JP2003071474A - Reaction apparatus for treating wastewater containing selenium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reaction apparatus for treating wastewater containing selenium in which it can be steadily operated with a stable selenium removing rate kept over a long period of time and in which the construction cost and the utilities cost of a device for removing selenium are reduced, when harmful substances in the wastewater containing selenium are separated and removed by using a catalytic reduction material made of a metal-fiber molding body of an iron-based metal. SOLUTION: The apparatus is for removing harmful substances in the wastewater by bringing the wastewater containing selenium into contact with a catalytic reduction material comprised of the metal-fiber molding body of the iron-based metal, and the apparatus is constituted in such a way that the inner space of the apparatus body is partitioned into a reaction region and a circulation region by a partition wall vertically installed at a nearly center part of the inner space, that the respective reaction and circulation regions are communicated in the upper and lower parts between these regions each other, that a catalytic reaction zone accommodating the catalytic reduction material in the above reaction region is formed, that an air introducing part for bubble-cleaning is installed in the lower part of the catalytic reaction zone, and that a wastewater circulating means circulating the wastewater in the inner space from a reaction region to the circulation region is disposed in the above circulation region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to selenium (dissolved selenium) and sulfur oxides which are dissolved in the form of harmful substances such as selenite ion (SeO ₄ ^2- ) and selenite ion (SeO ₃ ^2- ). The present invention relates to a reaction device used for bringing wastewater containing various oxidizing substances such as the like and iron-based metal into contact with each other, and separating and removing harmful substances in the wastewater.

[0002]

BACKGROUND OF THE INVENTION Selenium and selenium compounds are used for glass products, ceramic products, semiconductor materials, solar cells and movie films,
Infrared polarizers, pigments, sensitizers, dehydrogenating agents, foaming agents, etc. are widely used in the production of various industrial products.Also, from the production plants of industrial products using such selenium and selenium compounds, etc. Inevitably, selenium-containing wastewater containing dissolved selenium is discharged.

And, regarding the selenium-containing wastewater,
With the environmental standard set at a selenium concentration (as Se) of 0.01 mg / liter or less, various methods for separating and removing dissolved selenium in wastewater have been proposed. For example, in U.S. Pat.No. 4,405,464,
Hexavalent selenium ion [for example, selenate ion (Se
O ₄ ^{2 -)]} is contacted with an aqueous solution and metallic iron in pH6 below containing tetravalent selenium ions [e.g. hexavalent selenium ions, metal as well as reduced to selenite ions (SeO ₃ ^2-)] The iron is oxidized and dissolved, the dissolved iron oxide is precipitated in the form of iron hydroxide, and the precipitated iron hydroxide is solid-liquid separated to recover an aqueous solution in which hexavalent and lower selenium ions are reduced. The method is described. In addition, JP-A-7-
Japanese Patent No. 2,502 describes a method of contacting selenium and / or a selenium-containing waste liquid with metallic iron in a pH range of 0 to 6, precipitating selenium on the surface of metallic iron to reduce the selenium concentration in the waste liquid, and removing the selenium concentration. Has been done. Furthermore, JP-A-11-207,3
Japanese Unexamined Patent Publication No. 64 describes a method in which a selenium-containing solution is brought into contact with a packed bed of iron-based metal such as fibers at a temperature of 30 ° C. or higher to deposit selenium on the surface of this iron-based metal.

In these methods, the dissolved selenium is deposited on the surface of the iron-based metal (metallic iron) that is in contact with the waste water.
In the 7-2,502 publication, it is described that a shape having a large surface area, that is, a shape having a large specific surface area as compared with the entire volume of a thin wire rod, a small plate piece, a powder, a fine particle tip, and the like is preferable. 11-207,364 describes that a fibrous shape, a porous shape, a fine piece plate shape, a granular shape, a powder shape and the like are preferable.

However, selenium-containing wastewater generally contains various oxidizing substances such as sulfur oxides and nitrogen oxides in addition to dissolved selenium, and also contains dissolved oxygen. In order to reduce the selenium concentration to 0.1 mg / liter or less, which is stipulated as a standard, a large amount of selenium concentration in the wastewater, which is several thousand times to tens of thousands times, can be obtained in the reaction zone where the wastewater is contacted with the iron-based metal. It is necessary to generate iron ions. For this reason, the iron-based metals used in this reaction zone are heavily consumed, and the removal efficiency of dissolved selenium is poor, and a large amount of sludge (iron hydroxide, etc.) is generated more than necessary, resulting in a large amount of iron in the reaction zone. It is necessary to frequently supply the system metals and to treat a large amount of sludge, which imposes a heavy operational burden on the deselenium treatment of selenium-containing wastewater.

The problem of using a large amount of iron-based metals and the accompanying problem of generating a large amount of sludge are, for example, attached to equipment such as a coal-fired power plant and mainly used for flue gas desulfurization equipment for removing sulfur dioxide in flue gas. Flue gas desulfurization effluent that is discharged from water and contains a relatively large amount of oxidizing substances such as sulfur oxides, which can be quantified by the diethyl-p-phenylenediamine colorimetric method (industrial effluent test method), with dissolved selenium and these oxidizing substances. 1
If you try to remove them in one process at the same time,
Combined with the large amount of processing, it has become an even more serious problem.

In order to solve this problem, the present inventors have
Dissolved selenium and oxidizing substances can be efficiently separated and removed from the selenium-containing wastewater, the amount of ferrous metal used and the amount of sludge generated can be reduced as much as possible, and the operational burden of wastewater treatment is reduced. Considering means that can be reduced, using a metal fiber molded body in which metal fibers of an iron-based metal are molded into a predetermined shape and drainage is allowed to flow into the inside thereof as a contact reducing material, and a pH of 5 to 7 is used. It has been found that a stable selenium removal rate can be maintained for a long time by operating at a relatively high pH value and at a relatively low liquid hourly space velocity (SV) of 0.03 to 0.5 hr ⁻ . .

However, the catalytic reducing material composed of such a metal fiber molded body of an iron-based metal is packed in a column type packed tower type reactor which is commonly used in this type of deselenization treatment, and a conventional comparison is made. When operating at extremely high liquid hourly space velocity (SV), it is necessary to increase the iron dissolution rate, so that the low p
Operation in the H region is essential, oxygen deficiency occurs inside the catalytic reducing material, and a ferrite-like scale is generated to coat the surface of the metal fiber forming the catalytic reducing material, and for this purpose, the catalytic reducing material is used. In addition to the internal drainage flowability being impaired and its reactivity sharply reduced, it is difficult to desorb and remove sludge adhering to the surface of the catalytic reduction material, and
There is a problem that the capacity of the electric motor for realizing the piston flow in the column type packed tower reactor becomes enormous.

Further, in the de-selenium treatment using a conventional column type packed tower reactor, the selenium-containing waste water and the iron-based metal catalytic reducing material are treated under the conditions of pH 2-3 in this column type packed tower reactor. The dissolved selenium is reduced by contact (selenium reduction reaction), and then p
The H value is increased to pH 8 or more to cause divalent or trivalent iron ions in water to be aggregated as water-insoluble ferrous hydroxide or ferric hydroxide, and the selenium reduction reaction is generated on the iron hydroxide generated at this time. Although the reduced selenium generated in step 3 is adsorbed and immobilized (selenium immobilization reaction), a reactor for this selenium immobilization reaction was constructed and operated separately from the column-type packed tower reactor. There was also the problem that construction costs and utility costs for that purpose increased.

[0010]

Therefore, the present inventors have used a catalytic reducing material composed of a metal fiber molded body of an iron-based metal to stably remove selenium over a long period of time while maintaining a stable selenium removal rate. As a result of diligent study on a reactor capable of operating selenium treatment, the internal space of the apparatus main body was divided into a reaction region and a circulation region, and the reaction region and the circulation region were communicated with each other at their upper and lower portions. In the reaction region, a catalytic reaction zone for accommodating the catalytic reducing material is formed, and a gas introduction section for bubbling cleaning is provided below the catalytic reaction zone. A drainage circulation means for circulating between the
As a result, it was found that the selenium reduction reaction and the selenium immobilization reaction can be carried out in the same reactor by operating at a relatively high pH value and a relatively low liquid hourly space velocity (SV), and the present invention was completed. did.

Therefore, an object of the present invention is to provide a stable selenium removal rate for a long time when separating and removing harmful substances in selenium-containing wastewater by using a catalytic reducing material composed of a metal fiber molding of iron-based metal. It is to provide a reactor for treating wastewater containing selenium, which can be stably operated while maintaining the above.

Another object of the present invention is to provide stable selenium for a long time in separating and removing harmful substances from selenium-containing wastewater by using a catalytic reducing material composed of a metal fiber molding of iron-based metal. The removal rate can be maintained and long-term stability of operation can be achieved, and at the same time, the selenium reduction reaction and the selenium immobilization reaction are performed in the same reactor, resulting in the construction cost of wastewater deselenization equipment and utility. An object of the present invention is to provide a reactor for treating selenium-containing wastewater, which can reduce costs.

[0013]

[Means for Solving the Problems] That is, according to the present invention, waste water containing dissolved selenium or a harmful substance consisting of dissolved selenium and an oxidizing substance is contacted with a contact reducing agent composed of a metal fiber molding of an iron-based metal. Is a reaction device for removing harmful substances in the waste water, and the internal space of the device main body is divided into a reaction region and a circulation region by a partition wall that is erected approximately at the center thereof, and these reaction regions and The circulation region is made to communicate with each other at the upper part and the lower part of the partition wall, and the reaction region is provided with a catalytic reaction zone for accommodating the catalytic reducing material, and a gas introduction part for bubbling cleaning is provided below the catalytic reaction zone. A reactor for selenium-containing wastewater treatment is provided, in which a wastewater circulation means for circulating the wastewater in the internal space from the reaction area to the circulation area is provided in the circulation area.

The catalytic reducing material used in the present invention
Is a small amount selected from the group consisting of Fe, Mn, Ni, and Cu.
A metal fiber made of one type of iron-based metal
-Shaped, spherical, columnar, disc-shaped, and other reaction devices
Metal fiber composite obtained by molding into a shape that can be filled in the reaction zone
The shape is preferably 0.002 to 0.2
m ³, More preferably 0.02-0.04 m³And
Its bulk density is 50-100 kg / m³, Preferably 50
~ 70kg / m³Is. The volume of this metal fiber molding is
0.002m³Smaller, the resulting catalytic reducing material
The liquid flow inside becomes too high, and it is consumed quickly and selenium is removed.
The reduction rate is rapid and the need for frequent addition of catalytic
Therefore, the operational burden of wastewater treatment increases, and the contact reaction equipment
Equipment for catalytically reducing material in the reactor
There may be problems such as damage or blockage of the
0.2m in pair³The larger, the catalytic reduction obtained
The liquid flowability inside the material becomes too low and the reactivity decreases.
In some cases, the desired removal rate of selenium cannot be achieved.
Contact occurs because ferrite is generated due to lack of oxygen inside the contact reducing material
The reducing agent may be deactivated, and the weight is too heavy to make contact.
The handling property of the reducing material is also reduced. Also, metal fiber
The bulk density of the shape is 50 kg / m³The lower the contact obtained
The liquid flowability inside the contact-reducing material becomes too high, and the wear is quick.
The selenium removal rate drops quickly, and it is often necessary to add catalytic reducing agents.
When it becomes necessary, the operational burden of wastewater treatment increases, and on the contrary,
100 kg / m³Higher, inside the obtained catalytic reducing material
The liquid flowability to the liquid becomes too low and the reactivity decreases
In some cases, it may not be possible to achieve the selenium removal rate.
Accumulation of dice and the like becomes remarkable and the reaction rate decreases.

The metal fiber for forming the catalytic reducing material used in the present invention is not particularly limited, but it is preferable that the metal fiber is produced by a cutting method or the like which does not use fats and oils. Fiber diameter is preferably 25 to 7
It is 0 μm, more preferably 50 to 70 μm, and the average fiber length thereof is preferably 100 mm or more, more preferably 100 to 200 mm. If the average fiber diameter of the metal fibers is smaller than 25 μm, the formed catalytic reducing material is likely to break, while if it is thicker than 70 μm, problems such as defective molding and an increase in the filling amount occur. Further, if the average fiber length is shorter than 100 mm, it may be difficult to maintain the shape of the metal fiber molded body after molding, and there is a problem that the broken metal fiber overflows to the downstream. When the average fiber length becomes longer than 200 mm,
Molding failure may occur.

In the present invention, a partition wall is provided for partitioning the internal space of the main body of the reactor into a reaction area and a circulation area, and the reaction area and the circulation area are communicated with each other above and below the partition wall. The method is not particularly limited, and the reaction region can be filled with the catalytic reducing agent efficiently and evenly in the catalytic reaction zone formed by filling the catalytic reducing agent. It is sufficient if the drainage circulation means can be arranged in the circulation region so that the circulation efficiency of the drainage is good. For example, the partition is used to completely divide the internal space into the reaction region and the circulation region, and the partition wall has a desired size above and below the partition region. The through holes may be opened to communicate with each other, or a predetermined gap may be left above and below the partition wall to allow the reaction region and the circulation region to communicate with each other.

Further, in the reaction region, a contact reaction zone in which the catalytic reducing material is accommodated and in which the liquid can flow is formed, and below the catalytic reaction zone, the catalytic reducing material adheres to the surface of the catalytic reducing material by a catalytic reduction reaction, Further, a gas introduction part for bubbling and cleaning the deposits staying in the contact reaction zone is provided, and the circulation region is provided with waste water charged in the internal space from the reaction zone of the reaction region. A drainage circulation means for circulating the circulation area is provided. Here, in order to form the contact reaction zone in which the liquid can flow, for example, a liquid flowable shelf is disposed between the standing partition wall and the reaction region side inner wall of the apparatus main body, and this water flow Appropriate methods can be adopted, such as filling a part or all of the area defined by the shelves with the partition walls and the reaction area side inner wall of the apparatus main body with a contact reducing material to form a contact reaction zone in which the liquid can flow. .

Further, with respect to the gas introduction section disposed below the contact reaction zone, a gas such as air for bubbling cleaning is introduced into the contact reaction zone through the gas introduction section, and the contact reaction zone is contacted. It suffices if the deposits attached to the reducing material can be washed, for example, plant air or the like is used.
Regarding the wastewater circulation means arranged in the circulation region, the wastewater in the internal space is subjected to the flow of the wastewater circulation which goes up through the lower part of the partition wall to the contact reaction zone of the reaction region, and then goes through the upper part of the partition wall and descends in the circulation region. It can be given as long as it can be given, and examples thereof include an axial flow stirrer and a circulation pump.

Regarding the positions of the inlet for the selenium-containing wastewater (untreated wastewater) and the outlet for the treated wastewater (treated wastewater) provided in this reactor, the liquid space velocity (SV) in the contact reaction zone is set. 0.03～0.5Hr ^- because to operate at a relatively slow speed of, but in which position the outlet of the treatment and drainage spout of untreated wastewater may be provided in the reactor, is introduced into the reactor It is preferable to provide these inlets and outlets so that the untreated wastewater can surely come into contact with the catalytic reducing material in the catalytic reaction zone.The inlet for the untreated wastewater is preferably the equipment for the untreated wastewater. The inlet is opened upstream of the catalytic reaction zone and relatively close to the catalytic reaction zone, and more preferably in the vicinity of the lower part of the partition wall that divides the reaction region and the circulation region. Is the circulation of the device body It is preferable to provide it at a lower portion of the side wall on the region side and relatively far from the charging port for the untreated wastewater.

Further, in the present invention, in order to easily cope with the change in the selenium concentration of the selenium-containing wastewater introduced into this reaction apparatus and the change in the wastewater treatment amount in this reaction apparatus, the apparatus is preferably used. A plurality of internal spaces (for example, 2
~ 5 internal spaces), and formed so that the drainage moves from the upstream side to the downstream side between the internal spaces via the upper part of each partition wall. Preferably, the untreated waste water is provided upstream of the catalytic reaction zone of each of the internal spaces and relatively close to the catalytic reaction zone, and more preferably near the lower part of the partition wall partitioning the reaction zone and the circulation zone. The inlet is opened, and regarding the discharge outlet of the treated wastewater, preferably, it is located at a lower portion of the side wall on the circulation region side forming the innermost space on the most downstream side, more preferably relatively far from the inlet for the untreated wastewater. A discharge port for treated wastewater is formed at a position, and only the internal space of the first stage is operated from the downstream side, or the first stage is operated from the downstream side according to changes in the selenium concentration in the wastewater and the wastewater treatment amount. Second stage internal space, first from downstream As such the second stage and the internal space of the third stage may be configured to be operated a plurality of internal spaces counted from the downstream side.

At this time, with respect to the moving direction of drainage (drainage moving direction) between the internal spaces, the drainage moved from inside the internal space on the upstream side to inside the internal space on the downstream side is The flow of drainage circulation in the internal space (that is, the flow of drainage circulation that goes up the contact reaction zone of the reaction region through the lower part of the partition wall and then goes down through the upper part of the partition wall in the circulation region) It is circulated from the reaction area in the internal space to the circulation area, and substantially passes through the contact reaction zone provided in the reaction area during this, and is finally provided on the side wall on the circulation area side that forms the most downstream internal space. It is designed so that it is led out of the reactor through the outlet of the treated wastewater. The relationship between the drainage movement direction and the drainage circulation direction in each internal space may be substantially the same as each other or may be substantially orthogonal to each other. It can be appropriately determined for the sake of convenience.

Further, in the present invention, the apparatus body is provided with a pH meter for measuring the pH value of the waste water in each internal space and a DO meter for measuring the dissolved oxygen concentration, and a reaction region and a circulation region in each internal space are provided. The pH value and the dissolved oxygen concentration of the effluent that circulates between the two are within a predetermined range (preferably, the pH value is 5
It is preferable to control the dissolved oxygen concentration to be within the range of 0 to 7 and within the range of 0 to 8 mg / liter. To control the pH value at this time, a hydrochloric acid aqueous solution is usually used as an acid,
An aqueous solution of sodium hydroxide is used as the alkali, and an oxygen-containing gas such as air or plant air is used for controlling the dissolved oxygen concentration.

When the selenium-containing wastewater is subjected to the deselenization treatment using the reaction apparatus of the present invention, it is preferable that the volume V ₁ of the catalytic reaction zone filled with the catalytic reducing agent and the contact volume filled in the catalytic reaction zone. The ratio (V ₂ / V ₁ ) to the total volume V ₂ of the reducing material is 0.15 to 0.4, preferably 0.2 to
A 0.3, the contacting liquid hourly space velocity of the waste water passing through the reaction zone (liquid permeation speed) SV is 0.03～0.5Hr ^-1, preferably 0.05～0.1Hr ^-1, Further, the average passing speed of the wastewater passing through this catalytic reaction zone is 0.5 to 2.
It is 5 m / sec, preferably 0.2 to 0.5 m / sec. By adopting such treatment conditions, it is possible to achieve a stable high selenium removal rate over a long period of time.

The treated effluent thus extracted from the reaction apparatus of the present invention is then subjected to a treatment such as solid-liquid separation in a settling tank, a membrane separator, a centrifuge, a belt filter, a filter press or the like. It

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be specifically described below with reference to the embodiments shown in the accompanying drawings.

Example 1 FIG. 1 schematically shows a reactor for treating selenium-containing wastewater according to Example 1 of the present invention. In FIG. 1, the apparatus main body 1 is provided with a partition wall 5 standing substantially at the center of the internal space 2 for partitioning the internal space 2 into a reaction area 3 and a circulation area 4. Gaps 6a and 6b are formed on the upper side and the lower side to connect the reaction area 3 and the circulation area 4 to each other. Further, in the reaction area 3, the partition wall 5 and the reaction area of the apparatus main body 1 are formed. A water-permeable shelf 7 through which liquid can flow is disposed between the inner wall 1a on the third side and the water-permeable shelf 7 and the partition wall 5 and the reaction region-side inner wall 1a of the apparatus main body 1 to accommodate the contact reducing material 8. A contact reaction zone 9 through which a liquid can flow is formed for this purpose, and below this contact reaction zone 9, there is a gas introduction part 10 for introducing and ejecting bubbling cleaning air from an air source 10a. Further, the drainage in the internal space 2 is provided in the circulation region 4 from the upper part of the partition wall 5. Circulation area 4, the partition wall 5 lower, and the reaction region 3
For example, an axial-flow type agitator (drainage circulation means) 11 having a high discharge performance that circulates through the contact reaction zone 9 above the partition wall 5 is provided.

In the reactor of this Example 1, the untreated wastewater inlet pipe 13 is located above the circulation region 4
Of the apparatus main body 1 which extends downward from the axial flow type agitator 11 inside, the opening 13a of which is located in the vicinity of the gap 6b below the partition wall 5, and the outlet 12 of the treated wastewater is relatively distant from the opening 13a. It is provided on the lower part of the side wall 1b on the region 4 side,
The untreated wastewater introduced from the opening 13a of 13 rises in the contact reaction zone 9 of the reaction region 3 through the lower part of the partition wall 5,
It flows so as to descend through the circulation region 4 through the upper portion, and is extracted to the outside from a discharge port 12 provided in the lower portion of the side wall 1b on the circulation region 4 side.

Further, in the reaction apparatus of this Example 1, a pH meter 15 for measuring the pH value of the waste water introduced into the internal space 2 of the apparatus main body 1 and subjected to the de-selenium treatment, and the dissolved oxygen concentration of this waste water And a DO meter 16 for measuring the pH, and an alkali supply device for supplying an aqueous sodium hydroxide solution based on the pH value of the wastewater measured by the pH meter 15.
17 or an acid supply device 18 for supplying a hydrochloric acid aqueous solution is driven,
A predetermined amount of sodium hydroxide aqueous solution or hydrochloric acid aqueous solution is supplied to control the pH value, and air is supplied from the oxygen-containing gas supply device 19 based on the dissolved oxygen concentration in the waste water measured by the DO meter 16. , The concentration of dissolved oxygen in wastewater is controlled.

Therefore, in the reaction apparatus of this Example 1, the selenium-containing wastewater (untreated wastewater) introduced through the opening 13a at the lower end of the introduction tube 13 is the contact reaction of the gap 6b below the partition wall 5 to the reaction region 3. The catalytic reducing material 8 flows along the drainage circulation direction in which the zone 9 → the gap 6a above the partition wall 5 → the circulation region 4 → the discharge port 12 below the partition wall 5 circulates in this order, and in the reaction region 3, the catalytic reaction zone 9 is filled. And the selenium dissolved in the wastewater is reduced in the contact reaction zone 9 of the catalytic reducing material 8 and the selenium produced by the reduction reaction is hydroxylated by the catalytic reducing material 8. The treated wastewater, which is fixed together with iron (fixed with selenium) and contains the fixed reduced selenium, is extracted to the outside from the discharge port 12 formed in the side wall 1b below the partition wall 5.

In the reaction apparatus having the structure shown in the above Example 1, the apparatus conditions are as follows: the internal space 2 has a volume of 122.5 liters.
Distribution flow 10 liters / hr of waste water into the inner space 2, the waste water circulating liquid hourly space velocity 0.08Hr ^-, drainage of the liquid temperature 35-4
0 ° C., catalytic reaction zone 9 of catalytic reducing material 8 (catalytic reaction zone)
Average passage velocity of 0.25 m / sec, pH value of 7, dissolved oxygen concentration of 0 to 8 mg / liter, and bubbling cleaning frequency of 12
Every 24 hours, and the conditions of the catalytic reduction material 8 are: fiber diameter: 70 μm fibrous metallic iron, volume ratio: 20-30%, and surface area per treatment volume: 80 m ² / m ³ , selenium-containing wastewater Was performed to remove selenium. As a result, the deselenium treatment could be continued for 720 hours without suspending the apparatus, and the desired selenium removal rate (90%) could be maintained during this period.

Example 2 FIG. 2 schematically shows a reactor for treating selenium-containing wastewater according to Example 2 of the present invention. The reactor shown in FIG. 2 is different from the case of the above-described first embodiment in that the apparatus body 1 is divided into two partition walls 20a, 20b, and three internal spaces 2a are located in series in the left-right direction in the drawing. , 2b, 2c are formed, and slit holes 21a, 21b are provided in the upper part of each partition wall 20a, 20b, respectively, and are inserted into the internal spaces 2a, 2b on the upstream side and subjected to de-selenium treatment. The treated wastewater is formed so as to move from the upstream side to the downstream side through the slit holes 21a, 21b in the upper part of each of the partition walls 20a, 20b, and the circulation area forming the innermost space 2c on the most downstream side. A discharge port 12 for the treated wastewater is formed in the lower part of the side wall 1b on the side of 4a, and the untreated wastewater is discharged near the lower end of each partition wall 5 in the circulation regions 4a, 4b, 4c of the internal spaces 2a, 2b, 2c. The opening 13a of the introduction tube 13 is located.

According to the reactor of Example 2, only the internal space 2c of the first stage from the downstream side is operated, or the internal spaces 2b and 2b of the first and second stages from the downstream side are operated. 2c
Such as driving all internal spaces 2a, 2b, 2c from the first stage to the third stage, etc.
It is possible to easily cope with variations in the selenium concentration of the selenium-containing wastewater and the wastewater treatment amount without changing the liquid hourly space velocity of the wastewater circulation in 2a, 2b, 2c.

[0033]

As described above, according to the reactor for treating selenium-containing wastewater of the present invention, harmful substances in selenium-containing wastewater are separated and removed by using a catalytic reducing material composed of a metal fiber molding of iron-based metal. In doing so, it is possible to operate stably while maintaining a stable selenium removal rate for a long time,
In addition, a reactor for reducing the dissolved selenium in the wastewater by the catalytic reducing material and a device for immobilizing the reduced selenium that immobilizes the reduced selenium produced by this reducing reaction together with the iron hydroxide produced by the catalytic reducing material are provided separately. Therefore, it is possible to reduce the construction cost and utility cost of drainage de-selenium equipment as a result.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a reactor for treating selenium-containing wastewater according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a reaction device for treating selenium-containing wastewater according to a second embodiment of the present invention.

[Explanation of symbols]

1 ... Device body, 1a, 1b ... Side wall, 1c ... Bottom wall, 2, 2a, 2b, 2c
... internal space, 3 ... reaction area, 4,4a, 4b, 4c ... circulation area,
5 ... Partition walls, 6a, 6b ... Gap, 7 ... Water shelf, 8 ... Catalytic reducing material, 9 ... Catalytic reaction zone, 10 ... Gas introduction part, 10a ... Air source, 11 ... Axial flow type agitator (drainage circulation means) , 12 ... outlet,
13 ... Introducing pipe, 13a ... Opening, 15 ... pH meter, 16 ... DO meter, 17
... Alkali supply device, 18 ... Acid supply device, 19 ... Oxygen-containing gas supply device, 20a, 20b ... Partition walls, 21a, 21b ... Slit holes.

Continued front page    (72) Inventor Eiji Awai             2-12 Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa             No. 1, inside Chiyoda Kakoh Construction Co., Ltd. (72) Inventor Masato Tada             15-1, Ushijima-cho, Toyama City, Toyama Prefecture, Hokuriku Electric Power Co., Inc.             In the company (72) Inventor Masaaki Hayashi             15-1, Ushijima-cho, Toyama City, Toyama Prefecture, Hokuriku Electric Power Co., Inc.             In the company F-term (reference) 4D050 AA12 AB59 BA02 BD02 BD08

Claims (4)

[Claims] 1. A contact reducing agent composed of a metal fiber molding of an iron-based metal is brought into contact with wastewater containing dissolved selenium or a harmful substance composed of dissolved selenium and an oxidizing substance to remove the harmful substance from the wastewater. Is a reactor for dividing the internal space of the apparatus main body into a reaction region and a circulation region by a partition wall provided upright in the substantially central portion thereof, and the space between the reaction region and the circulation region is above the partition wall. And the lower part are communicated with each other, a catalytic reaction zone for accommodating the catalytic reducing material is formed in the reaction zone, and a gas introduction part for bubbling cleaning is provided below the catalytic reaction zone, and the internal space is provided in the circulation zone. A reactor for treating selenium-containing wastewater, characterized in that wastewater circulation means is provided for circulating the wastewater of (1) from the reaction area to the circulation area. 2. A discharge outlet for treated wastewater is provided on a side wall of the apparatus main body on the side of the circulation region, and an inlet for the untreated wastewater is opened in the vicinity of a lower portion of a partition wall which divides the reaction region and the circulation region. 1. A reactor for treating selenium-containing wastewater according to 1. 3. The apparatus main body is formed with a plurality of internal spaces that are partitioned by partition walls and are positioned in series with each other, and the spaces between the internal spaces are passed from the upstream side to the downstream side through the upper portions of the partition walls. The drainage is formed so as to move, and a discharge outlet for the treated wastewater is formed at the upper part of the side wall on the side of the circulation region that forms the innermost space on the downstream side. The reactor for treating selenium-containing wastewater according to claim 1, wherein a charging port for the untreated wastewater is opened. 4. The apparatus main body comprises a pH meter for measuring the pH value of waste water in each internal space and a DO for measuring the dissolved oxygen concentration.
The reactor for selenium-containing wastewater treatment according to claim 1, further comprising a meter.