JPH09174077A - Biological filtering method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological filtering apparatus capable of subjecting raw water to filtering treatment over a long time with high efficiency. SOLUTION: If a biological carrier with an average particle size of 1-5mm obtained by the dry distillation of raw material coal based on cooking coal at 1000-1300 deg.C and consisting of 80-95wt.% of fixed carbon and 5-20wt.% of ash and having a large number of viaholes 14a with an inner diameter of 50-500μm is used as the filter material 14 forming the filter bed 6 of a treatment tank 5, a specific surface area containing surface pores and viaholes 14a is large and not only lower miroorganisms but also higher microorganisms such as Rotatoria suitable for the purification of water can be strongly bonded and fixed. Since the carrier has high strength by the sintering of ash even if a particle size is small and the voids of the filter bed can be kept over a long time, SS, BOD, phosphorus and org. matter in raw water can be stably separated and removed over a long time with high efficiency, and sludge can be also continuously decomposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a biological filtration method and a biological filtration apparatus for filtering raw water such as tap water, sewage, waste water, and sewage while decomposing organic substances by microorganisms.

[0002]

2. Description of the Related Art As a microorganism carrier for immobilizing microorganisms, which is a filter medium for a general biological filtration apparatus which has been conventionally used, plastic materials such as urethane foam, ceramics, granular activated carbon, alumina, silica sand, anthracite or A film of microorganisms was formed on the surface of sand or the like. Therefore,
Raw water is passed through a filtration layer composed of these microbial carriers to separate and remove suspended solids (hereinafter referred to as SS) contained in the raw water, and decompose and remove soluble organic substances by microorganisms. To obtain treated water.

When the amount of SS trapped in the filtration layer increases as the filtration process continues, the pressure loss increases and the filtration process efficiency lowers. Therefore, backwash water is supplied from the lower side of the filtration layer to remove microorganisms. The SS is removed from the carrier to restore the filtration function, and the removed SS is discharged as a sludge out of the system.

However, the above-mentioned conventional general biological filtration apparatus has the problems to be solved as described below. The adherence of microorganisms to the microbial carrier which is a filter medium is weak, and the microbial membrane adhered to the microbial carrier is peeled off due to collision, flow, etc. of the microbial carriers due to backwashing, and it becomes impossible to retain sufficient microorganisms. Oxygen demand), COD (chemical oxygen demand), nitrogen, and other processing functions are degraded, and the decomposition efficiency of SS is also reduced, so the amount of sludge is increased. Filter media made of granular activated carbon or sand have a large particle size, resulting in a large pressure loss, which makes it difficult to increase the filtration rate.Because it is easily clogged, filtration cannot be continued for a long time, and the filtration capacity is high. It has the drawback of being low.
Of course, if the particle size is increased, it will be possible to continue filtration for a long time, but inevitably the surface area of the filter will be small, and it will not be possible to retain a sufficient amount of microorganisms.
The particle size of the filter medium cannot be increased. A filter material consisting of plastic materials such as urethane foam, granular activated carbon, and microbial carriers such as alumina has weak strength and is easily broken, so a certain particle size cannot be maintained, and 60% of the total amount of the filter material passes through the sieve mesh. Uniformity coefficient defined as the ratio of the particle size corresponding to the size of the filter to the effective diameter corresponding to the size of the sieve mesh through which 10% of the total amount of the filter medium passes (better to be closer to 1 It is said that) becomes larger. Therefore, it becomes difficult to secure voids in the filtration layer, pressure loss increases, and frequent replacement of the filter medium is required, which increases the cost of filtering the raw water and is uneconomical.

By the way, a microbial filtration device capable of solving some of the above-mentioned drawbacks is disclosed in, for example, Japanese Unexamined Patent Publication Nos. 3-123687, 2-152596, and 5-253587. Etc. have been proposed. First, the "biological contact filtration device" according to the conventional example 2 disclosed in JP-A-3-123687.
Introducing the outline of the above, this is one in which microorganisms are immobilized on the surface of a microbial carrier made of cylindrical granular activated carbon having a diameter of 2.0 to 4.0 mm as a filter medium constituting a filtration layer. . The size and shape of this microbial carrier are determined in consideration of surface area, filtration duration and strength.

An outline of the "fixed-bed biological treatment method for raw water" according to Conventional Example 3 disclosed in Japanese Patent Application Laid-Open No. 2-152596 is introduced, which considers the surface area of the microbial carrier. A granular filter medium to which microorganisms are attached is filled in a treatment tank to form a filtration layer, and an oxygen-containing gas is blown from the lower portion of the treatment tank to treat organic wastewater under aerobic conditions. The filtration layer has a particle size of 15
A porous large-diameter filter medium having a diameter of up to 25 mm and a small-diameter porous medium having a particle size of 4 to 6 mm are mixed and filled.

[0007] Further, "filtrate for treating sewage" according to Conventional Example 4 disclosed in Japanese Patent Laid-Open No. 5-253587.
This is to eliminate the filter blockage of the filtration layer. It has a pore size of 5 to 50 μm and is filtered with a filter material made of porous ceramics with an open porosity of 40 to 50%. It forms a layer. The filter layer is formed by mixing and filling a porous filter medium having a particle size of 4 to 20 mm.

[0008]

The above-mentioned conventional examples 2 to 4 are reasonably excellent because they achieve their respective purposes, but as described above, the problems to be solved are as follows.
Not all of them can be solved. That is, in the "biological contact filtration device" according to Conventional Example 2, the strength of the microbial carrier made of granular activated carbon used as the filter medium is weak, and the filter medium must be frequently replaced. It is uneconomical because it must be done frequently.

In the "fixed-bed biological treatment method for raw water" according to Conventional Example 3, a filter medium having a small diameter gradually moves to the upper layer of the filtration layer during backwashing due to the difference in the sedimentation speed of two types of filter medium, large and small. However, since it becomes increasingly difficult to secure a void above the filtration layer, there is a problem to be solved that it is difficult to continue the filtration process for a long time.

In the "filtrate for treating sewage" according to Conventional Example 4, since the fine pores of the filter medium are as small as 5 to 50 μm, it is necessary to immobilize microorganisms such as relatively low bacteria such as bacteria to a high concentration because of the ecological system. However, since it is inevitable that microorganisms such as relatively high-grade protists and metazoans will not adhere to and be fixed, sludge decomposition performance will be poor and the amount of sludge generation cannot be reduced. There are issues to be solved.

Therefore, the present invention solves the problems of the conventional biological filtration apparatus used, can firmly immobilize microorganisms, and can continue stable filtration for a long time. An object of the present invention is to provide a biological filtration method and a biological filtration device that use a filter medium that comprises a microorganism carrier that can be tightened and whose replacement frequency can be reduced.

[0012]

The present invention has been made in view of the above circumstances, and therefore, the gist of the biological filtration method according to claim 1 of the present invention is a raw material containing caking coal as a main component. Microorganisms are immobilized on a microbial carrier having fixed carbon 80-95 wt%, ash content 5-20 wt%, and a large number of through pores with an inner diameter of 50-500 μm, obtained by dry-distilling coal at 1000-1300 ° C. The method is characterized in that raw water is filtered through a filtration layer composed of an immobilized microbial carrier.

The gist of the biological filtration method according to claim 2 of the present invention is that in the biological filtration method according to claim 1, when the dissolved oxygen concentration contained in the raw water is less than 4 mg / l, The raw water is filtered while blowing an oxygen-containing gas from the lower part toward the filtration layer.

The gist of the biological filtration method according to claim 3 of the present invention is that in the biological filtration method according to claim 1 or 2, a coagulant is added to and mixed with the raw water.

The main means adopted by the biological filtration device according to claim 4 of the present invention is that a filtration layer made of a filter material on which microorganisms are immobilized is provided in the treatment tank, and an oxygen-containing gas is provided below the filtration layer. In the biological filtration device provided with an air diffuser blown toward the filtration layer, the filter medium has an average particle size of 1 to 5 mm and the raw material coal containing caking coal as a main component at 1000 to 1300 ° C. Fixed carbon 8 obtained by dry distillation
0 to 95 wt%, ash 5 to 20 wt% and inner diameter 50
It is characterized by being a microbial carrier having a large number of through pores of ˜500 μm.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 of the present invention will be described below.
The description will be given with reference to FIG. 1A which is a schematic configuration explanatory view of a biological filtration device for carrying out the biological filtration method, and FIG. 1B which is a configuration explanatory view of a microbial carrier which is a filter medium constituting a filtration layer. .

That is, reference numeral 1 shown in FIG. 1 (a) is a biological filtration device, and the biological filtration device 1 includes raw water 2 and an inorganic coagulant 3 added to the raw water 2 (the water quality of the raw water 2). And the coagulant 3 is mixed by the mixing mixer 4 and the mixing mixer 4 which mixes the raw water 2 with the raw water 2 and does not need to be added when the water quality of the raw water 2 is relatively good. The raw water flows in, and a filter layer 6 formed by being filled with a filter medium 14 composed of a microbial carrier described later is disposed inside the filter layer 6. Below the filter layer 6, an oxygen-containing gas is directed toward the filter layer 6. Is provided with an air diffuser 7 for ejecting air as air bubbles, and S captured by the filter medium
A backwash blower 12 that blows air for backwashing and removing S and the like is provided, and a treatment tank 5 that receives the supply of backwash water from the lowermost portion, and this treatment tank 5 by the beat of the pump P.
Treated water tank 9 for storing biological filtration treated water 8 that is supplied as backwash water 11 to the outside and is drained outside the system as treated water 10.
It is composed of Reference numeral 13 is sludge that is separated from the filter medium by backwashing and discharged to the outside of the system.

As shown in FIG. 1 (b), the filter medium 14 is a microbial carrier having an irregular particle size of 1 to 5 mm and a large number of through pores 14a. More specifically, the filter medium 14 is made of 100% raw coal containing caking coal as a main component.
Fixed carbon 80-95 obtained by dry distillation at 0-1300 ° C
50% to 5% suitable for attaching and fixing to a high concentration of bacteria, fungi, algae such as nitrifying bacteria, etc., which have a relatively low content of 5% to 20% by weight and ash content of 5%, and protists and metazoans.
It is a microorganism carrier having a large number of through pores 14a with an inner diameter of 00 μm.

Therefore, the through pores 14a of the filter medium 14
In addition, for example, rotifers, which play an extremely important role in water purification, can be attached and immobilized, so that a great function can be exerted in water purification of the raw water 3. By the way,
Most of the size of rotifers is 100 to 500 μm.

A filter medium 14 comprising such a microorganism carrier
Has excellent advantages as described below. Since this filter medium 14 has a high affinity with various microorganisms and is a porous body having a large number of fine through-pores 14a, it can hold many types of microorganisms at a high concentration and its surface. Since the specific surface area including the through pores 14a is as wide as 0.5 to ⁵ m ² per 1 g and thus the contact area with the raw water is large, the solubility of the soluble BOD and COD and the nitrification performance of ammonia are excellent, and the surface and Since various kinds of microorganisms are abundantly adhered and immobilized inside the through pores 14a, the decomposition of SS is promoted and the amount of sludge generated can be reduced. The shape of the filter medium 14 is indefinitely granular, and since the ash is sintered by dry distillation at 1000 to 1300 ° C. to form a strong porous body, even if the filtration process is continued for a long time. Hard to break. Therefore, even if this filter medium 14
Even if the particle size is as small as 1 to 5 mm, the voids in the filtration layer 6 continue to be stably secured, and the pressure loss during the filtration process does not increase, so that the filtration rate can be increased and over a long period of time. The raw water 2 can be continuously filtered. Since the filter medium 14 is strong as described above, the surface and the through pores 14a are hard to be broken, and it is not necessary to regenerate it unlike the granular activated carbon. Therefore, the replacement frequency of the filter medium is low, and the cost of filtering the raw water 2 can be reduced.

Hereinafter, a case where raw water is filtered by the biological filtration device 1 having the above-mentioned configuration will be described. An inorganic coagulant 3 is added to the raw water 2 and mixed by a mixing mixer 4 immediately after that to coagulate SS, phosphorus, soluble organic substances and the like. Then, raw water containing aggregates of aggregated SS, phosphorus, soluble organic substances, etc. is caused to flow into the treatment tank 5, and the oxygen-containing gas (air) is blown from the diffuser 7 in the form of bubbles to pass through the filtration layer 6. And S remaining due to the filter medium 14
S, aggregated SS, phosphorus, organic substances, etc. are separated and removed, and soluble BOD, COD, etc. are decomposed and removed, and ammonia, etc. are nitrified, etc., and biological filtration treated water 8 having excellent water quality is obtained.

The dissolved oxygen concentration in the raw water 2 is 4 mg /
When it is 1 or more, the raw water 2 is in an aerobic state, so it is not necessary to blow the oxygen-containing gas from the air diffuser 7,
Further, the addition of the aggregating agent 3 aggregates SS, phosphorus, soluble organic substances, etc. to improve the removal rate of SS in the filtration step, and also has an effect on phosphorus, BOD, COD, chromaticity, etc. in a short time. The coagulant 3 is not necessarily added depending on the water quality of the raw water.

[0023]

EXAMPLES Examples of the first embodiment will be described below. In this example, as the raw water 2, a water quality much lower than the average secondary treated water generally treated by the standard activated sludge method (water quality causing extremely bulking etc.) was used, and this was filtered at 165 m / day. Filtered at speed. In this case, the average particle size of the filter medium 14 is as small as 1 to 5 mm, but voids are stably ensured in the filtration layer 6, and it contacts the raw water 2, and has a large specific surface area for immobilizing microorganisms. Therefore, the raw water 2 can be stably filtered for a long time, and the treated water 10 having excellent water quality as shown in Table 1 below can be obtained. As mentioned above,
Although the overspeed is set to 165 m / day in this embodiment, it is possible to perform the filtration treatment at a filtration speed of 165 m / day or more depending on the water quality of the raw water 2. The water quality of the treated water 10 obtained by the filtration treatment as described above is shown in Table 1 below in comparison with the water quality of the raw water 2.

[0024]

[Table 1] According to Table 1 above, regarding BOD, COD, and SS,
5 mg / l or less, but 1 mg for ammoniacal nitrogen
/ L or less and 0.5 mg / l or less for phosphorus have been achieved, and it is well shown that the nitrification ability of ammoniacal nitrogen is particularly excellent.

When the amount of sludge generated was determined by measuring the amount of SS in the backwash wastewater, it was 3% of the total amount of SS in the treatment tank 5.
It was found that about 0 to 40% was decomposed and that it exhibited an excellent function for reducing the amount of sludge generated. Furthermore, the pressure loss is small, and the filtration process can be continued for 24 hours.
Moreover, the shape of the filter medium 14 and the through pores 14a showed almost no change even after a long period of operation, and it was confirmed that the filter medium 14 had an extremely high strength.

A biological filtration apparatus according to Embodiment 2 of the present invention is shown by omitting a mixing mixer, an air diffuser, a treated water tank, a backwash blower and the like with reference to FIG. To explain, this biological filtration device 1 has a treatment tank having a two-stage configuration, as is well understood from the figure.

More specifically, the raw water 2 has a first-stage treatment tank 5a having a first-stage filtration layer 6a filled with a large-diameter filter medium.
To the final stage treatment tank 5b having a final stage filtration layer 6b which is filled with a filter medium having a small particle size. The filtered treated water 8'is configured to be drained from the final stage treatment tank 5b to a treated water tank (not shown) as the biological filtration treated water 8 filtered by the final stage filtration layer 6b.

Therefore, the raw water 2 is filtered in two stages by the first-stage filtration layer 6a and the final-stage filtration layer 6b.
The decomposition / removal processing performance of S, phosphorus, BOD, COD, chromaticity, etc. is superior to that of the first embodiment. In the second embodiment, an inorganic coagulant may be added to the primary biological filtration treated water 8 '.

A biological filtration apparatus according to a third embodiment of the present invention is shown by omitting a mixing mixer, an air diffuser, a treated water tank, a backwash blower and the like with reference to FIG. To explain, this biological filtration device 1 has a configuration in which two stages of filtration layers are provided in a treatment tank, as is well understood from the figure.

More specifically, the raw water 2 is supplied to the upper filtration layer 6a in the treatment tank 5 which is filled with a large-diameter filter medium,
Then, the primary biological filtration-treated water filtered by the upper filtration layer 6a is further filtered by the lower filtration layer 6b, which is filled with a filter medium having a small particle diameter, and discharged as biological filtration treatment water 8 to a treatment water tank (not shown). Is configured. The filter media filled in the upper filtration layer 6a and the lower filtration layer 6b can move only in the upper filtration layer 6a and the lower filtration layer 6b, respectively, and are configured not to move each other. ing.

Therefore, since the raw water 2 flowing into the treatment tank 5 is filtered in two stages by the upper filtration layer 6a and the lower filtration layer 6b, the third embodiment has the same effect as the second embodiment. is there. Although the upper filtration layer 6a and the lower filtration layer 6b are in close contact with each other in the third embodiment, a space may be provided between the upper filtration layer 6a and the lower filtration layer 6b. .

A biological filtration apparatus according to Embodiment 4 of the present invention will be described with reference to FIG. 4 which is a schematic configuration explanatory view thereof. As will be well understood from FIG.
Is different from Embodiment 1 in that raw water 2 is treated in treatment tank 5
Is supplied from the lower side and the biological filtration treated water 8 is discharged to the treated water tank 9 from the upper side, and the filtration layer has a two-stage configuration including an upper filtration layer 6a and a lower filtration layer 6b. The other configurations are exactly the same as those of the first embodiment.

The particle size of the filter media forming the upper filtration layer 6a and the lower filtration layer 6b in the fourth embodiment is completely opposite to that in the third embodiment. That is,
The upper filtration layer 6a is filled with a small-diameter filter medium, and the lower filtration layer 6b is filled with a large-diameter filter medium.

Therefore, the inorganic coagulant 3 is added to the raw water 2 and mixed by the immediately following mixing mixer 4,
SS, phosphorus, soluble organic substances, etc. are aggregated. Then, raw water containing aggregates of aggregated SS, phosphorus, soluble organic substances, etc. is caused to flow into the treatment tank 5 as an upward flow, and oxygen-containing gas (air) is blown as bubbles from the diffuser 7 while performing lower filtration. When passed through the layer 6b and the upper filtration layer 6a in this order, the remaining SS, aggregated SS, phosphorus, organic substances, etc. are separated and removed, and the soluble BOD, COD, etc. are decomposed and removed, and ammonia etc., are nitrified, etc. Is carried out and biological filtration treated water 8
Therefore, the present embodiment has the same effect as the above embodiment.

[0035]

As described in detail above, according to the biological filtration method and biological filtration device of the first to fourth aspects of the present invention,
The microbial carrier used as a filter medium has a large number of through pores of 50 to 500 μm which are preferable for adhesion and fixation of higher microorganisms and metazoans, has a large specific surface area, and even if the average particle diameter is 1 to 5 mm, it is present in the filtration layer. Not only can wide voids be secured, but since the ash content is in a sintered state due to the temperature during dry distillation of 1000 to 1300 ° C. and has high strength, the outer diameter and the through pores can be maintained in the initial state. Therefore, the microorganisms can be firmly immobilized, stable filtration can be continued for a long time, and the frequency of replacement of the microorganism carrier can be reduced, which is an extremely excellent effect.

[Brief description of the drawings]

FIG. 1 (a) is a schematic configuration explanatory diagram of a biological filtration device according to a first embodiment of the present invention, and FIG. 1 (b) is a configuration explanatory diagram of a microbial carrier serving as a filter medium constituting a filtration layer. is there.

FIG. 2 relates to a second embodiment of the present invention, which is a mixing mixer,
It is a typical structure explanatory view of the biological filtration apparatus which abbreviate | omits an air diffuser, a treated water tank, a backwash blower, etc.

FIG. 3 relates to a third embodiment of the present invention, which is a mixing mixer,
It is a typical structure explanatory view of the biological filtration apparatus which abbreviate | omits an air diffuser, a treated water tank, a backwash blower, etc.

FIG. 4 is a schematic configuration explanatory diagram of a biological filtration device according to a fourth embodiment of the present invention.

[Explanation of Codes] 1 ... Biological filtration device, 2 ... Raw water, 3 ... Flocculant, 4 ... Mixing mixer, 5 ... Treatment tank, 5a ... First stage treatment tank, 5b ... Final stage treatment tank, 6 ... Filtration layer, 6a ... First stage filtration layer or upper stage filtration layer, 6b ... Final stage filtration layer or lower stage filtration layer, 7 ... Air diffuser, 8 ... Biological filtration treated water, 8 '... Primary biological filtration treated water,
9 ... Treated water tank, 10 ... Treated water, 11 ... Backwash water, 12 ... Backwash blower, 13 ... Backwash drainage. 14 ... Filter material, 14a ... Through pores.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shintaro Suzuki 1-3-18 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo Kobe Steel Works, Ltd. Kobe headquarters (72) Inventor Kazunobu Fujinuma Takatsuka, Nishi-ku, Kobe-shi, Hyogo 1-5-5 Taiwan Kobe Works, Kobe Steel Co., Ltd. (72) Inventor Nobuki Hayase 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Co., Ltd. (72) Inventor Hiroshi Tanimura 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Works, Ltd. Kobe Research Institute

Claims (4)

[Claims] 1. A raw material coal containing caking coal as a main component is 100
Fixed carbon 80-95 obtained by dry distillation at 0-1300 ° C
wt%, ash content 5-20 wt%, and inner diameter 50-500
A method for biological filtration, characterized in that a microorganism is immobilized on a microorganism carrier having a large number of through pores of μm, and raw water is filtered through a filtration layer composed of the microorganism carrier on which the microorganism is immobilized. 2. The concentration of dissolved oxygen contained in raw water is 4
When it is less than mg / l, the raw water is subjected to a filtration treatment while blowing an oxygen-containing gas from the lower part of the filtration layer toward the filtration layer, and the biological filtration method according to claim 1. 3. The biofiltration method according to claim 1, wherein a flocculant is added to and mixed with the raw water. 4. A biological filter comprising a treatment tank provided with a filter layer made of a filter material on which microorganisms are immobilized, and an air diffuser for blowing an oxygen-containing gas toward the filter layer below the filter layer. In the apparatus, the filter medium has an average particle size of 1 to
10 mm of raw material coal having a diameter of 5 mm and containing caking coal as a main component.
Fixed carbon 80-9 obtained by dry distillation at 00-1300 ° C
5 wt%, ash content 5-20 wt%, and inner diameter 50-50
A biological filtration device, which is a microorganism carrier having a large number of through pores of 0 μm.