JPH08257560A - Wastewater collection method - Google Patents

Abstract

(57) [Summary] [Structure] Waste water is supplied to a reverse osmosis membrane device for desalination and separated into concentrated water and permeated water. An electric deionized water producing device is provided in the latter stage of the reverse osmosis membrane device, and the permeated water is supplied to the desalting chamber and the electrode chamber of the device, and the concentrated water is supplied to the concentrating chamber of the device to adjust the voltage. Demineralization is performed by applying the voltage. The demineralized water obtained is collected and reused. [Effect] Since the concentrated water flowing out from the reverse osmosis membrane device is supplied to the concentrating chamber, the concentrated water flowing through the concentrating chamber has a high ion concentration, so that the electric resistance of the concentrating chamber is reduced and is lower than the conventional one. Demineralized water (recovered water) with good water quality can be obtained by the applied voltage, which can contribute to reduction in power consumption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater recovery method for treating wastewater such as industrial wastewater in the semiconductor manufacturing industry, plating industry and the like for reuse.

[0002]

2. Description of the Related Art Collecting and reusing wastewater such as industrial wastewater not only saves water resources but also helps prevent environmental pollution, and recovery and reuse of wastewater is technically important. Problem.

Generally, industrial wastewater contains acids and salts, and therefore, it is necessary to perform desalting treatment when recovering wastewater. Conventionally, industrial wastewater is first passed through a reverse osmosis membrane device for desalination treatment, and then the permeated water is passed through an ion exchange resin device to remove salts that cannot be completely removed by the reverse osmosis membrane device. The device was sufficiently removed to obtain demineralized water having a certain water quality, and the demineralized water was reused as recovered water.

[0004]

As described above, the conventional waste water recovery method is one in which an ion exchange resin device is provided after the reverse osmosis membrane device for desalination treatment. In the salt treatment, when the ion exchange resin is saturated with ions, it is necessary to regenerate it with an acid and alkali aqueous solution, and the treatment operation is troublesome.
While the regeneration process is being performed, the operation of the apparatus is stopped, and there is a drawback that the processing efficiency is unavoidably reduced.

In order to solve the above-mentioned drawbacks, the present inventors have replaced the ion exchange resin device with an electric deionized water producing device (hereinafter referred to as EDI) which does not require regeneration by chemicals.
I considered using. Such a reverse osmosis membrane device and E
Desalination systems that combine DI are known in the art. Therefore, the present inventors have attempted to perform wastewater recovery using an existing desalination system configured by combining a reverse osmosis membrane device and EDI.

The existing desalination system is as shown in FIG. 3, but this system is intended only to obtain pure water or ultrapure water from raw water such as city water, industrial water and river water. Therefore, although it is known as a pure water or ultrapure water production system, it is not known as a waste water recovery system. That is, there has not been an example in which the pure water or ultrapure water production system of FIG. 3 is applied to wastewater collection, and the present inventors made an attempt to apply the system to wastewater collection for the first time.

In FIG. 3, 1 is a reverse osmosis membrane device, and 2 is E.
It is DI. The procedure for collecting wastewater using the pure water or ultrapure water production system consisting of these two devices will be described below.

First, the wastewater (raw water) is passed through the reverse osmosis membrane device 1 to form concentrated water (hereinafter referred to as RO concentrated water) and permeated water (hereinafter, referred to as RO concentrated water).
RO permeate) and then the RO permeate is passed through EDI2 for sufficient desalting. EDI2 forms a desalination chamber by filling an ion exchanger such as an ion exchange resin between a cation exchange membrane and an anion exchange membrane, and a concentration chamber is provided on both outer sides of the desalination chamber. It has a structure in which a plurality of concentrating chambers are alternately arranged in parallel between the positive electrode and the negative electrode. In the figure, 3 is a desalting chamber, 4
Indicates a concentrating chamber and 5 indicates an electrode chamber.

Although only one desalting chamber 3 and one concentrating chamber 4 are shown in FIG. 3 for the sake of convenience, a plurality of these chambers are alternately arranged side by side, and the electrode chambers 5 are also provided on the positive electrode side and Each is provided on the negative electrode side.

In desalting the RO permeate with EDI2, the RO permeate as the water to be treated flows into the desalination chamber 3 of the EDI. When EDI is used, it is necessary to supply concentrated water to the concentration chamber 4 and electrode water to the electrode chamber 5, respectively. In this case, RO permeated water is used for both the concentrated water and the electrode water.

Thus, when RO permeated water is made to flow into the desalting chamber 3, the concentrating chamber 4 and the electrode chamber 5 while applying a voltage between both electrodes, impurity ions (that is, The impurity ions such as acid and salt which cannot be completely removed by the reverse osmosis membrane device 1 are removed, and the impurity ions are electrically sucked and move to the concentration chamber 4, and the concentrated water flowing in the concentration chamber 4 is removed. (Hereinafter referred to as EDI concentrated water) receives the moving impurity ions and flows out from the concentrating chamber 4.

In this way, the RO permeated water is desalted in the desalting chamber 3 to produce desalted water. According to the experiments conducted by the present inventors, it was found that the demineralized water produced using the above-mentioned device has a water quality necessary for use as recovered water that is recycled by recycling it to the production line. Was given.

However, during the study, it was found that there are some problems in adopting this conventional pure water or ultrapure water production system as a waste water recovery system.
First, there is the problem of power consumption. That is, when performing desalination by EDI, there is a problem in that since the treatment is performed while applying a voltage between both electrodes, the power consumption is large and the cost is increased. Two methods can be considered to solve this problem. The first method is to circulate the EDI concentrated water flowing out of the EDI concentration chamber 4 by circulating it to the inlet of the concentration chamber 4, thereby increasing the concentration of the EDI concentrated water in the concentration chamber 4.
This is a method for reducing the electric resistance of the concentrating chamber 4, and the second method is a method for reducing the electric resistance of the concentrating chamber 4 by adding a chemical such as acid or salt to the EDI concentrated water in the concentrating chamber 4. .

In either method, the electric resistance of the concentrating chamber 4 can be reduced, and as a result, the applied voltage when operating under the same current condition can be reduced. In that case, a tank for temporarily storing the EDI concentrated water and a pump for sending the EDI concentrated water from the tank for circulation are required, and the equipment becomes large,
There is a drawback that the operation management becomes complicated, and in the second method, new equipment for supplying chemicals such as acid and salt must be provided, and the equipment also becomes large. There are drawbacks, and neither method is an effective solution after all.

Next, as another problem caused by adopting the conventional pure water or ultrapure water production system as a waste water recovery system, there is a problem of treatment of RO concentrated water, EDI concentrated water and electrode water. Since the RO concentrated water flowing out from the reverse osmosis membrane device has a high ion concentration, if it is discharged as it is, it may cause a problem of environmental pollution. Further, when RO permeated water is supplied to the EDI concentration chamber and the electrode chamber, the EDI concentrated water and the electrode water flowing out from the EDI have a low ion concentration and can be discharged as they are, but in an environment where natural discharge is disliked. It is necessary to take some measures below.
As this measure, for example, evaporation to dryness can be considered. But,
When RO permeated water is supplied to the EDI concentrating chamber and the electrode chamber, since the EDI concentrating water and the electrode water have low ion concentrations as described above, a large amount of thermal energy is required to separate the solid content of the solute by evaporation to dryness. Is required and is not suitable for evaporation to dryness.

A third problem is the system recovery rate of water. That is, according to the experiments conducted by the present inventors, the system recovery rate of water is low in the desalination system shown in FIG. 3, and it is necessary to improve the system recovery rate of water in order to adopt the system as a waste water recovery system. I got the knowledge that there is.

Therefore, the present inventors have attempted to recover wastewater by adopting a system as shown in FIG. 4 for the purpose of improving the system recovery rate of water. This system recirculates the EDI concentrated water and the electrode water flowing out from the concentrating chamber 4 and the electrode chamber 5 to the raw water (drainage) side and circulates them. Although such a method could improve the system recovery rate of water to some extent, it was not yet sufficient.
Moreover, since the above-mentioned circulation system is adopted, the flow rate of the supply water supplied to the reverse osmosis membrane device is larger than that of the system shown in FIG. 3, and therefore there is a problem that the load on the device is also increased.

Thus, as a result of the study by the present inventors, when constructing a wastewater recovery system, problems specific to wastewater recovery accompany, and therefore, the conventional pure water or ultrapure water production system is used as it is. It proved impossible to apply it to wastewater recovery systems.

The present inventors have solved the drawbacks of the conventional waste water recovery system comprising a reverse osmosis membrane device and an ion exchange resin device, and have developed a conventional pure water or ultrapure water production system comprising a reverse osmosis membrane device and EDI. After conducting diligent research to solve the technical problems associated with applying to a wastewater recovery system and establish a new wastewater recovery system, RO concentrated water should be supplied to an EDI concentrating chamber and used as EDI concentrated water. Based on this finding, it was found that the above-mentioned drawbacks and problems can be solved all at once, and the present invention has been completed based on this finding.

Therefore, it is an object of the present invention to provide a wastewater recovery method capable of reducing the electric resistance of the EDI concentrating chamber to reduce the power consumption during operation.

The present invention also provides a waste water recovery method suitable for evaporation to dryness when EDI concentrated water and further electrode water is not naturally discharged.

Still another object of the present invention is to provide a wastewater recovery method with an improved system recovery rate of water.

[0023]

Means for Solving the Problems The present invention (1) is an electrical system in which waste water is supplied to a reverse osmosis membrane device for desalination, and permeated water flowing out of the device is provided in a subsequent stage of the reverse osmosis membrane device. While supplying the concentrated water flowing out of the reverse osmosis membrane device to the concentration chamber of the electric deionized water production device while supplying it to the deionization chamber of the electric deionized water production device, a voltage is applied to the deionization chamber. A method for recovering waste water, characterized in that the permeated water supplied to the above is desalted, and the resulting desalted water is recovered and reused, (2) Concentration of an electric deionized water production apparatus The concentrated water flowing out from the reverse osmosis membrane device is supplied not only to the chamber but also to the electrode chamber, and (3) the drainage recovery method described in (1) above, which flows out from the concentrating chamber of the electric deionized water manufacturing device. The concentrated water to be subjected to evaporation to dryness treatment step is sent to the above (1). Waste water recovery method, (4) The concentrated water flowing out from the concentrating chamber of the electric deionized water manufacturing apparatus and the electrode water flowing out from the electrode chamber are both sent to the evaporation dryness treatment step. The main point is the wastewater recovery method.

The present invention is mainly applied to the treatment for recovering industrial wastewater, but if the wastewater contains acid and salt,
Even if the wastewater does not belong to the industrial field, the present invention can be similarly applied to the recovery of the wastewater. When the wastewater is industrial wastewater, the present invention is particularly useful as a means for recovering inorganic wastewater, but the present invention is not limited to this, for example, even wastewater containing a small amount of organic matter of the present invention. Applicable.

Examples of the case of recovering the above-mentioned inorganic waste water include NH ₄ OH, HF, HN in a semiconductor manufacturing plant.
Examples thereof include recovery of waste water containing O ₃ , H ₂ SO _4, etc., recovery of waste water in the plating industry, etc. In these cases, the ion concentration in the waste water is not particularly limited in carrying out the present invention. The rate is preferably 500 μS / cm or less.

The present invention will be described below with reference to the drawings. FIG. 1 shows the wastewater recovery system of the present invention.
Is a reverse osmosis membrane device, and 12 is an EDI provided after the reverse osmosis membrane device 11. In FIG. 1, the EDI 12 has a desalting chamber 13 formed by filling an ion exchanger 30 such as an ion exchange resin between a cation exchange membrane and an anion exchange membrane. 14 are provided in the desalting chamber 1
3 and the concentrating chamber 14 are alternately arranged side by side and are arranged between the positive electrode and the negative electrode.
In the present invention, the EDI does not have to have a special structure, and a conventionally known structure can be used. In the figure, 15 is an electrode chamber, 16 is a drainage supply line, and 17 is RO.
Permeate supply line, 18 is RO concentrated water supply line, 19
Is a desalinated water outflow line, 20 is an EDI concentrated water outflow line,
Reference numeral 21 is an electrode water outflow line, and 22 is a heating device.

In recovering and reusing wastewater such as industrial wastewater, the wastewater is first supplied from the wastewater supply line 16 to the reverse osmosis membrane device 11 for desalination. Desalted R
O permeated water is fed through the RO permeated water supply line 17 to the EDI 12
Is supplied to the desalination chamber 13 and the electrode chamber 15.

On the other hand, the RO concentrated water separated from the RO permeated water in the reverse osmosis membrane device 11 is supplied to the concentration chamber 14 of the EDI 12 through the RO concentrated water supply line 18.

It should be noted that drainage water (raw water) or RO concentrated water can be supplied instead of supplying RO permeated water into the electrode chamber 15, but RO concentrated water is most preferably supplied as described later.

A voltage is applied between an anode and a cathode (not shown),
A direct current is passed in a direction perpendicular to the flow direction of the RO permeated water in the desalination chamber 13 (and further the RO concentrated water in the concentration chamber 14).

Impurity ions are removed from the water to be treated (RO permeated water) flowing in the demineralization chamber 13 when passing through the ion exchange resin packed bed in the demineralization chamber 13, whereby demineralized water is obtained, This demineralized water flows out from the demineralized water outflow line 19.

Impurity ions in the RO permeate removed in the desalting chamber 13 are electrically sucked and move to the concentrating chamber 14 through the cation exchange membrane or the anion exchange membrane. That is,
Among the impurity ions, cations are attracted to the cathode side and move to the concentration chamber 14 through the cation exchange membrane, and anions are attracted to the anode side and pass through the anion exchange membrane to concentrate chamber 1.
Move to 4. The concentrated water (RO concentrated water) flowing through the concentrating chamber 14 receives the moving impurity ions, and is ED as concentrated water (EDI concentrated water) in which the impurity ions are concentrated.
It flows out from the I concentrated water outflow line 20.

The electrode water (RO permeate water) flowing through the electrode chamber 15 flows out from the electrode water outflow line 21.

The demineralized water flowing out from the demineralized water outflow line 19 becomes recovered water for the purpose of the present invention, and the demineralized water is sent to a recovered water feeding line (not shown) for reuse. ED flowing out of the EDI concentrated water outflow line 20
I concentrated water is preferably subjected to evaporation to dryness treatment as described below.

In general, when desalting is performed using EDI, the concentrated water supplied to the inlet side of the concentrating chamber has an increased ion concentration while passing through the concentrating chamber, and the concentrated water flowing out from the outlet side of the concentrating chamber is considerably The ion concentration is high.
In the present invention, the RO concentrated water is used as the concentrated water to be supplied to the concentrating chamber 14 of the EDI 12, so that the concentrated water supplied to the inlet side of the concentrating chamber 14 originally has a high ion concentration. The concentrated water flowing out from the outlet side has an extremely high ion concentration. This ion concentration shows a dramatically higher value than the conventional method.

Since the EDI concentrated water flowing out from the EDI concentrated water outflow line 20 has a high concentration, it is a suitable condition for performing evaporation to dryness. Therefore, it is preferable to subject the EDI concentrated water to an evaporation to dryness treatment. This evaporation to dryness allows the solute to be discarded in a solidified state, which is also preferable from the viewpoint of preventing environmental pollution.

However, in the present invention, it is not essential to evaporate the EDI concentrated water to dryness, and the EDI concentrated water may be discharged without evaporating to dryness. However, if the ion concentration is high and it is not appropriate to release it as it is, it is necessary to take measures such as diluting with water or the like and then releasing it. Needless to say, even if the ion concentration is high, it can be discharged as it is if it is within the allowable range.

When the evaporation-drying treatment is carried out, the EDI concentrated water is sent to the heating device 22 where the evaporation-drying is carried out. The solid content obtained by evaporation to dryness (solute such as inorganic substances contained in EDI concentrated water) is recovered and discarded by a safe method.

On the other hand, the electrode water in this case has a relatively low concentration because RO permeated water is used, and is therefore not suitable for evaporating to dryness. Moreover, since the ion concentration is relatively low, there is no problem even if it is discharged as it is. Therefore, in the case of the present embodiment, the electrode water flowing out from the electrode water outflow line 21 is normally discharged naturally.

There are two electrode chambers, one on the positive electrode side and one on the negative electrode side.
Since there are only a plurality of chambers, the number of concentrating chambers is usually larger than that of the concentrating chamber. Therefore, the amount of electrode water flowing out from the EDI device is significantly smaller than the amount of concentrating water. In this case, the electrode water may be evaporated to dryness together with the concentrated water.

Since the present invention supplies RO concentrated water to the concentration chamber 14 of the EDI 12, the performance of the ion exchange membrane (cation exchange membrane, anion exchange membrane) is affected depending on the type of impurity ions in the RO concentrated water. May be affected. For example, when the RO concentrated water contains hardness components such as Ca ions and Mg ions, if the concentration is high, scale may be deposited on the ion exchange membrane. In this case, the scale can be removed by washing with an acid, but the scale deposition causes deterioration of the ion exchange membrane in the long term.

Therefore, the wastewater applied to the present invention does not contain a hardness component, or even if it contains RO, when the RO concentrated water is obtained, the concentration of the hardness component in the RO concentrated water causes scale precipitation in the EDI apparatus. It is preferable that the concentration be such that it does not occur. Here, it is difficult to accurately specify the concentration that does not cause scale precipitation, but for example, when the hardness component in RO concentrated water is 1 mg / L or more in terms of calcium carbonate, scale precipitation may occur. Can be said.

According to the present invention, all the RO concentrated water is supplied to the concentrating chamber 14 of the EDI 12.
The supply amount of the RO concentrated water may be excessive depending on the relationship with the flow rate when flowing into In this case, the excess is not sent to the EDI12, but is sent directly to the heating device 22 through a liquid sending line (not shown), where the EDI is added.
Twelve concentrating chambers 14 flow out and are heated together with the EDI concentrated water sent to the heating device 22 to evaporate to dryness.

In the present invention, RO concentrated water is supplied to the concentrating chamber 14 of the EDI 12, so that the ion concentration of the concentrated water flowing through the concentrating chamber 14 becomes high, which lowers the electric resistance of the concentrating chamber 14 and increases the conductivity. To be As a result, it is possible to obtain demineralized water having the same treated water quality even if the applied voltage is lowered as compared with the conventional method, and it is possible to reduce the power consumption.

Further, in the present invention, RO concentrated water is supplied as concentrated water in the concentrating chamber 14 of the EDI 12, so that FIG.
Unlike the wastewater recovery system shown in, RO permeated water is concentrated in chamber 1.
4 need not be supplied to the demineralization chamber 13
It is possible to increase the amount of RO permeated water supplied to the water, which means that the amount of water that can be effectively used as recovered water can be increased. As a result, the present invention provides the advantage of improving the system recovery of water.

In the embodiment of the present invention described above, RO
Although the concentrated water was supplied only to the concentration chamber 14 of the EDI 12, as shown in FIG. 2 as another embodiment of the present invention, RO concentrated water is supplied to both the concentration chamber 14 and the electrode chamber 15 of the EDI 12. Good.

In this embodiment, RO concentrated water is used as the concentrated water in the concentrating chamber 14, and the electrode chamber 15 is also used.
RO concentrated water is also used as the electrode water in. Therefore, the electrode water flowing out from the electrode water outflow line 21 has a high concentration and is suitable for the evaporation to dryness treatment. Therefore, normally, the electrode water is sent to the heating device 22 together with the EDI concentrated water, and the evaporation dry treatment is performed.

As in the case of the EDI concentrated water, it is not always necessary to subject the electrode water to the evaporation to dryness treatment.
Instead of evaporating to dryness, it may be diluted with water or the like (or, if the concentration is within an allowable range, diluted) and discharged.

As in this example, RO concentrated water was added to EDI1.
In the case of supplying to both the second concentrating chamber 14 and the electrode chamber 15, not only the concentrating chamber 14 but also the electric resistance of the electrode chamber 15 can be reduced, so that the RO concentrated water is concentrated in the concentrating chamber 14
There is an advantage that the electric resistance can be further reduced as compared with the case of supplying only to only. Therefore, from the viewpoint of reducing the power consumption, the present embodiment is preferable to the above-described embodiment in which the RO concentrated water is supplied only to the concentration chamber 14.

Further, according to the present embodiment, since the RO concentrated water is used as the concentrated water in the EDI 12 and the electrode water, it is possible to supply the entire amount of the RO permeated water to the desalting chamber 13, and thus the RO permeated water. The whole amount can be desalted and used effectively as recovered water. As a result, the system recovery rate of water can be increased in this embodiment as compared with the above-mentioned embodiment in which RO permeated water is supplied to the electrode chamber 15 as well as the desalting chamber 13.

[0051]

【Example】

Example 1 Waste water was processed by the waste water recovery system of the present invention shown in FIG. 1 to obtain recovered water. As the waste water, conductivity 100 μS / c prepared by dissolving CuSO ₄ and NiSO ₄ in pure water
m simulated drainage (hereinafter referred to as raw water) was used. Concentration of hardness component contained in this raw water (calcium carbonate conversion value)
Was measured, the lower limit of quantification (0.05 mg CaCO
₃ / L) or less.

As the reverse osmosis membrane device, a polyamide synthetic membrane SU-720 manufactured by Toray Industries, Inc. was used.
As the EDI, a 12-cell pair (having 12 desalting chambers) structure was used.

First, raw water was supplied to a reverse osmosis membrane device at a flow rate of 1 m ³ / h and treated under the conditions of a water temperature of 25 ° C. and a set recovery rate of 80%.

Next, RO permeate and R at the following flow rates
O concentrated water was supplied to the EDI, and the voltage shown in Table 1 was applied to perform desalting treatment. Flow rate of RO permeate supplied to the desalting chamber: 0.77 m ³ / h Flow rate of RO concentrated water supplied to the concentrating chamber: 0.2 m ³ / h Flow rate of RO permeating water supplied to the electrode chamber: 0 0.03 m ³ / h

The flow rates of the demineralized water, the concentrated water, and the electrode water flowing out from the EDI demineralizing chamber, the concentrating chamber, and the electrode chamber were the same as the flow rates at the time of supply to the above chambers.

The concentration of water obtained by mixing EDI concentrated water and electrode water (that is, water discharged outside the system other than demineralized water) was measured,
The concentration ratio was determined in relation to the concentration of raw water. Here, the concentration ratio is a value obtained by dividing the concentration of water discharged to the outside of the system (excluding demineralized water) by the concentration of raw water. By obtaining this concentration ratio, the water discharged to the outside of the system It can be determined how much the concentration has increased relative to the concentration of the raw water.

Further, the system recovery rate of water was obtained in relation to the flow rate of raw water and the flow rate of demineralized water. Further, the specific resistance of the obtained demineralized water was measured, and it was evaluated whether or not the water quality required for reuse as recovered water was provided. Table 1 shows the results.

Example 2 Waste water was treated by the waste water recovery system of the present invention shown in FIG. 2 to obtain recovered water. Example 1 except that the wastewater recovery system of FIG. 2 was used, the EDI applied voltage was as shown in Table 1, and the flow rate of each supply water was as follows.
Processing was carried out under the same conditions as above. Of RO permeate water supplied to the desalting rate: 0.8 m ³ / h concentration of RO concentrate supplied to the chamber flow: 0.17 m ³ / h of RO concentrate supplied to the electrode chamber flow: 0 0.03 m ³ / h

The flow rates of demineralized water, concentrated water, and electrode water flowing out from the EDI demineralizing chamber, the concentrating chamber, and the electrode chamber were the same as the flow rates at the time of supply to the respective chambers.

The concentration ratio was determined by the same method as in Example 1. The results are shown in Table 1. Table 1 also shows the system recovery rate of water and the specific resistance of demineralized water.

Comparative Example 1 Wastewater was treated by the wastewater recovery system shown in FIG. 3 to obtain recovered water. Points and ED using the wastewater recovery system in Fig. 3
The treatment was performed under the same conditions as in Example 1 except that the I applied voltage was changed as shown in Table 1 and the flow rate of each supply water was changed as follows. Flow rate of RO permeate supplied to the desalting chamber: 0.64 m ³ / h Flow rate of RO permeate supplied to the concentrating chamber: 0.14 m ³ / h Flow rate of RO permeate supplied to the electrode chamber: 0 0.02 m ³ / h

The flow rates of the demineralized water, the concentrated water, and the electrode water flowing out from the EDI demineralization chamber, the concentration chamber, and the electrode chamber were the same as the flow rates at the time of supply to the above chambers.

The concentration of water obtained by mixing RO concentrated water, EDI concentrated water and electrode water (that is, water discharged to the outside of the system other than demineralized water) was measured, and the concentration ratio was calculated in relation to the concentration of raw water. . The results are shown in Table 1. Also the system recovery rate of water,
The specific resistance of demineralized water is also shown in Table 1.

Comparative Example 2 Waste water was processed by the waste water recovery system shown in FIG. 4 to obtain recovered water. Points and ED using the wastewater recovery system of FIG.
The treatment was carried out under the same conditions as in Example 1 except that the I applied voltage was changed as shown in Table 1 and the flow rate of each supply water was changed as follows. Since this system circulates concentrated water and electrode water through the reverse osmosis membrane device, the flow rate of the supply water supplied to the reverse osmosis membrane device is the raw water flow rate plus the total circulation flow rate of the concentrated water and the electrode water. It will be the amount. Raw water flow rate: fed to 1.19 m ³ / h desalting: 1 m ³ / h total circulation flow rate of the concentrated water, and electrode water: 0.19 m ³ / h of reverse osmosis membrane supply water supplied to the apparatus flow rate RO permeate flow rate: 0.76 m ³ / h RO permeate flow rate supplied to the concentrating chamber: 0.16 m ³ / h RO permeate flow rate supplied to the electrode chamber: 0.03 m ³ / h

The flow rates of demineralized water, concentrated water, and electrode water flowing out from the EDI demineralizing chamber, concentrating chamber, and electrode chamber were the same as the flow rates at the time of supply to the above chambers.

The concentration of RO concentrated water (that is, water discharged to the outside of the system other than desalted water) was measured, and the concentration ratio was determined in relation to the concentration of raw water. The results are shown in Table 1. Table 1 also shows the system recovery rate of water and the specific resistance of demineralized water.

[0067]

[Table 1]

As shown in Table 1, the specific resistance of the demineralized water was 10 MΩ · cm in each of the Examples and Comparative Examples, and recovered water of good water quality was obtained. Also, from the table, it is understood that in the case of the example, the recovered water of the same water quality can be obtained at a lower applied voltage (EDI voltage) than the comparative example. Further, the examples show superior values in concentration ratio and water system recovery rate to the comparative examples.

[0069]

As described above, according to the present invention, waste water is supplied to the reverse osmosis membrane device for desalination treatment, and RO concentrated water flowing out from the reverse osmosis membrane device is discarded during the desalination treatment. Since the concentrated water is supplied to the EDI concentration chamber without being used as concentrated water, the concentrated water flowing through the concentration chamber has a high ion concentration, and as a result, the electrical resistance of the concentration chamber can be reduced. It is possible to obtain recovered water with good water quality even at a lower applied voltage. Therefore, according to the present invention, it is possible to reduce the power consumption during operation and to provide an economically advantageous wastewater recovery method.

Further, since the concentrated water flowing out from the concentrating chamber has a high concentration, it is suitable for evaporating the concentrated water to dryness.
The solute in concentrated water can be solidified and separated by performing evaporation to dryness treatment if necessary, and this can be disposed of by a safe method, thereby solving the problem of preventing environmental pollution.

Further, according to the present invention, it is not necessary to use RO permeated water as the concentrated water to be supplied to the concentrating chamber,
As a result, the amount of RO permeate supplied to the desalination chamber increases,
This means that the amount obtained as demineralized water (recovered water) increases, and as a result, the present invention has the effect of improving the system recovery rate of water.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a wastewater recovery system of the method of the present invention.

FIG. 2 is an explanatory diagram showing another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example in which a conventional pure water or ultrapure water production system is applied to a waste water recovery system.

FIG. 4 is an explanatory diagram showing another example in which a conventional pure water or ultrapure water production system is applied to a waste water recovery system.

[Explanation of symbols]

 11 Reverse Osmosis Membrane Device 12 Electric Deionized Water Production Device 13 Desalination Room 14 Concentration Room 15 Electrode Room

Claims (4)

[Claims] 1. Drainage is supplied to a reverse osmosis membrane device for desalination, and permeated water flowing out from the device is supplied to a desalination chamber of an electric deionized water production device provided at a subsequent stage of the reverse osmosis membrane device. Concentrated water that flows out from the reverse osmosis membrane device as well as supplied,
Supply the voltage to the concentration chamber of the electric deionized water production device, apply a voltage to perform desalination treatment of the permeated water supplied to the desalination chamber, and collect the obtained desalted water for reuse. A wastewater recovery method characterized in that 2. The method for collecting waste water according to claim 1, wherein the concentrated water flowing out from the reverse osmosis membrane device is supplied not only to the concentration chamber of the electric deionized water producing apparatus but also to the electrode chamber. 3. The waste water recovery method according to claim 1, wherein the concentrated water flowing out from the concentration chamber of the electric deionized water manufacturing apparatus is sent to the evaporation dry treatment step. 4. The waste water recovery method according to claim 2, wherein both the concentrated water flowing out from the concentrating chamber and the electrode water flowing out from the electrode chamber of the electric deionized water manufacturing apparatus are sent to the evaporation dryness treatment step. .