Desilting and sand washing integrated treatment process for lakes and reservoirs

Abstract

The invention discloses a lake and reservoir desilting and sand washing integrated treatment process, and relates to the technical field of lake and reservoir environmental governance and resource recovery, in particular to the lake and reservoir desilting and sand washing integrated treatment process. Cleaning and crushing are carried out in a mode of combining machinery with hydraulic power, and collected objects are conveyed to a sand washing system through a closed conveying channel. According to the sand washing system, solid-liquid preliminary separation is carried out through a slurry sedimentation tank, and then gravel aggregate and building soil with different particle sizes are effectively separated out through the procedures of multi-stage screening, hydraulic cyclone classification and the like. And the separated sand is dehydrated and graded to realize resource recycling. And residual water separated by the system is guided into a surface water treatment system, and is recycled or discharged after reaching the standard after being subjected to multi-stage treatment. A real-time monitoring link is arranged in the technological process, pollutants are controlled in the whole process, and the whole-process integrated operation of desilting, sand washing, water treatment and material recycling is achieved.

Description

Technical Field

[0001] This invention relates to the field of lake and reservoir environmental management and resource recycling technology, specifically an integrated treatment process for lake and reservoir dredging and sand washing. Background Technology

[0002] With the rapid advancement of urbanization in my country, industrial and domestic sewage discharge activities have become increasingly frequent. Large amounts of wastewater containing silt, impurities, and even pollutants are collected through municipal pipe networks and ultimately discharged into natural water bodies via sewage outlets along lakes and reservoirs. For a long time, due to factors such as regulatory oversight, combined sewer overflows, aging pipe networks, and initial rainwater runoff erosion, large amounts of suspended solids, silt, and organic matter have continuously accumulated at sewage outlets and in surrounding lake and reservoir areas, leading to serious siltation problems. These silt deposits not only directly cause a significant reduction in the flow capacity of sewage outlets, leading to localized blockages or even overflows and affecting the normal operation of drainage systems, but they can also become a "reservoir" for endogenous pollution. Under certain conditions, pollutants such as heavy metals, organic matter, nitrogen, and phosphorus can be continuously released, posing a persistent threat to the water quality safety of downstream lakes and reservoirs, and even related lakes and reservoirs, exacerbating the risks of eutrophication and blackening / odorization of water bodies.

[0003] On the other hand, dredging is a common and necessary engineering measure in many water conservancy projects and ecological environment management projects, especially in the periodic maintenance of water bodies such as reservoirs, waterways, and urban rivers. As important water resource regulation, supply, and flood control facilities, reservoir siltation directly leads to a reduction in effective storage capacity, weakens flood and drought resistance capabilities, shortens the project's lifespan, and may affect water quality. Traditional reservoir dredging aims to remove silt to restore storage capacity, but often treats the dredged silt (which often contains a significant proportion of sand and gravel) as waste soil, simply dumping or landfilling it. This method not only occupies a large amount of land resources but may also cause secondary pollution due to improper disposal, failing to achieve the resource recovery of effective components in the silt material, making dredging a purely consumable operation with high investment and single benefit.

[0004] In more complex and higher-risk scenarios such as lake and reservoir outfalls, the sediment composition is mixed, including sewage transported from pipelines and riverbed sediments, often containing construction debris, domestic waste, organic sludge, and sand and gravel aggregates of varying sizes. If traditional, single-function dredging methods are used, merely removing and transferring the sediment, there are significant limitations: first, the operation process easily disturbs and spreads deposited pollutants, causing secondary water pollution; second, potentially recyclable sand and gravel resources are mixed with polluted sludge and discarded, resulting in resource waste; and third, the lack of effective separation and deep treatment of the sediment leads to significant environmental risk transfer issues.

[0005] Therefore, for the specific location of lake and reservoir sewage outlets, there is a need to develop an integrated process that closely combines efficient dredging operations with the refined treatment and resource recycling of silt. This process must overcome the shortcomings of traditional methods, not only thoroughly and cleanly removing silt and clearing sewage channels to ensure drainage function, but also efficiently separating and cleaning the complex mixture removed, especially recycling and purifying the sand and gravel aggregates into qualified raw materials usable in the construction industry, thus achieving a transformation from "waste removal" to "resource regeneration." Simultaneously, this process must adhere to environmental protection principles throughout, strictly controlling pollutant emissions, and properly treating and utilizing the separated mud and water, ultimately achieving multiple goals of dredging, pollution control, resource recycling, and ecological protection, providing an innovative technological solution for the sustainable maintenance of reservoirs, lakes, and other water bodies. Summary of the Invention

[0006] The purpose of this invention is to provide an integrated dredging and sand washing process for lakes and reservoirs. By setting up a dredging and sand washing collaborative system adapted to the working conditions, mechanical excavation combined with hydraulic conveying is used to remove silt. The silt is then transported to the sand washing system in a closed manner to achieve sand purification and recycling. At the same time, secondary pollution is controlled, linkage control parameters are set up and monitored in real time to improve operation efficiency and resource utilization.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an integrated dredging and sand washing process for lakes and reservoirs, comprising the following steps: setting up a dredging system and a sand washing system to work in tandem; activating the dredging system to clean, collect, and transport the silt in the internal channels of the lake / reservoir discharge outlet and the surrounding waters; sending the silt collected by the dredging system into the sand washing system via a pipeline; and in the sand washing system, performing sand washing, mud-sand separation, screening, grading, and dewatering on the silt; thus achieving continuous integrated operation of dredging, sand recovery, and resource utilization.

[0008] Furthermore, the dredging system is a specialized dredging device adapted to the size and structural characteristics of the sewage outlet. Its working components can extend into and clean the inside of the sewage outlet pipe, while covering the riverbed siltation area within a set range outside the sewage outlet. The mud-water mixture generated during the dredging operation is continuously transported to the mud sedimentation tank connected to the sand washing system through a closed mud conveying pipeline.

[0009] Furthermore, the dredging system uses mechanical excavation components to break up and loosen the compacted silt, while simultaneously using a hydraulic suction device to form a slurry from the mixture of the broken silt and water. The slurry is then transported to a sand washing system via a pressure pipeline. The sand washing system is sequentially connected to a slurry settling tank, a grading and screening device with different apertures, and a hydraulic cyclone device. The slurry from the dredging system first enters the slurry settling tank for preliminary solid-phase sedimentation and liquid-phase separation.

[0010] Furthermore, the sand washing system performs multi-stage washing and screening of the solid mixture extracted from the mud sedimentation tank: firstly, stones with a particle size greater than 5 cm are separated by a primary coarse screen; then, stones with a particle size between 2 cm and 5 cm are separated by a secondary screen; the large-particle stone obtained from the two-stage screening is transported to the stone processing plant; the remaining material is then finely filtered by a vibrating screen or drum screen with finer mesh to separate sand and gravel aggregates with a particle size between 2 mm and 2 cm, which are then transported to construction sites for building material production.

[0011] Further, the remaining fine particle mixture after the precision filtration step enters the hydrocyclone device; inside the hydrocyclone, centrifugal force is used to classify the material, separating fine sand with a particle size between 150 micrometers and 2 millimeters. This fine sand is also transported to the construction site; the overflow material after hydrocyclone classification is mainly mud, which enters mechanical dewatering equipment for dewatering treatment. The mud cake formed after dewatering is used for backfilling low-lying areas, greening soil, or road construction soil.

[0012] Furthermore, the dredging system and the sand washing system are connected by a closed pipeline or a sealed conveyor belt to form a closed conveying channel, ensuring that the material is transported from the dredging point to the sand washing point in a closed state throughout the entire process, preventing the spillage of silt or the dripping of mud from causing secondary pollution to the lake and reservoir; the residual water separated from the supernatant of the mud sedimentation tank is collected through the diversion main channel and transported to the surface water treatment system for deep purification.

[0013] Furthermore, the process is equipped with a central control unit, which dynamically adjusts the water flow and water pressure of each level of the sand washing unit in the sand washing system according to the sand content of the silt monitored in real time at the dredging point, so as to realize the linkage control of dredging intensity and sand washing intensity. The surface water treatment system is arranged in sequence along the water flow direction, including a coagulation tank for adding coagulant, a primary sedimentation tank for floc settling, a stirring tank for adding coagulant aid, a turbulence tank for forming large flocs, and a secondary sedimentation tank for final solid-liquid separation. The treated water is discharged after meeting the discharge standards, or returned to the process system as sand washing makeup water for reuse.

[0014] Furthermore, the sand washing system first dehydrates the qualified sand separated from the washing process by passing it through a dewatering screen or dewatering chamber to reduce its moisture content. After dewatering, the sand is then precisely classified according to different particle size specifications by a grading screen to form different specifications of construction sand products, which are then collected, stored, or loaded onto trucks to achieve resource recycling of the sand. The outlet of the secondary sedimentation tank is connected to a clear water tank. The clear water treated by the secondary sedimentation tank is stored in the clear water tank. Part of the clear water is returned to the sand washing system as flushing water through a pump set, and the remaining part is discharged in compliance with standards.

[0015] Furthermore, the process is equipped with online monitoring instruments at the dredging operation point, material conveying line, sand washing unit, and water treatment unit, forming a full-process operation monitoring link. The monitoring data is transmitted to the control center in real time. The monitoring content includes: the thickness of silt accumulation and the dredging area in the sewage outlet area, the mud content and purity of the finished sand after sand washing, the concentration of suspended solids, chemical oxygen demand, five-day biochemical oxygen demand, total phosphorus concentration, and the concentration indicators of heavy metal ions such as fluoride, lead, chromium, and cadmium in the water discharged from each process stage.

[0016] Furthermore, after the dredging system completes the dredging operation on the target sewage outlet and surrounding area, pipeline inspection equipment is used to test and video evaluate the dredging effect of the sewage outlet channel; after the sand washing system completes a batch of sand washing operations, clean water is used to backwash and maintain the inside of the sand washing equipment, screens, and all conveying pipelines to ensure that there is no material caking or blockage inside the system; the entire process ultimately separates the silt accumulated at the lake and reservoir sewage outlet into sand and mud that can be utilized for resource recovery, as well as clean water that can be reused or discharged after treatment to meet standards, achieving complete separation and resource recovery of mud, sand, and water.

[0017] This invention provides an integrated process for dredging and sand washing in lakes and reservoirs, which has the following beneficial effects: 1. Significantly improves the overall efficiency of sewage outlet dredging and sand resource recovery. This process systematically integrates dredging and sand washing, achieving a closed-loop connection between dredging, transportation, and treatment of silt through a sealed conveying channel. This not only solves the problems of disconnect between dredging and material disposal, and the secondary pollution caused by transfer, common in traditional operations, but also addresses the characteristics of silt at sewage outlets (which often contain a large amount of construction waste and a mixture of mud and sand) by directly washing, sorting, and recycling aggregates on-site. The dredging system effectively clears stubborn silt from the internal channels and surrounding areas of the sewage outlet, while the sand washing system precisely separates qualified construction sand and stone of different particle sizes through multi-stage screening, water washing, and cyclone processes. Compared to the traditional "dredging-transportation-landfill" model, this process significantly improves the resource recovery efficiency and economic benefits of the operational chain, truly turning waste into treasure.

[0018] Effective prevention and control of secondary water pollution and environmental risks during operation This process incorporates meticulous environmental control design. A closed-loop transportation system is used between the dredging and sand washing systems, preventing secondary pollution of the lake and reservoir water from sludge spillage and leakage. The sludge generated during sand washing first enters a sedimentation tank for preliminary solid-liquid separation. The supernatant is then introduced into a surface water treatment system that includes coagulation, flocculation, and multi-stage sedimentation, effectively removing pollutants such as suspended solids (SS), carbon dioxide (COD), and heavy metals, ensuring that the final effluent meets standards or is recyclable. Simultaneously, real-time monitoring of operating conditions and pollutant emission indicators (such as SS, COD, and heavy metals) is implemented throughout the entire process, enabling proactive monitoring and early warning of environmental risks. This multi-layered protection system of "closed process + terminal treatment + real-time monitoring" significantly reduces the negative impact of traditional dredging and sand washing operations on the surrounding waters and environment, meeting stringent environmental protection construction requirements.

[0019] To achieve the coordinated recovery and recycling of water, mud, and sand resources. One of the core advantages of this process is the complete separation and resource utilization of water, mud, and sand in the silt. After multi-stage screening and hydrocyclone grading, the sand and gravel portion yields stones larger than 5cm, stones between 2-5cm, and various sizes of aggregate, which can be directly used as building materials. The separated fine-particle mud can be dewatered and used as backfill soil. The water treatment system deeply purifies the sand washing wastewater; the treated water can be reused in the sand washing process or discharged in compliance with standards, forming an internal water cycle and saving a significant amount of fresh water resources. Ultimately, the entire process transforms the silt at the discharge outlet into usable sand, stone, backfill soil, and clean water, achieving near-zero waste discharge and maximum resource recovery, aligning with the concepts of circular economy and green development.

[0020] Improve process adaptability and operational stability through intelligent linkage control. This process possesses a certain degree of intelligent control capability. The system can adjust the washing intensity of the sand washing system in conjunction with the real-time sand content of the dredged material, thus maintaining high sand washing efficiency and sand quality under different types of silt conditions, enhancing the process's adaptability. The continuous operational monitoring not only monitors the silt removal progress and sand separation purity but also provides real-time data on key pollutant indicators at each stage, offering data support for optimizing process parameters. This real-time data-driven, coordinated control and monitoring ensures the stable, efficient, and coordinated operation of the entire complex system, from dredging to sand washing to water treatment, improving the overall automation level of the process and its ability to handle different siltation conditions at discharge outlets.

[0021] Ensuring the long-term unobstructed flow of sewage outlets and the sustainable operation of process systems This process not only focuses on the effectiveness of a single operation but also emphasizes long-term maintenance and the system's sustainability. After dredging, the drainage outlet is inspected to ensure its drainage function is fully restored, preventing re-accumulation. After sand washing, related equipment and pipelines are thoroughly cleaned and maintained to prevent residues from corroding equipment or clogging pipelines, ensuring the system's long-term reliable cyclical operation capability. This integrated "operation-maintenance-inspection" design allows the process to be applied periodically or routinely as a complete solution for the maintenance and cleaning of drainage outlets, ensuring continuous unobstructed drainage while achieving sustainable operation through the resource-based disposal of silt. Attached Figure Description

[0022] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating the integrated process of dredging and sand washing at lake and reservoir discharge outlets according to the present invention. Figure 2 This is a flowchart of the dredging system operation process of the present invention; Figure 3 This is a flow chart of the graded water washing process of the sand washing system of the present invention; Figure 4 This is a flow chart of the wastewater purification and reuse process of the present invention; Figure 5 This is a flowchart of the operation and maintenance process of the working condition monitoring and system of the present invention. Detailed Implementation

[0024] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses consistent with some aspects of this disclosure as detailed in the appended claims.

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] How to use: Step 1: Dredging Operation The operation utilizes a dredging system specifically designed for sewage outlet conditions (i.e., a dedicated dredging system). The work area must cover the silted area within the sewage outlet's internal channels and the surrounding waters. First, a combination of mechanical excavation and hydraulic conveying is used to break up and loosen the deposited silt. Subsequently, using hydraulic pipelines, the broken silt (in a muddy state) is transported through a closed conveyor system to the subsequent sand washing system in a completely sealed manner to avoid secondary pollution of the work area.

[0027] Step 2: Mud sedimentation and preliminary separation The delivered mud first enters the mud sedimentation tank of the sand washing system, where preliminary solid-liquid separation takes place. The separated supernatant water is then diverted to the surface water treatment system for further treatment via a main channel.

[0028] Step 3: Multi-stage screening and coarse material separation The solid mixture at the bottom of the sedimentation tank is transferred to the sand washing process. This process first purifies the sand through multi-stage washing and screening. First, a primary coarse sand screening removes large particles; then a secondary coarse sand screening further separates the particles. During the screening process, stones larger than 5 cm and stones between 2 cm and 5 cm in diameter are separated and transported to a stone processing plant for use. Sand and gravel aggregates between 2 mm and 2 cm in diameter can be directly transported to construction sites.

[0029] Step 4: Fine Classification of Hydrocyclones The mixture after passing through a coarse screen enters a hydrocyclone device for upstream classification. This step separates fine sand with particle sizes ranging from 150 micrometers to 2 millimeters, and this qualified sand is transported to the construction site. The remaining material after classification, after mechanical dewatering, can be used as backfill soil for construction.

[0030] Step 5: Sand dewatering and collection The qualified sand materials of various specifications separated by washing are dewatered and collected according to different particle size specifications to realize the resource recycling of sand materials.

[0031] Step 6: Wastewater Treatment and Reuse The residual water separated from the mud sedimentation tank, as well as the wastewater generated during sand washing, are all introduced into the surface water treatment system. This system treats the wastewater sequentially through a coagulation tank, a primary sedimentation tank, a mixing tank, a turbulence tank, and a secondary sedimentation tank. The clear water treated in the secondary sedimentation tank is stored in a clear water tank and can be used for on-site process reuse or discharged / returned to the reservoir after ensuring compliance with standards.

[0032] Step 7: System Integration and Operating Condition Monitoring Throughout the entire operation, system-wide coordinated control and real-time operational monitoring are required. Based on changes in the sand content of the dredged material, the dredging depth of the dredging system and the washing intensity of the sand washing system should be adjusted in a coordinated manner to optimize overall energy efficiency and recovery rate. Simultaneously, real-time monitoring is necessary to ensure that the silt removal progress at the discharge outlet, the purity of the sand discharged from the sand washing system, and the pollutant emission indicators at each stage (primarily including SS, COD, BOD, TP, fluorides, and heavy metals) meet environmental protection standards.

[0033] Example: Example 1 This embodiment details the basic implementation of an integrated dredging and sand washing process for lakes and reservoirs. This process targets the sewage outlet areas of lakes and reservoirs, using a coordinated dredging system and a sand washing system to remove accumulated sediment and recover sand.

[0034] First, the dredging system is activated for operation. In this embodiment, the dredging system is a specialized dredging system adapted to the specific working conditions of the sewage outlet. Its operating range must fully cover the internal channels of the sewage outlet and the silted area of ​​the surrounding waters outside the outlet. During operation, the system uses mechanical excavation components to break up and loosen the hardened silt, while simultaneously using a hydraulic conveying unit to extract the broken material in the form of slurry. All the slurry generated during the dredging operation is pumped to the slurry sedimentation tank within the sand washing system area through a pre-set conveying pipeline.

[0035] Subsequently, the sand washing system is introduced. The delivered slurry first enters a sedimentation tank for preliminary solid-liquid separation. The separated liquid phase (residual water) is transported to the subsequent surface water treatment system via a main diversion channel. The solid mixture at the bottom of the tank then enters the sand washing process. This process employs multi-stage washing and screening to purify the sand: it undergoes primary and secondary coarse sand screening to effectively remove muddy impurities from the mixture. During screening, stones larger than 5 cm and stones between 2 cm and 5 cm in diameter are sorted out and transported to a stone processing plant; aggregates between 2 mm and 2 cm in diameter are directly transported to construction sites for use.

[0036] Further fine separation is achieved through a hydrocyclone device. The mixture is classified upwards by the hydrocyclone, separating sand particles ranging from 150 micrometers to 2 millimeters in diameter. This qualified sand is transported to the construction site. The remaining material after classification is mechanically dewatered and used as backfill soil for construction. All qualified sand particles separated by the entire sand washing system are dewatered and collected according to particle size specifications to achieve resource utilization.

[0037] Throughout the process, the dredging system and the sand washing system are connected by a closed conveying channel to ensure the sealed transport of silt and prevent secondary pollution. The surface water treatment system treats the wastewater to ensure it meets discharge standards or is reused. Ultimately, this embodiment achieves effective separation of mud, sand, and water from the silt at the discharge outlet, and completes the resource utilization of mud and sand and the compliant treatment of water.

[0038] Example 2 This embodiment focuses on describing the combination of mechanical and hydraulic methods in the dredging system, as well as the specific collaborative operation of mud sedimentation and grading screening in the sand washing system.

[0039] During implementation, a dedicated sludge removal system is activated. Its core principle lies in combining mechanical excavation with hydraulic conveying to remove sludge. Mechanical components (such as cutters and scrapers) first forcefully break up and loosen the sludge at and around the discharge outlet, altering its compacted state. Immediately afterwards, the system's built-in high-pressure water pump generates water flow, mixing the broken sludge with the water to form a uniform slurry, which is then continuously transported out through hydraulic pipelines. This method is particularly suitable for complex deposits that may exist within discharge outlets, effectively clearing them and transporting them over long distances to designated locations.

[0040] The slurry is transported to the initial unit of the sand washing system—the mud settling tank. In this tank, the slurry settles naturally by gravity, achieving initial solid-phase separation and concentration. The excess water separated from the upper layer of the settling tank is drawn out through a main diversion channel. The higher-concentration solid mixture at the bottom of the tank is pumped to the subsequent screening unit.

[0041] The sand washing process then begins. The solid mixture first enters a primary coarse sand screening device (such as a vibrating screen) to filter out large impurities and some pebbles. Stones larger than 5 cm in diameter are separated from the oversize material. The mixture then enters a secondary coarse sand screening device for finer separation. This step mainly separates stones with a diameter of 2 to 5 cm and sand and gravel aggregates with a diameter of 2 to 2 mm. The separated stones are transported to a stone processing plant, while the sand and gravel aggregates are transported directly to the construction site.

[0042] The finer mixture after two-stage screening enters a hydrocyclone device. Inside the hydrocyclone, the upstream classification is carried out using the principle of centrifugal sedimentation, which can efficiently separate fine sand with a particle size of 150 micrometers to 2 millimeters as the product. The remaining muddy material in the underflow of the hydrocyclone is then dewatered by mechanical dewatering equipment (such as a centrifuge or filter press), and the resulting mud cake can be used as low-grade fill or construction soil for resource-based backfilling.

[0043] This embodiment demonstrates the entire process from silt crushing and slurry transportation to multi-stage screening and hydraulic classification through clear step connections, ensuring the efficiency of sand recovery and the clear path to resource utilization.

[0044] Example 3 This embodiment focuses on illustrating the multi-stage processing flow of solid mixtures in the sand washing system, as well as the resource utilization destination of materials with different particle sizes.

[0045] Once the dredging system delivers the sludge to the sand washing system, the core solid-phase mixture sand washing process begins. This process strictly follows multi-stage washing and screening steps, aiming to gradually purify the sand and classify it for resource utilization.

[0046] The first step is primary coarse sand screening. The mixture at the bottom of the sludge settling tank is fed into the first screening device (such as a bar screen or drum screen), where, with the help of flushing water, very large debris and floating matter are removed, and solids with significantly larger particle sizes are initially separated. From this step, stones with a particle size greater than 5 cm can be separated.

[0047] The second step is secondary coarse sand screening. Material that has passed the primary screening enters a second screening device with finer mesh (such as a high-frequency vibrating screen). This step is one of the key stages in sand and gravel aggregate sorting. Here, stones with a particle size of 2 to 5 centimeters are effectively separated. Simultaneously, sand and gravel with a particle size of 2 millimeters to 2 centimeters, meeting the standards for coarse aggregate used in construction, are also screened out. These two types of stones will be transported to a stone processing plant for further processing, while the 2-millimeter to 2-centimeter sand and gravel aggregate will be directly loaded onto trucks and transported to construction sites for use.

[0048] The third step is hydrocyclone upflow classification. After two stages of coarse screening, the remaining material is mainly a mixture of fine sand, silt, and mud. This is pumped into a hydrocyclone assembly. Inside the hydrocyclone, a strong rotating flow field is used to classify the material according to particle size and density. Sand particles with a diameter between 150 micrometers and 2 millimeters are separated and collected as overflow products. This portion is the higher-quality fine sand and is also transported to the construction site as a product.

[0049] Finally, the extremely fine particles (mainly mud and silt) remaining after hydrocyclone classification become the underflow material. This residue has a high moisture content and needs to be processed by mechanical dewatering equipment to form solid blocks with lower moisture content. These blocks can be used as backfill soil for construction sites or roadbed fill, realizing the resource utilization of mud. This embodiment clearly illustrates the classification path from coarse to fine and the determination of the destination of each stage's product.

[0050] Example 4 This embodiment details the environmental protection measures and system linkage control methods in the process, including closed-loop transportation, wastewater treatment, and operating condition monitoring.

[0051] This process places great emphasis on environmental protection during operation. First, a completely enclosed transport channel (such as a pipe or sealed trough) is set up between the dredging system and the sand washing system. The sludge drawn from the discharge outlet is transported to the sludge sedimentation tank through this completely sealed channel, completely eliminating the possibility of secondary pollution to the lake or reservoir water caused by sludge leakage or spillage during transportation.

[0052] Secondly, the water treatment process constitutes a crucial environmental safeguard. The residual water separated from the mud sedimentation tank, as well as the wastewater generated from the various screening and grading units during sand washing, are collected through a main diversion channel and introduced into a surface water treatment system for further treatment. This system is designed with a flow path, sequentially passing through a coagulation tank (where coagulants are added to coagulate fine suspended solids), a primary sedimentation tank (for initial flocculent settling), a mixing tank (for water quality adjustment), a flocculation tank (potentially for further flocculation), and a secondary sedimentation tank (for final solid-liquid separation). The purified water, after deep purification by this system, is then transported to a clear water storage tank. This clear water can be used for process reuse within the sand washing system itself (such as screening rinse water), or, after meeting relevant discharge standards, can be discharged back into lakes, reservoirs, or natural water bodies, achieving water resource recycling or safe discharge.

[0053] Furthermore, this process implements system-wide coordinated control. Under the management of the central control unit, the dredging depth of the dredging system and the washing water volume (or water pressure) of the sand washing system do not operate independently, but are coordinated according to real-time conditions. For example, when the sand content of the dredged material is detected to be high, the washing intensity of the sand washing system can be automatically increased to ensure sand washing efficiency; conversely, it can be appropriately reduced to save water. This coordination ensures the optimization of overall process energy efficiency and resource recovery rate.

[0054] Finally, a process monitoring system was implemented throughout the entire process. Monitoring points were located at key workstations: real-time monitoring of the silt removal progress at the sewage outlets to ensure that the dredging area met standards; monitoring of indicators such as the mud content of the sand discharged from the sand washing system to assess the purity of the separated sand; and most importantly, real-time online monitoring of wastewater from the main diversion channel and the final discharge outlet, with indicators including suspended solids (SS), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total phosphorus (TP), as well as characteristic pollutants such as fluorides and heavy metals, to ensure that all emissions meet environmental protection requirements.

[0055] Example 5 This embodiment comprehensively describes the maintenance and system cycle preparation after a complete operation cycle, as well as the final resource utilization goal of the process.

[0056] A complete cycle of integrated dredging and sand washing at a lake or reservoir discharge outlet includes not only the core cleaning and separation process, but also post-operation system maintenance and inspection to ensure the sustainable and cyclical application of the process.

[0057] The work does not end immediately after the dredging system has cleared the silt from the designated discharge outlet and its surrounding area. A specialized inspection of the discharge outlet itself is required. This may involve using CCTV or other inspection methods to confirm that there are no remaining blockages inside the discharge outlet, that the water flow is unobstructed, and that its function has been fully restored. This is a crucial step in ensuring the long-term normal operation of the discharge outlet.

[0058] Simultaneously, after the sand washing system completes the treatment of a batch of silt, and all sand and stone are collected and classified, and the wastewater is treated, a shutdown maintenance is mandatory. Maintenance includes: thoroughly backflushing or cleaning all screening devices (primary and secondary coarse sand screens), hydrocyclones, conveying pumps, and connecting pipelines with clean water to prevent residual silt from caking and clogging the equipment; inspecting the filter cloths or worn parts of the mechanical dewatering equipment; and draining and cleaning all tanks in the surface water treatment system. This cleaning and maintenance procedure ensures the equipment is in good condition and ready for the next operating cycle.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An integrated treatment process for lake and reservoir dredging and sand washing, characterized in that, This process involves dredging and sand washing at sewage outlets. It sets up a dredging system and a sand washing system that work together. The dredging system cleans and collects the silt accumulated at and around the sewage outlet, and then the collected silt is transported to the sand washing system for sand washing and separation, thus achieving the coordinated operation of dredging and sand washing.

2. The integrated dredging and sand washing process for lakes and reservoirs according to claim 1, characterized in that, The dredging system is a dedicated dredging system adapted to the working conditions of sewage outlets. The operating range of the dredging system covers the internal channels of the sewage outlet and the silted area of ​​the surrounding water outside the sewage outlet. The sludge generated during the dredging operation is transported to the sludge sedimentation tank through pipelines.

3. The integrated dredging and sand washing process for lakes and reservoirs according to claim 1, characterized in that, The dredging system cleans up silt by combining mechanical excavation with hydraulic conveying. First, the silt is broken up and loosened, and then the broken silt is conveyed to the sand washing system through hydraulic pipelines. The sand washing system includes a mud sedimentation tank, a grading and screening device and a hydraulic cyclone device. The silt undergoes preliminary solid-liquid separation in the mud sedimentation tank.

4. The integrated dredging and sand washing process for lakes and reservoirs according to claim 3, characterized in that, The solid-phase mixture washing process of the sand washing system adopts a multi-stage water washing and screening method. It sequentially removes muddy impurities from the solid-phase mixture through primary coarse sand screening, secondary coarse sand screening and precision filtration steps to achieve sand purification. Among them, the screened stones >5cm and 2cm-5cm stones are transported to the stone processing plant, and the 2mm-2cm sand and gravel aggregates are transported to the construction site.

5. The integrated dredging and sand washing process for lakes and reservoirs according to claim 4, characterized in that, The solid-phase mixture sand washing process of the sand washing system also includes a hydraulic cyclone upflow classification step. The classified 150um-2mm sand is transported to the construction site, and the remaining material after classification is mechanically dewatered and used as backfill soil for construction.

6. The integrated dredging and sand washing process for lakes and reservoirs according to claim 1, characterized in that, A closed conveying channel is set between the dredging system and the sand washing system. The silt is transported in a closed manner throughout the entire process to avoid secondary pollution of the surrounding waters during the transportation process. The residual water separated from the mud sedimentation tank is transported to the surface water treatment system through the diversion main channel.

7. The integrated dredging and sand washing process for lakes and reservoirs according to claim 1, characterized in that, During operation, the process involves coordinated control of the dredging depth and the sand washing water volume of the sand washing system. The washing intensity of the sand washing system is adjusted according to the sand content of the dredged sediment. The surface water treatment system includes a coagulation tank, a primary sedimentation tank, a mixing tank, a turbulence tank, and a secondary sedimentation tank. Wastewater is treated to meet discharge standards or reused on-site.

8. The integrated dredging and sand washing process for lakes and reservoirs according to claim 1, characterized in that, The qualified sand material after being cleaned and separated by the sand washing system is dewatered and graded, and then collected according to particle size specifications to realize the resource recycling of sand material; the clean water after being treated by the secondary sedimentation tank is transported to the clean water tank for on-site reuse or discharge in compliance with standards.

9. The integrated dredging and sand washing process for lakes and reservoirs according to claim 1, characterized in that, The process incorporates a monitoring system throughout the dredging and sand washing operations, which monitors in real time the progress of dredging at the discharge outlet, the purity of sand separation in the sand washing system, and pollutant emission indicators at each stage. The monitoring system includes real-time monitoring of SS, COD, BOD, TP, fluorides, and heavy metal indicators.

10. The integrated dredging and sand washing process for lakes and reservoirs according to claim 1, characterized in that, After the dredging system completes the dredging operation at the sewage outlet, it conducts a dredging and inspection of the sewage outlet channel. After the sand washing system completes the sand washing operation, it cleans and maintains the equipment and pipelines to ensure the cyclical operation capability of the entire process system. The process ultimately achieves the separation of mud, sand and water in the silt, and realizes the resource utilization and recycling of mud and sand, and the water is returned to the reservoir after treatment to meet standards.

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