JP3095965B2 - Automatic control system for methane fermentation tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In recent years, the use of methane fermentation for organic waste treatment and wastewater treatment has been increasing.
Methane fermentation has a small amount of excess sludge emission,
Since methane gas can be recovered as an energy source, costs associated with processing can be reduced.

However, it is extremely difficult to keep methane fermentation in a good condition at all times, and it has been difficult to automatically operate a methane fermentation tank. But recently,
It was found that the activity of methane bacteria can be measured by measuring the fluorescence intensity of the fluorescent substance _F420 unique to methane bacteria (hereinafter, this method is referred to as a fluorescence method). The present invention focuses on the fact that the activity of methane bacteria can be measured by a fluorescence method, and by measuring the fluorescence intensity of the methane bacteria, the methane fermentation tank is automatically controlled to always maintain a good state in the methane fermentation tank. The present invention relates to a control device.

[0003]

2. Description of the Related Art At present, sludge amount in a reactor, gas generation amount, pH and the like are generally used as operation control indexes for methane fermentation. In basic research, etc.,
Digestion gas composition, organic acid content, alkalinity, SS removal rate, C
Only the state in the methane fermentation tank is grasped by analyzing the OD removal rate and the like.

[0004]

However, the most important factor for the operation and control of methane fermentation is the activity of methane bacteria. However, since many types of microorganisms coexist and function in methane fermentation, it has been extremely difficult to separate and measure only methane bacteria and to know the cell activity. Further, in order to measure the digestion gas composition, the amount of organic acid, the alkalinity, the SS removal rate, the COD removal rate, and the like, the measurement method is complicated, it takes a long time to perform the measurement, and the experimenter requires skill.

[0005] In addition, methane bacteria are very sensitive to changes in the growth environment, are susceptible to changes in the environment in the digestion tank, and generally have a low growth rate. Decrease and increase in organic acid concentration,
Eventually, it becomes rancid and stops functioning completely. Once in modulation, recovery can take a lot of time and effort, and sometimes it may even be necessary to replace the digester contents and start up again. Therefore, automation of methane fermentation has been difficult. Even more, in methane fermentation using anaerobic sludge in which various types of microorganisms coexist, instead of using pure strains of methane bacteria, even if it is very difficult even in manual operation, automation is extremely difficult. Was.

[0006] However, from the industrial point of view and the point of view of pollution prevention, methane fermentation is becoming more and more important, and accordingly, there is a strong demand for the development of an automatic control system for methane fermentation. The present invention has been made to meet such needs in the art, and has as its object to newly develop an efficient automatic control system for methane fermentation.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and in the course of research from various fields, by knowing the activity of methane bacteria by a fluorescence method, a fermentation tank is provided. To be able to know the state inside
It became clear in our study. In addition, gas generation amount, CO
Since the activity of methane bacteria changes faster than the changes in the D removal rate, SS removal rate, etc., by examining the change in the activity of methane bacteria, appropriate measures can be taken before the condition in the fermenter deteriorates. I got a new finding. Further, the present inventors first paid attention to the fact that the operation was extremely simple and could be automated and did not require the skill of a measurer, and as a result of further research, the present invention was completed.

That is, the gist of the present invention is to automatically control the methane fermentation tank by measuring the fluorescence intensity of _F420 present in the methane bacteria and adjusting the input amount of the raw material. is there.

[0009] It is difficult to directly measure the activity of methane bacteria in a methane fermentation tank. As a result of intensive studies, the present invention has focused on the fluorescent substance _F420 . Fluorescent substance F ₄₂₀ is, in all methanogens a fluorescent coenzymes specifically present (8-hydroxy-5-Jiazafurabin derivative), Wavelength 420n
m has an absorption maximum, and its oxidized form emits strong blue-green fluorescence with a wavelength of 472 nm and has a molecular weight of 843.

[0010] In addition to the above-mentioned unique properties, the fluorescent substance _F420 is a substance that exists only in methane bacteria and does not exist in other bacteria.
It is a substance with very characteristic properties that it is present in all methane bacteria regardless of species.

The present invention makes use of these excellent properties of the fluorescent substance _F420 , and further includes preprocessing, data analysis,
It was the first successful construction of an automatic control system for a methane fermentation tank by newly selecting each process and equipment, such as a flow controller and a feed pump, and combining them organically. Hereinafter, the automatic control system according to the present invention will be described in detail with reference to the apparatus of FIG. 1 showing one embodiment of the apparatus according to the present invention.

FIG. 1 is a conceptual diagram of the present apparatus. The fermentation broth is
From the methane fermentation tank (5), it is sampled from the sampling line (9) and sent to the pretreatment device (10). The operation shown in FIG. 2 or FIG. 3 is performed by the pre-processing device. The pre-processing device (10) is a fluorescence spectrophotometer (11) to be performed next.
The fermentation liquor is diluted (FIG. 2) or the F exists in the methane bacteria.
_In order to elute _{420 out} of the cells, alkali treatment or heat treatment is performed. As the alkali treatment, in addition to the NaOH treatment (FIG. 3), a KOH treatment and other treatments capable of bringing the fermentation liquor to the alkali side are widely included. For example, in the case of NaOH, NaO is adjusted to a concentration of about 0.5 to 5N, preferably about 0.8 to 1.5N.
H may be added to the fermentation broth. In addition, F ₄₂₀
In the case where F is sufficiently present, the pre-processing device can be omitted. Conversely, when the F ₄₂₀ concentration is very high, the pre-processing is performed by further diluting than in the case of FIG. is necessary.

Usually, the method shown in FIG. 2 is simple as a preprocessing method. However, when the raw material contains a large amount of impurities, fluorescence is scattered or absorbed by the impurities, and the fluorescence intensity is reduced. Therefore, the method of FIG. 3 is preferable. The sample after the pretreatment is sent to a fluorescence spectrophotometer (11), and the fluorescence intensity is measured. The fluorescence intensity data is sent to the data analyzer (12). The data analyzer (12) analyzes the transmitted data and controls the flow controller (3) through the control line (13). FIGS. 4 and 5 show control examples of the flow controller.

Example of pump control during steady operation (FIG. 4)
In addition, the raw material input pump (2) is operated according to the example of pump control at startup (FIG. 5), and the raw material liquid is supplied from the raw material tank (1) into the methane fermentation tank (5) via the raw material input line (4). Add only the required amount when needed. In the tank, anaerobic methane fermentation is carried out according to a conventional method, and the generated gas is taken out from the digestion gas line (8) through the desulfurization device (6) and the gas meter (7).

In the methane fermentation tank (5), methane fermentation is carried out using anaerobic sludge according to a conventional method, but it is of course possible to carry out methane fermentation using one or more pure methane bacteria strains. . As the methane bacteria pure strain, conventionally known methane bacteria can be appropriately used, and the following are non-limiting examples: Methanobacterium thermoautotro
phicum ATCC 29183, M. formiciucum, M. bryantii, etc.
Methanobacterium sp .; Methanococcus mazei, M. volt
Methanococcus sp., such as ae; Methanosarcina barkerii A
Methanosarcina sp. Such as TCC 29894, M. acetivorance;
Methanomona such as Methanomonas methylovora ATCC 21963
s sp.Met such as Methanogenium cariaci, M. marisnigri
hanogenium spp. and others.

[0016]

The apparatus of the present invention performs automatic control of the methane fermentation apparatus by measuring the activity of methane bacteria and measuring the fluorescence intensity of _F420 specific to methane bacteria. Therefore, when the activity of the methane bacteria becomes weak, the methane fermentation tank can be controlled immediately. Therefore, the state of the methane fermentation tank can be always kept in a good state, and the problem such as rancidity of the methane fermentation tank, which has conventionally been a problem, does not occur (Example 2).

The apparatus of the present invention can also be applied at the start-up of methane fermentation. When starting up the methane fermentation tank by the conventional method, the load was slowly increased so as not to cause rancidity while monitoring the amount of gas generated.
However, by applying the present invention, the startup which conventionally took about six months can be reduced to about 40 days (Example 1).

An embodiment in which the methane fermentation apparatus is started up and the garbage is treated while controlling the methane fermentation apparatus using the apparatus of the present invention will be described below. However, the present invention can be applied to any methane fermentation apparatus (fluidized bed, fixed bed) without being limited to the following. Pretreatment method,
The control of the flow controller is not limited to the method shown in the figure. In the present embodiment, the control of the raw material input amount is performed by controlling the flow controller. However, the present invention is not limited to this, and the rotation speed of the pump, the intermittent operation of the pump, and the like may be used. Of course, the bacterium to be used is not only anaerobic digested sludge but also pure bacterium and mixed bacterium can be used.

[0019]

Example 1 A methane fermentation tank using the apparatus of the present invention was started up. In this example, crushed garbage was used as a raw material. The composition of the kitchen garbage is shown in Table 1 below. Use a 3 liter methane fermentation tank at 55 ° C
Driven by The control of the methane fermentation tank was performed by a method as shown in FIG. The pre-processing performed the operation shown in FIG.

Table 1 Composition of kitchen waste ───────────────────── T-COD 130,000 mg / l S-COD 50,000 mg / l T-BOD 80, 000 mg / l S-BOD 45,000 mg / l SS 50,000 mg / l VSS 50,000 mg / l

The high-temperature digested sludge was charged into a methane fermentation tank and digested until no gas was generated, that is, until there was no remaining organic matter. Thereafter, as shown in FIG. 6, start-up was performed while controlling the amount of kitchen waste. As a result, the startup was completed in about 40 days. FIG. 7, FIG. 8, and FIG. 9 show changes with time in the load and the fluorescence intensity, changes with time in the fluorescence intensity and the gas generation amount, and changes with time in the fluorescence intensity and the amount of the organic acid. The fluorescence intensity changes more sensitively than the amount of gas generated, and shows almost the same change as the amount of organic acid. For this reason, it can be understood that since the control can be performed more precisely than when the control is performed only by the gas generation amount, the control can be performed at an early stage when the state in the methane fermentation tank deteriorates. Therefore, startup was possible in a short time of 40 days.

[0022]

Example 2 The wastewater treatment was performed while controlling the methane fermentation apparatus using the apparatus of the present invention. Crushed garbage was used for wastewater. The composition of the garbage is as shown in Table 1. Use a 3 liter methane fermentation tank at 55 ° C
Driven by The control of the methane fermentation tank was performed by a method as shown in FIG. The pre-processing performed the operation shown in FIG.

The kitchen waste was charged as shown in FIG. 10 while controlling the raw material charging pump. The relationship between the COD load and the fluorescence intensity at this time is shown in FIG. The amount of gas generated is
The fluorescence intensity decreased, and after about one day (FIG. 12).
Further, the change in the amount of the organic acid was almost the same as the change in the fluorescence intensity (FIG. 13). From these facts, it was confirmed that by applying the present invention, it is possible to control the methane fermentation tank in an initial state where the state of the methane fermentation tank deteriorates.

[0024]

The following effects can be obtained by applying the present invention to a methane fermentation apparatus. 1. The activity of methane bacteria in the methane fermentation tank can be measured. 2. The methane fermentation tank can be easily controlled. 3. The methane fermentation tank can be controlled before the condition of the methane fermentation tank deteriorates. 4. Startup of the methane fermentation tank can be easily performed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an automatic control system for a methane fermentation tank according to the present invention.

FIG. 2 shows an operation example 1 of the pretreatment device.

FIG. 3 shows an operation example 2 of the pretreatment device.

FIG. 4 shows an example of pump control during steady operation.

FIG. 5 shows an example of pump control at startup.

FIG. 6 shows the change over time in the amount of garbage input and the fluorescence intensity in Example 1.

FIG. 7 shows changes over time in the COD load and the fluorescence intensity.

FIG. 8 shows the change over time in the fluorescence intensity and the gas generation amount.

FIG. 9 shows changes over time in the fluorescence intensity and the amount of organic acid.

FIG. 10 shows the change over time in the amount of garbage input and the fluorescence intensity in Example 2.

FIG. 11 shows changes over time in the COD load and the fluorescence intensity.

FIG. 12 shows changes with time in the fluorescence intensity and the gas generation amount.

FIG. 13 shows changes over time in the fluorescence intensity and the amount of organic acid.

Continued on the front page (72) Inventor Kosaku Osato 2-9-1-1, Tobita-Shi, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Mizue Yoshida 2-1-1, Tobita-Shi, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Tamano Hatano 2-9-1-1, Tobita-Shi, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (56) References JP-A-62-288569 (JP, A) Kaihei 5-23169 (JP, A) Special table Hei 6-509718 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3/34 C12M 1/34-1/36 C12Q 1/06 C12Q 3/00

Claims (5)

(57) [Claims] 1. A fermentation liquor is sampled from a methane fermentation tank, and the fermentation liquor is subjected to an alkali treatment or a heat treatment to elute the fluorescent substance _F420 present in the methane bacteria out of the cells.
A method for automatically controlling a methane fermentation tank, comprising measuring the activity of methane bacteria by measuring the fluorescence intensity of a fluorescent substance _F420 , and adjusting the input of raw materials. 2. Sampling the fermentation liquor from the methane fermentation tank, diluting the fermentation liquor, or performing alkali treatment or heat treatment, and then measuring the fluorescence intensity of the fluorescent substance _F420 ,
Processing the data of the fluorescence intensity by a data analyzer, analyzing the activity data of the obtained methane bacteria, controlling the flow controller, and controlling the input amount and / or the input timing of the raw material. Automatic control method of methane fermentation tank. 3. The method according to claim 1, wherein when the activity of the methane bacterium decreases, the methane fermentation tank is immediately controlled to avoid the deterioration of the state in advance. Automatic control method of methane fermentation tank. 4. The method according to claim 1, wherein the activity of the methane bacterium is measured, and the load is promoted based on the measured value, thereby shortening the start-up period of the methane fermenter. 3. The method for automatically controlling a methane fermentation tank according to item 1. 5. A methane fermentation tank for performing methane fermentation, a sampling line for sampling a fermentation liquid from the methane fermentation tank, a pretreatment device for diluting or alkali-treating or heating the fermentation liquid, and measuring the fluorescence intensity of the fluorescent substance _F420. fluorescence spectrophotometer, the data analysis device for analyzing data of fluorescence intensity consists flow controller which is controlled by a control line on the basis of the analysis data, with the activity of the methane bacteria were measured by fluorescence intensity of the fluorescent substance F _420, the it Controlling the methane fermentation by adjusting the raw material input accordingly,
An automatic control device for a methane fermentation tank.