JPH05192132A - Reaction method for immobilized microorganism - Google Patents

Abstract

PURPOSE:To accomplish treatment with immobilized microorganisms economically in high efficiency by contact with a reactive substrate of such immobilized microorganisms obtained by dehydrating at a specified temperature microorganisms either cultured or collected from the natural world followed by drying. CONSTITUTION:Microorganisms selected from bacteria representing aerobic microorganism treatment sludge such as activated sludge (e.g. Aerobacter), acidic bacteria representing anaerobic bacteria treatment sludge such as for methane fermentation, and methanogen (methane bacteria), are dehydrated at <=70 deg.C and dried in a solid form to obtain immobilized microbial cells with a water content of <=85wt.%. Thence, the microbial cells are cut or ground to uniformize granular size into immobilized microorganisms 1-5mm in granular diameter. A reactor is then packed with the microorganisms at a specified packing rate followed by introducing a reactive substrate such as synthetic effluent into the reactor to effect reaction while feeding air to treat the effluent, thus giving desired treated water.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a biological reaction method using immobilized microorganisms. When the present invention is applied to a water treatment technique, for example, the water treatment operation can be simplified and the cell density can be remarkably increased, resulting in highly efficient water treatment.

2. Description of the Related Art Immobilized microorganisms used in biological reaction methods have hitherto been microorganisms or sludge composed of microorganisms,
It was prepared by a method of adsorbing and immobilizing it on the surface of a particle carrier such as zeolite or anthracite, or a method of entrapping and immobilizing bacterial cells with a gel such as polyacrylamide, polyvinyl alcohol, agar, and galagenan.

However, in the former method of adsorption and immobilization, it is difficult to control the adsorption amount of microorganisms or sludge composed of microorganisms, and the effective volume of the reactor is reduced by the volume of the carrier itself. Therefore, it is difficult for the immobilized microorganisms to efficiently react with the substrate. In the latter gel encapsulation method, the treatment procedure for immobilization is complicated, the cost of the gel agent is high, and there is no example adopted on a real scale in the field of water treatment. Therefore, the present inventors have aimed to develop an economical and highly efficient biological reaction method, and based on water treatment technology, have a high concentration of microorganisms which dramatically increases the treatment rate of a bioreactor as compared with the conventional method. As a result of research on the immobilization method, microorganisms collected from culture or the natural world were dehydrated at a temperature of 70 ° C or lower, and dried in a fixed shape to have a moisture content of 85%.
When the water was prepared in the following manner and the water in the intercellular spaces was substantially removed, the cells were fixedly bound to each other, and the fixed cells contacted the reaction solution and absorbed water, causing swelling, but fixing after swelling. The present invention has been completed by finding that the morphology is maintained and the activity is maintained.

The present invention will be described in more detail below. In the present invention, a microorganism that can be immobilized is a microorganism that has been collected from culture or nature and does not require any specialized microorganism. Moreover, it is not necessary that the microorganisms are purely separated, and examples thereof include mixed microorganisms, activated sludge, methane fermentation sludge, and the like. Specific examples include the following microorganisms. Bacteria that compose aerobic microbial-treated sludge such as activated sludge: Achromobacter, Aerobacter, Alcaligenes, Bacillus, Previva bacterium, Corynebacterium, Comamonas, Flavobacterium, Micrococcus, Pseudomonas, Spirillam, Zugrea, Arsulo Bactor, Nitrosomonas, Staphylococcus, Nocardia, Sphaerotils, Escherichia, Azotobacter, etc. Fungi: Penicillium, Cephalosporum, Cladosporium, Fusarium, Trichoderma, Candida, Rhodotorula, Saccharomyces, etc. Bacteria that compose sludge treated with anaerobic microorganisms such as methane fermentation: (Acid-producing bacteria) Corynebacterium, Lactobacillus,
Actinomyces, bihidobacteria, lamybacteria, eubacteria, clostridia, bacteroides, vibrio, spirillum, peptococcus, fusobacterium, sphaerophorus, veronea etc. (Methane-producing bacterium) Methanobacterium, Methanosarcina, methanospirillum, methanoslix, methanococcus Immobilization treatment is usually performed by dehydration at a temperature of 70 ° C or lower, and drying treatment in a solid form. It is for promoting drying and is determined according to the temperature tolerance of the target microorganism. For example, the activity of methane-oxidizing bacteria having excellent heat resistance can be maintained even at a high treatment temperature, but in this case as well, it is desirable that the temperature is about 70 ° C or lower. Dehydration, drying, and particle formation are appropriately performed. For example, after dehydrating sedimentation concentrated microorganisms or sludge with a filter press or the like, the solid form is dried at a predetermined temperature and then pulverized to obtain a particulate immobilized product. You can In addition, the dehydrated product can be semi-dried in an appropriately solid form, then cut by a cutter or the like to be granulated, and then further dried to increase the immobilization strength. In order to increase the immobilization strength, it is desirable that the water content of the treated cells be sufficiently dried until the water content in the cell spaces is exhausted, but the water content in the cell spaces should be 85% or less. And the cells are dried until they are fixed and immobilized. For the fixation and fixation of microbial cells, a wide variety of substances produced outside the microbial cells during the growth of the microorganisms, particularly polysaccharides, proteins, glycoproteins, are prepared by adjusting the water content of the microorganisms to about 85% or less in the solid form. It is considered that this is because the polymer substance such as is dehydrated and dried, and is denatured, and the bond strength between cells is increased. in this way,
The extracellular product of the microorganism serves as a kind of binder to fix and immobilize the cells, and then the immobilized cells are cut or pulverized to adjust the particle size. The particle size can be arbitrarily selected depending on the reaction conditions, but when the particle size becomes extremely large, the reaction rate decreases due to diffusion resistance.
Therefore, it is usually desirable that the particle size after swelling is about 1 mm to 5 mm. In this way, once immobilized, the bacterial cells have sufficient strength even if they contact the reaction solution and swell, and can be subjected to the reaction without being micronized even with general aeration and stirring means. It is possible. Therefore, in the reaction, it can be used in exactly the same manner as conventional comprehensively immobilized cells.
For example, in an anaerobic treatment method, it can be used as a reactor which is packed in a column or the like and flows the reaction solution in an upward flow. Further, in the aerobic treatment method, a method of adding the immobilized microorganisms of the present invention to a treatment tank having a precipitation portion in the upper portion of the reaction tank and aerating and fluidizing it, or providing a ventilation portion and a filling portion separately,
It can be used for a method of circulating and treating a reaction solution. Further, since the bacterial cell concentration is fixed and immobilized between the bacterial cells as compared with the entrapped immobilized bacterial cells, it is possible to prepare an immobilized bacterial cell having a bacterial cell concentration several times higher. Hereinafter, an example of a method for preparing the immobilized microorganism used in the present invention and an experimental example for the activity of the immobilized microorganism will be shown.

[Experimental Example 1] -Method for preparing immobilized microorganisms-According to the present invention, it is possible to immobilize any of microorganisms cultured or collected from the natural world. The method for preparing immobilized microorganisms when activated sludge and methane fermentation sludge are used as the immobilized objects is described. Activated sludge is glucose 1 g / l, polypeptone 0.5 g / l, KH ₂ PO
₄ Synthetic wastewater with pH 7 consisting of 0.088 g / l (BOD
A concentration of about 10,000 mg / l) and a BOD load of 0.
What was cultured by the batch method at 5 kg / m ² · day was used. Sludge mixed solution 51 with sludge concentration of 1,000 mg / l
Was dehydrated with a filter paper, and then the dehydrated sludge was spread on the filter paper to a thickness of about 5 mm and air-dried at 25 ° C., 50 ° C. and 100 ° C. and used for the immobilization strength test. Methane fermentation sludge is glucose 35g / l, corn steep liquor 35g / l, K ₂
HPO ₄ 3 g / l, KH ₂ PO ₄ 2 g / l, (N
_{H 4) 2 CO 2 · H} 2 O 5g / l, Na 2 CO 3 3
Synthetic wastewater (organic matter concentration of 50,000 mg / l) consisting of g / l and FeCl ₃ .6H ₂ O 1 g / l was used, and the one that was cultured by the batch method at an organic matter load of 0.5 kg / m ² · day was used. After the sludge mixed solution 51 having a sludge concentration of 10,000 mg / l was centrifuged and dehydrated with filter paper, the dehydrated sludge was spread on the filter paper to a thickness of about 5 mm, 25 ° C, 40 ° C,
It was air-dried at 70 ° C and 100 ° C and used for the immobilization strength test. The relationship between the water content and the immobilization strength after swelling was examined for 25 ° C dried sludge. In this case, the water content is 50%
In the above case, it is cut into about 0.5 mm to 2 mm with a cutter, swollen with tap water, and has a water content of 10%.
For the measurement of 5% and 5%, after sludge having a water content of about 50% was cut into 0.1 mm to 1 mm by a cutter, it was further dried to a predetermined water content, and then swollen with tap water and subjected to the test. .. The sludge may be cut or pulverized in a semi-dried state and then dried, or after dried. As shown in Tables 1 and 2, the effect of immobilization did not appear due to dehydration in sludge having a water content of more than 85%, but the effect of immobilization came to appear when the water content was 85% or less, When it was 50% or less, an extremely stable immobilized product was obtained. Next, the influence of the temperature during the drying treatment on the immobilization strength was examined. 25 for activated sludge
25 ℃ for methane fermentation sludge at ℃, 50 ℃, 100 ℃
Water content of 6 ℃ at 40 ℃, 70 ℃, 100 ℃
After drying to less than 10%, it was swollen with tap water. Since all of the sludges have sufficient immobilization strength against aeration and agitation, it can be seen that the temperature during the drying treatment hardly affects the immobilization strength.

[Table 1]

[Table 2]

[Experimental Example 2] -Activity of immobilized microorganisms-Of the immobilized microorganisms prepared in Example 1, activated sludge was 25 ° C, 50 ° C, and 100 ° C, and methane-fermented sludge was 25 ° C. ℃, 40 ℃, 70 ℃, 1
After sludge sufficiently dried at 00 ° C. was cut and swelled so as to have a particle size after swelling of 2 mm or less and swelled, the treatment activity of the synthetic wastewater used for sludge culture was examined. As shown in Table 3, the activated sludge dried at 100 ° C. completely lost its activity, but the sludge dried at 25 ° C. had a moisture content of only 6% after drying. Regardless of the original activity of 50 after swelling
It retains about% activity. The apparent sludge concentration after swelling of the dried and immobilized sludge was 150,000 mg / l, which was 15 times the original activated sludge concentration (10,000 mg / l), so the maximum treatment activity per reaction volume was 7 times. That is all. Also, when dried at 50 ° C, the activity is greatly reduced to about 20% of the original sludge, but the maximum treatment activity is 3 times or more that of normal sludge because the sludge concentration can still be high. .. Next, Table 4 shows the results of the methane fermentation sludge. When it is dried at 25 ° C, it maintains the same level of 55% activity as activated sludge, and the sludge concentration after swelling is as high as 160,000 mg / l.
Compared to the original methane fermentation sludge (concentration 10,000 mg / l), the maximum treatment activity per reactor volume is 8 times or more. The methane-fermented sludge remains slightly active even after drying at 70 ° C, but loses its activity when dried at 100 ° C, like activated sludge. From the above results, it is necessary to perform the drying treatment at a temperature of at least 70 ° C or less, preferably 25 ° C.
It is better to carry out at a relatively low temperature. But 0
Freeze-drying at or below ℃ is not a good idea because it reduces the concentration of microorganisms after swelling.

[Table 3]

[Table 4] Hereinafter, the present invention will be described in detail with reference to examples.

[Examples] Immobilized activated sludge prepared in Experimental Example 1 (dried at 25 ° C., water content 6%, particle size after adjustment 0.5 to 2)
mm) in a reactor having a capacity of 100 ml shown in FIG. 1, a filling rate of 30%, and a sludge concentration of 50,000 mg / l per reactor.
Then, a treatment test of the synthetic wastewater for activated sludge shown in Experimental Example 1 was conducted at a temperature of 25 ° C. In the treatment test, first aeration was stopped once a day (aeration volume 5 vvm), the immobilized sludge was allowed to settle, 50 ml of the supernatant (treated water) was withdrawn, and 50 ml of synthetic wastewater was newly added.
d Draw method. After that, Fill and Dr
The number of aws was increased from once to twice, three times a day, and the progress of the treatment was observed. The added BOD is 2 to
It took about 10 minutes or less to remove 90% or more in 3 days. Thereafter, the number of times of Fill and Draw was increased per day to increase the load, but stable treatment results were obtained even at a BOD volume load of 5 kg / m ² · day 10 times per day. This value is 10 for a standard activated sludge BOD volume load of 0.5 kg / m ² · day.
It will be about double. Such a treatment test was conducted for about 3 months, but the form of the immobilized sludge could be used without breaking. In the PVA gel entrapping fixation of sludge or microorganisms, the maximum concentration of immobilized sludge is about 50,000 mg.
It is considered that the stable and stable BOD load range is as low as about 1/3 of the present method and about ^{2 to 3} kg / m ² · day. Next, the immobilized methane fermentation sludge (25 ° C.) prepared in Experimental Example 1 was used.
(Drying, water content 5%, swelling granules 0.5-2 mm)
In a 100 ml capacity reactor shown in FIG.
%, The sludge concentration per reactor was 64,000 mg / l, and the temperature was 35 ° C., the methane fermentation sludge synthetic wastewater 5 times diluted wastewater (organic matter concentration 10, 0
A treatment test was carried out at a concentration of 00 mg / l and a TOC concentration of about 4,000 mg / l). The treatment test was performed by an upflow treatment method in which waste water was supplied from the lower part of the reactor and treated water was discharged from the upper part of the reactor. The liquid in the reaction vessel was circulated at an upward flow rate of about 10 cm / min in order to prevent flow channeling. As a result, the packed fixed sludge bed expanded from 40% to 80% of the packing ratio, and a good upflow stirring state could be obtained. First, load organic matter at 1 kg / m ²
・ When set to day and gradually increasing the load while observing the process progress, the organic load was 20 kg / m ² · day.
The TOC removal rate was about 80%. This is a normal methane fermentation processing rate of 2-3 kg / m ² · d
It has a speed that is an order of magnitude higher than that of ay and has the highest treatment speed at present. Upflow anaerobic sludge bed (UA
It showed the same speed as the SB) method. Considering that UASB has a narrow stable range, etc., this method can be said to be an extremely effective processing method.

INDUSTRIAL APPLICABILITY The present invention provides an economical and highly efficient biological reaction method, and when it is applied to, for example, water treatment, an immobilized bacterial cell having a bacterial cell concentration several times higher than that of the conventional comprehensive immobilization method is obtained. The obtained BOD can be processed at a high load.

[Brief description of drawings]

FIG. 1 shows an activated sludge treatment reactor, and FIG. 2 shows a methane fermentation treatment reactor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoo Suzuki, 1-3-1, Higashi 1-3, Tsukuba, Ibaraki Prefecture

Claims (1)

[Claims] 1. An immobilized microorganism obtained by dehydrating a microorganism collected from culture or the natural world at a temperature of about 70 ° C. or lower, drying it in a solid form and adjusting the water content to 85% or less. A biological reaction method comprising contacting with a substrate.