JPH05137906A - Method and device for upflow filtration - Google Patents

Abstract

PURPOSE:To suppress an increase in the filtration resistance of a packed bed and to easily clean a filter medium by carrying out treatment without preventing the floating of a packing due to the clogging of a packed bed, cleaning the packed bed with an upflow and a cleaning gas and discharging the water from a waste cleaning water outlet provided above a treated water outlet. CONSTITUTION:A space B is formed between the boundary surface A of a packed bed 3 and a net. When the filtration resistance is increased, the whole packed bed 3 is raised by the pressure, hence the packed bed 3 is not compressed, and the elastic porous granular material constituting the packed bed 3 is loosely packed. This packed state is maintained until the SS is leaked into the treated water. At this time, the supply of raw water is stopped, and the packed bed 3 is cleaned. Namely, cleaning water from a cleaning water feed pipe 11 and the air from a cleaning air feed pipe 12 are supplied from below the packed bed 3, the SS collected on the granular material surface and in the gap between the grains is removed, and the waste cleaning water contg. a large amt. of SS is discharged from a waste cleaning water outlet 8.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and an apparatus for clarifying a suspension containing SS by filtration.

[0002]

2. Description of the Related Art A sponge-like elastic porous granular material having a three-dimensional network structure is used as a filter medium, and a packing layer containing the filter medium as a packing material is provided in a filtration tank, and raw water is supplied to the packing layer in an upward flow. The upflow filtration device has already been disclosed in JP-A-60-147207.

As shown in FIG. 3, this prior art upflow filtration apparatus has a net 26 on the top of a packing layer filled with a filler 24 made of elastic porous particles (hereinafter also referred to as sponge particles). It is provided to prevent the filler 24 from floating on the lower surface of the net 26, compress the filler 24, and intentionally reduce the porosity of the filter medium composed of sponge-like particles to direct the raw water from the raw water supply pipe 21 upward. This is a device for performing flow filtration to obtain treated water (also referred to as filtered water) from the treated water outflow pipe 27. Further, when the packed bed filled with the packing material 24 is blocked by the filtered material and the filtration resistance is increased, in order to regenerate the packed bed, the cleaning water from the cleaning water supply pipe 25 and the cleaning air supply pipe 23 are added to the packed bed. It is a device for cleaning the filter medium by supplying cleaning air from the.

However, as a result of carrying out a supplementary test of the conventional technique of raw water filtration using this conventional device, the present inventor has found out the following drawbacks. Since the SS is filtered off while the sponge granules are compressed to reduce the porosity, the packed bed filled with sponge granules is severely clogged with SS in a short time after the start of filtration, and the filtration resistance rapidly increases. Increase to. Cleaning of the packed bed filled with sponge granules is performed by supplying air and washing water upward from the lower part of the packed bed, and at this time, the cross section is covered on the upper part of the packed bed of the conventional filtration tank. The stretched porous material (to prevent the floating and outflow of the filter medium), which is simply called a mesh here, the sponge-like particles are pressed against the lower surface of the mesh even more strongly, and the filter medium does not fluidize. Therefore, cleaning the filter medium is extremely difficult.

In the above prior art, as a result of pursuing the cause of such a defect, as shown in FIG. 2, the upper surface of the packing layer filled with elastic porous granular material such as sponge which is easily compressed is contacted. Since the net for preventing floating is provided, the sponge granules are strongly compressed to the lower surface of the net by the upward flow pressure of the raw water, and the sponge granules are SS
Have been found to be easily clogged, resulting in a rapid increase in the filtration resistance of the packed bed. It was also confirmed that when SS is trapped in the packed bed, the filtration resistance of the packed bed increases, so that a vicious cycle occurs in which the sponge-like granular material is more and more compressed.

That is, the basic idea of the prior art exists in the point that raw water is supplied to a packed bed filled with a filter medium composed of sponge-like particles, and SS of the raw water is filtered while the filter medium is compressed. However, there are major problems inherent in such technical ideas themselves.
Therefore, the present inventor has confirmed that the conventional technique cannot be a practically excellent filtration technique.

[0007]

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned drawbacks of the conventional method and apparatus.
In a filtration tank having a packed bed containing a filter material as a packing material, S
An elastic porous granular material having a three-dimensional network structure with a large S trapping capacity is used as a filter medium, and raw water is supplied to the packed bed in an upward flow,
An object of the present invention is to provide an upflow filtration method and device in which an increase in filtration resistance of the packed bed when the SS is filtered in the packed bed is small and the filter material of the packed bed is easily washed.

[0008]

The above object can be achieved by the upflow filtration method and apparatus of the present invention described below. 1) When the raw water is supplied in an upward flow to a packed bed made of a packing material of an elastic porous granular material having a three-dimensional network structure and the raw water is filtered through the packed bed to obtain treated water, the packing material caused by clogging of the packed bed. The treatment is carried out without blocking the floating of the water, the packed bed is washed with an upflow and a cleaning gas at any time, and the drainage thereof is caused to flow out from the washing drainage outlet provided above the treated water outlet. Upflow filtration method. 2) A packing layer formed of a packing material of elastic porous particles having a three-dimensional network structure is formed on the porous support bed below the filtration tank, and at least a raw water supply pipe is provided under the porous support bed.
An air cleaning means and, if necessary, a water cleaning means are provided, a treated water outlet is provided in the vicinity of the upper interface of the packed bed and below the interface, and a space is placed above the upper interface of the packed bed. An upflow filtration device that is equipped with a washing drain outlet. 3) Preferably, the upflow filtration device according to 2) above, further comprising an air diffuser for microbial curing in the filtration tank. Particularly preferably, it is achieved by the upflow filtration method described in 1) above, wherein the washing water used in the water washing means is raw water.

The essence of the technical idea of the present invention lies in the finding of an ideal method of constructing an upflow filtration by a filler made of elastic porous particles having a three-dimensional network structure such as sponge, that is, a filter medium.

More specifically, it is necessary to eliminate the immovable net which was placed in contact with the upper part of the packed layer of the filter material made of elastic porous particles so that the sponge-like filter material is not compressed on the lower surface of the net in principle. The point is that smooth upflow filtration can be performed in the packed bed. Therefore, in order to prevent the outflow of the elastic porous particles to the outside of the system, a newly devised means for taking out filtered water was adopted. Also, when the filtration resistance of the packed bed increases due to the blockage of the filter medium, a space is formed on the surface of the packed bed so that the filter medium of the packed bed can be effectively washed by using upward flow and a cleaning gas as needed. This is because the newly adopted cleaning drainage means that is unique and suitable for the cleaning method of the present invention is provided.

In the present invention, the treated water outlet is located at or near the upper end of the packed bed in order to eliminate compression of the elastic porous granular material, maintain good treated water quality, and use the space efficiently. It is preferable to provide. Therefore, in the device of the present invention, it is possible to prevent an increase in filtration resistance due to compression of the elastic porous particles and to prevent the elastic porous particles from flowing out of the system from the treated water outlet. A water-permeable member such as a net is provided on the tank wall near the upper interface of the packed bed (position covering the treated water outlet). Here, the vicinity of the upper interface of the filling layer means that the upper end surface of the filling layer can be included. Therefore, the upper end surface of the packed bed can exist immediately below the water permeable member or above the water permeable member.

That is, above the water-permeable member, the same elastic porous granular material as the filling layer is provided exposed to the atmosphere. Further, it is important to provide a space portion on the filling layer or the exposed layer of the device of the present invention in order to enhance the cleaning effect of the elastic porous particulate matter.

The present invention is not limited to the physical removal of SS, but by supplying oxygen-containing bubbles to the packed bed to maintain aerobic conditions, microorganisms are allowed to adhere and propagate to the filter medium. A biofilm is formed on the surface, and at least aerobic biofilterable sewage components such as BOD, NH ₃ -N
It is possible to perform biological removal and physical removal of components such as, and an oxygen-containing bubble supply device (aeration device) for that purpose can be appropriately arranged in the lower part of the packed bed or the like.

Alternatively, the inside of the tank may be maintained under anaerobic conditions to provide an anaerobic biological filtration device. Further, a filtration device in which an aerobic biological filtration layer and an anaerobic biological filtration layer coexist in a single tank may be constituted by the packed bed. Also,
At the desired position of the packed layer made of elastic porous granules, a packed layer made of other granular solids or a combination layer of the elastic porous granules and those granular solids may be provided in addition to the elastic porous granules as desired. Good.

In the present invention, the packed bed is washed after a lapse of time for which filtration can be continued, but the means therefor is not particularly limited, and known means can be applied. In this case, the air diffusing device may also be used for cleaning, or a separate dedicated means, for example,
An air supply device for cleaning air, a water supply device for cleaning water, and the like can be provided. In this case, the treated water by the apparatus of the present invention is usually used for washing, but raw water may be used if desired.

Instead of the cleaning air, an inert gas containing no oxygen, such as nitrogen gas, may be used, and such gas is particularly preferable when an anaerobic packing layer is provided. When the aerobic filling layer is also used, the cleaning gas supply device may be arranged at a position where they can be commonly cleaned.

Further, an outflow prevention device (9) is provided so that the filter material made of elastic porous particles does not flow out of the tank during washing or the like.
And it is important to deploy 10). As the outflow prevention device (9 and 10), a porous water permeable member such as a net can be used. The cleaning waste water containing SS and the like generated by cleaning the packed bed by the cleaning device is discharged from the cleaning waste water outlet 8 provided above the treated water outlet 6.

The elastic porous granules used in the present invention are:
It is a porous small body that has elasticity when it is compressed under atmospheric pressure and contracts by removing the internal air, and when compression is stopped it absorbs air inside and restores to its original state. Any shape, material, hole structure, etc. can be applied.

The elastic porous granular material is formed so as to have continuous holes from the surface to the inside, and can be produced by a known foaming method or the like. The material of the elastic porous granular material is not particularly limited as long as it has the above properties, and known materials such as organic polymers and inorganic compounds can be used. Among them, the material itself has appropriate elasticity and strength. Materials having and are preferable, and urethane resin is particularly preferable.

For example, an elastic porous granular material such as polyurethane foam is produced by foaming plastics such as urethane resin by a foaming method for producing open cells, and is used as it is or cut into a desired shape and size. To use. The size of the elastic porous granular material is 10 to 30 mm,
It is preferably 15 to 20 mm, and its shape can be square, spherical, or various other shapes, but the square is preferable. Its specific gravity is usually preferably about 0.8 to 1.2. The porosity of the elastic porous granular material is preferably 90% or more. Further, the pore diameter, that is, the hole diameter is 0.1 to 6 mm, preferably 2
It is desirable to select from the range of up to 4 mm. Also, 1
The number of holes per cm length is preferably 5 to 20.

[0021]

The operation and one embodiment of the present invention will be described with reference to FIG. Reference numeral 1 is an upward flow filtration tank, 2 is a raw water supply pipe equipped with a valve 13, and 3 is a packed bed (fixed layer) filled with a filter medium made of elastic porous granular material (polygonal polyurethane foam). Layer). The elastic porous granular material has a particle size of 1 to 3
cm, open cells with a hole size of 1 to 4 m
It is suitable to have a very large hole of m. Reference numeral 9 is a mesh or a perforated plate that prevents the filter medium from flowing out. Further, 4 is a porous support bed for supporting the packed bed.

In the present invention, it is important that the surface interface A of the filling layer 3 does not come into contact with the mesh for preventing the floating of the filter medium as in the conventional method (shown in FIG. 3). Reference numeral 11 denotes a cleaning water supply pipe for supplying cleaning water, which is provided with a valve 14 for cleaning the packed bed 3. Reference numeral 12 is an air supply pipe provided with a valve 15 for supplying air for air cleaning. 6 is an outlet for treated water from which SS has been filtered out, and a treated water outflow pipe 5 equipped with a valve 17 is provided. The water level in the tank is at the same level as the outflow level of treated water.

[0023] Further, 10 is for cleaning the packed bed 3
It is a net that prevents the filter medium from flowing out into the cleaning drainage flowing out from the cleaning drainage outlet 8. A treated water outflow pipe 7 is provided at the washing drainage outlet 8. B is a space provided above the filling layer 3 and plays an important role in the present invention. To explain the operation of the present invention, when an SS-containing suspension (that is, raw water) is passed through the packed layer 3 of elastic porous granular material such as urethane foam in an upward flow, the raw water is SS is trapped in the innumerable voids of the filling layer 3, and particularly effectively in the voids inside the elastic porous granular material.

As the filtration is continued by such a method, the SS trap amount of the packed bed 3 increases and the filtration resistance increases. In the conventional device of FIG. 3, since the pressure applied to the packed bed 3 increases as the filtration resistance increases, the packed bed 3 is pressed against the net, and the porosity further decreases.
As a result, a vicious circle in which the filtration resistance is further increased is caused.

However, in the present invention shown in FIG. 1, since the interface A on the upper surface of the packing layer 3 is not in contact with the net and the space B exists, when the filtration resistance increases, the entire packing layer 3 is caused by the pressure. It can move upward (in other words, the filter medium filled in the packed bed can float), and the packed bed 3 is not compressed. In other words, the position of the interface A of the filling layer 3 moves upward as the filtration resistance increases, and is exposed to the space B by the amount of the movement, so that the filtration resistance is just balanced by the weight of the filter medium at the exposed portion. Can be maintained.

In this way, as the filtration resistance increases, the whole packed bed gradually moves upward, so that the elastic porous particles constituting the packed bed 3 can be maintained in a coarse packed state,
This state continues until SS leaks into the treated water. At this point, the supply of raw water is stopped and the packed bed 3 is washed. The cleaning is performed as follows. That is, the valve 13 attached to the raw water supply pipe 2 and the valve 1 of the treated water (filtered water) outflow pipe 5
7 is closed, the valve 14 of the cleaning water supply pipe 11 is opened, the valve 15 of the cleaning air supply pipe 12 is opened, and the cleaning water from the cleaning water supply pipe 11 and the air from the cleaning air supply pipe 12 are packed in a bed. Supply from the bottom of 3. Then, the inside of the packed bed 3 is agitated by a violent gas-liquid mixed phase turbulent flow, and the SS trapped in the surface of the elastic porous granular material filter medium and in the mutual voids are washed and a large amount is discharged from the washing drainage outlet 8. Washing wastewater containing SS is discharged.

FIG. 2 shows the state of the filtration tank in the state where the filter medium is being washed. The net 10 is for preventing the filter medium from flowing out when the filter medium is washed. Further, as the cleaning water, filtered water may be stored and used.
Further, it may be washed with raw water. By continuing the above washing for the required time (usually about 10 to 20 minutes), the filter medium is washed and returns to a clean state. Therefore, the valves 14 and 15 are closed, and the washing water from the washing water supply pipe 11 is closed. The supply of air from the cleaning air supply pipe 12 is stopped. After that, the valve 16 of the drain pipe 18 is opened to lower the water level in the tank to the filtered water outflow level. Then open valves 13 and 17,
Start filtration again.

As described above, according to the present invention, the point of the filtration method using the elastic porous granular material as the filter medium is to devise so as not to compress the elastic porous granular material as much as possible contrary to the conventional method. It was found and completed. (The conventional method is based on filtering the elastic porous granular material in a state of being compressed as much as possible.)

[0029]

EXAMPLES Specific examples of the present invention will be shown below, but the present invention is not limited thereto. The upflow filtration apparatus of the present invention shown in FIG. 1 (made of transparent PVC, column diameter 200 m
sewage (SS98-186 mg / liter, BOD8) of Fujisawa housing complex using mφ and column height of 3000 mm)
6 to 178 mg / liter) from the sewage
S was removed. Table 1 shows the processing conditions and the processing results.

[0030]

[Table 1]

The following facts are clear from Table 1. 1. With the device of the present invention, the duration of filtration was about 5 times longer than with the conventional device, and the generation rate of cleaning wastewater was reduced to 1/10. (Comparison between Present Invention-1 and Conventional Device) The present invention-2 uses the polyurethane foam having the same physical properties as the filter medium used in the conventional apparatus, but the filtration can be continued for a longer time than in the conventional apparatus, and the generation rate of cleaning waste water is reduced. 3. In the present invention-1, as a result of performing filtration while changing the porosity and the pore diameter with the filter medium of the present invention-2, the filter medium exhibits high efficiency as compared with the case of the present invention-2. That is, in the apparatus of the present invention, it is shown that the porosity and the pore diameter of the filter medium are very important factors.

In the present invention, the structure of the filtration tank is the first important constituent factor, and the second important constituent factor is the selection of the physical properties of the elastic porous granular material, that is, the porosity and the pore diameter. Therefore, the best filtration can be performed by using such an elastic porous granular material having a small porosity and a large pore diameter and having such a packing material as shown in FIG.

[0033]

EFFECTS OF THE INVENTION In a filtration tank having a packed bed filled with elastic granular solids having a three-dimensional network structure, raw water is supplied from the lower part of the packed bed in an upward flow to perform filtration, and the treated water for filtration is discharged. The structure is such that the outlet is provided below the cleaning drainage outlet that discharges the cleaning drainage.This structure does not prevent the packing material from floating due to the blockage of the packing layer as the filtration continues, and when cleaning the packing layer. By continuing to wash the packed bed with an upward flow and a cleaning gas at any time and letting the washing waste water flow out from the washing waste water outlet, the filtration is continued more than in the conventional filtration tank having a packed bed filled with the same elastic granular solid. The best filtration can be performed which can prolong the time and reduce the generation rate of washing wastewater.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of an upflow filtration device of the present invention.

FIG. 2 is a cross-sectional view showing a state of the upflow filtration device of the present invention in a state where the filter medium is being washed.

FIG. 3 is a cross-sectional view showing the structure of a conventional upflow filtration device.

[Explanation of symbols]

1 Filtration Tank 5 Treated Water Outflow Pipe 2 Raw Water Supply Pipe 6 Treated Water Outlet 3 Packed Bed 7 Washing Drainage Outflow Pipe 4 Porous Support Floor 8 Washing Drainage Outlet 9 Net (For Filtered Water Outlet) 23 Washing Air Supply Pipe 10 Net (For cleaning drainage outlet) 24 Filling material 11 Cleaning water supply pipe 25 Cleaning water supply pipe 12 Cleaning air supply pipe 26 Net (for preventing packing material outflow) 13 to 17 valve 27 Treated water outflow pipe 18 Drain pipe 28 Cleaning drainage Outlet 20 Filtration tank 29 Washing drainage outflow pipe 21 Raw water supply pipe 30-35 Valve 22 Porous support bed 36 Drain pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication C02F 3/06 6647-4D 3/10 A 6647-4D 3/20 C 3/28 B 7158-4D 7824-4D B01D 23/24 A 7824-4D Z 7112-4D 29/38 Z

Claims (3)

[Claims] 1. When the raw water is supplied in an upward flow to a packed bed made of a packing material of an elastic porous granular material having a three-dimensional network structure and the raw water is filtered through the packed bed to obtain treated water, the packed bed is blocked. It is possible to perform the treatment without blocking the accompanying floating of the packing material, wash the packed bed with an upflow and a cleaning gas at any time, and let the drainage flow out from the washing drainage outlet provided above the treated water outlet. Characteristic upward flow filtration method. 2. A packing layer made of a packing material of elastic porous particles having a three-dimensional network structure is formed on the porous support bed below the filtration tank, and at least a raw water supply pipe is provided under the porous support bed. A means for air cleaning and optionally a means for water cleaning are provided, a treated water outlet is provided in the vicinity of the upper interface of the packed bed and below the interface, and a space is provided above the upper interface of the packed bed. An upflow filtration device that is installed and provided with a wash drain outlet. 3. The upflow filtration apparatus according to claim 2, further comprising an air diffuser for microbial curing provided in the filtration tank.