JP2007007494A - Method of operating methane fermentation tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methane fermentation tank-operating method which enables an efficient and stable control of a methane fermentation tank when the concentration of acetic acid contained in treated wastewater by methane fermentation is measured to carry out the operation control of the methane fermentation tank. <P>SOLUTION: In the methane fermentation tank-operating method, organic acids-containing organic wastewater is treated by the methane fermentation in the methane fermentation tank to separate methane gas, and then the treated wastewater is taken out. After the treated wastewater undergoes ion exchange treatment beforehand, the concentration of acetic acid in the treated wastewater is quantitatively analyzed by using gas chromatography, and the supply amount of the organic wastewater is controlled by using the obtained acetic acid concentration as an index. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for operating a methane fermenter, and more particularly to a method for operating a methane fermenter that efficiently and stably controls the methane fermenter.

  As described in Non-Patent Document 1, methane fermentation treatment reacts a component that can be a nutrient source of microorganisms present in nature in organic wastewater in the presence of specific bacterial cells in an anaerobic atmosphere, as methane gas. It is a process that removes it from organic wastewater by volatilization. It is a technology that prevents the increase of water pollutants such as rivers and oceans, and also uses useful methane gas as an energy source such as fuel. The amount of a component that can be a nutrient source for microorganisms in the wastewater can be measured as a biological oxygen demand (BOD). Hereinafter, components that can serve as nutrient sources for microorganisms are sometimes referred to as BOD components.

  Conventionally, activated sludge treatment has been used as a method for treating BOD components in wastewater, but there has been a problem that excess sludge is generated as industrial waste. On the other hand, in the methane fermentation treatment, surplus sludge can be reduced and methane gas can be used as an alternative to the energy. Therefore, the cost of the entire process can be reduced, and has attracted much attention in recent years.

  In the methane fermentation treatment, a BOD component is hydrolyzed using a group of cells with a specific gravity slightly higher than water with a diameter of about 2 mm, which is called granule, followed by an acetic acid production reaction, and finally a reaction that generates methane gas from acetic acid. It decomposes into methane gas via Each of these is played by the different cells present in the granule, and this series of reactions is called methane fermentation.

  As an index for determining the quality of bacterial activity in methane fermentation treatment, there is acetic acid concentration in treated wastewater. In methane fermentation, acetic acid is a reaction intermediate for various organic substances, but the growth rate of the activity of bacteria that convert acetic acid into methane (methane bacteria) compared to those responsible for hydrolysis and acetic acid production reactions Is known to be slow.

  Acetic acid is also a nutrient source for granules, but at the same time it becomes a poisonous substance at high concentrations. For this reason, it is thought that in many cases where the methane fermentation treatment is unsuccessful, the phenomenon results in acetic acid accumulating in the treated water. As acetic acid accumulates, it will fall into a vicious cycle in which the activity of the cells further decreases, which is called overload. Therefore, if acetic acid is accumulated, it is necessary to immediately reduce the load of the methane fermenter to reduce the acetic acid concentration.

  As a method of preventing overload of the methane fermentation tank, a method of managing by organic acid analysis (also referred to as volatile fatty acid VFA: Volatile Fatty Acid) so that acetic acid that adversely affects the cells used in the methane fermentation treatment does not accumulate. Is often used.

Organic acid analysis is widely recognized as a simple method for analyzing acetic acid in treated water, but the analytical method is to boil the treated water in a flask to drive off the remaining acidic component CO ₂ and then A strong acid such as sulfuric acid is added to adjust the pH to 3.5 to release the weak acid once, and then caustic soda is added to calculate by titration between pH 4 and 7. In organic acid analysis, almost all organic acids are detected, and there is a possibility that acidic substances other than organic acids may be added. It is called.

  Methane fermentation treatment has been widely used in foods, especially beer factories, shochu factories, pulp factories, and other industries that process organic wastewater containing a large amount of biodegradable substances discharged after processing plants. This is because the BOD component in the wastewater is originally derived from plants and has high biodegradability and few toxic substances, so that there is an advantage that it is not necessary to consider adverse effects on the cells. When wastewater from some specific plants that contain a lot of easily decomposable substances is treated by methane fermentation, the amount of organic acid is almost equal to the amount of acetic acid. In other words, there was no hindrance to the operation management of methane fermentation.

  However, when treating a wide variety of wastewater, there is a high possibility that an organic acid other than acetic acid is contained in the wastewater to be treated, and the result of the organic acid analysis may detect components other than acetic acid.

  For example, carboxylic acids such as terephthalic acid, p-toluic acid, and benzoic acid belong to a class of hardly decomposable components for methane fermentation treatment, and at a low concentration of 1000 mg / L or less, it does not have an adverse effect but is difficult to decompose. There is a high possibility of being discharged as it is. If this is the case, these difficult-to-decompose carboxylic acid components other than acetic acid will increase the organic acid analysis value, and the organic acid analysis value that should be judged as the concentration of acetic acid will increase. Will cause the load (processing amount) to be misjudged.

  On the other hand, gas chromatography can be considered as a method for effectively measuring only acetic acid. Gas chromatography is widely used for component analysis of all substances. Hydrogen or an inert gas such as helium or argon is used as a carrier gas, and the substance to be detected is gasified and flowed through the carrier gas, followed by chromatographic separation in a column. This is a device that detects changes in temperature detection due to thermal conductivity or combustion with a detector.

  However, if an analysis of acetic acid in the treated effluent is performed by gas chromatography, the treated effluent is neutralized in the preparation tank for pretreatment of the methane fermentation tank, so acetic acid and organic acids exist as salts. There is a problem that there is something that cannot be detected. In the organic acid analysis, the organic acid was liberated by a technique of weak acid liberation by a strong acid. However, liberation of the organic acid by this technique in the gas chromatography analysis cannot be adopted due to fear of corrosion of the apparatus by the strong acid.

Therefore, the organic acid analysis used for the methane fermentation treatment cannot quantitatively analyze only acetic acid, and if the organic wastewater contains organic acids such as persistent carboxylic acids, It was difficult to operate efficiently and stably.
RESpeece original, anaerobic biotechnology for industrial wastewater treatment, Gihodo Publishing, 1999

  The object of the present invention is to control the methane fermentation tank efficiently and stably when measuring the acetic acid concentration contained in the treated wastewater of the methane fermentation process by gas chromatography analysis and controlling the operation of the methane fermentation tank. An object of the present invention is to provide a method of operating a methane fermenter that makes it possible to do this.

  The operation method of the methane fermenter of the present invention that achieves the above object is an operation method of a methane fermenter that separates methane gas from an organic wastewater containing an organic acid by methane fermentation treatment in the methane fermenter and takes it out as treated wastewater. Then, after treating the treated wastewater with ion exchange treatment in advance, the acetic acid concentration in the treated wastewater is quantitatively analyzed using gas chromatography, and the supply amount of organic wastewater is controlled using the obtained acetic acid concentration as an index. This is the driving method.

  In the operation method of the methane fermenter of the present invention, the acetic acid concentration is quantitatively analyzed using gas chromatography by removing the partner ion in the neutralized salt of acetic acid in the treated wastewater by ion exchange treatment. be able to. Using the obtained acetic acid concentration as an index, it is possible to accurately grasp the load status of the methane fermenter, so that it is possible to operate the methane fermenter efficiently and stably without mistaking whether or not the load can be increased. can do.

  The present invention is described in detail below.

  The operation method of the methane fermentation tank of this invention supplies the organic waste water containing an organic acid to a methane fermentation tank, isolate | separates BOD component as methane gas by carrying out methane fermentation process, and takes out as a treated waste water operation method of the methane fermentation tank A methane fermenter that performs quantitative analysis of acetic acid concentration in the treated wastewater after ion exchange treatment of the treated wastewater, and controls the supply amount of organic wastewater using the acetic acid concentration as an index. This is the driving method.

  FIG. 1 is an explanatory diagram of a typical process flow of the methane fermentation treatment of the present invention. One or more kinds of organic waste water 1 containing the BOD component is received in the buffer tank 2 and supplied to the adjustment tank 5 in a certain amount. In the adjustment tank 5, the temperature and pH are adjusted, and then supplied to the methane fermentation tank 7. Biogas is generated from the methane fermentation tank 7, and after passing through the gas flow meter 10, is effectively used as a gas for a combustion furnace or the like. A part of the wastewater treated in the methane fermentation tank 7 is returned to the adjustment tank 5 to adjust the COD (Cr) exposure concentration to the granules, but the supply amount is discharged as treated wastewater 11 to the outside of the system. Is done.

  On the other hand, the treated wastewater contains acetic acid contained in the organic wastewater 1 and / or a neutralized salt of acetic acid produced in the methane fermentation treatment tank 7. In order to quantitatively analyze this, the present invention includes a step of quantitatively analyzing the treated waste water for analysis by the gas chromatography 14 after performing the ion exchange treatment 12.

  Further, in order to calculate the load of the methane fermentation treatment tank 7, a flow meter 3 for quantifying the supply amount of the organic waste water 1 and a COD (Cr) meter 4 for measuring the COD or TOC of the organic waste water 1 are arranged.

  Although BOD is effective as an index for the original purpose of suppressing the nutrient supply of living organisms, there is a problem that a long period of 5 days is required for analysis, and it is difficult to quickly respond to management. Therefore, in proceeding with management indicators and chemical studies, chemical oxygen consumption (COD) and total organic carbon (TOC) are indicators that show a similar similarity to BOD in a short time. Carbon) can be used as an indicator.

COD indirectly measures the influence of the oxidant consumption of a reference oxidant on the eutrophication of organisms, and KMnO ₄ , K ₂ Cr ₂ O _7, or the like is used as the oxidant. CODs using these are expressed as COD (Mn) and COD (Cr), respectively.

  In the operation method of the methane fermenter of the present invention, COD (Cr), COD (Mn), TOC, and BOD are preferably used as indicators of biological eutrophication, and COD (Cr), COD (Mn), TOC Is more preferable, and COD (Cr) is more preferable.

  The present invention is a method of operating a methane fermentation tank for subjecting an organic wastewater containing an organic acid to a methane fermentation treatment. The organic acid preferably contains acetic acid, and preferably contains an organic acid other than acetic acid in order to exhibit the effects of the present invention. The organic acid other than acetic acid is preferably at least one carboxylic acid, and preferred examples of the carboxylic acid include fatty acids other than acetic acid, aromatic carboxylic acids, and alicyclic carboxylic acids.

  In the present invention, among these carboxylic acids, aromatic carboxylic acids are hardly decomposable for the methane fermentation treatment, and are preferable for exhibiting the effects of the present invention. Further, it is particularly preferable that the aromatic carboxylic acid is at least one of p-toluic acid, benzoic acid, isophthalic acid, and terephthalic acid.

  In the present invention, as described in Non-Patent Document 1, the organic wastewater to be supplied needs to have a substance having no toxic effect at a high concentration. For example, the cation of sodium, potassium, calcium, or magnesium is 1900-7400 mg / L or less.

  Moreover, it is desirable that the concentration range is such that no toxic effects are observed even with organic substances. For example, it is preferable that phenol is 1500 mg / L or less and benzoic acid is 4000 mg / L or less.

  However, when supplying the same organic wastewater again to a granule that has been exposed to the same organic wastewater for a long time, or when using a granule that has been exposed to an organic wastewater containing a toxic substance for a long time. It is also possible to exceed this range.

  The process for supplying organic wastewater is not particularly limited. For example, high-boiling residues after terephthalic acid reaction / filtration, methyl acetate waste liquid, wastewater from polyester chip polymerization process, p-toluic acid, p-toluylaldehyde production process Reaction waste liquid, etc. are mentioned. Of course, it is more preferable that there are many substances which are easily decomposable by methane fermentation, such as acetic acid and methanol.

  In this invention, the COD (Cr) density | concentration in the supply part of the methane fermenter, ie, the adjustment tank 5, becomes like this. Preferably it is 5000-10000 mg / L, More preferably, it is 5000-8000 mg / L. If the COD (Cr) concentration in the adjustment tank 5 exceeds the above range, there is a high possibility that granule activity will be reduced and overload will occur due to concentration inhibition as described above. Since mutual predation (cannibalism) is concerned, it is not preferable.

  That is, it is preferable for stable operation that the organic waste water supply amount is adjusted in accordance with the activity of the granule, and the exposure concentration is as constant as possible within the appropriate range. It is also desirable to adjust the amount of waste water circulated from the methane fermentation tank 7 to the adjustment tank 5 so that the COD (Cr) concentration in the adjustment tank 5 is stable within the above range.

  If the COD (Cr) concentration of the organic wastewater supplied to the methane fermenter is within the above range, the COD (Cr) exposure concentration to the granule is almost the same as the COD (Cr) concentration during culture. It is suitable and the activity of the granule can be efficiently exhibited. For this reason, it is preferable to adjust the circulation amount returned from the methane fermentation tank 7 to the adjustment tank 5 so as to achieve this COD (Cr) concentration.

  In the present invention, the methane fermentation tank 7 is preferably operated at a pH of 6 to 8, more preferably at a pH of 6 to 7. Therefore, the pH of the organic waste water is adjusted in the adjustment tank 5. In pH adjustment, caustic soda is inexpensive and often used. However, it is preferable to supply an inorganic alkali source in a concentration range that does not give toxicity to granules.

  In this invention, if the setting conditions of the methane fermenter 7 are a normal granule, the temperature 30 to 40 degreeC and the operation at 50 to 55 degreeC are preferable when using a high temperature tolerance microbe. For temperature adjustment, steam may be directly blown in the adjustment tank 5 or the like, or a heater or a cooler may be used indirectly by a heat exchanger or the like.

  The methane fermentation tank 7 used in the present invention may have any shape, but it is preferable that the granule and the waste water are mixed well. However, care must be taken not to crush the granules due to strong agitation in the methane fermenter. For example, a complete mixing tank, a batch type, a fluidized bed, etc. are preferable.

  In the present invention, the form of the methane fermenter is an upward anaerobic sludge blanket (UASB) in which organic wastewater is supplied from the bottom and passed through a vertical tower filled with granules in an upward flow to generate biogas. The method is preferred. More preferably, an internal circulation (IC) reactor manufactured by Ishikawajima-Harima Heavy Industries Co., Ltd. in which the inside is stirred with the generated gas is most preferable.

In the present invention, the amount of granules to be filled is preferably about 1/100 to 1/20 [ton-dry granule / m ³ -volume of tank], more preferably 1/100 to the methane fermentation tank. 40 to 1/60 [ton-dry granule / m ³ -tank volume]. The granule filling amount may be appropriately determined according to the COD (Cr) load of the organic wastewater to be supplied.

In the present invention, the COD (Cr) load of the organic waste water supplied to the methane fermentation tank is preferably 10 to 40 kg-COD (Cr) / m ³ -methane fermentation tank · Day, more preferably 20 to 30 kg-COD ( Cr) / m ³ -methane fermenter · Day.

  In the present invention, the treated wastewater discharged from the methane fermenter after biodegradation of organic matter has a COD (Cr) concentration of preferably 10,000 mg / L or less, more preferably 8000 mg / L or less. If the COD (Cr) concentration of the treated wastewater exceeds the above range, there is a concern that untreated COD (Cr) is large and COD (Cr) removal becomes insufficient. A part of the treated wastewater is returned to the adjustment tank 5 for condition adjustment, but most of the treated wastewater is discharged out of the system as treated wastewater after the organic substance decomposition treatment is completed.

  In the present invention, a part of the treated waste water is used for analysis of acetic acid concentration. The analytical treatment wastewater collected from the treatment wastewater is first subjected to ion exchange treatment. The ion exchange resin used for the ion exchange treatment is preferably a cation exchange resin, and more preferably an H (hydrogen) type cation exchange resin. Examples of such a cation exchange resin include Levacit (manufactured by Mitsui Chemicals), Diaion (manufactured by Mitsubishi Chemical), Amberlite (manufactured by Organo), and the like.

  The ion exchange treatment method of the present invention is not particularly limited as long as it releases acetic acid from the neutralized acetate, but is a method in which an ion exchange resin is added to the treated waste water and stirred and mixed. For example, the regenerated H-type cation exchange resin is preferably added in an amount of 50 to 70 parts by weight, more preferably 55 to 65 parts by weight, and more preferably 10 to 30 minutes, relative to 100 parts by weight of the treated wastewater. May be stirred and mixed for 15 to 25 minutes. The solution is then filtered with suction and the filtrate is used for gas chromatography analysis.

  The gas chromatography used in the present invention may be any method as long as acetic acid can be detected, but the detector is preferably an FID method.

  An example of a method for measuring the acetic acid concentration in the treated waste water in the present invention will be described. First, 60 parts by volume of the regenerated cation exchange resin is added to 100 parts by volume of the treated wastewater sample, stirred for 20 minutes and then filtered by suction. The filtrate is placed in a 100 ml volumetric flask and aligned with a marked line with ion-exchanged water for analysis. Use liquid. Next, 8 ml of analytical solution volume measurement + internal standard solution (1,4-dioxane 25.4 mg / ion exchange water 2 ml) 2 ml is put in a test tube and stirred well. Inject 1 μL into gas chromatography, start the analysis, measure for about 30 minutes, and then read the analysis result.

  Gas chromatographic measurement is, for example, GC7A manufactured by Shimadzu Corporation for the main body, PEG-20M chromosorb WA A-DMCS 20% mesh 80 to 100 (manufactured by Shimadzu Corporation) for the column, and column length of φ3.1 mm × 2.1 m, Column temperature 60 → 150 ° C., Initial time 4 minutes, heating rate 8 ° C./min, detector temperature 200 ° C., detector type FID, carrier can be measured by He (40 ml / min).

  In the present invention, the concentration of acetic acid in the treated wastewater can be analyzed by gas chromatography by performing ion exchange treatment, the correct acetic acid concentration can be measured, and the acetic acid concentration in the methane fermentation tank can be accurately grasped. In view of operation management, it is possible to accurately determine whether or not the load can be increased.

  The operating method of the present invention is an operating method of a methane fermenter that increases the load of the methane fermenter when the concentration of acetic acid in the treated wastewater is preferably 300 ppm or less, more preferably 60 ppm or less. When the concentration of acetic acid in the treated wastewater exceeds 300 ppm, it is not preferable to increase the load on the methane fermentation tank because the generation of methane gas tends to decrease due to acetic acid poisoning due to overload.

The load of the methane fermenter is the total amount of chemical oxygen consumption [COD (Cr)] using K ₂ Cr ₂ O ₇ as an oxidant in the daily supply of organic wastewater. The value divided by the volume. The load can be adjusted by adjusting the amount of organic wastewater supplied to the methane fermentation tank and / or the COD (Cr) concentration of the organic wastewater.

  In the operation method of the methane fermenter of the present invention, the ratio of (load increase amount) / (load amount before load increase) is preferably less than 1.0, more preferably 0.25 per one time to increase the load. Is less than. If the rate of increase in load per cycle is 1.0 or more, it is not preferable because the concentration is inhibited by a large concentration change, resulting in overload, acetic acid accumulating and a decrease in activity.

  In the operation method of the methane fermenter of the present invention, the period until the load is increased after the load of the methane fermenter is once increased is preferably 3 days or more, more preferably 3 to 5 days. If the period from the load increase of the methane fermenter to the next load increase is less than 3 days, there is a concern of overloading because the cells that are not accustomed to the change in concentration will be exposed to higher concentrations. Absent.

  Moreover, the operation method of the methane fermentation tank of the present invention is an operation method of the methane fermentation tank that reduces the load of the methane fermentation tank when the concentration of acetic acid in the treated wastewater is preferably 300 ppm or more, more preferably 150 ppm or more. is there. When the concentration of acetic acid in the treated wastewater is 500 ppm or more, the inside of the methane fermentation tank is overloaded, and there is a risk of falling into a vicious circle where acetic acid concentration accumulates. It is preferable to reduce.

  The present invention is not limited to the following examples.

[Methane fermentation treatment equipment]
Reactor made by Ishikawajima-Harima Heavy Industries (capacity of methane fermentation tank: 550 m ³ ), temperature: 35 ° C., pH: 6.5-6.8, packed granule: 10 tons (dry basis) The amount is 100 m ³ / h.

[Ion exchange treatment]
30 g of cation exchange resin (Lebatit manufactured by Mitsui Chemicals, Inc.) is added to 50 g of treated waste water, and after stirring for 20 minutes, suction filtration is performed. Use liquid.

[Gas chromatography measurement]
Place 8 ml of sample solution for analysis (volumetric measurement) + 2 ml of internal standard solution (1,4-dioxane 25.4 mg / ion-exchanged water 2 ml) in a test tube and stir well. Inject 1 μL into gas chromatography and start analysis.

  The gas chromatographic measurement is GC7A manufactured by Shimadzu Corporation for the main body, PEG-20M chromosorb WA A-DMCS 20% mesh 80-100 (manufactured by Shimadzu Corporation) for the column, the column length is φ3.1 mm × 2.1 m, the column temperature 60 → 150 ° C., Initial time 4 minutes, temperature rising rate 8 ° C./min, detector temperature 200 ° C., detector type FID, carrier was He (40 ml / min).

[Method of organic acid concentration analysis]
Take 100 parts of treated wastewater in a round bottom flask, add 1 part of 0.1 N sulfuric acid, cook for 10 minutes with an alcohol lamp, etc., then titrate with 0.1 N caustic soda, pH 4-7 The organic acid concentration was measured by the method of reading the equivalent amount from the amount consumed during It should be noted that the organic acid concentration is handled assuming that all equivalents show values converted as acetic acid.

Comparative Example 1
Organic wastewater containing paratoluic acid, benzoic acid, terephthalic acid, and acetic acid mainly composed of high boiling waste liquid and methyl acetate waste liquid from the terephthalic acid production process was subjected to methane fermentation using the above methane fermentation treatment equipment. The organic acid concentration and the acetic acid concentration in the organic waste water (feed solution) and the treated waste water were measured, and the results are shown in Table 1. In addition, the load of the methane fermentation tank in a table | surface remove | divides the COD (Cr) supply amount to the methane fermentation tank per day by the volume of the methane fermentation tank.

  Moreover, the acetic acid density | concentration in process waste_water | drain was analyzed by the said method by a gas chromatography, without performing an ion exchange process in advance. The organic acid concentration in the treated waste water continuously indicated 300 to 600 mg / L, and the analysis result of the acetic acid concentration by gas chromatography without ion exchange treatment also showed ND.

Moreover, since the generation amount of biogas was stable, the load of the methane fermentation tank was increased by increasing the supply flow rate from 27 m ³ / h to 32 m ³ / h.

  However, since then the amount of biogas generated decreased, the load was immediately reduced. Later, the acetic acid concentration in the treatment liquid was measured using gas chromatography after ion exchange treatment.

  Table 1 shows the results of the organic acid concentration and the acetic acid concentration after the load increase, and the acetic acid concentration by gas chromatography after the ion exchange treatment.

  As a result of measuring the acetic acid concentration by gas chromatography after the ion exchange treatment, the acetic acid concentration in the treated water was 350 ppm before the load was increased and increased to 1800 ppm after the load was increased.

Example 1
Organic wastewater (feed liquid) having the same components as in Comparative Example 1 was subjected to methane fermentation in the same manner as in Comparative Example 1. Table 2 shows the organic acid concentration / acetic acid concentration in the treated waste water and the subsequent load increase results.

The organic acid concentration before the load increase was 400 ppm, which was equivalent to Comparative Example 1. However, when acetic acid was measured in advance by introducing ion exchange treatment as described above, it was found to be less than 10 ppm. found. For this reason, the load of the methane fermenter was increased from 22 m ³ / h to 26 m ³ / h [(load increase amount) / (load amount before load increase) ratio of 0.18].

  As a result, the amount of biogas generated increased and the performance of the methane fermentation treatment followed. At this time, the acetic acid concentration after 3 days was less than 10 ppm.

  The difference between Example 1 and Comparative Example 1 was that Example 1 was 4 days after the previous load up of the methane fermentation layer, whereas Comparative Example 1 was 2 days. For this reason, the comparative example 1 was the stage before the methane microbe in a methane fermenter fully stabilized. Therefore, in the case of Comparative Example 1, if the acetic acid concentration is measured by gas chromatography by ion-exchange treatment of the treated wastewater in advance by the operation method of the present invention, it is found that the acetic acid concentration is 400 ppm, and the load It is expected that the app could be accurately judged to be inappropriate.

Example 2
Organic wastewater (feed liquid) having the same components as in Comparative Example 1 was subjected to methane fermentation in the same manner as in Comparative Example 1. Table 3 shows the organic acid concentration / acetic acid concentration in the treated waste water and the subsequent load increase results.

The organic acid concentration before the load increase was 400 ppm, which was the same as that in Comparative Example 1. However, when ion exchange treatment was introduced in advance as described above and the acetic acid was measured by gas chromatography, it was found to be less than 10 ppm. . The load increased from 15 m ³ / h to 35 m ³ / h [(load increase amount) / (load amount before load increase) ratio 1.3].

  As a result, the amount of biogas generated temporarily increased, but acetic acid accumulated thereafter. Since the acetic acid concentration after 3 days was 700 ppm, the load was reduced.

It is explanatory drawing which shows an example of the flow of the methane fermentation equipment used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic waste water 2 Buffer tank 3 Flow meter 4 COD (Cr) meter 5 Adjustment tank 6 Reactor supply water 7 Methane fermentation tank (reactor)
8 Reflux water 9 Reactor exhaust biogas 10 Gas flow meter 11 Treatment wastewater 12 Ion exchange treatment 13 Analytical treatment wastewater (after ion exchange treatment)
14 Gas chromatography

Claims (8)

  An operation method of a methane fermentation tank that separates methane gas from an organic wastewater containing an organic acid by a methane fermentation treatment in a methane fermentation tank and takes out the treated wastewater as a treated wastewater. A method for operating a methane fermenter that quantitatively analyzes the concentration of acetic acid in a gas chromatograph and controls the amount of organic wastewater supplied using the obtained acetic acid concentration as an index.   The operation method of the methane fermenter of Claim 1 which uses a cation exchange resin for the said ion exchange process. In the daily supply amount of the organic waste water, a value obtained by dividing the total amount of chemical oxygen consumption [COD (Cr)] using K ₂ Cr ₂ O ₇ as an oxidizing agent by the volume of the methane fermenter is methane. The operation method of the methane fermenter of Claim 1 or 2 which increases the load of the said methane fermenter, when the acetic acid density | concentration in the said treated wastewater is 300 ppm or less as a fermenter load.   The operation method of the methane fermenter in any one of Claims 1-3 in which the said organic acid contains at least 1 carboxylic acid other than an acetic acid.   The method for operating a methane fermentation tank according to claim 4, wherein the carboxylic acid is an aromatic carboxylic acid.   The method for operating a methane fermenter according to claim 5, wherein the aromatic carboxylic acid is at least one of p-toluic acid, benzoic acid, isophthalic acid, and terephthalic acid.   The methane fermentation according to any one of claims 3 to 6, wherein when the load of the methane fermentation tank is increased, the ratio of (load increase) / (load before the load increase) is less than 1.0. How to operate the tank.   The method for operating a methane fermenter according to any one of claims 3 to 7, wherein when the load of the methane fermenter is increased, a period until the load is increased next after the load increase is 3 days or more.

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