JP6939296B2 - Treatment method and treatment equipment for selenium-containing water - Google Patents

Description

The present invention relates to a method and an apparatus for reducing selenium-containing water by contacting it with a mixture or alloy of metallic titanium and a metal lower than titanium, and in particular, the selenium-containing water is sulfite ion, thiosulfate ion, nitrite ion. The present invention relates to a method and an apparatus for treating selenium-containing water containing such substances.

By bringing selenium-containing water such as coal gasified wastewater into contact with a mixture of metallic titanium particles and lower metal particles (for example, aluminum particles) and elution of aluminum or the like by lowering the pH at that time. , A method for treating selenium, which is removed by reducing selenium in wastewater by a local battery action, is known (Patent Documents 1 to 3).

In the selenium reduction reaction by the reducer, hydrogen gas, hydrogen sulfide, hydrogen selenium gas, etc. are generated by the following by-product reactions (see the reaction formula below, etc.). It was necessary to reduce the gas concentration. Patent Document 3 describes that a column filled with an iron oxide-based hydrogen sulfide absorber is ventilated, or an alkaline scrubber is ventilated with a gas generated from a reduction tower to remove a trace amount of hydrogen sulfide. ..
<Hydrogen gas generation reaction formula>
In the case of iron reducer Fe + 2HCl → Fe ²⁺ + 2Cl ⁻ + H ₂
In the case of composite metal reducer 2Al + 6HCl → 2Al ³⁺ + 6Cl ⁻ + 3H ₂
<Hydrogen sulfide gas generation reaction mechanism>
When the raw water contains sulfite ions and thiosulfate ions, they are also reduced at the same time under the condition that the redox potential is low, and hydrogen sulfide is generated.
<Hydrogen selenide gas generation reaction mechanism>
Selenium (Se (VI)) is reduced to selenous acid (Se (IV)) and then becomes zero-valent solid elemental selenium (Se (0)) such as amorphous selenium and metallic selenium. a (Se (0)) of the part is further reduced gaseous hydrogen selenide _(H 2 Se).

Japanese Unexamined Patent Publication No. 2008-30020 Japanese Unexamined Patent Publication No. 2009-11914 JP-A-2015-39652

According to Patent Document 3, after the step of passing the water to be treated to the reduction tower, the passage of the water to be treated is stopped, and air and washing water are flowed upward to the reduction tower to wash the reduction tower. Have been described. When the water to be treated is passed through the reducing tower filled with the reducing body, the generated gas accumulates in the gap between the reducing body and the reducing body over time during the normal operation, and a large amount of gas is generated when the normal operation is shifted to the backwashing operation. Is released from the reduction tower and supplied to the gas treatment facility. Therefore, it is necessary to increase the size of the gas treatment equipment.

An object of the present invention is to provide a method and an apparatus for treating selenium-containing water in which a large amount of gas is prevented from being generated from the reduction tower at the start of washing.

In the method for treating selenium-containing water of the present invention, the selenium-containing water is passed through a reduction tower and brought into contact with a mixture or alloy of metallic titanium filled in the reduction tower and a metal lower than titanium to bring the selenium-containing water into contact with the base. A method for treating selenium-containing water in which selenium in the selenium-containing water is reduced by eluting a part of a single metal. The method for treating selenium-containing water, which carries out a washing step of washing with air and water, is characterized in that, prior to the washing step, degassing to discharge gas from the reduction tower is performed.

In one aspect of the method for treating selenium-containing water of the present invention, the degassing is performed by draining water from the reduction tower and refilling it with water.

In one aspect of the method for treating selenium-containing water of the present invention, the degassing is performed by aerating air and / or an inert gas into the reducing tower.

In the selenium-containing water treatment apparatus of one aspect of the present invention, the selenium-containing water is brought into contact with a mixture or alloy of metallic titanium and a simple substance of a metal lower than titanium to elute a part of the base metal. In a selenium-containing water treatment apparatus having a reduction tower for reducing selenium in the selenium-containing water and a cleaning means for supplying air and water to the reduction tower for cleaning, water is drained from the reduction tower. It is characterized by being provided with a degassing means for degassing from the inside of the reduction tower by refilling with water.

In the selenium-containing water treatment apparatus of one aspect of the present invention, the selenium-containing water is brought into contact with a mixture or alloy of metallic titanium and a simple substance of a metal lower than titanium to elute a part of the base metal. In a selenium-containing water treatment apparatus having a reduction tower for reducing selenium in the selenium-containing water and a cleaning means for supplying air and water to the reduction tower for cleaning, air and / / in the reduction tower. Alternatively, it is characterized by being provided with a degassing means for venting an inert gas and venting the gas from the inside of the reduction tower.

The present invention is a method and apparatus for treating selenium-containing wastewater in which selenium is reduced by bringing selenium-containing water into contact with a mixture or alloy of metallic titanium and a base metal thereof and eluting a part of the base metal. Since the gas is degassed from the reduction tower before the start of the cleaning process, it is possible to prevent a large amount of gas from being generated from the reduction tower at the start of cleaning. According to the present invention, it is not necessary to increase the size of the gas treatment equipment, and the cost increase is prevented.

It is a system diagram which shows the embodiment of the selenium-containing water treatment apparatus of this invention.

Hereinafter, embodiments of the selenium-containing water treatment method and treatment apparatus of the present invention will be described in detail.

The selenium-containing water to be treated in the present invention contains hexavalent selenium such as selenic acid and tetravalent selenium such as selenic acid as selenium. Examples include raw water for water, wastewater from the metal refining industry, wastewater from the glass industry, wastewater from the combustion exhaust gas treatment process for coal or oil, wastewater from flue gas desulfurization at thermal power plants, and wastewater from semiconductor factories.

When selenium-containing water is brought into contact with a mixture or alloy of titanium and a base metal (hereinafter, may be referred to as a mixture or the like), base metal ions are eluted in the water. The electrons generated when the base metal elutes move to the surface of the metallic titanium, and selenium in the selenium-containing water, for example, hexavalent selenium, is reduced on the surface of the metallic titanium according to the following reaction formula.
_{^{SeO 4 2- + 6e - + 8H}} + → Se 0 + 4H 2 O

As the base metal such as the titanium / base metal mixture used in this reduction treatment, various metals lower than titanium can be used, but the sludge made of hydroxide generated by pH adjustment after elution of the base metal ion exhibits a white color. Those are preferable. That is, when the sludge is white, it is easier to dispose of the sludge than when it is colored brown or the like. Base metals that generate white sludge, preferably aluminum, zinc (Zn), tin (Sn), etc., are particularly excellent in terms of solubility, and are preferably used in the present invention. can. The base metal may be only one kind of metal, but may be a mixture or alloy of two or more kinds of metals.

The shape of the titanium / base metal mixture or the like preferably has a large surface area. For example, a powdery substance, a granular substance, a fibrous substance, a fine thin film-like substance (scale-like substance), or the like having a particle size of about 10 μm to 5 mm can be used. The titanium / base metal mixture may be a mixture of metallic titanium having the same shape and size and a base metal alone, or a mixture of metallic titanium having a different shape or size and a base metal alone. Further, each of the metallic titanium and the base metal alone may have different shapes and different dimensions. As the metallic titanium, it is preferable to use sponge titanium because it has a large specific surface area.

As for the ratio of metallic titanium to base metal such as titanium / base metal mixture, if the amount of metallic titanium is large, the amount of electrons generated when the base metal is melted increases to the surface of metallic titanium, and the amount of selenium reduced on the surface of metallic titanium increases. It increases and the reduction efficiency is improved, but if the proportion of the base metal is too small, most of the electrons generated during the dissolution of the base metal are released on the surface of the base metal and move to the surface of the metallic titanium to reduce selenium. It is inefficient because the amount of electrons that contribute is small. Therefore, the ratio M / Ti of the volume M of the packed layer of the base metal alone and the volume Ti of the packed layer of metallic titanium is preferably 1/4 or more, particularly 1/2 or more, and 4 or less, particularly 2 The following is preferable. Aluminum is particularly preferable as the base metal, and when the volume of the packed layer of metallic titanium is Ti and the volume of the packed layer of aluminum is Al, Al / Ti is 1/4 to 4 and particularly 1/2 to 2. Then, the selenium can be reduced very efficiently.

In order to bring the selenium-containing water into contact with the titanium / base metal mixture or the like, the selenium-containing water is preferably passed through an upward flow through a reduction tower having a filling layer (filler layer) filled with the titanium / base metal mixture or the like. ..

This reduction treatment is preferably carried out under acidic conditions in order to increase the elution rate of the base metal. Here, the amount of acid added to make the acidic condition is determined by calculating the required base metal elution amount from the relationship between the base metal (for example, aluminum) elution amount and the selenium removal rate obtained in advance, and using that base metal elution amount. It can be obtained by converting it into the amount of acid (for example, hydrochloric acid) added for this purpose. That is, since there is a correlation between the base metal elution amount and the selenium removal rate, it is possible to determine the amount of acid added so that the base metal elution amount can obtain the desired selenium removal rate. Further, the pH may be easily set to 1 to 3, particularly 1.5 to 2.5 as a suitable range.

By such a reduction treatment, most of the selenium in the selenium-containing water, for example, hexavalent selenium becomes zero-valent selenium, and is precipitated and removed on the surface of the titanium / base metal mixture or the like. The residual selenium is reduced from hexavalent to low valence, for example, tetravalent selenium, and becomes a form that easily precipitates by agglutination treatment.

In the present invention, it is preferable that the reduction-treated water is coagulated and separated after the above-mentioned reduction treatment. The coagulation separation treatment is carried out by adjusting the pH of the reduction-treated water, precipitating the eluted base metal or the like as an insoluble compound such as a hydroxide, and solid-liquid separating the precipitated metal compound.

The pH of the reduction-treated water is usually adjusted by adding an alkali such as sodium hydroxide, potassium hydroxide, or slaked lime. When the base metal used together with the metallic titanium is aluminum, an alkali is added to the reduction-treated water to precipitate the dissolved aluminum as aluminum hydroxide. In this case, it is preferable to adjust the pH of the reduction-treated water to 5 to 8 by adding an alkali, and aluminum hydroxide dissolves at pH 4 or less or pH 9 or more, which is inappropriate. When the base metal used together with the metallic titanium is zinc, zinc can be precipitated as a hydroxide by adjusting the pH of the reduction-treated water to 9 to 10.

When the metal compound is precipitated by the above pH adjustment, an organic flocculant and an inorganic flocculant can be added to improve the solid-liquid separability.

A solid-liquid separation operation is performed to separate the precipitated metal compound from water. For the solid-liquid separation, any commonly used method can be adopted, and the treated water and sludge composed of an insoluble metal compound are separated by precipitation, filtration, centrifugation, membrane separation, or the like.

By adjusting the pH of the reduction-treated water and solid-liquid separation, the base metal eluted during the reduction treatment is insolubilized, separated from the water, and discharged as metal-free treated water. Further, when this eluted metal is precipitated as an insoluble compound, for example, aluminum hydroxide, the reduced low-valent selenium remaining in water is also adsorbed on the flocs of aluminum hydroxide and precipitated by the co-precipitation phenomenon.

When aluminum and / or boron coexist in the selenium-containing wastewater, if aluminum is used as the base metal such as the titanium / base metal mixture, the fluorine and / or boron will be deposited when aluminum hydroxide is precipitated by pH adjustment after the reduction treatment. Can be precipitated and removed by the co-precipitation phenomenon.

By such a reduction treatment, selenium in the selenium-containing water is usually removed to a concentration of 0.1 mg / L or less.

<Degassing and cleaning of reduction tower>
In the treatment method of selenium-containing wastewater, in which selenium-containing water is brought into contact with a mixture of metallic titanium and metallic aluminum, selenium is reduced by eluting a part of metallic aluminum, and the dissolved aluminum is coagulated, the wastewater is in the wastewater. 90% or more of selenium is reduced to elemental selenium (zero valence) in a reduction tower filled with a metal mixture or the like, and is insolubilized. Usually 50% to 70% of the insolubilized elemental selenium is transferred to the reduction tower treated water. Normally, 30% to 50% of the insolubilized elemental selenium does not transfer to the reduction tower treated water, but accumulates in the packed bed such as a metal mixture in the reduction tower. Therefore, after passing a predetermined amount of selenium-containing water for a predetermined time, the reduction tower is washed. Further, if the selenium-containing water is continuously passed through the reduction tower, gas will be accumulated in the packed bed. Therefore, in the present invention, the gas is degassed from the inside of the reduction tower before the start of this cleaning.

In order to clean the reduction tower, it is preferable to flow a mixed fluid of air and water as a cleaning fluid through the reduction tower in an upward flow. The volume ratio of air to water in the cleaning fluid is preferably about 0.5 to 3.0 volumes (standard state) of air with respect to 1 volume of water. The upward flow velocity (LV) of the cleaning fluid is preferably about 150 to 250 m / hr, particularly about 200 m / hr in the water-air mixed state.

In order to degas from the reduction tower, it is preferable to perform the following degassing method A or B.
Degassing method A: The reducing body filling layer is formed by draining all or most of the water from the reducing tower to expose all or most of the filler in the gas phase, and then refilling with water at a water supply rate within a predetermined range. The target gas is released from. At this time, the gas can be efficiently released by controlling the water supply speed at the time of filling with water within an appropriate range.
Degassing method B: Air or a mixed gas of air and an inert gas (for example, nitrogen) is blown as a gas from the lower part of the reduction tower, and the gas is released from the reducing material packed bed. At this time, by controlling the gas supply amount within an appropriate range, the gas can be efficiently released.

The degassing method A is preferably performed by the following first and second steps.
First step: Draining water (total amount to near the lower surface of the filler layer) (preferably LV1 to 15 m / hr)
Second step: Water filling (up to a little above the upper surface of the filler layer) (preferably LV1.5 to 30 m / hr)

When water is removed from the filler layer and air is introduced in the first step, the locally high concentration of gas existing in the gaps between the fillers is dispersed in the air due to the decrease in surface tension. Is released. If the LV is raised too much in the first step in an attempt to shorten the cleaning operation time, SS physically trapped in the filler layer (metal selenium generated by the reduction treatment, fine SS due to wear of the filler, etc.) Is discharged to the outside of the reduction tower, so the LV is preferably in the above range. (It is preferable that these SSs are discharged to the outside of the tower in the reduction tower cleaning step.)

In the second step, it is preferable to supply the gas extruded from the reduction tower to the scrubber. If the LV of the second step is raised too much in an attempt to shorten the cleaning operation time, the gas flow rate supplied to the scrubber becomes too large, so the LV is preferably in the above range.

The degassing method B is preferably performed by the following first and second steps.
1st step: Drain a small amount of water. (Up to a little higher on the upper surface of the filler layer)
Second'step: Slow aeration with air and / or inert gas. (Preferably LV 0.025 to 0.5 Nm ³ / m ² / min)

In the second'step, the locally high-concentration gas existing in the gap between the fillers is slowly dispersed into the aerated gas over time, and is gradually discharged to the outside of the tower and supplied to the scrubber. .. If the aeration is too strong, the gas flow rate supplied to the scrubber will be too large. On the other hand, if the aeration is too weak, the degassing operation will take a long time, and the contact efficiency between the fillers with the gas will be low. Therefore, the LV is preferably in the above range.

After performing such a degassing method A or B, the above cleaning is performed, and then water filling (until full water) and resumption of water flow (switching to normal operation) are performed.

The insolubilized selenium in the cleaning wastewater can be selectively removed from the treated water by filtering the reduction tower cleaning wastewater with a filter. Filtration means include sand filtration, anthracite filtration, membrane filtration, long-hair fiber filtration, etc., but the water flow temperature is high, solids have high adhesion, and elemental selenium is insoluble in acids and alkalis and is chemically washed. Considering the constraint conditions such as difficulty, it is desirable to use sand filtration, anthracite filtration, or double-layer filtration in which these are combined.

In the process of reducing selenium by bringing selenium-containing water into contact with a mixture of metallic titanium and metallic aluminum and eluting a part of metallic aluminum, hydrogen gas is generated as a by-product. By recovering this hydrogen gas, it can be used for various purposes. For example, it can be used as a reducing agent for fuel and wastewater treatment. The hydrogen gas from the reduction tower contains a small amount of hydrogen sulfide and the like. These can be removed by aerating the generated gas through a column filled with an alkaline scrubber or a hydrogen sulfide absorbent, and high-purity hydrogen gas can be obtained.

[Processing device]
Hereinafter, it will be described with reference to FIG. 1 showing an embodiment of the selenium-containing water treatment apparatus of the present invention.

The raw water (selenium-containing water) is introduced into the pH adjusting tank 2 by the raw water pipe 1, and an acid such as hydrochloric acid is added by the adding means 2a, and the pH is preferably adjusted to 3 to 5, particularly 3.5 to 4.5. Further, in this embodiment, a scale dispersant may be added from the adding means 2b in addition to the acid depending on the concentration of the scale component contained in the raw water. As the scale dispersant, an acrylic acid-based polymer, a polyphosphate, or the like can be used, but the scale dispersant is not limited thereto.

The water from the pH adjusting tank 2 is sent to the reduction tower 7 via the relay tank 3, the pump 4, and the pipe 5. In this pipe 5, steam is added from the steam adding means 6a and heated to 40 to 80 ° C., particularly 50 to 65 ° C., and an acid such as hydrochloric acid is added from the acid adding means 6b to pH 1-3, especially 1.5. The pH is adjusted to ~ 2.5. This water is passed through the reduction tower 7, and selenium is reduced and removed in the packed bed 7A such as a titanium / base metal mixture.

The reduction-treated water flowing out of the reduction tower 7 is introduced into the pH adjusting tank 13 via the pipe 8, and an alkali such as NaOH is added from the alkali adding means 13a to adjust the pH to a pH at which hydroxides are precipitated. When the base metal is aluminum, the pH is adjusted to 5 to 8, preferably 7 to 8, and when zinc is used, the pH is adjusted to 9 to 10.

The water from the pH adjusting tank 13 is introduced into the coagulation tank 14, the polymer coagulant is added from the coagulant adding means 14a, the coagulation treatment is performed, and then the water is introduced into the settling tank 15 and is subjected to the precipitation treatment. The supernatant water is taken out from the pipe 17 as treated water. A part of the settled sludge is returned to the pH adjusting tank 13 by the return pipe 18, and the rest is discharged by the pipe 19. As the above polymer flocculant, polyacrylamide, acrylamide-sodium acrylate copolymer and the like are suitable.

Gas containing hydrogen sulfide is generated in the reduction tower 7. This gas is extracted from the top of the tower by the pipe 10, and the hydrogen sulfide gas is absorbed and treated by the scrubber 11.

The following are preferable as the water flow conditions for the reduction tower 7.
Water flow: Upward flow Filling layer: Mixture of aluminum and titanium (preferably titanium sponge)
(Volume ratio: Al / Ti = 1/4 to 4, preferably 1/2 to 2)
Water flow temperature: 30 to 90 ° C, preferably 40 to 80 ° C, particularly preferably 50 to 65 ° C.
Water flow rate (SV): ^{1 to} 20 hr -1, preferably 5 to 10 hr ^-1

Further, in this embodiment, in order to supply gas to the reduction tower 7 to perform the degassing method B, or to supply cleaning water and air for cleaning, the cleaning water and / or air is supplied to the pipe 5. The adding means 6c is connected. When the cleaning water and air are supplied by the adding means 6c with the selenium-containing water stopped flowing to the reduction tower 7, and the inside of the reduction tower 7 is cleaned with a mixed fluid of cleaning water and air, the cleaning drainage is pipe 9 Is sent to the washing and wastewater treatment facility.

In this embodiment, in order to perform the degassing step (degassing method A) before starting the cleaning of the reduction tower 7, the pipe 20 for draining the water in the reduction tower 7 is connected to the lower part of the reduction tower 7. Has been done. A valve 21 is provided in the pipe 20. A suction pump may be provided in the pipe 20. The connection height of the drainage pipe 20 is not limited to the bottom of the tower or the lower part of the reducing body filling layer, and may be between the filling layers.

Suitable methods and conditions for degassing the reduction tower 7 and cleaning the reduction tower 7 are as described above.

In the present invention, the concentrations of hydrogen, hydrogen sulfide, and hydrogen selenide in the reduction tower outflow gas may be measured by a gas sensor, and the water flow rate or the ventilation rate may be controlled so that the gas concentration becomes a predetermined value or less. Examples of the installation position of the gas sensor include the upper part of the reduction tower, the gas suction pipe, and the scrubber equipment.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

[Example 1 (degassing by degassing method A)]
An experimental column of φ20 × 2500 mmH was filled with a mixed reducing body of the following reducing body a and reducing body b in a bulk volume of 600 mL to form a reducing tower, and the following prepared wastewater was used as test raw water for 96 hours at a speed of ^SV10hr-1. Water was passed in the upward flow (normal operation).
Reduced body a: 300 mL of titanium sponge with a particle size of 2 to 4 mm and a purity of 99% or more
Reduced body b: Metallic aluminum 300 ml having a particle size of 2.0 mm and a purity of 99.7%
Prepared wastewater: Se (VI) 2 mg / L, Na ₂ SO ₄ 5,000 mg / L
The prepared wastewater is prepared by adding 300 mg / L of HCl after adjusting the pH to 4.

The experimental column has a structure with an inlet for prepared wastewater, an inlet for water and air at the bottom, an air inlet for gas dilution, and an outlet for treated water and gas at the upper part. The treated water was collected from the water and the outlet gas concentration was measured. Air for gas dilution was blown at a flow rate of 3.6 L / min.

After normal operation, water flow was stopped, and degassing and cleaning were performed as follows. That is, the water in the column is drawn out to the lower part of the reducing body filling layer at LV10 m / hr (drainage), and then water is sent from the lower part of the reducing tower at LV7 m / hr to fill the upper part of the reducing body packed layer with water to degas. rice field. Then, gas-liquid mixed water (water: air = 1: 1.5 (volume ratio)) was supplied from the lower part of the reduction tower at LV 200 m / hr for 2 minutes to wash the filler. After that, the reduction tower was filled with water.

[Example 2] (Degassing by degassing method B (slow aeration))
In Example 1, the degassing and cleaning operations after the normal operation were performed as follows.

After draining water slightly above the upper surface of the filler layer, air was blown from the lower part of the reduction tower at LV 0.12 Nm ³ / m ² / min to degas. Then, the same gas-liquid mixed water as in Example 1 was supplied from the lower part of the reduction tower at LV 200 m / hr for 2 minutes to wash the filler. After that, the reduction tower was filled with water.

[Comparative Example 1] (No degassing step)
In Example 1, after the normal operation, the washing operation was performed as follows without degassing. After draining water slightly above the upper surface of the filler layer, the same gas-liquid mixed water as in Example 1 is supplied from the lower part of the reduction tower at LV 200 m / hr for 2 minutes to wash the filler, and the reduction tower is filled with water. Filled with water.

<Result>
The hydrogen gas concentration (maximum) at the outlet of the reduction tower at the start of cleaning was as follows, and it was confirmed that the gas was sufficiently discharged from the reduction tower by the degassing methods A and B.
Example 1: 1.3%
Example 2: 2.7%
Comparative Example 1: 58%

7 Reduction tower 11 Scrubber

Claims (6)

The selenium-containing water is passed through a reduction tower and brought into contact with a mixture or alloy of metallic titanium filled in the reduction tower and a metal lower than titanium (hereinafter referred to as "filler") to bring the selenium-containing water into contact with the base. A method for treating selenium-containing water, which reduces selenium in the selenium-containing water by eluting a part of a single metal.
In a method for treating selenium-containing water, a washing step of washing the inside of the reduction tower with air and water is performed after stopping the flow of selenium-containing water to the reduction tower.
After stopping the flow of selenium-containing water to the reduction tower, selenium is degassed from the inside of the reduction tower to discharge the gas existing in the gap between the fillers, prior to the cleaning step. Method of treating contained water. The method for treating selenium-containing water according to claim 1, wherein the degassing is performed by draining water from the reduction tower and refilling it with water. The method for treating selenium-containing water according to claim 1, wherein the degassing is performed by aerating air and / or an inert gas into the reducing tower. The method for treating selenium-containing water according to claim 1, wherein the degassing from the reduction tower is performed by the following degassing method A or B.
Degassing method A: Water is drained from the reduction tower to the entire amount or the lower surface of the filler layer at LV1 to 15 m / hr to expose all or most of the filler in the gas phase, and then a small amount on the upper surface of the filler layer. Fill the upper part with water at LV 1.5 to 30 m / hr.
Degassing method B: After draining water slightly above the upper surface of the filler layer, air and / or the inert gas is discharged from the lower part of the reduction tower at LV 0.025 to 0.5 Nm. ³ / M ² Blow at / min for slow aeration. The selenium-containing water is brought into contact with a mixture or alloy (hereinafter referred to as "filler") of metallic titanium and a simple substance of a metal less base than titanium, and a part of the base metal is eluted to elute the selenium. A reduction tower that reduces selenium in the contained water,
In a selenium-containing water treatment apparatus having a cleaning means for supplying air and water to the reduction tower for cleaning.
After stopping the flow of selenium-containing water to the reduction tower and before supplying air and water to the reduction tower for cleaning, the reduction is performed by draining water from the reduction tower and refilling it with water. processor of selenium-containing water, characterized in that it comprises a venting means for performing degassing for discharging gas present in the gap between the filler from the tower. The selenium-containing water is brought into contact with a mixture or alloy (hereinafter referred to as "filler") of metallic titanium and a simple substance of a metal less base than titanium, and a part of the base metal is eluted to elute the selenium. A reduction tower that reduces selenium in the contained water,
In a selenium-containing water treatment apparatus having a cleaning means for supplying air and water to the reduction tower for cleaning.
After stopping the flow of selenium-containing water to the reduction tower and before supplying air and water to the reduction tower for cleaning , air and / or an inert gas is ventilated in the reduction tower. selenium-containing water treatment apparatus characterized by comprising a venting means for performing degassing for discharging gas present in the gap between the filler from the reducing tower to.

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