JP2001179288A - Method and apparatus for anaerobically treating starch- containing liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus, for anaerobically treating starch-containing liquid, capable of anaerobically treating the whole of a starch particle-containing liquid efficiently at a high rate under high load. SOLUTION: A starch particle-containing liquid 11 is separated into starch particles 45 and a starch separated liquid 13 in a sedimentation tank 1 and a starch particle concentrate 12 containing starch particles 45 is introduced into a liquefying treatment tank 2 and hydrochloric acid 16 and stem 15 are blown in the starch particle concentrate 12 to hold the concentrate 12 to pH 4.6-5.4 at 50-70 deg.C for 3-5 hr to liquefy starch particles. Next, the treated liquid us introduced into an acid forming tank 3 while modified protein is separated in a flocculation tank 7 and a solid-liquid separator 8 to be mixed with the starch separated liquid 13 and an anaerobic state is kept to form an organic acid by acid producing bacteria and the acid formed liquid is introduced into a methane fermentation tank 4 to be passed through a sludge blanket 37 as an ascending flow and the organic acid is anaerobically decomposed by methane producing bacteria to be converted to methane and carbon dioxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for anaerobic treatment of a starch particle-containing liquid, and more particularly to a starch particle-containing liquid suitable for treating starch-producing effluent discharged from a step of producing starch from potato, sweet potato or the like. The present invention relates to a method and an apparatus for anaerobic treatment of a liquid.

[0002]

2. Description of the Related Art Generally, starch is produced by grinding raw materials such as potatoes and sweet potatoes, exposing the raw materials to cold water, collecting starch particles, dehydrating, drying and purifying the starch particles. The wastewater discharged from such a starch manufacturing process contains about 500 to 5000 mg / l of SS mainly composed of unrecovered fine starch particles, crushed potato scum, and precipitated protein, and has a BOD of 2000 to 30000 mg / l. This is a wastewater with a very high concentration of pollution, a BOD load of several thousand kg or more per day, and a very high pollution load. Further, as represented by potato starch, the starch production period is concentrated for a few months and a short time per year.

The conventional method of treating wastewater for producing starch is mainly aerobic treatment represented by activated sludge treatment, but requires a large-capacity aeration tank and aerobic lagoon due to a very large load. The construction and maintenance costs are enormous.
Further, the treatment of excess sludge generated and the measures against odor generated from a drainage storage tank, an aeration tank, and the like have become major issues. Anaerobic treatment is an alternative to aerobic treatment. Among these anaerobic treatment methods, there is an anaerobic digestion method in which the entire wastewater is retained in a digestion tank to perform anaerobic digestion (methane fermentation).
There is a problem that a large capacity digestion tank is required because a long residence time is required.

Recently, in order to solve the problems of these processing methods, a UASB (Upflow Anaerobic) has been proposed.
An application of a high-load anaerobic treatment typified by a sludge blanket method, an upward flow anaerobic sludge blanket method, a fluidized bed method, a fixed bed method, and the like is being studied. This method removes anaerobic microorganisms into sludge blankets,
It is mainly soluble B in sludge accumulated at high density on fixed beds.
This is a method for efficiently decomposing organic substances by contacting a liquid to be treated containing OD with a high load and a high flow rate.

However, when the starch production wastewater is treated by this anaerobic treatment method, it is necessary to remove the SS component in the wastewater in advance, and if the entire wastewater including the SS component is treated, the treatment performance deteriorates. . This is because the anaerobic decomposition rate of the fine starch particles contained in the starch production wastewater is extremely slow. For this reason, SS containing starch particles is removed in advance in a sedimentation tank or a raw water tank, and wastewater with a small amount of starch particles is subjected to high-load anaerobic treatment.

[0006] However, in such conventional high-load anaerobic treatment, it is necessary to separately treat the SS separated in advance, and this SS is returned to farmland or landfilled. The generated odor is a major problem. In addition, when returning to farmland, there are problems such as excess nitrogen and disease sources. For this reason, there is a demand for a method capable of performing anaerobic treatment of the entire starch production wastewater at a high load without separating and removing the starch particles.

[0007]

An object of the present invention is to provide a method and an apparatus for anaerobic treatment of a starch particle-containing liquid which can efficiently and efficiently perform anaerobic treatment of a starch particle-containing liquid at a high load and at a high speed. is there.

[0008]

The present invention provides the following anaerobic treatment method and apparatus for a starch particle-containing liquid. (1) A starch particle-containing solution was prepared at pH 4.6 to 5.4 and at a temperature of 5.
An anaerobic treatment method for a starch particle-containing liquid, comprising: a liquefaction treatment step of liquefaction treatment at 0 to 70 ° C; and an anaerobic treatment step of anaerobic treatment of the liquefaction treatment liquid in the presence of sludge containing anaerobic microorganisms. (2) a concentration separation step of separating the starch particle-containing solution into a starch particle concentrate and a starch separation solution;
A liquefaction treatment step of liquefaction treatment at a temperature of 4.6 to 5.4 and a temperature of 50 to 70 ° C., and an anaerobic treatment in which the liquefaction treatment liquid and the starch separation liquid are introduced and subjected to anaerobic treatment in the presence of sludge containing anaerobic microorganisms An anaerobic treatment method for a starch particle-containing liquid having a treatment step. (3) The starch particle-containing liquid or the concentrated liquid is adjusted to pH 4.6 to
5.4. Starch particle-containing having a liquefaction treatment device for liquefaction treatment at a temperature of 50 to 70 ° C. and an anaerobic reaction tank for introducing at least a liquefaction treatment solution and performing anaerobic treatment in the presence of sludge containing anaerobic microorganisms Anaerobic treatment device for liquids.

The starch particle-containing liquid to be treated in the present invention is waste water containing starch particles, and may contain proteins, lipids and the like. This is a starch production wastewater discharged from a process of separating and producing starch from a plant containing starch. As such a starch particle-containing liquid, starch production wastewater discharged from a potato starch production step is typical,
Waste water from starch production from other plants may be used. The wastewater discharged from the potato starch production process includes:
BOD is around 30000mg / l, SS is 5000mg
/ L high concentration decanter drainage and BOD of 200
The water is roughly classified into hydrocyclone wastewater of around 0 mg / l and SS of around 500 mg / l. In the present invention, both wastewaters can be treated. Further, these wastewaters can be mixed and treated. Starch particles are contained in a large amount in the hydrocyclone wastewater, and sometimes there is also a hydrocyclone wastewater in which most of the SS is starch particles, but the present invention can be suitably applied to the treatment of such a hydrocyclone wastewater. .

[0010] The liquefaction treatment step of the present invention is a step of liquefying starch particles physicochemically without using biological sludge.
The starch particle-containing solution is adjusted to pH 4.6 to 5.4, preferably 4.
6-5.0, temperature 50-70 ° C, preferably 60-70
C. and liquefy the starch particles. This liquefaction treatment hydrolyzes the starch particles. For the liquefaction treatment, an apparatus equipped with a pH adjusting means and a heating means capable of adjusting the pH and temperature of the starch particle-containing liquid can be used.

[0011] The starch particles in the starch particle-containing liquid are almost completely liquefied in 3 to 5 hours by maintaining the above pH and temperature. Here, being liquefied means that starch particles are no longer observed under a microscope and no color reaction due to iodine-starch reaction is observed. Preferably, the starch particles are almost completely liquefied, but may remain partially without liquefaction.

To adjust the pH to the above range, mineral acids such as hydrochloric acid and sulfuric acid; alkalis such as sodium hydroxide can be used. In the case of starch-producing effluent, the pH is usually around neutral, so that the pH is usually adjusted by adding an acid. in this case,
Hydrochloric acid is preferred from the viewpoint of reducing the generation of hydrogen sulfide in the anaerobic treatment in the subsequent step. In order to adjust the temperature to the above range, methane gas generated in anaerobic treatment in a later step can be used. For example, methane gas is burned to generate steam, which is blown into the liquid to be processed and heated. be able to.

When the pH of the liquefaction treatment is less than 4.6, the ratio of the protein in the liquid to be treated being acid-denatured to become a gel increases, and therefore the amount of starch particles included in the gel also increases. The liquefaction efficiency is undesirably reduced. PH 5.4
If it exceeds, the liquefaction reaction rate of the starch particles decreases, which is not preferable. When the temperature of the liquefaction treatment exceeds 70 ° C., the rate of heat denaturation of the protein and the formation of a gel increases, and the liquefaction efficiency decreases similarly to the above, which is not preferable. The temperature is 50 ℃
If it is less than 1, the liquefaction reaction rate of the starch particles decreases, which is not preferable.

The liquid to be subjected to the liquefaction treatment is mainly composed of insoluble starch particles, and contains 10000 SS containing proteins and lipids.
mg / l or more, preferably 10,000 to 20,000 mg
/ L is desirable. Since the SS concentration in the starch production wastewater is usually about 500 to 5000 mg / l, it is preferable to provide a concentration separation step before the liquefaction treatment step, and perform liquefaction treatment on the starch particle concentrated liquid in which the starch particles are concentrated. By liquefying the concentrated starch particles, it is possible to reduce the size of the liquefaction apparatus, reduce the amount of the pH adjuster, reduce the heating energy, and the like.

In the present invention, the concentration separation step provided before the liquefaction treatment step as necessary is a step of separating the starch particle-containing liquid into a starch particle concentrated liquid and a starch separation liquid. The concentration separation step can be performed using a known device or means capable of separating or concentrating a solid content from a liquid, for example, a decanter centrifuge, a separation plate centrifuge, a sedimentation tank by sedimentation, a filter cloth. For example, a filtration / separation device using such a method can be used. For example, when a starch particle-containing liquid is separated using a precipitation tank, sedimentation and separation can be performed with a residence time of 2 to 4 hours. The concentrated starch particle concentrate obtained in the concentration separation step is subjected to the liquefaction treatment, and the starch separation liquid is subjected to the anaerobic treatment described later.

The anaerobic treatment step of the present invention is a step of anaerobically treating the liquefied liquified liquid in the presence of sludge containing anaerobic microorganisms. When the concentration separation step is provided, it is generally preferable to perform anaerobic treatment on the liquefaction treatment liquid and the starch separation liquid obtained in the concentration separation step, but it is also possible to perform anaerobic treatment on only the liquefaction treatment liquid.

In performing the anaerobic treatment, when a large amount of gelled and precipitated protein is contained in the liquefied liquid, it is preferable to perform anaerobic treatment on the protein separated liquid from which the precipitated protein has been removed. Thus, it is possible to prevent the methanogenic bacteria from being inhibited by ammonia nitrogen generated in the post-anaerobic treatment process, and to efficiently perform the high-load anaerobic treatment.

A decanter-type centrifuge is suitable for removing proteins, but other separator-type centrifuges, pressurized flotation, sedimentation, and filtration devices using a filter cloth and the like are also available. Can be used. Since the separated protein has a high nutritional value, it is dried if necessary, and can be effectively used as feed for livestock and poultry, and can also be used as fertilizer.

The anaerobic treatment can be performed by a known method using a known apparatus, but it is preferable to perform a high-load anaerobic treatment using a UASB, a fluidized bed, a fixed bed, or the like. In high-load anaerobic treatment, soluble organic matter is to be treated, and solid matter is preferably removed in advance, and other solid matter is also removed when the protein is separated. If the protein is not separated from the liquefaction treatment solution, it is preferable to provide a separate step of removing solids. The high-load anaerobic treatment is a method in which the methane-producing bacterium is highly concentrated and held in an anaerobic treatment tank, and the anaerobic treatment is performed in a short time by contacting the liquid to be treated with a high load at a high speed. .

The UASB method is a method in which a liquid to be treated is brought into contact with a sludge blanket made of granulated sludge formed by highly concentrating sludge containing methane-producing bacteria in an upward flow at a high speed to treat the sludge blanket. . The fluidized bed system is a system in which a carrier such as sand is carried to form a fluidized bed and brought into contact with the liquid to be treated. The fixed bed system is a system in which the liquid to be treated is brought into contact with a fixed bed in which sludge is formed on a carrier. In any case, by maintaining sludge in a high concentration state, high-load and high-speed treatment can be performed.

The anaerobic treatment comprises an acid generation step of decomposing organic substances into organic acids by acid-producing bacteria, and a methane generation step of decomposing organic acids into methane by methane-producing bacteria. A UASB that separates the acid generation step and the methane generation step from each other, generates an organic acid from the solubilized starch by the acid generation bacterium in the first stage of the methane generation step, and then retains the methanogen at a high concentration A two-phase system in which methane is produced from an organic acid under a high load by a method or the like is preferable from the viewpoint of a processing speed and a methane production amount. Anaerobic treatment using methanogens at 30 to 38 ° C., preferably 35 to 36 ° C., for both the one-phase type and the two-phase type
D concentration 2000 to 30000 mg / l, preferably 30
By keeping the anaerobic state at 00-6000 mg / l,
The treatment can be performed efficiently by increasing the activity of the methanogen.

The load in the anaerobic treatment step is 5 to 20 kg / m ³ / d as BOD load, preferably 10 to 15 kg / m ³ / d.
It is desirable that the pressure be kg / m ³ / d. When the BOD load is in the above range, higher quality treated water can be obtained more efficiently.

The anaerobic treatment decomposes starch and other soluble organic substances to generate methane and carbon dioxide. The gas generated here can be recovered and used as fuel for heating in the liquefaction process. The processing solution is
Alternatively, if necessary, it can be diluted with other low-concentration wastewater or industrial water and discharged to a sewer or the like, or can be subjected to aerobic treatment together with other low-concentration wastewater to decompose the remaining organic matter.

As described above, according to the present invention, the starch particles are liquefied in the liquefaction treatment step, whereby the liquefied liquid can be subjected to anaerobic treatment, and the starch particles can be reduced to agricultural land as in the conventional method. There is no need to landfill,
The whole starch production wastewater can be efficiently anaerobic treated at high load and at high speed. Therefore, it is possible to prevent the odor generated when the land is returned to the farmland and landfilled. In addition, the present invention can be carried out with existing anaerobic treatment equipment by installing a liquefaction treatment apparatus, so that treatment can be performed at low cost. Further, advanced treatment under high load is possible, and the amount of methane gas generated in the entire wastewater treatment for starch production is increased, so that effective use is possible.

[0025]

It has been found that the anaerobic reaction of starch particles proceeds in the following three steps. 1) First reaction A liquefaction reaction for converting crystalline starch particles into solubilized starch. 2) Second reaction An organic acid generating reaction for generating organic acids such as acetic acid and propionic acid from the solubilized starch. 3) Third reaction A methane generation reaction for generating methane gas from an organic acid.

Among the times required for the above series of reactions, the time of the liquefaction reaction as the first reaction is the longest, and it takes 3 to 4 days under anaerobic conditions in which the pH is around neutral and the liquid temperature is around 36 ° C. I understand. The organic acid generation reaction, which is the second reaction, proceeds in 4 to 12 hours when the liquefaction reaction has sufficiently proceeded. The third reaction, the methane production reaction,
When the organic acid generation reaction has sufficiently proceeded, a high load treatment with a BOD load of 10 kg / m ³ / d or more is also possible.

In the present invention, a liquefaction treatment step is provided,
By performing liquefaction at 4.6 to 5.4 and a temperature of 50 to 70 ° C, the liquefaction reaction proceeds almost completely in about 3 to 5 hours. For this reason, starch particles are separated and returned to farmland,
The need for landfill treatment is eliminated, and the entire starch production wastewater can be efficiently and anaerobically treated at high load and at high speed.

[0028]

According to the anaerobic treatment method for a starch particle-containing liquid of the present invention, a starch particle-containing liquid or a starch particle concentrated liquid having a pH of 4.
Since anaerobic treatment is performed after liquefaction treatment at 6 to 5.4 at a temperature of 50 to 70 ° C., the entire starch particle-containing liquid is efficiently subjected to anaerobic treatment at a high load, at a high speed, without separately treating the starch particles. be able to. The apparatus for anaerobic treatment of a starch particle-containing liquid according to the present invention uses the starch particle concentrate at a pH of 4.6 to 5.5.
4. Since there is a liquefaction treatment device for liquefaction at a temperature of 50 to 70 ° C., the entire starch particle-containing liquid can be efficiently subjected to anaerobic treatment at a high load, at a high speed, and without a separate treatment of the starch particles. .

[0029]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram illustrating an apparatus for anaerobic treatment of a starch particle-containing liquid according to an embodiment. In FIG. 1, 1 is a sedimentation tank, 2 is a liquefaction treatment tank, 3 is an acid generation tank, 4 is a UASB methane fermentation tank, 5 is a gas storage tank, 6 is a boiler, 7 is a coagulation tank, and 8 is a solid-liquid separator. It is.

The settling tank 1 is connected to a raw water channel 11, a concentrated liquid channel 12, and a starch separated liquid channel 13. The liquefaction processing tank 2 has a concentrated liquid path 12, a liquefaction processing liquid path 14, a steam supply path 1
5 and the pH adjusting agent supply path 16 are connected, and the concentrated starch particles separated and settled in the precipitation tank 1 are introduced from the concentrated liquid path 12,
The pH of the solution in the tank is 4.6 to 5.4, preferably 4.6 to 5.4.
5.0, liquid temperature 50-70 ° C, preferably 60-70 ° C
The liquefaction process is performed while maintaining the pH and temperature so that

The coagulation tank 7 has a liquefaction treatment liquid path 14 and a communication path 2.
1 and a coagulant supply path 22 are connected, and a stirrer 2 is
3 are provided. The solid-liquid separator 8 has communication paths 21 and 2
6 and the protein discharge channel 27 are connected. 28 is a dehydrator and 29 is a protein recovery path.

The acid generation tank 3 is connected with a starch separation liquid path 13, a communication path 26, and an acid generation liquid path 31, and has a stirrer 32 inside.
Is provided. Acid production liquid passage 31
Is connected to a lower portion, a treatment water passage 35 and a gas discharge passage 36 are connected to an upper portion, and a sludge blanket 37 is formed inside. The acid production tank 3 and the methane fermentation tank 4 constitute an anaerobic reaction tank. The gas storage tank 5 has a gas discharge path 36.
And the communication path 41 are connected. The boiler 6 has a communication channel 41, a steam supply channel 15, a water supply channel 42, and a drain channel 43.
Is connected.

In order to treat the starch particle-containing liquid with the anaerobic treatment apparatus shown in FIG.
Into the sedimentation tank 1 and separated by gravity sedimentation into starch particles 45 and a starch separation liquid. The starch particle concentrate containing the starch particles 45 is introduced into the liquefaction tank 2 from the concentrate path 12 to be liquefied, and the starch separated liquid is passed from the starch separation path 13 to the acid generation tank 3.
To produce an organic acid.

In the liquefaction treatment tank 2, a concentrated starch particle solution containing starch particles 45 is introduced from the concentrated liquid passage 12, and hydrochloric acid is supplied from the pH adjusting agent supply passage 16 so that the pH of the liquid in the tank becomes the above-mentioned pH. Then, liquefaction is performed by blowing steam from the steam supply path 15 so that the temperature of the liquid in the tank becomes the above-mentioned temperature. Usually, in 3 to 5 hours, the starch particles 45 are almost completely liquefied. The water vapor is generated by heating water supplied from the water supply channel 42 to the boiler 6 by burning fuel gas from the gas storage tank 5. The concentrated water is discharged from the drain 43.

The liquefaction treatment liquid is introduced into the flocculation tank 7 from the liquefaction treatment liquid path 14, and the flocculant is supplied from the flocculant supply path 22, and is stirred by the stirrer 23 to form floc.
This coagulation treatment liquid is introduced into the solid-liquid separator 8 through the communication path 21 to perform solid-liquid separation. The separated protein solution is introduced into the acid generating tank 3 through the communication path 26, and the separated solid is sent from the protein discharge path 27 to the dehydrator 28, where it is dehydrated and recovered from the protein recovery path 29 as recovered protein. Although a decanter-type solid-liquid separator is used as the solid-liquid separator 8, another solid-liquid separator may be used.

In the acid generating tank 3, the protein separated liquid separated in the solid-liquid separator 8 and the starch separated liquid separated in the precipitation tank 1 are introduced, and while the anaerobic condition is maintained, the acid is stirred slowly with the stirrer 32. The organic acid is generated by mixing with the liquid in the tank containing the producing bacteria. Thereby, the organic matter in the tank is decomposed by the acid-producing bacteria to produce an organic acid.

The organic acid producing liquid is introduced into the lower part of the methane fermentation tank 4 from the acid producing liquid passage 31 and passes through the sludge blanket 37 in an upward flow. At this time, the permeated liquid comes into contact with the granular sludge under anaerobic conditions, whereby the organic acid is anaerobically decomposed and converted into methane and carbon dioxide by the action of methane-producing bacteria contained in the granular sludge. The methane fermentation treatment liquid is discharged from the treatment water passage 35 as treatment water. The generated gas is introduced from the gas discharge path 36 into the gas storage tank 5 and stored until it is used as a fuel gas for generating steam.

In the apparatus shown in FIG. 1, the coagulation tank 7 can be omitted. When the amount of protein precipitated in the liquefaction treatment tank 2 is small, the coagulation tank 7 and the dehydrator 8 can be omitted. In addition, a floating methane fermentation tank can be used instead of a high-load anaerobic treatment apparatus such as a UASB method. In this case, the coagulation tank 7 and the dehydrator 8 can be omitted. Further, the precipitation tank 1 may be omitted, and the raw water may be directly introduced into the liquefaction treatment tank 2 for liquefaction treatment.

[0039]

EXAMPLE 1 The starch production wastewater was anaerobically treated by the apparatus shown in FIG. However, the coagulation tank 7 was omitted. That is, anaerobic treatment was performed on mixed wastewater of decanter wastewater and hydrocyclone wastewater discharged from the potato starch production process. The decanter wastewater has a BOD of around 30,000 mg / l,
SS is around 5000 mg / l, BOD is around 2000 mg / l and SS is 500
It is around mg / l, and the particulate starch is contained in a large amount in the hydrocyclone wastewater. The mixed wastewater to be treated is a mixed wastewater obtained by diluting the decanter wastewater with hydrocyclone wastewater ten times, and the SS of this mixed wastewater is 1000 mg.
/ L, BOD is 4800-5000 mg / l (see Table 1). About 80% of the SS was settled and separated from the mixed wastewater in a sedimentation tank 1 (initial sedimentation tank) also serving as a raw water tank with a residence time of 4 hours to obtain a starch particle concentrated liquid and a starch separated liquid. These S
Table 1 shows S and BOD.

The concentrated starch particle liquid was introduced into the liquefaction tank 2 and liquefied under the conditions of pH 5.0, liquid temperature of 60 ° C. and residence time of 4 hours. This liquefaction treatment liquid has an SS of 2000 to 3
Although it was 000 mg / l, no blue color was observed in the color reaction by the iodine-starch reaction, and no starch particles were observed by microscopic observation. From the measurement result of the organic nitrogen of SS, it was clarified that the main component of SS in the liquefaction treatment liquid was protein precipitated by gelation. The liquefied solution was subjected to solid-liquid separator 8 (small centrifugal separator) to remove gelled and precipitated proteins. The resulting gelled protein separation solution had an SS of 200 to 300 mg / l and a BOD of 140
It was 00-23000 mg / l. The recovered sludge contained 35 to 40% protein.

The gelled protein separation liquid is mixed with the starch separation liquid obtained in the precipitation tank 1, and this mixed liquid is introduced into the acid generation tank 3, where the pH is 6.3 to 6.7, the temperature is 33 to 35 ° C., and the retention time is 30 minutes. Organic acid generation was performed under the conditions of 6 hours. The SS of the obtained organic acid generation liquid (the methane fermentation tank introduction liquid) is 200 to 250 m.
g / l, BOD is 4300-4700 mg / l,
60 to 75% of the BOD component is an organic acid such as acetic acid, propionic acid, lactic acid, and butyric acid and ethanol, and a sufficient organic acid generation reaction has progressed.

The organic acid-producing liquid was introduced into a UASB-type methane fermentation tank 4 and passed therethrough in an upward flow to be subjected to methane fermentation. The residence time of the methane fermentation tank 4 was set to 8 hours with respect to the amount of the separated liquid in the precipitation tank 1, and the pH in the tank was 6.8 to 7.3.
The liquid temperature was adjusted to 35 to 36 ° C. The calculated BOD load of the methane fermenter 4 reached a high load of 13-14 kg / m ³ / d. BOD of methane fermentation treatment liquid (treated water) is 30
0 to 350 mg / l, and the amount of generated gas reached 8.5 to 9 times per 4 volumes of the methane fermenter. The content of carbon dioxide in the generated gas was 20%. Table 1 shows the results.

[0043]

[Table 1]

Example 2 In Example 1, the gelled protein separated solution was treated with an organic acid alone without mixing the starch separated solution with the gelled protein separated solution. The residence time in the acid production tank 3 was 24 hours, and the residence time in the methane fermentation tank 4 was 48 hours. Other conditions are the same as in the first embodiment. The BOD concentration of the organic acid producing liquid (the methane fermentation tank introduction liquid) is 12000 to 21000 mg / l,
BOD load of methane fermenter 4 is 6 to 10.5kg / m
³ / d, which is 3/4 to 1 / compared to the load of the first embodiment.
Set to 2. Table 2 shows the results.

[0045]

[Table 2]

The SS and BOD of the methane fermentation solution (treated water) of Example 2 are higher than those of Example 1, and if the methane fermentation solution cannot be discharged as it is, further aerobic treatment is performed.

Reference Example 1 The organic acid production solution obtained in Example 2 was diluted 5 times with city water (BOD = 2400 to 4200 mg / l), and this diluted solution was introduced into the methane fermentation tank 4 to load the BOD. Amount 2.4-4.
When the methane fermentation treatment was performed at 2 kg / m ³ / d (residence time: 24 hours), the BO of the methane fermentation treatment liquid (treated water) was
As for D, 300 to 350 mg / l equivalent to that of Example 1 was obtained.

Comparative Example 1 In Example 1, the starch separated solution obtained in the precipitation tank 1 was used alone to produce an organic acid. Example 1 is the condition of the acid generation tank 3.
Is the same as The obtained organic acid solution is supplied to the methane fermenter 4
(Residence time: 8 hours), and methane fermentation treatment was performed. As a result, the load of the methane fermenter 4 is 10 to 10.
5 kg / m ³ / d, the generated gas amount was 6.5 to 6.9 times per 4 volumes of the methane fermentation tank, and the BOD of the methane fermentation treatment liquid was 300 to 350 mg / l, which is equivalent to that of Example 1. Table 3 shows the results.

[0049]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a system diagram illustrating an apparatus for anaerobic treatment of a starch particle-containing liquid according to an example of the present invention.

[Explanation of symbols]

 Reference Signs List 1 sedimentation tank 2 liquefaction treatment tank 3 acid generation tank 4 methane fermentation tank 5 gas storage tank 6 boiler 7 coagulation tank 8 solid-liquid separator 11 raw water passage 12 concentrated liquid passage 13 starch separation liquid passage 14 liquefaction treatment liquid passage 15 steam supply passage 16 pH adjuster supply path 21, 26, 41 Communication path 22 Coagulant supply path 23, 32 Stirrer 27 Protein discharge path 28 Dehydrator 29 Protein recovery path 31 Acid generation liquid path 35 Treatment water path 36 Gas discharge path 37 Sludge blanket 42 Water supply Channel 43 Drainage channel 45 Starch particles

Continued on the front page F term (reference) 4D040 AA02 AA12 AA13 AA14 AA61 AA62 AA63 4D059 AA06 AA30 BA12 BK12 CA07 CA27

Claims (3)

[Claims] 1. A starch particle-containing liquid having a pH of 4.6 to 5.4,
An anaerobic treatment method for a starch particle-containing liquid, comprising: a liquefaction treatment step of liquefaction treatment at a temperature of 50 to 70 ° C; and an anaerobic treatment step of anaerobic treatment of the liquefaction treatment liquid in the presence of sludge containing anaerobic microorganisms. 2. A concentration separation step of separating a starch particle-containing liquid into a starch particle concentrate and a starch separation liquid; and said starch particle concentrate at a pH of 4.6 to 5.4 and a temperature of 50 to 50%.
Anaerobic treatment of starch particle-containing liquid comprising: a liquefaction treatment step of liquefaction treatment at 70 ° C .; and an anaerobic treatment step of introducing the liquefaction treatment liquid and the starch separation liquid and anaerobic treatment in the presence of sludge containing anaerobic microorganisms. Sex treatment method. 3. A starch particle-containing solution or a concentrated solution having a pH of 4.
Starch having a liquefaction treatment device for liquefaction treatment at 6-5.4 and a temperature of 50-70 ° C., and an anaerobic reaction tank for introducing at least a liquefaction treatment solution and performing anaerobic treatment in the presence of sludge containing anaerobic microorganisms Anaerobic treatment device for particle-containing liquid.