JP2001269506A - Flocculation and sedimentation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flocculation and sedimentation apparatus capable of obtaining an extremely clarified treated liquid. SOLUTION: In the flocculation and sedimentation apparatus 10 equipped with a sedimentation tank 12, a mixing chamber 14 arranged in the sedimentation tank to mix and stirr a liquid to be treated and an additive and a rotatable discharge pipe 48 for distributing and supplying the liquid to be treated in the mixing chamber 14 the sedimentation tank 12, vertical buffle plates 52 deflecting the flows of the liquid to be treated from the discharge holes 50 of the discharge pipe 48 in a vertical downward direction are provided at the adjacent positions on the outside of the tank of the discharge holes 50. By this constitution, the oblique flows of the liquid to be treated from the discharge holes are reduced to contribute to the formation of equal rising flows.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for coagulating and sedimenting suspended substances and the like in a liquid to be treated in a sedimentation tank to clarify the liquid to be treated.

[0002]

2. Description of the Related Art A coagulating sedimentation apparatus is a type of sedimentation-separation type water treatment apparatus, in which suspended substances and the like contained in a liquid to be treated such as raw wastewater are aggregated and flocculated by a suitable additive.
It is intended to remove suspended substances and the like from the liquid to be treated by precipitation.

[0003] As this type of coagulation sedimentation apparatus, Japanese Patent Publication No.
What is disclosed by JP-B-38523 is known. In the coagulating sedimentation apparatus described in this publication,
A cylindrical mixing chamber for coagulating suspended substances and the like is provided upright at the center of the sedimentation tank, and the liquid to be treated having the flocculated floc in the mixing chamber is supplied to the internal space of the sedimentation tank by the distributor. In this specification, the internal space is distributed and supplied to a “sedimentation space”.

A conventional general distributor is basically composed of a plurality of radially extending discharge tubes arranged below a mixing chamber. Each discharge pipe communicates with the inside of the mixing chamber, and a plurality of discharge holes are formed in a lower portion of each discharge pipe along its longitudinal direction. Since the outer end of the discharge pipe is closed, the liquid to be treated containing the flocculated floc in the mixing chamber passes through the discharge pipe and is discharged from the discharge hole into the processing space in the sedimentation tank. The discharge pipe is rotated together with the mixing chamber or separately from the mixing chamber. Therefore, when the distributor is driven to rotate, each discharge hole draws a circular locus, and the floc-containing liquid to be treated discharged from the discharge hole is distributed to the sedimentation space.

In the sedimentation space in the sedimentation tank, flocculated flocs in the liquid to be treated settle and separate, forming a concentrated sludge layer at the bottom of the sedimentation tank. On the other hand, the supernatant liquid rises to the upper part of the sedimentation tank and flows out from the upper part of the sedimentation tank as a clarified treated liquid.

[0006]

The coagulating sedimentation apparatus of the above type is used for various purposes such as wastewater treatment and papermaking white water recovery. In recent years, the quality of various industrial products has been improved.
From the viewpoint of environmental conservation, the need for a coagulating sedimentation apparatus capable of obtaining a further clarified treated liquid is increasing.

[0007] Therefore, an object of the present invention is to provide a coagulation sedimentation apparatus capable of obtaining an extremely clarified treated liquid.

[0008]

In order to achieve the above object, it is desirable that the ascending flow generated in the settling space in the settling tank is as uniform as possible over the entire area of the tank. However, in the conventional coagulation sedimentation apparatus, the upflow is slightly disturbed. This turbulence is considered to be due to various causes.The inventors of the present invention have conducted intensive studies and as a result, the liquid to be treated discharged from the discharge hole of the distributor is not flowed downward in the vertical direction, but is directed outward in the radial direction. I found that this was partly due to the diagonal flow towards.

That is, since the liquid to be treated flows radially outward from the center of the tank in the discharge pipe, the liquid to be treated discharged from the discharge hole exerts a considerable radial inertia force outward. The liquid to be treated flows out obliquely downward from the discharge holes.
In addition, since the discharge pipe is driven to rotate, a centrifugal force is also applied to the liquid to be processed, and the liquid to be processed flows obliquely outward. As described above, when the discharge flow from the discharge hole is inclined, the formation of a uniform ascending flow in the settling tank is inhibited, and a swirl flow is generated in the settling tank to form a sludge layer at the bottom of the settling tank. It is considered that fine particles such as suspended substances are mixed into the supernatant liquid because of stirring.

[0010] Based on the above research results, the present invention provides a sedimentation tank, a mixing chamber disposed upright in the sedimentation tank, into which the liquid to be treated and additives are introduced, mixed and stirred, A discharge pipe communicating with the inside of the mixing chamber to distribute and supply the liquid to be processed to the precipitation space between the settling tank and the mixing chamber, and having a plurality of discharge holes formed in the longitudinal direction, A coagulating sedimentation device having a discharge pipe rotatable about the center axis of the mixing chamber, and deflects the flow of the liquid to be treated from the discharge hole downward to a position adjacent to the outside of the tank of each discharge hole. A vertical baffle plate is provided. Thereby, the diagonal flow of the liquid to be treated from the discharge holes is reduced, which contributes to the formation of a uniform upward flow.

When a horizontal baffle plate extending parallel to the discharge pipe is provided below the discharge pipe, supporting the horizontal baffle plate with all or a part of the vertical baffle plate reduces the number of parts. It is preferable to prevent the rotation and reduce the resistance when rotating the discharge pipe.

Furthermore, it is effective to reduce the resistance by making the horizontal cross-sectional shape of each vertical baffle plate an arc shape with a radius of curvature equal to the distance from the central axis to the mounting position of the vertical baffle plate. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the coagulation and sedimentation apparatus according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a partial cross-sectional view showing a coagulation-sedimentation apparatus according to the present invention. A coagulation sedimentation apparatus 10 shown in FIG. 1 includes a sedimentation tank 12 that sediments and separates suspended substances and coagulated flocs from a liquid to be treated such as raw wastewater and takes out a clarified supernatant as a treated liquid. The mixing chamber 14 is disposed inside the mixing chamber 14 for aggregating and flocculating suspended substances and the like in the liquid to be treated in advance. The coagulating sedimentation apparatus 10 of this type can perform a so-called sludge blanket type operation or a slurry circulation type operation depending on the characteristics of the liquid to be treated, and can perform wastewater treatment, papermaking white water recovery, DIP wastewater recovery, and caustic greening. It can be applied to various uses such as liquid clarification, water treatment, and inorganic precipitate washing treatment.

The settling tank 1 in the illustrated coagulation settling apparatus 10
2 is a tank depth of about 4000 to 5000 mm, a tank diameter of 1500
These dimensions are about 3,000 mm, but these dimensions are arbitrarily set according to the installation space of the sedimentation tank, the properties and amount of the liquid to be treated, and the like. Settling tank 12
Is formed by fixing a steel plate side wall 18 on a foundation 16 made of concrete or the like provided in an area installed in the coagulation sedimentation apparatus 10.

A gantry 20 is suspended from the upper edge of the side wall of the settling tank 12. The gantry 20 is mainly used as a work space for workers during various maintenance work. From the center of the gantry 20, the mixing chamber 1
4 is erected. The mixing chamber 14 has an elongated and substantially cylindrical shape, and has a total length of, for example, about two thirds of the depth of the settling tank 12. Mixing chamber 14
Is fixed to the gantry 20 with its central axis aligned with the central axis of the settling tank 12. As a result, the mixing chamber 14 is fixed upright in the sedimentation tank 12, and a predetermined space (space) is formed between the lower end of the mixing chamber 14 and the bottom surface of the sedimentation tank 12.

An introduction pipe 24 is connected to an upper part of the mixing chamber 14 and communicates with a to-be-processed liquid inflow pipe 22 connected to a pump outside the system. That is, in the coagulating sedimentation apparatus 10, the liquid to be treated such as raw wastewater supplied through the liquid to be treated inflow pipe 22 is first introduced into the mixing chamber 14 through the introduction pipe 24. Introductory pipe 2
4 is a liquid level in the sedimentation space in the sedimentation tank 12 during the operation of the coagulation sedimentation apparatus 10 and the mixing chamber 1.
4 is provided below the liquid level. This prevents generation of bubbles and the like due to the introduction of the liquid to be treated. The height of the liquid level in the sedimentation space in the sedimentation tank 12 is defined by the upper edge of the weir plate 26, and the treated liquid (supernatant) in the sedimentation tank 12 passes over the weir plate 26, Side wall 18
The liquid is discharged out of the system through an outlet 28 formed at the bottom of the system.

Further, the mixing chamber 14 is provided with a plurality of injection nozzles 30 for injecting various additives for aggregating suspended substances and the like in the liquid to be processed to form flocs. As an additive to be introduced into the mixing chamber 14, a polymer flocculant or the like is used, but it is needless to say that the additive is appropriately selected depending on the liquid to be treated and the substance contained therein.
Each injection nozzle 30 is disposed along the height direction of the mixing chamber 14.
Are provided in the upper, middle, and lower sections, respectively.
Further, an additive introduction pump (not shown) is connected to the injection nozzle 30, and the injection amount of the additive is controlled by each injection nozzle 3.
It can be controlled every 0.

Further, as shown in FIG. 1, the mixing chamber 14 has a built-in mixer 32 for mixing and stirring the liquid to be treated and the additive. The mixer 30 includes a hollow cylindrical body 34 that is rotatably suspended from the gantry 20 so as to be coaxial with the mixing chamber 14, and a plurality of mixer blades 36 attached to a peripheral surface of the hollow cylindrical body 34.
The cylindrical body 34 of the mixer 32 is rotated by a mixer driving device 38 mounted on the gantry 20 when the coagulation and sedimentation device 10 is operated. Further, a center shaft 40 is inserted inside the mixer cylinder 34. This center shaft 40 is also used in the mixing chamber 1.
4 is rotatably suspended from the gantry 20 in a state of being coaxially arranged with the gantry 4 and is rotationally driven by a driving device 42 mounted on the gantry 20.

The lower portion of the center shaft 40 projects below the lower end of the mixing chamber 14. A distributor 44 is fixed to this lower portion of the center shaft 40. The distributor 44 basically has a cup-shaped rotary support 46 fixed coaxially to the center shaft 40 and arranged so as to close the lower end of the mixing chamber 14. The distributor 44 communicates with the inside of the rotary support 46 and supports the rotary support 46. A plurality (four in the illustrated embodiment) of discharge pipes 48 extending radially outward from the outer peripheral surface of the body 46 in the horizontal direction. The outer end of each discharge pipe 48 is closed. As shown in FIG. 2, a plurality of discharge holes 50 are arranged in a line along the longitudinal direction at the bottom of each discharge pipe 48.
Are drilled. During the operation of the coagulating sedimentation apparatus 10, the distributor 44 is rotated together with the center shaft 40 by the driving device 42, and the liquid to be treated including the flocculated flocs in the mixing chamber 14 is discharged from the discharge port 5 of the discharge pipe 48.
It is discharged from 0 to the sedimentation space in the sedimentation tank 12.

As clearly shown in FIG. 2, in this embodiment,
A flat vertical baffle plate 52 is fixed to the lower part of each discharge pipe 48 at a position adjacent to each discharge hole 50 and radially outward, and extends vertically downward. Due to the presence of the vertical baffle plate 52, the flow of the liquid to be treated radially outward and downward from the discharge hole 50 is deflected vertically downward.

In order to ensure the effect of this deflection, it is preferable that the height (vertical length) of the vertical baffle plate 52 is long. However, since the vertical baffle plate 52 rotates together with the discharge pipe 48, If the length is too long, there is a risk of forming a swirling flow in the sedimentation tank 12. Therefore, it is effective to set the height of the vertical baffle plate 52 to about 1.5 to 2 times the diameter of the discharge hole 50, since the generation of the swirling flow can be prevented. Specifically, in the general coagulation sedimentation apparatus 10 in which the inner diameter of the sedimentation tank 12 is 10 m, the diameter of the discharge hole 50 is 70 to 80 mm, so that the height of the vertical baffle plate 52 is preferably about 105 mm to 160 mm. is there.

The width of the vertical baffle plate 52 needs to be equal to or larger than the diameter of the discharge hole 50.
It is preferable to set the outer diameter to about.

By providing a vertical baffle plate 52 of such dimensions and shape for each discharge hole 50,
The liquid to be treated from flows substantially vertically downward. Thereby, a uniform ascending flow is formed in the sedimentation tank 12 and the stirring of the sludge layer A (see FIG. 1) at the bottom can be prevented, so that a clear supernatant liquid can be obtained. .

Further, below each discharge pipe 48, a horizontal baffle plate 54 is attached. The horizontal baffle plate 54 has a function of dispersing the liquid to be treated discharged from the discharge holes 50, prevents the sludge layer A from being agitated by the liquid to be treated discharged from the discharge pipe 48, and provides a coagulating sedimentation apparatus. 10 contributes to the improvement of the sedimentation separation efficiency.

Conventionally, the horizontal baffle plate 54 has been attached to the discharge pipe 48 by a dedicated attachment. However, as shown in FIG. 2, a part or all of the vertical baffle plate 52 is used as an attachment. Can be fixed. This makes it possible to suppress an increase in the number of parts, and to prevent an increase in resistance due to an increase in the number of parts.

On the other hand, the center shaft 40 to which the distributor 44 is fixed, as shown in FIG.
It extends below the distributor 44,
It reaches the bottom of the settling tank 12. A rake 56 and a cone scraper 58 that rotate together with the distributor 44 are attached to the tip of the center shaft 40.

The rake 56 is for condensing sludge formed by flocculation of flocculated floc in the liquid to be treated discharged from the discharge pipe 48, and for scraping the sludge to the sludge withdrawal recess 60 at the center of the bottom of the tank. It is. Thereby, the concentrated sludge layer A is formed in a region below the distributor 44 in the settling tank 12.

The cone scraper 58 is disposed in the sludge extracting recess 60. The recess 60 is provided in the settling tank 12.
Is connected to a sludge withdrawal pipe 62 formed on the base 16 of the base material. The sludge extraction pipe 62 is connected to a sludge extraction pump 64 and a sludge return pump 66. For example, when performing a sludge blanket operation, the sludge extraction pump 64 is operated based on the indication value of an interface detector (not shown) provided in the sedimentation tank 12 to move the concentrated sludge in the sedimentation tank 12 out of the system. By discharging, the interface height of the sludge blanket layer B is kept within a certain range. At this time, since the cone scraper 58 is rotating, the concentrated sludge in the settling tank 12 is uniformly discharged. When performing a slurry circulation type operation,
The sludge return pump 66 is operated based on the indicated value of the interface detector to return and circulate the sludge. On the other hand, the supernatant liquid flows out of the system from an outlet 28 provided in the upper part of the sedimentation tank 12.

Next, a procedure for clarifying the liquid to be treated by using the above-described coagulation / sedimentation apparatus 10 will be described. Here, a case where a sludge blanket type operation is performed to obtain a clear treated liquid will be described.

First, the to-be-treated liquid inflow pipe 22 and the introduction pipe 24
Then, the liquid to be treated is supplied into the mixing chamber 14. At this time, the liquid to be treated flowing out of the liquid to be treated introduction pipe 24 first flows into the liquid to be treated receiving chamber 68. Then, the liquid to be processed flows through the space defined by the bottom of the receiving chamber, the side wall of the receiving chamber, and the inner peripheral surface of the mixing chamber 14, and then overflows into the mixing chamber 14 from above the liquid receiving chamber 68. Will be done.

As a result, compared with the case where the liquid to be treated is directly introduced into the mixing chamber 14 from the liquid introduction pipe 24, particles or coarse flocs having a large specific gravity settle in the mixing chamber 14 and fall to the bottom. Accumulation can be extremely effectively reduced. As a result, the inlet of the liquid to be treated of the discharge pipe 48 of the distributor 44 is prevented from being blocked, so that the sedimentation tank 1
The liquid to be treated is always efficiently distributed and supplied into 2, so that the operation performance of the coagulation and sedimentation apparatus 10 is improved and the clarity of the supernatant is also improved.

An additive is injected at an arbitrary timing into the processing liquid flowing into the mixing chamber 14 from the processing liquid receiving chamber 66 from any or all of the injection nozzles 30 provided in multiple stages. Is done. As a result, the effect of the additive is maintained for a long time, and an aggregate floc having good sedimentation properties is formed. Then, the liquid to be treated and the additive in the mixing chamber 14 are stirred by the mixer 32 which is rotated by the mixer driving device 38, and the suspended substances and the like in the liquid to be treated are aggregated to form flocculated flocs (initial flocs). To form

The liquid to be treated containing flocculated flocs is supplied from the rotary support 46 of the distributor 44 disposed at the lower end of the mixing chamber 14 through the discharge holes 50 of the discharge pipe 48 into the precipitation tank 12. During operation of the coagulating sedimentation apparatus 10, the distributor 44
, The discharge hole 5 of the discharge pipe 48
The liquid to be treated discharged from 0 is drawn into a circle while drawing a circle.
Is distributed to the sedimentation space inside. And, as mentioned above,
The flow of the liquid to be treated, which is going to flow radially outward from each of the discharge holes 50, is corrected downward in the vertical direction by the vertical baffle plate 52, so that an even upward flow is generated in the sedimentation tank 12. A good sludge blanket layer B is formed above 44.

Further, of the floc in the liquid to be treated,
What settled and separated in the sedimentation tank 12 forms a sludge layer A at the bottom of the sedimentation tank 12. At the bottom of the settling tank 12 rake 5
6, the sludge layer A is concentrated, and at the same time, is raked into the sludge withdrawal concave portion 60 at the center of the tank. Sludge is drawn from the concentrated sludge layer A by a sludge drawing pump 64 which is controlled based on the value supported by the interface detector, so that the interface height of the sludge blanket layer B is kept within a certain range.

On the other hand, fine flocks and other fine particles are also included in the upward flow. However, as a result of the provision of the vertical baffle plate 52, the upward flow is very uniform with very little disturbance. Etc. are reliably captured by the large flocks of the sludge blanket layer B,
Removed from the ascending flow. In this way, flocs and other particles are settled and removed from the upward flow, and the extremely clear supernatant liquid rises in the sedimentation tank 12 to form the fining layer C.
Then, the supernatant liquid flows out from the outlet 28 above the precipitation tank 12 as a treated liquid.

Although the preferred embodiments of the present invention have been described in detail, it goes without saying that the present invention is not limited to the above embodiments.

For example, in the above-described embodiment, the vertical baffle plate 52 has a flat plate shape. However, as shown by reference numeral 53 in FIG. The arc of the horizontal cross section of each vertical baffle plate 53 has a radius of curvature as the distance from the center of rotation (the center axis of the mixing chamber 14 or the center shaft 40) to the mounting position of the vertical baffle plate 53. With such a shape, the resistance of the vertical baffle plate 53 is reduced,
Is suppressed. This may be useful where the distributor 40 is rotated at a relatively high speed.

[0039]

As described above, in the coagulation and sedimentation apparatus according to the present invention, an extremely uniform and stable ascending flow can be formed in the sedimentation tank as compared with the conventional one, so that the treatment is extremely clarified. It is possible to obtain spent liquid, which can greatly contribute to quality improvement of various industrial products and environmental protection.

Further, since the performance of the apparatus is improved, there is an effect that the whole apparatus can be made compact.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a coagulation-sedimentation apparatus to which the present invention can be applied.

FIG. 2 is a side view schematically showing a discharge pipe configured according to the present invention.

FIG. 3 is a view showing a modified embodiment of the present invention, and is a view in which a part of a discharge pipe is viewed from below.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Coagulation sedimentation apparatus, 12 ... Precipitation tank, 14 ... Mixing chamber, 16 ... Basic, 18 ... Side wall, 32 ... Mixer, 4
0: Center shaft, 42: Drive unit, 44: Distributor, 48: Discharge pipe, 50: Discharge hole, 52: Vertical baffle plate, 54: Horizontal baffle plate.

Claims (3)

[Claims] 1. A coagulation and sedimentation apparatus for clarifying a liquid to be treated by settling and separating suspended substances, flocculated flocs and the like in a liquid to be treated in a sedimentation tank, wherein A mixing chamber into which a liquid to be treated and an additive are introduced and mixed and stirred; and the mixing chamber for distributing and supplying the liquid to be treated in the mixing chamber to a precipitation space between the precipitation tank and the mixing chamber. A discharge pipe communicating with the inside of the mixing chamber and having a plurality of discharge holes formed along the longitudinal direction, the discharge pipe being rotatable about a center axis of the mixing chamber. A vertical baffle plate for deflecting the flow of the liquid to be treated from the discharge hole substantially vertically downward from the discharge pipe is provided at a position adjacent to the outside of the tank of the discharge hole. Coagulation sedimentation equipment. 2. The apparatus according to claim 1, further comprising a horizontal baffle plate extending parallel to said discharge pipe below each of said discharge pipes, wherein said horizontal baffle plate is supported by all or a part of said vertical baffle plate. 2. The coagulation sedimentation apparatus according to 1. 3. The vertical baffle plate according to claim 1, wherein a horizontal cross-sectional shape of the vertical baffle plate is an arc shape having a radius of curvature as a distance from the center axis to a mounting position of the vertical baffle plate. The coagulation sedimentation apparatus according to the above.