JP2000254697A - Treatment of organic waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method of organic waste, which performs high efficient and effective methane fermentation of night soil or sludge and is suitable for the methane fermentation of the night soil or the sludge with garbage or the like mixed. SOLUTION: This treating method includes a process of adding a lytic enzyme into the night soil or the sludge and after pretreating at 20-80 deg.C under an aerobic atmosphere, treating with the methane fermentation. And the treating method includes also a process of treating with the methane fermentation after pretrearting the night soil or the sludge with a lytic enzyme producing bacteria under the same condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for treating organic waste widely including night soil, septic tank sludge, sewage sludge, livestock wastewater sludge, and kitchen waste such as garbage and fish ash. The present invention relates to a method for treating organic waste, which enables effective methane fermentation of night soil and sludge, and is particularly useful when methane fermentation is performed by mixing it with kitchen waste such as garbage.

[0002]

2. Description of the Related Art Techniques for methane fermentation of organic wastes such as night soil and sludge have been conventionally known. However, there are few examples in which these methane fermentation technologies have been put to practical use, and they are used only for some treatments such as sewage. In recent years, from the viewpoint of effective use of resources, a resource recovery method for generating methane gas after mixing and treating sludge of human waste processing and kitchen garbage such as garbage and fish in a conventional human waste processing plant has been desired. . The treatment plant having such a system is called a sludge regeneration treatment center because its function is greatly different from that of a conventional human waste treatment plant.
Such a sludge regeneration treatment center is not limited to the conventional methane fermentation technology for sewage and wastewater treatment, but in the night soil sludge treatment, it mixes kitchen garbage such as raw garbage and fish ash to ferment methane. New technology is required.
As a processing technique for organic wastes such as sludge and kitchen waste, there is a method of performing methane fermentation on sludge and garbage in the same processing. In this method, human waste sludge, sewage sludge, etc., and garbage are treated almost simultaneously from the beginning to the end of the treatment, and methane fermentation is performed.

However, such a method has a problem in that the decomposition rate of sludge and the like is low, and the conversion rate of methane gas from organic waste such as sludge is about 30%. Generally, sludge is hardly decomposed and hardly decomposes to methane. Therefore, when sludge and garbage are to be treated, in order to increase the amount of methane gas generated, it is necessary to increase the decomposition rate of waste such as sludge, and to form sludge into methane gas as easily as possible. There is a need. On the other hand, kitchen garbage such as garbage can be relatively easily converted into methane gas.
This is disadvantageous in terms of energy and is not preferable from the viewpoint of resource efficiency. Also, depending on the mixing ratio of sludge and kitchen garbage, due to the difference in characteristics leading to each methane fermentation, fine adjustment may be required, and when mainly garbage and other easily decomposable components are mainly used, For example, problems such as rancidity due to the production of organic acids in a methane fermentation tank were also likely to occur.

[0004] On the other hand, as a sewage treatment system that does not generate sludge, a technique of adding a highly thermophilic microorganism to sewage sludge is known. However, a technique for efficiently methane fermenting human waste and sludge has not been sufficiently studied, and a technique capable of effectively performing methane fermentation on hardly decomposable sludge is desired.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the present inventors have found that in treating organic waste, human waste and sludge can be methane fermented with high efficiency and efficiency and mixed with garbage and the like. Intensive study to develop an organic waste treatment method suitable for methane fermentation treatment. As a result, the present inventors have found that such a problem can be solved by causing a lytic enzyme or a lytic enzyme-producing bacterium to act under specific conditions before the methane fermentation treatment of night soil or sludge. Was. The present invention has been completed from such a viewpoint.

[0006]

That is, the present invention relates to human waste or sludge (including waste consisting of human waste and sludge).
The present invention provides a method for treating organic waste, comprising adding a lytic enzyme to a solution, pretreating the solution in an aerobic atmosphere at a temperature of 20 to 80 ° C., and then treating the solution by methane fermentation. Here, after performing the above pretreatment, mixed with kitchen garbage,
It is effective to treat this mixture by methane fermentation. According to this method, even when kitchen garbage such as garbage and sludge are to be treated, the decomposition rate of waste such as sludge can be increased. Can be raised. And
The temperature is usually 20 to 80 ° C, preferably 40 to 70 ° C.
° C, and it is preferable to forcibly introduce air to obtain an aerobic atmosphere. The pH is preferably in the range of 4 to 10.

[0007] The present invention also relates to a method of pre-treating human waste or sludge using a lytic enzyme-producing bacterium placed in an aerobic atmosphere at a temperature of 20 to 80 ° C, followed by methane fermentation. An object of the present invention is to provide a method for treating organic waste. Also in this case, it is effective to mix the garbage with the garbage after performing the above-mentioned pretreatment, and to treat this mixture by methane fermentation, and effective methane fermentation is possible. The temperature is preferably 40 to 70 ° C., and it is preferable to forcibly introduce air in order to obtain an aerobic atmosphere. The pH is preferably in the range of 4 to 10.
And fermented sludge (digested sludge) after the above methane fermentation
It is preferable to return a part of the wastewater to the preceding stage of the pretreatment and mix it with human waste or sludge. This is because the fermented sludge after methane fermentation contains lytic enzyme-producing bacteria, so that the bacteria can start growing rapidly using the returned recycled liquid.

Further, in the method for treating organic waste according to the present invention, a lytic enzyme is added to night soil or sludge, and the temperature is adjusted to 20 ° C.
Pretreatment is performed in an aerobic atmosphere at ~ 80 ° C, and pretreatment is performed using a lytic enzyme-producing bacterium placed in an aerobic atmosphere at a temperature of 20 to 80 ° C, followed by methane fermentation. There are also aspects. Also in this embodiment, it is preferable that a part of the fermented sludge after the methane fermentation is returned to the pre-treatment stage and mixed with human waste and sludge.

[0009] The hardly decomposable components in the organic waste are human waste and sludge, the main components of which are microorganisms. Therefore, a lytic enzyme that is an enzyme that dissolves the cell membrane is allowed to act on these hardly degradable microorganisms, or a microorganism that produces an enzyme that dissolves the cell membrane (a lytic enzyme-producing bacterium) is acted on. This makes it easier for microorganisms to dissolve in the liquid and to break down into methane. FIG. 3 schematically shows how the hardly decomposable microorganisms, such as sludge, are solubilized. In the treatment method of the present invention, hardly decomposable night soil and sludge are pre-treated, and kitchen garbage such as garbage is directly led to the methane fermentation process together with the pre-treated sludge. As a pretreatment method for sludge or the like, there is a method in which the above-mentioned "lytic enzyme" or "a bacteriolytic enzyme-producing bacterium that dissolves sludge or the like" acts. When a lytic enzyme is used, it is performed by adding an enzyme such as cellulase or amylase. When a bacteriolytic enzyme-producing bacterium is used, the bacterium is produced by introducing sludge or the like into an environment in which the producing bacterium easily grows in a pretreatment tank.

According to the present invention, it is possible to efficiently perform methane fermentation on hardly decomposable organic waste such as sludge.
If garbage is mixed with sludge after pretreatment, and the mixture is treated for methane fermentation, resources can be efficiently recovered, and waste is saved with less energy. Can handle things.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, specific embodiments of the method for treating organic waste according to the present invention will be described in detail. FIG. 1 schematically shows the steps of the embodiment performed in the present invention. In the embodiment (No. 1), the lytic enzyme 1 is used.
Is added in the pretreatment, and the embodiment (No. 2)
Is an embodiment in which the fermented sludge 4 is reused so that a lytic enzyme-producing bacterium exists in the pretreatment stage instead of the addition of the lytic enzyme 1, and the embodiment (No. 3) combines the above-described aspects. In this embodiment, the addition of the lytic enzyme 1 and the presence of the producing bacterium are performed at the same time.

Embodiment (1) In this embodiment, a lysing enzyme is added to night soil and / or sludge, and pretreatment is performed in an aerobic atmosphere at a temperature of 20 to 80 ° C. Mixed with kitchen waste such as garbage,
This mixture is processed by methane fermentation. Pretreatment is performed by dissolving the cell membrane of microorganisms, which are the main components of sludge, by the action of lytic enzymes. Representative lytic enzymes include α-amylase, proteinase, cellulase, α-glucosidase, lysozyme, and the like.
FIG. 4 shows the results obtained by measuring the solubilization rate with respect to time for each lytic enzyme. Although the final solubilization rate is slightly different for each enzyme, there is a solubilizing effect of about 40 to 60%. Therefore, by using these lytic enzymes, excess sludge can be dissolved, and by using it for pretreatment, methane fermentation treatment becomes easy.

The temperature for the pretreatment using a lytic enzyme is usually 20 to 80 ° C, preferably 40 to 70 ° C. If the temperature is higher than 80 ° C., it is not preferable because inconveniences such as damage to the enzyme itself may occur. Conversely, if the temperature is lower than 20 ° C., the enzyme becomes inactive and a sufficient dissolving effect is not exerted. Absent. FIG. 5 shows the solubilization rate of α-amylase, which is a kind of lytic enzyme, as a function of temperature. From this figure, it can be confirmed that the lytic enzyme works sufficiently in the above temperature range.

The pretreatment environment is preferably an aerobic atmosphere, and a mode in which air is forcibly added to a pretreatment tank or the like is preferred. Then, when performing the pretreatment, since it is preferable that the action of the lytic enzyme is an active environment,
The pH of the liquid such as sludge is preferably about 4 to 10. In the pretreatment stage, the above lytic enzyme is preferably added in the range of 0.01 to 10 g, particularly preferably in the range of 0.1 to 1 g, per kg of night soil or sludge. It is also possible to select a plurality of enzymes from the above lytic enzymes and use them in the pretreatment in any combination, for example, α-amylase and proteinase,
It can also be added in a combination of α-amylase and cellulase, or proteinase and cellulase.

Embodiment (Part 2) In this embodiment, night soil and / or sludge are pretreated using a lytic enzyme-producing bacterium placed in an aerobic atmosphere at a temperature of 20 to 80 ° C. After that, it is mixed with kitchen garbage, and this mixture is treated by methane fermentation. And
It is effective to return a part of the digested sludge after the methane fermentation to a stage before the pretreatment and mix it with human waste or sludge or both.

A lytic enzyme-producing bacterium refers to a microorganism that produces an enzyme that dissolves the cell membrane. Examples of the enzyme include the lytic enzymes α-amylase, proteinase, cellulase, α-glucosidase, and lysozyme. . The lytic enzyme producing bacterium used in the present invention is not particularly limited as long as it has the ability to produce the lytic enzyme as described above, and is widely used regardless of the type of the bacterium. Can be. Specifically, for example, Bacillus subtilis IFO14140 (α-amylase producing bacterium), Bacillus subtilis (Bacillus subtili)
s) IFO3007 (α-amylase producing bacterium), Pseudomonas ialdinosa IFO3080 (proteinase producing bacterium), Streptomyces glicias IFO13
689 (bacteriolytic enzyme producing bacterium), Thermomonospora fasca IFO 14071 (cellulase producing bacterium) and the like.

By culturing a microorganism producing such a lytic enzyme, a solubilizing effect on sludge and the like is exhibited. For example, when the solubilization rate with respect to time is measured for Bacillus and Pseudomonas among the above lytic enzyme-producing bacteria, the results are as shown in FIG. The final solubilization rate is slightly different for each enzyme, but is about 20-40.
% Solubilizing effect. Therefore, by using these lytic enzyme-producing bacteria, excess sludge can be dissolved, and methane fermentation can be easily performed by using it for pretreatment.

When pretreating with a lytic enzyme-producing bacterium, it is important to create an environment in which the cells can easily grow.
And the temperature condition is usually 20 to 80 ° C, preferably 40 to 70 ° C. If the temperature exceeds 80 ° C., it is not preferable because inconveniences such as damage of the cells themselves may occur. Conversely, if the temperature is lower than 20 ° C., the enzyme becomes inactive and a sufficient lysis effect is not exhibited. Not preferred.

The pretreatment environment is preferably an aerobic atmosphere, and a mode in which air is forcibly added to a pretreatment tank or the like is preferred. This is because all microorganisms are aerobic. When performing the pretreatment, the pH in the pretreatment tank is adjusted to 5 from the viewpoint of promoting the culture of the cells.
It is preferably about 9 to about 9. The lytic enzyme-producing bacterium as described above is preferably present in the pretreatment tank in the range of 0.5 to 10 g, and particularly preferably in the range of 2 to 5 g, per 1 kg of the liquid fed.

It is also possible to select a plurality of cells from the above lytic enzyme-producing bacteria and use them in any combination in the pretreatment. And Streptomyces IFO1368
9. Bacillus IFO14140 and Pseudomonas IFO
A combination of 3080 and Streptomyces IFO13689 can also be present in the pretreatment tank.

In the present embodiment, a lysing enzyme-producing bacterium may be added one after another in the pretreatment step. It can be returned to the pretreatment tank and reused (recycled). This is because lytic enzyme-producing bacteria are present in the methane fermentation liquor and are used as seeds. Since the methane fermentation liquor contains production bacteria, the use of such a recycle liquor causes rapid growth. Therefore, in this embodiment, the fermented sludge treated using the production bacteria is returned, and the pretreatment is performed again with new sludge and the like. Requires less.

Embodiment (Part 3) In this embodiment, a lytic enzyme is added to night soil or sludge or both, and pretreatment is performed in an aerobic atmosphere at a temperature of 20 to 80 ° C. After pretreatment with a lytic enzyme-producing bacterium placed in an aerobic atmosphere at ８０80 ° C., the mixture is mixed with kitchen waste and the mixture is treated by methane fermentation. Then, as in the above embodiment (No. 2), it is effective to return a part of the fermented sludge after methane fermentation to the stage before the pretreatment and mix it with human waste or sludge or both.

This embodiment is a mode in which the above-described embodiments (Part 1) and (Part 2) are combined, and the lytic enzyme and the lytic enzyme-producing bacterium used in each of them are the same as those described above. Used. Hereinafter, experiments for confirming the action of the lytic enzyme and the lytic enzyme-producing bacterium used in the present invention will be described as examples, but the present invention is not limited to these examples.

[0024]

EXAMPLES Example 1 With respect to a lytic enzyme effective for solubilizing sludge, the solubilizing effect of the pretreatment was confirmed as follows. (1) Selection of bacteriolytic enzyme The following enzymes having a bacteriolytic action on surplus sludge were selected. As the reaction conditions, the optimal p
The conditions were H and temperature. Α-amylase (pH 5.0, temperature 70 ° C.), proteinase (pH 9.0, temperature 37 ° C.), cellulase (pH 5.0, temperature 40 ° C.), α-glucosidase (pH 7.2, temperature 40 ° C.) ), Lysozyme (pH 9.0, temperature 35 ° C.) The values in parentheses indicate the pH conditions and temperature conditions performed for each enzyme.

(2) Confirmation of the solubilization function of the selected lytic enzyme The experiment was carried out in a culture volume of 6.0 ml, a culturing time of about 7 hours, an enzyme concentration of 100 mg / l, and a human waste excess sludge concentration of 2000 mg / l.
1) The enzyme solution was mixed at a mixing ratio of 50%. Five kinds of the above lytic enzymes were selected from the microbial composition of the excess sludge from human waste, and the presence or absence of the effect was examined. As a result, as shown in FIG. 4, when compared with the value after 6 hours when the solubilization rate was almost constant, the cellulase and the thermostable α-amylase showed high solubilization rates. Here, the solubilization ratio is a value calculated by dividing the difference between the value of the initial absorbance and the value of the absorbance after a certain period of time by the value of the initial absorbance.

The high solubilization rate due to the thermostable α-amylase may be due to the reaction temperature range of 70 ° C. and the effect of heat treatment. Carried out. The result is shown in FIG.
From these results, it was found that solubilization treatment was possible in these temperature ranges.

Example 2 A lytic enzyme producing bacterium producing a lytic enzyme effective for solubilizing sludge was confirmed for its solubilizing effect in the pretreatment as follows. (1) Selection of strains producing lytic enzyme-producing bacteria From Example 1 described above, the following microorganisms that produce enzymes that are considered to have a lytic effect on excess sludge were selected.・ Bacteria to be solubilized: Bacillus subtilus
subtilis) IFO14140 (α-amylase producing bacterium), Bacillus subtilis I
FO3007 (α-amylase producing bacterium), Pseudomonus aeruginosa IFO3
080 (proteinase-producing bacterium), ・ Bacteriolytic enzyme-producing bacterium: Streptomyces glicias
(Streptomyces griseus) IFO13689, ・ Thermomonospora fusc
a) IFO14071 (cellulase producing bacterium)

(2) Confirmation of the solubilization function of the selected production bacteria The experiment was performed using a culture volume of 0.40 l, a culture time of about 14 hours,
H7, culture temperature 30 ° C. (standard medium conditions), lytic enzyme-producing bacteria addition rate 50% (v / v), and the production bacteria were added by using the supernatant of the lytic enzyme-producing bacteria culture solution for buffering the cells to be solubilized. Performed by mixing into the suspension. And α
-The effect of solubilizing enzymes produced by amylase, cellulase and complex lytic enzyme-producing bacteria was examined. FIG. 6 shows an example of the results obtained when a test for the bacteriolysis effect was performed using cells to be solubilized (Bacillus and Pseudomonas) which are considered to constitute excess human waste sludge. Streptomyces griseus, a lytic enzyme-producing bacterium
It was confirmed that the cells to be solubilized were solubilized by the lytic action of IFO13689.

Next, human waste excess sludge (concentration: 2000 mg)
/ L), the enzyme produced by each lytic enzyme-producing bacterium was added, and the solubilizing effect was examined. As a result, the proteinase lytic enzyme produced by Pseudomonus aeruginosa IFO3080 showed a high solubilization rate, and the effect on excess human sludge was confirmed. The solubilization rates of the enzymes produced by the lytic enzyme-producing bacteria were as follows.・ Bacillus subtilis IFO
14140 (α-amylase producing bacterium): solubilization rate 2
6.9% ・ Pseudomonus aeruginosa
inosa) IFO 3080 (proteinase-producing bacterium): 53.5% solubilization rate ・ Streptomyces gris
eus) IFO13689 (bacteriolytic enzyme-producing bacterium): solubilization rate 16.3%,

[0030]

As described above, according to the treatment method of the present invention, the lytic enzyme or the lytic enzyme-producing bacterium dissolves and decomposes the hardly decomposable sludge (mainly microorganisms) to form methane fermentation. Becomes easier. And, since it is possible to make methane fermentation of night soil and sludge effectively, it is particularly useful when mixing with kitchen garbage and the like to perform methane fermentation. In the mixing treatment of sludge and garbage, methane generation is remarkable. As a result, resources can be efficiently recovered, and waste can be advantageously treated with little waste in terms of energy.

[Brief description of the drawings]

FIG. 1 is a process diagram schematically showing an example of a method for treating organic waste according to the present invention.

FIG. 2 is a diagram illustrating an example of a process assumed when the method for treating organic waste according to the present invention is performed.

FIG. 3 is a diagram schematically illustrating a state in which a hardly degradable microorganism, which is a main component of sludge, is solubilized.

FIG. 4 is a diagram plotting the solubilization rate versus time for each lytic enzyme. In the figure, Δ indicates α-amylase, □ indicates proteinase, ● indicates cellulase, ○ indicates α-glucosidase, and Δ indicates lysozyme.

FIG. 5 is a diagram plotting the solubilization rate versus time for the lytic enzyme α-amylase. In the figure, ■
Indicates a value at 37 ° C., □ indicates a value at 50 ° C., and ● indicates a value at 70 ° C.

FIG. 6 is a diagram plotting the solubilization rate versus time for a lytic enzyme produced by a producing bacterium.
In the figure, ○ indicates a value for Bacillus IFO 3007, and ● indicates a value for Pseudomonus IFO 3080.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lytic enzyme 2 Air 3 Garbage (garbage) 4 Fermented sludge 5 Dehydration sludge 6 Treated water 7 Methane fermentation tank 8 Persistent microorganism 9 Cell membrane

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 3/34 B09B 3/00 D 11/02 ZABC (72) Inventor Tomoaki Omura Kanazawa-ku, Yokohama-shi, Kanagawa 1-8-1, Sachiura Mitsubishi Heavy Industries, Ltd. Basic Technology Research Laboratory (72) Inventor Takao Hashizume 12 Nishikicho, Naka-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Heavy Industries, Ltd. Yokohama Works F-term (reference) 4D004 AA02 AA03 AA04 AC04 BA03 CA18 CA19 CA20 CB04 CC02 DA02 DA06 4D040 AA12 DD03 4D059 AA01 AA02 AA03 AA07 BA03 BA12 BA21 BA22 BA26 BA31 BA48 BK12 BK13 EB06

Claims (5)

[Claims] (1) adding a lytic enzyme to human waste or sludge,
A method for treating organic waste, comprising: performing a pretreatment in an aerobic atmosphere at a temperature of 20 to 80 ° C, followed by a methane fermentation. 2. Excreting human waste or sludge at a temperature of 20 to 80 ° C.
A method for treating organic waste, comprising: performing a pretreatment using a lytic enzyme-producing bacterium placed in an aerobic atmosphere, followed by methane fermentation. 3. A lysing enzyme is added to night soil or sludge,
The pretreatment is performed in an aerobic atmosphere at a temperature of 20 to 80 ° C, and the pretreatment is performed using a lytic enzyme-producing bacterium placed in an aerobic atmosphere at a temperature of 20 to 80 ° C. A method for treating organic waste, comprising treating. 4. After performing the above pretreatment, mixing with kitchen garbage,
The method for treating organic waste according to any one of claims 1 to 3, wherein the mixture is treated by methane fermentation. 5. The organic waste according to claim 2, wherein a part of the fermented sludge after the methane fermentation is returned to a stage preceding the pretreatment and mixed with human waste or sludge. Processing method.