A method for dredging river sediments and simultaneously extracting organic carbon sources in situ

Abstract

To provide a treatment method capable of extracting an organic carbon source and recycling the organic carbon source on the site, concurrently with the dredging of river bottom mud.SOLUTION: Slurry dredged from river bottom sludge is continuously sent into a screening unit using a mud suction device. The slurry having been subjected to the screening treatment is fed into a high-speed agitation device to physically separate organic components and inorganic components present in the bottom sludge. The mixed slurry discharged from the high-speed agitation device is sent to a centrifugal unit. Substances each having a different specific gravity are continuously made to form layers in the vertical direction, by the swirl flow centrifugal action of the centrifugal unit, and a liquid of a high concentration of organic substances is discharged to a municipal sewage inspection well located nearby.EFFECT: The method enhances the self-cleaning capability of a water area, increases the concentration of organic substances in the water flowing into a sewage disposal plant, decreases the risk of malodor in the water area and decreases the amount of greenhouse effect gas to be discharged, does not require chemicals to be fed into the process, and contributes to the development of greening initiatives and low-carbon initiatives of the industry.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of urban drainage and wastewater treatment technology, and more particularly to a method for dredging river sediments and simultaneously extracting organic carbon sources in situ. [Background technology]

[0002] The inflow of pollutants from direct discharge of domestic wastewater, sewage runoff during the dry season, and overflow pollution from rainfall into rivers, resulting in their deposition and the occurrence of anaerobic black color and foul odors, is a difficult water environment management issue that many cities will have to face in the long term. The deposition of bottom sludge and foul odors caused by pollutants entering rivers requires regular dredging to maintain the water quality in the long term, and is also a serious cause of the generation and emission of non-carbon dioxide greenhouse gases such as CH4.

[0003] Traditional river dredging often involves wastewater dredging, which not only damages the water's ecological environment but also impacts the function and structural safety of pollution control box culverts, roads, buildings, and other urban infrastructure along the waterway. Dredging also generates large amounts of sediment with a relatively high water content, necessitating the construction of additional sediment dredging sites, sediment transport channels, and temporary storage areas, as well as the need for on-site dewatering procedures. Furthermore, the sediment treatment outlet must be determined in advance, and the related management regulations and requirements are cumbersome and complex. The dredging process is characterized by a large amount of work, high costs, and time.

[0004] Research and analysis have shown that the volatile matter content of polluted river sediments in many cities is over 10% (VSS / SS), with some reaching 20%-30%. Anaerobic reactions in sediments rich in surface organic pollutants are the main cause of odorous water. Removing the organic matter from sediments can address this issue. Meanwhile, discharging large amounts of organic matter from polluted sediments into sewer pipes and then discharging them into municipal wastewater treatment plants can increase the organic matter concentration in the influent and improve biological treatment efficiency. Therefore, simultaneous sediment dredging and organic carbon source extraction not only solves practical challenges associated with conventional sediment dredging, such as the large amount of work required and the high treatment pressure, but also has a positive effect on the self-purification capacity of water bodies, reducing the risk of increased organic matter (COD, BOD5) concentrations in the influent of wastewater treatment plants, reducing the risk of water pollution and bromide, and reducing the production and emission of non-carbon dioxide greenhouse gases.

[0005] Therefore, it is urgent to develop and develop methods for extracting organic carbon sources while dredging river bottom sediments. This will innovate river dredging, management, resource utilization, and utilization methods, improve the self-purification ability of water bodies and the operating efficiency of sewage treatment systems, and is of great significance in supporting the green, low-carbon, and high-quality development of the wastewater industry.

[0006] Compared with related patents, Chinese invention patent CN201811611507.5, "Bottom Sediment Dissolution Vessel for Dredging the Bottom of Water Bodies," provides a ship-mounted bottom sediment dissolution device whose overall structure includes a hinged suction head, a ship-mounted sludge conditioning system, a screw pump, and a ship-mounted rotary filter press. The device only uses a hinged suction head to suck up bottom sediment, then performs dewatering processes such as sludge removal, compression, and sedimentation. It does not have the functions of carbon source extraction or organic / inorganic separation, and both the overall structure and the overall structure are significantly different from those of this patent. Chinese invention patent CN202110154231.8, "Multi-Chamber Centrifugal Bottom Sediment Dissolution Purification Platform," provides a multi-chamber centrifugal bottom sediment dissolution purification platform including a movable platform body on the water surface. This device mainly uses a visualization unit and an intelligent control unit to separate bottom sediment into solids and liquids, and then reduces nitrogen pollution in the separated wastewater. Its main function is significantly different from that of this patent, and the main structure and purpose of the centrifugal device are also different from those of this patent. Summary of the Invention

[0007] The present invention overcomes the shortcomings of conventional techniques and aims to provide a method for simultaneously dredging river sediment and extracting organic carbon sources in situ. This method is particularly suitable for dredging river sediment, which is currently carried out regularly in most Chinese cities to eliminate water odors and maintain water quality. The present invention achieves rapid removal of organic contaminants from the sediment during dredging and simultaneous on-site resource utilization, effectively resolving the practical issues of traditional rivers, such as the large volume of dredging work and the difficulty of treating and disposing of the dredged sediment. This method improves the self-purification capacity of water bodies and the concentration of organic matter (COD, BOD5) flowing into sewage treatment plants, reducing the risk of water odors and greenhouse gas emissions, eliminating the need for chemicals during the process and contributing to the green, low-carbon development of the industry.

[0008] To achieve the above technical objectives, the technical solution adopted in the embodiments of the present invention is a method for dredging river bottom sediment and simultaneously extracting organic carbon sources in situ, which includes the following steps: In step S1, a mud suction device is used to continuously pump slurry dredged from the bottom of the river into a screening unit. In step S2, the sieved slurry is fed into a frequency conversion high-speed mixer by gravity or pressure, and rapidly mixed at a mixing speed exceeding 200 r / min, during which the organic matter is separated from the inorganic particles and placed in the liquid phase. In step S3, the organic / inorganic mixed liquid discharged from the high-speed agitator is transferred to a centrifugal unit by a slurry transfer pump. In step S4, the swirl flow centrifugal action of the centrifugal unit continuously stratifies materials having different specific gravities into upper and lower layers. In step S5, the high organic matter concentration mixed liquid with a specific gravity of <1 that flows out from the middle and upper outlets of the centrifugal unit is discharged via a conveying pipeline near the municipal sewage inspection well, and is continuously flowed into the town's sewage treatment plant together with the sewage for recycling. The sludge with a specific gravity >1 at the bottom, which is mainly composed of inorganic inactive components, is discharged into a sludge bucket by the action of the centrifugal force of the swirling flow and gravity, and is used to maintain the river bottom and slopes after dredging.

[0009] Furthermore, the water content of the slurry entering the sieving unit is more than 90%, and the hole diameter of the lattice plate of the sieving unit is in the range of 0.2 to 5 mm.

[0010] Furthermore, the inorganic particulate matter including gravel separated by the screening unit is used on the spot for maintenance of rivers and slopes.

[0011] Furthermore, the mixing strength and retention time of the high-speed mixing device are determined according to the separation characteristics of organic and inorganic substances in the dredged slurry, and the apparent flow velocity in the tangential direction is 0.2 m / s or more, the hydraulic retention time is 30 s or more, and the maximum water power The residence time is 2 minutes or less.

[0012] Furthermore, a low-speed stirring paddle is provided inside the centrifugal unit, a sludge bucket is provided at the bottom, and a high organic matter concentration mixed liquid discharge outlet is provided at a height of 1 / 2 to 2 / 3.

[0013] Furthermore, the slurry transfer pump sends the slurry mixture to the centrifugal unit in a tangential direction at a tangential angle of 20° to 45°, and the slurry mixture is turned into a swirling flow by low-speed stirring at less than 50 r / min. The low-speed swirling flow causes the slurry mixture to be centrifuged, collecting the organic component-based slurry mixture with a specific gravity <1 in the upper and middle parts of the centrifugal unit, while the inorganic inactive components with a specific gravity >1 are settled in the sludge bucket at the bottom of the centrifugal unit by centrifugal force and gravity, eliminating the need for chemicals during the process.

[0014] Furthermore, the sieving unit, high-speed stirring device and centrifugal unit may be provided as separate structures or as a combined structure, as required.

[0015] Furthermore, the high organic matter concentration mixed solution obtained by extraction has a VSS / SS ratio of 0.5 or more, and can be used as a carbon source for biological treatment in urban sewage treatment plants.

[0016] Compared with the prior art, the technical solutions of the embodiments of the present invention have the following beneficial effects: 1. This invention uses physical separation methods to rapidly remove organic pollutants from river bottom sediments, and directly connects them to the urban sewer network through an organic discharge pipeline, while simultaneously realizing the local reuse of the removed organic matter as a resource. This effectively solves multiple problems, such as the large treatment pressure of traditional dredged river bottom sediments, the lack of biological carbon sources in sewage treatment plants, and the generation and emission of foul odors and greenhouse gases in water bodies. 2. Compared with the existing traditional river bottom sludge dredging treatment method, this invention changes the river dredging method that required all the malodorous river bottom sludge to be removed and then sent out for treatment and disposal by simultaneously treating the dredged bottom sludge on site and utilizing it as a resource, thereby saving the costs of dewatering, transportation, stacking, treatment and disposal. 3. The innovation of this invention uses organic pollutants in bottom sediments as a carbon source for biological treatment, suppressing odors in water bodies and reducing carbon emissions from water bodies. At the same time, it effectively increases the organic matter concentration in the water entering the sewage treatment plant, improving the effectiveness of biological treatment, and has the advantages of being green, low-carbon, and highly efficient. 4. The present invention is highly accurate, practical and easy to operate, and can provide a new model for dredging river bottom sediment and recycling it at the same time, which is of great practical significance for the green, low-carbon and high-quality development of China's urban drainage industry. 5. This invention simultaneously recycles resources during the rapid removal of organic pollutants from river bottom sludge, effectively solving practical problems such as the large volume of traditional river dredging processes and the difficulty of treating and disposing of dredged bottom sludge. It can significantly improve the self-purification ability of water bodies and the organic matter concentration in the water entering sewage treatment plants, reduce the risk of odor in water bodies and the production and emission of greenhouse gases, and eliminate the need for chemicals during the process, contributing to the green and low-carbon development of the industry. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing the process of dredging river bottom sediment and simultaneously extracting organic carbon sources in situ according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] This method involves dredging river sediments and simultaneously extracting organic carbon sources in situ, and involves the following steps: In step S1, a mud suction device is used to continuously pump slurry dredged from the bottom of the river into a screening unit. The water content of the slurry entering the sieving unit is over 90%, and the pore size of the lattice plate of the sieving unit is in the range of 0.2 to 5 mm. The inorganic particulate matter including gravel separated by the sieving unit is used on-site for maintenance of rivers and slopes. In step S2, the sieved slurry is fed into a frequency conversion high-speed mixer by gravity or pressure, and rapidly mixed at a mixing speed exceeding 200 r / min, during which the organic matter is separated from the inorganic particles and placed in the liquid phase. The mixing strength and retention time of the high-speed mixing device are determined according to the separation characteristics of organic and inorganic substances in the dredged slurry, and the apparent flow velocity in the tangential direction is 0.2 m / s or more, the hydraulic retention time is 30 s or more, and the maximum water powerThe residence time is 2 minutes or less. In step S3, the organic / inorganic mixed liquid discharged from the high-speed agitator is transferred to a centrifugal unit by a slurry transfer pump. A low-speed stirring paddle is installed inside the centrifugal unit, a sludge bucket is installed at the bottom, and a high organic matter concentration mixed liquid outlet is installed at a height of 1 / 2 to 2 / 3. In step S4, the swirl flow centrifugal action of the centrifugal unit continuously stratifies materials having different specific gravities into upper and lower layers. Specifically, the slurry transfer pump feeds the slurry mixture into the centrifugal unit in a tangential direction at a tangential angle of 20° to 45°, and the slurry mixture is turned into a swirling flow by low-speed stirring at less than 50 r / min. The low-speed swirling flow causes the slurry mixture to be centrifuged. The organic-based slurry mixture with a specific gravity of <1 is collected in the upper and middle parts of the centrifugal unit, and the inorganic inert components with a specific gravity >1 are precipitated in the sludge bucket at the bottom of the centrifugal unit by centrifugal force and gravity, eliminating the need for chemicals during the process. In step S5, the high organic matter concentration mixed liquid with a specific gravity of <1 that flows out from the middle and upper outlets of the centrifugal unit is discharged via a conveying pipeline near the municipal sewage inspection well, and is continuously flowed into the town's sewage treatment plant together with the sewage for recycling. The sludge with a specific gravity >1 at the bottom, which is mainly composed of inorganic inactive components, is discharged into a sludge bucket by the action of the centrifugal force of the swirling flow and gravity, and is used to maintain the river bottom and slopes after dredging.

[0019] Furthermore, the sieving unit, high-speed stirring device and centrifugal unit can be installed as separate structures or as a combined structure as required.

[0020] The high organic matter concentration mixture obtained by extraction in step 5 has a VSS / SS ratio of 0.5 or more and can be used as a carbon source for biological treatment in urban wastewater treatment plants.

[0021] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to illustrate the present invention, and are not used to limit the present invention.

[0022] Example 1 As shown in Figure 1, the method for simultaneously dredging river sediment and extracting organic carbon sources in situ is as follows: In step S1, a mud suction device 1 is used to continuously pump slurry with a water content of 98% dredged from the bottom mud of a canal into a screening unit 2. The pore size of the grid plate in the screening unit 2 is 2 mm. The inorganic particulate matter with a diameter of 2 mm or more obtained by separation in the screening unit 2 is used for maintenance of rivers and slopes. In step S2, the sieved slurry is fed into the frequency conversion high-speed mixer 3 by gravity or pressure, and is rapidly mixed and stirred at a mixing speed of 1000 r / min. During the mixing process, the particulate matter rubs against each other, causing the organic matter to separate from the inorganic particles and enter the liquid phase, thereby completing the physical separation of the organic and inorganic components in the bottom mud. The mixing intensity and retention time of the high-speed mixer 3 are determined according to the separation characteristics of organic and inorganic substances in the dredged slurry, with an apparent tangential flow velocity of 0.5 m / s and a hydraulic retention time of 1 min. In step S3, the slurry mixture discharged from the high-speed agitator 3 is transferred to the centrifugal unit 5 by the slurry transfer pump 4. The slurry transfer pump 4 transfers the slurry mixture to the centrifugal unit 5 in a tangential direction, with a tangential angle of 30°. A low-speed stirring paddle is provided inside the centrifugal unit 5, a sludge bucket is provided at the bottom, and a high organic matter concentration mixed liquid discharge outlet is provided at 2 / 3 of the height. In step S4, the centrifugal action of the swirling flow of the centrifugal unit 5 continuously stratifies the materials having different specific gravities into upper and lower layers. Specifically, the slurry mixture is turned into a swirling flow by low-speed stirring at 30 r / min, and then centrifuged using the low-speed swirling flow, collecting the slurry mixture, mainly composed of organic components with a specific gravity of <1, in the upper middle part of the centrifugal unit 5, while the inorganic inactive components with a specific gravity >1 are precipitated in the sludge bucket at the bottom of the centrifugal unit 5 by centrifugal force and gravity, and the centrifugation is maintained for 1 minute. In step S5, the high organic matter concentration mixed liquid with a specific gravity of <1 that flows out of the middle and upper outlets of the centrifugal unit 5 by gravity is discharged through a conveying pipeline near the municipal sewage inspection well 7, and then flows continuously together with the sewage into the municipal sewage treatment plant, increasing the organic carbon source content of the influent. The lower sludge with a specific gravity >1, which is mainly composed of inorganic inert components, is discharged by gravity into a sludge bucket and used for maintaining the river slope after dredging.

[0023] The sieving unit 2, the high-speed stirring device 3 and the centrifugal unit 5 are integrated into one structure, thereby reducing the volume of the entire apparatus.

[0024] The high organic matter concentration mixture obtained by extraction in step 5 has a VSS / SS ratio of 0.6 and can be used as a carbon source for biological treatment in urban wastewater treatment plants.

[0025] Example 2 A method for dredging river sediment and simultaneously extracting organic carbon sources in situ, which is applied to the improvement of the sediment in a pond, includes the following steps: In step S1, a mud suction device 1 is used to continuously send slurry with a water content of 96% dredged from the bottom mud of a river into a sieving unit 2. The pore size of the grid plate of the sieving unit 2 is 5 mm. The inorganic particulate matter with a diameter of 5 mm or more obtained by separating in the sieving unit 2 is used for maintaining rivers and slopes. In step S2, the sieved slurry is fed into the frequency conversion high-speed mixer 3 by gravity or pressure, and is rapidly mixed and stirred at an average mixing speed of 500 r / min. During the mixing process, the particulate matter rubs against each other, causing the organic matter to separate from the inorganic particles and enter the liquid phase, thereby completing the physical separation of the organic and inorganic components in the bottom mud. The mixing intensity and retention time of the high-speed mixer 3 are determined according to the separation characteristics of organic and inorganic substances in the dredged slurry, with an apparent tangential flow velocity of 0.2 m / s and a hydraulic retention time of 2 min. In step S3, the slurry mixture discharged from the high-speed agitator 3 is transferred to the centrifugal unit 5 by the slurry transfer pump 4. The slurry transfer pump 4 transfers the slurry mixture to the centrifugal unit 5 in a tangential direction, and the tangential angle is 45°. A low-speed stirring paddle is provided inside the centrifugal unit 5, a sludge bucket is provided at the bottom, and a high organic matter concentration mixed liquid outlet is provided at half the height. In step S4, the centrifugal action of the swirling flow of the centrifugal unit 5 continuously stratifies the materials having different specific gravities into upper and lower layers. Specifically, the slurry mixture is turned into a swirling flow by low-speed stirring at 20 r / min, and then centrifuged using the low-speed swirling flow. The slurry mixture, mainly composed of organic components and having a specific gravity of <1, is collected in the upper middle part of the centrifugal unit 5, and the inorganic inactive components with a specific gravity >1 are precipitated in the sludge bucket at the bottom of the centrifugal unit 5 by centrifugal force and gravity, and the centrifugation is maintained for 1 minute. In step S5, the high organic matter concentration mixed liquid with a specific gravity of <1 that flows out by gravity from the middle and upper outlets of the centrifugal unit 5 is discharged via a conveying pipeline 6 to a nearby municipal sewage inspection well 7, where it flows continuously together with the sewage into the town's sewage treatment plant, increasing the organic carbon source content of the influent. The lower sludge with a specific gravity >1, which is mainly composed of inorganic inert components, is discharged by gravity into a sludge bucket and used to maintain the river slope after dredging.

[0026] Furthermore, the sieving unit 2, the high-speed stirring device 3 and the centrifugal unit 5 are installed in separate structures, which reduces the difficulty of operation and makes cleaning and maintenance easier.

[0027] The high organic matter concentration mixture obtained by extraction has a VSS / SS ratio of 0.8, and can be used as nutrient soil for the grassland and trees around the pond, improving soil fertility.

[0028] Finally, it should be mentioned that the above embodiments are used to illustrate but not to limit the technical solutions of the present invention. Those skilled in the art may make modifications or equivalent substitutions to the technical solutions of the present invention without departing from the technical principles of the present invention, and all such modifications and equivalent substitutions shall fall within the scope of the claims of the present invention. [Explanation of symbols]

[0029] 1 Mud suction device 2. Sieving unit 3. High-speed mixing device 4. Slurry transfer pump 5 Centrifugal Unit 6. Conveying pipeline 7. Sewerage Inspection Wells

Claims

1. A method for dredging river bottom sediments and simultaneously extracting organic carbon sources in situ, comprising: Step S1: Using a mud suction device, dredged slurry from the bottom mud of a river with a water content of more than 90% is continuously sent into a screening unit, and the hole diameter of the grid plate of the screening unit is in the range of 0.2 to 5 mm; Step S2: The sieved slurry is fed into a frequency conversion high-speed mixer by gravity or pressure, and is rapidly mixed and stirred at a mixing speed exceeding 200 r / min, and the organic matter is separated from the inorganic particles and placed in a liquid phase during the mixing and stirring process; Step S3: transferring the organic-inorganic mixed liquid discharged from the frequency conversion high-speed stirring device to a centrifugal unit by a slurry transfer pump; Step S4: Continuously stratifying materials having different specific gravities into upper and lower layers by the swirling centrifugal action of the centrifugal unit without using chemicals; Step S5: the mixed liquid with a specific gravity of <1 and a high organic matter concentration flowing out from the middle and upper outlets of the centrifugal unit is discharged through a conveying pipeline near the municipal sewage inspection well, and is then flowed together with sewage into the town's sewage treatment plant for recycling; and the sludge with a specific gravity >1 and mainly composed of inorganic inactive components is discharged into a sludge bucket by the action of the centrifugal force of the swirling flow and gravity, and is used for maintaining the river bottom and slopes after dredging. A method for extracting an organic carbon source in situ while dredging river bottom sediment, characterized in that the frequency to be converted by the frequency conversion high-speed agitator is the power supply frequency of the motor that drives the agitator, and the frequency is the output frequency of the frequency converter.

2. The method for extracting an organic carbon source simultaneously with dredging river bottom sediment as described in claim 1, characterized in that the inorganic particulate matter including gravel obtained by separation in the screening unit is used on site for maintenance of rivers and slopes.

3. The stirring intensity and retention time of the frequency conversion high-speed stirring device are determined according to the separation characteristics of organic and inorganic substances in the dredged slurry, and the apparent flow velocity is 0.2 m / s or more, the hydraulic retention time is 30 s or more, and the longest hydraulic retention time is 2 minutes or less; 2. The method for dredging river bottom sediment and simultaneously extracting an organic carbon source in situ according to claim 1, wherein the apparent flow velocity is the average velocity at which the sieved slurry is fed into the frequency conversion high-speed mixer, the hydraulic residence time is the average residence time of the sieved slurry in the frequency conversion high-speed mixer, and the maximum hydraulic residence time is the longest average time required for the sieved slurry to be discharged from the frequency conversion high-speed mixer after being fed into the frequency conversion high-speed mixer.

4. The method for extracting an organic carbon source in situ while dredging river bottom mud as described in claim 1, characterized in that a low-speed stirring paddle is provided inside the centrifugal unit, a sludge bucket is provided at the bottom, and a high organic matter concentration mixed liquid outlet is provided at a height of 1 / 2 to 2 / 3 of the height of the sludge bucket at the bottom of the centrifugal unit.

5. 2. The method for extracting an organic carbon source in situ while dredging river bottom sediment as described in claim 1, characterized in that the organic-inorganic mixed liquid is made into a swirling flow by low-speed stirring at less than 50 r / min, and centrifuged by the low-speed swirling flow, so that a slurry mixed liquid mainly composed of organic components and having a specific gravity of <1 is collected in the middle and upper part of the centrifugal unit, and inorganic inactive components having a specific gravity >1 are precipitated in a sludge bucket at the bottom of the centrifugal unit by centrifugal force and gravity.

6. The method for dredging river bottom sediment and simultaneously extracting organic carbon sources in situ, as described in claim 1, characterized in that the sieving unit, the frequency conversion high-speed stirring device, and the centrifugal unit are installed as separate structures or as a combined structure.

7. The method for extracting an organic carbon source in situ while dredging river bottom mud as described in claim 1, characterized in that the high organic matter concentration mixed liquid obtained by extraction has a VSS / SS ratio of 0.5 or more and can be used as a carbon source for biological treatment in urban sewage treatment plants.

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