A construction method for an evaluation index system of carbon emissions from a sewage treatment plant

Abstract

The present invention discloses a method for constructing a carbon emission evaluation index system for sewage treatment plants, comprising the following steps: S1. Constructing a carbon emission index system framework for sewage treatment plants, using the analytic hierarchy process to divide the hierarchical structure into layers and the element indicators contained in each layer; S2. Determining the weights of each layer and each element indicator based on the relative importance of each layer and each element indicator on carbon emissions, and grading the values of each element indicator; S3. Collecting sewage treatment plant operating data, calculating the values of each element indicator, and determining the graded values of each element indicator; S4. Constructing a variable-weighted carbon emission comprehensive evaluation index that satisfies normalization, completing the construction of a dynamic sewage treatment plant carbon emission comprehensive evaluation index system; S5. Using the obtained carbon emission comprehensive evaluation index to evaluate the carbon emission level of the sewage treatment plant. This method is suitable for evaluating the carbon emission level of sewage treatment plants and has the advantages of dynamic evaluation and accurate evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater biological treatment, and in particular to a method for constructing a carbon emission evaluation index system for a sewage treatment plant. Background Art

[0002] Reducing carbon emissions is a crucial task for promoting ecological progress and sustainable development. The wastewater treatment industry plays a crucial role in controlling water pollution, but it is also a significant source of carbon emissions. Currently, the trend of "high-quality effluent at the expense of high energy and material consumption"—and the resulting trend of "reducing water pollutants while increasing greenhouse gas emissions"—is intensifying year by year. According to rough estimates, greenhouse gas emissions from China's entire wastewater treatment industry will account for 2.95% of national greenhouse gas emissions by 2030. Exploiting the potential of wastewater treatment plants to reduce energy and material consumption, improve the resource utilization of wastewater and sludge, and integrate the application of ecological treatment technologies such as carbon sequestration to reduce wastewater pollutants while simultaneously reducing emissions of greenhouse gases such as carbon dioxide—is the inevitable path for sustainable development in the wastewater treatment industry.

[0003] Traditional wastewater treatment plant carbon emissions assessments focus solely on a single factor, but due to the complexity of wastewater treatment plants, a single indicator is insufficient to comprehensively and accurately assess the carbon emissions level of the entire plant. Currently, there is a lack of a scientifically sound method for constructing a carbon emissions assessment indicator system for wastewater treatment plants that can dynamically and accurately assess their carbon emissions. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for constructing a carbon emission evaluation index system for a sewage treatment plant, so as to dynamically and accurately evaluate the carbon emission level of a sewage treatment plant.

[0005] To achieve the above objectives, the present invention provides a method for constructing a carbon emission evaluation index system for a sewage treatment plant, the method comprising:

[0006] S1. Construct a carbon emission indicator system framework for sewage treatment plants and use the analytic hierarchy process to divide the hierarchical structure, including the levels and the element indicators contained in each level;

[0007] S2. Determine the weights of each level and each factor indicator based on their relative importance to carbon emissions, and rank the values of each factor indicator;

[0008] S3. Collect the operating data of the sewage treatment plant, calculate the value of each factor index, and determine the graded value of each factor index;

[0009] S4. Construct a variable-weighted carbon emission comprehensive evaluation index that satisfies normalization and complete the construction of a dynamic sewage treatment plant carbon emission comprehensive evaluation index system;

[0010] S5. Use the obtained comprehensive carbon emission evaluation index to evaluate the carbon emission level of the sewage treatment plant.

[0011] Furthermore, the levels include energy consumption and material consumption, resource recycling, carbon sink and carbon emission.

[0012] Furthermore, the energy and material consumption levels include electricity consumption per unit of sewage, electricity consumption per unit of oxygen-consuming pollutants, carbon source consumption per unit of total nitrogen reduction, phosphorus removal agent consumption per unit of total phosphorus reduction, and agent consumption per unit of dry sludge.

[0013] Furthermore, the resource recycling level includes recycled water utilization rate, sludge resource energy self-sufficiency rate, solar photovoltaic power generation energy self-sufficiency rate, water source heat pump energy self-sufficiency rate, and other energy self-sufficiency rates.

[0014] Furthermore, the carbon sequestration level includes the greening rate of the factory area and the amount of carbon sequestered by plants in the ecological treatment process.

[0015] Furthermore, the carbon emissions level includes carbon emissions per unit of sewage and carbon emissions per unit of pollutants.

[0016] Furthermore, the calculation formula for unit pollutant carbon emissions is as follows:

[0017]

[0018] Among them F 42 is the unit pollutant carbon emission, kgCO2eq / kg; F 41 is the carbon emission per unit of sewage, kgCO2eq / m 3 , calculated in accordance with the Technical Guidelines for the Coordinated Control of Greenhouse Gases from Pollutant Removal in Urban Wastewater Treatment Plants (Trial); Q dai is the daily processing capacity of the sewage treatment plant, m 3 / d;COD rai is the daily average concentration of chemical oxygen demand in the influent, mg / L; COD eai is the daily average concentration of chemical oxygen demand in effluent, mg / L; BOD rai is the average daily concentration of biochemical oxygen demand in the influent for five days, mg / L; BOD eai is the average daily concentration of biochemical oxygen demand in the effluent for five days, mg / L; NH4 + -N rai is the daily average concentration of ammonia nitrogen in the influent, mg / L; NH4 + -N eai is the average daily concentration of ammonia nitrogen in the effluent, mg / L; TN rai is the daily average concentration of total nitrogen in the influent, mg / L; TN eai is the daily average concentration of total nitrogen in effluent, mg / L; TP rai is the daily average concentration of total phosphorus in the influent, mg / L; TPeai is the average daily concentration of total phosphorus in effluent, mg / L.

[0019] Furthermore, the calculation formula of the variable-weighted carbon emission comprehensive evaluation index that meets the normalization property is:

[0020]

[0021] Among them, F is the comprehensive evaluation index of carbon emissions, λ i is the weight of the i-th level, γ i is the weight of the j-th factor index, F i, j is the graded value of each factor indicator.

[0022] Compared with the existing technology, the present invention has the following technical effects: the present invention aims at constructing a carbon emission index system for sewage treatment plants. Starting from the four levels of energy consumption and material consumption, resource reuse, carbon sink and carbon emission, the present invention screens and extracts element indicators with universal adaptability that can reflect the characteristics of the relevant levels according to the basic characteristics of each level, constructs a comprehensive evaluation index system for carbon emissions of sewage treatment plants, and introduces the concept of variable weights to realize dynamic and accurate evaluation of the carbon emission levels of sewage treatment plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of a method for constructing a carbon emission evaluation index system for a sewage treatment plant in the present invention. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] like Figure 1 As shown, the present invention discloses a method for constructing a carbon emission evaluation index system for a sewage treatment plant, comprising the following steps S1 to S5:

[0026] S1. Construct a carbon emission indicator system framework for sewage treatment plants and use the analytic hierarchy process to divide the hierarchical structure, including the levels and the element indicators contained in each level;

[0027] Furthermore, the levels include energy consumption and material consumption, resource recycling, carbon sink and carbon emission.

[0028] Furthermore, the energy and material consumption levels include electricity consumption per unit of sewage, electricity consumption per unit of oxygen-consuming pollutants, carbon source consumption per unit of total nitrogen reduction, phosphorus removal agent consumption per unit of total phosphorus reduction, and agent consumption per unit of dry sludge.

[0029] Furthermore, the resource recycling level includes recycled water utilization rate, sludge resource energy self-sufficiency rate, solar photovoltaic power generation energy self-sufficiency rate, water source heat pump energy self-sufficiency rate, and other energy self-sufficiency rates.

[0030] Furthermore, the carbon sequestration level includes the greening rate of the factory area and the amount of carbon sequestered by plants in the ecological treatment process.

[0031] Furthermore, the carbon emissions level includes carbon emissions per unit of sewage and carbon emissions per unit of pollutants.

[0032] The framework of the carbon emission evaluation index system for sewage treatment plants constructed according to step S1 is shown in Table 1.

[0033] Table 1 Framework of carbon emission evaluation index system for sewage treatment plants

[0034]

[0035] S2. Determine the weights of each level and each factor indicator based on their relative importance to carbon emissions, and rank the values of each factor indicator;

[0036] Currently, more than 95% of cities at or above the county level across China have built and put into operation sewage treatment plants, with treatment processes, structures, and equipment already determined. New sewage treatment plants, however, give greater consideration to the resource reuse of sewage sludge and the application of carbon sequestration technologies during the design and planning stages. Therefore, in this embodiment, on the one hand, to facilitate the low-carbon operation of existing sewage treatment plants, respect reality, and serve the present; on the other hand, to facilitate the resource utilization and low-carbon construction of new sewage treatment plants. Furthermore, in order to balance the energy conservation and consumption reduction of mature technologies with resource utilization technologies, the balance between construction and operation management levels, and the balance between current and medium- to long-term economic development, in this embodiment, the weight of the energy and material consumption level (F1) is assigned to 0.3, the weight of the resource reuse level (F2) to 0.2, the weight of the carbon sequestration level (F3) to 0.1, and the weight of the carbon emission level (F4) to 0.4.

[0037] The weight distribution of each factor indicator at each level in this embodiment is as follows:

[0038] At the energy and material consumption level (F1), according to the calculation of carbon emissions from existing sewage treatment plants, the impact of electricity consumption on carbon emissions is significantly greater than the carbon emissions of carbon sources, phosphorus removal agents, and sludge agents. Therefore, in this embodiment, the unit sewage power consumption (F 11) is weighted as 0.4, and the power consumption per unit oxygen-consuming pollutant (F 12 ) is weighted as 0.3, and the reduction of carbon source consumption per unit of total nitrogen (F 13 ) is weighted as 0.1, and the consumption of phosphorus removal agents per unit of total phosphorus reduction (F 14 ) is assigned a weight of 0.1, and the unit dry sludge consumption (F 15 ) is assigned a weight of 0.1.

[0039] At the resource recycling level (F2), the main ways for sewage treatment plants to achieve resource recycling are: improving the effluent standards to reuse the effluent for river replenishment, industrial cooling, etc., to improve the recycling rate of sewage tail water; improving the resource utilization rate of sludge through technologies such as anaerobic digestion and incineration of residual sludge; using a new energy utilization system with renewable energy sources such as solar photovoltaic power generation, water source heat pumps, and wind energy as the core to increase energy supply, optimize energy structure, improve the energy self-sufficiency rate of the plant area, and create a multi-path, sustainable energy supply system. Among them, the carbon neutrality operation goal of the sewage treatment plant can be met to the greatest extent through the conversion of residual sludge into energy and sewage source heat pumps, while the energy available from solar photovoltaic power generation is slightly lower, and can only meet about 10% of the operating energy consumption. Therefore, in this embodiment, the recycled water utilization rate (F 21 ) is weighted as 0.2, sludge resource energy self-sufficiency rate (F 22 ) is weighted as 0.3, the self-sufficiency rate of solar photovoltaic power generation (F 23 ) is weighted as 0.1, the energy self-sufficiency rate of water source heat pump (F 24 ) is weighted as 0.3, and other energy self-sufficiency rates (F 25 ) is assigned a weight of 0.1.

[0040] Carbon sink level (F3), including plant greening rate (F 31 ), ecological treatment process plant carbon sequestration (F 32 ) are two factor indicators, and both are processes in which plants absorb carbon dioxide from the atmosphere, thereby reducing the concentration of greenhouse gases in the atmosphere. Therefore, in this embodiment, the green area ratio of the factory (F 31 ) is weighted as 0.5, the amount of carbon sequestered by plants in ecological treatment process (F 32 ) is assigned a weight of 0.5.

[0041] The carbon emission level (F4) not only considers the carbon emission of wastewater treatment unit (F 41 ), further considering the unit pollutant carbon emissions related to the influent water quality concentration (F 42 ). and unit wastewater carbon emissions (F 41 ) compared to the unit pollutant carbon emissions (F 42) can more clearly and objectively reflect the carbon emissions of removing unit chemical oxygen demand, five-day biochemical oxygen demand, ammonia nitrogen, total nitrogen and total phosphorus. Therefore, in this embodiment, the unit wastewater carbon emissions (F 41 ) is weighted to 0.4, unit pollutant carbon emissions (F 42 ) is assigned a weight of 0.6.

[0042] Based on the design scale of sewage treatment plants and the actual operation status of the sewage treatment industry, the numerical values of various factor indicators at each level are graded as follows:

[0043] Energy and material consumption (F1):

[0044] Table 2 Classification of indicators of various factors at the energy and material consumption level

[0045]

[0046] Resource recycling level (F2):

[0047] Table 3 Classification of indicators of various factors at the resource reuse level

[0048]

[0049] Carbon sink level (F3):

[0050] Table 4 Classification of indicators of various factors at the carbon sink level

[0051]

[0052] Carbon emissions level (F4):

[0053] Table 5 Classification of indicators of various factors at the carbon emission level

[0054]

[0055] S3. Collect the operating data of the sewage treatment plant, calculate the value of each factor index, and determine the graded value of each factor index;

[0056] Specifically, the calculation formulas for the indicators at the energy and material consumption level (F1) are as follows:

[0057] Unit sewage power consumption (F 11 ) is calculated as follows:

[0058]

[0059] Where: F 11 -Power consumption per unit of sewage, kWh / m 3 ;E ma - Monthly electricity consumption, kWh; Q da - Actual daily sewage treatment volume, m 3 / d; t--the number of effective running days of the evaluation cycle; tt--the number of calendar months of the evaluation cycle.

[0060] Power consumption per unit oxygen-consuming pollutant (F 12 ) is calculated as follows:

[0061]

[0062] Where: F 12 -Power consumption per unit oxygen-consuming pollutant, kWh / kg; BOD ra - Actual daily average concentration of influent BOD5, mg / L; BOD ea - Actual average daily concentration of effluent BOD5, mg / L; -Actual influent NH4 + -N daily average concentration, mg / L; -Actual NH4 output + -N daily average concentration, mg / L.

[0063] Reduction of carbon source consumption per unit of total nitrogen (F 13 ) is calculated as follows:

[0064]

[0065] Where: F 13 -Reduction in carbon source consumption per unit of total nitrogen, kg / kg; PA da - Daily consumption of external carbon source, kg; TN ra -Actual average daily concentration of TN in the influent, mg / L; TN ea -Actual average daily TN concentration in effluent, mg / L.

[0066] The consumption of phosphorus removal agent (F14) per unit of total phosphorus reduction is calculated as follows:

[0067]

[0068] Where: F 14 -Reduction in phosphorus removal agent consumption per unit of total phosphorus, kg / kg; PA da - Daily consumption of phosphorus removal agent, kg; TP ra -Actual average daily concentration of TP in influent, mg / L; TP ea -Actual average daily TP concentration in effluent, mg / L.

[0069] Unit dry sludge consumption (F 15 ) is calculated as follows:

[0070]

[0071] Where: F 15- Unit dry sludge consumption, kg / t; PM da -Daily consumption of flocculant, kg; SC da - Daily actual output of dewatered sludge, t; SW da - Daily average moisture content of dewatered sludge, %.

[0072] Specifically, the calculation formulas for each indicator at the resource reuse (F2) level are as follows:

[0073] Recycled water utilization rate (F 21 ) is calculated as follows:

[0074]

[0075] Where: F 21 - Recycled water utilization rate, %; Q za - Actual daily recycled water usage, m 3 / d;Q pa - Actual daily sewage discharge volume, m 3 / d.

[0076] Sludge resource energy self-sufficiency rate (F 22 ) is calculated as follows:

[0077]

[0078] Where: F 22 - Self-sufficiency rate of sludge resource energy, %; E W -Annual energy output of sludge resource utilization, kWh.

[0079] Solar photovoltaic power generation energy self-sufficiency rate (F 23 ) is calculated as follows:

[0080]

[0081] Where: F 23 - Solar photovoltaic power generation energy self-sufficiency rate, %; E g -Annual solar photovoltaic power generation, kWh.

[0082] Water source heat pump energy self-sufficiency rate (F 24 ) should be calculated as follows:

[0083]

[0084] Where: F 24 -Water source heat pump energy self-sufficiency rate, %; E b - Annual heating and cooling capacity of water source heat pump, kWh.

[0085] Other energy self-sufficiency rate (F 25 ) is calculated as follows:

[0086]

[0087] Where: F 25 - Other energy self-sufficiency rate, %; E q -Annual electricity generation from other sources, kWh.

[0088] Specifically, the calculation formulas for each indicator at the carbon sink (F3) level are as follows:

[0089] Plant greening rate (F 31 ) is calculated as follows:

[0090]

[0091] Where: F 31 - Plant greening rate, %; S g -Green area of the factory, m 2 ;S w -Green area of the factory, m 2 .

[0092] Ecological treatment process plant carbon fixation rate (F 32 ) is calculated as follows:

[0093]

[0094] Where: F 32 -Plant carbon sequestration rate in the ecological treatment process of sewage treatment plants, tCO 2eq / a;

[0095] A j -crown area of the jth plant in the ecological treatment process, m 2 .

[0096] EF CO2，j -Carbon sequestration coefficient of the jth plant in the ecological treatment process, Kg / (m 2 a), see Table 6;

[0097] E g -Total annual carbon emissions from sewage treatment plants, tCO 2eq / a.

[0098] GWP CO2 -CO2 global warming potential, which is set to 1.

[0099] Table 6 Recommended carbon sequestration coefficients for different plants

[0100] Plant name Plant Type <![CDATA[Carbon sequestration coefficient / (kgCO2 / m 2 ·a)]]> Black algae submerged plants 0.25 Potamogeton floating plants 0.41 Potamogeton spp. submerged plants 0.03 Chara spp. submerged plants 0.31 Ceratophyllum submerged plants 0.03 iris Emergent plants 3.14 Gladiolus Emergent plants 6.74 Lucky Grass Emergent plants 1.95 reed Emergent plants 3.70 White Mango Emergent plants 2.74 Red Fescue Emergent plants 4.68 Kentucky bluegrass Emergent plants 1.07 Yellow iris Emergent plants 5.49 Daylily Emergent plants 2.80 Lotus floating plants 4.50 Canna Emergent plants 4.77 Ophiopogon japonicus Emergent plants 1.37

[0101] Specifically, the calculation methods or formulas for each indicator at the carbon emission level (F4) are as follows:

[0102] Carbon emissions per unit of wastewater (F 41 ):Calculated in accordance with the "Technical Guidelines for Coordinated Control of Greenhouse Gases for Pollutant Removal in Urban Wastewater Treatment Plants" (Trial) issued by the Ministry of Ecology and Environment in April 2018.

[0103] Carbon emissions per unit of pollutant (F 42 ) is calculated using the following formula:

[0104]

[0105] Where: F 42 —Carbon emissions per unit of pollutant, kgCO2eq / kg;

[0106] Q dai — Daily average treatment capacity of sewage treatment plants, m 3 / d;

[0107] COD rai — Daily average concentration of chemical oxygen demand in influent, kg / m 3 ;

[0108] COD eai —Daily average concentration of chemical oxygen demand in effluent, kg / m 3 ;

[0109] BOD rai —Daily average concentration of biochemical oxygen demand in influent for five days, kg / m 3 ;

[0110] BOD eai —Daily average concentration of biochemical oxygen demand in effluent for five days, kg / m 3 ;

[0111] NH4 + -N rai —Daily average concentration of ammonia nitrogen in influent, kg / m 3 ;

[0112] NH4 + -N eai —Daily average concentration of ammonia nitrogen in effluent, kg / m 3 ;

[0113] TN rai —Daily average concentration of total nitrogen in influent, kg / m 3 ;

[0114] TN eai —Daily average concentration of total nitrogen in effluent, kg / m 3 ;

[0115] TP rai —Daily average concentration of total phosphorus in influent, kg / m 3 ;

[0116] TN eai —Daily average concentration of total phosphorus in effluent, kg / m 3 .

[0117] The following uses the construction method of the carbon emission evaluation index system of a sewage treatment plant disclosed in the present invention to illustrate the carbon emission per unit sewage (F 41 ) and unit pollutant carbon emissions (F 42 ) calculation method.

[0118] The sewage treatment scale of a sewage treatment plant is 200,000 m 3 / d, total variation coefficient K z It is 1.3, and adopts a sewage treatment process based on "AAO+deep bed filter filtration". The sludge is centrifugally dehydrated to a moisture content of 80% and then the mud cake is transported out. The disinfection adopts ultraviolet disinfection process, and the deodorization adopts microbial deodorization process. The greening rate of the plant is 35%, and there is no ecological treatment process. After treatment, the tail water has stably reached surface Class IV water and is discharged into the nearby river as a replenishment water source. The utilization rate of recycled water reaches 100%. The sewage treatment plant adopts distributed photovoltaic power generation. The total installed capacity of the project is 1.80792MW. It uses a 10kV voltage level to access the user-side power grid to supply electricity to the plant. The total solar power generation in 2020 was 1.32124 million kWh. The average influent concentration of the sewage treatment plant in 2020 is as follows: COD=198mg / L, BOD5=89.46mg / L, NH4 + -N=27.35mg / L,TN=34.53mg / L,TP=2.57mg / L;the annual average concentration of the effluent is as follows: COD=16.6mg / L,BOD5=4.00mg / L,NH4 + -N=0.14mg / L, TN=4.14mg / L, TP=0.10mg / L.

[0119] The unit sewage carbon emissions (F 41 ) is 0.391kg CO2 / m 3 Water, the specific calculation process is shown in Table 7. The sewage treatment process in Table 7 is the AAO process.

[0120] Table 7 Calculation of pollutant removal and greenhouse gas emission reduction of a sewage treatment plant in 2020

[0121]

[0122]

[0123]

[0124] Carbon emissions per unit of wastewater (F 41 )=20606.38×1000 / 52707283=0.391kg CO2 / m 3 water.

[0125] Carbon emissions per unit of pollutant (F 42 ) is calculated as follows:

[0126] F 42 =0.391×144009 / ((0.3×(198-16.6)+0.1×(89.46-4.00)+0.3×(27.35-0.14) +0.2×(34.53-4.14)+0.1×(2.57-0.14))×0.001×144009)=5.05kgCO2eq / kg.

[0127] In this implementation, the graded values of various factor indicators of a sewage treatment plant obtained according to steps S1 to S3 are shown in Table 8.

[0128] Table 8 Grading values of various factor indicators of a sewage treatment plant

[0129]

[0130] S4. Construct a variable-weighted carbon emission comprehensive evaluation index that satisfies normalization and complete the construction of a dynamic sewage treatment plant carbon emission comprehensive evaluation index system;

[0131] The calculation formula for the comprehensive carbon emission evaluation index is as follows:

[0132]

[0133] Among them, F is the comprehensive evaluation index of carbon emissions, λ i is the weight of the i-th level, γ i is the weight of the i-th factor, F i, j is the graded value of each factor indicator.

[0134] The comprehensive evaluation index of carbon emissions of the sewage treatment plant is F = 0.3 × (0.4 × 0.74 + 0.3 × 0.70 + 0.1 × 0.98 + 0.1 × 0.93 + 0.1 × 0.80) + 0.2 × (0.2 × 1 + 0.3 × 0 + 0.1 × 0.92 + 0.3 × 0 + 0.1 × 0) + 0.1 × (0.5 × 0.9 + 0.5 × 0) + 0.4 × (0.4 × 0.85 + 0.6 × 0.85) = 0.6765

[0135] As the overall operation level of sewage treatment plants improves and the industry's understanding of carbon emissions deepens, the weights of each level λi , the weight of each factor index γ i The classification of each factor indicator will change accordingly, thus obtaining a dynamic carbon emission indicator system for sewage treatment plants, and realizing dynamic and accurate evaluation of the carbon emission levels of sewage treatment plants.

[0136] S5. Use the obtained comprehensive carbon emission evaluation index to evaluate the carbon emission level of the sewage treatment plant.

[0137] The obtained carbon emission comprehensive evaluation index can be used to further evaluate the carbon emission level of the sewage treatment plant. The higher the carbon emission comprehensive evaluation index, the lower the overall carbon emission level of the sewage treatment plant; the lower the carbon emission comprehensive evaluation index, the higher the overall carbon emission level of the sewage treatment plant. The specific carbon emission level of the sewage treatment plant needs to be analyzed in combination with its actual operation and management level, resource recycling level, and whether carbon sink technology is adopted. The carbon emission comprehensive evaluation index F of the sewage treatment plant is 0.6765, and the carbon emission level is average. The analysis is as follows: First, since the average daily water volume of the sewage treatment plant is 144009m 3 / d, far from the designed scale of 200,000 m 3 / d, the sewage load rate is only 72%, which directly leads to the unit sewage power consumption (F 11 ), power consumption per unit oxygen-consuming pollutant (F 12 ) is relatively high. Secondly, the wastewater treatment plant's resource reuse involves only recycled water, lacking energy recovery methods such as sludge and water-source heat pumps, and lacks ecological treatment processes for plant carbon sequestration. A comprehensive analysis concludes that the wastewater treatment plant's current carbon emissions are average, with significant potential for future carbon reduction.

[0138] The above description is only one embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for constructing a carbon emission evaluation index system for a sewage treatment plant, characterized in that: The following steps are involved: S1. Construct a carbon emission indicator system framework for sewage treatment plants, using the analytic hierarchy process to divide the hierarchical structure, including the levels and the element indicators contained in each level; S2. Determine the weight of each level and each element indicator based on the relative importance of each level and each element indicator on carbon emissions, and grade the values of each element indicator; S3. Collect sewage treatment plant operation data, calculate the values of various factor indicators, and determine the graded values of each factor indicator; S4. Construct a variable-weighted carbon emission comprehensive evaluation index that satisfies normalization, and complete the construction of a dynamic sewage treatment plant carbon emission comprehensive evaluation index system; S5. Use the obtained carbon emission comprehensive evaluation index to evaluate the carbon emission level of the sewage treatment plant; The levels include energy and material consumption level (F1), resource recycling level (F2), carbon sink level (F3) and carbon emission level (F4); The carbon emission level (F4) includes the carbon emission per unit of wastewater (F 41 ) and unit pollutant carbon emissions (F 42 ); The unit pollutant carbon emission (F 42 ) is calculated as follows: Among them F 42 is the unit pollutant carbon emission, kgCO2eq / kg; F 41 is the carbon emission per unit of sewage, kgCO2eq / m 3 ;Q dai is the daily processing capacity of the sewage treatment plant, m 3 / d;COD rai is the daily average concentration of chemical oxygen demand in the influent, mg / L; COD eai is the daily average concentration of chemical oxygen demand in effluent, mg / L; BOD raii is the average daily concentration of biochemical oxygen demand in the influent for five days, mg / L; BOD eai is the average daily concentration of biochemical oxygen demand in the effluent for five days, mg / L; NH4 + -N rai is the daily average concentration of ammonia nitrogen in the influent, mg / L; NH4 + -N eai is the average daily concentration of ammonia nitrogen in the effluent, mg / L; TN rai is the daily average concentration of total nitrogen in the influent, mg / L; TN eai is the daily average concentration of total nitrogen in effluent, mg / L; TP rai is the daily average concentration of total phosphorus in the influent, mg / L; TP eai is the average daily concentration of total phosphorus in effluent, mg / L.

2. The method for constructing a carbon emission evaluation index system for a sewage treatment plant according to claim 1, characterized in that: The energy and material consumption level (F1) includes the unit sewage power consumption (F 11 ), power consumption per unit oxygen-consuming pollutant (F 12 ), reduction of carbon source consumption per unit of total nitrogen (F 13 ), reduction in phosphorus removal agent consumption per unit of total phosphorus (F 14 ) and unit dry sludge consumption (F 15 ).

3. The method for constructing a carbon emission evaluation index system for a sewage treatment plant according to claim 1, characterized in that: The resource reuse level (F2) includes the recycled water utilization rate (F 21 ), sludge resource energy self-sufficiency rate (F 22 ), solar photovoltaic power generation energy self-sufficiency rate (F 23 ), water source heat pump energy self-sufficiency rate (F 24 ), other energy self-sufficiency rate (F 25 ).

4. The method for constructing a carbon emission evaluation index system for a sewage treatment plant according to claim 1, characterized in that: The carbon sink level (F3) includes the green space ratio of the plant area (F 31 ), ecological treatment process plant carbon fixation rate (F 32 ).

5. The method for constructing a carbon emission evaluation index system for a sewage treatment plant according to claim 1, characterized in that: The calculation formula of the variable-weighted carbon emission comprehensive evaluation index that satisfies normalization is: Among them, F is the comprehensive evaluation index of carbon emissions, λ i is the weight of the i-th level, γ i is the weight of the j-th factor index, F i, j is the graded value of each factor indicator.

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