WO2012056826A1 - Method for processing toxic matter-containing water and processing device - Google Patents

Abstract

Provided is a method for processing toxic matter-containing water, comprising: a step for adding an insoluble metal oxide with a layered double hydroxide as a component thereof and a soluble metal compound to water containing toxic matter; a reaction step for reacting the insoluble metal oxide, the soluble metal compound, and the toxic matter-containing water under alkaline conditions and generating a slurry that includes a sludge with layered double hydroxides formed on the surface of the insoluble metal oxide; and a solid/liquid separation step for removing toxic matter captured in the sludge to outside the system, by precipitating the sludge and solid/liquid separating the slurry.

Description

Method and apparatus for treating water containing hazardous substances

The present invention relates to a method and apparatus for treating water containing harmful substances, and more specifically, a treatment system for removing these harmful substances from waste water containing harmful substances such as fluorine, boron, nitrogen compounds, phosphorus and heavy metals. In addition, the present invention relates to a treatment system that is excellent in solid-liquid separation of sludge incorporating toxic substances, and that sludge settles in a short time to remove toxic substances.
The present application claims priority based on Japanese Patent Application No. 2010-244772 filed in Japan on October 29, 2010, the contents of which are incorporated herein by reference.

A method for removing harmful substances contained in waste water by taking them into layered double hydroxides is conventionally known. For example, Japanese Patent Application Laid-Open No. 2003-285076 (Patent Document 1) discloses that a layered double hydroxide is produced by adding a divalent metal ion and a trivalent metal ion to wastewater containing fluorine to produce the layered double hydroxide. A treatment method for incorporating fluorine between the two layers is described.

In International Publication WO2005-087664 (Patent Document 2), an acidic solution containing aluminum ions and magnesium ions and an alkaline solution containing alkali are mixed, and no time is left after the mixing of the acidic solution and the alkaline solution is completed. By immediately removing or neutralizing water, the general formula: Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (A ⁿ⁻ is an anion) The hydrotalcite-like substance is formed, and a treatment method is described in which fluorine or the like is taken into the substance and fixed.

JP 2003-285076 A International Publication No. WO2005-087664

The conventional treatment method described above is a method for removing fluorine by producing a layered double hydroxide such as hydrotalcite, but has a problem that the treatment time is prolonged due to poor sedimentation of the produced sludge. Further, the treatment method of Patent Document 1 focuses on the recovery of the fluorine-containing emulsifier, and the ability to remove heavy metals is unclear. Moreover, in the processing method of patent document 2, the anion exchange capacity is enhanced by controlling the crystallite size of the hydrotalcite-like substance to 20 nm or less, and the adsorption effect on chromium is shown for heavy metal ions. The ability to remove heavy metals other than chromium is unclear.

The present invention solves the problem of inferior sedimentation of the produced sludge in the above-described conventional treatment method, and provides a treatment system excellent in the adsorption effect on fluorine and the sedimentation of the produced sludge. Moreover, the removal effect of boron, a nitrogen compound, phosphorus, and heavy metals is also excellent, Preferably, the processing system excellent in the removal effect of harmful substances, such as a boron, a nitrogen compound, phosphorus, and heavy metals, with fluorine is provided.

The present invention relates to a method for treating harmful substance-containing water having the following constitution.
A first aspect of the present invention includes a step of adding a hardly soluble metal oxide and a soluble metal compound, which are components of a layered double hydroxide, to harmful substance-containing water, and the hardly soluble metal oxide and the soluble metal compound. A reaction step of reacting toxic substance-containing water under alkaline conditions to produce a slurry containing sludge in which a layered double hydroxide is formed on the surface of the hardly soluble metal oxide; A method for treating harmful substance-containing water, comprising: a solid-liquid separation step of removing a harmful substance taken into the sludge out of the system by solid-liquid separation.
According to a second aspect of the present invention, in the treatment method according to the first aspect, part or all of the solid-liquid separated sludge is returned to the reaction step, and the returned sludge is used to form a layered double hydroxide. This is a method for treating water containing harmful substances.

A third aspect of the present invention is a method for treating harmful substance-containing water according to the first or second aspect, wherein the hardly soluble metal oxide is magnesium oxide, and the soluble metal compound is a soluble aluminum salt. Yes, by adding magnesium oxide and soluble aluminum salt to water containing harmful substances and reacting them under alkaline conditions to form hydrotalcite on the surface of magnesium oxide, harmful substances are incorporated into the hydrotalcite A method for treating toxic substance-containing water, in which a slurry containing sludge is produced and the slurry containing sludge is solid-liquid separated.
According to a fourth aspect of the present invention, there is provided a method for treating harmful substance-containing water according to any one of the first to third aspects, wherein the harmful substance is any one of fluorine, boron, nitrogen compounds, phosphorus, and heavy metals. This is a method for treating harmful substance-containing water, wherein one or two or more kinds are produced, and a slurry containing sludge incorporating the harmful substances is generated and solid-liquid separated.

According to a fifth aspect of the present invention, there is provided a method for treating harmful substance-containing water according to any one of the first to fourth aspects, per 1 L of harmful substance-containing water having a fluorine concentration of 1 to 50 mg / L. This is a method for treating harmful substance-containing water in which 0.05 to 10 g / L of magnesium oxide and a soluble aluminum salt are added so that the aluminum concentration in water is 10 to 1000 mg / L and the reaction is carried out at a pH of 7 to 11 in a reaction vessel. .
A sixth aspect of the present invention is a method for treating a hazardous substance according to any one of the first to fifth aspects, and when the slurry containing the generated sludge is allowed to stand, the stable volume after 30 minutes is 40. % Is a method of treating harmful substance-containing water that is less than or equal to%.
In the above treatment method, the slurry containing sludge is allowed to stand in the solid-liquid separation step, and after 30 minutes, the sludge volume after sedimentation (sludge sediment volume) is 40% or less of the initial slurry volume. Become.

A seventh aspect of the present invention is a method for treating a hazardous substance according to any one of the first to sixth aspects, wherein the pretreatment for reducing harmful substances and interfering substances contained in the harmful substance-containing water (raw water) A method for treating hazardous substance-containing water is provided, wherein a process is provided, and a hardly soluble metal oxide and a soluble metal compound as components of a layered double hydroxide are added to pretreated harmful substance-containing water.
In the above treatment method, in the pretreatment, harmful substances contained in the raw water containing harmful substances are reduced, and components that hinder uptake of harmful substances by the layered double hydroxide are reduced.
An eighth aspect of the present invention is a method for treating a hazardous substance according to any one of the first to seventh aspects, wherein a post-treatment step for post-treating treated water obtained by solid-liquid separation of sludge from the slurry is provided. This is a method for treating water containing harmful substances.

Moreover, this invention relates to the processing apparatus of the harmful | toxic substance containing water which consists of the following structures.
A ninth aspect of the present invention is a treatment apparatus for hazardous substance-containing water, comprising an addition tank for adding a chemical to the harmful substance-containing water, and a slurry containing sludge by reacting the added chemical with the harmful substance-containing water. A reaction tank to be generated and a solid-liquid separation tank for separating sludge in the generated slurry from water are connected in order by a pipe line, and each supply means for toxic substance-containing water and soluble metal compound is provided in the addition tank. Each of the reaction tanks is provided with means for supplying a hardly soluble metal oxide and a pH adjuster, and the solid-liquid separation tank is connected to the separated sludge and the treated water discharge pipe, Toxic substance-containing water to which a soluble metal compound is added in the addition tank is introduced into the reaction tank, and the hardly soluble metal oxide and the pH adjuster are added in the reaction tank, and the surface of the hardly soluble metal oxide is reacted by the reaction under alkaline conditions. In A toxic substance-containing water treatment apparatus characterized in that a slurry containing sludge formed with a particulate double hydroxide is generated, and the slurry containing the sludge is introduced into a solid-liquid separation tank and the sludge is settled and separated. It is.

According to a tenth aspect of the present invention, in the apparatus for treating harmful substance-containing water according to the ninth aspect, a return pipeline from the solid-liquid separation tank to the reaction tank is connected, and the sludge separated into solid and liquid Part or all of the above is a treatment apparatus for harmful substance-containing water that is returned to the reaction tank through the return conduit.
According to an eleventh aspect of the present invention, in the apparatus for treating harmful substance-containing water according to the tenth aspect, a return pipeline from the solid-liquid separation tank to the reaction tank is connected, and the insoluble metal is separated from the separated sludge. The 2nd addition tank which adds an oxide is the processing apparatus of the harmful | toxic substance containing water provided in the middle of the said return pipeline.

In the processing system (processing method and processing apparatus) of the present invention, the sludge to be generated is excellent in settling properties. For example, when the slurry containing the generated sludge is allowed to stand, the stable volume after 30 minutes is 40% or less. In addition, since sludge settles in a short time, solid-liquid separation can be performed in a short time, and the solid-liquid separation tank can be downsized.

The treatment system of the present invention is excellent in the effect of removing fluorine, and easily reduces the fluorine concentration in the wastewater to below the drainage standard [fluorine 8 mg / L (public water area other than sea area), fluorine 15 mg / L (sea area)]. Can be reduced. Furthermore, by returning the separated sludge to the reaction step, the effect of removing fluorine can be enhanced, and the fluorine concentration in the waste water can be easily reduced to the environmental standard (0.8 mg / L or less). In addition, harmful substances such as boron, nitrogen compounds, phosphorus, and heavy metals can be removed simultaneously with fluorine.

It is a SEM photograph of the section of sludge particles by the processing method of the present invention. It is a component analysis figure inside the sludge particle of FIG. 1A (part B). It is a component analysis figure of the sludge particle | grain surface (C part) of FIG. 1A. It is a photograph which shows the sedimentation property of sludge about the processing method of this invention, and the conventional processing method. It is process drawing which shows the processing method of this invention. It is process drawing which shows the example which provided the 2nd addition tank in the processing method of this invention. It is process drawing which shows the processing method of this invention which provided the pre-processing process and the post-processing process. It is a XRD analysis chart of the sludge by the processing method of the present invention.

Hereinafter, the present invention will be specifically described based on embodiments.
The treatment method of the present invention comprises a step of adding a hardly soluble metal oxide and a soluble metal compound, which are components of a layered double hydroxide, to water containing harmful substances, the above-mentioned hardly soluble metal oxide, a soluble metal compound and harmful substances. A reaction step of reacting the contained water under alkaline conditions to generate a slurry containing sludge having a layered double hydroxide formed on the surface of the hardly soluble metal oxide; and a slurry containing sludge by allowing the sludge to settle. This is a method for treating harmful substance-containing water, which has a solid-liquid separation step of removing harmful substances taken into the sludge out of the system by solid-liquid separation.
By this method, harmful substances contained in the water to be treated can be removed out of the water system.

It is preferable that the method for treating toxic substance-containing water includes a step of returning a part or all of the solid-liquid separated sludge to the reaction step and utilizing the returned sludge for forming the layered double hydroxide.

In the present invention, toxic substance-containing water broadly means water containing toxic substances, and includes various types of wastewater and wastewater generated naturally and artificially. Hazardous substance-containing water includes, for example, industrial wastewater and sewage, seawater, river water, lake and pond water, surface pool water, river and other dam water, underground running water and pool water, underdrain water, etc. Using reverse osmosis membranes and electrodialysis, wastewater containing harmful substances or wastewater with high salt concentration, such as purified water from soil contaminated by harmful substances, seawater and leachate from the final disposal site, etc. Concentrated water after separation (desalting) into clear water (fresh water) and concentrated water.

Toxic substances to be treated are, for example, heavy metals, fluorine, boron, nitrogen, phosphorus and the like. Heavy metals include cadmium, lead, copper, zinc, iron, nickel, selenium, hexavalent chromium, arsenic, manganese, and antimony. The treatment system of the present invention has an excellent removal effect on any one or more of these harmful substances contained in the harmful substance-containing water.

Further, harmful substances include halide ions, various halogen acids (halogen acids, perhalogen acids, halous acids, hypohalous acids, etc.), hexafluorophosphate ions (PF ₆ ⁻ ), borofluoride ions (BF ₄ ^- ), Silicofluoride ions (SiF ₆ ^2- ), organic acids, suspended solids (SS) and organic substances. The treatment system of the present invention has an excellent removal effect on one or more of these harmful substances.

[Addition process]
In the treatment system of the present invention, the hardly soluble metal oxide and the soluble metal compound, which are components of the layered double hydroxide in the adding step, are added to the harmful substance-containing water. This mixture is reacted under alkaline conditions in the reaction step to produce sludge in which a layered double hydroxide is formed on the surface of the hardly soluble metal oxide.

The hardly soluble metal oxide partly dissolves to become a component source of the layered double hydroxide, and most of it remains as an undissolved part. The dissolved hardly soluble metal oxide and the soluble metal compound react to form a layered double hydroxide on the surface of the hardly soluble metal oxide. Moreover, the melt | dissolved hardly soluble metal oxide becomes a component source of a layered double hydroxide, and plays the role as an alkali agent.

Examples of the hardly soluble metal oxide include magnesium oxide and calcium oxide. In addition, magnesium oxide is preferable for forming the hydrotalcite of the layered double hydroxide. This magnesium oxide can be added using magnesium oxide alone. Alternatively, it may be added using a dolomite [CaMg (CO ₃ ) ₂ ] baked product containing magnesium oxide as a part of the component, or a material containing magnesium oxide together with other components without being limited to Ca. it can.

Soluble aluminum salts and soluble iron salts can be used as the soluble metal compound. Among these, a soluble aluminum salt is preferable for forming hydrotalcite. Specifically, polyaluminum chloride, aluminum sulfate (sulfuric acid band), aluminum chloride, aluminum nitrate and the like are preferable. In addition, as a soluble aluminum salt, a waste liquid containing a high concentration of aluminum (a recovery waste liquid of a noble metal catalyst, a liquid in which metal aluminum is dissolved, or the like) can be used.

The amount of soluble aluminum salt added is appropriate such that the aluminum concentration in water is 10 to 1000 mg / L with respect to 1 L of harmful substance-containing water having a fluorine concentration of 1 to 50 mg / L. The amount of magnesium oxide added is suitably 0.05 to 10 g / L with respect to 1 L of harmful substance-containing water having a fluorine concentration of 1 to 50 mg / L.

In the process of adding the hardly soluble metal oxide and the soluble metal compound to the harmful substance-containing water, the addition tank adds the soluble metal compound and the hardly soluble metal oxide to the harmful substance-containing water and introduces it into the reaction tank. good. Alternatively, a soluble metal compound may be added to the harmful substance-containing water in the addition tank, introduced into the reaction tank, and the poorly soluble metal oxide and a pH adjuster may be added as necessary in the reaction tank. Moreover, you may add a soluble metal compound to harmful substance containing water in the pipe line which introduces harmful substance containing water to a reaction tank.

[Reaction process]
In the reaction step, the partially dissolved hardly soluble metal oxide and the soluble metal compound react to form a layered double hydroxide on the surface of the undissolved hardly soluble metal oxide. Moreover, the melt | dissolved hardly soluble metal oxide becomes a component source of a layered double hydroxide, and plays the role as an alkali agent. The alkaline condition in the reaction step is preferably pH 7-11.
For example, when magnesium oxide is used as a hardly soluble metal oxide, a soluble aluminum salt is used as a soluble metal compound, these are added to water containing harmful substances, and reacted under alkaline conditions (preferably pH 7 to 11), magnesium oxide However, the surface is partially dissolved and the eluted magnesium reacts with aluminum to form a layered double hydroxide on the surface of magnesium oxide. Specifically, magnesium and aluminum react with the magnesium oxide surface to form hydrotalcite [general formula: Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O ( ^An- is an anion)].

This state is shown in FIGS. 1A to 1C. FIG. 1A is an SEM photograph showing a cross section of sludge particles. When the EDX analysis is performed on the point B inside the sludge particles, the magnesium component is overwhelmingly large as shown in FIG. On the other hand, when EDX analysis is performed on the analysis point C near the surface of the sludge particles in FIG. 1A, it can be seen that peaks of magnesium and aluminum are detected and hydrotalcite is formed as shown in FIG. 1C.

Since the hardly soluble metal oxide may be hydrated into a metal hydroxide in the reaction process, a layered double hydroxide is formed on the surface of the coexisting substance of the hardly soluble metal oxide and the metal hydroxide. It may be formed.

The layered double hydroxide has a layered structure containing water molecules between layers, and has the property of taking in anions between layers in order to maintain electrical neutrality. Anionic harmful substances such as fluorine, organic acids, oxyanionic boron, nitrogen, phosphorus, selenium, hexavalent chromium, arsenic and antimony contained in this water are taken in between the layers. In addition, harmful heavy metals such as cadmium, lead, copper, zinc, iron, nickel, and manganese are incorporated by replacing some of the magnesium and aluminum forming the layered double hydroxide with cationic heavy metals. It is. The suspended matter (SS) is aggregated and taken in with the sludge containing the layered double hydroxide, and the organic matter is adsorbed and taken in the surface of the sludge containing the layered double hydroxide. Thus, the sludge containing the layered double hydroxide that has taken in the toxic substance settles, and the toxic substance can be removed by solid-liquid separation.

In the reaction step, a pH adjusting agent can be added as necessary. Examples of the pH adjuster include alkalis such as sodium hydroxide, calcium hydroxide and calcium oxide, and acids such as sulfuric acid and hydrochloric acid. Thereby, the pH is controlled to 7-11. The pH may be adjusted before the reaction, during the reaction, or after the reaction, but it is preferably during or after the reaction because it promotes the formation of the layered double hydroxide.

[Solid-liquid separation process]
The slurry containing the produced sludge is guided to a solid-liquid separation step to settle the sludge, and the slurry is solid-liquid separated. The sludge produced by the treatment method of the present invention has a structure in which a layered double hydroxide is formed on the surface of an undissolved hardly soluble metal oxide (magnesium oxide or the like), and thus has good sedimentation.

For example, as shown in FIG. 2, when the sludge slurry generated by the treatment method of the present invention is placed in a graduated cylinder and allowed to stand for 30 minutes, the volume of sludge slurry at the start of standing is 2300 mL. The volume of the subsequent sludge precipitate portion is about 550 mL, and the stable volume is 40% or less, preferably 25% or less in a short time. Here, the stable volume is an index calculated by the following equation [1]. A smaller stable volume indicates that sludge can be solid-liquid separated in a short time.
(Sludge sediment volume after a certain period of time) / (initial sludge slurry volume) × 100 ... [1]

The treatment system of the present invention has a small stable volume, so that sludge can be solid-liquid separated in a short time. If a flocculant is added before introducing into the solid-liquid separation tank, solid-liquid separation can be achieved in a shorter time. As the flocculant, inorganic flocculants and anionic, cationic, nonionic and amphoteric polymer flocculants can be used.

In addition, a soluble magnesium salt (such as magnesium chloride) is used instead of magnesium oxide, and this is added to a harmful substance-containing water together with a soluble aluminum salt, and further added with sodium hydroxide to adjust to alkalinity. When the sludge-containing slurry produced is placed in a graduated cylinder and allowed to stand for 30 minutes, as shown in FIG. 2, for example, the initial sludge-containing slurry volume at the start of standing is 2300 mL. The volume of sludge sediment after placement is about 2200 mL, and sludge hardly settles in about 30 minutes.

[Sludge return process]
In the treatment method of the present invention, preferably, part or all of the sludge solid-liquid separated from the slurry is returned to the reaction step, and the returned sludge is used for the formation of the layered double hydroxide. By returning some or all of the sludge to the reaction process, the formation of layered double hydroxides is promoted, and a large amount of harmful substances such as fluorine, boron, nitrogen compounds, phosphorus, and toxic heavy metals are taken into the sludge. Thus, the removal effect is improved.

In addition, about the sludge separated into solid and liquid, it is good to return the sludge concentrated to a thing with much amount of a hardly soluble metal oxide using the difference in weight, specific gravity, or sedimentation speed to a reaction process. For example, since sludge with a large amount of hardly soluble metal oxides is heavier than other sludges and settles quickly, it is possible to collect sludge at the initial stage of sedimentation and concentrate it to sludge with a large amount of hardly soluble metal oxides. By returning the sludge having a large amount of the hardly soluble metal oxide to the reaction step, the generation of the layered double hydroxide can be promoted. For example, when magnesium oxide is used as the hardly soluble metal oxide, the formation of hydrotalcite can be promoted by concentrating sludge having a large amount of magnesium oxide and returning it to the reaction step.

On the other hand, surplus sludge that is not returned to the reaction process can be recovered and recycled as a cement raw material. Alternatively, excess sludge can be used as a purification material for soil contamination and wastewater treatment.

[Pretreatment process]
In the treatment method of the present invention, a pretreatment step for reducing harmful substances and interfering substances contained in harmful substance-containing water (raw water) in advance can be provided before the addition step or the reaction step. The pretreatment can further enhance the effect of removing harmful substances. See FIG. Interfering substances (interfering components) are substances that are not harmful substances themselves but interfere with the treatment method of the present invention.
For example, one or more of heavy metals, phosphate ions, nitrate ions, borate ions, fluorine, suspended solids, organic matter, sulfate ions, sulfite ions, chloride ions, carbonate ions, dissolved silica, and silicate ions are more than the predetermined values. In the case of being contained in the harmful substance-containing water at a concentration of 1, the concentration can be reduced to be less than a predetermined value by the pretreatment step.

Specifically, for example, if the concentration of heavy metals (cadmium, lead, copper, zinc, iron, nickel, manganese, hexavalent chromium, arsenic, etc.) contained in the raw water is higher than 20 mg / L, heavy metals are incorporated. In some cases, the structure of the layered double hydroxide is partially broken, and the effect of removing harmful substances such as heavy metals is insufficient. Therefore, a pretreatment for reducing the concentration of heavy metals in the raw water may be performed. The pretreatment method is not limited. As a pretreatment, for example, a neutralizing agent (NaOH, Ca (OH) ₂ or the like) is added to adjust the pH of the raw water to a range of 5 to 10 to generate a hydroxide precipitate of heavy metals, which is agglomerated and precipitated. By processing, the heavy metal concentration of raw water may be less than 10 mg / L. Alternatively, after adding an aluminum salt or iron salt to the raw water, a neutralizing agent (NaOH, Ca (OH) ₂ etc.) is added to adjust the pH of the raw water to a range of 5 to 10 to generate a hydroxide precipitate. Alternatively, the precipitate may be co-precipitated and separated into solid and liquid to make the heavy metal concentration of raw water less than 10 mg / L.

In addition, if the phosphate ion of raw water is higher than 50 mg / L, the phosphate ion competes with other harmful substances and is adsorbed on the layered double hydroxide, reducing the effect of removing other harmful substances. There is. Therefore, a pretreatment for reducing the phosphate ion concentration in the raw water may be performed. The pretreatment method is not limited. As the pretreatment, for example, a calcium salt (Ca (OH) ₂ or the like) is added to the raw water to generate and remove the calcium phosphate salt, and the phosphate ion of the raw water is adjusted to a phosphorus concentration of less than 5 mg / L.

Similarly, if the nitrate ion of raw water is higher than 200 mg / L as the nitrogen concentration, the nitrate ion competes with other harmful substances and is adsorbed on the layered double hydroxide, which may reduce the effect of removing other harmful substances. is there. Therefore, a pretreatment for reducing the nitrate ion concentration in the raw water may be performed. The pretreatment method is not limited. As the pretreatment, for example, biological treatment (anaerobic denitrification method or the like) is performed, and nitrate ion of raw water is preferably set to a nitrogen concentration of less than 200 mg / L.

Furthermore, when the borate ions in the raw water are higher than 100 mg / L as the boron concentration, the borate ions compete with other harmful substances and are adsorbed on the layered double hydroxide, and the removal effect of other harmful substances decreases. There is. Therefore, a pretreatment for reducing the borate ion concentration in the raw water may be performed. The pretreatment method is not limited. As the pretreatment, for example, raw water is passed through a chelate resin having a methylglucamine group to adsorb borate ions, and the borate ions of the raw water are adjusted to a boron concentration of less than 100 mg / L.

Furthermore, if the fluorine concentration of the raw water is higher than 50 mg / L, the required amount of layered double hydroxide increases, so that the amount of chemicals to be introduced may increase. Therefore, a pretreatment for reducing the fluorine concentration in the raw water may be performed. The pretreatment method is not limited. As a pretreatment, for example, a calcium salt may be added to form poorly soluble calcium fluoride, which is then solid-liquid separated so that the fluorine concentration is less than 50 mg / L.

In addition, if the concentration of suspended solids (SS) in raw water is higher than 60 mg / L, the structure of the layered double hydroxide that has incorporated suspended solids will partially collapse, resulting in an insufficient removal effect of harmful substances. There is. Therefore, pretreatment for reducing the concentration of suspended solids in the raw water may be performed. The pretreatment method is not limited. As the pretreatment, for example, an inorganic flocculant or a polymer flocculant is added to precipitate and separate floating substances, so that the concentration of floating substances in raw water is less than 20 mg / L. *

Similarly, when the concentration of the organic substance contained in the raw water is higher than 200 mg / L as COD, the structure of the layered double hydroxide incorporating the organic substance may partially collapse, and the harmful substance removal effect may be insufficient. . Therefore, a pretreatment for reducing the concentration of organic substances in the raw water may be performed. The pretreatment method is not limited. As the pretreatment, for example, the organic matter concentration of raw water may be less than 80 mg / L as COD by a biological treatment method (such as activated sludge method) or an accelerated oxidation method (such as ultraviolet oxidation or photocatalyst).

In the pretreatment step, the treatment effect can be further enhanced by removing the disturbing components contained in the raw water. Interfering components include sulfate ions, sulfite ions, chloride ions, carbonate ions, dissolved silica and silicate ions.

For example, if the concentration of sulfate ion contained in the raw water is higher than 1500 mg / L, the sulfate ion competes with the harmful substance and is adsorbed on the layered double hydroxide, which may reduce the harmful substance removal effect. Therefore, a pretreatment for reducing the sulfate ion concentration in the raw water may be performed. The pretreatment method is not limited. As a pretreatment, for example, a Ca salt or a Ba salt is added to raw water to form a hardly soluble sulfate, which is solid-liquid separated to lower the sulfate ion concentration. When using a Ca salt, sulfate ions can be reduced to less than 1000 mg / L. When Ba salt is used, sulfate ion can be reduced to less than 5 mg / L.

Also, if the sulfite ion concentration of raw water is higher than 50 mg / L, sulfite ions react with aluminum ions, so a large amount of aluminum may be required. In addition, sulfite ions compete with harmful substances and are adsorbed on the layered double hydroxide, which may reduce the effect of removing harmful substances. Therefore, a pretreatment for reducing the sulfite ion concentration in the raw water may be performed. The pretreatment method is not limited. As pretreatment, for example, an oxidizing agent such as hydrogen peroxide may be added to raw water to oxidize sulfite ions to sulfate ions, so that the sulfite ions of raw water are less than 10 mg / L.

Furthermore, if the chloride ion concentration in the raw water is higher than 2000 mg / L, chloride ions may compete with harmful substances and be adsorbed on the layered double hydroxide, which may reduce the effect of removing harmful substances. Therefore, a pretreatment for reducing the chloride ion concentration in the raw water may be performed. The pretreatment method is not limited. As pretreatment, for example, chlorine may be gasified and removed by electrolytic decomposition, or the chloride ion concentration may be made less than 1000 mg / L by membrane treatment such as reverse osmosis or electrodialysis.

If the carbonate ion concentration in the raw water is higher than 500 mg / L, the carbonate ions compete with the harmful substances and are adsorbed on the layered double hydroxide, which may reduce the effect of removing the harmful substances. Therefore, a pretreatment for reducing the carbonate ion concentration in the raw water may be performed. The pretreatment method is not limited. As pretreatment, for example, aeration is performed to disperse carbonate ions, or Ca salt is added to form a hardly soluble carbonate, which is solid-liquid separated so that the carbonate ion concentration is less than 50 mg / L. .

If the dissolved silica and silicate ions in the raw water are higher than 20 mg / L as the Si concentration, the structure of the layered double hydroxide incorporating the dissolved silica and silicate ions will partially collapse, and the removal effect of harmful substances will be insufficient. May be. Therefore, a pretreatment for reducing the concentration of dissolved silica or silicate ions in the raw water may be performed. The pretreatment method is not limited. As pretreatment, for example, iron salt or aluminum salt is added, and further neutralizing agents (NaOH, Ca (OH) ₂ etc.) are added to adjust the pH of the raw water to a range of 5 to 10 to precipitate hydroxide. It is preferable that dissolved silica and silicate ions are co-precipitated in the precipitate, and this is solid-liquid separated to make the dissolved silica and silicate ions of raw water less than 10 mg / L as Si concentration.

[Post-treatment process]
Furthermore, the processing method of this invention can provide the process of post-processing the liquid component (process water) which isolate | separated sludge. See FIG.
In some cases, organic matter, suspended solids, and nitrogen compounds remain in the liquid (treated water) remaining after separating the sludge in the slurry in the solid-liquid separation step, or the pH of the treated water may be 9 or more. Therefore, a post-treatment process for treated water may be provided. The post-processing method is not limited.

Regarding the organic matter contained in the treated water, the organic matter may be reduced to a COD concentration of less than 80 mg / L by, for example, a biological treatment method (eg, activated sludge method) or an accelerated oxidation method (eg, ultraviolet oxidation or photocatalyst). In addition, for the suspended matter (SS) contained in the treated water, for example, an inorganic flocculant or a polymer flocculant is added to precipitate and separate the suspended matter, so that the concentration of suspended matter is less than 20 mg / L. Further, for nitrogen compounds contained in the treated water, for example, biological treatment (nitrification denitrification method or the like) may be performed to reduce the nitrogen concentration to less than 60 mg / L.

Since the pH of the treated water may be 9 or more, if the pH is high, it is better to neutralize the treated water to pH 6-8 by adding sulfuric acid or hydrochloric acid.

[Processing equipment]
The configuration of the processing apparatus of the present invention and the processing steps using the processing apparatus are shown in FIGS.
The illustrated treatment apparatus includes an addition tank 10 for adding a chemical to harmful substance-containing water (raw water), a reaction tank 30 for reacting the added chemical to generate sludge, and a solid-liquid separation tank for separating the generated sludge. 40, and the addition tank 10, the reaction tank 30, and the solid-liquid separation tank 40 are sequentially connected by a pipe 50.

Discharge pipes 51 and 52 for discharging the separated treated water and sludge are connected to the solid-liquid separation tank 40, respectively, and part or all of the separated sludge is sent to the reaction tank 30 in the sludge discharge pipe 52. A return pipeline 53 to be returned is connected. In the processing system shown in FIG. 4, the second addition tank 20 is provided in the middle of the return conduit 53.

The addition tank 10 is connected with a supply pipe 60 for toxic substance-containing water and a supply pipe 61 for a soluble metal compound. Note that the addition tank 10 may be omitted, the pipe 60 and the pipe 61 may be connected, and the soluble metal compound may be added to the raw water in the pipe.

3, the reaction tank 30 is provided with a supply line 62 for a hardly soluble metal oxide and a supply line 63 for a pH adjuster. In the example of the apparatus of FIG. 4, a supply line 62 of a hardly soluble metal oxide is provided in the second addition tank 20.

In the addition tank 10, a soluble metal compound such as polyaluminum chloride is added to water containing harmful substances, and this is introduced into the reaction tank 30. In the example of FIG. 3, sludge is added to the reaction tank 30 through a pipe 53, and further a hardly soluble metal oxide is added through a pipe 62. In the apparatus example of FIG. 4, the separated sludge is introduced into the reaction tank 30 after the hardly soluble metal oxide is added through the pipe line 62 in the second addition tank 20.

A pH adjusting agent is added to the reaction tank 30 through a pipe 63, and the inside of the reaction tank is controlled to pH 7-11. Although the reaction may be an open system or a closed system, the reaction tank 30 preferably has a structure in which the reaction system hardly absorbs carbon dioxide because it may inhibit removal of harmful substances due to absorption of carbon dioxide. In general, a closed reaction tank is preferred.

In the reaction vessel 30, the surface of the hardly soluble metal oxide partially dissolves and reacts with the soluble metal compound under alkaline conditions (preferably pH 7 to 11), and layered composites such as hydrotalcite are formed on the hardly soluble metal oxide surface. Sludge with hydroxide formed is produced. In the reaction vessel 30, the system is in a slurry state in which sludge particles are dispersed in water. Slurry containing sludge is guided to the solid-liquid separation tank 40, where the sludge is settled and solid-liquid separated. A flocculant may be added before being introduced into the solid-liquid separation tank 40. The flocculant may be added in the pipe by connecting the flocculant supply pipe and the pipe 50, or a flocculant addition tank is provided, and slurry containing sludge is added to the flocculant addition tank through the pipe 50. In addition, a flocculant may be added through a flocculant supply line. Part or all of the separated sludge is returned to the reaction tank 30 through the pipe line 53. Some sludge may be dehydrated and discarded, recovered and recycled as a raw material for cement, or used as a purification material for soil contamination and wastewater treatment.

The treatment apparatus of the present invention can be a portable apparatus that can be mounted on a vehicle, or can be separated into units such as an addition tank, a reaction tank, and a solid-liquid separation tank.

Hereinafter, examples of the present invention are shown together with comparative examples. In each of these examples, the fluorine concentration was measured by the ion electrode method. Further, the boron concentration, chromium (VI) concentration, arsenic concentration, copper concentration, manganese concentration, and zinc concentration were measured by ICP emission spectroscopy. Selenium concentration, cadmium concentration, and lead concentration were measured by ICP mass spectrometry. *

[Example 1]
In accordance with the treatment system shown in FIG. 4, the fluorine-containing water was treated as follows. First, fluorine-containing water (fluorine concentration 20 mg / L) was introduced into the addition tank 10, and polyaluminum chloride was added so that the aluminum concentration was 240 mg / L in water. On the other hand, the entire amount of sludge separated in the solid-liquid separation tank 40 was returned to the second addition tank 20, where 1 g / L of magnesium oxide was added to 1 L of fluorine-containing water. This sludge was introduced into the reaction tank 30, mixed with fluorine-containing water added with polyaluminum chloride, stirred for 30 minutes, and reacted at a temperature of 20 ° C. for 30 minutes. After the reaction, sodium hydroxide is added as a pH adjusting agent to adjust the pH to 8.5 to 9.5, and then the slurry containing the produced sludge is introduced into the solid-liquid separation tank 40 (thickener) and allowed to stand for 20 hours. Sludge was allowed to settle. In addition, 2 mg / L of anionic polymer flocculant was added to the slurry containing sludge before being introduced into the solid-liquid separation tank 40. The whole amount of sludge separated in the solid-liquid separation tank 40 was introduced into the second addition tank 20 as described above, and 1 g / L of magnesium oxide was added to 1 L of fluorine-containing water and returned to the reaction tank 30. This sludge generation was repeated 15 times. The processing conditions are shown in Table 1, and the processing results are shown in Table 2. Moreover, the X-ray analysis chart of sludge was shown in FIG. In FIG. 6, 1st to 10th are the number of repetitions. Note that initial is an X-ray analysis chart of sludge obtained in the initial cycle in which the above processing was performed except for returning sludge.

As shown in the treatment results, the fluorine concentration of treated water can be reduced to below the drainage standard (8 mg / L) for public water areas other than the sea area at the first iteration, and the treatment can be performed at the 12th iteration. The fluorine concentration of water can be reduced to the environmental standard (0.8 mg / L or less). Moreover, as shown in the X-ray analysis chart of sludge, the peak of hydrotalcite appears with magnesium oxide, and it turns out that the hydrotalcite is formed on the magnesium oxide surface. When the number of repetitions is 1, the hydrotalcite peak is small, but when the number of repetitions is 5 or more, the hydrotalcite peak increases and grows in proportion to the number of repetitions.

[Example 2]
In accordance with the treatment system shown in FIG. 3, the fluorine-containing water was treated as follows. First, fluorine-containing water (fluorine concentration 20 mg / L) was introduced into the addition tank 10, and aluminum sulfate was added so that the aluminum concentration was 240 mg / L in water. This was introduced into the reaction vessel 30. On the other hand, the entire amount of sludge separated in the solid-liquid separation tank 40 was returned to the reaction tank 30. Further, 1 g / L of magnesium oxide was added to 1 L of fluorine-containing water in the reaction tank 30, mixed with fluorine-containing water added with aluminum sulfate, stirred for 30 minutes, and reacted at a temperature of 20 ° C. for 30 minutes. After the reaction, sodium hydroxide is added as a pH adjusting agent to adjust the pH to 8.5 to 9.5, and then the slurry containing the produced sludge is introduced into the solid-liquid separation tank 40 (thickener) and allowed to stand for 20 hours. Sludge was allowed to settle. In addition, 2 mg / L of anionic polymer flocculant was added to the slurry containing sludge before being introduced into the solid-liquid separation tank 40. The sludge separated in the solid-liquid separation tank 40 was returned to the reaction tank 30 as described above, and 1 g / L of magnesium oxide was added to 1 L of fluorine-containing water. This sludge generation was repeated 15 times. The processing conditions are shown in Table 3, and the processing results are shown in Table 4. In the initial cycle before repetition, the above processing is performed except for returning sludge.

As shown in the treatment results, the fluorine concentration of the treated water can be reduced to the drainage standard (8 mg / L) or less in public water areas other than the sea area by the first repetition. Each time the number of repetitions is repeated, the fluorine concentration in the treated water can be reduced.

Example 3
In accordance with the treatment system shown in FIG. 4, water containing harmful substances containing fluorine and heavy metals was treated as follows. First, toxic substance-containing water (hazardous substance concentration in raw water is listed in Table 5) was introduced into the addition tank 10 and polyaluminum chloride was added so that the aluminum concentration was 240 mg / L in water. This was introduced into the reaction vessel 30. On the other hand, the entire amount of sludge separated in the solid-liquid separation tank 40 was returned to the second addition tank 20, where 1 g / L of magnesium oxide was added to 1 L of harmful substance-containing water. This sludge was returned to the reaction tank 30, mixed with harmful substance-containing water added with polyaluminum chloride, stirred for 30 minutes, and reacted at a temperature of 20 ° C. for 30 minutes. After the reaction, sodium hydroxide is added as a pH adjusting agent to adjust the pH to 8.5 to 9.5, and then the slurry containing the produced sludge is introduced into the solid-liquid separation tank 40 (thickener) and allowed to stand for 20 hours. Sludge was allowed to settle. In addition, 2 mg / L of anionic polymer flocculant was added to the sludge slurry before introducing into the solid-liquid separation tank 40. The total amount of sludge separated in the solid-liquid separation tank 40 is introduced into the second addition tank 20 as described above, and magnesium oxide is added at 1 g / L to 1 L of harmful substance-containing water and returned to the reaction tank 30. This sludge generation was repeated 5 times. The processing conditions are shown in Table 5, and the processing results are shown in Table 6. In the initial cycle before repetition, the above processing is performed except for returning sludge.

As shown in the treatment results, the fluorine concentration of the treated water can be reduced to the drainage standard (8 mg / L) or less in public water areas other than the sea area by the first repetition. Each time the number of repetitions is repeated, the fluorine concentration in the treated water can be reduced. Concerning other harmful substances, the concentration in the treated water can be reduced, and the concentration can be further reduced as the number of repetitions is repeated. *

Example 4
In accordance with the treatment system shown in FIG. 3, the fluorine-containing water was treated as follows. First, fluorine-containing water (fluorine concentration 20 mg / L) was introduced into the addition tank 10, and polyaluminum chloride was added so that the aluminum concentration was 240 mg / L in water. This was introduced into the reaction vessel 30. Thereafter, 1 g / L of magnesium oxide and water added with polyaluminum chloride are mixed in the reaction tank 30 and adjusted to pH 8.5 to 9.5 by adding sodium hydroxide as a pH adjuster, and then stirred for 30 minutes. And reacted at a temperature of 20 ° C. for 30 minutes. After the reaction, the slurry containing the generated sludge was introduced into the solid-liquid separation tank 40 (thickener) and allowed to stand for 30 minutes to settle the sludge. The processing conditions and processing results are shown in Table 7.

[Comparative Example 1]
In accordance with the treatment system shown in FIG. 3, the fluorine-containing water was treated as follows. First, fluorine-containing water (fluorine concentration 20 mg / L) was introduced into the addition tank 10, and polyaluminum chloride was added so that the aluminum concentration was 240 mg / L in water. This was introduced into the reaction vessel 30. Thereafter, 2.4 g / L of magnesium chloride and water added with polyaluminum chloride are mixed in the reaction tank 30 and adjusted to pH 8.5 to 9.5 by adding sodium hydroxide as a pH adjuster. The mixture was stirred for 30 minutes and reacted at a temperature of 20 ° C. for 30 minutes. After the reaction, the slurry containing the generated sludge was introduced into the solid-liquid separation tank 40 (thickener) and allowed to stand for 30 minutes to settle the sludge. The processing conditions and processing results are shown in Table 7.

As shown in the treatment results, both Example 4 and Comparative Example 1 can reduce the fluorine concentration of the treated water to below the drainage standard (8 mg / L) for public water areas other than sea areas, but the stable volumes are comparable. Example 1 is much larger and has poor separation. On the other hand, Example 4 has a small stable volume, good separability, and can perform solid-liquid separation in a short time.

According to the treatment method and the treatment apparatus of the present invention, a slurry containing sludge incorporating toxic substances can be solid-liquid separated in a short time, and harmful substances contained in water such as fluorine, nitrogen compounds, phosphorus and heavy metals. Substances can be removed efficiently.

Claims (12)

1. Adding a poorly soluble metal oxide and a soluble metal compound, which are components of the layered double hydroxide, to water containing harmful substances;
   A reaction process in which the hardly soluble metal oxide, the soluble metal compound, and harmful substance-containing water are reacted under alkaline conditions to generate a slurry containing sludge in which a layered double hydroxide is formed on the surface of the hardly soluble metal oxide. When,
   A method for treating harmful substance-containing water, comprising: a solid-liquid separation step of removing the harmful substances taken into the sludge by causing the sludge to settle and solid-liquid separation of the slurry.
2. The processing method according to claim 1, wherein a part or all of the solid-liquid separated sludge is returned to the reaction step, and the returned sludge is used for forming a layered double hydroxide.
3. The poorly soluble metal oxide is magnesium oxide, the soluble metal compound is a soluble aluminum salt, magnesium oxide and a soluble aluminum salt are added to harmful substance-containing water, and this is reacted under alkaline conditions. The method for treating harmful substance-containing water according to claim 1, wherein a slurry containing sludge in which a harmful substance is taken into the hydrotalcite is formed by forming hydrotalcite on the surface, and the slurry is solid-liquid separated. .
4. The poorly soluble metal oxide is magnesium oxide, the soluble metal compound is a soluble aluminum salt, magnesium oxide and a soluble aluminum salt are added to harmful substance-containing water, and this is reacted under alkaline conditions. 3. A method for treating harmful substance-containing water according to claim 2, wherein a slurry containing sludge in which harmful substances are taken into hydrotalcite is formed by forming hydrotalcite on the surface of the slurry, and the slurry is solid-liquid separated. .
   
5. The toxic substance is any one or more of fluorine, boron, nitrogen compounds, phosphorus, and heavy metals, and a slurry containing sludge incorporating the toxic substance is generated and solid-liquid separated. 4. The method for treating toxic substance-containing water according to any one of 4 above.
6. Add 1 to 50 mg / L of harmful substance-containing water with a fluorine concentration of 0.05 to 10 g / L of magnesium oxide and a soluble aluminum salt so that the aluminum concentration in water is 10 to 1000 mg / L. The method for treating toxic substance-containing water according to any one of claims 1 to 4, wherein the reaction is conducted at a pH of 7 to 11 in a reaction tank.
7. The method for treating toxic substance-containing water according to any one of claims 1 to 4, wherein when the slurry containing the produced sludge is allowed to stand, the stable volume after 30 minutes is 40% or less.
8. Pre-treatment process to reduce harmful substances and interfering substances contained in harmful substance-containing water is provided, and sparingly soluble metal oxides and soluble metals that become components of layered double hydroxides in pre-treated harmful substance-containing water The method for treating toxic substance-containing water according to any one of claims 1 to 4, wherein the compound is added.
9. The method for treating toxic substance-containing water according to any one of claims 1 to 4, further comprising a post-treatment step of post-treating treated water obtained by solid-liquid separation of sludge from the slurry.
10. An addition tank for adding chemicals to water containing harmful substances;
    A reaction tank for reacting the added chemical with harmful substance-containing water to produce a slurry containing sludge;
    A solid-liquid separation tank that separates sludge in the generated slurry from water is connected in order by a pipeline,
    Each addition tank is provided with means for supplying harmful substance-containing water and soluble metal compounds,
    Each reaction tank is provided with means for supplying a hardly soluble metal oxide and a pH adjuster,
    Separate sludge and treated water discharge pipes are connected to the solid-liquid separation tank.
    Hazardous substance-containing water to which a soluble metal compound is added in the addition tank is introduced into the reaction tank,
    In the reaction tank, a hardly soluble metal oxide and a pH adjuster are added,
    Sludge in which a layered double hydroxide is formed on the surface of a hardly soluble metal oxide is generated by a reaction under alkaline conditions,
    An apparatus for treating toxic substance-containing water, wherein the slurry containing the sludge is introduced into a solid-liquid separation tank and the sludge is settled and separated.
11. In the processing apparatus according to claim 10, a return pipe line from the solid-liquid separation tank to the reaction tank is connected, and part or all of the solid-liquid separated sludge is returned to the reaction tank through the return pipe line. Equipment for treating hazardous substance-containing water.
12. In the processing apparatus according to claim 10, a return pipeline from the solid-liquid separation tank to the reaction tank is connected, and a second addition tank for adding a hardly soluble metal oxide to the separated sludge is provided in the return pipeline. A treatment device for water containing hazardous substances installed on the way.

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