JPH08173993A - Method for controlling anaerobic treatment - Google Patents

Abstract

PURPOSE: To provide a method for controlling the amount of raw water supplied to a reaction tank at an optimum value in the treatment of an organic waste and wastewater by anaerobic treatment. CONSTITUTION: In anaerobic treatment of an organic waste and wastewater, as an index of the amount of raw water 2 to be supplied to a reaction tank 1, a method for controlling anaerobic treatment is provided in which the flow rate of the raw water is adjusted by a raw water pump 3 so that a control factor measured by an organic substance-actetic acid assimilating methane bacteria concentration measuring means 7 is in a proper range. An organic substance-acetic acid assimilating methane bacteria load can be calculated using an equation. In addition, the flow rate of the raw water 2 is calculated by substituting the control target value of the organic substance-acetic acid assimilating methane bacteria load into the equation, and a method is provided in which the proper values of HRT and an organic substance volume load are determined from the flow rate of the raw water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the amount of raw water input to a reaction tank in an anaerobic treatment method for organic waste and wastewater.

[0002]

2. Description of the Related Art For the anaerobic treatment of organic waste and waste water, a biodegradation reaction involving anaerobic microorganisms, for example, a methane fermentation tank is used. Figure 3 shows the solid content and potential energy content of organic substrates and the corresponding anaerobic treatment methods (Yuhei Inamori, Ryuichi Sudo; Water and Wastewater,
25 (10) 3 (1983) excerpt).

According to FIG. 3, the standard method is suitable for the anaerobic treatment of sludge having a high solid content and excrement of livestock, while anaerobic treatment is applied to an organic wastewater having a low solid content. The suitable filter bed method, the anaerobic fluidized bed method, and the UASB method are suitable.

Control of the substrate input amount in these various anaerobic treatment systems is generally performed by HRT (hydraulic retention time) and organic matter volume load. However, when the solid content is low, TOC is used instead of the organic volume loading.
(Total organic carbon content), COD (chemical oxygen demand), BO
Volumetric loads such as D (biochemical oxygen demand) are used.

For example, in controlling the substrate input amount in the standard fermentation system for sludge, HRT is set to 2 in medium temperature fermentation.
Generally, the volumetric load of organic matter is set to 3 (kg / m ³ · day) or less for 0 to 30 days. Also, U for industrial wastewater
In the ASB method, the COD volume load is 10 to 15 (kg / m ³ ·
It is often less than (day).

As described above, since the control target value of the input amount also differs depending on the type of substrate and the processing method, the HRT is different for each case.
The current situation is to determine the target value of organic matter, organic matter, or TOC, COD, and BOD loads. As another method of controlling the amount of the substrate charged into the anaerobic reaction tank, a method of controlling the sludge load, such as controlling the volume load of organic matter and the F / M ratio with respect to the amount of sludge in the tank, is also known.

[0007]

As described above, the control of the substrate input amount of the anaerobic treatment is carried out by the HRT and the organic substance volume load so as to fall within the target range.
Is empirically determined by the nature of the raw water to be treated and the treatment method. However, when the HRT is operated at a constant level, it may affect the treatment efficiency when the composition of raw water changes or the volumetric load of organic matter changes. For example, if the organic concentration of raw water is too high, the concentration of organic matter may increase or the pH may increase. Of the gas and the amount of gas generated decrease, which may result in inability to process. On the contrary, when the concentration of organic matter in the raw water becomes low, the HRT can be shortened to perform high load treatment, but the operation is continued at low load, which is economically disadvantageous. .

Further, in the case of the F / M ratio control or the method of controlling the sludge load, as a concrete expression method, the organic matter load rate, that is, the amount of organic matter in raw water / the amount of sludge organic matter in the tank, or the organic matter in the tank sludge is used. TOC when it is called VSS
(COD, BOD) -There is a VSS load. But F / M
In the ratio control or sludge load control method, since the organic matter in the sludge in the tank includes not only the microorganisms but also the non-decomposable organic matter in the input raw water, it cannot be said that the F / M ratio control is strict. Therefore, it is necessary to determine the appropriate target value of sludge load for each case. Further, when the sludge microbial concentration fluctuates, it becomes necessary to change the target value.

As described above, in the conventionally known method of controlling the substrate input amount of anaerobic treatment, it is necessary to empirically determine the control target value for each case. There is no choice but to rely on means such as setting a long HRT or searching for an appropriate control range by groping after starting with a low organic matter load, so that it takes a long time to perform steady operation. There is.

There are two possible reasons for the excessive organic matter load. The first is the case where a high concentration of raw water flows in with a change in the composition of the raw water even when the HRT is kept constant. In this case, the F / M ratio, that is, the TOC with respect to the sludge organic matter in the tank (hereinafter abbreviated as VSS) increases. In other words, the TOC / VSS load increases.

The second case is that sludge flows out of the tank and the amount of sludge in the tank is reduced due to deterioration of sludge sedimentation, and the TOC / VSS load increases even if the organic matter volume load does not change. Such changes in sludge sedimentation tend to occur when the ss concentration of raw water increases or when the HRT changes suddenly. Experience has shown that sludge floats up when the supply of raw water is stopped for a long time.

Therefore, the present invention solves the problem that the conventional substrate input amount control means in anaerobic treatment has, and is optimal for a reaction tank when anaerobicly treating organic waste and wastewater. The purpose of the present invention is to provide a raw water input control method.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the present invention uses an organic substance / acetic acid as an index of the amount of raw water input to a reaction tank during anaerobic treatment of organic waste and wastewater. Provided is a control method for anaerobic treatment, which is characterized in that a control factor, which is an oxidative methane bacterial load, is obtained and the flow rate of raw water is adjusted so that the control factor is in an appropriate range.

The above-mentioned organic matter / acetate-utilizing methane bacterial load is calculated by using the equation (1) described in claim 2,
Furthermore, the control target value of the organic matter / acetic acid-utilizing methane bacterial load is substituted into the equation (1) to calculate the flow rate of raw water, and the appropriate value of HRT and organic matter volume load is determined from this raw water flow rate. provide.

[0015]

According to the control method of the anaerobic treatment, the organic substance / acetate assimilating methane is calculated by using the formula (1) based on the value measured by the acetic acid assimilating methane bacteria concentration measuring means attached to the reaction tank. Bacterial load is calculated and the results provide optimal control of raw water flow to the reactor. Especially the above organic matter
When the acetic acid-utilizing methane bacterial load does not fall within the appropriate range, it is possible to perform control to adjust the flow rate of the raw water pump by calculating the raw water flow rate that falls within the appropriate range.

Further, by using the load of organic matter / acetate-utilizing methane bacteria as an index of load, the F / M ratio and sludge load are strictly controlled, and process defects due to overload or undigested phenomena occur. To be prevented. Since the amount of acetic acid-assimilating methane bacteria is an index of major active microorganisms that are directly related to methane generation, it is possible to easily predict the control target range even for a substrate or a treatment method that has not been previously treated. it can.

Since it is possible to determine an appropriate range of HRT or organic matter volume load from the control target range of the load of organic matter / acetate-utilizing methane bacteria, there is an effect that the time from the start of operation to the steady operation is shortened. can get.

[0018]

EXAMPLES Specific examples of the control method of the anaerobic treatment according to the present invention will be described below. One of the features of this example is that the concept of organic matter / acetate-utilizing methane bacterial load is defined as an index of the amount of raw water input in the anaerobic treatment, and a control method is used so that it falls within a certain range. There is.

The above-mentioned organic matter / acetate-utilizing methane bacterial load is a kind of F / M ratio, and is calculated using the following equation (1).

[0020]

[Equation 2]

In the equation (1), VS, TOC, COD, BOD, etc. are used as the concentration of the organic matter in the raw water input. The concentration of acetic acid-utilizing methane bacteria in the tank during anaerobic treatment is reported in the literature (D.Valche, W.Verstraete Journal WPCE, 55 (9)
1191, 1983), the ratio of acetic acid-utilizing methane bacteria concentration to VSS in tank sludge measured by the method described in (1191, 1983) is 6 to 8% in standard fermentation of sewage aquatic sludge, and 30 in the industrial wastewater UASB method. Values of ~ 60% have been reported.

FIG. 1 shows a control system aiming at the load of organic matter / acetic acid-utilizing methane bacteria to which this embodiment is applied.
In FIG. 1, 1 is an anaerobic treatment reaction tank (fermentation tank),
2 is raw inflow water, 3 is raw water pump, 4 is organic substance measuring means,
5 is a flow meter, 6 is VSS measuring means for sludge in the reaction tank, 7 is means for measuring acetic acid-assimilating methane bacteria concentration, 8 is control device, 9
Is a gas holder, and 10 is treated water.

Based on the measured values of the organic substance measuring means 4, the flow meter 5, the sludge VSS measuring means 6 and the acetic acid-utilizing methane bacteria concentration measuring means 7, the control device 8 uses the above equation (1) to calculate the organic matter. -The acetic acid-utilizing methane bacterial load can be calculated. The optimum drive of the raw water pump 3 is controlled by this result.

That is, in this embodiment, when the load of the organic matter / acetate-utilizing methane bacteria does not fall within the proper range, the flow rate of the raw water 2 that falls within the proper range is calculated to obtain the raw water pump 3 It is characterized by adjusting the flow rate of.

Methane bacteria are roughly classified into acetic acid assimilating and hydrogen assimilating, and it is known that 70% of them are decomposed via acetic acid in the usual anaerobic decomposition of organic substances. .
Therefore, in controlling the amount of raw water input, it is considered sufficient to measure only acetic acid-utilizing methane bacteria without measuring both acetic acid-utilizing ability and hydrogen-utilizing ability.

The appropriate range of the organic matter / acetate-utilizing methane bacterial load was calculated based on actual data as in Examples 1 and 2 below.

[Example 1] HRT = 30 at 35 ° C in standard anaerobic digestion using sewage aquatic sludge as a substrate
The organic matter / acetate-utilizing methane bacterial load was calculated when continuous operation was performed under day conditions. The effective volume of the tank was 9 liters. The sludge properties at this time are as shown in Table 1.

[0028]

[Table 1]

The concentration of acetic acid-utilizing methane bacteria in the digested sludge was 769 (mg / l), and the load of organic matter / acetic acid-utilizing methane bacteria was

[0030]

(Equation 3)

It is On the other hand, when the same substrate is used, HRT can be shortened to 20 days. Organic matter at this time
Acetogenic methane bacterial load is

[0032]

[Equation 4]

That is, the range of the appropriate organic matter / acetate-assimilating methane bacterial load in the sewage-enriched raw sludge medium temperature standard system anaerobic treatment is 1.7 to 2.5 (kg / kg · day).

[Example 2] An appropriate organic substance / acetate-utilizing methane bacterial load was estimated from the data of a UASB laboratory experiment using an artificial substrate composed of acetic acid, glucose, peptone, methanol yeast extract, inorganic hydrochloric acid and the like. .
In this case, the appropriate TOC / VSS load at 35 ° C. was 0.3 to 0.7 (kg / kg · VSS · day).

In the UASB method, the acetic acid-assimilating methane bacterium / VSS ratio is often in the range of 30 to 60%. Therefore, in this example also, it is said that 30 to 60% of VSS is the acetic acid-assimilating methane bacterium. I assumed.

The above-mentioned UASB method is an upflow anaerobic sludge blanket method.
Abbreviation for ctor process), Lettinga (1980), Froste
ll (1981) et al. try to allow a high volume load by keeping the anaerobic microorganisms with excellent sedimentation property in the reactor at a high concentration by using pellets of sludge itself or by growing granules without using an adherent carrier. It is a high-speed anaerobic treatment technology that can be said to be a self-immobilizing cell method.

TOC / VSS load is 0.7 (kgTOC
/ Kg · VSS · day), the TOC acetate-utilizing methane bacterial load is 0.7 × {1 / (0.3 to 0.6)} = 1.17 to 2.33 (kgTOC / kg · day). In the artificial substrate used here, 37% of the organic matter is carbon, so if the TOC is converted to the weight of the organic matter and then converted to the organic matter / acetate-utilizing methane bacterial load, (1.17 to 2.33) x (1 / 0.37) = 3.15 to 6.30 (kg / kg / day) TOC / VSS load lower limit of 0.3 (kgTOC / kg / day)
In VSS · day), TOC acetate-utilizing methane bacterial load is 0.3 × {1 / (0.3-0.6)} = 1 to 0.5 (kgTOC / kg · day) Furthermore, TOC is converted to organic matter as (1 to 0.5) X (1 / 0.37) = 2.70 to 1.35 (kg / kg · day). That is, in the UASB method, the proper range of the organic matter / acetate-utilizing methane bacterial load is 0.5 to 2.3 (kgTOC /
kg ・ day) or 1.35-6.30 (kg organic matter / kg ・
Days). This is considered to be because the UASB method has a higher load of organic matter / acetate-utilizing methane bacteria than the standard method because the decomposition rate of the substrate is different.

As described above, in the control of the input amount of the anaerobic treatment, the F / M ratio or the sludge load is controlled more strictly by using the organic matter / acetate-utilizing methane bacterial load as an index of the load. It is possible to prevent the process failure or undigestion due to overload.

The F / M ratio or the sludge load control index includes an organic matter load factor, TOC (COD, BOD) / VSS load, and the like. In these, the organic matter in the sludge in the tank is fed to the outside of the microorganisms in the raw water. The strict F / M ratio cannot be obtained because it contains non-decomposable organic substances. On the other hand, in the case of this example, since the amount of acetic acid-assimilating methane bacteria, which is a main active microorganism directly related to methane generation, is M,
The expression is closer to the F / M ratio or sludge load, and the appropriate range of HRT or organic matter volume load differs greatly due to the difference in anaerobic treatment method, whereas the organic matter / acetate-utilizing methane bacterial load differs in treatment method. It has an advantage that it is possible to predict the control target range even for substrates and treatment methods that have not been experienced in treatment in the past.

Further, there is an advantage that an appropriate range of HRT or organic matter volume load can be calculated from the control target range of organic matter / acetate-utilizing methane bacterial load, and accordingly, the time from start to steady operation can be calculated. It can be shortened.

On the other hand, a practical method for estimating the amount of acetic acid-utilizing methane bacteria in anaerobic sludge (D. Valche, W. Verst
According to raete Journal WPCE, 55 (9) 1191,1983), acetic acid serves as a precursor for 70% or more of the amount of methane produced by methane fermentation. The types of methane bacteria that can convert acetic acid to methane and carbon dioxide are limited.
Methanobacter; Soehngenii; Methanosarcina bacter; Met
There are hanosarcina strain 227 etc.

The measurement of the number of acetic acid-assimilating methane bacteria in a mixed solution or influent is often a problem in anaerobic digestion, and several methods for estimating the number of bacterial cells have been proposed. However, these methods have a problem that they are indirect or complicated in operation.

The method proposed here is a mixed solution 1 by increasing the amount of acetate added to a series of sludge treatments.
It measures the maximum methane generation rate per liter. That is, the method has minimal growth of organisms within a maximum incubation of 24 hours and an acetic acid conversion rate of 0.
Based on the following reaction formula, it is based on the finding that it is not affected by the substrate concentration within a certain range.

Further, in order to convert the maximum acetic acid conversion rate into the number of acetic acid-degrading methane bacteria, it was assumed that the maximum specific activity (methane generation rate per bacterial weight) was obtained under the present measurement conditions.

Regarding the maximum specific activity of acetic acid-utilizing methane bacteria, the number of data in aseptic culture or semi-sterile enrichment (enhancement) culture reactor is small. This example is effective for use in controlling an anaerobic digester, particularly a digester mainly supplying an acetic acid substrate.

Table 2 shows some examples of calculating the maximum specific activity (ml · CH ₄ / g · VSS · day) of acetic acid-utilizing methane bacteria in methane sludge grown in aseptic culture of methane bacteria and acetate.
All of these numbers correlate with the number of non-logarithmic growth cells, and the cell weight of acetic acid-utilizing methane bacteria is 717 g / g / day.
Methane ~3020ml 0.25~1.06 (gCH ₃ · C
OD / g acetic acid-degrading methane bacteria weight / day) is produced. Needless to say, more data are required, but the maximum specific activity at 30 to 35 ° C is about 1000 (ml · CH ₄ / g · VSS · day) from the values shown in Table 2.
(0.35 g CH ₃ · COD / g · VSS / day).

[0047]

[Table 2]

A specific measuring method will be described below. First, a relatively large amount (5-10 liters) from the digestion tank as a material
Pull out the sludge. At this time, the sampling operation is performed so as to obtain a sample representative of the sludge concentration in the reactor. Here, the ss component, VSS, and TOC of the sample are measured.

Next, 2.5 g of KH ₂ PO ₄ and 1.0 g of K ₂
HPO ₄ , 1.0 g NH ₄ Cl, 0.1 g MgCl ₂ ,
A stock solution of pH 6.7 containing abasic minerals is prepared by dissolving 0.2 g of yeast extract and 0.1 g of Na ₂ S.7H ₂ O in 1.0 liter of water. Then, the sludge sample was diluted with this stock solution so that the VSS concentration was about 5
(G / l) as a mixed solution, and put the mixed solution in an Erlenmeyer flask 11 having a volume of 2.0 liters shown in FIG.

Then, acclimation is carried out at 30 ° C. for 24 to 48 hours. In this example, different amounts of NaA are added to the Erlenmeyer flask 11.
c (1 gHAc = 1.37 gNaAc) was added to adjust the sludge concentration to the range of 0.3 to 1.0 (gHAc / g · VSS). If the maximum methane generation rate is observed at the maximum sludge load, 1.0 g (gHAc / g · VSS)
The test must be carried out at a higher sludge load.

Be careful not to introduce oxygen into the liquid during the above operation. After the addition of NaAc, the liquid in the Erlenmeyer flask 11 was adjusted to pH with 1.0N HCl or 1.0N NaOH.
Adjust to 6.7. Then, nitrogen gas is bubbled through for at least 1 minute, then placed on the magnetic stirrer 12, stirred every 5 minutes for 5 minutes, and kept at 30 ° C. for 24 hours.
The generated gas was bubbled into a 1N NaOH solution 13 to remove CO _2, and the volume of CH ₄ was changed to a gas collector 14
It is measured by displacement on water.

Next, enrichment culture is performed. In laboratory experiments, 90% each was obtained in two methane enrichment cultures using acetate as a substrate.
0.930 (mlCH ₄ / g · VSS · day) of methane was produced. Both culture systems were derived from a 12 m ³ pilot scale digester for brewery wastewater treatment, in which anaerobic sludge from a sewage treatment plant was set up as seed sludge.

The first enrichment culture was carried out in a water bath and the second enrichment culture was carried out in an upflow reactor. The medium in both culture systems contained the following components by weight per liter.

NaAc; 3.0 g, KH ₂ PO ₄ ; 3.0
g, K ₂ HPO ₄ ; 1.0 g, CaCl ₂ .2H ₂ O; 1.0
g, NH ₄ Cl; 1.0 g, MgCl ₂ .6H ₂ O; 0.1
g, Fe ₂ (SO ₄ ) ₃ ; 0.1 g, yeast extract; 0.2
g, ethanol; 1.5 ml Next, the verification of this test method was performed using the sludge of the upflow reactor for treating the wastewater from the flax peel fiber obtained at the flax bleaching plant. Manipulate different concentrations of NaAc
Was added and the change was observed for 30 hours. As a result, 275
It was found that the gas generation amount increased in proportion to time up to 425 (mlCH ₄ / mixed liquid volume (L) / day), and the methane generation rate also increased when the sludge concentration was high. However, each sludge is 0.40 (gHAc / g ・ VS
When the sludge load is S) or less, the acetate concentration becomes the rate-determining factor of the reaction, and it is necessary to dilute the sludge to 5 (gVSS / L) or less to make the substrate non-rate-limiting condition.

It is not recommended to add a large amount of acetate to the concentrated sludge. This is because variations in pH, salt concentration of the medium and the like cause a decrease in activity. Actually, the methane generation rate did not increase in this sludge even when 3.72 (gHAc / l) or more of acetate was added.

As shown in Table 2 above, the maximum specific activity of acetic acid-utilizing methane bacteria is about 1000 under any conditions.
Based on the assumption of (mlCH ₄ / g · VSS · day) and the observation result of the maximum specific methane production rate shown in Table 3,
Acetogenic methane bacteria will account for 9.9-10.3% of the sludge VSS during harvesting from an upflow reactor.

[0057]

[Table 3]

A retest was carried out two months later when the reactor was in full operation, at which time acetogenic methane bacteria increased to 33% of VSS. Methane production rate (m ³ CH ₄ /
The actual measured value of (kg · VSS · day) was obtained as a value corresponding to the methane production rate obtained in the above test, and it was found that the reactor was operated at a load close to the maximum load. In fact, it is expected that COD removal efficiency will fall rapidly if the load is further increased.

The second sludge used was drawn from a 12 m ³ upflow methane reactor for treating the acidified wastewater of an oxygen production plant. The main substrate of this reactor is acetic acid. The sludge sample is 24.3 (g /
It contains ss component of 1) and VSS of 16.2 (g / l). As shown in Table 4, the maximum activity was 395 (mlCH
₄ / g · VSS · day)

[0060]

[Table 4]

A two-phase anaerobic digester treating brewery wastewater was investigated for 10 months. One month after starting, the sludge in the methane reactor was originally the sludge from the wastewater digestion tank, and the VSS of acetic acid-utilizing methane bacteria was used.
The percentage of the total was 8%, but it increased to 31% after 10 months of operation.

Maximum of 15 in the upflow methane reactor
An upflow reactor of 00 m ³ treats the wastewater of the sugar beet factory. Sludge load 1.8g (HAc / g ・ VS
S) and the substrate concentration was 4.3 (gHAc / l), the maximum gas generation rate was 635 (mlCH ₄ / gVSS · day). This value indicates that 63% of VSS in sludge is acetic acid-degrading methane bacteria.

A value of 0.27 was obtained for P, which is the ratio of the latent methane production rate to the actual methane production rate. This reactor shows that there is no risk of acetic acid accumulating when treating wastewater containing acetic acid at higher loads.

Next, the activity of the sludge in the domestic digester was examined. Primary reactor (V = 80m ³ ) is 20-30, SR
The T had been in operation for 47 days. Sludge sample is 4.33 (g
It was diluted to ss / l) and 54% of the ss component was VSS. The methanogenic activity is low, and the maximum is ± 80 (mlC
H ₄ / g · VSS · day). From this value, the cell weight of acetic acid-utilizing methanogen occupies 8% of VSS.

The second reactor was a 6500 m ³ oval digester and the SRT was operating for 26 days. The sewage sludge charged into this reactor was thin containing 3% dry solids, and as a result of the test, it was found that the sludge in this digester tank had a low concentration of methane bacteria (see Table 4 above).

Finally, a test was conducted on digester sludge for treating pig manure. Screened pig manure (15g / l COD, 7-9g / l in a laboratory fermentor)
When VSS) was added, the concentration of acetic acid-utilizing methane bacteria was 1.0 g per liter. A full-scale digester (50-60g / lCO) for treating normal swine manure
D, 40 to 45 g / l · VSS), the weight ratio of acetic acid-utilizing methane bacteria in VSS was at a considerably low level.

As described above, methane fermentation is a microbial process that requires careful design and control, and actual engineers and plant operators generally use sludge load factor as a standard in methane fermentation process design. However, the VSS parameter has a drawback in that it has many ambiguous points in that it can also represent non-living organic particles as well as the biomass having a methanogenic activity.

In this example, information on the weight ratio of acetic acid-degrading methanogens in anaerobic digested sludge can be obtained quickly and easily. The operator can accurately estimate the amount of active ingredient in the digester.

It is also possible to estimate the maximum possible methane production rate of the reactor at a particular sludge concentration. Care must be taken to use fresh sludge samples in this test. This is because the sludge left at 10 to 15 ° C for 2 to 3 weeks often has a considerably low methane generation rate. In this test, it is necessary that the amount of acetic acid added to the sample should not be rate-limiting for the substrate.

Depending on the conditions, it may be better to measure the initial acetic acid concentration by gas chromatography, as in the case of targeting low activity digested sludge. However, in sludge, which is easily digested, acetate is usually below the substrate non-rate limiting range.

The maximum specific production rate of acetic acid-utilizing methane production is
Only Methanosarcina bacter and Methanosarcina strain 227 are known. These microorganisms are probably important species in anaerobic digested sludge.

Recently, Zehnder et al. Described the properties of acetic acid-decarboxylate, non-hydrogen-oxidizing Methanobacteriun sohgenil-like methane bacteria. The substrate affinity of this acetic acid-assimilating bacterium is Ks≈0.46, and Methanosarcina strain22
The substrate affinity is higher than that of Ks of about 5 mM. Ecologically, it is thought that this acetotrophic bacterium can become an acetotrophic microorganism that competes with sarcina, which is highly efficient and has a large growth rate. However, the maximum specific substrate conversion rate and methane production rate of this methane bacterium are not yet known.

The VSS present in the reactor that receives the soluble substrate is mainly composed of microbial organisms. However, in a reactor that accepts organic particles, the VSS parameter is composed of both the substrate and active microbial organisms. In such a case, the results of the test are only relative values, and in interpreting the latter data expressing what percentage of the VSS abundance present in the reactor is acetogenic methane bacteria, References must be made to optimally operate the reactor.

In the present invention, a soluble COD / stainable material such as sewage sludge or pig manure not separated by a screen is used.
Two substrates were tested with a VSS ratio of about 0.4. In these reactors, VSS 6.0-8.
0% was cells of acetic acid-utilizing methane bacteria. However, in the case of swine manure separated by a screen, the soluble COD / VSS ratio was 1.0, but the weight ratio of acetic acid-utilizing methane bacteria in VSS was 14%. Further experimentation and mathematical modeling are required to establish the optimum level of acetogenic biomass for any soluble COD / VSS in a fully mixed reactor.

Under the test conditions of 0.2 (mgHAc / g.
Since HAc is stoichiometrically converted to CH ₄ under a low sludge load of about VSS), 35 g / g of HAc is added.
0 ml of CH ₄ is generated. The value assumed as the maximum specific methane production rate of acetic acid-utilizing methane bacteria is 1000 (m
1 / g biomass dry weight / day). This value also relates to the test conditions. Further, in the case of logarithmic growth, it is the value applied to the bacteria after logarithmic growth or in the stationary growth phase.
In fact, methane bacteria in the logarithmic growth phase may show specific activity 2-3 times or more that in the stationary growth phase.

This has been reported especially by Vandel Berg et al., And is considered to be due to the presence of Methanosarcina strain 227. This value is an approximate value as it is, but as a result of measuring various sludges of the upflow reactor, it was found that this value is a realistic value.

This test is aimed mainly at measuring the ability of sludge to convert into acetic acid, methane and carbon dioxide, and therefore the number of bacteria such as hydrogen-utilizing methane bacteria and hydrogen-producing symbiotic acetogenic bacteria is determined. Is unknown, and the results of this study are not a comprehensive set of anaerobic bacteria. The test serves to control the wastewater treatment reactor when the main component of the substrate is acetic acid at the upstream of the two-phase wastewater treatment system. For other digesters, as pointed out earlier, comparison with reference digester, pH, fatty acid concentration higher than acetic acid, F
_{420 It} should be interpreted in the context of other parameters.

In conclusion, the amount of acetic acid-utilizing biomass in the reactor as well as the specific methanogenic capacity can be determined by a simple and simple test. The information obtained from this can be used for monitoring of the digestion tank and operation control.

[0079]

As described in detail above, according to the method for controlling anaerobic treatment according to the present invention, based on the measurement value of acetic acid-assimilating methane bacteria concentration measuring means attached to the reaction tank,
The load of organic matter / acetate-utilizing methane bacteria is calculated using the calculation formula, and from this result, the optimum control of the raw water flow rate to the reaction tank can be carried out. Therefore, unlike conventional control in which HRT and organic matter volume load are used as indicators, even if composition fluctuation of raw water or volumetric load of organic matter changes, treatment efficiency is not affected, and HRT longer than necessary due to lack of experience. It is also advantageous from the viewpoint of operating cost by not continuing the low-load operation set as above, and makes it possible to control the optimum amount of raw water input to the reaction tank when anaerobically treating organic waste and wastewater.

Further, by using the load of organic matter / acetate-utilizing methane bacteria as an index of load, it becomes possible to strictly control the F / M ratio and the load of sludge, and the phenomenon of process failure or undigestion due to overload can be avoided. Since there is no possibility of causing this, and the amount of the acetic acid-assimilating methane bacteria is an index of the major active microorganisms directly related to methane generation, it is easy to set the control target range even for a substrate or a treatment method that has no treatment experience. Can be predicted.

Further, since the HRT or the appropriate range of the organic matter volume load can be determined from the control target range of the organic matter / acetate-utilizing methane bacterial load, the effect that the time from the start of operation to the steady operation can be shortened Is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a control system to which this embodiment is applied.

FIG. 2 is a schematic diagram showing an example of a means for measuring the number of acetic acid-assimilating methane bacteria in a mixed solution.

FIG. 3 is a graph showing a solid content and a potential energy content of an organic substrate and a corresponding anaerobic treatment method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Anaerobic treatment reaction tank 2 ... Raw water inflow 3 ... Raw water pump 4 ... Organic matter measuring means 5 ... Flowmeter 6 ... Sludge VSS measuring means 7 ... Acetogenic methane bacteria concentration measuring means 8 ... Control device 9 ... Gas holder 10 ... Treated water 11 ... Erlenmeyer flask 12 ... Magnetic stirrer 14 ... Gas collector

Claims (3)

[Claims] 1. When anaerobically treating organic waste and wastewater, a control factor called organic matter / acetate-utilizing methane bacterial load is obtained as an index of the amount of raw water input to the reaction tank, and this control factor is A method for controlling anaerobic treatment, which comprises adjusting the flow rate of raw water so that it is within an appropriate range. 2. The organic substance / acetate-utilizing methane bacterial load is calculated using the following equation (1).
A method for controlling the anaerobic treatment described. [Equation 1] 3. The raw water flow rate is calculated by substituting the control target value of the organic matter / acetate-utilizing methane bacterial load into the above formula (1), and the appropriate values of HRT and organic matter volume load are determined from this raw water flow rate. The method for controlling anaerobic treatment according to claim 2, wherein