

[0003] The lack of a carbon emission flux calculation method for wastewater treatment processes is a typical example of the aforementioned challenges. This is because my country's wastewater treatment industry focuses on improving quality, increasing efficiency, reducing pollution, and reducing consumption. Research on carbon control and reduction began relatively late, resulting in a lack of a comprehensive greenhouse gas monitoring program and, consequently, a lack of comprehensive emission flux calculation methods. Summary of the Invention

[0004] In view of this, the present invention aims to propose a method for calculating the greenhouse gas emission flux of the sewage biochemical treatment process, puts forward a formula for calculating the greenhouse gas emission flux, and gives the key parameters for the flux box design, solving the two problems of flux box design and greenhouse gas emission flux calculation in the greenhouse gas monitoring process.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process, the method comprising the following steps:

[0007] (1) Design, process and manufacture the flux box and calculate the cross-sectional area of ​​the flux box;

[0008] (2) Sampling points are set up according to the flow of wastewater in each process unit, and flux boxes are placed on the water surface of the wastewater treatment pool at the sampling points to monitor the concentration of greenhouse gases in each flux box; greenhouse gases include CH4 and N2O;

[0009] (3) During the monitoring process, record the temperature and air pressure data of the sampling points, and understand the size of the tank. The aeration flux of the aeration tank needs to be understood;

[0010] (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux:

[0011] When monitoring aerobic tanks:

[0012] Ⅰ. When the aeration flux can be measured, the calculation formula is as follows:

[0013] ;

[0014] Ⅱ. When the aeration flux cannot be measured, the calculation formula is as follows:

[0015] ;

[0016] When monitoring anaerobic / anoxic tanks:

[0017] The calculation formula is as follows:

[0018] ;

[0019] Where E is the greenhouse gas emission flux of a single monitoring activity, kg / h; A s The area of ​​the pool to which the sampling point belongs, m 2 ; A c is the water area covered by the flux box, m 2 ; t is the emission time, hours; Q a is the aeration volume per square meter, m 3 / m 2 ·h;C tg is the mass concentration of greenhouse gases in the flux box, kg / m 3 ;q g is the average monitoring flow rate of the flux box at the monitoring sampling point under standard conditions of 101325 Pa and 273 K, m 3 / h;T S To monitor the gas temperature in the flux box at the sampling point, K; dC tg / dt is the rate of change of greenhouse gas mass concentration in the flux box at the monitoring sampling point, kg / (m 3 h); V c is the effective volume of the flux box, m 3 .

[0020] further, , C v is the average volume concentration of greenhouse gases in the flux box during the monitoring period, in ppm; ρ is the density of greenhouse gases, in kg / m 3 .

[0021] Furthermore, the calculation formula of ρ is as follows:

[0022] ;

[0023] Where ρ is the density of greenhouse gases, in kg / m 3 ; P is the gas pressure, which is 1 atm under standard conditions; M w is the molecular weight of the gas, g / mol; R is the ideal gas constant, which is 0.0821 when the gas pressure unit is 1 atm and 8.21 when the gas pressure unit is 1 kPa; T is the gas temperature, K.

[0024] Further, q g The calculation formula is as follows:

[0025] ;

[0026] Among them, q g is the average monitoring flow rate of the flux box at the sampling point under standard conditions of 101325 Pa and 273 K, m 3 / h;q s is the average monitoring flow rate of the actual monitoring sampling point flux box, m 3 / h; P s is the air pressure in the flux box at the sampling point, pa; T S To monitor the gas temperature in the flux box at the sampling point, K.

[0027] Furthermore, the height of the flux box is 0.25m-0.50m.

[0028] Furthermore, the area of ​​water covered by the flux box is A c 0.10 m 2 -1.0m 2 .

[0029] Furthermore, in step (2), single sampling monitoring can be carried out at the sampling point or long-term monitoring can be carried out at key emission points.

[0030] Furthermore, in step (2), the sampling points are continuously or intermittently monitored.

[0031] Compared with the existing technology, the greenhouse gas emission flux calculation method of the sewage biochemical treatment process described in the present invention has the following advantages:

[0032] The greenhouse gas emission flux calculation method for the biochemical treatment process of sewage described in the present invention provides different calculation formulas for different situations. During calculation, the corresponding formula can be selected according to the actual situation. The greenhouse gas emissions of the biological pool can be calculated more quickly and accurately, thereby providing basic data for the low-carbon transformation of the biochemical process and the effect evaluation before and after the transformation. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Example 1 Aerobic tank + aeration flux can be measured

[0036] A method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process, the method comprising the following steps:

[0037] (1) Design, process and manufacture the flux box and calculate the cross-sectional area of ​​the flux box;

[0038] (2) Before monitoring, the entire process of the sewage treatment plant must be understood; sampling points should be set according to the flow of sewage in each process unit, and flux boxes should be placed on the water surface of the sewage treatment pool at the sampling points. The flux boxes should be connected to the greenhouse gas online monitoring equipment through a hose, and the greenhouse gas online monitoring equipment should be used to monitor the concentration of greenhouse gases in each flux box;

[0039] Single sampling monitoring can be carried out at the sampling point, or long-term monitoring can be carried out at key emission points such as aeration tanks. Monitoring can be continuous or intermittent.

[0040] (3) During the monitoring process, record the temperature and air pressure data of the sampling points, and understand the size of the tank. The aeration flux of the aeration tank needs to be understood;

[0041] (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux.

[0042] The aerobic tank is monitored in this embodiment, and the aeration flux can be measured. The calculation formula is as follows:

[0043] ,

[0044] Right now ;

[0045] Where, E is the greenhouse gas CH4 or N2O emission of a single monitoring, kg / h; A s is the area of ​​the aerobic pool to which the sampling point is monitored, m 2 ; A c is the water area covered by the flux box, m 2 ; Q a is the aeration volume per square meter, m 3 / m2 ·h;C tg is the mass concentration of greenhouse gases in the flux box, kg / m 3 ;

[0046] ,

[0047] C v is the average volume concentration of greenhouse gases in the flux box during the monitoring period, in ppm; ρ is the density of greenhouse gases, in kg / m 3 .

[0048] The calculation formula for ρ is as follows:

[0049] ;

[0050] Wherein, P is the gas pressure, which is 1 atm under standard conditions; M w is the molecular weight of the gas, g / mol; R is the ideal gas constant, which is 0.0821 when the gas pressure unit is 1 atm and 8.21 when the gas pressure unit is 1 kPa; T is the gas temperature, K.

[0051] Example 2 Aerobic tank + aeration flux cannot be measured

[0052] A method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process, the method comprising the following steps:

[0053] (1) Design, process and manufacture the flux box and calculate the cross-sectional area of ​​the flux box;

[0054] (2) Before monitoring, the entire process of the sewage treatment plant must be understood; sampling points should be set according to the flow of sewage in each process unit, and flux boxes should be placed on the water surface of the sewage treatment pool at the sampling points. The flux boxes should be connected to the greenhouse gas online monitoring equipment through a hose, and the greenhouse gas online monitoring equipment should be used to monitor the concentration of greenhouse gases in each flux box;

[0055] Single sampling monitoring can be carried out at the sampling point or long-term monitoring can be carried out at key emission points. Monitoring can be continuous or intermittent;

[0056] (3) During the monitoring process, record the temperature and air pressure data of the sampling points, and understand the size of the tank. The aeration flux of the aeration tank needs to be understood;

[0057] (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux.

[0058] The aerobic tank is monitored in this embodiment, and the aeration flux is not measurable. The calculation formula is as follows:

[0059] ;

[0060] ;

[0061] Where E is the greenhouse gas CH4 or N2O gas emission of a single monitoring, kg / h; A s The area of ​​the aeration tank to which the sampling point belongs, m 2 ; A c is the water area covered by the flux box, m 2 ; C tg is the mass concentration of greenhouse gases in the flux box (calculated in the same way as in Example 1), kg / m 3 ;q g is the average monitoring flow rate of the flux box at the sampling point under standard conditions (9101325Pa, 273K), m 3 / h;q s is the average monitoring flow rate of the actual monitoring sampling point flux box, m 3 / h; P s The air pressure of the sampling tube of the flux box at the sampling point is monitored, pa; T S is the gas temperature in the sampling tube of the flux box at the sampling point, K.

[0062] Specifically, in this example, the sampled greenhouse gas concentrations of N2O and CH4 were 22.01 ppm and 26.7 ppm, respectively, and the calculated emission fluxes were 13.87 kg / d and 6.10 kg / d, respectively. Note: CO2 is assumed to be biogenic by default, with an emission of 0, so it is not calculated.

[0063] To demonstrate the accuracy of the data from the online greenhouse gas monitoring device, tests were conducted using both gas chromatography and the monitoring device at the same location. During the experiment, greenhouse gas samples were collected at a random sampling point using a sampling bag. Gas chromatography revealed N2O, CH4, and CO2 concentrations of 191.89 ppm, 4.84 ppm, and 17,336.61 ppm, respectively. The monitoring device measured concentrations of 210.58 ppm, 7.21 ppm, and 18,711.42 ppm, respectively. The close agreement between the monitoring device and gas chromatography data indicates the reliability of the monitoring device's data.

[0064] Example 3 Anaerobic / Anoxic Tank

[0065] A method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process, the method comprising the following steps:

[0066] (1) Design, process and manufacture the flux box and calculate the cross-sectional area of ​​the flux box;

[0067] (2) Before monitoring, it is necessary to understand the entire process of the sewage treatment plant; set up sampling points according to the flow of sewage in each process unit, and place flux boxes on the water surface of the sewage treatment pool at the sampling points. Connect the flux boxes to the online monitoring equipment through a hose, and use the greenhouse gas online monitoring equipment to monitor the concentration of greenhouse gases in each flux box;

[0068] Single sampling monitoring can be carried out at the sampling point or long-term monitoring can be carried out at key emission points. Monitoring can be continuous or intermittent;

[0069] (3) During the monitoring process, record the temperature and air pressure data of the sampling points, and understand the size of the tank. The aeration flux of the aeration tank needs to be understood;

[0070] (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux.

[0071] This example monitors the anaerobic / anoxic tank, and the calculation formula is as follows:

[0072] ;

[0073] Where E is the CH4 or N2O gas emission of a single monitoring, kg / h; dC tg / dt is the rate of change of greenhouse gas mass concentration in the flux box at the monitoring sampling point, kg / (m 3 h); V c is the effective volume of the flux box, m 3 ; A s The area of ​​the biological pool to which the sampling point belongs, m 2 ; A c is the water area covered by the flux box, m 2 ; C tg is the mass concentration of greenhouse gases in the flux box (calculated in the same way as in Example 1), kg / m 3 ;T S To monitor the gas temperature in the flux box at the sampling point, K.

[0074] The above formula can be transformed into:

[0075] ;

[0076] at this time, The value of is the height H of the flux box, so the key parameter of the flux box design is the height H, which is 0.25m-0.50m. At this height, the flux box is relatively small in size, easy to carry, and low in manufacturing cost.

[0077] The flux box can cover an area of ​​water that is not required, but it can generally be 0.10-1.0m 2 .

[0078] 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 principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process, characterized by: The method comprises the following steps: (1) Design, process and manufacture the flux box and calculate the cross-sectional area of ​​the flux box; (2) Sampling points are set up according to the flow of wastewater in each process unit, and flux boxes are placed on the water surface of the wastewater treatment pool at the sampling points, and the concentration of greenhouse gases in each flux box is monitored; (3) During the monitoring process, record the temperature and air pressure data of the sampling points, and understand the size of the tank. The aeration flux of the aeration tank needs to be understood; (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux: When monitoring aerobic tanks: Ⅰ. When the aeration flux can be measured, the calculation formula is as follows: ； Ⅱ. When the aeration flux cannot be measured, the calculation formula is as follows: ； When monitoring anaerobic / anoxic tanks: The calculation formula is as follows: ； Where E is the greenhouse gas emission flux of a single monitoring activity, kg / h; A s The area of ​​the pool to which the sampling point belongs, m 2 ; A c is the water area covered by the flux box, m 2 ; t is the emission time, hours; Q a is the aeration volume per square meter, m 3 / m 2 ·h;C tg is the mass concentration of greenhouse gases in the flux box, kg / m 3 ;q g The standard conditions are 101325Pa, 273K, and the average monitoring flow rate of the flux box at the monitoring sampling point is m 3 / h;T S To monitor the gas temperature in the flux box at the sampling point, K; dC tg / dt is the rate of change of greenhouse gas mass concentration in the flux box at the monitoring sampling point, kg / (m 3 h); V c is the effective volume of the flux box, m 3 .

2. The method for calculating greenhouse gas emission flux from a wastewater biochemical treatment process according to claim 1, characterized in that: , C v is the average volume concentration of greenhouse gases in the flux box during the monitoring period, in ppm; ρ is the density of greenhouse gases, in kg / m 3 .

3. The method for calculating greenhouse gas emission flux from a wastewater biochemical treatment process according to claim 2, characterized in that: The calculation formula for ρ is as follows: ； Where ρ is the density of greenhouse gases, in kg / m 3 ; P is the gas pressure, which is 1 atm under standard conditions; M w is the molecular weight of the gas, g / mol; R is the ideal gas constant, which is 0.0821 when the gas pressure unit is 1 atm and 8.21 when the gas pressure unit is 1 kPa; T is the gas temperature, K.

4. The method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process according to claim 1, wherein: q g The calculation formula is as follows: ； Among them, q g The standard conditions are 101325Pa, 273K, and the average monitoring flow rate of the sampling point flux box is m 3 / h;q s is the average monitoring flow rate of the actual monitoring sampling point flux box, m 3 / h; P s is the air pressure in the flux box at the sampling point, pa; T S To monitor the gas temperature in the flux box at the sampling point, K.

5. The method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process according to claim 1, wherein: The height of the flux box is 0.25m-0.50m.

6. The method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process according to claim 1, characterized in that: The water area covered by the flux box A c 0.10 m 2 -1.0m 2 .

7. The method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process according to claim 1, characterized in that: In step (2), single sampling monitoring is carried out at the sampling point or long-term monitoring is carried out at key emission points.

8. The method for calculating greenhouse gas emission fluxes from a wastewater biochemical treatment process according to claim 1, wherein: In step (2), the sampling points are monitored continuously or intermittently.

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