A sediment interception and treatment system in a plain river network area

Abstract

The present invention discloses a sediment interception and treatment system in a plain river network area, which includes a sediment interception tank arranged at the river connection point and the estuary, a conveying pipeline arranged along the river, a pneumatic pump, a treatment device, an automatic control system, and an estuary wetland system. The automatic control system includes a data center, a communication module, and water quality sensors and mud level sensors arranged in the sediment interception tank. The water quality sensors and mud level sensors are connected to the pneumatic pump through the data center via the communication module. The outlet of the treatment device is connected to the estuary wetland system. The sediment interception tank is formed by excavating the bottom sediment of the water body, and a support is arranged in the tank to support the communication module, water quality sensors, and mud level sensors. The present invention utilizes the characteristics of fine sediment particles, high water content, and large fluidity in the plain river network area to achieve automatic and rapid collection, in-depth treatment, and resource utilization of sediment from the river network to the estuary area, reduce the sediment and nutrient load entering the lake, and reduce the risk of eutrophication.

Description

Technical Field

[0001] The present invention belongs to the fields of water conservancy engineering and environmental engineering, and specifically relates to a system for sediment collection and purification in a plain river network area, which can be applied to river regulation and environmental protection. Background Art

[0002] The fundamental source of lake and reservoir water pollution is the excessive enrichment of pollutants in the basin in lake water bodies and sediments. Basin precipitation scouring or production and domestic water use will introduce a large amount of particulate matter into the river channel, and the river channel water flow will transport it into the lake and reservoir to form silt. The organic components in these formed particulate matters are one of the main causes of water pollution. Therefore, sediment dredging is one of the most commonly used and important means to solve the pollution problems of river channels and lakes and reservoirs.

[0003] However, there are still problems with current sediment dredging, such as being untimely, having a long cycle, being costly, and having difficulties in dealing with dredged silt. For example, the current inland river dredging is at most once a year, and investigations and evaluations are required before and after each dredging, which consumes a huge amount of time, manpower, and material resources. In addition, it is necessary to open up sites to bury the dredged silt to prevent secondary pollution. This occupies a large amount of land. Therefore, how to develop more economical, environmentally friendly, and efficient sediment dredging technology is an urgent question to be answered. Summary of the Invention

[0004] In view of the deficiencies of the prior art and the current situation of sediment deposition and pollution in the plain river network area, the present invention provides a sediment interception and treatment system and method for the plain river network area, which can achieve the purification of sediment and water, reduce the intensity of hydrodynamic disturbance, increase the sediment interception efficiency of the sediment interception tank at the estuary, reduce the pollution load, and provide a shelter for aquatic animals and a leisure place for residents.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A sediment interception and treatment system for a plain river network area includes a sediment interception system, a conveying system, an automatic control system, a treatment device, and an estuary wetland system.

[0007] The sediment interception system includes a number of sediment interception tanks arranged in the plain river network area, and one of the sediment interception tanks is arranged at each river channel connection point and the lake inlet in the plain river network area.

[0008] The conveying system includes an air pump and a conveying pipeline arranged along the river channel. The bottom of each sediment interception tank is connected to the treatment device through the conveying pipeline, and the air pump is arranged at the inlet of the treatment device.

[0009] The automatic control system includes a data center, a communication module, a water quality sensor, and a mud level sensor. A communication module, a water quality sensor, and a mud level sensor are arranged in each sediment interception tank. The water quality sensor and the mud level sensor are connected to the data center through the communication module, and the data center is electrically connected to the pneumatic pump.

[0010] The outlet of the treatment device is connected to the estuary wetland system.

[0011] The sediment interception tank is formed by excavating the bottom mud of the water body. A support is arranged in the sediment interception tank, the communication module is arranged on the support, and the water quality sensor and the mud level sensor are arranged below the water surface through the support. Preferably, it is arranged 1 m below the water surface.

[0012] Due to the fluidity of the bottom mud in the plain river network area, the sediment interception tank can effectively collect the silt in the river network and at the end. The water quality sensor can real-time sense the temperature, dissolved oxygen, and turbidity of the water body in the sediment interception tank; the mud level sensor can sense the silt depth. These information are sent to the data center through the communication module. The data center controls the pneumatic pump to collect the silt in the sediment interception tank network and transport it to the treatment device. The treatment device makes the obtained muddy water mixture into mud cakes and uses the mud cakes for the construction of the estuary wetland system, and the tail water generated is discharged into the wetland after reaching the standard. The wetland system can not only achieve secondary purification of the mud cakes and up-to-standard tail water (advanced treatment), but also beautify the lakeside environment.

[0013] Preferably, a controller is arranged between the data center and the pneumatic pump. After the data center makes a decision on the obtained data, it instructs the controller to control the use of the pneumatic pump.

[0014] Preferably, the sediment interception tank is in the shape of an inverted quadrangular pyramid.

[0015] Preferably, the opening size of the sediment interception tank is the same width as the intersection or the estuary, etc.

[0016] Preferably, the depth of the sediment interception tank arranged in the estuary area is determined by the following method:

[0017] (1-1) Use the Simulating WAves Nearshore (SWAN) model to calculate the wavelength of the lake wind waves in the lake estuary area. The control equation of the model is:

[0018]

[0019] Where: N is the dynamic spectrum density function; t, x, and y are the time and horizontal coordinate directions respectively; σ1 and θ are the frequency and wave direction respectively; c x , c y , c σ and cθ They are the wave propagation speeds in x, y, σ1, and θ respectively; S is the wave energy term, representing the wave energy budget caused by processes such as excitation, dissipation, and nonlinear interaction between waves.

[0020] (1 - 2) Determine the depth of the sediment interception trough according to Equation (2):

[0021]

[0022] Among them, L is the maximum annual wind wave wavelength of the lake, d is the vertical distance from the water surface to the original bottom, h is the depth of the sediment interception trough, and D is the maximum allowable sediment accumulation thickness of the sediment interception trough; among them, D is determined through in-situ observation experiments on sediment settlement flux;

[0023] Since when the wind wave wavelength is greater than 2 times the water depth of the lake, the lake bed will be affected by wind wave disturbance and erode and suspend, so Equation (2) is used as the basis for designing the safety depth of the sediment interception trough. When the designed depth of the sediment interception trough meets Equation (2), the sediment interception trough can safely store silt and ensure that the silt does not erode and suspend into the overlying water, improving the interception efficiency and reducing the occurrence of secondary pollution.

[0024] Preferably, the maximum allowable sediment accumulation thickness of the sediment interception trough is determined through in-situ observation experiments on sediment settlement flux. The steps of the in-situ observation experiment are as follows: Hang a sediment settlement cylinder at the position where the sediment interception trough is pre-excavated, and continuously measure the sediment settlement amount in the settlement cylinder month by month for one year to determine the monthly sediment settlement thickness. The maximum monthly sediment settlement amount is the maximum allowable sediment accumulation thickness D of the sediment interception trough.

[0025] Preferably, the safety angle of the slope of the sediment interception trough is determined by Equation (3):

[0026]

[0027] Among them, c is the cohesion of the silt on the side wall of the sediment interception trough, kPa; θ is the safety angle of the slope, °; is the internal friction angle, °; γ is the unit weight of the silt on the side wall of the sediment interception trough, kN / m 3 . The parameters in Equation (3) are determined through geotechnical tests on the original soil samples collected at the construction site.

[0028] Preferably, the bottom and four walls of the sediment interception trough are solidified with reinforced concrete.

[0029] Preferably, the conveying system further includes a suction head arranged at the end of the conveying pipeline.

[0030] Preferably, the suction head is 1 m away from the bottom of the sediment interception trough. The suction head is fixed on the bracket through a steel pipe.

[0031] Preferably, the bracket is composed of four pipe piles and an iron plate fixedly connected in the middle of the pipe piles. The iron plate is a square with a side length of 2 m.

[0032] The water quality sensor can real-time sense the temperature, dissolved oxygen and turbidity of the water body in the sediment interception tank; the mud level sensor can sense the depth of the silt. These data are connected to the junction box through a cable. The junction box is connected to the communication module. The communication module wirelessly sends the water quality, mud level and video data to the data center through a commercial network. The power supply of all devices is supplied by a power supply system composed of solar energy and storage batteries. The automatic control system can real-time sense the water quality, mud level and video in the sediment interception tank, and can wirelessly transmit the data to the data center.

[0033] The data center is composed of a dedicated computer and supporting software, and can real-time receive data such as water temperature, dissolved oxygen, turbidity, mud level and video in each sediment interception tank collected. The data center stores these data in the database, and at the same time calls the sedimentation warning critical value in the database. When the measured data exceeds the warning critical value, the data center sends a start instruction to the controller. The controller starts and stops the air pump. The air pump is connected to the suction head through a conveying pipeline. The silt sucked by the suction head is conveyed to the treatment device through the conveying pipeline. The device dehydrates and solidifies the silt and compresses it into mud cakes. At the same time, the device purifies the tail water generated during the silt solidification process. Finally, the mud cakes and up-to-standard tail water are sent to the estuary wetland system.

[0034] Preferably, the estuary wetland system includes ecological enclosure piles, L-shaped cofferdams and lakeside wetlands. The area surrounded by the ecological enclosure piles is the lakeside wetland. The L-shaped cofferdam is arranged at the lake inlet of the plain river network. The L-shaped cofferdam extends from the river mouth and bends at the lake inlet to form an L shape in plan view. The sediment interception tank is arranged inside the L-shaped cofferdam.

[0035] Preferably, the cofferdam body of the L-shaped cofferdam is built by piling wire mesh cages filled with stones, so the cofferdam body can be permeable. The top of the L-shaped cofferdam is filled with dredged silt or mud cakes and planted with emergent plants. The L-shaped cofferdam can effectively reduce the kinetic energy of the river water coming and the disturbance of the wind waves from the open lake area, and reduce the risk of secondary suspension of the silt and pollutants in the sediment interception tank.

[0036] Preferably, the top elevation value of the L-shaped cofferdam is 0.5 m higher than the average annual water level of the lake. Therefore, the "L"-shaped cofferdam is a seasonally flooded cofferdam, which can meet the requirements of flood discharge during the flood season.

[0037] Preferably, the ecological enclosure piles are round wooden piles, and the ecological enclosure piles are evenly arranged around the outside of the lakeside wetland. The ecological enclosure piles can effectively reduce the wind wave disturbance and reduce the soil erosion inside the enclosure piles.

[0038] Preferably, the lakeside wetland is obtained by filling with mud cakes. Aquatic plants are planted and aquatic animals are stocked in the lakeside wetland. Preferably, the mud cakes are obtained after dehydrating the sediment treated by the treatment device, and the tail water treated by the treatment device is purified and then discharged into the lakeside wetland. The lakeside wetland can secondary purify the mud and water generated by the treatment device and can provide shelters for aquatic animals and leisure places for residents.

[0039] The beneficial effects of the present invention are as follows:

[0040] 1. The sediment interception system is used to intercept the sediment in the entire river-lake system, shortening the migration distance of the polluted sediment and reducing the risk of water pollution caused by the sediment.

[0041] 2. The combination of the conveying system, the automatic control system and the treatment device realizes the real-time collection and rapid treatment of the silt, improves the timeliness of the treatment and reduces the treatment cost.

[0042] 3. The mud cakes made by the treatment device are used to construct the lakeside wetland and the L-shaped cofferdam, which not only realizes the resource utilization of the silt, but also secondary purifies the mud and water generated by the treatment device, realizes the in-depth treatment of the dredged silt and reduces the risk of secondary pollution.

[0043] 4. The L-shaped cofferdam and the lakeside wetland can not only increase the sediment interception efficiency of the sediment interception tank, resourcefully utilize the dredged and silted by-products, but also provide shelters for aquatic animals and leisure places for residents, achieving a win-win situation of social economy and ecological environment benefits.

[0044] The present invention designs a sediment interception system and constructs it in the river-lake system composed of river networks and lakes. Since the silt in the plain river network has strong fluidity, it will converge towards the sediment interception tank along with the water flow. When the dredging collected in the system exceeds the warning critical value, the data center will trigger the controller, and then start and stop the pneumatic pump. The pneumatic pump can suck the silt in the sediment interception tank through the pipe network composed of the mud conveying pipes and transport it to the treatment device. The device dehydrates and solidifies the silt into mud cakes for the construction of the estuary wetland and the L-shaped cofferdam, and the qualified tail water generated is discharged into the lakeside wetland system. In this way, the secondary purification of the mud and water is completed. At the same time, the L-shaped cofferdam and the lakeside wetland system can reduce the intensity of hydrodynamic disturbance, increase the sediment interception efficiency of the estuary sediment interception tank, reduce the pollution load, and can provide shelters for aquatic animals and leisure places for residents.

[0045] The present invention organically combines the above links to achieve low-cost, high-efficiency and high-quality sediment interception and purification treatment.

[0046] The present invention utilizes the characteristics of high water content and large fluidity of the sediment in the plain river network area to construct sediment interception tanks at the intersection points of the river channels in the river network and at the lake inlet at the end of the river network, forming a sediment interception tank system. The sediment interception tank system can intercept sediment quickly and efficiently, and realize the whole-process rapid automation treatment of monitoring, pumping, harmless treatment and resource utilization. This can greatly reduce the residence time of silt and related pollutants in the river network, reduce the total amount of silt and related pollutants entering the lake, and thus reduce the water pollution risk caused by silt and improve the ecological service value of the water system and the lake.

[0047] The morphological design of the sediment interception tank of the present invention is obtained through on-site investigation, sample collection and testing, and formula and model calculation and simulation, which can ensure that the silt stored within the maximum sediment accumulation thickness range does not erode and suspend, improve the interception efficiency, and reduce the occurrence of secondary pollution. Brief Description of the Drawings

[0048] Figure 1 It is a schematic structural diagram of the sediment interception tank.

[0049] Figure 2 It is a schematic overall structural diagram of the system of the present invention.

[0050] Figure 3 It is a schematic cross-sectional structure diagram at the lake inlet.

[0051] Figure 4 It is a schematic diagram of the automatic control system.

[0052] Figure 5 It is a schematic position diagram of the sediment interception tank at the Dapu Port flowing into Taihu Lake in Embodiment 1.

[0053] Figure 6 It is a three-dimensional image of the sediment interception tank at the Dapu Port obtained by sonar scanning in Embodiment 1.

[0054] Among them, 1 is the sediment interception tank, 2 is the support, 3 is the suction head, 4 is the concrete wall, 5 is the steel pipe, 6 is the conveying pipeline, 7 is the water quality sensor, 8 is the power and communication module, 9 is the camera, 10 is the river, 11 is the air pump, 12 is the treatment device, 13 is the controller, 14 is the data center, 15 is the lake shore dike, 16 is the lakeside wetland, 17 is the lake, 18 is the ecological enclosure pile, 19 is the L-shaped cofferdam, 20 is the cage stone, 21 is the mud level sensor, 22 is the mud cake, and 23 is the lake bed. Detailed Embodiment

[0055] Embodiment 1

[0056] Demonstration construction is carried out at the Dapu Port at the inlet of Taihu Lake and its river network area:

[0057] Such as Figures 1-5As shown in the figure, the adopted sediment interception and treatment system in the plain river network area includes a sediment interception system, a conveying system, an automatic control system, a treatment device, and an estuary wetland system. The sediment interception system includes several sediment interception tanks arranged in the plain river network area. One sediment interception tank is arranged at each river connection point and lake inlet in the plain river network area.

[0058] The conveying system includes a pneumatic pump and a conveying pipeline arranged along the river. The bottom of each sediment interception tank is connected to the treatment device through the conveying pipeline. The pneumatic pump is arranged at the inlet of the treatment device. The automatic control system includes a data center, a communication module, a water quality sensor, and a mud level sensor. A communication module, a water quality sensor, and a mud level sensor are arranged in each sediment interception tank. The water quality sensor and the mud level sensor are connected to the data center through the communication module. The data center is electrically connected to the pneumatic pump. The outlet of the treatment device is connected to the estuary wetland system. The sediment interception tank is formed by excavating the bottom mud of the water body. A bracket is arranged in the sediment interception tank. The communication module is arranged on the bracket. The water quality sensor and the mud level sensor are arranged 1 m below the water surface through the bracket.

[0059] A controller is arranged between the data center and the pneumatic pump. After making a decision on the obtained data by the data center, the controller is instructed to control the use of the pneumatic pump.

[0060] The sediment interception tank is in the shape of an inverted frustum of a pyramid.

[0061] The opening size of the sediment interception tank is the same as the width of the intersection or the estuary.

[0062] The depth of the sediment interception tank arranged in the estuary area is determined by the following method:

[0063] (1-1) Use the Simulating WAves Nearshore (SWAN) model to calculate the wavelength of the lake wind waves in the lake inlet area. The control equation of the model is:

[0064]

[0065] Where: N is the dynamic spectrum density function; t, x, and y are the time and horizontal coordinate directions respectively; σ1 and θ are the frequency and wave direction respectively; c x , c y , c σ and c θ are the wave propagation velocities in x, y, σ1, and θ respectively; S is the wave energy term, which represents the wave energy budget caused by processes such as excitation, dissipation, and nonlinear interaction between waves.

[0066] (1-2) Determine the depth of the sediment interception tank according to formula (2):

[0067]

[0068] Wherein, L is the maximum annual wind wave wavelength of the lake, d is the vertical distance from the water surface to the original bottom, h is the depth of the sediment interception tank, and D is the maximum allowable sediment accumulation thickness of the sediment interception tank; wherein, D is determined through in-situ observation experiments on sediment settlement flux.

[0069] The steps of the in-situ observation experiment are as follows: Hang a sediment settlement cylinder at the position where the sediment interception tank is to be pre-excavated, and continuously measure the sediment settlement amount in the settlement cylinder month by month for one year to determine the monthly sediment settlement thickness. The maximum monthly sediment settlement amount is the maximum allowable sediment accumulation thickness D of the sediment interception tank.

[0070] Preferably, the safety angle of the slope of the sediment interception tank is determined by formula (3):

[0071]

[0072] Wherein, c is the cohesion of the silt on the side wall of the sediment interception tank, in kPa; θ is the safety angle of the slope, in °; is the internal friction angle, in °; γ is the unit weight of the silt on the side wall of the sediment interception tank, in kN / m 3 . The parameters in formula (3) are determined through geotechnical tests on the original soil samples collected at the construction site.

[0073] In this example, the opening length of the small sediment interception tank is 10 m, the width is 8 m, the height of the tank is 3 m, the bottom length is 5 m, and the width is 4 m, which is arranged in the central area of the river confluence. The length of the large sediment interception tank is 200 m, the width is 100 m, and the depth is 4.5 m, which is arranged in the estuary area 25 m away from the lake shore. Prepare concrete to harden the surface of the interception tank. At the midpoints of the bottoms of the large and small interception tanks respectively, set up supports. The supports are composed of four pipe piles and an iron plate fixedly connected in the middle of the pipe piles. The iron plate is a square with a side length of 2 m. The bottoms of the pipe piles are fixed to the bottom surface, and the tops exceed the water surface by 2.5 m.

[0074] A suction head is arranged at the end of the conveying pipeline.

[0075] The suction head is 1 m away from the bottom of the sediment interception tank. The suction head is fixed on the support through a steel pipe.

[0076] The wetland system in the estuary area includes ecological enclosure piles, L-shaped cofferdams and lakeside wetlands. The area surrounded by the ecological enclosure piles is the lakeside wetland. The L-shaped cofferdam is arranged in the estuary area of the plain river network where it enters the lake. The L-shaped cofferdam extends from the river mouth and bends at the lake inlet to form an L shape in plan view. The sediment interception tank is arranged inside the L-shaped cofferdam.

[0077] The weir body of the L-shaped weir is made of wire mesh cages filled with stones, so the weir body can be permeable. The top of the L-shaped weir is filled with dredged silt or mud cakes and planted with emergent plants. The L-shaped weir can effectively reduce the kinetic energy of the river water inflow and the disturbance of the wind waves from the open lake area, and reduce the risk of secondary suspension of the silt and pollutants in the sediment interception tank.

[0078] The top elevation value of the L-shaped weir is 0.5 m higher than the average annual water level of the lake. Therefore, the "L"-shaped weir is a seasonally flooded weir, which can meet the requirements of flood discharge during the flood season.

[0079] The ecological pile is a round log pile, and the ecological piles are evenly arranged around the outside of the lakeside wetland. The ecological piles can effectively reduce the wind wave disturbance and reduce the soil erosion within the piles.

[0080] The lakeside wetland is obtained by filling with mud cakes. Aquatic plants are planted and aquatic animals are stocked in the lakeside wetland. Preferably, the mud cakes are obtained after the sediment treated by the treatment device is dehydrated. The tail water treated by the treatment device is purified and then discharged into the lakeside wetland. The lakeside wetland can secondary purify the mud and water generated by the treatment device and provide a shelter for aquatic animals and a leisure place for residents.

[0081] In this example, the river outlet is the inlet of Dapu Port into Taihu Lake (see Figure 2 、 Figure 5 ). The sediment interception tank is used to store the sediment. The upper mud level sensor transmits data to the data center in real time. When the warning value is reached, the data center sends an instruction to the controller to turn on the pneumatic pump and the bottom mud treatment device to start working, pump out and decontaminate the bottom mud. After the treated bottom mud and the remaining water meet the standards, they are discharged into the lakeside wetland for secondary deep purification by plants.

[0082] In this example, the mud level sensor, the water quality sensor and the camera 9 are connected to the power and communication module 8, and transmit data in real time through the communication module and the commercial 5G network. All devices are powered by the power module composed of solar panels and storage batteries.

[0083] In this example, the controller, data center, pneumatic pump, and processing device in the sludge automatic collection and treatment system are all installed in the factory building beside the lakeshore dike. The data center receives data transmissions from the communication module and cameras. When the monitoring value exceeds the full critical value, the data center sends instructions to the conveying system and the processing device. The system starts the pneumatic pump through the controller, and sucks the sludge in the sediment interception tank through the conveying pipeline and the suction head. The sludge is transported by the conveying pipeline to the processing device in the factory building. The device completes the dehydration and solidification of the sludge and compresses it into mud cakes. At the same time, the surplus water generated during the production process is discharged into the lakeside wetland after reaching the purification standard. In addition, the mud cakes made by the device can be used as soil for the construction of the lakeside wetland and the L-shaped cofferdam.

[0084] In the lakeside wetland system of the estuary area of this example, the L-shaped cofferdam extends from the river channel towards the center of the lake. After extending forward for 30m and then turning the corner and moving forward another 20m, it forms an "L" shape. The L-shaped cofferdam is composed of wire mesh cages filled with stones. The height of the L-shaped cofferdam is 2.5m, and the cross-sectional shape is trapezoidal. The top of the cofferdam is filled with treated bottom mud cakes, and emergent plants such as reeds are planted. The edge of the lakeside wetland is fixed with ecological piles to prevent bottom mud erosion. The ecological piles are driven at intervals of 0.5m and arranged along the shore to form a rectangle.

[0085] The system will be further described with reference to the attached drawings:

[0086] See Figure 2 , a small sediment interception tank at the river channel intersection is arranged upstream of the river channel for pre-treatment of sediment collection, and a large sediment interception tank in the estuary area is arranged at the lake inlet for re-treatment of river sediment collection.

[0087] See Figure 1 , the described sediment interception tank is in the shape of an inverted frustum of a pyramid. Its position and specific dimensions will be described in combination with the engineering practice of the Dapu Port sediment interception tank in this application:

[0088] (1) Based on the investigation results of the water volume, sediment volume, and estuary sediment distribution in the Dapu Port of Taihu Lake, the construction location of the sediment interception tank was determined as shown in Figure 5 .

[0089] (2) Using the wind wave numerical model based on Equation (1), under the water depth of 2m and the current annual wind field conditions, the calculated wavelength of the maximum wind wave at the sediment interception tank is 10.9m. Accordingly, based on the design basis of the sediment interception tank depth specified by Equation (2), the final determined excavation depth of the sediment interception tank here shall not be less than 4m.

[0090] (3) Rent the original sediment sampling equipment to collect a 10m-long sediment columnar mud sample at the position shown in Figure 5 , and divide the mud column into 20 samples at intervals of 0.5m. Seal and preserve this sample and quickly send it to the geotechnical laboratory to test the geotechnical parameters.

[0091] (4) After analyzing the c, γ of the Taihu mud column, they are 4 kPa and 16.5 kN / m respectively, 3 and 5°. The designed depth of the sediment interception tank is h = 4 m. Then, substituting these parameters into Equation (3), the calculated safe slope angle is 35.84°, and the corresponding slope coefficient is 4:5.54.

[0092] (5) The sediment interception tank designed and built according to the above standards can effectively capture and safely store the silt within the allowable maximum sediment accumulation thickness range, improving the interception efficiency and reducing the occurrence of secondary pollution. Figure 6 It is a three-dimensional image of the sediment interception tank at Dapu Port obtained by sonar scanning ( Figure 5 ).

[0093] See Figure 4 . There is a stainless steel outer cover on the bracket to protect the power supply system, communication module and camera. Among them, the power generation devices of the power supply system (solar energy, small wind turbine) are arranged outside the cover and are connected to the battery through wires. The battery supplies power to the communication module, camera, mud level sensor and water quality sensor through data lines.

[0094] The data center receives the data transmission from the communication module in real time and automatically generates the corresponding sediment deposition process line of the sediment interception tank. The air pump is connected to the suction head 1 m above the bottom of the sediment interception tank through a conveying pipeline.

[0095] See Figure 3 . The elevation value of the top of the L-shaped cofferdam is 0.5 m higher than the average annual water level of the lake. Therefore, the L-shaped cofferdam is a seasonally flooded cofferdam, which can meet the requirements of river flood discharge during the flood season. Emergent plants and aquatic animals are cultivated in the wetland to form a simple ecological cycle system.

[0096] Through the above technology, when the river transports sediment to the estuary, the flow velocity decreases after passing through the cofferdam, and the suspended matter deposits in the interception tank. When the river water passes through the cofferdam, the adsorption material on the cofferdam body adsorbs and purifies it, so that the amount of pollutants carried by the river water is reduced after flowing out of the cofferdam. The silt in the sediment interception tank can be pumped out and filled in the lakeside wetland, and plants such as reeds are planted for plant purification, thus forming a good ecological environment.

Claims

1. A sediment interception and treatment system in a plain river network area, characterized in that, It includes a sediment interception system, a conveying system, an automatic control system, a treatment device and an estuarine wetland system. The sediment interception system includes a number of sediment interception tanks arranged in the plain river network area, and one such sediment interception tank is provided at each river connection point and the lake inlet in the plain river network area. The conveying system includes an air pump and a conveying pipeline arranged along the river. The bottom of each sediment interception tank is connected to the treatment device through the conveying pipeline, and the air pump is arranged at the inlet of the treatment device. The automatic control system includes a data center, a communication module, a water quality sensor and a mud level sensor. A communication module, a water quality sensor and a mud level sensor are arranged in each sediment interception tank. The water quality sensor and the mud level sensor are connected to the data center through the communication module, and the data center is electrically connected to the air pump. The outlet of the treatment device is connected to the estuarine wetland system. The sediment interception tank is formed by excavating the bottom mud of the water body. A support is arranged in the sediment interception tank, and the communication module is arranged on the support. The water quality sensor and the mud level sensor are arranged below the water surface through the support. The estuarine wetland system includes ecological enclosures, L-shaped cofferdams and lakeside wetlands. The area surrounded by the ecological enclosures is the lakeside wetland. The L-shaped cofferdam is arranged in the lake inlet area of the plain river network. The L-shaped cofferdam extends from the river mouth and bends at the lake inlet to form an L shape in plan view. The sediment interception tank is arranged inside the L-shaped cofferdam. The safety angle of the slope of the sediment interception tank is determined by Equation (3): （3） Among them, L is the annual maximum wind wave wavelength of the lake, and h is the depth of the sediment interception tank. c is the cohesion of the silt on the side wall of the sediment interception tank, kPa; θ is the slope safety angle, °; φ is the internal friction angle, °; γ is the unit weight of the silt on the side wall of the sediment interception tank, kN / m 3 .

2. The sediment interception and treatment system in the plain river network area according to claim 1, wherein A controller is arranged between the data center and the air pump. After making decisions on the obtained data by the data center, it instructs the controller to control the use of the air pump.

3. The sediment interception and treatment system in the plain river network area according to claim 1, characterized in that, The sediment interception tank is in the shape of an inverted quadrangular pyramid.

4. The sediment interception and treatment system in the plain river network area according to claim 1, characterized in that, The depth of the sediment interception tank arranged in the estuarine area is determined by the following method: (1-1) Use the SWAN model to calculate the wavelength of the lake wind waves in the lake inlet area. The control equation of the model is: （1） where: is the dynamic spectral density function; t and x and y are the time and the horizontal coordinate direction respectively; σ 1 and θ are the frequency and the wave direction respectively; c x , c y , c σ and c θ are respectively x , y , σ 1 and θ the wave propagation speeds on; S is the wave energy term; (1-2) Determine the depth of the sediment interception tank according to Equation (2): （2） Where, L is the annual maximum wind wave wavelength of the lake, d is the vertical distance from the water surface to the original water bottom, h is the depth of the sediment interception tank, and D is the maximum allowable sediment accumulation thickness of the sediment interception tank; among them, D is determined by in-situ observation experiments of sediment settlement flux.

5. The sediment interception and treatment system in the plain river network area according to claim 1, characterized in that, The conveying system further includes a suction head arranged at the end of the conveying pipeline.

6. The sediment interception and treatment system in the plain river network area according to claim 5, characterized in that The suction head is 1 m away from the bottom of the sediment interception tank.

7. The sediment interception and treatment system in the plain river network area according to claim 1, characterized in that The body of the L-shaped cofferdam is made of wire mesh cage stones, and the top of the L-shaped cofferdam is filled with dredged silt or mud cakes and planted with emergent plants.

8. The sediment interception and treatment system in the plain river network area according to claim 1, characterized in that The ecological enclosures are round wooden stakes, and the ecological enclosures are equidistantly arranged around the outside of the lakeside wetland.

Images