JP3147720B2 - Cleaning method for down-flow filtration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for washing a downflow filtration device, in which raw water is passed through a filtration layer provided in a filtration tower in a downflow direction to collect filtered water.

[0002]

2. Description of the Related Art In a conventional downflow filtration device, a washing device is provided below a filter layer in a filtration tower to supply air and washing water to flow upward in the filter layer. When the filter layer captures the turbidity in the raw water during the sampling of the water, and when the trapped amount of the turbidity increases and the filtration differential pressure increases, the water sampling is interrupted, and the water on the filter layer is substantially extracted, and the washing device is used. From the filter layer, air and washing water are supplied into the tower to flow upward in the filter layer, the suspended matter trapped by the filter layer is separated from the filter medium with air and washing water, and the washing wastewater provided at the top of the filtration tower is removed. The water is washed out from the discharge pipe (backwashing), and then, the washing water is passed down through the filter layer in a downward flow to perform washing with water, and then water sampling is resumed.

[0003]

In the above-mentioned conventional filtration apparatus, the time required for cleaning is long because water must be extracted from the filtration layer, backwashed, and washed with water. Since the filtered water is used as the washing water, a large amount of the filtered water is used for backwashing and water washing, so that the efficiency of collecting the filtered water decreases. Since the time required for washing is long, water sampling from high turbidity raw water, which is frequently washed, is not suitable because the water sampling efficiency is further reduced.

[0004]

According to the present invention, in a downward flow filtration device, a large amount of turbid matter is trapped in a portion from the surface portion (upper surface) of the filtration layer to about 500 mm, and the filtration pressure difference increases in this portion. It was developed focusing on the fact that a filter tower having a filter layer filled with a filter medium inside, and provided under the filter layer in the filter tower, water on the filter layer was extracted out of the filter tower Thereafter, a washing device is provided for supplying air and washing water from below into the filter layer, flowing upward and washing the filter layer, and passing the raw water through the filter layer in a downward flow to perform a filtration treatment. A washing method for a down-flow filtration device, comprising: a filter bed swirling flow forming means for generating a swirling flow in a region from an upper surface to an intermediate position of the filter layer; and a shallow layer washing for washing by flowing washing water upward. Means for washing, and in the washing process, the water on the filter layer is attached to the filter medium without extracting water from the filter layer. After pulverizing the suspended matter, the suspended matter separated from the filter medium by the washing water flowing upward by the shallow layer washing means is discharged to the outside of the filtration tower, and when the filtration differential pressure cannot be recovered by the above two means, The cleaning is performed by a cleaning device provided below the filter layer.

In the illustrated embodiment, 10 is a filtration tower,
A water-permeable support plate 11 is provided below the inside thereof, and a filter layer 12 filled with sand, anthracite, an inert resin, an ion exchange resin, and any other filter material is provided on the support plate.
Reference numeral 13 denotes a raw water supply pipe for supplying raw water above the filter layer and passing the raw water through the filter layer in a downward flow. Water flows out of the water sampling pipe 14 at the bottom of the tower.

[0006] A washing device 15 is provided below the support plate 11 in the tower to supply air and washing water and to make washing flow by flowing upward in the filter layer. As shown in FIG. 3, the cleaning device 15 uniformly supplies air and cleaning water to the entire lower surface of the support plate. In the illustrated embodiment, the cleaning water supply pipe 16 is provided.
And a pressurized air supply pipe 17 from an air compressor or the like are connected to one cleaning device 15, but a cleaning device connected to a cleaning water supply pipe and a cleaning device connected to the pressurized air supply pipe are supported by a support plate. May be provided separately under

[0007] Washing wastewater, which flows upward in the filter layer together with air to remove turbidity from the filter medium, is discharged together with the turbidity from the washing drainage discharge pipe 18 at the top of the filtration tower, and the air is discharged into the discharge pipe at the top of the tower. Exhausted from 19. Numeral 20 denotes a water-supplying water supply pipe for carrying out water-washing by passing washing water in a downward direction through the filter layer. The water supply pipe 20 and the raw water supply pipe 13 are connected to valves V1,
Washing water and raw water are supplied to the upper portion in the filtration tower by switching at V2, but washing water and raw water may be supplied individually. The water supply pipe 20 is omitted and the supply pipe 1 is omitted.
Raw water may be used as washing water in combination with 3. 21
Is a drain pipe for draining almost all of the water on the filter layer to the outside of the filter layer before the backwashing to reduce the water level to about 100 mm above the filter layer.

FIG. 4 shows the rise in filtration pressure difference when suspended water having a turbidity of 3 is passed through a filter layer having a bed height of 1350 mm in a downward flow at a flow rate of 35 m / h for 24 hours. It is shown separately that it can be seen that the filtration differential pressure is most accumulated in the layer from the surface layer (upper surface) of the filter layer to 500 mm below. Therefore, if the filtration pressure difference of this layer is removed, the filtration pressure difference of the entire filtration layer can be greatly reduced.

Accordingly, a swirling flow nozzle 22 as a swirling flow forming means for generating a swirling flow (vortex flow) in the filter layer is provided at an intermediate portion of the filter layer 12, preferably at a position of 100 to 500 mm below the surface of the filter layer. And a shallow-layer washing nozzle 23 as a shallow-layer washing means for causing washing water to flow upward.

The swirling flow nozzle 22 is provided so as to jet rinsing water tangentially to the inner wall of the filtration tower, as is apparent from FIG. Further, the shallow layer cleaning nozzle 23 is provided with the cleaning device 15.
In the same manner as described above, the washing water is supplied uniformly into the tower. Of course, not only cleaning water but also cleaning water and air may be supplied.

Thus, each time the filtration pressure difference rises, cleaning is performed several times with the swirling flow nozzle 22 and the shallow layer cleaning nozzle 23. Then, the lower part of the filter layer also captures the suspended matter, and when cleaning by the swirling flow nozzle and the shallow layer cleaning nozzle cannot sufficiently recover the filtration differential pressure, backwashing is performed by the cleaning device 15.

A swirling flow nozzle 22 and a shallow layer cleaning nozzle 23
Is as follows. First, swirl nozzle 2
Water is briefly discharged from 2 to give a vortex to the filter medium, and the suspended matter adhered to the filter medium and the suspended matter in the form of a cake are refined. Next, washing water is discharged from the shallow layer washing nozzle 23, washed 100 to 500 mm below the surface of the filter layer with washing water flowing upward, and the separated turbid matter is drained from the discharge pipe 18 together with the washing drainage.

In this washing, since the swirling flow nozzle 22 and the shallow layer washing nozzle 23 are located 100 to 500 mm below the surface of the filter layer, it is not necessary to drain the water on the filter layer from the extraction pipe 21. It is. Therefore, the time required for draining is not required. Further, since the filter medium below the level where the shallow-layer washing nozzle is provided is not disturbed, it is not necessary to wash the washing water in a downward flow after washing, and the use of washing water can be omitted. By performing this washing several times, the drainage time and the rinsing water for flushing are greatly reduced.

[0014] PAC 0.3-0.5 ppm as aluminum is added to raw water adjusted to turbidity 3-5 degrees by addition of kaolin, pH is adjusted to 6.5 with H ₂ SO ₄ , and line coagulation is performed. Bed height of the downward flow filtration device shown
Was passed through the filter layer in a downward flow at LV = 35 m / hour. The swirling flow nozzle 22 and the shallow layer washing nozzle 23 are 50
It is provided at a position of 0 mm. Six hours after the passage of water, the water sampling was stopped when the filtration pressure difference increased to 0.7 kgf / cm ² ,
Water is discharged from the swirling flow nozzle 22 at LV = 35 m / hour for 1 minute to give a vortex to the filter medium to make the suspended matter fine, and then water is discharged from the shallow layer cleaning nozzle 23 at LV = 35 m / hour for 10 minutes to reverse. After washing, the suspended matter was discharged from the discharge pipe 18. After the water backwash was completed, the raw water was passed through the filter layer in a downward flow after the filter medium settled, and water sampling was resumed.

[0015] this swirling flow nozzle 22, filtration pressure difference at washing with shallow washing nozzle 23 was reduced from 0.7 kgf / cm ² to 0.3 kgf / cm ^2. The water quality of the filtered filtered water does not change before and after washing, and the turbidity is 0.2 to
0.3 degrees.

Washing is performed by the swirling flow nozzle and the shallow layer washing nozzle once every six hours, and water is collected. The fourth washing (24 hours after passing water) is performed by the washing device 15 below the support plate 11.
I went in. At this time, the filtration pressure difference was 1 kgf / cm ² . First, water was withdrawn from the extraction pipe 21 to a height of 100 mm above the surface of the filter layer, and air backwashing was performed at 0.4 kgf for 1 m ³ / m ² min.
/ Cm ² , 20 ° C. for 10 minutes, and then water backwashing was performed at LV = 35 m / hour for 15 minutes. Thereafter, water washing in a downward flow was performed for 10 minutes, and then water sampling was restarted. As a result, the filtration pressure difference is from 1 kgf / cm ² to 0.25 kg.
f / cm ² .

The time required for cleaning in the cleaning device 15 is 40.
The total amount of washing water used was 0.37 m ³ . On the other hand, the time required for cleaning by the swirling flow nozzle and the shallow layer cleaning nozzle was 11 minutes, and the total amount of cleaning water used was 0.2 m ³ . Therefore, as compared with performing each cleaning with the cleaning device 15, cleaning three times with the swirling flow nozzle and the shallow-layer cleaning nozzle and performing cleaning only once with the cleaning device can reduce the time required for cleaning and the cleaning time. The amount of water used can be greatly reduced.

Further, compared with the cleaning using only the shallow-layer cleaning nozzle, the cleaning effect using the combined use of the shallow-layer cleaning nozzle and the swirling flow nozzle is larger, and as a result, the cleaning time is shortened and the amount of the cleaning water is used. Savings. That is, in order to reduce the filtration pressure difference from 0.7 kgf / cm ² to 0.3 kgf / cm ² , when only a shallow layer cleaning nozzle is used, the amount of cleaning water used is 0.36 m ³ and the cleaning time is 20 minutes. On the other hand, when the swirl flow nozzle is used together, the amount of washing water used is 0.2 m
^{3. The} washing time was 11 minutes.

[0019]

As is apparent from the above, according to the present invention, it is possible to greatly reduce the time required for cleaning the filter layer of the downflow filtration device and to greatly reduce the amount of washing water used. And the efficiency of sampling the filtered water is greatly improved. or,
Since washing can be performed in a short time, in the case of high turbidity raw water, the treatment can be performed by increasing the frequency of backwashing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a downward flow filtration device of the present invention.

FIG. 2 is a cross-sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a graph showing an increase in filtration pressure difference due to water flow for each height of a filtration layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Filtration tower 11 Support plate 12 Filter layer 13 Raw water supply pipe 14 Sampling pipe 15 Washing device 18 Washing drainage discharge pipe 19 Release pipe 20 Water supply washing water supply pipe 21 Extraction pipe 22 Swirling flow nozzle (filter layer swirling flow forming Means) 23 Shallow layer cleaning nozzle (shallow layer cleaning means)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 24/00-24/48

Claims (1)

(57) [Claims] Claims: 1. A filter tower having a filter layer filled with a filter medium therein, and a filter tower provided below the filter layer in the filter tower. A washing device for supplying air and washing water from below and flowing upward to wash the filter layer; and a downflow filter device for performing filtration by passing raw water through the filter layer in a downward flow. In the washing method of (1), a filter layer swirling flow forming means for generating a swirling flow in a region from the upper surface of the filter layer to an intermediate position, and a shallow layer washing means for washing by flowing washing water upward, are provided. In this case, the suspended matter adhering to the filter medium is refined by the filter layer swirling flow forming means without extracting water from the filter layer, and then the suspended matter separated from the filter medium by the washing water flowing upward by the shallow layer washing means. If the filtration differential pressure cannot be recovered by both of the above means, A method for cleaning a downflow filtration device, wherein the cleaning is performed by a cleaning device provided below the bed.