JP5730626B2 - Selenium-containing water reduction treatment apparatus and selenium-containing water reduction treatment method - Google Patents

Description

  The present invention relates to a selenium-containing water reduction treatment apparatus and a selenium-containing water reduction treatment method. More specifically, the present invention relates to wastewater discharged from factories or the like that handle selenium as a raw material or product, smoke washed wastewater generated in factories or the like that contain selenium in flue gas, and selenium discharged from coal-fired power plants. The present invention relates to a selenium-containing water reduction treatment apparatus and a selenium-containing water reduction treatment method suitable for use in reduction treatment of selenium-containing water such as desulfurization effluent.

  Selenium (Se) was certified as a hazardous substance in the Water Pollution Control Law in 1993, and a 0.1 mg / L drainage standard and a 0.01 mg / L water quality environmental standard were established. Wastewater discharged from factories that use selenium as raw materials and products, smoke-washed wastewater generated in factories that contain selenium in flue gas, and coal-fired power plants to meet these wastewater standards and water quality environmental standards Appropriate measures for reducing the selenium concentration are required for selenium-containing water such as desulfurization effluent containing selenium.

Here, in selenium-containing water, selenium (Se) is dissolved in the form of selenic acid (SeO ₄ ²⁻ ) and selenious acid (SeO ₃ ²⁻ ).

Since selenite forms a sparingly soluble salt with iron, it can be easily removed from waste water or the like by coprecipitation treatment (Non-patent Document 1). It is also relatively easy to chemically reduce to insoluble elemental selenium (Se ⁰ ) (Non-patent Document 2).

  In contrast, most of the compounds of selenic acid have high solubility in water. Therefore, physicochemical treatment methods such as coagulation precipitation and adsorption for removing metals from wastewater are not effective. Therefore, it is necessary to reduce selenic acid to selenious acid and then perform coprecipitation treatment or reduce it to elemental selenium. As the reducing agent effective for the reduction of selenic acid, for example, titanium chloride, a reducing iron compound, a photocatalyst, and the like have been reported (Non-Patent Documents 3 to 5).

  However, during the chemical reduction of selenic acid, regardless of the type of reducing agent used, it is subjected to strong acid conditions such as “boiling under strong acidity of hydrochloric acid” in the factory wastewater test method (JIS K 0102). Must be set. For this reason, in the chemical reduction treatment of selenic acid, in addition to an expensive metal-based reducing agent, the chemical cost required for charging a large amount of acid and alkali for pH adjustment is a practical obstacle. .

  A biological treatment method using microorganisms is being studied as a treatment method that can reduce drug costs. In biological treatment methods using microorganisms, it is generally appropriate to set the pH to near neutral as a reaction condition (Non-Patent Document 6), and thus a large amount of acid or alkali for pH adjustment is required. The chemical cost for acid and alkali can be greatly reduced.

Pollution Prevention Technology and Regulations Editorial Committee, New Pollution Prevention Technology and Regulations 2009 Water Quality, Industrial Environment Management Association, Tokyo, 2009. Electric Power Central Research Institute report V07015 Kenjiro Goto, reduction / removal of Se (VI) in water with TiCl3, resources and materials, Vol. 116, 773-777, 2000. Hiroshi Hayashi et al., Continuous Demonstration Test of Selenium Contaminated Water Treatment by Green Last / Ferrite Circulation Method, Resources and Materials, Vol. 122, 415-422, 2006. Nobunari Kawabe et al., Effects of sulfate ion on selenate removal reaction by photocatalyst, resources and materials, Vol. 117, 282-287, 2001. Takada T. et al. : Kinetic study on biological reduction of selenium compounds, Process Biochem. , Vol. 43, 1304-1307, 2008.

  When treating wastewater by the biological treatment method, it is common practice to attach cells to a carrier with a high specific surface area such as porous ceramics, activated carbon, or fibrous material, and then contact it with wastewater. Is called. In this way, by attaching the bacterial cells at a high density to a carrier having a high specific surface area, the waste water can be brought into contact with more bacterial cells to increase the treatment efficiency. In addition, by attaching the bacterial cells to the carrier, the bacterial cells can be retained on the carrier, and when the treated wastewater is discharged from the treatment tank or the like, the bacterial cells are discharged along with the treated wastewater. Therefore, it is possible to perform the treatment stably for a long time.

  Similarly, the reduction treatment of selenate in selenium-containing water by the biological treatment method is also possible by increasing the selenate reduction efficiency by attaching selenate-reducing bacteria to a carrier with a high specific surface area at high density. It is conceivable to carry out processing stably for a period.

  However, as a result of investigations by the inventors of the present application, it was found that only by attaching selenate-reducing bacteria to a carrier having a high specific surface area such as rock wool (fibrinized blast furnace slag), a certain amount of bacteria was immediately attached. Although the ability to reduce selenate was observed, the ability was low and the ability quickly declined. Therefore, with regard to the reduction treatment of selenate in selenium-containing water by the biological treatment method, simply attaching selenate-reducing bacteria to a carrier having a high specific surface area makes the reduction treatment efficiency of selenate high and stable for a long time. It became clear that the process could not be performed. Therefore, it is desired to establish another method for stably treating selenic acid in selenium-containing water by a biological treatment method with a high selenic acid reduction treatment efficiency for a long period of time.

  Moreover, in order to reduce the total selenium concentration in the selenium-containing water, it is important to reduce not only the concentration of selenic acid but also the concentration of selenious acid. Therefore, in putting the selenic acid reduction treatment in the selenium-containing water by the biological treatment method into practical use, the selenic acid reduction treatment is considered to be highly efficient and the selenic acid reduction treatment At the same time or in succession to the reduction treatment of selenic acid, establishment of a technique capable of reducing the selenite concentration is also desired.

  The present invention provides a treatment apparatus and a treatment method for stably treating selenic acid in selenium-containing water by a biological treatment method with a high selenic acid reduction treatment efficiency for a long period of time. Objective.

  In addition, the present invention provides a highly effective reduction treatment of selenic acid in selenium-containing water by a biological treatment method, while performing treatment stably for a long period of time, simultaneously with the reduction treatment of selenic acid, or the reduction treatment of selenic acid. It aims at providing the processing apparatus and processing method which can reduce selenite concentration continuously.

  As a result of intensive studies by the inventors of the present application in order to solve such a problem, a column container is filled with a porous or fibrous structure carrier, and a suspension containing aggregated cells of selenate-reducing bacteria is contained in the column container. The inventors have found that the aggregated bacterial cells can be stably attached to the surface of the carrier by passing the liquid through. In other words, when the selenium-containing water is allowed to flow through the column container by adhering the aggregated cells of the selenate-reducing bacteria to the carrier, the aggregated cells are not discharged together with the selenium-containing water, It came to know that it was maintained stably in the state adhering to the support | carrier surface.

  Based on this finding, the inventors of the present application increased the aggregated cells of selenate-reducing bacteria on a porous or fibrous carrier by using aggregated cells of selenate-reducing bacteria instead of selenate-reducing bacteria. In order to complete the present invention, it was found that the reduction efficiency of selenic acid can be increased by adhering to the density, and that the treatment can be performed stably for a long period of time. It came.

That is, in the selenium-containing water reduction treatment apparatus according to claim 1, the flocculated cells containing selenate-reducing bacteria produced by adding a flocculant to a suspension containing selenate-reducing bacteria adhere to the surface. A column container filled with a porous or fibrous carrier and an organic substance supply device for supplying an organic substance into the column container. Further, in the selenium-containing water reduction treatment method according to claim 7, the aggregated cells containing the selenate-reducing bacteria produced by adding a flocculant to the suspension containing the selenate-reducing bacteria adhere to the surface. The porous or fibrous structure carrier includes a step of bringing selenium-containing water into contact with an organic substance.

  Therefore, according to the selenium-containing water reduction treatment apparatus according to claim 1 and the selenium-containing water reduction treatment method according to claim 7, the aggregated cells containing selenate-reducing bacteria on the surface of the porous or fibrous structure carrier Therefore, the aggregated cells are stably held on the surface of the carrier, and by supplying the organic matter, selenate is stably reduced for a long period of time and efficiently. In addition, the aggregated cells are more stably held on the surface of the carrier by supplying the organic matter.

Next, the selenium-containing water reduction treatment apparatus according to claim 2 is the selenium-containing water reduction treatment apparatus according to claim 1, wherein an active iron hydroxide-based selenite adsorbent is attached to the surface of the support. It is supposed to be. The selenium-containing water reduction treatment method according to claim 8 is the selenium-containing water reduction treatment method according to claim 7, wherein an active iron hydroxide-based selenite adsorbent is attached to the surface of the support. It is said.

  Therefore, according to the selenium-containing water reduction treatment apparatus according to claim 2 and the selenium-containing water reduction treatment method according to claim 8, selenic acid is stably reduced and efficiently reduced over a long period of time, and Selenic acid is adsorbed. As a result, selenic acid and selenous acid in the selenium-containing water are simultaneously reduced, and the total selenium concentration in the selenium-containing water is reduced.

  Here, like the selenium-containing water reduction treatment apparatus according to claim 3, the column container in the selenium-containing water reduction treatment apparatus according to claim 1 is used as a first column container, and the first column container is disposed downstream of the first column container. A second column container filled with a selenious acid adsorbent may be further included. Further, as in the selenium-containing water reduction treatment method according to claim 9, the step in the selenium-containing water reduction treatment method according to claim 7 is the first step, and the selenium-containing water treated by the first step May be further included in the second step of contacting the selenious acid adsorbent with the adsorbent.

  In this case, selenic acid is stably reduced and efficiently reduced for a long time in the former stage, and selenous acid is adsorbed in the latter stage. Thereby, after selenic acid in selenium-containing water is reduced in the former stage, selenious acid is continuously adsorbed in the latter stage, and the total selenium concentration in the selenium-containing water is reduced.

  Next, the selenium-containing water reduction treatment apparatus according to claim 4 is the selenium-containing water reduction treatment apparatus according to claim 1, wherein the selenium-containing water reduction treatment apparatus further includes bacteria having a function of insolubilizing selenite in the aggregated cells. It is supposed to be. Further, the selenium-containing water reduction treatment method according to claim 10 is the selenium-containing water reduction treatment method according to claim 7, wherein a bacterium having a function of insolubilizing selenite is further included in the aggregated cells. It is supposed to be.

  Therefore, according to the selenium-containing water reduction treatment apparatus according to claim 4 and the selenium-containing water reduction treatment method according to claim 10, selenic acid is stably reduced and efficiently reduced over a long period of time, and By containing bacteria having a function of insolubilizing in the aggregated cells, selenious acid is stably and efficiently insolubilized for a long period of time and adheres to the surface of the carrier. As a result, selenic acid and selenous acid in the selenium-containing water are simultaneously reduced, and the total selenium concentration in the selenium-containing water is reduced.

  Next, in the selenium-containing water reduction treatment apparatus according to claim 5, a bacterium having a function of insolubilizing selenite is separated from the aggregated cells in the selenium-containing water reduction treatment apparatus according to claim 1 or 4. It is assumed that the aggregating bacterial cells are attached to the surface of the carrier. In addition, the selenate-containing water reduction treatment method according to claim 11 is characterized in that, apart from the aggregated cells in the selenium-containing water reduction treatment method according to claim 7 or 10, a bacterium having a function of insolubilizing selenite is used. It is assumed that the aggregating bacterial cells are attached to the surface of the carrier.

  Therefore, according to the selenium-containing water reduction treatment apparatus according to claim 5 and the selenium-containing water reduction treatment method according to claim 11, selenic acid is stably reduced and efficiently reduced over a long period of time. Since aggregated cells containing bacteria having a function of insolubilization are attached to the surface of the carrier, selenious acid is stably and efficiently insolubilized for a long period of time and attached to the surface of the carrier. As a result, selenic acid and selenous acid in the selenium-containing water are simultaneously reduced, and the total selenium concentration in the selenium-containing water is reduced.

  Here, like the selenium-containing water reduction treatment apparatus according to claim 6, the column container in the selenium-containing water reduction treatment apparatus according to claim 1 is used as a first column container, and is provided downstream of the first column container. A second column container filled with a porous or fibrous structure carrier on which aggregated cells containing bacteria having a function of insolubilizing selenite are attached may be further included. Moreover, like the selenium-containing water reduction treatment method according to claim 12, the step in the selenium-containing water reduction treatment method according to claim 7 is the first step, and the selenium-containing water treated by the first step. May further include a second step of contacting the organic substance with the porous or fibrous structure carrier on which the aggregated cells containing bacteria having a function of insolubilizing selenite are attached.

  In this case, selenic acid is stably reduced efficiently for a long period of time in the former stage, and selenite is insolubilized in the latter stage and adsorbed on the surface of the carrier. Thereby, after selenic acid in selenium-containing water is reduced in the former stage, selenious acid is continuously insolubilized in the latter stage, and the total selenium concentration in the selenium-containing water is reduced.

Next, the selenium-containing water reduction treatment carrier according to claim 13 is prepared by adding a flocculant to a suspension containing a selenate-reducing bacterium and / or a bacterium having a function of insolubilizing selenious acid. Aggregated cells containing selenate-reducing bacteria and / or bacteria having a function of insolubilizing selenite are attached to the surface of the porous or fibrous structure carrier.

  Therefore, according to the carrier for selenium-containing water reduction treatment according to claim 13, the function of the cells contained in the aggregated cells is stably and efficiently exhibited for a long period of time.

Next, in the method for producing a carrier for selenium-containing water reduction treatment according to claim 14 , a flocculant is added to a suspension containing a selenate-reducing bacterium and / or a bacterium having a function of insolubilizing selenite. The method includes a step of passing a solution in which the produced aggregate cells containing selenate-reducing bacteria and / or bacteria having a function of insolubilizing selenite are suspended through a porous or fibrous carrier.

Thus, according to the manufacturing method of the selenium-containing water reduction carrier according to claim 1 4, a carrier of porous or fibrous structures, the cells having the ability to insolubilize the selenate reducing bacteria and / or selenite The aggregating bacterial cells can be stably attached for a long time. Thereby, the function of the microbial cells contained in the aggregated microbial cells is stably and efficiently exhibited for a long period of time.

  According to the first aspect of the present invention, it is possible to stably and efficiently reduce selenic acid contained in selenium-containing water for a long period of time by a biological treatment method using microorganisms. In addition, selenic acid can be reduced stably and efficiently for a long period of time by a very simple operation of passing selenium-containing water into the column container, and thus it takes a reduction treatment of selenic acid contained in selenium-containing water. It is possible to greatly reduce labor and the like as compared with the conventional case.

  According to the invention described in claim 2, it is possible to stably reduce selenic acid contained in selenium-containing water for a long period of time by a biological treatment method using a microorganism, Can be removed by chemically adsorbing to the carrier itself (selenous acid originally contained in selenium-containing water, selenious acid produced by reduction of selenic acid). Therefore, the total selenium concentration in the selenate-containing water can be reduced. Moreover, the selenium-containing water can be passed through the column vessel, and the selenium acid can be removed by adsorbing and removing selenite at the same time while reducing selenate stably and efficiently for a long time. Therefore, the total selenium concentration reduction treatment of selenium-containing water can be easily performed. Furthermore, since the reduction process of selenic acid and the adsorption process of selenious acid can be performed in the same column, the apparatus can be made compact.

  According to the third aspect of the present invention, it is possible to stably and efficiently reduce selenic acid contained in selenium-containing water for a long period of time by a biological treatment method using microorganisms in the preceding column container. In addition, the selenite contained in the selenate-containing water (the selenite originally contained in the selenium-containing water, selenite produced by the reduction of the selenate) in the column container at the latter stage is adsorbed to the carrier itself. It can be removed. Therefore, the total selenium concentration in the selenate-containing water can be reduced. In addition, the selenium-containing water is passed through the column vessel, and the selenium acid is continuously adsorbed and removed chemically while reducing selenate stably and efficiently over a long period of time. Therefore, the total selenium concentration reduction treatment of selenium-containing water can be easily performed. Furthermore, when the selenite adsorption capacity of the selenite adsorbent in the latter column container is reduced, the selenite adsorption capacity can be easily recovered by replacing with a new selenite adsorption material. Therefore, the convenience of the apparatus can be increased.

According to the inventions of claims 4 and 5, it is possible to stably and efficiently reduce selenic acid contained in selenium-containing water for a long period of time by a biological treatment method using microorganisms. Selenium acid contained in selenium-containing water (selenous acid originally contained in selenium-containing water, selenite produced by reduction of selenic acid) by elemental selenium It can be adsorbed on a carrier as insoluble selenium . Therefore, it is possible to reduce the total selenium concentration of selenate-containing water. In addition, the selenium-containing water is passed through the column vessel with a very simple operation, while reducing selenic acid stably and efficiently for a long period of time, while simultaneously insolubilizing selenite and attaching it to the carrier for removal. Therefore, the total selenium concentration reduction treatment of selenium-containing water can be easily performed. Furthermore, since the reduction treatment of selenic acid and the insolubilization / adhesion treatment of selenious acid can be performed in the same column, the apparatus can be made compact. Even when insoluble selenium such as elemental selenium accumulates on the support, insoluble selenium can be removed by backwashing, and the ability to reduce the total selenium concentration in selenate-containing water can be easily achieved without changing the support. Since it can be recovered, the convenience of the apparatus can be enhanced.

  According to the sixth aspect of the present invention, it is possible to stably and efficiently reduce selenic acid contained in selenium-containing water for a long period of time by a biological treatment method using microorganisms in a column container in the previous stage. In addition, selenite contained in selenate-containing water in the latter column container (selenite contained in selenium-containing water, selenite produced by reduction of selenate) was insolubilized. Due to the function of the fungus having the function of insoluble, it becomes possible to adsorb it to the subsequent carrier as insoluble selenium such as elemental selenium. Therefore, the total selenium concentration in the selenate-containing water can be reduced. In addition, the selenium-containing water is passed through the column container, and while the selenium acid is stably and efficiently reduced for a long period of time, the selenite is continuously insolubilized and adhered to the carrier. Since it can be removed, the total selenium concentration reduction treatment of selenium-containing water can be easily performed. Furthermore, even when insoluble selenium such as elemental selenium accumulates on the support in the column container, the insoluble selenium can be removed by backwashing, and the selenic acid-containing water can be removed without replacing the support in the column container. Since the ability to reduce the total selenium concentration can be easily recovered, the convenience of the apparatus can be enhanced.

  According to the seventh aspect of the present invention, selenic acid contained in selenium-containing water can be stably and efficiently reduced for a long period of time by a biological treatment method using microorganisms.

  According to the invention described in claim 8, it is possible to stably reduce selenate contained in selenium-containing water stably for a long period of time by a biological treatment method using microorganisms, Can be removed by chemically adsorbing to the carrier itself (selenous acid originally contained in selenium-containing water, selenious acid produced by reduction of selenic acid). Therefore, the total selenium concentration in the selenate-containing water can be reduced.

According to the ninth aspect of the present invention, it becomes possible to stably and efficiently reduce selenic acid contained in selenium-containing water for a long period of time by a biological treatment method using microorganisms in the column container in the previous stage. In addition, the selenite contained in the selenate-containing water (the selenite originally contained in the selenium-containing water, selenite produced by the reduction of the selenate) in the column container at the latter stage is adsorbed to the carrier itself. It can be removed. Therefore, the total selenium concentration in the selenate-containing water can be reduced.

According to the invention described in claim 10 or 11, it is possible to stably and efficiently reduce selenic acid contained in selenium-containing water for a long period of time by a biological treatment method using microorganisms. Selenium acid contained in selenium-containing water (selenous acid originally contained in selenium-containing water, selenite produced by reduction of selenic acid) by elemental selenium It can be adsorbed on a carrier as insoluble selenium . Therefore, it is possible to reduce the total selenium concentration of selenate-containing water.

  According to the twelfth aspect of the present invention, it is possible to stably and efficiently reduce selenic acid contained in selenium-containing water for a long period of time by a biological treatment method using microorganisms in the preceding column container. In addition, selenite contained in selenate-containing water in the latter column container (selenite contained in selenium-containing water, selenite produced by reduction of selenate) was insolubilized. Due to the function of the fungus having the function of insoluble, it becomes possible to adsorb it to the subsequent carrier as insoluble selenium such as elemental selenium. Therefore, the total selenium concentration in the selenate-containing water can be reduced.

  According to the invention described in claim 13, the aggregated cell containing the selenate-reducing bacterium and / or the bacterium having the function of insolubilizing selenite is attached to the surface of the porous or fibrous structure carrier. Therefore, the function of the microbial cells contained in the aggregated microbial cells can be stably and efficiently exhibited for a long period of time.

  According to the invention described in claim 14, agglomerated cells containing a selenate-reducing bacterium and / or a bacterium having a function of insolubilizing selenite are stably attached to a porous or fibrous carrier for a long period of time. Therefore, the function of the cells contained in the aggregated cells can be stably and efficiently exhibited for a long period of time.

It is the schematic which shows an example of the selenium containing water reduction processing apparatus concerning 1st embodiment. It is the schematic which shows an example of the selenium containing water reduction processing apparatus concerning 2nd embodiment. It is the schematic which shows an example of the selenium containing water reduction processing apparatus concerning 3rd embodiment. It is the schematic which shows an example of the selenium containing water reduction processing apparatus concerning 4th embodiment. It is the schematic which shows an example of the selenium containing water reduction processing apparatus concerning 5th embodiment. It is a figure which shows the time-dependent change of the selenate reduction rate per apparatus volume in the comparative example 1. It is a figure which shows the time-dependent change of the selenite reduction rate per apparatus volume in the comparative example 1. It is a figure which shows the density | concentration change of a selenic acid and selenious acid at the time of using a selenate reducing bacterium in Example 1. FIG. It is a figure which shows a time-dependent change of the reduction | restoration rate of a selenic acid and selenious acid at the time of using together a selenate reducing bacterium, a selenite reducing bacterium, and a sulfate reducing bacterium in Example 1. In Example 2, it is a figure which shows the experimental result of the front | former stage of 2 continuous 1 conditions. In Example 2, it is a figure which shows the experimental result of the back | latter stage of 2 continuous 1 conditions. In Example 2, it is a figure which shows the experimental result of the front | former stage of 2 continuous 2 conditions. In Example 2, it is a figure which shows the experimental result of the back | latter stage of double 2 conditions. In Example 2, it is a figure which shows the experimental result of the front | former stage of 2 continuous 3 conditions. It is a figure in Example 2 which shows the experimental result of the back | latter stage of 2 continuous 3 conditions. It is a figure in Example 2 which shows the experimental result of one single condition. It is a figure which shows the experimental result of single 2 conditions in Example 2. FIG. It is a figure which shows the experimental result of single 3 conditions in Example 2. FIG. It is a figure which shows the experimental result of the single 4 conditions in Example 2. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

<First embodiment>
Hereinafter, as an example of an embodiment of the present invention, a method and apparatus for biologically treating selenic acid in selenium-containing water will be described as a first embodiment.

  In the selenium-containing water reduction treatment method according to the first embodiment, selenium-containing water and an organic substance are brought into contact with a porous or fibrous structure carrier on which aggregated cells containing selenate-reducing bacteria are attached. The process is included.

  An example of an apparatus for carrying out the selenium-containing water reduction treatment method according to the first embodiment is shown in FIG. A selenium-containing water reduction treatment apparatus 1 shown in FIG. 1 includes a column container 2 filled with a porous or fibrous carrier 3 having aggregated cells 4 containing selenate-reducing bacteria attached to the surface, and a column container. 2 includes an organic substance supply device 5 for supplying an organic substance. In addition, in FIG. 1, the code | symbol 10 is a selenium containing water storage tank, and the code | symbol 11 is a liquid feeding pump.

The selenate-reducing bacterium is not particularly limited as long as it has a function of reducing selenate to selenite. For example, Pseudomonas sp. 4C-C is preferably used. This bacterium has the ability to reduce selenate to selenite under anaerobic conditions. Moreover, as an energy source, it is possible to use yeast extract, sulfur-containing amino acid, or lactate, as well as lower alcohols having 1 to 3 carbon atoms such as methanol, ethanol, and propanol. Furthermore, even in the presence of high concentrations of nitrate ions, nitrite ions, and sulfate ions, nitrate ions and nitrite ions can be reduced to harmless nitrogen gas simultaneously with the reduction of selenate . That is, a selenate-reducing bacterium suitable for use in the reduction treatment according to the present invention using desulfurization effluent discharged from a coal-fired power plant that can contain nitrate ions, nitrite ions, and sulfate ions in high concentrations as selenium-containing water. It can be said that. This bacterium has been deposited at the National Institute of Advanced Industrial Science and Technology Patent Biological Deposit Center as deposit number FERM P-20840 on March 13, 2006. Moreover, since this bacterium is a facultative anaerobic selenate-reducing bacterium, the bacterium itself consumes free oxygen without performing a nitrogen gas purge for making the inside of the column container anaerobic. The inside of the column container can be an anaerobic environment. Therefore, since the selenate reduction treatment can be performed without performing an operation for maintaining the inside of the column container under anaerobic conditions, the use of Pseudomonas sp. 4C-C is also preferable in this respect. This is true not only for Pseudomonas sp. 4C-C but also for other facultative anaerobic selenate-reducing bacteria.

  Aggregated bacterial cells 4 containing selenate-reducing bacteria are produced, for example, by appropriately adding an aggregating agent to a solution containing selenate-reducing bacteria. Examples of the flocculant include inorganic flocculants such as polyaluminum chloride and polymer flocculants such as acrylamide-N, N-dimethylaminoethyl acrylate copolymer, and these can be used alone or in combination. Selenate-reducing bacteria can be aggregated. The size of the agglutinating cells 4 may be set to a visible level. As a standard, about 300-500 mg / L for polyaluminum chloride and about 2-5 mg / L for acrylamide-N, N-dimethylaminoethyl acrylate copolymer are added to a solution containing selenate-reducing bacteria. By doing so, the aggregated bacterial cells 4 having a size that can be visually recognized can be formed.

  In addition, it is preferable that the size of the aggregated bacterial cell is a size that can be visually recognized, and more preferably about 0.5 mm to 1 mm. If the size of the aggregated bacterial cell 4 is too small, it is difficult to sufficiently adhere the aggregated bacterial cell 4 to the surface of the carrier 3. In addition, if the size of the aggregated bacterial cells 4 is too large, the aggregated bacterial cells 4 will not easily enter the voids of the carrier 3 and it will be difficult to uniformly disperse and support them on the surface of the carrier 3.

  The carrier 3 is not particularly limited as long as it has a fibrous structure. For example, a material having a high specific surface area such as porous ceramic, activated carbon, and fibrous substance can be used as appropriate. It is particularly preferable to use rock wool (fiberized blast furnace slag). Rock wool is a granular cotton in which fine fibers are gathered, and is a material mainly composed of calcium silicate, and hardly dissolves or dissolves in the vicinity of neutrality. Moreover, since it is the slag discharged | emitted from the blast furnace, it also has the advantage that it is cheap. That is, the cost for the support 3 can be suppressed, and the total cost for the reduction treatment of the selenium-containing water can be reduced.

  Aggregated cells 4 containing selenate-reducing bacteria can be attached to the surface of the carrier 3 by the following method, for example. That is, after the column container 2 is filled with the carrier 3, the solution containing the aggregated bacterial cells 4 is passed through the column container 2 so that the aggregated bacterial cells 4 enter the voids of the carrier 3 and the like. Stablely adheres to the surface.

  In addition, it is preferable that an organic substance that serves as an energy source of the selenate-reducing bacteria is supplied into the column container 2 after the aggregated cells 4 containing the selenate-reducing bacteria are attached to the surface of the carrier 3. Thereby, the effect that the agglomerated cells 4 are stably attached to and held on the carrier 3 is further increased.

  An organic substance that serves as an energy source for the selenate-reducing bacteria is supplied from the organic substance supply device 5. In this embodiment, the alcohol enclosing bag 5b is accommodated in the container 5a, and the selenium-containing water is supplied from the selenium-containing water storage tank 10 to the column container 2 via the container 5a by the liquid feeding pump 11. By supplying selenium-containing water to the column container 2 through the container 5a, the alcohol (lower alcohol having 1 to 3 carbon atoms, more preferably ethanol) gradually released from the alcohol-sealed bag 5b is mixed into the selenium-containing water. Thus, the alcohol can be supplied at the same time when the selenium-containing water is supplied into the column container 2.

  The supply of an organic substance such as alcohol serving as an energy source for microorganisms can be performed using, for example, a technique disclosed in International Publication No. 2006/135028. Specifically, alcohol, such as methanol, ethanol, and propanol, lactic acid, formic acid, acetic acid, and the like inside a sealed container (bag) partially including polyethylene, polypropylene, EVA (ethylene-vinyl alcohol copolymer), etc. By sealing an acid such as propionic acid as an organic substance, the organic substance required by the microorganism can always be gradually supplied without providing a pump or means for controlling the supply amount.

  However, the organic substance supply device 5 is not limited to the above-described form, and is an apparatus that supplies an organic substance simultaneously with selenium-containing water or separately from selenium-containing water using a pump or a means for controlling the supply amount. It is good.

  The selenium-containing water reduction treatment apparatus of this embodiment reduces selenium in selenium-containing water to selenious acid. This selenious acid can be removed and recovered by, for example, a known coprecipitation method (for example, a method in which iron salt is added to coagulate and precipitate selenious acid to separate solid and liquid) or a chemical reduction method. However, it is preferable to remove and collect by the method described below.

<Second Embodiment>
The selenium-containing water reduction treatment method according to the second embodiment is such that the selenite adsorbent 3a is attached to the surface of the carrier 3 in the selenium-containing water reduction treatment method of the first embodiment.

  An example of an apparatus for carrying out the selenium-containing water reduction treatment method according to the second embodiment is shown in FIG. A selenium-containing water reduction treatment apparatus 1a shown in FIG. 2 includes a column container 2 filled with a porous or fibrous carrier 3 having aggregated cells 4 containing selenate-reducing bacteria attached to the surface, and a column container. 2 includes an organic substance supply device 5 for supplying an organic substance, and a selenious acid adsorbent 3 a attached to the surface of the carrier 3.

  That is, the selenium-containing water reduction treatment device 1a according to the second embodiment is different from the selenium-containing water reduction treatment device 1 according to the first embodiment in that the selenite adsorbent 3a is fixed on the surface of the carrier 3. And other configurations are common.

  As the selenite adsorbent 3a, an adsorbent capable of adsorbing selenite and capable of maintaining the porous or fibrous structure of the carrier 3 and sufficiently maintaining the size of the specific surface area of the carrier 3 is appropriately used. be able to. As such a selenite adsorbent, for example, an active iron hydroxide (such as jarosite) adsorbent can be cited, and a lock ace SF (day of active iron hydroxide adsorbent adhering to the surface) Iron environmental engineering), but is not limited thereto.

  The adhesion of the selenite adsorbent 3a to the surface of the carrier 3 means that the carrier 3 and the fine particles of the selenite adsorbent 3a are mixed or a liquid containing the fine particles of the selenite adsorbent 3a is passed through the carrier 3. As a matter of course, the adhering due to the liquefaction includes a form in which the support 3 itself contains a selenite adsorbent and the selenite adsorbent is exposed on the surface thereof.

  Since the selenite adsorbent 3a is attached to the surface of the carrier 3 as in the present embodiment, the selenate contained in the selenium-containing water is reduced by the aggregate cells 4 of the selenate-reducing bacteria. As a result, selenious acid and selenous acid originally contained in the selenium-containing water are adsorbed on the surface of the carrier 3. Thereby, the total selenium concentration in the selenium-containing water can be reduced.

  Moreover, according to the experiments by the inventors of the present application, when Rockace SF is used as an adhesion carrier for the Pseudomonas sp. 4C-C strain, the reduction treatment of selenic acid can be performed very efficiently. It has been confirmed to be 32 mg / (L · day) per volume. From this, according to the processing method and processing apparatus of this embodiment, not only reduction of selenic acid and removal of selenious acid are performed, but also the effect of improving the reduction efficiency of selenic acid can be achieved. That is, it is possible to achieve a specific effect that selenite can be removed at the same time while improving the reduction efficiency of selenate. This effect is considered to be one of the factors, for example, because the selenite adsorbent 3a attached to the carrier 3 increases the area to which the aggregated bacterial cells 4 can be attached. Furthermore, selenic acid can be converted into insoluble selenium in the same column container, and there is an advantage that the apparatus can be easily made compact.

<Third embodiment>
In the selenium-containing water reduction treatment method according to the third embodiment, the step in the selenium-containing water reduction treatment method of the first embodiment is the first step, and the selenium-containing water treated in the first step is sublimated. A second step of contacting the selenate adsorbent 6 is further included.

  An example of an apparatus for carrying out the selenium-containing water reduction treatment method according to the third embodiment is shown in FIG. A selenium-containing water reduction treatment apparatus 1b shown in FIG. 3 includes a first column container 2 filled with a porous or fibrous carrier 3 having aggregated bacterial cells 4 containing selenate-reducing bacteria attached to the surface. , Further comprising an organic substance supply device 5 for supplying an organic substance into the first column container 2 and a second column container 12 which is installed at the rear stage of the first column container 2 and is filled with a selenious acid adsorbent 6 It is said.

  That is, the selenium-containing water reduction treatment apparatus 1b according to the third embodiment is different from the selenium-containing water reduction treatment apparatus 1 according to the first embodiment in the second column container 12 filled with the selenious acid adsorbent 6. Is different from the first column container 2 in the subsequent stage, and the other configurations are common.

  As the selenious acid adsorbent 6 filled in the second column container 12, a material having an ability to adsorb selenious acid can be appropriately used. Examples of such selenite adsorbents include Rockace SF (manufactured by Nippon Steel Environmental Engineering) with jarosite-based adsorbent attached to the surface, and Rockace FF with hydrotalcite-based adsorbent attached to the surface. (Manufactured by Nippon Steel Environmental Engineering Co., Ltd.) can be mentioned, and it is particularly preferable to use Rockace SF having a large specific surface area, but is not limited thereto.

  Containing selenium discharged from the first column container 2 by installing the second column container 12 filled with the selenious acid adsorbent 6 in the subsequent stage of the first column container 2 as in this embodiment. Selenious acid in water (selenous acid produced by reduction of selenic acid by aggregated cells 4 in the first column container 2 and further selenious acid originally contained in selenium-containing water) is contained in the second column container. 12 is adsorbed on the selenious acid adsorbent 6 in the inside. Thereby, the total selenium concentration in the selenium-containing water can be reduced.

  In addition, as in the case of the present embodiment, the second column container 12 filled with the selenious acid adsorbent 6 is installed at the subsequent stage of the first column container 2, so that When the selenate adsorption capacity decreases, the selenite adsorption capacity can be easily recovered by replacing with a new selenite adsorption material 6. Therefore, the convenience of the apparatus can be increased.

<Fourth embodiment>
The selenium-containing water reduction treatment method according to the fourth embodiment is a function of adding flocculated cells 4 to selenate-reducing bacteria and insolubilizing selenite in the selenium-containing water reduction treatment method of the first embodiment. It is assumed that it further contains a fungus having the above (aggregated bacterial cell 4 '). Alternatively, in addition to the aggregated cells 4 in the selenium-containing water reduction treatment method of the first embodiment, the aggregated cells 4 ″ including bacteria having a function of insolubilizing selenite are further included.

  An example of an apparatus for carrying out the selenium-containing water reduction treatment method according to the fourth embodiment is shown in FIG. The selenium-containing water reduction treatment apparatus 1c shown in FIG. 4 is a column container 2 filled with a porous or fibrous carrier 3 having aggregated bacterial cells 4 ′ and / or aggregated bacterial cells 4 ″ attached to the surface. And an organic substance supply device 5 for supplying an organic substance into the column container 2, and a selenite adsorbent adhering to the surface of the carrier 3.

  That is, the selenium-containing water reduction treatment apparatus 1c shown in FIG. 4 is different from the selenium-containing water reduction treatment apparatus 1 according to the first embodiment in that it further includes a bacterium having a function of insolubilizing selenite. Other configurations are common.

  The bacterium having the function of insolubilizing selenite may be included in the flocculated cell body 4 ′ containing the selenate-reducing bacteria to form the flocculated cell body 4 ′, or the bacterium having the function of insolubilizing selenite. The body 4 ″ may be prepared separately and attached to the carrier 3.

  Production of the aggregated microbial cell 4 ′ containing a selenate-reducing bacterium and a bacterium having a function of insolubilizing selenite is performed by, for example, the aggregation described in the first embodiment in a suspension in which these microbial cells are suspended. It can carry out by adding an agent suitably. The same applies to the production of aggregated bacterial cells 4 ″ containing bacteria having a function of insolubilizing selenite. However, among bacteria having the function of insolubilizing selenite, there are also cells that are difficult to aggregate, such as Paracoccus cells that have the function of reducing selenite to elemental selenium and making it insoluble. . As described above, it is preferable to use an inorganic flocculant and a polymer flocculant in combination for bacterial cells that are difficult to aggregate. Further, the size of the aggregated bacterial cells is as described in the first embodiment.

  Examples of bacteria having a function of insolubilizing selenite include, for example, selenite-reducing bacteria that directly reduce selenite to elemental selenium, and hydrogen sulfide is generated from sulfate ions as a raw material. Examples include sulfate-reducing bacteria that convert to insoluble selenium such as selenium, but the bacteria are not necessarily limited to these bacteria as long as they are capable of insolubilizing selenite directly or indirectly.

The selenite-reducing bacterium is not particularly limited as long as it has a function of reducing selenite to elemental selenium. Examples thereof include bacteria of the genus Paracoccus, preferably Paracoccus pantotrophus JCM-6892. . This bacterium is capable of reducing selenite to elemental selenium under anaerobic conditions. Moreover, as an energy source, it is possible to use yeast extract, sulfur-containing amino acid or lactate, as well as lower alcohols having 2 to 3 carbon atoms such as ethanol and propanol. Furthermore, even in the presence of high concentrations of nitrate ions, nitrite ions, and sulfate ions, nitrate ions and nitrite ions can be reduced to harmless nitrogen gas simultaneously with the reduction of selenite . That is, selenite reduction suitable for use in the reduction treatment according to the present invention using desulfurization effluent discharged from a coal-fired power plant that can contain nitrate ions, nitrite ions, and sulfate ions at high concentrations as selenium-containing water. It can be said that it is a fungus. In addition, since this bacterium is a facultative anaerobic selenite-reducing bacterium, the bacterium itself consumes free oxygen without performing a nitrogen gas purge or the like for making the inside of the column container anaerobic. Thus, the inside of the column container can be made an anaerobic environment. Therefore, since selenite reduction treatment can be performed without performing an operation for maintaining the inside of the column container under anaerobic conditions, the use of Paracoccus pantotrophus JCM-6892 strain is also suitable in this respect. . This is true not only for Paracoccus pantotrophus JCM-6892 but also other facultative anaerobic selenite-reducing bacteria.

  The sulfate-reducing bacterium is not particularly limited as long as it is a bacterium having a function of producing hydrogen sulfide using sulfate ions as a raw material. For example, an HT-1 strain which is a microorganism belonging to the genus Desulfovibrio is available. Can be mentioned. This bacterium is a bacterium that produces hydrogen sulfide using sulfate ions as a raw material under anaerobic conditions. Moreover, as an energy source, it is possible to use yeast extract, sulfur-containing amino acid, or lactate, as well as lower alcohols having 1 to 3 carbon atoms such as methanol, ethanol, and propanol. Furthermore, it is a bacterium that produces hydrogen sulfide using sulfate ions as a raw material even in the presence of high concentrations of nitrate ions and nitrite ions. That is, desulfurization wastewater discharged from coal-fired power plants that can contain nitrate, nitrite, and sulfate ions in high concentrations can be used as selenium-containing water, and hydrogen sulfide can be produced using sulfate ions as a raw material. It can be said that it is a sulfate-reducing bacterium suitable for use in the case of performing selenium reduction treatment according to the present invention as an object. This bacterium has been deposited at the National Institute of Advanced Industrial Science and Technology Patent Biological Deposit Center as deposit number FERM P-21577 on May 21, 2008.

  In addition, it becomes possible to share the organic substance supplied from the organic substance supply apparatus 5 as an energy source by utilizing the bacteria which can utilize the above C1-C3 lower alcohol, The above-mentioned 1st embodiment. The organic substance supply device 5 (container 5a, alcohol-filled bag 5b) can be used as an organic substance supply device for bacteria having a function of insolubilizing selenious acid. However, as a matter of course, the organic substance supply device for the fungus having the function of insolubilizing selenite may be provided separately from the organic substance supply device 5. In the case where an organic substance supply device is separately provided, an organic substance supply device may be used simultaneously with the selenium-containing water or separately from the selenium-containing water by using a pump or a means for controlling the supply amount. When sulfate-reducing bacteria are used, if sulfate ions are not contained in the selenium-containing water, sulfate ions may be added separately.

  Aggregated microbial cell 4 ′ containing a selenate-reducing bacterium and a bacterium having a function to insolubilize selenite, and an aggregated microbial cell 4 ″ containing a bacterium having a function to insolubilize selenite are the first embodiment described above. It can be made to adhere to the support | carrier 3 by the method similar to. In addition, a bacterial cell having a function of insolubilizing selenate-reducing bacteria and selenious acid after adhering to the surface of the carrier 3 an aggregating bacterial cell 4 ′ containing a selenate-reducing bacterium and a bacterium having a function of insolubilizing selenite. It is preferable to supply an organic substance as an energy source into the column container 2. In addition, after aggregating bacterial cells 4 '' containing bacteria having a function of insolubilizing selenite are attached to the surface of the carrier 3, an organic substance serving as an energy source of the bacteria having a function of insolubilizing selenite is used as a column container. 2 is preferably supplied. Thereby, the effect that the aggregated bacterial cells 4 ′, 4 ″ are stably attached to and retained on the carrier 3 is further increased.

  As in the present embodiment, by using a bacterium having a function of insolubilizing selenite together, the selenate contained in the selenium-containing water is an aggregated cell 4 or aggregated cell 4 ′ containing selenate-reducing bacteria. The selenious acid reduced by the above, and further selenious acid originally contained in the selenium-containing water is converted into insoluble selenium such as elemental selenium and adheres to the surface of the carrier 3. Thereby, the total selenium concentration in the selenium-containing water can be reduced.

  Moreover, according to the processing method and the processing apparatus of the present embodiment, selenic acid can be converted into insoluble selenium in the same column container, and there is an advantage that the apparatus can be easily made compact. In addition, since the carrier 3 is a carrier having a porous or fibrous structure, backwashing (removing insoluble selenium adhered by flowing water (treated water is possible) in the direction opposite to the water flow direction) is applied. It is possible to do this. Therefore, by performing backwashing at the stage where insoluble selenium such as elemental selenium is accumulated, there is also the convenience that the reduction ability of selenic acid can be easily recovered.

<Fifth embodiment>
In the selenium-containing water reduction treatment method according to the fifth embodiment, the step in the selenium-containing water reduction treatment method of the first embodiment is the first step, and the selenium-containing water treated in the first step is The method further includes a second step in which the aggregated cells containing bacteria having a function of insolubilizing selenate are brought into contact with a porous or fibrous structure carrier attached to the surface and an organic substance.

  An example of an apparatus for carrying out the selenium-containing water reduction treatment method according to the fifth embodiment is shown in FIG. A selenium-containing water reduction treatment apparatus 1d shown in FIG. 5 includes a first column container 2 filled with a porous or fibrous carrier 3 having aggregated bacterial cells 4 attached to the surface, and a first column container. 2 and a second column container filled with a porous or fibrous structure carrier 13 attached to the surface with agglomerated cells 4 '' containing bacteria having a function of insolubilizing selenite. 12, and an organic substance supply device 5 that supplies organic substances to the first column container 2 and the second column container 12.

  That is, the selenium-containing water reduction treatment apparatus 1d shown in FIG. 5 is different from the selenium-containing water reduction treatment apparatus 1 according to the first embodiment in that the aggregated microbial cells 4 '' containing bacteria having a function of insolubilizing selenite. Is different in that the second column container 12 filled with the porous or fibrous structure carrier 13 attached to the surface is installed in the subsequent stage of the first column container 2. Are common.

  As the carrier 13 filled in the second column container 12, a material having a high specific surface area such as porous ceramic, activated carbon, and fibrous substance can be used as appropriate, like the carrier 3 filled in the first column container. However, it is particularly preferable to use rock wool (fiberized blast furnace slag).

  As the bacteria having the function of insolubilizing selenite, the same bacteria as those mentioned in the fourth embodiment can be used. Further, as the method for producing the aggregated bacterial cell 4 ″, the same method as that described in the fourth embodiment can be used.

  In the case where an organic substance as an energy source of bacteria having a function of insolubilizing selenate-reducing bacteria and selenite is common, the organic substance is supplied from the organic substance supply device 5 to the first column container 2 as in the present embodiment. , And the remainder thereof is further supplied to the second column container 12 so that both the selenate-reducing bacteria and the bacteria having the function of insolubilizing selenite can be functioned.

  Aggregated bacterial cells 4 '' containing bacteria having a function of insolubilizing selenite can be attached to the carrier 13 by the same method as in the first embodiment. In addition, after aggregating bacterial cells 4 ″ containing bacteria having a function of insolubilizing selenite are attached to the surface of the carrier 13, an organic substance serving as an energy source of the bacteria having a function of insolubilizing selenite is added to the second organic substance. The column container 12 is preferably supplied. Thereby, the effect that the aggregated bacterial cells 4 ″ are stably attached to and held on the carrier 13 is further increased.

  As in this embodiment, by using a bacterium having a function of insolubilizing selenite in combination, selenate contained in the selenium-containing water is reduced by the aggregate cells 4 of the selenate-reducing bacteria. Selenic acid and further selenious acid originally contained in the selenium-containing water are converted into insoluble selenium such as elemental selenium and adhere to the surface of the carrier 13. Thereby, the total selenium concentration in the selenium-containing water can be reduced.

  Moreover, according to the processing method and the processing apparatus of this embodiment, selenic acid can be continuously converted into insoluble selenium using two column containers, so that element selenium is added to the carrier 13 of the second column container 12. When insoluble selenium such as selenium accumulates, a new second filler filled with a porous or fibrous structure carrier to which agglomerated cells 4 '' containing bacteria having a function of insolubilizing selenite are attached to the surface. By simply replacing the column container 12, the insolubilization ability of selenite can be easily recovered, or by performing backwashing when insoluble selenium such as elemental selenium has accumulated, It has the convenience that the insolubilization treatment capacity can be easily recovered.

  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, in the above-described embodiment, the aggregated cell body 4 includes a selenate-reducing bacterium or a selenate-reducing bacterium and a bacterium having a function of insolubilizing selenite. For example, according to the substance etc. which are contained in the selenium containing liquid, it is good also as what contains the microbe which can remove and convert the said substance suitably.

  In the above-described embodiment, the upward flow column apparatus is used, but a downward flow column apparatus may be used. The carrier may be immersed in a reaction tank and contacted with the selenium-containing water to be treated.

  Further, a plurality of first column containers 2 may be arranged in parallel or connected in series to treat selenium-containing water. A plurality of the second column containers 12 may be arranged in parallel or connected in series to treat the selenium-containing water. In this case, the retention time of the selenium-containing water can be lengthened to increase the treatment efficiency, and the treatment can be continued in the remaining column containers while the column containers are partially exchanged. It becomes a very suitable form for the treatment of actual waste water.

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

<Adjustment of bacteria>
The characteristics and culture method of the bacteria used in this example will be described below.

(1) Pseudomonas sp. 4C-C strain This bacterium is selenate-reduced, which was accepted under the accession number FERM P-20840 on March 13, 2006 at the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology. A selenate-reducing bacterium that has the ability to reduce selenate to selenite under anaerobic conditions using a lower alcohol such as methanol or ethanol as an energy source. Moreover, the bacteria even in the presence of nitrate or nitrite ions, are simultaneously nitrate ions and nitrite ions and the reduction of selenium acids have the ability to reduce the nitrogen gas. This bacterium also has the ability to reduce selenite to elemental selenium, but its reduction rate is low (see Power Central Laboratory Report V06017). In the following description, this bacterium is referred to as a selenate-reducing bacterium.

Selenate-reducing bacteria were pre-cultured in a general-purpose nutrient medium (Nutrient Broth 16.0 g / L, NaCl 5.0 g / L, pH 7.0) at 30 ° C., aerobic, 30 rpm for about 24 hours. Bacteria are collected by centrifugation at 8000 rpm for 10 minutes, suspended in phosphate buffer (Na ₂ HPO ₄ 9.0 g / L, KH ₂ PO ₄ 1.5 g / L, pH 7.5), and centrifuged under the same conditions. This was carried out twice for washing, and was finally suspended in an appropriate amount of phosphate buffer for the experiment.

(2) Paracoccus pantotrophus JCM-6892 strain (old species name: denitrificans)
This bacterium does not have the ability to reduce selenate, but has the ability to reduce selenite to elemental selenium under anaerobic conditions. Moreover, this bacterium has the ability to reduce nitrate ion and nitrite ion to nitrogen gas simultaneously with reduction of selenite even in the presence of nitrate ion and nitrite ion (Report of Central Research Institute of Electric Power Industry V06017). reference). In the following description, this bacterium will be referred to as a selenite-reducing bacterium.

  Selenite-reducing bacteria are pre-cultured, collected and washed under the same conditions as selenate-reducing bacteria except that the shaking speed is 120 rpm, and finally suspended in an appropriate amount of phosphate buffer. And used for the experiment.

(3) Desulfovibrio sp. HT-1 strain This bacterium is a sulfate-reducing bacterium that has been entrusted to the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology as the accession number FERM P-21577 on May 21, 2008. It has the ability to reduce sulfuric acid using lower alcohols such as methanol and ethanol as an energy source to produce hydrogen sulfide. Selenite is chemically reduced by this hydrogen sulfide (see Central Research Laboratory Report V07015). In the following description, this bacterium is referred to as a sulfate-reducing bacterium.

Sulfate-reducing bacteria can be cultured at 30 ° C, anaerobic (nitrogen substitution), 120 rpm, and about 1 week, with a medium for sulfate-reducing bacteria (Na ₃ (C ₃ H ₅ O ( COO) ₃ ) ・ 2H ₂ O 5.0 g / L, Na (C ₂ H ₅ OCOO) 3.5 g / L, Yeast extract 1.0 g / L, MgSO ₄・ 7H ₂ O 2.0 g / L, CaSO ₄ 1.0 g / L L, NH ₄ Cl 1.0 g / L, K ₂ HPO ₄ 0.5 g / L, pH 7.2), pre-culture, and then collect and wash under the same conditions as for selenate-reducing bacteria. Were suspended in an appropriate amount of phosphate buffer and used for the experiment.

<Analysis method>
Selenic acid and selenious acid were measured by combining an ion chromatography analyzer ISC-1500 with an AS12A column (both Dionex). As an organic matter index, soluble TOC was measured with a TOC-TN measuring device TNC-6000 (Toray Engineering). For the filtration of the sample, when measuring only selenic acid and selenious acid, the cellulose acetate filter paper DISMIC-13cp (Toyo Filter Paper) with a pore system of 0.2 μm is used, and when measuring TOC, the pore system is 0.3 μm. Glass fiber filter paper GF-75 (Toyo filter paper) was used.

[Comparative Example 1]
A selenate-reducing treatment ability was examined by filling a column-type container with a selenate-reducing bacteria entrapping immobilization support and making it flow upward.

(1) Production of entrapping immobilization carriers The following four types of entrapping immobilization carriers were produced.
(A) Selenate-reducing bacteria only (Ps)
(B) Selenate-reducing bacteria + selenite-reducing bacteria (Ps + Pa)
(C) Selenate-reducing bacteria + sulfate-reducing bacteria (Ps + De)
(D) Selenate-reducing bacteria + selenite-reducing bacteria + sulfate-reducing bacteria (Ps + Pa + De)

  For each carrier, selenate-reducing bacteria are collected from 750 mL of the culture solution used in <Bacterial preparation>, and selenite-reducing bacteria and sulfate-reducing bacteria are also collected from 500 mL of the culture solution as necessary. After washing, the bacterial suspension was adjusted to 15 mL.

  This was mixed with 45 mL of photocurable resin PVA-SbQ / SPP-H-13 (Toyo Gosei Co., Ltd.), poured into a petri dish with a diameter of 9 cm, and both sides were irradiated with metal halide lamps for 20 minutes each to harden the whole. Thereafter, the solid matter was taken out from the petri dish and cut so as to be a cube having a side of less than 1 cm.

  The completed carrier was immersed in an artificial substrate (low salinity) shown in Table 1 to which sodium selenate equivalent to 100 mg Se / L and ethanol equivalent to 1 g / L were added. When acclimatized for about one week across the medium exchange, reduction of selenate was confirmed immediately after immersion. Further, the carrier swelled to about 1.5 times the original size. The carrier in this state was used for a water flow experiment. In Table 1, Trace Metal Sol. (Mixed solution of essential elements) is published in the literature (Toshihiro Saito et al .: Effects of nitrite on the fate of two major polyphosphate-accumulating bacteria, Environmental Engineering Research Papers, Vol. 46, 659-663, 2009.) It was the same as what was posted.

(2) Setting of apparatus and operating conditions A cylindrical column having an effective volume of 150 mL (inner diameter: 4 cm, height: 12 cm) was filled with almost the entire amount of the entrapping immobilization support. A polyethylene bag filled with ethanol (polyethylene thickness: 0.05 mm thickness, 3 cm × 8 cm) was also installed in the column. Due to the ethanol permeability of the polyethylene film, the ethanol sealed in the bag is gradually released out of the bag, and ethanol equivalent to 9 mgC (25 ° C.) is supplied per day.

  The artificial substrate (low salinity) shown in Table 1 was passed through this apparatus. For the first 15 days, the selenate concentration was 20 mg / L and the flow rate was 620 mL / d, and for the following 22 days, the selenate concentration was 5 mg / L and the flow rate was 1300 mL / d. The hydraulic residence time (HRT) is 5.8 hours and 2.8 hours, respectively. Further, the supply organic substance concentrations are 15 mgC / L and 7 mg / L, respectively. The temperature was about 25 ° C. The operation was carried out without performing nitrogen substitution or ventilation for making the anaerobic state.

  About the reducing ability of selenic acid and selenious acid in this experiment, it converted into the reduction | restoration speed | rate per apparatus volume, and showed the result shown in FIG. 6A and FIG. 6B. 6A shows the reduction rate of selenate per unit volume, and FIG. 6B shows the reduction rate of selenite per unit volume. In the figure, the dotted line is the upper limit of speed (the speed when the total amount of inflowing selenic acid is reduced). The reduction rate of selenate is obtained by dividing the amount of decrease in selenate concentration by HRT, and the reduction rate of selenite is obtained by dividing the total decrease in selenate concentration and selenite concentration by HRT. Is.

  From the start of the experiment to the 15th day (inflow selenic acid concentration 20 mg / L), 80 to 90% of selenic acid was reduced, and it was about 70 mg / (L · day) in terms of the rate per volume. . There was little difference due to immobilized bacteria.

  Moreover, although it was slow compared with the reduction | restoration of selenic acid, the reduction | restoration of a fixed amount of selenious acid had also occurred. The rate of reduction of selenite was about 25 mg / (L · day) for the carrier mixed with three types of bacteria, which was higher than about 15 mg / (L · day) for the other carriers.

  From the 16th day to the 37th day of the experiment (inflow selenate concentration 5 mg / L), a difference was observed in the selenate reduction rate for each carrier. The carrier (a) containing only selenate-reducing bacteria was the fastest, and about 80% of selenate was reduced, and the rate was about 35 mg / (L · day). Hereinafter, the speed decreased in the order of the selenite-reducing bacteria mixed carrier (b), the three-type mixed carrier (d), and the sulfate-reducing bacteria mixed carrier (c). Moreover, these reduction | restoration rates were about half of the support | carrier (a) of only a selenate reducing bacterium.

  The reduction rate of selenious acid was about 15 mg / (L · day) with the three-type mixed carrier (d). However, with other carriers, almost no reduction of selenite occurred.

  From the above results, by using the entrapped immobilization support, selenic acid can be reduced to selenious acid by performing continuous continuous water treatment without nitrogen replacement or ventilation for anaerobic conditions. It became clear that this is possible. In other words, the configuration of the apparatus is an upward flow column type, and by supplying more organic matter than the amount necessary for the reduction of selenate, the contact area between the waste water and the air in the apparatus is extremely small. By letting the selenate-reducing bacteria, a bacterium, consume dissolved oxygen in the inflow water, most of the inside of the device can be made anaerobic, and the selenate-reducing bacteria can maintain anaerobic conditions sufficient to exert their ability to reduce selenate. I thought it was possible.

  It should also be noted that the carrier (a) in which only the selenate-reducing bacteria are immobilized has a higher selenate reduction rate than the other carriers (b) to (d). Since this tendency was conspicuous under conditions where the residence time was short, it is presumed that this tendency was caused by the contact efficiency between the bacterial cells and selenic acid or ethanol. Therefore, it is considered that the reduction rate of selenate may be increased by setting a condition that allows a large amount of selenate-reducing bacteria to be retained in a space in the vicinity of the surface in the carrier that is easily contacted with the substrate. Specifically, in addition to the method of immobilizing only selenate-reducing bacteria, a method of increasing the entire surface area can be considered.

  However, whichever method is selected, there may be a problem of accumulation of elemental selenium particles. In this experiment, after about 40 days of experiment, the carrier (a) in which only the selenate-reducing bacteria were immobilized had a red color that was considered to be elemental selenium. Selenate-reducing bacteria have not only the ability to reduce selenate to selenite, but also a slight ability to reduce selenite to elemental selenium. This is what can generally occur in selenate-reducing bacteria. As elemental selenium accumulates in the carrier, the effective space for the function of the selenate-reducing bacteria is narrowed, and therefore the reduction rate of selenate is expected to decrease. Also in this experiment, in the carriers (b) to (d) that were finally dark red, the reduction rate of selenic acid tended to decrease. In addition, since it is assumed that the load of selenic acid in the actual desulfurization effluent is considerably lower than in this experiment, it is considered that the speed does not decrease in such a short period. Nevertheless, it is considered that the possibility of renewing the carrier as the processing speed decreases is a problem to be considered in terms of processing costs.

[Example 1]
The present inventors examined a method capable of exhibiting a stable selenate reduction treatment ability over a longer period of time than when using a entrapping immobilization support.

  Specifically, using a microorganism-adhered carrier in which cells are adhered to a carrier having a large specific surface area as a column packing material, a treatment device that allows water to flow in an upward flow is prepared in the same manner as in Comparative Example 1 to reduce selenate. The processing ability was examined.

(1) Production of microorganism-adhering carrier Rock wool (Nippon Environmental Engineering) was used as the carrier. Rock wool is a granular cotton in which fine fibers are gathered. It is a material mainly composed of calcium silicate, and almost no dissolution or elution is observed near neutrality. Moreover, it confirmed beforehand that there is no adsorption ability of selenic acid or selenious acid alone.

  A cylindrical column having an effective volume of 1000 mL (inner diameter: 5 cm, height: 50 cm) was filled with the above-mentioned rock wool equivalent to 100 mL, and the volume filling rate was about 10%. In addition, a small container is placed in front of the column, and a methanol-enclosed polyethylene bag (polyethylene thickness: 0.05 mm thickness, 3 cm × 6 cm) or an ethanol-enclosed polyethylene bag (polyethylene thickness: 0.05 mm thickness) 3 cm × 8 cm) was accommodated, and water to be treated was passed through the column through a small container so that the organic substance was supplied to the column. In addition, methanol corresponding to 11 mgC (20 ° C.) to 18 mgC (25 ° C.) is supplied from the methanol-filled polyethylene bag per day. Further, methanol equivalent to 10 mgC (20 ° C) to 18 mgC (25 ° C) is supplied from the ethanol-filled polyethylene bag per day. From the start of the experiment to the 55th day, a methanol-filled polyethylene bag was used, and from the start of the experiment on and after the 56th day, an ethanol-filled polyethylene bag was used.

  The artificial substrate (low salinity) shown in Table 1 was passed through this apparatus at a flow rate of 2400 mL / d, so that the HRT was 10 hours. After the experiment was started with a selenate concentration of 20 mg / L in the influent water, the operation was continued with the concentration lowered to 10 mg / L. The temperature was 20-25 ° C. The feed organic concentration was 4 mg / L (20 ° C.) to 8 mg / L (25 ° C.).

  First, the selenate-reducing bacteria suspension was circulated through the column for 1 day from the start of the experiment to try to attach the selenate-reducing bacteria to the rock wool. In this method, reduction of a certain amount (1-2 mg / L with respect to the inflow selenate concentration of 20 mg / L) was observed immediately after the adhesion (FIG. 7, ●: selenate concentration, ◯: selenite concentration). ), The reduction ability quickly declined. From this, it was considered that the selenate-reducing bacteria could not be sufficiently adhered to the rock wool simply by passing the bacterial suspension through the column.

  Therefore, polyaluminum chloride (inorganic flocculant) equivalent to 300 to 500 mg / L is added to 30 mL of a suspension of selenate-reducing bacteria (the amount collected from 6 L of the culture solution) to agglomerate until the cells can be visually recognized. I let you. Then, the suspension containing the aggregated bacterial cells was passed through the column at a frequency of once a week from the 22nd day to the 49th day.

  As a result, the reduction rate of selenate gradually increased while repeating the rapid increase in the reduction rate immediately after adhesion and the reduction to about half of the increase. From this, it was clarified that the aggregated bacterial cells can be sufficiently adhered to the rock wool even after transient water passage after aggregation. Furthermore, on the 56th day of the experiment, when the supplied organic substance was changed from methanol to ethanol, almost all of the inflow selenic acid was reduced (FIG. 7).

  Next, experiments were conducted by attaching selenate-reducing bacteria, selenite-reducing bacteria, and sulfate-reducing bacteria to rock wool. Polyaluminum chloride equivalent to 300 to 500 mg / L (inorganic aggregation) in 30 mL of a suspension of selenate-reducing bacteria (collected from 6 L of culture solution) and selenite-reducing bacteria (collected from culture solution L) Agent) was added, and the cells were aggregated to a size allowing the cells to be visually recognized. Then, the suspension containing the aggregated cells was passed through the column immediately after the start of the experiment and on the 13th day. In addition, 30 mL of a suspension of selenite-reducing bacteria (collected from 0.5 to 1 L of the culture solution) is equivalent to 300 to 500 mg / L of polyaluminum chloride (inorganic flocculant) and 2 to 5 mg / L. Acrylamide-N, N-dimethylaminoethyl acrylate copolymer (polymer flocculant) was added to agglomerate the cells to a size that could be visually recognized. Then, the suspension containing the aggregated cells was passed through the column on the 37th day from the start of the experiment. Furthermore, 300-500 mg / L of polyaluminum chloride (inorganic flocculant) was added to a suspension of sulfate-reducing bacteria (the collected amount from 1 L of the culture solution), and the cells were aggregated to a size that allows visual recognition. . The suspension containing the aggregated cells was passed through the column on the 62nd, 69th, and 78th days from the start of the experiment.

  Moreover, ethanol was supplied to the column using the ethanol enclosure polyethylene bag over the whole experiment period.

  The experimental results are shown in FIG. The reduction rate in FIG. 8 is calculated by the same method as the reduction rate in FIG. It was confirmed that almost all of the inflow selenate was reduced at the third day of the experiment.

  Moreover, from the results shown in FIG. 7 and FIG. 8, it was confirmed that almost all the inflow selenic acid was reduced. The reduction rate at that time was 48 mg / (L · day) when the influent selenate concentration was 20 mg / L, and 24 mg / (L · day) when the inflow selenate concentration was 10 mg / L. Moreover, in any experiment, the selenate reducing ability was maintained for a long period of 150 days or more without decreasing. There were some cases where the total amount of selenate was not reduced, but there was a problem with air conditioning at this time, and it was thought that the ability to reduce selenate-reducing bacteria was reduced due to a decrease in temperature. It was.

  In addition, when three types of bacteria, selenate-reducing bacteria, selenite-reducing bacteria, and sulfate-reducing bacteria were attached, selenite corresponding to 10% of the inflow selenate concentration was reduced. In addition, red coloring seen as elemental selenium was seen in the entire column, but the treated water after passing through the column was colorless, and there was no problem such as a decrease in water flow rate due to column clogging.

  From the above results, using the column apparatus packed with the microorganism-adhering carrier in Example 1 is more stable for a long time than when using the column apparatus packed with the entrapping immobilization carrier of Comparative Example 1. It was revealed that reduction treatment of selenic acid can be performed.

  The rock wool used as the adherent carrier has a very large specific surface area, and the space for the function of the selenate-reducing bacteria is larger than that of the entrapping immobilization carrier. Furthermore, even if accumulation of insoluble selenium such as elemental selenium progresses, the structure can be dealt with by backwashing instead of replacement of the carrier. From these characteristics, it can be said that the microorganism-adhering carrier is more suitable for long-term use than the entrapping immobilization carrier.

[Example 2]
Based on the examination result of Example 1, the combined use of selenate treatment and selenite treatment was further examined.

  Specifically, the conditions shown in Table 2 were examined. In Table 2, Ps means selenate-reducing bacteria, Pa means selenite-reducing bacteria, and De means sulfate-reducing bacteria. In addition, methanol was supplied under the condition of 4 alone, but ethanol was supplied under other conditions, and the experiment was conducted.

  In Table 2, the raw carrier is the rock wool used in Example 1. The FF is a Rock Ace FF (Nippon Environmental Engineering) in which a hydrotalcite (magnesium) -based adsorbent is adhered to the rock wool used in Example 1. SF is Rock Ace SF (Nippon Environmental Engineering) in which an active iron hydroxide-based adsorbent is attached to the rock wool used in Example 1. Note that Lock Ace FF and Lock Ace SF were obtained as adsorbents for selenious acid. The artificial substrate (high salinity) shown in Table 1 was passed through for about one week to confirm that no adsorption of selenate ions was observed, and the adsorbent components that were not sufficiently adhered were washed away.

  When attaching microorganisms, the amount of bacteria used in one attachment is as follows: selenate-reducing bacteria are collected from 1.5 L of culture solution; selenite-reducing bacteria are collected from 0.5 L of culture solution The sulfate-reducing bacteria were collected from 1.2 L of the culture solution. For the production of aggregated bacterial cells, 300-500 mg / L equivalent polyaluminum chloride (inorganic flocculant) and 2-5 mg / L equivalent acrylamide-N, N-dimethylaminoethyl acrylate copolymer (polymer flocculant) ). The suspension containing the agglutinating cells was allowed to pass through immediately after the start of the experiment.

  In this experiment, in order to approach the treatment conditions of actual wastewater, the artificial substrate (high salinity) shown in Table 1 was passed through, and the inflow selenate concentration: 5 mg / L, the supply organic matter (ethanol) concentration: 4 mgC / L stepwise 1 column HRT: 3.8 hours. During operation, the temperature was kept at 30 ° C. Furthermore, in this experiment, since the 150 mL cylindrical column used in Comparative Example 1 was used, the inner diameter was reduced as compared with the column of Example 1, and as a result, the rock wool filling rate was 10% to 5%. Decreased to 7%.

(1) Results of duplicate experiments The results of duplicate experiments are shown in FIGS. FIG. 9A shows the result of the first stage of the second series, FIG. 10A shows the result of the second stage of the second series, and FIG. 11A shows the result of the second stage of the second series. 9B shows the result of the second stage of the second series, FIG. 10B shows the result of the second stage of the second series 2, and FIG. 11B shows the result of the second stage of the second series. In the figure, ● represents the selenate concentration, ◯ represents the selenite concentration, and x represents the TOC concentration. ▽ represents the addition of bacteria.

  First, the results of the first stage of the duplexes 1 to 3 shown in FIGS. 9A to 11A will be examined. In the period when the organic substance (ethanol) supply amount is 4 mg / L (from the start of the experiment to the 14th day), all three types increased the selenate concentration and decreased the selenite concentration in the treated water, that is, the ability to reduce selenate. The decline has progressed. Therefore, the organic substance supply amount was increased to 6 mg / L or equivalent (Experiment 14), and a suspension containing aggregated cells of selenate-reducing bacteria was passed through on Experiment 18; About half of them were reduced to selenious acid. When converted to a reduction rate per unit volume, this corresponds to 16 mg / (L · day). Subsequently, when the organic substance supply amount was increased to 8 mg / L equivalent in the hope of improving the reduction rate (Experiment 28th day), almost all of the selenic acid was temporarily reduced, The reducing ability showed a downward trend again. From the above results, it became clear that the high reducing ability of selenate-reducing bacteria selenate can be maintained by setting the organic substance supply amount to 6 mg / L or more and less than 8 mg / L under the operating conditions in this example. .

  Next, the results after the second series 1 to 3 shown in FIGS. 9B to 11B will be examined. For the treatment of selenious acid in the latter stage, the setting of duplex 1 (bacteria mixing) and the setting of duplex 3 (use of Rockace SF) were effective.

  In addition, in the second stage of the second series, Experiment 14 in which the amount of organic matter supplied in the previous stage was increased to 6 mg / L, although the selenite-reducing bacteria and the sulfate-reducing bacteria did not have the ability to reduce selenate. From day 35 onward, the total amount of selenic acid was reduced to 8 mg / L, and after day 35 of the experiment, the total amount of selenious acid was able to be reduced as a whole apparatus (FIG. 9B). This is probably because the selenate-reducing bacteria adhering to the former stage were unintentionally planted on the latter carrier.

  Moreover, although the supply of selenious acid from the former stage was not stable in the second and third stages, it was confirmed that the entire amount of selenious acid was removed from the start of the experiment to the 25th day (FIG. 11B). ).

  In addition, although a certain amount of selenite was decreased in the second stage of the second series, the residual amount of selenite was higher than the result of the second stage of the second series (FIG. 10B).

  From the above results, as a method of treating selenite for use in combination with the previous column under the operating conditions of this experiment, aggregated cells of selenite-reducing bacteria and aggregated cells of sulfate-reducing bacteria were obtained from rock wool ( Adopting a method using a microorganism-adhering carrier attached to an unprocessed), Rockace FF with a hydrosite adsorbent attached to rock wool, and Rockace SF with an active iron hydroxide adsorbent fixed to rock wool. In particular, a microbial adherent carrier in which aggregated cells of selenite-reducing bacteria and sulfate-reduced bacteria are adhered to rock wool (raw), and active iron hydroxide adsorbent is fixed to rock wool. It has become clear that it is preferable to adopt the method using the lock ace SF.

(2) Experimental results in single column type FIGS. 12 to 15 show the experimental results in the single column type. FIG. 12 shows a single 1 condition, FIG. 13 shows a single 2 condition, FIG. 14 shows a single 3 condition, and FIG. 15 shows a single 4 condition. In the figure, ● represents the selenate concentration, ◯ represents the selenite concentration, and ▽ represents the addition of bacteria.

  The amount of organic matter (ethanol) supplied in one condition where rock wool (raw) is aggregated with selenate-reducing bacteria, selenite-reducing bacteria, and sulfate-reducing bacteria. Characteristic properties were shown for each condition. That is, the reduction of selenate did not proceed at an organic substance supply amount of 4 mg / L. On the other hand, when the supply amount was increased to 6 mg / L, about half of the inflow selenate, 5 mg / L, was reduced to selenite without adding aggregated cells of selenate-reducing bacteria. However, reduction of the produced selenious acid did not proceed. Furthermore, when the organic substance supply amount was increased to 8 mg / L, the reduction ability of selenate increased slightly and reduction of selenite progressed. Eventually, the selenate concentration in the treated water was 1.5-2 mg / L, and the selenite concentration was below the detection limit. Therefore, in the conditions of this example, in addition to the aggregated cells of selenate-reducing bacteria, attaching aggregated cells of selenite-reducing bacteria and sulfate-reduced bacteria to the carrier It can be said that there was an effect of stabilizing the selenic acid reduction ability to a higher level.

  As one of the factors, for example, as the reduction of selenite progresses, the adverse effect of selenite on the selenate reduction can be reduced. Another possible cause is that many fine particles were generated in the column. For example, it is easily predicted that elemental sulfur and sulfide salts are precipitated from the presence of sulfate-reducing bacteria and the wastewater composition with a high sulfate concentration (Table 1). When these fine particles are captured by rock wool, it is considered that the surface of the fiber of the originally smooth rock wool is uneven and the specific surface area is increased, so that more bacteria can be retained.

  Next, no reduction of selenate was observed under the two independent conditions in which aggregated cells of selenate-reducing bacteria were attached to Rockace FF in which hydrotalcite-based adsorbent was fixed to rock wool (raw). (FIG. 13). This is because Rockace FF has a hydrotalcite-based adsorbent fixed as a result of inconspicuous shape of the fibers of the rock wool itself, and alkaline components are eluted in the drainage (the pH after water flow is It is thought that this is because it is not suitable for adhesion of bacterial aggregates.

  Next, single three conditions (ethanol supply) and single four conditions (methanol) in which aggregated cells of selenate-reducing bacteria were adhered to Rockace SF, in which active iron hydroxide-based adsorbent was fixed to rock wool (raw) In the case of (Supply), excellent results were obtained in both the reducing ability of selenic acid and the adsorption ability of selenious acid.

  In addition, it was confirmed that stable selenate-reducing ability was obtained at 6 mg / L when ethanol was supplied alone, and reduced until the selenate concentration was below the detection limit with 6 mg / L of ethanol. did it. Further, the selenite concentration also remained below the detection limit until the 40th day of the experiment, and thereafter remained below 1 mg / L. When converted to the rate per unit volume, the reduction rate of selenate is 32 mg / (L · day), and the selenite treatment is also performed at the same rate.

  Furthermore, stable reduction of selenic acid was possible even under four single conditions supplied with methanol. Specifically, when the organic substance (methanol) supply amount was 8 mg / L, the selenate concentration was 1 to 1.5 mg / L, and the selenite concentration was stable below the detection limit.

  From the results shown in the single three conditions and the single four conditions, it was found that using rock wool mixed with and adhering an active iron hydroxide adsorbent as a carrier not only provided selenite adsorption capability, but also selenium. It has been clarified that there is an effect of remarkably increasing the ability of acid-reducing bacteria to reduce selenate.

The presumed factors are thought to be the mitigation of the adverse effects caused by selenious acid and the increase of the specific surface area caused by the adsorbent particles, as in the case of single substance 1. However, while selenite was below the detection limit, selenic acid remained in single 1 (experiment 35 to 50 days), but not in single 3 (experiment 23rd and later). Therefore, the retention capacity of selenate-reducing bacteria has a greater influence on the reduction capacity of selenate than the concentration of selenite, and the adsorbent particles are more effective than the increase of retention capacity by sulfur-based particles. It is considered that the effect of increasing the holding ability by the is large.

1 Selenium-containing water reduction treatment device 2 (first) column container 3 (filled in the first column container) carrier 3a selenite adsorbent 4 aggregated cell body 4 'containing selenate-reducing bacteria 4' selenate-reducing bacteria And agglomerated cells containing bacteria having a function to insolubilize selenite 4 '' Aggregated cells containing bacteria having a function to insolubilize selenite 5 Organic substance supply device 6 Selenite adsorbent 12 Second column container 13 Carrier (packed in second column container)

Claims (14)

A column container filled with a porous or fibrous structure carrier, which is prepared by adding a flocculant to a suspension containing a selenate-reducing bacterium and having the flocculated microbial cell containing the selenate-reducing bacterium attached to the surface And a selenium-containing water reduction treatment apparatus, comprising: an organic substance supply apparatus that supplies an organic substance into the column container. The selenium-containing water reduction treatment apparatus according to claim 1, wherein an active iron hydroxide-based selenite adsorbent is attached to the surface of the carrier. The selenium-containing water reduction apparatus according to claim 1, further comprising a second column container filled with a selenious acid adsorbent at a subsequent stage of the first column container, wherein the column container is a first column container. The selenium-containing water reduction treatment apparatus according to claim 1, wherein a bacterium having a function of insolubilizing selenite is further contained in the aggregated cells. 5. The selenium-containing water reduction treatment apparatus according to claim 1, wherein, apart from the aggregated cells, aggregated cells containing bacteria having a function of insolubilizing selenite are attached to the surface of the carrier. The column container is a first column container, and a porous or fibrous structure in which agglomerated cells containing bacteria having a function to insolubilize selenite are attached to the surface after the first column container. The selenium-containing water reduction treatment apparatus according to claim 1, further comprising a second column container filled with a carrier. A selenium- containing water and a carrier having a porous or fibrous structure on which the agglutinating cells containing the selenate-reducing bacteria prepared by adding a flocculant to a suspension containing selenate-reducing bacteria are attached to the surface. A selenium-containing water reduction treatment method comprising a step of contacting an organic substance. The selenium-containing water reduction treatment method according to claim 7, wherein an active iron hydroxide-based selenite adsorbent is attached to the surface of the carrier. The selenium-containing water reduction treatment method according to claim 7, further comprising a second step in which the step is the first step, and the selenium-containing water treated in the first step is brought into contact with the selenious acid adsorbent. . The selenium-containing water reduction treatment method according to claim 7, wherein a bacterium having a function of insolubilizing selenite is further contained in the aggregated cells. The selenium-containing water reduction method according to claim 7 or 10, wherein aggregating bacterial cells containing bacteria having a function of insolubilizing selenite are attached to the surface of the carrier separately from the aggregating bacterial cells. Porous or fibrous, in which the above process is the first process, and the selenium-containing water treated in the first process has an agglomerated microbial cell containing bacteria having a function of insolubilizing selenite. The selenium-containing water reduction treatment method according to claim 7, further comprising a second step of bringing the structure carrier into contact with an organic substance. Has a function to insolubilize the selenate reducing bacteria and / or the selenite coagulant was prepared by adding to a suspension containing bacteria having the ability to insolubilize the selenate reducing bacteria and / or selenite A selenium-containing carrier for water reduction treatment, characterized in that aggregated bacterial cells containing bacteria are attached to the surface of a porous or fibrous carrier. Has a function to insolubilize the selenate reducing bacteria and / or the selenite coagulant was prepared by adding to a suspension containing bacteria having the ability to insolubilize the selenate reducing bacteria and / or selenite A method for producing a carrier for selenium-containing water reduction, comprising a step of passing a solution in which aggregated bacterial cells containing bacteria are suspended through a porous or fibrous structure carrier.