JP2010041954A - Method for treating drainage with microorganism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for removing water-soluble selenium from drainage without supplying an expensive energy source substance such as a yeast extract. <P>SOLUTION: Provided is the method for treating the drainage, comprising a process for supplying a lower alcohol to a selenic acid-reducing microorganism of a genus Pseudomonas bacterium (FERM P-20840) under an anaerobic environment and making contact with a water-soluble selenium-containing drainage to produce selenious acid from selenic acid contained in the water-soluble selenium-containing drainage, and a process for supplying a lower alcohol and sulfuric acid under an anaerobic environment to a sulfuric acid-reducing microorganism (FERM P-21577) which belongs to genus Desulfovibrio and has an ability for reducing the sulfuric acid and the selenious acid with a lower alcohol as an energy source under an anaerobic environment, bringing the produced hydrogen sulfide into contact with a water-soluble selenium-containing drainage to convert selenious acid contained in the water-soluble selenium-containing drainage and the selenious acid produced with the selenic acid-reducing microorganism into water-insoluble selenium. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method using microorganisms. More specifically, the present invention relates to a method for treating wastewater containing a water-soluble heavy metal such as water-soluble selenium using a novel microorganism having a sulfate reducing ability.

In this specification, selenic acid (SeO ₄ ²⁻ ) and selenious acid (SeO ₃ ²⁻ ) are collectively referred to as water-soluble selenium.

  Selenium is an industrially useful substance that has the property of increasing electrical conductivity when irradiated with light. At present, industrial production of selenium is around 1500 tons worldwide, and it is used for various purposes such as photoconductors for photovoltaic cells and photocopiers, achromatic agents in the glass industry, and feed supplements for livestock.

  Here, while selenium is an essential element for the human body, it exhibits high toxicity when taken in excess. For this reason, the drainage standard of selenium is strictly regulated by the Water Pollution Control Law, and its value is 0.1 mg-Se / L.

The chemical forms of water-soluble selenium contained in industrial wastewater are selenate (SeO ₄ ²⁻ ) and selenious acid (SeO ₃ ²⁻ ). As a method for removing water-soluble selenium, for example, a chemical coprecipitation method using iron is used (Non-Patent Document 1).

  However, although the method described in Non-Patent Document 1 is suitable for removing selenious acid, the removal efficiency of selenic acid is low. Industrial wastewater may contain not only selenious acid but also selenic acid. In particular, desulfurization effluents generated from coal-fired power plants contain selenic acid and selenous acid derived from coal. Therefore, Patent Document 1 proposes a method for treating water-soluble selenium contained in waste water by using both biological treatment and chemical treatment. Specifically, selenate is reduced to selenite or insoluble elemental selenium by a selenate-reducing bacterium (FERM BP-5562), and then iron salts such as iron chloride and iron sulfate are added to the waste water to reduce the amount of selenate. Water-soluble selenium is separated from waste water by coagulating and precipitating selenic acid and solid-liquid separation.

  However, when a chemical method is used in combination, a large amount of sludge is generated because many chemicals are used. Thus, a method has been proposed in which water-soluble selenium is reduced to insoluble elemental selenium only by biological techniques using microorganisms, and water-soluble selenium in the waste water is removed (Non-Patent Documents 2 to 7).

JP-A-10-309190 Yoshihiro Saito, Toshiji Nakahara: Inorganic wastewater treatment technology useful in the field, Industrial Research Committee (2005) Fujita M, et al .: J. Ferment. Bioeng. 83: 517-522 (1997) Kashiwa M, et al .: J. Biosci. Bioeng. 89: 528-533 (2000) Lortie L, et al .: Appl. Environ. Microbiol. 58: 4042-4044 (1992) Losi M E, et al .: Appl. Environ. Microbiol. 63: 3079-3084 (1997) Oremland R S, et al .: Appl. Environ. Microbiol. 60: 3011-3019 (1994) Steinberg N A, et al .: Appl. Environ. Microbiol. 58: 426-428 (1992)

  However, when reducing selenic acid using a biological technique together as in Patent Document 1, or when reducing selenic acid only by a biological technique as in Non-Patent Documents 2 to 7, it is expensive. It is necessary to supply the yeast extract, which is a medicine, to the microorganisms, and the cost for wastewater treatment becomes great. Therefore, when considering an actual biological wastewater treatment process, it is desired to perform wastewater treatment by supplying an inexpensive and easily available energy source material to microorganisms instead of yeast extract.

  In addition, desulfurization wastewater generated from coal-fired power plants and the like may contain not only coal-derived water-soluble selenium but also high-concentration nitrate nitrogen and sulfuric acid. Thus, wastewater containing high concentrations of nitrate nitrogen and sulfuric acid cannot be said to be an environment suitable for the activity of microorganisms, and the function of microorganisms may be hindered and wastewater treatment may not be performed properly. Therefore, establishment of a biological wastewater treatment method capable of efficiently removing water-soluble selenium even in a harsh environment where high concentrations of nitrate nitrogen and sulfuric acid exist is desired.

  Furthermore, not only water-soluble selenium but also various heavy metals that cause environmental pollution may be dissolved in industrial wastewater. Therefore, establishment of a method capable of removing not only water-soluble selenium but also water-soluble heavy metals in general from wastewater is desired.

  Then, this invention aims at providing the biological waste water treatment method which can remove water-soluble heavy metals, such as water-soluble selenium, without supplying expensive energy source materials like a yeast extract. To do.

  In addition, the present invention efficiently removes water-soluble heavy metal compounds such as water-soluble selenium from wastewater containing nitrate nitrogen and sulfuric acid at a high concentration without supplying expensive energy source materials such as yeast extract. An object of the present invention is to provide a biological wastewater treatment method.

  In order to solve such a problem, the inventors of the present application searched for a microorganism capable of insolubilizing a water-soluble heavy metal such as water-soluble selenium without supplying an expensive energy source material such as a yeast extract. . As a result, we succeeded in isolating a new microorganism belonging to the genus Desulfovibrio, which has a function of generating hydrogen sulfide by reducing sulfuric acid in an anaerobic environment using a lower alcohol such as ethanol as an energy source. The present inventors have also found that the novel microorganism has a function to directly reduce selenite to insoluble elemental selenium. The inventors have also found that water-soluble selenite can be converted to insoluble selenium by reacting hydrogen sulfide produced by this novel microorganism with selenious acid. And based on this knowledge, various investigations have been made and the present invention has been completed.

  That is, the sulfate-reducing microorganism according to claim 1 belongs to the genus Desulfovibrio, and has the ability to reduce sulfuric acid and selenious acid in an anaerobic environment using lower alcohol as an energy source, and has accession number FERM P-21577. This is a sulfate-reducing microorganism that has been commissioned in Japan.

  Therefore, this sulfate-reducing microorganism has the ability to reduce sulfuric acid and selenious acid in an anaerobic environment using lower alcohol as an energy source, so that hydrogen sulfide and insoluble selenium can be produced. A microorganism belonging to the genus Desulfovibrio having such a function is not known at the time of filing this application, and this sulfate-reducing microorganism is a novel microorganism.

  Next, in the water-insoluble heavy metal insolubilization method according to claim 2, hydrogen sulfide produced by supplying lower alcohol and sulfuric acid in an anaerobic environment to the sulfate-reducing microorganism of the present invention is brought into contact with the water-soluble heavy metal. And a step of converting the water-soluble heavy metal into an insoluble heavy metal.

  As described above, by bringing the hydrogen sulfide produced by supplying the lower alcohol and sulfuric acid to the sulfate-reducing microorganism of the present invention in an anaerobic environment with the water-soluble heavy metal, the water-soluble heavy metal can be reacted with the hydrogen sulfide. it can. Therefore, the water-soluble heavy metal can be an insoluble heavy metal.

  Moreover, the waste water treatment method according to claim 3 is characterized in that hydrogen sulfide produced by supplying lower alcohol and sulfuric acid in an anaerobic environment to the sulfate-reducing microorganism of the present invention is brought into contact with water-soluble heavy metal-containing waste water. A step of converting the heavy metal into an insoluble heavy metal is included.

  Thus, the water-soluble heavy metals contained in the wastewater are brought into contact with the water-soluble heavy metal-containing wastewater by contacting the hydrogen sulfide produced by supplying the lower alcohol and sulfuric acid in an anaerobic environment to the sulfate-reducing microorganism of the present invention. Can be reacted with hydrogen sulfide. Therefore, the water-soluble heavy metal contained in the waste water can be made into an insoluble heavy metal and can be separated from the waste water.

  Next, in the wastewater treatment method according to claim 4, hydrogen sulfide produced by supplying the lower alcohol and sulfuric acid to the sulfate-reducing microorganism of the present invention in an anaerobic environment is brought into contact with the selenite-containing wastewater. A step of converting selenic acid into insoluble selenium is included.

  Thus, the hydrogen sulfide produced by supplying the lower alcohol and sulfuric acid in an anaerobic environment to the sulfate-reducing microorganism of the present invention is brought into contact with the selenite-containing wastewater, whereby selenite contained in the wastewater. Can be reacted with hydrogen sulfide. Therefore, the selenious acid contained in the waste water can be made insoluble selenium and can be separated from the waste water.

  Next, the waste water treatment method according to claim 5 is characterized in that a lower alcohol is supplied to a selenate-reducing microorganism belonging to the genus Pseudomonas accepted under the accession number FERM P-20840 in an anaerobic environment and water-soluble selenium-containing waste water. Hydrogen sulfide produced by supplying a lower alcohol and sulfuric acid in an anaerobic environment to the sulfate-reducing microorganism of the present invention, and a step of producing selenious acid from selenic acid contained in water-soluble selenium-containing wastewater. Is brought into contact with the water-soluble selenium-containing wastewater, and the step of converting the selenite contained in the water-soluble selenium-containing wastewater and the selenite produced by the selenate-reducing microorganism into insoluble selenium is included.

  The selenate-reducing microorganism belonging to the genus Pseudomonas entrusted with the accession number FERM P-20840 is a microorganism having the ability to reduce selenate to selenite in an anaerobic environment using a lower alcohol as an energy source. Therefore, by supplying lower alcohol to this selenate-reducing microorganism in an anaerobic environment and contacting water-soluble selenium-containing wastewater, selenite can be generated from selenate contained in the water-soluble selenium-containing wastewater. it can. And it is originally contained in the water-soluble selenium-containing wastewater by contacting the hydrogen sulfide produced by supplying the lower alcohol and sulfuric acid in an anaerobic environment to the sulfate-reducing microorganism of the present invention with the water-soluble selenium-containing wastewater. Not only selenite but also selenite produced by selenate-reducing microorganisms can be reacted with hydrogen sulfide to form insoluble selenium. Therefore, the water-soluble selenium present as selenic acid and selenous acid in the waste water can be converted into insoluble selenium and can be separated from the waste water.

  Here, as in the wastewater treatment method according to claim 6, the selenate-reducing microorganism belonging to the genus Pseudomonas and the sulfate-reducing microorganism of the present invention, which are entrusted with the deposit number FERM P-20840, are coexisting in the same treatment tank. The waste water treatment may be performed.

  In this case, the water-soluble selenium contained in the waste water can be converted to insoluble selenium in the same treatment tank.

  Moreover, in addition to the selenate-reducing microorganism belonging to the genus Pseudomonas and the sulfate-reducing microorganism of the present invention, which are entrusted with the deposit number FERM P-20840 as in the wastewater treatment method according to claim 7, the paracoccus denitori Wastewater treatment may be performed by coexisting ficus (Paracoccus denitrificans) in the same treatment tank.

  In this way, by coexisting Paracoccus denitrificans in the same treatment tank, high-concentration nitrate nitrogen (nitric acid and nitrite, for example, desulfurization effluent discharged from coal-fired power plants, etc.) Etc.), water-soluble selenium can be efficiently converted into insoluble selenium.

  Here, it is preferable that at least the sulfate-reducing microorganism of the present invention is supported on a carrier as in the wastewater treatment method according to claim 8.

  In this case, insoluble heavy metals such as insoluble selenium can be recovered by adhering to the carrier, so that a treatment for separating the insoluble heavy metals such as insoluble selenium from the waste water is not required.

  Next, the waste water treatment method according to claim 9 uses the sulfuric acid contained in the waste water as sulfuric acid to be supplied to the sulfate-reducing microorganism of the present invention.

  For example, since desulfurization effluent discharged from a coal-fired power plant or the like may contain sulfuric acid, sulfuric acid contained in the effluent itself may be used. In such a case, the labor of supplying sulfuric acid to the sulfate-reducing microorganism of the present invention can be saved, and the concentration of sulfuric acid contained in the desulfurization effluent can be reduced.

  Next, the bioreactor according to claim 10 has a carrier on which the sulfate-reducing microorganism of the present invention is supported.

  Thus, by setting it as the bioreactor which has the support | carrier with which the sulfate reduction microorganisms of this invention are carry | supported, a lower alcohol and a sulfuric acid can be supplied to this bioreactor in an anaerobic environment, and hydrogen sulfide can be produced | generated. Therefore, by bringing hydrogen sulfide produced in this bioreactor into contact with water-soluble heavy metal-containing wastewater, the water-soluble heavy metal contained in the wastewater can be reacted with hydrogen sulfide. Therefore, the water-soluble heavy metal contained in the waste water can be made into an insoluble heavy metal. Moreover, the insoluble heavy metal can be recovered by adhering to the carrier.

  Moreover, the selenite contained in waste water can be made to react with hydrogen sulfide by making the hydrogen sulfide produced | generated in this bioreactor contact with selenite containing waste water. Therefore, selenious acid contained in the waste water can be converted to insoluble selenium. Moreover, insoluble selenium can be recovered by adhering to a carrier.

  Here, as in the bioreactor according to claim 11, in addition to the sulfate-reducing microorganism of the present invention, a selenate-reducing microorganism belonging to the genus Pseudomonas that is accepted under the accession number FERM P-20840 is further supported on the carrier. It is preferred that

  Thus, in addition to the sulfate-reducing microorganism of the present invention, a bioreactor having a carrier on which a selenate-reducing microorganism belonging to the genus Pseudomonas that has been accepted under the accession number FERM P-20840 is further supported. In addition to the function of generating hydrogen sulfide by supplying lower alcohol and sulfuric acid in an anaerobic environment, the bioreactor can be provided with a function of generating selenious acid from selenate. . Therefore, by bringing water-soluble selenium-containing wastewater into contact with this bioreactor, water-soluble selenium present as selenic acid and selenious acid in the wastewater can be converted into insoluble selenium. Moreover, insoluble selenium can be recovered by adhering to a carrier.

  Moreover, in addition to the sulfate-reducing microorganism of the present invention and the selenate-reducing microorganism belonging to the genus Pseudomonas which is entrusted with the deposit number FERM P-20840, as in the bioreactor according to claim 12, Paracoccus denitrificans Preferably, (Paracoccus denitrificans) is further supported on a carrier.

  Thus, in addition to the sulfate-reducing microorganism of the present invention and the selenate-reducing microorganism belonging to the genus Pseudomonas that has been entrusted with the accession number FERM P-20840, Paracoccus denitrificans is further carried. Even when treating water-soluble selenium-containing wastewater containing high-concentration nitrate nitrogen, such as desulfurization wastewater discharged from coal-fired power plants, etc. Insoluble selenium can be efficiently formed. Moreover, insoluble selenium can be recovered by adhering to a carrier.

  As described above, the sulfate-reducing microorganism according to claim 1 has a function of reducing sulfuric acid and selenious acid in an anaerobic environment using an inexpensive yeast extract as an energy source without using an expensive yeast extract as an energy source. It will be possible to demonstrate. Therefore, hydrogen sulfide can be produced at a low cost, and selenous acid can be converted into insoluble selenium at a low cost.

  According to the method for insolubilizing a water-soluble heavy metal according to claim 2, since the sulfate-reducing microorganism of the present invention is used, the water-soluble heavy metal can be converted into an insoluble heavy metal using an inexpensive lower alcohol as an energy source. It becomes possible. Therefore, the water-soluble heavy metal can be insolubilized at a low cost.

  According to the waste water treatment method of claim 3, since the sulfate-reducing microorganism of the present invention is used, the water-soluble heavy metal contained in the waste water can be made into an insoluble heavy metal using an inexpensive lower alcohol as an energy source. It becomes possible. Therefore, biological wastewater treatment using water-soluble heavy metals contained in wastewater as insoluble heavy metals can be performed at low cost.

  According to the waste water treatment method of claim 4, since the sulfate-reducing microorganism of the present invention is used, selenite contained in the waste water can be made into insoluble selenium using an inexpensive lower alcohol as an energy source. It becomes possible. Therefore, biological wastewater treatment using selenious acid contained in wastewater as insoluble selenium can be performed at low cost.

  According to the waste water treatment method of claim 5, since the selenate-reducing microorganism of the genus Pseudomonas and the novel sulfate-reducing microorganism of the present invention, which are entrusted with the deposit number FERM P-20840, are used in combination. By using an inexpensive lower alcohol as an energy source, water-soluble selenium contained in the wastewater can be converted into insoluble selenium. Therefore, biological wastewater treatment using water-soluble selenium contained in wastewater as insoluble selenium can be performed at low cost.

  According to the waste water treatment method of claim 6, waste water is produced by coexisting the selenate-reducing microorganism belonging to the genus Pseudomonas and the sulfate-reducing microorganism of the present invention, which are entrusted with the deposit number FERM P-20840, in the same treatment tank. Since the treatment is performed, water-soluble selenium contained in the wastewater can be converted into insoluble selenium in the same treatment tank using an inexpensive lower alcohol as an energy source.

  According to the waste water treatment method of claim 7, in addition to the selenate-reducing microorganism belonging to the genus Pseudomonas and the novel sulfate-reducing microorganism of the present invention, which are entrusted under the deposit number FERM P-20840, the Paracoccus denitrificans (Paracoccus denitrificans) coexist in the same treatment tank for wastewater treatment, which is the case where wastewater containing high concentrations of nitrate nitrogen is treated using inexpensive lower alcohol as an energy source. However, the water-soluble selenium contained in the waste water can be efficiently converted into insoluble selenium. Therefore, for example, even when desulfurization effluent discharged from a coal-fired power plant or the like is treated, biological wastewater treatment using water-soluble selenium contained in the effluent as insoluble selenium can be performed at low cost and efficiently. It becomes.

  According to the waste water treatment method of the eighth aspect, since at least the sulfate-reducing microorganism is supported on the carrier, it is possible to collect the insoluble heavy metal such as insoluble selenium by attaching it to the carrier. Therefore, it is possible to save the trouble of performing a process for separating insoluble heavy metals such as insoluble selenium from the waste water, for example, a solid-liquid separation process.

  According to the waste water treatment method of claim 9, since the sulfuric acid contained in the waste water is used as the sulfuric acid supplied to the sulfate-reducing microorganism of the present invention, it is contained in the desulfurization waste water generated in, for example, a coal-fired power plant. It is possible to reduce the sulfuric acid concentration in the desulfurization waste water while using sulfuric acid as a hydrogen sulfide generation source of the sulfate-reducing microorganism of the present invention. Accordingly, the cost for supplying sulfuric acid can be reduced, the cost for treating the sulfuric acid contained in the desulfurized waste water can be reduced, and the waste water treatment cost can be reduced comprehensively.

  According to the water-soluble heavy metal insolubilization method and wastewater treatment method of the present invention, as in the case of adding hydrogen sulfide directly to a wastewater treatment tank or the like, strict control of the supply amount of hydrogen sulfide, operation management, etc. There is no need to do it. Moreover, it is not necessary to manage hydrogen sulfide from leaking from a hydrogen sulfide supply source or the like installed outside a wastewater treatment tank or the like. That is, according to the present invention, since hydrogen sulfide generated by microorganisms is used, microorganisms inhabit places where hydrogen sulfide is to be generated, and by supplying lower alcohol and sulfuric acid to the microorganisms, Hydrogen sulfide can be generated in an anaerobic environment. That is, hydrogen sulfide can be directly generated at a place where it is desired to generate hydrogen sulfide, and there is no need to supply hydrogen sulfide from outside such as a waste water treatment tank. Moreover, since the amount of hydrogen sulfide produced can be controlled by the amount of sulfuric acid supplied, the amount of lower alcohol supplied, the number of microorganisms, etc., the amount of hydrogen sulfide supplied is higher than when hydrogen sulfide is added directly to a wastewater treatment tank. The time and effort required for control and operation management can be greatly reduced, and insolubilization treatment and drainage treatment can be performed very easily. In short, according to the water-insoluble heavy metal insolubilization method and the wastewater treatment method of the present invention, it is possible to significantly reduce the cost of the microorganism energy source material by using an inexpensive lower alcohol, and to the treatment. Such labor is greatly reduced as compared with the case of chemically supplying hydrogen sulfide, and it becomes possible to carry out very easily.

  Next, according to the bioreactor described in claim 10, since it has a carrier on which the sulfate-reducing microorganism of the present invention is supported, it is brought into contact with sulfuric acid in an anaerobic environment using an inexpensive lower alcohol as an energy source. Thus, the function of generating hydrogen sulfide can be exhibited. Therefore, by contacting the bioreactor with lower alcohol, sulfuric acid, and wastewater containing water-soluble heavy metals such as selenite in an anaerobic environment, water-soluble heavy metals such as selenite contained in wastewater are insoluble. It can be an insoluble heavy metal such as selenium. Moreover, insoluble heavy metals such as insoluble selenium can be recovered by adhering to a carrier.

  According to the bioreactor of claim 11, in addition to the sulfate-reducing microorganism of the present invention, the bioreactor further comprises a carrier on which a selenate-reducing microorganism belonging to the genus Pseudomonas that is deposited under the deposit number FERM P-20840 is further loaded. Because it uses cheap lower alcohol as an energy source, it comes into contact with sulfuric acid under anaerobic conditions, thereby reducing selenic acid to selenious acid, and reducing hydrogen sulfate to generate hydrogen sulfide. Can be demonstrated. Therefore, the water-soluble selenium contained in the wastewater can be converted into insoluble selenium by contacting the bioreactor with lower alcohol, sulfuric acid, and wastewater containing water-soluble selenium in an anaerobic environment. Moreover, insoluble selenium can be recovered by adhering to a carrier.

  According to the bioreactor of claim 12, in addition to the sulfate-reducing microorganism of the present invention and the selenate-reducing microorganism belonging to the genus Pseudomonas which is entrusted with the deposit number FERM P-20840, Paracoccus denitrificans (Paracoccus) denitrificans) has a carrier that is further supported, so that it can be contacted with wastewater containing high concentrations of nitrate nitrogen by contacting it with sulfuric acid under anaerobic conditions using inexpensive lower alcohol as an energy source. Even in such a case, the function of reducing selenic acid to selenious acid and the function of reducing sulfuric acid to generate hydrogen sulfide can be exhibited. Therefore, for example, even when desulfurization effluent discharged from a thermal power plant or the like is treated, water-soluble selenium contained in the effluent can be efficiently converted into insoluble selenium. Moreover, insoluble selenium can be recovered by adhering to a carrier.

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

  The microorganism of the present invention is a novel sulfate-reducing microorganism belonging to the genus Desulfovibrio. So far, microorganisms belonging to the genus Desulfovibrio have the ability to reduce sulfuric acid and selenite using lower alcohols as energy sources without using expensive substances such as yeast extract as energy sources. There is no report example so far. This new microorganism has been entrusted to the Patent Organism Depositary of the National Institute of Advanced Industrial Science and Technology as an accession number FERM P-21577 on May 21, 2008. In the following description, this novel sulfate-reducing microorganism is referred to as HT-1 strain.

  As the lower alcohol supplied to the HT-1 strain as an energy source, an alcohol having 1 to 3 carbon atoms such as methanol, ethanol, and propanol can be used, and ethanol is particularly preferable.

  For supplying the lower alcohol as the energy source, a known or novel method may be appropriately used. For example, the technology disclosed in International Publication 2006/135028 or Central Research Institute Report V06023 (2007) may be used. Specifically, a pump or means for controlling the supply amount is provided by sealing lower alcohol such as ethanol inside a sealed container (bag) having a polyethylene film, polypropylene film or polyvinyl alcohol film in part. Therefore, the lower alcohol required by the microorganism can always be slowly supplied. Of course, the lower alcohol may be directly supplied to the wastewater by using a pump or a means for controlling the supply amount.

  The HT-1 strain uses sulfuric acid as an energy source to perform sulfuric acid respiration in an anaerobic environment to reduce sulfuric acid. By using the hydrogen sulfide generated at that time, water-soluble heavy metals represented by water-soluble selenium can be insolubilized. For example, by contacting selenite dissolved in wastewater with hydrogen sulfide produced by the HT-1 strain, selenite is reduced to elemental selenium, or selenite is treated as selenium sulfide in the wastewater. It can be deposited from. That is, selenite dissolved in the waste water can be made into a state in which solid-liquid separation is possible as insoluble selenium. The wastewater to be treated in the present invention includes not only industrial wastewater but also groundwater contaminated with heavy metals due to outflow of industrial wastewater or elution from waste landfilled in soil.

  Here, a known or new technique may be appropriately used for supplying sulfuric acid as a hydrogen sulfide generation source. For example, the technique disclosed in International Publication 2006/135028 may be used. Specifically, by sealing sulfuric acid inside a sealed container (bag) having a polyvinyl alcohol film in part, sulfuric acid required by microorganisms can be obtained without providing a pump or means for controlling the supply amount. It can be supplied slowly at all times. Of course, sulfuric acid may be supplied to the microorganisms supported on the carrier by supplying sulfuric acid to the wastewater using a pump or means for controlling the supply amount. Further, when wastewater containing sulfuric acid is treated like desulfurization wastewater discharged from a coal-fired power plant or the like, supply of sulfuric acid is not necessary. As described above, when the sulfuric acid contained in the wastewater is used, the cost for supplying sulfuric acid can be greatly reduced, and the sulfuric acid concentration in the wastewater can also be lowered.

Examples of insoluble heavy metals that can be insolubilized by hydrogen sulfide include selenious acid (SeO ₃ ²⁻ ), copper (Cu), silver (Ag), lead (Pb), and cadmium that are present in the form of cations. (Cd), mercury (Hg), tin (Sn), nickel (Ni), cobalt (Co), iron (Fe), zinc (Zn), manganese (Mn), aluminum (Al) and the like.

  Here, not only selenious acid but also selenic acid may be dissolved in the waste water. In particular, desulfurization effluent discharged from coal-fired power plants and the like often contains selenic acid and selenous acid derived from coal. However, although selenious acid can be insolubilized with hydrogen sulfide, selenic acid cannot be insolubilized with hydrogen sulfide.

  Therefore, in the wastewater treatment method of the present invention, a selenate-reducing microorganism (hereinafter referred to as 4C-C strain) belonging to the genus Pseudomonas that is entrusted with the deposit number FERM P-20840 is used in combination with the HT-1 strain. I am doing so. The 4C-C strain was entrusted to the National Institute of Advanced Industrial Science and Technology Patent Biological Deposit Center on March 13, 2006. Selenic acid was sublimated in an anaerobic environment using lower alcohols such as ethanol as an energy source. It is a known microorganism having a function of reducing to selenate (Electric Power Central Laboratory Report V06017 (2007), Eng. Life Sci. 7: p235-240 (2007)). Note that this microorganism has a function of reducing selenious acid to insoluble selenium, although only a few.

  Therefore, selenic acid contained in the water-soluble selenium-containing wastewater can be reduced to selenious acid by the 4C-C strain. Then, by contacting the hydrogen sulfide produced by the HT-1 strain with the water-soluble selenium-containing wastewater, not only selenite originally contained in the water-soluble selenium-containing wastewater but also selenate by the 4C-C strain The selenious acid produced by reduction can also be converted to insoluble selenium. That is, biological wastewater treatment in which all the chemical forms (selenate and selenite) of water-soluble selenium dissolved in wastewater are insoluble selenium by using both the 4C-C strain and the HT-1 strain. Can be realized.

  Here, the wastewater treatment using the 4C-C strain and the wastewater treatment using the HT-1 strain may be performed in separate wastewater treatment tanks, but are preferably performed in the same wastewater treatment tank. . The 4C-C strain and the HT-1 strain have a common property that their functions are exhibited in an anaerobic environment using a lower alcohol as an energy source. Further, even when sulfuric acid is present in the treatment tank, for example, when a high concentration of 500 mg / L sulfuric acid is present, the function of the 4C-C strain is not inhibited. Furthermore, even if 4C-C strain and HT-1 strain coexist, either activity or survival is not inhibited. Therefore, the 4C-C strain and the HT-1 strain are coexisted in the same waste water treatment tank, and both the 4C-C strain and the HT-1 strain are simultaneously supplied by supplying lower alcohol and sulfuric acid in an anaerobic environment. It can be made to function, and the process which makes water-soluble selenium insoluble selenium can be completed in the same waste water treatment tank.

  By the way, desulfurization effluent discharged from a coal-fired power plant or the like may contain not only coal-derived water-soluble selenium but also high-concentration nitrate nitrogen such as nitric acid and nitrous acid. According to the experiments by the inventors of the present application, the wastewater containing 100 mg-N / L of nitric acid is obtained by performing wastewater treatment by coexisting 4C-C strain and HT-1 strain in the same wastewater treatment tank. However, it was confirmed that water-soluble selenium can be converted into insoluble selenium, but the treatment speed was lower than that in the case of treating wastewater not containing nitric acid.

  Therefore, in the wastewater treatment method of the present invention, in addition to the 4C-C strain and the HT-1 strain, Paracoccus denitrificans (hereinafter referred to as Pd strain) is contained in the same wastewater treatment tank. It is preferable to make it coexist.

  The Pd strain has a function of reducing selenous acid to insoluble selenium in an anaerobic environment using a lower alcohol such as ethanol as an energy source, and a function of reducing nitric acid and nitrous acid to nitrogen gas. It is a microorganism (Electric Power Central Research Institute Report V06017 (2007), Eng. Life Sci. 7: p235-240 (2007)).

  That is, the Pd strain has the common property of exhibiting its function in an anaerobic environment using a lower alcohol as an energy source, like the 4C-C strain and the HT-1 strain. Further, even when sulfuric acid is present in the treatment tank, for example, even when sulfuric acid having a high concentration of 500 mg / L is present, the function of the Pd strain is not inhibited. Furthermore, even when the 4C-C strain and the HT-1 strain coexist with the Pd strain, the activity and survival of any of these microorganisms are not inhibited.

  In addition to the 4C-C strain and the HT-1 strain, the P-d strain coexists in the same wastewater treatment tank, so that high concentration nitrate nitrogen, for example, 100 mg-N / L nitric acid is contained in the wastewater. Even in the case where it is contained, water-soluble selenium can be converted into insoluble selenium at a treatment rate substantially the same as the case of treating wastewater not containing nitric acid. Therefore, it is possible to efficiently insolubilize water-soluble selenium contained in the wastewater of coal-fired power plants that may contain a large amount of nitrate nitrogen such as nitric acid and nitrous acid.

  The HT-1 strain, 4C-C strain, and Pd strain are microorganisms that exhibit their functions in an anaerobic environment, that is, in an environment where dissolved oxygen is not substantially present in the waste water. Therefore, the function of these microorganisms may be reduced due to the dissolved oxygen concentration in the waste water. In such a case, an inert gas such as nitrogen gas or rare gas may be introduced into the waste water to reduce the dissolved oxygen concentration.

  Further, in order to maintain the anaerobic environment of the wastewater for a long period of time, an oxygen absorbing device filled with an oxygen absorbing substance may be immersed in the wastewater in a sealed container having a non-porous membrane in part ( International Publication 2006/135028). 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.

  It should be noted that the Pd strain may lose its function or die if the concentration of lower alcohol in the wastewater is 4% by volume or more (Electric Power Research Laboratory Report V06023 (2007)). Moreover, about HT-1 stock | strain and 4C-C stock | strain, when the lower alcohol concentration in waste_water | drain is raised too much, there exists a possibility that the function may not be exhibited or it may die. Therefore, the alcohol concentration in the waste water is preferably less than 4% by volume.

  Here, when the wastewater treatment is performed using the microorganisms, the microorganisms may be released (suspended) in the wastewater treatment tank, but it is preferable that the microorganisms be supported on a carrier and used for wastewater treatment. . In this case, most of the insoluble heavy metal such as insoluble selenium in the waste water can be collected by being attached to the carrier. Therefore, most of the insoluble heavy metals such as insoluble selenium can be recovered from the waste water by simply removing the carrier from the treated waste water. Therefore, the trouble of performing solid-liquid separation treatment of insoluble heavy metals such as insoluble selenium from waste water can be saved.

  The carrier carries at least the HT-1 strain. As a result, insoluble heavy metals such as insoluble selenium can be recovered by adhering to the carrier. And by carrying | supporting 4C-C strain | stump | stock in addition to HT-1 stock | strain, all the chemical forms (selenic acid and selenious acid) of the water-soluble selenium in waste_water | drain are made to adhere to a support | carrier as insoluble selenium, and are collect | recovered. It becomes possible. Furthermore, in addition to the HT-1 and 4C-C strains, all of the water-soluble selenium in the wastewater can be treated even when treating wastewater containing a high concentration of nitrate nitrogen by supporting the Pd strain. The chemical forms (selenic acid and selenious acid) can be efficiently attached to the carrier as insoluble selenium and recovered. However, from the viewpoint of improving the simplicity of wastewater treatment, it is preferable that microorganisms other than the HT-1 strain are supported on the carrier, but microorganisms other than the HT-1 strain need not necessarily be supported on the carrier. You may make it suspend in.

  As the carrier, for example, activated carbon, alumina, foamed plastic, polymer gel, and the like can be used, and the use of polymer gel is particularly preferable. The polymer gel is particularly easy to fix microorganisms and to adhere insoluble heavy metals such as insoluble selenium. Examples of the polymer gel include natural polymers such as collagen, fibrin, albumin, casein, cellulose fiber, cellulose triacetate, agar, calcium alginate, carrageenan, agarose, polyacrylamide, poly-2-hydroxyethyl methacrylic acid, polyvinyl Synthetic polymers such as chloride, γ-methylpolyglutamic acid, polystyrene, polyvinylpyrrolidone, polydimethylacrylamide, polyurethane, photocurable resins (polyvinyl alcohol derivatives, polyethylene glycol derivatives, polypropylene glycol derivatives, polybutadiene derivatives, etc.), or composites thereof The body is mentioned. It is also possible to use a water-absorbing polymer. When a water-absorbing polymer is used, wastewater is more easily absorbed than when a polymer gel is used, and water-soluble selenium 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 shape of the carrier is not particularly limited, but it is preferable to increase the surface area as much as possible to increase the contact area with the waste water, thereby improving the waste water treatment efficiency.

  Here, insoluble selenium is a substance exhibiting a pink color, and the adhesion state of the insoluble selenium to the carrier can be easily confirmed visually. Therefore, if the bioreactor is sufficiently colored and taken out from the wastewater, water-soluble selenium can be easily recovered from the wastewater as insoluble selenium.

  In addition, by using a carrier carrying microorganisms, insoluble heavy metals such as insoluble selenium can be recovered by adhering to the carrier even in an environment where precipitation is difficult to collect, for example, in activated sludge. That is, by using a carrier carrying microorganisms, it is possible to recover the environment by collecting insoluble heavy metals such as insoluble selenium very easily without selecting a place.

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

  Here, a preferred embodiment of a bioreactor having a carrier carrying at least the HT-1 strain will be described below.

  FIG. 1 shows an embodiment of the bioreactor of the present invention. In this bioreactor 1, a carrier 2 carrying at least the HT-1 strain is applied and fixed on a nonwoven fabric 3, the nonwoven fabric 3 is formed into a bag shape on the surface side, and lower alcohol as an energy source is supplied from the internal space 4. Like to do. Here, the configuration of the bioreactor 1 is not limited to a form in which the nonwoven fabric 3 is provided only on the outer surface of the bag, and may be a form in which the nonwoven fabric 3 is provided only on the inner surface of the bag. And on the inner surface. Further, the strength of the bioreactor 1 may be improved by a rigid frame or the like, or a nylon net may be used instead of the nonwoven fabric 3 to protect the surface of the bioreactor 1. However, it is not essential to provide a protective material such as the nonwoven fabric 3 on the surface of the bioreactor 1.

  The method for supplying the energy source from the internal space 4 is not particularly limited, but may be implemented using the technology disclosed in the above-mentioned International Publication 2006/135028 or the Central Research Institute Report V06023 (2007). preferable. That is, a lower alcohol 12 such as ethanol is sealed in a sealed container (bag) 10 having a non-porous film 11 such as a polyethylene film, a polypropylene film or a polyvinyl alcohol film in part, so that a pump and a supply amount Therefore, the lower alcohol 12 required by the microorganism can be always slowly supplied without providing a means for controlling the above. Therefore, as shown in FIG. 1, the container (bag) 10 is accommodated in the internal space 4 of the bioreactor 1, so that the lower alcohol 12 is always loosened to the microorganism (HT-1 strain) carried on the carrier 2. Can be supplied to.

  The method for supplying sulfuric acid as a hydrogen sulfide generation source is not particularly limited, but it is preferable to use the technique disclosed in the above-mentioned International Publication 2006/135028. That is, by sealing sulfuric acid inside a sealed container (bag) having a polyvinyl alcohol film in part, the sulfuric acid required by microorganisms can be gradually and gradually reduced without providing a pump or means for controlling the supply amount. Can be supplied. Therefore, by accommodating this container (bag) in the internal space 4 of the bioreactor 1, sulfuric acid can always be gradually supplied to the microorganism (HT-1 strain) supported on the carrier. Of course, when wastewater containing sulfuric acid is treated, it is not necessary to supply sulfuric acid.

  The bioreactor 1 configured as described above is immersed in waste water, or placed in an environment containing a water-soluble heavy metal such as water-soluble selenium to create an anaerobic environment, whereby the carrier 2 of the bioreactor 1 and further the nonwoven fabric Insoluble heavy metals such as insoluble selenium can be attached to 3 and recovered. Then, by removing the bioreactor 1 after collecting insoluble heavy metals such as insoluble selenium, the environment can be purified by reducing the concentration of heavy metals such as selenium.

  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 gist of the present invention. For example, the HT-1 strain and the Pd strain may be used together in the same treatment tank. When selenate is not included in the wastewater, even if HT-1 strain and Pd strain are used together in the same treatment tank, even if the drainage contains high concentration of nitrate nitrogen, It becomes possible to efficiently treat water-soluble heavy metals as insoluble heavy metals.

  Moreover, you may make it utilize strains other than 4C-C strain | stump | stock as a selenate reducing microorganism. That is, as in the 4C-C strain, a known or novel microorganism having a function of reducing selenate to selenite in an anaerobic environment using a lower alcohol such as ethanol as an energy source may be used. Further, known or novel microorganisms having a function of reducing selenate to selenite in an anaerobic environment using yeast extract, sulfur-containing amino acid, lactate, etc. as an energy source, such as Azoaculus, Pseudomonas, Paracoccus, Delayer You may make it utilize microorganisms, such as a genus, Bacillus genus, and Enterobacter genus.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Analysis method)
In the examples described below, the concentrations of sulfuric acid, selenic acid, selenious acid, nitric acid and nitrous acid were measured using an AS9-HC column and an ion chromatograph analyzer (ICS-1500, DIONEX).

(1) Examination of chemical reactivity between hydrogen sulfide and water-soluble selenium The chemical reactivity between hydrogen sulfide and water-soluble selenium was examined.

  Hydrogen sulfide was generated as follows. That is, 0.4 g of iron sulfide and 1 mL of 2N hydrochloric acid were enclosed in a bag (length: 50 mm, width: 30 mm) of a 0.05 mm thick polyethylene film (Mitsuwa Co., Ltd.). . As a result, iron sulfide and hydrochloric acid were reacted inside the bag to generate iron chloride and hydrogen sulfide, and the hydrogen sulfide was permeated from the polyethylene film and supplied to the outside of the bag.

  The polyethylene bag was put into a 200 mL tall beaker containing a 100 mg-Se / L selenate aqueous solution and a 200 mL tall beaker containing a 100 mg-Se / L selenious aqueous solution, respectively. After introducing the polyethylene bag, the aqueous solution in the tall beaker was continuously stirred at 20 ° C. for 18 hours, and a sample was collected over time to analyze the chemistry of hydrogen sulfide and water-soluble selenium (selenic acid, selenious acid). Responsiveness was examined.

  The result of examining the chemical reactivity of selenate to hydrogen sulfide is shown in FIG. From the results shown in FIG. 2, it was confirmed that there was no change in the selenate concentration, and hydrogen sulfide and selenate did not cause a chemical reaction.

  Next, the result of examining the chemical reactivity of selenious acid to hydrogen sulfide is shown in FIG. From the results shown in FIG. 3, the selenious acid concentration rapidly decreased immediately after the introduction of the polyethylene bag, and became 24.3 mg-Se / L after 1 hour. At that time, a reddish brown precipitate was observed in the aqueous solution.

  From the above results, it became clear that selenite dissolved in water can be precipitated (insolubilized) with hydrogen sulfide. On the other hand, it became clear that selenic acid dissolved in water cannot be precipitated by hydrogen sulfide.

(2) Search for new microorganisms From the experimental results of (1) above, it was revealed that selenite can be precipitated by hydrogen sulfide. Therefore, a search was made for a novel microorganism capable of producing hydrogen sulfide by sulfuric acid reduction and using an inexpensive lower alcohol as an energy source.

  Eight types of sludge from wastewater treatment facilities were used as the source of microorganism isolation. 20 mL of a medium containing sulfuric acid shown in Table 1 was placed in a 50 mL glass vial, and 1 mL of a sludge sample was added thereto. Moreover, 0.2 mL of ethanol (99.5%) was added as a sole energy source. The vial was made anaerobic using nitrogen gas and then shaken at 30 ° C. and 120 rpm for 17 days of enrichment culture. By this operation, a novel microorganism capable of sulfate reduction using ethanol as an energy source was searched.

  Judgment whether or not sulfuric acid reduction was performed in the vial was performed as follows. That is, when sulfuric acid in the medium is reduced to hydrogen sulfide, iron sulfate and hydrogen sulfide in the medium react to form black precipitates of iron sulfide, and this color change is reduced in the vial. Judgment criteria for whether or not.

As a result, it was judged that sulfate reduction was carried out in all the vials. Therefore, for the samples in all the vials, 2 mL of the culture solution was transferred to 20 mL of new medium, and further cultured under the same conditions. Continued. As a result, even after the passage of the culture solution was performed twice, it was determined that all samples were subjected to sulfate reduction. Therefore, all samples were treated with phosphate buffer (Na ₂ HPO ₄ · 12H _2). Diluted appropriately using O (9 g / L), KH ₂ PO ₄ (1.5 g / L), pH 7.5) to obtain a diluted solution.

  Next, the diluted solution was applied to the agar medium shown in Table 2, and static culture was performed for 11 days under anaerobic conditions at 30 ° C. And what reduced sulfuric acid was found in one sample among the acquired colonies. Therefore, this colony was selected, diluted and transplanted to a new agar medium and isolated, and it was confirmed that the sulfate reduction ability was maintained and that no other microorganisms were mixed. This strain was named HT-1 strain.

  After the HT-1 strain was isolated, it was confirmed by the following method whether this strain was capable of sulfate reduction using ethanol as an energy source. That is, the HT-1 strain was added to a liquid medium containing sulfuric acid shown in Table 1 to examine whether or not black precipitation of iron sulfide occurred. As a result, a black precipitate of iron sulfide was generated, and it was revealed that the HT-1 strain can be sulfate-reduced using ethanol.

  Next, the morphology of the HT-1 strain was observed with an optical microscope. Further, physiological characteristics were examined based on the method of Barrow et al. (Barrow G L, Feltham R K .: Cowan and Steel's manual for the Identification of Medical Bacteria, 3rd ed., Cambridge University Press. (1993)). For 16S rDNA base sequence analysis, DNA was extracted by a conventional method, followed by PCR and sequencing.

  Table 3 shows the morphological and physiological characteristics of the HT-1 strain. The HT-1 strain was a gram-negative and gonococcal curved gonococcus. Based on these results and 16S rDNA nucleotide sequence analysis results, Kriig et al. (Krieg NR, Holt JG: Bergey's Mannual of Systematic Bacteriology: Volume One. Williams and Wilkins, Baltimopre. (1984)) Identified as Desulfovibrio sp.

  The HT-1 strain was deposited with the Patent Microorganism Depositary, National Institute of Advanced Industrial Science and Technology under the accession number FERM P-21577 on May 21, 2008.

  In addition, since it was confirmed that HT-1 strain functions as an energy source, ethanol is a lower alcohol similar in structure to ethanol, particularly methanol and propanol having only one carbon number different from ethanol. Can also be used as an energy source.

(3) Pre-culture and preparation of the test strain The HT-1 strain used in the subsequent experiments and the inventor of the present application to the National Institute of Advanced Industrial Science and Technology Patent Organism Depositary on March 13, 2006 Pre-culture and preparation of Pseudomonas sp. (4C-C strain) commissioned as FERM P-20840 was performed.

  Pre-culture of the HT-1 strain was performed by anaerobically shaking at 30 ° C. and 120 rpm using the liquid medium shown in Table 4.

  The preculture of the 4C-C strain was carried out by aerobically shaking at 30 ° C. and 30 rpm using the liquid medium shown in Table 5.

After incubation, the cells were collected by centrifugation (20,000 g, 4 ° C., 10 minutes), and phosphate buffer (Na ₂ HPO ₄ · 12H ₂ O (9 g / L), KH ₂ PO ₄ (1.5 g) was collected. / L), pH 7.5). The washed cells of the HT-1 strain and the 4C-C strain were each suspended in a phosphate buffer and used for the subsequent experiments.

(4) Examination of characteristics of HT-1 strain The HT-1 strain was examined for the presence or absence of reducing ability for various anions.

  30 mL of artificial waste water shown in Table 6 is placed in a 50 mL glass vial, and 20 mg / L sulfuric acid, 20 mg-Se / L selenic acid, 20 mg-Se / L selenious acid, 20 mg-N / L nitric acid. , 20 mg-N / L nitrous acid was added to each sample. Next, the HT-1 strain prepared in (3) above was added to each sample so as to be 0.415 mg-wet weight / mL, and 0.3 mL of ethanol was added as an energy source. After making the inside of a vial anaerobic using nitrogen gas, it was cultured with shaking at 30 ° C. and 120 rpm for 14 days, and various anion concentrations were analyzed.

  Table 7 shows the presence or absence of reducing ability of the HT-1 strain for various anions. In Table 7, ++ means having a reducing ability, + means having a reducing ability slightly, and-means not having a reducing ability.

  The sulfuric acid concentration was below the detection limit after 14 days. From this, it was shown that the HT-1 strain can be sulfate-reduced using ethanol as an energy source.

  Regarding selenite concentration, a decrease of 2.4 mg-Se / L was observed after 14 days. From this, it became clear that the HT-1 strain can reduce selenite by using ethanol as an energy source.

  For selenic acid, nitric acid and nitrous acid, almost no change in concentration was observed. This revealed that the HT-1 strain does not have the ability to reduce selenate, nitric acid and nitrous acid.

(5) Examination of selenite treatment using HT-1 strain The selenite treatment in a state where the HT-1 strain was suspended in artificial waste water was examined.

  30 mL of artificial waste water shown in Table 6 is placed in a 50 mL glass vial, a sample added with 10 mg-Se / L selenious acid, a sample added with 500 mg / L sulfuric acid, and 10 mg-Se / L A sample to which selenious acid and 500 mg / L sulfuric acid were added was prepared. To each of these samples, the HT-1 strain prepared in (3) above was added to 0.77 mg-wet weight / mL, and 0.3 mL of ethanol was added as an energy source. After making the inside of the vial anaerobic using nitrogen gas, it was cultured with shaking at 30 ° C. and 120 rpm for 8 days, samples were collected over time, and various anion concentrations were analyzed.

  FIG. 4 shows the change over time in the sulfuric acid concentration of each sample. In FIG. 4, □ is the result when a sample obtained by adding 10 mg-Se / L selenious acid to artificial wastewater, and Δ is the result obtained when a sample obtained by adding 500 mg / L sulfuric acid to artificial wastewater. The results are as follows. The black circles are the results when a sample obtained by adding 10 mg-Se / L selenious acid and 500 mg / L sulfuric acid to artificial waste water is used. It was confirmed that the sulfuric acid concentration gradually decreased in both the artificial drainage sample to which only sulfuric acid was added and the artificial drainage sample to which sulfuric acid and selenious acid were added.

  Next, the time-dependent change of the selenite concentration of each sample is shown in FIG. In FIG. 5, the meanings of □, Δ, and ● are the same as those in FIG. In the artificial drainage sample to which sulfuric acid and selenious acid were added, it was confirmed that the selenious acid concentration was below the detection limit after 21 hours. The artificial drainage sample to which only selenite was added also showed a slight decrease in concentration due to the ability of HT-1 strain to reduce selenite at the beginning of the experiment, but after that, the concentration was almost constant. It was. From this result, in the case of an artificial drainage sample to which sulfuric acid and selenious acid were added, hydrogen sulfide produced by reducing sulfuric acid by the HT-1 strain reacted with selenious acid to form insoluble selenium, and the selenite concentration Was thought to have declined.

  From the above results, it became clear that sulfuric acid in artificial wastewater can be reduced by using HT-1 strain and using ethanol as an energy source. And it became clear that selenious acid can be treated as insoluble selenium by hydrogen sulfide produced by reduction of sulfuric acid.

(6) Examination of selenate treatment by combined use of HT-1 strain and 4C-C strain 1
As revealed by the experiment (1) above, hydrogen sulfide does not react with selenate at all. Therefore, when considering the treatment of selenate, it is necessary to reduce selenate to selenite. Then, the 4C-C strain | stump | stock which is a selenate reducing microorganism which reduces selenic acid to selenious acid was used together with HT-1 strain | stump | stock, and it examined about processing selenic acid as insoluble selenium.

30 mL of artificial waste water (containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid) shown in Table 8 was added to a 50 mL glass vial, and the 4C-C strain and HT prepared in (3) above were added. -1 strain was added to 0.77 mg-wet weight / mL. In addition, 0.3 mL of ethanol was added to the vial as an energy source. After making the vial bottle anaerobic using nitrogen gas, it was shaken at 30 ° C. and 120 rpm and cultured for 4 days. The experimental conditions were the following four conditions (a) to (d). After the start of culture, samples were collected over time and used for analysis.
(A) No microorganisms added (control group)
(B) Add only 4C-C strain (c) Add only HT-1 strain (d) Add both 4C-C strain and HT-1 strain

  FIG. 6 shows the change over time in the selenate concentration, FIG. 7 shows the change over time in the selenite concentration, FIG. 8 shows the change over time in the total selenium concentration (total of selenate and selenite), The change with time is shown in FIG. 6 to 9, ◇ indicates the experimental result under the condition (a), Δ indicates the experimental result under the condition (b), ■ indicates the experimental result under the condition (c), and ● indicates the experimental result. The experimental result in the conditions of (d) is shown.

  From the experimental results shown in FIG. 6, when the 4C-C strain was used alone and when the 4C-C strain and the HT-1 strain were used in combination, the selenate concentration decreased with time and was detected after 24 hours. It was confirmed that it was below the limit. On the other hand, it was confirmed that the selenate concentration did not change when the microorganism was not added and when the HT-1 strain was used alone.

  From the experimental results shown in FIG. 7, it was confirmed that selenite was not detected when the microorganism was not added and when the HT-1 strain was used alone. Further, it was confirmed that selenite was not detected even when the 4C-C strain and the HT-1 strain were used in combination. On the other hand, when the 4C-C strain was used alone, it was confirmed that the selenite concentration increased to 8.6 mg-Se / L after 24 hours, and thereafter kept almost constant. That is, it was confirmed that the 4C-C strain has the ability to reduce selenate to selenite.

  From the experimental results shown in FIG. 8, when the 4C-C strain and the HT-1 strain were used in combination, the total selenium concentration was below the detection limit after 24 hours. Further, in this case, it was confirmed that the artificial drainage changed to pink. On the other hand, since it was confirmed that the selenate concentration did not change when the microorganism was not added and when the HT-1 strain was used alone, there was almost no change in the total selenium concentration. Further, when the 4C-C strain was used alone, it was confirmed that the total selenium concentration became a constant value after a slight decrease due to the ability to reduce selenic acid to selenious acid.

  From the experimental results shown in FIG. 9, it was confirmed that when the 4C-C strain and the HT-1 strain were used in combination, the sulfuric acid concentration decreased with time and decreased to 14.1 mg / L after 96 hours. On the other hand, it was confirmed that the sulfuric acid concentration was almost constant except when the 4C-C strain and the HT-1 strain were used in combination. In addition, it was thought that the reason why the sulfate reduction activity was not observed in the case of HT-1 strain alone was that sulfate reduction was inhibited by selenate in the artificial waste water.

  From the above results, when the 4C-C strain and the HT-1 strain were used in combination, selenite produced as a result of selenate reduction by the 4C-C strain was generated as a result of sulfate reduction by the HT-1 strain. It was clarified that the total selenium concentration in artificial wastewater can be made below the detection limit by reacting with hydrogen sulfide which has been formed to become insoluble selenium.

  Moreover, since it became clear that the total selenium concentration in artificial waste water can be made below the detection limit by using 4C-C strain and HT-1 strain together, these strains inhibit each other's survival. It became clear that there was nothing to do. Furthermore, it was also revealed that the 4C-C strain functions sufficiently even in a harsh environment where sulfuric acid is present at a high concentration.

  Next, Paracoccus denitrificans JCM-6892 strain (Pd strain), which is a microorganism that reduces selenite to insoluble selenium even in an environment where nitrate nitrogen and sulfuric acid are present in high concentrations using ethanol as an energy source, The same experiment was carried out in place of the -1 strain, and the treatment rate of water-soluble selenium when the 4C-C strain and the HT-1 strain were used in combination, and the 4C-C strain and the Pd strain were used in combination. We compared the processing rate of water-soluble selenium with this method. The details of the function of the Pd strain are reported in the following documents (Electric Power Research Center Report V06017 (2007), Eng. Life Sci. 7: 235-240 (2007)).

  Here, in determining the processing rate of water-soluble selenium, the time required for water-soluble selenium in artificial wastewater to reach below the detection limit and the amount of initial water-soluble selenium in artificial wastewater, Calculated as value.

  As a result, compared with the case where the 4C-C strain and the Pd strain were used in combination, when the 4C-C strain and the HT-1 strain were used in combination, the water-soluble selenium treatment rate was 5.6 times. It was confirmed that That is, it was confirmed that the treatment speed of water-soluble selenium is improved when the 4C-C strain and the HT-1 strain are used in combination, compared with the case where the 4C-C strain and the Pd strain are used together. It was.

  In addition, when the 4C-C strain and the HT-1 strain were used in combination, selenate fell below the detection limit within 24 hours, and no selenite accumulation was observed. From this, it was clarified that when 4C-C strain and HT-1 strain were used in combination, the process of converting selenious acid to insoluble selenium was not the rate-limiting step. On the other hand, when the 4C-C strain and the Pd strain were used in combination, selenite accumulation was observed, and the process from selenite to insoluble selenium is considered to be the rate-limiting step. It was. Therefore, it was considered that the difference in the processing rate of water-soluble selenium mainly arises from the difference in whether or not the process of converting selenious acid to insoluble selenium is in the rate-limiting step.

  As described above, it has been clarified that by using the 4C-C strain and the HT-1 strain in combination, selenate can be converted into insoluble selenium via ethanol and selenite as an energy source. Moreover, since the process of producing insoluble selenium from selenious acid is not the rate-determining step, it has been clarified that the treatment rate can be sufficiently high.

(7) Examination of selenate treatment by combined use of HT-1 strain and 4C-C strain 2
As is clear from the experiment of (6) above, it was possible to treat water-soluble selenium as insoluble selenium by using the 4C-C strain and the HT-1 strain together. However, in the experiment of (6) above, since the 4C-C strain and the HT-1 strain were suspended in the artificial wastewater, the microorganisms and insoluble selenium were in a state of being mixed in the artificial wastewater. When considering an actual wastewater treatment process, it is desirable to establish a method for efficiently removing insoluble selenium from wastewater. Then, about the simplification of the collection | recovery process of insoluble selenium, examination of the selenic acid process in the state fixed to the support | carrier by using together 4C-C strain and HT-1 strain was performed.

The microorganisms were fixed as follows. Both the 4C-C strain and the HT-1 strain prepared in (3) above were applied to a nonwoven fabric made of polyethylene terephthalate (G2260-1S, Toray Industries, Inc.) processed into an envelope shape (length: 40 mm, width: 20 mm). The mixed polymer gel was applied to a thickness of 0.7 mm. As the polymer gel, a mixture of a microbial suspension and a photocurable resin PVA-SbQ (SPP-H-13, Toyo Gosei Co., Ltd.) in a ratio of 1: 3 was used. In order to cure the polymer gel, light irradiation (1,000 μmol / m ² / s) for 20 minutes was performed using a metal halide lamp (MT-250DL, Iwasaki Electric Co., Ltd.). During light irradiation, the polymer gel was ice-cooled to prevent inactivation of microorganisms by heat. The polymer gel was applied and cured on each side of the nonwoven fabric processed into an envelope shape.

  An envelope-type non-woven fabric has a void that can be filled with an energy source of microorganisms. A polyethylene film having a thickness of 0.05 mm processed into a bag shape was sealed with 0.3 mL of 99.5% ethanol as an energy source, and the polyethylene bag was sealed in an envelope-type nonwoven fabric. Ethanol sealed inside the polyethylene film is gradually released and oozes out into an envelope-type non-woven fabric to be supplied as an energy source to microorganisms fixed to the polymer gel (International Publication 2006/135028, Electric Power). Central Research Institute Report V06023 (2007)).

30 mL of artificial waste water (containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid) shown in Table 8 was added to a 50 mL glass vial, and the above envelope-type nonwoven fabric was charged. The 4C-C strain and the HT-1 strain prepared in the above (3) were fixed to the polymer gel so as to be 0.77 mg-wet weight / mL in terms of the concentration in the artificial waste water. After making the vial bottle anaerobic using nitrogen gas, it was shaken at 30 ° C. and 120 rpm and cultured for 5 days. The experimental conditions were the following four conditions (a) to (d). After the start of culture, samples were collected over time and used for analysis.
(A) No addition of microorganism with polymer gel only (control group)
(B) Fix only 4C-C strain (c) Fix only HT-1 strain (d) Fix both 4C-C strain and HT-1 strain

  The time course of the selenic acid concentration is shown in FIG. 10, the time course of the selenite concentration is shown in FIG. 11, the time course of the total selenium concentration (the sum of selenate and selenite) is shown in FIG. The change with time is shown in FIG. 10 to 13, ◇ indicates the experimental result under the condition (a), Δ indicates the experimental result under the condition (b), ■ indicates the experimental result under the condition (c), and ● indicates the experimental result. The experimental result in the conditions of (d) is shown.

  From the experimental results shown in FIG. 10, when the 4C-C strain was used alone and when the 4C-C strain and the HT-1 strain were used in combination, the selenate concentration decreased with time, and the 4C-C strain was When used alone, it was confirmed that it was below the detection limit after 44 hours, and when it was used together with the 4C-C strain and the HT-1 strain, it was below the detection limit after 20 hours. On the other hand, it was confirmed that the selenate concentration did not change when the microorganism was not added and when the HT-1 strain was used alone.

  From the experimental results shown in FIG. 11, it was confirmed that selenite was not detected when the microorganism was not added and when the HT-1 strain was used alone. In contrast, it was confirmed that selenite was detected when the 4C-C strain and the HT-1 strain were used in combination and when the 4C-C strain was used alone. In the case where the 4C-C strain and the HT-1 strain were used in combination, the strain increased to 4.7 mg-Se / L after 20 hours, but then decreased and became below the detection limit after 44 hours. In the case where the 4C-C strain was used alone, it was confirmed that the selenite concentration increased up to 44 hours and became 8.4 mg-Se / L, and thereafter became almost constant. That is, it was confirmed that the 4C-C strain exhibited the ability to reduce selenate to selenite even in a state where it was fixed to the polymer gel.

  From the experimental results shown in FIG. 12, it was confirmed that when the 4C-C strain and the HT-1 strain were used in combination, the total selenium concentration gradually decreased with time and became below the detection limit after 44 hours. In addition, when the 4C-C strain and the HT-1 strain are used in combination (when both the 4C-C strain and the HT-1 strain are fixed to the polymer gel), all insoluble selenium generated in the artificial drainage is used. As shown in FIG. 14, it is confirmed that the non-woven fabric that was milky white at the start of the experiment (A) turns pink after the end of the experiment (B). It was done. At that time, no precipitation occurred in the artificial waste water. In FIG. 14, reference numeral 13 indicates a vial, and reference numeral 14 indicates artificial drainage. On the other hand, except when the 4C-C strain and the HT-1 strain were used in combination, the nonwoven fabric coated with the polymer gel remained milky white throughout the culture period. However, when the 4C-C strain was used alone, it was confirmed that the total selenium concentration reached a certain value after the total selenium concentration slightly decreased due to the ability to reduce selenic acid to selenious acid.

  From the experimental results shown in FIG. 13, when the 4C-C strain and the HT-1 strain were used in combination, the sulfuric acid concentration decreased with time and reached 235.7 mg / L after 116 hours. On the other hand, it was confirmed that the sulfuric acid concentration was almost constant except when the 4C-C strain and the HT-1 strain were used in combination. In addition, it was thought that the reason why the sulfate reduction activity was not observed in the case of HT-1 strain alone was that sulfate reduction was inhibited by selenate in the artificial waste water.

  From the above results, when the 4C-C strain and the HT-1 strain were immobilized on a carrier such as a polymer gel and used together, selenite produced as a result of selenate reduction by the 4C-C strain was -1 by reacting with hydrogen sulfide produced as a result of sulfate reduction by the strain, it becomes insoluble selenium, the total selenium concentration in the artificial wastewater can be below the detection limit, and insoluble selenium can be recovered by adhering to the carrier It became clear.

  Moreover, since it became clear that the total selenium concentration in artificial waste water can be made below the detection limit by immobilizing the 4C-C strain and the HT-1 strain on a carrier such as a polymer gel and using them together, these It has also been clarified that the strains of these do not inhibit each other's survival even when immobilized on a carrier such as a polymer gel. Furthermore, it became clear that the 4C-C strain immobilized on a carrier such as a polymer gel functions sufficiently even in a harsh environment where sulfuric acid is present at a high concentration.

  Next, the same experiment was performed using ethanol as an energy source and the Pd strain instead of the HT-1 strain, and treatment of water-soluble selenium when the 4C-C strain and the HT-1 strain were used in combination. The speed and the treatment speed of the water-soluble selenium when the 4C-C strain and the Pd strain were used in combination were compared.

  The treatment rate of water-soluble selenium was calculated in the same manner as (6) above. Table 9 shows comparative data on the processing speed of water-soluble selenium obtained in the experiments (6) and (7).

  Even when the microorganisms are fixed, the treatment rate of water-soluble selenium is higher when the 4C-C strain and the HT-1 strain are used together than when the 4C-C strain and the Pd strain are used together. It was confirmed to be 4.2 times. That is, it is clear that the treatment speed of water-soluble selenium is improved when the 4C-C strain and the HT-1 strain are used in combination, compared with the case where the 4C-C strain and the Pd strain are used together. became.

  This result was the same tendency as when the microorganisms were not fixed and suspended in artificial waste water as in (6) above. However, the treatment rate of water-soluble selenium and the reduction rate of sulfuric acid were lower in the state where the microorganisms were fixed than in the suspended state. The reason was considered as follows. In other words, when microorganisms are fixed, the reaction of microorganisms does not occur unless water-soluble selenium or sulfuric acid enters the polymer gel, so the diffusion of water-soluble selenium or sulfuric acid into the polymer gel is rate limiting. Was considered.

  Here, when the 4C-C strain and the HT-1 strain are used in combination, unlike the case of the suspension state as described in (6) above, the selenium subselenium at the initial stage of the culture in the state fixed to the polymer. It was confirmed that acid accumulation was observed. That is, the process from selenious acid to insoluble selenium was the rate-limiting step. In the state where the microorganism is suspended, the solution is in a completely mixed state because stirring is performed, but in the state where the microorganism is fixed to the polymer, mass transfer is not performed inside the polymer gel. This is done only by diffusion. Therefore, with regard to selenious acid reduced from selenate by the 4C-C strain, it was considered that the rate of movement in the polymer gel by diffusion became rate-limiting.

  From the above results, even in the state where the microorganism was fixed to the polymer gel, by using the 4C-C strain and the HT-1 strain in combination, selenate was insoluble selenium via selenious acid using ethanol as an energy source. It became clear that it can be. Moreover, unlike the state in which microorganisms are suspended, when microorganisms are immobilized on a polymer gel, all insoluble selenium accumulates on the nonwoven fabric and the polymer gel coated on the nonwoven fabric, and precipitation occurs in the artificial drainage. Therefore, it was shown that the process of recovering insoluble selenium can be simplified by fixing the 4C-C strain and the HT-1 strain on a carrier such as a polymer gel.

(8) Examination of selenate treatment when nitric acid is present in artificial wastewater 1
Desulfurization effluent generated from coal-fired power plants and the like may contain high concentrations of nitrate nitrogen. Therefore, whether or not selenic acid in the wastewater can be treated even when high concentration of nitrate nitrogen is contained in the wastewater was examined.

First, an experiment was performed under the same conditions as in the above (6) except that the concentration of nitric acid in the artificial waste water was 100 mg-N / L. The addition conditions of the microorganisms were as follows, as in (6) above.
(A) No addition of microorganisms (control group)
(B) Add only 4C-C strain (c) Add only HT-1 strain (d) Add both 4C-C strain and HT-1 strain

  FIG. 15 shows the change over time in the selenate concentration, FIG. 16 shows the change over time in the selenite concentration, FIG. 17 shows the change over time in the total selenium concentration (the sum of selenate and selenite), FIG. 18 shows the change over time, FIG. 19 shows the change over time in the nitric acid concentration, FIG. 20 shows the nitrous acid concentration, and FIG. 21 shows the total nitrogen concentration (sum of nitric acid and nitrous acid). 15 to 21, □ indicates the experimental result under the condition (a), ◇ indicates the experimental result under the condition (b), ○ indicates the experimental result under the condition (c), and Δ indicates The experimental result in the conditions of (d) is shown.

  From the experimental results shown in FIG. 15, it was revealed that selenic acid can be reduced to below the detection limit after 21 hours from the culture by using the 4C-C strain and the HT-1 strain together. In addition, even when only the 4C-C strain was used, it became clear that selenate could be reduced to below the detection limit after 21 hours. However, from the experimental results shown in FIG. 16, even when the 4C-C strain and the HT-1 strain are used in combination, 332 hours may be required from the culture in order to reduce selenite to below the detection limit. It became clear. Also, from the experimental results shown in FIG. 17, it has been clarified that it takes 332 hours from the culture to reduce both selenate and selenite to below the detection limit.

  Here, as in the experiment conducted in the above (6), when nitric acid was not contained in the artificial drainage, both water-soluble selenium could be reduced to below the detection limit within 24 hours from the culture. . From this, it became clear that insoluble treatment of water-soluble selenium is hindered when nitric acid is contained in the artificial waste water. However, although the processing speed was slow, it became clear that the water-soluble selenium could be reduced below the detection limit by using the 4C-C strain and the HT-1 strain together.

  Further, from the experimental results shown in FIGS. 19 to 21, when the 4C-C strain was used alone and when the 4C-C strain and the HT-1 strain were used in combination, nitric acid and nitrous acid were within 69 hours. It became clear that it fell below the detection limit and reduced to nitrogen. From this, it was confirmed that the 4C-C strain has nitric acid and nitrite reducing ability.

  Next, additional experiments were conducted under the same experimental conditions as described above for the case where the Pd strain was used alone and for the case where the 4C-C strain, the HT-1 strain and the Pd strain were used in combination.

FIG. 22 shows the change over time in the selenate concentration, FIG. 23 shows the change over time in the selenite concentration, FIG. 24 shows the change over time in the total selenium concentration (total of selenate and selenite), FIG. 25 shows the change over time, FIG. 26 shows the change over time in the nitric acid concentration, FIG. 27 shows the nitrous acid concentration, and FIG. 28 shows the total nitrogen concentration (sum of nitric acid and nitrous acid). The experimental conditions for obtaining the results shown in FIGS. 22 to 28 are the following (a) to (e), □ indicates the experimental results under the conditions (a), and ◇ indicates the conditions under the conditions (b). The experimental results are shown, ◯ shows the experimental results under the condition (c), x shows the experimental results under the condition (d), and Δ shows the experimental results under the condition (e).
(A) No microorganisms added (control group)
(B) Add only 4C-C strain (c) Add only Pd strain (d) Add only HT-1 strain (e) Add 4C-C strain, HT-1 strain and Pd strain

  From the experimental results shown in FIG. 22, it was clarified that selenic acid can be reduced to below the detection limit after 24 hours from the culture by using the Pd strain in addition to the 4C-C strain and the HT-1 strain. . In addition, from the experimental results shown in FIG. 23, selenite was not detected by using the Pd strain in combination with the 4C-C strain and the HT-1 strain, and from the experimental results shown in FIG. It was found that both selenite and selenious acid can be reduced to below the detection limit within 24 hours.

  Further, from the experimental results shown in FIGS. 26 to 28, nitric acid and nitrous acid were used when the Pd strain was used alone and when the 4C-C strain, the HT-1 strain and the Pd strain were used in combination. Was reduced to below the detection limit within 24 hours and reduced to nitrogen.

  From the above results, by using the Pd strain in addition to the 4C-C strain and the HT-1 strain, nitric acid is present in the wastewater even in an environment where nitric acid is present at a high concentration in the wastewater. It was revealed that water-soluble selenium can be insolubilized at a treatment rate equivalent to that of the case where it is not.

(9) Study of selenate treatment when nitric acid is present in artificial wastewater 2
As clarified in the experiment of (8) above, by using the 4C-C strain, the HT-1 strain, and the Pd strain in combination, in an environment where nitric acid is present at a high concentration in the wastewater. In addition, it was possible to efficiently treat water-soluble selenium as insoluble selenium. However, since the 4C-C strain, the HT-1 strain, and the Pd strain were suspended in the artificial drainage in the experiment of (8) above, the microorganisms and the insoluble selenium were mixed in the artificial drainage. Met. Therefore, in order to simplify the process for recovering insoluble selenium, nitric acid is present in high concentration in the wastewater in a state where the 4C-C strain, the HT-1 strain, and the P-d strain are combined and fixed to the carrier. Whether or not selenic acid treatment was possible was also examined in the environment.

First, an experiment was performed under the same conditions as in the above (7) except that the concentration of nitric acid in the artificial waste water was 100 mg-N / L. The addition conditions of the microorganisms were as follows as in (7) above.
(A) No addition of microorganism with polymer gel only (control group)
(B) Fix only 4C-C strain (c) Fix only HT-1 strain (d) Fix both 4C-C strain and HT-1 strain

  FIG. 29 shows the change over time in the selenate concentration, FIG. 30 shows the change over time in the selenite concentration, FIG. 31 shows the change over time in the total selenium concentration (the sum of selenate and selenite), FIG. 32 shows the change with time, FIG. 33 shows the change with time of the nitric acid concentration, FIG. 34 shows the nitrous acid concentration, and FIG. 35 shows the total nitrogen concentration (sum of nitric acid and nitrous acid). 29 to 35, □ indicates the experimental result under the condition (a), ◇ indicates the experimental result under the condition (b), ○ indicates the experimental result under the condition (c), and Δ indicates The experimental result in the conditions of (d) is shown.

  From the experimental results shown in FIG. 29, it was revealed that selenate can be reduced to the detection limit or less after 20 hours from the culture by using the 4C-C strain and the HT-1 strain together. In addition, even when only the 4C-C strain was used, it became clear that selenic acid could be reduced below the detection limit after 20 hours. However, from the experimental results shown in FIG. 30, even when the 4C-C strain and the HT-1 strain are used in combination, 332 hours may be required from the culture in order to reduce selenite to below the detection limit. It became clear. In addition, from the experimental results shown in FIG. 31, it has become clear that 332 hours are required from the culture in order to reduce both selenate and selenite to below the detection limit.

  Here, as in the experiment conducted in the above (7), when nitric acid was not contained in the artificial drainage, both water-soluble selenium could be reduced to below the detection limit within 44 hours from the culture. . From this, it became clear that insoluble treatment of water-soluble selenium is hindered when nitric acid is contained in the artificial waste water. However, although the processing speed was slow, it became clear that the water-soluble selenium could be reduced below the detection limit by using the 4C-C strain and the HT-1 strain together.

  In addition, from the experimental results shown in FIGS. 33 to 35, when the 4C-C strain was used alone and when the 4C-C strain and the HT-1 strain were used in combination, nitric acid and nitrous acid were within 116 hours. It became clear that it fell below the detection limit and reduced to nitrogen. From this, it was confirmed that the 4C-C strain exhibited the ability to reduce nitric acid and nitrite even in a state where the 4C-C strain was fixed to a carrier such as a polymer gel.

  Next, additional experiments were conducted under the same experimental conditions as described above for the case where the Pd strain was used alone and for the case where the 4C-C strain, the HT-1 strain and the Pd strain were used in combination.

The time course of the selenate concentration is shown in FIG. 36, the time course of the selenite concentration is shown in FIG. 37, the time course of the total selenium concentration (the sum of selenate and selenite) is shown in FIG. FIG. 39 shows the change with time, FIG. 40 shows the change with time of the nitric acid concentration, FIG. 41 shows the nitrous acid concentration, and FIG. 42 shows the total nitrogen concentration (sum of nitric acid and nitrous acid). The experimental conditions for obtaining the results shown in FIGS. 36 to 42 are the following (a) to (e), □ indicates the experimental results under the conditions (a), and ◇ indicates the conditions under the conditions (b). The experimental results are shown, ◯ shows the experimental results under the condition (c), x shows the experimental results under the condition (d), and Δ shows the experimental results under the condition (e).
(A) No addition of microorganism with polymer gel only (control group)
(B) Fix 4C-C strain only (c) Fix Pd strain only (d) Fix HT-1 strain only (e) Fix 4C-C strain, HT-1 strain and Pd strain

  From the experimental results shown in FIG. 36, it was revealed that by using the Pd strain in combination with the 4C-C strain and the HT-1 strain, selenic acid can be reduced below the detection limit after 20 hours from the culture. . Moreover, from the experimental results shown in FIG. 37, by using the Pd strain in addition to the 4C-C strain and the HT-1 strain, the selenite concentration becomes below the detection limit after 116 hours from the culture. From the experimental results shown in (2), it was revealed that both selenic acid and selenious acid can be reduced to below the detection limit within 116 hours.

  Further, from the experimental results shown in FIGS. 40 to 42, nitric acid and nitrous acid were used when the Pd strain was used alone and when the 4C-C strain, the HT-1 strain, and the Pd strain were used in combination. Was reduced to below the detection limit within 20 hours and reduced to nitrogen.

  Here, in order to compare the case where the 4C-C strain and the HT-1 strain are fixed with the case where the 4C-C strain, the HT-1 strain and the Pd strain are fixed, FIG. The figure which summarized the time-dependent change of the selenium density | concentration at the time of fixing a strain | stump | stock and HT-1 stock | strain is shown in FIG. The figure which summarized the time-dependent change is shown. FIG. 45 shows a graph summarizing changes over time in nitrogen concentration when the 4C-C strain and the HT-1 strain are fixed, and FIG. 46 shows the 4C-C strain, the HT-1 strain, and the Pd strain. The figure which summarized the time-dependent change of the nitrogen concentration at the time of fixing is shown. 43 and 44, □ indicates the selenate concentration, ◇ indicates the selenite concentration, and ◯ indicates the total selenium concentration. 45 and 46, □ indicates the nitric acid concentration, 濃度 indicates the nitrous acid concentration, and ◯ indicates the total nitrogen concentration.

  As shown in FIGS. 43 to 46, it is clear that both the total selenium concentration and the total nitrogen concentration can be reduced more quickly by using the Pd strain together in an environment where a high concentration of nitric acid is present. It was.

  From the above results, even in the state where the microorganisms were fixed to the polymer gel, nitric acid was present in the wastewater at a high concentration by using the Pd strain in addition to the 4C-C strain and the HT-1 strain. It was revealed that water-soluble selenium can be insolubilized efficiently even in an environment. Moreover, unlike the state in which microorganisms are suspended, when microorganisms are immobilized on a polymer gel, all insoluble selenium accumulates on the nonwoven fabric and the polymer gel coated on the nonwoven fabric, and precipitation occurs in the artificial drainage. Therefore, in addition to the 4C-C strain and the HT-1 strain, the Pd strain was used in combination and fixed to a carrier such as a polymer gel, so that the nitric acid was highly concentrated in the wastewater. The possibility that the recovery process of insoluble selenium can be simplified even in the existing environment is shown.

It is a figure which shows one Embodiment of the bioreactor of this invention. It is a figure which shows the result of having investigated the chemical reactivity of the selenic acid with respect to hydrogen sulfide. It is a figure which shows the result of having examined the chemical reactivity of selenious acid with respect to hydrogen sulfide. It is a figure which shows a time-dependent change of a sulfuric acid concentration at the time of adding HT-1 stock | strain and ethanol to various artificial wastewater samples. It is a figure which shows the time-dependent change of selenite concentration at the time of adding HT-1 stock | strain and ethanol to various artificial wastewater samples. It is a figure which shows a time-dependent change of the selenic acid density | concentration at the time of culturing a microorganism by using ethanol as an energy source with the artificial waste water containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid. It is a figure which shows a time-dependent change of the selenious acid density | concentration at the time of culture | cultivating microorganisms by making the energy source ethanol into the artificial waste water containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid. It is a figure which shows a time-dependent change of the total selenium density | concentration at the time of culture | cultivating microorganisms by making the energy source ethanol into the artificial waste water containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid. It is a figure which shows the time-dependent change of a sulfuric acid concentration at the time of culturing a microorganism by using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid. It is a figure which shows a time-dependent change of the selenic acid density | concentration at the time of culture | cultivating the microorganisms fixed to the polymer gel by using ethanol as an energy source with the artificial waste water containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid. It is a figure which shows a time-dependent change of the selenite concentration at the time of culture | cultivating the microorganisms fixed to the polymer gel by using as an energy source ethanol with the artificial waste water containing 10 mg-Se / L selenate and 500 mg / L sulfuric acid. . It is a figure which shows a time-dependent change of the total selenium density | concentration at the time of culture | cultivating the microorganisms fixed to the polymer gel by making the energy source ethanol into the artificial waste water containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid. It is a figure which shows a time-dependent change of the sulfuric acid concentration at the time of culture | cultivating the microorganisms fixed to the polymer gel by using ethanol as an energy source with the artificial waste water containing 10 mg-Se / L selenic acid and 500 mg / L sulfuric acid. It is a figure which shows the state change before and behind immersing the polymer gel which fixed both 4C-C stock | strain and HT-1 stock | strain in the artificial waste water. When cultivating microorganisms (4C-C strain, HT-1 strain) using ethanol as an energy source in artificial wastewater containing 10 mg-Se / L selenate, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of a selenic acid density | concentration. When cultivating microorganisms (4C-C strain, HT-1 strain) using ethanol as an energy source in artificial wastewater containing 10 mg-Se / L selenate, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows the time-dependent change of selenite concentration. When cultivating microorganisms (4C-C strain, HT-1 strain) using ethanol as an energy source in artificial wastewater containing 10 mg-Se / L selenate, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of a total selenium density | concentration. When cultivating microorganisms (4C-C strain, HT-1 strain) using ethanol as an energy source in artificial wastewater containing 10 mg-Se / L selenate, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of a sulfuric acid concentration. When cultivating microorganisms (4C-C strain, HT-1 strain) using ethanol as an energy source in artificial wastewater containing 10 mg-Se / L selenate, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows the time-dependent change of nitric acid concentration. It is a figure which shows a time-dependent change of the nitrous acid density | concentration at the time of culturing a microorganism by using ethanol as an energy source with the artificial waste water containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid. . When cultivating microorganisms (4C-C strain, HT-1 strain) using ethanol as an energy source in artificial wastewater containing 10 mg-Se / L selenate, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows the time-dependent change of total nitrogen concentration. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the selenate density | concentration at the time of culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the selenite concentration at the time of culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the total selenium density | concentration at the time of culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the sulfuric acid concentration at the time of culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows the time-dependent change of the nitric acid concentration at the time of culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the nitrite density | concentration at the time of culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the total nitrogen concentration at the time of culture | cultivating. An artificial wastewater containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, using ethanol as an energy source and a microorganism (4C-C strain, HT-1 strain) as a polymer gel It is a figure which shows the time-dependent change of the selenate density | concentration at the time of fixing and culture | cultivating. An artificial wastewater containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, using ethanol as an energy source and a microorganism (4C-C strain, HT-1 strain) as a polymer gel It is a figure which shows a time-dependent change of the selenite concentration at the time of culture | cultivating by fixing. An artificial wastewater containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, using ethanol as an energy source and a microorganism (4C-C strain, HT-1 strain) as a polymer gel It is a figure which shows a time-dependent change of the total selenium density | concentration at the time of fixing and culture | cultivating. An artificial wastewater containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, using ethanol as an energy source and a microorganism (4C-C strain, HT-1 strain) as a polymer gel It is a figure which shows a time-dependent change of the sulfuric acid concentration at the time of fixing and culture | cultivating. An artificial wastewater containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, using ethanol as an energy source and a microorganism (4C-C strain, HT-1 strain) as a polymer gel It is a figure which shows the time-dependent change of nitric acid concentration at the time of fixing and culture | cultivating. An artificial wastewater containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, using ethanol as an energy source and a microorganism (4C-C strain, HT-1 strain) as a polymer gel It is a figure which shows a time-dependent change of the nitrite density | concentration at the time of culture | cultivating by fixing. An artificial wastewater containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, using ethanol as an energy source and a microorganism (4C-C strain, HT-1 strain) as a polymer gel It is a figure which shows a time-dependent change of the total nitrogen concentration at the time of fixing and culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the selenate concentration at the time of fixing to a polymer gel and culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows the time-dependent change of the selenite concentration at the time of fixing to a polymer gel and culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the total selenium density | concentration at the time of fixing to a polymer gel and culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the sulfuric acid concentration at the time of culture | cultivating by fixing to a polymer gel. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of nitric acid concentration at the time of culture | cultivating by fixing to a polymer gel. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the nitrous acid density | concentration at the time of fixing to a polymer gel and culture | cultivating. Microorganisms (4C-C strain, HT-1 strain, Pd strain) using ethanol as an energy source with artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid It is a figure which shows a time-dependent change of the total nitrogen concentration at the time of fixing to a polymer gel and culture | cultivating. Artificial drainage containing 10 mg-Se / L selenate, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid with ethanol as the energy source, and 4C-C and HT-1 strains fixed to polymer gel It is the figure which summarized the time-dependent change of the selenium density | concentration at the time of doing. An artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, the energy source is ethanol, and 4C-C strain, HT-1 strain and Pd strain are It is the figure which summarized the time-dependent change of the selenium density | concentration at the time of fixing to a polymer gel. Artificial drainage containing 10 mg-Se / L selenate, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid with ethanol as the energy source, and 4C-C and HT-1 strains fixed to polymer gel It is the figure which summarized the time-dependent change of the nitrogen concentration at the time of doing. An artificial drainage containing 10 mg-Se / L selenic acid, 500 mg / L sulfuric acid, and 100 mg-N / L nitric acid, the energy source is ethanol, and 4C-C strain, HT-1 strain and Pd strain are It is the figure which summarized the time-dependent change of nitrogen concentration at the time of fixing to a polymer gel.

Explanation of symbols

1 Bioreactor 2 Carrier 12 Lower alcohol

Claims (12)

  A sulfate-reducing microorganism that has been accepted under the accession number FERM P-21577, belonging to the genus Desulfovibrio and having the ability to reduce sulfuric acid and selenous acid in an anaerobic environment using lower alcohol as an energy source.   The method includes bringing hydrogen sulfide produced by supplying a lower alcohol and sulfuric acid to an sulfate-reducing microorganism according to claim 1 in an anaerobic environment with a water-soluble heavy metal to make the water-soluble heavy metal an insoluble heavy metal. A water-soluble heavy metal insolubilization method characterized by the above.   A step of bringing the water-soluble heavy metal into an insoluble heavy metal by bringing hydrogen sulfide generated by supplying lower alcohol and sulfuric acid to the sulfate-reducing microorganism according to claim 1 in an anaerobic environment with water-soluble heavy metal-containing wastewater. A wastewater treatment method characterized by that.   A step of bringing hydrogen sulfide produced by supplying a lower alcohol and sulfuric acid to an sulfate-reducing microorganism according to claim 1 in an anaerobic environment with wastewater containing selenite to convert the selenite into insoluble selenium. A wastewater treatment method characterized by that.   Included in the water-soluble selenium-containing wastewater by supplying a lower alcohol in an anaerobic environment to a selenate-reducing microorganism belonging to the genus Pseudomonas entrusted with the deposit number FERM P-20840 and contacting the water-soluble selenium-containing wastewater. A step of producing selenious acid from selenic acid, and contacting the hydrogen sulfide produced by supplying lower alcohol and sulfuric acid in an anaerobic environment to the sulfate-reducing microorganism according to claim 1 with the water-soluble selenium-containing wastewater. And a step of converting the selenious acid contained in the water-soluble selenium-containing wastewater and the selenious acid produced by the selenate-reducing microorganism into insoluble selenium.   The wastewater treatment method according to claim 5, wherein the selenate-reducing microorganism and the sulfate-reducing microorganism are coexisted in the same treatment tank for wastewater treatment.   The wastewater treatment method according to claim 6, wherein in addition to the selenate-reducing microorganism and the sulfate-reducing microorganism, wastewater treatment is performed by further allowing Paracoccus denitrificans to coexist in the same treatment tank.   The wastewater treatment method according to any one of claims 3 to 7, wherein at least the sulfate-reducing microorganism is supported on a carrier.   The wastewater treatment method according to any one of claims 3 to 8, wherein sulfuric acid contained in the wastewater is used as sulfuric acid to be supplied to the sulfate-reducing microorganism.   A bioreactor comprising a carrier on which the sulfate-reducing microorganism according to claim 1 is supported.   The bioreactor according to claim 10, wherein the carrier further carries a selenate-reducing microorganism belonging to the genus Pseudomonas, which is accepted under the accession number FERM P-20840, in addition to the sulfate-reducing microorganism.   12. The bioreactor according to claim 11, wherein the carrier further carries Paracoccus denitrificans in addition to the sulfate-reducing microorganism and the selenate-reducing microorganism.