JPH05130867A - Biocatalyst-immobilized gel - Google Patents

Abstract

PURPOSE:To simultaneously perform an aerobic reaction and an anaerobic reaction for the simplification of water clarification, etc., by employing a biocatalyst-immobilized gel consisting mainly of polyvinyl alcohol in which aerobic bacteria are immobilized at the neighborhoods of the surface and in which anaerobic bacteria are immobilized at the neighborhoods of the center. CONSTITUTION:An aerobic reaction and an anaerobic reaction are simultaneously carried out in the presence of a biocatalyst-immobilized gel for the treatment of waste water, the clarification of culture water, etc. The biocatalyst- immobilized gel is produced by immobilizing aerobic bacteria in the neighborhoods of the surface of a gel and immobilizing anaerobic bacteria in the neighborhoods of the center. The gel comprises polyvinyl alcohol therein having a point having the shortest distance of >=2mm between the point and the surface.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biocatalyst-immobilized gel containing polyvinyl alcohol as a main component, which is useful for biocatalytic reactions of both aerobic reaction and anaerobic reaction. The gel of the present invention can be used for general water purification, such as wastewater treatment, ornamental fish tank purification, and culture water purification.

[0002]

2. Description of the Related Art In recent years, studies have been carried out to immobilize biocatalysts such as enzymes and microorganisms and efficiently utilize their functions.
Some have been put to practical use. One of the methods for immobilizing the biocatalyst is the entrapping immobilization method in which the biocatalyst is wrapped as it is using a polymer material, and agar, alginate, carrageenan, polyacrylamide are commonly used polymer materials for this method. , Polyvinyl alcohol, and photo-curable resin. Of these, polyvinyl alcohol (hereinafter PV
It is known that hydrous gel (sometimes abbreviated as A) can be used as an excellent immobilization carrier by incorporating a biocatalyst. Conventionally, PVA gels have a spherical shape with a diameter of less than 4 mm or a side of 4 m in order to increase the active surface area.
Dice less than m have been used.

[0003]

In conventional spherical PVA gels having a diameter of less than 4 mm, when used in an aerobic reaction, oxygen permeates to the center of the gel, so that it is impossible to carry out an anaerobic reaction in the same gel. Yes, if an anaerobic reaction is to be used together, a separate reaction tank must be provided. For example,
In the removal of nitrogen in wastewater treatment, removal of ammonia nitrogen (nitrification) requires aerobic reaction using nitrifying bacteria, and removal of nitrate nitrogen (denitrification) requires anaerobic reaction using denitrifying bacteria. Therefore, it is difficult to make the device compact. INDUSTRIAL APPLICABILITY The present invention solves the above problems, and since it is possible to perform aerobic reaction and anaerobic reaction which were impossible in the past in one reactor, it greatly contributes to downsizing of the device. be able to.

[0004]

[Means for Solving the Problems] In order to solve the above problems, as a result of extensive studies, the shortest distance to the surface is 2 mm.
Completed the present invention to find a biocatalyst-immobilized gel containing polyvinyl alcohol as a main component, which has the above points inside the gel, aerobic bacteria are fixed near the surface, and anaerobic bacteria are fixed near the center. Came to let me. If the gel has at least one point where the shortest distance to the surface is 2 mm or more, preferably 2.5 mm or more, an anaerobic region appears near the center of the gel, and the gel is near the surface of the gel. Expresses an aerobic region, resulting in a biocatalyst-immobilized gel having both aerobic and anaerobic properties. On the other hand, the shortest distance from all points inside the gel to the surface is 2m.
If it is less than m, if the vicinity of the gel surface is an aerobic environment,
Oxygen also permeates near the center of the gel, and as a result, the whole becomes aerobic. If the gel has a point where the shortest distance to the gel surface is 2 mm or more, the shape of the gel is spherical,
There is no particular limitation such as dice, fiber, sheet, and tube. The PVA used in the present invention has an average degree of polymerization of 1000 or more, preferably 1700 or more, and a saponification degree of 98.5 mol% or more, preferably a saponification degree of 99.85 mol% or more. It is preferable for the formation of Further, as the PVA of the present invention, various known modified PVA can be used as long as the object of the present invention is not impaired. The concentration of the PVA aqueous solution when molding the gel is P
From the range of gel forming ability containing VA as a main component, 1 to 40% by weight is preferable, and the higher the PVA concentration is, the stronger the gel can be obtained. Lower PVA concentrations are advantageous. A water-soluble polymer polysaccharide such as sodium alginate may be used at the time of gel formation. Further, to the aqueous solution of PVA, a reinforcing agent for improving the strength of the culture medium of the microorganism or the immobilized carrier, a filler for adjusting the specific gravity of the produced gel, etc. are added within a range that does not inhibit the gelation of PVA. May be.

Various methods have been considered as the method of molding the gel, and the following two methods are mentioned. PV
The aqueous solution A is frozen at −5 ° C. or lower, preferably −10 ° C. or lower, kept for at least 1 hour or longer, preferably 10 hours or longer, and then thawed. At least one freezing and thawing operation
Repeat more than once, preferably twice or more. The aqueous PVA solution is brought into contact with an aqueous solution containing a substance having a syneresis action of PVA, for example, an aqueous sodium sulfate solution. The concentration of the sodium sulfate aqueous solution is preferably 100 mg / liter (hereinafter abbreviated as mg / l) or more, and more preferably a saturated aqueous solution. Immersion time is 10 minutes or more, preferably 3
0 minutes or more is preferable. In order to carry out the aerobic reaction and anaerobic reaction more efficiently using the gel of the present invention, it is preferable to use a gel on which microorganisms have been immobilized in advance.
The microorganism to be fixed may be an aerobic bacterium or an anaerobic bacterium. When the aerobic bacteria are fixed in advance, the vicinity of the central part becomes anaerobic, so that the anaerobic bacteria later grow near the central part. When anaerobic bacteria are fixed in advance, the vicinity of the surface becomes aerobic, so that the aerobic bacteria later grow near the surface. In either case, finally, the structure is such that aerobic bacteria are fixed near the surface and anaerobic bacteria are fixed near the center. PV obtained in this way
The gel containing A as a main component can simultaneously perform two reactions, an aerobic reaction and an anaerobic reaction, in one reactor.

[0006]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Example 1 PVA (average polymerization degree: 1740, saponification degree: 99.85 mol%) manufactured by Kuraray Co., Ltd. was washed with warm water at 40 ° C. for about 1 hour, and then water was added to PVA so that the PVA concentration became 16% by weight. In addition, the total amount was adjusted to 400 g and the pH was adjusted to 6. This was treated in an autoclave at 120 ° C. for 30 minutes to dissolve PVA and then allowed to cool to room temperature. To this PVA aqueous solution, 200 g of a 4% by weight sodium alginate aqueous solution was added and mixed, and then collected from the wastewater treatment tank of the Kuraray Okayama Plant (1-2-1, Kaigandori, Okayama City, Okayama Prefecture) and concentrated. Activated sludge obtained by applying [MLSS 80000 (m
g / l)] was added, and the mixture was thoroughly stirred. This mixed solution was fed at a rate of 1 ml / min by a roller pump using one vinyl tube having an inner diameter of 4 mmφ and stirred with a stirrer to give 0.5 mol / liter of calcium chloride (CaCl 2).
↓ 2) The solution was dropped into the aqueous solution from a height of 30 cm on the surface. The dropped liquid droplets immediately spheroidized and settled in the CaCl ↓ 2 aqueous solution. Spheroidized PVA-based gel is Ca
Separated from Cl ↓ 2 aqueous solution, lightly washed with distilled water,
After freezing in a freezer at 20 ° C. for 24 hours, it was thawed at room temperature. Further, this freezing and thawing operation was repeated twice. This gave an opaque brown flexible spherical gel. This gel is formed into a spherical shape and is not sticky. The particle size was 5 to 5.5 mmφ. A gel containing PVA, on which the bacterium is immobilized, obtained by the above method as a main component,
The cells in the gel were cultured by immersing them in an activated sludge aeration tank at Kuraray Okayama Plant for 10 days. 500 g of the gel after culturing and the untreated water discharged from the Kuraray Okayama Plant are TOC (Tot
al Organic Carbon) value 100 (mg
/ L) and 5 liters of drainage liquid with the ammonia nitrogen concentration adjusted to 50 (mg / l) were placed in a test aeration tank for aeration. Figure 1 shows TOC, ammonia nitrogen concentration, and nitrite / nitrate nitrogen concentration. As the TOC and ammonia nitrogen concentrations decrease with the passage of time, it can be seen that aerobic bacteria are working. Further, since the nitrite / nitrate nitrogen concentration was initially increased and then decreased, it can be seen that the nitrite / nitrate nitrogen generated by the oxidation of ammonia nitrogen was denitrified by the anaerobic bacterium. After observing the cross section of the gel after the experiment, it was found that aerobic microorganisms were present in the area up to about 1.5 mm from the surface and anaerobic microorganisms were present in the center.

Comparative Example 1 PVA was used as a main component in the same manner as in Example 1 except that PVA added with activated sludge and an aqueous solution of sodium alginate were dropped into a CaCl ↓ 2 aqueous solution at a rate of 1 ml / min from an injection needle having an inner diameter of 1 mmφ. A spherical gel was obtained. The gel was not tacky and had a particle size of 2.5-3 mmφ.
The obtained PVA gel on which the bacteria were fixed was immersed in an activated sludge aeration tank of Kuraray Okayama Plant for 10 days to culture the cells in the gel. 500 g of the gel after culturing and the untreated water discharged from the Kuraray Okayama Plant are combined with TOC (Total Org).
An aic carbon value of 100 (mg / l) and 5 liters of drainage liquid having an ammoniacal nitrogen concentration adjusted to 50 (mg / l) were placed in a test aeration tank for aeration. Figure 2 TO
C, ammonia nitrogen concentration, nitrous acid / nitrate nitrogen concentration are shown. Since TOC and ammonia nitrogen concentration decrease with the passage of time, it can be seen that aerobic bacteria are working. On the other hand, since the nitrite and nitrate nitrogen concentrations continue to rise, it indicates that anaerobic bacteria did not work and denitrification did not proceed. After observing the cross section of the gel after the experiment, it was found that aerobic microorganisms were present up to the center of the gel.

[0008]

The gel containing PVA as the main component of the present invention is
Due to the structure in which aerobic bacteria are fixed near the surface and anaerobic bacteria are fixed near the center, it is possible to perform biocatalytic reactions of both anaerobic reaction and aerobic reaction by using only one reactor. It can be carried out at the same time, and the practical application of the reaction by the biocatalyst is promoted in a wide range.

[Brief description of drawings]

FIG. 1 shows TOC (◯), ammoniacal nitrogen concentration (□), and nitrous acid / nitrate nitrogen concentration (Δ) in Example 1.

FIG. 2 shows TOC (◯), ammoniacal nitrogen concentration (□), and nitrous acid / nitrate nitrogen concentration (Δ) in Comparative Example 1.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C02F 3/30 B 7158-4D 3/34 101 D 7158-4D

Claims (2)

[Claims] 1. A gel having a point that the shortest distance to the surface is 2 mm or more, and aerobic bacteria are fixed near the surface,
A biocatalyst-immobilized gel whose main component is polyvinyl alcohol in which anaerobic bacteria are immobilized near the center. 2. A living body characterized by performing an aerobic reaction and an anaerobic reaction at the same time by using a gel whose main component is polyvinyl alcohol having a point having a shortest distance to the surface of 2 mm or more inside the gel. Reaction method by catalyst.