JP2003062582A - Treating method for waste water containing fluorine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method for waste water containing fluorine capable of fully reducing the fluorine contents in the waste water without complicating a process and a treating equipment. SOLUTION: A substance containing calcium, a substance containing aluminum, and a substance containing sulfate group are treated to be added into the waste water containing fluorine.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating wastewater containing fluorine.

[0002]

2. Description of the Related Art As a method for treating fluorine in fluorine-containing wastewater such as steelmaking process and semiconductor manufacturing wastewater, a calcium compound is added to the wastewater and fixed as hardly soluble calcium fluoride, and then solid-liquid separation is performed. However, this method can only reduce the fluorine concentration of the treated water to about 20 mg / L. Therefore, as a secondary treatment, a method of adding an aluminum compound and adsorbing fluorine to aluminum hydroxide produced in the neutralization region to cause sedimentation separation is well known. The aluminum hydroxide generated here is in the form of gel and has poor dewatering properties, and fluorine cannot be removed unless a large amount of an aluminum compound is added, so that a large amount of aluminum hydroxide sludge is generated. Further, even if added in a large amount, fluorine remains in the drainage in an amount of several mg / L, and thus there is a concern that it may affect the environment. Further, this aluminum hydroxide sludge has a high water content after dehydration and becomes industrial waste, but there is a shortage of waste treatment plants, and reduction of industrial waste has become a major issue.

As a method for reducing this sludge, a method of reusing a part of the generated sludge in the original wastewater treatment (Japanese Patent Laid-Open Nos. 60-241988 and 60-9).
7091, JP-A-6-154767, and JP-A-8-197070), or a method of dissolving sludge with an alkali to form aluminate, and recycling this aluminum solution for adsorption and removal of fluorine ( JP-A-1-
No. 107890), adsorbed fluorine is desorbed by adding excess calcium compound to sludge having adsorbed fluorine to generate calcium fluoride, and the sludge is dissolved with alkali, and further carbon dioxide is aerated to give crystalline. A method of producing aluminum hydroxide (Japanese Patent Laid-Open No. 9-248577) has been proposed.

[0004]

However, JP-A-60-
In Japanese Patent Laid-Open No. 97091 and Japanese Patent Laid-Open No. 60-241988, fluorine in the waste water is precipitated and separated as calcium fluoride, and the sludge containing the separated fluorine is circulated. However, in order to circulate the sludge containing fluorine, However, depending on the conditions, there is a risk that fluorine will elute from the sludge and pollute the wastewater, and the fluorine concentration in the wastewater will be 10
It only drops to about mg / L. JP-A-6-1547
67 and JP-A-8-197070, a calcium compound and an aluminum compound are added to fluorine-containing wastewater, and fluorine is adsorbed to the generated calcium fluoride or aluminum hydroxide precipitate to cause solid-liquid separation. Although this is a recycling method, there is a possibility that the wastewater may be contaminated by the elution of fluorine from the precipitate containing fluorine. JP-A-1-107890, JP-A-9-
In JP 248577, a step and an apparatus for adding a calcium compound to gel-like aluminum hydroxide having adsorbed fluorine to generate sparingly soluble calcium fluoride, and desorbing fluorine adsorbed to gel-like aluminum hydroxide, and after desorption A step and a device for adding an alkali to the gel-like aluminum hydroxide to dissolve the gel-like aluminum hydroxide are required, which complicates the steps and facilities, and requires a large amount of acid or alkali for neutralization and alkalizing. In addition, either method can finally reduce the fluorine concentration in the wastewater to below the drainage standard, but it has not been possible to reduce the fluorine concentration to a safe concentration from the viewpoint of human and environmental protection.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is possible to sufficiently reduce the fluorine concentration in wastewater without complicating the process and the treatment equipment. An object of the present invention is to provide a method for treating wastewater containing water.

[0006]

In order to solve the above-mentioned problems, the first invention is a treatment for adding a substance containing calcium, a substance containing aluminum and a substance containing sulfate to a wastewater containing fluorine. A method for treating waste water containing fluorine is provided.

A second aspect of the present invention is a fluorine-containing wastewater characterized by adding a cement substance comprising at least one of cement and cement raw material and a substance containing a sulfate group to the fluorine-containing wastewater. Provide a processing method.

According to the first aspect of the present invention, the substance containing calcium, the substance containing aluminum, and the substance containing sulfate are added to the wastewater containing fluorine.
Calcium ions, aluminum ions, and sulfate ions can be eluted in the waste water, and fluorine can be fixed in ettringite or monosulfate generated by the reaction of these ions, which can reduce the fluorine concentration. . The ethrin guide and monosulfate produced here are crystalline hydrates, which have a higher dehydration property than aluminum hydroxide produced by a neutralization reaction in water, and generate less and are easier to process.

Further, according to the second aspect of the present invention, by adding a cement substance composed of at least one of cement and a cement raw material and a substance containing a sulfate group to the wastewater containing a fluorine, a substance containing a sulfate group is added. Sulphate ion is eluted from the sulphate ion, and ettringite, monosulfate, CaO—SiO ₂ —H ₂ O—SO generated by the reaction between the sulfate ion and the components contained in the cement substance
Fluorine can be fixed in the _quaternary compound, whereby the fluorine concentration can be reduced. The CaO—SiO ₂ —H ₂ O—SO ₄ system compound produced here is a crystalline hydrate, like ethrin guide and monosulfate, and therefore has a higher dehydration property than aluminum hydroxide and a small amount of generation, and easy treatment. Is.

In the first aspect of the present invention, the treatment can be carried out by adding the substance that elutes calcium, the substance containing aluminum, and the substance containing sulfate group and reacting them all at once. Further, when the fluorine concentration in the waste water is high, after reacting by adding a part of the substance containing calcium, the remainder of the substance containing calcium, the substance containing aluminum, and the sulfate group. It is preferable to perform a treatment of adding a substance containing the substance to cause a reaction.

Further, in the case of performing the above-mentioned reaction for one-time reaction, it is more preferable to adjust the pH of the waste water to be treated to 9 to 12, and in the case of performing the above-mentioned two-step reaction treatment, the above-mentioned calcium is added. After adding a part of the substance containing and reacting, the pH of the wastewater is adjusted when adding and reacting the rest of the substance containing calcium, the substance containing aluminum, and the substance containing sulfate. More preferably, it is set to 9-12.

In the second aspect of the invention, the treatment can be carried out by adding the cement substance and the substance containing the sulfate group and reacting them all at once. Further, when the fluorine concentration in the wastewater is high, after the cement material is added and reacted, the substance containing the sulfate group is added to react, or the wastewater is added with a substance containing calcium. It is preferable to perform a treatment of adding the cement substance and the substance containing the sulfate group to cause the reaction.

Further, in the case of carrying out the above-mentioned treatment for reacting all at once, it is more preferable to adjust the pH of the waste water to 9-12. Furthermore, in the case of performing the treatment in which the reaction is carried out in the above two steps, the pH of the waste water is adjusted to 9 when the cement substance is added and reacted, and then the substance containing the sulfate group is added and reacted. Or 12 or, when the substance containing calcium is added and reacted, and then the substance containing the cement substance and the sulfate group is added and reacted, the pH of the waste water is set to 9 to 12. More preferably.

Examples of the substance containing calcium in the first and second inventions include natural calcium-containing minerals, calcium-containing slag produced as a by-product in the iron making process, and water-soluble calcium compounds. At least one kind can be used. Further, as the substance containing aluminum, natural aluminum-containing minerals, aluminum compounds by-produced in the aluminum processing process, aluminum sulfate, polyaluminum chloride,
Further, a water-soluble aluminum compound is exemplified, and at least one of them can be used. Furthermore, as substances containing sulfate, natural sulfuric acid-containing minerals,
Examples are gypsum produced as a byproduct in the flue gas cleaning process, gypsum produced as a byproduct in the acid neutralization process, and gypsum produced as a byproduct in the alkali neutralization process, and at least one of these can be used.

According to the first and second aspects of the present invention, the cooling water for the exhaust gas of the steelmaking plant, the cooling water for the exhaust gas of the municipal waste incinerator,
Direct smelter exhaust gas cooling water, semiconductor factory cleaning water, ceramic manufacturing factory cleaning water, and glass etching processing factory cleaning water can be treated with one kind or a mixture of two or more kinds of waste water. .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. First, a first embodiment of the present invention will be described. In the present embodiment, the effluent containing fluorine is subjected to a treatment of adding a substance containing calcium, a substance containing aluminum, and a substance containing sulfate, thereby producing insoluble ettringite and monosulfate in the wastewater. By fixing fluorine in these substances and separating them from the wastewater, the fluorine in the wastewater is removed and reduced.

The calcium-containing substance in the present embodiment is a mineral or compound that elutes calcium ions when it comes into contact with water, including natural minerals such as CaO and Ca (OH) ₂ , and calcium-containing by-products in the iron making process. Examples include slag and water-soluble calcium compounds, and of these, one kind or a combination of two or more kinds can be used. In addition, the substance containing aluminum is a mineral or compound that elutes aluminum ions and aluminate ions when it comes into contact with water, such as natural aluminum-containing minerals, aluminum compounds by-produced during the aluminum processing process, aluminum sludge, and aluminum sulfate. , Polyaluminum chloride, aluminum chloride, aluminum hydroxide, sodium aluminate, and other water-soluble aluminum compounds are exemplified, and one or two of these are used.
Combinations of more than one type can be used. Furthermore, substances containing sulfate radicals are minerals and compounds that elute sulfate ions when contacted with water.
Examples of the gypsum produced as a by-product in the flue gas cleaning process, the gypsum produced as a by-product in the acid neutralization process, and the gypsum produced as a by-product in the alkali neutralization process are listed. One or more of these may be combined. Can be used. These substances may be added as a solid, or may be added as an aqueous solution or suspension.

The mechanism of immobilizing fluorine in the waste water in this embodiment will be described as follows. Ca ²⁺ ions from substances containing calcium in waste water, and AlO ₂ ²⁻ with a pH value of 5.1 or more from substances containing aluminum.
Ions are eluted, SO ₄ ²⁻ ions are eluted from the substance containing sulfate, and these eluted ions react with each other to form ettringite and / or monosulfate. In the course of this production reaction, sulfate ions (SO that contribute to the production of ettringite and / or monosulfate)
₄ ²⁾ part of fluorine ions (F ^- by being replaced or taken as), fluorine is fixed in ettringite and / or monosulfate, fluorine in the waste water is reduced. The immobilization mechanism of fluorine associated with the formation of ettringite is shown in equation (1), and the immobilization mechanism of fluorine associated with the production of monosulfate is represented in equations (2) and (2) ′.

[0019]

[Chemical 1]

According to this embodiment, fluorine in wastewater is fixed by adding a substance containing calcium, a substance containing aluminum, and a substance containing sulfate to the wastewater containing fluorine and reacting them at once. The treatment can be carried out, and then the solid-liquid separation can be performed to obtain waste water having a low fluorine content. Even by such a simple treatment of reacting at once, the fluorine content in the waste water can be fixed and the fluorine content can be reduced, and when the fluorine content in the waste water is low, such treatment is sufficient.

However, when the fluorine content in the waste water is high, a part of the substance containing calcium is added to the waste water and reacted, and then the remainder of the substance containing calcium, the substance containing aluminum, and the sulfuric acid. It is preferable to add a substance containing roots to react. By performing such a two-step reaction, it is possible to obtain a higher fluorine reduction effect. The process of reacting in these two stages will be described below.

First, a part of the substance containing calcium is added to the wastewater to be treated, and the eluted calcium ions are reacted with the fluorine in the wastewater to make the sparingly soluble calcium fluoride (Ca).
F ₂ ) is generated and a part of fluorine is precipitated as calcium fluoride. Next, to the supernatant liquid obtained by solid-liquid separation of the precipitate of calcium fluoride, the rest of the substance containing calcium, the substance containing aluminum, and the substance containing sulfate are added, and the eluted aluminum ion and sulfate ion, Calcium and fluorine ions remaining in the wastewater are reacted with each other to generate ettringite and / or monosulfate partially incorporating fluorine, whereby fluorine is fixedly removed and separated from the wastewater. As described above, first, a part of the fluorine in the waste water is precipitated as calcium fluoride, and then the residual fluorine in the waste water is fixedly removed in ettringite and / or monosulfate, so that the fluorine content in the waste water is reduced. Even when it is high, fluorine can be sufficiently reduced.

Further, in the case where the treatment for reacting at once is performed as described above, it is more preferable to adjust the pH of the wastewater to be treated to 9 to 12, and in the case where the treatment for reacting in two steps is performed, the above-mentioned calcium is added. After adding and reacting a part of the substance including the substance, the balance of the substance including the calcium, the substance including the aluminum, and the substance including the sulfate group are added and reacted. 9 to 12
Is more preferable. By setting the pH of the wastewater in this way, a higher fluorine reduction effect can be obtained. The pH of the wastewater can be easily adjusted by adding an alkali or an acid to the wastewater.

When the predetermined substance is added to the wastewater for reaction as described above, it is preferable to mix the wastewater to which the predetermined substance is added. By doing this,
It is possible to promote the elution of ions from a predetermined substance and the reaction of the eluted ions with fluorine and the like. The mixing of the waste water may be started before the addition of the predetermined substance, or may be started after the addition of the predetermined substance.

Next, equipment for wastewater treatment to which this embodiment is applied will be described. FIG. 1 is a schematic diagram showing an example of wastewater treatment equipment for performing wastewater treatment to which this embodiment is applied. As shown in FIG. 1, this wastewater treatment facility adds a reaction tank 1 for storing wastewater and a wastewater in the reaction tank 1 with a substance containing calcium, a substance containing aluminum, and a substance containing sulfate radical. For treating agent supply unit 4 and reaction tank 1
A stirring mechanism 8 for stirring the waste water inside, and a solid-liquid separator (thickener) 2 for separating the waste water after treatment in the reaction tank 1 into solid and liquid.
And have.

In this wastewater treatment facility, after supplying a predetermined amount of wastewater into the reaction tank 1 from the storage tank 5 which stores wastewater containing fluorine, the treatment agent supply unit 4 contains a substance containing calcium and aluminum. A substance and a substance containing sulfate are added, and the waste water is stirred by the stirring mechanism 8. At this time, an alkali or an acid is supplied from the pH adjusting mechanism 6 as needed, and the pH of the waste water is adjusted to 9 to 12 so that fluorine fixation can be efficiently performed. After stirring for a predetermined time, reaction tank 1
The wastewater treatment is completed by guiding the wastewater inside to the solid-liquid separator 2 and separating the precipitated sludge. Since the fluorine content of the wastewater thus treated is sufficiently reduced, it can be discharged into the environment after being further subjected to a predetermined treatment such as a neutralization treatment. In addition, here, the case of performing the above-described process of reacting once is described,
Returning the waste water after solid-liquid separation into the reaction tank 1, or adding a part of the substance containing calcium in the reaction tank 1 to cause a reaction, and then reacting the remainder of the substance containing calcium and the substance containing aluminum in the same tank. It is also possible to carry out the treatment in which the reaction is carried out in the above-mentioned two steps by adding a substance containing a sulfate group.

FIG. 2 is a schematic view showing another example of wastewater treatment equipment for carrying out the present invention. As shown in FIG. 2, this wastewater treatment facility includes a first reaction tank 11 for adding and mixing a part of a substance containing calcium to wastewater, a balance of the substance containing calcium, a substance containing aluminum, and a sulfate group. Although the second reaction tank 21 for adding and mixing the substance containing is separately provided, the respective configurations of the first reaction tank 11 and the second reaction tank 21 are the reaction tanks in the wastewater treatment facility shown in FIG. The same as 1. A first solid-liquid separator (thickener) is provided between the first reaction tank 11 and the second reaction tank 21 so as to perform solid-liquid separation on the waste water after treatment in the first reaction tank 11 and supply the separated waste water to the second reaction tank 21. ) 12 are provided. Also, the first
A first processing agent supply unit 14 for adding a part of a substance containing calcium to the wastewater in the reaction tank 11, a balance of the substance containing calcium in the wastewater in the second reaction tank 21, a substance containing aluminum, and sulfuric acid. Second for adding root-containing substances
A treatment agent supply unit 24 and a second solid-liquid separator (thickener) 22 that separates the waste water after treatment in the second reaction tank 21 into solid and liquid are provided.

In this wastewater treatment facility, a predetermined amount of wastewater is supplied from the storage tank 15 storing wastewater containing fluorine into the first reaction tank 11, and then a substance containing calcium is supplied from the first processing agent supply unit 14. Add a part of the stirring mechanism 18
Stir the wastewater with and separate the fluorine in the wastewater as CaF ₂ . At this time, if necessary, alkali is supplied from the first pH adjusting mechanism 16 and the pH of the waste water is adjusted to 6 or more so that the fluorine can be fixed efficiently. After stirring for a predetermined time, the wastewater in the first reaction tank 11 is guided to the first solid-liquid separator 12, and the wastewater from which the precipitated sludge has been separated is supplied into the second reaction tank 21. Then, the remainder of the substance containing calcium, the substance containing aluminum, and the substance containing sulfate are added to the wastewater in the second reaction tank 21 from the second treatment agent supply unit 24, and the wastewater is stirred by the stirring mechanism 28. , Fluorine in wastewater is fixed and removed in ettringite and / or monosulfate. At this time, if necessary, an alkali or an acid is supplied from the second pH adjusting mechanism 26, and the pH of the waste water is adjusted to 9 to 12 so that the fluorine can be fixed efficiently. After stirring for a predetermined time, the wastewater in the second reaction tank 21 is guided to the second solid-liquid separator 22 to separate the precipitated sludge, whereby the treatment of the wastewater is completed. In this wastewater treatment facility, the first reaction tank and the second
Fluorine is reduced by a two-step reaction using a reaction tank, so even in wastewater with a high fluorine concentration, the fluorine content can be sufficiently reduced, and a predetermined treatment such as neutralization treatment can be performed. After application, it can be discharged into the environment.

Next, a second embodiment of the present invention will be described. In the present embodiment, the fluorine-containing wastewater is subjected to a treatment of adding a cement substance composed of at least one of cement and a cement raw material, and a substance containing a sulfate group, so that insoluble ettringite in the wastewater, monosulfate or fluorine together to produce _{CaO-SiO 2 -H 2 O-} SO 4 based compounds fixed on these materials, removing reduced fluorine in the waste water by separating from the waste water.

The cement substance in this embodiment may be a product cement, a cement raw material (cement clinker), or a mixture of both. Also, a material intermediate between the two may be used. Here, as the cement, for example, Portland cement, early strength Portland cement, ultra early strength Portland cement, medium heat Portland cement, sulfate resistant Portland cement, blast furnace cement, silica cement, fly ash cement,
Alumina cement, expansion cement, oil well cement, geothermal well cement, etc. are exemplified, and one or two of them are used.
It may be a combination of two or more species. In addition, as the cement raw material, the clinker of the above cement is exemplified, and among these, one kind or a combination of two or more kinds can be used.

Further, the substance containing a sulfate group in the present embodiment is a mineral or compound that elutes a sulfate ion when it comes into contact with water, such as a natural sulfuric acid-containing mineral, a gypsum by-produced in a flue gas cleaning process, Gypsum produced as a byproduct in the neutralization process of acid, and gypsum produced as a byproduct in the neutralization process of alkali are exemplified.
Of these, one kind or a combination of two or more kinds can be used. The cement material and the material containing sulfate may be added as a solid, or may be added as an aqueous solution or suspension.

The mechanism for immobilizing fluorine in waste water in this embodiment will be described as follows. In drainage, calcium aluminate contained in cement material,
From calcium aluminum ferrite, etc., calcium ion (Ca ²⁺ ion) and aluminum ion (p
When the H value is 5.1 or more, AlO ₂ ²⁻ ion) is eluted.
By reacting these ions with sulfate ions (SO ₄ ^2- ions) eluted from substances containing sulfate, ettringite and monosulfate are produced, and some sulfate ions are discharged into the wastewater in the course of this production reaction. It is substituted with the contained fluorine ion (F ⁻ ion), and fluorine is fixed in ettringite and monosulfate.

Further, in the waste water, the cement substance is contained.
Calcium silicate, calcium aluminum
Calcium ion (Ca²⁺ion)
And silicon ions (when the pH value is 10 or more, HSiO_Three
⁻Ion, SiO above 12 _Three ^2-) Elutes. this
Sulfate ion eluted from substances containing sulfate
(SO_Four ^2-Ca) by reacting with₁₀
(SiO_Four)_Three(SO _Four)_Three(OH)_TwoAnd Ca₅[(S
i, S) O_Four]_ThreeCaO-SiO such as (OH) _Two-H_Two
O-SO_FourGenerates system compounds and eliminates them in the course of this production reaction.
Fluorine ion in water (F⁻Ions are hydroxyl groups (OH⁻I
On) It is built into the site and fixed.

For example, Ca ₁₀ (SiO ₄ ) ₃ (SO ₄ ) reacts with fluorine ions and sulfate ions in the presence of water.
_{3 The} reaction of [(OH) _1-y F _y ] ₂ is represented by the formula (3).

[0035]

[Chemical 2]

Further, calcium ions and silicon ions react with fluorine ions and sulfate ions to cause Ca
₅ [(Si, S) O ₄ ] ₃ (OH, F) is generated.

These CaO-SiO_Two-H_TwoO-SO
_FourThe immobilization of fluoride ions by the formation of -F compounds
In addition, Ca₅(S
iO _Four)_Two(OH, F)_TwoAnd Ca₆Si_TwoO₇(O
H)₆CaO-SiO etc._Two-H_TwoOF compounds and
Gel-like CaO-SiO_Two-H_TwoOF system amorphous compound
Thing, Ca_TwoAl_TwoSiO₆(OH, F)_TwoCaO-
Al_TwoO_Three-SiO_Two-H_TwoOF compound is produced,
Fluorine is fixed.

According to this embodiment, it is possible to reduce the fluorine content by immobilizing the fluorine in the wastewater by the treatment of adding the cement substance and the substance containing the sulfate group to the wastewater containing fluorine and reacting them at once. If the content of fluorine in the waste water is small, such a simple treatment of reacting at once is sufficient.

However, when the fluorine content in the wastewater is high, after adding a cement substance to the wastewater to cause a reaction,
Either add a substance containing sulfate or react to react,
Alternatively, it is preferable to perform a treatment of adding a substance containing calcium to the waste water and reacting the same in advance, and then adding and mixing the substance containing the cement substance and the substance containing the sulfate group. According to the treatment in which the reaction is carried out in such two steps, it is possible to obtain a further higher fluorine reducing effect. Hereinafter, these processes will be described.

First, a process of adding a cement substance to waste water to cause a reaction, and then adding a substance containing a sulfate group to cause a reaction will be described. First, a cement material is added so that a slightly larger amount of calcium ions than the reaction equivalent to the fluorine contained in the wastewater to be treated is eluted, and a part of the fluorine in the wastewater is reacted to make the sparingly soluble calcium fluoride ( C
precipitate as aF ₂ ). Next, a substance containing a sulfate group is added to the supernatant liquid obtained by solid-liquid separation of the precipitate of calcium fluoride, and the eluted sulfate ions are allowed to react with the calcium ions and fluoride ions remaining in the wastewater. Fluorine is fixedly removed by generating ettringite, monosulfate, CaO—SiO ₂ —H ₂ O—SO ₄ type compound, etc., which partially incorporates fluorine, and then separated from the wastewater.

Next, the process of adding a substance containing calcium to the waste water to react it, and then adding the substance containing the cement substance and the substance containing sulfate to react the same will be described. First, a substance containing calcium is added in a slightly larger amount than the reaction equivalent with the fluorine contained in the wastewater to be treated, and it reacts with a part of the fluorine in the wastewater to precipitate as insoluble calcium fluoride (CaF ₂ ). Let Next, cement substances and substances containing sulfate are added to the supernatant liquid obtained by solid-liquid separation of the precipitate of calcium fluoride, and the ions eluted from these substances and the calcium ions and fluorine remaining in the wastewater are added. By reacting with ions and the like, fluorine is fixed and removed in the same manner as the above treatment, and separated from the waste water.

The substance containing calcium used in this treatment is a mineral or compound that elutes calcium ions when it comes into contact with water, and is a natural mineral such as CaO or Ca (OH) ₂ or a by-product in the iron making process. Examples of calcium-containing slag, and water-soluble calcium compounds,
Of these, one kind or a combination of two or more kinds can be used.

According to such a two-step reaction, ettringite, monosulfate, CaO—SiO ₂ —H ₂ O—SO ₄ are precipitated after part of the fluorine is precipitated as calcium fluoride as described above. Since fluorine is fixed to the system compound or the like, the fluorine can be sufficiently reduced even when the fluorine content in the waste water is high.

Further, in the case where the treatment for reacting at once is carried out as described above, it is more preferable to adjust the pH of the waste water to be treated to 9 to 12, and in the case where the treatment for reacting in two steps is carried out, the above-mentioned cement is used. It is more preferable to adjust the pH of the waste water to 9 to 12 when the substance containing the sulfate group is added and reacted after the substance is added and reacted. In addition, when the cement-containing substance and the sulfate-containing substance are added and reacted after the calcium-containing substance is added and reacted, the cement-containing substance and the sulfate-containing substance are added and reacted. PH of drainage
Is more preferably 9-12. By setting the pH of the wastewater in this way, a higher fluorine reduction effect can be obtained. The pH of the wastewater can be easily adjusted by adding an alkali or an acid to the wastewater.

When the predetermined substance is added to the wastewater for reaction as described above, it is preferable to mix the wastewater to which the predetermined substance is added. By doing this,
It is possible to promote the elution of ions from a predetermined substance and the reaction of the eluted ions with fluorine and the like. The mixing of the waste water may be started before the addition of the predetermined substance, or may be started after the addition of the predetermined substance.

Next, equipment for performing wastewater treatment to which this embodiment is applied will be described. The equipment for performing wastewater treatment to which the present embodiment is applied has substantially the same configuration as the wastewater treatment equipment described in the above-described embodiments, and therefore is not shown again and will be described based on FIGS. 1 and 2. The first example of the wastewater treatment facility that performs the treatment to which the present embodiment is applied has the same basic configuration as the wastewater treatment facility shown in FIG. 1. However, the treatment agent supply unit 4 is configured to add a substance including a cement substance and a sulfate group.

In this wastewater treatment facility, after supplying a predetermined amount of wastewater into the reaction tank 1 from the storage tank 5 storing the wastewater containing fluorine, the treating agent supply unit 4 removes the cement material and the sulfate radical. The substance containing is added, and the waste water is stirred by the stirring mechanism 8. At this time, if necessary, a pH adjusting mechanism 6
The pH of the waste water is adjusted to 9 to 12 so that the alkali or acid is supplied more and fluorine is efficiently fixed. After stirring for a predetermined time, the waste water in the reaction tank 1 is led to the solid-liquid separator 2,
The wastewater treatment is completed by separating the settled sludge. Since the fluorine content of the wastewater thus treated is sufficiently reduced, it can be discharged to the environment after being subjected to a predetermined treatment such as neutralization treatment. In addition, here, the case where the reaction is performed at once is described, but it is also possible to perform the reaction in two steps.

The second example of the wastewater treatment equipment for carrying out the treatment to which this embodiment is applied has the same basic configuration as the wastewater treatment equipment shown in FIG. However, a cement substance is added from the first treatment agent supply unit 14, and a substance containing sulfate is added from the second treatment agent supply unit 24.

In this wastewater treatment facility, after supplying a predetermined amount of wastewater into the first reaction tank 11 from the storage tank 15 that stores wastewater containing fluorine, a cement substance is added from the first processing agent supply unit 14. Then, the stirrer 18 stirs the wastewater to separate the fluorine in the wastewater as CaF ₂ . After stirring for a predetermined time, the waste water in the first reaction tank 11 is discharged into the first solid-liquid separator 1
The waste water which was led to No. 2 and separated the settled sludge, was sent to the second reaction tank 2
Supply within 1. Then, a substance containing a sulfate group is added to the wastewater in the second reaction tank 21 from the second treatment agent supply unit 24, the wastewater is stirred by the stirring mechanism 28, and the fluorine in the wastewater is mixed with ettringite, monosulfate, or CaO—SiO 2. ₂ -H ₂ O
Fixed removed during -SO ₄ based compounds. At this time, if necessary, an alkali or an acid is supplied from the second pH adjusting mechanism 26 so that the pH of the wastewater is adjusted so that the fluorine can be fixed efficiently.
To 9-12. After stirring for a predetermined time, the second reaction tank 2
The wastewater in 1 is guided to the second solid-liquid separator 22 and the precipitated sludge is separated, whereby the treatment of the wastewater is completed. In this wastewater treatment facility, fluorine is reduced by the two-stage reaction process using the first reaction tank 11 and the second reaction tank 21, so the fluorine content is sufficiently reduced even in wastewater having a high fluorine concentration. After being subjected to a predetermined treatment such as neutralization treatment, it can be discharged into the environment.

Here, among the treatments in which the reaction is carried out in the two stages described above, the case where the cement substance is added to the wastewater to cause the reaction and then the substance containing the sulfate group is added to cause the reaction is shown. The treatment of adding a substance containing calcium to the waste water and reacting it in advance, and then adding the substance containing the cement substance and the substance containing sulfate to react them can be performed in the same manner.

According to the first and second embodiments of the present invention as described above, for example, cooling water for exhaust gas from a steelmaking plant,
Fluorine-containing wastewater such as exhaust gas cooling water for municipal waste incinerators, exhaust gas cooling water for direct melting furnaces, cleaning water for semiconductor factories, cleaning water for ceramic manufacturing plants, and cleaning water for glass etching treatment factories is treated. The fluorine content in the waste water can be reduced.

[0052]

EXAMPLES Examples of the present invention will be described below. [Example 1] 1 mmol / l (20 mg / l) of fluorine
5mM of calcium oxide crushed to 0.1mm or less, 1.5mmol of water-soluble aluminum sulfate, and 3m of gypsum crushed to 0.1mm or less as wastewater
mol at the same time, and the pH of the solution is adjusted to a predetermined pH of 7-12.
The mixture was stirred for 30 minutes while being adjusted to H with sodium hydroxide or hydrochloric acid. After leaving still for 30 minutes, the supernatant was filtered with a membrane filter having an opening diameter of 0.45 μm, and the fluorine concentration in the obtained filtrate was measured according to JIS K0102.
It was quantified by the method specified in 34.2. FIG. 3 shows the relationship between the pH of the wastewater in such treatment and the fluorine concentration in the wastewater after the treatment. As shown in FIG. 3, the pH of the wastewater is 9
In the range from 1 to 12, the decrease rate of fluorine concentration is higher, especially p
When H was 11, the fluorine concentration decreased to 2 mg / l or less.

[Example 2] 1 mmol / l (2
Calcium oxide, water-soluble aluminum sulphate crushed to 0.1 mm or less as an additive in wastewater containing 0 mg / l),
Gypsum crushed to a size of 0.1 mm or less was added at the same time in the proportion shown in Table 1, and the mixture was stirred for 30 minutes while adjusting the pH of the solution to 9 with sodium hydroxide or hydrochloric acid. 30 more
The supernatant after standing for a minute was filtered with a membrane filter having an opening diameter of 0.45 μm, and the fluorine concentration in the obtained filtrate was quantified by the method specified in JIS K0102 34.2. The fluorine concentration measured after the treatment at each addition level is shown in FIG. As shown in FIG. 4, the fluorine concentration decreases as the addition amount of each substance increases from the addition level A to the addition level C.
The fluorine concentration was 2 mg / l.

[0054]

[Table 1]

[Embodiment 3] The same drainage as in Embodiment 1 is shown in Table 1.
Add the additive in the same ratio as above, and adjust it with sodium hydroxide or hydrochloric acid so as to keep the pH in the solution at 11.
The mixture was stirred at 0 ° C for 30 minutes. Further, after standing for 30 minutes, the supernatant was filtered through a membrane filter having an opening diameter of 0.45 μm, and the fluorine concentration in the filtrate obtained in the same manner as in Example 1 was measured. The fluorine concentration measured after the treatment at each addition level is shown in FIG. As shown in FIG. 5, as in Example 2, the fluorine concentration decreased as the amount of each substance added increased, and in this case, the fluorine content reduction effect higher than that in Example 2 was obtained. And the fluorine concentration at the addition level C is 0.2 m
It decreased to g / l.

[Comparative Examples 1 and 2] In the same drainage as in Example 1, 10 mm of calcium oxide crushed to 0.1 mm or less was crushed.
ol addition (Comparative Example 1), water-soluble aluminum sulfate 10m
After adding mol (Comparative Example 2) and stirring for 10 minutes, pH
Sodium hydroxide or hydrochloric acid was added so as to keep 10 and the mixture was stirred for another 30 minutes. After standing for 30 minutes, when the fluorine concentration was measured by the same method as in Example 1, the fluorine concentrations were 17 mg / l (Comparative Example 1) and 14 mg / l (Comparative Example 2), respectively. Could not be reduced.

[Example 4] 20 mmol / l of fluorine
To the wastewater containing (400 mg / l), 50 mmol of calcium oxide pulverized to 0.1 mm or less was added, and the mixture was stirred for 10 minutes. After leaving it to stand for 30 minutes, the total amount is 1 μm
It was filtered with a membrane filter. 6 mmol of calcium oxide and 3 mmo of water-soluble aluminum sulfate in the filtrate
l, 6 mmol of gypsum crushed to 0.1 mm or less was added, and the mixture was stirred for 10 minutes while adding sodium hydroxide or sulfuric acid so as to keep the pH at 11. After leaving it for 30 minutes,
When the supernatant was filtered with a membrane filter having an opening diameter of 0.45 μm, the concentration of fluorine ions in the obtained filtrate was 1 mg / l or less.

[Example 5] 20 mmol / l of fluorine
To the wastewater containing (400 mg / l), 50 mmol of calcium oxide pulverized to 0.1 mm or less was added, and the mixture was stirred for 10 minutes. Then, 6 mmol of calcium oxide, 3 mmol of water-soluble aluminum sulfate, and 6 mmol of gypsum crushed to 0.1 mm or less were added, and the mixture was stirred for 10 minutes while adding sodium hydroxide or sulfuric acid so as to keep the pH at 11. After leaving it for 30 minutes, the supernatant was 0.45
When filtered through a μm membrane filter, the concentration of fluorine ions in the obtained filtrate was 1 mg / l or less.

Example 6 Fluorine was added at 1 mmol / l (2
To 100 parts by volume of waste water containing 0 mg / l), 1 part by weight of powdered Portland cement and 1 part by weight of gypsum crushed to 0.1 mm or less were added, respectively, and stirred for 10 minutes. Then p
Hydrochloric acid was added so as to keep H at 11, and the mixture was further stirred for 10 minutes. After standing for 30 minutes, the supernatant liquid was 0.4
When filtered with a 5 μm membrane filter, the concentration of fluorine ions in the obtained filtrate was 2 mg / l.

Example 7 20 mmol / l of fluorine
2 parts by weight of powdered Portland cement was added to 100 parts by volume of drainage containing (400 mg / l), and the mixture was stirred for 10 minutes. After leaving it to stand for 30 minutes, the whole amount was filtered with a membrane filter having an opening diameter of 1 μm. Water-soluble aluminum sulfate (3 mmol / l, 0.5 part by weight of gypsum crushed to 0.1 mm or less) was added to the obtained filtrate, and the mixture was stirred for 10 minutes while adding sodium hydroxide or hydrochloric acid so as to keep the pH at 11. did. After standing for 30 minutes, the supernatant was filtered through a membrane filter having an opening diameter of 0.45 μm, and the obtained filtrate had a fluorine ion concentration of 2 mg / l or less.

Example 8 Fluorine was added at 1 mmol / l (2
0 mg / l) to 100 parts by volume of drainage, 2 parts by weight of powder obtained by pulverizing secondary refining slag produced as a by-product in the iron making process to 0.1 mm or less, and 2 parts by weight of gypsum pulverized to 0.1 mm or less, respectively. Parts by weight were added and stirred for 30 minutes. When the supernatant liquid after standing for 30 minutes was filtered with a membrane filter having an opening diameter of 0.45 μm, the fluorine concentration in the obtained filtrate was 1 mg / l or less.

Example 9 Using the equipment shown in FIG. 1, first, in a reaction tank 1, waste water (fluorine concentration: 20 mg / l,
pH8), a calcium chloride solution was added so that the calcium ion concentration was 100 mg / l, and then 0.1
The gypsum crushed to less than mm has a sulfate ion concentration of 150 m
g / l, polyaluminum chloride is further added so that the aluminum ion concentration is 60 mg / l, and sodium hydroxide is added so that the pH becomes 11 while stirring in the reaction tank 1. I adjusted it. After stirring for 10 minutes, solid-liquid separation was performed in a solid-liquid separator (thickener) 2 to obtain a supernatant solution and a sludge for precipitation. When the fluorine concentration of this supernatant solution was measured, the concentration of fluorine ions in the solution was lowered to 2 mg / l, and it was confirmed that the solution could be discharged after neutralization.

[Embodiment 10] Using the equipment shown in FIG.
In the first reaction tank 11, waste water (fluorine concentration 100 mg
/ L, pH 8), calcium chloride solution was added so that the calcium ion concentration was 400 mg / l, and the mixture was stirred for 20 minutes, and then solid-liquid separated in the first solid-liquid separator (thickener) 12 to obtain a supernatant solution and a precipitate. I got sludge.
This supernatant liquid was introduced into the second reaction tank 21, where calcium chloride solution was adjusted to a calcium ion concentration of 100 mg / l, and dihydrate gypsum was adjusted to a sulfate ion concentration of 150.
mg / l, polyaluminum chloride is further added so that the aluminum ion concentration is 60 mg / l, the pH is adjusted to 11 with sodium hydroxide,
Stir for 10 minutes. This solution was transferred to the second solid-liquid separator 22 to perform solid-liquid separation, and a supernatant solution and a precipitated sludge were obtained. When the fluorine concentration of this supernatant solution was measured,
The fluoride ion concentration in the solution had dropped to 1 mg / l or less, and it was confirmed that the solution could be released after neutralization.

[0064]

As described above, according to the present invention, wastewater containing fluorine is treated by adding a substance containing calcium, a substance containing aluminum, and a substance containing sulfate, or Insoluble ettringite or monosulfate is generated in wastewater by adding a cement material and a substance containing sulfate, and fluorine is fixed in these materials to separate it from the wastewater. It is possible to remove and reduce the amount of fluorine, which makes it possible to sufficiently reduce the concentration of fluorine in the wastewater without complicating the process and the treatment equipment.

[Brief description of drawings]

FIG. 1 is a schematic diagram of equipment for performing wastewater treatment to which the method of the present invention is applied in a one-step process.

FIG. 2 is a schematic diagram of equipment for performing wastewater treatment in which the method of the present invention is applied in a two-step process.

FIG. 3 is a treatment pH of wastewater containing fluorine in Example 1.
6 is a graph showing changes in the fluorine concentration in the treated water according to.

FIG. 4 is a graph showing a change in fluorine concentration in treated water when a treatment containing calcium oxide, aluminum sulfate, and gypsum was added to the wastewater containing fluorine in Example 2 at pH 9.

FIG. 5: In Example 3, the addition of calcium oxide, aluminum sulfate, and gypsum to the wastewater containing fluorine was adjusted to pH 11
3 is a graph showing changes in the concentration of fluorine in the treated water when the process is carried out in.

[Explanation of symbols]

1; Reaction tank 2; Solid-liquid separator 4; Treatment agent supply unit 5; Storage tank 6; pH control mechanism 8; stirring mechanism 11; First reaction tank 12; first solid-liquid separator 14; First treatment agent supply section 15; Storage tank 16; First pH control mechanism 18; Stirring mechanism 21; Second reaction tank 22; Second solid-liquid separator 24; Second processing agent supply section 26; Second pH adjusting mechanism 28; Stirring mechanism

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobutaka Nakayama             2-15-1 Konan, Minato-ku, Tokyo Steel pipe mining industry             Within the corporation (72) Inventor Yuki Kusama             2-15-1 Konan, Minato-ku, Tokyo Steel pipe mining industry             Within the corporation (72) Inventor Hiroyuki Mitsufuji             2-15-1 Konan, Minato-ku, Tokyo Steel pipe mining industry             Within the corporation (72) Inventor Atsushi Yamaguchi             2-15-1 Konan, Minato-ku, Tokyo Steel pipe mining industry             Within the corporation (72) Inventor Hideaki Mizuwata             1-25 Yagiyamahonmachi, Taihaku-ku, Sendai City, Miyagi Prefecture             No. 1 (72) Inventor Ryo Inoue             4-29-4 Minami-Nakayama, Izumi-ku, Sendai City, Miyagi Prefecture F-term (reference) 4D038 AA08 AB40 AB41 AB42 BA02                       BA04 BA06 BB18

Claims (13)

[Claims] 1. A method for treating wastewater containing fluorine, which comprises adding a substance containing calcium, a substance containing aluminum, and a substance containing sulfate to the wastewater containing fluorine. 2. The method for treating wastewater containing fluorine according to claim 1, wherein the substance containing calcium, the substance containing aluminum, and the substance containing sulfate are reacted at the same time. 3. A part of the substance containing calcium is added and reacted, and then the rest of the substance containing calcium, the substance containing aluminum and the substance containing sulfate are added and reacted. The method for treating wastewater containing fluorine according to claim 1, characterized in that. 4. A method for treating wastewater containing fluorine, which comprises adding to the wastewater containing fluorine a cement substance composed of at least one of cement and a cement raw material and a substance containing sulfate. 5. The method for treating wastewater containing fluorine according to claim 4, wherein the cement material and the material containing the sulfate group are reacted at one time. 6. The method for treating fluorine-containing wastewater according to claim 4, wherein the cement substance is added and reacted, and then the substance containing the sulfate group is added and reacted. 7. The method according to claim 4, wherein the wastewater containing fluorine is added with a substance containing calcium to react therewith, and then the substance containing the cement material and the sulfate group is added to react therewith. Method for treating wastewater containing fluorine. 8. The method for treating wastewater containing fluorine according to claim 2, wherein the pH of the wastewater is set to 9 to 12. 9. When the substance containing aluminum and the substance containing sulfate are added and reacted, the p
The method for treating wastewater containing fluorine according to claim 3, wherein H is set to 9 to 12. 10. The method for treating fluorine-containing wastewater according to claim 6, wherein the pH of the wastewater is set to 9 to 12 when the substance containing a sulfate group is added and reacted. 11. When the cement material and the material containing the sulfate group are added and reacted, the pH of the waste water is adjusted to 9 to 10.
12. The method for treating wastewater containing fluorine according to claim 7, wherein the wastewater is 12. 12. The substance containing calcium is at least one of a natural calcium-containing mineral, a calcium-containing slag produced as a by-product in an iron making process, and a water-soluble calcium compound, or the substance containing aluminum. Is at least one of natural aluminum-containing minerals, aluminum compounds by-produced during aluminum processing, aluminum sulfate, polyaluminum chloride, and water-soluble aluminum compounds, or the substance containing the sulfate group is At least one of natural sulfuric acid-containing minerals, gypsum produced as a by-product during flue gas cleaning, gypsum produced as a by-product in acid neutralization, and gypsum produced as a by-product in alkali neutralization
The method for treating wastewater containing fluorine according to any one of claims 1 to 11, which is a seed. 13. The fluorine-containing waste water is exhaust gas cooling water of a steelmaking plant, exhaust gas cooling water of a municipal waste incinerator,
13. At least one kind of exhaust water cooling water for a direct melting furnace, cleaning water for a semiconductor factory, cleaning water for a ceramic manufacturing factory, and cleaning water for a glass etching treatment factory. Item 1. A method for treating wastewater containing fluorine according to Item 1.