JPH081146A - Waste water treatment method by floatation - Google Patents

Abstract

PURPOSE:To materialize stable floatation for a long period of time by reducing the possibility of scum stuck between parallel plates. CONSTITUTION:Raw water in which fine bubbles adhere to a flock produced by coagulation treatment by adding chemicals is introduced to the lower part of a water flow rotary pipe 2 in a floatation tank 1 to generate torque by the kinetic energy, and after most of scum containing bubbles being separated by the centrifugal force, the residual scum in the raw water is separated in a floatation zone in which parallel plates are piled.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to chemical treatment of organic and inorganic pollutants in industrial wastewater such as petroleum, petrochemical, food industry, large-scale cleaning industry and general wastewater such as polluted rivers, lake water and sewage. TECHNICAL FIELD The present invention relates to a wastewater treatment method for causing flocculation and coagulation by a chemical action due to addition of a class, and then contacting and adhering fine bubbles such as air to physically float and separate.

[0002]

2. Description of the Related Art Conventionally, flocs produced by coagulating and aggregating organic and inorganic pollutants in raw wastewater by adding chemicals are used to bring fine air bubbles generated when air is dissolved under pressure into contact with them. Alternatively, a wastewater treatment method is generally performed in which air bubbles having a relatively large diameter are brought into contact with each other under atmospheric pressure to physically and chemically remove contaminants by flotation separation.

That is, in the conventional wastewater treatment method by levitation separation, as shown in FIG. 10 (A), the density difference between the treated water and the bubble-containing scum (floating debris) is used to allow the levitation force to contaminate by standing. Material is being removed. However, the static levitation speed of bubble-containing scum is slow at about several meters / hour in general pressure levitation separation (bubble diameter is on the order of several tens of μm), and the atmospheric levitation separation developed by our company (bubble diameter is several hundreds). Even in the (μm order), the level is about several tens of meters / hour.

Therefore, as a plan for improving the floating separation property, conventionally, as shown in FIG. 10B, a rectangular parallel plate 50 is used.
Have been developed to shorten the flying distance and improve the separation efficiency. However, with this method, the scum floating separation efficiency until entering the parallel plate 50 is low, and therefore, the amount of scum captured by the parallel plate 50 is increased compared to the present invention described later, so that the parallel scum separation is particularly effective. There is a high possibility that the plate 50 will be blocked and the separation ability will be reduced.

[0005]

In the conventional method shown in FIG. 10 (B), by stacking a large number of parallel plates in the vertical direction, the floating separation operation can be performed in an area corresponding to the total area, and Since the levitation separation can be performed within a short distance between the parallel plates, the levitation separation efficiency with high performance and the levitation separation tank body can be downsized.

However, the more parallel plates are stacked in the vertical direction, the slower the speed of the treated water passing between the parallel plates becomes, and if the separation efficiency before entering the parallel plates is poor, scum that has once adhered will be generated. It has the contradiction that it is difficult to drain and the possibility of blockage increases.

The present invention is to improve the above-mentioned conventional improvement plan using parallel plates to one having a higher floating separation effect. Since the floating speed of bubble-containing scum in levitation separation is essentially slow, this is covered by parallel plates that reduce the levitation distance, and the combined use of centrifugal separation reduces the possibility of scum blockage between parallel plates. An object of the present invention is to provide a wastewater treatment method by flotation, which can realize stable flotation for a long period of time.

[0008]

Therefore, the method for treating wastewater by flotation according to the present invention is a method for flotation of treated water in which fine bubbles are brought into contact with flocs produced by flocculation by adding chemicals. Inject into the bottom of the water flow rotary tube in the tank,
The kinetic energy at that time is used to generate a rotational force, and the centrifugal force is used to separate most of the bubble-containing scum, and then the fine scum remaining in the treated water is separated in the levitation separation zone where multiple parallel plates are stacked. It is characterized by doing. In addition,
Embodiments of the present invention include the following configurations.

[0009] A water flow rotating pipe installed upright in the center of the flotation tank, a water flow reversing plate provided above the water flow rotating pipe, and a rotation stop plate disposed above the water flow reversing plate.
A configuration including a plurality of parallel plates stacked under the water flow reversal plate, and a support / rectifying plate that is fixed to the inner wall of the flotation separation tank and supports the parallel plates. The parallel plate has an inverted conical shape, a flat shape, a corrugated shape, or a polygonal shape. A configuration in which the rotation stop plate is provided at the outlet of the water flow rotary tube. A configuration in which an orifice-shaped rotation stop plate is provided at the outlet of the water flow rotary pipe. The support / rectifying plate is arranged at an angle with respect to the radial direction, and the confluence portion between the parallel plate and the support / rectifying plate is inclined, and the inclined portion is a triangular scum collecting plate. A parallel plate is horizontally stacked on the upper part of the water flow rotary pipe, and the arrangement angles of the upper support / rectifying plate and the lower support / rectifying plate intersect in a plan view. A structure in which another water flow rotary pipe is provided outside the water flow rotary pipe to form a double structure, and the treated water is transferred to a lower outside of the water flow rotary pipe inside.

[0010]

In the present invention, most of the scum is separated and removed by centrifugal force in advance, and after that, the treated water is spread to the peripheral portion of the flotation separation tank to extremely reduce the flow velocity. Since the plates are passed through the parallel plates, the levitation separation efficiency in the stage before entering the parallel plates is increased, the levitation separation efficiency of the total equipment is increased, and the possibility of the parallel plates being blocked can be greatly reduced.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a wastewater treatment method by levitation separation according to the present invention. FIG. 1A is a vertical sectional view of a levitation separation device, and FIG. 1B is taken along line BB in FIG. 1A. It is sectional drawing seen in the arrow direction.

A water flow rotary tube 2 is provided upright in the center of the floating separation tank 1, and an inverted conical water flow reversal plate 3 is provided above the water flow rotary tube 2. A plurality of inverted conical parallel plates 4 are stacked below the water flow reversal plate 3. Parallel plate 4
Is provided so as to have a gap between the inner wall of the levitation separation tank 1 and the water flow rotary tube 2, and is supported by a support / rectifying plate 5 fixed to the inner wall of the levitation separation tank 1. A rotation stop plate 6 for stopping the rotation of the water rising from the water flow rotary tube 2 is arranged above the water flow reversal plate 3. A scraper 8 rotatably driven by a motor 7 is arranged above the floating separation tank 1. The floating scum is discharged to the discharge path 9 by the scraper 8.

The treated water, which has been subjected to a coagulation treatment by adding chemicals and having fine air bubbles in contact with it, is injected into the lower part of the water flow rotary tube 2, and kinetic energy at the time of injection causes a rotational force, which is accompanied by centrifugation. Most of the bubble-containing scum is separated and removed by utilizing the centrifugal separation effect using the force and the flow velocity reduction effect in the water flow reversal plate 3 and the rotation stop plate 6. Next, fine bubbles and scum remaining in the treated water are treated in the floating separation zone where the parallel plates 4 are stacked. In this case, the fine scum floated and trapped between the parallel plates 4 is made to flow backward in the upper outer peripheral direction, and the fine sludge settled and separated is sent in the lower inner peripheral direction. Is preferred. At the bottom of the flotation tank 1, a pressurized water injection mechanism for floating and removing sludge as needed is provided.

Inside the water-flow rotary tube 2, the centrifugal force separates the scum from the treated water and at the same time, the rotational force is important in order to obtain the effect of collecting the fine bubbles and scum. It is necessary to suppress the rotation in order to prevent the scum that has been once separated from being caught. The inner surface of the water flow rotary tube 2 may be provided with a spiral groove or a guide plate or the like in order to retain the rotational force.

FIG. 2 shows a modification of the embodiment shown in FIG. 1, in which FIG. 2A is a partially vertical sectional view, and FIG. 2B is BB of FIG.
It is sectional drawing seen in the arrow direction along a line. In the example of FIG. 2, the rotation stop plate 10 is provided at the outlet of the water flow rotary tube 2.

FIG. 3 is a partial vertical sectional view showing a modification of the embodiment shown in FIG. In this example, an orifice-shaped rotation stop plate 11 is provided at the outlet of the water flow rotary tube 2.

FIG. 4 shows a modification of the embodiment shown in FIG. 1. FIG. 4A is a plan view of the parallel plate and FIG. 4B is a side view of the parallel plate. This example shows an example in which corrugated parallel plates 12 are stacked and the fine bubbles and the treated water are floated and separated without using the rotational force. The finely separated scum that has been floated and collected gathers in the high corrugated portion of the parallel plate 12 and is separated from the treated water that is collected in the low corrugated portion, so that the scum once separated can be prevented from mixing into the treated water.

FIG. 5 is a plan view showing a modification of the embodiment shown in FIG. The figure (A) shows the quadrangular parallel plate 13, and the figure (B) shows the octagonal parallel plate 14, but it can be configured by any polygon.

FIG. 6 is a vertical sectional view showing another embodiment of the flotation device according to the present invention. The same components as those in the embodiment of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, a lattice-shaped rotation stop plate 6 is provided above the outlet of the water flow rotary tube 2 to prevent the floating scum from being caught and to keep the rotation of the lower portion of the rotation stop plate 6. Also, the water flow reversal plate 3 and the parallel plate 4 are horizontal,
A water flow reversal plate 15 is also provided between the water flow reversal plate 3 and the parallel plate 4, and the rotation stop plate 6 and the support / rectifying plate 5 are fixed to the water flow reversal plate 15.

FIG. 7 shows a modification of the embodiment of FIG. 6, FIG. 7A being a plan view and FIG. 7B being a partial side view. In this example, in order to prevent the scum which has once been separated from being caught in the treated water when the floating force is separated between the parallel plates 4 while retaining the rotational force, the support / rectifying plate 5 is arranged in the radial direction. In addition to arranging at an angle, the confluence part of the parallel plate 4 and the support / rectifying plate 5 is inclined obliquely, and the inclined part is formed as a triangular scum collecting plate 16.

FIG. 8 shows another embodiment of the flotation device according to the present invention. FIG. 8A is a vertical sectional view, and FIG. 8B is a direction of an arrow along the line BB in FIG. FIG. The same components as those in the embodiment of FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, parallel plates 4'are also horizontally stacked on the upper part of the water flow rotary tube 2. The upper parallel plate 4 ′ is supported by a support / rectifying plate 5 ′ fixed to the inner wall of the levitation separation tank 1. The support / rectifying plate 5 ′ and the support / rectifying plate 5 supporting the lower parallel plate 4 are arranged so that the arrangement angles thereof intersect each other in a plan view to suppress the rotational force of the water flow. In the present embodiment, after the bubble-containing scum is roughly separated and removed by the centrifugal force due to the rotational force from the center of the levitation separation tank 1 toward the outside on the upper surface of the water flow reversal plate 3, the upper parallel plate 4 ′ is floated and separated, In the space below the water flow reversal plate 3, the parallel plates 4 are again floated and separated.

9A and 9B show another embodiment of the flotation device according to the present invention. FIG. 9A is a vertical sectional view, and FIG. 9B is a direction of an arrow along line BB in FIG. FIG. The same components as those in the embodiment of FIG. 8 are designated by the same reference numerals and the description thereof will be omitted.

Similar to the embodiment of FIG. 1, the parallel plates 4 and 4'are conical, and another water flow rotary tube 2'is provided outside the water flow rotary tube 2 to form a double structure, and the treated water is a water flow rotary tube. 2 is injected into the outer lower part, a rotational force is generated by the kinetic energy at the time of injection, the centrifugal force accompanying it is used for centrifugal separation to remove most of the bubble-containing scum, and then the parallel plate 4 is passed. At this time, the rotational force of the water flow by the support / rectifying plates 5, 5'is suppressed, and then the fine scum remaining in the treated water is removed by the parallel plate 4 ', and the treated water is lowered inside the water flow rotary pipe 2. I am trying. Since the fine sludge mixed in the treated water settles in the lower part of the flotation separation tank 1 over time, this discharge mechanism (not shown) is provided.

[Brief description of drawings]

1 shows an embodiment of a wastewater treatment method by levitation separation according to the present invention, FIG. 1 (A) is a vertical sectional view of a levitation separation device, and FIG. 1 (B) is taken along line BB of FIG. It is sectional drawing seen in the arrow direction.

2 shows a modification of the embodiment of FIG. 1, FIG. 2 (A) is a partial vertical sectional view, and FIG. 2 (B) is a sectional view taken along the line BB of FIG. Is.

FIG. 3 is a partial vertical sectional view showing a modification of the embodiment of FIG.

4A and 4B show modifications of the embodiment of FIG. 1, FIG. 4A is a plan view of the parallel plate, and FIG. 4B is a side view of the parallel plate.

5 is a plan view showing a modification of the embodiment of FIG.

FIG. 6 is a vertical sectional view showing another embodiment of the flotation device according to the present invention.

7 is a modification of the embodiment shown in FIG. 6, FIG. 7 (A) is a plan view, and FIG. 7 (B) is a partial side view.

8A and 8B show another embodiment of the flotation device according to the present invention, FIG. 8A is a vertical sectional view, and FIG. 8B is B- of FIG.
It is sectional drawing seen in the arrow direction along the B line.

9A and 9B show another embodiment of the levitation separation device according to the present invention, FIG. 9A is a vertical sectional view, and FIG. 9B is B- of FIG.
It is sectional drawing seen in the arrow direction along the B line.

FIG. 10 is a diagram showing an example of a conventional flotation device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Floating separation tank, 2 2 '... Water flow rotating tube 3, 15 ... Water flow reversing plate 4, 4', 12, 13, 14 ... Parallel plate 5, 5 '... Support and straightening plate 6, 10 ... Rotation Stop plate, 7 ... motor, 8 ... scraper,
11 ... Rotation inhibiting plate 16 ... Scum collecting plate

Claims (1)

[Claims] 1. Treated water in which fine bubbles are brought into contact with the flocs produced by the coagulation treatment by adding chemicals is injected into the lower part of the water flow rotary tube in the flotation tank, and the kinetic energy at that time is used. It is characterized by generating a rotational force and separating most of the bubble-containing scum using the centrifugal force, and then separating the fine scum remaining in the treated water in the floating separation zone where multiple parallel plates are stacked. Wastewater treatment method by flotation.