Calculation Method for Paying According to Effect of Sewage Collection Service Based on Pollutant Collection Load

Abstract

The present invention discloses a method for calculating the payment according to the effect of sewage collection services based on the pollutant collection load, which relates to the technical field of urban sewage collection and treatment. The present invention comprehensively considers the integrated construction and operation and maintenance of sewage pipe network collection and sewage treatment plant treatment, gradually covers the construction and operation and maintenance costs of sewage collection pipe network with the collected sewage treatment fees, and innovatively establishes a "payment according to the effect" mathematical relationship between the sewage collection service fee and the pollutant concentration in the influent of the sewage treatment plant and the pollutant reduction amount, which can be used to guide the calculation of the sewage pipe network collection service fee charged according to the pollutant collection effect. This method can not only simply and quickly calculate the service fee for collecting pollutants in the sewage system, but also has a certain replicability and popularization, providing a reference for the establishment of the "payment according to the effect" model mechanism to support the integrated construction and operation and maintenance of sewage treatment plants and pipe networks.

Description

Technical Field

[0001] The present invention belongs to the technical field of urban sewage collection and treatment, and specifically relates to a method for calculating the payment for sewage collection services according to effectiveness based on the pollutant collection load. Background Art

[0002] The urban sewage collection pipe network system is a large-scale, complex in spatial structure, and highly concealed underground pipe network system. A perfect urban sewage collection system is a necessary condition for the efficient and high-quality operation of the city. Due to the traditional urban development model of "emphasizing the above-ground and neglecting the underground", the construction of the urban sewage collection system lags behind, and there are still common pipe network diseases such as blank areas in the pipe network, rain-sewage mixed connection and wrong connection, pipeline quality defects, and "scattered and polluted" emissions, resulting in a series of "urban water diseases" such as direct sewage discharge, leakage, overflow pollution, urban waterlogging, blackening and odor return of water bodies, and poor operation efficiency of sewage collection and treatment facilities.

[0003] In recent years, the country has focused on making up for the shortcomings of the urban sewage system and improving the sewage collection efficiency, and has successively proposed to accelerate the transformation and construction of domestic sewage collection and treatment facilities, implement projects such as the transformation of mixed and wrongly connected pipe networks, pipe network renewal, and damaged repair and transformation, so as to achieve full coverage, full collection, and full treatment of the sewage system, and comprehensively improve the operation efficiency of existing urban sewage collection facilities.

[0004] Therefore, by studying the integrated construction, operation and maintenance of sewage pipe network collection and sewage treatment plant treatment, gradually covering the construction and operation and maintenance costs of the sewage collection pipe network with the collected sewage treatment fees, a method for calculating the payment for sewage collection services according to effectiveness based on the pollutant collection load is proposed, and a mathematical model of "payment according to effectiveness" is established between the operation service fee of the sewage collection pipe network and the pollutant concentration in the influent of the sewage treatment plant and the pollutant reduction amount, which can be used to accurately calculate the sewage pipe network collection service fee quantitatively, and provide a reference for the research and practice of formulating a full-life cycle pricing, dynamic adjustment and cost guarantee mechanism covering sewage collection and treatment. Summary of the Invention

[0005] Aiming at the problem of payment for urban sewage collection and treatment according to effectiveness, the technical problem to be solved by the present invention is to propose a method for calculating the payment for sewage collection services according to effectiveness based on the pollutant collection load.

[0006] The technical object of the present invention is to establish a mathematical model of "payment according to effectiveness" between the operation service fee of the sewage collection pipe network and the pollutant concentration in the influent of the sewage treatment plant and the pollutant reduction amount, which is used to accurately calculate the sewage pipe network collection service fee quantitatively.

[0007] The technical solution of the present invention is a method for calculating the payment for sewage collection services according to effectiveness based on the pollutant collection load, including the following steps:

[0008] S1. Establish a mathematical model for calculating the sewage collection service fee based on the pollutant collection load;

[0009] S2. Calculate the pollutant collection volume of the sewage collection system, including the baseline pollutant collection volume, the target pollutant collection volume, and the actual pollutant collection volume;

[0010] S3. Determine the unit price for measuring pollutants in the sewage collection system;

[0011] S4. Determine the pollutant collection load weight coefficient in combination with the characteristics of pollution sources and the sewage collection pipe network;

[0012] S5. Determine the concentration adjustment coefficient for collecting pollutants based on the concentration of pollutants in the influent of the sewage treatment plant;

[0013] S6. Determine the operation and maintenance costs of the sewage collection system;

[0014] S7. Use the mathematical model for calculating the sewage collection service fee to calculate the sewage collection service fee of the sewage collection system.

[0015] Preferably, in step S1, the mathematical model for calculating the sewage collection service fee is:

[0016] Cost = P×(S - S 0 )×Wt + P×(S 1 - S 0 )×Wa×J + Op

[0017] Where Cost represents the sewage collection service fee; P represents the unit price for measuring pollutants; S represents the target pollutant collection volume; S 0 represents the baseline pollutant collection volume; S 1 represents the actual pollutant collection volume; Wt represents the target pollutant collection load weight coefficient; Wa represents the actual pollutant collection load weight coefficient; J represents the concentration adjustment coefficient for collecting pollutants; Op represents the operation and maintenance costs.

[0018] Furthermore, the step S2 includes the following sub-steps:

[0019] S201. Calculate the baseline pollutant collection volume of the sewage collection system;

[0020] The baseline pollutant collection volume S 0 is the total COD load of the influent of all sewage treatment plants in the area served by the sewage collection system project in the natural year before the project implementation. It is calculated by weighted cumulative calculation of the daily total sewage inflow Q 0 of the sewage treatment plant and the average COD concentration C 0 , that is:

[0021]

[0022] In the formula, S 0 is the benchmark collection quantity of pollutants; n f is the number of sewage treatment plants, and the subscript j represents the j-th sewage treatment plant; N d is the number of days in a natural year, and the subscript i represents the i-th day; Q 0 is the total daily influent sewage volume of the sewage treatment plant; C 0 is the average COD concentration of the influent to the sewage treatment plant per day.

[0023] S202, calculate the target collection quantity of pollutants in the sewage collection system;

[0024] The target collection quantity of pollutants S is the total annual collectable COD load calculated according to the target requirement of the urban sewage centralized collection rate within the service area of the sewage collection system project, and is calculated through the per capita pollutant discharge standard of the permanent population, that is:

[0025] S = (T BOD5 / b) × n p × d × r / 10 6

[0026] In the formula, S is the target collection quantity of pollutants; T BOD5 is the BOD 5 pollution load discharged per person per day; b is the biodegradability index of sewage; n p is the total number of permanent population within the service area of the sewage collection system project; d is the total number of days in that year; r is the target value of the urban sewage centralized collection rate;

[0027] Determine the initial values of T BOD5 , b, n, d, r according to the actual situation of the base year, and the initial annual target collection quantity of pollutants can be calculated. In principle, the value of r in the base year is consistent with the target of the urban domestic sewage centralized collection rate of the city where the sewage collection system project is located.

[0028] S203, calculate the actual collection quantity of pollutants in the sewage collection system;

[0029] The actual collection quantity of pollutants S 1 refers to the total in-plant COD load of all sewage treatment plants in the service area of the sewage collection system project during the current year of the operation period, and can be calculated by weighted cumulative calculation of the daily actual influent sewage volume Q 1 and the average COD concentration Q 1 , that is:

[0030]

[0031] In the formula, S 1 is the benchmark collection quantity of pollutants; Q 1is the total daily actual influent sewage volume of the sewage treatment plant; C 1 is the average COD concentration of the daily actual influent of the sewage treatment plant.

[0032] In step S3, the unit price P for calculating the pollutants collected by the sewage collection system is the cost required for the sewage collection system to collect each unit of pollutant load, and the calculation formula is:

[0033] P = I 0 / (S - S 0 )

[0034] In the formula, P is the unit price for calculating the collected pollutants; I 0 is the annual construction cost of the sewage collection system.

[0035] In step S4, the pollutant collection load weight coefficient is determined according to the target pollutant collection volume that can be increased by the sewage collection system and the actual pollutant collection volume increased after the implementation of the sewage collection system project. Considering the influencing factors such as the pollutant generation situation in the sewage collection system, the background situation of the sewage pipe network, the transformation cost of the sewage pipe network, the construction quality of the sewage pipe network, and the operation and maintenance situation of the sewage pipe network, the specific values of the target pollutant collection load weight coefficient and the actual pollutant collection load weight coefficient are determined.

[0036] Furthermore, the sum of the target pollutant collection load weight coefficient and the actual pollutant collection load weight coefficient is 1, that is

[0037] Wt + Wa = 1.

[0038] In step S5, the concentration adjustment coefficient J of the collected pollutants is used to evaluate the contribution of the new construction cost of the sewage collection system to the influent concentration, and the concentration adjustment coefficient of the collected pollutants is calculated by weighted averaging the annual average concentration of the influent pollutants of each sewage treatment plant within the service range of the sewage collection system.

[0039] If only considering the annual influent concentration of one pollutant such as COD or BOD 5 The calculation formula for the concentration adjustment coefficient J of the collected pollutants is:

[0040]

[0041] In the formula, is the annual average concentration of COD or BOD in the influent of each sewage treatment plant; Q 5 is the total annual influent volume of each sewage treatment plant; F is the annual influent pollutant concentration gradient score coefficient, and the step interval and the corresponding score coefficient are set according to the actual distribution of the influent pollutant concentration. j If considering both COD and BOD

[0042] at the same time 5For the annual influent concentrations of the two pollutants, the calculation formula for the concentration adjustment coefficient J of the collected pollutants is as follows:

[0043]

[0044] In the formula, A and B are the weight coefficients of COD and BOD respectively 5 respectively; is the average annual concentration of influent COD of each sewage treatment plant; is the influent BOD of each sewage treatment plant 5 average annual concentration; F COD is the score coefficient of the annual influent COD pollutant concentration gradient; F BOD5 is the annual influent BOD 5 pollutant concentration gradient score coefficient.

[0045] Compared with the prior art, the beneficial effects of the present invention include:

[0046] 1) The method for charging sewage collection services according to effectiveness based on the pollutant collection load proposed by the present invention establishes a mathematical model for calculating the payment of sewage collection service fees based on the pollutant collection load, and establishes a mathematical relationship between the sewage collection service fees, the target pollutant collection volume, and the actual collection volume, which can be used to guide the calculation of sewage network collection service fees charged according to the pollutant collection load, making the sewage treatment service charging more scientific and reasonable.

[0047] 2) The present invention innovatively proposes to calculate the sewage collection service fees based on the load of pollutants collected by the sewage network system, which is different from the traditional method of charging according to the sewage volume. It focuses more on the background that affects the water environment quality, that is, the load of pollutants discharged into the receiving water body. By making up for the shortcomings of sewage collection, improving the sewage collection efficiency, increasing the amount of pollutants collected and treated in sewage, and reducing the discharge of pollutants into the water environment. Taking the pollutant collection volume as the standard for payment according to effectiveness can solve problems such as the lack of funds for drainage network construction and insufficient operation and maintenance.

[0048] 3) The present invention realizes a rapid calculation method for the benchmark collection volume, target collection volume, actual collection volume of pollutants in the sewage system, and the cost required for the sewage collection system to collect each unit of pollutants, which can provide reference for similar research and practice on calculating pollutant collection load and cost.

[0049] 4) The method of the present invention can not only simply and quickly calculate the service fees for the sewage collection system to collect pollutants, but also has a certain degree of replicability and popularization, and can be used for the establishment of a payment mechanism according to effectiveness for urban sewage quality improvement and efficiency increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The present invention will be further described below with reference to the drawings and embodiments.

[0051] Figure 1Schematic diagram of the process of the sewage collection service charging method according to the effectiveness of the embodiments of the present invention.

[0052] Figure 2 Schematic diagram of the influencing factors of the COD collection load weight coefficient according to the embodiments of the present invention. Specific embodiments

[0053] Taking the sewage collection system in the main urban area of a midstream city in the Yangtze River Economic Belt as an example, calculate the sewage collection service fee of this city. There are 7 operating sewage treatment plants in the main urban area of this city, with a total service population of about 783,000 people, and the centralized collection rate of urban domestic sewage reaches more than 70%. Taking 2021 as the base year, collect the operation data of the sewage treatment plants, and use the sewage collection service payment calculation method based on pollutant collection load proposed by the present invention to calculate the sewage collection service fee in the main urban area of this city.

[0054] As Figure 1 shown, the sewage collection service payment calculation method based on pollutant collection load includes the following steps:

[0055] Step 1, establish a mathematical model for calculating the sewage collection service fee based on the pollutant treatment load;

[0056] Cost = P × (S - S 0 ) × Wt + P × (S 1 - S 0 ) × Wa × J + Op

[0057] Among them, Cost represents the sewage collection service fee;

[0058] P represents the unit price of pollutant measurement;

[0059] S represents the target collection volume of pollutants;

[0060] S 0 represents the benchmark collection volume of pollutants;

[0061] S 1 represents the actual collection volume of pollutants;

[0062] Wt represents the target collection load weight coefficient of pollutants;

[0063] Wa represents the actual collection load weight coefficient of pollutants;

[0064] J represents the concentration adjustment coefficient for collecting pollutants;

[0065] Op represents the operation and maintenance cost.

[0066] Step 2, calculate the COD collection volume of the sewage collection system;

[0067] Step 2.1: Select COD as the pollutant index and calculate the baseline collection volume, target collection volume, and actual collection volume of pollutants in the sewage collection system.

[0068] Step 2.2: Calculate the baseline collection volume of COD in the sewage collection system. The baseline collection volume S of COD 0 is the total inlet COD load of 7 sewage treatment plants in the main urban area in 2021. It is calculated by weighted cumulative calculation of the daily inlet sewage volume Q 0 and the average COD concentration C 0 of the 7 sewage treatment plants, that is:

[0069] ton

[0070] In the formula, n f is the number of sewage treatment plants, and the subscript j represents the jth sewage treatment plant; N d is the number of days in a natural year, and the subscript i represents the ith day; Q 0 is the total daily inlet sewage volume of each sewage treatment plant in 2021, with the unit of m 3 ; C 0 is the average daily inlet COD concentration of the sewage treatment plant in 2021, with the unit of mg / L.

[0071] Step 2.3: Calculate the target collection volume of COD in the sewage collection system;

[0072] According to the urban sewage centralized collection rate target of 70%, calculate the target collection volume S of COD. It is calculated through the per capita COD discharge standard of the permanent population, that is:

[0073] S = (T BOD5 / b) × n × d × r / 10 6 = (45 / 0.4) × 783000 × 365 × 70% / 10 6 = 22506 tons

[0074] In the formula, T BOD5 is the BOD 5 pollution load discharged per person per day, and its value in the embodiment is 45 g / (person·day); b is the biodegradability index of sewage, and b = 0.4 is determined by statistical analysis of the daily actual inlet BOD 5 and COD average concentrations of 7 sewage treatment plants in 2021; n is the permanent population of 783000 people within the service area of the sewage collection system project; d is the total number of days in the year, d = 365 days; r is the target value of the urban sewage centralized collection rate, and r = 70% in the embodiment.

[0075] Step 2.4: Calculate the actual collection volume of COD in the sewage collection system;

[0076] Actual COD collection volume S 1 is the total influent COD load of 7 sewage treatment plants in the main urban area in a future operating year, calculated by weighted accumulation of the daily influent sewage volume Q 1 and the average COD concentration C 1 of the 7 sewage treatment plants in 2022, that is:

[0077] S 1 =∑C 1 ×Q 1 / 10 6 =19553 tons

[0078] In the formula, Q 1 is the total daily influent sewage volume of each sewage treatment plant in 2022, with the unit of m 3 ; C 1 is the average daily influent COD concentration of the sewage treatment plant in 2022, with the unit of mg / L.

[0079] Step 3, determine the COD measurement unit price of the sewage collection system;

[0080] The COD measurement unit price P of the sewage collection system is the cost required for the sewage collection system to collect a unit of COD load, and the calculation formula is:

[0081] P=I 0 / (S - S 0 )

[0082] In the formula, P is the COD collection measurement unit price, in ten thousand yuan; I 0 is the annual construction cost of the sewage collection system, with the unit of ten thousand yuan / ton.

[0083] Step 4, determine the COD collection load weight coefficient;

[0084] Based on comprehensive consideration of influencing factors such as the pollutant generation situation in the sewage collection system of the main urban area of the city, the background situation of the sewage pipe network, the cost of sewage pipe network transformation, the construction quality of the sewage pipe network, and the operation and maintenance situation of the sewage pipe network, as Figure 2 shown, determine that the COD target collection load weight coefficient is 0.7 and the COD actual collection load weight coefficient is 0.3.

[0085] Step 5, determine the concentration adjustment coefficient of the collected pollutants;

[0086] Step 5.1, in this embodiment, both the annual influent concentrations of COD and BOD 5 are considered, and the calculation formula for the concentration adjustment coefficient of the collected pollutants is as follows:

[0087]

[0088] Wherein, A and B are COD and BOD 5 weight coefficients. In the embodiments, the values of A and B can be determined according to the actual situation; are the annual average concentrations of influent COD and BOD of each sewage treatment plant respectively, with the unit of mg / L; Q 5 is the annual total influent volume of each sewage treatment plant, in m j ; F 3 ; F COD is the score coefficient of the concentration gradient of influent COD pollutants; F BOD5 is the score coefficient of the concentration gradient of influent BOD 5 pollutants.

[0089] Step 5.2: According to the actual influent COD and BOD 5 concentration conditions of each sewage treatment plant in the main urban area in 2021, and the expected influent COD and BOD 5 concentrations in each operation year after implementing the quality improvement and efficiency enhancement project in batches according to the target requirement of the sewage centralized collection rate of 70% in the future, set the influent water quality concentration ladder intervals and the corresponding score coefficient F as shown in Table 1.

[0090] Table 1 Influent water quality concentration gradient and corresponding score coefficient table

[0091] Annual influent COD (mg / L) <![CDATA[F COD > Annual influent BOD (mg / L) <![CDATA[F BOD5 > >260 1.2 >100 1.2 1.0 1.0 <210 0.8 <80 0.8

[0092] Step 5.3: According to the actual influent COD and BOD 5 concentration conditions of each sewage treatment plant in the main urban area in 2022, calculate the concentration adjustment coefficient J = 0.8 of the collected pollutants according to the calculation formula of the concentration adjustment coefficient of the collected pollutants in Step 5.1.

[0093] Step 6: Determine the operation and maintenance cost of the sewage collection system;

[0094] The specific operation and maintenance cost of the sewage collection system project shall be determined by the local competent department according to the operation cost application report submitted by the project investment and operation and maintenance unit and the daily performance assessment results issued by the government department. The specific performance assessment shall be clarified through the operation service contract.

[0095] Step 7: Calculate the sewage collection service fee of the sewage collection system

[0096] Step 7.1: Substitute the parameters such as the pollutant collection volume, pollutant measurement unit price, pollutant collection load weight coefficient, concentration adjustment coefficient of the collected pollutants, and operation and maintenance cost of the sewage collection system in the main urban area of the city calculated and determined in Steps 2 to 6 into the sewage collection service fee calculation mathematical model in Step 1 to calculate the sewage collection service fee. Taking 2022 as an example, the calculation results are as follows:

[0097] Sewage collection service fee = P×(22506 - 19106)×0.7 + P×(19553 - 19106)×0.3×0.8 + operation and maintenance costs, where P and the operation and maintenance costs need to be determined according to the actually signed contract.

[0098] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The embodiments and the features in the embodiments in this application can be arbitrarily combined with each other without conflict. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for calculating payment according to performance of sewage collection service based on pollutant collection load, Characterized in that, It includes the following steps: S1. Establish a mathematical model for calculating the sewage collection service fee based on the pollutant collection load; S2. Calculate the pollutant collection volume of the sewage collection system, including the benchmark pollutant collection volume, the target pollutant collection volume and the actual pollutant collection volume; S3. Determine the unit price for measuring pollutants in the sewage collection system; S4. Combine the characteristics of pollution sources and sewage collection pipe networks to determine the pollutant collection load weight coefficient; S5. Determine the concentration adjustment coefficient of the collected pollutants according to the concentration of pollutants in the influent of the sewage treatment plant; S6. Determine the operation and maintenance costs of the sewage collection system; S7. Use the mathematical model for calculating the sewage collection service fee to calculate the sewage collection service fee of the sewage collection system; The step S2 includes the following sub-steps: S201. Calculate the benchmark pollutant collection volume of the sewage collection system; Pollutant baseline collection volume S 0 is the total influent COD load of all wastewater treatment plants in the area served by the wastewater collection system project in the natural year before the implementation of the wastewater collection system project, calculated by weighted accumulation of the daily total influent wastewater volume Q 0 of the wastewater treatment plants and the average COD concentration C 0 That is: ； Where S 0 is the benchmark collection amount of pollutants; is the number of sewage treatment plants, and the subscript j indicates the j th sewage treatment plant; is the number of days in a natural year, and the subscript i indicates the i th day; Q 0 is the total daily influent sewage volume of the sewage treatment plant; C 0 is the average daily influent COD concentration of the sewage treatment plant; S202. Calculate the target pollutant collection volume of the sewage collection system; The target pollutant collection volume S is the total annual COD collection load calculated according to the target requirements of the urban sewage centralized collection rate within the service area of the sewage collection system project, and is calculated through the per capita pollutant discharge standard of the permanent population, that is: S = (T BOD5 / b) × n p × d × r / 10 6 ; In the formula, S is the target pollutant collection volume; T BOD5 BOD emissions per person per day 5 Pollution load; b is the biodegradability index of sewage; n p is the total number of permanent residents within the service area of the sewage collection system project; d is the total number of days in that year; r is the target value of the urban sewage centralized collection rate; S203. Calculate the actual pollutant collection volume of the sewage collection system; Actual pollutant collection volume S 1 Refers to the total COD load entering the sewage treatment plants within the service area of the sewage collection system project during the current year of the operation period, which can be calculated by weighted accumulation of the daily actual total inflow sewage volume Q 1 of the sewage treatment plants and the average COD concentration Q 1 That is: ； Where S 1 is the benchmark collection amount of pollutants; Q 1 is the total actual influent sewage volume of the sewage treatment plant per day; C 1 is the average daily actual influent COD concentration of the sewage treatment plant; In step S1, the mathematical model for calculating the sewage collection service fee is: ； Where Cost represents the sewage collection service fee; P represents the unit price for measuring pollutants; S represents the target pollutant collection volume; S0 represents the benchmark pollutant collection volume; S1 represents the actual pollutant collection volume; Wt represents the target pollutant collection load weight coefficient; Wa represents the actual pollutant collection load weight coefficient; J represents the concentration adjustment coefficient of the collected pollutants; Op represents the operation and maintenance costs; In step S3, the unit price P for measuring pollutants collected by the sewage collection system is the cost required for the sewage collection system to collect each unit of pollutant load, and the calculation formula is: P = I 0 / (S - S 0 ); where P is the unit price for calculating the collected pollutants; I 0 is the annual construction cost of the sewage collection system; In step S5, the concentration adjustment coefficient J of the collected pollutants is used to evaluate the contribution of the new construction cost of the sewage collection system to the influent concentration, and the concentration adjustment coefficient of the collected pollutants is calculated by weighted average of the annual average concentration of pollutants in the influent of each sewage treatment plant within the service area of the sewage collection system.

2. The method for calculating payment according to performance of sewage collection service according to claim 1, Characterized in that, In step S4, the pollutant collection load weight coefficient is determined according to the target pollutant collection volume that can be increased by the sewage collection system and the actual increased pollutant collection volume after the implementation of the sewage collection system project; Comprehensively consider the pollutant generation situation in the sewage collection system, the background situation of the sewage pipe network, the renovation cost of the sewage pipe network, the construction quality of the sewage pipe network, and the operation and maintenance situation of the sewage pipe network to determine the specific values of the target pollutant collection load weight coefficient and the actual pollutant collection load weight coefficient.

3. The method for calculating payment according to performance of sewage collection service according to claim 1, Characterized in that, The sum of the target pollutant collection load weight coefficient and the actual pollutant collection load weight coefficient is 1, that is Wt + Wa = 1。 4. According to the pay-for-performance calculation method for sewage collection services described in claim 1, characterized in that in step S5, if only the annual influent concentration of one pollutant, namely COD or BOD5, is considered, the calculation formula for the concentration adjustment coefficient J of the collected pollutant is: ； wherein, is the annual average concentration of influent pollutants of each sewage treatment plant; is the annual total influent volume of each sewage treatment plant; F is the annual influent pollutant concentration gradient score coefficient; If both COD and BOD are considered simultaneously 5 For the annual influent concentrations of the two pollutants, the calculation formula for the concentration adjustment coefficient J for collecting pollutants is as follows: ； Wherein, A and B are the weight coefficients of COD and BOD respectively 5 ; is the average annual concentration of influent COD of each sewage treatment plant; is the influent BOD of each sewage treatment plant 5 average annual concentration; is the score coefficient of the annual influent COD pollutant concentration gradient; is the annual influent BOD 5 pollutant concentration gradient score coefficient.

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