In-situ ecological restoration system for river sewage outlet based on hydrodynamic optimization technology and design method

Abstract

The present application relates to a river sewage outlet in-situ ecological restoration system design method based on water power optimization technology, in the wet season, different forms of stone cage are arranged near the sewage outlet drop point of the river, the purpose is to slow down the water flow, the principle is to take the parallel shoreline, the water flow of the river and the sewage outlet is generalized as a particle, and the reflection path of the water flow particle is assumed, numerical simulation and correction are adopted, and finally the optimal distance of the stone cage from the sewage outlet and the best length, quantity and spacing of the stone cage are determined; aquatic plants and fillers are planted in the target nearshore slow flow area to construct a subsurface flow-surface flow interaction area and improve the pollutant removal effect. In addition, considering the different water flow characteristics and pollutant purification characteristics in the dry season, a relatively closed area is constructed by using the stone cage, and the sewage of the sewage outlet is pretreated by using the electrochemical technology + membrane biological technology to relieve the water purification pressure of the river in the dry season. The beneficial effect is that the environment-friendly in-situ restoration technology can reduce the cost while achieving the best restoration effect.

Description

Technical Field

[0001] This invention relates to the field of sewage treatment technology for river outfalls, specifically to an in-situ ecological restoration system and design method for river outfalls based on hydrodynamic optimization technology. Background Technology

[0002] In recent years, with the rapid development of urban economies and the continuous improvement of residents' living standards, people have paid increasing attention to the quality of their living environment. Urban rivers are an important part of regional ecosystems, and their water quality directly affects residents' quality of life, ecological stability and balance, and the sustainable development of the regional economy. Especially in northern cities, due to climatic conditions, there are significant differences in water volume between the wet and dry seasons. This hydrological characteristic further exacerbates the complexity of river management. Against this backdrop, sewage treatment plant effluent, as an important source of water for urban rivers, directly affects the entire water environment system. However, due to incomplete renovation and poor separation effects of stormwater and sewage separation systems in upstream urban areas, coupled with the continuous discharge of industrial wastewater, agricultural non-point source pollution, and mixed sewage and stormwater runoff from urban river outlets, the pollutant concentrations are far higher than the background values ​​of natural water bodies. When these large and continuous sewage discharges into rivers with insufficient ecological base flow, they can easily lead to eutrophication, biodiversity loss, and other environmental problems in downstream water bodies, resulting in the deterioration of river water quality.

[0003] In response to the declining water quality of urban rivers, a comprehensive system of measures has been established, encompassing pipeline construction, sewage treatment, and regulatory enforcement. However, urban river pollution control faces dynamic hydrological challenges. During the high-water season, heavy rainfall can cause sewage overflows from treatment plants, resulting in large volumes and rapid flows that expand the pollution area and further increase the difficulty of treatment. During the dry season, the self-purification capacity of rivers is significantly weakened, and the continuous discharge of high-concentration sewage from outlets can lead to the accumulation of pollutants exceeding the river's capacity, exacerbating water quality deterioration.

[0004] Currently, traditional river management approaches primarily focus on dredging, diluting, or intercepting sewage in the riverbed itself, failing to achieve precise and efficient control over river discharge outlets. Although various water purification devices are highly anticipated, existing devices still have some shortcomings: At the technical application level, the processing capacity of the device is difficult to dynamically adapt to the complex hydrological conditions of the river. During the high water season, the hydraulic load caused by heavy rain makes the device's processing capacity insufficient, pollutants are not completely removed and the system is unstable. During the low water season, the input of high-concentration sewage does not match the processing scale of the device, and low temperature further inhibits the processing efficiency. From an economic perspective, highly efficient physical and chemical treatment equipment is highly specialized and expensive to maintain, making it difficult to promote and apply on a large scale. Regularly adding external agents further increases the cost burden and can easily cause secondary pollution to rivers.

[0005] Therefore, in-situ discharge outlet treatment technologies that are tailored to local conditions, environmentally friendly, low-cost, and low-energy have attracted attention and are gradually being applied and promoted in engineering projects. However, some problems still exist: current research on in-situ discharge outlet treatment technologies focuses more on lake environments. For example, patent CN109761368B discloses an ecosystem for reducing pollutants from stormwater and sewage discharge outlets into lakes. This involves setting up a biofilm treatment zone composed of connected ecological floating beds around the outlet, combined with aeration and oxygenation, to degrade pollutants entering the lake while enriching the lake's surface landscape. Patent CN212076747U discloses a system for reducing pollutants from lake sewage outlets, which uses soft barriers and the synergistic effect of aquatic plants and biological fillers to reduce the pollutant content in the water.

[0006] In contrast, there are relatively few practical applications in river management. For example, patent CN212669348U discloses a point source pollution treatment device that pre-treats piped drainage directly into the river using aerators and aeration pipes to increase dissolved oxygen in the water, thereby enhancing the overall purification capacity of polluted water. However, this method relies on external power supply, fails to effectively utilize the river's own flow characteristics for oxygen enrichment, has high operating energy consumption, requires frequent maintenance, and exhibits poor adaptability to dynamic water bodies. Patent 2021231830841 discloses a high-performance river discharge outlet sewage purification system that reduces the river's self-purification pressure by setting up a filter pool and multi-stage purification pool below the river discharge outlet. Although this process improves treatment efficiency, the system structure is complex, occupies a large area, and does not fully consider the diffusion and migration characteristics of pollutants under different hydrological conditions, resulting in high construction and operation costs and limited overall benefits.

[0007] Overall, existing river management technologies generally lack attention to river hydrodynamics and pollutant diffusion patterns, resulting in poor adaptability of management solutions to dynamic water flow conditions. They also ignore the differences in water volume and water quality purification effects during high and low water seasons, leading to increased management costs and unsatisfactory management results. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide an in-situ ecological restoration system and design method for river sewage outlets based on hydrodynamic optimization technology, so as to overcome the shortcomings of the prior art.

[0009] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: The design method for in-situ ecological restoration systems of river sewage outlets based on hydrodynamic optimization technology includes the following steps: S10. Establish a hydrodynamic model for the target river channel water ecological restoration area during the high-water season; S20. Based on hydrodynamic model simulation, gabions of different forms are deployed near the sewage outlet in the river to create a slow-flow zone. S30. With the aim of slowing down the water flow, the river flow and the sewage outlet flow are generalized into point masses, and the optimal distance between the gabion and the sewage outlet and the optimal length of the gabion are determined. S40. Based on the principle of parallel shoreline, the sewage outlet and gabions are generalized as point masses, and the reflection path of the water flow point is assumed to determine the center distance between two adjacent gabions along the water flow direction in the river channel. S50. Numerical simulation is used to correct the simulation based on real-world factors, and the number, length and spacing of gabions are determined based on the principle of ensuring that the near-bank flow velocity downstream of the sewage outlet reaches the target slow flow value. S60. Plant aquatic plants in the nearshore slow-flow area that meets the target slow-flow value, and arrange filler material at the bottom of the nearshore slow-flow area.

[0010] Based on the above technical solution, the present invention can be further improved as follows.

[0011] Furthermore, the hydrodynamic model in S10 was built using Delft3D.

[0012] Furthermore, in S30, when the river flow and the sewage outlet flow are generalized as point masses, the irregular motion of the water flow is not considered, and the flow velocity and direction near the sewage outlet are the geometric superposition of the river flow velocity and direction and the sewage outlet flow velocity and direction. It is assumed that the angle between the direction of sewage movement and the perpendicular line to the shoreline is θ, and that the upstream end of the gabion is level with the sewage outlet, and that the furthest distance of the initial straight-line movement of the sewage reaches exactly the downstream end of the gabion. The length of the gabion parallel to the shoreline is set as... The vertical distance between the gabion and the shoreline is Then the following conditions are met: in, This represents the maximum annual average flow velocity of the river channel. The flow velocity at the sewage outlet.

[0013] Furthermore, in S40, when assuming the reflection path of water flow particles, energy loss, turbulent mixing, and elastic collision of particles are not considered. It is assumed that the reflection path of water flow particles is similar to the specular reflection of light. It is also assumed that the sewage outlet water flow mixes with the river water flow and hits the first gabion, and after being reflected to the bank, it hits its adjacent gabion again. Then the center distance between two adjacent gabions is twice the length of a single gabion, and this process is repeated.

[0014] Furthermore, S50 stipulates that the target slow flow value in the near-shore slow flow zone downstream of the river discharge outlet should be less than 0.3 m / s.

[0015] Furthermore, the gabion includes: a cage net and a filler layer inside the cage net, with plants planted on top of the filler layer; the aquatic plants are reeds or calamus.

[0016] Based on the above technical solution, the present invention also provides an in-situ ecological restoration system for river sewage outlets based on hydrodynamic optimization technology, which is designed using the above design method.

[0017] Furthermore, each gabion has slots on its water-facing, water-repellent, and bank-facing sides, with each slot extending through its upper and lower ends. Upstream of the discharge outlet, between the gabion directly opposite discharge outlet 1 and the bank wall, an inlet baffle is installed. One end of the inlet baffle is secured in a slot on the corresponding gabion, and the other end is secured in a groove on the bank wall. Side baffles are installed between any two adjacent gabions located between the inlet baffles and the aquatic plant planting area. The two ends of each side baffle are secured in slots on the adjacent two gabions. Both the inlet baffles and the side baffles are higher than the river level line, located downstream of the discharge outlet and adjacent to the aquatic plant planting area. A water outlet baffle is installed between the gabion and the bank wall. One end of the water outlet baffle is locked in a slot on the corresponding gabion, and the other end is locked in a groove on the bank wall. The outlet of the water outlet baffle is lower than the inlet baffle and the side baffle. Downstream of the sewage outlet, between the inlet baffle and the water outlet baffle, an anode, a bipolar electrode, and a cathode are installed along the direction of water flow. One end of the anode, bipolar electrode, and cathode is locked in a slot on the bank-facing surface of the corresponding gabion, and the other end is locked in a groove on the bank wall. The anode is connected to the positive terminal of an external power source, and the cathode is connected to the negative terminal of an external power source. An artificial aquatic plant film is installed between the cathode and the water outlet baffle.

[0018] Furthermore, the anode is a mesh titanium-based mixed metal oxide coated electrode, the bipolar electrode is a mesh titanium-based mixed metal oxide coated electrode, and the cathode is a stainless steel mesh; one end of the anode, bipolar electrode, and cathode are respectively inserted into the slots on the gabion's shore-facing surface at the corresponding positions, while the other end rests against the shore wall.

[0019] Furthermore, the upper part of the inlet baffle, side baffle, and outlet baffle are all serrated, and the height of the baffle decreases sequentially along the water flow direction, forming a natural gravity waterfall. The inlet baffle, side baffle, and outlet baffle are all higher than the water level line, ensuring that the sewage from the discharge outlet enters the river after being treated by the closed in-situ remediation system. The serrations provide oxygen enrichment, which is beneficial for the removal of COD and ammonium nitrogen.

[0020] The beneficial effects of this invention are: The high-water season corresponds to summer and autumn, when plants grow well, microbial activity is good, river flow is large, pollutant dilution effect is good, pollutant concentration is relatively low, and river self-purification capacity is strong. The low-water season corresponds to spring and winter, when river flow is small, lower temperature makes the effect of plants reducing pollutants poor, and microbial activity is low, all of which result in poor pollutant purification effect near sewage outlets. The purification principle during the high-water season is as follows: Based on the principle of hydrodynamics, the location and number of gabions are rationally selected. Multiple parallel gabions are placed in the river channel near the sewage outlet to slow down the water flow and create a slow-flow zone. This constructs a "deceleration-buffering-purification" system, providing conditions for aquatic ecological restoration. Pollutants are then reduced in an ecological way. At the same time, it can effectively guide the direction of sewage discharge, making the near-bank flow of the river lower and the water flow more slow. The gabions are used to make the sewage diffuse as much as possible in the lower part of the river channel, reducing the direct scouring of the riverbed by the water flow. This provides favorable conditions for aquatic plants and fillers to further weaken pollutants and creates stable hydraulic conditions for the subsequent water purification process. It is highly feasible and combines ecological safety with low construction and maintenance costs. It achieves the maximum slow-flow effect at the lowest cost, providing a foundation for improving the pollutant removal effect. During the high-water season, a stable growth environment is provided for aquatic plants. Based on hydrodynamic principles, suitable planting areas for aquatic plants are determined, further reducing the water flow velocity in slow-flowing areas and laying the foundation for enhanced pollutant removal. Multiple gabions are used to slow down the water flow, creating low-velocity areas that provide favorable conditions for plant cultivation. This method is more stable and effective than traditional river interception measures. Planting aquatic plants such as reeds and cattails in low-velocity areas near the riverbank provides strong resistance and absorption capacity to water flow and pollutants, thereby improving water purification efficiency. During the high-water season, a water ecological restoration enhancement measure is formed as a whole, which is similar to the interaction between subsurface flow and surface flow. Plants, fillers, and microorganisms work together to remove pollutants, which is equivalent to the effect of surface flow wetlands. Gabion groups are composed of fillers (zeolite, gravel) and a large number of microorganisms attached to them, as well as aquatic plants growing on them. Their effect is equivalent to subsurface flow wetlands. The combined effect of subsurface and surface flow enhances the pollutant removal effect in slow-flow areas.

[0021] The purification principle during the dry season is as follows: By installing inlet baffles, side baffles, outlet baffles, anodes, bipolar electrodes, cathodes, and attached artificial aquatic plants, a closed electrochemical + membrane-biological coupled treatment zone is formed, which is an electrochemical + membrane-biological pretreatment synergistic purification. The attached artificial aquatic plants are placed downstream of the electrochemical zone, which can make full use of the naturally formed water storage and slow flow environment in this area, significantly prolonging the hydraulic residence time and creating ideal conditions for the full contact reaction between the biofilm and pollutants. At the same time, the electrochemical technology enhances the system's buffering capacity against pollution load, realizing the deep coupling of electrochemical oxidation and biodegradation. The electrochemical technology has a good removal effect on nitrate nitrogen, total phosphorus, recalcitrant organic matter, and new pollutants such as antibiotics, while the biofilm technology has a good removal effect on ammonia nitrogen and COD. Through functional complementarity, the pollutant removal efficiency is significantly improved. Based on the different water flow characteristics and pollutant purification features of the high-water and low-water seasons, corresponding measures are adopted to optimize the in-situ remediation system of the sewage outlets, in order to achieve the best pollutant purification effect at low cost. Considering the differences in river flow during the high-water and low-water seasons and the seasonal impact on water quality purification function, different in-situ treatment measures are adopted for the high-water and low-water seasons, in order to achieve the best remediation effect while reducing costs. Attached Figure Description

[0022] Figure 1 A schematic diagram illustrating the selection principle for the optimal distance between the gabion and the sewage outlet, as well as the optimal length of the gabion; Figure 2 A schematic diagram illustrating the design principle of the number of gabions and the center-to-center spacing. Figure 3 A structural diagram of an in-situ ecological restoration system for river sewage outlets based on hydrodynamic optimization technology during the high-water season; Figure 4 A structural diagram of an in-situ ecological restoration system for river sewage outlets based on hydrodynamic optimization technology during the dry season; Figure 5 This is a structural diagram of a gabion; Figure 6 This is a three-dimensional schematic diagram of the electrochemical region; Figure 7 (a) represents the absence of gabions, and (b) represents a simulated flow velocity in the river when the gabions are 0.5m away from the sewage outlet. Figure 8 Figures (c) and (d) represent simulated flow velocities in the river when the gabions are 1m and 1.5m away from the sewage outlet, respectively. Figure 9 (e) represents a simulated flow velocity diagram in the river channel when the gabion is 2m away from the sewage outlet; Figure 10 (a) represents a simulated flow velocity diagram in the river channel when there is 1 gabion and (b) represents a simulated flow velocity diagram when there are 3 gabions. Figure 11 (c) represents a simulated flow velocity diagram in the river channel when there are 5 gabions and (d) represents a simulated flow velocity diagram when there are 7 gabions. Figure 12 (e) represents a simulated flow velocity diagram in the river channel when there are 9 gabions; Figure 13 (a) and (b) represent simulated flow velocities in the river channel with and without vegetation measures, respectively.

[0023] The attached diagram lists the components represented by each number as follows: 1. Sewage outlet; 2. Gabion; 210. Slot; 220. Netting; 230. Filler layer; 240. Plants; 3. Inlet baffle; 4. Side baffle; 5. Outlet baffle; 6. Anode; 7. Bipolar electrode; 8. Cathode; 9. Power supply; 10. Artificial aquatic plants with attached biofilm; 11. Aquatic plants. Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1 like Figure 1 , Figure 2 , Figure 3 As shown, the design method for in-situ ecological restoration system of river sewage outlets based on hydrodynamic optimization technology includes the following steps: S10. Establish a hydrodynamic model of the target river water ecological restoration area during the high-water season. The hydrodynamic model can preferably be established using Delft3D. S20. Based on hydrodynamic model simulation, gabions 2 are arranged in different forms near the water drop point of the sewage outlet 1 in the river channel to create a slow flow zone. S30. With the aim of slowing down the water flow, the river flow and the sewage outlet 1 flow are generalized into point masses, and the optimal distance between the gabion 2 and the sewage outlet 1 and the optimal length of the gabion 2 are determined. S40. Based on the principle of parallel shoreline, that is, the gabion 2 is parallel to the direction of river flow, the sewage outlet 1 and gabion 2 are generalized as point masses, and the reflection path of the water flow point is assumed to determine the center distance between two adjacent gabions 2 along the direction of river flow. S50. Combine real-world factors and use numerical simulation for simulation correction. Based on the principle of ensuring that the slow flow near the bank downstream of the sewage outlet 1 reaches the target slow flow value, determine the number, length and spacing of gabions 2 so that a slow flow zone is formed near the bank, providing a foundation and conditions for the implementation of ecological restoration measures. S60. Plant aquatic plants 11 in the near-shore slow-flow zone that meets the target slow-flow value, and arrange filler material at the bottom of the near-shore slow-flow zone. The filler material can be zeolite, gravel, etc., to form a complete ecological purification chain. The aquatic plants 11 directly absorb nutrients such as nitrogen and phosphorus in the water through their roots to purify the water quality. Moreover, the dense stems and leaves of the aquatic plants 11 can reduce the water flow velocity a second time, consolidate and expand the slow-flow zone created by the gabion 2, and make the near-shore flow field of the river discharge outlet 1 more stable. The filler material such as zeolite and gravel can provide a large attachment surface for aerobic and anaerobic microorganisms, accelerate the removal of pollutants from the water by microorganisms, and at the same time, the filler material can enhance the adsorption effect of ammonia nitrogen, total phosphorus, heavy metals, etc.

[0026] Example 2 like Figure 1As shown, this embodiment is a further improvement on embodiment 1, as detailed below: Because the flow velocity of a natural river varies constantly, the greater the flow velocity, the wider and farther the sewage from discharge outlet 1 will spread. Therefore, the farther the gabion 2 is from discharge outlet 1, the longer the gabion 2 should be. Thus, to ensure that the gabion 2 can block most of the sewage discharged from discharge outlet 1, the average annual flow velocity of the river is selected. Design the position of the corresponding gabion 2 in the maximum value scenario; In S30, when the river flow and the flow from sewage outlet 1 are generalized as point masses, the irregular motion of the water flow is not considered. The flow velocity and direction near sewage outlet 1 are assumed to be the geometric superposition of the river flow velocity and direction and the flow velocity and direction of sewage outlet 1. It is assumed that the angle between the direction of sewage movement and the perpendicular line to the shoreline is θ, and that the upstream end of gabion 2 is flush with sewage outlet 1. Furthermore, the furthest distance the sewage initially travels in a straight line is exactly at the downstream end of gabion 2. The length of gabion 2 parallel to the shoreline is set as... The vertical distance between gabion 2 and the shoreline is Then the following condition is met: in, This represents the maximum annual average flow velocity of the river channel. The flow velocity of the water at the sewage outlet is 1.

[0027] In this case, the gabion 2 can effectively weaken the kinetic energy of the sewage, prolong its hydraulic retention time, minimize its length, reduce costs, and lay an ideal hydrodynamic foundation for the subsequent ecological restoration process.

[0028] Example 3 like Figure 2 As shown, this embodiment is a further improvement on embodiment 1 or 2, as detailed below: Based on determining the optimal distance between gabion 2 and sewage outlet 1, and the optimal length of gabion 2, the number of gabions 2 and the spacing between gabions 2 are further optimized according to the principle of parallel shoreline. In S40, when assuming the reflection path of water flow particles, energy loss, turbulent mixing, and elastic collision of particles are not considered. It is assumed that the reflection path of water flow particles is similar to the specular reflection of light. It is also assumed that the water flow from sewage outlet 1 mixes with the river flow and hits the first gabion 2. After being reflected to the bank, it hits its adjacent gabion 2 again. Then the center-to-center distance between two adjacent gabions 2 is twice the length of a single gabion 2, and so on.

[0029] Example 4 like Figure 3 , Figure 5As shown, this embodiment is a further improvement on embodiment 1, 2, or 3, as detailed below: In S50, numerical simulation is used to correct for simulation based on real-world factors. When water flows into gabion 2, most of the kinetic energy is drastically consumed through turbulence, friction, and morphological resistance, resulting in a significant decrease in flow velocity. By using the reflection path of water particles and Delft 3D numerical simulation, it can be intuitively determined how many gabions 2 need to be arranged to reduce the near-bank flow velocity in the downstream of the river to a suitable area for plant growth. This is to block sewage as much as possible within the designed water purification area, ensuring that the target slow flow value in the near-bank slow flow zone downstream of the sewage outlet 1 is less than 0.3 m / s.

[0030] Based on the above principles, the most economical and effective location and quantity of gabions 2 are designed. During the high-water season, gabions 2 reduce the water flow velocity, creating a slow-flowing zone near the shoreline. This provides a foundation and conditions for the implementation of ecological restoration measures. Aquatic plants 11, such as reeds and calamus, are planted in the slow-flowing zone near the shore, and filler materials, such as zeolite and gravel, are placed at the bottom of the slow-flowing zone to form a complete ecological purification chain. Aquatic plants 11 directly absorb nutrients such as nitrogen and phosphorus from the water through their roots, purifying the water quality. The dense stems and leaves of aquatic plants 11 can further reduce the water flow velocity, consolidating and expanding the slow-flowing zone created by gabions 2, making the near-shore flow field of the river discharge outlet 1 more stable. Zeolite, gravel, and other filler materials can provide a larger attachment surface for aerobic and anaerobic microorganisms, accelerating the removal of pollutants from the water by microorganisms. At the same time, the filler materials can enhance the adsorption effect of ammonia nitrogen, total phosphorus, heavy metals, etc.

[0031] Gabion 2 is a streamlined gabion, comprising a cage mesh 220 and a packing layer 230 within the cage mesh 220. The packing layer 230 can be composed of zeolite, crushed stone, etc., while the cage mesh 220 can be made of iron mesh. Plants 240 are planted on top of the packing layer 230. Gabion 2 has the dual advantages of energy dissipation and impact reduction, as well as promoting pollutant reduction. During the high-water season, gabion 2 functions as a miniature subsurface flow wetland ecological treatment unit. The packing material within gabion 2 efficiently removes pollutants such as nitrogen and phosphorus through its strong adsorption capacity, while the plants planted on it can absorb microorganisms. Furthermore, the zeolite and plant roots in the packing layer provide a wider attachment surface for microorganisms, promoting microbial degradation and thus improving water purification efficiency.

[0032] Example 5 like Figure 3 As shown, the in-situ ecological restoration system for river discharge outlets based on hydrodynamic optimization technology is designed using the design method in any of the embodiments 1 to 4. In the in-situ ecological restoration system for river discharge outlets based on hydrodynamic optimization technology, the gabions 2 are distributed parallel to the direction of river flow, and the center-to-center distance between two adjacent gabions 2 is twice the length of a single gabion 2.

[0033] Based on the above design principles, an application example is established, simulating a wide and shallow river in northern China during its high-water season. A hydrodynamic model is used for simulation, and the sewage discharge from the river outlet 1 is set to 5000 m³. 3 / d, meaning: the flow rate of sewage outlet 1 is 0.058m³. 3 Sewage outlet 1 discharges sewage into the river using a DN300 pipe. The fill degree of outlet 1 is 1, therefore the flow velocity at outlet 1 is 0.8 m / s. The river is wide and shallow, 70 m wide, with an average depth of 0.7 m. Research indicates that the natural flow velocity in wide and shallow rivers is generally 0.2 m / s to 0.5 m / s. Assuming a flow velocity of 0.5 m / s, the river flow rate is 24.5 m³ / s. 3 / s, the river channel is set with inlet and outlet, the river water volume does not change much, and the water level at the river outlet is basically unchanged, in order to simulate the sewage diffusion of the actual river outlet. To simplify the model simulation, the river outlet 1 is set as a point source in the hydrodynamic model, and the gabion 2 is set as a "dry point", that is, no water flows through it.

[0034] ① Determine the distance between gabion 2 and the sewage outlet 1, as well as the length of gabion 2, based on the hydrodynamic model. Hydrodynamic simulations were conducted on gabions 2 at different distances from the sewage outlet 1 using a hydrodynamic model. During the simulation, different distances between the gabions 2 and the sewage outlet 1 were set, resulting in varying river flow velocities ( ). ) and the flow velocity at the sewage outlet ( The lengths of the gabions 2 installed below are different. The upstream end of gabion 2 is simulated to be flush with the sewage outlet 1. The simulated distances between gabion 2 and the sewage outlet 1 are 0.5m, 1m, 1.5m, and 2m, for a total of four working conditions. Based on: The length of gabion 2 at different distances from sewage outlet 1 can be calculated, as shown in Table 1: Table 1. Length of gabion 2 at different distances （m） 0.5 1 1.5 2 （m） 0.3 0.625 0.9 1.25 The placement of gabion 2 is to better facilitate the diffusion of sewage in the lower part of the river channel, and the low flow velocity below gabion 2 is conducive to the growth of aquatic plants. Therefore, determining the placement of gabion 2 requires considering the effect of hydrodynamic flow velocity distribution on the diffusion and guidance of sewage, as well as the range and stability of the low-velocity area below the gabion. Hydrodynamic models were used to simulate the local hydrodynamic conditions of the river outlet under five different working conditions, such as... Figure 7 , Figure 8 , Figure 9As shown, in simulation group (a) without gabions, the flow velocity is relatively high in most areas, the water flow forms a jet and there is no obvious deceleration area, indicating that the water flow is basically unrestrained without gabions 2. According to the different distances of gabions 2 from the sewage outlet, gabions 2 of different lengths are laid to block the diffusion of sewage. Compared with simulation group (a) without gabions 2, simulation groups (b), (c), (d), and (e) all form a certain low flow velocity area below gabions 2, and the flow velocity near the riverbank is reduced. Among them, the low flow velocity area formed behind gabions 2 in simulation group (b) with gabions 2 0.5m away from the sewage outlet is more concentrated and uniform. The gabions 2 laid at this distance provide more favorable hydrodynamic conditions for the growth of aquatic plants, and make the pollutants stay in the water between gabions 2 and sewage outlet 1 for a longer time, which can more effectively reduce the concentration of pollutants and purify the water quality. In summary, gabions 2 are laid at a distance of 0.5m from the sewage outlet of the river.

[0035] ② Optimization design of the number and spacing of gabions 2 based on hydrodynamic model The above examples determine the optimal length of gabion 2 and the optimal distance between gabion 2 and the sewage outlet 1. To further concentrate the area of ​​lower flow velocity behind gabion 2 and make the flow more concentrated, the number of gabions 2 at a distance of 0.5m from the sewage outlet was determined. The simulation process mainly involves different numbers of gabions 2. Based on the above principle of water flow particle reflection, multiple gabions 2 are arranged at intervals. The length of a single gabion 2 is 0.3m. Therefore, the distance between two adjacent gabions 2 is set to 0.6m (i.e., twice the length of a single gabion 2). Five working conditions are set with the number of gabions 2: 1, 3, 5, 7, and 9 to simulate the local hydrodynamic situation of the river sewage outlet. Figure 10 , Figure 11 , Figure 12 As shown in the figure, the number of gabions 2 shown in (a), (b), (c), (d) and (e) are 1, 3, 5, 7 and 9 respectively; The number of gabions 2 is designed to concentrate the low flow velocity in the near-shore area behind the gabions 2, making the near-shore flow velocity suitable for the growth of aquatic plants. When planting aquatic plants (such as reeds and calamus) near the riverbank, it is essential to ensure they do not fall over, can grow normally, and play a role in water purification. Research shows that most aquatic plants can grow well when the river flow velocity is less than 0.3 m / s, and their stems are not easily bent or broken by the continuous pressure of the water flow. Hydrodynamic model simulations show that as the number of gabions 2 increases, the near-shore flow velocity continuously decreases. When the flow velocity in the near-shore area of ​​the river outlet decreases to within 0.3 m / s, it is considered that the corresponding number of gabions 2 can effectively block water flow. Simulations of the hydrodynamic flow velocity distribution with different numbers of gabions 2 show that when the number of gabions 2 is 7 or more, the flow velocity in most of the near-shore area behind the gabions 2 is below 0.3 m / s. Considering further engineering costs, it is believed that a number of gabions 2 of 7 can effectively slow down the flow velocity and form a stable aquatic ecological restoration area.

[0036] ③ Optimized arrangement of aquatic plants based on hydrodynamic model The hydrodynamic velocity distribution under the optimal gabion 2 layout was simulated using a hydrodynamic model. The area suitable for planting aquatic plants was determined by the river velocity distribution. The optimal arrangement was selected with 7 gabions, each 0.5m away from the river discharge outlet and 0.3m in length. Starting from the fourth gabion, the near-shore velocity behind the gabion was below 0.3m / s. Reeds, cattails, and other aquatic plants were planted in this area. Filler material, such as zeolite or gravel, was placed at the bottom of the slow-flow area. The plants themselves can absorb some pollutants. At the same time, the presence of aquatic plants and filler material provides a place and space for the growth and reproduction of microorganisms. The filler material has an adsorption effect on pollutants. In addition, the plant stems have a water-blocking effect, which can further reduce the flow velocity and extend the pollutant flow path, thereby enhancing the pollutant removal effect.

[0037] A hydrodynamic model was used to simulate the local hydrodynamics of a sewage outlet in a river channel with aquatic plants. In the model, the Manning coefficient characterizes the influence of riverbed roughness on water flow. It is affected not only by riverbed roughness, flow velocity, and water depth, but also by the density of aquatic plants. The Manning coefficient reflects the effect of aquatic plants on hydrodynamics. Research showed that aquatic plants such as reeds and calamus have relatively high Manning coefficients, generally ranging from 0.05 to 0.2. Under the simulation conditions, the aquatic plant coverage was high, and the plants were relatively lush. The planting density of aquatic plants was set at 25 clumps / m². 2 The Manning coefficient for aquatic plant cover is calculated using a formula derived from the combined formulas of plant stem drag and average shear force in a riverbed without vegetation cover. In the formula: The Manning coefficient represents the riverbed without vegetation cover. Planting density, unit: plants / m² 2 ; Let be the drag coefficient of the plant stem, which is a function of the Reynolds number of the plant stem; Diameter of the plant stem, in meters (m). R The radius is the hydraulic radius, in meters; g is the acceleration due to gravity, 9.81 m / s². 2 ; Based on the above formula, the Manning coefficient for aquatic plants was set at 0.15 for simulation. Planting aquatic plants is intended to further block sewage and purify water quality. Hydrodynamic model simulation showed that planting aquatic plants in the near-shore low-velocity area of ​​gabion 2... Figure 13 Simulation group (b), the flow velocity behind gabion 2 compared to the group without vegetation. Figure 13The simulation group (a) showed a significant reduction, indicating that aquatic plants effectively blocked the water flow velocity and formed a water purification zone with a lower flow velocity behind the gabion 2. Aquatic plants can accumulate pollutants in the water, and at the same time, the surface of the plant roots provides an attachment site for microorganisms, which can effectively degrade pollutants. During the high water season, placing gabions 2 near the sewage outlet of the river and combining them with plant measures can effectively purify the river water quality and reduce the concentration of pollutants in the water. This device is more environmentally friendly at a lower cost and ensures that the water quality in the downstream of the river meets the standards.

[0038] Example 6 like Figure 4 , Figure 6 As shown, this embodiment is a further improvement on embodiment 5, as detailed below: Based on the optimization results of the hydrodynamic model for the location and quantity of gabions 2 during the high-water season, and to address the problem of reduced water volume, increased pollutant concentration, and near loss of the water body's self-purification capacity during the dry season, a slot 210 is installed on the water-facing side, the back side, and the bank-facing side of each gabion 2. The slots 210 on each gabion 2 extend through its upper and lower ends. An inlet baffle 3 is installed upstream of the sewage outlet 1 between the gabion 2 directly opposite the outlet 1 and the bank wall. One end of the inlet baffle 3 is secured to the corresponding gabion 2 at the water-facing side. Within the slot 210 on the water surface, the other end of the inlet baffle 3 is secured in a groove on the bank wall; then, side baffles 4 are evenly distributed between any two adjacent gabions 2 located between the inlet baffle 3 and the planting area of ​​aquatic plants 11, with each side baffle 4 having two ends secured in slots 210 on the adjacent two gabions 2, that is: one end of each side baffle 4 is secured in the slot 210 on the back side of the preceding gabion 2, and the other end is secured in the slot 210 on the front side of the following gabion 2; the inlet baffle 3 and the side baffles 4 All are higher than the water level in the river channel. A water outlet baffle 5 is installed between the gabion 2 and the bank wall, located downstream of the sewage outlet 1 and near the aquatic plant planting area 11. One end of the water outlet baffle 5 is secured in a groove 210 on the bank side of the corresponding gabion 2, and the other end is secured in a groove on the bank wall. The outlet at the upper end of the water outlet baffle 5 is lower than the inlet baffle 3 and the side baffle 4. An anode 6, a bipolar electrode 7, and a cathode 8 are installed downstream of the sewage outlet 1, between the inlet baffle 3 and the water outlet baffle 5, along the direction of water flow. One end of the anode 6 is secured on the bank side of the corresponding gabion 2. The anode 6 is inserted into the slot 210, and the other end of the anode 6 is inserted into the slot on the bank wall. One end of the bipolar electrode 7 is inserted into the slot 210 on the bank surface of the gabion 2 at the corresponding position, and the other end of the bipolar electrode 7 is inserted into the slot on the bank wall. One end of the cathode 8 is inserted into the slot 210 on the bank surface of the gabion 2 at the corresponding position, and the other end of the cathode 8 is inserted into the slot on the bank wall. The anode 6 is connected to the positive terminal of the external power supply 9, and the cathode 8 is connected to the negative terminal of the external power supply 9. The artificial aquatic plant 10 with attached biofilm is arranged between the cathode 8 and the water outlet baffle 5. That is, the artificial aquatic plant 10 with attached biofilm is located in the downstream section of the electrochemical treatment unit.

[0039] The above scheme constructs an electrochemical-membrane biological pretreatment zone. When the polluted water from outlet 1 flows through this zone, it first enters the water storage and slow-flow zone enclosed by the bank wall, gabion 2, inlet baffle 3, side baffle 4, and outlet baffle 5. Then, it passes through the anode 6, bipolar electrode 7, and cathode 8, i.e., the electrochemical zone, which has a good treatment effect on nitrate nitrogen, total phosphorus, and recalcitrant organic matter. Next, it passes through the attached artificial aquatic plants 10, i.e., the membrane biological zone, which has a good removal effect on ammonia nitrogen and COD. Finally, it flows into the river from the outlet on the outlet baffle 5. At the same time, this structure can play a water storage role during the dry season. The water-blocking structure with a specific height difference ensures that the water flow can fully pass through the electrochemical zone located within it, providing hydrodynamic conditions for the efficient degradation of pollutants. The recalcitrant organic matter in the water is first treated by electrochemical technology (which can effectively remove nitrogen and phosphorus and decompose recalcitrant organic matter) and then decomposed into easily biodegradable small molecule intermediates. When the water passes through the treatment area of ​​the attached artificial aquatic plant 10, these small molecule intermediates can be fully mineralized by the biofilm on the surface of the attached artificial aquatic plant 10. The synergistic effect of the two can significantly improve the treatment efficiency under low temperature conditions and achieve better economic benefits. Moreover, the combination of the two can effectively remove conventional pollutants and recalcitrant organic matter in the water. The synergistic purification achieved by electrochemical + membrane biological pretreatment not only effectively removes nitrogen and phosphorus, but also converts recalcitrant organic matter into easily biodegradable small molecules. The slow-flowing water storage zone is conducive to the attachment and growth of biofilm on the artificial aquatic plant 10, which can significantly prolong the contact time between pollutants and the artificial aquatic plant 10, greatly improving the purification efficiency of the artificial aquatic plant 10. The residual ammonia nitrogen, COD and other pollutants are also further purified here through the aerobic effect of the biofilm on the artificial aquatic plant 10. This method rationally sets pollutant reduction measures at the sewage outlet 1 according to the characteristics of the wet and dry seasons, without the need for the addition of chemicals, and is not affected by seasonal temperature. It can effectively reduce pollutants, achieve efficient removal of pollutants throughout the year with minimal cost, and is ecologically friendly and cost-controllable. It provides technical support for the reduction of pollutants at sewage outlets and the optimization of river water quality, and ultimately achieves the synergistic removal of multiple pollutants.

[0040] The highly active biofilm attached to the surface of artificial aquatic plants utilizes these intermediate products for complete mineralization and simultaneously completes the biochemical removal of pollutants such as residual ammonia nitrogen, thereby achieving synergistic deep purification of COD, nitrogen, phosphorus, and recalcitrant organic matter. This synergistic mechanism not only significantly improves the overall removal efficiency of pollutants under low-temperature conditions, but also effectively reduces system operating costs, forming a stable, economical, and sustainable in-situ treatment solution.

[0041] The core of this system's purification process during the dry season is a system based on bipolar electrodes. The in-situ electrochemical system based on the Electrode (BPE) principle consists of an anode 6, a bipolar electrode 7, and a cathode 8. Through precise circuit connections and layout, it achieves efficient degradation of pollutants using electrochemical methods. Its working principle is as follows: Only the anode 6 and cathode 8 are connected to an external power supply 9. The core functions of the anode 6 are twofold: firstly, it oxidizes pollutants through direct electron transfer; secondly, it generates highly oxidizing hydroxyl radicals by electrolyzing water molecules, non-selectively degrading recalcitrant organic matter, antibiotics, and other new pollutants, as well as conventional pollutants such as nitrogen and phosphorus. The cathode 8 mainly completes the circuit cycle and assists in purification through reduction processes such as hydrogen evolution reaction. The bipolar electrode 7 is not connected to the power supply 9. Its side facing the anode 6 induces a negative potential, becoming the cathode surface; its side facing the cathode 8 induces a positive potential, becoming the anode surface. Thus, the polluted water flow undergoes two electrochemical oxidation-reduction reactions in sequence, thereby achieving efficient and deep degradation of pollutants. Applying bipolar electrode technology to the treatment of open river water environments ensures efficient pollutant degradation capabilities while significantly reducing system complexity and external wiring costs.

[0042] Compared with traditional electrochemical technology, this bipolar electrode technology significantly simplifies system wiring, reduces engineering complexity and implementation costs, and is more suitable for the distributed, long river treatment scenarios faced by this system. Through the efficient use of bipolar electrode 7, energy consumption and costs are significantly reduced while ensuring purification efficiency.

[0043] Based on the above principles, both the anode and the bipolar electrode 7 that can serve as the anode surface must be selected to have resistance to anodic oxidation corrosion. Therefore, the anode 6 adopts a mesh titanium-based mixed metal oxide (MMO) coated electrode, and the bipolar electrode 7 adopts a mesh titanium-based mixed metal oxide (MMO) coated electrode. This electrode has extremely high catalytic activity, is corrosion resistant, has a strong bond between the coating and the substrate, a long service life, does not leach toxic ions, and does not cause secondary pollution.

[0044] The cathode 8 theoretically faces a reducing environment with a relatively slow corrosion rate. Therefore, stainless steel mesh is used for the cathode 8. This ensures a reducing environment while providing sufficient corrosion resistance, facilitating processing and installation, and reducing costs, resulting in higher economic benefits. The anode 6, bipolar electrode 7, and cathode 8 are all mesh-like, which reduces material usage and water flow resistance while maintaining the reaction area. The outlet baffle 5, inlet baffle 3, and side baffle 4 can all be made of plastic.

[0045] To achieve energy self-sufficiency and green operation of the electrochemical purification device, solar photovoltaic power generation is adopted as the core power supply solution, that is, solar photovoltaic power generation charges the battery. This design aims to solve the problems of inconvenient access to the river power grid and high operating costs, and to ensure the continuous and stable operation of the device during the dry season by driving renewable energy.

[0046] Taking the aforementioned average water depth of the river channel as an example, during the dry season, in order to store water in the area of ​​gabion 2 to achieve the water depth for electrochemical treatment, the height of the inlet baffle 3 and the side baffle 4 can be 0.75m to prevent sewage from bypassing the electrochemical treatment unit, and the lowest point of the outlet on the outlet baffle 5 is 0.65m.

[0047] The upper ends of the inlet baffle 3, the side baffle 4, and the outlet baffle 5 are all serrated, and the height of the baffles decreases sequentially along the water flow direction, forming a natural gravity waterfall. The inlet baffle 3, the side baffle 4, and the outlet baffle 5 are all higher than the water level line, ensuring that the sewage from the discharge outlet enters the river after being treated by the closed in-situ remediation system. While ensuring that the water flow is sufficient, the serrated shape can disperse the water flow and increase the contact area with air, providing dissolved oxygen-rich water for the subsequent ecological plant area, which is conducive to the removal of COD and ammonium nitrogen.

[0048] During the high-water season, the hydrodynamic conditions of the sewage outlet are simulated and optimized using a hydrodynamic model. Appropriate locations, lengths, spacings, and quantities of gabions are set to provide a slow-flow area for the implementation of aquatic ecological restoration. Then, the pollutant removal effect is enhanced through the coupling mechanism of plants, microorganisms, and fillers. During the dry season, a closed electrochemical + membrane-biological coupled treatment zone is formed by installing inlet baffle 3, side baffle 4, outlet baffle 5, anode 6, bipolar electrode 7, cathode 8, and attached artificial aquatic plants 10. This achieves efficient degradation of polluted water. Compared with conventional river discharge outlet water purification systems, this integrated system has advantages such as multi-stage purification, facility synergy, and independent operation. It not only has low operation and maintenance costs and simple management, but also does not require the addition of chemicals throughout the process, making it ecologically friendly and effectively avoiding secondary pollution. It provides a sustainable and efficient pollutant reduction technology that is adaptable to different water volumes and seasons for improving river water quality.

[0049] The high-water season corresponds to summer and autumn, when plants grow well, microbial activity is high, river flow is large, pollutant dilution is effective, pollutant concentration is relatively low, and the river's self-purification capacity is strong. The purification principle during the high-water season is as follows: Based on hydrodynamic principles, the location and number of gabions are rationally selected. Multiple parallel gabions 2 are placed near the sewage outlet 1 in the river to slow down the water flow and create a slow-flow zone, constructing a "deceleration-buffering-purification" system to provide conditions for aquatic ecological restoration. Pollutants are then reduced in an ecological way. At the same time, the direction of sewage discharge can be effectively guided, resulting in a lower flow velocity and slower water flow near the riverbank. The gabions allow sewage to diffuse as much as possible in the lower part of the river, reducing the direct scouring of the riverbed by the water flow. This provides favorable conditions for aquatic plants and fillers to further weaken pollutants, creating stable hydraulic conditions for the subsequent water purification process. This method is highly feasible, ecologically safe, and has low construction and maintenance costs. It achieves the maximum slow-flow effect at the lowest cost, providing a foundation for improving pollutant removal efficiency. During the high-water season, a stable growth environment is provided for aquatic plants. Based on hydrodynamic principles, suitable planting areas for aquatic plants are determined, further reducing the water flow velocity in slow-flowing areas and laying the foundation for enhanced pollutant removal. Multiple gabions are used to slow down the water flow, creating low-velocity areas that provide favorable conditions for plant cultivation. This method is more stable and effective than traditional river interception measures. Planting aquatic plants such as reeds and cattails in low-velocity areas near the riverbank provides strong resistance and absorption capacity to water flow and pollutants, thereby improving water purification efficiency. During the high-water season, an enhanced water ecological restoration measure is formed, which is similar to the interaction between subsurface flow and surface flow. In the slow-flow area, plants, fillers, and microorganisms work together to remove pollutants, which is equivalent to the effect of surface flow wetlands. Gabion groups are composed of fillers (zeolite, gravel) and a large number of microorganisms attached to them, as well as aquatic plants growing on them. Their effect is equivalent to subsurface flow wetlands. The combined effect of subsurface and surface flow enhances the pollutant removal effect in the slow-flow area.

[0050] The dry season corresponds to spring and winter, with low river flow and low temperatures, resulting in poor pollutant reduction by plants and low microbial activity. This leads to poor pollutant purification near the discharge outlet. The purification principle during the dry season is as follows: by installing inlet baffle 3, side baffle 4, outlet baffle 5, anode 6, bipolar electrode 7, cathode 8, and attached artificial aquatic plants 10, a closed electrochemical + membrane biological coupling treatment zone is formed, which is an electrochemical + membrane biological pretreatment synergistic purification. The attached artificial aquatic plants 10 are deployed downstream of the electrochemical zone to make full use of the naturally formed water storage and slow flow environment in the area, significantly extending the hydraulic residence time and creating ideal conditions for full contact reaction between the biofilm and pollutants. At the same time, the electrochemical technology enhances the system's buffering capacity against pollution load, achieving deep coupling of electrochemical oxidation and biodegradation. Electrochemical technology has a good removal effect on nitrate nitrogen, total phosphorus, recalcitrant organic matter, and new pollutants such as antibiotics, while biofilm technology has a good removal effect on ammonia nitrogen and COD. Through functional complementarity, the pollutant removal efficiency is significantly improved. Considering the differences in river flow during the wet and dry seasons and the seasonal impact on water purification function, different in-situ treatment measures are adopted for the wet and dry seasons respectively, in order to achieve the best restoration effect while reducing costs.

[0051] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A design method for in-situ ecological restoration systems of river sewage outlets based on hydrodynamic optimization technology, characterized in that, Includes the following steps: S10. Establish a hydrodynamic model for the target river channel water ecological restoration area during the high-water season; S20. Based on hydrodynamic model simulation, gabions (2) of different forms are set up near the water drop point of the sewage outlet (1) in the river to create a slow flow zone; S30. With the aim of slowing down the water flow, the river flow and the sewage outlet (1) flow are generalized into point masses, and the optimal distance between the gabion (2) and the sewage outlet (1) and the optimal length of the gabion (2) are determined. S40. Based on the principle of parallel shoreline, the sewage outlet (1) and gabion (2) are generalized as particles, and the reflection path of the water flow particles is assumed to determine the center distance between two adjacent gabions (2) along the water flow direction in the river channel. S50. Combine real-world factors and use numerical simulation for simulation correction. Based on the principle of making the near-shore flow velocity of the sewage outlet (1) downstream of the river reach the target slow flow value, determine the number, length and spacing of the gabions (2). S60. Plant aquatic plants (11) in the nearshore slow-flow area that meets the target slow-flow value, and arrange filler at the bottom of the nearshore slow-flow area.

2. The design method according to claim 1, characterized in that, The hydrodynamic model in S10 was built using Delft3D.

3. The design method according to claim 1 or 2, characterized in that, In S30, when the river flow and the sewage outlet (1) flow are generalized as point masses, the irregular motion of the water flow is not considered, and the flow velocity and direction near the sewage outlet (1) are the geometric superposition of the river flow velocity and direction and the sewage outlet (1) flow velocity and direction. It is assumed that the angle between the direction of sewage movement and the vertical line of the shoreline is θ, and the upstream end of the gabion (2) is level with the sewage outlet (1), and the furthest distance of the initial straight-line movement of the sewage is exactly to the downstream end of the gabion (2). The length of the gabion (2) parallel to the shoreline is set as... The vertical distance between the gabion (2) and the shoreline is Then the following condition is met: in, This represents the maximum annual average flow velocity of the river channel. (1) Water flow velocity at the sewage outlet.

4. The design method according to claim 1, 2, or 3, characterized in that, In S40, when assuming the reflection path of water flow particles, energy loss, turbulent mixing, and elastic collision of particles are not considered. It is assumed that the reflection path of water flow particles is similar to the specular reflection of light. It is also assumed that the water flow from the sewage outlet (1) mixes with the river flow and hits the first gabion (2), and after being reflected to the bank, it hits its adjacent gabion (2) again. Then the center distance between two adjacent gabions (2) is twice the length of a single gabion (2), and this is repeated.

5. The design method according to claim 1, 2, or 3, characterized in that, In S50, the target slow flow value of the downstream near-shore slow flow zone of the sewage outlet (1) of the river channel is less than 0.3 m / s.

6. The design method according to claim 1, characterized in that, The gabion (2) includes: a cage net (220) and a filling layer (230) inside the cage net (220), with plants (240) planted on top of the filling layer (230); the aquatic plants (11) are reeds or calamus.

7. An in-situ ecological restoration system for river sewage outlets based on hydrodynamic optimization technology, characterized in that, Designed using the design method described in any one of claims 1 to 6.

8. The in-situ ecological restoration system for river sewage outlets based on hydrodynamic optimization technology according to claim 7, characterized in that, Each gabion (2) has a slot (210) on its water-facing side, back side, and bank side. The slot (210) on each gabion (2) extends through its upper and lower ends. An inlet baffle (3) is installed upstream of the sewage outlet (1) between the gabion (2) directly opposite the sewage outlet 1 and the bank wall. One end of the inlet baffle (3) is inserted into the slot (210) on the water-facing side of the corresponding gabion (2), and the other end of the inlet baffle (3) is inserted into the groove on the bank wall. Side baffles (4) are evenly arranged between any two adjacent gabions (2) between the inlet baffle (3) and the aquatic plant (11) planting area. The two ends of each side baffle (4) are respectively locked in the slots (210) on the two adjacent gabions (2). The inlet baffle (3) and the side baffles (4) are both higher than the river water level line. The gabion (2) located downstream of the sewage outlet (1) and adjacent to the aquatic plant (11) planting area is arranged between the gabion (2) and the bank wall. The outlet baffle (5) is fitted into a slot (210) on the bank side of the gabion (2) at the corresponding position, and the other end of the outlet baffle (5) is fitted into a groove on the bank wall; the outlet of the outlet baffle (5) is lower than the inlet baffle (3) and the side baffle (4); downstream of the sewage outlet (1), an anode (6), a bipolar electrode (7) and a cathode (8) are arranged in the direction of water flow between the inlet baffle (3) and the outlet baffle (5). One end of the anode (6), bipolar electrode (7) and cathode (8) is respectively locked in the slot (210) on the bank side of the gabion (2) at the corresponding position, and the other end of the anode (6), bipolar electrode (7) and cathode (8) is locked in the groove set on the bank wall; the anode (6) is connected to the positive terminal of the external power supply (9), the cathode (8) is connected to the negative terminal of the external power supply (9), and artificial aquatic plants (10) with attached film are arranged between the cathode (8) and the water outlet baffle (5).

9. The in-situ ecological restoration system for river sewage outlets based on hydrodynamic optimization technology according to claim 8, characterized in that, The anode (6) is a mesh titanium-based mixed metal oxide coated electrode, the bipolar electrode (7) is a mesh titanium-based mixed metal oxide coated electrode, and the cathode (8) is a stainless steel mesh. One end of the anode (6), the bipolar electrode (7), and the cathode (8) are respectively stuck in the slot (210) on the bank side of the gabion (2) at the corresponding position, and the other end is against the bank wall.

10. The in-situ ecological restoration system for river sewage outlets based on hydrodynamic optimization technology according to claim 8, characterized in that, The upper ends of the inlet baffle (3), the side baffle (4) and the outlet baffle (5) are all serrated, and the height of the baffle decreases sequentially along the water flow direction, forming a natural gravity waterfall. The inlet baffle (3), the side baffle (4) and the outlet baffle (5) are all higher than the water level line.

Images