CN112084649A - Carbon emission model calculation method based on whole process link of town sewage treatment - Google Patents

Abstract

The invention relates to a carbon emission model calculation method based on the whole process link of town sewage treatment, which establishes a comprehensive urban sewage treatment system measurement method and model based on carbon emission, is used for comprehensively measuring the benefits generated by the carbon emission sewage treatment and evaluating the negative influence and value of high-standard emission on the water environment, and the carbon emission model calculation method covers the whole-process energy-saving and emission-reducing comprehensive measurement and calculation method of the sewage treatment system including the links of sewage treatment, sludge treatment and reclaimed water utilization, solves the problem of missing carbon emission calculation methods in each link of sewage treatment, the method can provide method guidance for carbon emission intensity change calculation and environmental impact analysis of engineering design schemes in the upgrading and modifying process of the sewage treatment plant, and is beneficial to calculating the net carbon emission of the sewage treatment plant according to the improvement requirement of the sewage treatment plant.

Description

Carbon emission model calculation method based on whole process link of town sewage treatment

Technical Field

The invention relates to the technical field of sewage treatment methods, in particular to a carbon emission model calculation method based on a whole process link of town sewage treatment.

Background

The social circulation of water is an essential step for maintaining the normal operation of life, work and society of residents. In the course of water circulation, natural water areaIs a part of consumption, but most of water is converted into domestic sewage and production wastewater, and a main source of water quality pollution is an important factor for limiting the coordinated development of social economy and environmental protection. In order to relieve the influence of domestic sewage and production wastewater on the natural water environment, governments of various countries around the world construct expensive sewage collecting network systems and centralized sewage treatment plants to treat sewage. Traditional sewage treatment methods require additional energy and chemicals to maintain good conditions and high pollutant removal efficiency of microorganisms in the sewage biological reaction tank, which can convert polymer organic matters into CO₂、H₂O and an energy source. Other social entities consume non-renewable energy sources such as coal and produce greenhouse gases such as carbon dioxide when producing electricity and chemicals. While the end products of sewage treatment are also greenhouse gases, such as CH₄，CO₂And N₂And O. Thus, traditional wastewater treatment methods are not sustainable from an energy balance and "carbon footprint" point of view, creating new energy and environmental issues.

The traditional wastewater treatment method wastes 4MJ biomass energy contained in organic matters in the wastewater, and 0.4kg of CO is released into the atmosphere by per cubic meter of the wastewater treated by the traditional wastewater treatment method₂. Meanwhile, the operation of the sewage treatment facility needs to consume 2.5MJ energy and generate 0.22kg of CO₂. In 2017, the total amount of wastewater discharged in China is 49270 million tons, and if all wastewater treatment consumes electric energy and chemicals, about 3500 million tons of CO may be discharged to the environment₂About 32145 billion energy is wasted, which corresponds to 1.1 million tons of standard coal. The existing urban social water circulation model is an unsustainable carbon-intensive model from the perspective of the entire social life cycle. Therefore, there is a need to research and plan a new social water circulation system from the viewpoint of reducing carbon emission and energy consumption.

The applicable technology of carbon emission reduction becomes the development direction of urban water systems, and the core of the technology is to integrate mature technology and systems. For example, the japanese decentralized small-scale on-site wastewater treatment technology can reduce energy consumption over long distances. The united states and germany attach importance to anaerobic digestion of sludge to convert organic matter in the sludge into a biogas energy source that can be collected and utilized. Israel and the United states pay great attention to the sewage recycling technology, and a large amount of sewage is treated to a certain standard and can be used for agriculture, forestry and industry. The key points of urban water system construction in China are drinking water guarantee, pollutant reduction in sewage and water environment quality improvement. Although some measures have been taken to implement energy conservation and emission reduction, the development goal in the international low carbon direction is far away.

At present, the method for accounting the carbon emission of the sewage treatment plant mainly adopts the method provided by the guidance of the inter-government special committee for climate change (IPCC). In view of the lack of basic data in most countries, the parameter values used to guide nationwide carbon emission calculations are essentially the recommended values for foreign experts generated by rough judgment of national population data and per-capita pollution capacity. Therefore, the applicability of the carbon emission calculation method of IPCC in chinese sewage treatment carbon emission management has not been completely determined. Greenhouse gas inventory and data estimation research of each subunit of urban sewage treatment is not independently developed in China, and the research on greenhouse gas emission in the sewage treatment process on an urban scale is less. Meanwhile, the pollutant emission standard of urban sewage treatment plants is improved blindly in various parts of China, which is not necessarily beneficial to carbon emission reduction and comprehensive environmental benefit, and even may generate negative influence.

Therefore, a comprehensive urban sewage treatment system measuring method and model based on carbon emission needs to be established by those skilled in the art for comprehensively measuring the benefits generated by carbon emission sewage treatment and evaluating the negative influence and value of high-standard emission on water environment, so as to effectively calculate the net carbon emission of a sewage treatment plant.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a carbon emission model calculation method based on the whole process link of town sewage treatment.

A carbon emission model calculation method based on a town sewage treatment full-flow link is characterized in that a carbon emission model is used for calculating the net carbon emission W of a sewage plant in an operation stage, and the net carbon emission W is equal to the carbon emission E of the sewage plant in the operation stage_{Carbon row}Carbon removal and emission reduction J_{Emission reduction}(ii) a Carbon emission E_{Carbon row}Equal to direct carbon emission E_{Direct connection}And indirect carbon emission E_{Indirect connection}The sum of (a); direct carbon emission E_{Direct connection}Comprises the carbon emission E of the sewage denitrification link_{Denitrification of sewage}And the carbon emission E of the sanitary landfill of the sludge_{Sanitary landfill}Carbon emission in sludge land utilization link E_{Land utilization}(ii) a Indirect carbon emission E_{Indirectly comprise}Including electricity consumption of sewage treatment plant E_{Electric energy}And agents E used_{Pharmaceutical production}Indirectly resulting in carbon emissions; carbon emission reduction J_{Emission reduction}Comprises water quality improvement and carbon emission reduction J_{Water quality improvement}Carbon emission reduction amount J for anaerobic digestion of sludge_{Anaerobic digestion}Carbon emission reduction amount J in sludge aerobic digestion process_{Aerobic digestion}And sludge land utilization as soil fertilizer carbon emission reduction J_{Soil fertilizer}(ii) a The measurement formula of the net carbon emission W is as follows:

in addition, the carbon emission in the sewage denitrification link E sewage denitrification comprises N₂Class O carbon emissions E_{N2O, Sewage treatment}And CO₂Carbon-like emissions E_{CO2 external carbon source}The two measurement formulas are as follows:

A、N₂class O carbon emissions E_{N2O, Sewage treatment}：

M_{N2O, Sewage treatment}＝Q×(TN_{Inflow water}－TN_{Discharging water})×EF_{N2O, Sewage treatment}×10^-2 (2)

＝4×10^-4×Q×(TN_{Inflow water}－TN_{Discharging water})

In the formula M_{N2O,Treatment of sewage}Sewage treatment Process N₂O production amount tN₂O/month; q-treated water volume of sewage treatment plant is ten thousand meters³A month; TN water inlet and TN water outlet-TN concentration mg/L of the water inlet and outlet; EF_{N2O, Sewage treatment}—N₂O conversion, 0.04kgN₂O/kgTN；

Combining the formula (2) to obtain E_N2OThe sewage treatment has the following measurement formula:

E_{N2O, Sewage treatment}＝G_N2O×M_{N2O, Sewage treatment}＝0.1184×Q×(TN_{Inflow water}－TN_{Discharging water}) (3)

In the formula, E_{N2O, Sewage treatment}Sewage treatment step N₂Carbon emissions tCO of O type₂A month; g_N2O—N₂Taking 296tCO based on the global warming potential of O on a hundred-year scale₂/tN₂O，

B、CO₂Carbon-like emissions E_{CO2 external carbon source}：

An external carbon source is used as an electron donor and is oxidized into alkalinity HCO in the denitrification process₃ ^-Is converted into CO in the nitration process₂(ii) a Therefore, the stoichiometric equation of the nitrification and denitrification process is as follows:

and (3) denitrification process:

NO₃ ^－+1.08CH₃OH+0.24H₂CO₃→0.056C₅H₇O₂N+0.47N₂+1.68H₂O+HCO₃ ^-

and (3) nitration process:

NH₄ ⁺+1.83O₂+1.98HCO₃ ^-→0.02C₅H₇O₂N+1.04H₂O+0.98NO₃ ^－+1.88H₂CO₃

the stoichiometric equations of the nitrification and denitrification processes are combined into:

NH₄ ⁺+NO₃ ^－+1.83O₂+2.14CH₃OH→0.13C₅H₇O₂N+5.77H₂O+1.4CO₂+0.93N₂

0.9kgCO is produced for every 1kg of methanol consumed₂(ii) a When the oxygen equivalent of methanol is combined with 1.5mg/mg, the CO of the external carbon source in the denitrification process is calculated according to the oxygen equivalent₂Theoretical conversion of 0.9kgCO₂/kgBOD_{Carbon source}(ii) a Conversion of CO by external carbon source₂The carbon-like emissions can be calculated as follows:

E_{CO2 external carbon source}＝M_{Carbon source}×η_{Carbon source}×BOD_{Carbon source}×EF_{CO2 external carbon source} (4)

＝0.9×M_{Carbon source}×η_{Carbon source}

In the formula, E_{CO2 external carbon source}CO converted with external carbon source₂Emission tCO₂A month; m_{Carbon source}Adding an additional carbon source for t/month; eta_{Carbon source}-the content of active ingredients of the external carbon source; BOD_{Carbon source}-oxygen equivalent of the external carbon source; EF_{CO2 external carbon source}Conversion of CO by external carbon source₂Class theory conversion rate, 0.9kgCO is taken₂/kgBOD_{Carbon source}(ii) a Wherein M is_{Carbon source}、η_{Carbon source}、BOD_{Carbon source}And selecting according to the actual operation condition of the sewage treatment plant.

Furthermore, the sludge sanitary landfill carbon emission E_{Sanitary landfill}The C, N element from the sludge will produce CH in the sanitary landfill₄Therefore, the measurement formula is as follows:

EF_{CH4, sanitary landfill}＝MCF×DOC×DOC_F×F×16/12＝0.15kgCH₄/kg of dry mud (5) formula, EF_{CH4, sanitary landfill}Sanitary landfill CH₄An emission factor; MCF-a methane production correction factor, and taking 0.92 according to actual sludge and sludge quality in China; DOC-proportion of decomposable organic carbon in the sludge; DOC_FCan be decomposed into CH₄DOC proportion of (1); F-CH₄The proportion in the landfill gas; 1.33-CH₄And C molecular weight ratio%; DOC, DOC_FF and F both adopt IPCC guideline recommended values which are respectively 0.5kgC_DOCPer kg of dry sludge and 0.5kgtCH₄-C/kg C_DOC；

Based on equation (5) it follows:

M_{CH4, sanitary landfill}＝[ω_{Sanitary landfill}×Q_w×(1-γ)×EF_{CH4, sanitary landfill}－R_{CH4, sanitary landfill}]×(1－OX) (6)

＝0.14×ω_{Sanitary landfill}×Q_w×(1-γ)

In the formula, M_{CH4, sanitary landfill}Sludge sanitary landfill link CH₄Discharge tCH₄A month; omega_{Sanitary landfill}-sludge landfill rate%; q_w-the amount of dewatered sludge t/month; gamma-water content of sludge; r_{CH4, sanitary landfill}Sludge landfill CH₄Taking the recovery amount of 0; OX is the oxidation factor of carbon in sludge; omega_{Sanitary landfill}The actual sanitary landfill amount and the sludge treatment total amount of a sewage treatment plant can be obtained by simple calculation; r_CH4,_{Sanitary landfill}Taking 0 and generally not counting in a sewage plant; OX adopts IPCC guideline recommended value, and 0.1 is taken;

combining equation (5) and equation (6) yields:

E_{sanitary landfill}＝G_CH4×M_{CH4, sanitary landfill}＝21×M_{CH4, sanitary landfill} (7)

＝2.94×ω_{Sanitary landfill}×Q_w×(1-γ)

In the formula, E_{Sanitary landfill}Sludge landfill CH₄Carbon-like emissions tCO₂A month; g_CH4—CH₄Based on the global warming potential on the scale of one century, the value of (A) is 21tCO₂/tCH₄。

Moreover, the carbon emission E in the sludge land utilization link_{Land utilization}Middle requirement for CH₄Emission amount and N₂The O emission is calculated by adopting an emission coefficient method, and CH is utilized in land₄The emission coefficient of (A) is 0.003kgCH₄Per kg of dry mud, N₂The emission coefficient of O is 0.017kgN₂O/kg dry mud, and the N content of the cytoplasm of the mud is 0.12, so the CH of the mud land is utilized₄、N₂The O emission measurement formula is as follows:

M_{CH4 land utilization}＝ω_{Land utilization}×Q_w×(1-γ)×EF_{CH4 land utilization} (8)

＝3×10^-3×ω_{Land utilization}×Q_w×(1-γ)

M_{N2O land utilization}＝ω_{Land utilization}×Q_w×(1-γ)×f×_N×EF_N2O-N_{Land utilization}×44/28 (9)

＝1.2×10^-3×ω_{Land utilization}×Q_w×(1-γ)

In the formula: m_{CH4 land utilization}—CH₄Discharge capacity; omega_{Land utilization}-sludge land utilization; m_{N2O land utilization}—N₂O discharge amount; EF_CH4,_{Land utilization}Land utilization CH₄The discharge coefficient of (a); EF_N2O-N_{Land utilization}Land utilization N₂The emission coefficient of O;_Ntaking the content of cytoplasmic N of the sludge to be 0.12;

therefore, the carbon emission in the sludge land utilization link can be calculated according to the following formula:

E_{land utilization}＝G_CH4×M_{CH4 land utilization}+G_N2O×M_{N2O land utilization}＝21×M_{CH4 land utilization}+298×M_{N2O land utilization}＝0.42×ω_{Land utilization}×Q_w×(1-γ) (10)

In the formula, E_{Land utilization}Carbon emission tCO for land utilization of sludge₂A month; m_{CH4 land utilization}Sludge land utilization CH₄Yield tCH₄A month; m_{N2O land utilization}Sludge land utilization N₂O production tN₂O/month; the land utilization amount of the sludge and the total amount of the sludge are measured by a sewage treatment plant.

Furthermore, the operation power consumption and carbon emission E of the sewage treatment plant_{Electric energy}Used for conveying, mixing, oxygen supply, sludge dewatering and special substance O of sewage and sludge₃、ClO₂The on-site preparation equipment is operated, and the average value is taken to be 0.94tCO₂the/MW-h is taken as the carbon emission factor of the electric energy production, and the carbon emission of the electric energy production can be calculated according to the following formula:

E_{electric energy}＝D×EF_D×10^-3＝9.4×10^-4×D (11)

In the formula, E_{Electric energy}-carbon emission tCO from running power consumption of sewage treatment plant₂A month; d, using kW.h/month of electric power; EF_D-carbon emission factor for electric energy production, value 0.94tCO₂/MW·h。

Furthermore, the carbon emission E of the production process of the medicament required by the sewage treatment plant_{Pharmaceutical production}Comprises the carbon emission generated in the production process of an additional carbon source, a phosphorus removal medicament and a sludge dewatering medicament, wherein the carbon emission factor of methanol can be 1.54kgCO₂The carbon emission factors of the methanol, the phosphorus removal agent and the dehydration agent can be 25 kgCO/kg₂The carbon emission factor EF lime of lime can be 1.74kg/kg lime, so that the carbon emission E medicament production of the medicament production can be calculated according to the following formula:

E_{pharmaceutical production}＝M_{Carbon source}×EF_{Carbon source}+M_{Phosphorus removal medicament}×EF_{Phosphorus removal medicament}+M_{Dehydration medicament}×EF_{Dehydration medicament} (12)

In the formula, E_{Pharmaceutical production}Carbon emission tCO in medicament production₂A/t agent; m_{Carbon source}、M_{Phosphorus removal medicament}、M_{Dehydration medicament}-dose t/month; EF_{Carbon source}-carbon emission factor of a carbon source of a sewage treatment plant; EF_{Phosphorus removal medicament}-carbon emission factor of a phosphorus removal agent of a sewage treatment plant; EF_{Dehydration medicament}-carbon emission factor of dewatering agent of sewage treatment plant; EF_{Carbon source}、EF_{Phosphorus removal medicament}、EF_{Dehydration medicament}The determination is carried out according to the type of the medicament selected by the actual operation of the sewage treatment plant.

Moreover, the water quality improves the carbon emission reduction J_{Water quality improvement}Middle CH₄、N₂The emission factor of O is 0.06kgCH respectively₄/kgBOD、0.008kgN₂O/kgTN, 0.06kgCH will be discharged to atmosphere every time 1kgBOD or 1kgTN is discharged to receiving water₄、0.008kgN₂O, so the carbon emission reduction formula generated by water quality improvement is as follows:

J_{water quality improvement}＝[Q×(BOD_{Inflow water}－BOD_{Discharging water})×G_CH4×EF_{CH4, water body}+Q×(TN_{Inflow water}－TN_{Discharging water})×G_N2O×EF_{N2O, water body}]×10^-2 (13)

In the formula: j. the design is a square_{Water quality improvement}Water quality raising carbon emission reduction tCO₂A month; BOD_{Inflow water}、BOD_{Discharging water}The BOD content mg/L of the inlet water and the outlet water of the sewage plant; EF_{CH4, water body}Discharge of 1kgBOD from a Sewage treatment plant into the receiving water and discharge of CH to the atmosphere₄The value of (1) is 0.06kgCH₄/kgBOD；EF_{N2O, water body}Discharging 1kgTN into receiving water body by sewage treatment plant, and discharging N into atmosphere₂The amount of O is 0.008kgN₂O/kgTN；

The simplified equation (13) is as follows:

J_{water quality improvement}＝0.0126×Q×(BOD_{Inflow water}－BOD_{Discharging water})+0.02368×Q×(TN_{Inflow water}－TN_{Discharging water})。 (14)

Moreover, anaerobic digestion of sludge with carbon reduction J_{Anaerobic digestion}Middle CH₄The yield was calculated according to the form of the chemometric equation derived from the Buswell-Mueller general formula:

C₅H₇O₂N+1.33H₂O→1.67CH₄+NH₃+3.33CO₂

further, the calculation formula for carbon emission reduction in anaerobic sludge digestion treatment is as follows:

ΔVSS_{anaerobic digestion}＝Q_W×(1-γ)×f×β_VSS/(1-β_VSS)

J_{Anaerobic digestion}＝_{Anaerobic digestion}×G_CH4×(_{Filling in land}×ΔVSS_{Anaerobic digestion}×EF_{CH4, landfill}+_{Soil (W) for building}×ΔVSS_{Anaerobic digestion}×EF_{CH4, land}) (15)

In the formula: j. the design is a square_{Anaerobic digestion}Carbon reduction of anaerobic sludge digestion process, tCO₂A month;_{anaerobic digestion}，_{Sanitary landfill}、_{Land utilization}-sludge treatment measure selection parameters; f, taking the proportion of the organic components of the sludge to be 0.6; delta VSS_{Anaerobic digestion}Removing the organic components in the anaerobic digestion process of the sludge for t/month; beta is a_VSSThe removal rate of organic components in the anaerobic digestion process of the sludge is 54.5 percent; EF_{CH4, landfill}-sanitary landfill CH₄Coefficient of release, EF_{CH4, land}CH for land use₄A release factor;

in addition, EF_{CH4, landfill}The value is 0.16; EF_{CH4, land}The value is 0.003; beta is a_VSSThe value is 54.5%; f is 0.6; equation (15) reduces to:

J_{anaerobic digestion}＝_{Anaerobic digestion}×Q_w×(1-γ)(2.414×_{Sanitary landfill}+0.045×_{Land utilization})。 (16)

Moreover, the sludge aerobic digestion carbon emission reduction amount J_{Aerobic digestion}The calculation formula of (a) is as follows:

ΔVSS_{aerobic digestion}＝Q_W×(1-γ)×f×α_VSS/(1-α_VSS)

J_{Aerobic digestion}＝_{Aerobic digestion}×G_CH4×(_{Filling in land}×ΔVSS_{Aerobic digestion}×EF_{CH4, landfill}+_{Soil (W) for building}×ΔVSS_Aerobic×EF_{CH4, land}) (17)

Δ VSS in the above equation_{Aerobic digestion}Removing organic components in the aerobic digestion process of the sludge for t/month; alpha is alpha_VSS50% of organic component removal rate in the sludge aerobic digestion process; j. the design is a square_{Aerobic digestion}Carbon reduction of aerobic sludge digestion process, tCO₂A month;_{aerobic digestion}-sludge treatment process selection parameters; therefore, the above formula is simplified as follows:

J_{aerobic digestion}＝_{Aerobic digestion}×Q_w×(1-γ)×(2.016×_{Sanitary landfill}+0.038×_{Land utilization})。 (18)

Furthermore, sludge land utilization as soil fertilizer carbon emission reduction J_{Soil fertilizer}The calculation formula of (a) is as follows:

J_{soil fertilizer}＝ω_{Land utilization}×Q_w×1-γ×f×EF_{Natural gas}×2.8×0.61×_N×EF_{Ammonium nitrate}+3.8×0.7×_P×EF_{Superphosphate}×10^-3 (19)

In the formula, J_{Soil fertilizer}Carbon emission reduction tCO for replacing chemical fertilizer by sludge land utilization₂A month; 2.8, 3.8-NH₄NO₃And N, Ca (H)₂PO₄)₂Molecular ratio to P; EF_{Natural gas}Carbon emission factor tCO of natural gas₂TJ, value 51.6; EF_{Ammonium nitrate}Energy consumption of ammonium nitrate production; EF_{Superphosphate}Energy is consumed for the production of the calcium superphosphate;_Nthe content of N in sludge cells is 0.12, wherein 61 percent of N can be utilized by plants;_Pthe content of the sludge cell P is 0.02, wherein the content can be utilized by plants by 70%; the above formula is simplified as follows:

J_{soil fertilizer}＝0.0068×ω_{Land utilization}×Q_w×1-γ。 (20)

The invention has the advantages and technical effects that:

the carbon emission model calculation method based on the whole process link of town sewage treatment combines the system characteristics of the town sewage treatment plant and uses E_{Denitrification of sewage}、E_{Sanitary landfill}、E_{Land utilization}、E_{Electric energy}、E_{Production of medicine machine}、J_{Water quality improvement}、J_{Anaerobic digestion}、J_{Aerobic digestion}And J_{Soil fertilizer}As the main calculation parameter, CH generated by a sewage treatment system₄、N₂O, CO produced by biological metabolism₂And CO produced by energy consumption₂As the object of study, pair A²The carbon emission of sewage treatment systems and sludge treatment and disposal systems represented by/O was subjected to accounting and research.

The invention discloses a carbon emission model calculation method based on a whole-flow link of town sewage treatment, which is characterized in that a comprehensive energy-saving and emission-reducing calculation method of the whole-flow of town sewage treatment based on carbon emission is established in a system, a carbon emission accounting method and a carbon emission accounting model for sewage treatment and sludge treatment are provided, and reference is provided for later-stage bidding project decision of a sewage treatment plant and environmental impact analysis of an engineering design scheme.

Drawings

FIG. 1 is a schematic diagram of a measuring and calculating boundary of carbon emission in the standard-extracting operation of a municipal wastewater treatment plant according to the present invention;

FIG. 2 shows a²An analysis diagram of the carbon emission source of the operation of the/O sewage plant;

FIG. 3 is a schematic view of the anaerobic sludge digestion process of the present invention;

FIG. 4 is a schematic diagram of the aerobic digestion process of sludge according to the present invention.

Detailed Description

For a further understanding of the contents, features and effects of the present invention, reference will now be made to the following examples, which are to be considered in conjunction with the accompanying drawings. It should be noted that the present embodiment is illustrative, not restrictive, and the scope of the invention should not be limited thereby.

The technical scheme adopted by the invention is that a carbon emission model calculation method based on the whole process links of town sewage treatment is shown in figure 1, the research range of carbon emission change is calculated in the upgrading operation of a town sewage treatment plant, and carbon emission or carbon emission reduction occurs in each link of sewage treatment, sludge treatment and disposal, tail water emission and reclaimed water utilization. The method is based on the currently generally adopted main process (A)²And (4) analyzing the carbon emission of the/O) unit, and providing a comprehensive measuring and calculating method for energy conservation and emission reduction in the whole process. And figure 2 lists the carbon emissions for each process unit and table 1 lists the carbon emission sources for each process unit.

TABLE 1A²Analysis of operating carbon emission source of/O sewage plant

According to analysis by combining with the carbon emission path of the sewage plant, the net carbon emission (W) in the operation stage of the sewage plant refers to the carbon emission (E) in the operation stage of the sewage plant_{Carbon row}) Deducting carbon emission (J)_{Emission reduction}). Carbon emission (E)_{Carbon row}) Refers to the direct carbon emission (E)_{Direct connection}) And indirect carbon emission (E)_{Indirect connection}) The sum of (a) and (b). Direct carbon emissions can be broken down intoCarbon emission (E) in the denitrification step of wastewater_{Denitrification of sewage}) Sanitary landfill of sludge (E)_{Sanitary landfill}) Carbon emission (E) in the sludge land utilization link_{Land utilization}). Indirect carbon emission (E)_{Indirect connection}) The power consumption of sewage treatment plants is mainly considered (E)_{Electric energy}) And the agents used (E)_{Pharmaceutical production}) Indirectly resulting in carbon emissions. Carbon emission reduction (J)_{Emission reduction}) Can be decomposed into water quality according to the implementation way to improve carbon emission reduction (J)_{Water quality improvement}) Carbon emission reduction (J) for anaerobic sludge digestion_{Anaerobic digestion}) Carbon emission reduction (J) in sludge aerobic digestion process_{Aerobic digestion}) And sludge land utilization as soil fertilizer carbon emission reduction (J)_{Soil fertilizer}). In summary, the basic form of the sewage plant operation carbon emission measurement formula can be written as the following equation system:

W＝E_{carbon row}－J_{Emission reduction}

E_{Carbon row}＝E_{Direct connection}+E_{Indirect connection}

E_{Direct connection}＝E_{Denitrification of sewage}+E_{Sanitary landfill}+E_{Land utilization}

E_{Indirect connection}＝E_{Electric energy}+E_{Production of medicine machine}·

J_{Emission reduction}＝J_{Water quality improvement}+J_{Anaerobic digestion}+J_{Aerobic digestion}+J_{Soil fertilizer}

The invention is also characterized by a calculation formula derivation process:

1 derivation of calculation formula

1.1 direct carbon emissions (E)_{Direct connection}) Measurement and calculation process

1.1.1 carbon emission (E) in the denitrification step of wastewater_{Denitrification of sewage})

Two carbon discharge ways exist in the sewage denitrification process, one is N released in the sewage treatment process₂O, the second is that the added carbon in the sewage treatment is converted into CO by the utilization of microorganisms₂。

(1)N₂Carbon O-type emission (E)_{N2O, Sewage treatment})

Either as a by-product of the nitration process or as a denitrification processThe intermediate products in the process are released, the release process is influenced by a plurality of factors such as process types, carbon-nitrogen ratios, DO concentration, monitoring methods and the like, and a unified calculation method is not formed yet. N is a radical of₂The estimation of O release is usually based on empirical conversion, where the IPCC guidelines recommend a value of 0.008kgN₂O/kgN～0.39kgN₂Between O/kgN, and simultaneously, by inoculating the sludge of the actual sewage plant, the N under different conditions is measured₂The average conversion of O was 0.04kgN₂O/kgTN, taking N in view of the actual characteristics of domestic sewage₂The conversion of O was 0.04kgN₂O/kgTN calculation of sewage treatment Process N₂The amount of O produced is shown by the following formula:

M_{N2O, Sewage treatment}＝Q×(TN_{Inflow water}－TN_{Discharging water})×EF_{N2O, Sewage treatment}×10^-2

＝4×10^-4×Q×(TN_{Inflow water}－TN_{Discharging water})

In the formula M_{N2O, Sewage treatment}Sewage treatment Process N₂O production (tN)₂O/month); q-amount of treated Water of Sewage treatment plant (ten thousand meters)³A/month); TN (twisted nematic)_{Inflow water}、TN_{Discharging water}Inlet and outlet water TN concentrations (mg/L); EF_{N2O, Sewage treatment}—N₂O conversion, 0.04kgN₂O/kgTN。

According to N₂O's global warming potential on a hundred year scale, so N₂Carbon O-type emission (E)_{N2O, Sewage treatment}) Can be written as:

E_{N2O, Sewage treatment}＝G_N2O×M_{N2O, Sewage treatment}＝0.1184×Q×(TN_{Inflow water}－TN_{Discharging water})

In the formula, E_{N2O, Sewage treatment}Sewage treatment step N₂Carbon emissions of O type (tCO)₂A/month); g_N2O—N₂Taking 296tCO based on the global warming potential of O on a hundred-year scale₂/tN₂O。

(2)CO₂Carbon-like emissions (E)_{CO2 external carbon source})

The added carbon source is used as an electron donor and is oxidized into alkalinity (HCO) in the denitrification process₃ ^-) Is converted into CO in the nitration process₂. The stoichiometric equation of the nitrification and denitrification process is as follows:

and (3) denitrification process:

NO₃ ^－+1.08CH₃OH+0.24H₂CO₃→0.056C₅H₇O₂N+0.47N₂+1.68H₂O+HCO₃ ^-

and (3) nitration process:

NH₄ ⁺+1.83O₂+1.98HCO₃ ^-→0.02C₅H₇O₂N+1.04H₂O+0.98NO₃ ^－+1.88H₂CO₃

the stoichiometric equations of the nitrification and denitrification processes are combined into:

NH₄ ⁺+NO₃ ^－+1.83O₂+2.14CH₃OH→0.13C₅H₇O₂N+5.77H₂O+1.4CO₂+0.93N₂

calculated to produce 0.9kgCO per 1kg of methanol consumed₂. When the methanol oxygen equivalent (1.5mg/mg) is combined, CO of an external carbon source (calculated by oxygen equivalent) is added in the denitrification process₂Theoretical conversion of 0.9kgCO₂/kgBOD_{Carbon source}. Conversion of CO by external carbon source₂The carbon-like emissions can be calculated as follows (in methanol):

E_{CO2 external carbon source}＝M_{Carbon source}×η_{Carbon source}×BOD_{Carbon source}×EF_{CO2 external carbon source}

＝0.9×M_{Carbon source}×η_{Carbon source}

In the formula, E_{CO2 external carbon source}CO converted with external carbon source₂Emission (tCO)₂A/month); m_{Carbon source}-the amount of added carbon source (t/month); eta_{Carbon source}-the content (%) of active ingredients of the external carbon source; BOD_{Carbon source}-oxygen equivalent of the external carbon source; EF_{CO2 external carbon source}Conversion of CO by external carbon source₂Class theory conversion rate, 0.9kgCO is taken₂/kgBOD_{Carbon source}。M_{Carbon source}、η_{Carbon source}、BOD_{Carbon source}The selection can also be carried out according to the actual operation condition of the sewage treatment plant.

1.1.2 sludge sanitary landfill carbon emission (E)_{Sanitary landfill})

C, N elements in the sludge will generate CH in the sanitary landfill link₄The treatment process can produce carbon emission effects. Aiming at estimating the carbon emission of the sludge sanitary landfill, IPCC guidelines provide two methods, namely a mass balance method and a first-order attenuation method. The first-order decay method needs monitoring data of a sludge landfill for more than 50 years, and the calculation method is not suitable for China, so the mass balance method is adopted. Sanitary landfill CH₄The emission factor adopts an IPCC guideline recommendation formula:

EF_{CH4, sanitary landfill}＝MCF×DOC×DOC_F×F×16/12＝0.15kgCH₄Per kg of dry mud

In the formula, EF_{CH4, sanitary landfill}Sanitary landfill CH₄An emission factor; MCF-a methane production correction factor, and taking 0.92 according to actual sludge and sludge quality in China; DOC-proportion (%) of decomposable organic carbon in the sludge; DOC_FCan be decomposed into CH₄DOC ratio (%); F-CH₄Proportion in landfill gas (%); 1.33-CH₄And C molecular weight ratio (%). DOC, DOC_FF and F both adopt IPCC guideline recommended values which are respectively 0.5kgC_DOCPer kg of dry mud, 0.5kgtCH₄-C/kg C_DOC、0.5。

Based on the method, the actual sludge treatment way and the treatment amount information of the sewage treatment plant in China are combined, and the CH is buried in the sludge₄The emission measurement formula is shown as the following formula:

M_{CH4, sanitary landfill}＝[ω_{Sanitary landfill}×Q_w×(1-γ)×EF_{CH4, sanitary landfill}－R_{CH4, sanitary landfill}]×(1－OX)

＝0.14×ω_{Sanitary landfill}×Q_w×(1-γ)

In the formula, M_{CH4, sanitary landfill}Sludge sanitary landfill link CH₄Discharge capacity (tCH)₄A/month); omega_{Sanitary landfill}-sludge landfill rate (%); q_w-amount of dewatered sludge (t >Month); gamma-sludge moisture content (%); r_{CH4, sanitary landfill}Sludge landfill CH₄Taking the recovery amount of 0; OX is the oxidation factor of carbon in sludge. Omega_{Sanitary landfill}The actual sanitary landfill amount and the sludge treatment total amount of a sewage treatment plant can be obtained by simple calculation; r_{CH4, sanitary landfill}Taking 0 (generally not counted in a sewage plant); OX adopted IPCC guideline recommended value, and 0.1 is taken.

Sludge landfill CH₄The formula for measuring and calculating the carbon-like emission is shown as the following formula:

E_{sanitary landfill}＝G_CH4×M_{CH4, sanitary landfill}＝21×M_{CH4, sanitary landfill}

＝2.94×ω_{Sanitary landfill}×Q_w×(1-γ)

In the formula, E_{Sanitary landfill}Sludge landfill CH₄Carbon-like emissions (tCO)₂A/month); g_CH4—CH₄Based on the global warming potential on the scale of one century, the value of (A) is 21tCO₂/tCH₄(ii) a The other indicators have the same meanings as above.

1.1.3 sludge land utilization link carbon emission (E)_{Land utilization})。

Carbon emission in the sludge land utilization link is mainly CH₄And N₂And discharging in the form of O. CH (CH)₄Emission amount and N₂And the O emission is calculated by adopting an emission coefficient method. Land utilization CH₄The emission coefficient of (A) is 0.003kgCH₄Per kg of dry mud, N₂The emission coefficient of O is 0.017kgN₂O/kg dry sludge, wherein the content of N in the cytoplasm of the sludge can be 0.12, and the CH for land utilization of the sludge is combined with the actual sludge treatment way and treatment amount information of the sewage treatment plant in China₄、N₂The O emissions can be written as:

M_{CH4 land utilization}＝ω_{Land utilization}×Q_w×(1-γ)×EF_{CH4 land utilization}

＝3×10^-3×ω_{Land utilization}×Q_w×(1-γ)

M_{N2O land utilization}＝ω_{Land utilization}×Q_w×(1-γ)×f×_N×EF_{N2O-N, land benefitBy using}×44/28

＝1.2×10^-3×ω_{Land utilization}×Q_w×(1-γ)

In the formula: m_{CH4 land utilization}—CH₄Discharge capacity; omega_{Land utilization}-sludge land utilization; m_{N2O land utilization}—N₂O discharge amount; EF_{CH4 land utilization}Land utilization CH₄The discharge coefficient of (a); EF_{N2O-N, land utilization}Land utilization N₂The emission coefficient of O;_N-sludge cytoplasmic N content, 0.12. Other indicators are as defined above.

Therefore, the carbon emission in the sludge land utilization link can be calculated according to the following formula:

E_{land utilization}＝G_CH4×M_{CH4 land utilization}+G_N2O×M_{N2O land utilization}＝21×M_{CH4 land utilization}+298×M_{N2O land utilization}＝0.42×ω_{Land utilization}×Q_w×(1-γ)

In the formula, E_{Land utilization}Carbon emission (tCO) for land utilization of sludge₂A/month); m_{CH4 land utilization}Sludge land utilization CH₄Yield (tCH)₄A/month); m_{N2O land utilization}Sludge land utilization N₂O production (tN)₂O/month). The land utilization amount of the sludge and the total sludge treatment amount can be obtained by actual calculation of a sewage treatment plant. Other indicators are as defined above.

1.2 Indirect carbon emission (E)_{Indirect connection}) Measurement and calculation process

1.2.1 operating power consumption carbon emission of sewage treatment plant (E)_{Electric energy})

The energy consumption required by the operation of the sewage plant is mainly electric energy, wherein the electric energy consumption is mainly used for conveying, mixing and oxygen supply of sewage and sludge, sludge dehydration and special substances (O)₃、ClO₂) And equipment such as field preparation and the like is operated.

The 2016 published emission factor (survey draft) of regional grid baseline in China, published by the national development and transformation committee, provides emission factors of carbon in electric energy production in the regions of north China, northeast China, east China, northwest China and south China, and the average emission factor is takenValue 0.94tCO₂the/MW-h is taken as the carbon emission factor of the electric energy production, and the carbon emission of the electric energy production can be calculated according to the following formula:

E_{electric energy}＝D×EF_D×10^-3＝9.4×10^-4×D

In the formula, E_{Electric energy}Power consumption carbon emission (tCO) for operation of a wastewater treatment plant₂A/month); d, power consumption (kW.h/month); EF_D-carbon emission factor for electric energy production, value 0.94tCO₂/MW·h。

1.2.2 carbon emissions from the production of chemicals required by wastewater treatment plants (E)_{Pharmaceutical production})

The medicaments required by the operation of the sewage plant comprise an external carbon source, a phosphorus removal medicament, a sludge dehydration medicament and the like. The emission factor of greenhouse gases in the production process of the medicaments can be obtained from related documents, for example, the carbon emission factor of methanol can be 1.54kgCO₂The carbon emission factors of the methanol, the phosphorus removal agent and the dehydration agent can be 25 kgCO/kg₂Carbon Emission Factor (EF) of/kg coagulant, lime_Lime) 1.74kg/kg lime can be taken, etc. Carbon emissions from pharmaceutical production (E)_{Pharmaceutical production}) Can be calculated as follows:

E_{pharmaceutical production}＝M_{Carbon source}×EF_{Carbon source}+M_{Phosphorus removal medicament}×EF_{Phosphorus removal medicament}+M_{Dehydration medicament}×EF_{Dehydration medicament}

In the formula, E_{Pharmaceutical production}Carbon emissions from pharmaceutical manufacturing (tCO)₂A/t agent); m_{Carbon source}、M_{Phosphorus removal medicament}、M_{Dehydration medicament}-dose (t/month); EF_{Carbon source}-carbon emission factor of a carbon source of a sewage treatment plant; EF_{Phosphorus removal medicament}-carbon emission factor of a phosphorus removal agent of a sewage treatment plant; EF_{Dehydration medicament}-carbon emission factor of dewatering agent of sewage treatment plant. EF_{Carbon source}、EF_{Phosphorus removal medicament}、EF_{Dehydration medicament}The determination is carried out according to the type of the medicament selected by the actual operation of the sewage treatment plant.

1.3 carbon emission reduction (J)_{Emission reduction}) Measurement and calculation process

Carbon reduction (J)_{Emission reduction}) According to the implementationRadial decomposition into water quality to promote carbon emission reduction (J)_{Water quality improvement}) Anaerobic sludge digestion carbon emission reduction (J)_{Anaerobic digestion}) Carbon emission reduction in sludge aerobic digestion process (J)_{Aerobic digestion}) And carbon reduction as soil fertilizer for sludge land utilization (J)_{Soil fertilizer})。

1.3.1 Water quality improvement carbon emission reduction (J)_{Water quality improvement})

The carbon emission reduction of the water environment caused by the improvement of the water quality, and the influence of a sewage treatment plant on the environment are positive overall effects. The receiving water body discharges greenhouse gases to the atmosphere. If the sewage is directly discharged to the receiving water body, the amount of the greenhouse gas discharged to the atmosphere is counted as E₁(ii) a The amount of greenhouse gas discharged to the atmosphere is calculated as E₂(ii) a Then the carbon emission reduction brought by water quality promotion and recycling is J ═ E₁-E₂。

According to the IPCC guidelines, the surface water CH₄、N₂The discharge factor of O is provided based on BOD and TN quality discharged into receiving water body, and 0.06kgCH is taken respectively₄/kgBOD、0.008kgN₂O/kgTN. Discharging 0.06kgCH into the atmosphere when discharging 1kgBOD or 1kgTN into the receiving water body₄、0.008kgN₂And O. The carbon emission reduction formula generated by water quality improvement is as follows:

J_{water quality improvement}＝[Q×(BOD_{Inflow water}－BOD_{Discharging water})×G_CH4×EF_{CH4, water body}+Q×(TN_{Inflow water}－TN_{Discharging water})×G_N2O×EF_{N2O, water body}]×10^-2

In the formula: j. the design is a square_{Water quality improvement}Water quality carbon emission reduction (tCO)₂A/month); BOD_{Inflow water}、BOD_{Discharging water}BOD content (mg/L) in the inlet water and the outlet water of the sewage plant; EF_{CH4, water body}Discharge of 1kgBOD from a Sewage treatment plant into the receiving water and discharge of CH to the atmosphere₄The value of (1) is 0.06kgCH₄/kgBOD；EF_{N2O, water body}Discharging 1kgTN into receiving water body by sewage treatment plant, and discharging N into atmosphere₂The amount of O is 0.008kgN₂O/kgTN; other indicators are as defined above.

The formula is simplified as follows:

J_{water quality improvement}＝0.0126×Q×(BOD_{Inflow water}－BOD_{Discharging water})+0.02368×Q×(TN_{Inflow water}－TN_{Discharging water})

1.3.2 sludge digestion carbon reduction (J)_{Anaerobic digestion}、J_{Aerobic digestion})

Carbon emission reduction in the process of sludge anaerobic digestion and biogas recovery refers to that after sludge is subjected to anaerobic digestion or aerobic digestion treatment, organic components are reduced, so that CH is discharged into the atmosphere in the treatment links of sanitary landfill or land utilization and the like₄The amount is reduced. Therefore, the calculation of the partial carbon emission reduction amount is divided into two stages, namely, the calculation of the reduction amount of the organic components of the sludge is carried out, and theoretical calculation is carried out according to the stoichiometry of the sludge digestion process; secondly, the reduction amount of the organic components of the sludge can generate CH in the sludge disposal link₄And (4) calculating the quantity. In the total electricity consumption data of the sewage treatment plant, the electricity generation amount of the part of energy recovery is deducted, and the value of the energy recovery cannot be counted in, otherwise, the process is repeated. The following FIGS. 3 and 4 show the anaerobic sludge digestion process and the aerobic sludge digestion process, respectively.

(1) Carbon reduction by anaerobic digestion of sludge (J)_{Anaerobic digestion})

The sludge treatment link mainly considers CH generated in the anaerobic digestion process of sludge₄And then collected for use. The essence of anaerobic digestion is anaerobic degradation of sludge cytoplasm, CH₄The yield was calculated according to the form of the chemometric equation derived from the Buswell-Mueller general formula:

C₅H₇O₂N+1.33H₂O→1.67CH₄+NH₃+3.33CO₂

further deducing a calculation formula for carbon emission reduction in anaerobic sludge digestion treatment as follows:

ΔVSS_{anaerobic digestion}＝Q_W×(1-γ)×f×β_VSS/(1-β_VSS)

J_{Anaerobic digestion}＝_{Anaerobic digestion}×G_CH4×(_{Filling in land}×ΔVSS_{Anaerobic digestion}×EF_{CH4, landfill}+_{Soil (W) for building}×ΔVSS_{Anaerobic digestion}×EF_{CH4, land})

J_{Anaerobic digestion}Carbon reduction of anaerobic sludge digestion process, tCO₂A month;_{anaerobic digestion}，_{Sanitary landfill}、_{Land utilization}-sludge treatment measure selection parameters; f, taking the proportion of the organic components of the sludge to be 0.6; delta VSS_{Anaerobic digestion}Removing the organic components in the anaerobic digestion process of the sludge for t/month; beta is a_VSSAnd the removal rate of organic components in the anaerobic digestion process of the sludge is 54.5 percent. EF_{CH4, landfill}-sanitary landfill CH₄Coefficient of release, EF_{CH4, land}CH for land use₄The release factor. Other indicators are as defined above.

Method according to IPCC guidelines, EF_{CH4, landfill}The value is 0.16; EF_{CH4, land}The value is 0.003; beta is a_VSSThe value is 54.5%; f is 0.6. The above formula is simplified as follows:

J_{anaerobic digestion}＝_{Anaerobic digestion}×Q_w×(1-γ)(2.414×_{Sanitary landfill}+0.045×_{Land utilization})

(2) Sludge aerobic digestion carbon emission reduction (J)_{Aerobic digestion})

The following calculation formula for reducing the carbon emission of the sludge aerobic digestion can be obtained by the same method:

ΔVSS_{aerobic digestion}＝Q_W×(1-γ)×f×α_VSS/(1-α_VSS)

J_{Aerobic digestion}＝_{Aerobic digestion}×G_CH4×(_{Filling in land}×ΔVSS_{Aerobic digestion}×EF_{CH4, landfill}+_{Soil (W) for building}×ΔVSS_Aerobic×EF_{CH4, land})

Δ VSS in the above equation_{Aerobic digestion}Removing organic components in the aerobic digestion process of the sludge for t/month; alpha is alpha_VSS50% of organic component removal rate in the sludge aerobic digestion process; j. the design is a square_{Aerobic digestion}Carbon reduction of aerobic sludge digestion process, tCO₂A month;_{aerobic digestion}-sludge treatment process selection parameters; . Other indicators have the meaning given above. The above formula is simplified as follows:

J_{aerobic digestion}＝_{Aerobic digestion}×Q_w×(1-γ)×(2.016×_{Sanitary landfill}+0.038×_{Land utilization})

1.3.3 sludge land utilization carbon emission reduction (J) as soil fertilizer_{Soil fertilizer})

The sludge N, P can be used by plants to replace ammonium nitrate, calcium superphosphate and other fertilizer raw materials. According to estimation, the sludge land utilization can increase the plant carbon fixation amount by 12-137%. The energy consumption for producing the ammonium nitrate and the calcium superphosphate is 1GJ/t ammonium nitrate and 1.3GJ/t calcium superphosphate respectively, and the content of the N in the sludge cells is combined_N) 0.12% (61% available to plants), P content: (_P) 0.02 (70% of the available for plants), the carbon emission reduction of the sludge land utilization alternative fertilizer is as follows:

J_{soil fertilizer}＝ω_{Land utilization}×Q_w×(1-γ)×f×EF_{Natural gas}×(2.8×0.61×_N×EF_{Ammonium nitrate}+3.8×0.7×_P×EF_{Superphosphate})×10^-3

In the formula, J_{Soil fertilizer}Carbon emission reduction (tCO) of sludge land utilization alternative fertilizer₂A/month); 2.8, 3.8-NH₄NO₃And N, Ca (H)₂PO₄)₂Molecular ratio to P; EF_{Natural gas}Carbon emission factor (tCO) of natural gas₂TJ), the value is 51.6; EF_{Ammonium nitrate}Energy consumption of ammonium nitrate production; EF_{Superphosphate}Energy is consumed for the production of the calcium superphosphate;_Nthe content of N in sludge cells is 0.12, wherein 61 percent of N can be utilized by plants;_Pthe content of the sludge cell P is 0.02, wherein the content can be utilized by plants by 70 percent. Other indicators have the meaning given above. The above formula is simplified as follows:

J_{soil fertilizer}＝0.0068×ω_{Land utilization}×Q_w×(1-γ)

1.4 summary of the respective sub-terms basic Algorithm

The summary of the elementary algorithms for each sub-term is shown in table 2 below.

TABLE 2 calculation method of each subentry

2 analysis of carbon emission change in upgrading operation of sewage treatment plant

At present, the upgrading and modification of a sewage treatment plant mainly have two ways: firstly, adding a biological carbon source and a phosphorus removal agent, and secondly, adding advanced treatment processes such as ozone activated carbon and the like. Although the water quality of sewage plants is gradually improved, the input energy consumption and material consumption, equipment engineering and labor cost are increased year by year, and further the carbon emission is increased. The establishment of the carbon emission increment model taking sludge increase, additional carbon source, phosphorus removal agent and power consumption increase as the core can provide reference for environmental capacity stability, emission standard formulation and government decision. The improvement of the effluent quality of the sewage plant from the first grade B to the first grade A is the future upgrading and reconstruction trend of the sewage treatment plant, and the incremental contribution values of carbon emission and the contribution proportion of different upgrading and reconstruction items can be calculated. Through calculation of three cases, the proportion of carbon emission increment caused by adding a carbon source and a phosphorus removal agent in the process of upgrading and transforming the sewage plant is up to more than 80%.

2.1 case Sewage plant selection basis

According to data in the basic information tables of the Beijing, Tianjin and Jiangsu sewage plants, the COD, BOD, TN and TP of the effluent of the sewage plant in each month from 07 years to 17 years are searched and a chart is drawn. And screening typical sewage plants of Beijing, Tianjin and Jiangsu according to the change trend on the graph to carry out carbon emission increment calculation. Sewage plant characteristics of screening: and (4) upgrading the effluent quality from second grade to first grade A, from second grade to first grade B, from first grade B to first grade A, and then performing carbon emission increment calculation on the screened sewage plant.

2.2 case analysis

2.2.1 case 1

After the mark of the yellow village sewage treatment plant in the great Xingdistrict of Beijing in 2013 is increased in 11 months, the effluent water quality standard is improved from the second level to the first level B, and the design treatment scale is 8 ten thousand meters before the mark is increased³D is increased to 12 ten thousand meters³D, actual processing scale about 10 km³D; the standard is increased again in 2016 (1 month), and the water quality of the effluent is improved from first grade B to first gradeAnd (4) stage A. The sludge has no digestion process and is completely subjected to dehydration and landfill treatment, and the water content gamma of the sludge is 79 percent. BOD before and after twice bid lifting_{Inflow water}、BOD_{Discharging water}、TN_{Inflow water}、TN_{Discharging water}And the Ke month average value of the power consumption per ton of the sewage treatment system is shown in Table 3, the carbon source is added to be methanol, and the phosphorus removal agent is aluminum sulfate.

TABLE 3 monthly mean of the run items before and after two benchmarks

TABLE 4 list of carbon emission increment of wastewater treatment plant in yellow village in great Kyoto Beijing

The data and the parameters are substituted into a carbon emission model formula, and the carbon emission increment delta M of each ton of water can be obtained by calculation after the water quality standard of the factory effluent is upgraded from the second level to the first level B₁＝-199.39g CO₂/m³Resulting in a daily reduction of 19.94tCO in carbon emissions to the outside environment₂. After the effluent water quality standard is upgraded from first grade B to first grade A, the carbon emission increment delta M of each ton of water₂＝145.33gCO₂/m³This results in a daily increase in carbon emissions to the outside environment of 14.53tCO₂。

2.2.2 case 2

After the standard of the Tianjin Yangyang road sewage treatment plant is improved at 12 months in 2010, the effluent water quality standard is improved from a secondary standard to a primary standard B, and the design treatment scale is 45 km³D, actual processing scale about 35 km³And d. The sludge has no digestion process and is completely subjected to dehydration and landfill treatment, and the water content gamma of the sludge is 80%. BOD before and after bid lifting_{Inflow water}、BOD_{Discharging water}、TN_{Inflow water}、TN_{Discharging water}And Ke-month average value of water and electricity consumption per ton of the sewage treatment system are shown in the following table, a carbon source is added to be methanol, and a phosphorus removal agent is polyaluminium chloride.

TABLE 5 monthly mean of the before and after benchmarking operation project

TABLE 6 Substratelist of carbon emission increment of Tianjin Yangyang road sewage treatment plant

Through calculation, after the water quality standard of the factory effluent is upgraded from the second level to the first level B, the carbon emission increment delta M of each ton of water is-174.34 g CO₂/m³Resulting in a daily reduction of 61.02tCO in carbon emissions to the outside environment₂。

2.3.3 case 3

After the first sewage treatment plant in gold Tan City of Changzhou area of Jiangsu province is upgraded at 9 months in 2009, the effluent water quality standard is improved from primary B to primary A, and the design treatment scale is 3 km³D, actual processing Scale 2.85m³And d. The sludge has no digestion process and is completely subjected to dehydration and landfill treatment, and the water content gamma of the sludge is 79.4 percent. BOD before and after bid lifting_{Inflow water}、BOD_{Discharging water}、TN_{Inflow water}、TN_{Discharging water}And Ke-month average value of water and electricity consumption per ton of the sewage treatment system are shown in the following table, a carbon source is added to be methanol, and a phosphorus removal agent is polyaluminium chloride.

TABLE 7 monthly mean values of operational items before and after upgrading

TABLE 8 list of carbon emission increment items of the first sewage treatment plant in the gold Tan City

Through calculation, after the water quality standard of the factory effluent is upgraded from a first grade B to a first grade A, the carbon emission increment delta M of each ton of water is 22.35g CO₂/m³Resulting in a daily increase of 0.64tCO to carbon emissions in the outside environment₂。

2.3 conclusion

The change situation of carbon emission after upgrading and modification of the sewage treatment plant is analyzed and calculated by combining the example data of the three sewage treatment plants in the data platform, and the result shows that the proper improvement of the effluent water quality standard of the sewage treatment plant is beneficial to carbon emission reduction, mainly because the water environment carbon emission reduction caused by water quality improvement and the influence of the sewage treatment plant on the environment generally play a positive role. However, the effluent standard is improved once, the power consumption of sewage units is improved, and the indirect carbon discharge caused by the power consumption is also greatly increased; in addition, the phosphorus removal pressure is increased, the medicine consumption is correspondingly increased, and the indirect carbon emission is increased, the material consumption is increased and the chemical sludge amount is increased. Therefore, the sewage discharge standard is properly improved, the carbon discharge generated in each flow link of the sewage treatment plant can be effectively reduced, the sewage treatment plant becomes more energy-saving and environment-friendly, and the sewage treatment plant can generate adverse effects on the aspects of energy, resources, greenhouse gas discharge and the like by further improving the water outlet standard.

Therefore, in the process of improving the target of the sewage treatment plant, the rigid indexes such as effluent quality and operation cost are considered, and the environmental benefits generated by energy conservation and emission reduction of the whole process of the sewage treatment plant are comprehensively considered, so that the environmental positive benefits generated in the process of improving the effluent standard of the sewage treatment are prevented from being offset by the negative benefits of carbon emission increment caused by consumption of energy, resources and medicaments.

Table 9: the main formula related to the invention

Table 10: character definitions of the formulas in Table 9

Finally, the inexhaustible parts of the invention are calculated by adopting the mature means in the prior art.

It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.

Claims (10)

1. A carbon emission model calculation method based on a whole flow link of town sewage treatment is characterized by comprising the following steps: the carbon emission model is used for calculating the net carbon emission W of the sewage plant in the operation stage, and the net carbon emission W is equal to the carbon emission E of the sewage plant in the operation stage_{Carbon row}Carbon removal and emission reduction J_{Emission reduction}(ii) a The carbon emission E_{Carbon row}Equal to direct carbon emission E_{Direct connection}And indirect carbon emission E_{Indirect connection}The sum of (a); the direct carbon emission E_{Direct connection}Comprises the carbon emission E of the sewage denitrification link_{Denitrification of sewage}And the carbon emission E of the sanitary landfill of the sludge_{Sanitary landfill}Carbon emission in sludge land utilization link E_{Land utilization}(ii) a The indirect carbon emission E_{Indirectly comprise}Including electricity consumption of sewage treatment plant E_{Electric energy}And agents E used_{Pharmaceutical production}Indirectly resulting in carbon emissions; the carbon emission reduction amount J_{Emission reduction}Comprises water quality improvement and carbon emission reduction J_{Water quality improvement}Carbon emission reduction amount J for anaerobic digestion of sludge_{Anaerobic digestion}Carbon emission reduction amount J in sludge aerobic digestion process_{Aerobic digestion}And sludge land utilization as soil fertilizer carbon emission reduction J_{Soil fertilizer}(ii) a The measurement formula of the net carbon emission W is as follows:

2. the town-based sewage treatment overall process according to claim 1The carbon emission model calculation method of the link is characterized by comprising the following steps: the sewage denitrification link carbon emission E sewage denitrification comprises N₂Carbon O-type emissions

And CO₂Carbon-like emissions

The two measurement formulas are as follows:

A、N₂carbon O-type emissions

In the formula

Sewage treatment Process N₂O production amount tN₂O/month; q-treated water volume of sewage treatment plant is ten thousand meters³A month; TN water inlet and TN water outlet-TN concentration mg/L of the water inlet and outlet;

—N₂o conversion, 0.04kgN₂O/kgTN；

Combining the formula (2) to obtain

The formula of the measurement is as follows:

in the formula (I), the compound is shown in the specification,

sewage treatment step N₂Carbon emissions tCO of O type₂A month; g_N2O—N₂Taking 296tCO based on the global warming potential of O on a hundred-year scale₂/tN₂O，

B、CO₂Carbon-like emissions

An external carbon source is used as an electron donor and is oxidized into alkalinity HCO in the denitrification process₃ ^-Is converted into CO in the nitration process₂(ii) a Therefore, the stoichiometric equation of the nitrification and denitrification process is as follows:

and (3) denitrification process:

NO₃ ^－+1.08CH₃OH+0.24H₂CO₃→0.056C₅H₇O₂N+0.47N₂+1.68H₂O+HCO₃ ^-

and (3) nitration process:

NH₄ ⁺+1.83O₂+1.98HCO₃ ^-→0.02C₅H₇O₂N+1.04H₂O+0.98NO₃ ^－+1.88H₂CO₃

the stoichiometric equations of the nitrification and denitrification processes are combined into:

NH₄ ⁺+NO₃ ^－+1.83O₂+2.14CH₃OH→0.13C₅H₇O₂N+5.77H₂O+1.4CO₂+0.93N₂

0.9kgCO is produced for every 1kg of methanol consumed₂(ii) a When the oxygen equivalent of methanol is combined with 1.5mg/mg, the CO of the external carbon source in the denitrification process is calculated according to the oxygen equivalent₂Theoretical conversion of 0.9kgCO₂/kgBOD_{Carbon source}(ii) a Conversion of CO by external carbon source₂The carbon-like emissions can be calculated as follows:

in the formula (I), the compound is shown in the specification,

CO converted with external carbon source₂Emission tCO₂A month; m_{Carbon source}Adding an additional carbon source for t/month; eta_{Carbon source}-the content of active ingredients of the external carbon source; BOD_{Carbon source}-oxygen equivalent of the external carbon source;

conversion of CO by external carbon source₂Class theory conversion rate, 0.9kgCO is taken₂/kgBOD_{Carbon source}(ii) a Wherein M is_{Carbon source}、η_{Carbon source}、BOD_{Carbon source}And selecting according to the actual operation condition of the sewage treatment plant.

3. The carbon emission model calculation method based on the whole process link of town sewage treatment as claimed in claim 1, wherein: the sludge sanitary landfill carbon emission E_{Sanitary landfill}The C, N element from the sludge will produce CH in the sanitary landfill₄Therefore, the measurement formula is as follows:

in the formula (I), the compound is shown in the specification,

sanitary landfill CH₄An emission factor; MCF-a methane production correction factor, and taking 0.92 according to actual sludge and sludge quality in China; DOC-proportion of decomposable organic carbon in the sludge; DOC_FCan be decomposed into CH₄DOC proportion of (1); F-CH₄The proportion in the landfill gas; 1.33-CH₄And C molecular weight ratio%; DOC, DOC_FF and F both adopt IPCC guideline recommended values which are respectively 0.5kgC_DOCPer kg of dry sludge and 0.5kgtCH₄-C/kg C_DOC；

Based on equation (5) it follows:

in the formula (I), the compound is shown in the specification,

sludge sanitary landfill link CH₄Discharge tCH₄A month; omega_{Sanitary landfill}-sludge landfill rate%; q_w-the amount of dewatered sludge t/month; gamma-water content of sludge;

sludge landfill CH₄Taking the recovery amount of 0; OX is the oxidation factor of carbon in sludge; omega_{Sanitary landfill}The actual sanitary landfill amount and the sludge treatment total amount of a sewage treatment plant can be obtained by simple calculation; r_{CH4, sanitary landfill}Taking 0 and generally not counting in a sewage plant; OX adopts IPCC guideline recommended value, and 0.1 is taken;

combining equation (5) and equation (6) yields:

in the formula, E_{Sanitary landfill}Sludge landfill CH₄Carbon-like emissions tCO₂A month; g_CH4—CH₄Based on the global warming potential on the scale of one century, the value of (A) is 21tCO₂/tCH₄。

4. The carbon emission model calculation method based on the whole process link of town sewage treatment as claimed in claim 1, wherein: carbon emission E in the sludge land utilization link_{Land utilization}Middle requirement for CH₄Emission amount and N₂The O emission is calculated by adopting an emission coefficient method, and CH is utilized in land₄The emission coefficient of (A) is 0.003kgCH₄Per kg of dry mud, N₂The emission coefficient of O is 0.017kgN₂O/kg dry mud, and the N content of the cytoplasm of the mud is 0.12, so the CH of the mud land is utilized₄、N₂The O emission measurement formula is as follows:

in the formula:

—CH₄discharge capacity; omega_{Land utilization}-sludge land utilization;

—N₂o discharge amount;

land utilization CH₄The discharge coefficient of (a);

land utilization N₂The emission coefficient of O;_Ntaking the content of cytoplasmic N of the sludge to be 0.12;

therefore, the carbon emission in the sludge land utilization link can be calculated according to the following formula:

in the formula, E_{Land utilization}Carbon emission tCO for land utilization of sludge₂A month;

sludge land utilization CH₄Yield tCH₄A month;

sludge land utilization N₂O production tN₂O/month; the land utilization amount of the sludge and the total amount of the sludge are measured by a sewage treatment plant.

5. The carbon emission model calculation method based on the whole process link of town sewage treatment as claimed in claim 1, wherein: the operation power consumption and carbon emission E of the sewage treatment plant_{Electric energy}Used for conveying, mixing, oxygen supply, sludge dewatering and special substance O of sewage and sludge₃、ClO₂The on-site preparation equipment is operated, and the average value is taken to be 0.94tCO₂the/MW-h is taken as the carbon emission factor of the electric energy production, and the carbon emission of the electric energy production can be calculated according to the following formula:

E_{electric energy}＝D×EF_D×10^-3＝9.4×10^-4×D (11)

In the formula, E_{Electric energy}-carbon emission tCO from running power consumption of sewage treatment plant₂A month; d, using kW.h/month of electric power; EF_D-carbon emission factor for electric energy production, value 0.94tCO₂/MW·h。

6. The carbon emission model calculation method based on the whole process link of town sewage treatment as claimed in claim 1, wherein: carbon emission E in production process of medicament required by sewage treatment plant_{Pharmaceutical production}Comprises the carbon emission generated in the production process of an additional carbon source, a phosphorus removal medicament and a sludge dewatering medicament, wherein the carbon emission factor of methanol can be 1.54kgCO₂The carbon emission factors of the methanol, the phosphorus removal agent and the dehydration agent can be 25 kgCO/kg₂The carbon emission factor EF lime of lime can be 1.74kg/kg lime, so that the carbon emission E medicament production of the medicament production can be calculated according to the following formula:

E_{pharmaceutical production}＝M_{Carbon source}×EF_{Carbon source}+M_{Phosphorus removal medicament}×EF_{Phosphorus removal medicament}+M_{Dehydration medicament}×EF_{Dehydration medicament} (12)

In the formula, E_{Pharmaceutical production}Carbon emission tCO in medicament production₂A/t agent; m_{Carbon source}、M_{Phosphorus removal medicament}、M_{Dehydration medicament}-dose t/month; EF_{Carbon source}-carbon emission factor of a carbon source of a sewage treatment plant; EF_{Phosphorus removal medicament}-carbon emission factor of a phosphorus removal agent of a sewage treatment plant; EF_{Dehydration medicament}-carbon emission factor of dewatering agent of sewage treatment plant; EF_{Carbon source}、EF_{Phosphorus removal medicament}、EF_{Dehydration medicament}The determination is carried out according to the type of the medicament selected by the actual operation of the sewage treatment plant.

7. The carbon emission model calculation method based on the whole process link of town sewage treatment as claimed in claim 1, wherein: the water quality improves the carbon and reduces the discharge amount J_{Water quality improvement}Middle CH₄、N₂The emission factor of O is 0.06kgCH respectively₄/kgBOD、0.008kgN₂O/kgTN, 0.06kgCH will be discharged to atmosphere every time 1kgBOD or 1kgTN is discharged to receiving water₄、0.008kgN₂O, so the carbon emission reduction formula generated by water quality improvement is as follows:

in the formula: j. the design is a square_{Water quality improvement}Water quality raising carbon emission reduction tCO₂A month; BOD_{Inflow water}、BOD_{Discharging water}The BOD content mg/L of the inlet water and the outlet water of the sewage plant;

discharge of 1kgBOD from a Sewage treatment plant into the receiving water and discharge of CH to the atmosphere₄The value of (1) is 0.06kgCH₄/kgBOD；

Discharging 1kgTN into receiving water body by sewage treatment plant, and discharging N into atmosphere₂The amount of O is 0.008kgN₂O/kgTN；

The simplified equation (13) is as follows:

J_{water quality improvement}＝0.0126×Q×(BOD_{Inflow water}－BOD_{Discharging water})+0.02368×Q×(TN_{Inflow water}－TN_{Discharging water})。 (14)

8. The carbon emission model calculation method based on the whole process link of town sewage treatment as claimed in claim 1, wherein: carbon emission reduction by anaerobic digestion of sludge J_{Anaerobic digestion}Middle CH₄The yield was calculated according to the form of the chemometric equation derived from the Buswell-Mueller general formula:

C₅H₇O₂N+1.33H₂O→1.67CH₄+NH₃+3.33CO₂

further, the calculation formula for carbon emission reduction in anaerobic sludge digestion treatment is as follows:

ΔVSS_{anaerobic digestion}＝Q_W×(1-γ)×f×β_VSS/(1-β_VSS)

In the formula: j. the design is a square_{Anaerobic digestion}Carbon reduction of anaerobic sludge digestion process, tCO₂A month;_{anaerobic digestion}，_{Sanitary landfill}、_{Land utilization}-sludge treatment measure selection parameters; f, taking the proportion of the organic components of the sludge to be 0.6; delta VSS_{Anaerobic digestion}Removing the organic components in the anaerobic digestion process of the sludge for t/month; beta is a_VSSThe removal rate of organic components in the anaerobic digestion process of the sludge is 54.5 percent;

toiletRaw landfill CH₄The coefficient of release is such that,

CH for land use₄A release factor;

in addition, the first and second substrates are,

the value is 0.16;

the value is 0.003; beta is a_VSSThe value is 54.5%; f is 0.6; equation (15) reduces to:

J_{anaerobic digestion}＝_{Anaerobic digestion}×Q_w×(1-γ)(2.414×_{Sanitary landfill}+0.045×_{Land utilization})。 (16)

9. The carbon emission model calculation method based on the whole process link of town sewage treatment as claimed in claim 1, wherein: the sludge aerobic digestion carbon emission reduction amount J_{Aerobic digestion}The calculation formula of (a) is as follows:

ΔVSS_{aerobic digestion}＝Q_W×(1-γ)×f×α_VSS/(1-α_VSS)

Δ VSS in the above equation_{Aerobic digestion}Removing organic components in the aerobic digestion process of the sludge for t/month; alpha is alpha_VSS50% of organic component removal rate in the sludge aerobic digestion process; j. the design is a square_{Aerobic digestion}Carbon reduction of aerobic sludge digestion process, tCO₂A month;_{aerobic digestion}-sludge treatment process selection parameters; therefore, the above formula is simplified as follows:

J_{aerobic digestion}＝_{Aerobic digestion}×Q_w×(1-γ)×(2.016×_{Sanitary landfill}+0.038×_{Land utilization})。 (18)

10. The carbon emission model calculation method based on the whole process link of town sewage treatment as claimed in claim 1, wherein: carbon emission reduction J for utilizing sludge land as soil fertilizer_{Soil fertilizer}The calculation formula of (a) is as follows:

J_{soil fertilizer}＝ω_{Land utilization}×Q_w×1-γ×f×EF_{Natural gas}×2.8×0.61×_N×EF_{Ammonium nitrate}+3.8×0.7×_P×EF_{Superphosphate}×10^-3 (19)

In the formula, J_{Soil fertilizer}Carbon emission reduction tCO for replacing chemical fertilizer by sludge land utilization₂A month; 2.8, 3.8-NH₄NO₃And N, Ca (H)₂PO₄)₂Molecular ratio to P; EF_{Natural gas}Carbon emission factor tCO of natural gas₂TJ, value 51.6; EF_{Ammonium nitrate}Energy consumption of ammonium nitrate production; EF_{Superphosphate}Energy is consumed for the production of the calcium superphosphate;_Nthe content of N in sludge cells is 0.12, wherein 61 percent of N can be utilized by plants;_Pthe content of the sludge cell P is 0.02, wherein the content can be utilized by plants by 70%; the above formula is simplified as follows:

J_{soil fertilizer}＝0.0068×ω_{Land utilization}×Q_w×1-γ (20)。

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