Method for calculating greenhouse gas emission flux of sewage biochemical treatment process

Abstract

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

Description

Technical Field

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

[0002] Although the sewage treatment industry accounts for a relatively small proportion in the social economy, it is an energy-intensive industry. Some studies have shown that the electricity consumption of the sewage treatment industry accounts for about 1% of the total electricity consumption of the whole society, but the carbon emissions caused account for about 2%-3% of the total carbon emissions of the whole society. Therefore, the carbon emissions generated by sewage treatment cannot be ignored. Different from industries such as energy, industry, construction, and transportation, in addition to the indirect emissions caused by energy consumption, the sewage treatment process also generates non-CO2 greenhouse gases such as CH4 and N2O. Calculated over a 100-year period, the global warming potentials (GWPs) of CH4 and N2O are 25 times and 298 times that of CO2 respectively. How to achieve the coordinated improvement of pollution reduction and carbon reduction in China's sewage treatment industry requires solving many problems.

[0003] The lack of a method for calculating the carbon emission flux of sewage treatment processes is a relatively typical problem among the above-mentioned many problems. The reason is that the focus of China's sewage treatment industry is on improving quality, increasing efficiency, reducing pollution, and lowering energy consumption, while the research on carbon control and reduction started relatively late, and a complete and perfect greenhouse gas monitoring plan has not been formed, so there is a lack of a complete emission flux calculation method. 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 a sewage biochemical treatment process, propose a formula for calculating the greenhouse gas emission flux, and give the key parameters for the design of the flux chamber, solving two problems: the design of the flux chamber in the process of greenhouse gas monitoring and the calculation of the greenhouse gas emission flux.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows: A method for calculating the greenhouse gas emission flux of a sewage biochemical treatment process, the method comprising the following steps: (1) Design, process and manufacture a flux chamber, and calculate the cross-sectional area of the flux chamber; (2) Set sampling points according to the flow direction of the sewage in each process unit, place the flux chamber on the water surface of the sewage treatment tank at the sampling point, and monitor the concentration of greenhouse gases in each flux chamber; the greenhouse gases include CH4 and N2O; (3) During the monitoring process, record the temperature and air pressure data of the sampling point, and master the size of the pool body. For the aeration tank, it is necessary to find out the aeration flux; (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux: When monitoring the aerobic tank: 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 the anaerobic / anoxic tank: The calculation formula is as follows: ; Among them, E is the greenhouse gas emission flux of a single monitoring activity, kg / h; A s is the area of the tank body to which the monitoring sampling point belongs, m 2 ; A c is the water area covered by the flux chamber, m 2 ; t is the emission time, hours; Q a is the aeration volume per square meter, m 3 / h; C tg is the mass concentration of greenhouse gas in the flux chamber, kg / m 3 ; q g is the average monitoring flow rate of the flux chamber at the monitoring sampling point under standard conditions of 101325 pa and 273 K, m 3 / h; T S is the gas temperature in the flux chamber at the monitoring sampling point, K; dC tg / dt is the change rate of the mass concentration of greenhouse gas in the flux chamber at the monitoring sampling point, kg / (m 3 ·h); V c is the effective volume of the flux chamber, m 3 .

[0006] Furthermore, , C v is the average volume concentration of greenhouse gas in the flux chamber during the monitoring time, unit ppm; ρ is the density of greenhouse gas, unit kg / m 3 .

[0007] Furthermore, the calculation formula of ρ is as follows: ; Among them, ρ is the density of greenhouse gas, unit kg / m 3 ; P is the gas pressure, taking 1 atm under standard conditions; M w is the molecular weight of the gas, g / mol; R is the ideal gas constant, taking 0.0821 when the gas pressure unit is 1 atm, and taking 8.21 when the gas pressure unit is 1 kpa; T is the gas temperature, K.

[0008] Furthermore, the calculation formula of q g is as follows: ; Among them, q g is the average monitoring flow rate of the flux chamber 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 flux chamber at the actually monitored sampling point, m 3 / h; P s is the air pressure inside the flux chamber at the sampling point, Pa; T S is the gas temperature inside the flux chamber for monitoring the sampling point, K.

[0009] Furthermore, the height of the flux chamber is 0.25 m - 0.50 m.

[0010] Furthermore, the water area A covered by the flux chamber c is 0.10 m 2 -1.0 m 2 .

[0011] Furthermore, in step (2), single - time monitoring can be carried out at the sampling point or long - term monitoring can be carried out on key emission points.

[0012] Furthermore, in step (2), continuous monitoring or intermittent monitoring is carried out on the sampling points.

[0013] Compared with the prior art, the method for calculating the greenhouse gas emission flux of the sewage biochemical treatment process described in the present invention has the following advantages: The method for calculating the greenhouse gas emission flux of the sewage biochemical treatment process described in the present invention gives different calculation formulas for different situations. During calculation, the corresponding formula can be selected according to the actual situation, which can calculate the greenhouse gas emissions of the biological pond more quickly and accurately, thus providing basic data and effect evaluation before and after the transformation for the low - carbon transformation of the biochemical process. Specific Embodiments

[0014] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0015] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0016] Embodiment 1 Aerobic tank + Measurable aeration flux A method for calculating the greenhouse gas emission flux of a sewage biochemical treatment process, the method comprising the following steps: (1) Design, process and fabricate a flux chamber, and calculate the cross-sectional area of the flux chamber; (2) Before monitoring, it is necessary to understand all the technological processes of the sewage treatment plant; set sampling points according to the flow direction of sewage in each process unit, place the flux chamber on the water surface of the sewage treatment tank at the sampling point, connect the flux chamber with the on-line greenhouse gas monitoring equipment through a hose, and use the on-line greenhouse gas monitoring equipment to monitor the concentration of greenhouse gases in each flux chamber; Single sampling monitoring can be carried out at the sampling point, or long-term monitoring can be carried out on key emission points such as the aeration tank. The monitoring can be continuous monitoring or intermittent monitoring; (3) During the monitoring process, record the temperature and air pressure data of the sampling point, and master the size of the pool body. For the aeration tank, it is necessary to understand the aeration flux; (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux.

[0017] What is monitored in this embodiment is the aerobic tank, and the aeration flux can be measured. The calculation formula is as follows: , That is ; Among them, E is the emission amount of greenhouse gas CH4 or N2O per single monitoring, kg / h; A s is the area of the aerobic tank to which the monitoring sampling point belongs, m 2 ; A c is the water area covered by the flux chamber, m 2 ; t is the emission time, with a value range of 0 - 24 hours; Q a is the aeration volume per square meter, m 3 / h; C tg is the mass concentration of greenhouse gas in the flux chamber, kg / m 3 ; , C v is the average volume concentration of greenhouse gas in the flux chamber during the monitoring time, with the unit ppm; ρ is the density of the greenhouse gas, with the unit kg / m 3 .

[0018] The calculation formula of ρ is as follows: ; Among them, P is the gas pressure, taking 1 atm under standard conditions; M w is the molecular weight of the gas, g / mol; R is the ideal gas constant. When the gas pressure unit is 1 atm, the value is 0.0821. When the gas pressure unit is 1 kPa, the value is 8.21; T is the gas temperature, K.

[0019] Example 2 Aeration Tank + Unmeasurable Aeration Flux A method for calculating the greenhouse gas emission flux of a sewage biochemical treatment process, the method comprising the following steps: (1) Design, fabricate and manufacture a flux chamber, and calculate the cross-sectional area of the flux chamber; (2) Before monitoring, it is necessary to understand the entire process flow of the sewage treatment plant; set sampling points according to the flow direction of the sewage in each process unit, place the flux chamber on the water surface of the sewage treatment tank at the sampling point, connect the flux chamber to the greenhouse gas online monitoring device through a hose, and use the greenhouse gas online monitoring device to monitor the concentration of greenhouse gases in each flux chamber; Single sampling monitoring can be carried out at the sampling point or long-term monitoring can be carried out on key emission points, and the monitoring can be continuous monitoring or intermittent monitoring; (3) During the monitoring process, record the temperature and air pressure data of the sampling point, and know the size of the pool body. For the aeration tank, it is necessary to understand the aeration flux; (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux.

[0020] In this example, the monitored is the aerobic tank, and the aeration flux is unmeasurable. The calculation formula is as follows: ; ; Among them, E is the emission of greenhouse gas CH4 or N2O per single monitoring, kg / h; A s is the area of the aeration tank to which the monitoring sampling point belongs, m 2 ; A c is the area of the water area covered by the flux chamber, m 2 ; C tg is the mass concentration of greenhouse gases in the flux chamber (the calculation method is the same as that in Example 1), kg / m 3 ; q g is the average monitoring flow rate of the flux chamber at the sampling point under standard conditions (9101325pa, 273K), m 3 / h; q s is the average monitoring flow rate of the flux chamber at the actual monitored sampling point, m 3 / h; P s is the monitoring air pressure of the sampling tube of the flux chamber at the sampling point, pa; T S is the gas temperature of the sampling tube of the flux chamber at the sampling point, K.

[0021] Specifically, in this example, the concentrations of the sampled greenhouse gases N2O and CH4 are 22.01 ppm and 26.7 ppm respectively, and the calculated emission fluxes are 13.87 kg / d and 6.10 kg / d respectively. Note: CO2 is defaulted to be of biological origin and the emission is 0, so it is not calculated.

[0022] In addition, to illustrate the accuracy of the data of the greenhouse gas online monitoring device, gas chromatography and this monitoring device were used to test the same point. During the experiment, another sampling point was randomly selected, and greenhouse gas samples were collected using a sampling bag. The concentrations of N2O, CH4, and CO2 measured by gas chromatography were 191.89 ppm, 4.84 ppm, and 17336.61 ppm respectively; the data measured by the monitoring device were 210.58 ppm, 7.21 ppm, and 18711.42 ppm. The data measured by the monitoring device was close to that measured by gas chromatography, indicating that the data of this monitoring device is reliable.

[0023] Example 3 Anaerobic / anoxic tank A method for calculating the greenhouse gas emission flux of a sewage biochemical treatment process, the method comprising the following steps: (1) Design, process, and manufacture a flux chamber, and calculate the cross-sectional area of the flux chamber; (2) Before monitoring, it is necessary to understand the entire process flow of the sewage treatment plant; set sampling points according to the flow direction of the sewage in each process unit, place the flux chamber on the water surface of the sewage treatment tank at the sampling point, connect the flux chamber to the online monitoring device through a hose, and use the greenhouse gas online monitoring device to monitor the concentration of greenhouse gases in each flux chamber; Sampling single monitoring or long-term monitoring of key emission points can be carried out at the sampling point, and the monitoring can be continuous monitoring or intermittent monitoring; (3) During the monitoring process, record the temperature and air pressure data at the sampling point, and master the size of the pool body. For the aeration tank, it is necessary to understand the aeration flux; (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux.

[0024] What is monitored in this example is the anaerobic / anoxic tank, and the calculation formula is as follows: ; Among them, E is the emission amount of CH4 or N2O gas for single monitoring, kg / h; dC tg / dt is the change rate of the mass concentration of greenhouse gases in the flux chamber at the monitoring sampling point, kg / (m 3 ·h); V c is the effective volume of the flux chamber, m 3 ; A s is the area of the biological tank to which the monitoring sampling point belongs, m 2 ; A c is the area of the water area covered by the flux chamber, m 2 ; C tg is the mass concentration of greenhouse gases in the flux chamber (the calculation method is the same as in Example 1), kg / m 3 ; TS To monitor the gas temperature, in K, inside the flux chamber at the sampling point.

[0025] The above formula can be transformed into: ; At this time, the value of is the height H of the flux chamber. Therefore, the key parameter for the design of the flux chamber is the height H, and the value of H ranges from 0.25 m to 0.50 m. At this height, the volume of the flux chamber is relatively small, easy to carry, and the manufacturing cost is low.

[0026] There is no requirement for the water area that the flux chamber can cover, and generally it can be taken as 0.10 - 1.0 m 2 .

[0027] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for calculating the greenhouse gas emission flux of a sewage biochemical treatment process, characterized in that: The method includes the following steps: (1) Design, process and fabricate a flux chamber, and calculate the cross-sectional area of the flux chamber; (2) Set sampling points according to the flow direction of sewage in each process unit, place the flux chamber on the water surface of the sewage treatment pool at the sampling point, and monitor the concentration of greenhouse gases in each flux chamber; (3) During the monitoring process, record the temperature and air pressure data of the sampling point, and know the size of the pool body. For the aeration tank, it is necessary to find out the aeration flux; (4) Substitute the measured data into the following formula to calculate the greenhouse gas emission flux: When monitoring the aerobic tank: 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 the anaerobic / anoxic tank: The calculation formula is as follows: ； Among them, E is the greenhouse gas emission flux of a single monitoring activity, kg / h; A s is the area of the pond body to which the monitoring sampling point belongs, m 2 ; A c is the water area covered by the flux chamber, m 2 ; t is the emission time, hours; Q a is the aeration rate per square meter, m 3 / h; C tg is the mass concentration of greenhouse gas in the flux chamber, kg / m 3 ; q g is the average monitoring flow rate of the flux chamber at the monitoring sampling point under standard conditions of 101325 pa and 273 K, m 3 / h; T S is the gas temperature in the flux chamber at the monitoring sampling point, K; dC tg / dt is the change rate of the mass concentration of greenhouse gas in the flux chamber at the monitoring sampling point, kg / (m 3 ·h); V c is the effective volume of the flux chamber, m 3 .

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

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

4. The method for calculating the greenhouse gas emission flux of the sewage biochemical treatment process according to claim 1, wherein: q g The calculation formula is as follows: ； Among them, q g is the average monitoring flow rate of the flux chamber 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 flux chamber at the actually monitored sampling point, m 3 / h; P s is the air pressure in the flux chamber at the sampling point, pa; T S is the gas temperature in the flux chamber at the monitored sampling point, K.

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

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

7. The method for calculating the greenhouse gas emission flux of the sewage biochemical treatment process according to claim 1, characterized in that: In step (2), single sampling monitoring can be carried out at the sampling point or long-term monitoring can be carried out on key emission points.

8. The method for calculating the greenhouse gas emission flux of the sewage biochemical treatment process according to claim 1, wherein: In step (2), continuous monitoring or intermittent monitoring is carried out on the sampling points.

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