JPH0810523A - Floating filter media cleaning method - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the amount of washing water and drainage when washing floating filter media. In the method of cleaning the floating filter medium 1 in the treatment tank of the water treatment / filtration apparatus, (1) the position of the water surface 10 in the tank is adjusted to be lower than the lower surface of the upper outflow prevention means 2. After the step, (2) supplying air or the like to wash, and (3) stopping the supply of air or the like, the water is drained so that the position of the water surface 10 is lowered by a value smaller than the thickness of the floating filter medium layer 8. A method for cleaning a floating filter medium, the method comprising:

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a filter medium for a water treatment / filtration apparatus using a floating filter medium.

[0002]

2. Description of the Related Art Conventionally, the following methods have been known as water treatment methods for removing pollutants contained in water using microorganisms. (1) An activated sludge method for treating biological microorganisms with suspended microorganisms in the water to be treated. (2)
A contact oxidation method in which a contact material is filled in the treatment tank and stable treatment is performed by microorganisms adhering to the surface. (3) A biofilm filtration method using a packed filter medium. In recent years, a water treatment method (floating filter medium method) using a floating filter medium such as foamed plastic as a filler has been proposed. In addition, the water treatment method by the biofilm filtration method has a function of treating with the biofilm attached to the surface of the filter medium, and since the area of the filter medium surface can be made large, the amount of microorganisms that can live on the surface increases, and the treatment efficiency increases. Can be higher.

On the other hand, as a filter medium for a conventional filter treatment apparatus for removing suspended substances in treated water by filtration, sand, gravel, anthracite, etc. are mainly used, but in recent years, floating filter medium such as foamed plastic has also been used. It has come to be used. This is called deep-layer filtration, and unlike filtration only by the surface, suspended solids are captured in the depth direction, so the amount of suspended solids captured is large, pressure loss does not easily increase, cleaning is easy, and wear is small. Have the advantage of.

The water treatment device and the filtration device using the floating filter medium as described above exhibit only one of the functions of water treatment when used as a water treatment device and only filtration when used as a filtration device. Rather, it has more or less both functions, and either function has priority by changing the design conditions of the device. In such a water treatment / filtering device, although any function is designed to be prioritized, clogging is caused by the suspended substances trapped in the gaps of the floating filter medium or the bacterial cells grown on the surface of the floating filter medium. wake me up,
Its efficiency is decreasing. Therefore, it is necessary to restore the treatment efficiency by washing and removing the suspended substances and the proliferated bacterial cells trapped in the spaces of the floating filter medium at appropriate time intervals.

In order to wash the floating filter medium in the treatment tank of this water treatment or filtration device, the washing water is made to flow in the same direction as or a direction opposite to the flow of the ordinary raw water to let out suspended substances and bacterial cells, and sometimes with it. At the same time, air is blown in to stir the filter medium layer to separate and remove the trapped suspended substances and cells. In order to carry out this cleaning, the cleaning water piping for the cleaning operation, and if necessary, the cleaning air piping and the cleaning discharge drain piping are provided at the bottom of the processing tank for the raw water (treated water) in the case of upward flow processing. It is arranged together with the pipe and the air pipe for aeration.

[0006]

However, in the conventional method for cleaning a floating filter medium, since the floating filter medium lighter than water is washed while being pressed by the upper outflow preventing means by its buoyancy, the floating filter medium is not cleaned. There was a problem that the fluid was not sufficiently agitated and flowed, the development thereof was deteriorated, and the number of washing operations was increased or a large amount of washing water was used.
The upper outflow prevention means is a net, bar screen, or the like provided for preventing outflow of the floating filter medium to the upper side.
For example, a perforated plate.

Furthermore, when draining after finishing the washing operation, the sludge and the like are not sufficiently drained unless the water surface is lowered below the lower part of the filter medium layer, and in order to efficiently perform the filter medium cleaning, it is larger than the height of the filter medium layer. Since it was necessary to raise and lower the water surface within the range, this was also the cause of an increase in the amount of washing water and the amount of drainage, similar to the above.

Further, in order to carry out the conventional cleaning method, it is necessary to provide various pipes in the lower part of the processing tank as described above, and there is a problem that the structure of the apparatus is complicated and the installation area and height are required. there were.

The present invention has been made to solve these problems, and is capable of satisfactorily washing a floating filter medium with a small amount of washing water and drainage, thereby making it possible to simplify and downsize the device. The purpose is to provide a method.

[0010]

SUMMARY OF THE INVENTION The above object of the present invention is to provide a water treatment or filtration device in a treatment tank having at least upper outflow preventing means for preventing the floating filter medium from flowing out to the upper side. In the method of washing the floating filter medium,
(1) a step of adjusting the position of the standing surface of the water surface in the treatment tank to a position lower than the lower surface of the upper outflow prevention means, and (2) a gas or cleaning water or a gas after the adjustment. (3) a step of flowing and washing the floating filter medium by supplying washing water into the treatment tank;
After stopping the supply of the gas or the cleaning water or the gas and the cleaning water into the processing tank, the position of the stationary state of the water surface in the processing tank is lowered by a value smaller than the thickness of the floating filter medium layer. And a step of draining water from the inside.

The present invention will be described in more detail below.

In the present invention, the upper outflow preventing means provided in the treatment tank of the apparatus is a means for preventing the floating filter medium from flowing out to the upper side, and has, for example, a hole through which treated water and the like can pass without hindrance. Any member that does not interfere with water treatment or filtration may be used. The material is not particularly limited, and for example, a net, a bar screen, a perforated plate or the like having an appropriate strength can be used, and further, the net, the bar screen, the perforated plate or the like can be used in combination.

Further, in the present invention, it is desirable that the processing tank is provided with a lower outflow preventing means for preventing outflow to the lower side of the floating filter medium. The lower outflow preventing means may be a member having an outflow preventing function and not hindering water treatment or the like, like the above-described upper outflow preventing means, and the same members as those exemplified above may be used. . This lower outflow prevention means is necessary, for example, when a downward flow is generated in the treatment tank, but the lower outflow prevention means for covering the inlet of each pipe on the lower side of the treatment tank so as not to be blocked by the floating filter medium. It is also possible to substitute for the means.

In the present invention, the floating filter medium in the treatment tank of the water treatment or filtration device is not particularly limited. As the material of the floating filter medium, for example, a resin having a smaller specific gravity than water, particularly a porous substance of a foamed resin such as expanded polystyrene, expanded polypropylene, expanded polyethylene, etc. is preferable because it increases the surface area of the filter medium. One kind or two or more kinds of filter media may be mixed and used. Further, the floating filter medium may have any shape as required, but for example, a spherical shape, a small piece shape, a granular shape, a cylindrical shape, a hollow cylindrical shape, a hollow spherical shape or the like is preferable. Also,
When this device is used for water treatment, the average diameter of the floating filter medium is preferably about 5 mm to 20 mm. On the other hand, if the device is used for filtration,
The average diameter of the floating filter medium is preferably about 0.5 mm to 5 mm.

When this device is used for water treatment, the value of the thickness of the floating filter medium layer (the layer formed in the treatment tank by the filling of the floating filter medium) and the upper outflow prevention means. The ratio with the value of the distance from the lower surface to the upper surface of the lower outflow prevention means is preferably in the range of 1: 1.2 to 1: 1.8. If this ratio is less than 1: 1.2 (that is, the distance between the vertical outflow preventing means is too short), the state of fluid agitation of the floating filter medium may be poor during the washing operation, and the washing effect may be insufficient. The flow of the floating filter medium at the time of air cleaning may suddenly apply a load to the lower outflow prevention means, which may cause deformation or damage of the lower outflow prevention means. Further, when this ratio is larger than 1: 1.8 (that is, the distance between the vertical outflow prevention means is too long), the flowability of the floating filter medium is improved and the cleaning effect is improved, but at the same time, the height of the processing tank is increased. Construction costs tend to rise. In addition, the volume of the space below the treatment tank increases, and the amount of cleaning drainage tends to increase.

When this device is used for water treatment, it can be used as an aerobic biofilm treatment method of blowing aeration air into waste water. Further, it can be used as a method for anaerobic biofilm treatment without blowing air.

On the other hand, when this device is a device used for filtration, the ratio of the value of the thickness of the filter medium layer to the value of the distance from the lower surface of the upper outflow prevention means to the upper surface of the lower outflow prevention means. Is preferably in the range of 1: 1.5 to 1: 2.5. If this ratio is less than 1: 1.5 (that is, the distance between the vertical outflow preventing means is too short), the state of fluidized stirring of the floating filter medium may be poor during the washing operation, and the washing effect may be insufficient. The flow of the floating filter medium at the time of air cleaning may suddenly apply a load to the lower outflow prevention means, which may cause deformation or damage of the lower outflow prevention means. Further, if this ratio is larger than 1: 2.5 (that is, the distance between the vertical outflow preventing means is too long), the flowability of the floating filter medium is improved and the cleaning effect is improved, but at the same time, the height of the processing tank is increased. Construction costs tend to rise. In addition, the volume of the space below the treatment tank increases, and the amount of cleaning drainage tends to increase.

In the case of a filtration device, it is preferable to add a flocculant to the raw water to flocculate the suspended substance to facilitate filtration.

FIGS. 1 (a) to 1 (c) are schematic views illustrating changes in the positions of the filter medium and the water surface in the apparatus in the method for cleaning a floating filter medium according to the present invention.

As shown in FIG. 1 (a), the water surface 4 in the treatment tank during water treatment or filtration treatment usually exerts its effect in order to enhance the rectification effect on the outlet side of the treated water. It is set at a position higher than the upper outflow prevention means 2 by a height required to do so.

In the method for cleaning a floating filter medium according to the present invention, as shown in FIG. 1 (b), the position of the water surface 10 in the tank in the stationary state before the cleaning operation is set to the upper outflow prevention means 2. The position is adjusted to be lower than the lower surface [step (1) of the present invention]. In the conventional method, for example, air / washing water is supplied and agitated while the water surface 10 is kept at a position higher than the upper outflow prevention means 2, so that the floating filter medium 1 is suspended by the buoyancy. Since it is in a state of being pressed against, it cannot be sufficiently stirred and flowed, and the cleaning efficiency becomes low. Specifically, when the water surface 10 is cleaned at a position higher than the upper outflow prevention means 2, the amount of cleaning wastewater is 10% to 30% of the amount of treated water, and when the amount is large, the amount is almost half. In this case, the design capacity of the processing tank needs to be increased by this amount in order to re-process. On the other hand, in the present invention, since the water surface 10 is adjusted so as to be lower than the normal position of the water surface, the floating filter medium is agitated and fluidized without being obstructed by the upper outflow prevention device during agitation, and the cleaning effect is improved. Specifically, according to the present invention, the amount of cleaning wastewater is about 2 to 5% with respect to the amount of treated water. Hereinafter, this adjustment is referred to as "upper water surface adjustment". Further, the position of the water surface 10 in the adjustment of the upper water surface is a position within a range of ¼ of the thickness of the floating filter medium layer 8 from the lower surface of the upper outflow prevention means 2, that is, the stirring and flowing state of the floating filter medium. It is suitable for such points.

This upper water level adjustment may be adjusted by, for example, draining the water level if the water level in the treatment tank is too high, or supplying wash water or raw water if the water level is too low. This adjustment can be performed, for example, by a water level gauge and a water level adjusting valve provided on the side surface of the treatment tank, or by an inverted U-shaped pipe that is raised from the lower portion of the tank to the water surface position.

After the adjustment of the upper water level, the floating filter medium 1 is washed by supplying gas or cleaning water or gas and cleaning water into the treatment tank [step (2) of the present invention]. That is, stirring of the floating filter medium in the cleaning step may be performed by supplying gas into the treatment tank, cleaning water may be supplied together with the gas, or only cleaning water may be supplied. This gas is typically air. On the other hand, the washing water may be any liquid that can wash the floating filter medium. For example, water after water treatment or filtration (treated water) can be used as washing water. Moreover, when raw water can be used as washing water, it may be used as it is.

The method of supplying the gas or the cleaning water or the gas and the cleaning water into the processing tank may be, for example, any of the following methods. 1. Gas or cleaning water or gas and cleaning water is supplied from the lower side of the floating filter medium layer. 2. Cleaning water is supplied from the upper side of the floating filter medium layer, and gas is supplied from the lower side of the floating filter medium layer. 3. Gas or cleaning water or gas and cleaning water is tangentially supplied from the side surface of the floating filter material layer.

The purpose can be achieved if the floating filter medium is brought into a fluidized state in the treatment tank, and the suspended substances trapped on the surface of the floating filter medium and the suspended bacterial cells can be washed and removed.

To maintain the position of the water surface when washing the filter medium while supplying the washing water, use the above-mentioned water level gauge and water level adjusting valve, or an inverted U-shaped pipe that is erected from the lower part of the processing tank to the water level position. Can be done by.

After performing this cleaning for a desired time, it is desirable to stop the supply of cleaning air and the like to keep the water surface in the processing tank stationary for a certain period of time. By this standing, the floating filter medium 1 settles to the upper part of the treatment tank, and sludge and the like settles to the lower part, so that separation and discharge are facilitated.

Next, as shown in FIG. 1 (c), the water in the tank is drained so that the position of the standing surface of the water surface 10 of the processing tank is smaller than the thickness of the filter medium layer 8 [the present invention. Step (3)]. Hereinafter, this adjustment is referred to as "lower water level adjustment".
By this step, the pollutants separated together with water can be discharged from the lower part of the treatment tank. That is, the water surface should be lowered to such an extent that the settled sludge can be discharged. As a result, the amount of cleaning wastewater is reduced, the amount of recirculation is reduced, and the scale of the processing tank can be reduced.

The steps (1) to (3) described above may be carried out only once if the desired degree of washing of the floating filter medium is carried out, or may be carried out repeatedly if necessary. When repeating a plurality of times, after the step (3) is finished, the upper water level is adjusted again so that the position of the water surface 10 returns to the same position as the step (1), and then the steps (2) and (3) may be performed. . Further, these steps can be started at a fixed time interval or an arbitrary time by a device such as a computer or a sequencer, and automatically proceed according to a program. It can also be pre-programmed to perform sequential cleaning when multiple processing tanks are installed.

After the above-mentioned cleaning is completed, the water to be treated is passed through the treatment tank as water treatment or filtration operation to be recovered as treated water. Instead, it can be returned to the raw water tank and circulated again to the treatment tank. In addition, in the example shown in FIG. 1, the apparatus in the case where the flow direction of the water to be treated is the upward flow is shown, but the present invention can be applied even in the case of the downward flow.

In order to carry out the above-mentioned steps for treatment and cleaning, it is sufficient to install pipes for supplying raw water, aeration, cleaning air, etc. in the lower part of the treatment tank. Even if the gas for aeration is continuously circulated during the operation period, including during the step of washing the floating filter medium of the present invention, the amount of aeration is small and does not significantly affect other steps. Rather, it may be easier to design because it is not necessary to consider the load fluctuation of the blower. These pipes may be installed separately, but in this case, since the arrangement is complicated, the height of the processing tank becomes relatively high. On the other hand, if the raw water pipe and the cleaning air pipe, and the cleaning and drainage pipes are used together, the height of the treatment tank can be reduced and substances such as sludge accumulated inside the raw water pipe can be discharged to the outside of the system when draining water. It is preferable in terms of preventing clogging of the pipe, the opening of the pipe, and the nozzle.

[0032]

The present invention will be described in more detail with reference to the following examples.

<Example 1> FIG. 2 is a schematic view showing a filtering device used in this example. This device is an upflow biofilm filtration device (water treatment device) made of reinforced concrete,
The height of the processing tank is 6 m, the width is 4 m, and the vertical width is 5 m. The floating filter medium 1 is filled in the processing tank, and the layer thickness of the floating filter medium layer is 3 m. As the floating filter medium 1, a small piece of expanded polypropylene having an average diameter of 8 mm is used. Further, wire nets are provided as the upper outflow preventing means 2 and the lower outflow preventing means 3, and the interval between the upper and lower wire nets is 4 m. In addition, a pipe 6 for raw water / washing air / washing drainage and an aeration air pipe 7 are arranged in the lower part of the treatment tank. Further, a cleaning water pipe 5 is arranged above the processing tank. The raw water treatment capacity of this equipment is 5800 m ³ /
It is a day, and the filter media should be washed once a day.

In order to wash the floating filter medium in this apparatus,
The cleaning method of the present invention was carried out according to the flowchart shown in FIG. In the present embodiment, the upper water level is adjusted by lowering the water level from the upper outflow prevention means 2 by 0.5 m, and the lower water level is adjusted by lowering the water level to a position 2 m above the lower outflow prevention means 3. . In addition, in this cleaning step, 20% of cleaning air is applied to the filter medium layer.
It was supplied at m ³ / min and the filter medium was stirred.

Further, the process No. of FIG. In 3-11
The amount of washing wastewater is the amount of treated water (5800 m ³ ) About 2%
Became the amount. In addition, the process No. Drainage when cleaning 14 through water
The amount was about 2%. As a result, in this embodiment, processing
Only 4% of total amount of water (ie 232m³ ) In the amount of drainage
It was washed, but sufficient washing was possible.

<Comparative Example 1> The floating filter medium was washed in the same manner as in Example 1 except that the water surface 10 of the washing water was not adjusted and the water surface 10 was kept above the upper outflow prevention means 2. It was In this case, washing with the same amount of washing water as in Example 1 was insufficient. The amount of cleaning waste water required to obtain the same cleaning effect as that of Example 1 is 2 with respect to the amount of treated water.
0% (1160 m ³ ), about 5 times the amount of Example 1 was required.

[0037]

According to the cleaning method of the present invention described above, the position of the water surface in the treatment tank is adjusted before and after stirring and cleaning by supplying air and cleaning water, so that the floating filter medium can be used with a small amount of cleaning water and drainage. Can be washed well. In particular,
When the position of the water surface is not adjusted before and after supplying air and washing water as in the conventional method, the amount of washing wastewater is 10 to 30% of the amount of treated water.
However, in the cleaning method of the present invention, it is extremely small at 2 to 5%. Further, when the amount of washing water is reduced in this way, the amount of recirculation is also reduced, so that the scale of the processing tank can be reduced. From these points, the method of the present invention is very economically advantageous.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating changes in the positions of a filter medium and a water surface in an apparatus in a method for cleaning a floating filter medium of the present invention.

FIG. 2 is a schematic view showing an upflow biofilm filtration device used in Example 1.

FIG. 3 is a diagram showing a flowchart of a cleaning process in Example 1.

[Explanation of symbols]

 1 Floating filter medium 2 Upper outflow prevention means 3 Lower outflow prevention means 4 Water surface of treated water 5 Pipe for cleaning water 6 Pipe for raw water / wash air / wash drainage 7 Air pipe for aeration 8 Floating filter layer 10 Water surface

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B01D 29/08 530 C 540 A (72) Inventor Kuji Miyagawa 1039 Takashi, Mobara, Chiba

Claims (9)

[Claims] 1. A method of washing a floating filter medium in the treatment tank of a water treatment or filtering device, which comprises at least an upper outflow preventing means for preventing the floating filter medium from flowing out to the upper side, (1) Adjusting the stationary position of the water surface in the treatment tank to a position lower than the lower surface of the upper outflow prevention means, (2) after the adjustment, gas or cleaning water or gas and cleaning water In the treatment tank by causing the floating filter medium to flow to be washed by supplying the same to the treatment tank, and (3) after the supply of the gas or the cleaning water or the gas and the cleaning water into the treatment tank is stopped, And a step of draining the water in the treatment tank so that the position of the surface of the water in a stationary state is lowered by a value smaller than the thickness of the floating filter medium layer. 2. The method for cleaning a floating filter medium according to claim 1, wherein the steps (1) to (3) are repeated once or plural times. 3. The position lower than the lower surface of the upper outflow prevention means in the step (1) is a position within a range of ¼ of the thickness of the floating filter medium layer from the lower surface of the upper outflow prevention means. The method for cleaning a floating filter medium according to claim 1 or 2. 4. The drainage of water in the treatment tank in the step (3) is performed after the supply of the gas or the cleaning water or the gas and the cleaning water into the tank is stopped, and The method for cleaning a floating filter medium according to any one of claims 1 to 3, wherein the method is carried out after once being kept in a stationary state. 5. The method for cleaning a floating filter medium according to claim 1, wherein the water in the treatment tank in the step (3) is drained while supplying cleaning water from the upper portion of the treatment tank. . 6. The floating filter medium according to claim 1, wherein the water treatment or filtration device has a lower outflow prevention means for preventing outflow to the lower side of the floating filter medium in the treatment tank. Cleaning method. 7. The apparatus is an apparatus used for water treatment, wherein the floating filter medium has an average diameter of 5 mm to 20 mm,
The ratio of the thickness of the floating filter medium layer to the value of the distance from the lower surface of the upper outflow prevention means to the upper surface of the lower outflow prevention means is in the range of 1: 1.2 to 1: 1.8. Claim 6
The method for cleaning a floating filter medium described. 8. The device is a device used for filtration, wherein the floating filter medium has an average diameter of 0.5 mm to 5 mm, and the thickness of the floating filter medium layer and the lower surface of the upper outflow prevention means are the same. The method for cleaning a floating filter medium according to claim 6, wherein the ratio to the value of the distance to the upper surface of the lower outflow prevention means is in the range of 1: 1.5 to 1: 2.5. 9. After the completion of the steps (1) to (3), a desired amount of water to be treated is passed through the treatment tank according to the same operation as the water treatment or filtration operation, and the treated water after the start of the passage of water. The method for cleaning a floating filter medium according to any one of claims 1 to 8, further comprising the step of returning the water to the raw water tank.