JPH09817A - Descending flow filtering apparatus - Google Patents

Abstract

PURPOSE: To shorten the washing time of the filter bed of a descending flow filtering apparatus and to conserve a use quantity of washing water. CONSTITUTION: In a descending flow filtering apparatus 15 wherein a filter bed 12 packed with a filter material is formed in a filter tower 10 and air and washing water are supplied to the lower part of the filter bed to be allowed to flow through the filter bed upwardly and raw water is passed through the filter bed downwardly to be subjected to filtering treatment, the revolving stream nozzles 22 generating revolving streams in the filter bed and the shallow bed washing nozzles 23 allowing washing water to flow upwardly are arranged at the intermediate part of the filter bed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a down-flow filtration device for collecting filtered treated water by passing raw water in a down-flow through a filter layer provided in a filtration tower.

[0002]

2. Description of the Related Art In a conventional down-flow filtration device, a washing device is provided below a filter layer in a filtration tower to supply air and washing water to flow upward through the filter layer. When the filter layer captures suspended solids in the raw water in the sampled water, and the amount of suspended solids increases, and the filtration differential pressure rises, the sampled water is interrupted, the water on the filter layer is extracted, and the cleaning device Air and wash water are supplied into the tower from above to flow upward in the filter layer, the suspended matter captured by the filter layer is separated from the filter medium with air and wash water, and It is washed out from the discharge pipe to the outside (backwash), and then the washing water is passed through the filter layer in a downward flow to perform washing with water, and then water sampling is restarted.

[0003]

In the above-mentioned conventional filtration device, since the water on the filter layer must be extracted, backwashed, and washed with water, the time required for washing is long. Since the filtered water is used as the washing water, a large amount of the filtered water is used for the backwashing and the passing-through washing, so that the water collection efficiency of the filtered water decreases. Since the time required for cleaning is long, it is not suitable to collect water from high-turbidity raw water, which is frequently washed, because the water collection efficiency is further reduced.

[0004]

According to the present invention, in a down-flow filtration device, a large amount of suspended matter is captured in a portion up to about 500 mm from the surface layer portion (upper surface) of the filter layer, and the filtration differential pressure increases in this portion. It was developed with this in mind, with a filter layer filled with a filter medium inside the filter tower, and a cleaning device that supplies air and cleaning water below the filter layer to make it flow upward through the filter layer. In a down-flow filtration device that performs a filtering process by passing raw water through the filter bed in a downward flow, a swirling flow nozzle for generating a swirling flow in the filter layer in the middle part of the filter layer and a washing water A shallow layer cleaning nozzle for countercurrent flow is provided.

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 or 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 from the water sampling pipe 14 at the bottom of the tower.

A cleaning device 1 for supplying air and cleaning water below the support plate 11 in the tower to cause upward flow in the filter bed for cleaning.
5 is provided. As shown in FIG. 3, the cleaning device 15 is configured to uniformly supply air and cleaning water to the entire lower surface of the support plate. In the illustrated embodiment, the washing water supply pipe 16
And a pressurized air supply pipe 17 from an air compressor or the like is connected to one cleaning device 15. The cleaning device connected to the cleaning water supply pipe and the cleaning device connected to the pressurized air supply pipe are provided as support plates. It may be separately provided under the.

The washing wastewater which has flown upward in the filter bed together with air to remove suspended solids from the filter medium is discharged together with the suspended solids from the cleaning drainage discharge pipe 18 at the upper part of the filtration tower, and the air is discharged from the discharge pipe at the top of the tower. Exhausted from 19. Reference numeral 20 is a water-passing water supply pipe for passing washing water through the filter layer in a downward flow for washing with water. The water supply pipe 20 and the raw water supply pipe 13 are connected to valves V1,
Although the cleaning water and the raw water are supplied to the upper part of the filter tower by switching to V2, the cleaning water and the raw water may be supplied individually. The water supply pipe 20 is omitted and the supply pipe 1
Alternatively, the raw water may be used as the washing water in combination with No. 3. Reference numeral 21 is an extraction pipe that draws out most of the water on the filter layer to the outside prior to backwashing and brings the water level to about 100 mm on the filter layer.

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

Therefore, a swirling flow nozzle 22 for generating a swirling flow (vortex flow) in the filter layer and a washing water are provided above the filter layer 12 at a position of 100 to 500 mm below the surface layer of the filter layer. A shallow layer cleaning nozzle 23 for countercurrent flow is provided.

As is apparent from FIG. 2, the swirling flow nozzle 22 is provided on the inner wall of the filtration tower so as to jet the washing water tangentially. Further, the shallow layer cleaning nozzle 23 is used for the cleaning device 15
Similarly, the washing water is uniformly supplied into the tower. Of course, not only the wash water but also the wash water and air may be supplied.

As a result, each time the filtration pressure difference rises, the swirling flow nozzle 22 and the shallow layer washing nozzle 23 perform washing several times to trap turbidity in the lower part of the filter layer, and the swirling flow nozzle and the shallow layer are washed. If the filtration differential pressure cannot be sufficiently recovered by the washing with the layer washing nozzle, the back washing with the washing device 15 may be performed.

A swirling flow nozzle 22 and a shallow layer cleaning nozzle 23
Washing with is as follows. First, the swirl nozzle 2
Water is discharged from 2 for a short time, and a vortex flow is applied to the filter medium to atomize the suspended matter and cake-shaped suspended matter attached to the filter medium. Next, the washing water is discharged from the shallow layer washing nozzle 23, and is washed with the washing water that flows upward 100 to 500 mm downward from the surface of the filter layer, and the separated suspended matter is drained from the drain pipe 18 together with the washing drainage.

In this cleaning, since the swirling flow nozzle 22 and the shallow layer cleaning 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. Is. Therefore, the time required for draining the water is not necessary. Furthermore, since the filter material below the level at which the shallow layer cleaning nozzle is provided is not disturbed, it is not necessary to pass the washing water in a downward flow after washing, so that the washing water can be omitted. By performing this washing several times, the omission of the water removal time and the omission of the washing water for water passing washing are largely eliminated.

PAC 0.3 to 0.5 ppm as aluminum was added to raw water whose turbidity was adjusted to 3 to 5 degrees by addition of kaolin, pH was adjusted to 6.5 with H ₂ SO ₄ , and line aggregation was performed. Water was passed through the filter layer having a bed height of 1300 m of the illustrated downflow filter at a downflow of LV = 35 m / hour. The cleaning flow nozzle 22 and the shallow layer cleaning nozzle 23 are 500
It is provided at the position of mm. After 6 hours of water flow, water sampling was stopped when the filtration differential pressure increased to 0.7 kgf / cm ² .
Water is discharged from the swirling flow nozzle 22 for 1 minute at LV = 35 m / hour to give a vortex to the filter medium to atomize suspended matter, and then water is discharged from the shallow layer washing nozzle 23 for 10 minutes at LV = 35 m / hour to reverse. After washing, the suspended matter was discharged from the discharge pipe 18. After the backwashing with water was completed, the raw water was allowed to flow downward through the filter layer after the filter material settled, and water sampling was restarted.

[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. In addition, the quality of the collected filtered water does not change before and after washing, and the turbidity is 0.2-
0.3 degrees.

The swirling flow nozzle and the shallow layer washing nozzle are used to wash once every 6 hours to continue collecting water, and the fourth washing (24 hours after passing water) is performed by the washing device 15 under the support plate 11.
I went in. The filtration pressure difference at this time was 1 kgf / cm ² . First, water is drained from the drain pipe 21 up to 100 mm above the surface of the filter layer, and air backwashing is performed at 1 m ³ / m ² min at 0.4 kgf.
/ Cm ² , 20 ° C for 10 minutes, and then backwashing with water at LV = 35 m / hour for 15 minutes. After that, a downward flow water washing 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.
Recovered to 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, compared with the case where each cleaning is performed by the cleaning device 15, when the cleaning is performed three times by the swirling flow nozzle and the shallow layer cleaning nozzle, and only one cleaning is performed by the cleaning device, the time required for cleaning and the cleaning The amount of water used can be largely omitted.

Further, as compared with the cleaning using only the shallow layer cleaning nozzle, the cleaning effect using the shallow layer cleaning nozzle and the swirling flow nozzle in combination has a greater cleaning effect, and as a result, the cleaning time is shortened and the amount of cleaning water used is increased. Can be saved. That is, in order to reduce the filtration differential pressure from 0.7 kgf / cm ² to 0.3 kgf / cm ² , the amount of cleaning water used is 0.36 m ³ and the cleaning time is 20 minutes when only the shallow layer cleaning nozzle is used. On the other hand, when the swirling flow nozzle is also used, 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 significantly reduce the time required for washing the filter layer of the downflow filtration device and to greatly reduce the amount of wash water used. As a result, the water collection efficiency of filtered water is greatly improved. or,
Since washing can be performed in a short time, in the case of raw water with high turbidity, the treatment can be performed by increasing the frequency of backwashing.

[Brief description of drawings]

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

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

FIG. 3 is a sectional view taken along line BB in FIG.

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

[Explanation of symbols]

 10 Filtration Tower 11 Support Plate 12 Filtration Layer 13 Raw Water Supply Pipe 14 Water Collection Pipe 15 Washing Device 18 Cleaning Drainage Pipe 19 Discharge Pipe 20 Water Passage Pipe for Washing Water 21 Extraction Pipe 22 Swirling Flow Nozzle 23 Shallow Layer Washing Nozzle

Claims (1)

[Claims] 1. A filter layer filled with a filter medium is provided in a filter tower, and a washing device is provided below the filter layer to supply air and wash water to cause an upward flow in the filter layer. In a down-flow filtration device that performs a filtration process by passing water in a down-flow to a swirl flow nozzle that generates a swirl flow in the filter bed in the middle part of the filter bed, and a shallow layer cleaning that causes the wash water to flow upward. A downflow filtration device provided with a nozzle.