A system for effectively solving the problem of filter clogging caused by the expansion of viscous sludge

Abstract

The utility model relates to a system for effectively solving the expansion and blockage of filter tank by sticky sludge, which comprises a biochemical tank, a secondary sedimentation tank, a fine grid, a tertiary sedimentation tank and a filter tank connected in sequence, and further comprises an anaerobic fermentation tank connected with the biochemical tank. The fine grid of the system is arranged at the rear end of the sedimentation tank, and the sticky and expanded sludge is physically separated through the interception of the grid. The high nutrient substances in the extracellular secretion are used for anaerobic fermentation, and the fermentation liquor is used as a growth factor for the sticky sludge to promote the explosion of the sticky sludge, which is beneficial to the rapid entry of the sludge into the explosion period. The sticky sludge is completely physically separated through artificial auxiliary sludge discharge. The system can reduce the treatment cycle of the sticky sludge expansion and reduce the operation cost.

Description

Technical Field

[0001] This utility model belongs to the field of water treatment applications, specifically relating to a system for effectively solving the problem of filter clogging caused by the expansion of sticky sludge. Its main purpose is to prevent filter clogging caused by the expansion of sticky sludge by physically separating sludge agglomerates. It is suitable for treating various industrial wastewaters. Background Technology

[0002] The activated sludge process is the most widely used biological treatment technology for domestic sewage and industrial wastewater. In the activated sludge process, sewage and activated sludge enter the aeration tank together to form a mixed liquor. Aeration provides dissolved oxygen to the sewage and provides the driving force for the mixed liquor, keeping it in a state of intense agitation, improving the mixing of sludge and sewage, enhancing mass transfer, and thus promoting the metabolism of aerobic microorganisms in the activated sludge, thereby purifying the sewage.

[0003] The filter bed is a treatment unit for deep denitrification and COD degradation. Typically, the filter bed uses 3-4 mm quartz sand media. The filter bed can ensure that the suspended solids in the effluent are below 5 mg / L and the total nitrogen (TN) in the effluent is 5-7 mg / L.

[0004] Sludge bulking is a common problem in activated sludge processes, referring to the phenomenon where sludge becomes loosely structured, increases in volume, and has a higher sludge settling ratio (SV), making it difficult to settle and separate, thus affecting effluent quality. Non-filamentous bacterial bulking mainly occurs when wastewater temperature is low and sludge load is too high. At these times, bacteria adsorb large amounts of organic matter with low metabolic rates. A large amount of high-viscosity extracellular secretions accumulate, representing a high concentration of organic matter, greatly increasing surface adhesion and making sedimentation difficult. Furthermore, flocculants alone are insufficient to remove this substance from the water. Old viscous substances act as catalysts for new viscous substances, leading to increasingly severe viscous bulking. When bulked sludge enters the filter, it easily clogs or hardens the filter surface, deteriorating the treatment effect.

[0005] Currently, most methods to solve the problem of viscous sludge bulking are to increase the sludge return ratio; increase aeration to prevent the formation of anaerobic conditions; and add nutrients to adjust the material balance in the mixed liquor. However, all of these methods will increase the operating costs of wastewater treatment plants. Summary of the Invention

[0006] This invention provides a system for effectively solving the problem of viscous sludge bulking and clogging of filter beds. A fine screen is placed at the rear end of the sedimentation tank. The viscous bulking sludge is physically separated by the screen's interception. An anaerobic fermentation tank is set up to generate growth factors for the viscous sludge, causing an outbreak of viscous sludge bulking. The viscous sludge is then completely physically separated by manual sludge discharge, reducing operating costs.

[0007] To address the problem of sludge loss and filter bed clogging caused by viscous sludge bulking in conventional activated sludge processes, and based on the aforementioned background technology, this invention provides a system for effectively solving viscous sludge bulking. It primarily utilizes physical interception methods to directly remove viscous flocs, subjecting early-stage viscous sludge to anaerobic fermentation. The fermentation broth acts as a growth factor for viscous substances, promoting the explosive expansion of viscous sludge and improving the physical removal rate. The main content is: A system for solving viscous sludge bulking.

[0008] The technical solution of this utility model is as follows:

[0009] A fine screen and a tertiary sedimentation tank are added between the sludge settling tank and the filter tank to intercept severely bulking and difficult-to-break viscous sludge-water mixtures, preventing them from entering the filter tank and causing blockage. High-viscosity secretions can undergo anaerobic fermentation. The fermentation broth, acting as a growth factor that promotes sludge bulking, is reintroduced into the biological treatment tank, accelerating the growth of viscous substances until the fine screen can completely intercept them, facilitating complete removal using physical methods. The specific method is as follows:

[0010] A system for effectively solving the problem of bulking and clogging of filter beds by sticky sludge includes a biological treatment tank, a secondary sedimentation tank, a fine screen, a tertiary sedimentation tank, and a filter bed connected in sequence, and also includes an anaerobic fermentation tank connected to the biological treatment tank.

[0011] The mud-water mixture in the biological treatment tank enters the secondary sedimentation tank for mud-water separation. The settleable sludge is kept at a concentration of 2000-5000 mg / L in the biological treatment tank through the system's sludge return system and sludge discharge system, so as to maintain the normal operation of the reaction in the biological treatment tank.

[0012] Unsedimentary sludge, i.e., a sticky mud-water mixture, passes through a fine screen along with the effluent.

[0013] When a sludge-water mixture with low viscosity sludge content passes through a fine screen, its aggregate structure is disrupted, allowing it to pass through the screen into the tertiary settling tank and filter. By adding flocculants (such as polyferric flocculants and / or polyaluminum flocculants), the settling properties of the sludge are increased, ensuring that the suspended solids in the effluent entering the filter do not exceed 20 mg / L. Since the sludge loss due to sludge bulking is relatively large, this part of the sludge can be returned to the secondary settling tank to participate in the biochemical reaction.

[0014] The sludge mixture with a high degree of expansion will not have its structure destroyed by the hydraulic action of the water flow. Instead, it will be trapped on the grid plate and removed by the grid cleaner to prevent the grid from clogging.

[0015] The sludge-water mixture containing extracellular secretions, after being swept away, enters the anaerobic fermentation tank. After being converted into a liquid by anaerobic fermentation, it acts as a promoter for sludge bulking, accelerating the expansion of sticky sludge and promoting sludge aggregation. Severely bulky sticky sludge can be completely physically separated by the interception of fine screens and manual scraping.

[0016] A further improvement of this invention is as follows: Addressing system blockage and sludge loss caused by viscous sludge bulking, a fine screen is added to trap sludge, retaining sludge with low levels of bulking viscosity. Furthermore, the addition of flocculants reduces suspended solids in the filter bed's influent, lowering the probability of filter bed blockage. Simultaneously, by removing severely bulking sludge, anaerobic fermentation generates growth factors that promote viscous sludge bulking, and the hydraulic retention time in the biological treatment tank is shortened, accelerating the explosive expansion of viscous sludge and facilitating sludge separation, thus reducing the treatment cycle for viscous sludge bulking.

[0017] The key features of this invention are: the development of a system that effectively solves the problem of filter clogging caused by bulking viscous sludge, preventing bulking viscous sludge from entering the filter and significantly alleviating filter clogging. Furthermore, compared to traditional methods of increasing the return ratio and enhancing aeration, this invention reduces the content of extracellular secretions in the biological treatment tank through physical separation, thereby reducing the outbreak and treatment time of bulking viscous sludge, lowering the operating costs of the biological treatment tank, and promptly returning uncontaminated sludge to the biological treatment tank, maintaining the sludge concentration in the tank and ensuring the normal operation of the system. Attached Figure Description

[0018] Figure 1 A schematic diagram of a system for effectively solving the problem of filter bed clogging caused by viscous sludge bulking.

[0019] Explanation of reference numerals in the attached figures:

[0020] 1. Biological treatment tank; 2. Secondary sedimentation tank; 3. Expanded sludge-water mixture; 4. Fine screen; 5. Retainable sludge; 6. Tertiary sedimentation tank; 7. Filter tank; 8. Effluent; 9. Sludge return I; 10. Sludge return II; 11. Anaerobic fermentation tank; 12. Fermentation broth; 13. Severely expanded sludge; 14. Manual assisted sludge scraping; 15. Sludge discharge system; 16. Flocculant. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and examples:

[0022] Figure 1 A schematic diagram of a system for effectively solving the problem of filter bed clogging caused by viscous sludge bulking.

[0023] A system for effectively solving the problem of filter bed clogging caused by bulking viscous sludge is established. The operation process of this system is described as follows:

[0024] During normal operation of biological treatment tank 1, the sludge-water mixture flows into secondary sedimentation tank 2. The settled sludge is maintained at a sludge concentration of 2000-5000 mg / L through sludge return system I9 and sludge discharge system 15. However, if viscous sludge bulking occurs, resulting in high levels of extracellular secretions in the sludge, it will not settle in sedimentation tank 2. The floating bulked sludge-water mixture 3 will flow into fine screen 4 with the effluent. Fine screen 4 is a mesh screen with a mesh width of 1000-3000 mm and an aperture of 1-20 mm.

[0025] Because of the hydraulic shear force when the water flows through the fine screen 4, the sludge flocs with low viscosity and expansion will break down quickly when passing through the fine screen. Before entering the sedimentation tank 2, 0.1-1‰ flocculant 16 (such as iron-based and / or aluminum-based flocculants) is added by pumping to accelerate sludge sedimentation, ensuring that the suspended solids in the effluent of the tertiary sedimentation tank are 1-20 mg / L. The sedimented retainable sludge 5 is re-entered into the secondary sedimentation tank 2 through sludge return II10 for sludge circulation, maintaining the sludge concentration in the biological treatment tank 1.

[0026] Severely expanded sludge 13 will not be broken by water impact when it comes into contact with fine screen 4. It will be blocked by the screen and adhere to the screen. This part of the sludge will be removed by the relative self-cleaning operation between the screen rake teeth and the reverse movement of the cleaner. The severely expanded sludge 13 will be directly sent into the anaerobic fermentation tank 11 by the conveyor belt for anaerobic fermentation.

[0027] The anaerobic fermentation tank 11 operates at ambient temperature and controls the pH value between 5.5 and 6.5. It does not consume additional energy and hydrolyzes and ferments the severely bulky sludge 13. The fermentation liquid 12 is returned to the biological treatment tank 1 as a growth factor. At the same time, the hydraulic retention time of the biological treatment tank is shortened by 5-20%, which promotes the bulking of the viscous sludge into the explosive phase.

[0028] When the foam on the surface of biological treatment tank 1 exceeds 20 cm and stops rising, it indicates the end of the bulking phase of the viscous sludge. In addition to using fine screen 4 for interception, a manual scraper 14 is added to remove the foam from the surface of biological treatment tank 1, ensuring that all the viscous bulking sludge is removed by physical methods. At the same time, the hydraulic retention time of biological treatment tank 1 is restored to normal levels to stop the fermentation of viscous bulking sludge. Example

[0029] The simulated biological treatment process showed good sludge settling in the secondary sedimentation tank during the initial operation. The sludge concentration was approximately 3500 mg / L during operation, with the operating temperature between 25-27 ℃. Aerobic dissolved oxygen was controlled at 2-3 mg / L. The influent was artificially prepared, using sodium acetate:glucose (1:1 ratio) as the carbon source, ammonium chloride as the nitrogen source, and potassium dihydrogen phosphate as the phosphorus source, with a COD:N:P ratio of 100:10:1. The cycle was four times daily: 5 minutes of influent, 30 minutes of anoxic conditions, 15 minutes of aerobic conditions, alternating six times, followed by 80 minutes of sedimentation and 5 minutes of effluent discharge. After 43 days of operation, the extracellular secretions of the sludge were found to be 10 times higher than those of the inoculated sludge, indicating improved sludge settling volume (SV). 30 >50%, SVI>400mL / g, and a large number of clump-shaped sludge flocs were produced.

[0030] To address the bulking of viscous sludge, sludge trapping was implemented. A fine screen was added at the effluent outlet, and 0.5‰ polyferric sulfate was added after the water sample passed through the screen. Simultaneously, the collected extracellular secretions underwent anaerobic fermentation at room temperature. The fermentation broth was returned to the biological treatment tank, with the hydraulic retention time shortened to 25 minutes of anoxic followed by 13 minutes of aerobic followed by 5 alternations. After one day, the white foam on the surface of the biological treatment tank reached a height of 40 cm. Fermentation broth recirculation was stopped, and the surface foam was manually removed. All sludge trapped by the fine screen was also removed, and the operating cycle was changed back to 4 cycles per day: 5 minutes of influent, 30 minutes of anoxic followed by 15 minutes of aerobic followed by 6 alternations, 80 minutes of sedimentation, and 5 minutes of effluent discharge. After 2 days of operation, sludge parameters returned to inoculation levels, and the surface foam in the biological treatment tank disappeared and returned to normal.

Claims

1. A system for effectively solving the problem of filter bed blockage caused by bulking of sticky sludge, the system comprising a biological treatment tank (1), a secondary sedimentation tank (2), a fine screen (4), a tertiary sedimentation tank (6), and a filter bed (7) connected in sequence; characterized in that, The system also includes an anaerobic fermentation tank (11), which is connected to a biochemical tank.

2. The system as described in claim 1, characterized in that: The fine grid is a mesh grid with a width of 1000-3000mm and an aperture of 1-20mm.

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