JPH08197080A - Biological filtration device - Google Patents

Abstract

PURPOSE: To prevent the SS (suspended solid) released from a filtration medium when the filter medium constituting a floating filter bed in a filtration tower is discharged outside the tower, cleaned and then returned to the tower from being mixed in treated water when filtration is resumed. CONSTITUTION: This biological filter is provided with a filter bed 13 formed by sticking a biological member on a floatable filter medium packed in a filtration tower 10, a means 14 placed below the filter bed 13 and passing raw water upward through the filter bed 13 and a means 15 furnished above the filter bed 13 and discharging the treated water outside the tower 10, and a means 21 for discharging the filter medium at the lower part of the filter bed 13 outside the tower 10 and cleaning the filter medium is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biofiltration device for passing raw water in an upward flow through a flotation filter layer having a biofilm attached to a flotation filter medium packed in a filtration tower.

[0002]

2. Description of the Related Art A biological filtration device can retain a high concentration of organisms in a tank as compared with a floating treatment method such as activated sludge, so that organic matter and nitrogen in sewage, night soil and various industrial wastewaters can be efficiently treated. Can be removed well. In addition, since it is not necessary to provide a sedimentation tank for sludge separation in the latter stage of the device, it is possible to save a lot of site area. However, on the other hand, the gap of the filter medium is closed due to the capture of SS and the growth of biofilm, and the pressure loss gradually increases.
It must be backwashed and the sludge in the tank must be discharged. Normally, backwashing is performed using treated water, but as the concentration of organic substances and nitrogen in the raw water increases, the backwashing water ratio (ratio of backwashing water to treated water) increases and Therefore, the equipment required (backwash drainage tank, etc.) will be enlarged.

Therefore, the entire amount of the buoyant filter material constituting the levitation filter layer is extracted outside the filtration tower for washing, and after washing, it is returned to the inside of the filtration tower again to form the levitation filtration layer. There is.

[0004]

However, when the entire amount of the buoyant filter medium which constitutes the levitation filter layer is moved in this way, or when the levitation filter medium is extracted outside the column and washed and then returned to the inside of the column to form the filtration layer again. , The SS trapping ability of the filter layer is lowered, or the SS separated during the returning of the filter medium cannot be trapped at the beginning of the filtration process, so that the SS is mixed in the treated water,
Deteriorates the quality of treated water.

[0005]

The present invention was developed in order to solve the above problems and to reduce the backwash water ratio, and a biofilm is attached to a floatable filter medium filled in a filtration tower. The adhered floating filter layer, a raw water supply unit provided below the filter layer for passing raw water through the floating filter layer in an upward flow, and a treated water provided above the floating filter layer. In a biological filtration device equipped with a means for discharging treated water to be discharged outside the filtration tower,
It is characterized in that extraction means is provided for extracting and cleaning the filter material under the floating filter layer outside the filtration tower.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the biological filtration apparatus of the present invention shown in the figure, 10 is a filtration tower, a water collecting plate 12 is installed below a closed upper wall 11 in the tower, and below this water collecting plate. For example, a levitation filter layer 13 is provided by filling a levitation filter material made of expanded polystyrene having a particle diameter of 3.5 mm and a specific gravity of 0.03 g / cm ² . The aperture of the water collecting plate is smaller than the particle size of the filter medium,
The buoyant filter medium is buoyantly packed under the water collecting plate and is in a fixed state. A biofilm is attached to the floatable filter medium.

A supply pipe 14 is provided below the floating filter layer in the filtration tower.
Supplies raw water. Further, the filter tower is provided with a discharge pipe 15 above the water collecting plate for discharging treated water to the outside of the tower. As a result, the raw water supplied through the supply pipe 14 flows upward in the floating filter layer 13, the SS contained therein is captured by the filter layer and undergoes a filtering process, and at the same time, the organic matter contained therein adheres to the filter medium. Exhaust pipe 15
It is discharged from (Fig. 3).

A washing tank 20 having an open upper surface is provided standing beside the filtration tower, the upper end of which is slightly higher than the filtration tower and the lower end of which is lower than the filtration tower. At the upper part of the washing tank, the water is inserted laterally into the water between the upper wall 11 and the water collecting plate 12 in the filtration tower, and the lower end is positioned in the floating filter layer 13 by penetrating the water collecting plate downward and extracting. The pipe 21 is connected, and the extraction pipe 21 is connected to the extraction pipe 2
A sluice valve V1 for opening and closing 1 is attached. Further, a sluice valve V2 for opening and closing the washing tank is attached to the washing tank at a position substantially at the same level as the lower surface of the floating filter layer 13 in the filtration tower or a position slightly below. An upper connecting pipe 22 having an opening / closing valve V3 is connected immediately below the sluice valve of the washing tank and directly below the lower surface of the floating filter layer of the filtration tower, and an opening / closing valve V4 is provided at the bottom of the filtration tower and below the washing tank. The lower connecting pipe 23 has is connected. It is preferable that the upper connecting pipe 22 be provided obliquely upward as shown in the drawing from directly below the sluice valve V2 toward the filtration tower.

A drain pipe 24 having an opening / closing valve V5 is attached to the bottom of the cleaning tank. Further, the bottom of the washing tank and the circulation pipe 25 having a circulation pump P1 are connected to the upper end above the connecting position of the extraction pipe 21, and the water at the bottom of the washing tank is supplied to the upper end by the operation of the pump. It is designed to circulate.

A washing water pipe 16 for supplying washing water is provided above the water collecting plate 12 in the filtration tower, and a drain pipe 17 having an opening / closing valve V6 is provided at the bottom.

When the filtration process is performed as described above and the pressure loss reaches, for example, 2 m, the valves of the supply pipe 14 and the discharge pipe 15 are closed to interrupt the filtration process, and the most SS is captured by the following procedure. Partly backwash the lower part of the floating filter layer. The sluice valve V1 of the extraction pipe 21 is opened. Since the lateral portion 21a of the discharge pipe that projects into the filtration tower is below the water surface in the tower, the discharge pipe is connected to the filtration layer 13 from the lower end together with the water in the tower.
The buoyant filter material in the lower part of the pipe flows in and rises in the pipe to wash the tank 2.
It overflows to 0, and the water and the filter medium collect on the sluice valve V2 in the washing tank (see FIG. 2). The amount of the buoyant filter medium overflowing into the washing tank is adjusted by the time for which the sluice valve V1 is left open, and the sluice valve V1 is closed when a predetermined amount of the buoyant filter medium has entered the washing tank.

Next, the sluice valve V2 of the cleaning tank and the opening / closing valve V4 of the lower connecting pipe 23 are opened to introduce the water in the filtration tower into the cleaning tank through the lower connecting pipe 23. As a result, the filter medium floats in the cleaning tank. The circulation pump P1 of the circulation pipe 25 is operated to supply the water at the bottom of the cleaning tank to the upper end of the cleaning tank to cause a downward flow in the tank, and the downward flow causes the filter medium to flow to adhere to the filter medium. The excessive growth portion of the biofilm and the SS captured by the filter medium are peeled off from the surface of the filter medium. At this time, the on-off valve V4 is closed. After operating the pump P for a predetermined period of time, for example, 5 minutes, stop the pump, open the opening / closing valve V5 of the drain pipe 24, drain almost all the dirty water in the cleaning tank from the drain pipe, and close the opening / closing valve V5 after draining. To do. The above operation is repeated a plurality of times, for example, twice. The water in the washing tank is drained from the drain pipe, the on-off valve V5 is closed, and when the filter medium falls below the sluice valve V2 in the washing tank, the sluice valve V2 is closed. Then, the open / close valves V3 and V4 of the upper connecting pipe 22 and the lower connecting pipe 23 are opened, the water in the filtration tower is introduced from the lower connecting pipe 23 into the washing tank, and the floating water is introduced into the upper connecting pipe 22 by the introduced water. Through a filter tower.

As described above, the sluice valve V is connected to the upper connecting pipe 22.
If it is installed diagonally upward from directly below 2 toward the filter tower, the filter material floats due to the water that has flowed into the washing tank, and the filter material efficiently moves to the filter tower by buoyancy through the upper connecting pipe 22 and the on-off valve V3. . All of the floating filter material in the washing tank flows into the filter tower and floats in the tower, and when the floating filter layer 13 is formed, the on-off valves V3, V
Close 4 and restart the filtration process.

Thus, each time the pressure loss increases to 2 m, for example, the filter material under the floating filter layer is partially washed and subjected to a filtering treatment. If the pressure loss does not recover even after the partial washing, the washing water is supplied from the washing water pipe 16. Flow through the filter bed to create a downward flow and backwash all of the filter media.

In order to use the filtered water for backwashing, a washing water storage tank 26 for receiving the filtered water discharged from the discharge pipe 15 is provided, and a certain amount of washing water is secured in the tank, and the excess filtering treatment is carried out. The water is overflowed and stored in another storage tank (not shown).
Then, the bottom portion of the wash water storage tank 26 is connected to the wash water pipe 16 by a wash pipe 27 having a backwash pump P2.

Further, an air diffusing pipe 28 is provided just below the lower end of the extracting pipe 21 in the filtration tower. During the filtration process, air is diffused from the air diffusing tube 28 to denitrify below the air diffusing tube and nitrify above the air diffusing tube to effectively remove BOD, SS and nitrogen.

The procedure for backwashing the entire amount of the filter medium is as follows. The backwash pump P2 of the washing pipe 27 is operated to wash the washing water pipe 1
The washing water is supplied into the tower from 6 and at the same time, the opening / closing valve V6 of the drain pipe 17 is opened. As a result, a downward flow is generated in the floating filter layer 13, and the floating filter layer is developed by this downward flow. Downflow LV is 20-40, which is lower than the conventional 50-70 m / hr.
m / hour is sufficient. About 15 seconds after the backwash pump was operated, air was diffused from the air diffusing tube 28, the floating filter layer was washed with a combination of water and air, and the excessive growth portion of the biofilm adhering to the filter material and the filter material were captured. SS
Is peeled off from the filter medium and discharged from the drain pipe 17 together with the cleaning drainage. After the above washing for 5 minutes, the operation of the backwash pump P2 and the air diffusion are stopped, the on-off valve V6 is closed, and the operations of and are repeated once or several times. Then the filtration process is restarted.

In the total backwashing of the filter medium, the purpose is to wash the fixed bed above the floating filter layer. Since this part is a nitrification part, the amount of attached SS is smaller than that in the lower part of the SS trapping and denitrifying part, so that it can be sufficiently washed without intensive mixing.

[0019]

As is clear from the above, according to the present invention, SS is captured by the upward flowing water and the filter material under the most contaminated floating filter layer is overflowed into the cleaning tank 20 and washed in the tank. The filter material on the upper part of the floating filter layer remains in the fixed bed in the filter tower. Therefore, since the upper part of the flotation filter layer remaining in the tower is not disturbed, even if SS is separated from the filter material when the washed lower filter material is transferred into the filtration tower, the upper part of the flotation filter layer remains The SS can be captured. Therefore, the separated SS at the beginning of the restart of the filtration step does not mix with the treated water, and the SS concentration of the treated water can be improved. Further, conventionally, the whole filter layer was washed once a day, whereas in the present invention, it may be washed once a week. Furthermore, the amount of water used for washing out of the tank is
It is possible to reduce the amount of water used conventionally (about 3 times the filter layer capacity), and about 2 times the filter layer capacity is sufficient, so the backwash water ratio becomes low.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state in which a filter material under a floating filter layer is transferred to a cleaning tank and cleaned.

FIG. 2 is an explanatory diagram showing a state in which a filter material under a floating filter layer is being transferred to a cleaning tank.

[Explanation of symbols]

 10 Filtration Tower 12 Water Collection Plate 13 Floating Filtration Layer 14 Raw Water Supply Pipe (Supply Means) 15 Filtered Water Discharge Pipe (Drainage Means) 16 Wash Water Pipe 17 Drain Pipe 18 Wash Pipe 19 Diffuser Pipe 20 Wash Tank 21 Ejection Pipe (Extraction means) 22 Upper connecting pipe 23 Lower connecting pipe 24 Drain pipe 25 Circulating pipe V1 Gate valve V2 Gate valve V3 Open / close valve V4 Open / close valve V5 Open / close valve V6 Open / close valve P1 Circulating pump P2 Backwash pump

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01D 29/62

Claims (1)

[Claims] 1. A flotation filter layer having a biofilm attached to a flotation filter medium filled in a filtration tower, and a floatation filter layer provided below the filtration layer,
An organism provided with a raw water supply means for passing raw water through the floating filter layer in an upward flow, and a treated water discharge means provided above the floating filter layer for discharging the treated water to the outside of the filtration tower. The biological filtration device, wherein the filtration device is provided with an extraction means for extracting the filter material below the floating filter layer to the outside of the filtration tower for washing.