JPH0773702B2 - PVA high water content gel, microbial embedding high water content gel, and purification method of wastewater containing organic substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a highly water-containing polyvinyl alcohol gel having a uniform fine network structure, a microorganism-embedded highly water-containing gel in which microorganisms are embedded between the fine networks of the gel, and The present invention relates to a method for purifying wastewater by bringing a gel in which the microorganisms are embedded into contact with wastewater containing organic substances, particularly wastewater containing phenols.

<Prior Art and Its Defects> Various methods have been conventionally known as a method for producing a polyvinyl alcohol (hereinafter abbreviated as PVA) gel or a method for producing a gel in which microorganisms are embedded in the PVA gel. Among them, a method for producing a high-strength gel by freezing / dehydrating an aqueous polyvinyl alcohol solution or supporting freezing / thawing has been previously proposed (JP-A-58-36630).
No. 59-56446). According to these methods, a water-insoluble high-strength and high-hydration gel can be obtained, but the gel obtained by these methods does not lead to a gel having a uniform microbial network structure, and its mesh width is several tens of μm. It is a wide one that contains many. Also, a method of embedding a microorganism in the gel has been previously proposed (JP-A-57-141292 and JP-A-48-47).
No. 492). However, the embedding gel obtained by these methods, when embedding a relatively large bacterial cell of 5 to 10 μm such as yeast,
Well-embedded with little leakage, but several μm of methane-producing bacteria
However, there is a drawback in that leakage occurs when embedding bacteria.

In the above-mentioned publication, it is described that agar, gelatin, etc. may be added as a substance that does not inhibit gelation during the production of gel, but these additives are substances that do not inhibit gelation. It is a description of the possibility of addition as, and it is not shown in these specifications that a gel having a uniform fine network structure actually referred to in the present application was obtained,
Further, it is not disclosed that microorganisms can be embedded in the fine network structure gaps. Further, there is no disclosure of purification of organic substances, particularly emissions containing phenols, using the same.

The fluid catalytic cracking unit of an oil refining plant is a device that mainly catalytically cracks relatively heavy petroleum using a fluid catalyst to obtain a gasoline raw material. In this device, the steam at the time of steam stripping for removing hydrocarbons adhering to the surface of the catalyst particles, and the steam column introduced into the distillation column to increase the distillation efficiency when the decomposition products are distilled Waste water, or waste water from the bottom water of the product storage tank, contains phenols of several tens to several hundreds mg / more, such as 500 mg / more, in some cases 10 g / more, and purifies these waste water. Under the present circumstances, the method of doing so is not always effective.

<Problems to be Solved by the Invention> An object of the present invention is to purify wastewater containing organic substances, particularly wastewater from a fluid catalytic cracking apparatus or a fluid catalytic cracking product storage tank of a petroleum refining plant that is phenol-containing wastewater. It is possible to provide a PVA high water content gel, a microorganism-embedded high water content gel, and a purification method thereof.

<Means for Solving the Problems> According to the present invention, (i) 5 to 25 wt% of polyvinyl alcohol having a saponification degree of 95 mol% or more and a viscosity average polymerization degree of 1,500 or more
And (ii) a uniform fine mesh structure having a mesh width of 2 to 3 μm, which is obtained by heating an aqueous solution containing 0.01 to 5 wt% of a polysaccharide, cooling it, and then repeating freezing and dehydration or freezing and thawing. A polyvinyl alcohol high water content gel is provided.

According to the present invention, (i) 5 to 25 wt% of polyvinyl alcohol having a saponification degree of 95 mol% or more and a viscosity average degree of polymerization of 1,500 or more.
% And (ii) 0.01 to 5 wt% polysaccharide aqueous solution was heated and then cooled, and then (iii) microorganisms were added and the mesh width 2 was obtained by repeating freezing / dehydration or freezing / thawing. Provided is a highly hydrous gel containing microorganisms, which has a uniform fine network structure of ˜3 μm.

Furthermore, according to the present invention, (i) the degree of saponification is 95 mol% or more,
Polyvinyl alcohol with a viscosity average degree of polymerization of 1,500 or more 5-2
A mesh width obtained by heating an aqueous solution containing 5 wt% and (ii) 0.01 to 5 wt% polysaccharide, cooling it, and then adding (iii) microorganisms and repeating freeze-dehydration or freeze-thawing. There is provided a method for purifying organic matter-containing wastewater, which comprises contacting an organic matter-containing wastewater with a microorganism-embedded highly hydrous gel having a uniform fine network structure of 2 to 3 μm to remove the organic matter.

The present invention will be described in more detail below.

The highly hydrous PVA gel of the present invention contains a specific PVA (hereinafter referred to as (i) component) and a polysaccharide (hereinafter referred to as (ii) component) and has a uniform fine network structure with a mesh width of 2 to 3 μm. Have.
Here, the mesh width indicates the width of the gap formed by the polymer. It is desirable that the degree of saponification of PVA as the component (i) is 95 mol% or more, preferably 98 mol% or more. If the saponification degree is less than 95 mol%, a high-strength gel cannot be obtained. I can not use it. The viscosity average degree of polymerization of PVA is
It is desirable that it is 1,500 or more, preferably 1,800 or more. If the viscosity average degree of polymerization is less than 1,500, a gel having high strength cannot be obtained, and therefore it cannot be used. Furthermore, examples of the polysaccharide as the component (ii) include natural polysaccharides having a relatively large molecular weight such as agar, carrageenan, and konjac. Further, the content ratio of the component (i) and the component (ii) in the PVA high water content gel is 5 to 25 wt%, preferably 10 to 20 wt% of PVA as the component (i). At this time, if the amount of the component (i) is less than 5 wt%, a gel having sufficient strength cannot be obtained, and if it exceeds 25 wt%, the aqueous solution is not sufficiently dispersed and a uniform fine network structure cannot be obtained. . The content ratio of the polysaccharide (ii) component is 0.
It is 01 to 5 wt%, preferably 0.1 to 1.0 wt%. At this time, if the amount of component (ii) is less than 0.01 wt%, the mesh width is 10μ
When a coarse mesh structure of m is generated and microorganisms or the like are buried, the leakage rate increases. On the other hand, if it exceeds 5 wt%, the strength of the gel is lowered and a uniform network structure cannot be obtained. Therefore, the components (i) and (ii) must be used in the respective content ratio ranges.

The PVA high hydrous gel of the present invention comprises the above-mentioned component (i) and (ii)
After heating the components, they are cooled, and then repeatedly frozen and dehydrated or frozen and thawed.

That is, for example, powdered PVA is added to distilled water and stirred, then a polysaccharide is added, preferably in an autoclave at a temperature of 120 to 1
20 ℃ to 60 ℃ at high temperature and pressure of 60 ℃ and pressure of 1.2 to 2kg / cm ^2.
Stir for a minute to obtain an aqueous solution with a uniform concentration.However, since air may be entrained by the stirring operation, after leaving it to cool, it is heated again at about 90 to 110 ° C without stirring and degassed under normal pressure or reduced pressure. It is desirable to be careful. Next, before cooling the aqueous solution, it is poured into a mold having a desired shape and size, housed in a freezer and cooled to −15 ° C. or lower, preferably −20 to −40 ° C. and frozen. If the temperature is high, a high-strength, high-hydrate gel cannot be obtained, which is not preferable. Then, after freezing, a PVA high hydrous gel having a uniform fine network structure having a mesh width of 2 to 3 μm can be produced by a method such as dehydrating the system under reduced pressure. The degree of pressure reduction at this time is not limited to a certain time, but is generally 10 mm.
It is desirable that it is Hg or less, preferably 0.1 to 1 mmHg, and the dehydration rate (weight reduction rate of frozen body) is usually 5 wt% or more, preferably 5 to 30 wt%. If the dehydration rate is low, a high-strength gel cannot be obtained, which is not preferable.

In addition, the frozen body is left at 0 ° C. or higher, for example, 0 ° C. to room temperature without being subjected to the dehydration step after freezing, and is thawed, and after cooling and thawing, the cooling and thawing are repeated in the same manner. It is also possible to use a method in which the number of times is about 2 to 10 times. At this time, if the number of times of freezing and thawing is small, the obtained gel becomes soft, and if the number of times is more than 10, it is economically disadvantageous, which is not preferable.

In the above method example, PVA of (i) component and (i
In order to control the amount of the polysaccharide as the component i), for example, when performing freezing / dehydration, it is desirable to set the initial concentration in consideration of the water content removed by the dehydration rate. When freeze-thawing is repeated, it is preferable to adjust the concentration of components in the obtained gel so as not to change.

In the present invention, it is possible to add an optional additive which is inactive within a range that does not inhibit gelation.

Further, in the present invention, a microorganism-embedded highly hydrous gel can be obtained by embedding a microorganism in the interstices of the PVA highly hydrous gel having a fine network structure. The type of the microorganism to be added and contained is not particularly limited, and bacteria, yeast, etc. can be used, but preferably the average diameter is about 1 to 3 μ.
m bacteria and the like can be effectively used, and it is particularly preferable to use methane-producing bacteria typified by the genus Methanobacteria. The methane-producing bacterium grows in sludge, which can be separated and used.

In the present invention, the method for producing the microbial-embedded highly hydrous gel comprises the steps of heating the component (i) and the component (ii),
After cooling, the microorganism (iii) is added, and freeze-drying or freeze-thawing is repeated in the same manner as in the method for producing the PVA hydrogel. Specifically, for example, after obtaining an aqueous solution of the above-mentioned components (i) and (ii) under conditions of high temperature and pressure, the aqueous solution is cooled to a temperature of 40 ° C. or higher and 40 ° C. or lower, and then the microorganisms are removed. Add and gently mix and stir. Then, similar to the method for producing the PVA high water content gel, a method of repeating freezing / dehydration or freezing / thawing can be mentioned. It should be noted that it is desirable to add microorganisms aseptically so as to prevent contamination of various bacteria.

Further, in the present invention, the organic matter is removed by contacting the microorganism-containing highly hydrous gel with organic matter-containing wastewater,
The wastewater can be purified. As a purification method,
For example, the microorganism-embedded highly water-containing gel is cut into an arbitrary shape to form dice or granules having an average diameter of about 1 to 30 mm, preferably 3 to 15 mm, and filled in an empty cylinder or a drum to purify organic matter. -Containing wastewater is circulated at about 0 to 30 ° C, generally around room temperature, or a method of contacting it, or a method of mixing the microorganism-embedded highly hydrous gel and a waste solution in a stirring tank and slowly stirring them to bring them into contact with each other, etc. Can be used.

In the present invention, as the purifiable wastewater, various factory wastewater, wastewater containing organic substances in domestic wastewater, for example,
COD concentration is 10 mg / or more, preferably 100-500 mg / wastewater can be purified, in the present invention wastewater containing particularly phenols, specifically, fluid catalytic cracking or fluid catalytic contact of oil refinery The phenol-containing wastewater from the decomposition product storage tank can be effectively purified.

In the purification method of the present invention, if the circulation of wastewater is continued for a long period of time, the activity of the embedded microorganisms may decrease, but in this case, without stopping or stopping the circulation of wastewater,
For example, it can be activated by adding an aqueous solution containing a nutrient source such as corn starch, glucose, and sugar-tightness.

<Examples> The present invention will be described in more detail with reference to Examples.

Example 1 An autoclave having a capacity of 42 was added with 99.85 mol% of saponification degree, 14.5 wt% of PVA having a viscosity average polymerization degree of 1750, 0.5 wt% of agar powder and 85 wt% of distilled water. Then 121 ℃, pressure 1.2kg / c
After stirring and mixing at m ² for 30 minutes, the mixture was left for 20 minutes and deaerated.
After standing, when the temperature reached about 60 ° C, add 30 cm × 40 cm × 0 to this aqueous solution.
The mixture was poured into a 7 cm (vertical × horizontal × depth) box-shaped container and allowed to stand until room temperature. The container was placed in a freezer equipped with a decompression device, cooled at -35 ° C and frozen. After freezing, the decompressor was operated, the system was kept at about 0.1 mmHg for 240 minutes, and dewatered under reduced pressure so that the dehydration rate was 50%. Then, the container was taken out and left at room temperature to obtain a gel. The gel obtained is insoluble in water. When the fractured surface of the gel was measured by a scanning electron microscope, it was found that a fine mesh structure having a mesh width of 2 to 3 μm was uniformly present on the entire surface. An enlarged view of the frozen fractured section of the gel is shown in FIG.

Example 2 A gel was produced under the same conditions as in Example 1 except that carrageenan was used instead of the agar powder.

The resulting gel is water insoluble as in Example 1. Further, a fine mesh structure having a mesh width of 2 to 3 μm was uniformly present on the whole.

Example 3 In Example 1, instead of the agar powder, konjac flour was used.
A gel was produced under the same conditions except that 2.0 wt% was used.

The obtained gel is water-insoluble as in Example 1. In addition, a fine mesh structure having a mesh width of 2 to 3 μm was uniformly distributed over the whole.

Comparative Example 1 A gel was produced in the same manner as in Example 1, except that the agar powder was not used.

The obtained gel was insoluble in water, but the mesh having a mesh structure having a mesh width of 1 to 30 μm was randomly distributed widely and was nonuniform. The mesh structure is shown in FIG.

Example 4 Degree of saponification 99.85 in a disinfected autoclave with a volume of 42.
Mol%, PVA 14.5 wt% with viscosity average degree of polymerization 1750, agar powder
0.5 wt% and distilled water 85.0 wt% were added. Then 121
After stirring and mixing at 30 ° C. and a pressure of 1.2 kg / cm ² for 30 minutes, the mixture was left for 20 minutes. When the temperature reached 40 ° C after standing, 50 wt% of cells of the genus Methanobacteria were added and mixed. In addition, the above-mentioned bacterial cells were phenol 0.125 wt in advance from the bacterial cells separated from the anaerobic sludge.
The culture medium was used for acclimation and culture, and the culture solution was centrifuged.

30 cm x 40 cm x 0.7 cm (vertical x horizontal x
(Depth) box, and stored in a freezer with a decompression device, cooled at -35 ° C and frozen. After freezing, the pressure was reduced to 0.1 mmHg and dehydration was performed to obtain a gel in which cells were embedded. The cross-sectional view of the gel is shown in FIG.
Shown in the figure. As is clear from FIG. 3, the bacterial cells were uniformly embedded in the fine mesh structure. About 0.7 cm of the gel
A bioreactor was manufactured by cutting into a cube shape of × 0.7 cm × 0.7 × cm (vertical × horizontal × height), and filling this into a cylinder having a diameter of 15 cm and a height of 70 cm. Wastewater from an oil refinery having a phenol concentration of 300 mg / and a COD concentration of 550 mg / was passed through the bioreactor at a space velocity (SV) of 0.5 at room temperature. 1
After 0 days, the phenol concentration and COD concentration of the purified water on the outlet side were measured.
The D concentration was reduced to 50 mg /, and it was found that the organic substances in the wastewater were purified.

After 30 days, 0.1w of nutrient source (including phosphorus, sodium, magnesium salt and yeast extract) is added to the wastewater.
t% was mixed and distributed. Next, after 120 days, when the phenol concentration and COD concentration of the outlet side purified water were measured,
The phenol concentration was about 0.1 mg /, and the COD concentration was 50 mg /, and no reduction in the purification activity due to bacterial cells was observed, indicating that this is an extremely superior purification method.

Comparative Example 2 A bioreactor was prepared in the same manner as in Example 4 except that agar powder was not added during gel production. Distilled water was circulated in the bioreactor prepared in Example 4 and the bioreactor to which the agar powder was not added under the same conditions at a space velocity (SV) = 0.7 to measure the concentration of leaked cells at the outlet. As a result, the outlet cell concentration after 50 hours was about 4 in the case of Example 4.
The amount was 10 mg / l or less, whereas about 100 mg / leakage was large when agar powder was not added. It was almost the same after 140 hours. From the above, it was found that the cells were not sufficiently immobilized and embedded without the addition of agar.

Example 5 A bioreactor was prepared in the same manner as in Example 5 except that the agar powder was replaced with 0.5% by weight of carrageenan at the time of gel production, and waste water from an oil refinery with a phenol concentration of 500 mg / and a COD concentration of 1000 mg / was used. Distributed. After 10 days, the phenol concentration and COD concentration of the outlet side purified water were measured, and it was found that the phenol concentration was reduced to about 1 mg / and the COD concentration was reduced to 130 mg /, and the organic substances in the wastewater were purified. Even after 120 days, the phenol concentration was about 1 mg.
/, COD concentration was about 150 mg /, and no reduction in purification activity was observed, indicating that this is an excellent purification method.

[Brief description of drawings]

FIG. 1 is an enlarged view of a frozen fractured surface of a PVA high water content gel, and FIG. 2 is an enlarged view of a frozen fractured surface of a PVA high water content gel containing no agar powder. Further, FIG. 3 is an enlarged view of a freeze-fractured section of a highly water-containing gel containing microorganisms.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C08L 29/04 LGS C12N 11/04 (56) References JP-A-61-100193 (JP, A) JP-A-57-141292 (JP, A)

Claims (3)

[Claims] 1. An aqueous solution containing (i) 5 to 25 wt% of polyvinyl alcohol having a saponification degree of 95 mol% or more and a viscosity average polymerization degree of 1,500 or more and (ii) a polysaccharide of 0.01 to 5 wt% is heated and then cooled. Then, a polyvinyl alcohol high water content gel having a uniform fine network structure having a mesh width of 2 to 3 μm, which is obtained by repeating freeze-dehydration or freeze-thawing. 2. An aqueous solution containing (i) 5 to 25 wt% of polyvinyl alcohol having a saponification degree of 95 mol% or more and a viscosity average polymerization degree of 1,500 or more and (ii) a polysaccharide of 0.01 to 5 wt% is heated and then cooled. Then, (iii) microorganisms were added and obtained by repeating freezing / dehydration or freezing / thawing,
A highly hydrous gel containing microorganisms, which has a uniform fine mesh structure having a mesh width of 2 to 3 μm. 3. An aqueous solution containing (i) 5 to 25 wt% of polyvinyl alcohol having a saponification degree of 95 mol% or more and a viscosity average polymerization degree of 1,500 or more and (ii) a polysaccharide of 0.01 to 5 wt% is heated and then cooled. Then, (iii) microorganisms were added and obtained by repeating freezing / dehydration or freezing / thawing,
A method for purifying organic matter-containing wastewater, which comprises contacting an organic matter-containing wastewater with a microorganism-embedded highly hydrous gel having a uniform fine network structure having a mesh width of 2 to 3 μm to remove the organic matter.