JP2975269B2 - Cleaning method for floating filter media for biological filtration equipment - 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 cleaning a floating filter medium of an aerobic biological filtration apparatus used for purification of human waste and household wastewater.

[0002]

2. Description of the Related Art A biological filtration apparatus has a feature that the required processing tank volume can be reduced as compared with a conventional contact aeration processing apparatus and the like, and the processing apparatus can be significantly reduced in size. I have. By the way, this type of biological filtration device usually fills a filter medium floating in water having a specific gravity of less than 1.0 into a treatment tank to form a filtration layer, which contains aerobic or anaerobic microorganisms. After the sludge is attached, the sewage is circulated into the filtration layer, and the treatment of the organic pollutants in the sewage and the separation of the suspended matter are simultaneously performed.

[0003] When the filtration of sewage is continued for a certain period of time using a biological filtration device, a part of the organic pollutants accumulates in the filtration layer as sludge, and the suspended substances are similarly removed from the filtration layer. Will remain fixed in the interior. As a result, the sewage flow resistance of the filtration layer increases sequentially, and the biological filtration function decreases. Therefore, it is necessary to periodically wash the filtration layer and discharge the accumulated excess sludge and suspended solids out of the system to prevent the filtration layer from being closed. In many cases, a method is used in which washing water is passed through the inside, and the sludge and the like are washed away while the filtration layer is developed by a water flow.

However, in the case of a filter medium having an extremely small specific gravity, such as a foamable plastic filter medium, the filtration layer cannot be sufficiently developed unless the flow rate of the washing water is considerably high, resulting in a large amount of washing water. And various problems such as a decrease in the overall processing capacity of the biological filtration device are caused.

[0005] On the other hand, various measures have been developed to solve the above-mentioned problems. For example, a method in which a stirring blade is provided below a packed layer (filtration layer) formed in a treatment tank and the filtration layer is mechanically developed by the stirring blade during a washing operation (Japanese Patent Laid-Open No. 3-242294, etc.) Is continuously drawn out of the treatment tank from the treatment tank in small quantities, washed outside the tank and returned to the treatment tank (Japanese Patent Publication No. Sho 6).
No. 3-21553) has been developed. However, the above-mentioned method and the above-mentioned method, such as installing a stirring blade in the processing tank,
Since the circulating / washing mechanism for the floating filter medium is provided outside the tank, there is a problem that the processing apparatus itself becomes large and the operation and maintenance are troublesome.

On the other hand, in order to solve the above-mentioned problems, as shown in FIG. 7, a draft tube 2 and a compressed air supply tube 3 are arranged in a treatment tank 1 provided with a raw water supply pipe 7 and a sludge discharge pipe 8. When the filter layer 4 is washed, the air 5 is blown out from the compressed air supply pipe 3 so that the upward flow 6 of the sewage flows into the draft tube 2.
A technology has been developed in which wastewater in the treatment tank 1 is caused to flow in the direction of the arrow to forcibly expand the filtration layer 4 (Japanese Patent Publication No. Sho 62-13043).

However, also in this technique, it is necessary to provide the draft tube 2 in the processing tank 1 or to increase the capacity of the compressed air supply device, and it is inevitable to increase the size of the processing device. Further, it is practically difficult to completely expand the filtration layer 4 to completely remove the sludge or solid matter fixed on the filter medium 4a only by the flow of the sewage by the upward flow 6, especially the filter medium 4a. Is extremely light, such as styrofoam, it is not possible to completely clean it. Therefore, in practice, the circulation time of the fluidized sewage is considerably lengthened, the fluidized circulation is stopped, the separated sludge is settled, and then the washing / drain valve 9 is opened and the supernatant liquid in the treatment tank 1 is opened. The filter material 4a is re-washed. As a result, a large amount of cleaning water is required, and the time and labor required for the cleaning are increased, which causes various problems.

[0008]

SUMMARY OF THE INVENTION The present invention relates to the above-mentioned problems in the conventional method for cleaning a floating filter medium for biological filtration, that is, a method of separately providing a mechanism for cleaning a filter medium inside or outside a treatment tank. If this is the case, the purifier will be enlarged.
If the floating filter medium is particularly lightweight, it is difficult to develop the filter layer sufficiently only by the flow of the sewage by the air pump. Need cleaning water,
It is intended to solve the problems such as deterioration of the overall treatment performance of the sewage treatment equipment, and without providing a special filter material washing mechanism inside or outside the treatment tank, and using a very small amount of washing water. It is an object of the present invention to provide a method for cleaning a floating filter medium for a biological filtration apparatus, which can be used to wash almost completely even a lightweight floating filter medium.

[0009]

SUMMARY OF THE INVENTION The present inventors measured the relationship between the flow state in sewage and the flow rate of sewage of an extremely lightweight particulate buoyant filter medium for a biological filtration device made of foamable plastic or the like. When the water in the filter layer composed of the floating filter medium floating on the filter layer is pulled downward at a flow rate in a specific range, the filter layer itself slightly descends together with the water, and then the filter medium expands from above the inside of the filter layer. At the beginning, they found that the filter medium was disintegrated while rotating violently, and that the expansion range expanded gradually from the upper inside of the filter layer to the lower inside, and eventually the entire area of the filter layer was expanded. Was. The present invention was created by conducting a number of floating filter medium washing tests based on the above findings, and the specific gravity and particle size of the floating filter medium forming the filtration layer (filled layer), By maintaining a constant relationship with the flow rate of the washing water discharged from below, the filter layer can be efficiently developed with a very small amount of washing water, thereby completely removing the excess sludge fixed to the floating filter medium. It is one that can be removed.

That is, according to the present invention, a filtration layer is formed by filling a granular floating filter medium having a specific gravity of about 0.3 or less and a particle size of 1 to 15 mm into a treatment tank, and forming an upward flow or In a biological filtration device that allows sewage to pass through in a downward flow, 0.5 to 1.5 times the amount of the above-mentioned filter medium is discharged from the lower part of the filtration layer to the outside of the treatment tank in 5 to 90 seconds. Accordingly, it is a basic configuration of the present invention to peel off and remove excess sludge from the filter medium.

[0011]

[Function] The water is rapidly discharged from the lower part of the filtration layer to the outside of the treatment tank, so that the water surface above the filtration layer starts to descend, and at the same time, the filtration layer itself keeps the initial gathering state and the inside of the treatment tank is maintained. Descend. When the filter layer descends, the upper part inside the filter layer is agitated by the fast descending flow generated by the drainage, and the filter medium above the inner part which has been assembled is developed and scattered, and the filter medium above the filter layer inside the filter part has a scattered portion. The state of the flow of water changes intricately.

As a result, the granular filter medium whose mobility has been recovered by being disintegrated performs a vigorous upward movement due to buoyancy caused by a large specific gravity difference with water, and the dislodged filter medium floats in a spiral shape above the inside of the filter layer. A vortexing region is formed that moves. Further, the formed vortex agitating region is formed by a combination of buoyancy acting on each granular filter medium and a large number of filter media violently moving in the agitating region colliding with and breaking down the lower filter medium assembly. , Is rapidly expanded downward, and finally the entire filtration layer is in a state of being once separated.

Although the mechanism of the occurrence of the above-mentioned events has not been analyzed logically yet, rapid generation of a downward water flow due to drainage, downward movement of the filter layer, and large buoyancy that each filter medium receives It is assumed that the complicated synergism of the like causes a spiral flow inside the filtration layer and the flow gradually expands downward.

[0014] The filter media once broken through the above-mentioned process floats and re-assembles to the original state, and a so-called filter layer is formed again. In addition, due to repeated collisions between the filter media during the violent swirling motion after the dispersion, surplus sludge and the like are separated and dropped from the outer surface of the filter media. Further, the surplus sludge that has peeled off falls down sequentially below the reassembled filtration layer, and is discharged to the outside through the washing drain valve.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the embodiment, the same reference numerals are used for the same portions as those in FIG. FIG. 1 is a schematic longitudinal cross-sectional view of an aerobic biological filtration device using the method for cleaning a floating filter medium according to the present invention. In the figure, 1 is a treatment tank, 3 is a compressed air supply pipe (aeration pipe), and 4 is Filter layer, 4a is a floating filter medium, 7 is a raw water supply pipe, 8 is a sludge discharge pipe, 9 is a washing drain valve, 10 is a filter medium blocking plate, 11 is raw water, 12 is treated water,
3 is a raw water supply valve, and 14 is a surplus sludge discharge valve.

The treatment tank 1 is made of a steel plate or a synthetic resin material. A treatment water discharge port 1a is formed in an upper part, and a raw water supply port 1b is formed in a lower part. A porous filter medium blocking plate 10 is horizontally disposed above the inside of the processing tank 1 to prevent a floating filter medium 4a described later from flowing out of the tank. A raw water supply pipe 7 having a large number of small holes is provided near the bottom of the treatment tank 1. A sludge discharge pipe 8 is provided below the raw water supply pipe 7.
Further, an air diffuser 3 is arranged near the upper part of the raw water supply pipe 7, and an appropriate amount of air is supplied into the tank 1 through the air diffuser 3 so that the inside of the tank 1 is maintained under an aerobic environment. . In the present embodiment, one diffuser pipe 3 is provided below the tank 1, but another diffuser pipe 3 is provided at the center of the processing tank 1, You may make it diffuse from an intermediate part. In this embodiment, the processing tank 1 is an aerobic processing tank using aerobic microorganisms. However, the processing tank 1 may be an anaerobic processing tank using anaerobic microorganisms. Further, in the present embodiment, the raw water is passed through the inside of the filtration tank in an upward flow, but it goes without saying that the raw water may be passed in a downward flow.

The floating filter medium 4a for biological filtration is formed into small spheres by foaming polystyrene, and its diameter is selected to be about 1 to 15 mmφ. In addition, the floating filter medium 4a
Any material may be used as long as it is a porous material having a specific gravity of about 0.3 or less, for example, pumice or shirasu balloon, and the above-mentioned expandable polystyrene or urethane resin is convenient. If the specific gravity of the filter medium 4a exceeds 0.3, the filter layer 4 will not be sufficiently developed at the time of washing, which will be described later. The diameter of the spherical floating filter medium 4a is 1 to 15 m.
When the diameter is smaller than 1 mm, a problem occurs in terms of growth of a biofilm and prevention of the outflow of the filter medium 4a. This causes problems such as a decrease in the cleaning performance. Further, the shape of the floating filter medium 4a is optimally a spherical body from the viewpoints of fluidity in wastewater and removability of deposits during washing. However, it goes without saying that the shape may be a cube, a rectangular parallelepiped, an elliptical sphere, or the like.

Approximately 500 floating filter media 4a are placed in the processing tank 1.
mm to a height of 1500 mm. When the height of the filter medium is 500 mm or less, the filtration performance is sharply reduced. On the contrary, when the height of the filter medium exceeds 1500 mm, the filter medium is difficult to wash, so the filling height of 500 mm to 1500 mm is optimal.

Next, the operation of the biological filtration device of the present invention will be described. Raw water 11, which is raw water to be treated, is supplied to a raw water supply pipe 7 from a raw water pump (not shown) and discharged into the processing tank 1. The discharged raw water 11 passes through the gap of the biological filtration floating filter medium 4a as an upward flow, and during this time, the raw water 11 in the raw water 11 is formed by a biological film formed in advance on the outer surface of the floating filter medium 4a. Solid matter and organic matter are removed by a so-called biological filtration treatment. The treated water 12 that has been treated while passing through the floating filter medium 4a passes through the filter medium blocking plate 10, reaches the upper portion of the treatment tank 1, and is discharged from the treated water drain port 1a to the outside of the tank.

When the biological treatment tank 1 has been operated for about 24 to 48 hours, the floating filter medium 4a in the treatment tank 1 is washed. At the time of cleaning, first, the raw water supply valve 13 of the raw water supply pipe 7 is closed, and then the cleaning drain valve 9 is opened. The opening of the drain valve 9 is adjusted so as to discharge water from the treatment tank 1 about 0.7 times the filling amount of the filter medium in about 10 seconds by fully opening the drain valve. As a result, as described above, the entire filter layer 4 is slightly lowered integrally from the initial state as shown in FIG. 2 to a state as shown in FIG. Thereafter, a so-called spiral stirring area appears at the upper inside of the lowered filtration layer 4 as shown in FIG. 4, and the area is rapidly and gradually expanded downward. The bottom is
As shown in FIG. 5, the entirety of the filtration tank 4 is temporarily unfolded and diffused. In addition, processing tank 1
The drainage of the water inside is continuously continued while the swirling agitation area is expanding, and the drainage is stopped at the same time as or at the time when the lowermost part of the entire filtration layer 4 is developed, or before or after that. Will be. Further, in this embodiment, the water is drained out of the treatment tank 1 by opening the drain valve 9, but one side of the siphon pipe faces the lower part of the treatment tank 1, so-called a siphon pipe. The water may be rapidly drained from the lower part of the processing tank 1 to the outside of the tank by using the above method.

Each of the filter media 4a, which has been developed separately, floats sequentially upward due to its buoyancy, and assembles again to form the filter layer 4 as shown in FIG. Also,
Due to the swirling and stirring movement of each filter medium 4 a, the excess sludge 14 and the like that have separated and fallen from the outer surface of the filter medium sequentially settle to the bottom of the treatment tank 1. Further, if necessary, treated water is supplied from above the filtration layer 4 to raise the liquid level in the treatment tank 1 so that the separated sludge attached to the outer surface of the filter medium is settled and separated more completely downward. be able to. In addition, surplus sludge which settled 1
5 and the like are drawn out of the tank through a sludge discharge pipe 8.

As for the washing wastewater from the inside of the treatment tank 1, it is desirable to discharge 0.5 to 1.5 times of the filling amount of the filter medium for 5 to 90 seconds. Among them, 0.7-1.
It has been confirmed by actual tests that discharge in 0 to 20 seconds is most desirable in terms of cleanability and the overall processing capacity of the processing apparatus.

If the amount of drainage is less than 0.5 times the volume of the filling amount of the filter medium, there is a problem in the rate of reduction of the water level in the treatment tank 1 and the cleaning time, and sufficient cleaning cannot be performed. Further, when the amount of wastewater is 1.5 times or more, the post-treatment of the washing water is troublesome, the overall treatment performance is reduced, and the washing becomes excessive. Similarly, if the drainage time is shorter than 5 seconds, a complete developing time of the filter medium cannot be secured, and the degree of cleaning is insufficient. On the other hand, if the time is 90 seconds or more, the rate of decrease in the water level in the treatment tank becomes too slow, and the vortexing phenomenon of the filter medium does not occur, or excessive washing occurs, and the so-called nitrification effect of the nitrogen component is weakened. There is a concern that problems such as a reduction in the nitriding effect may occur.

The specific gravity of the filter medium 4a is 0.05 and the diameter is 4 mm.
Using a sphere made of polystyrene foam having a diameter of φ, the filter medium 4a is filled into a processing tank 1 having a diameter of 600 mmφ and a height of 700 mm.
Using a treatment apparatus having a filtration layer 4 formed thereon, raw water 11 having a BOD of 200 ppm and an SS of 100 ppm from the lower part of the filtration tank 1.
Was passed through an upward flow at a flow rate of 4 (l / m), the average BOD of the treated water 12 was 5 ppm, and the SS was 3 ppm. The pressure loss in the filtration layer 4 after the continuous operation for 48 hours was about 350 mmH ₂ O. On the other hand, the filter layer 4 after the use for 48 hours was washed with water 0.7 times the filling amount of the filter medium for about 10
After washing by draining in seconds, the filtration resistance was restored to 10 mmH ₂ O. Thereafter, by washing the filtration layer 4 by the same method every 48 hours, the raw water 11 could be continuously treated while maintaining substantially constant treated water quality.

[0025]

As described above, according to the present invention, the floating filter medium is made of a material having a specific gravity of not more than 0.3 and having a very large difference in specific gravity from water and having a particle size of 1 to 15 mm, and the filter medium. The filtration layer was filled from the lower part of the filtration
The cleaning is performed by discharging up to 1.5 times the water within a predetermined time. As a result, a spiral stirring motion occurs due to the large buoyancy of each filter medium above the inside of the filter layer once lowered by drainage at the time of washing, the filter layer sequentially collapses from the inside, and each filter medium once is After falling apart, they float and reassemble while performing a vigorous stirring motion to re-form the filtration layer. Therefore, excess sludge adhering to each filter medium is easily separated and dropped when each filter medium is stirred and floated, and the filter layer can be efficiently washed to a desired degree of washing with a small amount of washing wastewater. In addition, the surplus sludge that has peeled off falls down to the lower part of the treatment tank, and can be easily drawn out of the treatment tank. As described above, the present invention can highly clean a filtration layer having a small specific gravity and a small amount of development with a small amount of washing water, and a treatment device provided with an auxiliary mechanism for washing a filter medium as in a conventional biological filtration treatment device. Does not increase in size and exhibits excellent practical utility.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a biological filtration device embodying the present invention.

FIG. 2 is an explanatory view of a developed state of a filtration layer at the time of washing, showing just before washing drainage.

FIG. 3 shows a state of a filtration layer after a lapse of a short time from the start of washing and drainage.

FIG. 4 shows a developed state of a filtration layer.

FIG. 5 shows a state where a developed state of a filtration layer is expanded.

FIG. 6 shows a state in which all filtration layers have been developed and then reassembled, and the filtration layers have been re-formed.

FIG. 7 is an explanatory view of a conventional method for cleaning a floating filter medium for a biological filtration device.

[Explanation of symbols]

1 is a treatment layer, 2 is a draft tube, 3 is a compressed air supply pipe, 3a is a diffuser pipe, 4 is a filtration layer, 4a is a filter medium, 5 is air, 6 is sewage upflow, 7 is raw water supply pipe, and 8 is sludge. A discharge pipe, 9 is a washing → drain valve, 10 is a filter material blocking plate, 11 is raw water, 12 is treated water, 13 is a raw water supply valve, 14 is an excess sludge discharge valve, and 15 is an excess sludge.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-17908 (JP, A) JP-A 55-65197 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) C02F 3/02-3/10 B01D 29/00-29/48

Claims (4)

(57) [Claims] 1. A filtration layer is formed by filling a particulate floating filter medium having a specific gravity of about 0.3 or less and a particle size of 1 to 15 mm into a treatment tank, and an upward flow or a downward flow flows through the filtration layer. In a biological filtration apparatus that allows sewage to pass through, the water in the treatment tank 0.5 to 1.5 times the filling amount of the filter medium is removed by 5 to 90 times.
A method for cleaning a floating filter medium for a biological filtration apparatus, comprising discharging excess sludge from a filter medium by discharging the sludge from the lower part of the filter layer to the outside of the treatment tank in seconds. 2. The method for cleaning a floating filter medium for a biological filtration device according to claim 1, wherein the filter medium is a foamed plastic granule. 3. The method for cleaning a floating filter medium for a biological filtration device according to claim 1, wherein the inside of the treatment tank is kept anaerobic or aerobic. 4. The method according to claim 1, wherein water in the treatment tank is discharged from the lower part of the filtration layer to the outside of the treatment tank using a siphon tube.
The method for cleaning a floating filter medium for a biological filtration device according to claim 2 or 3.