JP2000228996A - Estimation of the content of acetic acid-assimilating methane bacteria in sludge and estimation of the amount of acetic acid-assimilating methane bacteria - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and exactly estimate the content of acetic acid-assimilating methane bacteria and the amount of the acetic acid-assimilating methane bacteria in the methane fermentation. SOLUTION: The methane formation activity of the sludge specimen collected from the fermentation tank in the methane tank is calculated from the VSS (crude suspended matter or organic suspended matter) and from the rate of the methane formation measured in an apparatus for measuring the acetic acid-assimilating methane bacteria by adding an adjusted culture medium and a prescribed amount of sodium acetate. Then, the calculated value of the methane formation activity is substituted into the computational equation between the content acetic acid-assimilating methane bacteria in the sludge and the methane formation activity whereby the content of the acetic acid-assimilating methane bacteria in the sludge can be estimated. Further the acetic acid-assimilating methane bacteria can be estimated from the relation between the content of the methane bacteria in the sludge, the value of the concentration of sludge specimen and the amount of the acetic acid-assimilating methane bacteria specimen concentration in the sludge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for simply measuring the activity of sludge in methane fermentation and estimating the sludge content ratio and the amount of acetic acid-utilizing methane-forming bacteria.

[0002]

2. Description of the Related Art In methane fermentation, the measurement of methane production activity and the amount of methane-producing bacteria is very significant in knowing the activity of sludge in a fermentation tank.

[0003] Usually, the methane production activity is determined by collecting a part of the sludge from the reactor, placing it in a vial containing a buffer containing an inorganic salt, and supplying a substrate such as acetic acid or hydrogen. It is calculated from the velocity and the sludge sample VSS (coarse or organic suspension) concentration. This is referred to as vial methane production activity. Shutsubo et al., Journal of Environmental Engineering, Vol. According to the description of methane production activity measurement for granulated sludge reported in 201-212 (1995), the outline of this measurement method is as follows. In the vial bottle, inorganic salts (NH ₄ Cl, MgCl ₂ .6H
Phosphate buffer solution (final concentration in vial: 25 mM) containing ₂ O, CaCl ₂ , FeCl ₂ · 4H ₂ O) and granule sludge collected from the reactor (homogenized)
Input. After sealing with a butyl rubber stopper and an aluminum cap, the gas phase was purged with nitrogen gas, and resazurin (indicator for determining the presence or absence of dissolved oxygen, final concentration in vials 1 mg / l), reducing agent (Na ₂ S. 9H ₂ O, 250 mg / l final concentration in the vial). About 30-40 minutes,
Shake in shaker (use rotary shaker,
Acetic acid and hydrogen (H ₂ : CO ₂ = 80: 20, 1.20) when the temperature in the vial was stabilized at 130 rpm and a shaking radius of 5 cm.
For each substrate such as 4 atm), the activity is determined by measuring the amount of methane in the vial at 5 to 7 points over time during the test time of 5 to 8 hours). The above operation is performed under a stream of nitrogen gas from which oxygen has been completely removed using heated metallic copper. The initial COD concentration in the liquid portion of the vial is 2000 mg COD / l.

With respect to the methane production activity in the vial method described above, the methane production activity can be calculated from the methane production rate of the reactor and VSS, and this is referred to as reactor methane production activity. Vial methanogenic activity is:
It represents the actual methanogenic activity on the substrate fed to the reactor.

On the other hand, several methods for measuring the amount of methane bacteria have been proposed, and the MPN method (most probable number method) is representative. How to fluorescence measuring the amount of coenzyme F ₄₂₀ that exist unique and and universal methane bacteria have been developed recently. However, the existing methods have not reached the practical level because the operation is too complicated or indirect, and there is no example of measuring the amount of methane bacteria on a daily basis.

[0006] Methane production in a fermentation tank is performed by anaerobic decomposition of organic matter by methanogens, 70 to 75% of which passes through acetic acid. Methanogens that can decompose acetic acid into methane and carbon dioxide are called acetic acid-utilizing methanogens. In addition, the remaining 30-25%
Is via a pathway that produces methane from hydrogen and carbon dioxide by hydrogen-assimilating methanogens.

[0007] Valcke et al. Proposed a practical method for measuring the weight of acetic acid-assimilating methane-producing bacteria.
Pollution Control Federation, 55 (9) 1191-1195 (1
983). This method measures the maximum methane production rate per liter of the mixed liquid per day by increasing the amount of sodium acetate added to a fixed amount of sludge sample. Assuming that the maximum methane production rate per weight) is constant, the amount of bacteria (the weight of bacteria per liter of sludge) is calculated.

Next, this method will be described sequentially.

(1) Measuring device for acetic acid-utilizing methane-producing bacteria In the method of Valcke et al., A measuring device as shown in FIG. 1 is used. The configuration of this device is as follows. That is, a sludge sample, a medium, and sodium acetate as a substrate are put into a 2 liter Erlenmeyer flask 1, a magnetic stirrer 5 is put therein, and the mixture is stirred using a magnetic stirrer 4. The gas generated by the decomposition of acetic acid is used to remove carbon dioxide.
After passing through the air-washing bottle 2 containing N and NaOH, it is stored in the gas collector 3. The gas collector 3 is configured by filling the measuring cylinder 6 with water and standing upside down on the water surface of the water tank 7, and when the gas accumulates, the water surface of the measuring cylinder 6 lowers. By reading the change in the water surface position of the measuring cylinder 6, the amount of methane generated can be determined. One set of the same device as shown in FIG. 1 is one measuring device.

FIG. 2 shows a partial configuration of an apparatus for measuring acetic acid assimilating methane-producing bacteria according to the method of Valcke et al. Although this device does not perform magnetic stirring and differs from the method of Valcke et al. In a gas collector and a heat retaining mechanism, the measurement principle is the same. In FIG. 2, reference numeral 21 denotes a small-mouthed bottle having a capacity of 1 liter. The small-mouthed bottle 21 is placed in a constant temperature water bath 22 and is hung with a string from a rod extending over both ends of the water bath. The narrow-mouthed bottle 21 floats on the water in the constant temperature water tank 22 and swings as the water is stirred. The sludge sample, mineral solution and sodium acetate are put in the narrow-mouthed bottle 21, and the generated gas passes through the gas conduit 23 from the gas outlet at the upper part of the narrow-mouthed bottle 21 and passes through the gas washing bottle 24 filled with 1N NaOH. I do. The gas from which CO ₂ has been removed by the gas washing bottle enters a gas holder 25 and is stored on a saturated saline solution 26. The vertical movement of the gas holder is read by a scale 27 to measure the amount of methane generated.

FIG. 3 shows the overall configuration of an apparatus for measuring acetic acid assimilating methane-producing bacteria according to the method of Valcke et al. The structure of this device is as follows. Six 1-liter narrow-mouthed bottles 31 are placed in a constant temperature water tank 34 (volume: 20 liters) in which a throw-in type heater 36 is installed. Two sticks 39 are passed over both ends of the constant temperature water tank 34, and the narrow mouth bottle 31 is tied to the sticks 39 with a string 40 and hung. The narrow-mouthed bottle 31 floats on the water in the constant temperature water bath 34 and swings as the water is stirred. The sludge sample, culture medium and sodium acetate are put in the narrow-mouthed bottle 31, and the generated gas passes through the gas conduit 38 from the gas outlet at the upper part of the narrow-mouthed bottle 31, and passes through the gas washing bottle 32 filled with 1N NaOH.
The gas from which CO ₂ has been removed in the air purifying bottle 32 is supplied to the gas holder 37.
The vertical movement of the gas holder 37 is read by the scale 33, and the methane generation amount is calculated.

The preparation of the culture medium and the sludge sample, the measurement of the generated methane, and the like will be described.

(2) Preparation of medium KH ₂ PO ₄ ; 2.5 g, K ₂ HPO ₄ ; 1.0 g, NH ₄ Cl;
1.0 g, MgCl ₂ ; 0.1 g, yeast extract; 0.2 g, Na ₂
A medium is prepared by dissolving 0.1 g of S · 9H ₂ O in 1 liter of water.

(3) Adjustment of sludge sample Approximately 2 liters of sludge is collected from a sludge digestion tank, and a part of the sludge sample is used for SS (suspended matter) and VSS.
(Coarse or organic suspended matter)
0.5 liter of medium and aerated with N ₂ gas for 1 minute or more, and then 0.25 liter of sludge sample. (V after mixing
Since the SS is about 5 g / l, it is necessary to adjust the mixing ratio depending on the level of the VSS of the sludge sample. (4) Measurement operation Connect the gas conduit 38 to the narrow-mouthed bottle 31 and keep it warm at 30 ° C for 1 to 2 days. Thereafter, 1.5, 2.3, 3.1, 3.9, and 4.6 g of sodium acetate were added to the five narrow-mouthed bottles 31 (sludge VS).
Acetic acid conversion amount per gram of S is 0.3, 0.45, 0.6, 0.75,
0.9 g), and the other one is a target sample without sodium acetate. The pH is adjusted to 6.7 using 1N HCl or NaOH, aerated with N ₂ gas, and the gas conduit 18 is connected again and kept warm for one to two days to measure the amount of methane generated.

(5) Calculation method From the relationship between the elapsed time and the accumulated methane generation amount, a point where the methane generation amount per 24 hours is maximum is selected, and this is calculated as V
max: The maximum amount of methane produced per day (ml / g VSS · day).

Assuming that the maximum amount of methane-producing methane-producing bacteria is 1000 ml / g VSS · day, the amount of acetic-acid-producing methane-producing bacteria (actually, the weight concentration of bacteria) is calculated by the following equation.

[0017]

(Equation 1)

In this equation, Vmax / 1000 corresponds to the sludge content ratio of acetic acid-utilizing methane-producing bacteria (acetic acid-utilizing methane-producing bacteria / VSS).
x / 10 is expressed in percentage (%).

[0019]

In the method of measuring the amount of acetic acid assimilating methane-producing bacteria according to the method of Valcke et al., The point at which the maximum amount of methane is obtained is selected by changing the amount of acetic acid added stepwise. Therefore, in order to perform one measurement, FIG.
It is necessary to prepare several sets of the same measuring apparatus as described in (1) and perform the same measuring operation for each set, which causes a problem that the time and effort required for the measuring operation are increased.

The present invention has been made in view of the above circumstances, and can save the labor required for the measurement operation without significantly lowering the measurement accuracy, and is useful in realizing the practical use of an automatic measurement device. It is an object of the present invention to provide a method for estimating the sludge content ratio of acetic acid assimilating methane-producing bacteria and the method of estimating the amount of acetic acid assimilating methane-producing bacteria in methane fermentation having a high level.

[0021]

Means for Solving the Problems In order to achieve the above object, the present invention is directed to a first invention in which a sludge sample and a medium collected from a methane fermentation tank are put into a container, and the container is kept warm for a certain period of time. After that, a certain amount of sodium acetate was added to the container, and then further kept for a certain period of time to obtain a methane production amount.Based on the obtained methane production amount, a certain amount of acetic acid was added to the sludge sample. Substituting the value of the methanogenic activity into an arithmetic expression derived from the correlation between the methanogenic activity when sodium was added and the acetic acid assimilating methanogen sludge content ratio measured for the same sludge sample It is characterized by estimating the acetic acid assimilating methanogen sludge content ratio.

A second invention is characterized in that the arithmetic expression comprises the following expression.

Y = Ax + B A: 31.6-32.8 B: 0.27-0.45 x; methanogenic activity (kgCH ₄ -COD / kgVSS / day) y; acetic acid assimilating methanogenic sludge content ratio (%) After putting the sludge sample and the medium collected from the methane fermentation tank into a container, keeping the container warm for a certain period of time, adding a certain amount of sodium acetate to the container, and then further keeping the container warm for a certain period of time to produce methane. After obtaining the specific methane production activity when a certain amount of sodium acetate is added to the sludge sample based on the obtained methane production amount and the acetic acid assimilating methane measured for the same sludge sample. After estimating the acetic acid-utilizing methane-producing sludge content ratio by substituting the value of the methane-producing activity into the arithmetic expression derived from the correlation with the producing bacterium sludge content ratio, the amount of acetic acid-utilizing methane-producing bacteria and acetic acid were estimated. Assimilable methanogen content Substituting the value of the acetic acid-utilizing methane-producing bacterium sludge content ratio and the value of the sludge sample concentration into an arithmetic expression indicating the relationship with the sludge sample concentration, and estimating the amount of acetic-acid-utilizing methane-producing bacteria, I have.

A fourth aspect of the present invention is characterized in that an arithmetic expression showing the relationship between the amount of acetic acid-utilizing methane-producing bacteria, the content ratio of acetic-acid-utilizing methane-producing bacteria, and the sludge sample concentration is as follows.

Z = xy / 100 x: sludge VSS (g / l) y: acetic acid-utilizing methane-producing sludge content ratio (%) z: amount of acetic-acid-utilizing methane-producing bacteria (g / l)

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the present invention, the present inventor has proposed a method different from the method for measuring the amount of acetic acid-utilizing methane-producing bacteria described in the prior art, namely, the methane-producing activity and specific methane in a methane fermentation tank. A method for estimating the amount of acetic acid-utilizing methane-producing bacteria and the sludge content ratio of acetic acid-utilizing methane-producing bacteria using an index called conversion activity was invented.

According to these methods, empirically, there is a correlation between the relationship between the methanogenic activity and the amount of acetic acid-utilizing methane-forming bacteria, and the relationship between the methane conversion activity and the sludge content ratio of acetic-acid-utilizing methane-forming bacteria. From, the methanogenic activity and methane conversion activity are measured, and the measured values are substituted into the correlation regression equation to estimate the amount of acetic acid-utilizing methane-forming bacteria and the sludge content ratio of acetic-acid-utilizing methane-forming bacteria. It is characterized by:

First, a method for estimating the amount of acetic acid-utilizing methane-producing bacteria will be described. After putting the sludge sample collected from the methane fermentation tank together with the medium into a container (small-mouthed bottle), the container is kept warm for a certain period of time, then a certain amount of sodium acetate is dissolved in the container, and then the methane is kept for another certain period of time. After obtaining the production amount, the sludge sample is measured for the methane production activity of the sludge calculated based on the obtained methane production amount and the VSS (coarse suspended matter or organic suspended matter) concentration of the sludge sample. The value of the methanogenic activity is substituted into a calculation formula derived from the correlation with the amount of acetic acid assimilating methane bacteria to estimate the amount of acetic acid assimilating methane bacteria.

The above calculation formula is represented by formula (1).

Y = Ax + B (1) A: 5.00 to 6.00 B: 0.08 to 0.15 x: Methanogenic activity (kgCH ₄ -COD / kgVSS / day) y: Amount of acetic acid assimilating methanogen (G / l) Since the methane production activity referred to here is calculated by equation (2), the definition is the same as that of the vial method, but the measurement method is different and the method is simpler than the vial method. Therefore,
Hereinafter, it is referred to as simple measurement (acetic acid addition) methane generation activity. The sludge VSS in the expression (2) is not the sample itself but a concentration adjusted by mixing a medium and a sludge sample so that the VSS concentration becomes about 5 g / l.

[0031]

(Equation 2)

Simple measurement (addition of acetic acid)
Using the same apparatus as the partial configuration of the apparatus for measuring acetic acid assimilating methane-forming bacteria according to the method of Valcke et al. Shown in FIG. Since the measurement is performed with the addition amount of, a single measurement can be performed if one set of the apparatus shown in FIG. 2 is used.

The amount of sodium acetate added was 0.45 as acetic acid.
g acetic acid / g VSS, but the amount added was similar to the vial method (initial COD concentration: 2200 mg / l)
Becomes The methane production rate was measured several times in two days after the start of the measurement.
The cumulative methane production is measured and calculated by performing regression by the least squares method from the relationship between the elapsed time and the methane production.

Next, a method for estimating the sludge content ratio of acetic acid-utilizing methane-producing bacteria will be described. After putting the sludge sample collected from the methane fermentation tank together with the culture medium in a container (small mouth bottle),
After holding the container for a certain period of time, a certain amount of sodium acetate is dissolved in the container, and then the temperature is further kept for a certain period to measure the methane production rate. Then, the methane conversion activity of the sludge is calculated based on the methane production rate, the amount of acetic acid added, and the VSS (coarse suspended matter or organic suspended matter) concentration of the sludge sample. Further, the value of the methane conversion activity is substituted into a calculation formula derived from the correlation between the methane conversion activity and the content ratio of the acetic acid-utilizing methane-producing bacterium sludge to estimate the acetic acid-utilizing methane-producing bacterium sludge content ratio.

The above equation is expressed by equation (3).

Y = Cx + D (3) C: 65.0 to 80.0 D: 0.20 to 0.60 x: Methane conversion activity (m ³ / kgVSS) y: Content ratio of acetic acid assimilating methanogen sludge (%) Here, the methane conversion activity is calculated by the formula (4) by dividing the methane production activity by the simple measurement (acetic acid addition) method by the amount of sodium acetate added in terms of COD.

[0037]

(Equation 3)

As described above, equation (1), which is an arithmetic expression used when the former method for estimating the sludge content ratio of acetic acid assimilating methane assimilating bacterium, is carried out by centrifugal concentration and gravity concentrated sewage sludge. The correlation regression was derived from the relationship between the methane production activity and the amount of acetic acid-utilizing methane-producing bacteria in a simple measurement (addition of acetic acid) in a medium-temperature semi-continuous sludge digestion laboratory experiment, as shown in Fig. 4. The relation number is 0.879 (n = 27)
Met. On the other hand, equation (3), which is an arithmetic expression used when the latter method for estimating the content ratio of acetic acid assimilating methane-forming bacterium sludge, is expressed by the following formula: The correlation coefficient was 0.971 (n = 2).
7).

Therefore, the former method of estimating the amount of acetic acid assimilating methane-producing bacteria from the methane-producing activity by simple measurement (addition of acetic acid) using the expression (1) uses the latter method (3). Therefore, there is a problem that the accuracy of the estimation is reduced because the correlation coefficient is low compared with the method of estimating the content ratio of the acetic acid assimilating methane-producing bacteria from the methane conversion activity by simple measurement (acetic acid addition). FIG. 4 shows that the dispersion tends to be large in a region where the methane production activity is high in the simple measurement (acetic acid addition).

The significance of the measurement of the methane production activity by the simple measurement is the same as in the case of the vial method, and is characterized in that it can be measured more easily than the vial method.

Therefore, in view of the above problems, in the embodiment according to the present invention, the simple measurement results (addition of acetic acid) from the methanogenic activity can be achieved more accurately and easily with the acetic acid assimilating methanogen sludge content ratio and acetic acid assimilation. The present invention provides a method for estimating the amount of soluble methanogens.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) Method of Estimating Sludge Content Ratio of Acetic Acid-Utilizing Methanogen Bacteria Sludge measurement method for a single measurement (partial configuration of the apparatus for measuring acetic acid-assimilating methane-producing bacteria shown in FIG. 2) Addition) Measure methanogenic activity. The specific measurement procedure is as follows (1) to (4).

(1) Preparation of medium KH ₂ PO ₄ ; 2.5 g, K ₂ HPO ₄ ; 1.0 g, NH ₄ Cl;
1.0 g, MgCl ₂ ; 0.1 g, yeast extract; 0.2 g, Na ₂
A medium is prepared by dissolving 0.1 g of S · 9H ₂ O in 1 liter of water.

(2) Preparation of Samples Sludge is collected from a sludge digestion tank, and VSS (coarse suspended matter or organic suspended matter) concentration is measured using a part of the sludge sample. VSS of the narrow mouth bottle 21 to the N ₂ gas is put mineral solution from 0.5 to 0.6 liters from the bubbling over 1 minute charged sludge samples from 0.2 to 0.3 liters (mixture,
Since it is about 5 g / l, it is necessary to adjust the mixing ratio depending on the level of the VSS of the sludge sample.)

(3) Measurement operation Next, the gas conduit 23 is connected, and the temperature is kept at 30 ° C. for 1 to 2 days.
Thereafter, 2.3 g of sodium acetate is added to the narrow-mouthed bottle 21.
The amount of acetic acid conversion per g of sludge VSS was 0.45 g, and the initial COD conversion concentration of acetic acid in the liquid phase was 2.2 g / g.
l. PH is adjusted using 1N HCl or NaOH.
Was adjusted to 6.7, and bubbling of N ₂ gas was performed. Then, the gas conduit 23 was connected again, and the temperature was maintained for 1 to 2 days to measure the amount of methane produced. The methane production rate is calculated by performing regression by the least squares method from the change over time of the accumulated methane production.

(4) Calculation method The sludge sample VSS after adjusting the methane production rate and concentration is calculated by the equation (2).
By simply substituting the concentration and the like, the methane generation activity is calculated by simple measurement (acetic acid addition).

Next, a simple measurement (addition of acetic acid) obtained from an empirically obtained simple measurement (addition of acetic acid) Equation (5), which is a correlation equation between the methane production activity and the content ratio of acetic acid-assimilating methane-producing bacteria sludge, was obtained. The measured value of the methanogenic activity is substituted to calculate the acetic acid-utilizing methanogen sludge content ratio.

Y = Ex + F (5) E: 31.6 to 32.8 F: 0.27 to 0.45 x: Simple measurement (addition of acetic acid) Methanogenesis activity (kgCH ₄ -CO)
Y: Amount of acetic acid-utilizing methanogen sludge content (%) Table 1 shows the reactor methane production activity and simple measurement (medium acetic acid) in a medium temperature semi-continuous sludge digestion laboratory experiment of centrifugally concentrated and gravity concentrated sewage sludge. Addition) shows the correlation coefficient between methane generation activity and other indices.

[0050]

[Table 1]

The correlation with a correlation coefficient of 0.9 or more was observed because of the relationship between the reactor methane production activity and the methane production rate (r = 0.966) and the simple measurement (addition of acetic acid). Relationship with the amount of methanogen (r =
0.949).

Next, FIG. 5 shows the relationship between the methane generation activity and the reactor methane generation activity and the methane generation activity of the simple measurement (addition of acetic acid) in the medium temperature semi-continuous sludge digestion laboratory experiment in the centrifugal concentration and gravity concentration sewage sludge.

Assuming that x is the organic substance volume load and y is the reactor methane production activity, the correlation regression equation excluding abnormal fermentation (portion surrounded by a dotted line in the figure) is y = 0.0258x + 0.05.
1 (r = 0.898, n = 17), indicating a high correlation.
On the other hand, assuming that x: organic substance volume load, y: simple measurement (acetic acid addition) methanogenic activity, the correlation regression equation excluding abnormal fermentation is y = 0.0084x + 0.107 (r = 0.474, n =
19). Comparing the reactor methanogenic activity with the simple measurement (acetic acid addition) methanogenic activity shows that the former is more dependent on the organic matter volume load than the latter. Also, under relatively low load conditions with an organic substance volume load of 3 kg / m ³ · day as a boundary, the latter tended to have a higher activity than the former.

This is because under a low load condition, the increase in the activity of the reactor methane formation is suppressed by a small supply of the substrate, whereas the simple measurement (acetic acid addition) is performed.
It is considered that the substrate is sufficiently supplied to the acetic acid assimilating methanogen under the measurement conditions of the methane production activity. On the other hand, under high load conditions, the reactor methanogenic activity is higher than the simple measurement (acetic acid addition) methanogenic activity because hydrogen is supplied and supplied as a substrate in addition to acetic acid in the reactor. Is thought to contribute to methane production.

From the above results, it can be seen that the methane production activity in the simple measurement (addition of acetic acid) is closely related to the amount of acetic acid assimilating bacteria and the sludge content ratio.

In this embodiment, the equation (5) used for estimating the content ratio of the acetic acid assimilating methane-forming bacteria sludge from the measured value of the methane-forming activity in the simple measurement (addition of acetic acid) is represented by the following equation: Measurement shown in Fig. 6 (addition of acetic acid) in a medium-temperature semi-continuous sludge digestion laboratory experiment of sewage sludge and gravity concentrated
This is an equation derived by correlation regression from the relationship between the methanogenic activity and the content ratio of acetic acid-assimilating methanogen sludge measured according to the method of Valcke et al. The correlation coefficient for only digested sludge in the medium temperature semi-continuous sludge digestion laboratory experiment of centrifugal concentration and gravity concentrated sewage sludge is 0.962 (n = 21), and when other digested sludge and raw sludge are also included. 0.949 (n
= 27), indicating a high correlation. In addition, since the variation is small even in the region where the methane generation activity is high as compared with the case of FIG. 4, there is an effect that the estimation accuracy of the acetic acid-utilizing methane-producing bacterium sludge content rate is increased.

(Second Embodiment) Method for Estimating the Amount of Acetate-Utilizing Methanogen In this embodiment, the amount of acetic-acid-utilizing methane-producing bacteria is easily estimated from the simple measurement (addition of acetic acid) methane-producing activity. Devised a way to do that.

First, according to the first embodiment, a simple measurement (addition of acetic acid) of methane generation activity was measured for sludge serving as a sample, and this measured value was substituted into equation (5) to produce acetic acid assimilating methane. Calculate the estimated value of the bacterial sludge content.

Next, the estimated value of the acetic acid assimilating methane-producing sludge content ratio and the measured value of the sludge sample VSS are substituted into the equation (6) to estimate the amount of acetic acid assimilating methane produced. Note that the VSS in this case is the VSS of the sludge sample before performing the concentration adjustment.

Z = xy / 100 (6) x: sludge sample VSS (g / l) y: acetic acid-utilizing methane-forming bacterium sludge content ratio (%) z: acetic acid-utilizing methane-forming Bacterial amount (g / l) Table 2 shows the amount of acetic acid-utilizing methane-producing bacteria, the ratio of acetic acid-utilizing methane-producing bacteria sludge, and other indexes in a medium-temperature semi-continuous sludge digestion laboratory experiment of centrifugally concentrated and gravity-concentrated sewage sludge. (N = 19 to 22, including abnormal fermentation).

[0061]

[Table 2]

The correlations with a correlation coefficient of 0.9 or more were observed because the sludge content ratio of acetic acid-assimilating methane-producing bacteria and the methane generation activity in simple measurement (with acetic acid) and the methane conversion activity in simple measurement (with acetic acid). The relationship was.

The correlation coefficient with the amount of acetic acid-assimilating methane-producing bacteria was
Since no index indicating a correlation of 0.9 or more was obtained, the ratio of acetic acid assimilating methane-producing bacteria sludge was estimated in the second embodiment by the method of the first embodiment with high estimation accuracy. The method of substituting the measured value of VSS into the above is adopted, but there is an effect that the same high estimation accuracy as in the first embodiment can be obtained.

[0064]

As described above, according to the method of the present invention, acetic acid resources can be accurately and easily obtained using the value of methane production activity measured by adding a fixed amount of sodium acetate to sludge in a methane fermentation tank. It is possible to estimate the sludge content ratio of methane-producing bacteria and the amount of methane-utilizing methane-producing bacteria.

Furthermore, the method according to the present invention is a method for controlling methane fermentation such as the amount of acetic acid-utilizing methane-producing bacteria and the content ratio of acetic acid-utilizing methane-producing bacteria by relatively simple measurement of sludge activity. There is an advantage that useful information can be obtained, and the method for measuring sludge activity is simplified, so that automation becomes possible and its practicality is enhanced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an apparatus for measuring acetic acid assimilating methane-producing bacteria.

FIG. 2 is a partial configuration diagram showing an apparatus for measuring acetic acid assimilating methane-producing bacteria.

FIG. 3 is a schematic configuration diagram showing an apparatus for measuring acetic acid assimilating methane-producing bacteria.

FIG. 4 is a characteristic diagram showing the relationship between the methane production activity and the amount of acetic acid-assimilating methane-producing bacteria in a simple experiment (addition of acetic acid) in a medium-temperature semi-continuous sludge digestion laboratory experiment.

FIG. 5 is a characteristic diagram showing the relationship between the methane production activity and the methane production activity of the reactor (measured with acetic acid) in the semi-continuous sludge digestion laboratory at medium temperature and the organic matter volume load.

FIG. 6 is a characteristic diagram of the method of the present invention showing the relationship between the methane production activity and the acetic acid-assimilating methane-producing bacteria sludge content ratio in a simple experiment (addition of acetic acid) in an intermediate temperature semi-continuous sludge digestion laboratory experiment.

[Explanation of symbols]

 21 ・ ・ ・ Narrow-necked bottle (capacity: 1 liter) 22 ・ ・ ・ Constant temperature water tank 23 ・ ・ ・ Gas conduit 24 ・ ・ ・ Gas washing bottle (1N, NaOH) 25 ・ ・ ・ Gas holder 26 ・ ・ ・ Saturated saline 27 ・··scale

Claims (4)

[Claims] After a sludge sample and a medium collected from a methane fermentation tank are put into a container, the container is kept warm for a certain period of time, and then a certain amount of sodium acetate is added to the container. After obtaining methane production
Based on the obtained amount of methane production, the methane production activity when a certain amount of sodium acetate was added to the sludge sample based on the obtained methane production amount, and the acetic acid assimilating methane-producing bacteria sludge content ratio measured for the same sludge sample, A method for estimating the content ratio of acetic acid-utilizing methane-forming bacteria sludge by substituting the value of the methane-producing activity into an arithmetic expression derived from the correlation of 2. The method for estimating the acetic acid-utilizing methane-producing bacterium sludge content ratio according to claim 1, wherein the arithmetic expression comprises the following expression. y = Ax + B A: 31.6 to 32.8 B: 0.27 to 0.45 x; methanogenic activity (kgCH ₄ -COD / kgVSS / day) y; acetic acid assimilating methanogen sludge content ratio (%) 3. A sludge sample and a medium collected from a methane fermentation tank are put into a container, the container is kept warm for a certain period of time, and then a certain amount of sodium acetate is added to the container. After obtaining methane production
Specific methane production activity when a fixed amount of sodium acetate was added to the sludge sample based on the obtained methane production amount and the acetic acid assimilating methane-producing bacteria sludge content ratio measured for the same sludge sample After substituting the value of the methane production activity into the equation derived from the correlation with the above and estimating the sludge content ratio of acetic acid-utilizing methane-forming bacteria, the amount of acetic acid-utilizing methane-forming bacteria and The value of the acetic acid-utilizing methane-producing bacteria sludge content ratio and the value of the sludge sample concentration are substituted into an arithmetic expression showing the relationship between the bacterial content ratio and the sludge sample concentration, and the amount of acetic acid-utilizing methane-producing bacteria is estimated. A method for estimating the amount of acetic acid-utilizing methane-producing bacteria, characterized in that: 4. An arithmetic expression representing the relationship between the amount of acetic acid-utilizing methane-producing bacteria, the content ratio of acetic acid-utilizing methane-producing bacteria, and the concentration of a sludge sample is represented by the following expression.
The method for estimating the amount of acetic acid assimilating methane-producing bacteria described in the above. z = xy / 100 x: sludge sample VSS (g / l) y: acetic acid assimilating methanogen sludge content ratio (%) z: acetic acid assimilating methanogen amount (g / l)