A refined method for calculating total pollutant discharge under complex river conditions

Abstract

This invention discloses a refined calculation method for total pollutant discharge under complex river conditions, relating to the field of pollutant discharge control technology. It involves establishing a physical experimental model and setting the pollution load for each river segment within the model; based on the established physical experimental model, a mathematical model of the complex river's aquatic environment is built to calculate the pollutant concentration in the study river segment under preset environmental conditions; the pollutant aquatic environmental capacity of the study river segment during the dry and wet seasons is calculated separately, and the dry and wet season options are weighted for the study river segment to calculate the total permissible pollutant discharge for the study river segment. This invention achieves accurate calculation of the total permissible discharge of characteristic pollutants under complex river conditions.

Description

Technical Field

[0001] This invention relates to the field of pollutant emission control technology, and more specifically to a method for refining the calculation of total pollutant emissions under complex river conditions. Background Technology

[0002] In the field of river pollution control and management, accurately calculating the permissible total discharge of characteristic pollutants in a watershed is crucial for protecting river water quality. While some progress has been made in calculating total river pollutant discharge, existing technologies still have many shortcomings when dealing with complex river conditions. On the one hand, current research lacks sufficient understanding of the discrete characteristics of complex rivers. Complex river morphology, large seasonal variations in water volume, high sediment content, and the coexistence of icy and non-icy sections make the transport and mixing mechanisms of pollutants in rivers extremely complex. However, existing technologies struggle to comprehensively and accurately grasp the impact of these factors on pollutant transport and mixing, and cannot precisely determine the lateral and longitudinal dispersion coefficients, leading to significant errors in calculating the diffusion range and concentration changes of pollutants.

[0003] On the other hand, existing mathematical models for constructing river water environment models have limitations. Traditional two-dimensional water environment mathematical models use relatively simple methods to determine the longitudinal dispersion coefficient, lateral dispersion coefficient, and pollutant attenuation coefficient, failing to fully consider the comprehensive influence of various factors under complex river conditions. For example, the calculation of the longitudinal dispersion coefficient does not comprehensively cover key factors such as river flow characteristics, frictional characteristics, and cross-sectional dimensions; the calculation of the lateral dispersion coefficient often ignores its complex relationship with the longitudinal dispersion coefficient; and the pollutant attenuation coefficient does not fully consider the impact of special conditions such as high sediment content and ice formation on the water body's self-purification capacity, resulting in significant deviations between the model calculation results and actual conditions, and failing to provide a reliable basis for river pollution control.

[0004] Therefore, how to calculate the permitted total discharge of characteristic pollutants under complex river conditions is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for refining the calculation of total pollutant discharge under complex river conditions, in order to solve the problems existing in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A refined method for calculating total pollutant emissions under complex river conditions includes:

[0008] Establish a physical experimental model and set the pollution load for each river section of the physical experimental model;

[0009] Based on the established physical experimental model, a mathematical model of the complex river water environment is established to calculate the pollutant concentration in the study section under preset environmental conditions.

[0010] The pollutant water environment capacity of the study river section during the dry season and the wet season are calculated separately. The dry season and wet season options are weighted and the total permitted discharge of pollutants in the watershed of the study river section is calculated.

[0011] Preferably, the preset environmental conditions include:

[0012] The first presupposed environmental condition is a complex riverbed morphology;

[0013] The second presupposed environmental conditions include complex river morphology and high sediment content.

[0014] The third pre-set environmental conditions include complex river morphology and freezing conditions.

[0015] The fourth presupposed environmental conditions include complex river morphology, high sand content, and freezing conditions.

[0016] Any preset environmental conditions.

[0017] Preferably, calculating the pollutant concentration in the study river section under the first preset environmental conditions specifically includes:

[0018] ;

[0019] ;

[0020] in, H For water depth; W The river is wide; a, b, γ, m, d, i It is a constant; u, v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the first preset environmental conditions; C The concentration of pollutants; S external source ; DO It refers to the dissolved oxygen content in the water. Q Water flow rate; t It is time; Δx, Δy These are the longitudinal and lateral transport distances, respectively.

[0021] Preferably, calculating the pollutant concentration in the study river section under the second preset environmental conditions specifically includes:

[0022] ;

[0023] ;

[0024] ;

[0025] in, H For water depth; W The river is wide; a, b, γ, m, d, i It is a constant; u, v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the second preset environmental conditions; C The concentration of pollutants; S External source; DO s This represents the effect of water and sediment content on dissolved oxygen; T Represents water temperature. ρ Represents sand content, a 1 、b 1 、c For coefficients; Q Water flow rate; t It is time; Δx, Δy These are the longitudinal and lateral transport distances, respectively.

[0026] Preferably, calculating the pollutant concentration in the study river section under the third preset environmental conditions specifically includes:

[0027] ;

[0028] ;

[0029] ;

[0030] in, H For water depth; W The river is wide; a, b, γ, m, d, i It is a constant; u, v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the third preset environmental condition; CThe concentration of pollutants; S External source; This represents the impact of freezing on dissolved oxygen levels in water bodies; h Represents the thickness of the ice layer. e, f, g For coefficients; Q Water flow rate; t It is time; Δx, Δy These are the longitudinal and lateral transport distances, respectively.

[0031] Preferably, calculating the pollutant concentration in the study river section under the fourth preset environmental conditions specifically includes:

[0032] ;

[0033] ;

[0034] in, This is the pollutant attenuation coefficient under the fourth preset environmental condition.

[0035] Preferably, the pollutant water environmental capacity of the study river section is calculated separately during the dry season and the wet season, represented by the following formula:

[0036] ;

[0037] in, It is the inflow rate at the inlet section. This refers to the water quality standard for that water body. It refers to the water quality concentration at the inlet section. K It is the pollutant attenuation coefficient. V It refers to the volume of water.

[0038] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a refined calculation method for the total amount of pollutants discharged under complex river conditions. Through physical experiments, the transport and mixing mechanisms of pollutants in complex river morphology models are measured and analyzed. The effects of different cross-sectional morphologies, changes in hydrodynamic conditions, water sediment content, and ice formation on the changes in flow velocity and pollutant concentration in the river channel are measured. Thus, the influencing factors of the lateral and longitudinal dispersion coefficients are determined, the transport and mixing mechanisms of pollutants under complex river conditions are analyzed and revealed, and the lateral and longitudinal dispersion coefficient calculation formulas are established to comprehensively consider the diverse river morphologies, large seasonal variations in water volume, high water and sediment content, and the coexistence of ice-covered and non-ice-covered sections in the watershed. This achieves accurate calculation of the total permissible discharge of characteristic pollutants under complex river conditions. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0040] Figure 1 A flowchart of the method steps provided by the present invention;

[0041] Figure 2 This is a schematic diagram of the planar shape of the physical model provided by the present invention;

[0042] Figure 3 A schematic diagram of the cross-sectional shape of the physical model provided by the present invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] This invention discloses a method for refined calculation of total pollutant emissions under complex river conditions, such as... Figure 1 As shown, it includes:

[0045] Establish a physical experimental model and set the pollution load for each river section in the physical experimental model;

[0046] Based on the established physical experimental model, a mathematical model of the complex river water environment is established to calculate the pollutant concentration in the study section under preset environmental conditions.

[0047] The pollutant water environment capacity of the study river section during the dry and wet seasons was calculated separately, and the dry and wet season options were weighted for the study river section to calculate the total permitted discharge of pollutants in the watershed of the study river section.

[0048] In one specific embodiment, the preset environmental conditions include:

[0049] The first presupposed environmental condition is a complex riverbed morphology;

[0050] The second presupposed environmental conditions include complex river morphology and high sediment content.

[0051] The third pre-set environmental conditions include complex river morphology and freezing conditions.

[0052] The fourth presupposed environmental conditions include complex river morphology, high sand content, and freezing conditions.

[0053] Any preset environmental conditions.

[0054] Complex river channels generally refer to rivers with varying cross-sectional shapes across different sections, including bends, straight sections, narrow sections, and bifurcations. Different channel shapes have different impacts on pollutant transport, making them difficult to accurately simulate using simple straight river models. Sedimentary conditions refer to rivers with high sediment content, typically characterized by high suspended solids (suspended sediment), large suspended solids particle size, shallow riverbed depth, and slow flow velocity. Specifically, suspended solids content exceeds 10 mg / L in the water, with suspended solids particles larger than 4 mm exceeding 2 mg / L.

[0055] In one specific embodiment, calculating the pollutant concentration of the study river section under the first preset environmental conditions specifically includes:

[0056] ;

[0057] ;

[0058] in, H For water depth; W The river is wide; a, b, γ, m, d, i It is a constant; u, v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the first preset environmental conditions; C The concentration of pollutants; S external source ; DO It refers to the dissolved oxygen content in the water. Q Water flow rate; t It is time; Δx, Δy These are the longitudinal and lateral transport distances, respectively.

[0059] In one specific embodiment, calculating the pollutant concentration of the study river section under the second preset environmental conditions specifically includes:

[0060] ;

[0061] ;

[0062] ;

[0063] in, H For water depth; W The river is wide;a, b, γ, m, d, i It is a constant; u, v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the second preset environmental conditions; C The concentration of pollutants; S External source; DO s This represents the effect of water and sediment content on dissolved oxygen; T Represents water temperature. ρ Represents sand content, a 1 、b 1 、c For coefficients; Q Water flow rate; t It is time; Δx, Δy These are the longitudinal and lateral transport distances, respectively.

[0064] In one specific embodiment, calculating the pollutant concentration of the study river section under the third preset environmental conditions specifically includes:

[0065] ;

[0066] ;

[0067] ;

[0068] in, H For water depth; W The river is wide; a, b, γ, m, d, i It is a constant; u, v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the third preset environmental condition; C The concentration of pollutants; S External source; This represents the impact of freezing on dissolved oxygen levels in water bodies; h Represents the thickness of the ice layer. e, f, g For coefficients; Q Water flow rate; t It is time; Δx,Δy These are the longitudinal and lateral transport distances, respectively.

[0069] In one specific embodiment, calculating the pollutant concentration of the study river section under the fourth preset environmental conditions specifically includes:

[0070] ;

[0071] ;

[0072] in, This is the pollutant attenuation coefficient under the fourth preset environmental condition.

[0073] In one specific embodiment, the pollutant water environmental capacity of the study river section is calculated separately during the dry season and the wet season, represented by the following formula:

[0074] ;

[0075] in, It is the inflow rate at the inlet section. This refers to the water quality standard for that water body. It refers to the water quality concentration at the inlet section. K It is the pollutant attenuation coefficient. V It refers to the volume of water.

[0076] In one specific embodiment, a physical experimental model of the Yellow River's straight-curved-straight channel was constructed to address the complex channel morphology of the upper and middle reaches. The physical experimental model is 12m long, with a maximum water surface width of 1m, and the main experimental section is approximately 10m long, with an adjustable bottom slope. Inlet and outlet water systems are installed at the upstream and downstream ends of the physical experimental model, respectively. By adjusting the water depth within the model, the cross-section can exhibit various morphologies, such as a wide-shallow type and a narrow-deep type. The two straight sections before the bend entrance and at the end of the outlet are each 2m long. Figure 2 and Figure 3 As shown.

[0077] Conduct the physical experiment following these steps:

[0078] i. Along the continuous curved section of the physical experimental model, monitoring sections were selected at 45° intervals. The three-dimensional flow velocity distribution in the model was measured using an ADCP measuring instrument. Tracers were also added, and the pollutant changes along the cross section were measured using a concentration measuring instrument. The transport and mixing mechanisms of pollutants in the complex river morphology model were analyzed.

[0079] ii. By adjusting the water depth in the tank and changing the cross-sectional shape of the tank, the effect of different cross-sectional shapes on the change of pollutant concentration was measured;

[0080] iii. By changing the inlet flow rate, the effects of changes in hydrodynamic conditions on changes in flow velocity and concentration distribution within the river channel were measured;

[0081] iv. Add different amounts of sediment, repeat step i, and analyze the effects of sediment content in the water on changes in flow velocity and pollutant concentration;

[0082] v. Based on relevant research, select a suitable plywood to float on the water surface and fix it to the side wall of the model. Repeat steps i and iv to simulate the effect of freezing on changes in water flow velocity and pollutant concentration.

[0083] By thoroughly analyzing and sorting out the above physical experimental data, we determined the influencing factors of the lateral and longitudinal dispersion coefficients, analyzed and revealed the transport and mixing mechanism of pollutants under complex river conditions, and established calculation formulas for the lateral and longitudinal dispersion coefficients of the upper and middle reaches of the Yellow River, taking into account the diverse river morphology, large seasonal variation in water volume, high water and sediment content, and the coexistence of icy and non-icy sections.

[0084] The spatiotemporal variation of pollutant concentrations in water bodies mainly includes the convective diffusion process of pollutants flowing with the water body and the biochemical degradation and decay process of the pollutants themselves. In a two-dimensional planar model, the water quality process control mass balance equation is usually expressed by the following pollutant convective diffusion decay equation:

[0085] (1)

[0086] in, H Indicates water depth. C It refers to the concentration of pollutants. u, v They are x, y velocity components in the direction, D x 、D y They are x, y The horizontal dispersion coefficient in the direction, namely the longitudinal dispersion coefficient and the lateral dispersion coefficient of the river. S c The attenuation term is related to the concentration of the transported substance. S For external sources or sinks.

[0087] (2)

[0088] k It represents the rate of decay of pollutants in water bodies through biochemical degradation.

[0089] The most important task in calculating the river water environment capacity based on a two-dimensional mathematical model of the water environment is to clarify... D x 、D y and k The value of .

[0090] In this project, the longitudinal dispersion coefficient of the river D x Calculations are based on empirical formulas derived from river flow characteristics, friction characteristics, and cross-sectional dimensions:

[0091] (3)

[0092] in, W For the river width, H Because of the water depth, u’ The cross-sectional average velocity is... This represents the frictional velocity at the bottom of the riverbed. (Constant) m, d, i Calculations are performed based on physical experiments.

[0093] For the horizontal dispersion coefficient D y Since the lateral flow velocity in a river is generally much lower than the longitudinal flow velocity, the impact of lateral dispersion is relatively small. This invention uses empirical formulas to solve for the lateral dispersion coefficient using the longitudinal dispersion coefficient.

[0094] (4)

[0095] Pollutant attenuation coefficient k Determined by multiple factors and considering the complex conditions in the upper and middle reaches of the Yellow River, this invention mainly considers the impact of the coexistence of sediment-rich, ice-covered, and non-ice-covered sections on the dissolved oxygen content of the water body, i.e., on the water body's self-purification capacity. Furthermore, it uses a combination of numerical simulation and physical modeling to calibrate the equation for solving the pollutant attenuation coefficient.

[0096] (5)

[0097] in, C It refers to the concentration of pollutants. DO It refers to the dissolved oxygen content in the water. Q For water flow rate, t It is time. Δx, Δy These are the longitudinal and lateral transport distances, respectively. Therefore, dissolved oxygen... DO Content is an important variable in calculating the pollutant decay coefficient.

[0098] In this invention, the dissolved oxygen content in water is mainly affected by the sediment content and freezing conditions. The impact of freezing on the water's self-purification capacity only occurs during the dry season. The relationship between dissolved oxygen and sediment content can be expressed as:

[0099] (6)

[0100] in, DO s This represents the impact of water and sediment content on dissolved oxygen. T Represents water temperature.ρ Represents sediment content, coefficient a 1 、b 1 、c It can be calculated based on physical experiments.

[0101] Therefore, considering only the effects of water and sediment, the pollutant attenuation coefficient is,

[0102] (7)

[0103] Regarding the impact of freezing on dissolved oxygen content in water bodies, the dissolved oxygen content exhibits a U-shaped change curve during the freezing period, and the proposed equation is as follows:

[0104] (e>0) (8)

[0105] in, DO i This represents the impact of freezing on dissolved oxygen levels in water. h Represents ice thickness, coefficient e, f, g It can be calculated based on actual physical experiments.

[0106] Therefore, considering only the effect of icing, the pollutant attenuation coefficient is,

[0107] (9)

[0108] Taking into account the effects of water sediment and ice formation, the pollutant attenuation coefficient is:

[0109] (10)

[0110] In summary, the improved mass balance equation for water quality process control in the two-dimensional model under complex river channel morphology is as follows:

[0111] (11)

[0112] Under complex river morphology and sediment-rich conditions, the water quality process control mass balance equation in the two-dimensional model is improved as follows:

[0113] (12)

[0114] Under complex river morphology and freezing conditions, the water quality process control mass balance equation in the two-dimensional model is improved as follows:

[0115] (13)

[0116] Under conditions of complex river morphology, high sediment content, and ice formation, the water quality process control mass balance equation in the two-dimensional model is improved as follows:

[0117] (14)

[0118] The study of watershed pollution load includes two categories: point source and non-point source pollution. Non-point source pollution is mainly concentrated during the high-water season. Therefore, from the perspective of total quantity control, the permissible discharge of pollutants is calculated separately for point source and non-point source pollution loads corresponding to different water conditions. The combined amount of both is the total permissible discharge of pollutants for the watershed.

[0119] The specific calculation steps are as follows:

[0120] i. Based on the actual location of sewage outlets into the river, the point source pollution load is generalized to each river section, while the non-point source pollution is divided into each river section surrounding the land area.

[0121] ii. Using the established complex two-dimensional water environment mathematical model of the river, the pollutant concentration in each river section is calculated;

[0122] iii. Calculate the pollutant water environmental capacity of the study river section during the dry and wet seasons, respectively. The calculation formula is as follows:

[0123] (15)

[0124] in: Q 0 It is the inflow rate at the inlet section. Cs This refers to the water quality standard for that water body. C 0 It refers to the water quality concentration at the inlet section. K It is the pollutant attenuation coefficient. V It refers to the volume of water.

[0125] iv. Based on the actual situation, weights are assigned to the water environment capacity during the dry season and the wet season, and the water environment capacity of the basin is calculated in a comprehensive manner to obtain the total permitted discharge of pollutants in the basin.

[0126] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0127] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A refined method for calculating total pollutant emissions under complex river conditions, characterized in that, include: Establish a physical experimental model and set the pollution load for each river section of the physical experimental model; Based on the established physical experimental model, a mathematical model of the complex river water environment is established to calculate the pollutant concentration in the study section under preset environmental conditions. The pollutant water environment capacity of the study river section during the dry season and the wet season are calculated separately, and the dry season and wet season options are weighted for the study river section to calculate the total permissible discharge of pollutants in the watershed of the study river section. The preset environmental conditions include: The first presupposed environmental condition is a complex riverbed morphology; The second presupposed environmental conditions include complex river morphology and high sediment content. The third pre-set environmental conditions include complex river morphology and freezing conditions. The fourth presupposed environmental conditions include complex river morphology, high sand content, and freezing conditions. Any preset environmental condition; The calculation of pollutant concentrations in the study river section under the first preset environmental conditions specifically includes: in, H For water depth; W The river is wide; a, b, γ, m, d, i It is a constant; u、v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the first preset environmental conditions; C The concentration of pollutants; S external source ;DO It refers to the dissolved oxygen content in the water. Q Water flow rate; t It is time; Δx, Δy These are the longitudinal and lateral transport distances, respectively. The calculation of pollutant concentrations in the study river section under the second preset environmental conditions specifically includes: in, H For water depth; W The river is wide; a, b, γ, m, d, i It is a constant; u、v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the second preset environmental conditions; C The concentration of pollutants; S External source; DO s This represents the effect of water and sediment content on dissolved oxygen; T Represents water temperature. ρ Represents sand content, a 1 、b 1 、c For coefficients; Q Water flow rate; t It is time; Δx, Δy These are the longitudinal and lateral transport distances, respectively. The calculation of pollutant concentrations in the study river section under the third preset environmental conditions specifically includes: in, H For water depth; W The river is wide; a, b, γ, m, d, i It is a constant; u、v They are x, y Velocity component in the direction; u’ The cross-sectional average velocity is... The velocity is the frictional velocity at the bottom of the riverbed. Q Water flow rate; D x The longitudinal dispersion coefficient of the river; The pollutant attenuation coefficient under the third preset environmental condition; C The concentration of pollutants; S External source; This represents the impact of freezing on dissolved oxygen levels in water bodies; h Represents the thickness of the ice layer. e, f, g For coefficients; Q Water flow rate; t It is time; Δx, Δy These are the longitudinal and lateral transport distances, respectively. The calculation of pollutant concentrations in the study river section under the fourth preset environmental conditions specifically includes: in, This is the pollutant attenuation coefficient under the fourth preset environmental condition.

2. The method for refined calculation of total pollutant discharge under complex river conditions according to claim 1, characterized in that, The pollutant water environmental capacity of the study river section was calculated separately during the dry and wet seasons, using the following representative formula: ； in, It is the inflow rate at the inlet section. This refers to the water quality standard for that water body. It refers to the water quality concentration at the inlet section. K It is the pollutant attenuation coefficient. V It refers to the volume of water.

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