JP2003326263A - Treatment method for water by concentration electrolysis - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method for water by concentration electrolysis by which waste water treatment is performed at a drastically low cost compared to the conventional methods in the treatment of industrial drainage by electrolysis and to perform the waste water treatment of the industrial waste water at a low cost by using the electrolysis. <P>SOLUTION: The treatment method for water by concentration electrolysis is provided with a concentration process (103) for concentrating water to be treated to obtain a concentrated liquid to be treated and an electrolysis process (104) for electrolyzing the concentrated liquid to be treated after the concentration process, and preferably, with a dilution process (109) for diluting the treated liquid after the electrolysis with a separated water except the concentrated liquid to be treated which is obtained by the concentration process. Further, it is desirable that the method is provided with a biodegradation process for biologically degradation treating the water to be treated before the concentration process. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentrated electrolyzed water treatment method, and more particularly to a concentrated electrolyzed water treatment method for treating industrial wastewater economically and effectively.

[0002]

BACKGROUND OF THE INVENTION Industrial wastewater contains a wide variety of chemical substances in parallel with the progress of chemical technology, and it is difficult to effectively treat such industrial wastewater, and the conventional activated sludge method is sufficient. There are many things that can not correspond to.

For example, polyvinyl alcohol contained in industrial wastewater is a substance discharged from dyeing plants and the like, but it is poor in biodegradability and requires a long-term treatment of 20 days or longer if it is treated by the activated sludge method. Has been done.

Therefore, in the present situation, most of them are concentrated and incinerated, but a large amount of carbon dioxide is discharged by such incineration, which is regarded as a problem from the viewpoint of global environment conservation.

Such an organic substance having poor biodegradability is generally referred to as a hardly decomposable organic substance, and various methods have been proposed for treating wastewater containing the hardly decomposable organic substance.

[0006] Generally, the treatment method of wastewater containing hardly decomposable organic matter is roughly classified into a chemical oxidant addition method, a catalytic oxidation promotion method and an electrolysis method.

Hydrogen peroxide, manganese dioxide, peroxodisulfuric acid and the like are often used as the oxidizing agent used in the chemical oxidizing agent addition method. However, in general, the cost is high when chemicals are used, and at present, they are used only in limited cases.

Further, the Fenton method in which a divalent iron ion is added to hydrogen peroxide as a catalyst to generate a hydroxy radical and the organic matter is oxidatively decomposed is also famous. However, this feton treatment method requires high maintenance costs,
The disadvantage is that a large amount of sludge is produced.

Further, although an oxidation method using ozone, a method using ozone and hydrogen peroxide, etc. have been proposed, a large expense is required for equipment and running costs are high.

For example, as described in JP-A No. 11-309468, many methods of oxidizing an organic substance by adding an oxidizing agent in the presence of a metal catalyst have been disclosed. However, these methods are disadvantageous in that the oxidizing agent used is a deleterious substance and is difficult to handle, and the cost is high.

Further, there has been proposed a treatment method in which wastewater is oxidized and then irradiated with light in the presence of a semiconductor catalyst to photodecompose organic matter. In this method, a semiconductor catalyst such as titanium dioxide is irradiated with light to generate active oxygen on the surface of the catalyst and oxidize an organic substance. In such a method, when the wastewater is turbid or the wastewater contains a large amount of suspended matter, it is difficult to allow light to pass therethrough, and it is difficult to put it into practical use even though many related patents have been filed.

Further, in order to express a strong oxidizing power, many methods of electrochemically generating active oxygen or a water treatment method by electrolysis have been disclosed. For example, JP-A-6-
No. 254568 proposes a method in which a nascent active oxygen generated by causing a direct current to flow in an electrolyte solution or a waste solution made into an electrolyte solution reacts with an oxidizable substance in the waste solution to oxidize and decompose it. ing. In addition, Japanese Patent Laid-Open No.
JP-A-000-254650 proposes a water treatment method and a water treatment apparatus in which a diamond electrode is used as an anode and a gas diffusion electrode is used as a cathode, and oxygen-containing gas is supplied to generate a hydrogen peroxide. .

Generally, in the method using electrolysis, since the reaction occurs on the surface of the electrode, the investment of the device is expensive to secure a sufficient reaction area, the electricity consumption is large, and further maintenance is required. There is a problem that the cost becomes high.

[0014]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and particularly in treating industrial wastewater by electrolysis, wastewater treatment is effective at overwhelmingly low cost as compared with conventional methods. It is to provide a concentrated electrolyzed water treatment method that can be realized.

[0015]

The concentrated electrolyzed water treatment method of the present invention comprises a concentration step of concentrating water to be treated to obtain a concentrated liquid to be treated, and an electrolysis of the concentrated liquid to be treated after the concentration step. It is characterized by comprising an electrolysis step of treating.
The method of concentrating the water to be treated in the concentrating step is not particularly limited, and any method such as electrodialysis, freeze concentration, reverse osmosis membrane, and evaporation may be used. In the method of treating decomposed water, concentration is performed by evaporation. The method for concentrating the treated water by evaporation may be either a method using steam or a method using a heat pump.

Further, the power source for electrolysis in the electrolysis step of electrolyzing the concentrated liquid to be treated obtained in the concentration step is:
Any of direct current, alternating current, and pulsed power supply may be used, and the electrode is also selected from the group consisting of diamond, lead dioxide, tin dioxide, graphite, titanium, platinum, vanadium, gold, palladium, titanium, platinum, vanadium and palladium. One coated with one or more selected, one coated with niobium with one or more selected from the group consisting of platinum, vanadium and palladium, or niobium laminated with carbon atoms to form a diamond structure, The part may be mixed with boron, and a substance having arbitrary conductivity can be used.

More preferably, in the above-mentioned concentrated electrolyzed water treatment method, after the electrolysis step, the treated water after electrolysis is further diluted with separated water other than the concentrated liquid to be treated obtained during concentration. It is characterized by comprising a dilution step. The concentrated liquid to be treated in the diluting step is preferably in the range of 1 to 50% by volume in the total amount of the liquid in the diluting step from the viewpoint of reducing the treatment cost, but is not particularly limited.

More preferably, in the concentrated electrolyzed water treatment method, a biodegradation treatment step for biodegrading the water to be treated is provided before the concentration step. In this biodegradation treatment step, among the organic substances contained in the water to be treated, the decomposable organic substances are previously decomposed by the organism, and the energy of electrolysis is concentrated on the hardly decomposable organic substances. The biodegradation treatment step includes all treatment methods having a bio-oxidizing effect such as an activated sludge method, a biofilm method, and a carrier method.

Further preferably, in the concentrated electrolyzed water treatment method, separated water other than the concentrated liquid to be treated obtained in the concentrating step is separated from the electrolyzing step of electrolyzing the concentrated liquid to be treated. It is characterized by comprising a separated water electrolyzing step for electrolyzing.

For example, in the concentration step, when the wastewater containing a substance such as an organic acid having a boiling point lower than that of the organic matter contained in the wastewater is separated by distillation, a large amount of organic matter is involved in the separated water other than the concentrated water. included. In such a case, if many organic substances are contained in the separated water, it is preferable to electrolyze the obtained separated water. When both the concentrated water and the separated water contain organic substances, the concentrated water and the separated water may be separately subjected to electrolysis treatment. Furthermore, in the case where concentrated water contains concentrated organic matter or heavy metals with low volatility, the concentrated water may be treated as industrial waste and only the separated water containing organic matter may be electrolyzed. good.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will next be described based on preferred examples, but the present invention is not limited thereto. Figure 1
An example of an embodiment of the concentrated electrolyzed water treatment method of the present invention is shown in FIG. In FIG. 1, 101 is a raw water tank, 103 is an evaporative concentrator, 104 is an electrolyzer, and 108 is a distilled water storage tank. Reference numerals 102, 105 and 107 are communication pipes connected to each tank, 106 is a discharge pipe, and 109 is a distilled water supply pipe.

The water to be treated stored in the raw water tank 101 is sent to the evaporative concentration device 103 via the communication pipe 102. The concentrated liquid to be treated concentrated by the evaporative concentration device 103 is
Water is sent to the electrolysis tank 104 via the communication pipe 105. The water to be treated that has been electrolyzed in the electrolysis tank 104 is discharged as a discharge liquid through the discharge pipe 106.

On the other hand, the distilled water generated in the evaporative concentrator is
It is accumulated in the distilled water storage tank 108 via the communication pipe 107. Distilled water is sent to the discharge pipe 10 via the distilled water supply pipe 109.
6 may be used to dilute the discharged liquid, if necessary.

FIG. 2 shows a change in TOC (total organic carbon) concentration of polyvinyl alcohol with respect to time when the polyvinyl alcohol is decomposed by electrolysis.
From this figure, it can be seen that the TOC concentration decreases at a constant rate until the TOC concentration reaches about 200 mg / l, but thereafter the rate of decrease slows down.

In the case of decomposing organic substances by electrolysis, if the TOC concentration is about 100 mg / l or less, the treatment efficiency is extremely lowered. It is considered that this is because when the density of organic molecules that undergo oxidation reaction on the electrode surface becomes low, much energy is used for electrolysis of water in addition to oxidative decomposition of the molecules themselves.

In this embodiment, the TOC is about 650 m.
The polyvinyl alcohol waste water of g / l was concentrated by the evaporative concentrator 103 so that the volume became 1/10. In this case, the TOC of the concentrated water was about 6500 mg / l.

Next, the concentrated solution is electrolyzed in the electrolysis tank 104 through the communication pipe 105 for about 4 hours to reduce the TOC to about 200 mg / l, and the treated water after the electrolysis is treated. Was diluted with distilled water obtained from the evaporative concentration apparatus through the communication pipe 109, whereby treated water of about 20 mg / l could be obtained.

On the other hand, when the polyvinyl alcohol waste water with TOC of about 650 mg / l was directly electrolyzed, it was about 19 mg / l after about 8 hours of electrolysis. In this case, it takes a long time to obtain a low concentration, a large amount of electric power is required, and an extremely large amount of cost is required.

In this embodiment, since the electrolysis is carried out using the concentrated waste water, the oxidation efficiency per unit amount of electric power can be made higher than that of the conventional one. In addition, when electrolyzing the treated water, TOC100 with poor electrolysis efficiency is used.
Even in the case of mg / l or less, it is possible to easily omit the electrolysis treatment in the region where the electrolysis efficiency is poor by diluting with distilled water generated during the concentration.

As a rough estimate, the running costs of both the wastewater treatment of the present invention and the conventional wastewater treatment are about 2,988 yen / m per treated water, including the cost of performing the evaporative concentration when the evaporative concentration is performed. Whereas ^{3 is} required, in the case of only conventional electrolysis, 4,788 yen / m ^{3 is} required,
It has been found that the method of the present invention is economically extremely advantageous.

Further, in this embodiment, the amount of treated water imposed on the electrolysis step is one-tenth that of the conventional method, so that the initial cost of the electrolysis tank is greatly reduced and the evaporative concentration apparatus is reduced. Even considering the initial cost of
The cost is greatly reduced.

Next, FIG. 3 shows an example of another embodiment of the concentrated electrolyzed water treatment method of the present invention. In FIG. 3, 201 is a raw water tank, 202 is a biological treatment tank, 203 is an evaporative concentrator, 2
Reference numeral 04 is an electrolyzer, and 210 is a distilled water storage tank. Two
Reference numerals 05, 206, 207 and 209 are communication pipes connected to each tank, 208 is a discharge pipe, and 211 is a distilled water supply pipe.

The water to be treated stored in the raw water tank 201 is sent to the biological treatment tank 202 via the communication pipe 205, and the treated water subjected to the biodegradation treatment is passed through the communication pipe 206 to the evaporative concentration apparatus 203. Sent to. The evaporation concentration device 20
The water to be treated concentrated in 3 is sent to the electrolysis tank 204 via the communication pipe 207, and the water to be electrolyzed in the electrolysis tank 204 is discharged as a discharge liquid through the discharge pipe 208. It

On the other hand, the distilled water generated in the evaporative concentration apparatus 203 is stored in the distilled water storage tank 210 via the communication pipe 209. The distilled water is connected to the discharge pipe 208 via the distilled water supply pipe 211 and can be used for diluting the discharge liquid as needed.

In this example, about 9,000 mg /
In the biological treatment tank 202, 1 liter of polyvinyl alcohol was batch treated using MLSS 5,000 mg / l of activated sludge for about 3 days to obtain treated water of TOC of about 500 mg / l. This treated water is passed through the communication pipe 206,
Water was sent to the evaporative concentration apparatus 203, and evaporative concentration was performed so that the volume became about 1/10. The TOC of the concentrated treated water was about 5,000 mg / l. About 3.5% of the concentrated treated water is passed through the communication pipe 207 to the electrolysis tank 204.
The TOC can be lowered to about 80 mg / l by performing electrolysis for a period of time, and further diluted with distilled water supplied through the communication pipe 211 to about 9 mg / l.
It was possible to obtain treated water.

In the case of this embodiment, since the biological treatment is first performed, organic substances which are easily decomposed are removed by the biological treatment.
Therefore, the wastewater after concentration is efficiently electrooxidized. Furthermore, in this embodiment, it can be inferred that the biological treatment converts the organic matter into a structure that is easily decomposed, and synergistically affects the reduction of the electrolysis treatment time.

When the running cost in this case is roughly estimated, including the cost for biological treatment and the cost for evaporative concentration, it is about 1,900 yen / m ³ per treated water, which is 2,600 yen / m in the case of the above embodiment. It has become possible to further reduce the cost compared to m ³ .

FIG. 4 shows an example of another embodiment of the concentrated electrolytic water treatment method of the present invention. In FIG. 4, 301 is a raw water tank, 303 is an evaporative concentrator, 304 is a concentrated liquid storage tank,
307 is a distilled water storage tank, 309 is a distilled water electrolyzer,
210 is a distilled water storage tank. 302, 305, 30
Reference numerals 6 and 308 are communication pipes connected to the respective tanks, 310 is a discharge pipe, and 304 is a concentrated liquid storage tank.

The water to be treated stored in the raw water tank 301 is sent to the evaporative concentration apparatus 303 via the communication pipe 302,
The water to be treated concentrated by the evaporative concentrator 303 is connected to the communication pipe 3
The liquid is temporarily stored in the concentrated liquid storage tank 304 via 05, and industrial waste treatment is performed.

On the other hand, distilled water generated in the evaporative concentrator 303 is stored in a distilled water storage tank 307 via a communication pipe 306, and the distilled water is distilled water electrolysis tank 309 via a distilled water feed pipe 308. Sent to. The distilled water electrolyzed in the distilled water electrolysis tank 309 is discharged into the discharge pipe 31.
It is released through 0.

In this embodiment, the waste water of an electronic circuit manufacturing plant is mixed with acidic etching waste water and alkaline photoresist stripping waste water in a volume ratio of 1: 2,
Waste water from which suspension, precipitate and scum were separated was used.

This wastewater is multiplied by 10 to evaporative concentrator 303.
When the solution was distilled and concentrated in, the photoresist stripped material and metals such as copper and manganese were concentrated in the concentrated liquid to be treated. On the other hand, the distilled water generated in the evaporative concentration apparatus 303 is stored in the distilled water storage tank 307 via the communication pipe 306. The distilled water contains an organic acid and has a COD _Mn of 42.5 m.
It was g / l. Such distilled water exceeds the legal emission standards and cannot be discharged directly into rivers. Therefore, when the electrolysis treatment for about 30 minutes was performed in the distilled water electrolysis tank 309, the COD _Mn in the distilled water was 0.7 mg / l, and discharge was possible.

On the other hand, although the concentrated liquid was subjected to industrial waste treatment, the amount was reduced to 1/10 of the raw water, and the industrial waste treatment cost could be greatly reduced. Considering the costs of distillation concentration and electrolysis treatment. Was reduced to less than half the cost of conventional industrial waste treatment.

[0044]

The concentrated electrolyzed water treatment method of the present invention can significantly reduce the cost of wastewater treatment using electrolysis, and also enables rapid wastewater treatment, resulting in effective treatment of wastewater. can do.

[Brief description of drawings]

FIG. 1 is a flow chart schematically showing the steps of one embodiment of the concentrated electrolyzed water treatment method of the present invention.

FIG. 2 is a diagram showing the relationship between the time when polyvinyl alcohol is electrolyzed and the concentration of polyvinyl alcohol.

FIG. 3 is a flow chart schematically showing the steps of another embodiment of the concentrated electrolyzed water treatment method of the present invention.

FIG. 4 is a flow chart diagram schematically showing the steps of another embodiment of the concentrated electrolyzed water treatment method of the present invention.

[Explanation of symbols]

101, 201, 301: Raw water tank 103, 203, 303: Evaporative concentrator 104, 204, 304: Electrolyzer 106, 208, 310: Discharge pipe 108, 210: Distilled water storage tank 109, 211: Distilled water water pipe 202: Biological treatment tank 309: Distilled water electrolyzer

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) C02F 9/00 502 C02F 9/00 502M 503C 503 504A 504 504E 1/46 101C F term (reference) 4D028 AB00 BD00 4D034 AA26 BA01 CA12 4D061 DA08 DB18 DC11 EA03 EB01 EB04 FA02 FA15

Claims (5)

[Claims] 1. Concentrated electrolysis, comprising: a concentration step of concentrating treated water to obtain a concentrated treated liquid; and an electrolysis step of electrolyzing the concentrated treated liquid after the concentration step. Water treatment method. 2. The concentrated electrolyzed water treatment method according to claim 1, wherein the concentration is carried out by evaporation. 3. The concentrated electrolyzed water treatment method according to claim 1 or 2, wherein after the electrolysis step, the electrolyzed treatment liquid is separated from the concentrated liquid to be treated other than the concentrated liquid to be treated. A concentrated electrolyzed water treatment method comprising a diluting step of diluting with water. 4. The concentrated electrolyzed water treatment method according to claim 1, further comprising a biodegradation treatment step of biodegrading the water to be treated before the concentration step. Concentrated electrolyzed water treatment method. 5. The concentrated electrolyzed water treatment method according to any one of claims 1 to 4, separately from the electrolyzing step of electrolyzing the concentrated liquid to be treated, A concentrated electrolyzed water treatment method comprising a separated water electrolysis step of electrolyzing separated water other than the treatment liquid.