System and method for treating bottom mud in inland water area

Abstract

The invention relates to the technical field of environmental treatment, in particular to an inland water sediment treatment system and method. The system comprises a suction unit, a temporary storage unit, a mixing unit, a curing and adding unit and a dehydration storage yard, wherein the suction unit is used for extracting bottom mud of a water body and conveying the bottom mud to the temporary storage unit, the curing and adding unit is used for injecting a stabilizer into the mixing unit, and the mixing unit enables the bottom mud, airflow and the stabilizer to form a uniform gas-liquid-solid three-phase system; high-risk exchangeable heavy metal, high-risk carbonate combined heavy metal and high-risk iron and manganese oxide combined heavy metal are directionally converted into stable mineral phases, dewatering and pennisetum hydridum planting are matched, residual heavy metal is adsorbed for a long time by means of the hyperaccumulation characteristic of pennisetum hydridum, and end ecological management and control are achieved. According to the scheme provided by the invention, the links of desilting, heavy metal curing, dewatering and repairing are integrated, so that the equipment redundancy can be effectively reduced, meanwhile, the requirement of large-scale bottom mud outward transportation and disposal can be omitted, and the transportation and landfill cost is greatly reduced.

Description

Technical Field

[0001] This application relates to the field of environmental treatment technology, and in particular to an inland waterway sediment treatment system and method. Background Technology

[0002] With rapid industrialization and urbanization, the discharge of large amounts of industrial wastewater and domestic sewage has led to increasingly serious heavy metal pollution in inland water sediments. Heavy metals such as lead, cadmium, chromium, and mercury pose a serious threat to the ecological environment and human health due to their toxicity, persistence, and bioaccumulation. Traditional sediment treatment methods (such as landfill and incineration) suffer from secondary pollution, resource waste, and high treatment costs, making them unsuitable for modern environmental protection requirements. CN202510426826.2 discloses a treatment process for heavy metal contaminated sediment. This process involves screening and concentrating the sediment, adding Tween-80 dispersing slurry and releasing bound water, adding polyaluminum sulfate and a specially formulated heavy metal treatment agent prepared through functional modification with MOF-zeolite composite materials, maleic anhydride grafting, and copolymerization with 2-acrylamide-2-methylpropanesulfonic acid to achieve heavy metal adsorption and complexation. The precipitate is then dried, pulverized, and mixed with fly ash and quicklime for curing to form a solidified body. However, this process uses a wide variety of materials, involves a complex preparation process for the heavy metal treatment agent, and requires energy-intensive steps such as drying and pulverizing the precipitate. It suffers from drawbacks such as lengthy process steps, high energy consumption, and high operational complexity. Especially when treating large-scale (e.g., hundreds of thousands of tons) heavy metal contaminated sediment, the equipment investment and operating costs increase significantly, resulting in poor economic efficiency. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this application provides an inland water sediment treatment system that integrates dredging, heavy metal solidification, dewatering and remediation processes, which can effectively reduce equipment redundancy and eliminate the need for large-scale off-site sediment transportation and disposal, thereby significantly reducing transportation and landfill costs.

[0004] The first aspect of this application provides an inland water sediment treatment system, including a suction unit, a temporary storage unit, a mixing unit, a solidification and dosing unit, and a dewatering storage yard; The suction unit is used to extract bottom sediment from the water body and transport it to the temporary storage unit; The temporary storage unit is connected to the mixing unit, which includes an input pipeline, a static mixer, and an output pipeline connected in sequence. The input pipeline has a first input end and a second input end. The first input end is connected to the temporary storage unit through a flow pump, and the second input end is connected to the positive pressure pneumatic conveying unit. The solidification dosing unit is connected to the input end of the static mixer via a pipeline and is used to inject stabilizer into the static mixer. The stabilizer is used to directionally convert exchangeable, carbonate-bound, and iron-manganese oxide-bound heavy metals into mineral phases. The dewatering storage area includes a slurry storage tank, an impermeable membrane laid on the ground, and geotextile bags stacked on the impermeable membrane. The slurry storage tank is connected to an output pipeline, and the geotextile bags are used to fill the bottom mud of the slurry storage tank. The edge of the impermeable membrane is provided with a drainage channel surrounding the geotextile bags, and the drainage channel is connected to the seepage fluid treatment unit. After the bottom mud inside the geotextile bag is dehydrated to a preset moisture content, the bag is opened and Napier grass is planted.

[0005] In some embodiments, the suction unit includes a cutter suction vessel and a screening device. The cutter suction vessel is equipped with a conveying pipeline, the output end of which is suspended above the screening device by a bracket, and the discharge end of the screening device is connected to the temporary storage unit.

[0006] In some embodiments, the screening device includes a vibrating screen, wherein a conveying trough is inclinedly provided below the screening surface of the vibrating screen, and the screen mesh diameter of the screening surface is 8~12mm; The temporary storage unit includes a temporary storage tank, which is equipped with a stirring device, and the conveying trough is connected to the temporary storage tank via a conveying pump.

[0007] In some embodiments, the solidification dosing unit includes a first storage tank, a first metering pump, and a first check valve connected in sequence; the first storage tank is equipped with a stirring device, a water source interface, and a dosing port; the first check valve is connected to the input end of the static mixer; and the concentration of the stabilizer is 2% to 15%.

[0008] In some embodiments, the input pipeline is connected to the static mixer via a flange, and a nozzle is fixedly mounted at the output end of the input pipeline; the nozzle is aligned with the axis of the static mixer, and the inlet of the nozzle is connected to the output end of the curing dosing unit.

[0009] In some embodiments, the output pressure of the positive pressure pneumatic conveying unit is 100~200kPa.

[0010] In some embodiments, the seepage treatment unit includes a sedimentation tank, a sand filter tank, and a disinfection tank connected in sequence.

[0011] In some embodiments, a flocculant dosing device is also included; the flocculant dosing device includes a second storage tank, a maturation tank, and a second check valve, the second check valve being connected to an output pipeline, the second storage tank being equipped with a stirring device, a water source interface, and a dosing port; the second storage tank is connected to the second check valve via a second metering pump and a third metering pump; the maturation tank is connected to the second check valve via a third metering pump; the second storage tank is connected to the maturation tank via a delivery pump, and the concentration of the flocculant is 0.1%~0.3%.

[0012] In some embodiments, the stabilizer includes at least one of iron-based biochar materials, cement, nano-ferric oxide, phosphates, silicates, and sulfides.

[0013] The second aspect of this application provides a method for treating sediment in inland waterways, comprising the following steps: a. Divide the target water area into several independent treatment sections. Through grid sampling and five-step continuous extraction, determine the total content ω1 of exchangeable, carbonate-bound, and iron-manganese oxide-bound heavy metals in the bottom sediment of each treatment section. Set the water content of the bottom sediment extracted by the suction unit as ω2 and the flow rate of the flow pump as Q. b. Based on ω1, ω2 and Q, set the concentration of the stabilizer as S and the injection flow rate as α, and set the air pressure of the positive pressure pneumatic conveying unit as P; c. The suction unit transports the bottom sediment to the temporary storage unit; d. The flow pump delivers the bottom mud in the temporary storage unit to the first input end of the mixing unit input pipeline at a set flow rate Q; the positive pressure pneumatic conveying unit injects airflow into the second input end at a set air pressure P; e. The solidification dosing unit injects stabilizer into the static mixer at a set dosing flow rate α to perform gas-liquid-solid three-phase mixing; f. The treated sediment is transported to a slurry storage tank, and a pump is used to fill geotextile bags for dehydration and solidification. The leachate produced during dehydration enters the leachate treatment unit through a drainage channel and is discharged after meeting the standards. j. After the bottom mud in the geotextile bag is dehydrated to the preset moisture content, the bag is broken and Napier grass is planted at a spacing of 30×40cm.

[0014] As can be seen from the above, this application innovatively integrates chemical solidification, in-situ loading, and bioremediation technologies to form a highly efficient and synergistic sediment treatment solution. Specifically, pneumatic mixing technology ensures efficient and uniform mixing of the stabilizer and sediment, rapidly fixing most free heavy metals at the source and transforming them into stable mineral phases. Simultaneously, geotextile bags are used for in-situ loading; their closed structure provides a dehydration and solidification environment, eliminating the need for external sediment transportation and disposal, significantly reducing treatment costs. Within the geotextile bag area on the shoreline of inland waterways, simultaneous greening and planting can be carried out. The planted Napier grass can continuously adsorb and fix residual and potentially activated heavy metals, effectively blocking the pathways for heavy metals to re-enter the environment or food chain.

[0015] Ultimately, this application achieves efficient and harmless disposal of sediment through the synergistic effect of the entire chain of chemical fixation, in-situ preservation, and biological purification. Attached Figure Description

[0016] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0017] Figure 1 This is a schematic diagram illustrating the principle structure of an inland waterway sediment treatment system as shown in the embodiments of this application; Figure 2 This is another schematic diagram of the principle structure of the inland water sediment treatment system shown in the embodiments of this application; Figure 3 This is a schematic diagram of the structure of a static mixer shown in an embodiment of this application.

[0018] In the picture: 1. Suction unit; 10. Cutter suction dredger; 11. Screening device; 2. Temporary storage unit; 3. Mixing unit; 30. Input pipeline; 30a. First input end; 30b. Second input end; 31. Static mixer; 32. Output pipeline; 4. Positive pressure pneumatic conveying unit; 5. Solidification dosing unit; 50. First storage tank; 51. First metering pump; 52. First check valve; 6. Dewatering storage area; 60. Slurry storage tank; 61. Geomembrane; 62. Geotextile bag; 63. Drainage channel; 64. Leakage treatment unit; 7. Flocculant dosing device; 70. Second storage tank; 71. Maturation tank; 72. Second check valve. Detailed Implementation

[0019] Preferred embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0020] Inland waterways have long been plagued by heavy metal pollution, with cadmium, arsenic, and other heavy metals in the sediment exceeding safe levels. During the flood season, these substances spread and pollute surrounding farmland, threatening agricultural safety and human health. Current remediation solutions include dredging, dewatering, and co-processing in cement kilns. However, the limited processing capacity of cement kilns has become a bottleneck for large-scale remediation. Traditional mechanical mixing methods result in uneven mixing of chemicals and sediment, leading to poor solidification and stabilization of heavy metals and posing long-term environmental risks. Furthermore, traditional mechanical mixing also suffers from limited processing capacity.

[0021] To address the aforementioned issues, this application provides an inland water sediment treatment system. Through the synergistic effect of pneumatic mixing and solidification, geotextile bag dewatering, and Napier grass phytoremediation, it achieves efficient stabilization of heavy metals in sediment, prevention and control of secondary pollution during the dewatering process, and long-term ecological restoration of the treated site, thus solving the bottleneck problems of existing technologies.

[0022] To better illustrate this technical solution, this article defines some technical terms: Moisture content refers to the ratio of the mass of water in the soil to the mass of dry soil (the calculation formula is: Moisture content = (mass of water / mass of dry soil) × 100%).

[0023] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0024] Figure 1 This is a schematic diagram illustrating the principle and structure of an inland waterway sediment treatment system as shown in the embodiments of this application.

[0025] See Figures 1-3 This application proposes an inland waterway sediment treatment system, including a suction unit 1, a temporary storage unit 2, a mixing unit 3, a solidification and addition unit 5, and a dewatering storage area 6. The suction unit 1 is used to extract the bottom sediment of the water body and transport it to the temporary storage unit 2; The temporary storage unit 2 is connected to the mixing unit 3. The mixing unit 3 includes an input pipeline 30, a static mixer 31 and an output pipeline 32 connected in sequence. The input pipeline 30 is provided with a first input end 30a and a second input end 30b. The first input end 30a is connected to the temporary storage unit 2 through a flow pump, and the second input end 30b is connected to the positive pressure pneumatic conveying unit 4. The solidification dosing unit 5 is connected to the input end of the static mixer 31 through a pipeline and is used to inject stabilizer into the static mixer 31. The stabilizer is used to directionally convert exchangeable, carbonate-bound, and iron-manganese oxide-bound heavy metals into mineral phases. The dewatering storage yard 6 includes a slurry storage tank 60, an impermeable membrane 61 laid on the ground, and geotextile bags 62 stacked on the impermeable membrane 61. The slurry storage tank 60 is connected to an output pipeline 32, and the geotextile bags 62 are used to fill the bottom mud of the slurry storage tank 60. The edge of the impermeable membrane 61 is provided with a drainage channel 63 surrounding the geotextile bags 62, and the drainage channel 63 is connected to an infiltration liquid treatment unit 64. After the bottom mud inside the geotextile bag 62 is dehydrated to a preset moisture content, the bag is opened and Napier grass is planted.

[0026] Specifically, suction unit 1 refers to the equipment combination that extracts bottom sediment from the water body and transfers it to subsequent treatment stages. It can be a float-type suction device or a cutter suction dredger 10 combined with a screening device 11. Both the float-type suction device and the cutter suction dredger 10 can transfer bottom sediment with a certain moisture content to temporary storage unit 2. In this application, to balance mixing efficiency and treatment efficiency, the moisture content of the bottom sediment is in the range of 90% to 110%. At the same time, suction unit 1 is also equipped with a filtration device. For example, in the cutter suction dredger 10, the cutter head at the front end of the cutter suction dredger 10 rotates and breaks up the riverbed silt, mixes it with water to form mud, and the mud enters the pump body through the suction pipe. The pump adds water and pressurizes the mud and transports it to the screening device 11. After the mud enters the screening device 11, large particles of impurities (such as large-diameter sand, gravel, plastic products, branches, etc.) are removed by screening to reduce the problem of clogging in mixing unit 3. Temporary storage unit 2 is used to temporarily store raw sediment to ensure that the sediment remains in a uniform suspended state before entering the next treatment stage, and to ensure smooth process flow between units. The storage capacity of temporary storage unit 2 can be set according to the estimated total amount of sediment in the current water treatment section and the daily treatment capacity.

[0027] In this application, due to the relatively large water area, the types and contents of heavy metals (copper, cadmium, lead, mercury, etc.) vary significantly at different locations. Therefore, in practical operation, the water area to be treated can be divided into several independent treatment sections to accurately determine the types and contents of heavy metals in each independent treatment section. Meanwhile, heavy metals exist in different forms in the environmental medium, and these different forms have different mobility, bioavailability, and toxicity. In existing technologies, the forms of heavy metals in soil can be classified as exchangeable, carbonate-bound, iron-manganese oxide-bound, organic, and residual forms, with clear risk gradients for each form: exchangeable forms are high-risk, directly reflecting bioavailability; carbonate-bound forms are significantly affected by pH, and iron-manganese oxide-bound forms are affected by dissolved oxygen and redox conditions, both being of medium risk; organic forms have high stability and are of low risk; and residual forms have almost no bioavailability and are of extremely low risk. In this application, stabilizers are used to target and bind high / medium-risk exchangeable, carbonate-bound, and iron-manganese oxide-bound forms, reducing their bioavailability by forming insoluble precipitates or complexes.

[0028] The three types of high / medium risk heavy metals mentioned above—exchangeable, carbonate-bound, and iron-manganese oxide-bound—can be determined using the existing five-step continuous extraction method, the determination process of which will not be elaborated here.

[0029] Furthermore, arsenic (As) is a non-metallic element that poses a cumulative hazard to human health. In existing technologies, arsenic is classified into adsorbed, aluminum-bound, iron-manganese oxide-bound, calcium-bound, and occluded forms. The adsorbed form is highly risky and easily migrates; the calcium-bound form is significantly more toxic than other insoluble forms; the iron-manganese oxide-bound form is the most prevalent in most soils; and the occluded form has almost no migration. The stabilizer in this application reduces the bioavailability of adsorbed arsenic by forming insoluble precipitates or complexing with it.

[0030] The suction unit 1 extracts sediment from the water body and transports it to the temporary storage unit 2, which maintains the continuity of sediment treatment. The temporary storage unit 2 is connected to the mixing unit 3, which consists of an input pipe 30, a static mixer 31, and an output pipe 32. The input pipe 30 has two input ends: the first input end 30a is connected to the temporary storage unit 2 via a flow pump, and the second input end 30b is connected to the positive pressure pneumatic conveying unit 4. During operation, the flow pump transports the sediment from the temporary storage unit 2 to the input pipe 30 at a set flow rate Q; simultaneously, the positive pressure pneumatic conveying unit 4 injects airflow into the input pipe 30 at a set air pressure P, and the solidification dosing unit 5 delivers stabilizer to the front end of the static mixer 31 according to a preset stabilizer concentration and dosing flow rate. The sediment, airflow, and stabilizer form a uniform gas-liquid-solid three-phase mixture system in the static mixer 31, thereby achieving large-scale, uninterrupted sediment treatment. The positive pressure pneumatic conveying unit 4 added to the mixing unit 3 can improve the flow performance of the bottom sediment by means of airflow, thereby shortening the length of the spiral mixing section of the static mixer 31 and effectively increasing its processing capacity.

[0031] Furthermore, the solidification dosing unit 5 is connected to the input end of the static mixer 31 via a pipe. Its function is to inject a stabilizer for complexing free heavy metal ions into the static mixer 31. The stabilizer achieves in-situ solidification of exchangeable, carbonate-bound, and iron-manganese oxide-bound heavy metals, as well as adsorbed arsenic, through a chemical reaction. The stabilizer is composed of a combination of various chemical substances, such as iron-based biochar materials, cement, nano-ferric oxide, phosphates, silicates, and sulfides. Among them, iron-based biochar material is an environmentally friendly material made by high-temperature pyrolysis of biomass, followed by nitration and reduction processes. Its main component is iron-containing biochar. This material combines the high specific surface area and porous structure of biochar with the catalytic activity of iron. It contains porous structures and surface functional groups (such as carboxyl and hydroxyl groups), and can adsorb Pb. 2+ Cd 2+ As 3+ Plasma; Fe 3+ / Fe 2+ It can form stable iron-arsenic compounds (FeAsO4 or FeAsS) with arsenic, thereby reducing the mobility of arsenic; Fe 2+Fe forms Fe-Pb / Cd complexes or ferrotalcite with lead and cadmium, enhancing the curing effect; 2+ Simultaneously, it can reduce As(V) to As(III), promoting complexation with Fe(III) and enhancing stability; Fe 3+ It can also promote Pb 2+ Precipitation forms a stable mineral phase, achieving in-situ solidification.

[0032] After cement hydration, it forms a network structure that can encapsulate heavy metals, making them difficult to migrate. The Ca(OH)2 generated during cement hydration can increase the pH value of the entire sediment system, causing lead (Pb) and cadmium (Cd) to precipitate as hydroxides (Pb(OH)2, Cd(OH)2) or carbonates (PbCO3, CdCO3) with low solubility. At the same time, CSH (calcium silicate hydrate) and ettringite in cement can adsorb or ion exchange heavy metals, improving the solidification effect.

[0033] Soluble phosphates can form stable, water-insoluble phosphate precipitates with lead (Pb) and cadmium (Cd). Lead phosphate has extremely low solubility and can remain stable in sediment for extended periods; cadmium phosphate can reduce Cd concentrations. 2+ To mitigate the migration of pollutants and prevent secondary pollution of water bodies.

[0034] Sulfides are used to provide sulfur 2- It can form insoluble sulfides such as PbS, CdS, and As2S3 with heavy metal ions, and can stabilize heavy metals under weakly acidic to neutral conditions for a long time.

[0035] In some embodiments, if the content of heavy metal ions in the sediment is too high, nano-ferric oxide can be used to convert the free heavy metals in the sediment into heavy metal salts that are insoluble in water (mineral phase), preventing them from being released during the subsequent dehydration process and causing secondary pollution.

[0036] It is understandable that, due to differences in chemical properties, some components of the aforementioned iron-based biochar, cement, nano-ferric oxide, phosphate, silicate, and sulfide may interfere with each other. To facilitate practical application by those skilled in the art, several typical combinations are listed below: The first typical combination is iron-based biochar, cement, silicate, and nano-ferric oxide, which achieves the solidification and removal of heavy metal ions through the synergistic effect of alkaline stabilization and adsorption, suitable for scenarios with low to medium concentrations of heavy metal pollution; the second combination is sulfide and phosphate, requiring the sediment pH to be controlled within the range of 8-10: sulfide can react with heavy metals to form extremely insoluble sulfide precipitates, while phosphate supplements the precipitation of unreacted heavy metals; however, it should be noted that hydrogen sulfide gas is generated during the sulfide reaction, therefore, an air extraction device should be added to the corresponding process equipment to ensure operational safety.

[0037] It is worth noting that the technology for adjusting the pH value of sediment is now relatively mature, and those skilled in the art can refer to conventional methods for implementation.

[0038] The mixed sediment is transported to the dewatering storage area 6 via the output pipeline 32. The dewatering storage area 6 includes a slurry storage tank 60, a geomembrane 61 laid on the ground, and geotextile bags 62 stacked on the geomembrane 61. The slurry storage tank 60 receives the treated sediment and uses a pump to fill it into the geotextile bags 62 for natural dewatering. The edge of the geomembrane 61 is provided with a drainage channel 63 surrounding the geotextile bags 62. The leachate generated during the dewatering process is collected through the drainage channel 63 and directed to the leachate treatment unit 64, thereby effectively isolating the contaminated liquid and preventing pollution of the soil and groundwater.

[0039] In this embodiment, the geotextile bags are made of high-strength polypropylene, and the bottom geomembrane 61 is made of HDPE or a clay geomembrane. The discharge port of the slurry storage tank 60 is equipped with a conveying pump and a grouting pipe. When filling the geotextile bags 62, they are first laid on the geomembrane 61 or on top of already filled geotextile bags 62, forming a pyramid structure between the layers to allow for permeability. After the bottom mud inside the geotextile bags 62 has been dehydrated for a certain period and reaches a preset moisture content, such as 50%, or when the geotextile bags 62 no longer leak water, the bags can be opened and Napier grass can be planted. The root system of Napier grass allows it to absorb residual pollutants and promote soil remediation, thereby transforming the bottom mud from waste into ecological resources.

[0040] Through the above technical solutions, the inland water sediment treatment system provided in this application integrates sediment suction, mixing and solidification and ecological restoration, and constructs a high-efficiency and low-consumption treatment process. It effectively avoids the long process, high energy consumption and secondary pollution risks of traditional methods, and realizes the harmless disposal and resource utilization of sediment.

[0041] Furthermore, the suction unit 1 includes a cutter suction boat 10 and a screening device 11. The cutter suction boat 10 is equipped with a conveying pipeline. The output end of the conveying pipeline is suspended above the screening device 11 by a bracket. The discharge end of the screening device 11 is connected to the temporary storage unit 2.

[0042] Furthermore, the screening device 11 includes a vibrating screen, and a conveying trough is inclinedly provided below the screening surface of the vibrating screen, and the screen mesh diameter of the screening surface is 8~12mm; The temporary storage unit 2 includes a temporary storage tank, which is equipped with a stirring device, and the conveying trough is connected to the temporary storage tank through a conveying pump.

[0043] The suction unit 1 is the core of the bottom sediment treatment system, responsible for the efficient collection and directional transport of underwater bottom sediment. The suction unit 1 consists of three parts: a cutter suction dredger 10, a transport pipeline, and a support structure. The cutter suction dredger 10 is a specialized engineering vessel integrating excavation and transport functions. By adjusting the excavation depth and operating range, it adapts to different water dredging scenarios, enabling continuous extraction of underwater bottom sediment. The transport pipeline can use a combination of flexible or rigid pipes to connect the cutter suction dredger 10 and the screening device 11, ensuring the stability and continuity of the bottom sediment during transport. The support structure uses a height-adjustable steel structure to precisely fix the output end of the transport pipeline, aligning it with the inlet of the screening device 11 to ensure efficient sediment entry into the screening system.

[0044] The screening device 11 removes large particles of impurities through physical screening, providing qualified materials for subsequent processing. The screening device 11 is mainly composed of a vibrating screen, coupled with a conveying trough, a waste hopper, and a conveying pump. The vibrating screen adopts a three-dimensional vibration design driven by an eccentric block, with a screen mesh size of 8-12mm. For example, a 10mm mesh size can efficiently separate impurities of different particle sizes. During operation, the bottom mud transported by the cutter suction dredger 10 enters the vibrating screen, where three-dimensional vibration causes impurities such as stones, plastics, and branches with a particle size >10mm to slide along the screening surface into the waste hopper. The qualified bottom mud that passes through the screen is collected by an inclined conveying trough and then pumped to the temporary storage unit 2. To ensure equipment safety and material quality in subsequent processing stages, the screening efficiency can be checked and the screening surface cleaned every 2 hours during operation.

[0045] Temporary storage unit 2 is used to buffer and store qualified bottom sediment after screening, avoiding the impact of fluctuations in the upstream process on the continuous operation of the subsequent mixing unit 3 or the impact of fluctuations in the downstream process on the suction operation of the cutter suction dredger 10. Temporary storage unit 2 consists of a temporary storage tank and a mixing device. The temporary storage tank can be a concrete tank or a mixing cylinder structure, and its capacity is determined according to the daily processing capacity of the project. When using a concrete tank, the mixing device is installed and fixed above the center of the temporary storage tank by a mounting frame. By continuously mixing the bottom sediment in the tank, sedimentation and stratification are prevented, material uniformity is maintained, and the quality of the bottom sediment output to the mixing unit 3 is ensured to be stable. The temporary storage tank is directly connected to the conveying trough of the screening device 11 through a conveying pump, and the temporary storage tank is connected to the input pipeline 30 through the conveying pump.

[0046] Correspondingly, to ensure the standardization and environmental friendliness of the system operation, the impurities separated by screening should be bagged and disposed of in accordance with the requirements of the "Standard for Pollution Control of General Industrial Solid Waste Storage and Landfill" (GB18599-2020) to avoid secondary pollution. At the same time, the wear of the vibrating screen and the operating status of the stirring device should be checked regularly to ensure the long-term stable operation of each unit. The material storage capacity of the temporary storage tank should be matched with the processing capacity of the subsequent mixing unit 3. Reasonable inventory should be maintained through liquid level sensors or manual monitoring to ensure the continuous operation of the entire system.

[0047] Furthermore, the solidification dosing unit 5 includes a first storage tank 50, a first metering pump 51, and a first check valve 52 connected in sequence; the first storage tank 50 is equipped with a stirring device, a water source interface, and a dosing hole; the first check valve 52 is connected to the input end of the static mixer 31; the concentration of the stabilizer is 2%~15%.

[0048] Specifically, the first storage tank 50 is a steel mixing tank with a built-in level gauge to monitor the material quantity in real time. The first check valve 52 effectively prevents the high-pressure fluid in the mixing unit 3 from flowing back to the first metering pump 51 and the storage tank, avoiding equipment damage and material contamination, and ensuring stable system operation. When configuring the stabilizer, the content of various heavy metals in the sediment of the current treatment section can be considered, and the hourly processing capacity of the project can be determined by setting the metering pump flow rate and the air pressure of the positive pressure pneumatic conveying unit 4. The stabilizer concentration is set to 2%~15%. For example, if the total content of various heavy metals in a certain section reaches 2000 mg / kg, the flow rate of the flow pump is 500 m³ / kg. 3 The stabilizer concentration is set at 15% per hour. Based on the type of stabilizer, the dosage is calculated using the chemical reaction equation, and the stabilizer flow rate can be set at 10 m³ / h. 3 / h. When preparing the stabilizer, the operator adds the stabilizer through the dosing port and injects clean water through the water source interface, simultaneously starting the stirring device to complete uniform mixing. To improve the smoothness of the process, the solidification dosing unit 5 can also be equipped with two first storage tanks 50 for alternating operation. When one storage tank injects material into the mixing unit 3 through a metering pump, the other simultaneously replenishes the material and prepares for mixing, achieving uninterrupted dosing. In practical applications, to avoid the problem of incomplete solidification caused by fluctuations in the concentration of heavy metals in the sediment, the slurry storage tank 60 at the rear of the mixing unit 3 can also perform uniformity testing. By sampling every hour and using X-ray fluorescence spectrometry (XRF) to detect whether the coefficient of variation of lead and arsenic is ≤10%; if the test results exceed the standard, the stabilizer concentration is increased to 120% of the original concentration.

[0049] In actual treatment, the arsenic content in the sediment of different river sections varied significantly, ranging from a minimum of 20.1 mg / kg to a maximum of 86,300 mg / kg. Due to the extreme range of arsenic content and its co-occurrence with other heavy metals, a single solidification treatment is insufficient to achieve stabilization. Multiple cyclic treatments are required to address the issue of excessive arsenic levels, as detailed below: 1. XRF testing is performed by sampling the slurry tank every 60 hours. If the arsenic content exceeds the preset control standard (e.g., the target solidification rate of arsenic in the original treatment section does not reach 90%) or the coefficient of variation is >10%, it is judged as exceeding the standard and the cycle process is triggered.

[0050] 2. Turn on the connecting pipe and the conveying pump between the slurry storage tank 60 and the front end of the mixing unit 3, and send the excessive slurry back to the front end treatment stage at the original flow rate Q.

[0051] 3. Repeat the gas-liquid-solid three-phase mixing steps of the mixing unit, namely, the flow pump delivers the bottom mud, the positive pressure pneumatic conveying unit injects the airflow, and the solidification dosing unit injects the adjusted stabilizer.

[0052] 4. The sludge after secondary treatment is put back into the storage tank 60. Sampling is taken to test the arsenic content and distribution uniformity. If it still exceeds the standard, the cycle is repeated until the arsenic concentration reaches the standard (e.g., the proportion of adsorbed arsenic is <5%) and the coefficient of variation is ≤10%.

[0053] 5. Adjust the following parameters according to the degree of arsenic exceedance (low, medium, or high): When the arsenic content is 20.1~1000 mg / kg, iron-based biochar and phosphate are preferred; when the arsenic content is >1000 mg / kg, iron-based biochar, nano-ferric oxide and sulfide are selected, and the concentration is increased to 120%~150% of the original concentration. Based on the original addition flow rate, the addition flow rate is increased by 10% for every 1000 mg / kg increase in arsenic content; finally, if the arsenic content is >5000 mg / kg, the flocculant concentration is increased to 0.3% and the addition ratio is increased to 0.6% to enhance the fixation of arsenic during subsequent dehydration.

[0054] Furthermore, since the actual amount of sediment to be treated in inland waters can reach hundreds of thousands of tons, the required stabilizer (dry powder) can reach thousands of tons. For ease of handling, the solidification dosing unit 5 and the flocculant dosing device 7 can be implemented by shipboard, while the positive pressure pneumatic conveying unit 4 can be implemented by air-pressurized ship.

[0055] Furthermore, the front end of the static mixer 31 is equipped with a nozzle, which is aligned with the axis of the static mixer 31 and is connected to the curing dosing unit 5.

[0056] Furthermore, the output pressure of the positive pressure pneumatic conveying unit 4 is 100~200 kPa. The positive pressure pneumatic conveying unit 4 is connected to the second input terminal 30b of the input pipe 30 of the mixing unit 3. By injecting airflow into the mixing unit 3, the mixing efficiency of the sediment and the stabilizer is significantly improved. Setting the output pressure of the positive pressure pneumatic conveying unit 4 within the range of 100 to 200 kPa ensures that the airflow has sufficient kinetic energy to promote the uniform mixing of the sediment and the stabilizer, while maintaining the stable operation of the system and avoiding poor mixing effect or equipment failure caused by pressure fluctuations.

[0057] Furthermore, the leachate treatment unit 64 includes a sedimentation tank, a sand filter, and a disinfection tank connected in sequence. The leachate treatment unit 64 is responsible for the step-by-step purification of the leachate or wastewater generated during the process, ensuring that the final effluent meets environmental standards. The sedimentation tank is a horizontal flow gravity sedimentation tank, the size of which can be set according to actual needs. The sedimentation tank separates large suspended solids (SS) from the leachate through the gravity effect of the slow-flowing water. To avoid siltation at the bottom of the tank affecting settling efficiency, manual or mechanical sludge removal can be performed every 48 hours during operation. The sand filter, as a secondary treatment unit, aims to remove fine particles and dissolved pollutants. The sand filter can use a quartz sand filter layer with a thickness of 600-800 mm, and the quartz particle size can be selected as 0.5-1.2 mm. A 100 mm thick layer of anthracite filter media is added on top to enhance the adsorption effect. The quartz sand filter layer removes fine SS that was not retained in the sedimentation tank, while also adsorbing residual organic matter. To ensure the long-term effectiveness of the sand filter, a combined air-water backwashing system can be installed to restore the filtration performance of the filter media through backwashing. The disinfection tank is used to eliminate pathogenic microorganisms in the water, and sodium hypochlorite solution or ultraviolet disinfection can be selected according to project requirements. In some embodiments, to improve the organic matter removal efficiency, a composite filter layer enhancement module can be added to the sand filter. Specifically, a mixed layer of humus and activated carbon is alternately laid between the quartz sand layers and inoculated with anaerobic bacteria (such as methanogens, sulfate-reducing bacteria, etc.). The anaerobic respiration of the anaerobic bacteria decomposes the recalcitrant organic matter in the leachate, thereby reducing the problem of water odor. Correspondingly, the leachate treatment unit 64 is also equipped with an online monitoring system. During operation, it monitors the sedimentation tank level, sand filter pressure difference, and residual chlorine concentration in the disinfection tank in real time, automatically alarming in case of abnormalities. It also samples daily to test COD, SS, pathogen indicators, and heavy metal residues. If the residual chlorine in the disinfection tank is insufficient, the sodium hypochlorite dosage is immediately increased; if the SS removal rate of the sand filter decreases, the backwashing procedure is initiated in advance.

[0058] Furthermore, it also includes a flocculant dosing device 7; the flocculant dosing device 7 includes a second storage tank 70, a maturation tank 71, and a second check valve 72, the second check valve 72 being connected to an output pipeline 32, the second storage tank 70 being equipped with a stirring device, a water source interface, and a dosing hole; the second storage tank 70 is connected to the second check valve 72 via a second metering pump, and also via a third metering pump; the maturation tank 71 is connected to the second check valve 72 via a third metering pump; the second storage tank 70 is connected to the maturation tank 71 via a delivery pump, and the concentration of the flocculant is 0.1%~0.3%.

[0059] Specifically, the flocculant dosing device 7 is used to achieve solid-liquid separation of the sediment. By preparing, activating, and quantitatively adding flocculant, it promotes the aggregation of suspended particles into stable flocs, thereby improving the treatment efficiency of subsequent sedimentation and filtration units. The flocculant concentration can be dynamically adjusted according to the type of flocculant and the moisture content of the sediment, with a typical concentration of 0.3%.

[0060] The second storage tank 70 is used for dissolving and initially mixing the flocculant. The second storage tank 70 can be a steel mixing tank, equipped with a low-speed stirring device (e.g., stirring speed of 80~120 rpm), a water source interface, a dosing port, and a level gauge. The maturation tank 71 is used to fully mature the flocculant that needs activation. The maturation tank 71 can be an insulated vertical storage tank with a volume matching that of the second storage tank 70. It is equipped with internal baffles to ensure the flocculant molecular chains are fully extended. The second, third, and fourth metering pumps are all diaphragm pumps used to deliver the flocculant to the corresponding target.

[0061] This application can be divided into two operating procedures depending on whether the flocculant needs to be matured: 1. Applicable to inorganic flocculants that do not require activation, the process is as follows: Step 1: Add PAC powder to the second storage tank 70 through the dosing port, inject clean water into the water source interface, start the stirring device, and stir for 10-15 minutes until completely dissolved, with the concentration controlled at 0.2%-0.3%; Step 2: Turn on the second metering pump and deliver the solution to the output pipeline 32 according to the flow rate set in the engineering plan, so that it enters the target processing unit; Step 3: When the liquid level in the second storage tank 70 is lower than the warning value, repeat step 1 to replenish the material.

[0062] 2. Applicable to polymeric organic flocculants requiring activation, the process is as follows: Step 1: Slowly and evenly add PAM powder to the second storage tank 70, add water and stir at a speed of 80~120 rpm, and control the concentration at 0.1%~0.2%; Step 2: Turn on the third metering pump to deliver the solution to the maturation tank 71, let it stand for 30-60 minutes, and stir at low speed for 5 minutes every 10 minutes. Step 3: Turn on the fourth metering pump to deliver the matured solution to the output pipeline 32 through the second check valve 72; Step 4: Replenishment: When the liquid level in maturation tank 71 is lower than the warning value, repeat steps 1-2 to replenish the liquid.

[0063] This application also proposes a first method for treating sediment in inland waterways, including the following steps: a. Divide the target water area into several independent treatment sections. Through grid sampling and five-step continuous extraction, determine the total content ω1 of exchangeable, carbonate-bound, and iron-manganese oxide-bound heavy metals in the bottom sediment of each treatment section. Set the water content of the bottom sediment extracted by the suction unit as ω2 and the flow rate of the flow pump as Q. b. Based on ω1, ω2 and Q, set the concentration of the stabilizer as S and the injection flow rate as α, and set the air pressure of the positive pressure pneumatic conveying unit as P; c. Suction unit 1 transports the bottom sediment to temporary storage unit 2; d. The flow pump delivers the bottom mud in the temporary storage unit 2 to the first input end 30a of the input pipeline 30 of the mixing unit 3 at a set flow rate Q; the positive pressure pneumatic conveying unit 4 injects airflow into the second input end 30b at a set air pressure P; e. The solidification dosing unit 5 injects stabilizer into the static mixer 31 at the set dosing flow rate α to perform gas-liquid-solid three-phase mixing; f. The treated sediment is transported to the slurry storage tank 60, and the treated sediment is filled into geotextile bags 62 by a conveying pump for dehydration and solidification; the leachate generated during dehydration enters the leachate treatment unit 64 through the diversion channel 63 and is discharged after meeting the standards. j. After the bottom mud in geotextile bag 62 is dehydrated to the preset moisture content, the bag is broken and Napier grass is planted at a spacing of 30×40cm.

[0064] Furthermore, in step b, if the stabilizer is a mixture of phosphate and silicate, the phosphate addition ratio is set to α1 and the silicate addition ratio is set to α2 based on ω1, S and α, while the phosphate concentration is S1 and the silicate concentration is S2.

[0065] Furthermore, in step b, the concentration of the flocculant is set to y and the addition ratio is k, based on the water content of the bottom sediment of the treatment section being ω2.

[0066] In summary, this application organically combines pneumatic mixed-flow solidification, geotextile bag 62 dehydration and solidification, and Napier grass adsorption to form a rapid, stable, and low-risk new model for heavy metal sediment remediation. This model effectively addresses the challenge of insufficient cement kiln processing capacity without significantly increasing disposal costs, improving the stability and long-term environmental safety of contaminated sediment. Simultaneously, the introduction of Napier grass provides continuous ecological restoration and functional benefits, making it highly significant for demonstration and promotion. This process can effectively solve the problem of heavy metal pollution in sediment, achieving the goals of pollution source control, migration path blocking, and long-term improvement of soil environmental quality. It also enables the safe disposal and resource utilization of sediment, providing reliable technical support for the remediation of heavy metal pollution in inland waters.

[0067] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An inland waterway sediment treatment system, characterized in that, It includes a suction unit, a temporary storage unit, a mixing unit, a positive pressure pneumatic conveying unit, a solidification dosing unit, and a dehydration storage area; The suction unit is used to extract bottom sediment from the water body and transport it to the temporary storage unit; The temporary storage unit is connected to the mixing unit, which includes an input pipeline, a static mixer, and an output pipeline connected in sequence. The input pipeline has a first input end and a second input end. The first input end is connected to the temporary storage unit through a flow pump, and the second input end is connected to the positive pressure pneumatic conveying unit. The solidification dosing unit is connected to the input end of the static mixer via a pipeline and is used to inject stabilizer into the static mixer. The stabilizer is used to directionally convert exchangeable, carbonate-bound, and iron-manganese oxide-bound heavy metals into mineral phases. The dewatering storage area includes a slurry storage tank, an impermeable membrane laid on the ground, and geotextile bags stacked on the impermeable membrane. The slurry storage tank is connected to an output pipeline, and the geotextile bags are used to fill the bottom mud of the slurry storage tank. The edge of the impermeable membrane is provided with a drainage channel surrounding the geotextile bags, and the drainage channel is connected to the seepage fluid treatment unit. After the bottom mud inside the geotextile bag is dehydrated to a preset moisture content, the bag is opened and Napier grass is planted.

2. The inland waterway sediment treatment system according to claim 1, characterized in that, The suction unit includes a cutter suction vessel and a screening device. The cutter suction vessel is equipped with a conveying pipeline. The output end of the conveying pipeline is suspended above the screening device by a bracket. The discharge end of the screening device is connected to the temporary storage unit.

3. The inland waterway sediment treatment system according to claim 2, characterized in that, The screening device includes a vibrating screen, and a conveying trough is inclinedly provided below the screening surface of the vibrating screen. The screen mesh diameter of the screening surface is 8~12mm. The temporary storage unit includes a temporary storage tank, which is equipped with a stirring device, and the conveying trough is connected to the temporary storage tank via a conveying pump.

4. The inland waterway sediment treatment system according to claim 1, characterized in that, The solidification dosing unit includes a first storage tank, a first metering pump, and a first check valve connected in sequence; the first storage tank is equipped with a stirring device, a water source interface, and a dosing port; the first check valve is connected to the input end of the static mixer; the concentration of the stabilizer is 2%~15%.

5. The inland waterway sediment treatment system according to claim 4, characterized in that, The static mixer has a built-in nozzle at its front end, which is aligned with the axis of the static mixer and is connected to the curing dosing unit.

6. The inland waterway sediment treatment system according to claim 1, characterized in that, The output pressure of the positive pressure pneumatic conveying unit is 100~200kPa.

7. The inland waterway sediment treatment system according to claim 1, characterized in that, The seepage treatment unit includes a sedimentation tank, a sand filter tank, and a disinfection tank connected in sequence.

8. The inland waterway sediment treatment system according to claim 1, characterized in that, It also includes a flocculant dosing device; the flocculant dosing device includes a second storage tank, a maturation tank, and a second check valve, the second check valve being connected to an output pipeline, the second storage tank being equipped with a stirring device, a water source interface, and a dosing hole; the second storage tank is connected to the second check valve via a second metering pump, and is also connected to the second check valve via a third metering pump; the maturation tank is connected to the second check valve via a third metering pump; the second storage tank is connected to the maturation tank via a delivery pump, and the concentration of the flocculant is 0.1%~0.3%.

9. The inland waterway sediment treatment system according to claim 1, characterized in that, The stabilizer includes at least one of iron-based biochar materials, cement, nano-ferric oxide, phosphate, silicate, and sulfide.

10. A method for treating sediment in inland waterways, applied to the inland waterway sediment treatment system as described in any one of claims 1 to 9, characterized in that, Includes the following steps: a. Divide the target water area into several independent treatment sections. Through grid sampling and five-step continuous extraction, determine the total content ω1 of exchangeable, carbonate-bound, and iron-manganese oxide-bound heavy metals in the bottom sediment of each treatment section. Set the water content of the bottom sediment extracted by the suction unit as ω2 and the flow rate of the flow pump as Q. b. Based on ω1, ω2 and Q, set the concentration of the stabilizer as S and the injection flow rate as α, and set the air pressure of the positive pressure pneumatic conveying unit as P; c. The suction unit transports the bottom sediment to the temporary storage unit; d. The flow pump delivers the bottom mud in the temporary storage unit to the first input end of the mixing unit input pipeline at a set flow rate Q; the positive pressure pneumatic conveying unit injects airflow into the second input end at a set air pressure P; e. The solidification dosing unit injects stabilizer into the static mixer at a set dosing flow rate α to perform gas-liquid-solid three-phase mixing; f. The treated sediment is transported to a slurry storage tank, and a pump is used to fill geotextile bags for dehydration and solidification. The leachate produced during dehydration enters the leachate treatment unit through a drainage channel and is discharged after meeting the standards. j. After the bottom mud in the geotextile bag is dehydrated to the preset moisture content, the bag is broken and Napier grass is planted at a spacing of 30×40cm.

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