Radial-flow type double-zone sedimentation tank with middle inlet and periphery outlet

Abstract

The invention discloses a middle-inlet and peripheral-outlet radial-flow type double-zone sedimentation tank, belongs to the technical field of sewage treatment, and mainly solves the problems that the partition boundary of the existing double-zone sedimentation tank is fuzzy, sludge is easy to mix, and the separation effect is unstable. The device comprises a circular tank body, wherein the bottom of the circular tank body is a bottom surface inclined from the periphery to the center; the key improvement is as follows: an annular separation weir is fixedly arranged on the bottom surface and is used for physically separating the settling zone into an independent inner ring settling zone and an independent outer ring settling zone; a water inlet system is arranged in the center of the tank body; the first unit is used for the inner ring area and comprises a sludge scraping device, a sludge collecting hopper positioned in the center of the tank body and a sludge discharging pipe; the second unit is used for the outer ring area and comprises a sludge scraping device, a sludge collecting device (such as an annular groove) located on the outer side of the annular separation weir and a sludge discharging pipe. Through the rigid physical partition and space staggered independent collection system, clear separation of light and heavy sludge in the whole process of precipitation and collection is realized, the separation purity is high, the operation is stable, and a traditional radial-flow type precipitation tank is easy to transform.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a sedimentation tank structure for a continuous flow aerobic granular sludge (AGS) process, and in particular to a radial flow dual-zone sedimentation tank that achieves efficient separation and precise collection of light and heavy sludge through physical zoning. Background Technology

[0002] Aerobic granular sludge technology has shown great promise in continuous flow wastewater treatment processes due to its excellent settling performance and pollutant removal efficiency. The secondary settling tank, as the core solid-liquid separation unit of this process, directly affects the amount of granular sludge retained in the system, the quality of returned sludge, and the overall operational stability. Traditional single-zone sedimentation tanks cannot selectively separate sludge with different settling properties, leading to the mixing or return of high-density, fast-settling granular sludge with low-density, slow-settling flocculent sludge, resulting in granular sludge loss and system performance fluctuations.

[0003] To achieve sludge sorting, existing technologies have proposed the concept of "dual-zone sedimentation." For example, Chinese utility model patent CN218474923U discloses an "improved dual-zone sedimentation tank for selectively separating aerobic granular sludge." This device adopts a "peripheral inflow, central outflow" water flow pattern and a physical structure of "outer ring large tank nested within inner ring small tank." The mixed liquor enters from the periphery, with heavy sludge settling in the outer ring large tank and light sludge entering the central small tank for secondary sedimentation. However, the above structure has the following inherent defects: Low utilization rate of effective separation area: The nested tank structure leads to complex hydraulic conditions in the central area, and the effective sedimentation area is occupied by the inner tank wall, resulting in low overall utilization. Risk of secondary disturbance: The "peripheral inflow, central outflow" water flow path is long, and the flow changes from horizontal to upward in the central area, which can easily cause the light flocs that have already settled in the outer ring to be carried away by the upward flow and resuspended, affecting the effluent quality and separation purity. Complex structure and inconvenient to modify: The nested double pool structure has high requirements for civil engineering, which is not conducive to the economical and simple upgrading and modification of the large number of existing traditional radial flow sedimentation tanks.

[0004] Therefore, there is an urgent need to develop a new type of dual-zone sedimentation tank equipment with a more reasonable water flow path, a more compact and efficient structure, clearer and more stable zoning, and ease of implementation and modification. Summary of the Invention

[0005] (a) Purpose of the invention

[0006] The purpose of this invention is to address the problems of existing dual-zone sedimentation tanks, such as complex structure, limited separation efficiency, and high difficulty in modification, by providing an innovative center-inlet, periphery-outlet radial flow dual-zone sedimentation tank. This sedimentation tank achieves complete physical isolation and precise collection of light and heavy sludge by setting a fixed annular dividing weir within a single circular tank and equipping it with two completely independent sludge scraping and discharge systems. It boasts advantages such as simple structure, stable operation, high separation efficiency, and ease of modification.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A radial flow dual-zone sedimentation tank with a central inlet and peripheral outlet includes: a circular tank body with a conical bottom surface sloping from the periphery to the center; an annular dividing weir fixedly disposed on the sloping bottom surface, the annular dividing weir physically dividing the sloping bottom surface into an inner ring sedimentation zone and an outer ring sedimentation zone; a central water inlet system disposed at the geometric center of the tank body for uniformly distributing water to the inner ring sedimentation zone; a peripheral water outlet system disposed at the outermost periphery of the tank body for collecting and discharging clarified water; and a first sludge scraping and discharge unit and a second sludge scraping and discharge unit that are independent of each other.

[0010] The first sludge scraping and discharging unit includes a first sludge scraping device disposed above the inner ring sedimentation zone, a first sludge collecting hopper located at the bottom center inside the annular dividing weir, and a first sludge discharging pipe connected to the first sludge collecting hopper.

[0011] The second sludge scraping and discharging unit includes a second sludge scraping device disposed above the outer ring sedimentation zone, a second sludge collecting device located in the bottom area outside the annular dividing weir, and a second sludge discharging pipe connected to the second sludge collecting device.

[0012] As a further improvement of the present invention, the first sludge scraping device and the second sludge scraping device are two sets of sludge scrapers with independent mechanical structures and separate drives.

[0013] As a further improvement of the present invention, the rotation radius of the first sludge scraping device is smaller than the radius of the annular dividing weir, and the rotation radius of the second sludge scraping device is larger than the radius of the annular dividing weir.

[0014] As a further improvement of the present invention, the top of the annular dividing weir is provided with an overflow outlet. The weir crest elevation H1 is lower than the effluent weir crest elevation H2 of the surrounding effluent system, but higher than the designed sludge layer crest elevation H3 of the inclined bottom surface at the annular dividing weir. This design ensures that the supernatant in the inner ring zone can overflow smoothly to the outer ring zone, while preventing the sludge in the inner ring zone from crossing the weir body, which is key to achieving clear and stable zoning.

[0015] As a further improvement of the present invention, the central water inlet system includes a vertically arranged water inlet well, the upper side wall of which is provided with radial water distribution holes, and the bottom is connected to a water inlet pipe.

[0016] As a further improvement of the present invention, the second sludge collection device is an annular groove surrounding the annular dividing weir, and the bottom of the annular groove is provided with a slope toward the sludge discharge point.

[0017] As a further improvement of the present invention, the inclination angle α of the inclined bottom surface is 5° to 15°.

[0018] The present invention also provides a wastewater treatment system comprising a radial flow dual-zone sedimentation tank with central inlet and peripheral outlet as described in any of the preceding claims.

[0019] The present invention also provides a sludge separation method for an aerobic granular sludge process, employing a radial flow dual-zone sedimentation tank with a central inlet and peripheral outlet as described in any of the preceding claims, comprising the steps of: returning the sludge discharged from the first sludge discharge pipe to the aerobic granular sludge reactor; and discharging the sludge discharged from the second sludge discharge pipe as surplus sludge or further treating it.

[0020] (III) Beneficial Effects

[0021] Compared with the prior art, the present invention has the following significant advantages:

[0022] 1. Clear and stable zoning, high separation efficiency: Physical zoning is achieved through a fixed annular dividing weir, fundamentally preventing back-mixing of sludge between inner and outer zones. Combined with a precisely designed weir crest elevation (H1) <h2>H3 can form a stable hydraulic gradient and sludge layer barrier in the pool, ensuring that heavy granular sludge is effectively retained in the inner ring zone, while light flocculent sludge settles in the outer ring zone. The separation path is clear and the sorting purity is high.

[0023] 2. Compact and reasonable structure with high space utilization: It adopts the classic "center inlet and perimeter outlet" radial flow pool type and the integrated design of built-in annular partition weir, which avoids the structural waste of nested pools and achieves the largest effective sedimentation area with the same floor area. The overall layout is compact and the civil engineering cost is low.

[0024] 3. Flexible and reliable operation and control: The two sets of sludge scraping and discharge units are mechanically independent and driven separately. The scraping speed and discharge frequency can be adjusted independently according to the different characteristics of the sludge in the inner and outer zones (such as settling velocity and concentration), so as to achieve precise and flexible control of the amount of return sludge and the amount of excess sludge.

[0025] 4. Simple and economical implementation: The invention has a clear structural principle, and the main components (annular dividing weir, independent sludge scraper, sludge collection hopper / trough) can be standardized for production and installation. It is particularly suitable for upgrading existing traditional radial flow sedimentation tanks. Only an annular dividing weir needs to be installed in the tank and a sludge scraping and discharge system needs to be modified or added. There is no need to change the main structure of the tank or the hydraulic flow pattern. The modification cost is low, the cycle is short, and the applicability is wide. Attached Figure Description

[0026] Figure 1 This is a top view of the structure according to an embodiment of the present invention.

[0027] Figure 2 for Figure 1 A cross-sectional structural diagram.

[0028] Figure 3 This is a schematic diagram of one embodiment of the sludge scraping system of the present invention.

[0029] Numbering in the diagram: 1-Pool body; 2-Sloping bottom; 3-Annular dividing weir; 31-Inner ring sedimentation zone; 32-Outer ring sedimentation zone; 4-Inlet well; 41-Water distribution hole; 42-Inlet pipe; 5-Outlet weir; 6-First sludge scraping device (inner scraper arm); 7-First sludge collection device (central sludge collection hopper); 71-First sludge discharge pipe; 8-Second sludge scraping device (outer scraper arm); 9-Second sludge collection device (annular sludge collection trough); 91-Second sludge discharge pipe. Detailed Implementation

[0030] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0031] like Figures 1 to 3 As shown, the radial flow dual-zone sedimentation tank with central inlet and peripheral outlet provided by this invention has a circular reinforced concrete structure as its tank body 1. The bottom of the tank is a conical bottom surface 2 that slopes from the periphery to the center, with the inclination angle α preferably being 10°. A robust annular dividing weir 3, made of a sturdy material (such as stainless steel or reinforced fiberglass), is fixed to the bottom of the tank by pre-embedded parts, physically dividing it into an inner ring sedimentation zone 31 (occupying approximately 1 / 3 to 1 / 2 of the tank radius) and an outer ring sedimentation zone 32. The top of the annular dividing weir 3 is a flat weir or a sawtooth weir, and its weir crest elevation H1 is designed to be approximately 0.3-0.5 meters lower than the weir crest elevation H2 of the surrounding effluent weir 5, while being higher than the designed top elevation H3 of the sludge layer at the bottom of the tank, in order to form a clear functional interface.

[0032] The sludge-water mixture from the front-end bioreactor is fed from the bottom of the tank into the vertical central inlet well 4 through the inlet pipe 42. It is then evenly distributed horizontally and radially into the inner ring sedimentation zone 31 through the circumferentially distributed water distribution holes 41 at its upper part. Heavy solids such as aerobic granular sludge with good settling properties settle rapidly as they flow through this zone. Lighter flocs carried by the water flow continue to flow outwards and gradually settle after entering the outer ring sedimentation zone 32. The supernatant from the inner ring zone overflows the top of the annular dividing weir 3 and flows together with the supernatant from the outer ring zone to the tank edge. It is then collected by the peripheral effluent weir 5 (such as a triangular weir) and discharged through the main effluent channel.

[0033] The sludge removal system employs two independently driven, center-driven scrapers. The first scraper device 6 (inner scraper arm) is responsible for the inner ring sedimentation zone 31. Its scraper blades scrape the settled granular sludge towards the steel first sludge collection device 7 (central cone) at the center of the tank. After concentration, the sludge is continuously or intermittently returned to the front end of the biological treatment tank via the first sludge discharge pipe 71 by a return sludge pump to maintain the concentration of granular sludge in the reactor. The second scraper device 8 (outer scraper arm) is responsible for the outer ring sedimentation zone 32. Its scraper blades scrape the settled flocculent sludge into the second sludge collection device 9 (e.g., an annular steel trough with a sloped bottom) surrounding the annular dividing weir 3. After the sludge collects to the lowest point in the annular sludge collection trough 9, it is periodically discharged to the sludge treatment system as excess sludge via the second sludge discharge pipe 91.

[0034] Through the above-described specific structure, this invention achieves efficient and stable physical sorting and precise collection of light and heavy sludge within a single circular tank. The structure is simple and streamlined, and the operation and control are flexible. It provides a high-performance dedicated separation equipment for continuous flow aerobic granular sludge processes, and has outstanding engineering applicability and ease of modification.

[0035] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications and variations made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.< / h2>

Claims

1. A radial flow dual-zone sedimentation tank with central inlet and peripheral outlet, characterized in that, include: A circular pool (1) has a bottom surface (2) that slopes from the periphery to the center; an annular dividing weir (3) is fixedly installed on the inclined bottom surface (2), which divides the inclined bottom surface (2) into an independent inner ring sedimentation zone (31) and an outer ring sedimentation zone (32); a central water inlet system is set at the geometric center of the pool (1) for uniformly distributing water to the inner ring sedimentation zone (31); and a peripheral water outlet system is set at the outermost periphery of the pool (1) for collecting and discharging clarified water. The first and second scraping and sludge removal units are independent of each other; The first sludge scraping and discharging unit includes a first sludge scraping device (6) disposed above the inner ring sedimentation zone (31), a first sludge collecting hopper (7) located at the bottom center inside the annular dividing weir (3), and a first sludge discharging pipe (71) connected to the first sludge collecting hopper (7); The second sludge scraping and discharging unit includes a second sludge scraping device (8) disposed above the outer ring sedimentation zone (32), a second sludge collecting device (9) located in the bottom area outside the annular dividing weir (3), and a second sludge discharging pipe (91) connected to the second sludge collecting device (9).

2. The radial flow dual-zone sedimentation tank with central inlet and peripheral outlet as described in claim 1, characterized in that: The first sludge scraping device (6) and the second sludge scraping device (8) are two sets of sludge scrapers with independent mechanical structures and separate drives.

3. The radial flow dual-zone sedimentation tank with central inlet and peripheral outlet as described in claim 2, characterized in that: The rotation radius (R1) of the first sludge scraper (6) is smaller than the radius (R) of the annular dividing weir (3), and the rotation radius (R2) of the second sludge scraper (8) is larger than the radius (R) of the annular dividing weir (3).

4. The radial flow dual-zone sedimentation tank with central inlet and peripheral outlet as described in claim 1, characterized in that: The top of the annular dividing weir (3) is provided with an overflow outlet. The elevation of the weir top (H1) is lower than the elevation of the effluent weir top (H2) of the surrounding effluent system, and higher than the design elevation of the top of the sludge layer (H3) of the inclined bottom surface (2) at the annular dividing weir (3).

5. The radial flow dual-zone sedimentation tank with central inlet and peripheral outlet as described in claim 1, characterized in that: The central water inlet system includes a vertically arranged water inlet well (4), the upper side wall of which is provided with radial water distribution holes (41), and the bottom is connected to a water inlet pipe (42).

6. The radial flow dual-zone sedimentation tank with central inlet and peripheral outlet as described in claim 1, characterized in that: The second mud collection device (9) is an annular groove surrounding the annular dividing weir (3), and the bottom of the annular groove has a slope toward the mud discharge point.

7. The radial flow dual-zone sedimentation tank with central inlet and peripheral outlet as described in any one of claims 1 to 6, characterized in that: The angle (α) of the inclined bottom surface (2) is 5° to 15°.

8. A sludge separation method for an aerobic granular sludge process, characterized in that, The method of using the radial flow dual-zone sedimentation tank with center inlet and peripheral outlet as described in any one of claims 1 to 7 includes the following steps: The sludge discharged from the first sludge discharge pipe (71) is returned to the aerobic granular sludge reactor; The sludge discharged from the second sludge discharge pipe (91) is discharged as surplus sludge or further treated.

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