JPH11197689A - Drainage treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the accumulation of propionic acid and butyric acid due to the increase of a load, to prevent methane fermentation inhibition, to control the generation of hydrogen sulfide and to maintain good treatment water quality by using entrappingly fixed fungi which entrappingly fixed methane generation fungi and propionic acid assimilation fungi by polyvinyl alcohol. SOLUTION: A liquid containing anaerobic symbiotic bacteria is prepared so that the concentration of solids containing methane generation fungi and propionic acid assimilation fungi is 10-40 g/liter. The liquid and a PVA solution which was heated and allowed to stand still to be of an ordinary temperature are mixed in an even ratio, the mixture is poured into a container such as a vat, and the container is closed. The container is placed in a thermostat, refrigerated, for example, at -20 deg.C for about 20 hr, thawed at an ordinary temperature, and washed. A reducing agent is added into washing liquid, and oxygenless gas is passed to prevent the extinction of the anaerobic symbiotic bacteria. The refrigeration, thawing, and washing are repeated, for example, three times, and a entrappingly fixed fungi in which the symbiotic system of methane generation fungi and propionic acid assimilation fungi are entrappingly fixed in PVA.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment method for purifying an organic wastewater by methane fermentation by anaerobic treatment.

[0002]

2. Description of the Related Art In a typical methane fermentation method, organic substances in wastewater are decomposed into volatile lower fatty acids (acetic acid, propionic acid, butyric acid, etc.) under the anaerobic condition by the synergistic action of various anaerobic bacteria. Next, it is decomposed into methane and carbon dioxide by the action of methane-producing bacteria. In such a methane fermentation method, decomposition into acetic acid is delayed due to an increase in load, and propionic acid, butyric acid, and the like are accumulated, and methane fermentation inhibition occurs.

For this reason, for example, Japanese Patent Application Laid-Open No. 62-27989
No. 6 discloses a technique for incorporating propionic acid assimilating bacteria into digested sludge. Also, Japanese Patent Application Laid-Open No. 62-244
No. 500 discloses a technique for supplying a group of anaerobic fatty acid-decomposing bacteria including a group of propionic acid-decomposing bacteria and a group of methanogens into a methanation tank.

[0004]

In the prior art constructed as described above, the sludge retention time (SRT) needs to be long, and there is a problem that the reaction tank becomes large. In addition, since methane-producing bacteria generally have lower affinity for hydrogen than sulfate-reducing bacteria, hydrogen generated by decomposition of propionic acid is used by hydrogen-assimilating sulfate-reducing bacteria, which was originally slightly present, to generate methane gas. It reduces the rate and inhibits methane fermentation. In addition, hydrogen sulfide is generated, causing odor and corrosion of tanks and pipes.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and prevents the accumulation of propionic acid and butyric acid due to an increase in load, prevents methane fermentation from being inhibited, and prevents one of malodorous components.
It is an object of the present invention to obtain a wastewater treatment method that suppresses the generation of hydrogen sulfide, which is one of the two methods, and maintains good treated water quality.

[0006]

The present invention relates to a wastewater treatment method in which organic wastewater is subjected to methane fermentation by anaerobic treatment to perform wastewater treatment, wherein methane-producing bacteria and propionic acid assimilating bacteria are entrapped and fixed with polyvinyl alcohol. Comprehensive fixed cells were used. Further, a wastewater treatment method in which organic wastewater is subjected to methane fermentation by anaerobic treatment to carry out wastewater treatment, wherein a methanotrophic bacterium, a propionic acid assimilating bacterium and a butyric acid assimilating bacterium are entrapped and fixed with polyvinyl alcohol. Was.

[0007] In addition, entrapping immobilized cells in which acetic acid was used as a substrate and entrapped and immobilized with polyvinyl alcohol were used. In addition, entrapping immobilized cells in which nutrients acclimated using propionic acid as substrates were entrapped and immobilized with polyvinyl alcohol were used. In addition, entrapping immobilized cells in which butyric acid was used as a substrate and entrapped and immobilized with polyvinyl alcohol were used.

As the methanogen, Methanosarcina was used as an acetic acid-utilizing bacterium and a hydrogen-consuming bacterium. Further, as the methanogen, genus Methanothrix was used as the acetic acid assimilating bacterium, and genus Methanobacterium or Methanococcus was used as the hydrogen-consuming bacterium.

[0009] As the propionic acid assimilating bacterium, a genus Synthobacter was used. Further, as the butyric acid assimilating bacterium, a genus Syntrophomonas was used.

[0010]

Embodiment 1 FIG. 1 is an explanatory diagram of Embodiment 1 of the present invention. Embodiment 1 is a method in which a methane-producing bacterium and a propionic acid assimilating bacterium are entrapped and fixed by polyvinyl alcohol (hereinafter, referred to as PVA), and then put into a methane-producing tank to perform wastewater treatment.
Fig. 1 shows a process for producing the inclusive fixed cells in the method.

First, the concentration of the solid matter containing the methanogen and the propionic acid assimilating bacterium contained in the solution is 10 to 40 g /
An anaerobic symbiotic bacterium-containing solution is prepared so as to be L (step S-1). Further, the PVA is heated to 90 ° C. so that the concentration becomes 5 to 10%, preferably 7.5% (step S-2). Thus, the anaerobic symbiotic bacterium-containing solution and the PVA solution left to stand at room temperature are sufficiently mixed at a ratio of 1: 1 (step S-3).

[0012] At this time, preferably, a reducing agent such as sodium sulfide or L-cysteine is added so that its concentration becomes 0.5 to 2.0 g / L. Vent with oxygen-free gas such as carbon dioxide or a mixed gas thereof to minimize dissolved oxygen in the PVA solution.

The solution thus mixed is poured into a container such as a vat, for example (step S-4), and the container is closed with a lid. It should be noted that the bat and the lid are made of a metal or a plastic which has high secrecy and has a resistance to an increase in volume during solidification.

The solution contained in a container such as a vat is placed in a thermostat or the like and frozen at a temperature of, for example, -20 ° C. for about 20 hours (step S-5), and the frozen mixture is thawed at room temperature. Then, the thawed mixture is washed with a washing solution such as water (step S-6).
7). At this time, when a reducing agent such as sodium sulfide or L-cysteine shown above is added to the washing solution and an oxygen-free gas such as nitrogen or carbon dioxide or a mixed gas thereof is aerated, the anaerobic symbiotic bacterium is converted into oxygen. The chance of touching is reduced, and the death of anaerobic symbiotic bacteria can be prevented.

This cold thawing and washing (steps S-5 to S-5)
Step S-7) is repeated, for example, three times to produce inclusive fixed cells in which a symbiotic system of methanogens and propionate assimilating bacteria is immobilized in PVA. PVA generated
The inclusive fixed bacterial cells are cut into, for example, 3 to 5 mm squares (step S-8) to complete the symbiotic PVA inclusive fixed bacterial cells of methanogens and propionic acid assimilating bacteria.

As the methanogen shown above, it is preferable to use the genus Methanosarcina. In addition, as propionate assimilating bacteria,
Syntrophobacte
It is preferred to use r) genera. Before mixing with PVA, the concentration of solids in the anaerobic symbiotic bacterium containing liquid is 10 to 40 g.
In order to make L / L, it is also cultured and used with methanogens and propionic acid assimilating bacteria.

In the cultivation of the methane-producing bacteria, yeast extract, trypticase peptone, a mineral component such as ammonium chloride, sodium chloride, magnesium chloride, calcium chloride, etc .; a reducing agent such as sodium sulfide; Cysteine hydrochloride, vitamins, such as biotin and nicotinic acid; sodium metal carbonate, sodium molybdate, sodium tungstate, and cobalt chloride;

As a substrate, for example, methanol, trimethylamine, acetic acid and the like are used, but in order to preferentially grow cells having acetic acid assimilation ability, it is preferable to use acetic acid. Further, in order to visually observe the anaerobic degree in the liquid, an aqueous resazurin solution is dropped. This aqueous solution is an indicator that dyes blue when dissolved oxygen is high and red when dissolved oxygen is low.

Since the culture solution contains sodium sulfide and L-cysteine as reducing agents, dissolved oxygen in the solution is consumed, and the solution becomes anaerobic. However, since the consumption of dissolved oxygen is slow only with the reducing agent, dissolved oxygen is released by injecting an oxygen-free gas such as nitrogen or carbon dioxide or a mixed gas thereof. In addition, the headspace is also made anoxic, and the culture is performed in an absolutely anaerobic state. At this time, if the inside of the head space is cultured under a pressure of, for example, about 200 kPa,
Proliferates quickly. An appropriate culture temperature is, for example, 36 ° C.

Further, vancomycin and penicillin which are cell wall synthesis inhibitors are used.
, a protein synthesis inhibitor effective against bacteria having a 70S ribosome system of the prokaryotic type, streptomycin, tetracycline, kanamycin (kan)
When amycin is added, methanogens can be selectively grown. It is preferable to use Methanosarcina as a bacterial species. In the first embodiment,
As a methanogen, methanosarcina alkaliphila (Methanosarcina alcaliphy)
la, Strain NY-728) was used. Bacterial growth is confirmed by the amount of methane gas generated since it is impossible to count the number of cells. Culture is about 1 month to 2
Perform for months. In the case of a 500 mL culture solution, about 1 g of cells can be recovered.

Next, the cultivation of propionic acid assimilating bacteria will be described. For the culture of propionic acid assimilating bacteria, as a nitrogen source, trypticase peptone, as a mineral component,
Ammonium chloride, sodium chloride, magnesium chloride, calcium chloride, etc., as reducing agents, sodium sulfide, L-cysteine hydrochloride, vitamins, such as biotin, nicotinic acid, etc., trace metal components, nickel chloride, sodium molybdate, manganese chloride, chloride Sodium bicarbonate was used for pH adjustment, such as cobalt.

As a substrate, propionic acid was used. A resazurin aqueous solution is dropped into the culture solution in order to observe the anaerobic degree in the solution similarly to the culture solution of methanogens. Also,
During the culture, the headspace is also made anaerobic, and the culture is performed in an absolutely anaerobic state. An appropriate culture temperature is, for example, 35 ° C. In addition to the main culture solution, a culture solution using propionic acid as a carbon source can proliferate.

In the first embodiment, as the propionic acid assimilating bacterium, Synthrobacter wolny (Syntr) is used.
opobacter wolinii, DSM 28
05 ^T ) was used. Sintrophobacter wolligny is a combination of propionate-degrading bacteria and Desulfovibrio (De
Sulfovibrio), which is a symbiotic bacterium consisting of the genus Sulfovibrio and a substrate-specific bacterium having no ability to degrade substances other than propionic acid. This bacterium breaks down propionic acid into acetic acid, carbon dioxide (and hydrogen sulfide).

[0024] Sintrophobacter wolligny is a sulfate-reducing bacterium, Desulfovibrio.
io) Since it is a symbiotic bacterium with the genus, hydrogen sulfide is generated in the presence of sulfate ions. Therefore, a substance that becomes sulfate ions is not added to the fermentation solution, and the methane-producing bacteria described above as the hydrogen-consuming bacteria are added and then cultured. Since it is difficult to count the number of cells, the growth of bacteria is confirmed by the amount of acetic acid and carbon dioxide generated. Culture is about 1 month ~
Perform for 2 months.

[0025] These bacteria, which have been entrapped and fixed by PVA, are charged into a methane production tank. At this time, it is more effective that the cultured cells are acclimated in a nutrient solution using propionic acid as a carbon source and then comprehensively fixed. Habituation may use propionic acid as the only carbon source, other organic acids,
Saccharides or their inclusions may be used in combination as a carbon source. Further, it is more effective to add appropriate amounts of sewage and wastewater to be treated and acclimatize them.

The wastewater was treated using the PVA-entrapped fixed cells thus obtained. FIG. 2 is a diagram showing changes over time of methane gas, acetic acid, and propionic acid when using inclusive fixed cells in which methane-producing bacteria and propionic acid assimilating bacteria coexist, and FIG. 3 shows methane-producing bacteria. It is a diagram which shows the time-dependent change of methane gas, acetic acid, and propionic acid at the time of using only the inclusive fixed bacterial body.

In the case of only methane-producing bacteria, acetic acid is reduced by methane-producing bacteria, and methane gas is generated. However, propionic acid has not decreased. In the case of inclusive fixed cells in which methanogens and propionic acid assimilating bacteria coexist, both acetic acid and propionic acid decrease, and methane gas is generated.

The physical distance between a bacterium that oxidizes propionic acid and releases hydrogen and a methanogen is determined by the change in free energy and the diffusion rate of hydrogen for the progress of the reaction from propionic acid to methane, Considering the rate of diffusion of hydrogen due to the viscosity caused by polysaccharides and the like existing on the surface, extremely strict proximity of about 1 micron or less must be maintained. With comprehensive fixation of only methanogens, hydrogen cannot be transmitted because the distance to propionic acid assimilating bacteria naturally occurring in wastewater is too large,
By entrapping and fixing the methanogen and the propionic acid assimilating bacterium, it is possible to make contact with a distance where hydrogen transfer is easy. Therefore, the decomposition of propionic acid is performed smoothly.

According to the first embodiment, accumulation of propionic acid due to an increase in load can be prevented, good quality of treated water can be maintained, and generation of hydrogen sulfide, one of malodorous substances, can be suppressed. , Good methane gas generation can be obtained.

Second Embodiment In the first embodiment, the genus Methanosarcina is used as the methanogen. In the second embodiment, the genus Methanothrix and the genus Methanobacterium or Methanococcus are used. It uses two types of methane-producing bacteria of the genus.

The decomposition reaction of fatty acids such as propionic acid is carried out by at least two types of microorganisms: fatty acid oxidizing bacteria that produce acetic acid, hydrogen and carbon dioxide, and hydrogen-consuming bacteria that grow autotrophically from the produced hydrogen and carbon dioxide. If it does not exist, it will not proceed. There is also a need for the presence of acetic acid assimilating bacteria that contribute to the decomposition of the generated acetic acid.

In the first embodiment, the fatty acid oxidizing bacteria are:
The genus Sintrophobacter, and the acetic acid-utilizing bacterium and the hydrogen-consuming bacterium were Methanosarcina. Methanosarcina has both the ability to utilize acetic acid and the consumption of hydrogen.

In the second embodiment, the genus Methanothrix was used as the acetic acid assimilating bacterium, and the genus Methanobacterium or Methanococcus was used as the hydrogen-consuming bacterium. Methanothrix has the ability to utilize acetic acid but does not consume hydrogen. Methanobacterium and Methanococcus consume hydrogen but have no ability to utilize acetic acid. In order for the decomposition reaction of propionic acid to proceed, it is necessary to keep the concentration of hydrogen, one of the products, low at all times. Therefore, it is necessary to coexist with a group of bacteria responsible for these reactions.

According to the second embodiment, it is possible to prevent the accumulation of propionic acid due to an increase in load, to maintain good quality of treated water, and to obtain good methane gas generation.

Embodiment 3 When performing anaerobic treatment of wastewater, lower fatty acids such as butyric acid are generated in addition to acetic acid and propionic acid. FIG. 4 shows a manufacturing process of the inclusive fixed cells to which butyric acid assimilating bacteria are added in addition to the first and second embodiments. This manufacturing process proceeds in the same procedure as in the first embodiment. The method for culturing methane-producing bacteria and propionic acid assimilating bacteria is the same as in the first embodiment.

For the cultivation of butyric acid assimilating bacteria, trypticase peptone is used as a nitrogen source, ammonium chloride, sodium chloride, magnesium chloride, calcium chloride, etc. as mineral components, sodium sulfide, L-cysteine hydrochloride as a reducing agent, Biotin and nicotinic acid were used as vitamins, and nickel hydrogen chloride, sodium molybdate, manganese chloride and cobalt chloride were used as trace metal components, and sodium bicarbonate was used for pH adjustment.

Acetic acid was used as a substrate. In the same manner as in Embodiments 1 and 2, an aqueous resazurin solution is also dropped into the main culture solution in order to visually observe the anaerobic degree in the solution. During culturing, the head space is also made anaerobic, and culturing is performed in an absolutely anaerobic state. An appropriate culture temperature is, for example, 35 ° C.
In addition to the main culture, a culture using butyric acid as a carbon source can be proliferated.

In the third embodiment, as a butyric acid assimilating bacterium, Syntrophomonas wolfei (Syntrophophos) is used.
monas wolfei, using the DSM 2245B ^T). Syntrophomonas wolfei is a combination of butyric acid assimilating bacteria and methanospirillum hangatity.
nospirillum hungatei), decomposes valeric acid, caproic acid, heptanoic acid, caprylic acid, etc. in the presence of hydrogen-consuming bacteria in addition to butyric acid, and converts acetic acid from even-carbon fatty acids to acetic acid from odd-carbon fatty acids. Produces acetic acid and propionic acid.

At the time of culturing, a hydrogen-consuming bacterium is required. Therefore, the methane-producing bacterium and the propionic acid assimilating bacterium described in the first and second embodiments are cultivated. Since it is difficult to count the number of cells, the growth of bacteria is confirmed by the amount of methane gas, acetic acid, and propionic acid generated. Culture is about 1 month ~
Perform for 2 months.

[0040] Those obtained by entrapping and fixing these bacteria with PVA are charged into a methane production tank. At this time, as in Embodiments 1 and 2, it is more effective to fix and entrap and fix after acclimation with an acclimation solution using butyric acid as a carbon source. For acclimation, butyric acid may be used as the sole carbon source, or other organic acids, saccharides, or a combination thereof may be used as the carbon source. It is more effective to add an appropriate amount of sewage and wastewater to be further treated and acclimated.

According to the third embodiment, it is possible to prevent the accumulation of propionic acid and butyric acid due to an increase in load, to maintain good quality of treated water, and to suppress the generation of hydrogen sulfide, one of the malodorous substances. In addition, good methane gas generation can be obtained.

Fourth Embodiment In the first, second and third embodiments, pure bacteria are used as methanogens, propionic acid assimilating bacteria, and butyric acid assimilating bacteria. However, sludge obtained by acclimation may be used. good. For acclimation, the acclimatization solution (for methanogens) described in Embodiment 1 was used. As the substrate, propionic acid, acetic acid, or butyric acid is used. As the acclimatizing liquid, a mixture of the acid production tank sludge and the methane production tank sludge of the anaerobic wastewater treatment apparatus in a ratio of 1: 1 is added. Also, digested sludge from a sewage treatment plant may be charged.

Since it is difficult to count the number of cells, the growth of the bacteria is confirmed by the amount of methane gas generated. When the methane gas generation rate reaches about 70%, it is determined that the growth is saturated, and comprehensive fixation is performed. The period required for acclimation is about one to two months. For acclimation, methane-producing bacteria, propionic acid assimilating bacteria, and butyric acid assimilating bacteria may be added in advance.

According to the fourth embodiment, it is possible to prevent the accumulation of propionic acid and butyric acid due to an increase in load, to maintain good quality of treated water, and to suppress the generation of hydrogen sulfide, one of the malodorous substances. In addition, good methane gas generation can be obtained.

[0045]

Industrial Applicability The present invention relates to a wastewater treatment method in which organic wastewater is subjected to methane fermentation by anaerobic treatment to carry out wastewater treatment, wherein the methane-producing bacteria and propionic acid assimilating bacteria are comprehensively fixed by polyvinyl alcohol. As a result, the accumulation of propionic acid due to an increase in load can be prevented, good treated water quality can be maintained, and the generation of hydrogen sulfide, one of the malodorous substances, can be suppressed. Obtainable.

The present invention also relates to a wastewater treatment method in which organic wastewater is subjected to methane fermentation by anaerobic treatment to perform wastewater treatment, wherein the methane-producing bacteria, propionic acid assimilating bacteria and butyric acid assimilating bacteria are comprehensively fixed by polyvinyl alcohol. Since the body is used, accumulation of propionic acid and butyric acid due to increased load can be prevented, good quality of treated water can be maintained, and one of the malodorous substances can be maintained.
Generation of hydrogen sulfide,
Good methane gas generation can be obtained.

Furthermore, since entrapped bacterium using acetic acid as a substrate is entrapped and fixed with polyvinyl alcohol, good methane gas generation can be obtained. In addition, since the entrapping immobilized cells entrained with polyvinyl alcohol are used to acclimate and acclimate propionic acid as a substrate, the accumulation of propionic acid due to an increase in load can be prevented, and the quality of treated water can be maintained.
Generation of hydrogen sulfide,
Good methane gas generation can be obtained.

Furthermore, since the entrapping and immobilized cells, which are obtained by entrapping butyric acid as a substrate and entrapping and immobilizing with polyvinyl alcohol, are used, accumulation of propionic acid and butyric acid due to an increase in load can be prevented, and good treated water quality can be maintained. The generation of hydrogen sulfide, which is one of the offensive odor substances, can be suppressed,
In addition, good methane gas generation can be obtained.

Since methanotrophs use methanosarcina as an acetic acid assimilating bacterium and a hydrogen-consuming bacterium, accumulation of propionic acid due to an increase in load can be prevented, good treated water quality can be maintained, and good methane gas generation can be maintained. Can be obtained. In addition, the methanogens used the genus Methanothrix as an acetic acid assimilating bacterium and used the genus Methanobacterium or Methanococcus as a hydrogen-consuming bacterium,
It is possible to prevent the accumulation of propionic acid due to an increase in load, maintain good treated water quality, and obtain good methane gas generation.

Since the propionate assimilating bacterium used was of the genus Synthobacter, it was possible to prevent the accumulation of propionic acid due to an increase in the load, maintain good treated water quality, and obtain good methane gas generation. it can. Furthermore, since the butyric acid assimilating bacterium uses the genus Syntrophomonas, accumulation of propionic acid and butyric acid due to an increase in load can be prevented, good treated water quality can be maintained, and good methane gas generation can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a manufacturing process according to a first embodiment of the present invention.

FIG. 2 is a diagram showing changes over time of methane gas and the like according to the first embodiment;

FIG. 3 is a diagram showing changes over time of methane gas and the like according to the first embodiment;

FIG. 4 is an explanatory diagram illustrating a manufacturing process according to a third embodiment of the present invention.

[Explanation of symbols]

Step S-1 Step of preparing an anaerobic symbiotic bacterium-containing solution, Step S-2 Step of preparing a PVA solution, Step S-3
A mixing step of a bacterial cell-containing liquid, step S-4, a molding step,
Step S-5 Freezing step, Step S-6 Thawing step, Step S-7 Liquid washing step, Step S-8
Cutting process.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI (C12N 11/08 C12R 1:01)

Claims (9)

[Claims] 1. A wastewater treatment method in which organic wastewater is subjected to methane fermentation by anaerobic treatment and effluent treatment, wherein entrapped methanogen and propionic acid assimilating bacteria are entrapped and fixed with polyvinyl alcohol. And wastewater treatment method. 2. A wastewater treatment method in which organic wastewater is subjected to methane fermentation by anaerobic treatment to perform wastewater treatment, comprising the steps of: entrapping and fixing methane-producing bacteria, propionic acid assimilating bacteria, and butyric acid assimilating bacteria with polyvinyl alcohol; A wastewater treatment method characterized by using: 3. The wastewater treatment method according to claim 1 or 2, wherein entrapping immobilized cells obtained by entrapping immobilized acetic acid as a substrate and entrapping and immobilizing with polyvinyl alcohol are used. 4. The wastewater treatment method according to any one of claims 1 to 3, wherein entrapping fixed cells are entrapped and immobilized with polyvinyl alcohol and acclimated using propionic acid as a substrate. 5. The wastewater treatment method according to any one of claims 1 to 4, wherein entrapping immobilized cells obtained by entrapping butyric acid as a substrate and entrapping and immobilizing with polyvinyl alcohol are used. 6. The wastewater treatment method according to claim 1, wherein the methane-producing bacterium uses Methanosarcina as an acetic acid-utilizing bacterium and a hydrogen-consuming bacterium. 7. The method according to claim 1, wherein the methane-producing bacterium uses Methanothrix as an acetic acid assimilating bacterium, and Methanobacterium or Methanococcus as a hydrogen-consuming bacterium. A wastewater treatment method according to item 1. 8. The wastewater treatment method according to claim 1, wherein the propionic acid assimilating bacterium uses a genus Synthobacter. 9. The wastewater treatment method according to claim 2, wherein the butyric acid assimilating bacterium is of the genus Syntrophomonas.