Secondary sedimentation tank and sewage treatment system having the same

Abstract

The utility model discloses a secondary sedimentation tank and a sewage treatment system having the secondary sedimentation tank. The secondary sedimentation tank comprises: a tank body, the tank body comprises an inlet channel, the inlet channel comprises a clean water chamber and a floating mud chamber, the floating mud chamber is located above the clean water chamber; a mud discharge pipe, a part of the mud discharge pipe is located in the inlet channel, the mud discharge pipe has a first mud inlet and a first mud outlet, the first mud outlet of the mud discharge pipe extends out of the inlet channel; and a floating mud collecting pipe, the floating mud collecting pipe is movably arranged in the inlet channel along the up and down directions, the floating mud collecting pipe has a second mud inlet and a second mud outlet, the second mud inlet of the floating mud collecting pipe can be located in the floating mud chamber, and the second mud outlet of the floating mud collecting pipe is connected with the first mud inlet of the mud discharge pipe. The secondary sedimentation tank according to the embodiment of the utility model has the advantages of easy removal of floating mud, timely removal of floating mud, low energy consumption, simple structure, etc.

Description

Technical Field

[0001] The utility model relates to the field of sewage treatment, in particular to a secondary sedimentation tank and a sewage treatment system having the secondary sedimentation tank. Background Art

[0002] As one of the important process units of the sewage treatment plant, the secondary sedimentation tank has the function of solid-liquid separation. It is usually set after the biological treatment section to remove suspended matter. Because the inlet of the secondary sedimentation tank is the effluent of the biological pool, and the end of the biological pool is the aeration zone, sludge often floats above the liquid surface in the secondary sedimentation tank. If it is not removed in time, there is a risk of flowing into the effluent channel and polluting the effluent water quality, and it is extremely unsightly and affects the image development of the sewage treatment plant. At present, the floating sludge in the secondary sedimentation tank is mostly removed manually, which is labor-intensive. Utility Model Content

[0003] The utility model aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the utility model proposes a secondary sedimentation tank and a sewage treatment system having the secondary sedimentation tank.

[0004] According to the utility model, the secondary sedimentation tank comprises: a tank body, the tank body comprises an inlet channel, the inlet channel comprises a clean water chamber and a floating mud chamber, the floating mud chamber is located above the clean water chamber; a mud discharge pipe, a part of the mud discharge pipe is located in the water inlet channel, the mud discharge pipe has a first mud inlet and a first mud outlet, the first mud outlet of the mud discharge pipe extends out of the water inlet channel; and a floating mud collecting pipe, the floating mud collecting pipe is movably arranged in the water inlet channel along the up and down directions, the floating mud collecting pipe has a second mud inlet and a second mud outlet, the second mud inlet of the floating mud collecting pipe can be located in the floating mud chamber, and the second mud outlet of the floating mud collecting pipe is connected with the first mud inlet of the mud discharge pipe.

[0005] The secondary sedimentation tank according to the utility model has the advantages of being easy to remove floating sludge, timely removing floating sludge, low energy consumption and simple structure.

[0006] Optionally, the secondary sedimentation tank is a circumferential inlet and outlet type secondary sedimentation tank; and / or the second mud inlet of the floating mud collection pipe is spaced a preset distance from the upper surface of the floating mud chamber in the up and down direction.

[0007] Optionally, the mud discharge pipe includes an installation section, the installation section is arranged in the clean water chamber, and the floating mud collection pipe is movably arranged on the installation section along the up and down directions, wherein a part of the floating mud collection pipe is embedded in the installation section or a part of the floating mud collection pipe is sleeved on the installation section.

[0008] Optionally, a sealing ring is provided between the installation section and the floating mud collection pipe.

[0009] Optionally, the secondary sedimentation tank further includes: a mounting frame, which is arranged on the side wall of the water inlet channel, and the mounting frame has a first threaded hole, and the first threaded hole passes through the mounting frame in the up and down direction; a first threaded rod, a portion of the first threaded rod is threadedly engaged in the first threaded hole, and the lower end of the first threaded rod is connected to the floating mud collection pipe; and a first operating wheel, which is connected to the upper end of the first threaded rod.

[0010] Optionally, the floating mud collection pipe includes: a tube body, which is movably arranged on the mud discharge pipe in the up and down directions, and the lower end of the tube body constitutes the second mud outlet; and a cover plate, which is arranged on the upper end of the tube body, the lower end of the first threaded rod is relatively rotatably connected to the cover plate, and the second mud inlet is opened on at least one of the cover plate and the upper end of the tube body.

[0011] Optionally, the secondary sedimentation tank further comprises a flushing pipe, and the flushing pipe is connected to the installation section so as to flush the sludge discharge pipe.

[0012] Optionally, the mounting bracket has a second threaded hole, which passes through the mounting bracket in the up and down directions, and the secondary sedimentation tank further includes: a control valve, which is arranged on the flushing pipe; a second threaded rod, a portion of which is threadedly engaged in the second threaded hole, and the lower end of the second threaded rod is connected to the control valve to open and close the control valve; and a second operating wheel, which is connected to the upper end of the second threaded rod.

[0013] Optionally, the water inlet of the flushing pipe is located in the clean water chamber; and / or the mud discharge pipe also includes a buried section, the upper end of the buried section is connected to the lower end of the installation section, a part of the buried section is buried in the bottom wall of the water inlet channel, and the other part of the buried section extends out of the water inlet channel, and the installation section is vertically arranged in the water inlet channel.

[0014] The sewage treatment system of the utility model comprises: a biological pool; a secondary sedimentation tank, wherein the secondary sedimentation tank is the secondary sedimentation tank according to the utility model, wherein the water inlet channel of the secondary sedimentation tank is connected with the water outlet of the biological pool; and a sludge pool, wherein the sludge pool is connected with the first mud outlet of the mud discharge pipe of the secondary sedimentation tank.

[0015] The sewage treatment system according to the utility model has the advantages of being easy to remove floating mud, timely removing floating mud, low energy consumption and simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a secondary sedimentation tank according to an embodiment of the utility model. DETAILED DESCRIPTION

[0017] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but cannot be understood as limiting the present invention.

[0018] The secondary sedimentation tank 1 according to an embodiment of the present utility model is described below with reference to the accompanying drawings. Figure 1 As shown, the secondary sedimentation tank 1 according to the embodiment of the utility model includes a tank body 11, a mud discharge pipe 12 and a floating mud collection pipe 13.

[0019] The tank body 11 includes a water inlet channel 111, which includes a clean water chamber 112 and a floating mud chamber 113. The floating mud chamber 113 is located above the clean water chamber 112. The clean water chamber 112 is a space for containing clean water, and the floating mud chamber 113 is a space for containing floating mud (sludge).

[0020] A portion of the mud discharge pipe 12 is located in the water inlet channel 111. The mud discharge pipe 12 has a first mud inlet and a first mud outlet. The first mud outlet of the mud discharge pipe 12 extends out of the water inlet channel 111. The floating mud collection pipe 13 is movably arranged in the water inlet channel 111 in the up-down direction. The floating mud collection pipe 13 has a second mud inlet 131 and a second mud outlet. The second mud inlet 131 of the floating mud collection pipe 13 can be located in the floating mud chamber 113, and the second mud outlet of the floating mud collection pipe 13 is communicated with the first mud inlet of the mud discharge pipe 12.

[0021] The water treated by aeration in the biological pool enters the water inlet channel 111 of the pool body 11 , and part of the sludge floats on the clean water in the clean water chamber 112 to form floating sludge, that is, part of the sludge is located in the floating sludge chamber 113 .

[0022] The second mud inlet 131 of the floating mud collecting pipe 13 can be located in the floating mud chamber 113, which means that the second mud inlet 131 of the floating mud collecting pipe 13 is located in the floating mud chamber 113 by moving the floating mud collecting pipe 13 in the up-down direction. When there is no need to remove (discharge) the floating mud, the second mud inlet 131 of the floating mud collecting pipe 13 may be located in the floating mud chamber 113 or may not be located in the floating mud chamber 113.

[0023] Thus, the floating mud in the floating mud chamber 113 can enter the floating mud collection pipe 13 from the second mud inlet 131. Then, the floating mud in the floating mud collection pipe 13 enters the mud discharge pipe 12 through the second mud outlet and the first mud inlet in turn, so as to be discharged from the water inlet channel 111. As the floating mud is discharged, the liquid level of the floating mud in the floating mud chamber 113 continues to drop. At this time, the floating mud collection pipe 13 can be moved downward so as to continue to discharge the floating mud from the water inlet channel 111 through the floating mud collection pipe 13 and the mud discharge pipe 12 until all the sludge is discharged from the water inlet channel 111.

[0024] According to the second sedimentation tank 1 of the embodiment of the utility model, by arranging the mud discharge pipe 12 and the floating mud collection pipe 13 which can move up and down in the water inlet channel 111, the floating mud can be discharged from the water inlet channel 111 in a timely and easy manner. This can not only prevent the floating mud from flowing into the water outlet channel of the second sedimentation tank 1 and polluting the effluent water quality, but also eliminate the need to use an electric dredging device to remove the floating mud, thereby reducing the energy consumption of the second sedimentation tank 1 and simplifying the structure of the second sedimentation tank 1.

[0025] Moreover, by movably arranging the floating sludge collecting pipe 13 in the water inlet channel 111 in the up-down direction, the floating sludge can be discharged from the water inlet channel 111 in a timely and easy manner when the secondary sedimentation tank 1 is in any of the various operating modes such as the constant liquid level mode, the tidal mode, the intermittent mode, etc.

[0026] Therefore, the secondary sedimentation tank 1 according to the embodiment of the utility model has the advantages of easy removal of floating sludge, timely removal of floating sludge, low energy consumption, simple structure, etc.

[0027] like Figure 1 As shown, the secondary sedimentation tank 1 is a peripheral inlet and outlet type secondary sedimentation tank, and the secondary sedimentation tank 1 includes a tank body 11, a mud discharge pipe 12, and a floating mud collection pipe 13. The tank body 11 includes an inlet channel 111, and the inlet channel 111 includes a clean water chamber 112 and a floating mud chamber 113, and the floating mud chamber 113 is located above the clean water chamber 112. It can be understood by those skilled in the art that the thickness and height of the clean water chamber 112 and the floating mud chamber 113 may change with the operating mode of the secondary sedimentation tank 1 (constant liquid level operation, tidal operation, intermittent operation, etc.), the processing capacity, and other factors.

[0028] A portion of the mud discharge pipe 12 is located in the water inlet channel 111. The mud discharge pipe 12 has a first mud inlet and a first mud outlet. The first mud outlet of the mud discharge pipe 12 extends out of the water inlet channel 111. Optionally, the first mud outlet of the mud discharge pipe 12 extends out of the tank body 11.

[0029] like Figure 1 As shown, the mud discharge pipe 12 includes a mounting section 121 and a buried section 122, and the mounting section 121 is vertically arranged in the clean water chamber 112. This not only facilitates the installation of the floating mud collection pipe 13 on the mounting section 121, but also enables the second mud inlet 131 of the floating mud collection pipe 13 to be located below the liquid surface (upper surface) of the floating mud chamber 113, so as to more thoroughly remove the floating mud in the secondary sedimentation tank 1.

[0030] A portion 123 of the buried section 122 is buried in the bottom wall 115 of the water inlet channel 111, and another portion 124 of the buried section 122 extends out of the water inlet channel 111. For example, the other portion 124 of the buried section 122 extends out of the tank body 11. The upper end of the buried section 122 is connected to the lower end of the installation section 121. Optionally, the upper end of the buried section 122 is located in the water inlet channel 111, that is, the upper end of the buried section 122 extends upward from the bottom wall 115 of the water inlet channel 111, so that the upper end of the buried section 122 is more easily connected to the lower end of the installation section 121.

[0031] The floating mud collection pipe 13 is located in the water inlet channel 111, and the floating mud collection pipe 13 is movably arranged on the installation section 121 in the up-down direction. A part of the floating mud collection pipe 13 is embedded in the installation section 121, that is, a part of the floating mud collection pipe 13 is located on the inner side of the installation section 121. Alternatively, a part of the floating mud collection pipe 13 is sleeved on the installation section 121, that is, a part of the floating mud collection pipe 13 is located on the outer side of the installation section 121. As the floating mud collection pipe 13 moves up and down, the length of the part of the floating mud collection pipe 13 changes.

[0032] Optionally, a sealing ring is provided between the installation section 121 and the floating mud collection pipe 13. This can prevent mud from entering the gap between the floating mud collection pipe 13 and the installation section 121 (mud discharge pipe 12), so as to prevent the mud from hindering the floating mud collection pipe 13 from moving up and down.

[0033] The lower end of the floating mud collection pipe 13 constitutes the second mud outlet of the floating mud collection pipe 13, and the upper end of the installation section 121 (mud discharge pipe 12) constitutes the first mud inlet of the mud discharge pipe 12. The lower end of the floating mud collection pipe 13 can extend into the installation section 121 through the upper end of the installation section 121 (mud discharge pipe 12), so that the second mud outlet of the floating mud collection pipe 13 is connected to the first mud inlet of the mud discharge pipe 12. The lower end of the buried section 122 constitutes the first mud outlet of the mud discharge pipe 12, and the lower end of the buried section 122 is opposite to the upper end of the buried section 122 in the extending direction of the buried section 122.

[0034] like Figure 1 As shown, the secondary sedimentation tank 1 further includes a mounting frame 14, a first threaded rod 151 and a first operating wheel 161. The mounting frame 14 is arranged on the side wall surface 114 of the water inlet channel 111. A part of the mounting frame 14 can be embedded in the side wall of the water inlet channel 111, and the mounting frame 14 can also be installed on the embedded part of the side wall of the water inlet channel 111 by welding, fasteners, etc. The mounting frame 14 can be arranged horizontally.

[0035] The mounting frame 14 has a first threaded hole, which passes through the mounting frame 14 in the up-down direction. A portion of the first threaded rod 151 is threadedly engaged in the first threaded hole, so that the first threaded rod 151 can be moved up and down by rotating the first threaded rod 151. The lower end of the first threaded rod 151 is connected to the floating mud collection pipe 13, so that the floating mud collection pipe 13 can be driven to move up and down by rotating the first threaded rod 151. The first operating wheel 161 is connected to the upper end of the first threaded rod 151, and the operator can conveniently and labor-savingly drive the first threaded rod 151 to rotate by rotating the first operating wheel 161.

[0036] Therefore, the operator can conveniently rotate the first threaded rod 151 to drive the floating mud collecting pipe 13 to move up and down, so as to conveniently and timely discharge the floating mud through the floating mud collecting pipe 13 .

[0037] The floating mud collecting pipe 13 includes a pipe body and a cover plate. The pipe body is movably arranged on the mud discharge pipe 12 (installation section 121) in the up-down direction, and the lower end of the pipe body constitutes the second mud outlet. The cover plate is arranged at the upper end of the pipe body, and the second mud inlet 131 of the floating mud collecting pipe 13 is opened on at least one of the cover plate and the upper end of the pipe body.

[0038] The lower end of the first threaded rod 151 is connected to the cover plate in a relatively rotatable manner, that is, the rotation of the first threaded rod 151 will not cause the cover plate to rotate together. Therefore, when the first threaded rod 151 is rotated to drive the floating mud collection pipe 13 to move up and down, the floating mud collection pipe 13 will not rotate together with the first threaded rod 151, thereby reducing the friction between the floating mud collection pipe 13 and the mud discharge pipe 12 (installation section 121), so as to drive the floating mud collection pipe 13 to move up and down more effortlessly.

[0039] Optionally, the second mud inlet 131 of the floating mud collecting pipe 13 can be located in the floating mud chamber 113, and the second mud inlet 131 of the floating mud collecting pipe 13 is spaced apart from the upper surface of the floating mud chamber 113 by a preset distance in the vertical direction. In other words, the second mud inlet 131 of the floating mud collecting pipe 13 can be located in the floating mud, and the second mud inlet 131 of the floating mud collecting pipe 13 is spaced apart from the floating mud surface of the floating mud by a preset distance in the vertical direction. In this way, the floating mud can be more easily entered into the floating mud collecting pipe 13, so as to improve the mud discharge effect. For example, the preset distance can be 0.5 cm-2 cm, that is, the second mud inlet 131 of the floating mud collecting pipe 13 is located 0.5 cm-2 cm below the floating mud surface of the floating mud.

[0040] The second mud inlet 131 of the floating mud collection pipe 13 may be located at the end of the water inlet channel 111 of the secondary sedimentation tank 1, thereby being able to collect the floating mud more comprehensively.

[0041] like Figure 1As shown, the secondary sedimentation tank 1 further includes a flushing pipe 17, which is connected to the mounting section 121 to flush the mud discharge pipe 12. This can prevent mud from accumulating in the mud discharge pipe 12, thereby preventing the mud discharge pipe 12 from being blocked, thereby making the secondary sedimentation tank 1 operate more stably. For example, when discharging floating mud, clean water can first enter the flushing pipe 17 and then enter the mud discharge pipe 12, so as to drain the entry of floating mud and avoid mud accumulation in the mud discharge pipe 12.

[0042] Optionally, the water inlet of the flushing pipe 17 is located in the clean water chamber 112. Thus, the clean water in the clean water chamber 112 can be used to flush the mud discharge pipe 12, without the need to introduce additional clean water from the outside, so as to make the structure of the secondary sedimentation tank 1 simpler.

[0043] The mounting frame 14 has a second threaded hole, and the second threaded hole passes through the mounting frame 14 in the up-down direction. Figure 1 As shown, the secondary sedimentation tank 1 further includes a control valve 18, a second threaded rod 152 and a second operating wheel 162. The control valve 18 is arranged on the flushing pipe 17 so as to connect and cut off the flushing pipe 17 by using the control valve 18. For example, the control valve 18 can be a butterfly valve.

[0044] A portion of the second threaded rod 152 is threadably engaged in the second threaded hole, so that the second threaded rod 152 is rotatably mounted on the mounting frame 14. The lower end of the second threaded rod 152 is connected to the control valve 18 to open and close the control valve 18, thereby connecting and cutting off the flushing pipe 17. The second operating wheel 162 is connected to the upper end of the second threaded rod 152, and the operator can rotate the second operating wheel 162 to conveniently and labor-savingly drive the second threaded rod 152 to rotate.

[0045] For example, the lower end of the second threaded rod 152 is connected to the valve stem of the control valve 18 so that the valve stem of the control valve 18 can be rotated by rotating the second threaded rod 152, thereby causing the valve core (valve plate) of the control valve 18 to open or close.

[0046] The secondary sedimentation tank 1 according to the embodiment of the utility model does not need to adopt the traditional manual clearing method, which saves a lot of labor costs and does not incur any energy consumption. Compared with the electric clearing device, the operating cost is low.

[0047] The operation mode of the secondary sedimentation tank 1 according to the embodiment of the utility model is flexible and changeable. By adjusting the height of the floating mud collection pipe 13, various operation modes such as constant liquid level operation, tidal operation, and intermittent operation of the secondary sedimentation tank 1 can be satisfied at the same time.

[0048] The utility model also provides a sewage treatment system. The sewage treatment system according to the embodiment of the utility model comprises a biological pool, a secondary sedimentation tank 1 and a sludge tank. The water inlet channel 111 of the secondary sedimentation tank 1 is connected to the water outlet of the biological pool, and the sludge tank is connected to the first mud outlet of the mud discharge pipe 12 of the secondary sedimentation tank 1.

[0049] Therefore, the sewage treatment system according to the embodiment of the utility model has the advantages of easy removal of floating sludge, timely removal of floating sludge, low energy consumption, simple structure, etc.

[0050] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0051] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0052] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0054] In the present utility model, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0055] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A secondary sedimentation tank, characterized in that: include: A pool body, the pool body comprising a water inlet channel, the water inlet channel comprising a clean water chamber and a floating mud chamber, the floating mud chamber being located above the clean water chamber; A mud discharge pipe, a portion of which is located in the water inlet channel, the mud discharge pipe having a first mud inlet and a first mud outlet, the first mud outlet of the mud discharge pipe extending out of the water inlet channel; and A floating mud collecting pipe, wherein the floating mud collecting pipe is movably arranged in the water inlet channel along the up and down directions, and the floating mud collecting pipe has a second mud inlet and a second mud outlet. The second mud inlet of the floating mud collecting pipe can be located in the floating mud chamber, and the second mud outlet of the floating mud collecting pipe is connected to the first mud inlet of the mud discharge pipe.

2. The secondary sedimentation tank according to claim 1, characterized in that: The secondary sedimentation tank is a peripheral inlet and outlet secondary sedimentation tank; and / or The second mud inlet of the floating mud collecting pipe is spaced apart from the upper surface of the floating mud chamber by a preset distance in the up-down direction.

3. The secondary sedimentation tank according to claim 1 or 2, characterized in that: The mud discharge pipe includes a mounting section, which is arranged in the clean water chamber. The floating mud collection pipe is movably arranged on the mounting section along the up and down directions, wherein a part of the floating mud collection pipe is embedded in the mounting section or a part of the floating mud collection pipe is sleeved on the mounting section.

4. The secondary sedimentation tank according to claim 3, characterized in that: A sealing ring is provided between the installation section and the floating mud collecting pipe.

5. The secondary sedimentation tank according to claim 3, characterized in that: Further including: A mounting frame, the mounting frame is arranged on the side wall surface of the water inlet channel, the mounting frame has a first threaded hole, and the first threaded hole passes through the mounting frame in the up-down direction; a first threaded rod, a portion of which is threadably engaged in the first threaded hole, and a lower end of the first threaded rod is connected to the floating mud collection pipe; and A first operating wheel is connected to an upper end of the first threaded rod.

6. The secondary sedimentation tank according to claim 5, characterized in that: The floating mud collection pipe comprises: a pipe body, the pipe body being movably disposed on the mud discharge pipe in an up-down direction, and a lower end of the pipe body constituting the second mud outlet; and A cover plate is arranged at the upper end of the tube body, the lower end of the first threaded rod is relatively rotatably connected to the cover plate, and the second mud inlet is opened on at least one of the cover plate and the upper end of the tube body.

7. The secondary sedimentation tank according to claim 5, characterized in that: It further comprises a flushing pipe connected to the installation section so as to flush the mud discharge pipe.

8. The secondary sedimentation tank according to claim 7, characterized in that: The mounting frame has a second threaded hole, and the second threaded hole passes through the mounting frame in the up-down direction. The secondary sedimentation tank further comprises: A control valve, wherein the control valve is arranged on the flushing pipe; a second threaded rod, a portion of which is threadably engaged in the second threaded hole, and a lower end of the second threaded rod is connected to the control valve to open and close the control valve; and A second operating wheel is connected to an upper end portion of the second threaded rod.

9. The secondary sedimentation tank according to claim 7, characterized in that: The water inlet of the flushing pipe is located in the clean water chamber; and / or The mud discharge pipe also includes a buried section, the upper end of which is connected to the lower end of the installation section, a part of which is buried in the bottom wall of the water inlet channel, and another part of which extends out of the water inlet channel, and the installation section is vertically arranged in the water inlet channel.

10. A sewage treatment system, characterized in that: include: Biological pool; A secondary sedimentation tank, wherein the secondary sedimentation tank is the secondary sedimentation tank according to any one of claims 1 to 9, and the water inlet channel of the secondary sedimentation tank is connected to the water outlet of the biological pool; and A sludge tank is connected to the first sludge outlet of the sludge discharge pipe of the secondary sedimentation tank.

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