TW201922331A - Precipitation tank - Google Patents

Abstract

A precipitation tank in which raw water supplied to the lower part of the interior of a tank body from a center well 2 at the center part of the tank body 1 rises inside the tank body 1 and flows out as clear water from an overflow part at the upper part of the tank body 1, a plate 4 for changing the water flow direction being provided so as to face the lower end of the center well 2, wherein the precipitation tank is characterized in being provided with a nozzle unit 5a for discharging blow water for sludge removal towards the vicinity of the center of the plate 4.

Description

Sedimentation tank

The present invention relates to a sedimentation tank for sedimentation and separation of sludge, and more particularly to a sedimentation tank having a center well and a pallet facing the lower end of the center well.

Conventionally, in activated sludge treatment equipment, coagulation and sedimentation treatment equipment, and the like, a method for separating a sludge mixture liquid (condensation treatment liquid) into water and sludge is generally settling using a solid-liquid separation tank (precipitation tank) Separation. In this sedimentation and separation, it has been adopted to form a sludge region (sludge blanket layer) in a sedimentation tank in order to obtain good treated water in order to efficiently remove turbidity and fine SS in a sludge mixture. ), Through the central well (supply well), the sludge mixture liquid flows from the lower part of the sludge area and passes through the sludge area, and the turbidity and the fine SS in the sludge mixture are separated by a sludge blanket filtration method.

A well-known sedimentation tank of a center well type is a structure in which a supporting plate is installed horizontally opposite to the lower end of the center well in the center of the tank body, and the flow direction of the outflow water from the center well is changed to a radial direction (Japanese Patent Laid-Open No. 2005 -66533).

Those who prevent sludge from accumulating on this pallet, such as Japanese Patent Application Laid-Open No. 10-165714, describe that a conical pallet is provided instead of a horizontal pallet. For example, Japanese Patent Laid-Open No. 2007-69189 describes a rotary harrow that is provided to rotate along the upper surface of a pallet to pull out the accumulated sludge.

[Patent Document 1] Japanese Patent Laid-Open No. 10-165714 [Patent Document 2] Japanese Patent Laid-Open No. 2005-66533 [Patent Document 3] Japanese Patent Laid-Open No. 2007-69189

For example, in Japanese Patent Application Laid-Open No. 2005-66533, when the pallet is horizontal, the effect of changing the flow direction of the water from the center well to the horizontal direction is excellent, but the sludge is likely to stay near the center of the pallet. That is, the velocity in the circumferential direction near the center of the pallet is small, so that sludge is easily accumulated.

For example, when the pallet of Japanese Patent Application Laid-Open No. 10-165714 is conical, it is difficult for sludge to accumulate on the pallet. However, since the pallet is conical, the effect of changing the flow direction of water from the center well to the horizontal direction is weak.

For example, in Japanese Patent Application Laid-Open No. 2007-69189, a rotary harrow that rotates along the upper surface of the pallet is provided, and a uniform radial flow may be blocked by the rotary harrow.

An object of the present invention is to provide a sedimentation tank that can remove deposits on a pallet for changing the flow direction of water flowing from a supply well, and that the flow of outflow water from a center well is uniform, and the sludge separation efficiency is excellent.

The sedimentation tank of the present invention is such that raw water supplied from a central well in the central part of the tank body to the lower part of the tank body rises in the tank body, and the overflow part from the upper part of the tank body flows into clarified water, and is provided. A support plate for changing the flow direction of water is provided to face the lower end of the center well, and is characterized by being provided with a nozzle for spouting water for sludge flow away toward the center of the support plate.

In one aspect of the present invention, the nozzle is a nozzle portion connected to a lower portion of a nozzle extending along the center well.

In one aspect of the present invention, the nozzle portion extends toward the center side of the pallet with a descending slope of 40 to 90 ° or a vertical direction.

In one aspect of the present invention, the lower end of the nozzle portion is located at the same height as or higher than the lower end of the center well. [Effect of the invention]

In the sedimentation tank of the present invention, sludge is discharged from a nozzle to prevent sludge from being deposited on the pallet. In the present invention, since there is no rotating harrow on the pallet, and the treated water flows out smoothly from the center well and the pallet in a radial direction, the sludge is efficiently removed, and the pallet can be suppressed. Stacked on the board.

Hereinafter, embodiments will be described with reference to the drawings. Figures 1 to 3 show the coagulation and sedimentation device having the sedimentation tank of the example.

In the sedimentation tank of this embodiment, the tank body 1 is circular, and a central well 2 is provided at a central portion of the tank body 1. This center well 2 is cylindrical with its upper and lower ends open, and its upper end portion projects more upward than the water surface level in the tank body 1. In the upper part of the center well 2, a center well upper part 3 having a larger diameter than the center well 2 is provided. The center well upper part 3 has a bottom surface 3 a connected to the upper peripheral surface of the center well 2.

It is provided with a pallet 4 commonly referred to as a flat buffer plate, which faces the lower end of the center well 2 and converts the flow direction of the raw water from the center well 2 from a downward direction to a radiation direction. In this embodiment, the pallet 4 is in the shape of a horizontal circular plate. The pallet 4 is located below a predetermined distance from the lower end of the center well 2 and forms a raw water outlet (for example, about 20 to 150 mm). The pallet 4 and the center well 2 are arranged coaxially.

The rake shaft 10 described later penetrates the center portion of the pallet 4, and the pallet 4 is supported by being abutted and fixed to the rake shaft 10. However, the pallet 4 may be supported by the center well 2 through a support member (not shown).

A nozzle pipe 5 is provided to discharge the sludge from the tray 4 toward the vicinity of the center of the tray 4 and discharge the water.

In this embodiment, the nozzle 5 is supported by the center well 2 and is extended in the vertical direction along the inner peripheral surface of the center well 2. In addition, the nozzle 5 may be in contact with the inner peripheral surface of the center well 2, and may be slightly separated from the inner peripheral surface.

The lower part of the nozzle pipe 5 changes its direction toward the vicinity of the center of the pallet 4 and tilts downward to become the nozzle portion 5a. However, the nozzle portion 5 a may be changed in the horizontal direction toward the vicinity of the center of the pallet 4. The lower end of the nozzle portion 5a is located at the same height as or lower than the lower end of the center well 2 (for example, within 100 mm, particularly within 50 mm). If the lower end of the nozzle part 5a is lower than the lower end of the center well 2, the flow of the raw water discharged from the raw water outlet toward the tank is hindered, and the uniform flow in the radiation direction is affected. On the other hand, if the lower end of the nozzle part 5a is too high, the discharge flow rate of the water jet for sludge removal on the pallet 4 will increase, and the uniform flow in the same radiation direction will be easily blocked.

The angle θ of the horizontal plane of the nozzle portion 5a is preferably 40 to 90 °, particularly preferably 45 to 60 °. When the angle θ is smaller than 40 °, the flow in the horizontal direction becomes stronger, and the flow in the radial direction from the pallet 4 tends to become uneven, and the sludge is not easily discharged. On the other hand, as the angle θ becomes larger, it is necessary to approach the shaft at the lower end of the nozzle, which makes it difficult to fix the nozzle connected from the supply well to the nozzle portion 5 a, and there is a concern that the strength of the machine will decrease. It is preferable that the extension line W of the tube axis center of the nozzle portion 5 a intersects the upper surface of the pallet 4. In detail, it preferably intersects the upper surface of the pallet 4 near the rake shaft 10. The distance r between the intersection of the extension line W and the upper surface of the pallet 4 and the axial center of the center well 2 is less than half (50%) of the radius R of the center well 2, especially 40% or less, especially 30% or less Better. Since the lower end of the nozzle portion 5a is arranged as described above, the sprayed water discharged from the nozzle portion 5a changes to a gradually widening flow while the flow velocity decreases, so that it can affect a wide range of the pallet.

The radius of the pallet 4 is greater than or equal to 1.5 times the radius R of the center well 2 and preferably about 1 to 1.3 times the radius of R.

The bottom surface of the tank body 1 has a downward slope toward the center, and a groove 6 for collecting and discharging the settled sludge is provided in the center portion. The sludge in the trench 6 is discharged to the outside of the tank 1 through the sludge pipe 7.

The rake plate 11 is rotatably provided with a rake device along the bottom surface of the tank body 1. This rake device includes a rake shaft 10 extended in an up-down direction through an axial center portion of the center shaft 2, a support arm 12 extended in a radial direction from a lower portion of the rake shaft 10, and is mounted on The rake plate 11 of the arm 12 and the driving device (not shown) connected to the upper end of the rake shaft 10.

The rake plate 11 is arranged in a direction oblique to the longitudinal direction of each arm 12 so as to move the deposits on the bottom surface of the tank body toward the center of the bottom surface of the tank body when the rake rotates.

An overflow weir 13 as an overflow portion is provided along the upper portion of the inner peripheral wall surface of the tank body 1. The upper end of the overflow weir 13 is lower than the upper end of the center well 2 (for example, about 50 to 200 mm).

The water depth of the trough body 1 is the height from the bottom surface of the trough body to the upper end of the overflow weir 13, preferably 100 to 400 cm, and more preferably 100 to 250 cm.

The height of the upper surface of the supporting plate 4 from the bottom surface of the groove body (peripheral edge portion of the groove 6) is 20 to 80 cm, preferably 25 to 60 cm, and particularly 30 to 50 cm.

The descending flow velocity (LV) in the center well 2 is 40 cm / sec or less, for example, 5 to 30 cm / sec, and particularly preferably about 10 to 30 cm / sec.

The vertical interval H of the raw water outlet between the lower end of the center well 2 and the upper surface of the pallet 4 is, for example, approximately 20 to 150 mm as described above. The horizontal linear velocity of the raw water flowing from this raw water outlet is 4 to 10 cm / sec. , Especially the best setting is about 5 ~ 8cm / sec.

The ascending flow velocity (LV) in the tank 1 is 1 m / hr or more, for example, 1 to 20 m / hr, and particularly preferably about 2 to 10 m / hr.

The discharge flow velocity of the water spray from the nozzle portion 5a is 1 m / sec or more, and preferably about 1 to 5 m / sec. The discharge flow rate (m ³ / hr) from the nozzle portion 5a divided by the area (m ² ) of the pallet 4 is 1 to 8 m ³ / hr / m ² , that is, 1 to 8 m. / hr is better.

In the sedimentation tank configured in this way, the treated water is supplied into the upper part 3 of the center well 2 and flows into the center well 2 over the upper end of the center well 2 and descends in the center well 2 from the lower end of the center well 2 and the pallet 4 The raw water outlets between them flow out in a radial direction. Thereafter, the water rises in the tank body 1, overflows in the overflow weir 13, and is discharged from the clarified water outlet 14.

The sludge to be deposited on the upper surface of the pallet 4 is pushed by the water sprayed from the nozzle portion 5a, so that the sludge can be prevented from accumulating on the pallet 4. In addition, the discharge of the water jet may be performed continuously or intermittently.

The sludge settled on the bottom surface of the tank 1 is collected by being pulled toward the trench 6 by a rake, and is discharged from the sludge pipe 7.

In this embodiment, as described above, since the spray water is discharged from the nozzle portion 5a, it is possible to prevent sludge from being deposited on the pallet 4. In addition, because the rake does not exist on the pallet 4, the treated water flows gently into the sludge blanket from the raw water outlet between the lower end of the center well 2 and the pallet 4, and the sludge can be efficiently made. Separated by sedimentation.

In the above embodiment, although the pallet 4 is horizontal, at least the vicinity of the center may be an inclined surface that is less than 15 ° toward the radiation direction. However, it is preferable that at least the outer peripheral portion is level.

In the above embodiment, although the groove body 1 is cylindrical, an angular shape (a quadrangular shape or a polygonal shape) may be used. The bottom surface of the groove body 1 may be horizontal.

In the above-mentioned embodiment, although the nozzle 5 is provided along the inner peripheral surface of the center well 2, it is provided along the outer peripheral surface of the center well 2. The nozzle portion 5a penetrates the lower part of the center well 2 and is inserted into the center well 2. The internal structure is also possible.

In the above embodiment, although the nozzles 5 are arranged along the center well 2, they may be arranged along the harrow shaft 10. Moreover, two or more nozzles may be provided.

In the above-mentioned embodiment, although the center well 2 is formed to have an equal diameter from the upper end to the lower end, the lower portion may be formed to have a large diameter. In this case, a tapered surface having a larger diameter at the lower end may be used. In this case, in order to fix the nozzle 5, the upper small diameter portion and the lower large diameter portion of the center well 2 are integrated, or the lower large diameter portion is fixed to the upper small diameter portion, and the lower large diameter portion is not fixed. The structure of the harrow shaft 10 is preferred.

Although the present invention has been described in detail using specific aspects, those skilled in the art can obviously make various changes without departing from the intention and scope of the present invention.案 The present application is cited by citing the entirety of Japanese Patent Application No. 2017-217425 filed on November 10, 2017.

1‧‧‧ tank

2‧‧‧ center well

3‧‧‧upper center well

3a‧‧‧ Underside

4‧‧‧ pallet

5‧‧‧ Nozzle

5a‧‧‧Nozzle section

6‧‧‧ groove

7‧‧‧Drain pipe

10‧‧‧ Rake Shaft

11‧‧‧ Rake

12‧‧‧ support arm

13‧‧‧ overflow weir

14‧‧‧ clarified water outlet

[FIG. 1] A longitudinal sectional view of a sedimentation tank according to an embodiment.第 [Fig. 2] An enlarged view near the bottom of the central well of the sedimentation tank in Fig. 1.第 [FIG. 3] A perspective view of the vicinity of the bottom of the center well of the sedimentation tank of FIG.

Claims (5)

A sedimentation tank is a raw water that is supplied from a central well in the central part of the tank to the lower part of the tank body, rises in the tank body, and flows from the overflow part in the upper part of the tank body to clear water, and is provided with The lower end of the center well is opposed to a pallet for changing the flow direction of water, and is characterized in that: (a) a nozzle for ejecting water for sludge flow away toward the center of the pallet is provided. For example, the precipitation tank according to item 1 of the patent application scope, wherein the nozzle is a nozzle portion connected to a lower portion of a nozzle extending along the center well. For example, the sedimentation tank according to item 2 of the patent application scope, wherein: the nozzle portion extends toward the center side of the pallet with a descending slope of 40 to 90 ° or a vertical direction. For example, the sedimentation tank of the second or third aspect of the patent application scope, wherein the lower end of the nozzle part is located at the same height as or higher than the lower end of the center well. The sedimentation tank according to any one of claims 1 to 4, in which the aforementioned pallet is horizontal at least at the outer peripheral portion.