Sludge treatment system for water conservancy project

Abstract

The invention discloses a sludge treatment system for hydraulic engineering, and relates to the technical field of sludge dewatering. The system comprises a pretreatment unit, a mechanical dehydration unit and a low-temperature drying unit. The mechanical dehydration unit comprises an anode filter plate, an insulating filter plate and a cathode filter plate which are alternately arranged, the working surfaces of the anode filter plate and the cathode filter plate are covered with elastic conductive diaphragms, and ultrasonic transducers are embedded in the working surfaces of the anode filter plate and the cathode filter plate. An ultrasonic field, a direct-current electric field and a mechanical squeezing field are synchronized in the filter chamber, so that a deep synergistic dehydration effect is generated. Superposed ultrasonic waves can effectively destroy a particle polarization agglomeration structure caused by a direct-current electric field, densification and blockage of a filter cake layer are prevented, and the dehydration efficiency of the electric field is maintained; meanwhile, ultrasonic cavitation and electroosmotic flow synergistically improve the moisture migration rate, and are compounded with mechanical squeezing to form a dynamic drainage micro-channel. According to the system, the water content of the sludge can be further reduced to be lower than 45% with lower energy consumption, and the core problem of filter cake blockage in electroosmosis dehydration application is solved.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology for water conservancy projects, and in particular to a sludge treatment system for water conservancy projects. Background Technology

[0002] During the construction of water conservancy projects and the dredging of rivers and reservoirs, a large amount of sludge with high water content is generated. This type of sludge typically has a water content as high as 95%-98% and is bulky. If it is directly piled up or landfilled, it will not only occupy a large amount of land resources, but also easily cause secondary pollution, posing a serious threat to the ecological environment. Therefore, the reduction and harmless treatment of sludge is a key link in the environmental protection management of water conservancy projects.

[0003] In existing sludge treatment technologies for water conservancy projects, mechanical dewatering is the core means to achieve sludge reduction. Common equipment includes screw presses, plate and frame filter presses, and diaphragm filter presses. However, traditional mechanical dewatering equipment generally has the following drawbacks: First, insufficient dewatering depth; the moisture content of the treated sludge cake is mostly between 65% and 70%, requiring further drying and resulting in high subsequent processing costs. Second, low dewatering efficiency; the sludge has a stable colloidal structure, with water molecules tightly bound to sludge particles, making it difficult to quickly separate water using simple mechanical pressing. Third, the equipment is prone to clogging and has high maintenance costs; during dewatering, sludge easily adheres to the surface of the filter cloth or filter plate, leading to poor filtrate flow and requiring frequent cleaning, affecting continuous operation efficiency. Fourth, difficulty in sludge cake removal; after dewatering, the sludge cake adheres severely to the filter plate / filter cloth, making the unloading process cumbersome and further reducing treatment efficiency.

[0004] To address the aforementioned issues, existing technologies have developed synergistic treatment schemes combining mechanical pressing with electric field dewatering. These schemes utilize the electric field to break down the colloidal double layer of sludge, accelerating water molecule migration and increasing dewatering depth. However, these schemes still have shortcomings: firstly, uneven electric field distribution and insufficient contact between the electrodes and sludge lead to unstable dewatering effects; secondly, sludge particles easily aggregate to form a dense filter cake layer, hindering water penetration and limiting further improvements in dewatering efficiency.

[0005] Therefore, there is an urgent need for a sludge treatment system for water conservancy projects that combines deep dewatering, high efficiency, stable operation, and strong safety to overcome the many shortcomings of existing technologies. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, a sludge treatment system for water conservancy projects is provided. This system, through innovative structural design, organically integrates three dewatering mechanisms: ultrasonic cavitation, DC electric field electroosmosis, and diaphragm mechanical pressing. This achieves synergistic and synchronous action of the three fields, aiming to significantly improve dewatering efficiency and limits, reduce energy consumption and maintenance costs, and solve the problems of electrode contamination and ultrasonic integration.

[0007] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A sludge treatment system for water conservancy projects includes an installation frame. The lower part of the installation frame is provided with a pretreatment unit and a low-temperature drying unit. The system is characterized in that the upper part of the installation frame is also provided with a mechanical dewatering unit, and the pretreatment unit, the mechanical dewatering unit, and the low-temperature drying unit are connected in series through a sludge conveying pipeline.

[0008] The mechanical dewatering unit includes a support frame on which multiple sets of filter plate units arranged horizontally are fixed, and a hydraulic mechanism is disposed at one end of each filter plate unit. Each filter plate unit includes, in sequence along the material flow direction, an anode filter plate, an insulating filter plate, and a cathode filter plate. The side of the anode filter plate facing the insulating filter plate and the side of the cathode filter plate facing the insulating filter plate are both working surfaces, and both working surfaces are covered with an elastic conductive diaphragm. Multiple sets of piezoelectric ceramic ultrasonic transducers are embedded inside both the anode and cathode filter plates.

[0009] Preferably, the anode filter plate has a double-layer cavity sealed structure, with a water-pressing cavity formed between the outer cavity and the elastic conductive diaphragm. An ultrasonic mounting cavity is provided on the side of the anode filter plate away from the working surface, and the piezoelectric ceramic ultrasonic transducer is fixedly embedded in the ultrasonic mounting cavity.

[0010] Preferably, both the anode and cathode filter plates are made of titanium alloy, and both working surfaces are coated with a ruthenium-iridium conductive coating. Titanium alloy has high strength and corrosion resistance, while the ruthenium-iridium coating provides excellent conductivity and electrochemical stability.

[0011] Preferably, the output end of the hydraulic mechanism is fixedly connected to the end of the filter plate unit, and is used to drive multiple filter plate units to merge or separate synchronously.

[0012] Preferably, the elastic conductive diaphragm is made of carbon fiber reinforced polyurethane, with micron-sized protrusions pressed onto its surface. The carbon fiber imparts good conductivity to the diaphragm, the polyurethane substrate ensures elasticity and durability, and the surface protrusions help form micro-gaps with the filter cloth, facilitating the discharge of filtrate. The edges of the elastic conductive diaphragm are fixed to the electrode plate by sealing rings, ensuring reliable electrical contact and preventing leakage.

[0013] Preferably, both the anode filter plate and the cathode filter plate are provided with high-pressure water inlets on their sides that are connected to the pressing water chamber, and the high-pressure water inlets are connected to the hydraulic water supply system through insulated pipelines.

[0014] Preferably, both the anode filter plate and the cathode filter plate are covered with an insulating shell to ensure operational safety.

[0015] Preferably, the filter plate unit has a squeeze outlet at the bottom of its side, and a collection trough at the bottom of the squeeze outlet for collecting the filtrate.

[0016] Furthermore, the system also includes a low-voltage DC power supply and a control system. The positive and negative terminals of the low-voltage DC power supply are electrically connected to the anode filter plate and the cathode filter plate through conductive busbars, respectively. The piezoelectric ceramic ultrasonic transducer and the hydraulic mechanism are both electrically connected to the control system.

[0017] (III) Beneficial Effects The present invention aims to provide a sludge treatment system for water conservancy projects, which has the following significant advantages: First, the vibrational field of ultrasonic cavitation is deeply coupled with the DC electric field and the mechanical pressing field in a diaphragm filter press. While each field effect functions independently, they produce a synergistic effect that addresses key technological bottlenecks. Specifically: When an ultrasonic field acts alone, it can cavitate and break up flocs, aiding in dehydration. When a DC electric field acts alone, it can induce electroosmosis to drive the directional migration of water, but it can also cause particle polarization and agglomeration, leading to rapid densification of the filter cake layer and a sharp drop in dehydration efficiency. This invention superimposes an ultrasonic field onto a DC electric field. The ultrasonic vibration directly destroys the particle polarization and agglomeration structure induced by the electric field. While maintaining the high efficiency of the electric field in driving water, it effectively prevents the densification and clogging of the filter cake layer, allowing the electric field dehydration efficiency to be sustained.

[0018] Furthermore, the cavitation microjets effect of ultrasound accelerates the detachment of water molecules from the particle surface, which, combined with the directional electroosmotic force of the electric field, forms a synergistic mode of first stripping and then directional driving, increasing the overall migration rate of water molecules by more than 30%. In addition, the superposition of ultrasonic vibration and periodic mechanical pressing creates a combined effect of pressure and vibration, which can dynamically generate and refresh micropores inside the filter cake, creating a continuous and efficient channel for filtrate discharge.

[0019] By achieving three-field synchronization through an integrated structure, this system breaks through the dewatering limit of single or dual-field technologies with lower energy consumption, and can reduce the sludge moisture content to below 45% in one step, solving the core problem of filter cake clogging in electro-osmosis applications. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall sludge treatment system for water conservancy projects according to the present invention; Figure 2 This is a schematic diagram of a mechanical dewatering unit in a sludge treatment system for water conservancy projects according to the present invention; Figure 3 This is a schematic diagram of a filter plate unit in a sludge treatment system for water conservancy projects according to the present invention; Figure 4This is an exploded schematic diagram of a filter plate unit in a sludge treatment system for water conservancy projects according to the present invention. Figure 5 This is a schematic diagram of a single set of anode filter plates in a sludge treatment system for water conservancy projects according to the present invention; Figure 6 This is a cross-sectional view of a single set of anode filter plates in an expanded state in a sludge treatment system for water conservancy projects according to the present invention. In the diagram: 1. Mounting frame; 2. Pretreatment unit; 3. Low-temperature drying unit; 4. Mechanical dehydration unit; 41. Support frame; 42. Filter plate unit; 43. Hydraulic mechanism; 421. Anode filter plate; 4211. Pressing water chamber; 4212. Ultrasonic mounting chamber; 422. Cathode filter plate; 423. Insulating filter plate; 424. Elastic conductive diaphragm; 425. Piezoelectric ceramic ultrasonic transducer; 426. High-pressure water inlet; 427. Extrusion outlet; 428. Collection tank; 429. Insulating shell. Detailed Implementation

[0021] The following will refer to the appendix in the examples of this invention. Figure 1-6 The figures provide a clear and complete description of the technical solutions in the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] Example 1: The structure and working process of a sludge treatment system for water conservancy projects.

[0023] Please see Figures 1 to 6 This embodiment provides a specific structure and standard operation mode of a sludge treatment system for water conservancy projects.

[0024] like Figure 1 As shown, the system is mainly supported by a steel structure mounting frame 1. From left to right, a pretreatment unit 2 and a low-temperature drying unit 3 are fixed to the lower platform of the mounting frame 1. The pretreatment unit 2 is a cylindrical conditioning tank with a jacket and stirring device, with a volume of 5 cubic meters. The low-temperature drying unit 3 is a closed-loop heat pump low-temperature dryer with a processing capacity of 1.0 ton / hour and an operating temperature range of 40-60℃. The mechanical dewatering unit 4 is fixedly installed on the upper platform of the mounting frame 1. The discharge port of the pretreatment unit 2 is connected to the top inlet of the mechanical dewatering unit 4 via a sludge screw pump and pipeline; the bottom discharge port of the mechanical dewatering unit 4 is connected to the feed hopper of the low-temperature drying unit 3, thus forming a continuous sludge treatment production line.

[0025] The mechanical dewatering unit 4 includes a support frame 41, which is welded from structural steel and has a high load-bearing capacity. Multiple sets of filter plate units 42 arranged horizontally are fixed on the support frame 41. The number of filter plate units 42 is 20-30 sets, which can be adjusted according to the processing capacity requirements. A hydraulic mechanism 43 is fixed to one end of the support frame 41 by bolts. The output end of the hydraulic mechanism 43 is fixedly connected to the end of the filter plate unit 42. The hydraulic mechanism 43 is a plunger-type hydraulic cylinder with an output pressure range of 0.3-3.0MPa, which is used to drive multiple sets of filter plate units 42 to merge or separate synchronously.

[0026] Each filter plate unit 42 is a basic unit that constitutes the filtration and dewatering function, and includes, in sequence along the material flow direction: an anode filter plate 421, an insulating filter plate 423, and a cathode filter plate 422.

[0027] The insulating filter plate 423 is made of high-strength polypropylene (PP) through a one-time injection molding process. Its structural feature is a 120mm diameter circular feed hole at the center of the plate. When all filter plates are pressed together, the feed holes align to form a continuous feed channel. The two sides of the plate are concave, forming a 30mm deep chamber. This chamber, together with the working surfaces of the adjacent anode filter plate 421 or cathode filter plate 422, forms a filter chamber for containing sludge. The bottom of the insulating filter plate 423 has drainage channels communicating with the chambers. These channels ultimately converge to the extrusion outlet 427 located at the bottom of the filter plate's side. The insulating filter plate 423 serves two core functions: firstly, it constitutes the physical filter chamber space; secondly, it completely isolates adjacent anode filter plates 421 and cathode filter plates 422 electrically, preventing short circuits in the DC electric field.

[0028] The anode filter plate 421 and the cathode filter plate 422 are mirror images of each other in mechanical structure, only opposite in electrical polarity. The anode filter plate 421 will be described in detail below as an example: The substrate is made of titanium alloy through precision casting and CNC milling, and its dimensions are consistent with those of a standard diaphragm filter plate. On one side, which serves as the working surface, a layer of conductive composite oxide coating composed of RuO2 and IrO2 is uniformly sprayed using an atmospheric plasma spraying process, with the coating thickness controlled at 60±5μm. This coating provides extremely low surface resistivity and excellent electrochemical catalytic stability.

[0029] like Figure 5 and Figure 6 As shown, the anode filter plate 421 is designed with a double-layer cavity structure. (Including...) The pressing water chamber 4211 is located on the side of the filter plate near the working surface. It is a sealed cavity formed by the titanium substrate body and the elastic conductive diaphragm 424 covering it. This cavity is connected to the external high-pressure water supply pipeline through two high-pressure water inlets 426 located on the side of the filter plate.

[0030] Ultrasonic mounting cavity 4212: Located inside the filter plate on the side away from the working surface, it consists of four circumferentially evenly distributed cylindrical blind holes machined into the back of the titanium substrate. Within each ultrasonic mounting cavity 4212, a sandwich-type piezoelectric ceramic ultrasonic transducer 425 with a frequency of 40kHz and a rated power of 150W is fixedly mounted using high-temperature resistant, high-adhesion epoxy conductive adhesive. The radiating surface of the transducer 425 faces the water-pressing chamber 4211, separated from it by an 8mm thick titanium alloy plate wall. The power supply and signal wires of the transducer are led out through a seal at the top of the cavity. Except for the working surface, all other outer surfaces of the anode filter plate 421 are completely covered by an insulating shell 428 made of injection-molded polypropylene, ensuring operational safety and preventing accidental electrical short circuits.

[0031] like Figure 4 and Figure 5 As shown, the working surfaces of the anode filter plate 421 and the cathode filter plate 422 are covered with an elastic conductive diaphragm 424, which is a functional composite material component. Its matrix material is a polyurethane (PU) elastomer with 20 wt% chopped carbon fibers and 5 wt% conductive carbon black added, formed by hot vulcanization in a mold, with a thickness of 6 ± 0.2 mm. Due to the uniform dispersion of carbon fibers and carbon black, its volume resistivity is approximately 10 Ω·cm, enabling it to serve as a highly efficient ion current conduction medium between the electrode plates and the sludge. Furthermore, the working surface of the elastic conductive diaphragm 424 facing the filter chamber has a pre-set array of micro-bumps on the mold, resulting in regularly distributed micron-sized bumps on the surface of the finished diaphragm with a height of approximately 100 μm, a bottom diameter of approximately 200 μm, and a center-to-center spacing of approximately 500 μm. These bumps effectively form microscopic drainage channels when the diaphragm presses against the filter cloth, preventing the formation of a water-blocking film at the interface of the filtrate and greatly optimizing the filtrate discharge efficiency.

[0032] Finally, the elastic conductive diaphragm 424 is tightly pressed onto the working surface frame of the anode filter plate 421 by a stainless steel annular sealing ring. Conductive silicone grease is applied to the pressing interface to ensure extremely low contact resistance and long-term stable electrical connection, while achieving a reliable dynamic seal for the pressing water chamber 4211.

[0033] All anode filter plates 421 are connected in parallel to a positive conductive bus via flexible copper braided tape. This bus is ultimately connected to the positive output terminal of a programmable low-voltage, high-current DC power supply. Similarly, all cathode filter plates 422 are connected in parallel to the negative terminal of the power supply. The output voltage of this DC power supply is continuously adjustable within the range of 0-60V DC, and the maximum output current capability is 500A.

[0034] The filter plate unit 42 is provided with a squeeze outlet 427 on the side bottom, and a collection tank 429 is welded to the bottom of the squeeze outlet 427; the bottom of the working surface of the anode filter plate 421 and the cathode filter plate 422 is provided with a guide channel, and the outlet of the guide channel is connected to the squeeze outlet 427. The filtrate generated by dehydration flows into the squeeze outlet 427 through the guide channel and finally collects into the collection tank 429.

[0035] The workflow is as follows: S1 Pretreatment: The sludge enters the pretreatment unit 2, where 0.2% polyaluminum chloride (PAC) is added for conditioning. At the same time, the recovered waste heat is used to uniformly preheat the sludge to 38°C.

[0036] S2 Feeding and Compacting: The PLC-controlled hydraulic mechanism 43 drives all 25 filter plate units 42 to compact to 15MPa. The preheated and conditioned sludge is pumped into each filter chamber through the central feed channel by a high-pressure pump until the feed pressure reaches 1.0MPa, indicating that the filter chamber is full.

[0037] S3 Co-dehydration: The control system issues the following command: S31. Start the high-pressure water pump and inject deionized water at a pressure of 2.5MPa into the pressing water chambers 4211 of all anode and cathode filter plates, driving the elastic conductive diaphragm 424 to expand and apply uniform mechanical squeezing force to the sludge in the filter chamber.

[0038] S32. Start the low-voltage DC power supply and apply a stable DC voltage of 30V between all adjacent anode filter plates 421 and cathode filter plates 422 to establish a uniform electric field perpendicular to the plane of the filter plates.

[0039] S33. Start the ultrasonic controller to drive all transducers 425 to emit ultrasonic waves at a center frequency of 40kHz, a power of 150W, and a pulse mode of "2 seconds of operation followed by 1 second of rest". The ultrasonic waves are conducted through the titanium plate, through the squeezed water medium and the elastic conductive diaphragm 424, and finally act on the sludge layer.

[0040] The above workflow lasts for 15 minutes. During this period, the control system monitors the total current and filtrate flow rate in real time.

[0041] S4 Unloading and Final Drying: At the end of the dewatering stage, the ultrasonic and electric fields are sequentially shut off, releasing the pressure in the pressing water chamber. The hydraulic mechanism 43 moves in the reverse direction, sequentially pulling open the filter plates. The dewatered mud cake automatically falls onto the scraper conveyor and is sent to the low-temperature drying unit 3, where it is further dried at 50°C to a moisture content of approximately 20% before being packaged and discharged.

[0042] Treatment results: After treatment by mechanical dewatering unit 4, the average moisture content of the resulting sludge cake was 43.5%. The overall energy consumption of the system for treating this sludge (including pretreatment, three-stage synergistic dewatering, and low-temperature drying) was calculated to be approximately 88 kWh / ton of dry sludge.

[0043] Comparative Example 1: Traditional mechanical pressing and dehydration To highlight the advantages of this invention, a comparative example is provided. A conventional diaphragm filter press is used, with a filter plate having a structure similar to the insulated filter plate 423 in this invention (without electrode function and ultrasonic integration), and other peripheral conditions (such as pretreatment, feeding method, etc.) are consistent with those in Example 1.

[0044] Dehydration parameters: Mechanical pressing only, pressing pressure of 2.5 MPa, and holding pressure pressing time of 15 minutes.

[0045] Treatment results: The average moisture content of the treated sludge cake reached 69.2%. The filtrate outflow rate was extremely slow in the later stages of dewatering, and the sludge cake observed after unloading showed a dense and hard structure. This result clearly demonstrates that simple mechanical pressing has limited dewatering depth for highly viscous hydraulic sludge.

[0046] Comparative Example 2: Mechanical pressing and DC electric field dual-field dehydration To verify the crucial role of ultrasound in mitigating the side effects of electric fields, this comparative example was set up. A filter press was used, whose filter plates had the same electrode structure as those of this invention (i.e., anode filter plate 421 and cathode filter plate 422, with ruthenium-iridium coating and elastic conductive diaphragm 424), but no ultrasonic transducers were integrated inside the filter plates. The operating parameters were exactly the same as those for the electric field and mechanical pressing sections in Example 1.

[0047] Treatment Results: The average moisture content of the treated filter cake was 53.1%, significantly higher than that of Examples 1 and 2. Process monitoring showed that approximately 7 minutes after the start of electro-dehydration, the filtrate flow rate decreased significantly, and the loop current also slowly decreased from approximately 420A to approximately 300A. After dehydration, the filter plates were disassembled and inspected. It was found that the filter cake layer near the anode filter plate surface was abnormally dense, smooth, and tightly adhered to the diaphragm, forming a typical polarized dense layer of electro-osmotic filter cake. This phenomenon is a common bottleneck in electric field dehydration technology, which greatly increases the resistance to water migration, causing the dehydration efficiency to decrease during the process and ultimately limiting the dehydration limit.

[0048] Comparative Example 3: Mechanical pressing combined with external ultrasonic dual-field dehydration To illustrate the importance of the integrated ultrasonic structure of this invention, a comparative example is provided. A conventional diaphragm filter press is used, but high-power ultrasonic transducers are installed on both sides of the filter plate assembly to attempt to apply an ultrasonic field from the outside. The mechanical pressing parameters are the same as in Example 1, and the ultrasonic parameters (frequency, power, time) are simulated as much as possible.

[0049] Treatment effect: The average moisture content of the treated sludge cake was 59.7%. Although this is better than pure mechanical pressing (Comparative Example 1), it is far inferior to that of the present invention. The reason for this is that the externally applied ultrasonic waves suffer severe energy attenuation after penetrating the filter press frame and multiple filter plates, and it is difficult to act evenly on the sludge layer in the center of each filter chamber. The sound field intensity and efficiency cannot be guaranteed, thus limiting the synergistic effect.

[0050] in conclusion: The "ultrasonic field, DC electric field, and mechanical pressing field" three-field synchronous deep synergistic dewatering technology solution provided by this invention can reduce the sludge moisture content to about 42%-44% in one step, which significantly surpasses the effects of single mechanical pressing, mechanical and electric field synergy, and mechanical and external ultrasonic field synergy.

[0051] The results of Comparative Example 2 directly verify the core technical problem that this invention aims to solve: In the dual-field dewatering process involving both mechanical and electric fields, the DC electric field induces polarization and aggregation of sludge particles, thereby forming a dense, high-resistivity filter cake layer on the electrode surface—this is the phenomenon of "filter cake polarization clogging." This phenomenon hinders the continuous dewatering process and is a key bottleneck limiting the efficiency and depth of electroosmotic dewatering technology. This application, by simultaneously applying an ultrasonic field and an electric field, utilizes the mechanical force generated by ultrasonic vibration to directly destroy this polarization and aggregation structure, effectively preventing premature densification of the filter cake layer, thus maintaining the durability of the electric field dewatering efficiency and breaking through the dewatering limit.

[0052] The differences between Comparative Example 3 and the embodiments of the present invention highlight the superiority of the integrated structural design of the present invention, which embeds the ultrasonic transducer inside the electrode filter plate. This design ensures that ultrasonic energy can be efficiently, directly, and uniformly transmitted to the sludge layer in each filter chamber, achieving precise overlap and efficient coupling of the three fields in space and on the action surface. This is unmatched by external ultrasonic solutions and is the key structural guarantee for achieving the aforementioned excellent synergistic effect.

[0053] In summary, this invention, through its innovative principle of synergistic interaction of acoustic, electrical, and mechanical fields and integrated structure, particularly by utilizing synchronous ultrasonic waves, solves the problem of filter cake polarization clogging in electroosmotic dehydration, demonstrating outstanding substantive features and significant progress.

[0054] 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. A sludge treatment system for water conservancy projects, comprising a mounting frame (1), wherein the lower part of the mounting frame (1) is provided with a pretreatment unit (2) and a low-temperature drying unit (3), characterized in that, The upper part of the mounting frame (1) is also provided with a mechanical dewatering unit (4), and the pretreatment unit (2), the mechanical dewatering unit (4), and the low temperature drying unit (3) are connected in series through the sludge conveying pipeline. The mechanical dewatering unit (4) includes a support frame (41), on which multiple sets of filter plate units (42) arranged in a horizontal direction are fixed, and a hydraulic mechanism (43) is provided at one end of the filter plate unit (42). The filter plate unit (42) includes an anode filter plate (421), an insulating filter plate (423), and a cathode filter plate (422) in sequence along the material flow direction. The side of the anode filter plate (421) facing the insulating filter plate (423) and the side of the cathode filter plate (422) facing the insulating filter plate (423) are both working surfaces. Both working surfaces are covered with an elastic conductive diaphragm (424). Multiple sets of piezoelectric ceramic ultrasonic transducers (425) are embedded inside the anode filter plate (421) and the cathode filter plate (422).

2. The sludge treatment system for water conservancy projects according to claim 1, characterized in that, The anode filter plate (421) has a double-layer cavity sealed structure. The outer cavity and the elastic conductive diaphragm (424) form a water pressing cavity (4211). The anode filter plate (421) has an ultrasonic mounting cavity (4212) on the side away from the working surface. The piezoelectric ceramic ultrasonic transducer (425) is fixedly embedded in the ultrasonic mounting cavity (4212).

3. The sludge treatment system for water conservancy projects according to claim 1, characterized in that, The substrates of the anode filter plate (421) and the cathode filter plate (422) are both titanium alloys, and both working surfaces are coated with a ruthenium-iridium conductive coating.

4. The sludge treatment system for water conservancy projects according to claim 1, characterized in that, The output end of the hydraulic mechanism (43) is fixedly connected to the end of the filter plate unit (42) to drive multiple filter plate units (42) to merge or separate synchronously.

5. A sludge treatment system for water conservancy projects according to claim 1, characterized in that, The elastic conductive diaphragm (424) is made of carbon fiber reinforced polyurethane, and its surface is pressed with micron-level protrusions. The edge of the elastic conductive diaphragm (424) is fixed to the electrode plate by a sealing ring.

6. A sludge treatment system for water conservancy projects according to claim 1, characterized in that, Both the anode filter plate (421) and the cathode filter plate (422) are provided with high-pressure water inlets (426) that are connected to the pressing water chamber (4211) on their sides. The high-pressure water inlets (426) are connected to the hydraulic water supply system through an insulated pipeline.

7. A sludge treatment system for water conservancy projects according to claim 1, characterized in that, Both the anode filter plate (421) and the cathode filter plate (422) are covered with an insulating shell (428).

8. A sludge treatment system for water conservancy projects according to claim 1, characterized in that, The filter plate unit (42) has a squeeze outlet (427) at the bottom of its side, and a collection trough (428) is provided at the bottom of the squeeze outlet (427).

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