Combined treatment method for ecological dredging and residual water treatment of shallow lake bottom mud

Abstract

The invention belongs to the field of lake ecological desilting, and discloses a shallow lake bottom mud ecological desilting and residual water treatment combined treatment method which comprises lake bottom mud ecological desilting, solidification dehydration treatment and residual water treatment. Ecological dredging of the lake bottom mud is implemented by adopting an environment-friendly cutter suction dredger and a sealed pipeline to convey mud, and the bottom mud is conveyed to a mud discharge field to be solidified and dehydrated. A vacuum preloading technology is adopted for solidification and dehydration of the bottom mud, pore water of the bottom mud is effectively discharged by increasing the pressure difference between soil bodies of a drainage plate, and the overall solidification effect is improved. The residual water treatment comprises the treatment of desilting and solidifying residual water, the technologies of multi-stage precipitation, mechanical aeration, aquatic plant remediation and the like are adopted, and the residual water is discharged nearby after being treated to reach the standard. The combined treatment method aims at effectively reducing endogenous pollution of lakes, promoting lake water quality improvement and guaranteeing water safety of regional lakes and reservoirs, and is particularly suitable for ecological dredging engineering of shallow lakes, short construction period and fine-particle bottom mud.

Description

Technical Field

[0001] The present invention relates to the technical field of lake ecological dredging, and particularly to a combined treatment method for ecological dredging of shallow lake sediment and treatment of surplus water. Background Art

[0002] Years of experience and performance in lake and river pollution control have shown that under the condition that external pollution is basically controlled, removing endogenous pollution sediment and restoring and reconstructing the water ecosystem are important ways to achieve ideal treatment effects. Lakes are important surface water resources in cities. With the rapid improvement of urbanization level, most pollutants are transferred to lake suspended solids and sediments. A large amount of nitrogen and phosphorus nutrients, heavy metals and other major pollutants are deposited in lake sediment, and are slowly and continuously released into the water body, resulting in secondary pollution of the lake water body. Controlling the endogenous pollution problem of lakes through lake sediment dredging has become an important link in lake water environment treatment in the new era.

[0003] The reasonable treatment of sludge and surplus water is related to the environment, ecology, energy conservation and emission reduction. In particular, the effective treatment and disposal of lake sludge in large and medium-sized cities directly affect the sustainable development of the urban water environment, water ecology, urban human settlement life and urban economic construction. There are many research reports on the dredging and consolidation technology of polluted lake sediment, but the actual engineering implementation effect is not as expected. Usually, there are a series of problems such as high operating cost, large land occupation area, dehydration effect not reaching the expected level, and the effluent of surplus water treatment not meeting the discharge standard.

[0004] In summary, it is necessary to develop a combined method for lake ecological dredging and surplus water treatment with high sludge dehydration efficiency, up-to-standard surplus water treatment, less land occupation and economic feasibility. Summary of the Invention

[0005] The purpose of the present invention is to provide a combined treatment method for ecological dredging of shallow lake sediment and treatment of surplus water with high sludge dehydration efficiency, up-to-standard surplus water treatment, less land occupation and economic feasibility, so as to solve the foregoing problems existing in the prior art.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows: A combined treatment method for ecological dredging of shallow lake sediment and treatment of surplus water, which adopts ecological dredging of lake sediment, solidification and dehydration treatment, and multi-stage surplus water treatment, including the following steps:

[0007] (1) Implement ecological dredging of the lake sediment by using a cutter suction dredger and a closed pipeline mud transportation process, and transport the sediment to the sludge disposal site nearby, and perform physical treatment and precipitation by using the surplus storage capacity and water depth of the sludge disposal site;

[0008] (2) The precipitated sludge is solidified and dehydrated using vacuum preloading technology at the sludge discharge site, and the low-concentration dredging residual water and solidified residual water enter the residual water sedimentation tank, in which a separation cofferdam is set to form a multi-level residual water sedimentation tank;

[0009] (3) The multi-stage residual water sedimentation tank uses a comprehensive treatment method of chemical flocculation + aeration + aquatic plant purification to treat the residual water. After the treatment meets the discharge standards, it is discharged into the nearby river.

[0010] The water depth of the shallow lake is ≤1.20m, and the depth of 200~350m is adopted. 3 / h cutter suction dredger is used for dredging, among which: 200~250m / h is used in non-flood season 3 / h cutter suction dredger, 300~350m 3 / h cutter suction dredger.

[0011] The mud field is 6.50-7.50m deep, the average depth of the blown-in silt is 5.50-6.50m, the slope of the mud field is 1:2-1:3, and after blowing and filling to the designed elevation, the dredged material is drained and consolidated by the vacuum preloading method, the moisture content of the consolidated soil is ≤55%, and its settlement is stabilized.

[0012] The cutter suction dredgers are multiple groups of environmentally friendly cutter suction dredgers.

[0013] In the vacuum preloading technology, the insertion spacing of the forward plastic drain boards of the consolidation and dehydration system is 0.60-1.00m, and the spacing of the reverse vacuum pipes is 2.20-2.60m. The system is arranged with two rows of forward plastic drain boards and one row of reverse vacuum pipes. The insertion depth of the forward drain boards and reverse vacuum pipes in the mud solidification field is 4.00-8.00m, and the exposed length of the drain boards is controlled to be ≥50cm.

[0014] In the vacuum preloading technology, the bearing mechanical characteristic value of the sludge after consolidation and dehydration by the vacuum preloading method is ≥50kPa, and the moisture content of the consolidated soil meets 55% to 65%.

[0015] The multi-stage residual water sedimentation tank is arranged with 5 stages of sedimentation tanks according to the water flow direction. Flocculants such as PAC and PAM are added to the 1st and 2nd stage sedimentation tanks. The 4th stage sedimentation tank adopts an aeration treatment process, and the 5th stage sedimentation tank adopts planting aquatic plants to purify the residual water. After the residual water meets the treatment standards, it is discharged into the nearby river.

[0016] The average depth of the multi-stage residual water sedimentation tank is 5.50-6.50m, the slope of the sedimentation tank side slope is 1:2-1:3, and the sedimentation time of suspended matter in the water body after the residual water is added with flocculant is 24-36h.

[0017] The flocculants sprayed between the 1st and 2nd sedimentation tanks are polyaluminum chloride (PAC) and polyacrylamide (PAM). The mass percentage concentration of the PAC solution for flocculant addition is 5% - 10%, and the mass percentage concentration of the PAM solution for flocculant addition is 3‰ - 5‰.

[0018] The 4th sedimentation tank is set according to the service area of the aeration equipment being 500 - 800 m2; the aquatic plants planted in the 5th sedimentation tank are Vallisneria natans, Myriophyllum verticillatum, and Trapa bispinosa. The planting area of the aquatic plants accounts for 10% - 20% of the water surface area.

[0019] The beneficial effects of the present invention are as follows: Through the combined methods of sediment dredging, sedimentation, solidification dehydration, and surplus water treatment, by combining multiple technologies of physics, chemistry, and biology, the ecological dredging of sediment has a good treatment effect, and can effectively reduce and control the problem of lake endogenous pollution; the sediment discharge and solidification are completed in the same site, with a small floor area, low moisture content of the solidified soil, high dehydration efficiency, and stable effect; after the sediment is solidified, the bearing capacity of the foundation is high, and the post-construction settlement is small, which can meet the construction requirements such as roads, foundations, reclamation, and greening, with a high degree of resource utilization; the surplus water treatment adopts a combined process of multiple chemical flocculation + aeration + aquatic plant purification, and the effluent quality after multi-stage treatment of the surplus water is good, which can meet the relevant discharge standards; the method of the present invention has low treatment cost, little secondary pollution, is safe and environmentally friendly, and has a wide application range, especially suitable for ecological dredging projects of shallow lakes (water depth ≤ 1.20 m), tight construction periods, high content of fine particles, large viscosity, and small permeability coefficient of the lake bottom sediment, and is used as a supporting technology for related projects of lake bottom sediment dredging. Brief Description of the Drawings

[0020] Figure 1 is a process flow diagram of the combined treatment method for ecological dredging of sediment and surplus water treatment in shallow lakes of the present invention;

[0021] Figure 2 is a schematic diagram of the connection between the plastic drainage board and the vacuum pipeline of the present invention;

[0022] In the figure: 1. Environmental protection cutter suction dredger; 2. Sludge discharge pipe; 3. Sludge discharge site / solidification site; 4. 1st sedimentation tank; 5. 2nd sedimentation tank; 6. 3rd sedimentation tank; 7. 4th aeration tank; 8. 5th plant pond; 9. Mechanical aeration device; 10. Aquatic plants such as plant floating beds; 11. Drainage board; 12. Drainage board joint; 13. Reverse vacuum extraction board; 14. Vacuum main pipe; 15. Vacuum branch pipe; 16. Four-way joint; 17. Reducing tee; The direction indicated by the arrow is the direction of sediment / water flow or the direction of coagulant addition. Detailed Embodiments

[0023] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not all embodiments nor are they used to limit the present invention.

[0024] The combined treatment method for ecological dredging of sediment and residual water treatment in shallow lakes of the present invention adopts ecological dredging of lake sediment, solidification and dehydration treatment, and multi-stage residual water treatment, including the following steps:

[0025] (1) Ecologically dredge the lake sediment using a cutter suction dredger and a closed pipeline mud transportation process, and transport the sediment to the sludge disposal site nearby. Use the surplus storage capacity and water depth of the sludge disposal site for physical treatment and sedimentation.

[0026] (2) The sediment after sedimentation is solidified and dehydrated using vacuum preloading technology at the sludge disposal site. The low-concentration dredging residual water and solidification residual water enter the residual water sedimentation tank, and partition cofferdams are set in the residual water sedimentation tank to form a multi-stage residual water sedimentation tank.

[0027] (3) The multi-stage residual water sedimentation tank sequentially treats the residual water using a comprehensive treatment method of chemical flocculation + aeration + aquatic plant purification, and discharges it nearby into the nearby river after reaching the discharge standard.

[0028] The water depth of the shallow lake is ≤ 1.20 m, and a cutter suction dredger with a capacity of 200 - 350 m 3 / h is used for dredging. Among them: during the non-flood season, a cutter suction dredger with a capacity of 200 - 250 m 3 / h is used, and during the flood season, a cutter suction dredger with a capacity of 300 - 350 m 3 / h is used.

[0029] The depth of the sludge disposal site is 6.50 - 7.50 m, the average depth of the filled silt is 5.50 - 6.50 m, the slope of the sludge disposal site slope is 1:2 - 1:3. After filling to the designed elevation, the vacuum preloading method is used to drain and consolidate the dredged material, and the water content of the consolidated soil is ≤ 55%, and its settlement is stabilized.

[0030] The cutter suction dredger is a multi-group environmental protection cutter suction dredger.

[0031] In the vacuum preloading technology, the insertion spacing of the positive plastic drainage boards in the consolidation and dehydration system is 0.60 - 1.00 m, the spacing of the reverse vacuum extraction pipes is 2.20 - 2.60 m, and they are arranged according to two rows of positive plastic drainage boards and one row of reverse vacuum extraction pipes; the insertion depth of the positive drainage boards and reverse vacuum pipes in the sludge solidification site is 4.00 - 8.00 m, and the exposed length of the drainage boards is controlled to be ≥ 50 cm.

[0032] In the vacuum preloading technology, the mechanical bearing characteristic value of the silt after consolidation and dehydration by the vacuum preloading method is ≥50 kPa, and the water content of the consolidated soil satisfies 55% - 65%.

[0033] The multi-stage surplus water sedimentation tank is provided with 5 sedimentation tanks according to the water flow direction. Flocculants such as PAC and PAM are added to the 1st - 2nd sedimentation tanks; the 4th sedimentation tank adopts an aeration treatment process, and the 5th sedimentation tank adopts the method of planting aquatic plants to purify the surplus water. After the surplus water treatment reaches the standard, it is discharged into the river nearby.

[0034] The average depth of the multi-stage surplus water sedimentation tank is 5.50 - 6.50 m, the slope of the sedimentation tank slope is 1:2 - 1:3, and the sedimentation time of the suspended solids in the water body after adding the flocculant is 24 - 36 h.

[0035] The flocculants sprayed between the 1st - 2nd sedimentation tanks are polyaluminum chloride (PAC) and polyacrylamide (PAM). The mass percentage concentration of the PAC solution added as the flocculant is 5% - 10%, and the mass percentage concentration of the PAM solution added is 3‰ - 5‰.

[0036] The 4th sedimentation tank is set according to the service area of the aeration equipment of 500 - 800 m 2 ; the aquatic plants planted in the 5th sedimentation tank are Vallisneria natans, Myriophyllum verticillatum, Trapa bispinosa, etc. The planting area of the aquatic plants accounts for 10% - 20% of the water surface area.

[0037] Taking a certain lake ecological dredging project that adopts the technical solution of the present invention as an example, it is further described in combination with the attached drawings: In a certain lake ecological dredging project, the average water depth of the lake is 1.18 m, the dredging depth is about 0.18 - 0.30 m, and the total amount of dredged bottom mud is about 2.7047 million m 3 , and the dredging area is about 11.13 km 2 .

[0038] As Figure 1 , 2 shown, a lake bottom mud environmental protection cutter suction dredger 1 implements ecological dredging on the polluted bottom mud. A ship type with a capacity of 250 m 3 / h is adopted during the non-flood season, and a ship type with a capacity of 350 m 3 / h is adopted during the flood season. The diameter of the discharge pipe is DN400 - DN500, and the flow velocity in the pipe is taken as 1 m / s. The bottom mud is transported to the discharge site 3 through the discharge pipe 2 nearby. The discharge site utilizes the existing abandoned ditch and pond. The average transportation distance from the dredging area to the discharge site 3 is 11.50 km, and the basic discharge distance of the cutter suction dredger is 1.50 km. A relay pump needs to be set. The layout spacing of the relay pumps is 3 km, and the designed flow rate of a single relay pump is 2000 m 3 / h, the head is 65 m, and the power is 630 kW. The average depth of the discharge site 3 is 6.50 m, the average depth of the filled silt is 5.50 m, and the slope of the slope is 1:2 - 1:3.

[0039] The physical treatment and precipitation of the bottom mud are carried out by using the surplus storage capacity and water depth of the sedimentation pond. After precipitation, the bottom mud in the sedimentation pond 3 is solidified and dehydrated by using the vacuum preloading technology. The consolidation and dehydration system of the vacuum preloading method consists of a drainage system, a vacuum system and a pressurization system. ① The spacing of the forward plastic drainage boards 11 is 0.80 m, and the spacing of the reverse vacuum extraction pipes 13 is 2.40 m. They are arranged in accordance with two rows of forward plastic drainage boards 11 and one row of reverse vacuum extraction pipes 13. The length of the plastic drainage board 11 is 5 m, the average depth of the inserted boards in the sedimentation and solidification field is 5.50 m, and the exposed length of the drainage board 11 is more than 50 cm; the plastic drainage boards 11 are connected through joints 12, and the drainage board joints 12 are connected through vacuum branch pipes 15 (φ25 threaded steel wire hoses). ② The vacuum system consists of a vacuum pipeline, a gas-liquid separation tank and a vacuum unit, which form the vacuum system. The vacuum branch pipe 15 is connected to the vacuum main pipe 14 (φ50 threaded steel wire hose) through a four-way joint 16 and a reducing tee 17. The horizontal spacing of the pipe network is 0.8 m, and the vertical spacing is 30 - 40 m, and finally forms the vacuum pipeline. The volume of the vacuum extraction gas-liquid separation tank should be ≥2 m 3 . ③ The pressurization system includes a booster pump and a pressurization pipeline system. The pressurization pipeline system consists of a horizontal pressurization pipeline system and a vertical pressurization pipeline system. The pressurization pipes are arranged at the designed positions beside the adjacent drainage boards. The length of the pressurization pipe is 5 m. The 8 mm air pipe at the upper part of the pressurization pipe is directly connected to the pressurization system. 4 - 6 air injection holes with a pore diameter of about 3 mm are arranged within 200 mm at the end of the pipe, and it is wrapped with 150 g / m 2 geotextile. The connection joints of the pressurization pipeline are selected as tee joints, and the connection length is not less than 100 mm.

[0040] The trial vacuum extraction should be carried out for 7 - 10 d. After the vacuum pressure under the membrane reaches 0.08 Mpa and remains stable for 3 consecutive days, the formal vacuum extraction stage can be entered. The mechanical characteristic value of the bearing capacity of the silt after consolidation and dehydration by the vacuum preloading method is ≥50 kPa, the water content of the consolidated soil meets 55% - 65%, and 1.0 m of good soil reserved by the removal of the cofferdam and the excavation of the pond bottom is used for covering the soil, and then Manila grass and perennial ryegrass are sown (ratio 1:1, 0.025 kg / m 2 ), and the greening coverage rate is 100%.

[0041] The multi-stage surplus water treatment system is provided with five sedimentation tanks 4, 5, 6, 7, and 8 in the water flow direction, and adopts a comprehensive treatment method of chemical flocculation + aeration + aquatic plant purification. The designed average depth of the sedimentation tanks is 5.50 - 6.50 m, the slope of the side slope is 1:2, and the sedimentation time is 24 h. Flocculants PAC and PAM are sprayed between the first and second sedimentation tanks 4 and 5. After on-site mud and water pilot tests, the dosing mass percentage concentration of the PAC solution of the flocculant is 5% - 10%, and the dosing mass percentage concentration of the PAM solution is 3‰ - 5‰. The fourth-stage aeration tank 7 adopts mechanical aeration. Through a rotating device, the wastewater is fully contacted with air to dissolve oxygen in the water, further removing some pollutants such as organic matter and nitrogen that are difficult to remove. The aeration equipment is set according to 600 m 2 per unit. The fifth-stage plant pond 8 is planted with aquatic plants such as Myriophyllum verticillatum, Vallisneria natans, and water chestnut for further degradation and absorption of pollutants. The planting area accounts for about 10% of the water surface area.

[0042] After monitoring, the concentrations of various pollutants in the treated surplus water treatment tail water are: COD = 12 - 17 mg / L, NH3-N = 1.46 mg / L, TN = 1.76 - 3.15 mg / L, TP = 0.02 - 0.21 mg / L, SS = 6 - 22 mg / L. The tail water after surplus water treatment can meet the requirements of the design target, that is, the standards of COD ≤ 20 mg / L, NH3-N ≤ 1.50 mg / L, TN ≤ 6 mg / L, TP ≤ 0.15 mg / L, and SS < 30 mg / L.

[0043] Through the combined methods of sediment dredging, sedimentation, solidification dehydration, and surplus water treatment of the present invention, by combining multiple technologies of physics, chemistry, and biology, the ecological dredging of bottom mud has good treatment effects, can effectively reduce and control the problem of lake endogenous pollution; the bottom mud discharging and solidification are completed on the same site, with a small floor area, low moisture content of the consolidated soil, high dehydration efficiency and stable effects; after the bottom mud is solidified, the foundation bearing capacity is high and the post-construction settlement is small, which can meet the construction requirements such as roads, foundations, reclamation, and greening, and has a high degree of resource utilization; the surplus water treatment adopts a combined process of multiple chemical flocculation + aeration + aquatic plant purification, and the effluent quality after multi-stage treatment of the surplus water is good, which can meet the relevant discharge standards; this method has low treatment costs, little secondary pollution, is safe and environmentally friendly, and has a wide range of applications. It is especially suitable for ecological dredging projects in shallow lakes (water depth ≤ 1.20 m) with tight construction periods, high content of fine particles in the lake bottom mud, large viscosity, and small permeability coefficient. As a supporting technology for related projects of lake bottom mud dredging, it has broad guiding significance and popularization significance.

[0044] The method of the present invention is applicable to shallow lakes. Considering factors such as the application range of dredging equipment, the degree of disturbance and diffusion, the sludge discharge concentration, the construction accuracy, the amount of residual water treatment, the land occupation for sludge discharge, the equipment selection, and the comprehensive cost, the ship type of an environmental protection cutter suction dredger is selected. If the water depth at the dredging position is less than the minimum dredging depth of the dredger, the dredging sequence can be from the deep water area to the shallow water area to meet the performance and working conditions requirements of the dredger.

[0045] An environmental protection cutter suction dredger, with a sludge discharge concentration of 15 - 20% for this ship type and a basic discharge distance ≤ 1.50 km.

[0046] The bottom sludge is transported through the sludge pipeline 2 to the onshore sludge disposal site 3 for consolidation treatment. The sludge disposal site 3 is preferably selected around the lake as much as possible to reduce the distance for transporting the waste soil; preferably, the existing abandoned ditches and ponds are used as the sludge disposal site 3, and the bottom sludge of the existing ponds is cleared and then excavated.

[0047] The vacuum preloading consolidation and dewatering system consists of a drainage subsystem, a vacuum subsystem, and a pressurization subsystem. The insertion spacing of the positive plastic drainage plates is 0.60 - 1.00 m, and the spacing of the reverse vacuum extraction pipes is 2.20 - 2.60 m. They are arranged according to two rows of positive plastic drainage plates and one row of reverse vacuum extraction pipes. The insertion depth of the positive drainage plates and the reverse vacuum pipes at the sludge solidification site 3 is 4.00 - 8.00 m, and the exposed length of the drainage plates is controlled to be ≥ 50 cm.

[0048] The vacuum system for vacuum preloading consolidation and dewatering consists of a vacuum pipeline, a gas-liquid separation tank, and a vacuum unit. The plastic drainage plates 11 are connected through joints 12, and the drainage plate joints 12 are connected through vacuum branch pipes (steel wire hoses with a diameter of φ25). The vacuum branch pipes 15 are connected to the vacuum main pipe (steel wire hose with a diameter of φ50) through four-way joints 16 and reducing tees 17. The horizontal spacing of the pipe network is 0.80 - 1.00 m, and the vertical spacing is 30.00 - 40.00 m, finally forming the vacuum pipeline. The vacuum main pipe is connected to the gas-liquid separation tank, and the gas-liquid separation tank is connected to the vacuum unit through a PVC pipe. Among them, the volume of the vacuum extraction gas-liquid separation tank should be ≥ 2.00 m 3 .

[0049] The pressurization system for vacuum preloading consolidation and dewatering includes a booster pump and a pressurization pipeline system. The pressurization pipeline system consists of a horizontal pressurization pipeline system and a vertical pressurization pipeline system. The pressurization pipes are arranged at the designed points beside the adjacent drainage plates. The upper air pipes of the pressurization pipes are directly connected to the pressurization system. 4 - 6 air injection holes are arranged within 200 mm at the end of the pipe, and 150 - 200 g / m 2Geotextile wrapping. The booster pipeline connection joint is preferably a tee joint. The connection between the booster pipe connection joint and the booster pipe is firm, and the connection length is ≥100 mm. After laying the main vacuum pipe and branch pipes, lay 1 layer of non-woven geotextile and 2 - 3 layers of polyethylene sealing film (thickness 0.14 ± 0.02 mm) successively to complete the sealing of the vacuum system. The trial vacuum pumping should be carried out for 7 - 10 days, and the vacuum pressure under the film should reach 0.06 - 0.08 Mpa. When the vacuum pressure under the film reaches the design requirement and remains stable for 3 consecutive days, the formal vacuum pumping stage can be entered.

[0050] The time for the vacuum pumping to reach the design requirements of constant load and full load, and the load preloading time is ≥3 months. Stop pumping and unload when the monitoring results meet the design unloading requirements standard. The vacuum preloading unloading standard: the measured curve degree of consolidation ≥85%, the settlement rate evaluated continuously for 5 days <2 mm / d, the residual settlement or post-construction settlement value meets the design requirements. During the construction of booster vacuum preloading, construction monitoring and detection of the reinforcement effect should be carried out, and unloading can be carried out only when the unloading standard is met.

[0051] The mechanical characteristic value of the bearing capacity of the silt after consolidation and dehydration by the vacuum preloading method is ≥50 kPa, and the water content of the consolidated soil meets 55% - 65%. Deep plowing is carried out on the solidified site to remove the drainage plates in the vacuum preloading and then comprehensively utilized.

[0052] The above-mentioned vacuum preloading method for consolidation and dehydration system is an existing technology and will not be elaborated here.

[0053] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A combined treatment method for ecological dredging of sediment and treatment of surplus water in shallow lakes, characterized in that, Ecological dredging, solidification and dehydration treatment, and multi-stage surplus water treatment of lake sediment are adopted, including the following steps: (1) Ecologically dredge the lake sediment by using a cutter suction dredger and a closed pipeline mud transportation process, and transport the sediment to the sludge disposal site nearby. Use the surplus storage capacity and water depth of the sludge disposal site for physical treatment and precipitation. (2) The sediment after precipitation is solidified and dehydrated by using the vacuum preloading technology in the sludge disposal site. The low-concentration dredging surplus water and solidification surplus water enter the surplus water sedimentation tank, and partition cofferdams are set in the surplus water sedimentation tank to form a multi-stage surplus water sedimentation tank. (3) The multi-stage surplus water sedimentation tank sequentially adopts a comprehensive treatment method of chemical flocculation + aeration + aquatic plant purification to treat the surplus water. After the treatment reaches the discharge standard, it is discharged nearby into the nearby river.

2. The combined treatment method for ecological dredging of sediment and treatment of remaining water in shallow lakes according to claim 1, characterized in that, The water depth of the shallow lake is ≤ 1.20 m, and a cutter suction dredger with a capacity of 200 - 350 m 3 / h is used for dredging. Among them: during the non-flood season, a cutter suction dredger with a capacity of 200 - 250 m 3 / h is used, and during the flood season, a cutter suction dredger with a capacity of 300 - 350 m 3 / h is used.

3. The combined treatment method for ecological dredging of sediment in shallow lakes and treatment of surplus water according to claim 1, characterized in that, The depth of the sludge disposal site is 6.50 - 7.50 m, the average depth of the filled sludge is 5.50 - 6.50 m, the slope of the sludge disposal site slope is 1:2 - 1:

3. After filling to the designed elevation, the vacuum preloading method is used to drain and consolidate the dredged material, the water content of the consolidated soil is ≤ 55%, and its settlement is stable.

4. The combined treatment method for ecological dredging of sediment in shallow lakes and treatment of surplus water according to claim 1, characterized in that, The cutter suction dredger is a multi-group environmental protection cutter suction dredger.

5. The combined treatment method for ecological dredging of sediment and treatment of surplus water in shallow lakes according to claim 1, characterized in that, In the vacuum preloading technology, the insertion spacing of the positive plastic drainage boards in the consolidation and dehydration system is 0.60 - 1.00 m, and the spacing of the reverse vacuum extraction pipes is 2.20 - 2.60 m. They are arranged according to two rows of positive plastic drainage boards and one row of reverse vacuum extraction pipes; the insertion depth of the positive drainage boards and reverse vacuum pipes in the sludge solidification site is 4.00 - 8.00 m, and the exposed length of the drainage boards is controlled to be ≥ 50 cm.

6. The combined treatment method for ecological dredging of sediment and residual water treatment in shallow lakes according to claim 1, characterized in that, In the vacuum preloading technology, the bearing mechanical characteristic value of the sludge after consolidation and dehydration by the vacuum preloading method is ≥ 50 kPa, and the water content of the consolidated soil meets 55% - 65%.

7. The combined treatment method for ecological dredging of sediment in shallow lakes and treatment of surplus water according to claim 1, characterized in that According to the water flow direction, the multi-stage surplus water sedimentation tank is provided with 5 sedimentation tanks. Flocculants such as PAC and PAM are added to the 1st - 2nd sedimentation tanks; the 4th sedimentation tank adopts an aeration treatment process, and the 5th sedimentation tank adopts the planting of aquatic plants to purify the surplus water. After the surplus water treatment reaches the standard, it is discharged nearby into the river.

8. The combined treatment method for ecological dredging of sediment and residual water treatment in shallow lakes according to claim 7, characterized in that, The average depth of the multi-stage surplus water sedimentation tank is 5.50 - 6.50 m, the slope of the sedimentation tank slope is 1:2 - 1:3, and the sedimentation time of the suspended solids in the water body after adding the flocculant to the surplus water is 24 - 36 h.

9. The combined treatment method for ecological dredging of sediment and treatment of surplus water in shallow lakes according to claim 7, characterized in that, The flocculants sprayed between the 1st - 2nd sedimentation tanks are polyaluminum chloride (PAC) and polyacrylamide (PAM). The mass percentage concentration of the PAC solution added is 5% - 10%, and the mass percentage concentration of the PAM solution added is 3‰ - 5‰.

10. The combined treatment method for ecological dredging of sediment in shallow lakes and treatment of remaining water according to claim 7, characterized in that, The described 4th-level sedimentation tank is set according to the service area of the aeration equipment of 500 to 800 m 2 ; The aquatic plants planted in the 5th-level sedimentation tank are Vallisneria natans, Myriophyllum aquaticum, and water chestnut. The planting area of the aquatic plants accounts for 10% to 20% of the water surface area.

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