JPH0751687A - Upward current type biological filter device - Google Patents

Abstract

PURPOSE:To drastically decrease the frequencies of backwashing the entire part of filter beds by dividing the filter beds with horizontal grid to the upper filter bed and the lower filter bed, disposing an air diffusion pipes for aeration on the grid and providing the grid with a water spraying pipes for spraying washing water downward thereunder. CONSTITUTION:The filter bed 11 of a filter tank 10 is partitioned by the grid 14 which does not allow the passage of filter media unless descending flow of, for example, 40 to 50m/hour is imparted to the lower filter bed 13 for mainly capturing SS and the upper filter bed 12 mainly decomposing BOD. The grid 14 is provided thereon with the air diffusion pipes 19 for aeration to supply oxygen and air to living thing films sticking to the filter media of the upper filter bed 12 and to enhance the activity thereof, thereby the filter bed is sufficiently provided with the function to decompose the BOD. The lower filter bed 13 for mainly capturing the SS is increased in pressure drop by the SS in a short period and, therefore, the lower filter bed is formed by lowering its bed height and decreasing the amt. of the filter media so as to be effectively backwashed by the water spraying pipes 20 disposed under the grid 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an upflow type biological filtration device in which a filtration layer of a buoyant filtration material having microorganisms attached is provided in a filtration tank and raw water is supplied to the filtration layer in an upward flow.

[0002]

2. Description of the Related Art A filter layer is constructed in a filter tank by a floatable filter material having a very small specific gravity formed by foaming polypropylene or urethane resin into a spherical or irregular shape having a diameter of 3 to 10 mm, and microorganisms are added to this filter layer. Has been developed, and a biological filtration device has been developed for performing biological filtration by supplying raw water and air to the filter bed in an upward flow. Since this floatable filter medium has a small particle size and a large surface area because it is foam-molded, the retention amount of biofilm adhering to the filter medium is extremely large, and as a result, high load operation becomes possible and Treated water can be obtained.
Further, since the filter medium has a specific gravity of 0.1 or less and has a floating property,
It is easy to wash, and the amount of washing air and the amount of washing water required to remove the SS captured by the filter layer from the filter medium are reduced.

In the above-mentioned biological filtration apparatus, a water-permeable upper support plate is arranged above the water in the filtration tank, and a floating filter medium is present under the support plate to form a filter layer. When it is not possible to go up from the plate, air and raw water are supplied to the bottom of the filtration tank to activate microorganisms adhering to the filter medium by the air, and when the raw water flows upward in the filter layer. The BOD in the raw water is filtered while being biologically treated to obtain treated water.

[0004]

In this filtration device, the buoyant filter media forming the filter layer by the upward flowing raw water and the floating air bubbles is densely gathered under the upper support plate and fixed to the fixed bed. Then, the raw water goes up through the gap of the filter medium together with the air. Therefore, SS in the raw water and the generated sludge are mainly trapped at the bottom of the filter bed that is a fixed bed, and the sludge adhesion amount of the filter material located at the bottom and the trapped amount of SS increase,
The sludge adhesion amount and SS trapping amount of the filter medium located above the filter layer are extremely small. In addition, the biofilm that adheres to and grows on the surface of the filter medium also occurs mainly on the filter medium located at the bottom of the filter layer that has become the fixed bed, and adheres to the filter medium above it
Very few biofilms grow. Then, when the pressure loss at the bottom of the filter layer is increased, the portion above the low pressure loss must be washed together. in short,
The filter medium located above the bottom of the filter layer is not effectively utilized and the cleaning frequency is high. Therefore, in order to reduce the frequency of cleaning, low-concentration wastewater with SS of 50 mg / cubic or less is suitable as raw water to be treated by the biological filtration device, and in the case of wastewater with more SS than that, sedimentation is performed as pretreatment. At present, separation and floating separation are performed to separate and remove most of the contained SS.

[0005]

DISCLOSURE OF THE INVENTION The present invention was developed in view of the above, and a filter layer is provided in the filter tank by a floatable filter material having microorganisms attached thereto, and raw water is flown upward to the filter layer. In an upflow biological filtration device for supplying, the filter layer is divided into an upper filter layer and a lower filter layer by a grid horizontally provided in the filter layer, and an aeration diffuser tube is arranged on the grid. At the same time, a sprinkling pipe for sprinkling the washing water downward is provided under the grid.

[0006]

EXAMPLE In the illustrated example, 10 is a filter tank, 11
Is a filter layer composed of a floating filter material, 15 is a water-permeable upper support plate that defines the upper surface of the filter layer provided above the water in the filtration tank, and 16 supplies raw water to the bottom of the filtration tank. Raw water supply pipe, 17 is an extraction pipe for taking out treated water from the upper part in the filtration tank,
Reference numeral 18 denotes a wash water supply pipe for supplying wash water into the filtration tank from above, which are the same as those used in the conventional upflow type biological filtration device. A mesh-like or lattice-like grid 14 is horizontally provided in the filter layer 11, and the filter layer is divided into an upper filter layer 12 having a high bed height and a lower filter layer 13 having a low bed height.
An aeration diffuser tube 19 is arranged on the grid 14 and a downward sprinkler tube 20 is provided under the grid.
And a pump P using the in-tank liquid at the bottom of the tank as washing water,
The circulation pipe 21 supplies the water to the water spray pipe 20.

The filter medium constituting the filter layer 11 has a specific gravity of 0.0
3 kg / standing (dry state), fine particles made of styrofoam with an average particle diameter of 3 mm, and a mesh or strainer having a mesh size of 2 mm or less is used as the upper support plate 15, and the filter medium flows out from the upper support plate 15. Try not to. Grid 14
Is a mesh or grid having a mesh or grid size of 30 to 50 mm. When a downward flow velocity of 40 to 50 m / hr is applied to the filter medium as a linear velocity, or when upward flow of water is performed at a linear flow velocity of 2 to 10 m / hr while supplying aeration air. Since the flowability of the filter medium increases due to the presence of water flow and air, the filter medium moves through the mesh or grid of the grid, but when the liquid in the tank in the filter layer is discharged and the filter medium is separated from water, the The filter medium forms a bridge and the filter medium does not move. As the experimental equipment, a transparent column having a diameter of 370 mm and a height of 3500 mm was used as a filtration tank, and an upper filter layer 12 having a layer height of 2500 mm was provided on a grid 14 and a lower filter layer 13 having a layer height of 50 mm was provided below the grid.

To perform the operation, an excess amount of activated sludge in the sewage treatment plant is initially charged into the filter tank in an appropriate amount with respect to the amount of the filter medium, and oxygen or air is supplied to the aeration diffuser 19 on the grid. When the sludge is supplied to activate the microorganisms that compose the sludge to attach the sludge to the filter medium in a film form, and if a sufficient amount of biofilm is attached to the filter medium, continue supplying oxygen or air from the aeration diffuser tube 19. Raw water is supplied from the raw water supply pipe 16 to the bottom of the tank to cause an upward flow in the filter layer 11. As a result, the raw water is mainly trapped and removed by SS when flowing upward in the lower filter layer 13, and then adheres to the filter medium when flowing upward through the grid 14 in the upper filter layer 12. BOD is biologically treated with a biofilm and becomes treated water and overflows from the extraction pipe 17.
The upward flow rate of raw water (LV) is 2-10m /
At this time, the aeration linear velocity of oxygen or air from the aeration diffuser 19 is 8 to 20 m / hour.

When operated in this manner, the trapped SS first increases the pressure loss of the lower filter layer 13. When the pressure loss reaches 2000-3000 mm of water column, the supply of raw water and aeration air is stopped, and the liquid in the filtration tank is passed through the drain pipe 22 at the bottom of the tank to the height of the grid 14 at a flow velocity of 20 m / hr or less. Drain. After that, the circulation pump P is operated, the liquid in the tank is supplied to the water sprinkling pipe 20 through the circulation pipe 21, and the liquid is made to flow downward into the lower filter tank at a water flow linear velocity of 40 to 50 m / hour to form a lower filter layer. The filter material is spread and fluidized at a spreading rate of 5 to 10%, and the SS and BOD components adhering to the filter material are separated from the filter material. After performing this step for 2 to 10 minutes, the in-tank liquid is drained from the drain pipe 22 at the bottom of the tank together with the separated SS and the like.
Then, after the flush water is filled from the flush water supply pipe 18 to the height of the grid 14 with flush water (treated water or industrial water), the operation is restarted. The time required for backwashing the lower filter layer is 5 to 15 minutes. At the time of this backwashing, the liquid in the tank is gridded in advance.
Since it has been discharged to a height of 1, the filter medium of the upper filter layer 12 above the grid 14 does not mix with the lower filter layer 13 by forming a bridge at the upper part of the grid. When the linear velocity for discharging the liquid in the tank to the height of the grid 14 at the start of backwashing is increased to 40 m / hour or more, the upper filter layer passes through the mesh or grid of the grid and is mixed with the lower filter layer. There is a fear. This backwashing of the lower filter layer has a pressure loss of 2000-300 water column.
Perform every time it reaches 0 mm. In addition, the air diffuser 2 for cleaning is installed at the bottom of the tank.
3 is provided, and it is preferable that air is continuously or intermittently ejected from the air diffusing pipe 23 at the time of downward water sprinkling from the water sprinkling pipe 20 because the cleaning effect can be enhanced.

The pressure loss of the upper filter layer 12 in the raw water, which mainly decomposes BOD, is increased, which is caused by the water column 2000-3.
When reaching 000 mm, the entire upper filter layer and lower filter layer are backwashed. For this purpose, supply of raw water and aeration air is stopped, and wash water (treated water or industrial water) is supplied from above to the filter tank 10 through the wash water supply pipe 18 and flows downward into the upper filter layer and the lower filter layer. The drainage water is drained through the drain pipe 22 while passing water through. The water flow linear velocity of the downward flow of the washing water is 40 to 50 m / hour, whereby the filter media of the upper and lower filter layers are developed and flowed through the mesh or grid of the grid 14 at a development rate of 5 to 10%, and then filtered. The SS trapped in the layer and the biofilm excessively attached to the filter medium are peeled off and discharged together with the cleaning drainage. In this case as well, the cleaning effect is enhanced by continuously or intermittently ejecting air from the aeration diffuser 19 on the grid 14 and the cleaning diffuser 23 on the bottom of the tank. The amount of washing water is 1.5 to 3 times the total volume of the filter material in both the upper and lower filter layers. After the cleaning process is completed, the water is supplied from the cleaning water supply pipe 18 to perform a water filling process, and then the operation is restarted. The time required for this backwash is about 20 to 40 minutes.

When backwashing the lower filter layer and backwashing both the upper and lower filter layers, in addition to SS, the cleaning drainage discharged from the drain pipe is
A part of BOD is contained in a sludge or in a concentrated state adsorbed on SS. When this washing wastewater is dehydrated, the dehydrated filtrate generated contains a large amount of BOD components eluted from sludge and SS. Therefore, when the dehydrated filtrate is supplied to and passed through the biological filtration device, the load on the biological filtration device is increased. Therefore, before dewatering the cleaning wastewater, the aeration tank 2
4 to decompose BOD components in sludge and SS, and then concentrate them in a separation / concentration tank 25.
It is preferable to supply to No. 6 and dehydrate.

During backwashing, the filter material of the lower filter layer 13 is the drain pipe 2
In order to prevent the water from flowing out from 2, the lower surface of the lower filter layer 12 is provided with a water-permeable lower surface supporting member having openings, slits, etc. through which the filter medium does not pass, or the drain pipe is provided with a lower surface than the lower surface of the lower filter layer. The rising portion is provided as shown.

In this embodiment, in order to backwash the lower filter layer, the in-tank liquid is circulated and used as the water jetted downward from the sprinkling pipe 20, but not limited to this, treated water or industrial water may be used. it can. In that case, the supply pipe of the treated water or the industrial water is connected to the sprinkler pipe 20, and when the treated water or the industrial water is sprinkled from the sprinkler pipe 20, the tank liquid is drained from the drain pipe 22.

[0014]

As is apparent from the above, according to the present invention, the filter layer 11 does not allow the filter medium to pass therethrough unless a downward flow of 40 to 50 m / hour as a water-passing linear velocity is applied.
By the lower filter layer 13 which mainly captures SS,
The upper filter layer 12 that mainly decomposes BOD is partitioned, and an aeration diffuser tube 19 is provided on the grid, and oxygen or air is supplied to the biofilm adhering to the filter material of the layer to enhance the activity, and the BOD decomposition function is sufficiently achieved. I kept it. Since the lower filter layer, which mainly captures SS, has a high pressure loss in a short period of time, the layer height is reduced to reduce the amount of the filter medium, and backwashing is effectively performed by the water spray pipe 20 provided under the grid. I made it possible. When the pressure loss increases due to the captured SS, only the lower filter layer needs to be backwashed instead of backwashing the entire filter layer, and the frequency of backwashing the entire filter layer is greatly reduced.

[Brief description of drawings]

FIG. 1 is a flow sheet of an embodiment of an upflow type biological filtration device according to the present invention.

[Explanation of Codes] 10 Filter Tank 11 Filter Layer 12 Upper Filter Layer 13 Lower Filter Layer 14 Grid 15 Top Support Plate 16 Raw Water Supply Pipe 17 Treated Water Extraction Pipe 18 Wash Water Supply Pipe 19 Aeration Diffuser 20 Water Sprinkler

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location // B01D 24/02 8925-4D B01D 29/08 540 A 23/10 C

Claims (1)

[Claims] 1. An upflow type biological filtration device in which a filtration layer of a buoyant filter material having microorganisms attached thereto is provided in a filtration tank, and raw water is supplied to the filtration layer in an upward flow. A horizontal grid in the layer separates the upper filter layer and the lower lower filter layer, and an aeration pipe for aeration is arranged on the grid, and a sprinkler pipe for spraying washing water downward is also provided under the grid. An upflow type biological filtration device characterized by being provided.