WO2019092973A1

WO2019092973A1 - Sedimentation tank

Info

Publication number: WO2019092973A1
Application number: PCT/JP2018/033469
Authority: WO
Inventors: 哲清水; 守岩▲崎▼
Original assignee: 栗田工業株式会社
Priority date: 2017-11-10
Filing date: 2018-09-10
Publication date: 2019-05-16
Also published as: JP6601475B2; TW201922332A; JP2019089000A

Abstract

Provided is a sedimentation tank wherein raw water supplied from a center well 2 to the lower portion within the body of said tank rises within the body 1 of said tank, and becomes clarified water and flows out from an overflow part 13 on the upper portion of the body 1 of said tank. A plate 4 for changing the flow direction of water is provided facing the lower end of the center well 2. Water to be treated flows from an inlet pipe 8 to an annular water channel C in a circumferential direction, swirls within the annular water channel C, overflows an upper end 2t of the center well 2, and flows into the center well 2.

Description

Settling tank

The present invention relates to a settling tank for settling and separating sludge, and more particularly to a settling tank in which water to be treated is supplied to the lower portion of the settling tank via a center well.

Conventionally, in activated sludge treatment facilities, coagulation sedimentation treatment facilities, etc., sedimentation separation using a solid-liquid separation tank (precipitation tank) is generally used as a means for separating the sludge mixed liquid (coagulation treatment liquid) into treated water and sludge. It is adopted. In this sedimentation separation, a sludge zone (sludge blanket layer) is formed in the sedimentation tank in order to efficiently remove suspended solids and fine SS in the sludge mixed liquid to obtain good treated water, and The sludge blanket filtration system is used to filter and separate suspended solids and fine SS in the sludge mixed solution by passing the sludge mixed solution from the lower part of this sludge zone through the feed well and passing through the sludge zone. There is.

It is known that a plate is provided horizontally as opposed to the lower end of the center well in the central portion of the tank body as a center well type settling tank, and the flow direction of the effluent water from the center well is changed in the radial direction. (Patent Document 1).

In order to effectively perform solid-liquid separation in the sedimentation tank and obtain highly-clear treated water in the coagulation / sedimentation apparatus, it is important to introduce the produced flocculated flocs into the sedimentation tank without breaking it. That is, when the flocculated floc is broken down and refined, its sedimentation property deteriorates, and it flows out to the treated water side to deteriorate the water quality of the treated water.

In Patent Document 2, a cylindrical inflow portion having a diameter larger than that of the center well is formed in the upper portion of the cylindrical center well, and the water to be treated is supplied from the inflow pipe in the tangential direction of the peripheral wall of the inflow portion. In the inflow portion, a swirling flow is formed along the peripheral wall, and introduced into the center well as it is, forming a downward flow while swirling in the center well, thereby preventing the occurrence of drifting when introducing the water to be treated It is disclosed to suppress the destruction of flocculated floc.

However, there is a concern that the flow velocity introduced into the center well tends to be uneven between the vicinity of the introduction portion of the water to be treated and the inflow portion. When the flow velocity is locally high, the cohesive floc is likely to be broken locally.

JP 2005-66533 A JP 2017-87090 A

An object of the present invention is to provide a settling tank capable of uniformly introducing treated water into a center well.

In the settling tank of the present invention, the water to be treated supplied from the center well at the central portion of the tank body to the lower portion inside the tank body rises in the tank body and becomes clear water from the overflow portion at the top of the tank body. In the sedimentation tank which flows out, there is provided a center well upper member forming an annular water channel surrounding the upper outer periphery of the center well, the center well upper member having a bottom surface extending in a spreading direction from the center well And a peripheral wall standing up from the outer peripheral edge of the bottom surface, the water to be treated is introduced into the annular water channel by the introduction member in the circumferential direction along the peripheral wall, overflowing the upper end of the center well It is characterized by flowing into the center well.

In one aspect of the present invention, the upper end of the center well has a uniform height over the entire circumference.

In one aspect of the present invention, the difference between the level of the overflow and the level of the upper end of the center well is 0 to 20 cm.

In one aspect of the present invention, the bottom surface of the annular water channel is horizontal and located below the upper end of the center well.

In one aspect of the present invention, at least the center well side of the bottom surface of the annular water channel is an inclined surface which is lowered toward the outer periphery.

In one aspect of the present invention, the angle of the inclined surface with respect to the horizontal plane is 5 to 60 °.

In one aspect of the present invention, a plate is provided to face the lower end of the center well to change the flow direction of water.

In the sedimentation tank of the present invention, the water to be treated which has flowed into the annular water channel in the circumferential direction overflows the upper end of the center well and uniformly flows into the center well while forming a swirling flow in the annular water channel. Therefore, it is possible to prevent that the flow velocity is locally increased in the annular water channel or the center well to break the flocculated floc. In addition, by making the height difference between the height of the upper end of the center well and the water level in the center well as low as possible, it is possible to prevent the destruction of the flocculated floc due to the impact of falling overflowed treated water on the water surface in the center well Sludge can be separated efficiently.

It is a longitudinal cross-sectional view of the sedimentation tank which concerns on embodiment. It is a top view near the center well of the sedimentation tank of FIG. It is a longitudinal cross-sectional view of the center well vicinity of the sedimentation tank which concerns on another embodiment. It is a longitudinal cross-sectional view of the center well vicinity of the sedimentation tank which concerns on another embodiment. It is a top view near the center well of the sedimentation tank concerning another embodiment.

Hereinafter, embodiments will be described with reference to the drawings. 1 and 2 show a coagulating and settling apparatus having a settling tank according to the first embodiment.

In the sedimentation tank according to this embodiment, the tank body 1 is circular, and the center well 2 is installed at the central portion of the tank body 1. The center well 2 is in the form of a cylinder whose upper and lower ends are open, and its upper end 2 t protrudes above the water surface level WL in the tank body 1. This water level WL is the overflow level of the overflow weir 13 described later. The upper end 2t has a uniform height over the entire circumference.

A center well upper 3 having a diameter larger than that of the center well 2 is provided on the top of the center well 2 as a center well upper member. The center well upper 3 is connected to the upper outer peripheral surface of the center well 2 and has a flat bottom surface 3a which spreads in the horizontal direction, and a peripheral wall 3b standing up from the outer peripheral edge of the bottom surface 3a. A portion surrounded by the upper portion of the center well 2, the bottom surface 3 a and the peripheral wall 3 b is an annular water channel C surrounding the upper outer periphery of the center well 2. The difference (height difference) between the level of the water level WL and the level of the upper end 2t of the center well 2 is preferably 0 to 20 cm, more preferably 0 to 10 cm, particularly preferably 0 to 5 cm.

An introduction pipe 8 is provided as a member for introducing the water to be treated so that the water to be treated flows into the annular water passage C in the circumferential direction. The end portion of the introduction pipe 8 extends along the peripheral wall 3b as shown in FIG. 2, and the water to be treated flows into the annular water channel C along the peripheral wall 3b and is swirled in the annular water channel C. , Overflows the upper end 2t of the center well 2 and flows into the center well 2.

The diameter of the annular water channel C (diameter of the inner peripheral surface of the peripheral wall 3b) is preferably 1.2 to 2.0 times, particularly 1.4 to 1.8 times the outer diameter of the upper end 2t of the center well 2.

In this embodiment, the bottom surface 3a is horizontal. The height difference between the upper end 2t and the bottom 3a is preferably 5 to 50 cm, particularly preferably 10 to 40 cm.

A plate 4 commonly referred to as a flat baffle is provided facing the lower end of the center well 2 to make the flow direction of the raw water from the center well 2 a radial direction. In this embodiment, the plate 4 is in the form of a horizontal disk. The plate 4 is located below the lower end of the center well 2 by a predetermined distance. The plate 4 and the center well 2 are coaxially arranged.

A later-described rake shaft 10 passes through the central portion of the plate 4, and the plate 4 is supported by the rake shaft 10. However, the plate 4 may be supported by the center well 2 via a support member (not shown).

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

The bottom of the tank body 1 has a downward slope toward the center, and a pit 6 for collecting and discharging the sedimented sludge is provided at the center of the bottom. The sludge in the pit 6 is discharged to the outside of the tank body 1 through the mud pipe 7. However, the bottom surface of the tank body 1 may be horizontal.

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

The rake plate 11 is disposed in a direction oblique to the longitudinal direction of each arm 12 so as to move the deposit on the bottom of the tank body to the center side of the bottom of the tank body when the rake rotates.

An overflow weir 13 is provided along the upper part of the inner peripheral wall surface of the tank body 1 as an overflow part. The level at the upper end of the overflow weir 13 is the water level WL in the tank body 1.

The water depth of the tank body 1, ie, the height from the bottom of the tank body to the water level WL is preferably 100 to 400 cm, more preferably 100 to 250 cm.

The height of the upper surface of the plate 4 from the bottom of the tank body (peripheral portion of the pit 6) is 20 to 150 cm, preferably 25 to 120 cm, particularly 30 to 80 cm.

The downward flow velocity (LV) in the center well 2 is preferably 10 cm / sec or less, for example, about 1 to 6 cm / sec, particularly about 2 to 4 cm / sec.

The vertical distance between the lower end of the center well 2 and the upper surface of the plate 4 is such that the horizontal linear velocity of the raw water flowing out from this raw water outlet is about 1 to 10 cm / sec, especially about 2 to 6 cm / sec. It is preferable to set to.

The rising flow rate (LV) in the tank body 1 is preferably 1 m / hr or more, for example, 1 to 15 m / hr, particularly about 2 to 8 m / hr.

In the settling tank configured as described above, the water to be treated is supplied to the annular water channel C in the center well upper 3, swirls in the annular water channel C, overflows the upper end of the center well 2 and flows into the center well 2. And descend in the center well 2 and flow out radially between the lower end of the center well 2 and the plate 4. Thereafter, the water ascends in the tank body 1, overflows the overflow weir 13, and is discharged from the clear water outlet 14.

In this embodiment, the water to be treated flows gently into the sludge blanket from the raw water outlet between the lower end of the center well 2 and the plate 4 so that the sludge is efficiently separated and separated.

The sludge that has settled on the bottom of the tank body 1 is scraped into the pits 6 by the lake and discharged from the sludge pipe 7.

In this embodiment, it is possible to prevent the flow velocity from locally increasing in the annular water passage C and the center well 2 and the aggregation floc being broken. Also, by making the height difference between the height of the upper end 2t of the center well 2 and the water level in the center well (substantially equal to the water level WL) as small as possible, the broken floc of flocculated floe due to the impact of the water to be treated Sludge can be separated efficiently.

In the above embodiment, the bottom surface 3a of the center well upper 3 is horizontal, but in the second embodiment shown in FIG. 3, the bottom surface 3a is an inclined surface having a downward slope toward the outer periphery. Further, in the third embodiment shown in FIG. 4, the inner peripheral side of the bottom surface 3 a, that is, the center well 2 side is an inclined surface having a downward slope toward the outer periphery. The inclination angle θ of this inclined surface with respect to the horizontal plane is preferably about 5 to 60 °.

In FIGS. 3 and 4, the bottom surface 3 a is continuous with the upper end 2 t of the center well 2. However, it may be continued slightly below the upper end of the center well 2.

The other configuration of the second and third embodiments is the same as that of the first embodiment, and the same reference numerals indicate the same parts. The effects similar to those of the first embodiment can be obtained also by these embodiments.

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

In the said embodiment, although the tank body 1 is made into cylindrical shape, it may be square (square or more polygons). Further, the bottom surface of the tank body 1 may be horizontal.

In the said embodiment, although the introductory pipe 8 is provided as an introductory member, you may provide a weir-like water channel as an introductory member. In FIGS. 1 and 2, the introduction pipe 8 is bent halfway along the peripheral wall 3 b of the center well upper 3 so that the end thereof is positioned below the surface of the annular water channel C. However, in order to prevent water flow inhibition in the introduction pipe 8 and water flow inhibition of the swirling flow in the annular water channel C, the water flow port 8 flowing along the peripheral wall into the peripheral wall of the center well upper 3 as shown in FIG. It is preferable to provide '.

In the above embodiment, the center well 2 has an equal diameter from the upper end to the lower end, but the lower portion may have a large diameter. In this case, the lower end may be tapered with a larger diameter.

Although the invention has been described in detail with particular embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application 2017-217427 filed on November 10, 2017, which is incorporated by reference in its entirety.

1 tank body 2 center well 2t upper end 3 center well upper 3a bottom 3b peripheral wall 4 plate 6 pit 8 introduction pipe 10 rake shaft 13 overflow weir

Claims

In the settling tank, the water to be treated supplied from the center well at the central part of the tank body to the lower part inside the tank body rises up inside the tank body and becomes clear water from the overflow part at the top of the tank body,
A center well upper member is provided which forms an annular channel surrounding the upper periphery of the center well;
The center well upper member has a bottom surface extending in a spreading direction from the center well, and a peripheral wall standing up from an outer peripheral edge of the bottom surface,
Water to be treated is introduced into the annular water channel by the introduction member in the circumferential direction along the peripheral wall, overflows the upper end of the center well, and flows into the center well.
The sedimentation tank according to claim 1, wherein the upper end of the center well has a uniform height over the entire circumference.
The sedimentation tank according to claim 2, wherein the difference between the level of the overflow portion and the level of the upper end of the center well is 0 to 20 cm.
The sedimentation tank according to any one of claims 1 to 3, wherein the bottom surface of the annular water channel is horizontal and is positioned lower than the upper end of the center well.
The settling tank according to any one of claims 1 to 3, wherein at least the center well side of the bottom surface of the annular water channel is an inclined surface which becomes lower toward the outer periphery.
The settling tank according to claim 5, wherein the angle of the inclined surface with respect to the horizontal plane is 5 to 60 °.
The settling tank according to any one of claims 1 to 6, wherein a plate for changing the flow direction of the water is provided facing the lower end of the center well.