In-situ treatment method for river and lake sediment

Abstract

The application discloses a kind of river and lake bottom mud in-situ processing method, belong to water treatment technical field, comprising the following steps: step one, bottom mud extraction;Step two, bentonite compounding and mixing;Step three, corona discharge plasma modification treatment;Step four, bottom mud in-situ backfilling: closed conveying layered laying modified bottom mud, reduce sediment interface, avoid secondary pollution, realize bottom mud in-situ reuse;Step five, inhibit bottom mud resuspension.The river and lake bottom mud in-situ processing method, through the synergistic effect of corona discharge plasma and compounding bentonite, from chemical form conversion, microbial inactivation, adsorption fixation multidimensional block bottom mud nitrogen and phosphorus release path, not only can make the total nitrogen concentration, total phosphorus concentration in overlying water after treatment reduce, but also can realize the sustained inhibition to bottom mud nitrogen and phosphorus release, the total nitrogen, total phosphorus release amount of bottom mud is greatly reduced within 30 days, effectively solve the persistence, hidden problem of river and lake endogenous pollution, avoid water eutrophication repeatedly deteriorate.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a method for in-situ treatment of river and lake sediment. Background Technology

[0002] River and lake sediments, as an important component of aquatic ecosystems, receive and accumulate nutrients such as nitrogen and phosphorus from external sources over long periods. Under specific environmental conditions (such as hypoxia, low pH, and disturbance), nitrogen and phosphorus deposited in the sediments, especially active phosphorus and ammonium nitrogen in iron / aluminum bound, organic, and exchangeable forms, are easily desorbed, dissolved, or mineralized, and released back into the overlying water bodies, forming significant endogenous pollution. This endogenous release process is continuous, covert, and sudden. Even after effective control of external pollution, it can still drive eutrophication of water bodies for a long time, leading to repeated deterioration of water quality and seriously restricting the restoration and long-term management of aquatic ecosystems. Currently, the main control methods for endogenous pollution in sediments include covering, dredging, chemical passivation, and in-situ solidification. Covering involves laying inert materials on the sediment surface to block the release of pollutants. While this can inhibit nitrogen and phosphorus leaching in the short term, it is easily affected by water flow disturbances and has poor long-term stability. Traditional dredging can directly remove polluted sediments, but it involves large-scale engineering and high costs. The dredging process can also easily cause secondary suspended pollution, and the disposal of dredged sediments faces environmental risks and land resource pressures. Chemical passivation uses aluminum salts, iron salts, lime, or phosphate fixatives to precipitate or adsorb phosphorus. Although it is effective quickly, it has problems such as chemical residues, drastic pH fluctuations, and potential toxicity to aquatic organisms. Existing in-situ solidification technologies mostly rely on inorganic cementing materials, which often alter the physical structure of the sediment and are not conducive to the restoration of benthic ecosystems. In recent years, bentonite-based mineral materials have been widely explored for sediment remediation due to their high specific surface area, strong cation exchange capacity, and good environmental compatibility. Sodium-based bentonite can effectively adsorb and fix ammonium nitrogen, while bentonite modified with metals such as lanthanum, iron, and zirconium can efficiently capture phosphate ions through specific chemical reactions, forming insoluble precipitates and achieving long-term phosphorus locking. However, the addition of bentonite alone still has limitations: its ability to degrade organic matter is weak, making it difficult to block the biogeochemical driving forces of nitrogen and phosphorus release; and in high-moisture, reducing sediment environments, its fixation effect is easily affected by Fe. 2+ S 2— It is attenuated due to interference from reducing substances; For example, in the prior art 1 (Chinese patent application number CN201710907809.6, application date 2017-09-29), a method for treating wastewater using Venturi tube discharge plasma is used to generate low-temperature plasma for wastewater treatment. This method features simple equipment, small footprint, short process, and low energy consumption. The low-temperature plasma is generated in the liquid phase and can react in situ with highly toxic pollutants, improving the utilization rate of free radicals. The catalytic coating interacts with the low-temperature plasma to form a gas-liquid-solid three-phase reaction, increasing the yield of free radicals and improving the degradation efficiency of highly toxic pollutants.

[0003] While existing technologies are highly efficient in the degradation of organic wastewater, they are limited by narrow discharge areas, small gas-liquid contact areas, and high energy consumption, making them difficult to apply to complex sediment systems. Therefore, in-situ treatment methods for river and lake sediments have been proposed to effectively address these issues. Summary of the Invention

[0004] The purpose of this invention is to provide an in-situ treatment method for river and lake sediments, in order to solve the problem mentioned in the background art that the current market methods for organic wastewater degradation are highly efficient, but limited by narrow discharge area, small gas-liquid contact area, high energy consumption, and are difficult to apply to sediment systems with complex components, thus having high limitations.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for in-situ treatment of river and lake sediment, comprising the following steps: Step 1, Sediment extraction: accurately extracting 0.1m-5m of contaminated sediment, retaining it in slurry form for easy transport, providing raw materials for subsequent treatment, and controlling the treatment scope; Step 2, Bentonite compound addition and mixing: setting up a bentonite dry powder spraying device at the inlet of the pipeline for transporting the sediment slurry, and accurately spraying compound bentonite into the sediment; Step 3, Corona discharge plasma modification treatment: transporting the sediment slurry containing compound bentonite through a closed pipeline to a corona discharge plasma reactor, and starting the reactor for modification treatment; Step 4, In-situ sediment backfilling: layering and laying modified sediment in a closed system to restore the sediment interface, avoid secondary pollution, and achieve in-situ reuse of sediment; Step 5, Inhibiting sediment resuspension: creating a habitat for benthic organisms and promoting the restoration of the aquatic ecosystem.

[0006] Preferably, in step one, when extracting bottom sediment, an environmentally friendly cutter suction dredger is used to extract bottom sediment from rivers and lakes. The extraction depth is adjusted according to the degree of bottom sediment pollution and the thickness of sediment in the project area, with an extraction depth of 0.1m-5m. The extracted bottom sediment is continuously transported in a closed pipeline in slurry form, avoiding secondary suspension pollution of bottom sediment throughout the process.

[0007] Preferably, in step two, the bentonite sprayed in the bentonite dry powder spraying device is a compound bentonite, which is a mixture of sodium-based bentonite and lanthanum-modified bentonite in a certain proportion, with the mixing ratio of sodium-based bentonite to lanthanum-modified bentonite ranging from 1:1 to 5:1.

[0008] Preferably, in step two, the compound bentonite is evenly sprayed into the bottom mud slurry through a dry powder spraying device at the pipe inlet to achieve full mixing of the bottom mud and bentonite. Sodium-based bentonite is used to adsorb and fix ammonium nitrogen, and lanthanum-modified bentonite is used to capture phosphate ions through specific chemical reactions to form insoluble precipitates. In addition, the dry weight of the compound bentonite accounts for 2%-8% of the dry weight of the bottom mud.

[0009] Preferably, in step three, the corona discharge plasma reactor modifies the bottom sediment. During the operation of the corona discharge plasma reactor, the operating parameters are controlled, specifically: The corona discharge plasma reactor is supplied with high-voltage DC by a high-frequency DC voltage generator, with a voltage output adjustment range of 5kV-30kV. The corona discharge plasma reactor is equipped with a grounding electrode inside, and a stable high-voltage electric field is formed between the discharge electrode and the grounding electrode, providing the electric field conditions for corona discharge. When the corona discharge plasma reactor is working, air is continuously introduced into it by a blower, providing an air environment for the plasma to generate highly active free radicals and high-energy electrons.

[0010] Preferably, in step three, the corona discharge plasma reactor is equipped with a discharge electrode, on which needle-shaped electrodes are evenly distributed. The discharge electrode is driven by a motor to rotate at a constant speed of 5 r / min to 60 r / min; dynamic corona discharge is formed through the rotation of the discharge electrode.

[0011] Preferably, in step three, the discharge electrode tip of the discharge electrode generates a large number of hydroxyl radicals and high-energy electrons, which oxidize the organic nitrogen in the sediment to achieve the volatilization and conversion of ammonium nitrogen, and induce Fe in the sediment. 2+ Oxidation to produce Fe 3+ The plasma adsorbs and fixes phosphates while simultaneously inactivating ammonifying bacteria and phosphorus-releasing microorganisms in the sediment, thus blocking the biogeochemical driving force of nitrogen and phosphorus release. Furthermore, it activates the bentonite surface with high-energy electrons and active free radicals, enhancing the bentonite's adsorption and stabilization capacity for nitrogen and phosphorus, thereby achieving synergistic effects between plasma and bentonite. In addition, the residence time of slurry sediment in the corona discharge plasma reactor is adjusted according to the sediment moisture content and pollution load.

[0012] Preferably, in step four, the corona discharge plasma reactor is matched with a closed pumping system. After the bottom sediment is modified by the corona discharge plasma reactor, it is transported to the original dredging area through the closed pumping system. The modified bottom sediment is uniformly layered and laid using a positioning and spreading device, with the laying thickness matching the original dredging depth.

[0013] Preferably, the closed pumping system uses a screw pump as its power core, and the entire process of bottom mud extraction, compound bentonite addition and mixing, plasma modification, and in-situ backfilling is connected to closed equipment and pipelines.

[0014] Preferably, in step five, based on the needs of river and lake benthic ecological restoration, an ecological covering treatment is applied to the surface layer of the backfilled sediment. Aquatic plant substrate and inert ecological covering material are selected, and an ecological covering layer is applied to the layered modified sediment surface to enhance the inhibition of sediment resuspension.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: Through a five-step synergistic treatment, in-situ green remediation of river and lake bottom sediments is achieved, combining high efficiency and ecological benefits. Precise extraction and closed-loop transportation avoid secondary pollution caused by sediment disturbance. Bentonite is used for initial nitrogen and phosphorus fixation, and plasma modification deeply oxidizes and transforms nitrogen and phosphorus, inactivates phosphorus-releasing bacteria, and activates bentonite, significantly improving the nitrogen and phosphorus fixation effect. The total nitrogen and total phosphorus in the overlying water are reduced by more than 40% and 60%, respectively. Precise in-situ backfilling eliminates the costs of stockpiling and transportation. The surface ecological cover inhibits sediment resuspension, promotes benthic ecosystem restoration, and the entire process involves no chemical additives or harmful residues. It provides long-term inhibition of nitrogen and phosphorus release, blocks the endogenous sources of eutrophication in water bodies, and maintains the continuity of the aquatic ecosystem. Specifically: (1) The in-situ treatment method for river and lake sediments uses the synergistic effect of corona discharge plasma and compound bentonite to block the nitrogen and phosphorus release pathways of sediments from multiple dimensions, including chemical transformation, microbial inactivation, and adsorption fixation. This method can not only reduce the total nitrogen concentration in the overlying water by more than 40% and the total phosphorus concentration by more than 60%, but also achieve continuous inhibition of nitrogen and phosphorus release from sediments. Within 30 days, the total nitrogen and total phosphorus release from sediments will decrease significantly. This method effectively solves the problem of persistent and hidden pollution sources in rivers and lakes, avoids repeated deterioration of eutrophication, and provides technical support for the long-term management of aquatic ecosystems.

[0016] (2) The in-situ treatment method for river and lake sediments uses highly active free radicals and high-energy electrons generated by plasma to oxidize reducing substances in the sediment, degrade organic matter, improve the microenvironment of the sediment, and activate the surface of bentonite, significantly enhancing its adsorption and fixation capacity for nitrogen and phosphorus. The compound bentonite specifically achieves efficient locking of ammonium nitrogen and phosphate, making up for the shortcomings of single technology in not fully fixing nitrogen and phosphorus and being easily affected by environmental interference, and greatly improving the modification treatment effect of sediments with high solid content and different water content.

[0017] (3) The in-situ treatment method for river and lake bottom sediment uses environmentally friendly bentonite as a modifying material, avoiding the problems of chemical residues, drastic pH fluctuations and potential toxicity to aquatic organisms caused by traditional passivating agents such as aluminum salts and iron salts. At the same time, the entire process of bottom sediment extraction, transportation, modification and backfilling is carried out in a closed equipment, which effectively prevents secondary suspension pollution of bottom sediment. Moreover, the modified bottom sediment is backfilled in situ without the need for external transportation and disposal, thus avoiding the environmental risks caused by the external transportation of dredged bottom sediment and ensuring the safety of the water body and the surrounding ecological environment.

[0018] (4) This method of in-situ treatment of river and lake sediments realizes the integrated management of "green dredging - collaborative modification - ecological reuse". The modified sediments are backfilled in the original dredging area without the need to build sediment disposal sites, which greatly reduces the land resource occupation and disposal costs such as sediment transportation and storage site management. At the same time, it preserves the ecological continuity of the original sediment-water interface, avoids the damage to the physical structure of sediments caused by traditional dredging or solidification technologies, creates favorable conditions for the restoration of benthic ecosystems, realizes the in-situ resource utilization of sediments, and takes into account both ecological and economic benefits.

[0019] (5) The process parameters of this in-situ treatment method for river and lake bottom sediment can be flexibly adjusted according to the actual working conditions. The bottom sediment extraction depth of 0.1m-5m can be adapted to river and lake bottom sediment with different sediment thicknesses. The bentonite addition ratio and compound ratio can be adjusted according to the nitrogen and phosphorus pollution characteristics of the bottom sediment. The voltage of the plasma reactor and the discharge electrode speed can be optimized for bottom sediment with different water content and pollution load, which has strong adaptability. At the same time, standardized equipment such as environmentally friendly cutter suction boat, closed pipeline, and positioning material distribution device are used. The operation is simple and the process is continuous. It can be applied to the in-situ treatment of bottom sediment of lakes and rivers with different types and different pollution levels. The project has high feasibility.

[0020] (6) The traditional needle-tip static discharge is improved into a dynamic corona discharge of a rotating needle electrode. The discharge electrode rotates at a uniform speed of 5r / min-60r / min, which effectively expands the range of electric field and enhances the uniformity of electric field. It solves the problems of narrow discharge area and small gas-liquid contact area of ​​traditional plasma technology. It allows highly active free radicals and high-energy electrons to fully contact the sediment particles and bentonite, significantly improving the modification efficiency of slurry sediment and reducing the energy consumption problem of applying plasma technology to complex sediment systems. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the processing steps of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides the following technical solution: a method for in-situ treatment of river and lake bottom sediment. Step 1, Sediment Extraction: Accurately extract 0.1m-5m of contaminated sediment, retain it in slurry form for easy transportation, provide raw materials for subsequent treatment, and control the treatment base area; Step 1: When extracting bottom sediment, an environmentally friendly cutter suction dredger is used to extract bottom sediment from rivers and lakes. The extraction depth is flexibly adjusted according to the degree of bottom sediment pollution and the thickness of the sediment in the project area, with an extraction depth of 0.1m-5m. The extracted bottom sediment is continuously transported in a closed pipeline in slurry form, avoiding secondary suspension pollution of the bottom sediment throughout the process.

[0024] In step one above, a field survey of the river and lake bottom sediment is conducted before the operation to determine the distribution range, thickness, and water content of the polluted sediment. Based on this, the operation area of ​​the cutter suction dredger is delineated, and a precise sediment extraction depth is set, controlled within the range of 0.1-5m, to avoid excessive extraction that could damage the original bottom layer of the river and lake. During the operation, the environmentally friendly cutter suction dredger is driven into the designated operation area, and the hull is positioned and fixed to prevent water flow disturbance from affecting the extraction accuracy. The cutter system of the cutter suction dredger is then activated, and the cutter penetrates into the polluted sediment layer at the preset depth, rotating at low speed to cut the sediment. At the same time, the sludge pump is turned on, and the cutter head mixes the cut sediment with the water to form a homogeneous slurry, reducing sediment agglomeration and ensuring smooth subsequent pipeline transportation. During the extraction process, the depth, flow rate, and slurry concentration of the sediment extraction are monitored in real time using onboard monitoring equipment, and the cutter rotation speed and sludge pump power are precisely controlled to avoid sediment suspension and diffusion caused by excessive extraction speed, which could lead to secondary pollution of the water body. The slurry sediment is transported to the ship's transfer chamber via the slurry pipe of the cutter suction dredger. The transfer chamber briefly homogenizes and buffers the slurry sediment to eliminate concentration fluctuations during the extraction process. Then, the homogenized slurry sediment is continuously and stably transported to the next processing stage through a closed external pipeline. The pipeline is kept closed throughout the process to prevent sediment leakage and premature release of nitrogen and phosphorus. In step one, an environmentally friendly cutter suction dredger is used as the core operating equipment. The core objective is to accurately and without secondary disturbance extract polluted sediment from rivers and lakes, providing homogeneous slurry sediment raw materials for subsequent treatment.

[0025] Step 2, Addition and Mixing of Compound Bentonite: At the inlet of the pipeline for conveying bottom sediment in slurry form, a bentonite dry powder spraying device is installed to precisely spray compound bentonite into the bottom sediment. The bentonite sprayed in the bentonite dry powder spraying device is compound bentonite, which is a mixture of sodium-based bentonite and lanthanum-modified bentonite in a certain proportion. The mixing ratio of sodium-based bentonite and lanthanum-modified bentonite is adjusted according to the actual situation, ranging from 1:1 to 5:1.

[0026] The compound bentonite is evenly sprayed into the bottom sediment slurry through a dry powder spraying device at the pipeline inlet to achieve full mixing of the bottom sediment and bentonite. Sodium-based bentonite is used to adsorb and fix ammonium nitrogen, while lanthanum-modified bentonite is used to capture phosphate ions through specific chemical reactions to form insoluble precipitates. In addition, the dry weight of the compound bentonite accounts for 2%-8% of the dry weight of the bottom sediment.

[0027] In step two above, before the operation, the bentonite compounding scheme is determined based on the composition of the bottom sediment and the nitrogen and phosphorus content of the sediment in the early survey. Sodium-based bentonite and lanthanum-modified bentonite are mixed in a ratio of 1:1 to 5:1, accurately weighed and placed in a dry powder storage silo for later use. At the same time, the dosage is calculated to be 2% to 8% of the dry weight of the bottom sediment, and the dosage parameters are calibrated. At the inlet of the closed pipeline for conveying bottom mud, start the bentonite dry powder injection device. This device is linked with the pipeline mud conveying system. According to the real-time flow of bottom mud slurry, the bentonite injection rate is precisely adjusted by frequency conversion control to achieve dynamic matching of the dosage and avoid over- or under-dosing. The bentonite dry powder is injected at high speed into the slurry bottom mud inside the pipeline through the injection nozzle. The high-speed flow of the bottom mud slurry inside the pipeline creates a turbulent effect, which allows the bentonite particles to fully contact and initially mix with the bottom mud. At the same time, a static mixer is set in the middle section of the pipeline, which further disperses the bentonite agglomerates through internal guide vanes, improves the mixing uniformity, and fully exposes the adsorption sites of the bentonite. The mixed sediment slurry continues to be transported in a closed pipeline. During the transport process, bentonite, with its high specific surface area and ion exchange capacity, initially adsorbs and fixes ammonium nitrogen and phosphate in the sediment, reducing the release of nitrogen and phosphorus into the water during the transport process. The pipeline is kept closed throughout the process to prevent bentonite dust from escaping and sediment from leaking, ensuring that the mixed sediment slurry is stably transported to the corona discharge plasma reactor, thus preparing for subsequent modification treatment. Step two focuses on precise compounding and efficient mixing. Functional bentonite is added to the slurry sediment to achieve preliminary fixation of nitrogen and phosphorus, while creating conditions for plasma modification and activation of bentonite.

[0028] Step 3: Corona discharge plasma modification treatment: The bentonite-blended sediment slurry is transported to the corona discharge plasma reactor through a closed pipeline. The reactor is started for modification treatment. The corona discharge plasma reactor modifies the sediment. During the operation of the corona discharge plasma reaction, the operating parameters are controlled as follows: The corona discharge plasma reactor is supplied with high-voltage DC by a high-frequency DC voltage generator, with a voltage output adjustment range of 5kV-30kV. The corona discharge plasma reactor is equipped with a grounding electrode inside, and a stable high-voltage electric field is formed between the discharge electrode and the grounding electrode, providing the electric field conditions for corona discharge. When the corona discharge plasma reactor is working, air is continuously introduced into it by a blower, providing an air environment for the plasma to generate highly active free radicals and high-energy electrons. In addition, the corona discharge plasma reactor is equipped with a discharge electrode, on which needle-shaped electrodes are evenly distributed. The discharge electrode is driven by a motor to rotate at a constant speed of 5 r / min-60 r / min; dynamic corona discharge is formed through the rotation of the discharge electrode.

[0029] The discharge at the tip of the needle-shaped electrode generates a large number of hydroxyl radicals and high-energy electrons, which oxidize the organic nitrogen in the sediment, realizing the volatilization and conversion of ammonium nitrogen, and inducing Fe²⁺ in the sediment. + Oxidation to produce Fe³ + The plasma adsorbs and fixes phosphates while simultaneously inactivating ammonifying bacteria and phosphorus-releasing microorganisms in the sediment, thus blocking the biogeochemical driving force of nitrogen and phosphorus release. Furthermore, it activates the bentonite surface with high-energy electrons and active free radicals, enhancing the bentonite's adsorption and stabilization capacity for nitrogen and phosphorus, thereby achieving synergistic effects between plasma and bentonite. The residence time of the slurry sediment in the corona discharge plasma reactor is adjusted according to the sediment moisture content and pollution load.

[0030] Step three above is the core step in the deep fixation of nitrogen and phosphorus in the sediment. It relies on a corona discharge plasma reactor to generate active substances, thereby achieving sediment modification and bentonite activation. The specific workflow is as follows: First, complete the pre-start debugging of the corona discharge plasma reactor, check the high-frequency DC voltage generator, the discharge electrode rotation drive device and the air supply system for sealing. Based on the nitrogen and phosphorus content and water content of the sediment, set the core parameters of the reactor: adjust the voltage to the range of 5kV-30kV, control the discharge electrode speed at 5r / min-60r / min, and start the blower to continuously introduce air into the reactor to provide a medium for plasma generation. After the parameters stabilize, the slurry bottom mud mixed with bentonite is fed into the reactor at a constant speed through a closed feed port. The feed flow rate is controlled to match the reactor processing efficiency to avoid the bottom mud from accumulating in the reactor. After the corona discharge plasma reactor is started, the high-frequency DC voltage generator supplies power to the discharge electrode. A stable high-voltage electric field is formed between the discharge electrode and the ground electrode. The rotating needle electrode tip generates corona discharge, which instantly generates a large number of active substances such as hydroxyl radicals and high-energy electrons. The active material comes into full contact with the slurry sediment in the reactor, oxidizing and decomposing the organic nitrogen in the sediment, promoting the volatilization and conversion of ammonium nitrogen, and inducing Fe... 2+ Oxidized to Fe 3+ The process involves adsorbing and fixing phosphates while simultaneously inactivating biological pollutants such as ammonifying bacteria and phosphorus-releasing microorganisms. Simultaneously, it activates the bentonite surface, enhancing its adsorption and fixation capacity for nitrogen and phosphorus. During the modification process, a monitoring module within the corona discharge plasma reactor monitors the electric field strength, discharge electrode rotation speed, and sediment treatment status in real time, dynamically fine-tuning parameters to ensure treatment effectiveness. The treated modified sediment slurry is continuously transported to a closed pumping system through the corona discharge plasma reactor outlet, maintaining a sealed reactor throughout the process to prevent the release of active substances and secondary pollution.

[0031] Step 4: In-situ backfilling of bottom sediment: Modified bottom sediment is laid in layers through a closed conveying system to restore the sediment interface, avoid secondary pollution, and achieve in-situ reuse of bottom sediment; The corona discharge plasma reactor is matched with a closed pumping system. After the bottom sediment is modified by the corona discharge plasma reactor, it is transported to the original dredging area through the closed pumping system. The modified bottom sediment is laid in layers evenly using a positioning material distribution device, and the laying thickness matches the original dredging depth.

[0032] The closed pumping system uses a screw pump as its power core, and the entire process of bottom mud extraction, compound bentonite addition and mixing, plasma modification, and in-situ backfilling is connected to closed equipment and pipelines.

[0033] Step four above is a crucial step in achieving in-situ treatment of sediment and avoiding secondary pollution during transport. The core process involves closed-loop transportation and precise placement to restore the modified sediment to the original dredged area, maintaining the ecological continuity of the river and lake sediment-water interface. The specific workflow is as follows: Before the operation, the original dredged area is repositioned. Based on the coordinates and depth data of the bottom sediment extracted in the early stage, the backfill boundary and layer thickness are marked with positioning equipment. At the same time, the sealing performance and operation status of the closed pumping system and the positioning and placing device are checked, and the conveying pressure and placing speed are adjusted in advance.

[0034] Start the closed pumping system to uniformly draw the slurry modified by the corona discharge plasma reactor from the reactor outlet and transport it to the work area through the wear-resistant closed slurry conveying pipeline. The pumping pressure is controlled to be stable throughout the process to avoid excessive pressure leading to pipeline leakage or uneven slurry flow rate, and to prevent secondary release of nitrogen and phosphorus from the modified slurry during transportation. After the bottom sediment is transported to the designated area, the positioning and spreading device is activated. Relying on satellite positioning and underwater detection technology, the material is moved at a uniform speed along the route marked in the dredging area and spread evenly in layers according to the preset thickness. After each layer is laid, the underwater leveling device is used to lightly press and level it to avoid local accumulation, gaps or uneven thickness, and to ensure that the bottom sediment is closely attached to the original base. During the backfilling process, underwater monitoring equipment is used to monitor the laying thickness, flatness, and sediment suspension in real time. The moving speed and discharge volume of the material distribution device are dynamically adjusted. If local sediment suspension is found, the flow rate is immediately reduced and static pressure treatment is applied to prevent disturbance of the surrounding water bodies. Once the modified sediment has been accurately backfilled into the original dredged area and the thickness and flatness meet the standards, the pumping and spreading equipment will be shut down, the sediment conveying pipeline will be flushed with clean water, and any residual sediment will be removed to ensure that no pollutants remain at the work site, thus laying the foundation for the subsequent optional surface ecological coverage.

[0035] Step 5: Inhibit sediment resuspension: Create a habitat for benthic organisms and promote the restoration of the aquatic ecosystem; according to the needs of river and lake benthic ecological restoration, ecological covering treatment is applied to the surface of the backfilled sediment. Aquatic plant substrate and inert ecological covering material are selected and ecological covering layer is applied to the modified sediment surface layer laid in layers to strengthen the inhibition of sediment resuspension.

[0036] Step five above focuses on enhancing the suspension resistance of bottom sediments and restoring the aquatic ecosystem. Through scientific surface covering and ecological construction, it consolidates the nitrogen and phosphorus fixation effect of bottom sediments and promotes the restoration of river and lake benthic ecosystems. The specific workflow is as follows: Before the operation, based on the flatness, moisture content and hydrological conditions of the bottom mud after backfilling, and in conjunction with the regional water ecological restoration plan, select suitable ecological covering materials, such as aquatic plant substrate, environmentally friendly inert covering soil or composite ecological felt, and plan the covering thickness and aquatic plant planting area. The operation utilizes an environmentally friendly floating platform. First, underwater leveling equipment is used to perform a secondary fine leveling of the modified sediment surface after backfilling, eliminating localized unevenness and laying the foundation for surface covering. Then, a quantitative material distribution device on the platform is used to evenly spread the ecological covering material onto the sediment surface, controlling the covering thickness to be uniform, generally 5cm-15cm. This avoids the situation where too thin a layer is easily disturbed by water flow, or too thick a layer hindering the penetration of benthic organisms. After the covering material is laid, suitable submerged and emergent plants, such as Vallisneria natans and Acorus calamus, are transplanted on the surface according to the water quality and ecological needs of rivers and lakes. Underwater fixed-point planting method is adopted to control the spacing and planting density of plants, creating a composite aquatic plant community. The plant roots are used to fix the surface bottom mud, and the plants absorb and further reduce the residual nitrogen and phosphorus in the water. During construction, underwater monitoring equipment was used to monitor the integrity of the cover layer and the planting status of the plants in real time. If any local loss of cover material was found, it was promptly replenished and reinforced. After planting, the survival rate of the plants was monitored regularly, and water and fertilizer were added as needed to ensure plant growth. The entire process adopted a low-disturbance construction method to avoid disturbing the modified bottom sediment during the operation. After completion, the work platform and construction area were cleaned of debris to ensure that no external pollutants were left behind. Ultimately, the synergistic effect of anti-suspension of bottom sediment surface, long-term nitrogen and phosphorus locking and initial restoration of aquatic ecology was achieved.

[0037] Example 2 discloses: The contaminated sediment was dredged using an environmentally friendly cutter suction dredger to a depth of 0.4m, resulting in sediment with a moisture content of approximately 83%. The sediment was then transported through a closed pipeline to a corona discharge plasma reactor. A bentonite dry powder injection device was installed at the pipeline inlet, and lanthanum-modified bentonite was added at a ratio of 5% of the sediment's dry weight; no sodium-based bentonite was added.

[0038] Air was supplied by a blower, and the reactor was powered by a 22kV high-frequency DC voltage generator. The internal discharge electrodes were needle-shaped structures driven by a motor to rotate uniformly at 25 r / min, creating an electric field. The modified sediment was pumped back to the original dredged area via a screw pump through a sealed backfill pipe. Release tests showed that the total phosphorus release from the treated sediment decreased by 65% ​​and the total nitrogen release decreased by 35% within 30 days.

[0039] Example 3 discloses: The same sediment from the area selected in Example 1 was dredged using an environmentally friendly cutter suction dredger to a depth of 1m. The resulting sediment had a moisture content of approximately 75% and was transported to a corona discharge plasma reactor via a closed pipeline. A bentonite dry powder injection device was installed at the pipeline inlet, and bentonite was added at a ratio of 7% of the dry weight of the sediment. The mixing ratio of sodium-based bentonite and lanthanum-modified bentonite was 2:1.

[0040] Air was supplied by a blower, and the reactor was powered by a 25kV high-frequency DC voltage generator. The internal discharge electrodes were needle-shaped and driven by a motor to rotate uniformly at 45 r / min, creating an electric field. The modified sediment was pumped back to the original dredged area via a screw pump through a sealed backfill pipe. Release tests showed that the total phosphorus release from the treated sediment decreased by 58% and the total nitrogen release decreased by 46% within 30 days.

[0041] Example 4 discloses: The sediment from the same area as in Example 1 was dredged using an environmentally friendly cutter suction dredger to a depth of 0.2m. The resulting sediment had a moisture content of approximately 95% and was transported to a corona discharge plasma reactor via a closed pipeline. A bentonite dry powder injection device was installed at the pipeline inlet, and bentonite was added at a ratio of 8% of the dry weight of the sediment. The mixing ratio of sodium-based bentonite and lanthanum-modified bentonite was 5:1.

[0042] Air was supplied by a blower, and the reactor was powered by a 30kV high-frequency DC voltage generator. The internal discharge electrodes were needle-shaped and driven by a motor to rotate uniformly at 15 r / min, creating an electric field. The modified sediment was pumped back to the original dredged area via a screw pump through a sealed backfill pipe. Release tests showed that the total phosphorus release from the treated sediment decreased by 48% and the total nitrogen release decreased by 57% within 30 days.

[0043] The above is the entire working process of the device, and all contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0044] The contents not described in detail in this specification are existing technologies known to those skilled in the art. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for in-situ treatment of river and lake bottom sediment, characterized in that, Includes the following steps: Step 1, Sediment Extraction: Accurately extract 0.1m-5m of contaminated sediment, retain it in slurry form for easy transportation, provide raw materials for subsequent treatment, and control the treatment base area; Step 2, Bentonite compound addition and mixing: At the inlet of the pipeline for conveying bottom mud in slurry, a bentonite dry powder spraying device is set up to accurately spray the compound bentonite into the bottom mud; Step 3: Corona discharge plasma modification treatment: The bottom mud slurry of compound bentonite is transported to the corona discharge plasma reactor through a closed pipeline, and the reactor is started to carry out the modification treatment. Step 4: In-situ backfilling of bottom sediment: Modified bottom sediment is transported in a closed system and laid in layers to restore the sediment interface, avoid secondary pollution, and realize the in-situ reuse of bottom sediment. Step 5: Inhibit sediment resuspension: Create a habitat for benthic organisms and promote the restoration of the aquatic ecosystem.

2. The method for in-situ treatment of river and lake bottom sediment according to claim 1, characterized in that: In step one, when extracting bottom sediment, an environmentally friendly cutter suction dredger is used to extract bottom sediment from rivers and lakes. The extraction depth is adjusted according to the degree of bottom sediment pollution and the thickness of sediment in the project area, with an extraction depth of 0.1m-5m. The extracted bottom sediment is continuously transported in a closed pipeline in slurry form, avoiding secondary suspension pollution of bottom sediment throughout the process.

3. The method for in-situ treatment of river and lake bottom sediment according to claim 1, characterized in that: In step two, the bentonite sprayed in the bentonite dry powder spraying device is a compound bentonite, which is a mixture of sodium-based bentonite and lanthanum-modified bentonite in a certain proportion. The mixing ratio of sodium-based bentonite to lanthanum-modified bentonite is between 1:1 and 5:

1.

4. The method for in-situ treatment of river and lake bottom sediment according to claim 3, characterized in that: In step two, the compound bentonite is evenly sprayed into the bottom mud slurry through a dry powder spraying device at the pipe inlet to achieve full mixing of the bottom mud and bentonite. Sodium-based bentonite is used to adsorb and fix ammonium nitrogen, and lanthanum-modified bentonite is used to capture phosphate ions through specific chemical reactions to form insoluble precipitates. In addition, the dry weight of the compound bentonite accounts for 2%-8% of the dry weight of the bottom mud.

5. The method for in-situ treatment of river and lake bottom sediment according to claim 1, characterized in that: In step three, the corona discharge plasma reactor modifies the bottom sediment. During operation, the operating parameters are controlled, specifically: The corona discharge plasma reactor is supplied with high-voltage DC by a high-frequency DC voltage generator, with a voltage output adjustment range of 5kV-30kV. The corona discharge plasma reactor is equipped with a grounding electrode inside, and a stable high-voltage electric field is formed between the discharge electrode and the grounding electrode, providing the electric field conditions for corona discharge. When the corona discharge plasma reactor is working, air is continuously introduced into it by a blower, providing an air environment for the plasma to generate highly active free radicals and high-energy electrons.

6. The method for in-situ treatment of river and lake bottom sediment according to claim 5, characterized in that: In step three, the corona discharge plasma reactor is equipped with a discharge electrode, on which needle-shaped electrodes are evenly distributed. The discharge electrode is driven by a motor to rotate at a constant speed of 5 r / min to 60 r / min; dynamic corona discharge is formed through the rotation of the discharge electrode.

7. The method for in-situ treatment of river and lake bottom sediment according to claim 6, characterized in that: In step three, the discharge electrode tip generates a large number of hydroxyl radicals and high-energy electrons, which oxidize the organic nitrogen in the sediment, realizing the volatilization and conversion of ammonium nitrogen, and inducing Fe in the sediment. 2+ Oxidation to produce Fe 3+ The plasma adsorbs and fixes phosphates while simultaneously inactivating ammonifying bacteria and phosphorus-releasing microorganisms in the sediment, thus blocking the biogeochemical driving force of nitrogen and phosphorus release. Furthermore, it activates the bentonite surface with high-energy electrons and active free radicals, enhancing the bentonite's adsorption and stabilization capacity for nitrogen and phosphorus, thereby achieving synergistic effects between plasma and bentonite. In addition, the residence time of slurry sediment in the corona discharge plasma reactor is adjusted according to the sediment moisture content and pollution load.

8. The method for in-situ treatment of river and lake bottom sediment according to claim 1, characterized in that: In step four, the corona discharge plasma reactor is matched with a closed pumping system. After the bottom sediment is modified by the corona discharge plasma reactor, it is transported to the original dredging area through the closed pumping system. The modified bottom sediment is then uniformly layered and laid using a positioning material distribution device, with the layer thickness matching the original dredging depth.

9. A method for in-situ treatment of river and lake bottom sediment according to claim 8, characterized in that: The closed pumping system uses a screw pump as its power core, and the entire process of bottom mud extraction, compound bentonite addition and mixing, plasma modification, and in-situ backfilling is connected to closed equipment and pipelines.

10. The method for in-situ treatment of river and lake bottom sediment according to claim 1, characterized in that: In step five, based on the needs of river and lake benthic ecological restoration, an ecological covering treatment is applied to the surface of the backfilled sediment. Aquatic plant substrates and inert ecological covering materials are selected and an ecological covering layer is applied to the layered modified sediment surface to enhance the inhibition of sediment resuspension.

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