JPH0999298A - Treatment of sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the maintenance cost and safety of the treatment by forming an enzyme(s) capable of decomposing organic matter in sludge to solubilize suspended solid in the sludge and/or degrade it into lower molecular weight substances and to digest the sludge. SOLUTION: In this treatment, one part or all of sludge and/or microorganisms having sludge decomposing enzyme formation activity are thrown into an enzyme formation tank 1 and a liquid contg. an enzyme(s) formed from the microorganisms by cultivating them is transferred to a solubilization tank 2. If there is the other part of the sludge which is not thrown into the enzyme formation tank 1, this part of the sludge can be added to the solubilization tank 2. The sludge is solubilized and/or degraded into lower molecular weight substances in the solubilization tank 2 and thereafter, the resulting mixed liquid is supplied to a digestion tank 3 placed next to the solubilization tank 2 and when the digestion of the mixed liquid is completed, the digestion product can be discarded as a liquid and a gas. Thus, the total residence time required for the treatments in the solubilization tank 2 and digestion tank 3 can be reduced and therefore, the objective treatment can rapidly be completed and further, is excellent in cost and safety because the need of using large amounts of expensive or dangerous chemical agents is eliminated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for digesting sludge, and more specifically to organic sludge, for example, raw sludge and surplus sludge discharged from a sewage treatment process such as a sewage treatment plant and a human waste treatment plant. The present invention relates to a treatment method and treatment apparatus for biological sludge by biological digestion of organic high-concentration sludge discharged from wastewater treatment processes such as food factories and chemical factories.

[0002]

2. Description of the Related Art Conventionally, in order to dispose of the above-mentioned organic sludge, the contained organic components are biologically treated by an aerobic digestion method or an anaerobic methane fermentation method.
The method of digesting to gas components such as carbon dioxide and methane is adopted. In this method, treated sludge containing excess sludge consisting of microbial biomass generated by biological digestion and undigested residual sludge is subjected to solid-liquid separation in a sedimentation tank, etc., liquid components are appropriately drained, and excess sludge suspended. Solids will usually be disposed of by land or ocean dumping. However, dumping such excess sludge also leads to environmental destruction, and in recent years, when the need for global environmental protection is recognized, it is almost prohibited. is there.

Therefore, solid matter is solubilized and / or reduced in molecular weight physically, chemically or biologically by various methods or in combination, and then digested anaerobically or aerobically. Methods have been devised. When this solubilization and / or depolymerization cannot be carried out under the same conditions as in the usual digestion stage, a separate solubilization tank is provided and the treatment is carried out therein.

The physical method for solubilizing and / or lowering the molecular weight is, first, thermal decomposition. For example, there is a method of raising the temperature in the tank to 60 to 100 ° C. Although it requires a certain amount of energy to warm,
The efficiency of solubilization achieved is extremely low, about 20 to 30% of organic matter, and is not an effective means. Further, the so-called Ziemann process, in which the pressure is applied in addition to the temperature increase up to about 250 ° C., can be adopted as a more effective means. However, in order to raise the temperature to such a high temperature, a large amount of energy is required, and not only a considerably high cost is required to establish a system that can withstand high-pressure processing, but also the operation is complicated. I can't prohibit becoming. Furthermore, in order to crush the cell walls of microorganisms in sludge, a method has been proposed in which a solubilization is achieved by applying a mill, ultrasonic waves, or the like to make the solid matter fine, for example, JP-A-2-2112.
No. 99 discloses such a technique. It takes time to crush a large amount of sludge using specific equipment and devices.
It is not preferable for practical use in terms of cost and complexity of operation.

Next, as a chemical method, for example, a treatment method using a chemical such as hot alkali or acid can be mentioned. Japanese Patent Application Laid-Open No. 2-277597 discloses a technique in which mineral acid is added to sludge after aerobic biological treatment to bring the pH to 2.5 or lower and the organic matter is solubilized under a temperature condition of 50 ° C. or higher. In addition, JP-A-5-34
In No. 5200, organic sludge was first adjusted to pH 7.3-9.2 and
After solubilizing at ~ 100 ° C, a method of anaerobic digestion treatment is further disclosed in JP-A-6-99199, in which the first set sludge is subjected to alkaline anaerobic treatment at room temperature, and excess sludge is alkalinized at 50 to 100 ° C. A method for treating and treating both organic sludges collectively for anaerobic digestion is described. It seems that these methods achieve quite good solubilization, but the cost of chemicals and heating, safety issues for workers, and the waste liquid is strongly acidic or strongly basic. Ideal for practical use at a large-scale level because of the environmental problems associated with the disposal of large amounts of these substances and the additional cost of reagents required for pH adjustment as a post-treatment. It's hard to say how.

A biological solubilization method is, for example, a method of solubilizing a solid component by decomposing a protein contained in sludge into a low molecular weight by using an enzyme such as a protease. is there. After heat treating the excess sludge,
It has been reported that the solubilization rate after digestion for 5 days at various temperatures in acid fermentation system with various enzymes added (Ministry of Construction, "Development of new wastewater treatment system utilizing biotechnology, report Book (Sewer), pages 312-320, 1991, 2
It is shown that the highest solubilization rate is obtained by acid fermentation at 70 ° C using a protease alone as an enzyme. This reaction is carried out under relatively mild conditions,
Although it is considered preferable from the viewpoint of safety, it is practically difficult to apply such an enzyme to a large-scale treatment because it is quite expensive, and various enzymes that can be applied depending on various characteristics of the enzyme used. Since the conditions are severely limited and the operation tends to be complicated, it cannot be said to be preferable for practical use.

Further, as a biological method, a method for treating a yeast extract residue using a yeast lytic enzyme-producing bacterium is disclosed in Japanese Patent Laid-Open No.
18640. This invention includes Oerskophia (Oerskophia), which is a high-yielding bacterium of YLase (yeast lysing enzyme).
It is disclosed that YCW (yeast extract residue) solubilization is achieved using a culture solution of via sp. E24). Since the organic sludge and the yeast extract residue have substantially different compositions and the like, even if such a method is applied to the organic sludge, the same effect is unlikely.

[0008]

As described above, in the present technical field, it is possible to efficiently solubilize and / or reduce the molecular weight of a suspending solid substance in sludge containing an organic substance, which enables a more rapid digestion treatment. Up to now, no treatment device excellent in terms of treatment method, maintenance cost, and safety has been proposed. The present invention has been made in view of the current situation,
It is an object of the present invention to provide the following method and device.

[0009]

Means for Solving the Problems The present invention has been accomplished as a result of earnest studies for achieving the above-mentioned object in the prior art in a method for digesting sludge containing organic matter. Is characterized by.

That is, the present invention is a method of biologically digesting sludge containing organic matter, which comprises an enzyme production step for obtaining an enzyme for decomposing organic matter in sludge, and a suspended solid matter in sludge. Digestion treatment of sludge, which comprises a solubilization step for solubilization and / or depolymerization, and a digestion step for digesting sludge after solubilization and / or depolymerization of suspended solids. Provide a way.

Furthermore, the present invention also provides a method for digesting and treating sludge, which has the following features.

The enzyme obtained in the enzyme production step is used in the solubilization step.

The enzyme producing step includes various organic waste liquids or sludge suspensions as raw materials for the reaction for producing the enzyme.

The enzyme production step includes a sludge suspension obtained from the solubilization step and / or the digestion step or a supernatant thereof as a raw material for the reaction for producing the enzyme.

In the enzyme producing step, a microorganism having a sludge-decomposing enzyme producing activity obtained from another separation source is cultured, and the obtained enzyme is used in the solubilizing step.

After the solubilization step and / or the digestion step, a solid-liquid separation step of sludge suspension is further included, and the liquid supernatant obtained by the separation step is used as a raw material for the enzyme production reaction in the enzyme production step. The microorganisms used and contained in the supernatant are cultured in the enzyme production step.

The enzyme production step is performed under a temperature range of 50 to 90 ° C.

The sludge containing organic matter is sewage surplus sludge.

The microorganism having sludge-degrading enzyme-forming activity is a microorganism obtained by aerobically or anaerobically culturing sewage surplus sludge at 50 to 90 ° C.

The microorganism having sludge-degrading enzyme-forming activity is a microorganism obtained by aerobically culturing sewage surplus sludge at 60 to 70 ° C.

The microorganism having sludge-degrading enzyme-forming activity is a thermophilic microorganism separated from compost, for example, horse manure compost.

The present invention is also a digestion treatment apparatus used for biologically digesting sludge containing organic matter, which is an enzyme production tank for obtaining an enzyme capable of decomposing organic matter in sludge, A solubilization tank connected downstream of the enzyme production tank for solubilizing and / or depolymerizing suspended solids in sludge, and a suspended solid material connected downstream of the solubilization tank Disclosed is a digestion treatment apparatus including a digestion tank for digesting sludge after solubilization and / or molecular weight reduction.

As a raw material for the enzyme production reaction in the enzyme production tank, a suspension of various organic waste liquids or sludge, or a suspension or supernatant of sludge from the solubilization or digestion tank is used; A microorganism contained in a suspension or a supernatant and / or a microorganism having a sludge-degrading enzyme-forming activity obtained from another separation source is cultured in the enzyme-producing tank, and the obtained enzyme is obtained in the solubilizing tank. Further comprising means for solid-liquid separation of the sludge suspension after treatment in the solubilization tank and / or digestion tank; and the liquid supernatant obtained by the separation means is the enzyme. There is further provided a sludge digestion treatment device which is used as a raw material for an enzyme production reaction in a production tank and in which microorganisms contained in the supernatant are cultured in the enzyme production tank.

That is, the present inventors utilize microorganisms such as thermophiles which produce enzymes capable of decomposing organic matter in sludge during digestion of sludge containing organic matter such as raw sludge and surplus sludge. As a result, it was found that the solubilization / and / or lowering of the molecular weight of suspended solids in sludge and the subsequent digestion can be achieved sufficiently efficiently, and the present invention has been completed. According to the present invention, unlike the method conventionally used in the technical field, a microorganism having a sludge-degrading enzyme-forming activity is cultured in an independent tank, and the sludge-degrading enzyme is produced by the microorganism. Solubilization of sludge using an organic substance decomposition reaction by such an enzyme, by subsequently performing a digestion step, the residence time required for the treatment in the solubilization tank and the digestion tank can be reduced to enable rapid completion of the treatment, It is possible to reduce the volume of the solubilization tank, the reaction is performed under relatively mild conditions, and in addition, it is not necessary to use a large amount of expensive or dangerous reagents, so that the cost, An excellent processing method is provided in terms of safety.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1, 2, 3 and 4 are schematic views of steps for carrying out the present invention.

In the enzyme production process of the present invention, as shown in FIGS. 1 to 4, an independent enzyme production tank is provided separately from the solubilization and digestion processes described below, and the growth of microorganisms and the enzyme This is accomplished by culturing the microorganism under conditions that optimize secretion.

As the starting material in the enzyme production step,
Biological sludge, for example, excess sludge or compost discharged from a sewage treatment process such as a sewage treatment plant or a human waste treatment plant can be used. In addition, organic waste liquid or treated water flowing into the treatment facility, or a suspension or supernatant of excess sludge discharged from the treatment facility, and further a suspension obtained after solubilizing and / or digesting the sludge or upper Clarity can be utilized. Considering the efficiency of enzyme production and the convenience of its utilization, the supernatant obtained after solubilizing and / or digesting the sludge is preferable as a starting material for enzyme production.

As a solid-liquid separation method for obtaining this supernatant from a solid suspension, various methods such as precipitation in a precipitation tank, filtration including membrane separation, and centrifugation are possible, but are particularly expensive. The method by precipitation in the precipitation tank is the most preferable because it does not require any special equipment or labor.

Further, it is advisable to add an appropriate microorganism capable of solubilizing sludge, such as compost bacterium or digestive bacterium, to the enzyme production tank and grow it to efficiently produce the enzyme. Among these microorganisms, a thermophilic bacterium belonging to the genus Bacillus , which secretes the sludge solubilizing enzyme to the outside of the bacterial cell, is preferable. Examples of this bacterium include microorganisms obtained by aerobically or anaerobically culturing sewage excess sludge at 50 to 90 ° C, for example, sewage excess sludge aerobic at 60 to 70 ° C. Microorganisms obtained by culturing can be used. Further, Gram-positive long bacilli isolated from compost, for example, horse feces compost, which are thermophilic microorganisms and have protease and amylase activity are also preferably used in the enzyme production of the present invention.

The culture solution of the microorganism is yeast extract (DIFC
O-) 2 g and peptone (DIFCO) 4 g dissolved in 1 L of tap water, yeast-peptone medium or Nutr
Medium such as ient broth (manufactured by DIFCO) or supernatant of excess sludge from sewage treatment plant (1,000 to 10,000 as VM)
(ppm) etc., the enzyme can be produced more efficiently and rapidly.

The temperature for culturing the microorganism for producing the enzyme depends on the kind of the microorganism to be cultivated and the kind of raw material to be used. It should be set appropriately in consideration of the stability of the obtained enzyme. For example, as is clear from FIG. 5, when a certain microorganism having a high protease-producing activity is cultured in yeast-peptone medium,
It grows well when it is carried out at a temperature range of 70 ° C., and this temperature range is preferable from the viewpoint of the growth rate of microorganisms, the rate of enzyme secretion, and the stability of the obtained enzyme. Of the culture
From the viewpoint of both the growth rate of microorganisms and the rate of enzyme secretion, it is preferable that the pH is near neutral. However, it goes without saying that the optimum culture conditions should be determined depending on the type of the microorganism to be cultured.

The pH can be adjusted by appropriately adding a base such as sodium hydroxide or calcium hydroxide or an acid such as hydrochloric acid or sulfuric acid.

The culturing time should be appropriately selected according to the concentration of the microorganisms contained in the reaction tank and the amount of the added organic substance, but in general, even if the culturing is carried out for 12 hours or more, the enzyme can be more efficiently used. Therefore, the culture is preferably 3
~ 12 hours, more preferably 5-8 hours.

Culturing is carried out under normal pressure, preferably aerobically, and anaerobically depending on the type of microorganism to be cultured,
It is good to do it with stirring. Stirring is performed by providing a normal stirring device in the enzyme production tank.

The sludge-degrading enzyme obtained in the enzyme production tank means an enzyme capable of decomposing organic matter in sludge, which includes a proteolytic enzyme or protease (eg trypsin), a lipolytic enzyme (eg lipase) and a carbohydrate. Examples include, but are not limited to, degrading enzymes (eg amylase).

In the solubilization step in the method of the present invention, the enzyme obtained in the enzyme production step is responsible for lowering the sludge's molecular weight and decomposing reaction, thereby achieving solubilization. The solubilization is performed by appropriately selecting the conditions suitable for the enzymatic reaction. In particular,
It is operated in a temperature range of 50 to 90 ° C, preferably 60 to 70 ° C. The pH in the solubilization tank is preferably operated under neutral conditions. In addition, in order to adjust the pH value to an appropriate value, the acid or base as described above is appropriately added and adjusted. The solubilization time should be selected according to the degradability, concentration, etc. of the sludge to be solubilized, but is preferably 12 to 48 hours, most preferably about 24 hours. The solubilization may be carried out under normal pressure with stirring so that the organic substance to be reduced in molecular weight and decomposed by the enzyme and the enzyme are sufficiently mixed and contacted. Stirring can be performed by providing an ordinary stirring device in the tank. The reaction may be carried out anaerobically or aerobically, and in the case of aerobic reaction, a reaction tank equipped with an aeration device can be adopted.

The digestion step in the present invention is operated in a temperature range of 10 to 50 ° C., preferably 35 to 40 ° C. In addition, the pH in the digestion tank is preferably set to a neutral condition. In order to adjust the pH value to an appropriate value, an acid or a base is appropriately added and adjusted as described above. The digestion time should be appropriately selected depending on the degradability and concentration of the organic substance, but is preferably 3 to 48 hours, more preferably 6 to 24 hours. The digestion reaction is performed under normal pressure with stirring. Stirring can be performed by providing an ordinary stirring device in the digestion tank. As described above, the reaction environment in the enzyme production tank should be selected aerobic or anaerobic depending on the type of the microorganism that produces the enzyme, but the reaction in the solubilization tank and the digestion tank is anaerobic in terms of energy consumption. It is more advantageous to do this.

The structure of the reaction tank such as the enzyme production tank, the solubilization tank and the digestion tank used in the present invention is not particularly limited, and in the tank for performing aerobic reaction, aeration means and stirring means, The tank for carrying out the anaerobic reaction may be one provided with a stirring means or the like. These reaction vessels can be used in either a batch type or a continuous type.

A typical embodiment of the method of the present invention consisting essentially of three steps is shown in FIGS.

In the embodiment shown in FIG. 1, a part or all of sludge and / or a microorganism having a sludge-degrading enzyme-forming activity is put into the enzyme-producing tank 1, and a liquid containing an enzyme produced from the microorganism by culturing is solubilized in the solubilizing tank. Move to 2. The solubilization tank 2 can contain the remaining portion of the sludge, if any. After being solubilized and / or depolymerized in the solubilization tank 2, the obtained mixed liquid is supplied to the next digestion tank 3 and, when digestion is completed, it can be discarded as a liquid or a gas.

Next, in the embodiment of FIG. 2, the mixed solution after circulating the embodiment of the present invention shown in FIG. 1, that is, after the digestion treatment, is returned to the enzyme production tank 1 to start the enzyme production. Repeat each step as material and raw material. The use of such a circulation system is expected to improve the processing efficiency, shorten the processing time, and reduce the volume of the processing apparatus.

In the embodiment shown in FIG. 3, the solubilization step in the embodiment shown in FIG. 2 is added to the precipitation step in the precipitation tank 4, and the supernatant obtained here is used for enzyme production. The undecomposed sludge used in the solubilization step is returned to the solubilization tank 2 and again subjected to the solubilization reaction, whereby the decomposition rate can be improved. Further, the liquid containing the microorganism after the digestion step can also be used in the enzyme production tank.

Finally, FIG. 4, which shows the most preferred embodiment of the present invention, is the one in which, in addition to the embodiment described in FIG. 3, a treatment step in the precipitation tank 4b is further added after the enzyme production step, The supernatant containing the enzyme obtained in the precipitation step is used in the solubilization tank 2, and the precipitate containing the bacterial cells of the enzyme-producing bacteria is returned to the enzyme-producing tank 1 and reused as the enzyme source. Alternatively, it is added to the solubilization tank 2 together with the supernatant. As a result, the microorganisms can be concentrated in the enzyme production tank 1, the enzyme production rate can be increased, and thus excellent treatment efficiency can be obtained. Also in this embodiment, a precipitation tank 4 is provided next to the solubilization step, the supernatant obtained here is used for enzyme production, and undecomposed sludge is returned to the solubilization tank 2 to carry out the solubilization reaction again. To serve. Further, the liquid containing the microorganism after the digestion step can also be used in the enzyme production tank.

However, the present invention is not limited to these embodiments as a matter of course, and the order of carrying out the steps, the number of repetitions, etc., is such that the enzyme obtained in the enzyme production step plays a role in the solubilization step. It can be variously modified as long as possible. It should also be noted that a solid-liquid separation step can be added as appropriate.

In this way, when digesting sludge containing organic matter such as raw sludge and excess sludge, it is secreted from the sludge-derived microorganisms to be treated and / or separately isolated microorganisms such as thermophiles. It has been used in the art for a long time in order to efficiently solubilize and / or reduce the molecular weight of suspended solids in sludge and subsequent digestion by utilizing an organic matter decomposition reaction by a sludge-degrading enzyme. Unlike the method that has been done, the sludge degrading enzyme is produced by culturing the above-mentioned microorganism in an independent enzyme production tank,
By solubilizing sludge using such an enzyme and then performing a digestion process, the residence time required for the treatment in the solubilization tank and the digestion tank is reduced, which enables rapid completion of the treatment, and also the solubilization tank. It is also possible to reduce the volume of
In addition, the reaction is performed under relatively mild conditions, and it is not necessary to use a large amount of expensive reagents or dangerous reagents, so that a method excellent in cost and safety is provided.

[0047]

Example 1 Microorganisms having a sludge-degrading enzyme-forming activity were separated by the following method.

Excess sludge from a sewage treatment plant was cultivated at 70 ° C. for one year or more, a culture solution was appropriately diluted with sterilized water, the diluted solution was spread on a standard agar medium, and cultured in a constant temperature bath at 70 ° C. for 24 hours. .

Each of the formed colonies was subcultured twice.

Excess sludge from sewage treatment plant (about 10,000 p
agar medium containing 1% pm) was inoculated with each isolate and
After culturing at ℃ for 24 hours, formation of sludge dissolution spots was observed.

Here, in order to examine the enzyme-producing ability of the microorganisms found to form sludge-dissolving spots, 1
Bacteria were cultivated in surplus sludge supernatant from a sewage treatment plant sterilized for 5 minutes and yeast-peptone medium (manufactured by DIFCO), and the culture supernatant was collected with a micropipettor over time, and the protease activity was quantified. did. The culture was carried out at 70 ° C. at pH 7.0 with shaking at about 100 rpm.

The protease activity was quantified according to the following method. That is, azochol (trade name, manufactured by Sigma), which is a substrate for non-specific protease assay, was added to pH 7.
To 0.7 ml of a solution (5 mg / ml) suspended in 0 phosphate buffer,
An equal amount of sample was added and incubated at 70 ° C for 30 minutes. After the reaction was completed, the absorbance at 520 nm was measured. Trypsin (about 400 BAEE U / mg, Wako Pure Chemical Industries, Ltd.)
(30 μg / ml) in phosphate buffer solution (pH 7.0) was measured in the same manner, and the absorbance at 520 nm was 1.0.

The obtained results are shown in FIG. 6 (cultured in the sludge supernatant).
7 and FIG. 7 (cultured in yeast-peptone medium).
As is clear from the figure, it was suggested that the isolated microorganism produced a protease under all conditions and secreted it outside the cell.

Reference Example 1 A commercially available enzyme was used to examine the degradability of organic sludge. Enzymes are Samoases PC10 and Protin AC10 (Daiwa Kasei Co., Ltd.)
Manufactured by Wako Pure Chemical Industries, Ltd.)
And α-amylase (manufactured by Wako Pure Chemical Industries, Ltd.) were used. As the sludge to be tested, surplus sludge derived from a sewage treatment plant was heat-treated at 121 ° C. for 15 minutes in advance and washed with sterilized water. By such heat treatment, it is possible to eliminate the effect of thermal decomposition that may occur due to heating during the decomposition reaction, and it is possible to accurately quantify the enzymatic decomposition reaction.

This sterilized washed sludge was diluted to 1% with sterilized water, and each enzyme was added to 50 ml so as to be 0.1 w / v%.
After the pH was adjusted to 7.5, the solubilization reaction was performed at the optimum temperature of each enzyme while shaking at about 60 rpm. Solubilized samples were collected over time, the organic solid (vss) content was measured, and the solubilized rate (%) at each time was calculated based on the following formula.

[0056]

[Equation 1]

The measurement of vss was performed according to JIS K0102.

As a result, about 30% of protease, about 25% of lipase and about 20% of amylase were achieved, showing that the protease has remarkable sludge solubilizing ability.

Example 2 About 8 g / l of horse manure collected from the high temperature part of horse manure compost was used.
It is added to the sludge derived from the sewage treatment plant so that the amount of solid sludge is about 4 kg · ss / m ³ / d, and excess sludge is added at 70 ° C.
Bacteria were separated from the culture broth that had been acclimatized for a year according to the method described in Example 1, and two thermophilic bacteria A and B having high protease-producing activity were separated therefrom.

All of the bacteria were grown on standard agar at 70 ° C.
After culturing for 24 hours, colonies were formed, and it was revealed that they were Gram-positive long rods.

The protease activity of the culture solution and culture supernatant of each bacterium was measured by the method described in Example 1. As a result, as shown in Table 1, high enzyme activity was observed in both the culture solution and the culture supernatant. .

The sterilization excess sludge was decomposed using these two types of bacteria according to the method of Reference Example 1, and vss was measured to determine the solubilization rate. All the bacteria were aerobically cultivated in a yeast-peptone medium in a constant temperature bath at 70 ° C. for 24 hours, and added at a ratio of 5 v / v% to sludge. further,
The solubilization rate was similarly examined for the culture supernatant of each bacterium. The culture supernatant was used in the same amount as the sterilized washed sludge for the solubilization reaction.

The results are shown in Table 1 below.

[0064]

[Table 1]

Since both thermophiles A and B have a sludge solubilizing ability and can be solubilized even by using the culture supernatant, both thermophiles secrete the sludge-degrading enzyme outside the body. , It was suggested that sludge was decomposed by these enzymes.

Example 3 A jacket-type stainless steel reaction tank having an effective volume of 10 L was used as an enzyme production tank, and after inoculating the enzyme-producing bacterium into 5 L of yeast-peptone medium, it was kept at 70 ° C. for about 5 hours for about 0.4 hours. Enzyme production was performed by batch culture with aeration at the VVM rate. Here, as enzyme-producing bacteria, sewage surplus sludge was
5 v / v% using culture solution aerobically cultivated at ℃ for 10 days
Was inoculated into the medium at a ratio of. After completion of the enzyme production reaction,
The culture solution was allowed to stand and 1 L of the supernatant was taken out and put into a solubilization tank together with 1 L of surplus sludge derived from a sewage treatment plant, and the solubilization reaction was carried out anaerobically at 70 ° C while stirring. . A solubilized sample was taken over time, the organic solid content was measured, and the solubilization rate (%) at each time was calculated based on the formula described in Reference Example 1.

Comparative Example 1 Without culturing in the enzyme production tank described in Example 1,
The solubilization tank containing 2 L of the excess sludge was inoculated with the same amount of the enzyme-producing bacteria as in Example 1, and the anaerobic solubilization reaction was performed at 70 ° C. to obtain the solubilization rate over time. It was

The results obtained in Example 1 and Comparative Example 1 are shown in FIG. In the figure, ● indicates the solubilization rate in Example 1, and ○ indicates the solubilization rate in Comparative Example 1. In Comparative Example 1 in which no enzyme was produced, the solubilization rate was 33% even after the solubilization reaction for 24 hours, and 42% of vss was finally solubilized after 48 hours.
It is considered that this is because the soluble organic matter (DOC) required for the enzyme-producing bacterium to grow is low and the growth takes time, so that the enzyme is not secreted until a long time is passed.
On the other hand, in Example 1, the rate of the solubilization reaction was high because the enzyme obtained in the enzyme production tank exhibited the solubilization ability, and 40% or more vss was solubilized after 6 hours. Became. Therefore, it was suggested that the sludge treatment method using the enzyme production tank of the present invention realizes rapid and efficient solubilization of sludge.

[0069]

According to the method for digesting sludge of the present invention, when digesting sludge containing organic matter such as raw sludge and excess sludge, microorganisms derived from sludge to be treated and / or separately isolated, Utilizing an organic matter decomposition reaction by a sludge-degrading enzyme secreted from a microorganism such as a thermophile, solubilization / and / or lowering of molecular weight of suspended solids in sludge and subsequent digestion are sufficiently efficiently achieved.

That is, unlike the method which has been used in the art for a long time, the microorganisms are cultivated in an independent enzyme production tank to produce a sludge-degrading enzyme, and the sludge is solubilized using such an enzyme. A method for digesting sludge to perform a digestion step is provided.

Therefore, according to the method of the present invention, the residence time required for the treatment in the solubilization tank and the digestion tank can be reduced, the treatment can be completed quickly, and the volume of the solubilization tank can be reduced. Since the reaction is carried out under relatively mild conditions and it is not necessary to use a large amount of expensive reagents or dangerous reagents, the cost and safety are excellent.

[Brief description of drawings]

FIG. 1 is a schematic view of one embodiment of a sludge digestion treatment step of the present invention.

FIG. 2 is a schematic view of another embodiment of the sludge digestion treatment step of the present invention.

FIG. 3 is a schematic view of another embodiment of the sludge digestion treatment step of the present invention.

FIG. 4 is a schematic view of another embodiment of the sludge digestion treatment step of the present invention.

FIG. 5 is a graph showing the relationship between the growth amount and the temperature of a microorganism having an enzyme-producing activity of the present invention.

FIG. 6 shows the results of the microorganism having an enzyme-producing activity of the present invention,
It is a graph which shows the enzyme production amount in sewage surplus sludge supernatant liquid.

FIG. 7 shows the results obtained by the microorganism having the enzyme-producing activity of the present invention,
It is a graph which shows the enzyme production amount in a yeast-peptone medium.

FIG. 8 is a graph showing the results of solubilization of sludge using the enzyme obtained by the enzyme production step of the present invention.

[Explanation of symbols]

 1 ... Enzyme production tank 2 ... Solubilization tank 3 ... Digestion tank 4 ... Precipitation tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Yokoyama Room 13-7-7 Minami-ochiai 1-chome, Minamiochiai, Suma-ku, Hyogo Prefecture

Claims (15)

[Claims] 1. A method for biologically digesting sludge containing organic matter, which comprises an enzyme production step for obtaining an enzyme for decomposing organic matter in sludge, solubilizing suspended solids in sludge and / or Or a solubilization step for lowering the molecular weight, and solubilizing and / or solubilizing suspended solids
Alternatively, a method for digesting sludge, comprising a digestion step for digesting the sludge after being reduced in molecular weight. 2. The method for digesting sludge according to claim 1, wherein the enzyme obtained in the enzyme production step is used in the solubilization step. 3. The sludge digestion treatment method according to claim 1, wherein the enzyme production step includes various organic waste liquids or sludge suspensions as raw materials for the reaction for producing the enzyme. 4. The sludge suspension obtained from the solubilization step and / or the digestion step or a supernatant thereof is used as a raw material for the reaction for producing the enzyme in the enzyme production step. Or the method for digesting sludge according to the item 3. 5. The method of claim 1, wherein in the enzyme producing step, a microorganism having a sludge-degrading enzyme producing activity obtained from another separation source is cultured and the obtained enzyme is used in the solubilizing step. 3. The method for digesting sludge according to 3 or 4. 6. After the solubilization step and / or the digestion step, a sludge suspension solid-liquid separation step is further included, and the liquid supernatant obtained by the separation step is used as a raw material for the reaction in the enzyme production step. The microorganism used, which is contained in the supernatant and is cultured in the enzyme production step,
The method for digesting sludge according to 2, 3, 4 or 5. 7. The enzyme-producing step is carried out under a temperature range of 50 to 90 ° C., 1, 2, 3, 4, 5 or 6.
A method for digesting sludge as described. 8. The method for digesting sludge according to claim 1, wherein the sludge containing organic matter is sewage surplus sludge. 9. The microorganism having a sludge-degrading enzyme-forming activity is a microorganism obtained by aerobically or anaerobically culturing sewage surplus sludge at 50 to 90 ° C. Or the method for digesting sludge according to 8. 10. The method for digesting sludge according to claim 9, wherein the microorganism having an activity of producing sludge-degrading enzyme is a microorganism obtained by aerobically culturing sewage surplus sludge at 60 to 70 ° C. . 11. The microorganism having the sludge-degrading enzyme-forming activity is a thermophilic microorganism separated from compost,
The method for digesting sludge according to claim 5, 6, 7 or 8. 12. The method for digesting sludge according to claim 11, wherein the microorganism having a sludge-degrading enzyme-forming activity is a thermophilic microorganism separated from horse manure compost. 13. A digestion treatment apparatus used for biologically digesting sludge containing organic matter, comprising: an enzyme production tank for obtaining an enzyme capable of decomposing organic matter in sludge; Solubilization tank for solubilizing and / or lowering the molecular weight of suspended solids in sludge, which is connected downstream, and solubilization and / or solubilization of suspended solids, connected downstream of the solubilization tank Alternatively, a digestion treatment device including a digestion tank for digesting sludge after lowering the molecular weight. 14. A suspension of various organic waste liquids or sludge, or a suspension or supernatant of sludge from the solubilization or digestion tank is used as a raw material for the enzyme production reaction in the enzyme production tank. The microorganisms contained in the waste liquor, suspension or supernatant and / or microorganisms having a sludge-degrading enzyme-forming activity obtained from another separation source are cultivated in the enzyme production tank, and the obtained enzyme is obtained as described above. The digestion treatment apparatus according to claim 13, which is used for an organic substance decomposition reaction in a solubilization tank. 15. The method further comprises means for solid-liquid separating the sludge suspension after treatment in the solubilization tank and / or digestion tank, and the liquid supernatant obtained by the separating means is in the enzyme production tank. 15. The sludge digestion treatment device according to claim 13, wherein the microorganism used as a raw material for the enzyme production reaction and contained in the supernatant is cultured in the enzyme production tank.