JP2001276517A - Washing method for filter tower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily remove contaminants increased in the depositing amount to a filtering medium by the repetition of a filtration process and a back washing process. SOLUTION: Alcoholic solution is continuously fed from an alcoholic solution tank 2 into a filter tower 1, and a filtering medium (e.g. a continuous fiber bundle 24) is brought into contact with the alcoholic solution to be washed. The contaminants removed from the filtering medium, together with the alcoholic solution, is discharged outside the filter tower 1. As the alcoholic solution, an aqueous solution of methyl alcohol, ethyl alcohol, or the like is used. When washed with the alcoholic solution, air can be blown into the filter tower 1 to carry out bubbling.

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 filtration tower used for filtering raw water such as river water and industrial wastewater, and more particularly to a filtration tower in a case where a differential pressure is not recovered in a normal backwashing step. A cleaning method.

[0002]

2. Description of the Related Art In general, when drinking water is produced from river water or when factory wastewater is reused as industrial water, filtration is performed for the purpose of removing suspended substances and foreign substances in raw water. . In this filtration treatment, a filtration tower filled with a filter medium is used, and raw water is passed through the filtration tower to perform the treatment. Sand is generally used as a filter material to be filled in the filtration tower, but a fiber material such as a bundle of long fibers and a lump of short fibers is used in addition to sand.

[0003] When the filtration treatment is performed for a certain period of time, suspended solids in the raw water captured by the filter medium gradually accumulate, and the accumulation amount increases as the filtration treatment time elapses. Pressure difference between the inlet and the treated water outlet).
Due to the increase in the differential pressure in the filtration tower, the treatment performance is deteriorated, and the quality of treated water is reduced, and the treatment efficiency is also reduced.

Therefore, conventionally, the differential pressure in the filtration tower has been monitored,
When the pressure difference reaches a certain value, a backwashing process is performed to remove suspended substances. In this backwashing treatment, the flow of water is stopped, the backwash water and air flow in from the lower part of the filtration tower, and the filter medium is swung by the upward flow of the backwash water and the agitating action of the air. The suspended matter is separated from the filter medium, and the suspended matter separated from the filter medium is discharged to the outside of the filtration tower together with the backwash water through the upper part of the filtration tower.

[0005]

After the backwashing process is completed, water is passed through the filtration tower to restart the filtering process, and when the pressure difference rises again as the filtering process time elapses, the backwashing described above is performed. The treatment is performed, and thereafter, the filtration step and the backwashing step are similarly repeated. Here, while the elapsed time of the filtration step is relatively short, the differential pressure is restored to the initial differential pressure by the backwashing treatment, but the elapsed time of the filtration step is increased, and the filtration step and the backwashing step are performed many times. When repeated, there is a problem that the differential pressure does not recover to the initial differential pressure even if the backwashing process is performed. In particular, such a phenomenon occurs remarkably when a long fiber bundle is used as a filter medium.

[0006] Although the reason for the above-mentioned problems is not necessarily clear, trace amounts of organic substances contained in the raw water gradually adhere to the surface of the filter medium to contaminate the surface of the filter medium or are contained in the raw water. Some of the suspended solids that adhere to the surface of the filter media firmly and contaminate the surface of the filter media, and the attached organic contaminants and suspended contaminants (hereinafter collectively referred to as contaminants) This is considered to be due to the fact that the conventional backwashing treatment cannot sufficiently remove it. That is,
Contaminants cannot be sufficiently removed even if backwashing treatment is performed by supplying backwash water and air, and a small amount of contaminants remains in the filter medium. When the amount of the remaining contaminants gradually increases, and the amount of the contaminants adhered to the filter medium increases, a phenomenon occurs in which the differential pressure does not recover to the initial differential pressure even when the backwashing process is performed. When such a situation occurs, the processing performance deteriorates, and it is impossible to continue the operation (filtration processing) as it is.

Therefore, when such a situation occurs, it has conventionally been necessary to take out the filter medium from the filter tower and remove the contaminants adhering to the filter medium.
For example, when the filter medium is a long fiber bundle, the long fiber bundle is taken out of the filtration tower, washed with a detergent or the like, and after the washing, the long fiber bundle is refilled into the filtration tower. I was Such an operation is extremely time-consuming and reduces the efficiency of the filtration process.

Further, in consideration of the trouble of cleaning the long fiber bundle, the entire length of the long fiber bundle may be replaced with a new one without cleaning. However, there is a disadvantage that the cost is increased and the processing cost is increased.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a method for cleaning a filtration tower in which contaminants which cannot be sufficiently removed by a normal backwash treatment by supplying backwash water and air can be easily removed from a filter medium.

[0010] The present invention also provides a method for reducing the pressure difference in a filtration tower to the initial pressure difference when the pressure difference in the filtration tower does not recover to the initial pressure difference even after the backwashing treatment due to an increase in the amount of contaminants attached to the filter medium. It is an object of the present invention to provide a method for washing a filtration tower, which can be returned.

[0011]

SUMMARY OF THE INVENTION The present invention provides (1) a method for washing a filtration tower for removing contaminants adhering to the filtration medium in the filtration tower, the method comprising the steps of: A method for washing a filtration tower, characterized in that the filter medium is supplied to contact the alcohol solution for washing.
(2) The method for washing a filtration tower according to the above (1), wherein an aqueous solution of a lower alcohol having 1 to 4 carbon atoms is used as the alcohol solution, and (3) the method of (1), wherein the concentration of the alcohol solution is 0.2 to 5%. The method for cleaning a filtration tower according to the above (1), wherein (4) air is supplied into the filtration tower to perform bubbling on the alcohol solution.
(5) The gist is the method for cleaning a filtration tower according to the above (1), wherein the filter medium is a bundle of long fibers.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, contaminants that cannot be removed by ordinary backwashing treatment by supplying backwash water and air gradually accumulate, and the amount of contaminants adhering to the filter medium increases, so that the reverse When the pressure difference in the filtration tower does not recover to the initial pressure difference even after the washing treatment, the alcohol solution is supplied into the filtration tower and washed to remove contaminants adhering to the filter medium. It is discharged out of the system.

[0013] The alcohol solution used in the present invention is an aqueous solution of alcohol, and the alcohol concentration of the solution is preferably 0.2 to 5%, more preferably 0.5 to 1%.
It is. If the alcohol concentration is less than 0.2%, the removal of contaminants becomes insufficient, and the alcohol concentration is up to 5%.
%, A sufficient cleaning effect is exhibited, so that it is not necessary to use a higher concentration, and instead, if a concentration higher than 5% is used, the consumption of alcohol increases and the cost increases. Rinsing and cleaning after the completion of the cleaning treatment with the alcohol solution requires time, and the consumption of rinsing water increases, which is not economically advantageous.

As the alcohol, a monohydric alcohol is preferable, and among the monohydric alcohols, a lower alcohol having 1 to 4 carbon atoms is preferable. That is, examples of the alcohol used in the present invention include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol. The present invention uses one or a mixture of two or more of these alcohols.

In the present invention, in washing the filtration tower with the alcohol solution, a method of continuously flowing the alcohol solution in the filtration tower in a downward flow or an upward flow may be adopted.
Alternatively, a method in which the water in the filtration tower is replaced with an alcohol solution and allowed to stand still may be adopted.

In the present invention, as a method of supplying an alcohol solution of a predetermined concentration to the filtration tower, an alcohol solution of a predetermined concentration is prepared outside the filtration tower, and the alcohol solution is caused to flow into the filtration tower through a supply line. Alternatively, the prepared alcohol solution may be directly injected and filled into the filtration tower without passing through the supply line (for example, the injection and filling may be performed by opening the lid of the filtration tower). Also, without adopting a method of preparing an alcohol solution outside the filtration tower, an undiluted alcohol stock solution is injected into the filtration tower, and the alcohol stock solution is dissolved in water in the filtration tower to a predetermined concentration in the filtration tower. A method for preparing an alcohol solution may be employed.

When the former alcohol solution is prepared outside the filtration tower, an alcohol solution tank is prepared and an alcohol solution having a predetermined concentration is prepared in the alcohol solution tank.
Alternatively, a mode is adopted in which an alcohol solution having a predetermined concentration is prepared in another place, and this alcohol solution is put into an alcohol solution tank. When such an alcohol solution tank is prepared, the alcohol solution tank is supplied. It is preferable to connect to the filtration tower via a line and supply the alcohol solution from the alcohol solution tank to the filtration tower.

In the embodiment in which the alcohol solution is supplied from the alcohol solution tank to the filtration tower, the flow of the alcohol solution to the filtration tower may be a downward flowing liquid or an upward flowing liquid.
Further, the alcohol solution flowing out of the filtration tower may be returned to the alcohol solution tank to circulate and supply the alcohol solution.

The present invention is not limited to the case where the alcohol solution is supplied from the alcohol solution tank to the filtration tower for washing by continuously passing the alcohol solution through the filtration tower. The alcohol solution is supplied from the alcohol solution tank to the filtration tower to replace the water in the filtration tower with the alcohol solution. Thereafter, the supply of the alcohol solution into the filtration tower is stopped and the alcohol solution is allowed to stand in the filtration tower. Alternatively, cleaning may be performed. Further, after allowing the alcohol solution to stand still for a certain period of time in the filtration tower, the alcohol solution may be continuously passed through the tower.

In the present invention, in either case where the alcohol solution is continuously passed through the filtration tower or when the alcohol solution is allowed to stand still, air may be supplied into the tower for washing while bubbling. In this case, the air supply may be continuous or intermittent. The present invention can sufficiently remove contaminants from the filter medium only by continuously passing the alcohol solution through the tower or allowing the alcohol solution to stand still. However, if air is supplied into the tower to cause a stirring action, the contaminants from the filter medium are caused. Removal is promoted, and the cleaning effect is further increased.

Contaminants are removed from the filter medium by continuously passing the alcohol solution through the filtration tower for a certain period of time, and are discharged out of the tower together with the alcohol solution. After washing with the alcohol solution, backwashing is performed while bubbling by sending backwash water and air from the bottom of the tower, and residual contaminants that have not been completely removed from the filter medium are discharged out of the tower together with the backwash water. In performing the backwash, only the backwash water may be sent without sending air. In the case of washing in a stationary manner, back washing is similarly performed after washing.

After the completion of the backwashing process, the rinse water is introduced into the filtration tower with downward flowing water or upward flowing water for rinsing, and the rinse water is discharged from the filtering tower.

The filtration tower to which the present invention is applied may be any filtration tower generally used for water treatment.
It may be used alone for the purpose of filtration, or may be a filtration tower that is incorporated in various steps and performs filtration as pretreatment. Raw water applied to the filtration tower in the present invention includes river water, lake water, factory wastewater, sewage, city water, and the like. The filtration tower to which the present invention is applied is, for example,
It is used for filtration when producing drinking water from river water, when reusing industrial wastewater as industrial water, or when producing ultrapure water using city water as raw water.

Examples of the filter medium to be filled in the filtration tower include fiber materials such as bundles of long fibers and lumps of short fibers, sand and the like. Among them, in the case of bundles of long fibers, Considering that it is difficult to remove contaminants, it is most beneficial to apply the present invention when using the long fiber bundle.

When the filtration step and the washing step are repeated several times, the amount of contaminants adhering to the filter medium increases, and when the pressure difference in the filtration tower does not recover to the initial pressure difference even after the backwashing treatment,
Although the application of the cleaning method of the present invention is a basic embodiment of the present invention, the present invention is not limited to such an embodiment, and generally, a hard-to-remove contaminant is removed from a filter medium. The cleaning method of the present invention can be carried out as needed for any purpose. That is, the backwashing step may or may not be performed as a step before the washing step according to the present invention, and thus the washing according to the present invention may be started directly without performing the backwashing.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing an apparatus for carrying out the washing method of the present invention. In the figure, reference numeral 1 denotes a filtration tower in which a bundle of long fibers 24 is filled as a filter material, and 2 denotes a filtration tower. An alcohol solution tank containing an alcohol solution having a predetermined concentration.
A first pipe 3 is provided above the filtration tower 1, and a second pipe 4 is provided below the filtration tower 1. The first pipe 3 is connected to an alcohol solution supply pipe 5 provided in the alcohol solution tank 2. And the raw water supply pipe 6 and the backwash discharge pipe 2
5 are connected.

On the other hand, a treated water outflow pipe 7, an air supply pipe 8, and a rinse discharge pipe 9 are connected to the second pipe 4, respectively. One end of a backwash water supply pipe 10 is connected to the second pipe 4, and the other end of the backwash water supply pipe 10 is connected to a raw water supply pipe 6.

Further, one end of an alcohol solution reflux pipe 11 is connected to the treated water outflow pipe 7 in a branched manner, and the other end of the alcohol solution reflux pipe 11 is connected to the alcohol solution tank 2. 12 is a pump connected to the raw water supply pipe 6, 13
Is a pump connected to the alcohol solution supply pipe 5, 14 is a compressed air supply source, and 15, 16, 17, 18,
Reference numerals 19, 20, 21, 22, and 23 denote valves provided on the respective pipes.

When filtering raw water using the apparatus having the above structure, the raw water is supplied to the raw water supply pipe 6 by the pump 12 with the valves 15, 16 and 17 opened and the other valves closed. At the same time, the raw water flows into the filtration tower 1 from the raw water supply pipe 6 via the first pipe 3, and flows downward into the filtration tower 1. The suspended substance in the raw water is a bundle of long fibers 2
4 and filtration is performed. The filtrate, ie, the treated water, flows out from the outlet at the lower part of the filtration tower 1 through the second pipe 4 and flows out of the system via the treated water outflow pipe 7.

When the above-mentioned filtration is performed for a certain period of time,
The suspended matter in the raw water captured by the bundle of long fibers 24 gradually accumulates, and the accumulation amount increases with the elapse of the filtration treatment time, and the differential pressure in the filtration tower 1 increases. When this differential pressure rise is detected, backwashing is performed. In order to detect the increase in the differential pressure, a pressure gauge that measures the pressure at the inlet and the outlet of the filtration tower 1 and a reading device that reads the pressure difference may be provided.

In order to perform backwashing, the water flow is stopped and the valve 1 is turned off.
8, 19, and 20 are opened and backwash water is supplied from the raw water supply pipe 6 through the backwash water supply pipe 10 and the second pipe 4 with the other valves closed (raw water is used, but water other than raw water may be used). )
From the lower part of the filtration tower 1 into the filtration tower 1 in an upward flow. At this time, air is simultaneously sent from the lower part of the filtration tower 1 from the compressed air supply source 14 through the air supply pipe 8 and the second pipe 4. The long fiber bundle 24 oscillates due to the upward flow of the backwash water and the stirring action of the air, whereby the suspended substance is separated from the long fiber bundle 24, The separated suspended matter flows out of the upper part of the filtration tower 1 together with the backwash water, and is discharged out of the system through the backwash discharge pipe 25.

After the backwashing process is completed, the flow of water to the filtration tower 1 is resumed, and the filtration process is performed. When the differential pressure rises again with the passage of the filtration processing time, the above-described backwashing processing is performed,
Thereafter, the filtration step and the backwashing step are similarly repeated.

When the filtration step and the backwashing step are repeated several times, and the situation where the pressure difference does not recover to the initial pressure difference even when the backwashing process is performed, washing with an alcohol solution is performed. In this alcohol washing, beforehand, most of the suspended matter trapped in the bundle of long fibers 24 is removed by performing the above-mentioned usual back washing treatment, and then the valves 16 and 21 are removed. , 22 while the other valves are closed, the alcohol solution is fed from the alcohol solution tank 2 to the alcohol solution supply pipe 5 by the pump 13, and the alcohol solution is passed through the first pipe 3 from the alcohol solution supply pipe 5. The liquid is allowed to flow into the filtration tower 1 and flow therethrough in a downward flow.

The alcohol solution flowing down in the filtration tower 1 comes into contact with the long fiber bundle 24 and contaminants adhering to the long fiber bundle 24, and the long fiber bundle 24 is washed. Contaminants are removed from the long fiber bundle 24 by washing with an alcohol solution, and the removed contaminants are dispersed or dissolved in the alcohol solution. Thus, the contaminants flow out of the tower together with the alcohol solution from the outlet at the bottom of the filtration tower 1 through the second pipe 4. As will be described later, the alcohol solution is returned to the alcohol solution tank 2 through the alcohol solution reflux pipe 11 in order to circulate the alcohol solution, and contaminants are also sent to the alcohol solution tank 2 together with the alcohol solution. .

The alcohol solution returned to the alcohol solution tank 2 is mixed with the alcohol solution in the alcohol solution tank 2 and flows into the filtration tower 1 again through the above-described alcohol solution supply line. Thus, the alcohol solution is circulated through the circulation line connecting the filtration tower 1 and the alcohol solution tank 2. Naturally, the alcohol solution used in circulation contains contaminants in a dispersed or dissolved state, but it does not hinder the cleaning function.If the alcohol solution is replaced at an appropriate time in consideration of the contaminant content, Good.

In performing the above-described washing with the alcohol solution, air is blown from the lower portion of the filtration tower 1 through the air supply pipe 8 through the second pipe 4, and the air bubbling the alcohol solution in the tower. It may be performed. In this case, the blowing of air into the filtration tower 1 may be performed simultaneously with the initial supply of the alcohol solution to the filtration tower 1, or after the alcohol solution is circulated and supplied to the filtration tower 1 for a certain period of time.

After supplying the alcohol solution to the filtration tower 1 for washing for a certain period of time, the supply of the alcohol solution is stopped, and backwashing is performed. When performing backwashing, valves 18, 19, 20
With the other valves closed, backwash water (raw water is used in the present embodiment) is supplied from the lower portion of the filtration tower 1 through the backwater supply pipe 10 through the raw water supply pipe 6. And air is sent from the compressed air supply source 14 through the air supply pipe 8 and the second pipe 4 from the lower part of the filtration tower 1 into the tower. The backwash water flows upward in the filtration tower 1 and is stirred by the bubbling action of air. Residual contaminants not completely removed from the long fiber bundle 24 by the above-described washing with the alcohol solution are removed from the long fiber bundle 24 by backwashing. The removed residual contaminants flow out of the upper part of the filtration tower 1 together with the backwash water, and are discharged outside the system through the backwash discharge pipe 25.

After the backwashing is completed, the valves 15, 16, and 23 are opened,
With the other valves closed, rinsing water (raw water is used in this embodiment) is passed from the raw water supply pipe 6 through the first pipe 3 into the filtration tower 1 in a downward flow to perform rinsing. . The rinse water is discharged out of the system through the rinse discharge pipe 9.

In performing the above-described washing with the alcohol solution, the alcohol solution flows through the filtration tower 1 in an upward flow from the lower part of the filtration tower 1 and flows out from the upper part of the filtration tower 1.
The liquid may be refluxed to the alcohol solution tank 2.

Further, in performing the washing with the alcohol solution, the alcohol solution flows into the filtration tower 1 from the alcohol solution tank 2 through the alcohol supply line, and the water in the filtration tower 1 is replaced with the alcohol solution. When the water in 1 is completely replaced by the alcohol solution, the supply of the alcohol solution to the filtration tower 1 is stopped, and thereafter, the alcohol solution is left in the filtration tower 1 to wash the filtration tower 1 with the alcohol solution. It may be performed. Also in this case, air may be blown into the filtration tower 1 from the air supply pipe 8 to bubble the alcohol solution in a stationary state.

[0042]

Next, specific examples of the present invention will be described.

A perforated plate was installed at the bottom of a resin filtration tower having a diameter of 250 mm and a straight body height of 1250 mm. One end was fixed and provided. Industrial water (turbidity: 1.3 degrees) was passed through the filtration tower in a downward flow, and filtration was performed at an LV of 40 m / h. The flow rate of water was set to 2 m ³ / h, and the differential pressure at the start of water flow, that is, the initial differential pressure was measured.
was a. Also, when the turbidity of the treated water was measured,
0.14 degrees.

With the elapse of the filtration treatment time, the differential pressure increased, and when the differential pressure reached 0.075 MPa, the filtration was stopped and backwashing was performed. When performing backwashing, use water (LV
50 m / h) and air (LV 50 m / h) were simultaneously introduced from the lower part of the filtration tower, and the backwash wastewater containing suspended substances was discharged from the upper part of the filtration tower. Backwashing was repeated a total of three times with a drainage treatment interposed therebetween to make one cycle. After the backwash, the differential pressure was measured and found to be close to the initial differential pressure.

After repeating the filtration process and the backwashing process several times, the differential pressure returned to only 0.05 MPa even after the backwashing. At this point, cleaning with an alcohol solution was performed.

That is, after backwashing, an aqueous 0.8% methyl alcohol solution was put into a filtration tower, the water in the tower was replaced with the aqueous methyl alcohol solution, and the column was left standing for 1 hour with the aqueous methyl alcohol solution filled. did. After standing for 1 hour, while the column was filled with a methyl alcohol aqueous solution, air was blown from the lower portion of the filtration tower at an LV of 50 m / h to perform bubbling, and washing was continued for 5 minutes while rocking the filter medium of the long fiber bundle. .

Next, the blowing of air was stopped, water was introduced from the lower part of the filtration tower at an LV of 50 m / h, and the washing wastewater was discharged from the upper part of the filtration tower. After performing this washing for 3 minutes, the water in the filtration tower was drained, and then water and air were removed from the lower part of the filtration tower.
V was fed at 50 m / h and backwashed for 2 minutes. After the backwash, rinsing was performed by passing water from the upper part of the filtration tower in a downward flow for 5 minutes, and the rinse water was discharged from the lower part of the filtration tower.

After the completion of the rinsing process, the differential pressure was measured and found to be 0.035 MPa. This value was the same as the initial differential pressure, which confirmed that the differential pressure had recovered to the initial differential pressure.

[0049]

According to the present invention, since an alcohol solution is supplied into a filtration tower and the filter medium is brought into contact with the alcohol solution for washing, contaminants can be easily removed from the filter medium. It is possible to reliably remove contaminants that could not be sufficiently removed by ordinary backwashing.

Therefore, when the amount of contaminants adhering to the filter medium increases due to the repetition of the filtration step and the backwashing step, the pressure difference in the filtration tower does not recover to the initial pressure difference even after the backwashing treatment.
By applying the cleaning method of the present invention, contaminants adhering to the filter medium can be easily removed, and as a result, the above-mentioned differential pressure can be restored to the initial differential pressure.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an apparatus for performing a cleaning method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filtration tower 2 Alcohol solution tank 24 Bundle of long fibers

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 29/38 580Z

Claims (5)

[Claims] 1. A method for washing a filtration tower for removing contaminants adhering to the filtration medium in the filtration tower from the filtration medium, comprising:
A method for washing a filtration tower, characterized in that an alcohol solution is supplied into the filtration tower to bring the filter medium into contact with the alcohol solution for washing. 2. The method according to claim 1, wherein an aqueous solution of a lower alcohol having 1 to 4 carbon atoms is used as the alcohol solution. 3. The method according to claim 1, wherein the concentration of the alcohol solution is 0.2 to 5%. 4. The method for cleaning a filtration tower according to claim 1, wherein air is supplied into the filtration tower to perform bubbling on the alcohol solution. 5. The method according to claim 1, wherein the filter medium comprises a bundle of long fibers.