JPH0638958B2 - Wastewater treatment method and apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluidized bed-type wastewater treatment method for purifying wastewater by suspending solid particles (microorganism carrier) on which microorganisms are attached or encapsulated in wastewater. And its device.

"Conventional technology" Recently, the fluidized bed has an advantage that the waste water treatment method can take a higher BOD volume load than the activated sludge method, the contact aeration method, and the biofilm method such as the rotating disk method, and can make the apparatus compact. Law is drawing attention. As is well known, in this fluidized bed method, continuous use of solid particles in a fluidized state in a treatment tank is an essential condition.

As a wastewater treatment device used in such a fluidized bed method, a structure shown in FIG. 3 is conventionally known. As shown in the figure, this processing apparatus comprises a fluidized tank 1 and a precipitation tank 2. A draft tube 3 is erected at the center of the fluidized tank 1, and an overflow weir 4 is provided at the upper part thereof, and a solid-liquid separation column (outer cylinder tube) 5 is provided between the weir 4 and the tube 3. It is provided. An air diffuser 7 connected to the electric blower 6 is provided below the draft tube 3.

In such a wastewater treatment device, the wastewater in the fluidized tank 1 is
By the rising action of the air blown from the air diffuser 7 to the bottom of the tank, the air is circulated and circulated in the direction of the arrow in the figure, and along with the circulation of the waste water, the solid particles also circulate and come into contact with the waste water. Purification is performed. Here, as the solid particles, a carrier having a specific gravity of more than 1 such as sand, anthracite, activated carbon, and microbial entrapment is used, and microorganisms are attached or encapsulated on the surface of the solid particles.

Then, the purified wastewater is subjected to removal of solid particles in the solid matter separating portion 8 between the overflow weir 4 and the solid-liquid separation column 5, and then flows over the overflow weir 4 to become outflow water. It is designed to be sent to the settling tank 2.

In the wastewater treatment method using this wastewater treatment device, the fluidized tank 1
Increasing the amount of particles filled inside will increase the total surface area of the particles, or the amount of microorganisms contained in the chamber will increase, and the amount of microorganisms retained in the tank will increase. There are advantages.

"Problems to be Solved by the Invention" However, the wastewater treatment method using such a wastewater treatment apparatus has the following advantages, but has the following problems.

That is, from the viewpoint of processing efficiency, it is sufficient to increase the amount of particles as described above, but if the amount of particles is too large, it becomes difficult for the solid particles to completely flow, and a part of the particles is used in the flow tank 1.
There is a tendency for it to deposit at the bottom of the, and further increase will cause no flow at all. Further, when the amount of particles is large, solid particles are likely to be deposited in the tank due to slight fluctuations in operating conditions such as fluctuations in blown air pressure, and the flow of particles and the liquid circulation itself are easily stopped. When the particles are deposited in this way, as shown in FIG. 4, not only in the lower outer peripheral portion (A portion in the figure) of the draft tube 3 but also in the draft tube 3 to a position higher than the deposited particle surface of the outer peripheral portion. Solid particles are deposited (B portion in the figure). In this state, even if gas is blown from the air diffuser 7, the gas is obstructed by the accumulated particles in the portion B in the draft tube 3 and escapes to the outer periphery of the draft tube 3, so that the solid particles can be fluidized again. There was a drawback that it would be a fatal situation until it disappeared.

For this reason, there is a limit to the amount of solid particles that can be added to the fluidized tank 1, and the amount added to the tank volume is at most about 15-18%. 12
It was about%. With such an amount of solid particles added, the wastewater treatment efficiency is poor, and in order to improve the efficiency, the volume of the fluidized tank must be increased, and there was a problem that the cost due to the expansion of equipment increased. .

The present invention has been made in view of the above problems, and an object of the present invention is to provide a wastewater treatment method and apparatus capable of stably purifying wastewater while maintaining high reaction efficiency.

"Means for Solving Problems" The present invention is directed to waste water in a waste water treatment device consisting of a fluidized tank having an air diffuser at the bottom, a draft tube standing upright in the fluidized tank, and an outer cylinder part pipe. The present invention relates to a wastewater treatment method in which solid particles having microorganisms attached to or contained in the wastewater and having a specific gravity of more than 1 are caused to flow by the aeration device to purify the wastewater, and the cross-sectional area of the upper part of the draft tube is changed. It is larger than the lower part, and the upper part and the lower part are connected by a connecting part, and an opening is formed in either or both of the upper part and the connecting part, and the draft tube and the outer tube are formed at the upper part and the connecting part of this draft tube. It is characterized in that a deposition layer composed of solid particles deposited between the partial tube and the partial pipe is disintegrated and fluidized by convection passing through the opening.

Further, the wastewater treatment apparatus according to the present invention is composed of a fluid tank having an air diffuser at the bottom, an upper tube of a draft tube standing upright in the fluid tank, and an outer cylinder tube, and the cross section of the draft tube. It is characterized in that the area is larger than the lower part, the upper part and the lower part are connected by a connecting part, and an opening is formed in one or both of the upper part and the connecting part.

"Example" Hereinafter, the wastewater treatment method of this invention is demonstrated with reference to drawings.

FIG. 1 shows an example of the wastewater treatment apparatus of the present invention. In the figure, parts common to those of the conventional apparatus shown in FIG.

The configuration of the wastewater treatment device shown in FIG. 1 differs from the configuration of the conventional wastewater treatment device in that the cross-sectional area of the upper portion 3a of the draft tube 3 is set larger than the cross-sectional area of the lower portion 3b, and the upper portion of the draft tube 3 is 3a and the lower portion 3b are connected by an inclined surface portion (connecting portion) 3c, and a circular opening 3d ... Is formed in the inclined surface portion 3c.

The cross-sectional area of the upper portion 3a of the draft tube 3 is the first
In the figure, 30% or more of the cross-sectional area of the fluidized bed 1 at the position a is desirable, and during the processing operation, the fluidized bed 1
The content is preferably 50% or more, though it varies depending on the properties of the suspension composed of solid particles and waste water.
The ratio of the outer diameter of the draft tube 3 to the outer diameter of the solid-liquid separation column (outer tube portion tube) 5 is about 60 to 85%, preferably about 70 to 82%.

Further, the shape of the openings 3d ... may be any shape such as a rectangular shape and a slit shape other than the circular shape. The distribution of the openings 3d is preferably formed at equal intervals on the inclined surface portion 3c of the draft tube 3, and the number and the cross-sectional area per piece are the accumulated particles formed outside the inclined surface portion 3c. Although it is decided that the layer can be collapsed by convection passing through the openings 3d ...
The total cross-sectional area of the openings 3d ... is the upper part 3 of the draft tube 3.
It is preferably 50 to 120% of the cross-sectional area of b.

Next, a wastewater treatment method using the wastewater treatment device having such a configuration will be described. First, the wastewater is stored in the fluidized tank 1 in a predetermined treatment amount and mixed with solid particles such as diatomaceous earth at an appropriate mixing ratio. Since the solid particles have a specific gravity of more than 1, they naturally settle in the wastewater. The settled solid particles are generated together with the circulating flow by the ascending action of the gas of the air diffuser 7 blown from the lower part of the draft tube 3. It is pushed up and fluidized. The fluidized solid particles are partially passed through the openings 3d ...
Circulation descends along the wall of the draft tube 3
Of the draft tube 3 and the solid-liquid separation column 5 are lowered, and the draft tube 3 and the solid-liquid separation column 5 are separated. Between the lower side of the working column 5 and the inclined surface of the solid separating portion 8, deposits are made from above, and a substantially donut-shaped deposited particle layer is formed there. Here, the convection passing through the openings 3d ... Is both inflow and outflow, and generally enters the draft tube 3 at the upper part of the openings 3d ... and the draft tube 3 at the lower part of the openings 3d. It has leaked out. Then, the above-mentioned deposited particle layer is formed in the draft tube 3
Are gradually disintegrated from the lower part by convection passing through the openings 3d provided in the inclined surface part 3c and are fluidized again. Such flow increases the contact of the wastewater with the solid particles and is thereby purified. Then, the purified wastewater, after solid particles are removed in the solid matter separating section 8 between the overflow weir 4 and the solid-liquid separation circular column 5, passes through the overflow weir 4 to become outflow water. And sent to the settling tank 2.

In the above wastewater treatment, since the cross-sectional area of the upper part 3a of the wastewater rising from the lower part 3b to the upper part 3a in the draft tube 3 is larger than that of the lower part 3b, the flow velocity decreases when it moves into the upper part 3a. To do. Therefore, the upper part 3a
By sufficiently securing the reaction time inside, the effect of increasing the reaction efficiency can be obtained.

Moreover, the solid particles flow by the collapse of the deposited particle layer due to convection passing through the opening 3d.

As a result, even if the amount of solid particles added is increased to increase the reaction efficiency, the deposition of solid particles between the draft tube 3 and the solid-liquid separation column 5 is suppressed, and the solid particle aeration device 7 is suppressed.
Since clogging of the wastewater is avoided, wastewater can be stably purified while maintaining high reaction efficiency.

Therefore, wastewater can be stably purified while maintaining high reaction efficiency.

The above-mentioned wastewater treatment method was the case of aerobic wastewater treatment, but in the case of performing anaerobic wastewater treatment, the upper part of the fluid tank 1 is sealed as shown in FIG. An air diffuser 7 is provided by disposing a pipe 9 for connecting to the electric blower 6.
The gas of the electric blower 6 sent to the inside of the fluidized tank 1 via the above is collected at the upper part of the fluidized tank 1 and circulated and supplied to the electric blower 6 again. In this way, it is possible to perform anaerobic wastewater treatment using this wastewater treatment device.

Further, in the above embodiment, the openings 3d ... Of the draft tube 3 are formed in the inclined surface portion 3c, but the openings 3d ...
The part that can be formed is not limited to the inclined surface part 3c,
As shown in the figure, the opening 3d may be formed in the upper portion 3a.

Further, in the above-described embodiment, the connecting portion connecting the upper portion 3a and the lower portion 3b of the draft tube 3 of the wastewater treatment device to each other is the inclined surface portion 3c having an inclination angle, but the connecting portion is not a horizontal surface having an inclination angle. It is also possible to

Hereinafter, the effects of the present invention will be clarified by showing experimental examples.

[Experimental Example 1] The amount of solid particles that can be filled in the fluidized tank of the wastewater treatment apparatus shown in FIG. 1 was compared with the amount of solid particles that can be filled in the conventional fluidized tank. Both of them have the same volume of the fluidized tank, and the amount of waste water to be flown into the fluidized tank is also the same. Then, at the time of comparison and examination, whether or not the solid particles filled in the fluidized tank could flow was used as a criterion. The main specifications of the fluidized tank used are as follows.

Height of flow tank ………………………… 3300mm Outer diameter of solid-liquid separation column …… 500mm Outer diameter of draft tube… 400mm 〃 Lower outer diameter… 200mm Used diatomaceous earth having a diameter of 0.3 to 0.6 mm (Table 1) and activated carbon having an average diameter of 0.6 mm (Table 2). The numerical values in Tables 1 and 2 are the amount of solid particles added to the volume of the fluidized tank.

As is clear from these results, in any case, the device satisfying the requirements of the present invention can add flowable particles in an amount of about 2 to 3.5 times as compared with the conventional device, and therefore the amount of increase in the particles can be increased. It can be seen that the efficiency of wastewater treatment can be improved.

[Experimental Example 2] Solid particles were added to the flow tank of the wastewater treatment apparatus shown in FIG. The density of solid particles at the location was measured. The measurement results are shown in Table 3. The solid particles have 0.3
Diatomaceous earth with a diameter of ~ 0.6 mm was used.

As is clear from this result, the particle density at position b is
Since it increases in proportion to the particle addition rate and is always higher than the particle density at the position of c, solid particles that do not pass through the bottom of the flow tank at the position of b, that is, inside the upper part of the draft tube. It can be seen that the circulation flow of is occurring. In a fluidized bed that uses particles with a specific gravity of more than 1, it is common for particles to clog at the bottom of the fluidized tank and not to flow as the particles increase, but increase the amount of particles held at the top of such a fluidized tank. To prevent this. That is, there are many solid particles that are convective inside the draft tube, and some of these solid particles settle inside the draft tube due to their own weight and circulate down along the wall of the flow tank through the opening, The remainder of the solid particles rises above the draft tube, goes over the upper end of the draft tube, and descends between the draft tube and the solid-liquid separation column to form a deposited particle layer from the top. The accumulated particle layer is gradually collapsed from the lower portion by convection passing through the opening provided in the inclined surface portion of the draft tube and fluidized again.

[Advantages of the Invention] As described above, according to the present invention, the cross-sectional area of the upper portion of the draft tube is larger than that of the lower portion, and the upper portion and the lower portion are connected by the connecting portion, and the upper portion and the connecting portion Since the openings are formed in one or both of them, the following effects can be obtained.

I. The reaction time can be secured and the reaction efficiency can be improved by convection from the lower part having a small cross-sectional area to the upper part having a large cross-sectional area to reduce the flow velocity.

B. By causing solid particles to flow by convection through the openings, the deposition of solid particles can be suppressed even if the amount of solid particles added is increased to increase reaction efficiency, so while maintaining high reaction efficiency. Wastewater can be stably purified.

Therefore, there is an excellent effect that waste water can be stably purified while maintaining high reaction efficiency.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of the wastewater treatment device of the present invention, and FIG. 2 is a schematic configuration diagram showing an example of distribution of openings of draft tubes provided in the wastewater treatment device of the present invention, FIG. 3 is a block diagram of a conventional fluidized bed type waste water treatment device, and FIG. 4 is a state diagram when the flow of solid particles in a fluidized tank is stopped and particles are accumulated in the conventional fluidized bed type waste water treatment device. Is. 1 ... Fluid tank 3 ... Draft tube 5 ... Cylinder for solid-liquid separation (outer tube part) 7 ... Aeration device

Claims (2)

[Claims] 1. A waste water treatment device comprising a fluid tank having an air diffuser at the bottom, a draft tube standing upright in the fluid tank, and an outer cylinder tube, and waste water is allowed to flow into the waste water. In the wastewater treatment method of purifying wastewater by adhering or enclosing solid particles having a specific gravity of more than 1 by the aeration device, the cross-sectional area of the upper part of the draft tube is made larger than that of the lower part, and While connecting with the connecting part,
An opening is formed in either one or both of the upper portion and the connecting portion, and a deposition layer composed of solid particles deposited between the draft tube and the outer tube at the upper portion and the connecting portion of the draft tube is formed in the opening portion. A method for treating wastewater, characterized in that it is disintegrated and fluidized by passing convection. 2. A flow tank having an air diffusing device at the bottom, a draft tube and an outer tube part which are erected in the flow tank, and the cross-sectional area of the upper portion of the draft tube is larger than that of the lower portion. The wastewater treatment device is characterized in that the upper part and the lower part are connected by a connecting part, and an opening is formed in either or both of the upper part and the connecting part.