JPH09248404A - Flooculating and precipitating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce flocculated flocs with excellent precipitating property and efficiently carry out flocculation and precipitation by preventing precipitation in flocculated flocs in an inner cylinder and producing a stable swirling current independently of the weight of the flocculated flocs. SOLUTION: A screw 4 is installed in an inner cylinder 2 installed in a precipitation tank 1, a driving apparatus 6 is rotated to generate a whirling current for the process, a water to be treated is sent out of a tank 8 for water to be treated, a polymer flocculant is injected from a flocculant injecting path 9 and introduced into a lower part of the inner cylinder 2 in the tangential direction, the swirling current is accelerated to move the flocculated flocs spirally upward while the flocks being prevented from precipitating, flocculated flocs with a large diameter and excellent precipitating property are precipitated in a peripheral separation part 3b, fine flocs are separated in a separation part 3b in an upper part, the resultant treated water is take out through a treated water outlet 12, sludge is discharged out of a sludge discharging path 15 through a sludge collecting part 3d, and a part of the sludge is turned back to the inner cylinder 1 through a sludge turning back path 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flocculation / sedimentation apparatus using a swirling flow.

[0002]

2. Description of the Related Art As a coagulating sedimentation device for aggregating and separating SS and other impurities by sedimentation in wastewater treatment and the like, an inner cylinder is provided in a sedimentation tank, and water to be treated is mixed with a coagulant to form an inner cylinder. A device which is introduced tangentially to the lower part has been proposed (Actual Kaihei No. 6-72605).

In this apparatus, the water to be treated and the coagulant are mixed and introduced into the inner cylinder to generate a swirl upward flow in the inner cylinder, thereby forming coagulated flocs having a good sedimentation property. By introducing the solution into a settling tank for sedimentation and separation, efficient coagulation and sedimentation is performed.

[0004]

However, in such a flocculation-sedimentation apparatus, it is possible to operate without trouble when relatively light flocculation flocs are produced. For example, in order to ensure the clarification of treated water. When a large amount of the polymer flocculant is added, a part of the flocculated flocs, which have become heavy, precipitate in the inner cylinder. When coagulated flocs are deposited above the inlet of the water to be treated into the inner cylinder, the swirling force is lost due to the resistance of the flocs, and when the amount of ascending flocs decreases, they act synergistically to form large flocs. However, there is a problem that flocs with high cohesiveness cannot be obtained.

In order to solve the above-mentioned problems, the object of the present invention is to prevent the flocculation flocs from settling in the inner cylinder and to generate a stable swirling flow regardless of the weight of the flocs. Is to obtain a flocculating floc having an excellent settling property and to obtain a flocculating and precipitating apparatus capable of efficiently performing flocculating and precipitating.

[0006]

The present invention is the following coagulating sedimentation apparatus. (1) A settling tank for performing settling separation, an inner cylinder provided in the settling tank and having an upper part communicating with the settling tank, and a screw provided along the inner cylinder and rotating so as to generate a swirling flow. And a treated water introduction passage for introducing treated water to the lower part of the inner cylinder, and a treated water take-out passage provided at the upper part of the settling tank,
A coagulation-sedimentation device, comprising: a sludge discharge passage provided at the bottom of the sedimentation tank. (2) The coagulating sedimentation apparatus according to (1) above, which has a sludge return path for returning the sludge in the settling tank to the inner cylinder.

In the present invention, the inner cylinder provided in the settling tank is of a vertical type, has a diameter smaller than that of the settling tank, and has a height lower than that of the settling tank. To be done. In the separation part in the upper part of the inner cylinder, the flocculation flocs with a small particle size are mainly settled and separated, and the separation part in the outer peripheral part serves as a settling path of the floc particles with a large particle size.

The inner cylinder / sedimentation tank diameter ratio is (6/10) to
(9/10) is preferable, and if this diameter ratio is reduced,
In the separation portion between the inner cylinder and the outer cylinder, the influence of the swirling flow at the outlet of the inner cylinder is small, so that it is less susceptible to turbulence due to the water flow, and solid-liquid separation is efficiently performed to obtain clear treated water. Even if a water flow occurs in the separation section, separation is possible as long as floc flocs are generated. The ratio of the height of the inner cylinder / precipitation tank is (4/10) to (8
/ 10) is preferable. If the height of the inner cylinder is reduced, the time required for aggregation cannot be obtained, and if it is increased, solid-liquid separation becomes insufficient.

The screw provided in the inner cylinder has a rotary shaft extending in the vertical direction at the center, and the peripheral portion of the screw fin extends to the vicinity of the inner wall of the inner cylinder, and is formed like a screw conveyor. Although a swirl upward flow is generated in the inner cylinder due to the rotation of the screw, it is preferable that the treated water introducing passage is opened tangentially so as to introduce the treated water in the swirling direction. It is preferable to connect a coagulant injection passage to the treated water introduction passage, but it may be opened separately in the inner cylinder.

The treated water outlet is preferably connected to the upper part of the settling tank through an overflow. The sludge discharge passage is provided at the lower part of the sedimentation tank in the sludge collecting section, and it is preferable to provide a sludge collecting device such as a scraping device at this portion. It is preferable that the screw and the mud collecting device are coaxial and are rotated by the same drive source. It is preferable to form a gap of about 0.5 to 10 mm between the bottom of the inner cylinder and the rotating shaft to settle heavy particles such as sand.

The fin pitch of the screw is such that the flow velocity of the water to be treated is 0.05 to 0.
The value is set to 4 m / sec, preferably 0.2 to 0.3 m / sec. The residence time of the water to be treated in the inner cylinder can be 1 to 10 minutes, preferably 2 to 5 minutes. If the residence time is too short, aggregation will be insufficient, and if it is too long, the apparatus will unnecessarily increase in size. The rotation speed of the screw is appropriately 2 to 50 rpm, preferably 5 to 30 rpm, and it is preferable to rotate the screw at a high speed when the SS of the water to be treated is low and at a low speed when it is high.

In the above apparatus, it is preferable to provide a sludge return path for returning the sludge in the settling tank to the inner cylinder. In this case, the sludge can be returned directly from the settling tank to the inner cylinder by a screw conveyor or other means, and a part of the sludge can be directly introduced from the sludge discharge path to the treated water introduction path or through a coagulation reaction tank or the like. You can also return it.

In the coagulation-sedimentation method using the above apparatus, the water to be treated, which has undergone the coagulation reaction in the coagulation reaction tank or a conduit in the middle, is introduced into the inner cylinder from the water to be treated introduction path together with a coagulant, if necessary, and coagulated. Perform precipitation treatment. At this time, by rotating the screw in the inner cylinder, a swirling flow is generated to prevent the flocculation flocs from settling, and at the same time, the flocs of small diameter and the flocs of large diameter are caused to collide with each other to grow the flocs, thereby preventing the sedimentation property. Produces good flocculating flocs.

The liquid and coagulated flocs in the inner cylinder rise in a spiral swirling flow along the spiral flow path formed between the fins of the screw, and rise from the upper end of the inner cylinder to the upper part of the inner cylinder. It flows into the separation section. At this time, large-diameter aggregate flocs having good sedimentation property immediately pass through the separation section around the inner cylinder and settle to the bottom of the sedimentation tank. While the fine flocs stay with the liquid in the upper separating portion, they are subjected to a centrifugal force and move toward the periphery to collide with each other and gradually grow to a large diameter and settle. In this case, by installing an inclined plate used for general solid-liquid separation on the upper part of the inner cylinder, the separation effect of fine flocs can be enhanced.

The separated liquid from which the flocculation flocs have been separated in this way is taken out from the upper part of the settling tank to the treated water taking-out passage. The sludge that has settled is discharged from the sludge discharge channel. When returning sludge, it can be returned directly from the settling tank to the inner cylinder, or from the sludge discharge channel to the cylinder through the flocculation reaction tank or the treated water introduction channel. By returning sludge, the coagulation efficiency is increased.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a coagulation-sedimentation apparatus of the embodiment.

In FIG. 1, 1 is a settling tank, which is a vertical large-diameter upper cylindrical portion 1a from the upper portion to the middle portion, a conical portion 1b at its lower portion, and a small-diameter lower cylindrical portion 1c at its lower portion. And a bottom portion 1d. Inside the middle part of the settling tank 1, an inner cylinder 2 having a smaller diameter and a lower height is provided corresponding to the upper cylindrical portion 1a and the conical portion 1b. The inner cylinder 2 is a cylindrical portion 2 from the upper part to the middle part.
a, a conical portion 2b at the bottom, a bottom face 2c at the bottom, and a lower opening 2d.

Both the settling tank 1 and the upper part of the inner cylinder are opened, and the upper part of the settling tank 1, that is, the upper opening 2 of the inner cylinder 2 is opened.
An upper separating portion 3a is formed above e. A cylindrical peripheral separation part 3b is formed between the upper cylindrical part 1a and the cylindrical part 2a of the inner cylinder 2 in the middle part of the settling tank 1, and between the conical part 1b and the conical part 2b of the inner cylinder 2. Has a conical lower separating portion 3c. Lower cylindrical portion 1c of settling tank 1
A mud collecting portion 3d is formed inside.

A screw 4 is provided inside the inner cylinder 2, has a rotary shaft 5 extending in the vertical direction at the center, and is rotated by a drive device 6. The fins 4a of the screw 4 extend to the vicinity of the inner wall of the inner cylinder 2, and the spiral flow path 7 is formed between the pitches. The screw 4 is adapted to rotate in a direction forming a swirl upward flow in the liquid in the spiral flow path 7.

In the conical portion 2b at the bottom of the inner cylinder 2, a treated water introducing passage 8 is opened in the connecting direction so that the treated water is introduced into the lower portion of the spiral flow passage 7 to form a swirling flow. There is. The introduction passage 8 for the water to be treated is connected to a coagulation reaction tank (not shown), and is connected to a coagulant injection passage 9 in the middle thereof. Settling tank 1
An overflow portion 11 is provided around the upper end opening 1e of
The treated water extraction passage 12 communicates with the lower portion thereof.

A mud collecting device 13 is provided in the lower mud collecting portion 3d of the settling tank 1 and is attached so as to be rotated by a rotary shaft 5 extending through a lower opening 2d of the inner cylinder 2. Reference numeral 14 is a bearing. The sludge discharge path 15 is provided in the mud collecting section 3d.
The sludge return passage 16 for returning a part of the sludge is in contact with the untreated water introduction passage 8 from the middle thereof.

In the above construction, the diameter ratio of the inner cylinder 2 / precipitation tank 1 is (6/10) to (9/10), and the height ratio from the bottom surface 1d is (4/10) to (8 /). 10). Further, the pitch of the fins 4a of the screw 4 is such that the flow velocity of the water to be treated is 0.2 to
It is set to 0.3 m / sec. The rotation speed of the screw 4 is 5 to 30 rpm, the retention time of the water to be treated in the inner cylinder 2 is 2 to 5 minutes, and the gap of the lower opening 2d is 0.5 to 10 mm.

In the coagulation-sedimentation treatment method by the coagulation-sedimentation apparatus using the above-mentioned apparatus, the coagulation reaction is carried out by adding a coagulant and / or a pH adjusting agent in a coagulation reaction tank (not shown), It is supplied from the treatment introducing passage 8 and, if necessary, a polymer coagulant is injected from the coagulant injecting passage 9 and introduced into the lower part of the spiral passage 7 of the inner cylinder 2 in a state of causing an agglutination reaction.

At this time, when the screw 4 and the mud collecting device 13 are rotated by the drive device 6, a swirl flow is formed by the movement of the spiral flow passage 7, and a swirl flow is formed by the movement of the spiral flow passage 7. It In this case, since the water to be treated is introduced in the tangential direction, the swirling flow is accelerated. The flocculation flocs that are picked up by the rotation of the screw 4 are fluidized by the swirling flow and are prevented from settling to the lower part of the inner cylinder. As a result, the small-diameter aggregate flocs collide with the large-diameter aggregate flocs and are adsorbed, and the flocs grow to form flocs with excellent sedimentation.

While passing through the spiral flow path 7, the liquid and aggregated flocs in the inner cylinder 2 rise in a swirling flow while growing the flocs, and rise from the upper opening 2e to the upper separating portion 3a.
Flows into. At this time, large-diameter aggregated flocs having a good sedimentation property immediately enter the peripheral separation portion 3b by the centrifugal force and sediment. The delicate flocs collide with each other while moving in the peripheral direction by the centrifugal force while staying together with the liquid in the upper separating portion 3a, gradually growing to a large diameter and settling.

The separated liquid from which flocculated flocs have been separated is settling tank 1
The water overflows from the upper part of the water to the overflow portion 11 and is taken out from the treated water take-out path 12 as treated water. The flocs that have settled in the peripheral separating portion 3b are further concentrated in the lower separating portion 3c to be collected in the mud collecting portion 3d.
And is collected by the mud collecting device 13 and discharged from the sludge discharge path 15. A part of the sludge is returned from the sludge return passage 16 to the inner cylinder 2 via the treated water introduction passage 8.

In the above process, a stable swirling flow is generated by rotating the screw 4 at an appropriate speed,
As a result, aggregated flocs having excellent sedimentation properties are generated. Even if such flocs settle in the inner cylinder 2, they are scraped up by the screw 4, fluidized by the swirling flow, and extruded from the spiral flow path 7. Therefore, even if the flock is heavy, the sludge does not block the inside of the inner cylinder 2 and no operational trouble occurs.

Even when a large amount of settling flocs are deposited on the entire inner cylinder 2, since the screw 7 is fluidized in a high density state by the rotation of the screw 7, a sludge blanket is formed, whereby fine flocs are adsorbed. The solid-liquid separation effect is enhanced. Further, when the diameter ratio of the inner cylinder 2 / precipitation tank 1 is made small, the peripheral separation section 3b is less affected by the swirling flow at the outlet of the inner cylinder, so that it is less susceptible to turbulence due to the water flow, solid-liquid separation is efficiently performed, and clearing is performed. Treated water is obtained.

To obtain flocs with good sedimentation, S
The higher the S concentration, the better, but if it is too high, it is necessary to increase the amount of the polymer flocculant added, so 50 at the inlet SS.
It is desirable to set it to about 0 to 2000 mg / l. The sludge can be returned from the sludge return passage 16 to the water to be treated having a low SS. As a result, fine flocs are adsorbed on the sludge, and flocs having a good sedimentation property are generated, and the treatment efficiency is increased.

The sludge may be returned to the inner cylinder 2 from the sludge collecting section 3d by a screw conveyor or the like, and may be returned from the return passage 16 to the aggregation reaction tank or the inner cylinder 2. The polymer coagulant may not necessarily be added, and may be injected into the coagulation reaction tank or the inner cylinder 2. If clearer treated water is required, an inclined plate or the like can be provided in the upper separation section 3a.

[0031]

Since the coagulation-sedimentation apparatus of the present invention is provided with a screw in the inner cylinder and is rotated, the coagulation flocs are prevented from settling in the inner cylinder and stable regardless of the weight of the coagulation flocs. It is possible to obtain a flocculation-precipitation device capable of efficiently performing flocculation-precipitation by generating a swirling flow, thereby generating flocculation flocs having excellent sedimentation properties.

By returning a part of the sludge to the inner cylinder,
Even in the case of the water to be treated having a low SS concentration, it is possible to efficiently generate the flocculate flocs having a good sedimentation property.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a coagulation-sedimentation apparatus according to an embodiment.

[Explanation of symbols]

 1 Settling Tank 2 Inner Cylinder 3a Upper Separation Part 3b Peripheral Separation Part 3c Lower Separation Part 3d Soil Contamination Part 4 Screw 5 Rotating Shaft 6 Driving Device 7 Spiral Flow Path 8 Treated Water Introduction Path 9 Coagulant Injection Path 11 Overflow Section 12 Treated water extraction path 13 Mud collector 15 Sludge discharge path 16 Sludge return path

Claims (2)

[Claims] 1. A settling tank for performing settling separation, an inner cylinder provided in the settling tank and having an upper part communicating with the settling tank, and provided along the inner cylinder and rotating so as to generate a swirling flow. Screw, a treated water introduction passage for introducing treated water to the lower part of the inner cylinder, a treated water discharge passage provided at the upper part of the settling tank, and a sludge discharge passage provided at the lower part of the settling tank. A coagulating sedimentation device characterized by the above. 2. The coagulating sedimentation apparatus according to claim 1, further comprising a sludge return passage for returning the sludge in the settling tank to the inner cylinder.