JPH02107582A - Porous soft ceramics and production thereof - Google Patents

Abstract

PURPOSE:To render a compsn. and fine structure suitable for the living of microorganisms by mixing combustible foamable resin with a slurry contg. SiO2, Al2O3 and Fe2O3 and air-drying and sintering the mixture. CONSTITUTION:Combustible foamable resin is mixed with combustible fine powder and/or a combustible fibrous material such as PVA or natural glass and a slurry contg., by weight, 65-93% SiO2 having 0.1-2.0mum particle size, 5.2-15.2% Al2O3 and 0.1-0.7% Fe2O3 or further contg. 1.2-3.0% K2O, 0.5-3.0% Na2O, 0.5-3.2% CaO and 0.5-3.2% MgO. The mixture is air-dried to about 5% water content and sintered at <=1,100 deg.C.

Description

[Detailed Description of the Invention] [Background of the Invention] Field of Industrial Application The present invention relates to porous soft ceramics suitable for the inhabitation of microorganisms, and more specifically for biofilm (contact) treatment of domestic and industrial wastewater. The present invention relates to a porous soft ceramic that is a contact material for use in the industry and has a composition and microstructure suitable for the inhabitation of microorganisms.

BACKGROUND OF THE INVENTION Recently, biofilm treatment methods have been used again to replace the so-called activated sludge method, which has been widely used in the treatment of domestic and industrial wastewater.

The basic principle of this method is to attach microorganisms to the contact material,
The wastewater to be treated is circulated around and brought into contact with the contact material, and the organic substances are oxidized and decomposed by the microorganisms to treat the wastewater.

The advantages of this biofilm treatment method compared to the activated sludge method are (1) the quality of the treated water is stable; (2)
It is responsive to load fluctuations and easy to manage,
(3) Changes in treatment efficiency due to temperature changes are gradual due to fixed metazoan microfauna; (4) - In the activated sludge method for boat fishing, metazoan microfauna cannot coexist due to the movement of activated sludge bacteria. For example, it is possible to treat wastewater with a biochemical oxygen demand (BOD) of 50 ppIm or less, which is otherwise impossible to treat.

In this biofilm treatment method, the most important thing is the so-called contact material to which microorganisms adhere. Considerations regarding conventional contact materials have primarily focused on how to increase the surface area to allow more microorganisms to adhere. For example, the plastic contact material used in the rotary biological contact method has a surface area of 20Or&/TI due to its no.
l has been realized.

However, no consideration has been given to whether or not this plastic contact material has a composition that allows microorganisms to easily adhere to it, and since the surface is smooth, it is difficult for microorganisms to adhere to it. Furthermore, when microorganisms multiply and stack up, the plastic becomes anaerobic from the surface close to the surface, and when the thickness reaches about 25 m+s, a large amount of microorganisms peel off at once.

As a result, the processing efficiency is lowered, and the plastic contact material has the disadvantage that it will become clogged if there is not an interval of 50 fins.

At present, it can be said that there is not only the above-mentioned plastic contact material but also other materials that can solve the above problems.

The present invention was made in view of the above-mentioned problems, and the present invention was completed by discovering the composition and fine structure of a contact material suitable for the propagation of microorganisms.

[Summary of the invention]

SUMMARY The present invention comprises 65-93 wt% SiO2 and 5.2-1
5.2% by weight of A 1203 and 0.1-0.7% by weight
A ceramic containing Fe2O3,
It is a porous soft ceramic characterized by having a network structure having open pores with an average pore diameter of 20 to 120 μm so that the apparent porosity is 60 to 80%.

The present invention also provides a method for producing porous soft ceramics, which comprises a combustible foamable resin and 5iOAl2O.
3 and a slurry consisting of 2.sup.2.sup.3 containing Fe2O3, air-dried, and then fired at a temperature of 1100.degree. C. or lower.

Furthermore, the present invention provides another method for producing porous soft ceramics, in which combustible fine powder and/or fibrous material is mixed with a slurry containing SiO2, AIO, and Fe2O3, and the mixture is air-dried. After that, it is characterized by firing at a temperature of 1100° C. or lower.

Furthermore, the present invention provides still another method for producing this porous soft ceramic, which uses natural glass and 5iOA.
10 and 2.23 of Fe2O3 is air-dried and then calcined at a temperature of 1100° C. or less.

Effects The porous ceramics of the present invention not only have a larger surface area than conventional general-purpose contact materials, but also have a composition and microstructure suitable for the inhabitation of microorganisms, making them an excellent contact material for biofilm treatment. It can be used as a material.

Furthermore, according to the bolus ceramics of the present invention, a large amount of wastewater can be biofilm treated in an aerobic atmosphere in a short time.

[Detailed Description of the Invention (1) Porous Soft Ceramic The present invention relates to a ceramic having a certain composition,
Further, the ceramic is a so-called porous ceramic having a network structure having open pores with a predetermined average pore diameter so as to have a predetermined porosity.

The porous ceramics of the present invention has the following composition:
It is necessary to contain the ingredients shown in the table. General aspects and more preferred aspects of the components are also shown in Table 1. All numerical values in the table are weight % (hereinafter, the same applies to Table 2).

Table 1 Here, when SiO2 exceeds the above general condition, porous ceramics lose cohesive strength and become easily deformed, and if the firing temperature is increased to prevent this deformation, the surface vitrification occurs, making it difficult for microorganisms to adhere, which is undesirable.

Furthermore, if 5102 is less than the above-mentioned intra-membrane mode, the adhered microorganisms will not be peeled off for generational replacement, and the porous ceramics will become anaerobic over time, making it impossible for aerobic microorganisms to inhabit the porous ceramics, which is not preferable.

Furthermore, if A 120 B exceeds the above-mentioned general condition, the division and reproduction of microorganisms becomes slow and eventually they die, which is not preferable. Moreover, if A1203 is less than the above-mentioned -inner-membrane mode, the shear strength of the porous ceramic becomes small and it becomes easy to break, which is not preferable.

Moreover, if Fe2O3 exceeds the above-mentioned general condition, the reproduction of microorganisms will be suppressed and slow, and will eventually die, which is not preferable. Furthermore, if the Fe2O3 content is less than the above-mentioned -intra-membrane mode, the growth of algal bacteria etc. becomes slow, which is not preferable.

Further, the porous ceramic of the present invention preferably contains the components shown in Table 2 in addition to the components shown in Table 1. Furthermore, Table 2 shows preferred embodiments and more preferred embodiments of these components.

Table 2 In addition, if KO and Na2O3 exceed the above conditions, it is often difficult to generate algae bacteria (which is not preferable).Also, if K20 is less than the above conditions, even if algae bacteria occur, they will not grow. This is not desirable as it tends to be delayed.

Moreover, regarding CaO, if this exceeds the above aspect,
This is undesirable because it tends to make it difficult for protozoan animals to divide and multiply. Furthermore, if the condition is less than the above, it is not preferable that even if a protozoan is generated, it tends to be weak and weak.

Furthermore, with regard to MgO, if it exceeds the above-mentioned conditions, it tends to inhibit the growth of active bacteria, which is undesirable, and if it is below the above-mentioned conditions, it is often difficult for algae bacteria to grow, which is undesirable.

The porous ceramic of the present invention is a ceramic having the above composition provided with predetermined open pores, and as a result, the apparent porosity is 60 to 80, preferably 65 to 7.
0.

Here, the apparent porosity is defined as follows.

The apparent volume of all solids The open pores provided in the ceramics of the present invention so as to have the above apparent porosity are those with an average pore diameter of 20 to
120 μm 1 preferably 26-56, more preferably 3
The shape is not particularly limited as long as it is in the range of 0 to 50. For example, a network structure having continuous pores as open pores, that is, a sponge-like structure is particularly preferable.

Enclosed pores may be present in the present invention, but it is preferable that they be absent.

Furthermore, the porous ceramics of the present invention has on its surface,
Preferably, micropores are further provided. Here, the surface of porous ceramics includes not only the macroscopic surface of the ceramic molded body, but also the microscopic interior of the ceramic, that is, the surface of the inner walls of the open pores forming the above-mentioned network structure. . Therefore, the ceramic of the present invention has a double micropore structure.

The diameter of the micropores on the surface is not particularly limited, but specifically, it is 0.03 to 0. Preferably, it is in the form of 7 μm.

As a result of the presence of predetermined open pores in this way, the surface area of the porous ceramic of the present invention is approximately 2,000 to approximately 50
00 rf/butt (approximately 0.25 to approximately 0.65 bar/g).

Since the conventional plastic honeycomb-shaped contact material has a maximum surface area of approximately 200 rri"/m,
The porous ceramic of the present invention has a surface area approximately 25 times that amount. According to simple calculations, it is 1/25th of the conventional
This means that the same scale of sewage treatment as before can be achieved with a contact material of this size.

Applications of the present invention The porous ceramics of the present invention have a composition and microstructure suitable for attachment and propagation of aerobic microorganisms, and are in a state in which the microorganisms are not easily detached by contact with wastewater to be treated. It is possible to reliably retain microorganisms. Therefore, one of the uses of the porous ceramics of the present invention is that microorganisms can be propagated in the open pores of the porous ceramics, and this can be used as a contact material in a biofilm treatment method.

The porous ceramics of the present invention can be immediately used as a contact material in current biofilm treatment methods.

Microorganisms that can be grown in the porous ceramics of the present invention to treat wastewater are generally the same as those that grow in conventional contact materials used in biofilm treatment methods. That is, aerobic bacteria, protozoa, micrometazoa, etc. can be considered.

Among these, bacteria have a size of 0.5 to 1.0 μm.
Therefore, it goes without saying that protozoa and micrometazoans have a size of about 20 to 80 μm and can live in the open pores of the porous ceramics of the present invention.

The shape of the porous ceramic of the present invention may be selected from any shape suitable for the processing equipment used, and is not particularly limited, but hollow cylinder, cylinder, and prismatic shapes are particularly preferred.

In addition, because it is used as a contact material for rotary biological contact treatment,
It is also possible to use it by fixing it on a rotating disk. This rotary biological contact treatment method is no different from the conventional rotary biological contact treatment method, except for the use of the porous soft ceramics of the present invention as a contact material and some modifications accordingly. It is something. Regarding this rotating biological contact treatment method, for example, please refer to the monthly magazine Water Treatment Technology, Director of Institute of Pollution Resources, Agency of Industrial Science and Technology, Isamu Horozawa [Considerations on Rotating Disc Domestic Wastewater BOD 1100pp BOD
150ppta ROD 200ppm Formula Adaptability to Rotating Discs”.

The porous ceramic of the present invention has a larger surface area than conventional contact materials.

In other words, it is possible to retain a large amount of microorganisms compared to conventional contact materials, and as a result, wastewater treatment can be carried out efficiently with a smaller volume of contact material, that is, a smaller treatment device, compared to conventional contact materials. It is.

In addition, since the amount of microorganisms that can live in the porous ceramics of the present invention is larger than that in conventional contact materials, depending on the processing equipment used, the supply of oxygen to the processing tank may be lower than in the conventional case. There may be cases where it is necessary to do so in large quantities. This is because a lack of oxygen causes microorganisms in porous ceramics to become anaerobic.

In the porous ceramics of the present invention, generational alternation of microorganisms takes place smoothly in an aerobic state while adhering to the porous ceramics. That is, microorganisms that have reached the decline stage peel off from the porous ceramics, but since the rate of reproduction varies depending on the type of microorganism, a large amount of microorganisms does not peel off at once. This is very different from the case where a plastic contact material is used, where a large amount of microorganisms are removed at once due to anaerobic conditions.

(2) Manufacturing method (Part 2) The porous ceramics of the present invention can be manufactured by any method suitable for the purpose. In one aspect, the present invention provides a preferred method for producing the same.

In the method for producing porous ceramics of the present invention, as described below, a slurry that is a clay-like mixture having a predetermined component composition is first prepared, and then this slurry is mixed with a combustible pore-forming substance. This mixture is then dried and fired. The manufacturing method of the present invention will be explained in detail below.

Sludge The slurry, which is a clay-like mixture with a predetermined component composition and serves as the basic raw material for the porous ceramics of the present invention, is prepared by adding water to the component powders shown in Tables 1 and 2 and mixing them. be able to.

The particle size of this component powder is preferably 0.1 to 2.0 μm.
It is. Particularly, it is preferable that the particle size is in this mode because micropores of about 0.03 to 0.7 μm are formed on the surface of the resulting porous ceramic.

Also, this ingredient powder does not need to be pure;
For example, Gaitome clay, china clay, silica stone, and even diatomaceous earth,
Bentonite, montmorillonite, etc. can be used. Even in this case, it goes without saying that the mixing ratio must be determined so that the composition of the porous ceramics obtained is as shown in Tables 1 and 2.

Combustible void-forming substance A combustible void-forming substance that forms predetermined open pores in porous ceramics is a substance that is mixed with the above-mentioned slurry and then burned during firing to open up the space occupied by it. It refers to something that can be made into a void.

Here, the "flammability" of this combustible void-forming substance means 11
A substance that burns at temperatures below 00°C.

Specific examples of the combustible void-forming substance include a foamable resin foamed with a foaming agent, a fine powder or fibrous combustible substance, and polyvinyl alcohol.

Examples of resins foamed with a foaming agent include urethane resins, styrene resins, polypropylene resins, and the like. Examples of the blowing agent in this case include ethyleneamine and chlorofluorocarbon (CFCll).

In the method using foamed resin, the size of the bubbles formed in the resin corresponds to the pore size of the final porous ceramic, so the size of the bubbles is controlled by selecting the foaming agent. It is important to do so. The type and amount of the blowing agent are appropriately selected depending on the type of resin and the size of the bubbles, and the value is not particularly limited. You need to choose.

The foamable resin is preferably foamed and molded to form a foamable resin molded product, and then mixed with a slurry as described below. The foamable resin may be molded by a known method, but for example, the foamable resin may be dissolved in an organic solvent such as methylamine or dimethylformamide (DMF), and a foaming agent and a reaction inhibitor may be mixed in advance. It is preferable to obtain foamable resin molded products by injection (mold punching machine) using molds of various shapes coated with silicone oil as a release agent.

Further, specific examples of fine powder or fibrous combustible substances include sawdust, chopped cotton fibers, bulb fibers, and the like.

The size of these combustible substances corresponds to the pores of the porous ceramics that are finally obtained, similar to the bubbles of the foamable resin mentioned above, so controlling the size of these flammable substances is also important in foaming. It is as important as plastic resin.

To determine the size of these organic substances, for example, in the case of sawdust, a method of separating them using a sieve is preferably used.

In addition, these fine powder combustible substances and fibrous combustible substances can be used alone or in a mixed form,
It is possible to mix it with a slurry as described below.

Mixing of the slurry and the combustible void-forming material Subsequently, the above-mentioned slurry and the combustible void-forming material are mixed.

This mixing is carried out by simply adding or immersing the foamable resin or fine powder and/or fibrous combustible material into the slurry. Stirring is preferably performed after addition or immersion.

Moreover, it is preferable to add a binder during this mixing. Specific examples of binders include silica gel,
Examples include polyvinyl alcohol (PVA). It goes without saying that the amount of this binder component to be added should be determined taking into consideration that it will remain in the porous ceramics of the final product.

Firing The mixture of slurry and combustible void-forming material mixed as described above is air-dried and then calcined.

Further, when a fine powder or fibrous combustible material is used as the combustible void-forming material, it is preferable to shape the mixture before firing. This molding can be carried out using conventional means normally used for molding clay-like substances. Specific examples thereof include, for example, a three-core extruder.

On the other hand, the foamable resin can be molded in advance as described above, so there is no need to mold it at this stage.

The molded product obtained as described above is first air-dried. This air drying preferably brings the moisture content to about 5%. At this time, after natural drying to a moisture content of about 15% (usually 4 to 5 days), the temperature is raised slightly above room temperature, for example, in a continuous drying room that utilizes the recovered waste heat of the kiln.
It is preferable to dry to a moisture content of 15%.

Subsequently, the air-dried molded product as described above is fired at a temperature of 1100° C. or lower. If the firing temperature is 1100° C. or higher, the surface of the ceramic becomes vitrified, which is not preferable.

This firing is preferably performed in stages as described below.

First, heat to 150°C for 2 hours, then heat to 200°C.
℃ for 1 hour to burn off the combustible material and form pores. Thereafter, the temperature is raised to 800°C over 2 hours, and further to 1100°C over 3 hours, and the temperature of 1100°C is maintained for 1 hour to fuse the silica components in the molded product.

(3) Manufacturing method (Part 2) Further examples of the manufacturing method of the porous ceramics of the present invention will be described below.

This manufacturing method is a method for obtaining the porous ceramics of the present invention by mixing natural glass powder into the slurry described above in place of the combustible pore-forming substance described above, and then heating the natural glass to make it porous. It is. That is, this method utilizes the property that natural glass normally contains a large amount of volatile matter such as moisture, and becomes porous when heated.

The slurry used in this method contains natural glass and has a composition within the range given in Table 1. That is, in this method, since natural glass, which is a pore-forming substance, remains in the porous ceramic after firing, the composition of the slurry is within the composition shown in Table 1, taking into account the composition of this natural glass. It is necessary to mix the raw material powders as follows.

Specific examples of the natural glass used in this method include pearlite, obsidian, and the like.

Also in this method, it is preferable to include the compositions shown in Table 2 in addition to the compositions shown in Table 1.

Further, the powder supplying these compositions does not need to be pure, and the aforementioned Gaitome clay, china clay, silica powder, etc. can be used.

The powders having the compositions shown in Tables 1 and 2 are mixed, and water is added as appropriate to form a slurry. This slurry is then molded to obtain a molded product. The molding is preferably carried out by means similar to those described above.

After the molded product is air-dried, it is fired at a temperature of 1100° C. or lower to obtain the porous ceramic of the present invention.

If the firing temperature exceeds 1100° C., the ceramic surface becomes vitrified as in the case described above, which is not preferable.

Also in this method, it is preferable that air drying and firing be performed in stages as described above. Air drying is the same as described above, and firing is also preferably applied as described above, except that the natural glass is expanded and made porous by heating at 200°C for 1 hour. .

[Example] Example 1 Powder having the composition shown in Table 3 and having a particle size of approximately 0.1 to 2.0 μm was stirred and mixed to form a homogeneous slurry of 14,000 μm.
Prepare g.

Add ethylene amine (as a blowing agent) to 1 kg of urethane resin.
The pore size after foaming is 20. and chlorofluorocarbon (CFCII) (40 to 80 μm)
0g and catalytic organic acid (citric acid) (80-120μm)
) and 30g of it while stirring. This mixture was injected into the urethane resin injection line, and the outer diameter was 18 mm.
A hollow cylindrical molded product with a diameter of 20 mm, an inner diameter of 8 to 10 mm, and a length of 120 mm is obtained.

This molded product is immersed in a 10% aqueous sodium hydroxide solution for 6 hours to make the surface hydrophilic.

This foamable urethane resin molded product is immersed in 14,000 kg of slurry to which 14 kg of silica gel is added as a binder, and gently stirred for 2 hours to fix the slurry to the urethane resin.

The urethane resin molded product to which the slurry has adhered is taken out and placed on a mesh for 3 hours to remove excess slurry.

After that, it is naturally dried on an air drying rack for 4 to 5 days, and the moisture content is about 15.
%. The molded product is then dried to a moisture content of 5% in a heat recovery drying furnace of a firing furnace.

The urethane resin molded product that has been dried to a moisture content of 5% is packed into a firing box and placed in a continuous firing furnace.

Heat to 150°C for 2 hours to remove water content,
Heat at 200°C for 1 hour to burn off the urethane resin.

Thereafter, the temperature is raised to 800°C over 2 hours, and then to 1100°C over 3 hours. The porous ceramics of the present invention are obtained by firing at a temperature of 1100° C. for 1 hour.

The composition, apparent porosity and average pore diameter of the obtained porous ceramics are as shown in Table 6.

Example 2 A slurry having the composition shown in Table 4 is prepared in the same manner as in Example 1.

Next, sieve the sawdust and add 200 iesh (127, czm) 11.0 k
g.

300fflesh (84am) 9. 37
kg-400I! esha (63.5μm) 10.
7 kg-500iesh (50,8μm)
7. 5) Separate 4 stages of cg, add 3.8 kg of chopped cotton fibers with an average diameter of 10 μm and a length of 1000 μm, and 3.8 kg of bulb-cut fibers, and 1120 kg of water, and stir gently day and night.

This mixture of sawdust and fibers, the aforementioned slurry, and 14 kg of silica gel as a binder were mixed by stirring.

A hollow cylindrical molded product is obtained from the solidly kneaded mixture using a three-core extruder. The molded product is naturally dried on an air drying rack until the moisture content reaches 15%.

Next, it is placed in a continuous drying chamber where waste heat from the firing furnace is recovered and dried to a moisture content of 5%.

The molded product dried to a moisture content of 5% is packed into a firing box and placed in a continuous firing furnace. It is heated to 150°C for 2 hours to remove the water content, and heated to 200°C for 1 hour to burn off the sawdust and cut fibers.

Thereafter, the temperature is raised to 800°C over 2 hours, and then to 1100°C over 3 hours.

The porous ceramics of the present invention are obtained by firing at a temperature of 1100° C. for 1 hour.

The composition, apparent porosity, and average pore diameter of the obtained porous ceramics are as shown in Table 6.

Example 3 A homogeneous slurry is prepared by stirring and mixing powders having a particle size of about 0.1 to 2.0 μm and having the composition shown in Table 5.

Table 5 Pearlite was crushed and sieved to 1000mes100O, 4am)9.5)cg, and 1
500mesh (16.9μm) 7.5kg and 200
On+esh (12,7μm) 7.5kg and 2500
8.1 kg of mesh (10 μm) was collected and mixed in powder form until uniform.

Stir and mix the aforementioned slurry and perlite powder.

After being thoroughly kneaded, the mixture is passed through a three-core extruder to obtain a hollow cylindrical molded product. The molded product is naturally dried on an air drying rack until the moisture content is 15%.

Next, it is placed in a continuous drying chamber where waste heat from the firing furnace is recovered and dried to a moisture content of 5%.

The molded product dried to a moisture content of 5% is packed into a firing box and placed in a continuous firing furnace. It is heated to 150° C. for 2 hours to remove water content, and heated to 200° C. for 1 hour to expand the nacre and form a porous structure. After that, 800℃
The temperature was raised over 2 hours to 1100℃ over 3 hours.
Raise the temperature to ℃.

The porous ceramic of the present invention is obtained by firing at a temperature of 1100° C. for 1 hour.

The composition, apparent porosity and average pore diameter of the obtained porous ceramics are as shown in Table 6.

Example 4 and Comparative Example 1 Porous ceramics having compositions, apparent porosity, and average pore diameter as shown in Table 6 were produced as Example 4 and Comparative Example 1 by the same method as in Example 1. did.

Table 6 Note that the average pore diameter was measured using an average pore illumination machine. That is, a certain amount of calcium carbonate powder adjusted in advance to a diameter of 120 μm is sprayed onto the porous ceramic of the present invention. From the amount of calcium carbonate remaining without adhering to the porous ceramics, the amount of calcium carbonate adhering to the porous ceramics and the volume occupied by the calcium carbonate are calculated.

A similar operation is carried out using calcium carbonate of varying diameters, such as calcium carbonate of 8, 0.50 and 30 μm in diameter.

Then, the ratio of the volume of calcium carbonate of various diameters attached to the porous ceramic of the present invention obtained as a result of the above operation to the total pore volume determined by flFI by mercury porosimetry is calculated. Then, the pore diameter at which the volume obtained using calcium carbonate is larger than the volume obtained by this mercury intrusion method is defined as the average pore diameter.

Sewage Treatment Example 1 An example in which wastewater was treated by the rotary biological contact method using the porous ceramics of the present invention is shown below.

A total of 768 pieces of the hollow cylindrical porous ceramics of the present invention obtained in Example 1 were manually mounted in the diametrical direction near the outer periphery of a rotating disk having a diameter of 2000 II 1 m as a contact material. The volume and surface area of this contact material are as shown in Table 7. BOD200 +) I) The BOD removal ability and wastewater treatment ability of this rotating disk obtained as a result of treating the sewage of 11 are as shown in Table 7.

For comparison, similar wastewater was treated using a plastic honeycomb-shaped rotating disk contact material with a diameter of 2000 mm, which has been conventionally used in this treatment method. The volume and surface area of this contact material, as well as the BOD removal ability and wastewater treatment ability of this contact material, are as shown in Table 7.

Table 7 Sewage treatment example 2 Porous ceramics of Example 4 and Comparative example 1 were
Fix the 8 tubes with spacers and put them in a contact tank with a volume of 7.87 RL, BOD 173 ppIl, SS 11.
2 ppm wastewater was subjected to biofilm contact treatment while blowing 40 liters of air per minute.

When the porous ceramics of Example 4 was used, on average for -week, SS4ppm, BOD21ppm (
The wastewater could be purified to a removal rate of 88%. Even after that, stable sewage treatment was possible.

On the other hand, when using the porous ceramics of Comparative Example 1,
Five days after the start of treatment, the activated sludge became anaerobic during the growth phase, and the wastewater could no longer be treated.

Claims (1)

[Claims] 1. 65-93% by weight of SiO_2; 5.2-15.
A ceramic containing 2% by weight of Al_2O_3 and 0.1 to 0.7% by weight of Fe_2O_3, with open pores having an average pore diameter of 20 to 120 μm so that the apparent porosity is 60 to 80%. Porous soft ceramics characterized by having a network structure. 2, 1.2-3.0% by weight of K_2O, and 0.5-3.
0 wt% Na_2O and 0.5-2.0 wt% Ca
The porous soft ceramic according to claim 1, containing O and 0.5 to 3.2% by weight of MgO. 3. The porous soft ceramic according to claim 1 or 2, having micropores with a diameter of 0.03 to 0.7 μm. 4. The method of claim 1, 2 or 4, characterized in that a flammable foamable resin and a slurry containing SiO_2, Al_2O_3 and Fe_2O_3 are mixed, air-dried, and then fired at a temperature of 1100°C or less. 3. The method for producing porous soft ceramics according to 3. 5. Flammable fine powder and/or fibrous material and S
The method for producing porous soft ceramics according to claim 1, 2 or 3, characterized in that the slurry containing iO_2, Al_2O_3 and Fe_2O_3 is mixed, air-dried and then fired at a temperature of 1100°C or less. 6. The porous material according to claim 1, 2 or 3, characterized in that natural glass and a slurry containing SiO_2, Al_2O_3 and Fe_2O_3 are mixed, air dried and then fired at a temperature of 1100°C or less. Manufacturing method of soft ceramics. 7. A disc-shaped or hollow cylindrical contact material used in a rotary biological contact treatment method, characterized in that it is equipped with the porous soft ceramic according to claim 1, 2 or 3.
contact material.