JP5233812B2 - Anaerobic treatment facility and method, and starch production wastewater treatment facility and method - Google Patents

Description

  The present invention relates to an anaerobic treatment facility and method, and a starch production wastewater treatment facility and method.

  Patent Document 1 below discloses an anaerobic treatment method for starch production wastewater in a starch factory. The starch production effluent in the starch factory is mainly the juice (primary decanter juice) after grinding the potato, which is the raw material, and squeezing the starch with a decanter (horizontal continuous centrifuge). It is drainage. In the anaerobic treatment method, the primary decanter juice is heated and subjected to deproteinization treatment for coagulating and separating the protein, followed by methane fermentation treatment (anaerobic treatment). According to such an anaerobic treatment method, since the nitrogen concentration of the raw methane fermentation water can be reduced as compared with the conventional method, it is possible to realize an efficient starch production wastewater treatment without reducing the activity of the methanogen. Can do.

Japanese Patent No. 3846131

  By the way, although the said prior art is effective as a process of a primary decanter soup, it does not consider the process of a secondary decanter soup and has room for improvement. That is, in the starch factory, in order to improve the purification degree of starch, water is added to the starch obtained by separating the primary decanter juice and centrifuged again. The secondary decanter juice generated by the separation is not as high as the primary decanter juice but is a high protein-containing wastewater. It was confirmed that when such a secondary decanter juice was subjected to a methane fermentation treatment together with a primary decanter juice that had been deproteinized based on the above-described conventional technology, the methane fermentation treatment was not stable.

  In order to solve such problems, the applicant filed a Japanese Patent Application No. 2008-106736 on April 16, 2008. The invention according to the Japanese Patent Application No. 2008-106736 is based on the stabilization of methane fermentation. Although there is a sufficient effect, the amount of VFA (lower fatty acid which is a precursor of methane fermentation) remaining in the methane fermentation treated water is high and the amount of COD (chemical oxygen demand) load of the organic matter to be treated There is a problem that methane gas cannot be recovered. In other words, the invention according to Japanese Patent Application No. 2008-106736 is inadequate in terms of processing efficiency of anaerobic processing, and generates a recovery amount of methane gas expected from the COD (chemical oxygen demand) load of the organic matter to be processed. I can't let you.

The present invention has been made in view of the above-described circumstances, and has the following objects.
(1) Improve the anaerobic treatment efficiency of the organic matter to be treated.
(2) Improve the anaerobic treatment efficiency of the low-concentration protein wastewater generated in the secondary decanter juice or / and starch purification step.

  In order to achieve the above object, in the present invention, as a first solution for an anaerobic treatment facility, a sodium addition device for adding sodium to a treatment target organic substance, and a treatment target to which sodium is added by the sodium addition device A means is provided that includes an anaerobic treatment tank in which organic matter is subjected to methane fermentation in the presence of at least acetic acid-assimilating methanogenic bacteria.

  As the second solving means relating to the anaerobic treatment facility, in the first solving means, the sodium adding device adopts a means of adding sodium as a sodium compound to the organic substance to be treated.

  As a third solving means relating to the anaerobic treatment facility, a means is adopted in which the sodium compound is sodium chloride (NaCl) or sodium hydroxide (NaOH) in the second solving means.

  As a fourth solving means related to the anaerobic treatment facility, in any of the first to third solving means, the sodium addition device adds sodium to the organic substance to be treated at a predetermined time interval set in advance. Adopt the means.

  As a fifth solving means related to the anaerobic treatment facility, in any of the first to fourth solving means, sodium supplied from the sodium addition device and the organic substance to be treated are mixed and supplied to the anaerobic treatment tank. A means of further including a premixing tank is employed.

  As a sixth solving means related to the anaerobic treatment facility, in any of the first to fifth solving means, the sodium addition device is configured so that the amount of biogas produced by methane fermentation is a treatment load in the anaerobic treatment tank. Adopting a method of adding sodium so that the amount is suitable for the above.

  As the seventh solving means relating to the anaerobic treatment facility, in the sixth solving means, the amount of sodium added to the raw water of the anaerobic treatment tank is set to tens of mg / l to several tens of mg / l. Adopt the means.

  Further, in the present invention, as a first solving means related to the processing facility for starch production wastewater, it is a processing facility for processing starch production wastewater generated in a starch factory, and is a secondary decanter juice that is starch production wastewater or / and A storage tank that retains low-concentration protein wastewater generated in the starch refining process at a predetermined holding temperature and holding time, and first to seventh methane fermentation using the stored wastewater discharged from the storage tank as a fermentation stock solution. An anaerobic treatment facility according to any one of the above solution means and an aerobic treatment tank that aerobically treats the treatment liquid of the anaerobic treatment facility are employed.

  As a second solution relating to the processing facility for starch production wastewater, in the first solution means, a protein precipitation tank for coagulating and precipitating the protein contained in the primary decanter juice, which is one of the starch production wastewater, and the protein And a solid-liquid separation means for removing the coagulated protein from the treatment liquid in the precipitation tank, and the storage tank is a secondary decanter juice or / and a low concentration of the deproteinized primary decanter juice that is the separation liquid of the solid-liquid separation means. Adopting the method of mixing with protein wastewater.

  As 3rd solution means which concerns on the processing facility of starch manufacture waste_water | drain, in the said 1st or 2nd solution means, holding temperature and holding time are conditions for the activity of the enzyme contained in a secondary decanter juice to fall. The method of being set is adopted.

  As a fourth solution relating to the processing facility for starch production wastewater, in the second or third solution, in the storage tank, the secondary decanter juice or / and the low-concentration protein wastewater and the deproteinized primary decanter juice are A means of mixing at a ratio that is a holding temperature is adopted.

  Moreover, in this invention, the 1st solution means which concerns on anaerobic processing method employ | adopts the means of adding sodium to a process target organic substance and carrying out methane fermentation in the presence of at least an acetic acid utilization methanogen. .

  As a second solving means related to the anaerobic treatment method, in the first solving means, the sodium adding device adopts a means of adding sodium as a sodium compound to the organic substance to be treated.

  As a third solving means relating to the anaerobic treatment method, a means is adopted in which, in the second solving means, the sodium compound is sodium chloride (NaCl) or sodium hydroxide (NaOH).

  As a fourth solution means related to the anaerobic treatment method, in any of the first to third solution means, the sodium addition device adds sodium to the organic substance to be treated at a predetermined time interval set in advance. Adopt the means.

  As a fifth solving means related to the anaerobic treatment method, a means is used in which any one of the first to fourth solving means described above is premixed with sodium and an organic substance to be treated and then subjected to methane fermentation.

  As the sixth solving means relating to the anaerobic treatment method, in any of the first to fifth solving means, sodium is suitable for the amount of biogas produced by methane fermentation in accordance with the treatment load in the anaerobic treatment. Adopting a means of adding in an amount.

  As the seventh solving means related to the anaerobic treatment method, in the sixth solving means, the amount of sodium added to the raw water in the anaerobic treatment tank is set to tens of mg / l to several tens of mg / l. Adopt the means.

  Moreover, in this invention, it is the method of processing the starch manufacture waste_water | drain generate | occur | produced in a starch factory as a 1st solution means concerning the processing method of starch manufacture waste_water | drain, Secondary decanter juice which is starch manufacture waste_water | drain, and / or starch A retention step of retaining the low-concentration protein wastewater generated in the purification step for a predetermined retention temperature and retention time, and the retention step based on the anaerobic treatment method according to any one of the first to seventh solving means An anaerobic treatment step in which methane fermentation is carried out using the stored wastewater discharged from the fermentation as a fermentation stock solution, and an aerobic treatment step in which the treatment liquid in the anaerobic treatment step is aerobically treated is adopted.

  As a second solution relating to a method for treating starch production wastewater, a protein precipitation step for coagulating and precipitating the protein contained in the primary decanter juice, which is one of the starch production wastewater, in the first solution, and the protein A solid-liquid separation step for removing the coagulated protein from the treatment liquid in the precipitation step, and the storage step is mixed with the deproteinized primary decanter juice or / and the low-concentration protein waste water that is the separation liquid in the solid-liquid separation step , Is adopted.

  As 3rd solution means concerning the processing method of starch manufacture waste water, in the above-mentioned 1st or 2nd solution means, retention temperature and retention time are conditions for the activity of the enzyme contained in secondary decanter juice to fall. The method of being set is adopted.

  As a fourth solution according to the method for treating starch production wastewater, in the second or third solution, in the storing step, secondary decanter juice or / and low-concentration protein wastewater and deproteinized primary decanter juice are obtained. A means of mixing at a ratio that is a holding temperature is adopted.

According to the present invention relating to the anaerobic treatment equipment and method, at least acetic acid-assimilating methanogenic bacteria are present, so that sodium is added to the organic matter to be treated for methane fermentation, so that the activity of the methane fermentation bacteria is improved. Therefore, the processing efficiency of the anaerobic processing in general organic matter to be processed can be improved.
In addition, according to the present invention relating to the processing equipment and method for starch production wastewater, secondary decanter juice and / or low concentration protein wastewater generated in the starch purification process is added with sodium to cause methane fermentation. The activity of the anaerobic treatment in the low-concentration protein wastewater generated in the secondary decanter juice or / and starch purification step can be improved.

It is a block diagram which shows the function structure of the processing equipment of the starch manufacture waste_water | drain concerning one Embodiment of this invention. In one Embodiment of this invention, it is a 1st graph which shows the relationship (experimental result) with addition of the caustic soda X5, and the production amount of the methane fermentation product gas in the anaerobic processing tank 6. FIG. In one Embodiment of this invention, it is a 2nd graph which shows the relationship (experimental result) with addition of the caustic soda X5, and the production amount of the methane fermentation product gas in the anaerobic processing tank 6. FIG. In one Embodiment of this invention, it is a graph which shows the relationship (experimental result) with addition of a common salt and the production amount of the methane fermentation product gas in the anaerobic processing tank 6. FIG. In one Embodiment of this invention, it is a schematic diagram for qualitatively explaining the effect of addition of caustic soda X5. It is a graph which shows the experimental result of the experiment A in one Embodiment of this invention. It is a 1st graph which shows the experimental result of the experiment B in one Embodiment of this invention. It is a 2nd graph which shows the experimental result of the experiment B in one Embodiment of this invention. It is a graph which shows the examination result of the experiment C in one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a functional configuration of a starch production wastewater treatment facility (starch production wastewater treatment facility) according to the present embodiment. As shown in this figure, this starch production wastewater treatment facility A is provided in a starch factory for producing starch using potato as a raw material, and is a facility for processing starch production wastewater generated in the starch factory, A precipitation tank 1, a solid-liquid separator 2, a storage tank 3, a circulating water tank 4, a caustic soda supply device 5, an anaerobic treatment tank 6, an aerobic treatment tank 7, and a boiler 8 are provided.
In addition, among the said structural requirements which comprise this starch manufacture waste water treatment equipment A, the storage tank 3, the circulating water tank 4, the caustic soda supply apparatus 5, and the anaerobic treatment tank 6 comprise the anaerobic treatment equipment in this embodiment. ing.

  Here, the starch production wastewater (processing target organic matter) in this embodiment is the primary decanter juice X1, the secondary decanter juice X2, and the low-concentration protein wastewater X3. The primary decanter juice X1 is a sap after mashing the raw material potato and squeezing the starch with a decanter (horizontal continuous centrifuge), and is a liquid at room temperature containing high protein and organic components. The secondary decanter juice X2 is a juice obtained by adding substantially the same amount of water as the primary decanter juice X1 to the starch obtained from the above decanter and squeezing the starch again with the decanter, which is lower than the primary decanter juice X1. It is a liquid at room temperature that contains high protein and organic components. The low-concentration protein wastewater X3 is a room temperature wastewater in which a low-concentration protein generated in the step of purifying the starch separated from the secondary decanter juice X2 (starch purification step) is dissolved.

  The protein precipitation tank 1 heats (heat-treats) the primary decanter juice X1 using water vapor supplied from the boiler 8 to coagulate and precipitate the protein dissolved in the primary decanter juice X1. The solid-liquid separator 2 removes coagulated protein from the treatment liquid in the protein precipitation tank 1 and supplies the deproteinized primary decanter juice X4, which is a separation liquid, to the storage tank 3. The deproteinized primary decanter juice X4 is obtained from the primary decanter juice X1 heat-treated in the protein precipitation tank 1, and has a temperature of about 80 ° C.

  The storage tank 3 has a ratio at which the secondary decanter juice X2 (room temperature), the low-concentration protein waste water X3 (room temperature), and the deproteinized primary decanter juice X4 (about 80 ° C.) have a predetermined holding temperature (for example, 45 ° C.). Is a container having a predetermined capacity for holding the mixed liquid mixed in step (a) for a predetermined holding time (4H or more), and the stored drainage liquid X6 after the holding is supplied to the circulating water tank 4. Steam is supplied from the boiler 8 to the storage tank 3 as an auxiliary heat source in order to maintain a holding temperature (for example, 45 ° C.) over a holding time (4H). The holding temperature and holding time are set as conditions for reducing the activity of the enzyme contained in the secondary decanter juice X2 and / or the low-concentration protein waste water X3, as will be described in detail later.

As described above, the holding temperature (for example, 45 ° C) is realized by the mixing ratio of secondary decanter juice X2 (room temperature), low-concentration protein waste water X3 (room temperature) and deproteinized primary decanter juice X4 (about 80 ° C). In this case, the processing ratio of the secondary decanter juice X2, the low-concentration protein waste water X3, and the deproteinized primary decanter juice X4 is defined by the mixing ratio. In order to avoid such inconvenience, secondary decanter juice X2, low-concentration protein waste water X3, and deproteinized primary decanter juice X4 are mixed at an arbitrary ratio, and the holding temperature (for example, 45 ° C) is set to the supply amount of water vapor. You may make it prescribe.
Moreover, although one reservoir tank 3 is described in FIG. 1, a plurality of reservoir tanks 3 may be provided. In the case where a plurality of reservoirs 3 are provided, the reservoir drainage X6 is supplied to the circulating water tank 4 substantially continuously by performing a batch operation of each reservoir 3.

  The circulating water tank 4 includes a stored drainage liquid X6 (methane fermentation processing stock solution) supplied from the storage tank 3, a part of the methane fermentation processed liquid X8 discharged from the anaerobic processing tank 6, and a caustic soda supply device 5. The supplied caustic soda X5 is mixed and supplied to the anaerobic treatment tank 6 as a methane fermentation treatment mixed solution X7.

  The caustic soda supply device 5 adds sodium (more precisely, sodium ions) to the stored waste liquid X6 by supplying caustic soda X5 (sodium hydroxide (NaOH)), which is a kind of sodium salt, to the circulating water tank 4. This is a sodium addition device. The caustic soda supply device 5 supplies a predetermined amount of caustic soda X5 to the circulating water tank 4 at preset times (for example, twice a day, in the morning and in the afternoon). The supply amount of caustic soda per time is determined based on the operating conditions (for example, processing load (CODcr volume load), granule retention amount, retained waste liquid X5 (methane fermentation treatment stock solution) of the anaerobic treatment tank 6 in the subsequent stage. It is appropriately set according to the ion content.

  The anaerobic treatment tank 6 causes methane fermentation by causing a well-known methane-fermenting bacterium (granule) to act on the methane fermentation treatment mixed solution X7 supplied from the circulating water tank 4. The aerobic treatment tank 7 performs aerobic treatment on the fermentation treatment liquid in the anaerobic treatment tank 6 in a state where air is blown, and discharges the treatment liquid to a river or the like outside the starch factory. The boiler 8 generates water vapor using methane gas obtained from the anaerobic treatment tank 6 as a fuel, and supplies the water vapor to the protein precipitation tank 1 and the storage tank 3.

  Next, the processing method of the starch manufacture waste_water | drain (process target organic substance) in this starch manufacture waste water treatment equipment A comprised in this way is demonstrated in detail.

  In the starch production wastewater treatment facility A, among the various starch production wastewaters generated in the starch factory, the primary decanter juice X1 passes through the protein precipitation tank 1 and the solid-liquid separator 2 to deproteinize the primary decanter juice X4. Is supplied to the storage tank 3 and held for a predetermined holding temperature (for example, 45 ° C.) and a holding time (4H or more). On the other hand, the secondary decanter juice X2 and the low-concentration protein waste water X3 are directly supplied to the storage tank 3 without going through the protein precipitation tank 1 and the solid-liquid separator 2, and are confused with the deproteinized primary decanter juice X4. In this state, it is held for a holding temperature (for example, 45 ° C.) and a holding time (4H or more).

  Thus, the stored waste liquid X6 (methane fermentation treatment stock solution) retained in the storage tank 3 is supplied to the circulating water tank 4 and a part of the methane fermentation processed liquid X8 discharged from the anaerobic treatment tank 6 and It is mixed with the caustic soda X5 supplied from the caustic soda supply device 5 and supplied to the anaerobic treatment tank 6 as a methane fermentation treatment mixed solution X7. That is, the liquid obtained by mixing the secondary decanter juice X2, the low-concentration protein waste water X3, and the deproteinized primary decanter juice X4, which are held under the above-described holding conditions, with the methane fermentation treated liquid X8 and the caustic soda X5 is the methane fermentation mixed liquid X7. Is supplied to the anaerobic treatment tank 6.

  Such a methane fermentation treatment mixed solution X7 is subjected to methane fermentation treatment by the action of methane fermentation bacteria in the anaerobic treatment tank 6 and supplied to the circulating water tank 4 and the aerobic treatment tank 7 as a methane fermentation treated liquid X8. Here, most of the methane fermentation-treated liquid X8 is supplied to the aerobic treatment tank 7, detoxified by the aerobic treatment, and discharged outside the starch factory. A part of the methane fermentation-treated liquid X8 is mixed with the stored drainage liquid X6 (methane fermentation treatment stock solution) in the circulating water tank 4 and then circulated and supplied to the anaerobic treatment tank 6 for methane fermentation treatment again. .

Among the starch production wastewater treatment processes in the starch production wastewater treatment facility A, the most characteristic feature of the starch production wastewater treatment method is that the stored wastewater X6 (methane fermentation treatment stock solution) and caustic soda X5 Is mixed with methane fermentation treatment periodically.
The secondary decanter juice X2, the low-concentration protein waste water X3, and the deproteinized primary decanter juice X4 are held in the storage tank 3 under a holding condition of a predetermined holding temperature (for example, 45 ° C.) and a predetermined holding time (4H). Although this point is one of the features, details of this point are described in Japanese Patent Application No. 2008-106736 filed on April 16, 2008, and thus detailed description thereof is omitted here.

  2 and 3 show the relationship between the addition of the caustic soda X5 and the amount of methane fermentation product gas (biogas mainly composed of methane gas and carbon dioxide) produced in the anaerobic treatment tank 6 (biogas production amount). It is the experimental result (graph) measured over the day, and more specifically, the pH value (circulating water tank pH value) and temperature (circulating water tank temperature) in the circulating water tank 4, and the pH value in the anaerobic treatment tank 6 ( It is a measurement result of a processing tank pH value), temperature (processing tank temperature), and the said biogas production amount. 2 and 3, FIG. 2 shows changes in the amount of biogas produced during the first addition of caustic soda X5 and the second addition of caustic soda X5 after a predetermined time has elapsed since the first time. 3 shows the change in the amount of biogas produced in the third addition of caustic soda X5 after a predetermined time has elapsed since the second time.

  2 and 3 show that the addition of caustic soda X5 significantly increases the amount of biogas produced, that is, the methane fermentation treatment in the anaerobic treatment tank 6 is significantly accelerated. That is, when the caustic soda X5 is supplied from the caustic soda supply device 5 to the circulating water tank 4, the circulating water tank pH value and the treatment tank pH value rise as shown in the figure, and the biogas generation amount rapidly increases in synchronization with the change in the pH value. To increase. And the amount of biogas production gradually decreases after this rapid increase.

More specifically, as the first addition of caustic soda X5, caustic soda X5 is supplied with 20% (W / W) caustic soda X5 over about 2 hours until the pH value of the circulating water tank becomes 6.5 to 6.7. 5 was supplied to the circulation water tank 4, jumped biogas production amount of the anaerobic treatment tank 6 is higher than after the supply start ten minutes from 220 m 3 ^/ when to 440m 3 ^/ h. In addition, with such a rapid increase in the amount of biogas generated, the concentration of VFA (Volatile Fatty Acid; a lower fatty acid that is a precursor of methane fermentation) remaining in the anaerobic treatment tank 6 becomes 24 after the introduction of caustic soda X5. It decreased to 300 mg / l with time.

After the rapid increase described above, the amount of biogas generated once converged once at 300 m ³ / hour, which is the amount generated according to the processing load in the anaerobic treatment tank 6, that is, the COD (Chemical Oxygen Demand) chemical load. However, after 20 hours from the introduction of the caustic soda X5, it shows a gradual decreasing trend, and after 2 days from the introduction, the VFA concentration again rises to around 1000 mg / l, and the biogas production decreases to 230 m ³ / hour. It showed a tendency to return to the state before the introduction of X5.

Therefore, when caustic soda X5 was supplied to the circulating water tank 4 as the second addition of caustic soda X5, a rapid increase in the amount of biogas produced was confirmed as in the first time. However, in this second addition, caustic soda X5 was intermittently added over 12 hours so as to gradually increase the pH value of the circulating water tank from 6.5 to 6.7 to 6.9, and 8 hours from the resumption of addition. Later, the VFA concentration in the anaerobic treatment tank 6 dropped to around 200 mg / l, and the amount of biogas produced was maintained at 300 m ³ / hour, which was the amount of COD generated in the anaerobic treatment tank 6. .

Six days after the re-addition, the VFA concentration in the anaerobic treatment tank 6 increased again to 600 mg / l, and the biogas generation amount decreased to 260 m ³ / hour. When caustic soda X5 was added again, anaerobic treatment was performed. A rapid increase in the amount of biogas produced in the treatment tank 6 and a decrease in VFA concentration occurred again. Thereafter, caustic soda X5 was added intermittently at an addition amount of 360 (liters / hour) at 0.5 hours / times in the morning and at night, and the VFA concentration in the anaerobic treatment tank 6 became 200 mg / l or less. Moreover, the amount of biogas produced was an amount commensurate with the COD load of the anaerobic treatment tank 6.

Such experimental results indicate that the addition of caustic soda X5 has the effect of increasing the amount of biogas generated, that is, improving the processing efficiency of the methane fermentation process in the anaerobic processing tank 6. However, it is unclear which of the sodium ions (Na ⁺ ) and hydroxide ions (OH ⁻ ) constituting the caustic soda X5 (sodium hydroxide: NaOH) contributes to the improvement of the processing efficiency of the methane fermentation treatment. It is.

Of the sodium ions (Na ⁺ ) and hydroxide ions (OH ⁻ ), the former is expected to serve as an essential mineral source for methane bacteria and the latter as a pH adjuster. When the amount of biogas generated increases and the VFA concentration of the treatment liquid in the anaerobic treatment tank 6 decreases, the treatment tank pH value rises and the circulating water tank pH value also rises. That is, since the pH adjustment function is maintained, if there is an effect of hydroxide ions (OH ⁻ ), the activity of methane bacteria is stable even after the addition of caustic soda X5 is stopped, so an anaerobic treatment tank No increase in VFA concentration in the processing solution in 6 or a decrease in biogas generation amount should occur, but as described above, when the addition of caustic soda X5 is stopped in the experimental results, the biogas generation amount is reduced. It falls and falls into a worsening trend.

Therefore, the addition of the caustic soda X5 is stopped for 4 days under the operating condition where the CODcr volumetric load in the anaerobic treatment tank 6 is about 11 kg / m ³ / d, and the VFA concentration of the treated water in the anaerobic treatment tank 6 is 200 mg / l or less. When the biogas generation amount was 220 m ³ / hour, which showed a tendency to deteriorate from the state of 1, the common salt was added instead of the caustic soda X 5. The addition amount of this normal salt is an amount corresponding to the addition amount of sodium ions (Na ⁺ ) by the caustic soda X5.

That is, NaOH specific gravity = 1.22, NaOH concentration 20% (W / W), input amount 180 liter / time, NaOH molecular weight = 40, Na atomic weight = 23, Cl atomic weight = 35.5, NaCl molecular weight = 58.5. Then, the amount of sodium ion (Na ⁺ ) added from the caustic soda X5 is 25.3 kg (= 180 × 1.22 × 20 ÷ 100 × 23 ÷ 40), so the same amount of sodium ion (Na ⁺ ) Is required to supply 64.3 kg (= 25.3 × 58.5 ÷ 23) as normal salt (NaCl).

FIG. 4 is a graph showing the relationship (experimental results) between the addition of such normal salt and the amount of biogas produced in the anaerobic treatment tank 6. According to this experimental result, a rapid increase in the amount of biogas generated occurs 10 minutes after the addition of normal salt, as with the addition of caustic soda X5, and the amount of biogas generated increases to 320 m ³ / hour. did. This experimental result shows that the addition of sodium ions (Na ⁺ ), that is, sodium as a mineral source is effective for the treatment efficiency of the methane fermentation treatment in the anaerobic treatment tank 6.

Next, the following logical explanation can be considered for the experimental results shown in FIGS. That is, FIG. 5 shows a generally known reaction process of methane fermentation, but as shown in this figure, the reaction process of methane fermentation is divided into two reaction pathways for protein and starch contained in potato. That is, the reaction path L1 (acetic acid assimilating methane) which changes from sugar → fatty acid (CH _m CH _n COOH) → acetic acid (CH ₃ COOH) and finally produces methane (CH ₄ ) and carbon dioxide (CO ₂ ). Production reaction path) and a reaction path that changes from sugar → fatty acid (CH _m CH _n COOH) → propionic acid (CH ₃ CH ₂ COOH) → acetic acid (CH ₃ COOH), and hydrogen generated in the reaction process It is processed through a reaction path L2 (hydrogen-utilizing methane generation reaction path) for generating methane (CH ₄ ) from (H ₂ ) and carbon dioxide (CO ₂ ). Of these two reaction paths L1 and L2, it is generally said that the reaction path L1 is the main path and occupies nearly 70% of the entire reaction and the remaining 30% is occupied by the reaction path L2.

For such reaction paths L1 and L2, sodium ions (Na ⁺ ) act as a “sodium pump” on hydrogen-utilizing methanogens in the reaction path L2, and hydrogen (H ₂ ) in the reaction system. Is expected to lead to a rapid increase in methane (CH ₄ ). In fact, the theoretical biogas increase increased by converting VFA remaining before addition of sodium ion (Na ⁺ ) to methane (CH ₄ ) is larger than the actual increase, and hydrogen (H ₂ ) in the reaction system is increased. It can be inferred to be due to the synthesis of methane (CH ₄ ) due to consumption of methane. In addition, the consumption of hydrogen (H ₂ ) promotes a process in which propionic acid (CH ₃ CH ₂ COOH) is decomposed into acetic acid (CH ₃ COOH), and the concentration of propionic acid remaining in the treated water also decreases. For this reason, when sodium ion (Na ^<+> ) is added, it is thought that the VFA density | concentration of the treated water in the anaerobic processing tank 6 falls based on the acceleration | stimulation of the said conversion.

According to this embodiment, sodium ion (Na ⁺ ) is supplied to the circulating water tank 4 as caustic soda X5 or a common salt, so that low-concentration protein wastewater generated in the secondary decanter juice or / and starch purification process is removed. The processing efficiency of the methane fermentation treatment when the methane fermentation treatment is performed in the anaerobic treatment tank 6 can be improved. Therefore, according to this embodiment, the low concentration protein waste_water | drain generate | occur | produced in the refinement | purification process of a secondary decanter juice or / and starch can be processed efficiently.
In addition, since the VFA concentration of the treatment liquid in the anaerobic treatment tank 6 can be lowered by adding sodium ions (Na ⁺ ), the low concentration protein waste water generated in the secondary decanter juice and / or starch purification step can be used. Without being limited, it is effective for anaerobic treatment of general organic substances.

In addition, this invention is not limited to the said embodiment, The following modifications can be considered.
(1) In the above embodiment, sodium ion (Na ⁺ ) is added as caustic soda X5 or a common salt, but the addition form of sodium ion (Na ⁺ ) is not limited to this. For example, sodium compounds other than caustic soda X5 or normal salt or sodium ions (Na ⁺ ) may be added. Moreover, it is preferable to add sodium ion (Na ⁺ ) so that the biogas production amount corresponding to the COD load of the anaerobic treatment tank 6 can be maintained by monitoring the biogas production amount.

(2) In the above embodiment, the caustic soda X5 or the common salt for adding sodium ions (Na ⁺ ) to the organic substance to be treated is supplied to the circulating water tank 4, but the addition of sodium ions (Na ⁺ ) is circulated. It is not limited to the water tank 4. You may make it add to the anaerobic processing tank 6 directly, or may add sodium ion (Na ^<+> ) in the arbitrary places which belong to the upstream of the anaerobic processing tank 6. FIG.

(3) In the above embodiment, the primary decanter juice X1, the secondary decanter juice X2 and the low-concentration protein waste water X3 are treated organic substances. However, the present invention provides the primary decanter juice X1, the secondary decanter juice X2, and the low-concentration protein. This is also effective when any one or two of the waste water X3 is treated as an organic substance.

(4) Finally, as described in the above embodiment, the sodium ion (Na ⁺ ) in the present invention is a treatment load in the anaerobic treatment tank 6, that is, COD (Chemical Oxygen Demand; chemical oxygen). (Required amount) It should be added so that the amount is commensurate with the load. Therefore, for example, caustic soda (NaOH) added for pH adjustment and sodium ion (Na ⁺ ) in the present invention are completely different in technical significance.

〔Additions〕
Below, additional experiments were conducted to clarify the technical significance of the addition of sodium ions (Na ⁺ ) in methane fermentation of organic substances to be treated. The results will be described.

That is, the following three experiments A to C will be described below.
In Experiment A, the effect of adding sodium ions (Na ⁺ ) is confirmed by a lab scale test, not by a processing facility of an actual machine. Experiment B is for confirming the effect of adding sodium ions (Na ⁺ ) to acetic acid-utilizing methanogens and hydrogen-utilizing methanogens. As is well known, methane fermentation pathways are roughly classified into those using acetic acid (CH ₃ COOH) as substrates and those using hydrogen (H ₂ ) and carbon dioxide (CO ₂ ) as substrates. In the former, an acetic acid-utilizing methanogen plays a role of fermentation, and in the latter, a hydrogen-utilizing methanogen plays a role of fermentation. In Experiment B, the effect of the addition of sodium ion (Na ⁺ ) is to confirm which methanogenic bacteria among acetic acid-utilizing methanogens and hydrogen-assimilating methanogens. is there. Experiment C is for confirming the relationship between the addition concentration of sodium ions (Na ⁺ ) and the methane production rate (methane production activity).

In such experiments A to C, granule in which methanogenic bacteria are intertwined and granular IC raw water (sample) flowing into the actual IC reactor (anaerobic fermenter) as raw material for methane fermentation is used. Since these granule and IC raw water contain some sodium, in order to ensure the accuracy of the experiment, the sodium concentration contained in the granule and IC raw water is confirmed in advance, and sodium ions (Na ⁺ ) Was tightened.

  That is, the granules used in the experiments A to C have a sodium concentration of 230 mg / kg-dry per dry weight, and the IC raw water has a sodium concentration of 14 mg / l (COD4580 mg / l). The sodium content in 1 g of granule is 230 μg, and the sodium content in 9 ml of IC raw water (COD 2500 mg / l) is 68.76 μg / l (= 14 × 2500 ÷ 4580 × 9).

Therefore, when 40 mg / l of caustic soda (that is, sodium ion (Na ⁺ )) is added to 10 ml of raw IC water, the sodium content is 469 μg (≈400 + 68.76). Then, assuming that the injected granule has absorbed all sodium ions (Na ⁺ ), the above-mentioned 469 μg becomes 469 mg / kg-dry. Therefore, if 230 mg / kg-dry which is the content of granule is included, the total Is about 700 mg / kg-dry (≈469 + 230).

Further, when 200 mg / l sodium ion (Na ⁺ ) is added to 10 ml of IC raw water, the sodium content is 2069 μg (≈2000 + 68.76). Then, if the injected granule absorbs all sodium ions (Na ⁺ ), the above 2069 μg becomes 2069 mg / kg-dry. Therefore, if 230 mg / kg-dry which is the content of granule is included, the total It becomes about 2400 mg / kg-dry (≈2069 + 230).

Further, the sodium content when 1000 mg / l sodium ion (Na ⁺ ) is added to 10 ml of IC raw water is 10069 μg (≈10000 + 68.76). Then, assuming that the injected granule has absorbed all sodium ions (Na ⁺ ), the above 10069 μg becomes 10069 mg / kg-dry. Therefore, if 230 mg / kg-dry, which is the content of granule, is included, the total Is about 10300 mg / kg-dry (≈10069 + 230).

(1) Experimental method of experiment A 1 g of granule in a vial bottle (about 70 ml), 9 ml of IC raw water (COD 2500 mg / l), argon in the head space was sealed and sealed, and rotary culture was performed. And the methane gas density | concentration of the head space was measured for every fixed time using the gas chromatography, and the change of the production amount of methane gas was confirmed. Moreover, the methane production | generation rate (activity production | generation activity) was calculated | required from the change rate of the production amount of methane gas. Further, in this experiment A, a total of four bottles with no sodium ion (Na ⁺ ) (that is, caustic soda) added and 40 mg / l, 200 mg / l, and 1000 mg / l added sodium ion (Na ⁺ ) were prepared for the vial bottle. did. Furthermore, in this experiment A, it experimented about the series 1 which adds caustic soda to a vial bottle after 2 hours of elapsed time, and the series 2 which adds caustic soda from the beginning of a test.

(2) Experimental Results of Experiment A Experimental results related to series 1 and series 2 of experiment A are as shown in FIG. That is, for the sequence 1, methanogenic amount and methanogenic activity when adding sodium ions (Na ^+), in 2 hours elapsed after, in comparison with the case of sodium ions (Na ⁺⁾ no addition 1.5 Stretched by ~ 2.0 times. In addition, when sodium ions (Na ⁺ ) are added, methane formation is greater when sodium ions (Na ⁺ ) are added at 1000 mg / l than when 40 mg / l is added and when 200 mg / l is added. The tendency for the growth of the amount and methanogenic activity to be slow was confirmed.

This experimental result shows that the same phenomenon occurs in the laboratory scale with respect to the phenomenon in which the amount of gas generated increases rapidly after adding sodium ions (Na ⁺ ) in the actual equipment.
In addition, in the case of adding Series 2, that is, sodium ion (Na ⁺ ) from the start of the test, the amount of methane production and the activity of methane production increase immediately after the start of the culture, and 1.5 to 2.0 times as in Series 1. It was confirmed that

(3) Experimental method 1 of Experiment B
Add 9 g of granule 1 g, potassium acetate (CH ₃ COOK) adjusted to a COD concentration of 2500 mg / l to a vial (about 70 ml), seal the headspace with argon, seal tightly, and rotate. I did it. The methane gas concentration in the headspace was measured at regular intervals using gas chromatography, and the change in the amount of methane gas produced (methane production) was measured. Moreover, the methane production activity was calculated from the rate of change of the methane production amount. For the potassium acetate _(CH 3 COOK) solution, caustic soda (i.e. sodium ions ^(Na +)) of 0 mg / l (no additives), 40 mg / l, it was prepared which was added 200 mg / l or 1000 mg / l.
As the granule in Experiment B, an acetic acid-assimilating methane-producing bacterium that is generally referred to as “Methanosaeta” was used. This "Methanosaeta" is known as a mycelial methane bacterium that purifies methane using acetic acid as the only substrate.

(4) Experiment result 1 of experiment B
The experimental result regarding the experimental method 1 of the experiment B is as shown in FIG. That is, when sodium ion (Na ⁺ ) is added to potassium acetate (CH ₃ COOK), the methane production rate (activity production activity) is about 1.5 times higher than that without addition at 6 hours of culture time. Therefore, the effect of adding sodium ions (Na ⁺ ) was confirmed. However, when sodium ion (Na ⁺ ) is added to potassium acetate (CH ₃ COOK), the amount of methane produced and the amount of methane produced by adding 1000 mg / l is higher than that by adding 40 mg / l and 200 mg / l. Both generation activities are low. That is, when potassium (K) is contained in the substrate, the activity of the acetic acid-assimilating methanogen tends to be suppressed.

(5) Experimental method 2 of Experiment B
Granulite in a vial (70 ml) - Le 1g, the headspace and sealed by sealing with argon put industrial water 9 ml, 10 ml hydrogen gas _{(H 2)} with a syringe into the headspace, carbon dioxide (CO ₂₎ After preparing four vials filled with 2.5 ml, and after adding caustic soda (that is, sodium ion (Na ⁺ )) 0 (no addition), 40 mg / l, 200 mg / l, 1000 mg / l into each vial Rotational culture was performed. The methane gas concentration in the headspace was measured at regular intervals using gas chromatography, and changes in the amount of methane gas produced (methane production) were observed. The methane production activity was calculated from the change in methane production.
As the granule in this experiment B, what is generally called “Methanosarcina” was used as a hydrogen-assimilating methane-producing bacterium. This "Methanosarcina" is known as a parcel form of methane bacteria that inhabit freshwater anaerobic environments.

(6) Experiment result 2 of experiment B
The experimental result regarding the experimental method 2 of the experiment B is as shown in FIG. That is, in the case of hydrogen-utilizing methanogenic bacteria, no improvement in methane production and methane production activity due to the addition of sodium ions (Na ⁺ ) was observed.

(7) Experimental method of Experiment C Inactive to acetic acid-assimilating methanogen, hydrogen-assimilating methanogen, and mixed culture methanogenic caustic soda (ie, sodium ion (Na ⁺ )) addition concentration It was investigated. The mixed culture system uses IC raw water as the substrate, the acetic acid-assimilating methanogen system is the acetic acid substrate, and the hydrogen-assimilating methanogen system is the hydrogen substrate added concentration of sodium ion (Na ⁺ ). The methane production activity value at 0 mg / l (no addition) is 1.0 (reference value), and the ratio between the reference value and the methane production activity value at each sodium ion (Na ⁺ ) addition concentration is the specific activity. Defined. That is, the specific activity is obtained by dividing the methanogenic activity value at each sodium ion (Na ⁺ ) addition concentration by the reference value.

(7) Experimental Results of Experiment C The experimental results related to Experiment C are as shown in FIG. That is, FIG. 9 shows the specific activity calculated from the reference value obtained after 6 hours have elapsed from the start of culture and the methanogenic activity value at each sodium ion (Na ⁺ ) addition concentration. The concentration of sodium ion (Na ⁺ ) added is about several tens mg / l for both the mixed culture system (IC raw water) and the acetic acid-assimilating methanogen system. In addition, when 1000 mg / l of sodium ion (Na ⁺ ) is added, the specific activity tends to decrease in any case, and it is considered that sodium ion (Na ⁺ ) is inhibited by excessive addition.

(8) Summary The matters clarified in the above tests A to C are as follows.
a) As shown in FIGS. 7 and 8, the addition effect of sodium ions (Na ⁺ ) is effective for acetic acid-assimilating methanogenic bacteria and not effective for hydrogen-assimilating methanogenic bacteria. Absent. Therefore, the addition of sodium ion (Na ⁺ ) is performed in the presence of at least acetic acid-assimilating methanogenic bacteria, that is, only acetic acid-assimilating methanogenic bacteria or acetic acid-assimilating methanogenic bacteria and hydrogen-assimilating methanogens. This is effective when the organic matter to be treated is subjected to methane fermentation in the presence of methanogenic bacteria mixed with bacteria.

b) As FIG. 9 shows, there exists an optimal value about the addition amount of a sodium ion (Na ^<+> ). This optimum value exists between tens of mg / l to several tens of mg / l with respect to the IC raw water.

excessive addition of c) sodium ions (Na ⁺⁾ in the sodium ion (Na ⁺⁾ concentration inhibition, thereby diluting the effect of improving the methanogenic activity. When the anaerobic treatment tank 6 is overloaded, the pH value in the anaerobic treatment tank 6 due to the lower fatty acid (VAF) remaining in the treated water decreases, and when caustic soda is added as a neutralization purpose, Depending on the addition amount of sodium, there is a possibility that sodium ion (Na ⁺ ) concentration is inhibited contrary to the purpose of improving the activity. Therefore, for example, when sodium ion (Na ⁺ ) is added to the IC raw water as caustic soda, it is desirable to consider operating conditions (COD volumetric load) that can achieve both the purpose of adjusting the pH value and the improvement of methane production activity.

  DESCRIPTION OF SYMBOLS 1 ... Protein precipitation tank, 2 ... Solid-liquid separator, 3 ... Storage tank, 4 ... Circulating water tank, 5 ... Caustic soda supply apparatus, 6 ... Anaerobic treatment tank, 7 ... Aerobic treatment tank, 8 ... Boiler, X1 ... Primary decanter juice, X2 ... Secondary decanter juice, X3 ... Low concentration protein wastewater, X4 ... Deproteinized primary decanter juice, X5 ... Caustic soda, X6 ... Reserved effluent (methane fermentation treated solution), X7 ... Methane fermentation treatment stock solution , X8 ... Methane fermentation treatment mixture

Claims (12)

An anaerobic treatment facility for treating starch production wastewater generated in a starch factory,
A storage tank, a sodium addition device, a circulating water tank, and an anaerobic treatment tank,
The storage tank holds secondary decanter juice that is the starch production wastewater and / or low concentration protein wastewater generated in the starch purification process for a predetermined holding temperature and holding time, and the stored wastewater after holding is stored. Supply to the circulating water tank,
The sodium addition device supplies sodium chloride (NaCl) or sodium hydroxide (NaOH) as a sodium compound to the circulating water tank at predetermined time intervals,
The circulating water tank includes the stored waste liquid supplied from the storage tank, a part of the methane fermentation processed liquid discharged from the anaerobic processing tank, and the sodium compound supplied from the sodium addition device. And supply to the anaerobic treatment tank as a methane fermentation treatment mixture,
The anaerobic treatment tank causes the methane fermentation treatment mixed solution supplied from the circulating water tank to undergo methane fermentation in the presence of at least acetic acid-assimilating methane-producing bacteria, and the methane fermentation treatment obtained by the methane fermentation. A part of the spent solution is discharged to the circulating water tank, and the rest is discharged to the outside.
Anaerobic treatment equipment characterized by that. The said sodium addition apparatus supplies the said sodium compound to the said circulating water tank so that the production amount of the biogas produced | generated by methane fermentation may become the quantity corresponding to the processing load in the anaerobic processing tank. The anaerobic treatment facility according to 1. A processing facility for processing starch production wastewater generated in a starch factory,
Anaerobic treatment equipment according to claim 1 or 2,
Of the methane fermentation treated liquid discharged from the anaerobic treatment facility, an aerobic treatment tank for aerobically treating the methane fermentation treated liquid discharged to other than the circulating water tank,
A facility for treating starch production wastewater . A protein precipitation tank for coagulating and precipitating the protein contained in the primary decanter juice, which is one of the starch production wastewaters;
A solid-liquid separation means for removing the coagulated protein from the treatment liquid of the protein precipitation tank,
The storage tank of the anaerobic treatment facility mixes and holds the deproteinized primary decanter juice, which is the separated liquid of the solid-liquid separation means, in the secondary decanter juice or / and the low concentration protein waste water. The processing equipment of the starch manufacture waste_water | drain of Claim 3 . The processing equipment for starch production wastewater according to claim 3 or 4, wherein the holding temperature and holding time are set as conditions for reducing the activity of the enzyme contained in the secondary decanter juice . 6. The starch production wastewater according to claim 4 , wherein in the storage tank, the secondary decanter juice or / and the low-concentration protein wastewater and the deproteinized primary decanter juice are mixed at a ratio of the holding temperature . Processing equipment. An anaerobic treatment method for treating starch production wastewater generated in a starch factory,
A dwelling step, a sodium addition step, a mixing step, and an anaerobic treatment step;
In the storage step, the secondary decanter juice that is the starch production wastewater and / or the low-concentration protein wastewater generated in the starch purification step is held for a predetermined holding temperature and holding time, and the stored wastewater after holding is stored. Supplying to the mixing step,
In the sodium addition step, sodium chloride (NaCl) or sodium hydroxide (NaOH) is supplied as a sodium compound to the mixing step at a predetermined time interval,
In the mixing step, the stored waste liquid supplied from the storage step, a part of the methane fermentation processed liquid discharged from the anaerobic processing step, and the sodium compound supplied from the sodium addition step And supply to the anaerobic treatment step as a methane fermentation treatment mixture,
In the anaerobic treatment step, the methane fermentation treatment mixed solution supplied from the mixing step is subjected to methane fermentation in the presence of at least acetic acid-assimilating methanogenic bacteria, and the methane fermentation treatment obtained by the methane fermentation. Discharging part of the spent solution to the mixing step and discharging the rest to the outside;
The anaerobic processing method characterized by this. In the sodium addition step, according to claim 7, wherein the supplying the sodium compound as production of biogas is an amount corresponding to the processing load in the anaerobic treatment in the mixing step of generating by methane fermentation Anaerobic treatment method . A method for treating starch production wastewater generated in a starch factory,
An anaerobic treatment step of anaerobically treating the starch production wastewater based on the anaerobic treatment method according to claim 7 or 8;
Of the methane fermentation treated liquid discharged from the anaerobic treatment process, an aerobic treatment process for aerobically treating the methane fermentation treated liquid discharged other than the mixing process;
A method for treating starch production wastewater, comprising : A protein precipitation step for coagulating and precipitating the protein contained in the primary decanter juice that is one of the starch production wastewaters;
A solid-liquid separation step of removing the coagulated protein from the treatment liquid of the protein precipitation step,
The starch production wastewater according to claim 9 , wherein, in the storage step, the deproteinized primary decanter juice, which is the separated liquid in the solid-liquid separation step, is mixed with the secondary decanter juice or / and the low-concentration protein wastewater. Processing method . The method for treating starch production wastewater according to claim 9 or 10, wherein the holding temperature and holding time are set as conditions for reducing the activity of the enzyme contained in the secondary decanter juice . The starch production wastewater according to claim 10 or 11, wherein, in the storing step, the secondary decanter juice or / and the low-concentration protein wastewater and the deproteinized primary decanter juice are mixed at a ratio of the holding temperature . Processing method.

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