JP2002224686A - Anaerobic treatment method and equipment for starch particle-containing liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anaerobic treatment method and equipment for a starch particle-containing liquid capable of efficiently subjecting the entire part of the starch particle-containing liquid to anaerobic treatment under a high load at a high speed. SOLUTION: The starch particle-containing liquid is separated to starch particles 10 and a starch separating liquid in a settling tank 1. The starch particle concentrate containing the starch particles 10 is introduced into an ozone treating vessel 2 where the concentrate is subjected to ozone treatment after regulation to a pH <=5 by hydrochloric acid. The treated liquid is introduced into an acid forming vessel 3 where the liquid is mixed with the starch separating liquid and its anaerobic property is maintained. After organic acid formation is effected by acid forming bacteria and the acid forming liquid is introduced into a methane fermenter 4 where the acid forming liquid is passed in upward current through a sludge blanket 27. The organic acids are anaerobically decomposed by methane forming bacteria and are 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 anaerobically treating a starch particle-containing liquid, and more particularly to a starch particle-containing liquid suitable for treating starch-producing wastewater 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) Anaerobic starch starch-containing liquid having an ozone treatment step of ozone-treating a starch particle-containing liquid at a pH of 5 or less and an anaerobic treatment step of anaerobic-treating the ozonized liquid in the presence of sludge containing anaerobic microorganisms. Sex treatment method. (2) a concentration separation step of separating the starch particle-containing solution into a starch particle concentrate and a starch separation solution;
Anaerobic starch starch-containing liquid having an ozone treatment step of ozone treatment at H5 or less, and an anaerobic treatment step of introducing an ozone treatment liquid and the starch separation liquid and performing anaerobic treatment in the presence of sludge containing anaerobic microorganisms Sex treatment method. (3) An ozone treatment apparatus for ozone-treating a starch particle-containing liquid or a concentrated liquid at a pH of 5 or less, and an anaerobic reaction tank for introducing at least an ozone-treated liquid and performing anaerobic treatment in the presence of sludge containing anaerobic microorganisms. Anaerobic treatment device for starch particle-containing 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 has a BOD of around 30,000 mg / l and an SS of 50
High concentration decanter drainage around 00mg / l and BOD
Is roughly classified into hydrocyclone wastewater of around 2000 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 abundant in hydrocyclone wastewater, and sometimes there is hydrocyclone wastewater in which most of the SS is starch particles,
The present invention can be suitably applied to such treatment of hydrocyclone wastewater.

In the ozone treatment step of the present invention, the starch particles are modified so as to be easily liquefied. The starch particle-containing liquid is maintained at a pH of 5 or less, preferably 3 or less, and an ozone-containing gas is supplied. The starch particles are ozonated. This ozone treatment softens the surface of the starch particles, and facilitates liquefaction by anaerobic treatment. Proteins and other organic solids are also modified to facilitate liquefaction. For the ozone treatment, an apparatus provided with a pH adjusting means capable of adjusting the pH of the starch particle-containing liquid to the above-mentioned pH and an ozone-containing gas supply means can be used. As the ozone-containing gas, besides pure ozone, a mixed gas of ozone and another gas, for example, ozonized air can be used.

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.

The starch particles in the starch particle-containing liquid are maintained at the above-mentioned pH, and are supplied with 0.1 to 1% by weight of ozone-containing gas per SS to ozone-treat, so that they are almost completely treated in 1 to 2 hours. Be reformed. Here, "modified" means that starch particles are no longer observed under a microscope, or the surface is oxidized and deteriorated, and no color reaction by iodine-starch reaction is observed. When the starch particles are completely liquefied, the anaerobic treatment process is facilitated. However, since a large amount of ozone and a long treatment time are required, the surface of the remaining starch particles and other SS components without liquefaction is required. It is preferable to perform the ozone treatment to such an extent that the material is degraded and easily decomposed.

In the ozone treatment, it is preferable to supply an ozone-containing gas corresponding to 0.1 to 1% by weight of ozone per SS (amount of starch particles). 100 for 100 kg-DS / hr
It means supplying an ozone-containing gas of １０００1000 g-O ₃ / hr.

When the pH of the ozone treatment is 3 or less and the ozone treatment tank is sufficiently stirred, the effect of ozone treatment of the starch particles is high even if the supply amount of the ozone-containing gas is small. If it is 5, the effect is reduced.
When the pH exceeds 5, the ozone treatment effect becomes 1/3 or less as compared with the case where the pH is 3 or less, and the appropriate supply amount of the ozone-containing gas depends on the pH in the ozone treatment tank, the stirring state, and the like. You. Therefore, for example, when the concentration of starch particles is 10
000 mg / l or more, and the pH in the ozone treatment tank is 3
Hereinafter, the supply amount of the ozone-containing gas when sufficient stirring is performed may be 0.1% by weight of SS, and the residence time of the ozone treatment tank may be 1 to 2 hours.

On the other hand, when the pH of the ozone treatment is less than 4.6, the rate of protein denaturation in the liquid to be treated becomes a gel due to acid modification, and therefore the amount of starch particles contained in the gel also increases. However, since the protein gelled by the ozone treatment is also modified by oxidation and easily liquefied in the anaerobic treatment step, the liquefaction efficiency does not decrease even if the starch particles are included in the gelled protein. The main cause of the liquefaction of starch particles by ozone treatment is not clear, but it is estimated that liquefaction in the acid generation step of anaerobic treatment becomes easy because the structure (crystalline state) of starch particles is weakened by the oxidizing power of ozone. Is done.

The liquid to be subjected to the ozone treatment is mainly composed of insoluble starch particles, and contains SS containing proteins, lipids and the like at a concentration of 1000.
0 mg / l or more, preferably 10,000 to 20,000 m
g / l is desirable. Since the SS concentration in the starch production wastewater is usually about 500 to 5000 mg / l, a concentration separation step is provided before the ozone treatment step,
It is preferable to perform ozone treatment on a starch particle concentrate obtained by concentrating starch particles. The ozone treatment of the starch particle concentrate makes it possible to reduce the size of the ozone treatment apparatus, reduce the amount of pH adjuster, reduce the amount of ozone supplied, and the like.

In the present invention, the concentration separation step provided before the ozone 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 starch particle concentrate obtained in the concentration separation step is subjected to the above-mentioned ozone treatment, and the starch separation liquid is subjected to the later-described anaerobic treatment.

In the ozone supply apparatus used in the ozone treatment step, the amount of the starch particles in the starch particle concentrate is 50 to 50%.
100 kg-DS / hr, which is equivalent to 0.1 kg / starch particle amount.
When 1% by weight of ozone is supplied, 50 to 100 g-ozone / hr is required. Therefore, a large and highly efficient ozone supply device is suitable, and a discharge method using dry air or high-concentration oxygen gas as a raw material is used. preferable.

The anaerobic treatment step of the present invention is a step of anaerobically treating the ozonized solution subjected to the ozone treatment in the presence of sludge containing anaerobic microorganisms. When the concentration separation step is provided, it is usually preferable to perform anaerobic treatment on the ozonized liquid and the starch separated liquid obtained in the concentration separation step, but it is also possible to perform anaerobic treatment on only the ozonized liquid.

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 targeted for treatment, and solid matter is preferably liquefied in advance in the acid generation step. In the present invention, starch, proteins, and other organic solids are modified to be easily decomposed by ozone treatment, so that they can be liquefied at a high speed in the acid generation step. 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 contact 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. The acid generation step and the methane generation step may be separated from each other, and an organic acid is generated from liquefied starch, protein, and other organic substances by an acid-producing bacterium at a stage prior to the methane generation step. A two-phase system in which methane is generated from an organic acid under a high load by a UASB method or the like in which the concentration is maintained at a high concentration is preferable in terms of the processing speed and the amount of methane generated. Anaerobic treatment using methanogens at 30-38 ° C., preferably 35-36 ° C., BOD concentration of 2000-30000 mg in any of the one-phase type and the two-phase type.
/ L, preferably 3000 to 6000 mg / l, can maintain the anaerobic state to increase the activity of the methane-producing bacteria and perform the treatment efficiently.

In the acid generation step in the anaerobic treatment step, the surface structure of starch, protein, and other organic particles in the ozonized solution is weakened, and liquefaction and acid generation are likely to occur. The starch wastewater contains a large amount of acid-producing bacteria that convert ozonized starch into lower fatty acids (organic acids) such as formic acid, acetic acid, and propionic acid. However, even if it is killed or inactivated by the ozone treatment, the acid generation reaction is caused by the bacteria in the starch separated solution. Therefore, the starch wastewater is separated into solid and liquid, the concentrated solution is treated with ozone, and the ozonized solution is separated into the starch separated solution And anaerobic treatment is preferred.

Even when the starch wastewater is directly subjected to ozone treatment, liquefaction can be sufficiently performed by charging a carrier or the like into the acid generation tank and holding the sludge. A part of the treated water generated from the methane generation step can be returned to the acid generation step for the purpose of accelerating the acid generation reaction. In this case, the amount returned may be about 1% by volume of the inflow of the acid generation step.

The residence time of the acid generating step is 3 hours when the temperature of the solution in the tank is 3
When the pH is adjusted to 5 to 7 at a temperature of 5 to 37 ° C., it takes about 4 to 12 hours. When the pH in the acid generating tank is lowered by the inflow of the starch separation liquid, the pH can be adjusted with an alkaline agent such as sodium hydroxide.

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

[0028] The anaerobic treatment decomposes soluble organic substances obtained by liquefying starch and other solid substances, and generates methane and carbon dioxide gas. The gas generated here can be collected and used as fuel. The treatment liquid can be used as it is or diluted with other low-concentration wastewater or industrial water, etc., and discharged to sewers, etc., or by aerobic treatment with other low-concentration wastewater to decompose residual organic matter. You can also.

As described above, according to the present invention, the ozone-treated solution can be subjected to anaerobic treatment by subjecting the starch particles to ozone treatment in the ozone treatment step, and the starch particles can be reduced to agricultural land as in the conventional method. This eliminates the need for landfill treatment, and the entire starch production wastewater can be efficiently anaerobic treated at high load and at high speed. Therefore, farmland return,
Odors generated during landfill processing can be prevented. In addition, the present invention can be carried out with existing anaerobic treatment equipment by installing an ozone 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.

Usually, the anaerobic reaction of starch particles proceeds in the following three steps. 1) First reaction A liquefaction reaction for converting 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.

In the case of starch in a crystalline state, the time required for the liquefaction reaction, which is the first reaction, is the longest among the time required for the above series of reactions, and the pH is around neutral, and the anaerobic condition at a liquid temperature of around 36 ° C. It turns out that it takes three to four days. The organic acid generation reaction, which is the second reaction, proceeds in 4 to 12 hours when the liquefaction reaction has sufficiently proceeded. In the methane formation reaction as the third reaction, a high load treatment with a BOD load of 10 kg / m ³ / d or more is possible when the organic acid formation reaction is sufficiently proceeding.

In the method of proceeding the liquefaction reaction of starch particles by liquefaction at a pH of 4.6 to 5.4 and a temperature of 50 to 70 ° C., when a large amount of protein is contained in the starch particles, the pH is lowered. The liquefaction reaction efficiency is reduced because the protein gelled by the treatment wraps the starch particles.

In the present invention, the ozone treatment at a pH of 5 or less allows the ozone treatment to be carried out within the time required for the organic acid generating step.
Liquefaction of starch and other solids and acid generation can be performed simultaneously. For this reason, there is no need to separate the starch particles and reduce them to agricultural land, or to perform landfill treatment, and the entire starch production wastewater can be efficiently subjected to anaerobic treatment at high load and at high speed.

[0034]

According to the anaerobic treatment method of the starch particle-containing liquid of the present invention, the starch particle-containing liquid or the starch particle concentrated liquid is subjected to the anaerobic treatment after the ozone treatment at pH 5 or less, so that the starch particles are not separately treated. In addition, the entire starch particle-containing liquid can be efficiently subjected to anaerobic treatment at a high load and at a high speed. The apparatus for anaerobic treatment of starch particle-containing liquid of the present invention has an ozone treatment apparatus for ozone-treating the starch particle concentrated liquid at pH 5 or less, so that the entire starch particle-containing liquid can be treated without separately treating the starch particles. Anaerobic treatment can be performed efficiently at high load and at high speed.

[0035]

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 an ozone treatment tank, 3 is an acid generation tank, 4 is a UASB methane fermentation tank, and 5 is an ozone generator.

The settling tank 1 is connected to a raw water channel 11, a concentrated liquid channel 12, and a starch separated liquid channel 13. Ozone treatment tank 2
Is connected to a concentrate passage 12, an ozonation treatment passage 14, a pH adjusting agent supply passage 15, and an ozone supply passage 18, and a stirrer 17 is provided therein. The solution is introduced from the concentrate channel 12 and the pH of the solution in the tank is adjusted.
Is maintained at 5 or less, preferably 3 or less, and the ozone generator 5 generates an ozone-containing gas, supplies the ozone-containing gas from the ozone supply path 18, and performs ozone treatment. .

In the acid generating tank 3, a starch separating liquid path 13, an ozone treatment liquid path 14, an acid generating liquid path 21, a pH adjusting agent supply path 2
3 are connected, and a stirrer 22 is provided inside. The methane fermenter 4 is connected to an acid-generating liquid passage 21 at a lower portion and a gas recovery passage 28 to an upper portion. In the treated water channel 25, a return line 26 is branched, and a part of the treated water is returned to the acid generation tank 3. A sludge blanket 27 is formed inside the methane fermenter 4. The acid production tank 3 and the methane fermentation tank 4 constitute an anaerobic reaction tank.

In order to treat the starch particle-containing liquid with the anaerobic treatment apparatus shown in FIG.
Into the precipitation tank 1 and separated into starch particles 10 and a starch separation liquid by gravity sedimentation. The starch particle concentrate containing the starch particles 10 is introduced into the ozone treatment tank 2 from the concentrate passage 12 for ozone treatment, and the starch separated solution is introduced into the acid generation tank 3 from the starch separation passage 13 to generate an organic acid. .

In the ozone treatment tank 2, a concentrated starch particle solution containing the starch particles 10 is introduced from the concentrated liquid passage 12, and hydrochloric acid is supplied from the pH adjusting agent supply passage 15 so that the pH of the liquid in the tank becomes the above-mentioned pH. Then, an ozone-containing gas is supplied from the ozone supply path 18 to perform ozone treatment. Usually, in 1 to 2 hours, the starch particles 10 are almost completely modified to be liquefiable. The ozone-containing gas is generated by the ozone generator 5 and has a volume of 0.1 g / SS.
The ozone is supplied in an amount of 1 to 1% by weight.

In the acid generating tank 3, the ozone treatment liquid and the starch separation liquid separated in the precipitation tank 1 are introduced.
An aqueous solution of sodium hydroxide is supplied from the regulator supply channel 23, mixed with the solution in the tank containing the acid-producing bacterium while maintaining anaerobic and gently stirring with the stirrer 22 to remove starch and other modified solids. Liquefaction and organic acid generation. 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 21 and is passed upward through the sludge blanket 27. 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 channel 25 as treatment water,
A part is branched and returned to the acid generation tank 3 from the return path 26.
The amount returned may be about 1% of the amount of the inflow liquid into the acid generation tank 3. The generated gas is recovered from the gas recovery path 28 and used as fuel gas or the like.

In the apparatus shown in FIG. 1, a floating methane fermentation tank may be used instead of a high-load anaerobic treatment apparatus such as a UASB method. Furthermore, the precipitation tank 1 may be omitted, and the raw water may be directly introduced into the ozone treatment tank 2 for liquefaction.

[0043]

EXAMPLE 1 The starch production wastewater was anaerobically treated by the apparatus shown in FIG. That is, regarding the mixed wastewater of decanter wastewater and hydrocyclone wastewater discharged from the potato starch production process,
Anaerobic treatment was performed. The above decanter drainage has BOD of 3
0000mg / l, SS is around 5000mg / l, and hydrocyclone wastewater has BOD of 2000mg
/ L, SS is about 500 mg / l, and particulate starch is contained in a large amount in hydrocyclone wastewater. The mixed wastewater to be treated is a mixed wastewater obtained by diluting the decanter wastewater with hydrocyclone wastewater 10 times, and the SS of this mixed wastewater is 950 mg / l and the BOD is 4800 mg / l.
(See Table 1). The mixed waste water was settled and separated in the sedimentation tank 1 (initial sedimentation tank) also serving as a raw water tank for a residence time of 4 hours to obtain a starch particle concentrated liquid and a starch separated liquid. The SS and BOD are shown in Table 1.

The above-mentioned starch particle concentrate is introduced into an ozone treatment tank 2, adjusted to pH 3 with hydrochloric acid, and then brought into contact with an ozone-containing gas having an ozone content of 100 mg-ozone / l under vigorous stirring.
Ozone treatment was performed for 1 hour. The ozone amount is 15 mg-ozone / l corresponding to 0.1% by weight of the SS amount. This ozone-treated solution had an SS of 3000 mg / l, but no blue color was observed in a color reaction by an iodine-starch reaction, and no starch particles were observed by microscopic observation.
As a result of the measurement of organic nitrogen in SS, it was revealed that the main component of SS in the ozonized solution was a protein gelled and precipitated, but the surface structure was in a weakened state.

The ozonized solution was mixed with the starch separation solution obtained in the precipitation tank 1, and this mixture was introduced into the acid generation tank 3, and the pH of the mixture was adjusted to pH.
After adjusting to 6, the mixture was slowly stirred under the conditions of a liquid temperature of 36 ° C. and a residence time of 8 hours to produce an organic acid. The SS of the obtained organic acid-generating solution (introduced into the methane fermentation tank) increased to 550 mg / l due to the growth of acid-producing bacteria, and the BOD increased to 5500 mg / l because starch particles were liquefied and easily measured in BOD. did. 80% of the BOD component was lower fatty acids (organic acids) such as acetic acid, propionic acid, lactic acid, and butyric acid and ethanol, and a sufficient organic acid generation reaction had 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 methane production rate of the organic acid production liquid was measured by a batch method, and the load (removal amount) of the methane fermenter 4 was determined. The residence time in the methane fermentation tank 4 was set to 8 hours with respect to the amount of the separated liquid in the precipitation tank 1, the pH in the tank was adjusted to 7.0, and the liquid temperature was adjusted to 36 ° C. The methane production rate is obtained from the amount of generated methane gas, and the calculated BOD load of the methane fermenter 4 is 14 kg.
/ M ³ / d. The methane fermentation treatment liquid (treated water) had a BOD of 300 to 350 mg / l, and the amount of generated gas reached 9.1 to 9.7 times per 4 volumes of the methane fermentation tank. The content of carbon dioxide in the generated gas is 18-25.
% By volume. Table 1 shows the results.

[0047]

[Table 1]

Example 2 In Example 1, the ozone-treated solution was subjected to the organic acid generation treatment alone without mixing the ozone-treated solution with the starch separation solution. The residence time of the acid generation tank 3 is 24 hours, and the methane fermentation tank 4
Was 48 hours. Other conditions are the same as in the first embodiment. BO of organic acid production liquid (methane fermentation tank introduction liquid)
The D concentration was 12000 to 21000 mg / l, and the BOD load of the methane fermenter 4 was 6 to 10.5 kg / m ³ / d, which was set to 3/4 to て compared to the load of Example 1. . Table 2 shows the results.

[0049]

[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, aerobic treatment is further performed.

Reference Example 1 The organic acid solution obtained in Example 2 was diluted 5-fold 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 amount of generated gas was 6.5 to 6.9 times per 4 volumes of the methane fermentation tank, and the BOD of the methane fermentation solution was 300 to 350 mg / l, which is equivalent to that of Example 1. Table 3 shows the results.

[0053]

[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 ozone treatment tank 3 acid generation tank 4 methane fermentation tank 5 ozone generator 10 starch particles 11 raw water path 12 concentrated liquid path 13 starch separation liquid path 14 ozone treatment liquid path 15, 23 pH adjuster supply path 17, 22 Stirrer 18 Ozone-containing gas supply path 21 Acid generation liquid path 25 Treatment water path 26 Return path 27 Sludge blanket 28 Gas recovery path

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 9/00 503 C02F 9/00 503C 504 504A 504E

Claims (3)

[Claims] 1. A starch particle-containing liquid comprising: an ozone treatment step of ozone-treating a starch particle-containing liquid at a pH of 5 or less; and an anaerobic treatment step of anaerobic-treating the ozonized liquid in the presence of sludge containing anaerobic microorganisms. Anaerobic treatment method. 2. A concentration separation step of separating a starch particle-containing liquid into a starch particle concentrate and a starch separation liquid; an ozone treatment step of ozone-treating the starch particle concentrate at a pH of 5 or less; an ozone treatment liquid and the starch An anaerobic treatment step of introducing a separation liquid and anaerobic treatment in the presence of sludge containing anaerobic microorganisms. 3. An ozonation apparatus for ozone-treating a starch particle-containing liquid or a concentrated liquid at a pH of 5 or less, and an anaerobic reaction tank for introducing at least an ozonation liquid and anaerobic-treating in the presence of sludge containing anaerobic microorganisms. An anaerobic treatment apparatus for a starch particle-containing liquid, comprising: