JP2021137802A - Water treatment method - Google Patents

Abstract

To provide a water treatment method capable of suppressing the residual amount of copper contained in the obtained treated water in cases where water to be treated with a copper (I) compound contains cyanide ions and cyano complexes.SOLUTION: A water treatment method for treating water that contains cyanide ions and cyano complexes, comprises: a measuring step (A) in which the total cyanide concentration (mg-CN/L) and cyanide ion concentration (mg-CN/L) in the water to be treated are measured; a reaction step (B) in which hydrogen peroxide is added to, and reacted with, the water to be treated in such an amount that the concentration of hydrogen peroxide (mg-H2O2/L) as H2O2 in the water to be treated is 1.0 to 4.0 times that of the cyanide ion concentration (mg-CN/L) as measured in the measuring step (A); a reaction step (C) in which a copper(I) compound is added to, and reacted with, the reaction mixture obtained in the reaction step (B) in such an amount that the concentration of the copper (I) compound (mg-Cu/L) as Cu in the water to be treated is 1.0 to 4.0 times that of the concentration of the cyano complexes (mg-CN/L) obtained by subtracting the cyanide ion concentration value from the total cyanide concentration value in the treated water; and a step (D) in which the reaction mixture obtained in the step (C) is subjected to a solid-liquid separation to separate and remove insoluble materials produced in the step (C).SELECTED DRAWING: None

Description

The present invention relates to a water treatment method, and more particularly to a water treatment method for treating water to be treated containing a cyanide ion and a cyano complex.

As a treatment method for removing the cyanide component from wastewater containing a cyanide component such as cyanide ion, the alkaline chlorine method for oxidatively decomposing the cyanide component in the wastewater is widely applied. In the alkaline chlorine method, sodium hypochlorite is generally added to cyanide-containing wastewater under alkaline conditions to add cyanide ions in the wastewater and easily decomposable cyano complexes (cyano complexes such as zinc and copper). It can be oxidatively decomposed.

On the other hand, in the alkaline chlorine method, it is difficult to decompose a persistent cyano complex such as an iron cyano complex. Therefore, a cyan component in waste water is reacted with a metal salt to generate a poorly soluble salt. A method of separating and removing the mixture by a precipitation method (slightly soluble salt precipitation method) has also been proposed. Further, in Patent Document 1, a specific cuprous compound and hydrogen peroxide are allowed to coexist in the complex cyanide-containing wastewater under the condition of pH 6 to 9, and the water-insoluble salt generated in the wastewater is removed. , A method for treating complex cyanide-containing wastewater for treating complex cyanide in wastewater has been proposed.

Japanese Unexamined Patent Publication No. 2017-80699

In the method disclosed in Patent Document 1, an insoluble or sparingly soluble salt in water (hereinafter collectively referred to as "poorly soluble") is added to wastewater containing a cyano complex by adding a copper (I) compound or the like. By forming and removing the sparingly soluble salt from the wastewater, treated water from which the cyano complex has been removed can be obtained. In a water treatment method including the addition of a copper (I) compound in order to generate a sparingly soluble salt in wastewater as in this method, the amount of the copper (I) compound added is adjusted according to the characteristics of the wastewater. It was difficult to control, and it was thought that the addition of the copper (I) compound had to be done by quantitative injection.

When a copper (I) compound is added to wastewater containing a cyano complex in a quantitative manner, the amount of the copper (I) compound added tends to be excessive in order to more reliably generate a sparingly soluble salt. Therefore, it was found that after the poorly soluble salt was generated, the poorly soluble salt was removed by the solid-liquid separation treatment, and the copper tended to remain in the treated water obtained in a dissolved state. If copper remains in the treated water in this way, the permissible limit of copper content is regulated to 3 mg / L in the wastewater standards of the Water Pollution Control Law. A treatment for removing copper (for example, a treatment for converting copper into a hydroxide and removing it by precipitation) is required. Then, the processing cost and the equipment cost will increase due to the process and equipment for treating the residual copper, and the site area where the equipment will be installed will also be expanded. Therefore, if it is possible to suppress the residual amount of copper in the treated water to the extent that the steps and equipment for treating the residual copper can be omitted, it can be a more useful water treatment method.

Therefore, according to the present invention, when the water to be treated containing a cyanide ion and a cyano complex is treated with a copper (I) compound, the residual amount of copper in the obtained treated water can be suppressed. It is intended to provide a processing method.

That is, the present invention is a water treatment method for treating water to be treated containing cyanide ions and a cyano complex, and the total cyanide concentration (mg-CN / L) and cyanide ion concentration (mg) in the water to be treated. -CN / L) is measured, and the concentration (mg-H ₂ O _{2 / L) added to the water to be treated as H 2} O ₂ in the water to be treated is the said in the water to be treated. In the step (B) of adding and reacting an amount of hydrogen peroxide that is 1.0 to 4.0 times the measured value of the cyanide ion concentration (mg-CN / L) and reacting the mixture, and the step (B). The concentration (mg-Cu / L) added to the obtained reaction solution as Cu in the water to be treated was obtained by subtracting the measured value of the cyanide ion concentration from the measured value of the total cyanide concentration in the water to be treated. In the step (C) of adding and reacting the copper (I) compound in an amount 1.0 to 4.0 times the concentration value (mg-CN / L) of the cyano complex to be obtained, and in the step (C). Provided is a water treatment method including a step (D) of solid-liquid separation treatment of the obtained reaction solution and separation and removal of the poorly solubilized substance produced in the step (C).

According to the present invention, when the water to be treated containing a cyanide ion and a cyano complex is treated with a copper (I) compound, water capable of suppressing the residual amount of copper in the obtained treated water can be suppressed. A processing method can be provided.

It is explanatory drawing which shows an example of the schematic structure of the water treatment apparatus and the treatment flow which can execute the water treatment method of one Embodiment of this invention. It is explanatory drawing which shows another example of the schematic structure of the water treatment apparatus and the treatment flow which can carry out the water treatment method of one Embodiment of this invention. It is explanatory drawing which shows another example of the schematic structure of the water treatment apparatus and the treatment flow which can carry out the water treatment method of one Embodiment of this invention. It is explanatory drawing which shows the schematic structure of an example of the exhaust gas treatment facility and the treatment flow when it is assumed that the water treatment method of one Embodiment of this invention is applied.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

The water treatment method of one embodiment of the present invention (hereinafter, may be referred to as "the present method") is a method for treating water to be treated containing a cyanide ion and a cyano complex. The method comprises the step (A) of measuring the total cyanide concentration (mg-CN / L) and the cyanide ion concentration (mg-CN / L) in the water to be treated. _{Further, in this method, the concentration of H 2} O ₂ added to the water to be treated as H 2 O 2 (mg-H ₂ O ₂ / L) is a measured value of the cyanide ion concentration in the water to be treated (mg-CN /). The step (B) is included in which hydrogen peroxide is added in an amount 1.0 to 4.0 times that of L) and reacted. Further, in this method, the concentration of added Cu as Cu in the water to be treated (mg-Cu / L) to the reaction solution obtained in the step (B) is the cyanide ion concentration from the measured value of the total cyanide concentration in the water to be treated. The step (C) of adding a copper (I) compound in an amount 1.0 to 4.0 times as much as the cyano complex concentration value (mg-CN / L) obtained by subtracting the measured value of the above and reacting. include. Then, this method includes a step (D) of solid-liquid separation treatment of the reaction solution obtained in the step (C) and separation and removal of the poorly soluble substance produced in the step (C).

In this method, steps (A) to (D) may be performed separately, but it is preferable that the steps (A) to (D) are performed continuously. Further, although the word "step" is used in the steps (A) to (D) for convenience, another step may be started before one step in them is completed.

For example, in step (A), both the total cyanide concentration and the cyanide ion concentration in the water to be treated are measured, but the step (B) is started after the measurement of the cyanide ion concentration and before the measurement of the total cyanide concentration. It may have been. Further, for example, in the step (B), hydrogen peroxide is added to the water to be treated and reacted, but the step (C) may be started before the reaction of the hydrogen peroxide is completed. Therefore, the "reaction solution obtained in the step (B)" to which the copper (I) compound is added in the step (C) means the water to be treated to which hydrogen peroxide is added, and is based on hydrogen peroxide. In addition to the state in which the reaction is completed, the state in which the reaction is in progress, the state before the reaction starts, and the like can be included. Further, for example, in the step (C), the copper (I) compound is added to the reaction solution obtained in the step (B) and reacted, but before the reaction of the copper (I) compound is completed, the step (D) may be started. Therefore, the "reaction solution obtained in the step (C)" to be subjected to the solid-liquid separation treatment in the step (D) means the water to be treated to which the copper (I) compound is further added, and the copper (I) is added. In addition to the state in which the reaction with the compound is completed, the state in which the reaction is in progress, the state before the reaction starts, and the like can be included.

In this method, by the step (B) of adding a specific amount of hydrogen peroxide to the water to be treated, the cyanide in the water to be treated suppresses the residual hydrogen peroxide in the reaction solution obtained in the step (B). The ions can be sufficiently decomposed by hydrogen peroxide. Further, in this method, the reaction solution and the treatment obtained in the step (C) by the step (C) of adding a specific amount of the copper (I) compound to the water to be treated (the reaction solution obtained in the step (B)). While suppressing the residue of the copper (I) compound in water, the cyano complex in the water to be treated can be sparingly soluble to produce a sparingly soluble product thereof. Then, this poorly solubilized product can be separated and removed by the step (D).

Therefore, according to this method, it is possible to obtain treated water from which cyanide ions and cyano complexes have been removed, and it is possible to obtain treated water in which the residual amount of copper is suppressed. Therefore, it can be expected that the process and equipment for treating copper, which is required when copper remains in the treated water, can be omitted, thereby reducing the equipment cost and the treatment cost, and the site. It can be expected to reduce the area.

In this method, the water to be treated containing a cyanide ion (also referred to as free cyanide) and a cyano complex is treated. "Water to be treated" is a wording that means water to be treated, that is, water to be treated. The water to be treated is not particularly limited as long as it is water containing a cyanide ion and a cyano complex. Since the water to be treated contains a cyanide ion and a cyano complex, it may be referred to as cyanide-containing water.

Examples of the cyano complex in the water to be treated include an iron cyano complex, a zinc cyano complex, a nickel cyano complex, and a copper cyano complex (for example, [Cu (CN) ₃ ] ^3- etc.). One or more of these may be contained in the water to be treated. As the cyano complex, wastewater containing an iron cyano complex can be mentioned as a suitable water to be treated. Examples of the iron cyano complex include ferrocyanide ion ([Fe (CN) ₆ ] ^4- ; hexacyanoferrate (II) acid ion) and ferricyanide ion ([Fe (CN) ₆ ] ^3- ; hexacyanoferrate (III)). Acid ions) and iron carbonyl cyano complexes ([Fe (CN) ₅ (CO)] ^3- and [Fe (CN) ₄ (CO) ₂ ] ^2- ) and the like. One or more of these iron cyano complexes may be contained in the water to be treated. Wastewater containing these iron cyano complexes is disclosed in, for example, JP-A-2018-39004 and JP-A-2018-69227.

Generally, in wastewater containing a cyanide component such as a cyanide ion and an iron cyano complex (cyanide-containing wastewater) that flows into an actual wastewater treatment facility as a treatment target, the concentration of the cyanide component in the wastewater fluctuates daily. do. According to the study by the present inventors, if the cyanide-containing wastewater is treated by coexisting hydrogen and the copper (I) compound in an actual wastewater treatment facility, the cyanide-containing wastewater that changes daily may be temporarily treated. In addition, it was found that there is a problem that the removal performance of the cyanide component is lowered. Specifically, when both the cyanide ion concentration and the iron cyano complex concentration in the wastewater are low, the above-mentioned problems are unlikely to occur, but the iron cyano complex concentration is higher than the cyanide ion concentration in the wastewater. It was found that when the value is high, the above-mentioned problems tend to occur. Therefore, as a suitable treatment target in this method, water to be treated having a higher iron cyano complex concentration than the cyanide ion concentration can be mentioned.

Examples of the above-mentioned cyan-containing wastewater include wastewater discharged from a coal factory, a plating factory, a coke factory, a factory that uses a large amount of coke, and the like. Cyanide-containing wastewater includes cyanide ions and iron cyano complexes (ferrocyanide ions, ferrocyanide ions, [Fe (CN) ₅ (CO)] ^3- , and [Fe (CN) ₄ (CO) ₂ ]. ^Since it is considered that it is likely to contain at least one of 2-), cleaning wastewater of exhaust gas is more preferable. Exhaust gas cleaning wastewater also includes wastewater generated from an exhaust gas treatment device. A more suitable water to be treated is a solid for removing suspended solids from the dust collected water obtained by wet dust collecting the discharged gas containing suspended solids generated from a furnace using coke as fuel. Examples thereof include cleaning waste water of exhaust gas that has been subjected to liquid separation treatment.

In the step (A), the total cyanide (hereinafter, may be referred to as “T-CN”) concentration (mg-CN / L) and cyanide ion (hereinafter, “F-CN”) in the water to be treated are described. ) Measure the concentration (mg-CN / L).

The reason why the F-CN concentration in the water to be treated is measured in the step (A) is to control the amount of hydrogen peroxide added to the water to be treated in the step (B) described later based on the measured value of the F-CN concentration. Is. Further, in addition to the measurement of the F-CN concentration, the T-CN concentration in the water to be treated is measured in the step (A) of the copper (I) compound added to the water to be treated in the step (C) described later. This is because the amount is controlled based on the cyano complex concentration value obtained by subtracting the measured value of the F-CN concentration from the measured value of the T-CN concentration.

The amount of sodium hypochlorite added used in the conventional alkaline chlorine method may be controlled by the oxidation-reduction potential (ORP) of the water to be treated. However, in the case of the above-mentioned cyanide-containing wastewater suitable as water to be treated, various components such as ammonium nitrogen (NH ₄ ⁺ −N) and reducing sulfur compounds are contained in addition to the cyan component. , Control by ORP is difficult. In addition, sodium hypochlorite easily reacts with ammonia and is consumed in the reaction. Therefore, in this method, hydrogen peroxide is used, and the measured value of the F-CN concentration in the water to be treated is used to control the amount of hydrogen peroxide added.

In general, there is an ion electrode method as a method for measuring the cyanide ion concentration, and a method for measuring the total cyanide concentration includes a heat distillation-coloring method, a heat distillation-ion electrode method, and an ultraviolet (UV) complex decomposition-ion. There is an electrode method and the like. In the step (A), both the T-CN concentration and the F-CN concentration are preferably measured by the heat distillation-ion electrode method.

Specifically, in the step (A), a certain amount of water to be treated is used as a sample, the sample is pretreated, the pH is adjusted to 2 or less, heat aeration distillation is performed, and the cyanide ion electrode is used to prepare the water to be treated. It is preferable to include measuring the T-CN concentration (mg-CN / L) of. Further, in the step (A), a certain amount of water to be treated is used as a sample, the sample is pretreated, the pH is adjusted to 5 to 6, and heat aeration distillation is performed. Using a cyanide ion electrode, F in the water to be treated is used. It preferably comprises measuring the −CN concentration (mg-CN / L). By the measurement using these heat distillation-ion electrode methods, the F-CN concentration and the cyano complex concentration fluctuate daily like the above-mentioned cyanide-containing wastewater containing various components and the cyanide-containing wastewater. It is possible to accurately measure the T-CN concentration and the F-CN concentration even for water.

More specifically, the measurement of the T-CN concentration and the F-CN concentration by the above-mentioned heat distillation-ion electrode method is more preferably performed as follows. For the measurement of T-CN concentration, as a pretreatment of a certain amount of sample (water to be treated), a cuprous chloride solution (preferably a hydrochloric acid solution of cuprous chloride) and an aqueous phosphoric acid solution are added to the sample. The pH is adjusted to 2 or less, and heated aeration distillation is carried out under the condition of a heating time of about 10 to 30 minutes (more preferably 15 to 25 minutes, further preferably 20 minutes). In heated aeration distillation, the cyano complex is decomposed by setting the sample to an acidic condition of pH 2 or less with phosphoric acid, and cuprous chloride is a substance that promotes the decomposition of the cyano complex and interferes with the measurement (for example, sulfide). It also works as a masking agent for ions, etc.). Then, after the hydrogen cyanide gas generated by the heated aeration distillation is absorbed in the sodium hydroxide aqueous solution, the T-CN concentration can be measured using the cyanide ion electrode. Regarding the measurement of F-CN concentration, as a pretreatment of a certain amount of sample (water to be treated), a zinc acetate solution (preferably an aqueous solution of zinc acetate dihydrate) and an aqueous acetate solution are added to the sample. The pH is adjusted to 5 to 6 (more preferably pH 5.3 to 5.7, still more preferably pH 5.5), and the heating time is about 10 to 30 minutes (more preferably 15 to 25 minutes, still more preferably 20 minutes). Perform heating aeration distillation under the conditions. In the heated aeration distillation, the generation of hydrogen cyanide from the cyano complex such as hexacyanoferrate (II) acid ion is suppressed by adjusting the sample to the above pH with acetic acid and zinc acetate. Then, after the hydrogen cyanide gas generated by the heated aeration distillation is absorbed in the sodium hydroxide aqueous solution, the F-CN concentration can be measured using the cyanide ion electrode.

A commercially available measuring device can be used for the above-mentioned measurement of the T-CN concentration, and for example, the product name “All-cyanide automatic measuring device TCN-580” manufactured by Anatec Yanaco Co., Ltd. can be used. In this device, a fixed amount of sample (water to be treated), a cuprous chloride solution, and an aqueous phosphoric acid solution are introduced into a heating tank via each measuring tube, and negative pressure aeration distillation is performed for about 10 to 30 minutes. The hydrogen cyanide gas generated at this time can be absorbed and concentrated in a small volume sodium hydroxide aqueous solution prepared in advance in a measuring tank, and can be measured with a cyanide ion electrode. Further, for the measurement of the F-CN concentration, for example, an apparatus in which the cuprous chloride solution and the aqueous phosphate solution in the above-mentioned all-cyan automatic measuring apparatus are changed to a zinc acetate solution and an acetic acid aqueous solution can be used. ..

In the step (B), the concentration (mg-H ₂ O _{2 / L) added to the water to be treated as H 2} O ₂ in the water to be treated is the concentration of cyanide ion in the water to be treated in the above-mentioned step (A). Add hydrogen peroxide in an amount 1.0 to 4.0 times the measured value (mg-CN / L) and react. For example, when the cyanide ion (F-CN) concentration in the water to be treated is measured as 2 mg-CN / L in the step (A), in the step (B), 2 to 8 mg of hydrogen peroxide is added to the water to be treated. -H ₂ O ₂ / L can be added.

In step (B), by adding hydrogen peroxide to the water to be treated and reacting it, hydrogen peroxide can ^{oxidize with cyanide ions (CN −} ) in the water to be treated and decompose ^{CN −.} Is. From the viewpoint that this effect can be easily obtained, the amount of hydrogen peroxide added is such that the _{concentration of hydrogen peroxide added as H 2} O ₂ in the water to be treated is 1.2 times or more the measured value of the cyanide ion concentration in the water to be treated. It is preferably present, and more preferably 1.5 times or more. Since the cyanide ion is composed of carbon (C) and nitrogen (N), it is finally decomposed into _{carbon dioxide (CO 2} ) and nitrogen (N _2). When the water to be treated contains easily decomposable cyano complexes such as zinc cyano complex, nickel cyano complex, and copper cyano complex, such cyano complex is also decomposed by the step (B). You can expect to do it.

Regarding the amount of hydrogen peroxide added to the water to be treated in the step (B), the _{concentration of hydrogen peroxide added as H 2} O ₂ in the water to be treated is 1.0 to 4 with respect to the measured value of the F-CN concentration in the water to be treated. Since the amount is 0.0 times, the amount of hydrogen peroxide remaining in the reaction solution obtained in the step (B) can be suppressed. According to the study by the present inventors, when a copper (I) compound described later is added to the water to be treated, if a relatively large amount of hydrogen peroxide remains in the water to be treated, the cyan component from the water to be treated may be contained. It has been found that the removal performance tends to decrease. On the other hand, in this method, when the copper (I) compound is added, the amount of hydrogen peroxide remaining in the reaction solution obtained in the step (B) can be suppressed, so that the copper (I) compound is used. This makes it easier to improve the removal performance of the cyan component. In this respect, the amount of hydrogen peroxide to water to be treated, and 3.5 times or less with respect to the measurement value of F-CN concentration of the additive concentration water to be treated as of H ₂ O ₂ treatment water The amount of hydrogen peroxide is preferable, the amount of hydrogen peroxide is more preferably 3.0 times or less, and the amount of hydrogen peroxide is more preferably 2.5 times or less.

Further, in this method, the amount of hydrogen peroxide added to the water to be treated is an amount based on the measured value of the F-CN concentration in the water to be treated. Therefore, when the difference between the F-CN concentration and the cyano complex concentration in the water to be treated, in which the concentration of the cyanide component fluctuates daily, changes suddenly, such as cyanide-containing wastewater flowing into the actual wastewater treatment facility as a treatment target. Even so, it is easy to follow the change. That is, stable treatment performance can be realized even when the F-CN concentration and the cyano complex concentration in the water to be treated are various.

Further, in order to carry out the step (B) of adding hydrogen peroxide to the water to be treated and reacting it before adding the copper (I) compound to the water to be treated, the poorly solubilized substance is formed by adding the copper (I) compound. When it is generated, the amount of cyanide contained in the poorly solubilized material can be appropriately reduced. Therefore, since the amount of cyanide contained in the poorly solubilized material is reduced, there is an advantage that the possibility and degree of elution of cyanide can be reduced when the poorly solubilized material is disposed of.

As described above, in the step (B), the amount of hydrogen hydrogen remaining in the reaction solution obtained in the step (B) can be suppressed by adding a specific amount of hydrogen hydrogen to the water to be treated. A step of further reducing the residual amount of hydrogen hydrogen in the reaction solution obtained in the step (B) may be performed. For example, the reaction solution obtained in the step (B) is brought into contact with a hydrogen peroxide removing agent that reduces the concentration of hydrogen peroxide remaining in the reaction solution to cause a reaction, so that the reaction solution remains in the reaction solution. The hydrogen peroxide concentration may be further reduced.

The pH of the water to be treated during the treatment in the step (B) is preferably 5.0 to 10.0, more preferably 5.5 to 9.5, and even more preferably 6.0 to 8.0. At this time, the pH of the water to be treated may be adjusted with a pH adjusting agent (for example, hydrochloric acid, sodium hydroxide, etc.) or the like. The reaction time in the step (B) is preferably 3 to 60 minutes, more preferably 5 to 30 minutes. The reaction temperature in the step (B) is preferably 15 to 80 ° C, more preferably 20 to 60 ° C.

In the step (C), the concentration (mg-Cu / L) of Cu added to the reaction solution obtained in the above-mentioned step (B) as Cu is the cyano complex concentration value (mg-CN /) in the water to be treated. A copper (I) compound in an amount 1.0 to 4.0 times that of L) is added and reacted. The cyano complex concentration value in the water to be treated is obtained by subtracting the measured value of the cyanide ion (F-CN) concentration from the measured value of the total cyanide (T-CN) concentration in the water to be treated in the above step (A). .. Since the water to be treated contains cyanide ions and a cyano complex, the value obtained by subtracting the measured value of the F-CN concentration from the measured value of the T-CN concentration in the water to be treated is the cyano complex in the water to be treated. It can be regarded as a concentration value.

The amount of the copper (I) compound added in the step (C) will be described with an example. For example, in step (A), when the F-CN concentration in the water to be treated is measured as 2 mg-CN / L and the T-CN concentration is measured as 8 mg-CN / L, the cyano complex in the water to be treated The concentration value is determined to be 6 mg-CN / L. When a copper (I) compound is added in an amount such that the concentration of Cu added as Cu in the water to be treated is 1.0 to 4.0 times the concentration value of the cyano complex, the water to be treated (in step (B)) is used. To the obtained reaction solution), 6 to 24 mg-Cu / L of the copper (I) compound is added.

In the step (C), by adding the copper (I) compound to the reaction solution (water to be treated) obtained in the step (B), a cyano complex (for example, an iron cyano complex) and hydrogen peroxide in the water to be treated are added. Cyanide ions, which may remain undecomposed by hydrogen, can be reacted with a copper (I) compound to make them sparingly soluble. As a result, a poorly solubilized product of the cyan component (for example, iron cyano complex) can be produced in the reaction solution or the treated water obtained in the step (C). From the viewpoint that this effect can be easily obtained, the amount of the copper (I) compound added is preferably 1.2 times or more the concentration of Cu added in the water to be treated with respect to the concentration value of the cyano complex in the water to be treated. , 1.5 times or more is more preferable.

Further, the amount of the copper (I) compound added to the water to be treated (the reaction solution obtained in the step (B)) in the step (C) is such that the concentration of the copper (I) compound added as Cu in the water to be treated is the cyano complex concentration value. Since the amount is 1.0 to 4.0 times, the amount of copper remaining in the reaction solution or the treated water obtained in the step (C) can be suppressed. Therefore, after the step (C), equipment and treatment for removing copper, which is necessary when copper remains in the treated water (for example, a settling device for precipitating and removing copper as a hydroxide or the like). It is also possible to obtain treated water to the extent that it does not require treatment using. As a result, it can be expected that the process and equipment for processing copper can be omitted, and as a result, the equipment cost and the processing cost can be suppressed, and the site area can be expected to be suppressed. From the viewpoint that these effects can be easily obtained, the amount of the copper (I) compound added is such that the concentration of Cu added in the water to be treated is 3.8 times or less of the concentration value of the cyano complex in the water to be treated. It is preferably 3.5 times or less, more preferably 3.0 times or less.

Further, in this method, the amount of the copper (I) compound added to the water to be treated is an amount based on the cyano complex concentration value in the water to be treated. Therefore, when the difference between the F-CN concentration and the cyano complex concentration in the water to be treated, in which the concentration of the cyanide component fluctuates daily, changes suddenly, such as cyanide-containing wastewater flowing into the actual wastewater treatment facility as a treatment target. Even so, it is easy to follow the change. That is, stable treatment performance can be realized even when the F-CN concentration and the cyano complex concentration in the water to be treated are various.

The copper (I) compound is a monovalent copper compound (copper cuprous compound). Examples of the form of the copper (I) compound when the copper (I) compound is added include powder form and solution form dissolved in a solvent. Therefore, as the copper (I) compound, a copper (I) compound capable of producing ^{copper (I) ions (Cu +} ) in the water to be treated or a copper (I) compound capable of producing ^{Cu + in a solvent should be used.} Can be done. Examples of the copper (I) compound include copper (I) chloride, copper (I) oxide (copper oxide), and copper (I) sulfate. It is preferable to use one or more of these. Among these, it is more preferable to use copper (I) oxide.

The pH of the water to be treated (the reaction solution obtained in the step (B)) during the treatment in the step (C) is preferably 5.0 to 10.0, more preferably 5.5 to 9.5. 6.0 to 8.0 is more preferable. The pH may be adjusted by using the above-mentioned pH adjuster so as to have such a pH range. In the step (C), the time (reaction time) for adding the copper (I) compound to the reaction solution obtained in the step (B) and then reacting the compound is preferably 3 to 60 minutes. , 5 to 30 minutes is more preferable. The reaction temperature at that time is preferably 15 to 80 ° C, more preferably 20 to 60 ° C.

As described above, this method includes a step of bringing the reaction solution obtained in the step (B) into contact with a hydrogen peroxide removing agent for reducing the concentration of hydrogen peroxide remaining in the reaction solution to cause a reaction. You may be. In this case, the step (C) is obtained by bringing the reaction solution obtained in the step (B) into contact with a hydrogen peroxide removing agent for reducing the concentration of hydrogen peroxide remaining in the reaction solution and reacting them. The reaction solution obtained can include a step (C1) in which the copper (I) compound is added.

The reaction solution obtained in the step (B), which is the target for adding the copper (I) compound in the step (C1), is in a state where the residual amount of hydrogen peroxide in the reaction solution is sufficiently low or hydrogen peroxide. Can be left in a state where Therefore, even when the F-CN concentration and the cyano complex concentration value in the water to be treated are various, it is possible to stably and sufficiently remove the cyan component from the water to be treated.

For the contact between the reaction solution obtained in the step (B) and the hydrogen peroxide removing agent, the hydrogen peroxide removing agent may be brought into contact with the reaction solution obtained in the step (B) to remove hydrogen peroxide. The reaction solution obtained in step (B) may be brought into contact with the agent, or both may be carried out. The reaction time between the reaction solution obtained in the step (B) and the hydrogen peroxide removing agent is preferably 1 to 30 minutes, more preferably 1 to 15 minutes after the start of contact with them. preferable. The reaction temperature at that time is preferably 15 to 80 ° C, more preferably 20 to 60 ° C.

The hydrogen peroxide removing agent preferably contains one or both of a hydrogen peroxide reducing agent and a hydrogen peroxide decomposition catalyst. Examples of the reducing agent for hydrogen peroxide include sodium sulfite (Na ₂ SO ₃ ) and potassium sulfite (K ₂ SO ₃ ) and the like; sodium hydrogen sulfite (NaHSO ₃ ) and potassium hydrogen sulfite (KHSO ₃ ) and the like. Hydrogen sulfite (also known as sodium sulfite); iron (II) salts such as iron (II) sulfate and iron (II) nitrate (also known as divalent iron salt, ferrous salt); ascorbic acid and its salts, etc. Can be mentioned. When a hydrogen peroxide reducing agent such as these is used as a hydrogen peroxide removing agent, the hydrogen peroxide removing agent (hydrogen peroxide reducing agent) is added to the reaction solution obtained in the step (B). Therefore, it is preferable to bring the hydrogen peroxide removing agent into contact with the reaction solution obtained in the step (B). Examples of the form in which the reducing agent for hydrogen peroxide is added include a powder form and a solution form dissolved in a solvent, and a solution form is preferable.

As the decomposition catalyst of hydrogen peroxide, a liquid decomposition catalyst or a solid decomposition catalyst can be used. Examples of the liquid decomposition catalyst include catalase and activated sludge used in sewage treatment plants. Examples of the solid decomposition catalyst include powdered or granular manganese dioxide, granular or pelletized activated carbon, and the like. When the above-mentioned hydrogen peroxide decomposition catalyst is used as the hydrogen peroxide removing agent, the hydrogen peroxide removing agent (hydrogen peroxide decomposition catalyst) is added to the reaction solution obtained in the step (B). , It is preferable to bring the hydrogen peroxide removing agent into contact with the reaction solution obtained in the step (B). Further, a hydrogen peroxide decomposition catalyst supported on a base material may be immersed in a reaction solution, or a solid decomposition catalyst may be immersed in a fibrous or mesh-like processed solution. By passing the reaction solution through a tank filled with a solid decomposition catalyst, the reaction solution obtained in step (B) is brought into contact with a hydrogen peroxide removing agent (hydrogen peroxide decomposition catalyst). It is also preferable.

In the step (C), the amount of the reaction solution obtained in the step (B) is 1.0 to 4.0 times that of the above-mentioned cyano complex concentration value (mg-CN / L) in the water to be treated. It is preferable to include a step (C2) of further adding a quaternary ammonium compound and reacting it. In this case, the addition of the quaternary ammonium compound may be carried out before or after the addition of the copper (I) compound as long as it is carried out in the reaction solution obtained in the step (B), and copper. (I) It may be carried out at the same time as the addition of the compound.

The amount of the quaternary ammonium compound added in the step (C2) will be described with an example. For example, as in the above example, the cyano complex concentration value in the water to be treated is determined to be 6 mg-CN / L based on the T-CN concentration and the F-CN concentration in the water to be treated measured in the step (A). I will list the cases when it is done. When a quaternary ammonium compound in an amount 1.0 to 4.0 times the concentration value of the cyano complex is added, the fourth is added to the water to be treated (the reaction solution obtained in step (B)). Add 6 to 24 mg / L of the quaternary ammonium compound.

By adding a specific amount of the quaternary ammonium compound together with the copper (I) compound to the water to be treated in the step (C2) (the reaction solution obtained in the step (B)), a cyano complex (for example, the reaction solution) in the water to be treated is added. (Iron cyano complex, etc.) is easily solubilized. Further, as a complex of cyanide and copper dissolved in the water to be treated by adding the copper (I) compound to the water to be treated, a tetracyanocopper complex ([Cu (CN) ₄ ] ^3- ) or a tricyanocopper complex ([Cu) Where (CN) ₃ ] ^2- ) may occur, these complexes can also be made sparingly soluble by the combined use of a quaternary ammonium compound. Therefore, the step (C2) makes it easier to enhance the effect of making the cyan component sparingly soluble, and also makes it easier to suppress the residue of copper in the reaction solution and the treated water obtained in the step (C). Further, the step (C2) also makes it possible to reduce the required amount of the copper (I) compound.

From the viewpoint that the above-mentioned effects of the quaternary ammonium compound are likely to be exhibited, the amount of the quaternary ammonium compound added is 1.2 to 3.5 times the cyano complex concentration value in the water to be treated. More preferably, it is more preferably 1.5 to 3.0 times.

The quaternary ammonium compound is a compound having a quaternary ammonium cation, and may be a monomer or a polymer. As the quaternary ammonium compound, a tetraalkylammonium compound, a cationic polymer and the like can be preferably used. Examples of the form in which the quaternary ammonium compound is added include powder and a solution dissolved in a solvent, and a solution is preferable.

As the tetraalkylammonium compound, didecyldimethylammonium salt, hexadecyltrimethylammonium salt, dioctyldimethylammonium salt, didodecyldimethylammonium salt, trioctylmethylammonium salt, and benzyldodecyldimethylammonium salt are preferable. Further, the anion paired with the quaternary ammonium cation in these is preferably a halide ion, more preferably a chloride ion and a bromide ion.

The cationic polymer may be a polymer having a quaternary ammonium cation, for example, a polyacrylic acid ester compound, a polymethacrylic acid ester compound, a polyamine compound, a polydialyldialkylammonium salt compound, or a diallyldialkylammonium. Examples thereof include salt-acrylamide copolymer system compounds, polycondensates of dimethylamine and epichlorohydrin, and polycondensates of dimethylamine, epichlorohydrin and ammonia.

In the step (D), the reaction solution obtained in the step (C) is subjected to a solid-liquid separation treatment, and the poorly solubilized material produced in the step (C) is separated and removed. Thereby, the treated water from which the cyan component has been removed can be obtained. When the water to be treated or the reaction solution obtained in the step (C) contains other suspended solids (SS), the SS can be removed by the step (D).

Examples of the solid-liquid separation treatment method in the step (D) include a precipitation treatment, a membrane separation treatment, a filtration treatment, and the like, and among these, the precipitation treatment is preferable. At the time of the solid-liquid separation treatment, a flocculant may be added to the reaction liquid to be subjected to the solid-liquid separation treatment, or the reaction liquid may be agitated. Examples of the flocculant include inorganic flocculants such as polyaluminum chloride, aluminum sulfate, polyferric sulfate, and ferric chloride, and polymer flocculants, and one or two of these. The above can be used.

The pH of the water to be treated (reaction solution obtained in step (C)) during the treatment in step (D) is preferably 5.0 to 10.0, more preferably 5.5 to 9.5. 6.0 to 8.0 is more preferable. The pH may be adjusted by using the above-mentioned pH adjuster so as to have such a pH range. The reaction temperature during the treatment in step (D) is preferably 15 to 80 ° C, more preferably 20 to 60 ° C.

When this water treatment method is applied using the exhaust gas cleaning wastewater obtained by solid-liquid separation treatment of the above-mentioned dust collection water as water to be treated, the water treatment method according to the embodiment of the present invention is one embodiment thereof. , It is preferable to include the following steps (E) and (F). That is, the separated water obtained in the step (E) and the step (E) in which one or both of the concentration treatment and the dehydration treatment are performed on the slurry containing the solid content separated from the liquid content in the step (D). It is preferable to carry out the step (F) of sending the wastewater to the solid-liquid separation treatment for obtaining the washing wastewater of the exhaust gas. The slurry containing the solid content obtained in the step (D) contains a sparingly soluble substance or the like that may be produced by the above-mentioned step (C), and the water content in the slurry is affected by oxidation, pH change, temperature change and the like. May cause the cyan component to elute. On the other hand, by performing the above steps (E) and (F), it becomes possible to more stably remove the cyan component from the water to be treated. Examples of the solid-liquid separation treatment for removing suspended solids from the dust collected water obtained by wet dust collecting treatment of the discharged gas containing suspended solids include sedimentation separation treatment, membrane separation treatment, filtration treatment and the like. Of these, sedimentation separation treatment is preferable.

In the water treatment method of the embodiment of the present invention, as one aspect thereof, the water to be treated to which hydrogen peroxide is added in the step (B) and the copper (I) compound in the step (C) are added. A reducing agent may be further added to either or both of the reaction solutions to be treated. Examples of the reducing agent include thiosulfate, sulfite, bicarbonate, ferrous chloride, and alkali metal sulfides such as sodium sulfide and sodium tetrasulfide, and one or two of these. The above can be used. Among these, since it can also serve as the above-mentioned hydrogen peroxide removing agent (reducing agent for hydrogen peroxide), it is preferable to use at least one of sulfites and sulfites, which can be obtained in step (B). It is more preferable to add it to the reaction solution. Examples of the cations forming salts in thiosulfate, sulfites, and sulfites include sodium ion, potassium ion, calcium ion, ammonium ion, and organic ammonium ion. Examples of the form of the reducing agent when added to the water to be treated include a powder form and a solution form dissolved in a solvent, and a solution form is preferable.

Further, in the water treatment method of the embodiment of the present invention, as one aspect thereof, the step (B) using hydrogen peroxide and the step (C) using the copper (I) compound are carried out in a common reaction tank. It may be carried out in a separate reaction tank. Further, when the above-mentioned hydrogen peroxide removing agent is used, the hydrogen peroxide removing agent may be used in a reaction tank separate from each reaction tank in which the steps (B) and (C) are performed, and the step (B) It may be used in the reaction vessel performing the above-mentioned step (C), or it may be used in the reaction vessel performing the step (C). When the above-mentioned quaternary ammonium compound is used, the quaternary ammonium compound is preferably used in the reaction vessel in which the step (C) using the copper (I) compound is performed.

Hereinafter, each step in the water treatment method according to the embodiment of the present invention will be further described with reference to a drawing showing a schematic configuration of a water treatment apparatus and a treatment flow capable of executing those treatment methods. In addition, the same reference numerals may be given to the parts common to the drawings in the drawings, and the description thereof may be omitted. The solid arrows in FIGS. 1 to 3 represent the water to be treated and the flow of the liquid in the treatment process.

FIG. 1 is an explanatory diagram showing an example of a schematic configuration of a water treatment apparatus and a treatment flow capable of executing the water treatment method according to the embodiment of the present invention described above. As shown in FIG. 1, the water treatment device 10 includes a total cyanide (T-CN) concentration measuring device 32, a cyanide ion (F-CN) concentration measuring device 34, a first reaction tank 22, and a second reaction tank. 24 and a solid-liquid separation device 26 are provided. The above-mentioned step (A) can be performed by the T-CN concentration measuring device 32 and the F-CN concentration measuring device 34. Further, the above-mentioned step (B) is performed in the first reaction tank 22, the above-mentioned step (C) is performed in the second reaction tank 24, and the above-mentioned step (D) is performed in the solid-liquid separation device 26. Can be done.

Water treatment device 10, in the stage before sending the treatment water W ₁ to the first reaction vessel 22 is preferably provided with adjustment tank 21 for storing water to be treated. By providing the adjusting tank 21, _{the properties of the water to be treated W 1} are averaged when the properties are changed, and _{the inflow of the water to be treated W 1} is stabilized in the first reaction tank 22 when the inflow amount is changed. The effect of sending a certain amount can be expected. In this case, the adjustment tank 21 the water to be treated W ₁ which has been flowed in, was fractionated a certain amount as a sample, and fed to the T-CN concentration measuring device 32 and F-CN concentration measuring device 34, respectively it is preferable to perform the measurement of the T-CN concentration and F-CN concentration in the water to be treated _W during _1. If the adjusting tank 21 is not provided, the water to be treated that has flowed into the first reaction tank 22 may be separated and supplied to the measuring device (32, 34). Further, by branching the flow path of the _{water to be treated W 1 in} the previous stage of the first reaction tank 22, _{a certain amount of the water to be treated W 1} is taken as a sample, and the measuring device (32, 34) described above. May be supplied to.

As the T-CN concentration measuring device 32 and the F-CN concentration measuring device 34, it is preferable to use a measuring device using the heated aeration distillation-cyanide ion electrode method. As described above, as the T-CN concentration measuring device 32, for example, the product name “All-cyanide automatic measuring device TCN-580” manufactured by Anatec Yanaco Co., Ltd. can be used. Further, as the F-CN concentration measuring device 34, the same device as the above-mentioned automatic total cyanide concentration measuring device can be used except that the reagent used is changed. These devices (32, 34) are, for example, a means for supplying a sample (water to be treated), diluted water (diluted water tank and diluted water stored therein), and each reagent used (each reagent tank and stored therein). Each reagent) and its various measuring tubes, introduction collecting tube, heating tank, cooling pipe, measuring tank (measuring tank with stirrer), ventilation pump, cyanide ion electrode, comparison electrode, etc. In the T-CN concentration measuring device 32, an aqueous sodium hydroxide solution, a cuprous chloride solution (preferably a hydrochloric acid solution of cuprous chloride), and an aqueous phosphoric acid solution can be used as the above-mentioned reagents. Further, in the F-CN concentration measuring device 34, a sodium hydroxide aqueous solution, a zinc acetate solution (preferably an aqueous solution of zinc acetate dihydrate), and an acetic acid aqueous solution can be used as the above-mentioned reagents.

In the T-CN concentration measuring device 32, a certain amount of water to be treated W ₁ is supplied as a sample by supplying means, the supplied sample, dilution water, cuprous chloride solution, and the phosphoric acid aqueous solution introduction collecting pipe The sample collected in 1 and adjusted to pH 2 or less is supplied to the heating tank and heated for about 10 to 30 minutes (more preferably 15 to 25 minutes, still more preferably 20 minutes). On the other hand, the sodium hydroxide aqueous solution is supplied to the measuring tank and stored. Hydrogen cyanide gas generated by heated aeration distillation of a sample adjusted to pH 2 or less is collected in an aqueous sodium hydroxide solution in a measuring tank, and is charged into the water to be treated by a cyanide ion electrode and a comparative electrode provided in the measuring tank. The T-CN concentration can be measured.

In the F-CN concentration measuring device 34, a certain amount of water to be treated W ₁ is supplied as a sample by supplying means, the supplied sample, dilution water, zinc acetate solution, and aqueous acetic acid solution is set in the introduction for collecting pipe , The sample adjusted to pH 5 to 6 (more preferably 5.3 to 5.7, still more preferably 5.5) is supplied to the heating tank for 10 to 30 minutes (more preferably 15 to 25 minutes, even more preferably). Is heated for about 20 minutes). On the other hand, the sodium hydroxide aqueous solution is supplied to the measuring tank and stored. The hydrogen cyanide gas generated by the heated aeration distillation of the sample adjusted to the above pH is collected in the aqueous sodium hydroxide solution in the measuring tank, and is contained in the water to be treated by the cyanide ion electrode and the comparative electrode provided in the measuring tank. The F-CN concentration can be measured.

The first reaction tank 22 is a tank for reaction by adding hydrogen peroxide to the water to be treated W ₁ which has been flowed. At this time, in the first reaction tank 22, the measured value (mg-CN / L) of the F-CN concentration measured by the F-CN concentration measuring device 34 was used as H ₂ O _{2 in the} water to be treated. Hydrogen peroxide is added in an amount that increases the addition concentration (mg-H ₂ O _{2 / L) by 1.0 to 4.0 times.} The first reaction tank 22 can be provided with a device (hydrogen peroxide adding device) 42 for adding hydrogen peroxide.

The second reaction tank 24 is a tank in which the copper (I) compound is added _{to the reaction solution W 2 obtained in the first reaction tank 22 to react.} At this time, in the second reaction tank 24, the concentration of Cu added in the water to be treated (mg-Cu / L) is 1.0 with respect to the concentration value of the cyano complex in the water to be treated (mg-CN / L). ~ 4.0 times the amount of copper (I) compound is added. Cyanide complex concentration values in the water to be treated (mg-CN / L), from the measured value of T-CN concentration in the water to be treated _W in ₁ measured by T-CN concentration measuring device 32, F-CN concentration measuring device measured by 34 it is determined by subtracting the measured value of F-CN concentration in the water to be treated W during _1. The second reaction vessel 24 may be provided with an apparatus (copper (I) compound addition apparatus) 44 for adding the copper (I) compound.

The solid-liquid separation device 26 performs a _{solid-liquid separation treatment on the reaction solution W 4} containing the poorly solubilized material obtained in the second reaction tank 24, and separates and removes the poorly solubilized material produced in the second reaction tank 24. It is a device. By the solid-liquid separation treatment in the solid-liquid separation device 26, the treated water W ₆ from which the poorly solubilized material has been removed can be obtained. As the solid-liquid separation device 26, for example, a settling device such as a thickener, various filters, a membrane separator, and the like can be used. Among these, a settling device is preferable, and the settling device may be provided with a stirring mechanism. When a coagulant is used during the treatment by the solid-liquid separation device 26, the solid-liquid separation device may be provided with a device for adding the coagulant (coagulant addition device).

The hydrogen peroxide addition device 42, the copper (I) compound addition device 44, and the coagulant addition device described above are, for example, for supplying a tank for storing each material used in those devices and each material. Pump, supply pipe, etc. can be provided.

As one aspect thereof, the water treatment apparatus 10 preferably includes a control unit capable of controlling the addition amount of hydrogen peroxide and the addition amount of the copper (I) compound. The water treatment device 12 including the control unit 51 will be described with reference to FIG. FIG. 2 is an explanatory diagram showing another example of a schematic configuration of a water treatment apparatus and a treatment flow capable of executing the water treatment method according to the embodiment of the present invention described above.

The control unit 51 is preferably connected to and cooperates with the hydrogen peroxide addition device 42 described above. For example, by inputting the measured value of the F-CN concentration measured by the F-CN concentration measuring device 34 into the control unit 51, the measured value of the F-CN concentration is input to the control unit 51 to the hydrogen peroxide adding device 42. It can be output. Then, the control unit 51 adds the hydrogen peroxide addition device 42 to the hydrogen peroxide addition device 42 at a _{concentration of H 2} O ₂ added to the hydrogen peroxide addition device 42, which is 1.0 to 4.0 times the measured value of the F-CN concentration in the water to be treated. A certain amount of hydrogen peroxide can be added. In this way, in the first reaction tank 22, the amount of hydrogen peroxide added from the hydrogen peroxide addition device 42 can be semi-automatically controlled based on the measured value of the F-CN concentration in the water to be treated. It becomes.

Further, it is preferable that the control unit 51 is connected to and cooperates with the copper (I) compound addition device 44 described above. For example, in addition to the above-mentioned measured value of F-CN concentration, the measured value of T-CN concentration measured by the T-CN concentration measuring device 32 is input to the control unit 51, and the T-CN concentration is measured in the control unit 51. The difference between the value and the measured value of the F-CN concentration can be calculated, and the cyano complex concentration value, which is the difference, can be output to the copper (I) compound addition device 44. Then, the control unit 51 adds an amount of Cu to the copper (I) compound addition device 44 that is 1.0 to 4.0 times the concentration value of the cyano complex in the water to be treated. A copper (I) compound can be added. In this way, in the second reaction vessel 24, the amount of the copper (I) compound added from the copper (I) compound addition device 44 can be semi-automatically controlled based on the cyano complex concentration value in the water to be treated. It will be possible.

It is more preferable that the control unit 51 is connected to the T-CN concentration measuring device 32 and the F-CN concentration measuring device 34 and cooperates with them. For example, the control unit 51 can automatically input the measured value of the F-CN concentration measured by the F-CN concentration measuring device 34 and the measured value of the T-CN concentration measured by the T-CN concentration measuring device 32. can. Further, the control unit 51 is made to calculate the cyano complex concentration value, the measured value of the F-CN concentration is output to the hydrogenation hydrogenation device 42, and the cyano complex concentration value is output to the copper (I) compound addition device 44. Is possible. As a result, in the first reaction tank 22, the amount of hydrogen peroxide added from the hydrogen peroxide addition device 42 can be automatically controlled based on the measured value of the F-CN concentration in the water to be treated. Further, in the second reaction vessel 24, the amount of the copper (I) compound added from the copper (I) compound addition device 44 can be automatically controlled based on the cyano complex concentration value in the water to be treated. The control unit 51 can be configured to include, for example, a power supply unit, a CPU unit, an input unit, an output unit, a storage unit, and the like, and a personal computer or the like can be used.

When a reducing agent such as the above-mentioned sulfite is used together with hydrogen peroxide in the above-mentioned step (B), the first reaction tank 22 is an apparatus for adding the reducing agent to the first reaction tank 22. (Reducing agent addition device) can be provided. When the above-mentioned reducing agent or the above-mentioned quaternary ammonium compound is used together with the copper (I) compound in the step (C), a reducing agent addition device or a second reaction is used in the second reaction tank 24. A device for adding a quaternary ammonium compound can be provided in the tank 24. As an example, FIG. 2 shows an apparatus (quaternary ammonium compound addition apparatus) 45 for adding a quaternary ammonium compound.

Even in the case of the water treatment device 12 provided with the quaternary ammonium compound addition device 45, it is preferable that the above-mentioned control unit 51 is provided, and the control unit 51 is connected to the quaternary ammonium compound addition device 45 and is connected to the control unit 51. It is preferable to cooperate. For example, as described above, the control unit 51 can calculate the cyano complex concentration value, and the quaternary ammonium compound addition device 45 can output the cyano complex concentration value. As a result, in the second reaction vessel 24, the amount of the quaternary ammonium compound added from the quaternary ammonium compound addition device 45 is semi-automatically or automatically controlled based on the cyano complex concentration value in the water to be treated. It becomes possible to do.

In addition, in FIG. 1 and FIG. 2, the first reaction tank 22 and the second reaction tank are made so that the step (B) using hydrogen peroxide and the step (C) using the copper (I) compound can be easily described. Although 24 is shown separately, the first reaction tank 22 and the second reaction tank 24 may be the same (common) reaction tank. On the other hand, since it is preferable to proceed to the next step after the reaction with hydrogen peroxide in the step (B) is completed, it is preferable that the first reaction tank 22 and the second reaction tank 24 are separate tanks.

When the above-mentioned step (C) includes the above-mentioned step (C1), the water treatment apparatus according to the embodiment of the present invention is described as a hydrogen peroxide removing tank (hereinafter, simply referred to as "removing tank") as one aspect thereof. May be further provided.) The water treatment apparatus 14 including the hydrogen peroxide removing tank 23 will be described with reference to FIG. FIG. 3 is an explanatory diagram showing another example of a schematic configuration of a water treatment apparatus and a treatment flow capable of executing the water treatment method according to the embodiment of the present invention described above.

The removal tank 23 is a tank into which the reaction liquid W ₂ obtained in the first reaction tank 22 flows in, and is a tank in which the reaction liquid W ₂ and the above-mentioned hydrogen peroxide removing agent are brought into contact with each other for reaction. be. At this removing tank 23, it is possible that the concentration of hydrogen peroxide remaining in the reaction solution W ₂ to obtain a reaction liquid W ₃ which is reduced. The removal tank 23 may be provided with a device 43 (tank, pump, supply pipe, etc.) for adding a hydrogen peroxide removing agent _{to the reaction solution W 2} obtained in the first reaction tank 22. Further, when the above-mentioned decomposition catalyst is used as the hydrogen peroxide removing agent, a base material on which the decomposition catalyst is supported can be provided in the removing tank 23. _{By passing the reaction solution W 2} obtained in the first reaction tank 22 through the removal tank 23, the base material carrying the decomposition catalyst may be immersed in the _{reaction solution W 2.} Further, when the above-mentioned solid decomposition catalyst is used as the hydrogen peroxide removing agent, the removal tank 23 can be a tank filled with the solid decomposition catalyst. The reaction solution W ₂ and the hydrogen peroxide removing agent may be brought into contact with each other by _{passing the reaction solution W 2} obtained in the first reaction tank 22 through the removal tank 23.

In FIG. 3, the first reaction tank 22 is made so that the step (B) using hydrogen peroxide, the step using the hydrogen peroxide removing agent, and the step (C) using the copper (I) compound can be easily described. , The removal tank 23 and the second reaction tank 24 are shown separately, but the first reaction tank 22 and the removal tank 23; the removal tank 23 and the second reaction tank 24; and the first reaction tank 22, The removal tank 23 and the second reaction tank 24; may be the same (common) tank. On the other hand, it is preferable to proceed to the next step after the reaction with hydrogen peroxide in the step (B) is completed, and it is preferable to proceed to the next step after the reaction with the hydrogen peroxide removing agent is completed. It is preferable that the 22, removal tank 23, and the second reaction tank 24 are separate tanks.

As described above, since the exhaust gas cleaning wastewater is suitable as the water to be treated, the above-mentioned water treatment method can also be applied to the exhaust gas cleaning wastewater treatment equipment. FIG. 4 is an explanatory diagram showing a schematic configuration of an example of an exhaust gas treatment facility and a treatment flow when it is assumed that the water treatment method of one embodiment of the present invention is applied.

The exhaust gas G treatment facility 60 shown in FIG. 4 is a settling tank for settling and separating a wet dust collector (Venturi scrubber) 61 for continuously cleaning the exhaust gas G and a dust collecting water W _{61 obtained from the wet dust collector 61.} It is provided with 63 and a primary treatment water tank 65 for storing _{the supernatant liquid W 63 obtained by sedimentation separation as primary treatment water.} Further, a part of the supernatant liquid (primary treated water) sent to the primary treated water tank 65 is returned to the wet dust collector 61 while adding make-up water W _{60 as circulating water W 65, and is used for cleaning the exhaust gas G.} It may be used in a circulating manner. _{Further, a dehydrator 67 may be provided to dehydrate the sediment S 63} obtained by sedimentation separation in the settling tank 63, and a part of the dehydrator treated by the dehydrator 67 is treated as a dehydrated cake C, and another one. The portion may be retransmitted to the settling tank 63 as a desorbed liquid (dehydrated filtrate) W _67.

Primary treated water in the primary treating tank 65 described above, when the cyanide ions and cyanide complex is contained, to the primary treatment water, and the water to be treated W ₁ that is a processing target in the water treatment process described above Can be done. In FIG. 4, the primary treated water in the primary treated water tank 65 is used as blow water (water to be treated W ₁ ) in the above-mentioned water treatment devices 10, 12, 14 (the first reaction tank 22 or the adjusting tank 21 in them). feed, when processing of the water to be treated W ₁ is illustrated. The slurry containing the solid content separated from the liquid content by the solid-liquid separation device 26 in the water treatment devices 10, 12, and 14 is sent to the dehydrator 67 for dehydration treatment, and the separated water (desorption) obtained by the dehydrator 67 is performed. Liquid, dehydration filtrate) is preferably sent to the settling tank 63. The dehydrator 67 shown in FIG. 4 may be a concentrating tank, or the concentrating tank and the dehydrator 67 may be used in combination. Further, in addition to the dehydration filtrate, the separated water obtained in the concentration tank may be sent to the settling tank 63, or the surplus slurry may be sent to the settling tank 63. In addition, instead of the settling tank 63, various membrane separation devices, filters and the like may be used.

In the water treatment method of the embodiment of the present invention described in detail above, since a specific amount of hydrogen peroxide is added to the water to be treated with respect to the measured value of the cyanide ion concentration in the water to be treated, cyanide in the water to be treated While sufficiently decomposing the compound ion, it is possible to suppress the residual hydrogen peroxide in the reaction solution after the addition of hydrogen peroxide. Further, in the above water treatment method, a specific amount of the copper (I) compound is added to the water to be treated with respect to the concentration value of the cyano complex in the water to be treated. It is possible to suppress the residue of the copper (I) compound in the reaction solution (treated water) after the addition of the copper (I) compound, while being able to produce the product. Therefore, it can be expected that the process and equipment for treating copper, which is required when copper remains in the treated water, can be omitted, thereby reducing the equipment cost and the treatment cost, and the site. It can be expected to reduce the area.

Further, in this method, the amount of hydrogen peroxide added to the water to be treated is controlled to a specific amount based on the measured value of the F-CN concentration in the water to be treated, and the amount of the copper (I) compound added to the water to be treated. Is controlled to a specific amount based on the cyano complex concentration value in the water to be treated. Therefore, when the difference between the cyanide ion concentration and the cyano complex concentration in the treated water, in which the concentration of the cyanide component fluctuates daily, changes suddenly, such as cyanide-containing wastewater flowing into the actual wastewater treatment facility as a treatment target. Even so, it is easy to follow the change. Therefore, this method stably and effectively uses the cyanide ion and the cyano complex in the cyanide-containing wastewater even in the actual cyanide-containing wastewater in which the F-CN concentration and the cyano complex concentration fluctuate daily to various values. It is possible to remove it.

The water treatment method according to the embodiment of the present invention can have the following configuration.
[1] A water treatment method for treating water to be treated containing cyanide ions and a cyano complex, wherein the total cyanide concentration (mg-CN / L) and the cyanide ion concentration (mg-CN / L) in the water to be treated are treated. In the step (A) of measuring L), the concentration (mg-H ₂ O _{2 / L) added to the water to be treated as H 2} O ₂ in the water to be treated is the cyanide ion in the water to be treated. A step (B) of adding and reacting an amount of hydrogen peroxide in an amount 1.0 to 4.0 times that of the measured concentration value (mg-CN / L) and the above step (B) were obtained. A cyano complex obtained by subtracting the measured value of the cyanide ion concentration from the measured value of the total cyanide concentration in the water to be treated to add the concentration of Cu as Cu in the water to be treated (mg-Cu / L) to the reaction solution. A step (C) of adding and reacting an amount of the copper (I) compound in an amount 1.0 to 4.0 times the concentration value (mg-CN / L) and the above step (C) were obtained. A water treatment method comprising a step (D) of solid-liquid separation treatment of a reaction solution and separation and removal of a poorly solubilized substance produced in the step (C).
[2] In the step (A), a certain amount of the water to be treated is used as a sample, the sample is pretreated, the pH is adjusted to 2 or less, heat aeration distillation is performed, and the cyanide ion electrode is used to perform the treatment. To measure the total cyan concentration (mg-CN / L) in water; and to use a certain amount of the water to be treated as a sample, pretreat the sample, adjust the pH to 5 to 6, perform heat aeration distillation, and perform cyan. The water treatment method according to the above [1], which comprises measuring the cyanide ion concentration (mg-CN / L) in the water to be treated using a compound ion electrode.
[3] In the step (C), the reaction solution obtained in the step (B) is brought into contact with a hydrogen peroxide removing agent that reduces the concentration of the hydrogen peroxide remaining in the reaction solution to cause a reaction. The water treatment method according to the above [1] or [2], which comprises a step (C1) in which the copper (I) compound is added to the reaction solution thus obtained.
[4] In the step (C), 1.0 to 4.0 is added to the reaction solution obtained in the step (B) with respect to the cyano complex concentration value (mg-CN / L) in the water to be treated. The water treatment method according to any one of the above [1] to [3], which comprises a step (C2) of further adding and reacting a quadrupling amount of the quaternary ammonium compound.
[5] The water treatment method according to any one of the above [1] to [4], wherein the copper (I) compound contains copper (I) oxide.

Hereinafter, the effects of the water treatment method according to the embodiment of the present invention will be described in more detail with reference to test examples, but the present invention is not limited to the following test examples.

<Water to be treated>
The raw water described below was used as the water to be treated containing a cyanide ion (soluble F-CN) and a soluble metal cyano complex. A supernatant water obtained by sedimentation and separation of wastewater containing suspended solids such as unburned carbon, iron, and zinc discharged from an exhaust gas treatment device for cleaning exhaust gas in a predetermined factory was prepared. As shown in Table 1, three types of raw water (raw waters 1 to 3) having different soluble F-CN concentration and cyano complex concentration were prepared for the supernatant water. Raw water 1-3 is the same except that the dates of collection are different.

The total cyanide (T-CN) concentration and the cyanide ion (F-CN) concentration in each raw water are measured as follows, and the measured value of the F-CN concentration is subtracted from the measured value of the T-CN concentration. , Cyanide complex concentration was determined. To measure the T-CN concentration in each raw water, a sodium hydroxide solution is used in the measuring tank, and a hydrochloric acid solution of cuprous chloride and a phosphoric acid solution are used as reagents for pretreating the raw water. A measuring device using the ion electrode method (product name "All-cyan automatic measuring device TCN-580", manufactured by Anatec Yanaco Co., Ltd.) was used. In this analysis, as a pretreatment, a hydrochloric acid solution of cuprous chloride having a concentration of copper (I) of 2% by mass and a 1 + 2 phosphoric acid solution (special grade phosphoric acid: pure water = 1: 2 (mass ratio)). (Mixed solution) is added to the raw water sample, the sample is adjusted to pH 2 or less, heated aeration distillation is performed for 20 minutes, and the generated hydrogen cyanide gas is collected in a 0.5 mass% sodium hydroxide aqueous solution to generate cyanide. It was measured with a solute ion electrode. Further, for measuring the F-CN concentration in each raw water, the reagents (hydrochloric acid solution and phosphoric acid aqueous solution of cuprous chloride) in the above-mentioned automatic total cyanide measuring device are used, an aqueous solution of zinc acetate dihydrate, and an aqueous acetic acid solution. The device changed to was used. In this analysis, as a pretreatment, an aqueous solution of zinc acetate in which the concentration of zinc acetate dihydrate was adjusted to 66.4 g / L, and an aqueous solution of 0.5 M acetate and an aqueous solution of 0.5 M sodium acetate were 1: 4 (mass ratio). An aqueous acetic acid solution mixed at the ratio of It was collected in an aqueous sodium solution and measured with a cyanide ion electrode.

Regarding the water quality other than the cyan component in each raw water, the pH was 7.0 to 8.0, the water temperature was 50 to 60 ° C., the suspended solids concentration _{was 40 to 80 mg / L, and the COD Mn} was 5 to 15 mg / L. TN (total nitrogen) was in the range of 80 to 140 mg / L, and T-P (total phosphorus) was in the range of less than 1 mg / L. These were measured according to the regulations of JIS K0102.

Further, when each raw water was analyzed by the apparatus (liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) apparatus) described in JP-A-2018-69227 and the conditions, each raw water contained ferrocyanide. Compound ions, ferrocyanide ions, iron-carbonyl cyano complexes ([Fe (CN) ₅ (CO)] ^3- and [Fe (CN) ₄ (CO) ₂ ] ^2- ), and copper cyano complexes ([Cu (CN) 5 (CO) 2] 2-). ) ₃ ] It was confirmed that ^{3-) was contained.}

<Preliminary test example>
Using each raw water, the resolution of cyanide ions by adding hydrogen peroxide to the raw water and the residual amount of hydrogen peroxide in the treated water (reaction solution) were confirmed.

(Preliminary test examples 1 to 9)
The raw water was placed in a 500 mL beaker, the pH of the raw water was adjusted to 6.8 with hydrochloric acid, and then a hydrogen peroxide solution having a concentration of 35% by mass was added to the raw water. As for the amount of hydrogen peroxide solution _{added, the concentration of H 2} O ₂ added in the raw water was 1.0 times, 3.0 times, and 5.0 times the measured value of the F-CN concentration in the raw water. The amount was set to After adding the hydrogen peroxide solution to the raw water and reacting with hydrogen peroxide for 15 minutes, the reaction solution was filtered through a filter paper (Type 5C) to obtain a filtrate. The concentration of cyanide ion in this filtrate is pretreated by the "heat distillation method (hydrogen cyanide generated in the presence of zinc acetate at pH 5.5)" specified in 38.1.1.2 of JIS K0102. , JIS K0102, measured according to "4-pyridinecarboxylic acid-pyrazolone absorptiometry" specified in 38.3. In addition, the concentration of hydrogen peroxide (H ₂ O ₂ ) remaining in the filtrate is measured by a simple reflection photometer (product name "RQ Flex", test paper "Reflect Quant Peroxide Test", Kanto Chemical Co., Inc. Was measured using. The results of Preliminary Test Examples 1 to 9 are shown in Table 2 together with the test conditions.

In Preliminary Test Examples 1 to 9, as a result of adding hydrogen peroxide 1.0 times, 3.0 times, and 5.0 times the F-CN concentration of each raw water, the cyanide ion concentration in the filtrate was added. It was confirmed that all of them were less than 1 mg-CN / L. On the other hand, the concentration of hydrogen peroxide (residual concentration) in the filtrate was higher as the amount of hydrogen peroxide added was increased. From the results of Preliminary Test Examples 1 to 9, the amount of hydrogen peroxide added to the raw water is about 1.0 to 4.0 times (preferably 1.0 to 3.0 times) the F-CN concentration in the raw water. If so, the cyanide ion can be reduced to less than 1 mg-CN / L, and the concentration of residual hydrogen peroxide in the reaction solution obtained after the addition of hydrogen peroxide _{is suppressed to 10 mg-H 2} O ₂ / L or less. I found that I could do it. From the results of this preliminary test example, it was decided to carry out the subsequent tests with the amount of hydrogen peroxide added to the raw water as a guideline of 1.5 times the F-CN concentration in the raw water.

<Test example>
For each of the above raw waters, a test was conducted in which hydrogen peroxide and a copper (I) compound were used to attempt a treatment for removing the cyan component of the raw water. Test Example 1 (Test Examples 1.1 to 1.9) uses the raw water 1, and Test Example 2 (Test Examples 2.1 to 2.12) uses the raw water 2. Test Example 3 (Test Example 3. In 1-3.12), the raw water 3 was used. In Test Examples 1 to 3, the test was performed according to the following processing procedure.

(Processing procedure)
The raw water was placed in a 500 mL beaker, the pH of the raw water was adjusted to 6.8 with hydrochloric acid, and then 35% by mass hydrogen peroxide solution was added to the raw water and reacted for 15 minutes to obtain a reaction solution. The amount of hydrogen peroxide solution added was such that the _{concentration of H 2} O ₂ added to the raw water was 1.5 times the measured value of the F-CN concentration in the raw water. Further, in Test Examples 2.4 to 2.12 and 3.4 to 3.12, the peroxidation that may remain in the reaction solution after the addition of the hydrogen peroxide solution is further added. To remove hydrogen, sodium sulfite was added and reacted for 15 minutes to obtain a reaction solution. For the addition of sodium sulfite, an aqueous solution of sodium sulfite having a concentration of 30% by mass was used, and the amount added was 75 mg / L as _{Na 2} SO _3.

Next, copper (I) oxide was added as a copper (I) compound to the above reaction solution and reacted for 15 minutes to obtain a reaction solution. Regarding the amount of copper (I) added, the concentration of Cu added in the raw water was 1.1 to 1.6, 2.1 to 2.9, and 3. In 1 to 3.9, the range was 1.0 to 4.0 times, and in other test examples, the range was 1.0 to 4.0 times. To add copper (I) oxide, copper (I) oxide is dissolved in 1 + 1 hydrochloric acid (pure water: 35% by mass hydrochloric acid = 1: 1 (mass ratio) mixed solution), and 5% by mass as copper (Cu). A copper (I) oxide solution adjusted to a concentration was used.

Further, when copper (I) oxide was added to the above reaction solution, Test Examples 1.4 to 1.6, 2.7 to 2.9, 3.7 to 3.9, and Test Example 1.9 were added. , 2.12, and 3.12, a quaternary ammonium compound, didecyldimethylammonium chloride (DDAC), was added along with the copper (I) oxide solution. Regarding the amount of DDAC added, the concentration of DDAC added in the raw water was 1.4 to 1.6, 2.7 to 2.9, 3.7 to 3. In 9 and 3.12, the range was 1.0 to 4.0 times, and in Test Examples 1.9 and 2.12, the range was 1.0 to 4.0 times.

To the reaction solution obtained as described above, 1 mg / L of an anionic polymer flocculant (product name “KEA-730”, manufactured by Nippon Steel Environment Co., Ltd.) was added. The reaction solution after adding the anionic polymer flocculant was allowed to stand, and the insoluble cyanide compound generated in the reaction solution was separated by precipitation to solid-liquid separation, and the obtained supernatant water was used as treated water. For this treated water, the concentration of total cyanide in the treated water is pretreated with "total cyanide (hydrogen cyanide generated at pH 2 or less)" specified in 38.1.2 of JIS K0102, and 38.3 of JIS K0102. It was measured according to the specified "4-pyridinecarboxylic acid-pyrazolone absorptiometry". Further, the concentration of copper (soluble copper) in the treated water was measured according to the ICP emission spectroscopic analysis method specified in 52.4 of JIS K0102. All of the above reactions were carried out under stirring using a magnetic stirrer.

The results of Test Examples 1 to 3 are shown in Table 3 together with the test conditions.

In Test Examples 1.1 to 1.6, 2.1 to 2.9, and 3.1 to 3.9, the amount of hydrogen peroxide added to the raw water was 1.5 times the F-CN concentration in the raw water. In addition, by controlling the amount of the copper (I) compound added to the raw water within the range of 1.0 to 4.0 times the cyano complex concentration in the raw water, the concentration of total cyanide was sufficiently reduced. At the same time, it was possible to obtain treated water in which the residual amount of copper was suppressed. In addition, Test Examples 2.1 to 2.3 and 3.1 to 3.3 in which sodium sulfite was not added after hydrogen peroxide was added, and Test Examples 2.4 to 2.6 in which sodium sulfite was added, and In 3.4 to 3.6, the concentration of total cyanide in the treated water and the residual concentration of copper were about the same. Therefore, the amount of hydrogen peroxide added was set from the F-CN concentration in the raw water. It was confirmed that the problem that the removability of the cyan component due to the residual hydrogen peroxide was lowered could be suppressed. Further, in Test Examples 1.4 to 1.6, 2.7 to 2.9, and 3.7 to 3.9, the quaternary ammonium compound was added to the cyano complex concentration in the raw water together with the copper (I) compound. It was confirmed that the concentration of total cyanide in the treated water and the residual amount of copper could be further reduced by adding the amount in the range of 1.0 to 4.0 times that of the above.

On the other hand, in Test Examples 1.7 and 2.10, the amount of the copper (I) compound added was as small as 0.5 times the cyano complex concentration in the raw water, and in Test Example 3.10, copper (I) was added. ) Since no compound was added, the ability to remove the cyan component from the raw water was not sufficient.

Further, in Test Examples 1.8, 1.9, 2.11, 2.12, 3.11, and 3.12, the amount of the copper (I) compound added was 4.0 times the cyano complex concentration in the raw water. (It was about 6.7 times or 7.5 times), the concentration of total cyanide in the treated water decreased, but the concentration of copper remaining in the treated water increased. Therefore, in Test Examples 1.8, 1.9, 2.11, 2.12, 3.11, and 3.12, further treatment for treating the copper remaining in the treated water was required.

From the results of the above test examples, according to the water treatment method of the embodiment of the present invention described above, the cyanide ion in the raw water can be sufficiently decomposed and the cyano complex in the raw water is sufficiently sparingly solubilized. However, it was found that treated water with suppressed copper residue can be obtained. Therefore, according to the water treatment method of one embodiment of the present invention described above, it can be expected that the steps and equipment for treating the residual copper in the treated water can be omitted, thereby reducing the equipment cost and the treatment cost. It can be expected to reduce and reduce the site area.

10, 12, 14 Water treatment device 22 First reaction tank 24 Second reaction tank 26 Solid-liquid separation device 32 Total cyanide concentration measurement device 34 Cyanide ion concentration measurement device 42 Hydrogen peroxide addition device 44 Copper (I) compound Addition device

Claims (5)

A water treatment method for treating water to be treated containing a cyanide ion and a cyano complex.
The step (A) of measuring the total cyanide concentration (mg-CN / L) and the cyanide ion concentration (mg-CN / L) in the water to be treated, and
The concentration (mg-H ₂ O ₂ / L) added to the water to be treated as H ₂ O ₂ in the water to be treated is a measured value (mg-CN / L) of the cyanide ion concentration in the water to be treated. In the step (B) of adding hydrogen peroxide in an amount 1.0 to 4.0 times that of hydrogen peroxide and reacting with the amount of hydrogen peroxide.
The concentration (mg-Cu / L) of Cu added to the reaction solution obtained in the step (B) as Cu is the cyanide ion concentration from the measured value of the total cyanide concentration in the water to be treated. The step (C) of adding and reacting the copper (I) compound in an amount 1.0 to 4.0 times the cyano complex concentration value (mg-CN / L) obtained by subtracting the measured value, and the reaction.
A step (D) of solid-liquid separation treatment of the reaction solution obtained in the step (C) and separation and removal of the poorly soluble substance produced in the step (C).
Water treatment method including. In the step (A), a certain amount of the water to be treated is used as a sample, the sample is pretreated, the pH is adjusted to 2 or less, heat aeration distillation is performed, and the cyanide ion electrode is used to prepare the sample in the water to be treated. Measuring the total cyanide concentration (mg-CN / L); and using a certain amount of the water to be treated as a sample, pretreat the sample, adjust the pH to 5 to 6, perform heated aeration distillation, and perform cyanide ion electrode. The water treatment method according to claim 1, wherein the cyanide ion concentration (mg-CN / L) in the water to be treated is measured using. The step (C) is obtained by contacting and reacting the reaction solution obtained in the step (B) with a hydrogen peroxide removing agent that reduces the concentration of the hydrogen peroxide remaining in the reaction solution. The water treatment method according to claim 1 or 2, which comprises a step (C1) in which the copper (I) compound is added to the reaction solution. In the step (C), the reaction solution obtained in the step (B) is 1.0 to 4.0 times the concentration value (mg-CN / L) of the cyano complex in the water to be treated. The water treatment method according to any one of claims 1 to 3, which comprises a step (C2) of further adding an amount of a quaternary ammonium compound and reacting it. The water treatment method according to any one of claims 1 to 4, wherein the copper (I) compound contains copper (I) oxide.

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