With the continuous increase in the development and utilization of water resources, the discharge of waste and sewage in the country is increasing day by day, and some river sections have far exceeded the pollution-holding capacity of the waters. In recent years, some problems such as unreasonable setting of sewage outlets along the river, excessive sewage discharge, and private establishment of sewage outlets without consent have gradually emerged, which have threatened water supply safety, water environment safety and water ecological safety, and put pressure on the water quality safety assurance work along the river. increasing day by day. In 2011, the No. 1 central document decided to implement the most stringent water resources management system. In 2012, the State Council put forward clear opinions on implementing the most stringent water resources management system, and established the "red line for total water consumption control" and "red line for water use efficiency control". Together with the three red lines of "restricted pollutant collection in water function zones", four basic systems for the most stringent water resources management have been established. It is not difficult to see that among the three red lines, the most difficult and the most eye-catching is the "water function area limit pollution red line". key breakthrough. According to the "Water Law of the People's Republic of China" and the "Water Pollution Prevention and Control Law of the People's Republic of China", the establishment of sewage outlets in rivers and lakes requires the consent of the water administrative department or the competent department with jurisdiction over the river basin management organization. In 2017, the Ministry of Water Resources issued a notice on further improving the supervision and management of river sewage outlets, requiring strict approval for the establishment of river sewage outlets. According to the "Measures for the Supervision and Management of Sewage Outlets into Rivers", when applying for the establishment of sewage outfalls into rivers, it is necessary to submit demonstration materials for the establishment of sewage outfalls into rivers. In September 2018, the management authority for the establishment of sewage outlets into the river was assigned to the Ministry of Ecology and Environment. As of 2021, most of the management methods for the establishment of sewage outlets into the river will still follow the management methods of the Ministry of Water Resources, but the management will be more detailed and strict. In 2022, the General Office of the State Council will issue "Implementation Opinions on Strengthening the Supervision and Management of Sewage Outlets Entering Rivers and Seas" requires strict regulation of the approval of the establishment of sewage outlets entering rivers. Implementation Opinions > Notice, detailed regulations on the approval work for the establishment of sewage outlets.
Taking the cases of urban domestic sewage plants, papermaking projects, petrochemical projects, and pharmaceutical projects as clues, systematically explain the preparation process of the demonstration report for the establishment of sewage outlets into the river, and use the water quality model as a means to explain the working procedures of the water quality impact prediction model, and make a comparison Through in-depth discussions, the purpose of quickly grasping the main technical content of the demonstration report on the establishment of sewage outlets into the river can be achieved.
Link to the original article: Argumentation on the setting of sewage outlets into the river, water quality impact prediction and simulation, analysis of sewage treatment process and case analysis of the report on the sewage outlet scheme of typical construction projects
A comprehensive understanding of the legal basis for the demonstration of the establishment of sewage outlets into the river, the establishment process of the system, the approval authority and legal prohibitions:
1.1 The legal basis for the demonstration of the establishment of sewage outlets entering the river
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Figure 1 Legal system for the management of river sewage outlets
1.2 Systems related to the demonstration of the establishment of sewage outlets entering the river
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Figure 2 Relevant systems for the management of river sewage outlets
1.3 Specifications related to the demonstration of the establishment of sewage outlets entering the river
(1) Water environment quality standards
(2) Pollutant Discharge Standards
(3) Pollution-holding capacity accounting and standards for limiting the total amount of pollutant discharge
(4) Environmental access standards
(5) Standards related to design scale and process
1.4 General steps in the demonstration of setting up sewage outlets into rivers
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Fig. 3 Basic procedures for the demonstration of setting up sewage outlets into rivers
Topic 2 Accounting method for pollution-holding capacity of water areas (combination of lectures and practical exercises)
According to different water bodies, combined with specific examples, the accounting technology of waters' pollution-holding capacity is explained:
2.1 General provisions
Including method selection, design hydrological conditions, model application, calculation process, rationality analysis, etc.
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Figure 4 my country's water function zoning system
2.2 Calculation method of pollution-holding capacity of protected areas, reserved areas, and buffer areas
In protected areas, it is generally forbidden to set up new sewage outlets into rivers, and the pollution-holding capacity of water areas is taken as zero; in reserved areas and buffer zones, new sewage outfalls into rivers are generally prohibited, and the sewage-holding capacity of water areas adopts the survey method, and the current pollution load in rivers is equal to Pollution holding capacity of water area.
2.3 Calculation of pollution-holding capacity of small and medium-sized river development and utilization areas
The one-dimensional model is suitable for medium and small river sections where pollutants are uniformly mixed in the cross section. Concentration of pollutants is calculated according to formula (1).
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（1）
In the formula, Co is the background concentration of the initial section, mg/L; Cx is the concentration of pollutants after passing x distance, mg/L;
x is the longitudinal distance along the river section, m;
u is the average flow velocity of the channel section under the design discharge, m/s;
K is the comprehensive attenuation coefficient of pollutants, 1/s;
The corresponding pollutant-holding capacity M of the water area is calculated according to formula (2).
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（2）
2.4 Calculation of pollution-holding capacity of large river development and utilization areas
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Figure 5 Schematic diagram of accounting for pollution-holding capacity of large river waters
For straight river sections, the two-dimensional convection-diffusion equation is:
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（3）
The analytical solution of formula (3) in the case of continuous point source steady state is:
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（4）
Take the bank concentration as the control concentration of the downstream control section, that is, when z=0, it can be obtained
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（5）
In formula (5): Co is the initial section background concentration, mg/L;
C(x,o) Concentration of pollutants on the shore (z=0) of the control section downstream of the sewage outlet, mg/L;
K comprehensive attenuation coefficient of pollutants, 1/s;
M discharge rate of pollutants at the sewage outlet, g/s;
u The longitudinal average flow velocity in the pollution zone at the design flow rate, m/s;
h The average water depth of the initial section of the pollution zone at the design flow rate, m;
Ez lateral diffusion coefficient, m2/s;
x The distance between the calculation point and the sewage outlet, m.
The maximum allowable discharge of pollutants shall be:
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（6）
2.5 Calculation of pollution-holding capacity of lakes and reservoirs
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Figure 6 Schematic diagram of accounting for pollution-holding capacity of large lakes and reservoirs
For large and medium-sized reservoirs with non-uniform mixing, when pollutants enter the reservoir, the pollution will only appear in the waters near the outfall, and the concentration of non-persistent pollutants is:
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（7）
In formula (7):
Co is the background concentration of pollutants in the reservoir near the sewage outlet, mg/L;
C is the pollutant concentration at the distance r from the sewage outlet, mg/L;
M is the amount of pollutants discharged from the sewage outlet, g/s;
Qp is the amount of waste water at the sewage outlet, m3/s;
K is the comprehensive attenuation coefficient of pollutants, 1/s;
The angle between the reservoir bank on both sides of the sewage outlet, when the discharge outlet is discharged vertically on the open bank,
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, when discharged in the middle of the reservoir,
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h is the average water depth of the reservoir in the diffusion zone, m;
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（7）
r Calculate the distance from the outer boundary of the water area to the sewage outlet into the river, in m.
When the water quality concentration C just meets the water quality management target concentration Cs within the set radius range, the pollutant discharge amount of the sewage outlet is the allowable discharge amount, that is, the pollutant-holding capacity of the water area corresponding to the sewage outlet, according to the formula rewritten as ( 8):
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（8）
Converted to the allowable discharge in days, the calculation formula is rewritten as (9):
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（9）
Special Topic 3 Determination method of setting scheme, scope of analysis, scope of demonstration and scope of model prediction of sewage outlets entering the river
Combined with examples, the analysis scope, demonstration scope and model prediction scope of the river sewage outfall are introduced:
3.1 Setting scheme of sewage outlets into the river
It is necessary to introduce in detail and accurately the plan for setting up sewage outlets into the river proposed by the owner, and preliminarily evaluate the rationality of the plan.
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Fig. 7 The setting scheme of sewage outfall for a certain project
3.2 Scope of analysis
Generally, it is within the administrative area where the sewage discharge outlet of the construction project is located.
3.3 Scope of argument
Generally, it is the water functional area where the sewage outlet of the river is located and the river section where the downstream water functional area is located.
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Figure 8 Analysis scope and demonstration scope of a sewage treatment plant
3.4 Prediction range of water quality model
Principles and methods for determining the prediction range of water quality models.
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Fig. 9 Schematic diagram of prediction range of water quality model in a sewage treatment plant
Topic 4 Analysis of the current water quality and water intake and sewage discharge status of the water area where the sewage outlet of the river enters the river
The main content of study includes:
(1) Water quality data collection and supplementary monitoring methods
(2) Regional water quality assessment and water quality assessment of water function zones
(3) Investigation and evaluation of river sewage outlets
(4) Statistical analysis of river flow in water function areas
(5) Relationship between river inflow and total discharge limit
(6) Identification of water intakes or other third-party environmentally sensitive areas
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Special Topic 5 Forecasting the Ecological Environment Impact of Sewage Drain Water into the River (Part 1)
Learn how to use different water quality models to simulate and predict the impact of outfalls:
5.1 Prediction of water environmental impact of small and medium-sized rivers in areas without data
Focus on learning to use one-dimensional analytical solutions, including data collection, design boundary conditions, design calculation conditions, etc.
5.2 Prediction of water environmental impact of small and medium-sized rivers in areas with data
Starting with a typical case, it introduces the construction method of the MIKE11 one-dimensional numerical water quality model, including the creation of river network files, section files, boundary files, parameter files, and result files, and the extraction of calculation results.
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Figure 10 MIKE11 water quality mathematical model architecture
Special Topic 6 Prediction of Ecological Environment Impact of River Sewage Outlet Water (Part 2)
Using typical cases as textbooks, this paper explains the water environment impact prediction of large-scale river inflow sewage outlets based on two-dimensional water quality models.
6.1 Meshing
6.2 Terrain interpolation
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Fig.11 Mesh division and terrain interpolation of water quality model
6.3 Calculation working condition design
6.4 Values of boundary conditions
The Pearson III curve is drawn, and the design water level is selected for the water level flow relationship curve.
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6.5 Calculation result display and data processing
6.6 Analysis and evaluation of the impact of setting up sewage outlets into the river
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Figure 14 Display of calculation results of water quality model
Topic 7 Reliability Analysis and Rationality Analysis of Sewage Treatment Process at the Sewage Outlet of the River
(1) Use comparative analysis method and actual measurement method to analyze the feasibility and reliability of different types of sewage treatment facilities to discharge the tail water of sewage outlets into the river to meet the standard discharge, and analyze and evaluate.
(2) Analyze the rationality of setting up river sewage outlets through consistency evaluation with regional planning, industrial planning, industry planning and relevant policy requirements.
Topic 8: Case explanation on the preparation of the demonstration report on the establishment of sewage outlets for small rivers and urban sewage treatment plants
Taking the "Technical Guidelines for the Management of Sewage Outlets into Rivers" as the guiding basis, combined with the preparation, review and revision process of the demonstration report for the establishment of sewage outlets in a county sewage treatment plant, the key points and difficulties in the preparation of the report are explained.
The main difficulties are as follows:
(1) Level year, scope of analysis, scope of demonstration
(2) Analysis of the rationality of the demonstration scale of sewage outlets entering the river
(3) Analysis on the rationality of setting up sewage outlets into the river
(4) Regional restrictions on the total amount of pollutant discharge and emission reduction
Case explanation on the preparation of demonstration reports for setting up sewage outlets for nine large-scale river chemical enterprises
Based on the "Technical Guidelines for the Management of Sewage Outlets into Rivers" and "Guidelines for the Preparation of Demonstration Reports on the Setting up of Sewage Outlets into Rivers" (draft for approval), combined with the preparation, review and revision of the demonstration report for the establishment of sewage outfalls in rivers by a chemical company process, explaining the key points and difficulties of report preparation.
The main difficulties are as follows:
(1) Analysis of the setting scheme of sewage outlets entering the river (may involve other permits related to construction projects)
(2) Analysis of production process and product links
(3) The amount of sewage entering the river and the main pollutant loads entering the river are checked and approved
(4) Water environment impact prediction, analysis and evaluation
(5) Reliability and feasibility analysis of sewage treatment process
(6) Analysis on the rationality of setting up river sewage outlets
Exchange of experience