JP4719095B2 - Treatment method of wastewater containing selenate compound by microorganisms - Google Patents

Description

  The present invention relates to a method for treating a selenate compound in waste water using microorganisms. More specifically, the present invention relates to a method and bioreactor for reducing a water-soluble selenate compound to insoluble elemental selenium by causing a microorganism that reduces the selenate compound to function in wastewater.

  In the present specification, selenate ions and selenite ions are collectively referred to as selenate compounds.

  Selenium is known as an element that has the property of increasing electrical conductivity when irradiated with light, and its compounds are widely used in semiconductors, photovoltaic cells, photoconductors for photocopiers, achromatants in the glass industry, and colored glass. It is a useful substance. However, on the other hand, it is also known as a substance exhibiting high toxicity to living organisms, and when the Water Pollution Control Act was revised in 1993, the uniform drainage standard for selenium was established as 0.1 mg / L. Therefore, various methods for efficiently treating the selenate compound have been proposed in order to satisfy the wastewater standard value.

  For example, Patent Document 1 proposes a wastewater treatment method in which microorganisms are brought into anaerobic contact with wastewater containing selenate ions under conditions where yeast extract and sulfur-containing amino acids are present. Specifically, to reduce the biological reaction of microorganisms that occurs in the presence of a high concentration of selenic acid, add sulfur-containing amino acids such as methionine and cysteine or organic substances containing these substances, such as yeast extract, peptone, casamino acid, etc. In this way, the selenate ion in the waste water is reduced to selenite ion.

Patent Document 2 proposes a method for treating selenate compound-containing wastewater by using both microbial reduction treatment and physicochemical treatment. Specifically, after reducing hexavalent selenium (selenate ion) in the selenate compound-containing wastewater to selenate-reducing bacteria (FERM BP-5562) to tetravalent selenium (selenite ion) or elemental selenium, Iron salts such as iron chloride and iron sulfate are added to the waste water to coagulate and precipitate tetravalent selenium for solid-liquid separation.
JP 2001-104989 A JP-A-10-309190

  However, when it is necessary to continue supplying an expensive energy source material such as yeast extract or sulfur-containing amino acid to microorganisms, the cost for wastewater treatment becomes enormous. Therefore, it is desirable to perform wastewater treatment using an inexpensive energy source material that is easily available.

  Selenium is a useful element with high industrial utility value, but its annual production is relatively small at 1500 tons. Therefore, it is desirable not only to remove the selenate compounds present in the wastewater but also to recover them for reuse in order to prevent effective use and depletion of resources. Here, the elemental selenium obtained by further reducing the water-soluble selenite ion exists as an insoluble form that can be recovered by performing a filtration treatment or the like. Therefore, if the selenate compound can be reduced to elemental selenium, it can be processed by solid-liquid separation from the wastewater without using a physicochemical treatment with the addition of a coagulating precipitant, etc. If reduction of selenate ions can be performed by microbial reduction treatment, reduction treatment from selenate ions to elemental selenium can be performed only by microbial reduction treatment, which is ideal from the viewpoint of labor and cost.

  In addition, desulfurization effluents generated from thermal power plants and the like contain high concentrations of nitrate nitrogen and sulfate ions along with selenate compounds. When such waste water is treated, there is a problem that the function of the selenate-reducing microorganism is inhibited by nitrate nitrogen or sulfate ions. Therefore, a method for efficiently treating a selenate compound is desired even in an environment where high concentrations of nitrate nitrogen and sulfate ions are present.

  Then, an object of this invention is to provide the method of processing a selenate compound containing waste water, without using expensive energy source materials, such as a yeast extract and a sulfur-containing amino acid. In addition, a method and a bioreactor for reducing a selenate compound to elemental selenium only by microbial reduction treatment are provided, and even when selenate compound-containing wastewater contains nitrate nitrogen or sulfate ions at a high concentration. It is an object of the present invention to provide a method and a bioreactor capable of reducing a selenate compound to elemental selenium.

  In order to solve this problem, the inventors of the present invention diligently searched for microorganisms, and as a result of supplying ethanol as an energy source under anaerobic conditions, selenium was also obtained in an environment where nitrate nitrogen and sulfate ions exist at high concentrations. We succeeded in isolating microorganisms that can reduce acid ion to selenite ion. In addition, when Paracoccus denitrificans, a microorganism known as denitrifying bacteria, was supplied with ethanol as an energy source, selenite ions were reduced to elemental selenium even in environments where nitrate nitrogen and sulfate ions were present in high concentrations. I found a new function. Therefore, the inventors have found that a selenate compound can be reduced to elemental selenium only by microbial reduction treatment using a lower alcohol such as ethanol as an energy source, and the present invention has been achieved.

Processing method of selenate compound-containing wastewater of the present invention based on such findings, the lower alcohol having a carbon number of 1 to 3 as a source of energy, selenium ion, to simultaneously reduced nitrate ion and nitrite ion under anaerobic conditions that is a selenate reducing microorganisms Pseudomonas sp. 4C-C in (Pseudomonas sp. 4C-C) (FERM P-20840), under anaerobic conditions, selenate compound containing wastewater containing at least one of nitrate and nitrite ions And lower alcohol having 1 to 3 carbon atoms is supplied to reduce nitrate ions and nitrite ions in the selenate compound-containing wastewater to nitrogen gas, and to reduce selenate ions to selenite ions. ing.

  A selenate-reducing microorganism that uses a lower alcohol having 1 to 3 carbon atoms as an energy source can convert a selenate ion into a selenite ion by supplying the lower alcohol having 1 to 3 carbon atoms as an energy source under anaerobic conditions. Reduce. Therefore, selenic acid can be obtained under anaerobic conditions by supplying a lower alcohol having 1 to 3 carbon atoms such as methanol, ethanol, and propanol as an energy source without using an energy source such as yeast extract, sulfur-containing amino acid or lactate. It is possible to reduce the compound to selenite ion. In order to recover selenite ions, there is a method using a physicochemical treatment method in which iron salts such as iron chloride and iron sulfate are added to waste water to coagulate and precipitate selenite ions and separate into solid and liquid. .

Alternatively, selenite ions may be recovered by reduction to insoluble elemental selenium by microorganisms. Preferably, Pseudomonas sp. 4C-C (FERM P-20840) and selenium are selenate - reducing microorganisms that use selenate compound-containing wastewater as an energy source of lower alcohols having 1 to 3 carbon atoms . in that the acid reducing microbial Paracoccus denitrificans (Paracoccus denitrificans), under anaerobic conditions, of 1 to 3 carbon atoms with contacting a selenate compound containing wastewater containing at least one of nitrate and nitrite ions The lower alcohol is supplied to reduce nitrate ions and nitrite ions in the selenate compound-containing wastewater to nitrogen gas, and to reduce the selenate compound to elemental selenium.

  As described above, a selenate-reducing microorganism that uses a lower alcohol having 1 to 3 carbon atoms as an energy source can supply selenate ions by supplying the lower alcohol having 1 to 3 carbon atoms as an energy source under anaerobic conditions. Reduce to selenite ion. The selenite-reducing microorganism using a lower alcohol having 1 to 3 carbon atoms as an energy source is supplied with the lower alcohol having 1 to 3 carbon atoms, which is an energy source, under anaerobic conditions. Reduced to gaseous selenium. Therefore, selenic acid can be obtained under anaerobic conditions by supplying a lower alcohol having 1 to 3 carbon atoms such as methanol, ethanol, and propanol as an energy source without using an energy source such as yeast extract, sulfur-containing amino acid or lactate. It is possible to reduce the compound to elemental selenium. In this case, since the selenite ion is reduced to elemental selenium by a selenite-reducing microorganism, the microbial reduction treatment is performed without using a physicochemical treatment for coagulating and precipitating the selenite ion. The selenate compound can be reduced to elemental selenium alone.

Here , P seudomonas sp. 4C-C (hereinafter referred to as 4C-C) is used as the selenate-reducing microorganism. 4C-C can reduce selenate ions to selenite ions under anaerobic conditions. And as an energy source for functioning this microorganism, not only yeast extract, sulfur-containing amino acid or lactate can be used, but also lower alcohols having 1 to 3 carbon atoms such as methanol, ethanol and propanol can be used. Is possible. Furthermore, this microorganism does not interfere with the function of reducing selenate ions to selenite ions even in the presence of high concentrations of nitrate ions, nitrite ions, and sulfate ions. Can be reduced to harmless nitrogen gas. This microorganism has been entrusted to the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology as of March 13, 2006 under the accession number FERM P-20840.

In addition, as the selenite reducing microorganisms, Pa Rakokkasu denitrificans (Paracoccus denitrificans) is used. Paracoccus denitrificans can reduce selenite ion to elemental selenium under anaerobic conditions. And as an energy source for functioning this microorganism, not only yeast extract, sulfur-containing amino acid or lactate can be used, but also lower alcohols having 1 to 3 carbon atoms such as methanol, ethanol and propanol can be used. Is possible. Moreover, the function is not hindered even in an environment where nitrate nitrogen and sulfate ions are present at high concentrations, and at the same time, nitrate ions and nitrite ions can be reduced to harmless nitrogen gas. Therefore, by using together with a selenate-reducing microorganism, for example, 4C-C, it becomes possible to reduce the selenate compound to elemental selenium only by microbial reduction treatment. Since elemental selenium is insoluble, it is possible to remove and collect elemental selenium from the wastewater by filtering the wastewater.

  Here, when treating the wastewater, the selenate-reducing microorganism and selenite-reducing microorganism may be released in the same treatment tank, but the selenate-reducing microorganism and selenite-reducing microorganism are supported on the carrier. It is preferable to do. In this case, since most of the elemental selenium can be attached to the carrier, most of the elemental selenium can be recovered from the wastewater by separating the treated wastewater from the carrier. Here, activated carbon, alumina, foamed plastic, polymer gel, or the like can be used as the carrier, but is not limited thereto. The selenate-reducing microorganism and the selenite-reducing microorganism may be supported on the same carrier, or may be supported on separate carriers. Alternatively, one may be supported on a carrier and the other may be used in a free state. Alternatively, two treatment tanks may be provided to release the selenate-reducing microorganisms in the first treatment tank, and the selenate-reducing microorganisms in the second treatment tank to treat the waste water. In this case, it is preferable to treat the selenate-reducing microorganism and selenite-reducing microorganism on a carrier. The selenate-reducing microorganisms may be released in the first treatment tank and the selenate-reducing microorganisms in the second treatment tank may be supported on the carrier, or the selenate-reducing microorganisms in the first treatment tank may be loaded. The selenate-reducing microorganisms may be released on the second treatment tank by being supported on a carrier.

  In the method for treating selenate compound-containing wastewater of the present invention, the supply of lower alcohol having 1 to 3 carbon atoms to selenate-reducing microorganisms or selenite-reducing microorganisms is provided at least in part with a non-porous membrane. The lower alcohol having 1 to 3 carbon atoms is sealed in the container, and the lower alcohol having 1 to 3 carbon atoms is gradually released around the container from the non-porous film. The lower alcohol sealed in the container is gradually released at a rate governed by the molecular permeation performance of the non-porous membrane. Therefore, the lower alcohol is constantly supplied slowly by adjusting the non-porous membrane permeation rate of the lower alcohol with the membrane material, film thickness, membrane density, etc., which are the factors that determine the molecular permeation performance of the non-porous membrane. Thus, the selenate-containing wastewater can be efficiently treated by continuing to function the selenate-reducing microorganism or selenite-reducing microorganism.

  In addition, it is preferable from the environmental and economic viewpoints to use waste alcohol as an energy source for selenate-reducing microorganisms and selenite-reducing microorganisms. The non-porous membrane has a role like “molecular sieve”, and as the molecular weight of the molecule to be permeated increases, it becomes difficult to permeate the molecule. In addition, the permeability varies greatly depending on properties such as the polarity of the molecule. Therefore, when the non-porous membrane is a hydrophobic membrane represented by polyethylene or polypropylene, antibacterial molecules that are toxic to microorganisms such as impurities such as catechin and cyanide are mixed in the waste alcohol. However, catechins having a large molecular size or cyan compounds having a high polarity are difficult to permeate, and it is possible to permeate a lower alcohol that is harmless to microorganisms as a main component.

Next, selenate compound-containing wastewater treatment bioreactor of the present invention, the lower alcohol having 1 to 3 carbon atoms as an energy source, selenate ions, to simultaneously reduced in nitrate ion and nitrite ion to anaerobic conditions that is a selenate reducing microorganisms Pseudomonas sp. 4C-C (Pseudomonas sp. 4C -C) (FERM P-20840) as a selenite reducing microbial Paracoccus denitrificans and (Paracoccus denitrificans) are supported on a carrier A bioreactor for liquid treatment containing a selenate compound containing at least one of nitrate ions and nitrite ions .

  Here, in the bioreactor for selenate compound-containing wastewater treatment of the present invention, the supply of the lower alcohol having 1 to 3 carbon atoms is performed by supplying the lower alcohol having 1 to 3 carbon atoms in a container having at least a part of the non-porous membrane. The alcohol is sealed, and the lower alcohol having 1 to 3 carbon atoms is gradually released from the nonporous membrane around the container. Therefore, the amount of energy required by the selenate-reducing microorganism or selenite-reducing microorganism can always be gradually supplied.

  Further, waste alcohol may be sealed in a container having at least a part of the non-porous membrane. Even when waste alcohol is used, the non-porous membrane functions as a “molecular sieve”, so that a lower alcohol that is harmless to selenate-reducing microorganisms and selenite-reducing microorganisms and serves as an energy source is supplied as a main component.

  According to the method for treating selenate compound-containing wastewater of the present invention, the selenate compound-containing wastewater is brought into contact with a selenate-reducing microorganism that functions as a lower alcohol having 1 to 3 carbon atoms as an energy source and as an energy source. By supplying the lower alcohol having 1 to 3 carbon atoms, the selenate compound contained in the waste water can be reduced to selenite ion. Therefore, wastewater treatment costs can be greatly reduced because wastewater treatment can be performed with easily available and inexpensive lower alcohol without using an expensive energy source such as yeast extract, sulfur-containing amino acid or lactate.

  Further, the selenate compound-containing wastewater is brought into contact with selenate-reducing microorganisms and selenite-reducing microorganisms functioning as lower energy having 1 to 3 carbon atoms as an energy source and under anaerobic conditions, and as an energy source having 1 to 3 carbon atoms. By supplying the lower alcohol, the selenate compound contained in the waste water can be reduced to elemental selenium. Therefore, wastewater treatment costs can be greatly reduced because wastewater treatment can be performed with easily available and inexpensive lower alcohol without using an expensive energy source such as yeast extract, sulfur-containing amino acid or lactate. Since selenite ions are reduced to elemental selenium by the action of selenite-reducing microorganisms, only microbial reduction treatment can be performed without using physicochemical treatment for coagulating and precipitating selenite ions. Selenate compounds can be reduced to elemental selenium. Therefore, it is possible to save the trouble of adding a coagulating precipitation agent such as iron salt into the waste water, and it becomes possible to perform the waste water treatment more easily.

  Moreover, according to the selenate-reducing microorganism 4C-C which is a microorganism of the present invention, it is possible to use yeast extract or lactate as an energy source, as well as a lower alcohol having 1 to 3 carbon atoms such as methanol. Even when using ethanol, propanol or propanol as an energy source, selenate ions can be reduced to selenite ions under anaerobic conditions, and their functions can be achieved even in the presence of high concentrations of nitrate nitrogen and sulfate ions. At the same time, nitrate ions and nitrite ions can be reduced to harmless nitrogen gas. Therefore, by using 4C-C as the selenate-reducing microorganism in the method for treating selenate compound-containing wastewater of the present invention, selenate ions are sublimated under anaerobic conditions using a lower alcohol having 1 to 3 carbon atoms as an energy source. It can be reduced to selenate ions, and even in the presence of high concentrations of nitrate nitrogen and sulfate ions, its function is not hindered and at the same time nitrate ions and nitrite ions are reduced to harmless nitrogen gas Can do.

  Paracocccus denitrificans, a known microorganism, can reduce selenite ions to elemental selenium under anaerobic conditions even when C1-C3 lower alcohols, especially ethanol, are used as an energy source. In the presence of high concentrations of nitrate nitrogen and sulfate ions, the function is not inhibited, and a novel function that nitrate nitrogen can be reduced at the same time has been revealed. From the above, by using Paracoccus denitrificans as the selenite-reducing microorganism in the method for treating selenate compound-containing wastewater of the present invention, selenite ions under anaerobic conditions using a lower alcohol having 1 to 3 carbon atoms as an energy source Can be reduced to elemental selenium, and its function is not inhibited even in the presence of high concentrations of nitrate nitrogen and sulfate ions. , Capable of reducing nitrate ions and nitrite ions to harmless nitrogen gas at the same time.

  Furthermore, by bringing the selenate compound-containing wastewater into contact with the selenate-reducing microorganism 4C-C and the selenite-reducing microorganism Paracoccus denitrificans under anaerobic conditions and supplying lower alcohol having 1 to 3 carbon atoms as an energy source, The selenate compound can be reduced to elemental selenium in the presence of nitrate nitrogen or sulfate ions at a concentration, and nitrate nitrogen can also be reduced to harmless nitrogen gas. Therefore, selenate compounds are reduced to elemental selenium from wastewater containing high concentrations of nitrate nitrogen and sulfate ions, such as desulfurization effluent from thermal power plants. Nitrate nitrogen can also be reduced at the same time and converted into harmless nitrogen gas.

  Further, by supporting the selenate-reducing microorganism and the selenite-reducing microorganism on the carrier, most of the elemental selenium can be attached to the carrier. Therefore, elemental selenium can be recovered from the wastewater only by separating the treated wastewater from the carrier, and the removal and recovery of the elemental selenium from the wastewater becomes very easy.

  Next, according to the bioreactor for wastewater treatment containing a selenate compound of the present invention, a selenate-reducing microorganism and a selenite-reducing microorganism capable of functioning as an energy source of a lower alcohol having 1 to 3 carbon atoms are supported on a carrier. Therefore, the selenate compound can be reduced to elemental selenium by bringing the selenate compound-containing wastewater into contact with the carrier and supplying a lower alcohol having 1 to 3 carbon atoms. And since elemental selenium adheres to a support | carrier and becomes red, it can be easily judged visually whether the selenate compound in waste water has been processed. When the bioreactor support becomes sufficiently red, the selenate compound in the wastewater can be removed in a state reduced to elemental selenium simply by collecting the bioreactor, and the handling is very easy. Furthermore, since this bioreactor can collect and recover elemental selenium on a carrier, it is easy to collect elemental selenium not only in wastewater but also in environments where it is difficult to collect precipitates such as activated sludge. Can be recovered.

  Further, in the bioreactor for wastewater treatment containing selenate compound of the present invention, by using 4C-C as a selenate-reducing microorganism, selenate ions are obtained under anaerobic conditions using a lower alcohol having 1 to 3 carbon atoms as an energy source. Can be reduced to selenite ions, and even in the presence of high concentrations of nitrate nitrogen and sulfate ions, their functions are not hindered and at the same time nitrate ions and nitrite ions are reduced to harmless nitrogen gas can do.

  Further, in the bioreactor for wastewater treatment containing a selenate compound of the present invention, by using Paracoccus denitrificans as a selenite-reducing microorganism, selenite is obtained under anaerobic conditions using a lower alcohol having 1 to 3 carbon atoms as an energy source. Ions can be reduced to elemental selenium, and even in the presence of high concentrations of nitrate nitrogen and sulfate ions, their functions are not hindered and at the same time nitrate ions and nitrite ions are reduced to harmless nitrogen gas can do.

  Furthermore, in the bioreactor for selenate compound-containing wastewater treatment of the present invention, when 4C-C is used as the selenate-reducing microorganism and Paracoccus denitrificans is used as the selenite-reducing microorganism, the carbon number as an energy source under anaerobic conditions. By supplying 1 to 3 lower alcohols, it is possible to reduce selenate compounds to elemental selenium even in the presence of high concentrations of nitrate nitrogen and sulfate ions, and at the same time nitrate nitrogen also becomes harmless nitrogen gas. Can be reduced. Therefore, selenate compounds are reduced to elemental selenium from wastewater containing high concentrations of nitrate nitrogen and sulfate ions, such as desulfurization effluent from thermal power plants. Nitrate nitrogen is also in a more preferable form that can be reduced at the same time and converted into harmless nitrogen gas.

  Further, supply of the lower alcohol having 1 to 3 carbon atoms to the selenate-reducing microorganism or selenite-reducing microorganism is performed by sealing the lower alcohol having 1 to 3 carbon atoms in a container having at least a part of a non-porous membrane. Thus, by gradually releasing the lower alcohol having 1 to 3 carbon atoms around the container from the non-porous membrane, the energy amount required by the microorganism can be always gradually supplied.

  Furthermore, when the waste alcohol is sealed in a container having at least a part of the non-porous membrane, the non-porous membrane functions as a “molecular sieve”, and those having a certain molecular size or more do not pass through the membrane. Small molecules are preferentially transmitted. Therefore, even if antibacterial molecules that are toxic to microorganisms, such as catechin, are mixed in waste alcohol, catechins having a large molecular size cannot permeate, and are carbon that is harmless to microorganisms and is an energy source. A lower alcohol having a number of 1 to 3 is supplied as a main component. The recycling of waste alcohol can reduce the amount of waste, which is favorable for the environment and can make the waste useful and reduce the cost of the energy source. For example, waste alcohol that is currently regenerated through processes such as distillation and purification can be used as is without performing these treatments, and a significant cost reduction can be realized. More specifically, the energy of selenate-reducing microorganisms and selenite-reducing microorganisms can be obtained without going through the removal process such as distillation of toxic substances (such as catechin) from waste alcohol generated in food and pharmaceutical manufacturing processes. Can be used effectively as a source.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  The selenate compound-containing wastewater treatment method of the present invention is a method in which a selenate compound-containing wastewater is brought into contact with a selenate-reducing microorganism using a lower alcohol having 1 to 3 carbon atoms as an energy source under anaerobic conditions, and the lower one having 1 to 3 carbon atoms. Alcohol is supplied, and the selenate compound in the waste water is reduced to selenite ion. As a more preferred embodiment, the selenate compound-containing wastewater is brought into contact with a selenate-reducing microorganism and a selenite-reducing microorganism that use a lower alcohol having 1 to 3 carbon atoms as an energy source under anaerobic conditions and has 1 to 3 carbon atoms. Lower alcohol is supplied, and the selenate compound in the waste water is reduced to insoluble elemental selenium. The contact between the wastewater and these microorganisms is performed, for example, by introducing a selenate-reducing microorganism and a selenite-reducing microorganism into a wastewater treatment tank and allowing these microorganisms to coexist in the same environment. A lower alcohol having 1 to 3 carbon atoms (hereinafter simply referred to as a lower alcohol) is added periodically or optionally.

The selenate reducing microorganism, it is possible to use 4C-C. 4C-C is a selenate-reducing microorganism belonging to the genus Pseudomonas, and has been entrusted to the Patent Organism Depositary of the National Institute of Advanced Industrial Science and Technology as an accession number FERM P-20840 on March 13, 2006. As shown in the following chemical formula, the selenate-reducing microorganism 4C-C reduces selenate ions (hexavalent selenium) to selenite ions (tetravalent selenium).
[Chemical Formula 1] SeO ₄ ²⁻ → SeO ₃ ²⁻

  In order for selenate-reducing microorganisms to function and reduce selenate ions to selenite ions, the location where the selenate-reducing microorganisms are present under anaerobic conditions, that is, there is substantially no dissolved oxygen in the wastewater. Is preferred. In addition, when there is a lot of dissolved oxygen and the function of selenate reduction decreases, selenium is reduced by introducing an inert gas such as nitrogen gas or rare gas into the waste water to reduce the dissolved oxygen. What is necessary is just to make acid-reducing microorganisms function.

  As an energy source, it is possible to reduce the selenate ion to selenite ion by supplying yeast extract or sulfur-containing amino acid or lactate generally used for selenate-reducing microorganisms. Then, methanol, ethanol and propanol, which are lower alcohols having 1 to 3 carbon atoms, can be used. Therefore, the processing cost of the selenate compound-containing waste water can be greatly reduced.

  Here, the selenate-reducing microorganism 4C-C does not inhibit the reaction of reducing selenate ions to selenite ions even in an environment where nitrate ions are present in high concentrations, and at the same time, nitrate ions And nitrite ions can be reduced to harmless nitrogen gas. Furthermore, even in an environment where sulfate ions are present, the reaction of reducing selenate ions to selenite ions is not inhibited. In other words, when treating selenate compounds from desulfurization effluent discharged from thermal power plants, etc., the function does not deteriorate and nitrate nitrogen such as nitrate ions and nitrite ions is harmless. It can be reduced to nitrogen gas.

  The selenate-reducing microorganism 4C-C has a very excellent ability to reduce selenate ions to selenite ions, and also has the ability to reduce selenite ions to elemental selenium. This has been confirmed by experiments by the present inventors. Therefore, it can also play a role of reducing selenite ion to elemental selenium.

Next, as the selenite-reducing microorganism , Paracoccus denitrificans, which is a known microorganism as denitrifying bacteria, can be used. Paracoccus denitrificans can reduce selenite ion to elemental selenium by using ethanol as an energy source, and this function has been newly discovered by the present inventors. As shown in the following chemical formula, the selenite-reducing microorganism reduces selenite ions (tetravalent selenium) to elemental selenium (zero-valent selenium).
[Chemical Formula 2] SeO ₃ ²⁻ → Se

  Conditions and environment for functioning the selenite-reducing microorganism are the same as those of the selenate-reducing microorganism 4C-C described above. Therefore, even when these coexist, both microorganisms can sufficiently function. For example, when 4C-C is used as a selenate-reducing microorganism and Paracoccus denitrificans is used as a selenite-reducing microorganism, nitrate nitrogen and sulfate ions are present in high concentrations by supplying lower alcohol under anaerobic conditions. Harmless nitrogen gas by reducing selenate compounds to elemental selenium and reducing nitrate nitrogen such as nitrate ions and nitrite ions at the same time from effluents such as desulfurization effluents from thermal power plants It becomes possible to convert to.

  Elemental selenium, which is the final form after the reduction treatment of the selenate compound contained in the wastewater, is insoluble. Therefore, elemental selenium can be removed from the wastewater by subjecting the treated wastewater to filtration or the like.

  Here, the selenate-reducing microorganism and selenite-reducing microorganism may be supported on a carrier and introduced into the waste water. In this case, since most of the elemental selenium obtained by reduction by the microorganism adheres to the carrier, the selenium concentration in the waste water can be greatly reduced simply by removing only the carrier from the treated waste water. Can do. The carrier is not particularly limited as long as it is a material capable of supporting the microorganism and adhering elemental selenium, but a porous material such as activated carbon, alumina or foamed plastic, a polymer gel, or the like is used. Is preferred.

  In addition, if the supply of lower alcohol as an energy source is excessive, microorganisms cannot be consumed and remain in the wastewater, which may deteriorate water quality. On the other hand, if the supply amount of the lower alcohol is small, there is a possibility that these microorganisms do not function sufficiently because the energy source is insufficient, and the selenate compound cannot be processed sufficiently. Therefore, it is preferable to supply the lower alcohol by sealing the lower alcohol in a container having at least a part of the non-porous membrane and gradually releasing the lower alcohol from the non-porous membrane to the periphery of the container.

  FIG. 1 shows an embodiment of an electron donor supply apparatus in which a lower alcohol (hereinafter also simply referred to as alcohol) is sealed in a container having at least a part of a non-porous membrane. This electron donor supply device 1 includes an alcohol 3 and a container 4 having a sealed structure including at least a part of a non-porous membrane 2. The container 4 is filled with the alcohol 3, and the alcohol 3 is stored in the container 4. The porous membrane 2 is supplied to the periphery of the container 4 at a speed governed by the molecular permeation performance of the non-porous membrane 2, and the alcohol 3 is gradually released to the selenate-reducing microorganisms and selenite-reducing microorganisms around the container 4. To supply. In the present embodiment, the entire container 4 forms a bag shape composed of the non-porous membrane 2, and the alcohol 3 is sealed so that the periphery is welded by heat sealing or bonded with an adhesive. However, the form and structure are not particularly limited. For example, the container 4 may be a tube shape or a sheet shape. In addition, the bag-like container (sometimes simply referred to as a bag) 4 is not particularly limited to one constituted entirely by a non-porous membrane, and only one side may be constituted by a non-porous membrane, A part of the film may be composed of only a non-porous film. When a non-porous membrane is partially used, a metal or plastic rigid frame or a membrane that does not transmit alcohol may be used for other portions. If the container 4 floats when placed in the liquid to be treated, the container 4 is provided with a weight, or a portion that is not immersed in the liquid to be treated is formed as a film that does not allow alcohol to permeate. You may make it suppress slow release of alcohol from the part other than the part which is contacting the process liquid.

  The non-porous membrane 2 used in the electron donor supply device 1 is a slow release by allowing alcohol 3 molecules to pass through little by little. The non-porous membrane 2 can control the molecular weight of the alcohol 3 permeating per unit area according to the membrane material, film thickness, molecular weight and properties of the alcohol 3 to be sealed, temperature, and alcohol concentration. For example, even when the same container is used, if the concentration of alcohol 3 is increased, the permeation rate of alcohol can be increased. Moreover, the sustained release surface of the alcohol 3 can be increased or decreased by increasing or decreasing the surface area of the nonporous membrane 2. Therefore, the non-porous membrane 2 is brought into contact with a part of the liquid to be treated, and the sustained release surface can be increased or decreased according to the surface area of the contact surface between the liquid to be treated and the non-porous film. According to the inventors' experiments on polyethylene membranes, it has been confirmed that in the case of the same membrane material, the molecular permeation amount per unit area varies depending on the film thickness. Therefore, a necessary amount of alcohol can be supplied at a necessary rate by appropriately selecting a film thickness or the like according to the alcohol supply amount necessary for the selenate-reducing microorganism or selenite-reducing microorganism. At this time, the alcohol leaks at a moderate rate governed by the molecular permeation performance of the non-porous membrane 2. Therefore, even when using alcohol as a stock solution that may kill selenate-reducing microorganisms or selenite-reducing microorganisms when supplied directly, it is diluted to a concentration that does not affect the survival of microorganisms around the container. In this state, the selenate-reducing microorganism and selenite-reducing microorganism are supplied.

Here, in the non-porous membrane 2, the molecular permeation amount varies depending on the density and structure of the membrane constituent molecules. Taking polyethylene as an example, high-density polyethylene (density 942 kg / m3) is compared with the case of using low-density polyethylene (density 910 kg / m ³ or more and less than 930 kg / m ³ ) classified according to JIS K6922-2. When m ³ or more) is used, the permeation amount of alcohol 3 to the outside of the membrane decreases. Therefore, the supply amount of the alcohol 3 may be controlled according to the balance between the film thickness and the film density of the nonporous membrane 2 according to the desired supply amount of the alcohol 3. Moreover, since the molecular structure of the polyethylene chain inside the membrane can be changed by, for example, stretching treatment, it is possible to control the supply amount of alcohol 3 by changing the membrane density of a desired membrane material by the treatment. .

  The molecule of alcohol 3 has both an alkyl group that is a hydrophobic group and a hydroxyl group that is a hydrophilic group. Therefore, as the non-porous membrane 2, the alcohol 3 can be permeated by using any one of a hydrophobic membrane, a hydrophilic membrane, and a membrane having both hydrophilic and hydrophobic properties. Examples of the hydrophobic membrane include polyethylene, polypropylene, and other olefinic membranes. Examples of the hydrophilic film include a film having a hydrophilic group in the molecular structure, such as polyester, nylon (polyamide), polyvinyl alcohol, vinylon, cellophane, polyglutamic acid and the like. Examples of the membrane having both hydrophilic and hydrophobic properties include ethylene vinyl alcohol copolymer (EVOH), that is, a copolymer membrane having both a hydrophobic polyethylene structure and a hydrophilic polyvinyl alcohol structure. Can be mentioned. A membrane having both hydrophilic and hydrophobic properties can be made more hydrophobic or more hydrophilic by changing the content ratio of hydrophobic polyethylene and hydrophilic polyvinyl alcohol. In addition, the permeability is inferior to the above non-porous membrane, but when extremely slow sustained release performance is required, gas-liquid systems such as polyvinylidene chloride, polycarbonate, ethylene acrylic acid copolymer, polyethylene terephthalate mixture system, etc. A membrane, that is, a membrane whose permeability changes depending on the state of a hydrophilic group or a polar group in its molecular structure.

  Polyethylene and polypropylene can satisfactorily divide the water area, soil, and sludge, which are microbial activities, and other areas. Further, it has an appropriate substance permeability and thermoreversibility, and is flexible and easy to mold. Moreover, since polyethylene and polypropylene are inexpensive and easily available, it is very preferable to use polyethylene and polypropylene from the viewpoint of cost and performance.

  Here, permeation of the alcohol 3 through the non-porous membrane 2 occurs when the molecules of the alcohol 3 dissolve in the non-porous membrane 2 and the dissolved molecules diffuse inside the membrane and reach the opposite side. Therefore, catechins and the like having a molecular weight that is so large that the membrane does not dissolve hardly penetrate the non-porous membrane. In addition, since polyethylene, polypropylene, and the like are highly hydrophobic membranes that do not have a functional group compatible with water and have low polarity, water that is a polar molecule hardly dissolves in the membrane. Therefore, a cyanide compound, which is a highly polar substance that easily dissolves in water, can hardly pass through. In addition, since water has strong hydrogen bonds between water molecules, water hardly permeates the membrane at room temperature. Therefore, the non-porous film 2 functions as a “molecular sieve” that allows the alcohol 3 to permeate as a main component while hardly allowing impurities such as water, a highly polar cyanide compound, and a catechin having a large molecular weight to pass through. Therefore, when a hydrophobic membrane represented by polyethylene or polypropylene is used as the non-porous membrane, antibacterial molecules that are toxic to microorganisms such as impurities such as catechin and cyanide are mixed in the alcohol. Waste alcohol can be used. It is environmentally and economically preferable to use waste alcohol instead of alcohol. Further, alcohol is released in a molecular state to the outside of the container regardless of whether the container is in a liquid state or a volatilized state. That is, alcohol permeates through the non-porous membrane 2 and is gradually released in a gas (gas) state that does not aggregate due to the attractive force between molecules like a liquid. Therefore, the non-porous membrane 2 can also be expressed as a gas permeable membrane. Further, even when the environment outside the container is a liquid phase (drainage, groundwater, etc.), it is possible to gradually release alcohol in a molecular state outside the container.

  Next, FIG. 2 and FIG. 3 show another embodiment of the electron donor supply apparatus. The electron donor supply device of this embodiment is not a completely sealed independent container 4 made of a non-porous membrane 2, but a sealed bag-like container having means for introducing alcohol 3 The alcohol 3 can be replenished from the outside.

  The mechanism for replenishing the alcohol 3 may have a structure in which a supply unit 5 for injecting the alcohol 3 is provided at a part of the edge of the container 4 and a nozzle or pipe 7 is mounted, or a nozzle integrated with the container 4 in advance. Or a thing like the pipe 7 may be sufficient. The electron donor supply apparatus 1 shown in FIG. 3 stores the supply nozzle 7 detachably mounted on the supply unit 5 provided at the edge of the container 4 or the supply nozzle 7 integrated with the container 4 and the alcohol 3. The tank 6 to be connected is connected by a tube 8 or the like so that the alcohol 3 can be replenished as necessary. In this case, since the tank 6 and the container 4 are communicated with each other via the tube 8, if the alcohol 3 ′ is stored in the tank 6, the alcohol 3 in the bag 4 is reduced when the siphon 3 is reduced. Using the principle, the alcohol 3 'can be replenished from the tank by the pressure difference between the tube ends. Although the container 4 is provided with the supply unit 5 or the nozzle 7, it does not have a strict sealing structure. However, in the state where the supply nozzle 7 is filled with the alcohol 3 'supplied from the tank, the liquid level Becomes a seal, and the inside of the container is effectively sealed. For this reason, the liquid or gasified alcohol 3 does not leak out of the container 4 through the supply unit 5 and the nozzle 7.

  Next, FIG. 4 and FIG. 5 show an embodiment of a selenate compound-containing wastewater removal bioreactor according to the present invention. In this bioreactor 9, a selenate-reducing microorganism and a selenite-reducing microorganism are supported on a carrier, a selenate compound-containing wastewater is brought into contact with the carrier, and a lower alcohol is supplied to thereby convert the selenate compound into elemental selenium. It will be reduced. In the present embodiment, a carrier 11 carrying selenate-reducing microorganisms and selenite-reducing microorganisms is applied and fixed on the nonwoven fabric 10 to form a bag shape with the nonwoven fabric 10 as the surface side, and the internal space 12 has the structure shown in FIGS. The container 1 shown in FIG. 3 is accommodated and the lower alcohol 3 is supplied to the carrier 11. When the electron donor supply apparatus 1 shown in FIG. 1 to FIG. 3 is used, even if the lower alcohol is sealed as a stock solution, the microorganism is killed because it is slowly released from the non-porous membrane 2. Absent. In addition, the amount of energy required by the selenate-reducing microorganism or selenite-reducing microorganism can be always gradually supplied without providing a pump or means for controlling the supply amount. Further, in this case, waste alcohol can be used in place of lower alcohol, which is preferable from the environmental and economic viewpoints. The configuration of the bioreactor 9 is not limited to the form in which the nonwoven fabric 10 is provided only on the outer surface of the bag 4 as shown in FIGS. 4 and 5, and is provided only on the inner surface of the bag 4, that is, on the inner space 12 side surface. Alternatively, both the outer surface and the inner surface of the bag 4 may be provided. In addition, the strength of the bioreactor 9 may be improved by a metal or plastic rigid frame, or the surface of the bioreactor 9 is protected by using a nylon net or the like instead of the nonwoven fabric 10. Also good. However, it is not essential to provide a protective material such as the nonwoven fabric 10 on the surface of the bioreactor 9.

Here, as in the case described above, the selenate reducing microorganism, it is possible to use 4C-C. Paracoccus denitrificans can be used as the selenite-reducing microorganism.

  As the carrier 11, a polymer gel used for immobilizing microorganisms and enzymes can be used. Specifically, natural polymers such as collagen, fibrin, albumin, casein, cellulose fiber, cellulose triacetate, agar, calcium alginate, carrageenan, agarose, polyacrylamide, poly-2-hydroxyethyl methacrylic acid, polyvinyl chloride, Synthetic polymers such as γ-methylpolyglutamic acid, polystyrene, polyvinylpyrrolidone, polydimethylacrylamide, polyurethane, photocurable resins (polyvinyl alcohol derivatives, polyethylene glycol derivatives, polypropylene glycol derivatives, polybutadiene derivatives, etc.), or composites thereof Can be mentioned. It is also possible to use a water-absorbing polymer. In the case of using a water-absorbing polymer, wastewater is more easily absorbed than in the case of using a polymer gel, and the selenate compound in the wastewater can be treated more efficiently. As the water-absorbing polymer, those generally used can be used, and specific examples include polyacrylic acid, polyaspartic acid, polyglutamic acid, modified products thereof, modified polyethylene glycol, and the like. . The modified product referred to here is a product obtained by crosslinking a polymer having an ionic group to a part of the polymer.

  The bioreactor 9 of this embodiment is used by immersing it in waste water, whereby the selenate compound is reduced to elemental selenium by the action of the selenate-reducing microorganism and selenite-reducing microorganism coexisting in the carrier. That is, the selenate ion in the wastewater is reduced to selenite ion by the selenate-reducing microorganism, and both the reduced selenite ion and the selenite ion contained in the wastewater are both separated by the selenite-reducing microorganism. Reduced. Elemental selenium produced by the reduction of selenite ion adheres to the carrier. Elemental selenium is an insoluble substance exhibiting a red color, and the adhesion state of elemental selenium can be easily confirmed visually. Therefore, if the bioreactor 9 is sufficiently red, it can be easily recovered as elemental selenium from the wastewater by taking it out of the wastewater.

  In addition, the bioreactor 9 of the present embodiment can be recovered by attaching elemental selenium to a carrier even in activated sludge that is difficult to recover, such as precipitation. That is, the bioreactor 9 in this embodiment can be used very easily without selecting a place. If the method of use is also anaerobic, it is sufficient to simply immerse it in the target environment, which is very simple. Moreover, whether or not the selenate compound has been removed from the wastewater can be determined from the color of the bioreactor and can be used very easily.

  Furthermore, when 4C-C is used as the selenate-reducing microorganism and Paracoccus denitrificans is used as the selenite-reducing microorganism, even if high concentrations of nitrate nitrogen and sulfate ions exist in the selenate compound removal target environment, A reduction reaction of the selenate compound to elemental selenium occurs, and at the same time, it becomes a bioreactor with a very excellent function capable of converting nitrate nitrogen (nitrate ions and nitrite ions) into harmless nitrogen gas.

  Here, the method of supplying the lower alcohol is not limited to that shown in FIGS. 1 to 3. For example, the lower alcohol may be directly supplied into the waste water, or the lower alcohol may be directly supplied to the internal space of the bioreactor 9. 12 may be supplied. As described above, if the supply of lower alcohol, which is an energy source, is excessive, microorganisms may not be consumed and may remain in the wastewater to deteriorate the water quality. On the other hand, if the supply amount of the lower alcohol is small, there is a possibility that these microorganisms do not function sufficiently because the energy source is insufficient, and the selenate compound cannot be processed sufficiently. Therefore, it is preferable to control the supply amount and timing using a pump or the like.

  Further, when the lower alcohol is directly supplied to the internal space 12 of the bioreactor 9, if the lower alcohol is used as a stock solution, the microorganism may be killed. Therefore, the concentration is such that the microorganism does not die, for example, about 10% by volume. It is necessary to use lower alcohol diluted to a concentration.

  In addition, as a method for recovering elemental selenium adhering to the bioreactor 9, elemental selenium may be evaporated by burning the bioreactor 9, and selenium accompanying the combustion gas may be concentrated. Alternatively, elemental selenium adhering to the bioreactor 9 may be oxidized to form a water-soluble form and then immersed in water for recovery. In this case, the bioreactor 9 can be reused.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, selenate-reducing microorganisms and selenite-reducing microorganisms coexist in the same environment to perform wastewater treatment, but the selenate-reducing microorganisms and wastewater are contacted in the first treatment tank. After the treatment, a two-stage treatment such as contacting with a selenite-reducing microorganism in the second treatment tank may be performed. Also, when these microorganisms are supported in a bioreactor, a two-layer structure of a carrier supporting selenate-reducing microorganisms and a carrier supporting selenite-reducing microorganisms may be used.

  Further, the carrier is not limited to those described above, and for example, a gel carrier may be directly applied to the surface of the container 1 to carry microorganisms, and further, a nonwoven fabric is raised as a carrier, and microorganisms are applied to the raised portions. May be used, or the surface of a container sealed with lower alcohol or waste alcohol may be raised to carry microorganisms on the raised portion.

  Also, in order to maintain the anaerobic atmosphere of the liquid to be treated for a long period of time, an oxygen absorbing device filled with an oxygen absorbing substance is immersed in the liquid to be treated in a sealed container having a non-porous membrane in part. It may be. Any oxygen-absorbing substance may be used as long as it can absorb oxygen and does not corrode the non-porous membrane. A solid reducing agent such as reduced iron or a solution containing a reducing agent such as a sodium sulfite solution may be used. Although it can, it is not limited to these. According to this oxygen absorber, dissolved oxygen in the liquid to be treated can be absorbed at a moderate rate governed by the oxygen molecule permeation performance of the non-porous membrane, so that the anaerobic atmosphere of the liquid to be treated can be maintained for a long time. Can do.

  In addition, the bioreactor 9 is used as a simple monitor for determining whether or not a selenate compound is present in the environment by utilizing the fact that the bioreactor 9 exhibits red color due to elemental selenium obtained by reducing the selenate compound. It is also possible to use 9.

  The following examples further illustrate the present invention, but the present invention is not limited to these examples.

Example 1
Selenate-reducing microorganism 4C-C was cultured using NB medium as a medium. The composition of the medium is shown in Table 1. After culturing at 30 ° C. with shaking (110 rpm), the cells are collected by centrifugation, and phosphate buffer (9 g / l Na ₂ HPO ₄ · 12H ₂ O, 1.5 g / l KH ₂ PO ₄ , pH = 7.5). ) For 3 times. The washed cells were 230 mg wet wt. / Ml was used in the experiment after suspending in phosphate buffer.

The selenite-reducing microorganism Paracoccus denitrificans was cultured according to the following procedure. The medium used was a liquid medium based on JCM Medium List No. 22 (Nutrient agar No. 2) except for agar. Table 2 shows the composition of the medium. After culturing at 30 ° C. with shaking (110 rpm), the cells are collected by centrifugation, and phosphate buffer (9 g / l Na ₂ HPO ₄ · 12H ₂ O, 1.5 g / l KH ₂ PO ₄ , pH = 7.5). ) For 3 times. The washed cells were 230 mg wet wt. / Ml was used in the experiment after suspending in phosphate buffer.

(Example 2)
Selenate-reducing microorganisms 4C-C were cultured in artificial wastewater, and the ability to treat selenate ions in the presence of nitrate ions was investigated using yeast extract as an energy source. Table 3 shows the composition of the artificial waste water. The initial selenate ion (SeO ₄ ²⁻ ) concentration of the artificial waste water was 100 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 100 mg-N / L. The initial input amount of the selenate-reducing microorganism 4C-C into the artificial waste water is 1.38 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ) when cultured for 1 hour, 2 hours, 4 hours, 18 hours, 22 hours, 46 hours, and 70 hours ^-), nitrite (NO ₂ ^-) concentrations were measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₃ ^-) _{concentration,} ^NO 3 - is a graph showing the concentration ^- + NO _2. The selenate ion concentration became 0 mg-Se / L after 18 hours of culture. On the other hand, the selenite ion concentration became 105 mg-Se / L, which was almost the same concentration as the initial selenate ion after 18 hours. Therefore, it was confirmed that the selenate-reducing microorganism 4C-C is a microorganism that reduces selenate ions to selenite ions using yeast extract as an energy source. The nitrate ion concentration became 0 mg-N / L after 4 hours from the culture. On the other hand, the nitrite ion concentration was 91 mg-N / L after 4 hours from the culture, but then decreased and became 70 mg-N / L after 70 hours. Therefore, the selenate-reducing microorganism 4C-C has the function of reducing nitrate ions and nitrite ions to harmless nitrogen gas using yeast extract as an energy source and simultaneously reducing selenate ions to selenite ions. confirmed.

(Example 3)
(A) Evaluation of 4C-C treatment capacity when ethanol is used as energy source Selenate-reducing microorganism 4C-C is cultured in artificial waste water, and the treatment capacity of selenate ions in the presence of nitrate ions is determined as ethanol as an energy source. It investigated using. Table 4 shows the composition of the artificial drainage. The initial selenate ion (SeO ₄ ²⁻ ) concentration of the artificial waste water was 50 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 50 mg-N / L. The initial input amount of the selenate-reducing microorganism 4C-C into the artificial waste water is 0.38 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Moreover, 0.3 ml of ethanol was added. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ⁻ ), nitrite ion (NO ₂ ) when cultured for 17 hours, 41 hours, 65 hours, and 137 hours ^- ) The concentration was measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₃ ^-) _{concentration,} ^NO 3 - is a graph showing the concentration ^- + NO _2. The selenate ion concentration became 0 mg-Se / L after 137 hours of culture. On the other hand, the selenite ion concentration was 53 mg-Se / L, which was almost the same as the initial selenate ion after 137 hours. Therefore, it was confirmed that the selenate-reducing microorganism 4C-C is a microorganism that reduces selenate ions to selenite ions using ethanol as an energy source. The nitrate ion concentration became 0 mg-N / L after 41 hours of culture. On the other hand, the nitrite ion concentration became 41 mg-N / L after 41 hours from the culture, but then decreased and became 0 mg-N / L after 137 hours. Therefore, it is confirmed that the selenate-reducing microorganism 4C-C has the function of reducing nitrate ions and nitrite ions to harmless nitrogen gas using ethanol as an energy source and simultaneously reducing selenate ions to selenite ions. It was done.

(B) Evaluation of 4C-C treatment capacity when methanol is used as the energy source Selenate-reducing microorganisms 4C-C are cultured in artificial waste water, and methanol is used as the energy source for the treatment capacity of selenate ions in the presence of nitrate ions. It investigated using. The composition of the artificial waste water is shown in Table 5. The initial selenate ion (SeO ₄ ²⁻ ) concentration of the artificial waste water was 20 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 500 mg-N / L. The initial input amount of the selenate-reducing microorganism 4C-C into the artificial waste water is 0.38 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Further, 0.3 ml of methanol was added. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ⁻ ), nitrite ion (NO ₂ ) when cultured for 17 hours, 41 hours, 65 hours, and 137 hours ^- ) The concentration was measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₃ ^-) _{concentration,} ^NO 3 - is a graph showing the concentration ^- + NO _2. The selenate ion concentration became 0 mg-Se / L after 137 hours of culture. On the other hand, the selenite ion concentration became 18 mg-Se / L, which was almost the same as the initial selenate ion after 137 hours. The nitrate ion concentration reached 446 mg-N / L after 137 hours from the culture. On the other hand, the nitrite ion concentration became 70 mg-N / L after 137 hours from the culture. Accordingly, the selenate-reducing microorganism 4C-C has a function of reducing selenate ions to selenite ions using methanol as an energy source, and this reduction function has a high initial nitrate ion concentration of 500 mg-N / L. However, it became clear that it did not decrease. In addition, since the nitrate ion concentration decreased and the nitrite ion increased, it was confirmed that the nitrate ion was reduced but not the nitrite ion. This is because the initial nitrate ion concentration is high. That is, when the treatment time is further increased and the energy source is further supplied, the reduction reaction of nitrite ions also occurs.

(C) Evaluation of 4C-C treatment capacity when propanol is used as the energy source The selenate-reducing microorganism 4C-C is cultured in artificial waste water, and the treatment capacity of selenate ions in the presence of nitrate ions is determined by using propanol as an energy source. It investigated using. The composition of the artificial waste water is the same as in Table 5. The initial selenate ion (SeO ₄ ²⁻ ) concentration of the artificial waste water was 20 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 500 mg-N / L. The initial input amount of the selenate-reducing microorganism 4C-C into the artificial waste water is 0.38 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). In addition, 0.3 ml of propanol was added. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ⁻ ), nitrite ion (NO ₂ ) when cultured for 17 hours, 41 hours, 65 hours, and 137 hours ^- ) The concentration was measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₃ ^-) _{concentration,} ^NO 3 - is a graph showing the concentration ^- + NO _2. The selenate ion concentration became 0 mg-Se / L after 17 hours of culture. On the other hand, the selenite ion concentration became 18 mg-Se / L, which was almost the same as the initial selenate ion after 17 hours. The nitrate ion concentration became 359 mg-N / L after 137 hours of culture. On the other hand, the nitrite ion concentration became 119 mg-N / L after 137 hours from the culture. Therefore, the selenate-reducing microorganism 4C-C has a function of reducing selenate ions to selenite ions using propanol as an energy source, and this reduction function has a high initial nitrate ion concentration of 500 mg-N / L. It became clear that even if it was a case, it did not fall. In addition, since the nitrate ion concentration decreased and the nitrite ion increased, it was confirmed that the nitrate ion was reduced but not the nitrite ion. This is because the initial nitrate ion concentration is high. That is, when the treatment time is further increased and the energy source is further supplied, the reduction reaction of nitrite ions also occurs.

  In addition, in the artificial waste water used in Examples 2 and 3, as shown in Tables 3 to 5, various compounds other than nitrates, such as sulfates, chlorides, phosphates, carbonates, boric acid, etc. The selenate-reducing microorganism 4C-C reduced selenate ions to selenite ions and reduced nitrate nitrogen. That is, it has been clarified that the selenate-reducing microorganism 4C-C functions sufficiently even in wastewater containing such a compound, for example, in desulfurization wastewater such as a thermal power plant.

Example 4
The selenite-reducing microorganism Paracoccus denitrificans was cultured in artificial wastewater, and the ability to treat selenite ions in the presence of nitrate ions was investigated. Table 6 shows the composition of the artificial waste water. The initial selenite ion (SeO ₃ ²⁻ ) concentration of the artificial waste water was 50 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 50 mg-N / L. The initial input amount of the selenite-reducing microorganism Paracoccus denitrificans into the artificial waste water was 0.38 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Further, 0.3 ml of ethanol as an energy source was added. Selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ⁻ ), and nitrite ion (NO ₂ ⁻ ) concentrations were measured when cultured for 3 days and 14 days. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

  The results are shown in FIG. Three days after culturing, the nitrate ion concentration became 0 mg-N / L, and it was confirmed that all nitrate ions in the artificial waste water were reduced to nitrogen gas. The selenite ion concentration decreased to 46 mg-Se / L after 3 days from the culture, and decreased to 33 mg-Se / L after 14 days. Therefore, Paracoccus denitrificans, a microorganism known as denitrifying bacteria, has the function of reducing nitrate ions to nitrogen gas using ethanol as an energy source and reducing selenite ions to elemental selenium. At the same time, it was confirmed to function as a selenite-reducing microorganism.

  In addition, as shown in Table 6, the artificial waste water used in Example 4 includes various compounds other than nitrates, such as sulfates, chlorides, phosphates, carbonates, boric acids and the like. Nevertheless, the selenite-reducing microorganism Paracoccus denitrificans reduced selenite ion to elemental selenium and also reduced nitrate nitrogen. In other words, it has been clarified that the selenite-reducing microorganism Paracoccus denitrificans functions well even in wastewater containing such compounds, for example, in desulfurization wastewater such as a thermal power plant.

(Example 5)
A bag was formed using a polyethylene film as a non-porous film, and the amount of organic matter permeated when methanol and ethanol were sealed therein was measured to investigate the permeability of methanol and ethanol from the polyethylene film.
A polyethylene film (trade name: Mipolon film, manufactured by Mitsuwa Co., Ltd.) having a thickness of 0.05 mm, 0.1 mm, 0.3 mm, and 0.5 mm is formed into a bag shape, and methanol (manufactured by Wako Pure Chemical Industries, 99.8%) and ethanol (Wako Pure Chemical Industries, 99.5%) were sealed. The sealed solution volume was 5 mL. This was immersed in water, and the permeation amount of methanol and ethanol was evaluated by measuring the molecular permeation amount with respect to the elapsed days and the TOC concentration. The TOC concentration was measured by a combustion-infrared total organic carbon analyzer (TOC-650, manufactured by Toray Engineering). The results are shown in FIGS. 11A and 11B. In the figure, B is background, MeOH is methanol, EtOH is ethanol, and numerical values such as 0.05, 0.1, 0.3, and 0.5 represent polyethylene film thickness (unit: mm). From this experiment, both methanol and ethanol increase the TOC concentration as the polyethylene film thickness decreases. Therefore, the supply amount of alcohol such as methanol and ethanol can be controlled by the film thickness of the polyethylene film. Was confirmed.

(Example 6)
The bioreactor shown in FIG. 4 and FIG. 5 was actually produced and the wastewater treatment performance was evaluated. A photocurable resin PVA-SbQ (SPP-H-13, manufactured by Toyo Gosei Co., Ltd.) was used as a carrier. For the photocurable resin PVA-SbQ 0.8 g, (a) no microorganism is added, phosphate buffer (9 g / l Na ₂ HPO ₄ · 12H ₂ O, 1.5 g / l KH ₂ PO ₄ , pH = 7.5) Add only 0.3 ml, (b) 0.1 ml of bacterial suspension of selenate-reducing microorganism 4C-C and phosphate buffer (9 g / l Na ₂ HPO ₄ · 12H ₂ O, 1.5 g / L KH ₂ PO ₄ , pH = 7.5) 0.2 ml, (c) P. denitrificans cell suspension 0.1 ml and phosphate buffer (9 g / l Na ₂ HPO ₄ · 12H ₂ O , 1.5 g / l KH ₂ PO ₄ , pH = 7.5) 0.2 ml was added, (d) 0.1 ml of the selenate-reducing microorganism 4C-C suspension and P. denitrificans suspension 0.1ml phosphate buffer solution _{(9g / l Na 2 HPO 4} · 12H 2 O, 1.5g / l KH PO _4, pH = 7.5) to prepare four kinds of samples were added 0.1 ml, was immobilized. Each of the mixed liquids (a) to (d) is directly applied to the nonwoven fabric and irradiated for 20 minutes under a metal halogen lamp, thereby immobilizing the nonwoven carrier in a sheet form on one side of the nonwoven fabric (length 40 mm, width 20 mm, thickness 0. 7 mm).

  The energy source of the selenate-reducing microorganisms 4C-C and P. denitrificans is ethanol (Wako Pure Chemical Industries, Ltd.) in a 0.05 mm-thick low-density polyethylene film (trade name: Mipolon Film, manufactured by Mitsuwa Corporation). , 99.5%) Using 0.3-ml sealed bag-like polyethylene, ethanol was gradually released from the polyethylene membrane and supplied to the microorganisms.

The bag-like polyethylene was wrapped with a carrier fixed on one side of the nonwoven fabric so that the nonwoven fabric would be on the outside, and immersed in artificial drainage similar to Table 4 placed in a vial (FIG. 14A). The artificial wastewater had an initial concentration of selenate ions of 50 mg-Se / L and an initial concentration of nitrate ions of 50 mg-N / L. During the test, the lid of the vial was closed to make the inside of the vial anaerobic. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitric acid after 14 hours, 36 hours, 84 hours, 180 hours, 300 hours, 492 hours, 516 hours, 660 hours, 828 hours Ion (NO ₃ ⁻ ) and nitrite ion (NO ₂ ⁻ ) concentrations were measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX). The artificial drainage temperature during the test was 30 ° C.

  The result of the selenate compound concentration is shown in FIG. (A) is a figure which shows a time-dependent change of a selenate ion concentration, (B) is a figure which shows a time-dependent change of a selenite ion concentration, (C) is the density | concentration (( It is a figure which shows a time-dependent change of a selenate compound concentration. In the figure, “control” indicates a change in concentration when the bioreactor is not immersed. In the case of the bioreactor (b) using the carrier supporting only the selenate-reducing microorganism 4C-C, it was confirmed that selenate ions were reduced to selenite ions 36 hours after the start of the treatment. On the other hand, when the selenate-reducing microorganism 4C-C and Paracoccus denitrificans coexist, the selenate compound concentration becomes 7 mg-Se / L or less after about 516 hours from the start of the treatment, and after 828 hours, the selenate compound concentration becomes 0 mg-Se. / L. Therefore, it was confirmed that by coexisting the selenate-reducing microorganism 4C-C and the selenite-reducing microorganism Paracoccus denitrificans, it is possible to sufficiently reduce the selenate compound concentration in the wastewater to obtain elemental selenium. It was.

  The result of the concentration of nitrate nitrogen is shown in FIG. (A) is a figure which shows a time-dependent change of nitrate ion density | concentration, (B) is a figure which shows a time-dependent change of nitrite ion density | concentration, (C) is the density | concentration (nitrate nitrogen density | concentration which added nitrate ion density | concentration and nitrite ion density | concentration) FIG. In the bioreactor (a) produced only from the gel carrier, the nitrate nitrogen concentration was 0 mg-N / L after 180 hours, so that it was confirmed that nitrate nitrogen was reduced to nitrogen gas. This is probably because the gel carrier is used without being sterilized, and the denitrification reaction is caused by the action of microorganisms mixed during the production of the bioreactor. Therefore, it is not necessary to sterilize the carrier at the time of producing the bioreactor. Rather, the bioreactor is suitable for use in an environment where nitrate nitrogen is present by mixing with microorganisms that cause a denitrification reaction without sterilization. It became clear that. Next, in the case of the bioreactor (b) supporting the selenate-reducing microorganism 4C-C and the bioreactor (c) supporting the selenite-reducing microorganism Paracoccus denitrificans, the nitrate nitrogen concentration is 0 mg after 36 hours. Since it was -N / L, it was confirmed that the nitrate nitrogen treatment ability was improved as compared with the bioreactor (a) produced only from the gel carrier. In the case of the bioreactor (d) in which the selenate-reducing microorganism 4C-C and the selenite-reducing microorganism Paracoccus denitrificans are coexisted and supported, the nitrate nitrogen concentration became 0 mg-N / L after 14 hours. Compared with the bioreactors of (b) and (c), it was confirmed that the nitrate nitrogen treatment ability was further improved. That is, the reduction reaction of nitrate ion and nitrite ion is promoted by the selenate-reducing microorganism 4C-C and the selenite-reducing microorganism Paracoccus denitrificans. It has become clear that this is further promoted. From the above, according to the bioreactor of the present invention, it was confirmed that the reduction treatment of nitrate nitrogen (nitrate ion, nitrite ion) can be performed simultaneously with the reduction of selenate compound to elemental selenium. It was. That is, the selenate-reducing microorganism 4C-C and the selenite-reducing microorganism Paracoccus denitrificans can convert nitrate nitrogen to nitrogen gas by denitrification, and simultaneously reduce the selenate compound to elemental selenium. Was confirmed. Even when the gel carrier is used after sterilization, the denitrification reaction proceeds sufficiently by the selenate-reducing microorganism 4C-C and the selenite-reducing microorganism Paracoccus denitrificans.

  In the bioreactor (b) supporting the selenate-reducing microorganism 4C-C, a tendency that the selenite ion concentration gradually decreased was confirmed. Therefore, it was suggested that the selenate-reducing microorganism 4C-C has not only the ability to reduce selenate ions to selenite ions, but also the ability to reduce selenite ions to elemental selenium. .

  Next, FIG. 14 shows changes in the color of the bioreactor 9 before and after the immersion treatment in the artificial wastewater 14 of the bioreactor (d) in which the selenate-reducing microorganism 4C-C and the selenite-reducing microorganism Paracoccus denitrificans coexist. The color of the non-woven fabric 10 of the bioreactor in the vial 13 was white (A) immediately after the start of the immersion treatment, but changed to red after the end of the treatment (B). Therefore, it is confirmed that elemental selenium can be recovered by adhering to the carrier of the bioreactor 9, and the elemental selenium in the wastewater 14 can be recovered simply by removing the bioreactor 9 from the wastewater 14. confirmed.

(Example 7)
Regarding the effectiveness of methanol and propanol as energy sources of 4C-C conducted in (b) and (c) of Example 3, the amount of 4C-C bacteria was increased, and selenate ion concentration and selenite ion Examination was conducted by changing the concentration.

First, 4C-C processing capacity evaluation was performed when the energy source was methanol. The composition of the artificial waste water was the same as in Table 4. The initial selenate ion (SeO ₄ ²⁻ ) concentration of the artificial waste water was 50 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 50 mg-N / L. The initial input amount of the selenate-reducing microorganism 4C-C into the artificial waste water is 0.77 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Further, 0.3 ml of methanol was added. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ⁻ ) when cultured for 0 hours, 26 hours, 46 hours, 93 hours, 141 hours, 189 hours, Nitrite ion (NO ₂ ⁻ ) concentration was measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₂ ^-) _{concentration,} ^NO 3 ^- + ^NO ₂ - is a graph showing the concentration. The selenate ion concentration became 0 mg-Se / L after 141 hours from the culture. On the other hand, the selenite ion concentration was the same as the initial selenite ion after 141 hours. The nitrate ion concentration became 0 mg-N / L after 141 hours from the culture. On the other hand, the nitrite ion concentration continued to increase until 93 hours after culturing, and thereafter became a constant value. From the above results, it was reconfirmed that the selenate-reducing microorganism 4C-C has a function of reducing selenate ions to selenite ions using methanol as an energy source. The nitrate ion concentration decreased to 0 mg-N / L, but almost no decrease in the nitrite ion concentration was observed. Therefore, it was confirmed that when the initial nitrate ion concentration was 50 mg-N / L, almost the entire amount of nitrate ions could be reduced to nitrite ions. Moreover, it becomes possible to reduce nitrite ions to nitrogen gas by further extending the treatment time or further increasing the amount of methanol supplied as an energy source.

Next, the processing capability evaluation of 4C-C when the energy source was propanol was performed. The composition of the artificial waste water was the same as in Table 4. The initial selenate ion (SeO ₄ ²⁻ ) concentration of the artificial waste water was 50 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 50 mg-N / L. The initial input amount of the selenate-reducing microorganism 4C-C into the artificial waste water is 0.77 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Further, 0.3 ml of methanol was added. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ⁻ ) when cultured for 0 hours, 26 hours, 46 hours, 93 hours, 141 hours, 189 hours, Nitrite ion (NO ₂ ⁻ ) concentration was measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₂ ^-) _{concentration,} ^NO 3 ^- + ^NO ₂ - is a graph showing the concentration. The selenate ion concentration decreased rapidly until 46 hours after culturing and became 0 mg-Se / L after 93 hours. On the other hand, the selenite ion concentration became substantially the same as the initial selenite ion after 93 hours. The nitrate ion concentration became 0 mg-N / L after 26 hours of culture. On the other hand, the nitrite ion concentration continued to increase for 26 hours after the culture, and then decreased, and reached 0 mg-N / L after 46 hours from the culture. Therefore, it became clear that the selenate-reducing microorganism 4C-C has the ability to reduce nitrate ions to nitrogen gas at the same time as reducing selenate ions to selenite ions using propanol as an energy source. .

  As described above, even when methanol or propanol is used as an energy source, the selenate-reducing microorganism 4C-C can function to reduce nitrate ions and simultaneously reduce selenate ions to selenite ions. It was confirmed that. Further, it was found that when the same amount of energy source material was used, the reduction treatment ability of the selenate-reducing microorganism 4C-C could be increased in the order of propanol and methanol. That is, it was found that the use of alcohol having a large number of carbon atoms can improve the reduction treatment ability of the selenate-reducing microorganism 4C-C.

(Example 8)
We investigated the ability to reduce selenite when methanol and propanol were supplied as energy sources to the para selenite-reducing microorganism Paracocccus denitrificans.

(A) Evaluation of treatment capacity of selenite-reducing microorganism Paracoccus denitrificans when methanol is used as an energy source Culture of selenite-reducing microorganism Paracoccus denitrificans in artificial wastewater Investigated using methanol as an energy source. The composition of the artificial waste water was the same as in Table 6. The initial selenite ion (SeO ₃ ²⁻ ) concentration of the artificial waste water was 50 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 50 mg-N / L. The initial input amount of the selenite-reducing microorganism Paracoccus denitrificans into the artificial waste water is 1.53 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Further, 0.3 ml of methanol as an energy source was added. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ⁻ ) when cultured for 0 hours, 66 hours, 144 hours, 234 hours, 306 hours, 473 hours, Nitrite ion (NO ₂ ⁻ ) concentration was measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₂ ^-) _{concentration,} ^NO 3 ^- + ^NO ₂ - is a graph showing the concentration. The selenite ion concentration decreased to 32 mg-Se / L after 473 hours of culture. The nitrate ion concentration became 0 mg-N / L after 473 hours from the culture. Note that the nitrite ion concentration was 0 mg-N / L over the entire culture period. This is because the total amount of nitrite ions produced by the reduction of nitrate ions by Paracoccus denitrificans was reduced. Nitrogen gas, meaning that nitrite ions did not accumulate. Therefore, Paracoccus denitrificans, a microorganism known as denitrifying bacteria, has the function of reducing nitrate ions to nitrogen gas using methanol as an energy source and reducing selenite ions to elemental selenium. At the same time, it was confirmed to function as a selenite-reducing microorganism.

(B) Evaluation of treatment capacity of selenite-reducing microorganism Paracoccus denitrificans when propanol is used as the energy source Culture of selenite-reducing microorganism Paracoccus denitrificans in artificial wastewater Investigated using propanol as an energy source. The composition of the artificial waste water was the same as in Table 6. The initial selenite ion (SeO ₃ ²⁻ ) concentration of the artificial waste water was 50 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 50 mg-N / L. The initial input amount of the selenite-reducing microorganism Paracoccus denitrificans into the artificial waste water is 1.53 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Further, 0.3 ml of propanol as an energy source was added. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ²⁻ ), nitrate ion (NO ₃ ⁻ ), nitrite ion when cultured for 0 hours, 66 hours, 144 hours, 234 hours, 306 hours The (NO ₂ ⁻ ) concentration was measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₂ ^-) _{concentration,} ^NO 3 ^- + ^NO ₂ - is a graph showing the concentration. The selenite ion concentration became 0 mg-Se / L after 306 hours of culture. The nitrate ion concentration became 0 mg-N / L after 66 hours of culture. Note that the nitrite ion concentration was 0 mg-N / L over the entire culture period. This is because the total amount of nitrite ions produced by the reduction of nitrate ions by Paracoccus denitrificans was reduced. Nitrogen gas, meaning that nitrite ions did not accumulate. Therefore, Paracoccus denitrificans, a microorganism known as denitrifying bacteria, has the function of reducing nitrate ions to nitrogen gas using propanol as an energy source and reducing selenite ions to elemental selenium. At the same time, it was confirmed to function as a selenite-reducing microorganism.

  As described above, even when methanol or propanol is used as an energy source, Paracoccus denitrificans can function to reduce nitrate ion to nitrogen gas and simultaneously reduce selenite ion to elemental selenium. confirmed. It was also found that when the same amount of energy source material was used, the reduction treatment capacity of Paracoccus denitrificans could be increased in the order of propanol and methanol. In other words, it was found that the reduction capacity of Paracoccus denitrificans can be increased by using alcohol having a large number of carbon atoms.

Example 9
4C-C and Paracoccus denitrificans were cultured in artificial wastewater, and the ability to treat selenate ions in the presence of nitrate ions was investigated using propanol as an energy source. The composition of the artificial waste water was the same as in Table 4. The initial selenate ion (SeO ₄ ²⁻ ) concentration of the artificial waste water was 50 mg-Se / L, and the nitrate ion (NO ₃ ⁻ ) concentration was 50 mg-N / L. The initial input amount of 4C-C into the artificial waste water is 0.38 mg wet wt. / Ml. The initial input amount of Paracoccus denitrificans into the artificial waste water is 0.38 mg wet wt. / Ml. 30 ml of this artificial waste water was placed in a 50 ml vial, covered, and cultured at 30 ° C. with shaking (100 rpm). Further, 0.3 ml of propanol as an energy source was added. Selenate ion (SeO ₄ ²⁻ ), selenite ion (SeO ₃ ) when cultured for 0 hours, 15 hours, 39 hours, 63 hours, 135 hours, 240 hours, 305 hours, 407 hours, 544 hours, 688 hours ^2- ), nitrate ion (NO ₃ ⁻ ), and nitrite ion (NO ₂ ⁻ ) concentrations were measured. The measurement was performed with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX).

The results are shown in FIG. (A) is a selenate ion (SeO ₄ ²⁻ ) concentration, selenite ion (SeO ₃ ²⁻ ) concentration, SeO ₄ ² + + SeO ₃ ²⁻ concentration, and (B) is a nitrate ion (NO ₃ ⁻ ) concentration. nitrite ions (NO ₂ ^-) _{concentration,} ^NO 3 ^- + ^NO ₂ - is a graph showing the concentration. The selenate ion concentration became 0 mg-Se / L after 240 hours of culture. Selenite ion increased up to 240 hours after culture and then continued to decrease until 688 hours. The nitrate ion concentration became 0 mg-N / L after 63 hours from the culture. It should be noted that the nitrite ion concentration was approximately 0 mg-N / L over the entire culture period. This is because the total amount of nitrite ions produced by the reduction of nitrate ions was reduced and nitrogen gas was reduced. This means that accumulation of nitrite ions did not occur. Therefore, it was confirmed that by using 4C-C and Paracoccus denitrificans in combination, selenate ions can be reduced to elemental selenium via selenite ions and nitrate ions can be reduced to nitrogen gas.

It is a figure which shows the example of the sealing type which is one Embodiment of the lower alcohol supply method of this invention, (A) is a perspective view, (B) is a longitudinal cross-sectional view. It is a figure which shows the example of the replenishment type which is other embodiment of the lower alcohol supply method of this invention, (A) is a perspective view, (B) is a longitudinal cross-sectional view. It is a schematic explanatory drawing which shows the whole structure of the lower alcohol supply method of embodiment of FIG. It is a perspective view which shows an example of a structure of the bioreactor of this invention. It is a longitudinal cross-sectional view which shows an example of a structure of the bioreactor of this invention, (A) is an example using the container of FIG. 1 which is a lower alcohol sealed type, (B) is a lower alcohol replenishment type of FIG. Examples using containers are shown below. It is a figure which shows the time-dependent change of various ion density | concentrations when culture | cultivating selenate reducing microorganisms 4C-C by making an energy source a yeast extract with the artificial waste_water | drain containing a nitrate ion and a selenate ion. It is a figure which shows the time-dependent change of various ion density | concentrations when culture | cultivating selenate reducing microorganisms 4C-C by making the energy source ethanol with the artificial waste water containing a nitrate ion and a selenate ion. It is a figure which shows the time-dependent change of various ion density | concentrations when culture | cultivating the selenate reducing microorganism 4C-C by making into an energy source methanol the artificial waste water containing nitrate ion (20 mg / L) and a selenate ion (500 mg / L). It is a figure which shows the time-dependent change of various ion density | concentrations when culture | cultivating selenate-reducing microorganism 4C-C by using artificial effluent containing nitrate ion (20mg / L) and selenate ion (500mg / L) as an energy source propanol. It is a figure which shows the time-dependent change of various ion density | concentrations when culture | cultivating a selenite reducing microorganism Paracoccus denitrificans by making the energy source ethanol into the artificial waste_water | drain containing nitrate ion and selenite ion. It is a figure which shows the permeation | transmission amount measurement result of the lower alcohol from a polyethylene film, (A) is methanol, (B) is a measurement result of ethanol. It is a figure which shows the (A) selenate ion concentration at the time of using various bioreactors, (B) selenite ion concentration, (C) selenate compound concentration. It is a figure which shows (A) nitrate ion concentration, (B) nitrite ion concentration, and (C) nitrate ion + nitrite ion concentration at the time of using various bioreactors. It is a figure which shows the change of the color before and behind immersing the bioreactor of this invention in artificial waste_water | drain. This graph shows changes over time in various ion concentrations when culturing selenate-reducing microorganisms 4C-C using methanol as an energy source in artificial wastewater containing nitrate ions (50 mg-N / L) and selenate ions (50 mg-Se / L). FIG. This graph shows changes over time in various ion concentrations when selenate-reducing microorganisms 4C-C are cultured in artificial wastewater containing nitrate ions (50 mg-N / L) and selenate ions (50 mg-Se / L) using propanol as an energy source. FIG. It is a figure which shows the time-dependent change of various ion density | concentrations when culture | cultivating a selenite reducing microorganism Paracoccus denitrificans by using artificial effluent containing nitrate ion and selenite ion as an energy source methanol. It is a figure which shows the time-dependent change of various ion density | concentrations when culture | cultivating a selenite reducing microorganism Paracoccus denitrificans by using artificial drainage containing nitrate ion and selenite ion as an energy source propanol. It is a figure which shows the time-dependent change of various ion concentration at the time of culture | cultivating the selenate reducing microorganism 4C-C and the selenite reducing microorganism Paracoccus denitrificans in the artificial waste water containing a nitrate ion and a selenate ion by using propanol as an energy source.

Explanation of symbols

2 Non-porous membrane 3 Lower alcohol 4 Container 9 Bioreactor 11 Carrier

Claims (8)

A lower alcohol having a carbon number of 1 to 3 as a source of energy, selenium ion, Pseudomonas sp. 4C-C nitrate ion and nitrite ion is selenate reducing microbial you simultaneously reduced under anaerobic conditions (Pseudomonas sp. 4C in -C) (FERM P-20840) , under anaerobic conditions, the lower alcohol supplied with contacting a selenate compound containing wastewater containing at least one of nitrate and nitrite ions, the selenate compound containing wastewater A method for treating a selenate compound-containing liquid, characterized by reducing nitrate ions and nitrite ions therein to nitrogen gas and reducing selenate ions to selenite ions . A lower alcohol having a carbon number of 1 to 3 as a source of energy, selenium ion, Pseudomonas sp. 4C-C nitrate ion and nitrite ion is selenate reducing microbial you simultaneously reduced under anaerobic conditions (Pseudomonas sp. 4C -C) (in the FERM P-20840) as a selenite reducing microbial Paracoccus denitrificans (Paracoccus denitrificans), under anaerobic conditions, selenate compound containing at least one of nitrate and nitrite ions Contacting the wastewater contained , supplying the lower alcohol , reducing nitrate ions and nitrite ions in the wastewater containing selenate compound to nitrogen gas, and reducing the selenate compound to elemental selenium A method for treating a selenate compound-containing liquid. The method for treating selenate compound-containing wastewater according to claim 2, wherein one or both of the selenate-reducing microorganism and the selenite-reducing microorganism are supported on a carrier . The lower alcohol is supplied by sealing the lower alcohol or waste alcohol having 1 to 3 carbon atoms in a container having at least a part of the non-porous film, and the non-porous film from the non-porous film part of the container. The method for treating selenate compound-containing wastewater according to any one of claims 1 to 3, wherein the selenate compound-containing wastewater is gradually released around the container at a speed governed by the molecular permeation performance . The method for treating selenate compound-containing wastewater according to any one of claims 1 to 4, wherein the lower alcohol is one or more of methanol, ethanol, and propanol . Pseudomonas sp. 4C-C (Pseudomonas sp. 4C-C) is a selenate-reducing microorganism that simultaneously reduces selenate ions, nitrate ions and nitrite ions under anaerobic conditions using a lower alcohol having 1 to 3 carbon atoms as an energy source. (FERM P-20840) and selenium containing at least one of nitrate ion and nitrite ion, characterized in that paracoccus denitrificans, a selenite-reducing microorganism, is supported on a carrier. Bioreactor for treatment of acid compound-containing liquids . A lower alcohol or waste alcohol having 1 to 3 carbon atoms is sealed in a container provided with at least a part of the nonporous membrane, and is governed by the molecular permeation performance of the nonporous membrane from the nonporous membrane portion of the container. The bioreactor for treating a liquid containing a selenate compound according to claim 6, wherein the lower alcohol is supplied to the carrier by supplying the lower alcohol to the periphery of the container at a high speed . Selenate-reducing microorganism Pseudomonas sp. 4C-C that can simultaneously reduce selenate ion, nitrate ion and nitrite ion under anaerobic conditions and can use a lower alcohol having 1 to 3 carbon atoms as an energy source. Pseudomonas sp. 4C-C) (FERM P-20840) .

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