A system and method for sorting and conditioning bottom sediment floe

Abstract

The application discloses a kind of bottom mud flocculation sorting backflow conditioning system and method, belong to bottom mud processing technical field.System includes flocculation reaction unit, flocculation sorting unit, dehydration unit and backflow pipeline.Flocculation sorting unit is set to the downstream of flocculation reaction unit, and the mud after flocculation is separated into flocculated material and un-flocculated fine particles;Flocculated material enters dehydration unit, and un-flocculated fine particles are returned to flocculation reaction unit for secondary conditioning by backflow pipeline, and form the closed circuit circulation of sorting, backflow, conditioning again.The application is by flocculation sorting and selective backflow, so that un-flocculated fine particles obtain secondary flocculation opportunity, help to improve reagent utilization rate, reduce the influence of un-flocculated fine particles on dehydration efficiency into dehydration unit, and improve the uniformity and stability of dehydration material quality, suitable for river, lake, reservoir and other bottom mud flocculation dehydration pretreatment.

Description

Technical Field

[0001] This invention relates to the field of sediment treatment technology, specifically to a sediment floc separation and reflux conditioning system and method, applicable to the flocculation conditioning and dewatering pretreatment process of sediments in various water bodies such as rivers, lakes, and reservoirs. Background Technology

[0002] With the continuous advancement of water environment management in my country, the demand for dredging and treatment of sediment in rivers, lakes, reservoirs, and other water bodies continues to grow. Sediment dewatering is the core step in achieving sediment reduction, and flocculation conditioning, as a key pretreatment step before dewatering, directly determines the subsequent dewatering efficiency and the quality stability of the dewatered material.

[0003] Current sediment flocculation and conditioning processes generally employ a combination of pipeline mixing and geotextile bag dewatering: after the sediment slurry is mixed with flocculant in the delivery pipeline, it is directly fed into dewatering equipment such as geotextile bags for dewatering treatment. This type of process has the following three shortcomings in practical applications: First, the uniformity of flocculation effect is poor. Existing pipeline mixing methods mostly adopt simple static mixing or stirring mixing methods, which result in insufficient uniformity of flocculant dispersion in the mud system. This easily leads to colloidal agglomeration or localized excessively high / low agent concentrations, causing incomplete flocculation in some mud slurries and preventing some agents from effectively exerting their effects.

[0004] Secondly, unflocculated fine particles directly affect dewatering performance. In traditional processes, regardless of the quality of flocculation, the slurry that has undergone one flocculation conditioning is directly fed into the dewatering unit. Insufficiently flocculated fine particles entering the dewatering equipment may clog the filter pores of the dewatering medium, reducing the dewatering rate and leading to large fluctuations in the moisture content and unstable quality of the dewatered material.

[0005] Third, the utilization rate of the flocculants is low and the treatment cost is high. Due to the lack of a feedback and control mechanism for the flocculation effect, existing processes usually ensure the treatment effect by overdosing on flocculants, resulting in waste of the agents and increasing the overall cost of sediment treatment.

[0006] In the field of wastewater treatment, there are devices that use hydrocyclones to screen and recycle aerobic granular sludge. However, their application is in the cultivation of granular sludge in activated sludge wastewater treatment. The purpose of recycle is to enrich granular sludge and accelerate the sludge granulation process, not to selectively recycle and recondition unflocculated fine particles from sediment flocculation treatment. In the field of water treatment, there are technical solutions that recycle some of the formed flocs as flocculation nuclei. The recycle target is the mature flocs as a whole, rather than sorting the flocs first and then recycleing the unflocculated components. The purpose and technical principle of the recycle are fundamentally different from the sediment flocculation conditioning scenario.

[0007] In summary, existing technologies still lack a closed-loop treatment system for sorting flocs in sediment flocculation materials and selectively recirculating unflocculated fine particles for secondary conditioning, as well as a cyclic conditioning sediment flocculation process based on floc sorting results. Summary of the Invention

[0008] To address the technical problems of uneven flocculation effect, reduced dewatering efficiency due to unflocculated fine particles, and low reagent utilization in existing sediment flocculation and dewatering processes, the present invention aims to provide a sediment floc sorting and recirculation conditioning system and method. By constructing a closed-loop circulation conditioning system through floc sorting and selective recirculation of unflocculated fine particles, the system can improve flocculation effect, increase dewatering efficiency, and reduce reagent consumption.

[0009] To achieve the above objectives, the first aspect of the present invention provides a sediment floc sorting and reflux conditioning system, comprising a flocculation reaction unit, a floc sorting unit, a dewatering unit, and a reflux pipeline; The flocculation reaction unit is used to flocculate and condition the bottom mud slurry, so that the suspended particles in the mud slurry form flocs; The floc separation unit is located downstream of the flocculation reaction unit and is connected to the outlet of the flocculation reaction unit. It is used to separate the flocculated mud into flocculated materials and unflocculated fine particles. The dewatering unit is connected to the first outlet of the floc sorting unit and is used to receive the flocculated material and perform dewatering treatment. The return pipe connects the second outlet of the floc sorting unit to the inlet of the flocculation reaction unit, and is used to transport unflocculated fine particles back to the flocculation reaction unit for secondary flocculation conditioning. The floc sorting unit uses whether the floc particle size reaches a preset particle size threshold or whether the floc settling performance reaches a preset settling performance threshold as sorting criteria; materials that reach the corresponding preset threshold are transported to the dewatering unit as flocculated materials, while fine particles that do not reach the corresponding preset threshold are returned to the flocculation reaction unit as unflocculated fine particles through the return pipe.

[0010] Preferably, all the unflocculated fine particles output from the second outlet of the floc sorting unit are transported back to the flocculation reaction unit via the return pipeline, forming a closed-loop conditioning system.

[0011] Preferably, the floc separation unit is selected from any one of a hydrocyclone separator, a settling and grading tank, or a vibrating screen.

[0012] Preferably, the floc separation unit is a hydrocyclone separator, which includes a cylindrical body with a feed pipe tangentially connected to it. An overflow pipe is provided at the top of the cylindrical body, and an underflow port is provided at the bottom of the cylindrical body. The underflow port serves as the first outlet and is connected to the dewatering unit, while the overflow pipe serves as the second outlet and is connected to the return pipe. The preset threshold is the cutting particle size of the hydrocyclone separator. Flocs larger than the cutting particle size are discharged from the underflow port, while unflocculated fine particles smaller than the cutting particle size are discharged from the overflow pipe.

[0013] Preferably, the floc sorting unit is a sedimentation and grading tank, which uses the principle of gravity sedimentation to sort the flocs according to the difference in sedimentation velocity; the bottom outlet of the sedimentation and grading tank is connected to the dewatering unit as the first outlet, and the upper overflow outlet of the sedimentation and grading tank is connected to the return pipe as the second outlet; the preset threshold is controlled by adjusting the hydraulic residence time of the sedimentation and grading tank.

[0014] Preferably, the return pipe is equipped with a return pump and a return flow regulating valve.

[0015] Preferably, the return pipe is also equipped with a concentration detection device for real-time detection of the return concentration of unflocculated fine particles.

[0016] Preferably, the concentration detection device is an online suspended solids concentration meter, an online turbidity meter, or an online sludge concentration meter.

[0017] Preferably, the flocculation reaction unit includes a multi-stage dosing device and a mixing device arranged sequentially along the mud flow direction; the multi-stage dosing device includes at least two dosing points, the first dosing point is used to add an electrical neutralizing agent, and the second dosing point is used to add an adsorption bridging flocculant.

[0018] Preferably, the mixing device is a multi-stage vortex tube mixer, which is used to generate micro-vortices of controllable size and intensity after each dosing point of the multi-stage dosing device, so that the flocculant is uniformly dispersed in the mud.

[0019] A second aspect of the present invention provides a method for sediment floc separation, recirculation, and conditioning, wherein the conditioning method is implemented using the sediment floc separation, recirculation, and conditioning system, and includes the following steps: S1, the bottom mud slurry is sent into the flocculation reaction unit for flocculation conditioning, so that the suspended particles in the mud slurry form flocs; S2, the slurry after flocculation and conditioning is sent to the floc sorting unit, and the slurry is separated into flocculated material and unflocculated fine particles based on whether the floc particle size or floc settling performance reaches the preset threshold. S3, the flocculated material is sent to the dewatering unit for dewatering treatment; S4, the unflocculated fine particles are transported back to the flocculation reaction unit and mixed with the bottom mud slurry for secondary flocculation conditioning.

[0020] Preferably, in step S4, all the unflocculated fine particles are transported back to the flocculation reaction unit to form a closed-loop cycle of sorting, reflux, and conditioning.

[0021] Preferably, the preset threshold in step S2 is preset according to the flocculation characteristics of the bottom mud slurry and is dynamically adjusted by adjusting the operating parameters of the floc sorting unit.

[0022] Preferably, the flocculation conditioning in step S1 adopts a multi-stage point dosing method, first adding an electrical neutralizing agent to destabilize the suspended particles in the mud, and then adding an adsorption bridging flocculant to coagulate the destabilized particles into flocs.

[0023] Preferably, the dosage of the electrical neutralizing agent is adjusted in real time according to the Zeta potential of the mud, so that the Zeta potential of the mud is controlled within the range of -10mV to 5mV; the dosage of the adsorption bridging flocculant is adjusted in real time according to the suspended solids concentration of the mud.

[0024] The present invention has the following beneficial effects: 1. This invention classifies and screens flocculated materials through a floc sorting unit, allowing flocculated materials that have reached a preset threshold to enter the dewatering unit, reducing the mixing of unflocculated fine particles into the dewatering process, thereby improving the moisture content and quality stability of the dewatered materials.

[0025] 2. This invention constructs a closed-loop cycle of sorting, reflux, and reconditioning, allowing unflocculated fine particles to return to the flocculation reaction unit for secondary flocculation, thereby improving the utilization of flocculants, reducing waste of flocculants caused by insufficient flocculation of some mud in traditional processes, and lowering treatment costs.

[0026] 3. The materials entering the dewatering unit of this invention are all well-formed flocs, which can effectively avoid the problem of fine particles clogging the filter pores of the dewatering medium, improve the dewatering rate, and shorten the dewatering cycle.

[0027] 4. By dynamically adjusting the floc separation threshold and reflux parameters, this invention can adapt to the flocculation characteristics of different types of sediments, such as river sandy sediment, lake silt, and high organic matter sediment, and has good scene adaptability. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Figure 1 This is a structural diagram of the overall framework of the sediment floc separation and reflux conditioning system of the present invention; Figure 2This is an overall flow chart of the sediment floc separation and reflux conditioning system of the present invention; Figure 3 This is a process flow diagram of the sediment floc separation and recirculation conditioning method of the present invention.

[0030] In the diagram: 1-Flocculation reaction unit, 11-First-stage dosing point, 12-Second-stage dosing point, 13-Mixing device, 2-Floc sorting unit, 21-First outlet, 22-Second outlet, 3-Dewatering unit, 4-Recirculation pipe, 41-Recirculation pump, 42-Recirculation flow regulating valve, 43-Concentration detection device, 5-Fresh bottom sediment slurry inlet. Detailed Implementation

[0031] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are based on the implementation of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0032] I. System Overall Structure like Figure 1-2 As shown, the sediment floc sorting and reflux conditioning system of the present invention mainly consists of four parts: flocculation reaction unit 1, floc sorting unit 2, dewatering unit 3, and reflux pipe 4.

[0033] Fresh sediment slurry enters the flocculation reaction unit 1 through the fresh sediment slurry inlet 5. After flocculation and conditioning are completed in the flocculation reaction unit 1, all slurry (including formed flocs and unflocculated fine particles) is sent to the floc sorting unit 2. The floc sorting unit 2 divides the material into two paths according to preset sorting standards: one path consists of flocculated material that has reached the preset threshold, which is sent to the dewatering unit 3 for dewatering through the first outlet 21; the other path consists of unflocculated fine particles that have not reached the preset threshold, which enter the return pipe 4 through the second outlet 22. The return pipe 4 is then pumped back to the inlet of the flocculation reaction unit 1 by the return pump 41 and the return flow regulating valve 42, where it is mixed with the fresh sediment slurry for secondary flocculation and conditioning. The return pipe 4 is also equipped with a concentration detection device 43 to monitor the concentration of the return fine particles in real time, providing data support for the dynamic control of the flocculant dosage.

[0034] In a preferred embodiment, all the unflocculated fine particles separated by the floc sorting unit 2 are returned to the front end of the system through the return pipe 4, and do not directly enter the dewatering unit, forming a closed-loop circulation conditioning system, so that the fine particles have the opportunity to flocculate again before entering the dewatering process.

[0035] II. Specific Structure of Each Unit (a) Flocculation reaction unit The flocculation reaction unit 1 includes a multi-stage dosing device and a mixing device 13 arranged sequentially along the mud flow direction.

[0036] The multi-stage dosing device includes at least two dosing points: the first dosing point 11 is used to add electrical neutralizing agents, such as inorganic flocculants like polyaluminum chloride and aluminum sulfate, which destabilize negatively charged suspended particles in the mud through charge neutralization; the second dosing point 12 is located downstream of the first dosing point 11 and is used to add adsorption bridging flocculants, such as polymeric flocculants like anionic polyacrylamide, which cause destabilized particles to aggregate and form large-diameter flocs through the adsorption bridging effect of polymer chains.

[0037] The mixing device 13 is positioned downstream of each dosing point. In this embodiment, a multi-stage vortex tube mixer is used. The mixer is equipped with adjustable guide vanes. When the slurry flows through the mixer, the guide vanes induce micro-vortices of controllable size and intensity, enabling rapid and uniform dispersion of the flocculant at the microscale in the slurry. This reduces colloidal agglomeration and uneven reagent concentration gradients, improving the uniformity and efficiency of the flocculation reaction. The angle of the guide vanes can be adjusted according to the slurry flow rate, reagent type, and treatment load to adapt to the mixing requirements under different operating conditions.

[0038] (II) Floc Separation Unit The floc separation unit 2 can be any one of a hydrocyclone separator, a settling tank, or a vibrating screen, and the selection can be based on the processing scale, site conditions, and sediment characteristics. The following details two typical implementation methods: 1. Implementation of cyclone separators When a hydrocyclone separator is used as the floc separation unit 2, its structure includes a cylindrical body, a tangential feed pipe, a top overflow pipe, and a bottom outlet. The flocculated and conditioned slurry enters the cylindrical body at high speed through the tangential feed pipe, forming a rotating flow field inside the body. Under the action of centrifugal force, the larger flocculated flocs are thrown against the cylinder wall and move downwards in a spiral motion along the cylinder wall, eventually being discharged from the bottom outlet. The smaller, unflocculated fine particles move with the central upward flow and are discharged from the top overflow pipe.

[0039] The underflow outlet 21 is connected to the dewatering unit 3, and the overflow pipe 22 is connected to the return pipe 4. The preset threshold for sorting is the cutting particle size of the hydrocyclone separator, which can be dynamically adjusted by adjusting operating parameters such as feed pressure and overflow pipe insertion depth.

[0040] 2. Implementation method of sedimentation and grading pool When a settling and grading tank is used as the floc sorting unit 2, it is a tank structure with a set effective volume. The flocculated and conditioned slurry enters the tank smoothly from one side. Under the action of gravity, the large-diameter flocs with faster settling speed quickly settle to the bottom of the tank and are discharged from the bottom outlet; the unflocculated fine particles with slower settling speed remain suspended in the upper layer of the water and are discharged from the overflow outlet at the top of the tank.

[0041] The bottom outlet 21 is connected to the dewatering unit 3, and the upper overflow outlet 22 is connected to the return pipe 4. The preset sorting threshold is controlled by adjusting the hydraulic retention time of the tank: the longer the hydraulic retention time, the smaller the particle size of the settleable particles and the lower the sorting threshold; conversely, the shorter the hydraulic retention time, the higher the sorting threshold.

[0042] (III) Dehydration Unit Dewatering unit 3 can be any one or a combination of conventional sediment dewatering equipment such as geotextile bags, plate and frame filter presses, and belt filter presses. The type can be flexibly selected according to the properties of the sediment, the processing scale, and the required moisture content after dewatering.

[0043] (iv) Return pipeline and supporting equipment The return pipeline 4 is equipped with a return pump 41, a return flow regulating valve 42, and a concentration detection device 43 in sequence along the direction of mud return. The return pump 41 provides power for the return transport of unflocculated fine particles; the return flow regulating valve 42 is used to regulate the return flow. In the full return operation mode, the valve is kept fully open during normal operation and mainly undertakes the functions of system start-up and shutdown and emergency cut-off.

[0044] The concentration detection device 43 can be an online suspended solids concentration meter, an online turbidity meter, or an online sludge concentration meter, used to detect the concentration of unflocculated fine particles in the return pipe in real time. The detection data can be transmitted to the control system for dynamically adjusting the dosage of reagents in the flocculation reaction unit: when the return concentration increases, it indicates that the flocculation effect of the previous cycle may be insufficient, and the dosage of reagents should be increased accordingly; when the return concentration decreases, the dosage of reagents can be appropriately reduced to achieve on-demand dosing.

[0045] III. Complete Implementation of the System and Method Example 1: Basic Implementation Scheme of Hydrocyclone Separator and Geotextile Tube See Figure 2 This embodiment provides a complete method for sorting, recirculating, and conditioning sediment flocs. The corresponding system uses a hydrocyclone separator as the sorting unit and geotextile bags as the dewatering unit. The specific steps are as follows: (1) Flocculation Conditioning: Bottom mud with a moisture content of 85%–95% is fed into flocculation reaction unit 1 at a flow rate of 50–100 m³ / h. Polyaluminum chloride (PAC) is added at the first-stage dosing point 11 at a dosage of 5–15 mg / L (calculated as Al₂O₃). Simultaneously, the zeta potential of the mud is monitored in real time using an online zeta potential meter, and the PAC dosage is adjusted to stabilize the zeta potential within the range of -10 mV to 5 mV, thereby achieving sufficient destabilization of suspended particles. Anionic polyacrylamide (PAM) is added at the second-stage dosing point 12 at a dosage of 1–3 mg / L, causing the destabilized particles to agglomerate and form flocs through adsorption bridging. After flowing through each dosing point, the mud immediately enters a multi-stage vortex tube mixer, where the flocculant is instantly and uniformly dispersed under the controllable micro-vortex action.

[0046] (2) Floc sorting: The flocculated and conditioned slurry enters the floc sorting unit 2. In this embodiment, a hydrocyclone separator is used, with a preset cutting particle size of 74μm (corresponding to 200 mesh). Flocculated material larger than 74μm is discharged from the underflow port (first outlet 21) and sent to the dewatering unit 3; unflocculated fine particles smaller than 74μm are all discharged from the overflow pipe (second outlet 22) and enter the return pipe 4.

[0047] (3) Dewatering treatment: The flocculated material is sent into a geotextile tube (dewatering unit 3) and naturally dewatered under gravity. After dewatering, the moisture content of the material is reduced to 50% to 65%. It can be used as landscaping soil or building material raw material according to its composition test results. The tailwater is discharged or reused after subsequent treatment.

[0048] (4) Recirculation conditioning: Unflocculated fine particles are all transported back to the inlet of flocculation reaction unit 1 through recirculation pipe 4, and mixed with fresh bottom mud slurry for secondary flocculation conditioning. During system operation, unflocculated fine particles continuously undergo a cycle of sorting → recirculation → conditioning until flocs that meet the sorting threshold requirements are formed and then enter the dewatering unit.

[0049] Example 2: Sedimentation and Classification Pool Sorting Implementation Scheme The difference between this embodiment and embodiment 1 is that the floc sorting unit 2 uses a sedimentation and grading tank instead of a cyclone separator.

[0050] After flocculation and conditioning, the sludge smoothly enters the settling and classification tank, with the hydraulic retention time controlled at 5–15 minutes. The flocculated material with a faster settling velocity settles to the bottom of the tank, is discharged from the bottom outlet, and sent to the dewatering unit 3; the unflocculated fine particles with a slower settling velocity remain suspended in the upper water layer and are all discharged from the upper overflow outlet, returning to the flocculation reaction unit via the return pipe 4. In this embodiment, the sorting threshold can be dynamically controlled by adjusting the hydraulic retention time to adapt to the treatment needs of bottom sludge with different flocculation characteristics.

[0051] Example 3: Dewatering Implementation Scheme for Plate and Frame Filter Press The difference between this embodiment and embodiment 1 is that the dewatering unit 3 uses a plate and frame filter press instead of geotextile bags.

[0052] The flocculated material is pressurized and fed into a plate and frame filter press by a feed pump. It undergoes dewatering under a feed pressure of 1.0–2.0 MPa for 30–60 minutes. The moisture content of the dewatered filter cake can be reduced to 40%–50%, making it suitable for treatment scenarios requiring high moisture content after dewatering, such as sanitary landfill and incineration.

[0053] Example 4: Adaptation of operating parameters for different sediment types This embodiment matches corresponding system operating parameters for different types of sediment, illustrating that the system operating parameters can be adapted to different sediment types. The test results are shown in Table 1 below: Table 1. System operation test results under different sediment types

[0054] The experimental results show that, under the conditions listed in Table 1, the system of the present invention can be adapted to different types of sediment by adjusting the sorting threshold, with a reagent saving rate of 25% to 50%, which is superior to the traditional one-time flocculation process.

[0055] Example 5: Comparative Test with Traditional Processes To verify the technical effectiveness of this invention, parallel comparative tests were conducted using the same batch of riverbed sediment (88% water content, 18% organic matter content) and the system of this invention, employing both traditional processes (single-stage flocculation and direct entry into geotextile bags). The test results are shown in Table 2 below: Table 2 Results of parallel comparison experiments

[0056] Comparative test results show that, compared with traditional processes, the system of the present invention has improvements in terms of reagent consumption, dehydration efficiency, material quality and effluent quality, and its overall treatment performance has been enhanced.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sediment floc separation and recirculation conditioning system, characterized in that, It includes a flocculation reaction unit, a floc sorting unit, a dewatering unit, and a return pipeline; The flocculation reaction unit is used to flocculate and condition the bottom mud slurry, so that the suspended particles in the mud slurry form flocs; The floc separation unit is located downstream of the flocculation reaction unit and is connected to the outlet of the flocculation reaction unit. It is used to separate the flocculated mud into flocculated materials and unflocculated fine particles. The dewatering unit is connected to the first outlet of the floc sorting unit and is used to receive the flocculated material and perform dewatering treatment. The return pipe connects the second outlet of the floc sorting unit to the inlet of the flocculation reaction unit, and is used to transport unflocculated fine particles back to the flocculation reaction unit for secondary flocculation conditioning. The floc sorting unit uses whether the floc particle size reaches a preset particle size threshold or whether the floc settling performance reaches a preset settling performance threshold as sorting criteria; materials that reach the corresponding preset threshold are transported to the dewatering unit as flocculated materials, while fine particles that do not reach the corresponding preset threshold are returned to the flocculation reaction unit as unflocculated fine particles through the return pipe.

2. The sediment floc separation and reflux conditioning system according to claim 1, characterized in that: All the unflocculated fine particles output from the second outlet of the floc sorting unit are transported back to the flocculation reaction unit via the return pipeline, forming a closed-loop conditioning system.

3. The sediment floc separation and reflux conditioning system according to claim 1, characterized in that, The floc separation unit is selected from any one of a hydrocyclone separator, a settling and grading tank, or a vibrating screen.

4. The sediment floc separation and reflux conditioning system according to claim 3, characterized in that, The floc separation unit is a hydrocyclone separator, which includes a cylindrical body, a feed pipe tangentially connected to the cylindrical body, an overflow pipe at the top of the cylindrical body, and an underflow port at the bottom of the cylindrical body. The underflow port serves as the first outlet and is connected to the dewatering unit, while the overflow pipe serves as the second outlet and is connected to the return pipe. The preset threshold is the cutting particle size of the cyclone separator. Flocs larger than the cutting particle size are discharged from the underflow port, while unflocculated fine particles smaller than the cutting particle size are discharged from the overflow pipe.

5. The sediment floc separation and reflux conditioning system according to claim 3, characterized in that, The floc sorting unit is a sedimentation and grading tank, which sorts flocs based on the difference in sedimentation velocity using the principle of gravity sedimentation. The bottom outlet of the sedimentation and grading tank is connected to the dewatering unit as the first outlet, and the upper overflow outlet of the sedimentation and grading tank is connected to the return pipe as the second outlet. The preset threshold is controlled by adjusting the hydraulic retention time of the sedimentation and grading tank.

6. The sediment floc separation and reflux conditioning system according to claim 1, characterized in that, The return pipeline is equipped with a return pump and a return flow regulating valve.

7. The sediment floc separation and reflux conditioning system according to claim 6, characterized in that, The return pipe is also equipped with a concentration detection device to detect the return concentration of unflocculated fine particles in real time.

8. The sediment floc separation and reflux conditioning system according to claim 7, characterized in that, The concentration detection device is an online suspended solids concentration meter, an online turbidity meter, or an online sludge concentration meter.

9. The sediment floc separation and reflux conditioning system according to claim 1, characterized in that, The flocculation reaction unit includes a multi-stage dosing device and a mixing device arranged sequentially along the mud flow direction; the multi-stage dosing device includes at least two dosing points, the first dosing point is used to add an electrical neutralizing agent, and the second dosing point is used to add an adsorption bridging flocculant.

10. The sediment floc separation and reflux conditioning system according to claim 9, characterized in that, The mixing device is a multi-stage vortex tube mixer, which is used to generate micro-vortices of controllable size and intensity after each dosing point of the multi-stage dosing device, so that the flocculant is evenly dispersed in the mud.

11. A method for sorting, recirculating, and conditioning sediment flocs, characterized in that, The conditioning method is implemented using the sediment floc separation and recirculation conditioning system described in any one of claims 1-10, and includes the following steps: S1, the bottom mud slurry is sent into the flocculation reaction unit for flocculation conditioning, so that the suspended particles in the mud slurry form flocs; S2, the slurry after flocculation and conditioning is sent to the floc sorting unit, and the slurry is separated into flocculated material and unflocculated fine particles based on whether the floc particle size or floc settling performance reaches the preset threshold. S3, the flocculated material is sent to the dewatering unit for dewatering treatment; S4, the unflocculated fine particles are transported back to the flocculation reaction unit and mixed with the bottom mud slurry for secondary flocculation conditioning.

12. The sediment floc separation and recirculation conditioning method according to claim 11, characterized in that, In step S4, all the unflocculated fine particles are transported back to the flocculation reaction unit to form a closed-loop cycle of sorting, reflux, and conditioning.

13. The sediment floc separation and recirculation conditioning method according to claim 11, characterized in that, The preset threshold mentioned in step S2 is set in advance based on the flocculation characteristics of the bottom mud slurry and is dynamically adjusted by adjusting the operating parameters of the floc sorting unit.

14. The sediment floc separation and recirculation conditioning method according to claim 11, characterized in that, The flocculation conditioning described in step S1 adopts a multi-stage point dosing method. First, an electrical neutralizing agent is added to destabilize the suspended particles in the mud, and then an adsorption bridging flocculant is added to cause the destabilized particles to agglomerate and form flocs.

15. The sediment floc separation and recirculation conditioning method according to claim 14, characterized in that, The dosage of the electrical neutralizing agent is adjusted in real time according to the zeta potential of the mud, so that the zeta potential of the mud is controlled within the range of -10mV to 5mV; the dosage of the adsorption bridging flocculant is adjusted in real time according to the suspended solids concentration of the mud.

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