Process method for treating sewage and low-carbon coordinated treatment of trench sludge

Abstract

The present application relates to municipal drainage sludge resource technology field, specifically to a kind of process method for sewage treatment low carbon collaborative treatment ditch sludge.This method is by rotating vibrating screen, and the impurities such as wood block, stone block or fiber with size greater than 100mm are removed, the garbage or fiber with average size 5mm-100mm is separated and collected by broken screw and conveying screw under unloading pool and washing drum;Unloading pool is equipped with 5mm grid separation slurry and washing drum 5mm screen separation undersize slurry with size less than 5mm, and 0.2mm-5mm construction sand is separated by rotating sand washing device, and the best working condition is controlled to realize that organic matter is less than 2%, and it can be directly used for building materials according to national standard.Rotating sand washing device scum is separated by scum collecting pool or mud well, sludge thickening tank and sludge dewatering machine, and supernatant returns sewage treatment unit.

Description

Technical Field

[0001] This invention relates to the field of municipal drainage sludge resource utilization technology, specifically to a process method for low-carbon co-treatment of drainage sludge in sewage treatment. Background Technology

[0002] Sludge from drainage ditches is sediment removed during the maintenance and dredging of urban drainage pipes and channels. It is generally composed mainly of water and inorganic mineral particles, with some organic matter mixed in. Sludge from drainage ditches is formed by the accumulation of urban production and domestic waste, such as construction mud and industrial or domestic waste, within the drainage pipes and channels. Its presence in drainage pipes and channels can easily cause poor drainage, the accumulation of odors or hazardous gases leading to safety hazards, and, during the rainy season, it can be washed into rivers, causing river pollution and hindering the normal functioning of sewage treatment facilities.

[0003] Taking cities like Shanghai and Beijing as examples, early sampling and analysis of sludge from drainage ditches, and the construction of pilot projects, mostly relied on drainage pumping stations, aiming to maximize the utilization of gravel as building materials through multi-stage separation. However, this approach faced numerous technical bottlenecks, including high odor emissions, difficulties in constructing supporting wastewater treatment and flushing water facilities, and the incomplete separation of organic matter in ultrafine sand, hindering effective utilization as building materials. These problems resulted in high investment and costs for separately constructed sludge treatment facilities, leading to unsatisfactory building material utilization. Therefore, a more reliable and sustainable technical approach is urgently needed to solve this problem in the long term. This invention aims to combine the facilities and resources of urban wastewater treatment plants to design an intensive process method and complete set of equipment, providing an intensive, economical, and efficient solution for the final disposal of sludge from drainage ditches. Summary of the Invention

[0004] To address the challenges of high investment costs for separate treatment of drainage sludge, difficulties in implementing integrated wastewater treatment, odor control, and water reuse, and the inability to maximize the utilization of sand as building material, this invention proposes a low-carbon co-treatment process for drainage sludge.

[0005] The method described in this invention is performed according to the following steps:

[0006] Step 1: The sludge transported by truck is separated at the unloading station and coarse separation device to remove large pieces of waste, such as textiles, wood blocks, or stones, larger than 100mm x 100mm. Large pieces of waste are collected by a rotating vibrating screen above the unloading pool. After unloading, the screen is manually or automatically opened to push the waste to the rear waste pit for drainage. An I-beam and a fully automatic grab bucket are installed above to grab the waste and send it to waste bins for collection and transport. 5mm perforated grids are installed behind the unloading pool and below the large waste pile to release mud and sand mixtures with particles smaller than 5mm into the sand pit. Below the unloading pool are a double-screw crusher, a conveying screw, and their housing. The double-screw crusher has a certain crushing and uniform material distribution function. The crushed slurry is conveyed to the next unit, the washing drum.

[0007] Step Two: The material conveyed from the unloading station and coarse separation device to the washing drum is washed and filtered through a 5mm screen. The oversize material, which is garbage with an average particle size of 5mm-100mm, is sent to a sand collection basket by a screw conveyor for collection and disposal. The washing slurry containing sand particles with an average particle size of <5mm is pumped to a cyclone sand washing device by a sand suction pump.

[0008] Step 3: The slurry with an average particle size <5mm accumulated in the mud and sand pit of the unloading station and coarse separation device, along with the rinsing slurry from the washing drum screen, are combined and sent to the cyclone sand washing device to achieve the washing and separation of 0.2mm-5mm sand particles. By controlling the optimal cyclone conditions and rinsing water frequency, the organic matter content of the washed 0.2mm-5mm sand particles is <2%, that is, the total separation efficiency of 0.2mm-5mm sand particles is >98%. The clean construction sand is collected in sand collection baskets for later use and can be directly used as building materials.

[0009] Step Four: Overflow scum from the cyclone sand washing device, with an average particle size <5mm, is overflowed or pumped to a scum collection tank / sludge mixing well. The collected scum can be directly pumped to the sludge dewatering machine at the wastewater treatment plant for dewatering, or it can be transported to a sludge thickening tank for thickening and homogenization before entering the sludge dewatering machine at the wastewater treatment plant for dewatering. The scum collection tank / sludge mixing well, sludge thickening tank, and sludge dewatering machine can all be implemented using existing facilities at the wastewater treatment site, with the treatment of the supernatant completed in conjunction with wastewater treatment. This avoids the problem of incomplete separation of organic matter from sludge with an average particle size <0.2mm, resulting in unusable ultrafine sand that can only be landfilled. Sludge with an average particle size <0.2mm is combined with sludge treatment for a comprehensive solution.

[0010] Based on the resource conditions of the wastewater treatment plant, the basic process of low-carbon co-treatment of drainage sludge is as follows: After the drainage sludge is unloaded by a special tanker at the unloading station and coarse separation device, the first step is to separate large impurities with a size of more than 100mm; the second step uses a crushing double screw and a conveying screw to send impurities with a particle size between 5mm and 100mm to the washing drum and screw conveyor to achieve the separation of impurities with an average particle size of 5mm-100mm. The slurry with an average particle size of <5mm from the unloading station and coarse separation device and the washing slurry with a particle size of <5mm from the washing drum screen are combined and sent to the cyclone sand washing device.

[0011] The process design and selection of bar screens and gratings conform to the national standard GB / T14684-2022 "Construction Sand". The average particle size of the separated construction sand is between 0.2mm and 5mm. The separation and washing parameters are controlled to achieve a separation efficiency of >98% for 0.2mm-5mm sand particles and an organic matter content of <2%, making it suitable for direct use as construction sand. Large and medium-sized impurities separated in the first two stages can also be used as building materials after washing. The supernatant and scum from the final sand washing separation are combined with the sludge thickening and dewatering facilities of the wastewater treatment plant for sludge treatment. The flushing water throughout the process uses reclaimed water from the wastewater treatment plant, and the supernatant from washing, thickening, and dewatering is incorporated into the wastewater treatment facility for centralized treatment to save on project investment and operating costs.

[0012] Taking the data of sewage sludge from a certain city as an example, the average moisture content was 52.7%, the ash content was 82.8%, and the specific gravity was 1.5 kg / dm³. 3 The sludge, with an average particle size <0.2mm, accounts for 49.6% of the total inorganic sand, while organic matter accounts for only 17.2%, with a predominance of non-combustible components. Its moisture content, odor concentration, transverse shear strength, and fecal coliform count do not meet the requirements for "final cover soil for landfills" in the standard "Mixed Landfill Sludge Quality for Disposal of Sludge from Urban Wastewater Treatment Plants" (CJ / T249-2007). The final disposal options are mainly sanitary landfill and building material utilization. However, the sludge from the drainage ditches has a low sand content, fine particles, and is difficult to separate, limiting its usability.

[0013] This invention provides a low-carbon, synergistic treatment method for wastewater treatment of ditch sludge, which has the following beneficial effects:

[0014] Considering the characteristics of sewage sludge, a sewage sludge treatment facility is constructed within the sewage treatment plant, integrated with the sewage treatment sludge thickening and dewatering unit. The usable and unusable inorganic materials are roughly divided into four categories: (a) large pieces of waste >100mm, (b) medium-sized waste 5mm-100mm, (c) directly usable construction sand 0.2mm-5mm, and (d) sand particles <0.2mm and scum <5mm. The first three inorganic components can be utilized in building materials to varying degrees. The fourth type, scum and ultrafine sand, are difficult to separate due to their high organic matter content; however, combining them with sludge thickening and dewatering makes their final disposal relatively easy.

[0015] Step 1 integrates multiple functions such as unloading sludge from ditches, separating large pieces of waste >100mm, collecting slurry with an average particle size <5mm, and crushing and separating medium-sized waste from 5mm to 100mm. This makes the operation convenient and facilitates closed-loop deodorization throughout the entire process.

[0016] In accordance with the national standard GB / T14684-2022 "Construction Sand", selecting 0.2mm-5mm as the focus of fine separation can relatively easily realize the recycling of fine sand, avoiding the high investment in ultrafine sand recycling and the difficulty and lack of solutions in separating organic matter.

[0017] The scum with an average particle size of <5mm and the ultrafine sand with an average particle size of <0.2mm separated from the sand washing process are the most difficult to separate in the sludge of the drainage ditch. This material causes great wear on the equipment, is lightweight, and is difficult to separate from organic matter. Combining sludge treatment can alleviate the wear problem, and the final treatment solution is relatively easy to achieve, and the overall investment cost is relatively controllable.

[0018] Based on the city's testing and analysis results, and considering that nearly 50% of the sludge treatment consists of inorganic sand with an average particle size of <0.2mm, the supporting wastewater treatment and odor treatment can be relatively easily and comprehensively implemented in the wastewater treatment plant facilities without increasing the difficulty of operation and management.

[0019] End-of-pipe sludge thickening is an option, and the sludge dewatering process is highly adaptable. It can be used with belt dewatering machines, centrifugal dewatering machines, and plate and frame dewatering machines. Furthermore, the combination of inorganic sand with dewatering can effectively reduce the amount of sludge dewatering conditioner used in wastewater treatment plants, saving sludge dewatering agent costs, which is mutually beneficial. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process of a specific embodiment of the present invention.

[0021] The numbers in the diagram are as follows:

[0022] 1. Unloading pool; 2. Rotatable vibrating screen; 3. I-beams and fully automatic grab bucket; 4. Garbage bin; 5. Garbage storage pit drain screen; 6. Unloading pool drain screen; 7. Crushing double spiral; 8. Conveying spiral; 9. Sand suction pump; 10. Washing drum; 11. Screw conveyor; 12. Sand collection basket; 13. Cyclone sand washing device; 14. Sand collection basket; 15. Sand suction pump; 16. Scum collection pool / sludge mixing well; 17. Sludge thickening tank; 18. Sludge dewatering machine. Detailed Implementation

[0023] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0024] The method described in this invention is performed according to the following steps:

[0025] Step 1: The sludge transported by truck is separated at the unloading station and coarse separation device to remove large pieces of waste, such as textiles, wood blocks, or stones, larger than 100mm x 100mm. These large pieces of waste are collected by a rotating vibrating screen 2 above the unloading pool 1. After unloading, the screen is manually or automatically opened to push the waste to the rear waste pit for drainage. An I-beam and a fully automatic grab bucket 3 are installed above to grab the waste and send it to a waste bin for collection and transport. 5mm perforated grids are installed behind the unloading pool 1 and below the large waste pile to release mud and sand mixtures with particle sizes smaller than 5mm into the sand pit. Below the unloading pool 1 are a crushing double spiral 7, a conveying spiral 8, and their housings. The double spiral crusher has a certain crushing and uniform material distribution function. The crushed slurry is conveyed to the next unit, the washing drum 10.

[0026] Step 2: The material conveyed from the unloading station and coarse separation device to the washing drum 10 is washed and filtered through a 5mm screen. The oversize material, which is garbage with an average particle size of 5mm-100mm, is sent to the sand collection basket 12 by the screw conveyor 11 for collection and disposal. The washing slurry containing sand particles with an average particle size of <5mm is pumped to the cyclone sand washing device 13 by the sand suction pump 15.

[0027] Step 3: The slurry with an average particle size <5mm accumulated in the mud and sand pit of the unloading station and coarse separation device, along with the rinsing slurry under the screen of washing drum 10, are combined and sent to the cyclone sand washing device 13 to achieve the washing and separation of sand particles from 0.2mm to 5mm. By controlling the optimal cyclone conditions and rinsing water frequency, the organic matter content of the washed 0.2-5mm sand particles is <2%, that is, the total separation efficiency of 0.2mm-5mm sand particles is >98%. Clean construction sand is collected by sand collection basket 14 for later use and can be directly used as building materials.

[0028] Step 4: The overflow scum from the cyclone sand washing device 13, with an average particle size <5mm, is overflowed or pumped to the scum collection tank / sludge mixing well 16. The collected scum can be directly pumped to the sludge dewatering machine 18 of the sewage treatment plant for dewatering, or it can be transported to the sludge thickening tank 17 for thickening and homogenization before entering the sludge dewatering machine 18 of the sewage treatment plant for dewatering. The scum collection tank / sludge mixing well 16, sludge thickening tank 17, and sludge dewatering machine 18 can all be implemented using existing facilities at the sewage treatment plant, and the treatment of the supernatant is completed in conjunction with the sewage treatment. This avoids the problem that the ultrafine sand after separation is difficult to use and can only be landfilled due to incomplete separation of organic matter in mud and sand with an average particle size <0.2mm. Mud and sand with an average particle size <0.2mm are combined with sludge treatment to solve the problem together.

[0029] Based on the resource conditions of the wastewater treatment plant, the basic process for low-carbon co-treatment of drainage sludge is as follows: After the drainage sludge is unloaded by a dedicated tanker truck at the unloading station and coarse separation device, the first step is to separate large impurities larger than 100mm. The second step utilizes a crushing double screw 7 and a conveying screw 8 to send impurities with particle sizes between 5mm and 100mm to a washing drum 10 and a screw conveyor 11 to achieve the separation of impurities with an average particle size of 5mm-100mm. The slurry with an average particle size <5mm from the unloading station and coarse separation device, and the washing slurry with a particle size <5mm from the washing drum screen, are combined and sent to a cyclone sand washing device. The process design and selection of bar screens and grates conform to the national standard GB / T14684-2022 "Construction Sand". An average particle size <0.075mm is considered mud or stone powder, and the applicable particle size distribution range for construction sand is 0.15-4.75mm. The separated construction sand has an average particle size between 0.2mm and 5mm. Separation and washing parameters are controlled to achieve a separation efficiency of >98% for 0.2mm-5mm sand particles and an organic matter content of <2%, making it suitable for direct use as construction sand. Large and medium-sized impurities from the initial two-stage separation can also be used as building materials after washing. The supernatant and scum from the final sand washing separation are incorporated into the sludge treatment plant's sludge thickening and dewatering facilities. The entire process uses reclaimed water from the wastewater treatment plant for rinsing, and the supernatant from washing, thickening, and dewatering is treated within the wastewater treatment facility to save on project investment and operating costs.

[0030] Taking the data of sewage sludge from a certain city as an example, the average moisture content was 52.7%, the ash content was 82.8%, the specific gravity was 1.5 kg / dm³, and sand with an average particle size <0.2 mm accounted for 49.6% of the total inorganic sand, while organic matter accounted for only 17.2%, with non-combustible components being the majority. The moisture content, odor concentration, transverse shear strength, and fecal coliform count did not meet the requirements for "final cover soil for landfills" in the standard "Mixed Landfill Sludge Quality for Sludge Disposal from Urban Wastewater Treatment Plants" (CJ / T249-27). The final disposal options are mainly sanitary landfill and building material utilization. However, the low sand content and fine particles of the sewage sludge make separation difficult, limiting its usability.

[0031] This invention relates to a low-carbon co-treatment method for wastewater treatment of ditch sludge, characterized by the following features:

[0032] In response to the characteristics of sludge from sewage drainage ditches, a sludge treatment facility is constructed within the sewage treatment plant, integrated with the sludge thickening and dewatering unit. The usable and unusable inorganic materials are roughly divided into four particle sizes: (a) large pieces of waste >100mm, (b) medium-sized waste 5mm-100mm, (c) sand directly usable for construction 0.2mm-5mm, and (d) sand particles <0.2mm and scum <5mm. The first three inorganic components can be utilized in building materials to varying degrees. The fourth type, scum and ultrafine sand, are difficult to separate due to their high organic matter content; however, their final disposal is relatively easy to achieve by combining sludge thickening and dewatering.

[0033] Step 1 integrates multiple functions such as unloading sludge from ditches, separating large pieces of waste >100mm, collecting slurry with an average particle size <5mm, and crushing and separating medium-sized waste from 5mm to 100mm. This makes the operation convenient and facilitates closed-loop deodorization throughout the entire process.

[0034] In accordance with the national standard GB / T14684-2022 "Sand for Construction", a particle size distribution of 0.2mm-5mm is selected as the focus of fine washing and separation. This can relatively easily realize the recycling of fine sand and avoid the high investment required for ultrafine sand recycling and the difficulty and lack of solutions for organic matter separation.

[0035] The scum with an average particle size of <5mm and the ultrafine sand with an average particle size of <0.2mm separated from the sand washing process are the most difficult to separate in the sludge of the drainage ditch. This material causes great wear on the equipment, is lightweight, and is difficult to separate from organic matter. Combining sludge treatment can alleviate the wear problem, and the final treatment solution is relatively easy to achieve, and the overall investment cost is relatively controllable.

[0036] Compared with the test and analysis results of a certain city, and considering that the average particle size of the sludge treatment is <0.2mm and the proportion of inorganic sand is nearly 50%, which is difficult to separate, the supporting sewage treatment and odor treatment can be relatively easily and comprehensively implemented in the sewage treatment plant facilities, and the operation and management difficulty has not increased.

[0037] End-of-pipe sludge thickening is an option, and the sludge dewatering process is highly adaptable. It can be used with belt dewatering machines, centrifugal dewatering machines, and plate and frame dewatering machines. Furthermore, the combination of inorganic sand with dewatering can effectively reduce the amount of sludge dewatering conditioner used in wastewater treatment plants, saving sludge dewatering agent costs, which is mutually beneficial.

[0038] In this embodiment, Table 1 lists five specific implementation methods that can be used in combination to cover most application scenarios of sludge removal equipment for urban drainage facilities.

[0039] Table 1 Brief operating parameters of the production line in the embodiment

[0040]

[0041] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes, substitutions, or combinations made by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A process for treating sewage and low carbon synergistically treating trench sludge, characterized in that, The method comprises the following steps: Step one: The channel sludge transported by the vehicle is separated from the inorganic impurities with a size greater than 100mmx100mm by the unloading station and the coarse separation device. The large block garbage is received by the rotatable vibrating screen (2) above the unloading pool (1). After unloading, the garbage is pushed to the storage pit behind by manually or automatically opening the upward turning to realize water draining. The upper part is provided with an I-beam and a full-automatic grab (3) to grab the garbage bin (4) for collection and transportation. The rear of the unloading pool (1) and the lower part of the large block garbage storage place are provided with 5mm aperture grids to release the mixture of mud and sand with a particle size less than 5mm to the mud and sand pit. The unloading pool (1) is provided with a crushing double screw (7), a conveying screw (8) and a box body below to crush and uniformly distribute the material. The crushed slurry is conveyed to the next unit washing drum (10); The unloading pool (1) has a bottom slope of not less than 45° to facilitate the automatic removal of the slurry with an average particle size less than 5mm to the mud and sand pit after unloading. The liquid drained from the large block garbage separated by the rotatable vibrating screen (2) is combined into the mud and sand pit. The garbage storage pit water draining grid (5) has the same aperture as the unloading pool water draining grid (6), both of which are 5mm. The slurry with large block garbage removed by the automatically or manually opened crushing double screw (7) below falls into the crushing double screw (7) and the conveying screw (8) and the box body above after draining the liquid with an average particle size less than 5mm. The slurry is fed to the next unit washing drum (10) by the conveying screw (8). Step two: The garbage on the screen after the screen washing and filtration of the material conveyed by the unloading station and the coarse separation device to the washing drum (10) is sent to the sand collecting basket (12) by the screw conveyor (11) for centralized collection and disposal. The washing slurry with an average particle size less than 5mm under the screen is pumped to the cyclone sand washing device (13) by the sand suction pump (15). The washing drum (10) is provided with a 5mm aperture screen. The recycled water in the sewage treatment plant is used as washing water for washing and screening. The garbage on the screen is sent to the sand collecting basket (12) by the screw conveyor (11). The garbage on the screen, i.e. the medium-sized garbage with a size of 5mm-100mm, is collected and disposed of. Step three: The slurry with an average particle size less than 5mm accumulated in the mud and sand pit of the unloading station and the coarse separation device and the washing slurry under the screen of the washing drum (10) are combined to the cyclone sand washing device (13) to realize the washing and separation of the sand particles with a size of 0.2mm-5mm. The best cyclone conditions and washing water frequency are controlled to realize the organic matter content less than 2% after the washing of the sand particles with a size of 0.2-5mm, and the total separation efficiency greater than 98%. The construction sand is collected by the sand collecting basket (14) for standby use. Step four: The overflow scum of the cyclone sand washing device (13) with an average particle size less than 5mm is overflowed or pumped to the scum collecting pool / mud well (16). The collected scum is pumped to the sludge dewatering machine (18) of the sewage treatment plant for dewatering treatment, or is conveyed to the sludge concentration pool (17) to realize concentration and homogenization, and then is fed into the sludge dewatering machine (18) of the sewage treatment plant for dewatering treatment. The supernatant after the treatment is combined with the sewage treatment to be completed. The mud and sand with an average particle size less than 0.2mm are combined to the sludge treatment to be solved.

2. The process for treating sewage and low carbon synergistically treating trench sludge according to claim 1, characterized in that, The block-shaped inorganic impurities in step one include wood, fiber, metal or stone, ceramic or glass; the rotatable vibrating screen mesh (2) has a grid size of 100 mm x 100 mm, which is used to separate large pieces of garbage with a size greater than 100 mm to a storage pit, and the I-shaped steel and the full-automatic grab bucket (3) are used to grab the garbage to the garbage can (4) for external transportation.

3. The process for treating sewage and low carbon synergistically treating trench sludge according to claim 1, characterized in that, The washing drum (10) in step two is provided with a 5 mm aperture screen, and the screen undersize flushing liquid and fine sand are pumped to the cyclone sand washing device (13) by the sand suction pump (15).

4. The process for treating sewage and low carbon synergistically treating trench sludge according to claim 1, characterized in that, The cyclone sand washing device (13) in step three uses the recycled water in the sewage treatment plant for flushing to achieve the best working condition.

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