JP2004050096A - Method for treating wastewater containing harmful substance without producing sludge, and chemical agent used therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for effectively treating wastewater containing a harmful substance without producing sludge, and and also to provide a a chemical agent used therein. <P>SOLUTION: Copper is added in wastewater containing a harmful substance so that the content of copper in sludge becomes 10 mass % or more and alkali is added to adjust the pH of wastewater to 8 to 12. By this method, the harmful substance is removed from wastewater by the coprecipitation of the harmful substance along with a copper hydroxide and further formed sludge is treated in a copper recovery process to perform the treatment of wastewater containing the harmful substance without yielding sludge. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating wastewater containing no harmful substances without producing sludge, and a chemical used for the method.
[0002]
[Prior art]
Conventionally, as a method of removing harmful substances in wastewater, a method of adding an alkali such as calcium hydroxide to precipitate and separate as sludge has been generally used. In this case, it has been known that if the amount of sludge is increased by adding calcium hydroxide or the like, the amount removed by coprecipitation or the like increases accordingly, and the removal rate increases. However, sludge generated by such treatment contains harmful substances and has a low product value of calcium compounds, and has been disposed of as industrial waste. On the other hand, in Japan, the shortage of industrial waste disposal sites is a serious problem, which has led to a rise in disposal costs and is feared to affect industrial activities.
On the other hand, the concentration of copper in the etching effluent discharged from the copper etching treatment step is usually as high as 8 to 20%, but the concentration of chlorine which hinders the recovery and reuse of copper is also usually 5%. Up to 30%. Since there is no technology for recovering only copper from a waste liquid containing a large amount of such chloride ions, the etching waste liquid is generally taken as waste by an industrial waste treatment company and disposed of without being reused.
As described above, according to the conventional technology, a large amount of sludge is generated when harmful substances in wastewater are removed, and most of the sludge is disposed of at an industrial waste disposal site without being recovered and reused. Further, copper cannot be recovered and reused from an etching waste liquid containing concentrated copper chloride or etching cleaning water, and most of the copper has been disposed of at an industrial waste disposal site after a neutralization treatment. However, there is a strong demand for the reduction or recycling of waste from both environmental and economic perspectives, such as the problem of shortage of disposal sites and soaring disposal costs.
[0003]
[Problems to be solved by the invention]
It is an object of the present invention to provide a method of separating and removing harmful substances from wastewater containing harmful substances to be treated and a method of collecting and treating sludge generated by separation and removal without generating sludge outside the system. An object of the present invention is to provide a method for treating wastewater containing harmful substances to be treated, and a chemical used in these methods. In addition, as a means for generating sludge, harmful substances to be treated by using a high-concentration copper chloride-containing liquid prepared from a concentrated copper chloride-containing etching waste liquid that has not been conventionally disposed of and used as a processing agent. It is an object of the present invention to provide methods for treating wastewater containing substances, as well as the agents used in these methods.
[0004]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found the following and completed the present invention.
The wastewater containing the harmful substance to be treated is composed of the harmful substance produced by adding an alkali, the substance produced by reacting with the harmful substance in the treatment step, and the copper hydroxide produced in the subsequent treatment. Copper is present so that the copper content in the sludge to be produced is 10% by mass or more, that is, when the harmful substance contains no copper ion or copper compound, the copper content becomes 10% by mass or more. Copper compound is added, and when the harmful substance contains insufficient copper ions or copper compound, the insufficient amount of copper compound is added, and further, copper is contained in the harmful substance. When ions or copper compounds are sufficiently contained, harmful substances can be converted to copper by adding an alkali to adjust the pH of the wastewater to 8 to 12 without adding the copper compounds. Can be coprecipitated with the oxide, so that, by finding that it is possible to separate and remove harmful substances from the waste water, thereby completing the present invention. And, as a means for generating sludge, the copper content is reduced by using a high-concentration copper chloride-containing liquid prepared from a concentrated copper chloride-containing etching waste liquid, which was conventionally discarded and not used, as a treatment agent. The present invention has been completed by finding that the compound can be used as an additive or a modifier for adding a copper compound so that the content becomes 10% by mass or more.
Further, sludge having a copper content of 10% by weight or more separated and removed is returned to a smelter to recover copper, so that copper can be recovered without generating sludge as waste. The present inventors have found that wastewater treatment can be performed without generating sludge outside, and completed the present invention.
In addition, the present inventors have found that by using a copper etching waste liquid as a copper solution to be added, copper can be more economically recovered from a copper etching waste liquid that has been disposed of as industrial waste, and completed the present invention.
[0005]
That is, according to the present invention, the following method is provided.
(1) Copper is added to a wastewater containing a harmful substance to be treated by adding an alkali to adjust the pH of the wastewater to 8 to 12 so that the copper content in the sludge generated is 10% by mass or more. The harmful substances to be treated are characterized in that the harmful substances and the harmful substances generated in the treatment step are coprecipitated with the copper hydroxide by separating ions from the wastewater by adjusting the pH to the presence of ions. A method for treating wastewater containing substances.
(2) Copper is added to the wastewater containing harmful substances to be treated by adding alkali so as to adjust the pH of the wastewater to 8 to 12 so that the copper content in the sludge generated becomes 10% by mass or more. Presence of ions and adjustment to the pH, the harmful substances, harmful substances generated in the treatment step are coprecipitated with copper hydroxide, separated and removed from the wastewater, and copper or copper compound is separated from the separated and removed sludge. A method for treating wastewater containing harmful substances to be treated, wherein the wastewater is treated without discharging sludge containing harmful substances by recovering copper.
(3) In order to adjust the copper content in the initial wastewater so that the copper content in the sludge becomes 10% by mass or more, the copper solution to be added is a copper solution having a copper concentration of 1 to 30% by mass. A drug characterized by the fact that:
(4) A chemical added to adjust the copper content used in the method according to (3), wherein an etching waste liquid discharged from the copper etching step is used. 2. The method for treating wastewater containing harmful substances to be treated according to 2.
(5) The chemical according to (4), wherein the chemical is prepared by reducing the content of hydrogen chloride from a copper etching waste liquid.
(6) Copper hydroxide by adding or using an oxidizing agent until the pH of the waste water containing harmful substances to be treated or the pH of the waste water is adjusted to 8 to 12 by adding an alkali. (1) or (2), wherein a part or all of the wastewater is made of copper oxide.
(7) The method for treating wastewater containing harmful substances to be treated according to (6), wherein the oxidizing agent is a chlorine-based oxidizing agent containing 1 to 13% of available chlorine.
(8) The method according to (1) or (2), wherein sludge is added to wastewater containing harmful substances to be treated, and a part of the copper-containing sludge generated by insolubilization is returned to raw water. A method of treating wastewater containing harmful substances to be treated.
(9) The method for treating wastewater containing harmful substances to be treated according to any one of (1) and (2), wherein the alkali is sodium hydroxide.
(10) The method for treating wastewater containing a harmful substance to be treated according to any one of (1) and (2), wherein a coagulant is added to the wastewater containing the harmful substance to be treated.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The wastewater to be treated in the present invention refers to wastewater containing harmful substances to be treated. This harmful substance is not preferable for humans or animals such as heavy metal compounds such as copper, lead, zinc, cadmium, nickel, mercury, iron, chromium, cobalt, tin, bismuth, or heavy metal ions, chromic acid, and phosphate ions. Say substance.
In the method of the present invention, it is precipitated as copper hydroxide. However, it is not necessary that copper ions or copper compounds are always contained in the wastewater from the beginning. be able to.
The wastewater includes wastewater discharged from the metal refining process and heavy metal treatment process, sludge generated in the process, sludge used for treating these wastewater, and the like. Further, the present invention may be related to a comprehensive wastewater treatment for performing a comprehensive treatment for treating various kinds of wastewater collectively.
[0007]
Describing wastewater containing copper ions and copper compounds, wastewater generated from the copper smelting process, wastewater used for cleaning generated from the copper plate etching process, wastewater generated from the copper plating process, copper Sludge and sludge generated by these wastewater treatments, such as wastewater generated from a recycling process and various copper ion-containing washing wastewaters, can be mentioned. In particular, remarkable effects can be expected in wastewater containing copper ions. In this case, the concentration of copper in the water to be treated is not particularly defined.
In addition, wastewater containing metals other than copper is generated from various metal refining processes, various metal recycling processes, semiconductor manufacturing processes, wastewater discharged from electrolytic facilities and various manufacturing processes, washing wastewater, motor oil treatment, and the like. It may be drainage. In addition, wastewater contaminated by heavy metals and wastewater generated from soil treatment contaminated by heavy metals are naturally subject to treatment. The concentrations of the substances to be treated such as heavy metals do not pose any particular problems.
Further, the present invention can be applied to comprehensive wastewater treatment in which industrial wastewater and domestic wastewater are mixed and treated.
[0008]
In the wastewater treatment method of the present invention, the pH of the wastewater is adjusted to 8 to 12 by adding an alkali to the wastewater containing the harmful substance to be treated, and then the harmful substances and harmful substances generated in the treatment step are added. A sludge composed of the substance and the resulting copper hydroxide is produced.
It is important that the copper content in the sludge is 10% by mass or more. It is important that the copper content be 10% by weight or more. By setting the content of copper to 10% by weight or more, the wastewater can be treated as a copper compound-containing wastewater by a treating company, and the final copper recovery operation can be easily performed. Finally, a recovery operation for recovering copper can be easily performed.
[0009]
When the harmful substance in the wastewater to be treated does not contain copper ions or copper compounds, a copper compound is added so that the copper content becomes 10% by mass or more, and copper is contained in the harmful substance. If the ion or copper compound is insufficiently contained, add the insufficient amount of the copper compound, and further, if the harmful substance contains enough copper ion or copper compound, It is not necessary to add a copper compound. The copper compound can be appropriately used without any problem as long as it is a compound containing copper. In the case of adding, as long as it can be uniformly dissolved after the addition, it may be in the form of powder or lump, or may be an aqueous solution.
It is important to adjust the content of the copper compound in the initial wastewater and coprecipitate it as a sludge of copper hydroxide containing 10% by mass or more of copper in the sludge to be generated.
In the present invention, copper is present in the water to be treated. This serves as an agent for removing harmful substances (hereinafter, also simply referred to as a remover).
[0010]
In the treatment of the present invention, the concentration of copper after the addition of the copper solution is not particularly limited. However, in order to perform the treatment without changing the existing wastewater treatment system, the concentration is in the range of 100 to 3000 mg / L, preferably 100 to 1000 mg / L. It is.
[0011]
In the treatment of the present invention, as a preferred embodiment, there is a method of returning generated copper-containing sludge to a raw water tank in order to increase the copper content of sludge. According to this method, the pH of the raw water tank can be increased, and as a result, the amount of alkali added can be reduced. Furthermore, returning sludge can increase the amount of sludge.
[0012]
Conventionally, the concentration of copper in an etching effluent discharged from a copper etching process is usually as high as 8 to 20%, but the concentration of chlorine which hinders the recovery and reuse of copper is also usually 5 to 30%. And high. As described above, in the present invention, if the weight of copper contained in the sludge can be increased to 10% by weight or more, there is no problem in treatment, and there is no need to use an aqueous solution obtained from a pure copper compound. Use of this waste liquid leads to effective utilization of waste.
That is, the copper solution used as the removing agent in the present invention is to dissolve the copper compound in water, dissolve the crude copper with an acid, prepare it from waste such as copper etching waste liquid, dissolve copper-containing sludge with an acid, etc. Although it can be prepared by various methods, it is preferable to prepare it from a waste such as an etching waste liquid because it is the most economical and enables the effective use of the waste.
[0013]
When the etching waste liquid is used as a remover in the present invention, the etching waste liquid may be used as it is, but in that case, the amount of alkali used increases, so the hydrogen chloride content of the copper etching waste liquid is reduced and the pH is adjusted. It is preferable to use one that has been used. The pH to be adjusted at this time is not particularly limited, but usually the pH of the etching waste liquid is about −0.7, but it is preferable to adjust the pH to about 0 to 3, preferably about 0.5 to 2.
[0014]
As a method of adjusting the pH of the copper etching waste liquid, it may be carried out by adding the most common alkali, but in the case of copper chloride etching waste liquid, it may be carried out by heating the waste liquid to remove hydrogen chloride. It is possible. In this case, the heating temperature and time are such that the hydrogen chloride can be removed, but the heating temperature is 80 ° C. or more and the heating time is about 4 hours or less. The pH after heating will be 0.5-2.
[0015]
As another method of adjusting the pH of the copper etching waste liquid, a method of adding a copper compound and diluting with water can be used. The copper compound at this time is not particularly limited, and commercially available copper compounds such as copper sulfate, copper oxide, copper carbonate, and copper chloride may be used, but copper-containing sludge may be used.
[0016]
Since the removing agent (I) using or prepared by using the copper etching waste liquid of the present invention partially removes strongly acidic hydrogen chloride by the above-mentioned treatment, when used for wastewater treatment, the amount of alkali used is reduced. It becomes possible to remarkably reduce. Further, it is possible to avoid mixing of sodium chloride generated by the reaction between hydrogen chloride and alkali into sludge.
[0017]
Since the remover (I) prepared from the copper etching waste liquid of the present invention is a chemical having a reduced chlorine content, if it is used, the sludge to be produced is a copper sludge having a small chlorine content, which is easily used. And can be recycled for recycling.
[0018]
The removing agent of the present invention does not contain harmful impurities, and the copper contained in the removing agent precipitates by adjusting the pH to 8 to 12 and does not remain in the treated water. Alternatively, any wastewater that can react with harmful substances in the treatment process and contains harmful substances that coprecipitate with copper hydroxide can be treated. For example, a heavy metal-containing wastewater that produces a precipitate of heavy metal hydroxide by adjusting the pH to 8 to 12, a wastewater containing a substance that forms an insoluble precipitate with copper, and a substance that adsorbs to the copper hydroxide precipitate It can be used for wastewater treatment.
[0019]
In the practice of the present invention, it is preferable to use an oxidizing agent in combination. By using an oxidizing agent together, copper can be precipitated as an oxide instead of a hydroxide, so that the amount of generated sludge can be reduced and the copper content in the sludge can be increased. The timing of addition of the oxidizing agent is not particularly limited, and the oxidizing agent is present in the wastewater, and then alkali is added to the wastewater to precipitate copper ions contained in the water as insoluble copper oxide. It may be recovered, or by adding an alkali to the wastewater to be treated and causing an oxidizing agent to exist, copper ions contained in the water can be precipitated and recovered as insoluble copper oxide.
Which method is selected may be determined as appropriate.
[0020]
In the practice of the present invention, the presence of the oxidizing agent can be achieved by adding the oxidizing agent to the wastewater to be treated. If the wastewater to be treated contains sufficient oxidizing agent, there is no particular need to add it. The oxidizing agent is capable of converting a copper hydroxide to an oxide, and specific examples of such an oxidizing agent include hypochlorous acid, chlorous acid, perchloric acid and the like. And chlorine-based oxidizing agents such as water-soluble salts, hydrogen peroxide, ozone and the like. Among them, it is convenient and preferable to use a chlorine-based oxidizing agent having an effective chlorine amount (in terms of Cl) of 1 to 13% from the viewpoint of economy. As the chlorine-based oxidizing agent, agents such as the above hypochlorous acid, chlorous acid, chloric acid, perchloric acid, etc. and their water-soluble salts may be used, but chlorine gas is introduced into the sodium hydroxide solution. Alternatively, a product prepared in this manner may be used.
[0021]
As the oxidizing agent to be added to the wastewater to be treated in the present invention, it is preferable to use a chlorine-based oxidizing agent having an effective chlorine amount of 1 to 13%, and the amount is an amount capable of converting copper ions in water to copper oxide. In general, the amount of effective chlorine (Cl) contained in the drug is 0.1 to 50 mol, preferably 0.1 to 20 mol, more preferably 0.1 to 10 mol per mol of copper. Is the amount
[0022]
As the alkali for insolubilizing copper dissolved in the water to be treated, conventionally known ones such as sodium hydroxide, calcium hydroxide, magnesium hydroxide, potassium hydroxide, sodium carbonate, and ammonium hydroxide are used. In the present invention, it is particularly preferable to use sodium hydroxide from the viewpoint of recovering copper.
[0023]
The amount of the alkali added to the water to be treated may be any amount at which the copper dissolved in the water is insolubilized, and generally, the pH of the treated water is controlled in the range of 8 to 12, preferably 9 to 11. Such an amount may be used.
[0024]
In the operation of the present invention, when only an alkali is simply added to the water to be treated, copper generally only produces a hydroxide, but when an oxidizing agent is present, copper oxide is produced and insolubilized. Can be separated and recovered from the liquid with a reduced amount of sludge.
[0025]
The time when the oxidizing agent is added to the water to be treated is not particularly limited, and before adjusting the pH to 8 to 12 by adding an alkali, the pH is adjusted to 8 to 12 at the same time as the addition of the alkali or by adding an alkali. Could be later. However, when the pH of the water to be treated is acidic of 4 or less, it is preferable to adjust the pH to 4 or more by adding an alkali before adding the oxidizing agent.
[0026]
The preferred preparation of the agent of the present invention (removal agent (I)) is as follows. A high-concentration copper chloride waste liquid (concentrated copper etching waste liquid) is heated at 80 ° C. or higher to remove hydrogen chloride to prepare. The heating time is until almost all of the hydrogen chloride is removed, and is within about 4 hours. The pH of the liquid after removing hydrogen chloride is 0.5 to 2.0. Water may be added to this liquid in consideration of operability.
[0027]
In the present invention, a coagulant is preferably used in combination. The flocculant in this case is one used for floc flocculation. Examples of such flocculants include calcium chloride, ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, and sulfuric acid. In addition to inorganic coagulants such as aluminum and polyaluminum chloride, cationic coagulants such as cationically modified polyacrylamide, dimethylaminoethyl polyacrylate, dimethylaminoethyl polymethacrylate, polyethyleneimine and chitosan , Nonionic organic coagulants such as polyacrylamide, and anionic organic coagulants such as polyacrylic acid, copolymers of acrylamide and acrylic acid, and salts thereof. In the present invention, it is preferable to add an organic coagulant, which requires only a small amount, in order to minimize impurities which cause problems when copper is recovered and reused. In this case, the coagulant may be added to the water to be treated either before or after the addition of the chemical, but generally, the coagulant is preferably added last.
[0028]
In the present invention, when the harmful substances are removed and the generated copper-containing sludge is returned to the raw water again, the amount of the returned sludge is 1 to 15%, preferably 4 to 10% of the sludge with respect to one volume of the raw water. , More preferably 6 to 8%. The specific gravity of the sludge to be returned is in the range of 1.00 to 1.10, preferably 1.01 to 1.08, and more preferably 1.02 to 1.05.
[0029]
The separation operation of the separated and removed sludge obtained so that the copper content in the sludge constituted by the harmful substances, the harmful substances generated in the treatment step, and the generated copper hydroxide is 10% by mass or more is a solid operation. Solved by liquid separation. As a solid-liquid separation method in this case, a conventional method, for example, filtration separation, centrifugation, pressure flotation separation, sedimentation separation, or the like is appropriately adopted according to the processing amount and processing time.
[0030]
The sludge having a copper content of 10% by mass or more in the sludge constituted by the harmful substance, the harmful substance generated in the treatment process, and the generated copper hydroxide recovers copper from the copper compound composed of copper or copper oxide. be able to. Copper oxide is reduced by yamamoto and reused as copper. The copper concentration of the treated water thus obtained can be 1.0 mg / L or less.
[0031]
【Example】
Next, the present invention will be described in more detail with reference to examples. The present invention is not limited to this embodiment.
[0032]
Reference Example 1
When 1 L of concentrated copper chloride waste liquid (pH of about -0.87, copper concentration of 127,300 mg / L) was heated at 80 ° C. or higher for 4 hours to remove hydrogen chloride, a pH 0.5 solution was obtained. Water was added to make up 1L. This solution is referred to as a removing agent (I).
[0033]
Example 1
The remover (I) was added to the wastewater having a zinc concentration of 20 mg / L to adjust the copper concentration to 3000 mg / L. An aqueous solution of sodium hydroxide was added thereto to adjust the pH to 10. 2 mL / L of sodium hypochlorite containing 12% of available chlorine was added, and the mixture was stirred for 40 minutes. 8 mg / L of a polymer flocculant AP120C was added to perform solid-liquid separation. The zinc concentration of the treated water was 0.007 mg / L, and the copper concentration was 0.846 mg / L. The content of copper in the sludge was 78.2%, and the content of chlorine was 0.3%. All of this sludge can be returned to Yamamoto for a fee. Therefore, it is possible to treat the wastewater without generating any sludge.
[0034]
Example 2
The remover (I) was added to the wastewater having a lead concentration of 20 mg / L to obtain treated water having a copper concentration of 3000 mg / L. An aqueous solution of sodium hydroxide was added thereto to adjust the pH to 10. 2 mL / L of sodium hypochlorite containing 12% of available chlorine was added, and the mixture was stirred for 40 minutes. 8 mg / L of a polymer flocculant AP120C was added to perform solid-liquid separation. The lead concentration of the treated water was 0.009 mg / L, and the copper concentration was 0.054 mg / L. The content of copper in the sludge was 77.1%, and the content of chlorine was 0.6%. All of this sludge can be returned to Yamamoto for a fee. Therefore, it is possible to treat the wastewater without generating any sludge.
[0035]
Example 3
The remover (I) was added to wastewater having a hexavalent chromium concentration of 20 mg / L to adjust the copper concentration to 3000 mg / L. The pH was adjusted to 10 with an aqueous sodium hydroxide solution. Thereafter, 8 mg / L of a polymer flocculant (AP120C, manufactured by Dyanitrix) was added, and solid-liquid separation was performed. The chromium concentration of the supernatant water was 0.33 mg / L, and the copper concentration was 0.063 mg / L. The copper content in the generated sludge was 54.3%, and the chlorine content was 4.7%. This sludge can be returned to Yamamoto for a fee.
[0036]
Example 4
10 mL / L of the removing agent (I) was added to the plating wastewater having a copper concentration of 23 mg / L, an iron concentration of 66 mg / L, and a nickel concentration of 1.36 mg / L, and the pH was adjusted to 10 with an aqueous sodium hydroxide solution. After that, a polymer flocculant (AP120C manufactured by Danitrix Co.) was added, and solid-liquid separation was performed. The copper concentration of the treated water was 0.07 mg / L, the iron concentration was not detected, and the nickel concentration was 0.09 mg / L. The copper content in the generated sludge was 61%, and the chlorine content was 1.9%. All of this sludge can be returned to Yamamoto for a fee. Therefore, it is possible to treat the wastewater without generating any sludge.
[0037]
Example 5
25 mL / L of the remover (I) was added to wastewater having a phosphorus concentration of 139 mg / L, and the pH was adjusted to 10 with an aqueous sodium hydroxide solution. After that, a polymer flocculant (AP120C manufactured by Danitrix Co.) was added, and solid-liquid separation was performed. The phosphorus concentration of the treated water was 2.3 mg / L. The copper content in the generated sludge was 65%, and the chlorine content was 2.3%. All of this sludge can be returned to Yamamoto for a fee. Therefore, it is possible to treat the wastewater without generating any sludge.
[0038]
【The invention's effect】
According to the present invention, from wastewater containing harmful substances to be treated, a method for separating and removing harmful substances and a method for collecting and treating sludge generated by separation and removal without generating sludge outside the system. A method for treating wastewater containing harmful substances to be treated is obtained. Also, the drug used in this method is obtained.
In addition, as a means for generating sludge, harmful substances to be treated by using a high-concentration copper chloride-containing liquid prepared from a concentrated copper chloride-containing etching waste liquid that has not been conventionally disposed of and used as a processing agent. A method for treating wastewater containing substances is obtained.

Claims (10)

Copper ions are present in the wastewater containing the harmful substances to be treated by adding alkali to adjust the pH of the wastewater to 8 to 12 so that the copper content in the sludge generated becomes 10% by mass or more. And adjusting the pH to include the harmful substances to be treated, wherein the harmful substances, harmful substances generated in the treatment step are coprecipitated with copper hydroxide, and separated and removed from the wastewater. Wastewater treatment method. Copper ions are present in the wastewater containing the harmful substances to be treated by adding alkali to adjust the pH of the wastewater to 8 to 12 so that the copper content in the sludge generated becomes 10% by mass or more. By adjusting to the pH, the harmful substances, harmful substances generated in the treatment step are co-precipitated with copper hydroxide, separated and removed from the wastewater, and copper or copper as a copper compound is separated from the separated and removed sludge. A method for treating wastewater containing harmful substances to be treated, wherein the wastewater is treated without discharging sludge containing the harmful substances. In order to adjust the copper content in the initial wastewater so that the copper content in the sludge becomes 10% by mass or more, the copper solution to be added is a copper solution having a copper concentration of 1 to 30% by mass. Characteristic drug. 3. A chemical added to adjust the copper content used in the method according to claim 3, wherein an etching waste liquid discharged from the copper etching treatment step is used. A method for treating wastewater containing harmful substances to be treated. 5. The chemical according to claim 4, wherein the chemical is prepared by reducing the content of hydrogen chloride from a copper etching waste liquid. Until the pH of the waste water containing harmful substances to be treated or the alkali is added to adjust the pH of the waste water to 8 to 12 or after the pH adjustment, the copper water is added or used in combination with an oxidizing agent. The method for treating wastewater containing harmful substances to be treated according to claim 1 or 2, wherein a part or all of the oxide is made of copper oxide. 7. The method for treating wastewater containing harmful substances to be treated according to claim 6, wherein the oxidizing agent is a chlorine-based oxidizing agent containing 1 to 13% of available chlorine. The sludge is added to wastewater containing harmful substances to be treated, and a part of the copper-containing sludge generated by the insolubilization is returned to the raw water. A method for treating wastewater containing harmful substances. The method for treating wastewater containing harmful substances to be treated according to any one of claims 1 and 2, wherein the alkali is sodium hydroxide. 3. The method for treating wastewater containing harmful substances to be treated according to claim 1, wherein a coagulant is added to the wastewater containing harmful substances to be treated.