JPH09253700A - Method and apparatus for treating sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more stably supply a material excellent in enzyme forming capacity by using heat treated sludge obtained by a heat treatment process as a culture soln. for bacteria forming enzyme decomposing org. matter. SOLUTION: In a heat treatment tank 1, sludge containing org. matter is heated to obtain heat-treated sludge used as a culture soln. of bacteria forming enzyme. This heat-treated sludge is delivered to an enzyme forming tank 2 and cultured to form and secrete enzyme capable of decomposing and solubilizing org. matter by bacteria. A mixed soln. obtained by solubillzing org. matter and/or reducing a mol.wt. thereof in a solubilizing tank 3 is supplied to a next digestion tank 4 and digested to be discarded as a liquid and gas. As mentioned above, by applying heat treatment to sludge to be treated and appropriately diluting treated sludge, a liquid suitable as a bacteria culture soln. can be obtained and a material for forming enzyme can be stably supplied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating sludge, and more specifically, to organic sludge, for example, raw sludge and surplus sludge discharged from sewage treatment processes such as sewage treatment plants and human waste treatment plants, and A suitable method for biologically treating biological sludge, and further organic high-concentration sludge discharged from a manufacturing process and a wastewater treatment process of a food factory, a chemical factory, etc., by using an enzyme produced by a microorganism. And a processing apparatus in which the processing method is achieved.

[0002]

2. Description of the Related Art Conventionally, in order to dispose of the above-mentioned organic sludge, the liquid components are appropriately drained after solid-liquid separation in a sedimentation tank, etc., and the precipitated solids are usually dehydrated or dehydrated and incinerated. Later, it is dumped on land or in the ocean. However, dumping sludge into the ocean is not desirable because it leads to environmental destruction, and it is becoming almost banned in recent years when the need for global environmental protection is recognized, and dumping on land. However, securing landfill is becoming difficult.

Therefore, a method is devised in which a solid substance is physically, chemically or biologically combined, or a combination thereof is used to solubilize and / or reduce the molecular weight of the solid substance, and then anaerobically or aerobically digested. It has been. This solubilization and /
Alternatively, in the case of lowering the molecular weight, the treatment may be performed in a solubilization tank separately provided.

Examples of physical methods for solubilizing and / or lowering the molecular weight include so-called Zieman-man process in which pressure is applied in addition to thermal decomposition and temperature increase, and cell walls of microorganisms in sludge. In order to crush the product, a method such as applying a mill or ultrasonic waves to make the solid substance fine can be mentioned, but it has drawbacks in terms of solubilization achievement efficiency, time, cost, operation complexity, etc. It was unfavorable for chemical conversion.

Next, as a chemical method, for example, a treatment method using a chemical such as a hot alkali or an acid can be mentioned (JP-A-2-277597, JP-A-5-345200 and JP-A-6-99199). . 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. However, it is difficult to say that it is an ideal method for practical application at a large-scale level because pH adjustment is required as a post-treatment and the cost of reagents increases. .

As a biological method, there has been proposed a method of solubilizing a solid component by decomposing components in sludge to lower the molecular weight by using an enzyme such as protease. Although this method is performed under relatively mild conditions and is considered to be preferable from the viewpoint of safety, such an enzyme is considerably expensive and practically difficult to apply to large-scale processing. Also, the applicable conditions (pH, temperature, etc.) are severely limited depending on the various characteristics of the enzyme used,
Since the operation tends to be complicated, it is not preferable for practical use.

Therefore, the present inventors have proposed a sludge digestion treatment method and apparatus including an enzyme production step for obtaining an enzyme that decomposes organic matter (Japanese Patent Application No. 7-260287). The present invention discloses a method of utilizing an enzyme produced by, for example, a microorganism contained in sludge to solubilize sludge and / or reduce its molecular weight. In this method, the sludge to be treated and the treatment liquid after the solubilization and / or digestion step can be used as materials for enzyme production, and the enzyme produced by these liquids can solubilize the sludge. Therefore, the sludge can be efficiently solubilized and / or reduced in molecular weight.

However, in the sludge digestion treatment method including the enzyme production step, a liquid having a low concentration of soluble organic carbon (DOC) such as raw sewage (low-concentration wastewater) is used as a material for enzyme production. In this case, the growth of the microorganism capable of producing an enzyme is insufficient, so that the amount of the enzyme produced is remarkably reduced, and the desired effect is often not achieved. Further, when the treatment liquid after being subjected to the solubilization step and / or the digestion step is used as a material for enzyme production, although the efficiency of enzyme production is excellent,
Immediately after the start of operation, the enzyme-producing material cannot be properly and stably supplied, and it takes time until the system is stable and the material is obtained. When an abnormality occurs, there is a big problem in that the enzyme-producing material cannot be supplied immediately. In addition, the solubilization treatment liquid contains various microorganisms that do not have the ability to produce sludge digestive enzymes and do not contribute to the solubilization of sludge, and the treatment liquid containing these miscellaneous bacteria should be added to the enzyme production tank. In some cases, the bacteria may preferentially grow over the microorganisms that produce the enzyme, which may result in the efficiency of the enzyme production being reduced.

[0009]

As described above, when introducing an enzyme production step in a treatment method for solubilizing and / or reducing the molecular weight of sludge containing organic matter, a material excellent in enzyme production ability is more preferable. There is a demand for a stable supply method. The present invention has been made in view of the above circumstances, and an object thereof is to provide the following method and device.

[0010]

The present invention has been accomplished as a result of intensive studies to achieve the above-mentioned object in the prior art relating to a method for treating sludge containing organic matter. Is characterized by.

(1) A biological treatment method for sludge containing organic matter, which comprises a step of subjecting at least a part of the sludge to heat treatment, and an enzyme for decomposing organic matter in the heat-treated sludge obtained by the heat treatment step. A method for treating sludge, which is used as a culture solution for a microorganism that produces water.

(2) In the biological treatment method, the heat treatment sludge is used as a culture solution to obtain an enzyme for decomposing an organic matter in the sludge, and the enzyme obtained in the enzyme production step. The method for treating sludge according to (1), which comprises a solubilization step for solubilizing and / or lowering the molecular weight of suspended solids in the sludge.

(3) The biological treatment method further comprises a digestion step for digesting the sludge and the solubilized product after solubilizing and / or lowering the molecular weight of the suspended solid. ) The method for treating sludge as described.

(4) The method further comprises a step of diluting the heat-treated sludge obtained by the heat treatment so that the soluble organic carbon concentration becomes 200 to 3,000 mg / L, before and / or after the heat treatment step. The sludge treatment method according to any one of (1) to (3).

(5) The sludge treatment method according to (4), wherein the dilution is performed using low-concentration wastewater having a soluble organic carbon concentration of less than 200 mg / L.

(6) The method for treating sludge according to any one of (1) to (5), wherein the heat treatment is performed at 50 to 90 ° C.

(7) The method for treating sludge according to any one of (1) to (6), wherein the heat treatment is performed for 0.5 to 24 hours.

(8) In the biological treatment method,
The sludge treatment method according to any one of (2) to (7), wherein a part of the treated sludge is directly subjected to the solubilization step.

(9) The biological treatment method further comprises a solid-liquid separation step in at least one of a step before the enzyme production step, a step before the solubilization step, and a step after the solubilization step, and the solid obtained by the separation step. The sludge treatment method according to any one of (2) to (8), wherein the product is subjected to the solubilization step, and the liquid portion obtained in the separation step is subjected to the enzyme production step.

(10) The solid-liquid separation step includes at least one means of precipitation, centrifugation or filtration.
(9) The sludge treatment method described in (9).

(11) The sludge treatment method according to any one of (1) to (10), wherein the sludge containing organic matter is sewage surplus sludge.

(12) A device for biologically treating sludge containing organic matter, wherein a part or all of the treated sludge is preheated and an enzyme for decomposing the organic matter in an enzyme production tank in the next step is used. Used as a culture solution of the microorganisms that produce,
Heat treatment tank for obtaining heat-treated sludge, using a microbial culture solution for producing the enzyme, for obtaining an enzyme capable of decomposing organic matter in sludge, an enzyme production tank connected downstream of the heat treatment tank, And a solubilization tank connected downstream of the enzyme production tank for solubilizing and / or lowering the molecular weight of suspended solids in sludge using the enzyme obtained in the enzyme production tank. Processing equipment including.

(13) A device used for biologically treating sludge containing organic matter, which is solubilized and / or reduced in molecular weight of suspended solids connected downstream of the solubilization tank. The treatment apparatus according to (12), further including a digester tank for later digesting the sludge and the solubilized product.

(14) In the above apparatus, a solid-liquid separation means is provided at least at one of the connecting portion between the heat treatment tank and the enzyme producing tank, the connecting portion between the enzyme producing tank and the solubilizing tank, or the downstream of the solubilizing tank. (12) or (13), further comprising: a solid matter obtained by the separating means is attached to the solubilization tank, and a liquid portion obtained by the separating means is attached to the enzyme production tank. The processing device described.

The inventors of the present invention produce an enzyme that decomposes organic matter in sludge when treating sludge containing organic matter such as raw sludge and surplus sludge, and solubilize sludge and / or low molecular weight using the enzyme. When performing oxidization, prior to enzyme production,
By heating the sludge to be treated to obtain heat-treated sludge and using this as a culture solution for microorganisms that produce enzymes, the enzymes can be obtained stably and with high efficiency. Therefore, suspended solids in sludge can be obtained. It was found that the solubilization / and / or depolymerization of the fraction and the subsequent digestion can be sufficiently achieved, and the present invention has been completed.

[0026]

Embodiments of the present invention will be described below.

The sludge treatment method of the present invention is a biological treatment method of sludge containing organic matter, which comprises a step of heat-treating at least a part of the sludge, and the heat-treated sludge obtained by the heat-treatment step is It is characterized by being used as a culture solution for a microorganism that produces an enzyme that decomposes organic matter. By such a heat treatment, an environmental liquid suitable for the growth of a microorganism that produces an enzyme that decomposes organic matter, that is, the concentration of soluble organic carbon increases with the solubilization of solid matter in sludge, and A liquid having a low content of microorganisms (miscellaneous bacteria), which is unfavorable and sometimes prevents its growth, can be obtained. If the soluble organic carbon concentration is too high,
And / or, if the concentration of a substance capable of inhibiting the growth of a desired microorganism and the enzyme production by the microorganism (for example, salts) is considered to be too high, dilute appropriately to obtain an optimum concentration. It suffices to carry out, and a preferable culture solution for the microorganism that produces the enzyme can be freely obtained by using the heat-treated sludge.

The material of the heat treatment is 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, and biological sludge,
Furthermore, organic sludge discharged from a manufacturing process such as a food factory or a chemical factory and a wastewater treatment process can be used, and the concentration of soluble organic carbon is not particularly limited. As the material, starch, beer, organic sludge discharged from manufacturing processes such as chemicals is preferably used,
Sewage surplus sludge is particularly preferably used.

The heat treatment of the material is preferably 50 to 90.
C., most preferably in the temperature range of 60 to 70.degree. If the treatment temperature is too low, the removal rate of microorganisms unfavorable for enzyme production may be low, and solubilization may be insufficient, which may be a factor of inferior efficiency of enzyme production in the next step. In addition, subjecting it to high temperature treatment more than necessary consumes a large amount of energy and is economically disadvantageous.

The heat treatment time is preferably 0.5 to 24 hours, most preferably 3 to 12 hours. If the treatment time is too short, the removal rate of microorganisms unfavorable for enzyme production will be low, and the solid matter will not be solubilized, so that a soluble organic substance having a preferable concentration for enzyme production cannot be obtained. Therefore, the efficiency of enzyme production may be poor in the next step. If the heat treatment time is too long, thermophilic miscellaneous bacteria, which are disadvantageous for enzyme production, may increase, and the cost also increases, which is not preferable.

The heating may be carried out at normal pressure. In order to heat the entire liquid to a uniform temperature, it is preferable to heat the liquid while stirring. Usually, the heating is carried out under anaerobic conditions.

The sludge may be supplied to the heat treatment tank either continuously or batchwise.

The heat-treated sludge obtained by such heat treatment is then subjected to a biological treatment, and the first step in this biological treatment is the enzyme production step. As the culture solution for the enzyme production step, as described above, the heat-treated sludge is preferably used by diluting it to an appropriate concentration,
A substance capable of inhibiting the growth of a desired microorganism and the enzyme production by the microorganism so that the concentration of the soluble organic carbon is in the range of 200 to 3,000 mg / L, preferably 500 to 1,500 mg / L ( For example, a diluted product is preferable in order to reduce the concentration of salts and the like. If the soluble organic carbon concentration after dilution is too low, the microorganisms that produce the enzyme will not be sufficiently propagated, and the amount of the enzyme produced will be extremely reduced. Further, if the concentration of soluble organic carbon is too high, it is highly likely that miscellaneous bacteria other than such microorganisms will propagate, and the concentration of substances that are harmful to the microorganisms that produce the enzyme may also increase, This may lead to a decrease in enzyme production.

The dilution has a soluble organic carbon concentration of 200.
It can be performed using low-concentration wastewater of less than mg / L, but may be diluted with groundwater, river water, miscellaneous water in factories, or the like.

In the biological treatment method, the heat-treated sludge is used as a culture solution of a microorganism that produces an enzyme that decomposes organic matter in the sludge, and a suspended solid matter in the sludge is treated as described above. It includes a solubilization step for solubilizing and / or lowering the molecular weight using the enzyme obtained in the enzyme production step. The biological treatment method may further include a digestion step for digesting sludge and a solubilized product after solubilizing and / or depolymerizing the suspended solids.

In this biological treatment method, a part of the sludge to be treated may be directly subjected to the solubilization step.

In the enzyme production step, an independent enzyme production tank is provided separately from the solubilization and digestion steps described below.
This is a step of culturing a microorganism under conditions that optimize the growth of the microorganism and the accompanying secretion of an enzyme.

In the enzyme production step, the heat-treated sludge obtained in the heating step is used as a culture solution of a microorganism that produces an enzyme that decomposes organic matter in sludge, and a desired enzyme is produced as the microorganism grows. can get. In addition, in the enzyme production step, an enzyme can be efficiently produced by adding and proliferating a suitable microorganism capable of solubilizing sludge, such as compost bacterium and digestive bacterium.

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 appropriately set in consideration of the stability of the obtained enzyme, but it is usually performed at 50 to 90 ° C. For example, SPT2-1 strain belonging to Bacillus stearothermophilus
When culturing [Accession number: FERM P-15395] (see Japanese Patent Application No. 8-42496) in yeast-peptone medium, 60 to 70
Proper growth occurs in the temperature range of ° C, and this temperature range is preferable in terms of the growth rate of microorganisms, the rate of enzyme secretion, and the stability of the obtained enzyme.

It is preferable that the pH of the liquid used is near neutral in terms of both the growth rate of microorganisms and the rate of enzyme secretion. 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. Generally, the culturing time is 24 hours or more, and the enzyme is more efficient. The culture is preferably 0.
It is carried out for 5 to 24 hours, more preferably 3 to 12 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.

However, it goes without saying that the optimum culture conditions in the enzyme production step should be determined depending on the type of the microorganism to be cultured.

The sludge-degrading enzyme obtained in the enzyme-producing 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).

The solubilization step in the method of the present invention is a step in which the enzyme obtained in the above-mentioned enzyme production step is responsible for lowering the molecular weight of sludge and a decomposition reaction, thereby achieving solubilization. The solubilization is performed by appropriately selecting the conditions suitable for the enzymatic reaction. Specifically, the temperature range of 50 ~ 90 ℃, preferably
Try to operate in the range of 60-70 ℃. 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 of the sludge to be solubilized, the concentration, etc., but is preferably 3 to 48 hours, and most preferably 6 hours.
~ Do about 24 hours. The solubilization may be carried out under normal pressure either anaerobically or aerobically, and in the case of aerobic reaction, a reaction tank equipped with an aeration device can be adopted. In the case of anaerobic solubilization, it is particularly preferable to carry out with stirring so that the organic substance to be depolymerized 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 digestion step in the present invention may be carried out 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 according to the decomposability and concentration of organic substances, but is preferably 3 to 48 hours, more preferably 6 hours.
Perform for ~ 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.

Each step of the biological treatment of the present invention can be performed in either a batch system or a continuous system.

Further, the biological treatment can further include a solid-liquid separation step in at least one of the steps before the enzyme production step, before the solubilization step or after the solubilization step. The solid matter obtained by the separation step may be subjected to the solubilization step, and the liquid portion obtained by the separation step may be subjected to the enzyme production step.

The solid-liquid separation step includes at least one means of precipitation, centrifugation or filtration (including membrane separation). Of these, precipitation or centrifugation is preferred because it does not require a particularly expensive device or labor, and precipitation in a precipitation tank is most preferred if the separation is easy depending on the properties of the treatment liquid.

Furthermore, the present invention is an apparatus for biologically treating sludge containing organic matter, wherein a part or all of the treated sludge is preheated and the organic matter is decomposed in the enzyme production tank of the next step. A heat treatment tank for obtaining a heat-treated sludge used as a culture solution for a microorganism that produces an enzyme, in order to obtain an enzyme capable of decomposing organic matter in sludge from a microorganism culture solution that produces an enzyme, Enzyme production tank connected downstream, and solubilization of suspended solids in sludge and / or low molecular weight using the enzyme obtained in the enzyme production tank connected downstream of the enzyme production tank The present invention relates to a processing device including a solubilization tank for liquefaction. The above apparatus may further include a digestion tank connected downstream of the solubilization tank for digesting sludge and solubilized product after solubilization and / or depolymerization of suspended solids.

Further, a solid-liquid separation means is further provided in at least one of the connecting portion between the heat treatment tank and the enzyme producing tank, the connecting portion between the enzyme producing tank and the solubilizing tank, or the downstream of the solubilizing tank in the above apparatus. It is preferable that the solid material obtained by the separation means is included in the solubilization tank, and the liquid portion obtained by the separation means is included in the enzyme production tank.

The structure of the reaction tank such as the enzyme production tank, the solubilization tank and the digestion tank used in each step of the biological treatment of the present invention is not particularly limited, and a tank for performing an aerobic reaction. In the above, as long as it is equipped with an aeration means and a stirring means, and a tank for performing an anaerobic reaction, a stirring means and the like may be used.

An embodiment of the present invention will be described below with reference to FIGS.

In the embodiment of FIG. 1, first, in the heat treatment tank 1 which is the first step of the sludge treatment method of the present invention, the sludge containing organic matter is heated and used as a culture solution of a microorganism that produces an enzyme. Sludge is obtained. If dilution is required, it may be done either before or after the heat treatment step. The heat-treated sludge is delivered to the enzyme production tank 2 and cultured therein, whereby the enzyme capable of decomposing and solubilizing the organic matter is produced and secreted by the microorganism.
It is also possible to separately add a microorganism having an enzyme-producing ability to the enzyme-producing tank 2. Next, the obtained liquid containing the enzyme is transferred to the solubilization tank 3. If there is a residual portion of the sludge containing the organic matter in the solubilization tank 3, it can be charged. After being solubilized and / or depolymerized in the solubilization tank 3, the obtained mixed liquid is supplied to the next digestion tank 4, and when digestion is completed, it can be discarded as a liquid or a gas.

Next, in the embodiment of FIG. 2, after the treatment in the heat treatment tank 1 of the embodiment of the present invention shown in FIG. 1 and appropriate dilution, the heat-treated sludge is subjected to solid-liquid separation in the settling tank 5,
The supernatant obtained here is delivered to the enzyme production tank 2. The precipitate obtained in the settling tank 5 is charged into the solubilization tank 3,
Utilizing the enzyme-containing liquid from the enzyme production tank 2, solubilization and / or molecular weight reduction are performed together with the remaining sludge containing organic matter. Next, the treatment in the digestion tank 4 is performed, the gas and liquid are digested, and the sludge can be discarded.
In this way, by introducing the precipitation tank 5 to the next stage of the heat treatment tank 1 to reduce the solid content flowing into the enzyme production tank 2, it is expected that the enzyme production can be achieved more smoothly.

The embodiment shown in FIG. 3 is obtained by adding a step of precipitation in the precipitation tank 5b after the solubilization tank 3 in the embodiment shown in FIG. 2, and the supernatant obtained here is the supernatant of the next step. The undecomposed sludge, which is attached to the digestion tank 4 and obtained as a precipitate, is returned to the solubilization tank 3 and is again subjected to the solubilization reaction, whereby the decomposition rate can be improved.

The above-described embodiments of the present invention are intended only as examples, and in carrying out the present invention, the number of times each step is repeated can be variously changed. Of course, it is not limited to these embodiments.

As described above, when treating sludge containing organic matter such as raw sludge and excess sludge, the sludge to be treated is subjected to heat treatment and appropriately diluted, so that it is suitable for the growth of microorganisms that produce enzymes. It is possible to stably supply the enzyme-producing material by obtaining a liquid having a high soluble organic carbon concentration and a low content of various bacteria, which is preferable as the microorganism culture liquid. Thus, the solubilization / and / or reduction of the molecular weight of the suspended solids in the sludge utilizing the enzymatic decomposition reaction of the organic matter can be achieved sufficiently efficiently. Therefore, the residence time required for treating sludge is reduced, and the treatment can be completed quickly.

[0059]

[Example] Example 1 : Soluble organic carbon (DOC: Dis) by heat treatment
Solved Organic Carbon) Change in concentration According to the sludge treatment method of the present invention, excess sludge (2% (weight / volume) of volatile suspended solid matter) discharged from a sewage treatment plant.
200 ml (containing) was heat-treated in a 500 ml Erlenmeyer flask at 70 ° C. for 6 hours while shaking at 50 rpm, and then the change in DOC concentration was measured.

The DOC concentration was determined by subjecting heat-treated sludge to high-speed centrifugation at 18,000 G for 15 minutes, and measuring the TOC (Total Organic Carbon) in the supernatant thereof according to JIS K0102.

The DOC concentration before the heat treatment was about 200 mg / L, but the DOC concentration after the heat treatment increased to about 3,500 mg / L. From this result, by heating the sludge containing organic matter, 15 to 20% of the solid matter was solubilized, and
It was revealed that the C concentration was increased.

Example 2 Effect of Soluble Organic Carbon Concentration in Culture Solution on Protease-Producing Activity Identification of protease as a bacterium capable of solubilizing solid content in sludge In liquid
To find out how DOC concentration affects
The following experiment was performed.

As the culture solution, a diluted solution of heat-treated sludge and Y-
P (east-peptone) medium was used. The heat-treatment sludge dilution liquid contains 2% (weight / volume) of volatile suspended solids, excess sludge discharged from a sewage treatment plant is heated at 70 ° C for 5 hours, and then tap water is used. It was diluted to the prescribed DOC concentration (see Figure 4). The YP medium was prepared by mixing yeast extract (manufactured by DIFCO) and peptone (manufactured by DIFCO) at a weight ratio of 1: 2, and then adjusting each DOC concentration (see FIG. 4). 200 ml each of the heat-treated sludge dilution liquid and the YP medium culture liquid having a predetermined DOC concentration were placed in a 1 L Erlenmeyer flask.

The SPT2-1 strain was used as a bacterium having a protease-producing ability, and precultured in YP medium at 70 ° C. for 15 hours while shaking at 100 rpm.

2% by volume of each of the preculture liquid of the SPT2-1 strain was added to an Erlenmeyer flask containing the culture liquid adjusted to the above predetermined concentration. Then, at 70 ℃ for 5 hours, 100 rpm
After culturing with shaking at 1, each liquid was collected and the protease activity was measured.

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. Almost no protease was produced when the culture medium with low DOC concentration (100-200 mg / L) was used, but when using the culture medium with DOC concentration higher than 500 mg / L, YP medium and heat-treated sludge were used. It was revealed that the enzyme was produced at a high level in each of the diluted solutions. In particular, 500-1,500 mg /
It was suggested that the enzyme production efficiency was high at L DOC concentration.

Example 3 : Effect of treatment temperature on solubilization rate by heat treatment As in Example 1, 200 ml of excess sludge containing 2% of volatile suspended solids was placed in a 500 ml Erlenmeyer flask. ,
Heat treatment was carried out at each temperature shown in FIG. 5 for 24 hours while shaking at 50 rpm.

After the treatment, each treated sludge was sampled and the solubilization rate was measured. The solubilization rate is determined by measuring the volatile suspended solids (VSS) in the sample before and after heat treatment.
After measuring by the method according to JIS K0102, it was calculated according to the following formula.

[0070]

[Equation 1]

The results are shown in FIG. It was shown that sludge was solubilized at a high rate by heat treatment at 50-90 ℃. Therefore, by performing heat treatment in such a temperature range, the DOC concentration increases with an increase in solubilization rate, and it is clarified that a desired heat-treated sludge suitable as a culture solution of a microorganism having an enzyme-producing ability can be obtained. It was

Example 4 : Effect of treatment time on solubilization rate by heat treatment As in Example 3, 200 ml of excess sludge containing 2% of volatile suspended solids was placed in a 500 ml Erlenmeyer flask, 70
The heat treatment was continued while shaking at 50 rpm at 50 ° C. FIG.
Samples were collected at each time shown in, and the solubilization rate of each sample was measured by the method described in Example 3.

The results are shown in FIG. It was found that 10% solubilization was achieved in 1 hour when heat treatment was performed at 70 ° C, and about 25% solubilization was achieved after 24 hours treatment.

[0074]

According to the sludge treatment method of the present invention, in the biological treatment of sludge containing organic matter such as raw sludge and surplus sludge, when utilizing an organic substance decomposition reaction by a sludge decomposing enzyme, such enzyme is used. A culture solution suitable for growth of microorganisms that can be produced and secreted can be obtained by an extremely simple and economical method. That is, by heating the sludge to be treated, the concentration of soluble organic carbon is increased, and as a result, a liquid is obtained in which the microorganisms sufficiently proliferate and the enzyme-producing ability is exhibited. Moreover, as a result of the heat treatment, the content of other microorganisms that are not preferable for the growth of the microorganisms and sometimes hinder the growth of the microorganisms is reduced in the liquid, so that an enzyme having sludge-decomposing ability is produced. , The secreted microorganisms can be preferentially grown. When the concentration of soluble organic carbon in the obtained culture broth is too high, the culture broth having a preferable soluble organic concentration can be freely adjusted by diluting with a liquid having a low concentration.

Therefore, the desired enzyme can be sufficiently obtained by utilizing the above culture solution, and the solubilization and / or molecular weight reduction of the suspended solids in the sludge using the enzyme and the subsequent digestion are efficient. The effect is achieved well.

Further, according to the present invention, in a method of producing an enzyme by using a microorganism and utilizing the enzyme for treating sludge, for example, an abnormality occurs at the time of start-up of operation or in the middle of equipment, so that a solubilization tank or the like is generated. Even when the operation of (3) becomes defective, the culture solution for enzyme production is stably supplied in a preferable state. In order to supply the culture solution by the method of the present invention, it is not necessary to use a particularly large amount of expensive reagents or dangerous reagents, so that the present invention provides a method and apparatus excellent in terms of cost and safety. .

[Brief description of drawings]

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

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

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

FIG. 4 is a graph showing the influence of the concentration of soluble organic carbon in the culture medium on the protease-producing activity.

FIG. 5 is a graph showing the influence of treatment temperature on the solubilization rate by heat treatment.

FIG. 6 is a graph showing the influence of treatment time on the solubilization rate by heat treatment.

[Explanation of symbols]

 1 ... Heat treatment tank 2 ... Enzyme production tank 3 ... Solubilization tank 4 ... Digestion tank 5, 5a, 5b ... Precipitation tank

Claims (14)

[Claims] 1. A method of biologically treating sludge containing organic matter, comprising the step of heat-treating at least a part of the sludge,
A method for treating sludge, which comprises using the heat-treated sludge obtained by the heat treatment step as a culture solution for a microorganism that produces an enzyme that decomposes organic matter. 2. The biological treatment method, wherein the heat treatment sludge is used as a culture solution, an enzyme production step for obtaining an enzyme that decomposes organic matter in sludge, and an enzyme obtained in the enzyme production step. The sludge treatment method according to claim 1, further comprising a solubilization step for solubilizing and / or lowering the molecular weight of suspended solids in the sludge by utilizing the solubilization step. 3. The biological treatment method further comprises a digestion step for digesting sludge and a solubilized product after solubilizing and / or depolymerizing the suspended solids. The described sludge treatment method. 4. The step of further diluting the heat-treated sludge obtained by the heat treatment so that the soluble organic carbon concentration becomes 200 to 3,000 mg / L, before and / or after the heat treatment step. Item 4. The sludge treatment method according to any one of Items 1 to 3. 5. The method for treating sludge according to claim 4, wherein the dilution is performed using a low-concentration wastewater having a soluble organic carbon concentration of less than 200 mg / L. 6. The sludge treatment method according to claim 1, wherein the heat treatment is performed at 50 to 90 ° C. 7. The sludge treatment method according to claim 1, wherein the heat treatment is performed for 0.5 to 24 hours. 8. The biological treatment method according to claim 2, wherein a part of the treated sludge is directly subjected to the solubilization step.
The method for treating sludge according to any one of 1. 9. The solid product obtained by the biological treatment method further comprising a solid-liquid separation step in at least one of a step before the enzyme production step, a step before the solubilization step, and a step after the solubilization step. Is applied to the solubilization step, and the liquid portion obtained in the separation step is subjected to an enzyme production step. 10. The method for treating sludge according to claim 9, wherein the solid-liquid separation step includes at least one means of precipitation, centrifugation or filtration. 11. The sludge treatment method according to claim 1, wherein the sludge containing organic matter is sewage surplus sludge. 12. An apparatus for biologically treating sludge containing organic matter, wherein a part or all of the treated sludge is preheated to produce an enzyme that decomposes the organic matter in an enzyme production tank in the next step. A heat treatment tank for obtaining a heat-treated sludge, which is used as a culture solution of microorganisms, and a heat treatment tank for obtaining an enzyme capable of decomposing organic matter in sludge using the enzyme-producing microorganism culture solution And a solubilizing and / or reducing suspended solids in sludge using the enzyme production tank connected downstream of the enzyme production tank and the enzyme obtained in the enzyme production tank connected downstream of the enzyme production tank. A processing apparatus including a solubilization tank for molecularizing. 13. A device used for biologically treating sludge containing organic matter, which is connected downstream of the solubilization tank after solubilization and / or depolymerization of suspended solids. The treatment apparatus according to claim 12, further comprising a digester tank for digesting sludge and solubilized products. 14. A solid-liquid separation means is further provided in at least one of a connecting portion between the heat treatment tank and the enzyme producing tank, a connecting portion between the enzyme producing tank and the solubilizing tank, or a downstream side of the solubilizing tank in the apparatus. 14. The treatment according to claim 12 or 13, which is configured so that the solid matter obtained by the separating means is applied to the solubilization tank, and the liquid portion obtained by the separating means is applied to the enzyme production tank. apparatus.