JPH10305204A - Cleaning method of fiber filter material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method of a fiber filter material by which a suspended material trapped in the fiber filter material can be efficiently peeled from the fiber filter material with a small amt. of a cleaning water in a short cleaning time and can be discharged out of a filter tower. SOLUTION: This cleaning method of a fiber filter material 2 is carried out as described below. Water 6 containing suspended substance is supplied to a filter tower 1 packed with a fiber filter material 2 to trap the suspended material by the fiber filter material 2. When the fiber filter material 2 which traps the suspension material is cleaned with a cleaning water 9, the cleaning water 9 is supplied through the lower part of the filtering tower 1 while inside of the tower 1 is aerated, and the waste cleaning water 8 containing the suspended material is discharged through the upper part of the filter tower 1 while flowing of the fiber filter material 2 is prevented by a preventing plate 4 against flowing of the filter material disposed inside of the filtering tower 1.

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 fiber filter medium used for separating and removing suspended substances in water.

[0002]

2. Description of the Related Art Filtration has been widely used as a water treatment technique for separating and removing suspended substances in water. For example, in the field of tap water treatment, a method called rapid filtration has been adopted in which raw water containing fine suspended substances is treated with a flocculant to aggregate the suspended substances to facilitate separation, followed by filtration and separation. In this rapid filtration, two-layer filtration is generally performed in which a filter medium in which crushed anthracite is formed on a sand layer is used at a flow rate of 5 to 7 m / hour. In the field of sewage treatment, wastewater with a relatively large particle size and a high concentration of suspended matter, such as activated sludge treated water, is often targeted for filtration. Processing is performed only in special cases. Sand and crushed anthracite are often used as the filter medium in the same manner as for water treatment, and a method of passing water at a high speed of 4 to 25 m / hour is generally adopted. In sewage treatment, this method is used. Is called rapid filtration.

[0003] In recent years, as a filter medium replacing sand and anthracite, a floatable filter medium made of expanded polystyrene resin, an acrylic long fiber filter medium, a polyester flat elliptic fiber filter medium, a polyvinylidene chloride spherical fiber filter medium, and sewage sludge incineration ash have been used. Granulation /
A fired lightweight fine-grained filter medium has been developed, and a filtration speed of 25 m / hour or more is possible. JP-A-4-0274
No. 95 and JP-A-6-292808 describe an ultrahigh-speed filtration device using a polyester fiber filter medium. When any of these filter media is used, suspended matter is trapped in the filter media together with the passage of water, the water flow resistance increases, and eventually the filter media becomes unusable. Therefore, it is necessary to wash the filter media at regular intervals. As a washing method, usually, washing water is supplied to the inside of the filtration tower, and the filter medium layer is vibrated by aeration or the like, thereby loosening the filter medium layer, peeling off suspended substances from the filter medium, and containing the suspended substance at a high concentration. A method is adopted in which the washing wastewater is discharged from a filtration tower and returned to a sedimentation pond or the like.

[0004]

When a filter medium made of sand, crushed anthracite, etc. used in two-layer filtration is washed, the difference in specific gravity between the filter medium and the suspended substance is large. In general, a method of forming an upward flow of washing water inside a filtration tower, floating only suspended substances having a low specific gravity, and discharging washing wastewater containing suspended substances at a high concentration from the upper part of the filtration tower is usually performed. I have. On the other hand, when washing the fiber filter medium, the specific gravity difference between the fiber material and the suspended substance is small, so when the washing water in the upward flow is supplied inside the filtration tower, the fiber filter medium itself floats, and the fiber filter medium is removed from the filtration tower. There are problems such as spills and insufficient separation of suspended solids and fiber filter media.To wash fiber filter media, first fill the filter tower with washing water and vibrate the filter media layer by aeration. Accordingly, a method of loosening the filter medium layer and discharging the washing wastewater containing the suspended matter from the lower portion of the filtration tower has been performed.

However, in this method, when the washing wastewater is discharged from the lower part of the filtration tower, the washing wastewater passes through the filter medium layer, so that the suspended solids are captured by the filter medium again, and the filter medium is sufficiently washed. There was no problem. The present invention can efficiently separate suspended substances trapped in a fiber filter medium from a fiber filter medium with a small amount of washing water and a short washing time, and can discharge the suspended substance out of a filtration tower. An object of the present invention is to provide a method for cleaning a fiber filter medium, which can reduce the frequency of filter medium cleaning by high-speed filtration.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve such problems, and as a result, aerated the inside of the filtration tower and supplied washing water from the lower part of the filtration tower. By discharging the washing wastewater from the upper part of the filtration tower while preventing the outflow of the fiber filter medium by the installed filter medium outflow prevention plate, the suspended substances trapped in the fiber filter medium can be efficiently removed with a small amount of washing water and a short washing time. Peeled from the fiber media,
Found the fact that it can be discharged outside the filtration tower,
The present invention has been reached. That is, the present invention supplies suspended substance-containing water to a filtration tower filled with a fiber filter medium to trap the suspended substance in the fiber filter medium, and when the suspended fiber substance is washed with washing water, While aerating the inside of the filtration tower, supplying washing water from the bottom of the filtration tower, and preventing the outflow of fiber filter media by the filter medium outflow prevention plate installed inside the filtration tower, washing wastewater containing suspended solids from the top of the filtration tower The gist of the present invention is a method for cleaning a fiber filter medium, which is characterized by discharging.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic view showing an example of a cross section of a filtration tower used in the method for cleaning a fiber filter material of the present invention. In FIG. 1, reference numeral 1 denotes a filtration tower in a filtration device capable of high-speed filtration, and a filter medium support plate 3 holding a fiber filter medium 2 is provided at a lower part of the filtration tower 1, A filter medium outflow prevention plate 4 for preventing the fiber medium 2 from flowing out during washing is installed, and the fiber medium 2 is filled on the filter medium support plate 3. By passing suspended substance-containing water (raw water) 6 through the fiber filter medium 2, suspended substances in the raw water 6 can be captured and removed, and a high-quality treated water 7 without suspended substances can be obtained. Can be. Here, as for the size of the filtration tower 1, the water passing speed in the filtration tower 1 is 25 m.
It is preferable to determine the diameter and the like so that ultra-high-speed filtration of / h or more can be performed. In addition, when the filtering effect is taken into consideration, the height of the fiber filter medium layer is usually about 1 m, and in consideration of the washing efficiency at the time of washing the filter medium, a space above the fiber filter medium layer is provided above the height of the filter medium layer. Is preferably provided.

The material and the like of the filter medium support plate 3 and the filter medium outflow prevention plate 4 are not particularly limited as long as the water passage holes are smaller than the fiber filter medium 2 and have a size that allows only water to pass without passing through the filter medium. However, considering air aeration at the time of washing, it is preferable to use one having strength enough to withstand this, and it is preferable to use a steel grid, a punching plate, a screen plate, or the like.

As the fiber filter medium 2, various materials and shapes can be used. In order to further improve the washing efficiency of the fiber filter medium, unstretched filaments having a single fiber fineness of 50 denier or less are used. It is preferable to use a fiber filter medium obtained by collecting and binding 100 to 500 yarns formed by assembling 100 to 500 yarns and cutting them while leaving 50 to 300 mm from the collected portion. Further, a polyester flat elliptical fiber filter medium having a diameter of 5 to 30 mm is also suitable as the fiber filter medium 2 in the present invention. Further, the number of the fiber filter media 2 to be filled in the filtration tower 1 is, for example, in the case of a fiber filter medium having a diameter of 150 mm, 2000 to ⁶ per m ³ of the filtration tower.
Preferably, the number is 000. The flow direction of the raw water 6 in the filtration tower 1 may be a downward flow or an upward flow. Further, as the filtration tower 1, a pressure type in which the upper end of the filtration tower 1 is sealed and pressurized or a gravity type in which the upper end is opened can be applied.

[0010] With the passage of the raw water 6, suspended matter is trapped in the fiber filter medium 2 and the water pressure loss increases, and the fiber filter medium 2 needs to be washed. The degree of increase in the passing water pressure loss, the concentration and type of suspended solids in the raw water, water flow rate, varies greatly depending on the type of the fiber filter material, usually fibrous filter material 2 slag material layer 1 m ³ per suspension of 1~10kg When capturing suspended matter dry weight,
Passing water head loss is increased to 100~2000mmH ₂ O, it enters the washing step of the fiber filter media. The transition to the washing step can be controlled at a fixed interval by a timer, but automatic control is preferred in which the water level is sensed by a water level gauge and the washing step is started when the water level reaches a certain level.

In the present invention, in the above-mentioned washing step, washing water 9 for aerating the inside of the filtration tower 1 and washing the fiber filter medium is supplied from the lower part of the filtration tower 1, and the washing waste water 8 containing suspended substances is removed. It is necessary to discharge from the upper part of the filtration tower 1. Further, it is necessary to prevent the outflow of the fiber filter medium by the filter medium outflow prevention plate 4 installed inside the filtration tower as described above. As the washing water 9 used in the present invention, the raw water 6 may be used, but the use of the treated water 7 containing a small amount of suspended substances increases the washing efficiency. The amount of the washing water 9 is preferably such that the water flow rate in the filtration tower 1 is 2 to 50 m / hour. 2m water flow speed
If the flow rate is less than / m / h, the discharge of suspended matter tends to be insufficient, and if the water flow rate is 50 m / h or more, the flow rate increases, which is not preferable. The water passage time is determined in consideration of the amount of water passage, but is preferably 2 to 30 minutes. In the case of less than 2 minutes, the discharge of suspended substances tends to be insufficient, and in the case of more than 30 minutes, the amount of washing wastewater increases and the washing time becomes longer, which is not preferable.

Further, in the washing method of the present invention, when the washing water 9 flows, the filter medium layer is vibrated by supplying air 10 from the air diffuser 5 disposed below the filtration tower 1 and aerating the same. By loosening the filter medium layer, the separation of the suspended substance from the fiber filter medium 2 can be promoted. Here, as the air diffuser 5, an air diffuser, a disk diffuser, or the like can be used. The air diffuser 5 blows air from the entire lower surface of the filter medium support plate 3 or blows air from one side. However, it is preferable to use an air diffuser that alternately ejects air from each side and then ejects air from both sides. The supply amount of the air 10 from the air diffuser 5 is preferably 0.5 to ⁵ m ³ / min per 1 m ² of the filtration area of the filtration tower 1. When the supply amount of the air 10 is 0.5 m ³ / min or less, the vibration of the filter medium layer tends to be insufficient, and the separation of the suspended substance from the fiber filter medium 2 tends to be insufficient. On the other hand, when the supply amount of the air 10 is 5 m ³ / min or more, the peeling effect may not be as high as the aeration power.

[0013] After the passage of the washing water 9 and the end of the aeration, the washing wastewater remaining in the filtration tower 1 may be left as it is to proceed to the filtration step. However, the washing remaining from the lower part of the filtration tower 1 is continued while the aeration is continued. The effect can be improved by discharging the wastewater and then proceeding to the filtration step. In addition, the above-described washing step of the fiber filter medium 2 may be completed once, but the washing step may be repeated several times by combining drainage and filling of remaining washing wastewater from the lower part of the filtration tower 1. Good.

[0014]

Next, the present invention will be described specifically with reference to examples and comparative examples. Example 1 A yarn obtained by assembling 192 undrawn polyester filaments having a single yarn fineness of 10.4 denier was used as a raw material, and a processed yarn obtained by bulky processing the untwisted yarn was 4
00 fiber bundles were collected and bundled, and a fiber filter medium cut into a substantially spherical shape leaving 75 mm from this bundled portion was formed. Vertical, horizontal and height dimensions are 1.2m and 1.2m respectively
A trough for supplying raw water is installed at the top of a gravity type filtration tower (filtration area 1.44 m ² ) with an open top at 5 m and 5 m. A board is installed. At the bottom of the filtration tower, a filter medium support plate made of steel lid was installed, and 6,000 of the above-mentioned fiber filter materials were filled thereon, and the height of the filter medium layer was set to 1 m. In addition, two diffusers are provided below the filter media support plate.
Air is supplied from these air diffusers during cleaning.

[0015] From the top of the filtration tower, the suspended solids (SS)
Activated sludge treated water (raw water) having a concentration of 10 mg / L was supplied such that the flow rate in the filtration tower was 30 m / hour, and the treated water was discharged from a discharge port at the lower end side of the filtration tower. Raw water was passed through until 10.1 kg of suspended solids (SS) was captured in all the fiber media, and the washing process was started. In the washing step, the raw water was supplied from the lower part of the filtration tower as washing water at a flow rate of 48 m ³ / hour (flow rate 3).
(0 m / h) and the air is supplied into the filtration tower in an upward flow at the same time as an air supply amount of 2.5 m ³ / min.
(7 m / min) for one minute, and then one-sided aeration from the other air diffuser under the same conditions for one minute. As a result, the filter medium layer was loosened, the fiber filter medium started turning inside the filtration tower, and the separation of suspended substances from the fiber filter medium was promoted. Next, the washing wastewater was continuously discharged from the upper part of the filtration tower, and at the same time, the entire air was aerated from both air diffusers at an air supply rate of 2.5 m ³ / min, and the supply of the washing water from the lower part of the filtration tower was continued for 10 minutes. After the supply of the washing water was completed, the washing wastewater remaining in the filtration tower was discharged from the lower part of the filtration tower while performing the entire aeration under the above conditions, and the process returned to the filtration step. By the above washing method, 8.5 kg of suspended solids (SS) was discharged, and the rejection rate (the ratio of the weight of the discharged suspended substances to the weight of the suspended substances trapped in the fiber filter medium) was 84%. became. Incidentally, head loss during filtration water flow resumes is 200 mm ₂ O, it was comparable in the case of using a fibrous filter material new.

Comparative Example 1 A fiber filter, a filtration tower, and filtration conditions were the same as in Example 1. In the washing step, air was simultaneously supplied from two air diffusers at the bottom of the filtration tower at a rate of 2.5 m ³ / min for 5 minutes, and the washing wastewater was discharged from the bottom of the filtration tower while aeration was continued. Next, while aeration was continued, washing water was supplied from the lower part of the filtration tower until the inside of the filtration tower became full, and aeration of the entire surface and discharge of washing wastewater from the lower part of the filtration tower were repeated twice. By the above cleaning method,
7.1 kg of suspended solids (SS) are discharged and the rejection rate is
70%. The head loss when restarting filtration is 3
35 mmH ₂ O, compared with the case where a new fiber filter medium is used or the case where the fiber filter medium according to the cleaning method of the present invention is used, the head loss of 100 mmH ₂ O or more increases,
It became clear that washing (discharging of suspended substances) of the fiber filter medium was not sufficiently performed.

[0017]

According to the present invention, the suspended matter trapped in the fiber filter can be efficiently separated from the fiber filter with a small amount of washing water and a short washing time, and can be discharged out of the filtration tower. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a cross section of a filtration tower used in the method for cleaning a fiber filter material of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filtration tower 2 Fiber filter medium 3 Filter medium support plate 4 Filter medium outflow prevention plate 5 Aerator 6 Water containing suspended substances (raw water) 7 Treated water 8 Washing drainage 9 Washing water 10 Air

Claims (2)

[Claims] 1. A suspended solid containing water is supplied to a filtration tower filled with a fibrous filter medium to trap the suspended substance in the fibrous filter medium. When the suspended fiber substance is washed with washing water, filtration is performed. While aerating the inside of the tower, washing water is supplied from the lower part of the filtration tower, and washing water containing suspended substances is discharged from the upper part of the filtration tower while preventing outflow of the fiber filter medium by the filter medium outflow prevention plate installed inside the filtration tower. A method for cleaning a fiber filter medium, characterized in that the method comprises: 2. A fibrous filter medium is a yarn obtained by assembling 50 to 1000 undrawn filaments having a single-filament fineness of 50 denier or less, and 100 to 500 assembles bulk-processed untwisted yarns. 2. The method for cleaning a fiber filter medium according to claim 1, wherein the fiber filter medium is a fiber filter medium that is bundled by being bundled and cut while leaving an appropriate length from the bundle.