CN111201073A

CN111201073A - Settling tank

Info

Publication number: CN111201073A
Application number: CN201880064684.8A
Authority: CN
Inventors: 清水哲; 岩崎守
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2017-11-10
Filing date: 2018-09-10
Publication date: 2020-05-26
Anticipated expiration: 2038-09-10
Also published as: JP2019088998A; TW201922331A; WO2019092971A1; KR102541106B1; CN111201073B; JP6508293B1; KR20200078491A

Abstract

A settling tank in which raw water supplied from a center well (2) in the center of a tank body (1) to the lower part of the tank body rises in the tank body (1) and clarified water flows out from an overflow part in the upper part of the tank body (1), and which is provided with a support plate (4) facing the lower end of the center well (2) for changing the flow direction of the water, characterized in that a nozzle part (5a) for discharging water for discharging sludge toward the vicinity of the center of the support plate (4) is provided.

Description

Settling tank

Technical Field

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

Background

Conventionally, in activated sludge treatment facilities, coagulation sedimentation treatment facilities, and the like, sedimentation separation using a solid-liquid separation tank (sedimentation tank) has been generally employed as a means for separating a sludge mixed solution (coagulation treatment liquid) into treated water and sludge. In this settling separation, the following were used: in order to efficiently remove turbid materials and fine SS in the sludge mixed liquid and obtain good treated water, a sludge blanket filtration system is used in which a sludge zone (sludge blanket layer) is formed in the settling tank, and the sludge mixed liquid is caused to flow from the lower portion of the sludge zone through a center well (supply well) and to pass through the sludge zone, thereby filtering and separating turbid materials and fine SS in the sludge mixed liquid.

A well type settling tank is known in which a pallet is horizontally disposed to face a lower end of a well in a central portion of a tank body, and a flow direction of effluent from the well is changed in a radial direction (japanese patent application laid-open No. 2005-66533).

As a patent for preventing sludge from accumulating on the pallet, japanese patent laid-open publication No. 10-165714 discloses that a conical pallet is provided instead of a horizontal pallet. Japanese patent application laid-open No. 2007-69189 discloses a rotary rake that is provided to rotate along the upper surface of a pallet and to discharge accumulated sludge.

[ patent document 1] Japanese patent application laid-open No. 10-165714;

[ patent document 2] Japanese patent laid-open No. 2005-66533;

[ patent document 3] Japanese patent application laid-open No. 2007-69189.

As disclosed in jp 2005-66533 a, the effect of changing the flow direction of water from the center well to the horizontal direction is excellent when the pallet is horizontal, but sludge is likely to accumulate near the center of the pallet. That is, the flow velocity in the circumferential direction is small near the center of the pallet, and therefore sludge is likely to accumulate.

If the pallet of jp 10-165714 a is conical, sludge is less likely to accumulate on the pallet. However, since the pallet is formed in a conical shape, the effect of changing the flow direction of water from the center well to the horizontal direction is weak.

As disclosed in jp 2007 a-69189 a, when a rotary rake is provided that rotates along the upper surface of the pallet, the uniform radial flow may be obstructed by the rotary rake.

Disclosure of Invention

The invention aims to provide a settling tank which can remove deposits on a supporting plate for changing the flowing direction of water flowing out of a supply well, and has uniform flowing of water flowing out of a central well and excellent sludge separation efficiency.

The settling tank of the present invention is a settling tank in which raw water supplied from a center well in the center of the tank to the lower part of the tank is made to rise in the tank and clarified water flows out from an overflow part in the upper part of the tank, and the settling tank is provided with a support plate facing the lower end of the center well to change the flow direction of the water, and is characterized in that a spray nozzle for spraying water for flowing sludge toward the vicinity of the center of the support plate is provided.

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

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

In one aspect of the present invention, the lower end of the nozzle unit is located at the same height as or above the lower end of the center well.

[ Effect of the invention ]

In the settling tank of the present invention, the water is sprayed from the nozzles to prevent sludge from being deposited on the blade. In the present invention, since there is no rotating rake on the pallet and the water to be treated smoothly flows out in the radial direction from between the center well and the pallet, sludge is efficiently removed and the accumulation on the pallet can be suppressed.

Drawings

FIG. 1 is a longitudinal sectional view of a precipitation tank of an embodiment.

Fig. 2 is an enlarged view of the vicinity of the lower end of the centerwell of the settling tank of fig. 1.

Fig. 3 is a perspective view of the settling tank of fig. 1 near the lower end of the centerwell.

Detailed Description

Hereinafter, embodiments will be described with reference to the drawings. FIGS. 1 to 3 show a coagulation-sedimentation device having a sedimentation tank according to an embodiment.

In the settling tank of this embodiment, the tank body 1 is circular, and a center well 2 is provided in the center of the tank body 1. The center well 2 is cylindrical with both upper and lower ends open, and its upper end protrudes above the water 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 bottom surface 3a of the center well upper portion 3 is connected to the upper outer peripheral surface of the center well 2.

Is provided with: a pallet 4, which is a flat buffer plate, facing 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 radial direction. In this embodiment, the pallet 4 is a horizontal circular plate. The pallet 4 is located below the lower end of the center well 2 at a predetermined distance and forms a raw water outlet (for example, about 20 to 150 mm). The pallet 4 and the center well 2 are arranged coaxially.

A rake shaft 10 described later penetrates the center of the blade 4, and the blade 4 is supported by the rake shaft 10 while being in contact with and fixed to the rake shaft 10. The pallet 4 may be supported by the center well 2 via a support member (not shown).

A nozzle 5 for discharging water is provided and is directed toward the vicinity of the center of the pallet 4 to allow sludge to flow from the pallet 4.

In this embodiment, the nozzle 5 is supported by the center well 2 and extends in the vertical direction along the inner peripheral surface of the center well 2. The nozzles 5 may be disposed next to or slightly away from the inner circumferential surface of the center well 2.

The lower portion of the nozzle 5 is turned obliquely downward toward the vicinity of the center of the pallet 4 to form a nozzle portion 5 a. However, the nozzle portion 5a may be formed so as to change its direction horizontally 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 slightly (e.g., within 100mm, particularly within 50 mm) above the lower end of the center well 2.

If the lower end of the nozzle portion 5a is lower than the lower end of the center well 2, the flow of the raw water discharged from the raw water outlet into the tank is blocked, and the uniform flow in the radial direction is affected. On the other hand, if the lower end of the nozzle portion 5a is too high, the discharge flow rate of the water jet for removing sludge on the pallet 4 increases, and uniform flow in the same radial direction is easily hindered.

The angle theta of the nozzle section 5a with respect to the horizontal plane is 40 to 90 DEG, and particularly preferably 45 to 60 deg. If the angle θ is smaller than 40 °, the horizontal flow becomes strong, the flow from the pallet 4 in the radial direction tends to be uneven, and the sludge is not likely to be discharged constantly. On the other hand, the larger the angle θ, the closer the lower end of the nozzle is to the axis, and the more difficult it is to fix the nozzle connected to the nozzle portion 5a from the supply well, which may cause a decrease in mechanical strength. Preferably, an extension W of the pipe axis of the nozzle portion 5a intersects with the upper surface of the blade 4, and more specifically, preferably intersects with the upper surface of the blade 4 in the vicinity of the rake shaft 10. The distance R between the axis of the center well 2 and the intersection point of the extension line W and the upper surface of the pallet 4 is not more than half (50%) of the radius R of the center well 2, particularly preferably not more than 40%, and particularly preferably not more than 30%. Since the lower end of the nozzle portion 5a is disposed as described above, the water ejected from the nozzle portion 5a flows with a gradually wider width while the flow velocity decreases, and therefore, most of the range of the pallet can be affected.

The radius of the pallet 4 is not less than the radius R of the center well 2 but not more than 1.5 times, preferably about 1 to 1.3 times, the radius R.

The bottom surface of the tank body 1 is a downward slope toward the center, and a groove 6 for collecting and discharging settled sludge is provided in the center thereof. The sludge in the groove 6 is discharged out of the tank body 1 through the sludge discharge pipe 7.

A rake device is provided to rotate the rake plate 11 along the bottom surface of the tank body 1. The rake device comprises: a drag shaft 10 extending vertically through the axial center portion of the center well 2, a support arm 12 extending radially from the lower portion of the drag shaft 10, a drag plate 11 attached to the arm 12, and a driving device (not shown) connected to the upper end of the drag shaft 10.

The rake plate 11 is disposed in a direction oblique to the longitudinal direction of each arm 12 so that deposits on the bottom surface of the tank body move 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 an upper portion of the inner peripheral wall surface of the tank body 1. The upper end of the overflow weir 13 is slightly (e.g., about 50 to 200 mm) lower than the upper end of the centerwell 2.

The depth of the water in the tank 1, i.e., the height from the bottom of the tank to the upper end of the overflow weir 13, is preferably 100 to 400cm, more preferably 100 to 250 cm.

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

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

The vertical distance H between the lower end of the center well 2 and the upper surface of the pallet 4 is, for example, about 20 to 150mm as described above, and the horizontal linear velocity of the raw water flowing out from the raw water outlet is preferably set to about 4 to 10cm/sec, particularly about 5 to 8 cm/sec.

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

The discharge flow velocity of the water jet from the nozzle section 5a is 1m/sec or more, and particularly preferably about 1 to 5 m/sec. The discharge flow rate (m) from the nozzle section 5a is preferably set³Hr) divided by the area of the pallet 4 (m)²) The calculated discharge flow rate per unit pallet area is 1-8 m³/hr/m²I.e., 1 to 8 m/hr.

In the settling tank configured as described above, the water to be treated is supplied into the center well upper portion 3, flows into the center well 2 over the upper end of the center well 2, descends in the center well 2, and flows out radially from the raw water outlet between the lower end of the center well 2 and the pallet 4. Thereafter, the water rises in the tank 1, overflows the overflow weir 13, and is discharged from the clarified water outlet 14.

The sludge accumulated on the upper surface of the pallet 4 may be pushed and flowed away by the water jet discharged from the nozzle portion 5a, and therefore, the sludge can be prevented from accumulating on the pallet 4. The water spray may be continuously or intermittently discharged.

The sludge settled on the bottom surface of the tank body 1 is stirred by the harrow to be collected to the groove 6 and is discharged from the sludge discharge pipe 7.

In this embodiment, as described above, the water is discharged from the nozzle portion 5a, so that the sludge can be prevented from being deposited on the pallet 4. Moreover, since the rakes are not present on the pallets 4, the water to be treated can be gently flowed into the sludge blanket from the raw water outlet between the lower end of the center well 2 and the pallets 4, and the sludge can be efficiently separated by sedimentation.

In the above embodiment, the pallet 4 is horizontally disposed, but at least the vicinity of the center may be an inclined surface having an angle of less than 15 ° in the radial direction. However, preferably, at least the outer peripheral portion is horizontal.

In the above embodiment, the tank body 1 has a cylindrical shape, but may have a square shape (a polygon of a square shape or more). The bottom surface of the tank body 1 may be horizontal.

In the above embodiment, the nozzle 5 is provided along the inner peripheral surface of the center well 2, but may be provided along the outer peripheral surface of the center well 2, and the nozzle portion 5a may be inserted into the center well 2 through the lower portion of the center well 2.

In the above embodiment, the nozzles 5 are arranged along the central well 2, but may be arranged along the rake shaft 10. Also, more than 2 nozzles may be provided.

In the above embodiment, the center well 2 has a constant diameter from the upper end to the lower end, but the lower portion may have a large diameter. In this case, the tapered surface may have a larger diameter as the lower end is located. Further, in this case, a preferable configuration is: 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 to the rake shaft 10.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes can be made therein without departing from the spirit and scope thereof.

The present application is based on japanese patent application No. 2017-217425, filed on 11/10/2017, which is incorporated herein by reference in its entirety.

Description of reference numerals

1: trough body

2: central well

3: upper part of central well

3 a: bottom surface

4: supporting plate

5: spray pipe

5 a: nozzle part

6: groove

7: sludge discharge pipe

10: rake shaft

11: rake plate

12: support arm

13: overflow weir

14: and a clear water outlet.

Claims

1. A settling tank in which raw water supplied from a center well at the center of a tank body to the lower part of the tank body rises in the tank body and clarified water flows out from an overflow part at the upper part of the tank body,

and the settling tank is provided with a supporting plate which is opposite to the lower end of the central well and is used for changing the flowing direction of water, and is characterized in that,

a nozzle for jetting water for flowing sludge toward the vicinity of the center of the pallet is provided.

2. A precipitation tank according to claim 1, wherein,

the nozzle is a nozzle portion connected to a lower portion of a nozzle tube extending along the centerwell.

3. A precipitation tank according to claim 2, wherein,

the nozzle portion extends toward the center side of the pallet with a descending slope of 40 to 90 degrees or extends in the vertical direction.

4. A precipitating bath according to claim 2 or 3, characterized in that,

the lower end of the nozzle portion is located at the same height as or above the lower end of the centerwell.

5. A precipitation tank according to any of claims 1 to 4, wherein,

at least the outer periphery of the support plate is horizontal.