JP3773187B2 - Desalination wastewater treatment method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a processing method and a processing apparatus for desalted waste water discharged from an apparatus for manufacturing ultrapure water for washing used in, for example, a semiconductor device manufacturing process, boiler water supply, and water for injection used in pharmaceutical manufacturing.
[0002]
[Prior art]
As demineralized water for cleaning an object to be cleaned, which is required to obtain an extremely clean surface such as a semiconductor wafer, a high-purity “ultra-high” in which fine particles, colloidal substances, organic substances, metals and ions are removed as much as possible. Water called “pure water” is used. The high-purity water described in the term “ultra-pure water” is not necessarily clearly defined, but in general, raw water is used using a coagulating sedimentation device, sand filtration device, activated carbon filtration device, etc. To obtain pre-treated water, and then using pre-treated water using a two-bed / three-column ion exchange device, a reverse osmosis membrane device, a mixed bed ion exchange device, a vacuum deaeration device, a precision filter, etc. The water from which impurities have been removed is called pure water or primary pure water, and this primary pure water is further put into primary pure water using an ultraviolet irradiation device, a mixed bed type polisher, an ultrafiltration membrane device, a reverse osmosis membrane device, etc. A material obtained by removing impurities such as fine particles, colloidal substances, organic substances, metals and ions as much as possible is called ultrapure water or secondary pure water.
[0003]
Such ultrapure water is manufactured by an ultrapure water manufacturing apparatus (hereinafter also referred to as “desalting apparatus”) 40 and supplied to a use place 50 for cleaning an object to be cleaned. Waste water discharged from the place of use 50 is sorted by conductivity and TOC, and the less polluted one is directly returned to the raw water storage tank 30 by the pipe 51. What is significantly contaminated is sent to the wastewater treatment apparatus 70 through the pipe 52. The moderately polluted wastewater is sent to a desalting means 60 that performs desalting, TOC decomposition, and the like through the drainage recovery pipe 53, and the desalted water is directly returned to the raw water storage tank 30 and collected. It is sent to the waste water treatment device 70. In the wastewater treatment apparatus 70, the wastewater is discharged after neutralization and reduction treatment of organic matter, nitrogen, phosphorus and the like (FIG. 6). In such an ultrapure water production apparatus 40, a large amount of desalted wastewater must be generated at the same time as high-purity desalted water, and this must be discharged. Cannot cope with water intake restrictions to prevent subsidence, and rising raw water and sewage charges.
[0004]
Due to such restrictions due to site conditions and discharge regulations, desalination wastewater is not provided with discharge facilities, but concentrated with an evaporator, and the concentrated solution is treated as it is or with a drum dryer, and the evaporated and dried product is sent to a waste disposal contractor. A closed-system wastewater treatment apparatus is also known. However, the conventional closed system type wastewater treatment apparatus has a problem that it consumes enormous energy because it uses an evaporation device such as an evaporator or a drum dryer. Especially in existing factories, when the amount of water used for washing increases, the amount of desalted wastewater increases, and it is necessary to add the above-mentioned evaporators to handle this, resulting in large equipment and operating costs. It becomes a burden. On the other hand, desalted wastewater contains calcium ions derived from well water and industrial water, and salts containing fluoride ions and sulfate ions derived from semiconductor device cleaning wastewater, and these salts have low solubility. For this reason, some insoluble salts are precipitated and suspended, and there is a problem that they cannot be treated with a normal desalting apparatus. For this reason, there has been a demand for a wastewater treatment method and a wastewater treatment apparatus that can further desalinate desalted wastewater in a suspended state where insoluble salt is deposited, and recover the treated water into raw water.
[0005]
As a solution to this, the applicant first treated the desalted wastewater supplied to the wastewater treatment device in advance with a polarity conversion electrodialyzer, then treated the treated water with a reverse osmosis membrane device, Provided a method for treating desalted wastewater, wherein the permeated water of the reverse osmosis membrane device is returned to the raw water supply side of the desalting device, and the concentrated water of the polarity switching electrodialyzer and the reverse osmosis membrane device is treated by the waste water treatment device. (Japanese Patent Application No. 2000-293601). According to this wastewater treatment method, desalted wastewater containing a high concentration of insoluble salt can be further desalted, and the water utilization rate is high and the amount of discharged wastewater is small. Especially in closed systems, treatment of evaporators and drum dryers is required. It is extremely effective in reducing water consumption and reducing energy consumption. And in the polarity conversion type electrodialysis apparatus used in this waste water treatment method, demineralized waste water having high conductivity is supplied to the electrode chamber in order to reduce the electrical resistance in the electrode chamber as much as possible.
[0006]
[Problems to be solved by the invention]
However, since this desalted wastewater has a high fluoride ion concentration, it corrodes the positive electrode of platinum-coated SUS material or platinum-coated titanium material used in the electrode chamber. The corrosive power of fluoride ions is so strong that normally usable electrodes can be dissolved in less than half a year for several years and the electrodes must be replaced. Such replacement work associated with the corrosion of the positive electrode generates cost for expensive electrode parts and increases wastewater treatment costs. Moreover, the apparatus must be stopped for electrode replacement work, which is not preferable for stable operation of the apparatus. Further, in the anode chamber, chloride ions in the raw water are converted into chlorine gas by the electrode reaction and are discharged along with the electrode water. Since this chlorine gas corrodes the surrounding metal and is harmful to the human body, after gas-liquid separation, it is necessary to install a separate scrubber on the gas phase side, which increases the installation space of the equipment, etc. There was a problem.
[0007]
Accordingly, an object of the present invention is to provide a desalination treatment method and a desalination treatment apparatus that can further desalinate desalination wastewater containing a high concentration of insoluble salt, and have a high water utilization rate and low discharge wastewater. Another object of the present invention is to provide a wastewater treatment method using a polarity-changing electrodialysis apparatus, which can suppress corrosion of the positive electrode of the apparatus and eliminate generation of chlorine gas in the anode chamber. The object is to provide a salt treatment method and a desalination treatment apparatus.
[0008]
[Means for Solving the Problems]
In such a situation, the present inventor has intensively studied, and as a result, the desalted waste water that has been supplied to the waste water treatment device is treated in advance with a polarity conversion type electrodialyzer, and then the treated water is treated with a reverse osmosis membrane device. In this case, the permeated water of the reverse osmosis membrane device is returned to the raw water supply side of the demineralizer, and the concentrated water of the polarity switching electrodialyzer and the reverse osmosis membrane device is treated with a wastewater treatment device, so that insoluble salts are formed. The desalted waste water in a suspended state that precipitates can be further desalted, and the treated water can be recovered into raw water, and the amount of discharged waste water can be reduced. It has been found that the use of at least a part of the concentrated water obtained from the osmotic membrane device can suppress the corrosion of the positive electrode of the device and the generation of chlorine gas in the anode chamber, thereby completing the present invention.
[0009]
That is, the present invention (1) treats a desalinated waste water having a calcium ion concentration of 10 to 800 mg / l and a fluoride ion concentration of 10 to 300 mg / l discharged from the desalting apparatus with a polarity conversion type electrodialyzer, The treated water is treated with a reverse osmosis membrane device to obtain permeated water and concentrated water, and the permeated water of the reverse osmosis membrane device is returned to the raw water supply side of the desalting device. The present invention provides a method for treating desalted wastewater using concentrated water obtained from the reverse osmosis membrane device as electrode water for a conversion-type electrodialyzer. By adopting such a configuration, it is possible to further desalinate desalted wastewater that is treated directly by a wastewater treatment device using a polarity conversion type electrodialyzer if it contains a large amount of low-solubility salt. The polarity conversion type electrodialyzer has a low removal rate of silica and organic substances, but these can be removed by the reverse osmosis membrane device, so the permeated water of the reverse osmosis membrane device can be recovered as the raw water of the desalination device, increasing the water utilization rate be able to. Further, since the concentrated water of the reverse osmosis membrane apparatus from which fluoride ions and chloride ions have been almost removed is used as electrode water, the positive electrode is not corroded and chlorine gas is not generated in the positive electrode chamber.
[0010]
Moreover, this invention (2) provides the processing method of the said desalted waste water in which the said electrode water circulates and is used. By adopting such a configuration, the same effects as those of the above-described invention can be obtained, the water utilization rate can be increased, the electrical conductivity of the electrode water can be improved, and the electric resistance of the electrode chamber can be reduced, so that power saving can be achieved.
[0011]
Moreover, this invention (3) provides the processing method of the said desalted waste water by which the said electrode water is adjusted to the electrical conductivity equivalent to or more than the said desalted waste water by addition of salts. . By adopting such a configuration, the same effect as that of the present invention can be obtained, and the electrical resistance of the electrode chamber can be further reduced.
[0012]
Moreover, this invention (4) provides the processing method of the said desalination waste_water | drain whose said electrode water is what added the acid, and was adjusted to pH 4 or less, or the scale generation inhibitor was added. . In the electrode chamber, there is an inflow of ions from an adjacent desalting chamber or concentrating chamber partitioned by a cation exchange membrane. In particular, in the cathode, the pH tends to increase due to the inflow of cations. In this case, if the electrode water is circulated, for example, the inflowed calcium ions may precipitate as hydroxide and block the flow path, but the addition of acid increases the solubility of the compound. Since scale generation can be prevented, stable continuous operation is possible. Further, by adding a scale generation inhibitor, scales such as calcium silicate can be dispersed by charge repulsion due to micelle formation or stabilized by chelation.
[0013]
In the present invention (5), the circulating electrode water of the above (2) is adjusted to pH 4 or less by adding an acid or to which a scale generation inhibitor is added, and the circulating electrode A part of the water provides a method for treating desalted waste water used as the concentrated water of the polarity-changing electrodialyzer. By adopting such a configuration, electrode water with high conductivity to which scale generation prevention ability is imparted is used as concentrated water, and therefore scale generation in the concentration chamber of the polarity conversion electrodialysis apparatus can be prevented.
[0014]
Moreover, this invention (6) makes the desalination waste_water | drain of calcium ion density | concentration 10-800 mg / l and fluoride ion density | concentration 10-300 mg / l discharged | emitted from a desalination apparatus to be treated water, A polarity-changing electrodialyzer that removes ionic impurities, a reverse osmosis membrane device that uses treated water of the polarity-changing electrodialyzer as treated water, at least the concentrated water and the reverse of the polarity-changing electrodialyzer Treatment of desalted waste water comprising a wastewater treatment device for treating the concentrated water of the osmosis membrane device and provided with a pipe for allowing the concentrated water of the reverse osmosis membrane device to flow into the electrode chamber of the polarity switching electrodialysis device A device is provided. By adopting such a configuration, the invention can be applied to a conventional ultrapure water production apparatus, and the invention of the wastewater desalination method can be reliably implemented.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, the desalinating waste water treatment apparatus in the first embodiment of the present invention will be described with reference to FIG. In FIG. 1, a desalinating wastewater treatment device 10a uses a desalted wastewater supplied from a desalted wastewater supply pipe 12 as treated water, and removes ionic impurities in the desalted wastewater. 1, a reverse osmosis membrane device 2 connected to the polarity-changing electrodialyzer 1 and a pipe 15, waste water for treating the concentrated water and electrode water of the polarity-changing electrodialyzer 1 and the concentrated water of the reverse osmosis membrane device 2 A processing device 6 is provided.
[0016]
As the polarity conversion type electrodialysis apparatus 1, a known one can be used, and the polarity of the electrode of the electrodialysis apparatus can be alternately switched every desired time, for example, every 15 to 20 minutes. That is, as shown in FIGS. 2 and 3, the cation exchange membrane C and the anion exchange membrane A are alternately arranged between the electrodes 1c, and the desalting chamber 1a and the concentration chamber 1b are alternately formed between the two membranes. By changing the polarity of the electrodes, that is, by converting the anode to the cathode and the cathode to the anode, the flow path that was the desalination chamber 1a or the concentration chamber 1b before the conversion is changed to the concentration chamber 1b after the conversion. Alternatively, the desalination chamber 1a is provided. When the lowermost stage is a cathode, it is in a reverse phase state (FIG. 2), when the anode is in a normal phase state (FIG. 3), and the flow of water is represented by X line and Y line, the polarity conversion type electrodialyzer 1 Since the flow of treated water and concentrated water is switched by switching the polarity, the X line becomes the treated water line when in the reverse phase, the concentrated water line when in the normal phase, and the concentrated water when the Y line is in the reverse phase. Line is treated water line during positive phase. For this reason, a three-way valve (not shown) is provided in each of the inflow side pipe and the outflow side pipe of the X line and the Y line, and the flow path is switched corresponding to the change of polarity. In particular, when the flow path is changed from the flow of concentrated water to the flow of treated water, it is possible to provide a process for purging the concentrated water remaining in the desalination chamber or the piping, which reduces the load on the reverse osmosis membrane device in the subsequent stage. This is preferable in that it can be reduced.
[0017]
In such a desalting process of the polarity conversion type electrodialysis apparatus 1, in addition to the conventional desalting, for example, a scale such as calcium fluoride attached on the ion exchange membrane surface in the concentration chamber 1b, If the polarity of the electrode is changed to make the concentration chamber 1b a desalination chamber 1a, calcium fluoride is decomposed into calcium ions and fluoride ions, the calcium ions pass through the cation exchange membrane C, and the fluoride ions are anion-exchanged. It moves to the concentration chamber 1b side through the membrane A, and the concentrated water is sent to the waste water treatment device 6 through the concentrated water outflow pipe 16 and the waste water pipe 191. In the desalting process, if scale adheres to the surface of the ion exchange membrane in the concentration chamber, the polarity of the electrode is changed again to make the desalination chamber a concentration chamber and the concentration chamber as a desalination chamber. The operation is continued by repeating. Since the operation of the polarity switching type electrodialyzer is usually performed in a neutral range, treated water whose pH is adjusted is supplied. In this way, if the polarity switching type electrodialysis apparatus is used, impurities in the desalted waste water that are significantly contaminated can be efficiently removed.
[0018]
In the desalination wastewater treatment apparatus 10a, the concentrated water pipe 17 of the reverse osmosis membrane apparatus 2 branches, one pipe 171 is connected to the electrode chamber 1c of the polarity-changing electrodialyzer, and the other pipe 172 is connected to the waste water pipe 191. Connected. In addition, the electrode water outflow pipe 19 of the electrode chamber 1c of the polarity switching type electrodialysis apparatus is connected to the waste water pipe 191. Further, the desalinized wastewater treatment apparatus 10a is further provided with a known salt addition means 7 for adjusting the conductivity of the concentrated water of the reverse osmosis membrane apparatus 2 which adds salts to the pipe 171 and flows into the electrode chamber 1c. Yes. The salt is not particularly limited as long as it does not contain fluoride or chloride, and examples thereof include sodium sulfate and sodium nitrate. Note that the salt addition means 7 may be omitted.
[0019]
The ultrapure water production system 100 includes a raw water storage tank 3, a desalting apparatus 4, and a desalted water use place 5. The raw water storage tank 3 and the desalinating apparatus 4 are connected by a pipe 11, and the desalting apparatus 4 and the desalted water use place 5 are The pipes 20 are connected to each other. The desalting apparatus 4 and the polarity switching type electrodialysis apparatus 1 are connected by desalting drainage supply pipes 12, 13, and 14, and waste water from the desalted water use place 5 that is significantly contaminated is directly connected to the pipe 18. It is sent to the waste water treatment device 6. The demineralizer 4 is a known ultrapure water production apparatus, for example, a pretreatment device comprising a coagulation sedimentation device, a sand filtration device, an activated carbon filtration device, etc., and a primary comprising an ion exchange device, a deaeration device, and a regenerative polisher. Examples include a pure water production apparatus and a secondary pure water production apparatus including an ultraviolet irradiation device, a mixed bed polisher, an ultrafiltration membrane device, a reverse osmosis membrane device, and the like.
[0020]
Next, a method of using the desalinating wastewater treatment apparatus 10a will be described. The ultrapure water obtained by treating the raw water with the desalting apparatus 4 is purified water from which impurities such as fine particles, colloidal substances, organic substances, metals and ions are removed as much as possible, and is supplied to the use place 5. On the other hand, the desalted waste water discharged from the desalting apparatus 4 is processed by the polarity conversion type electrodialysis apparatus 1. Examples of the desalination drainage discharged from the desalination apparatus 4 include regeneration waste liquid by chemicals discharged from the ion exchange apparatus through the pipe, regeneration waste liquids by chemical discharge from the regeneration type polisher through the pipe, and the like. . The desalted wastewater contains high concentrations of calcium ions derived from well water and industrial water, fluoride ions and sulfate ions derived from semiconductor device cleaning wastewater, and these salts have low solubility. Some insoluble salts are precipitated and suspended, and are conventionally sent directly to a wastewater treatment apparatus. The water quality of the desalted waste water has a calcium ion concentration of 10 to 800 mg / l and a fluoride ion concentration of 10 to 300 mg / l. Those whose calcium ion concentration or fluoride ion concentration is less than the above range can often be recovered by directly returning to the raw water without being treated by the polarity conversion type electrodialysis apparatus 1, and those exceeding the above range are polarity-converted. It is a concentrated waste liquid that cannot be treated even with the system electrodialysis apparatus 1, and must be treated with a wastewater treatment apparatus. When the desalted waste water is treated with the polarity conversion electrodialysis apparatus 1, ionic impurities such as calcium ions and fluoride ions are efficiently removed. The reason why the impurities in the desalted waste water, which is extremely contaminated in this way, is efficiently removed by the polarity changing type electrodialyzer is that the polarity of the power source of the electrodialyzer can be changed every desired time, as will be described later. is there. On the other hand, although silica and organic substances are difficult to remove, they are removed by a reverse osmosis membrane device at a later stage.
[0021]
Next, the treated water of the polarity switching electrodialyzer 1 is treated by the reverse osmosis membrane device 2. In the reverse osmosis membrane device 2, ionic impurities such as silica that are difficult to remove by the polarity switching electrodialysis device 1 are removed. A known reverse osmosis membrane device 2 can be used. The permeated water of the reverse osmosis membrane device 2 is collected in the raw water storage tank 3 by the pipe 9 and reverse osmosis.
A part of the concentrated water of the membrane device 2 is sent to the waste water treatment device 6 through the pipes 17 and 172, and the remaining part is sent to the electrode chamber 1 c of the polarity switching type electrodialyzer 1 through the pipes 17 and 171. Further, salts are added to the concentrated water supplied to the electrode chamber 1c through the pipe 171. The amount of salt added is not particularly limited, but for example, a concentrated water having a conductivity of 1,000 μS / cm is added so that the concentrated water has a conductivity equal to or higher than the conductivity of the raw water of 12,000 μS / cm. The amount is appropriately determined. By increasing the electrical conductivity, the electrical resistance of the electrode chamber 1c can be reduced, so that power saving can be achieved. In this example, the electrode water is sent to the waste water treatment device 6 through the electrode water outflow pipe 19 and the waste water pipe 191. A known apparatus can be used as the wastewater treatment apparatus 6, and examples thereof include an apparatus that performs treatments such as neutralization, organic substance reduction, and nitrogen and phosphorus reduction. The treated water of the waste water treatment device 6 is discharged.
[0022]
According to the first embodiment, raw water is treated in an ultrapure water production system to obtain ultrapure water having a high level of water quality, while being discharged from a desalinator used in the ultrapure water production system. In the past, desalted effluent that would be treated directly by a wastewater treatment device would be desalted by a polarity-changing electrodialyzer and a reverse osmosis membrane device. The permeated water of the osmosis membrane device can be recovered as raw water of the desalting device, and the water utilization rate is increased. Further, since the concentrated water of the reverse osmosis membrane apparatus from which fluoride ions and chloride ions have been almost removed is used as electrode water, the positive electrode is not corroded and chlorine gas is not generated in the positive electrode chamber. Therefore, the positive electrode replacement period is extended, the generation of costs associated with electrode replacement, etc. are suppressed, and the cost can be reduced. In addition, a facility for removing chlorine gas is not required, and space can be saved. Moreover, since the electrical conductivity of the electrode water can be maintained high, the electrical resistance of the electrode chamber can be kept low.
[0023]
Next, a second embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing a different form of the portion 90 in the frame of the two-dot chain line in FIG. 1. The same components as those in FIG. explain. That is, FIG. 4 is different from FIG. 1 in that the electrode water of the polarity switching type electrodialysis apparatus 1 is used for circulation and a drug addition means for adding a drug to the piping of the electrode water circulation system is provided. That is, in the desalination waste water treatment apparatus 10b of this example, the electrode water supply system of the polarity switching electrodialysis apparatus 1 is the circulation pipe 21, and the branch pipe 171 of the concentrated water pipe 17 of the reverse osmosis membrane apparatus is connected to the circulation pipe 21. At the same time, the medicine addition means 8 is arranged so that the medicine is added to the circulation pipe 21. The drug addition means 8 is a pH adjustment means or a scale generation inhibitor addition means for adjusting the pH to 4 or less, and these may be used alone or both. The pH adjustment means consists of a pump that adds an acidic solution such as sulfuric acid other than hydrofluoric acid and hydrochloric acid, and an acid solution storage tank. If necessary, a control system that maintains a constant pH using a pH meter and a controller is provided. May be. As the scale generation inhibitor addition means, a publicly known one composed of a pump for adding a scale generation inhibitor and a chemical reservoir can be used. Examples of the scale generation inhibitor include organic polymer compounds such as acrylic acid (co) polymers, maleic acid (co) polymers, and sulfonic acid (co) polymers; amine polymers, aminocarboxylic acids And a chelating agent such as gluconic acid and citric acid. The injection method and the injection amount of the scale generation inhibitor are not particularly limited and are appropriately determined.
[0024]
The desalination / drainage treatment device 10b of the second embodiment also has the same effect as the desalination / drainage treatment device 10a of the first embodiment, and further improves the conductivity of the electrode water and improves the electricity of the electrode chamber. Since the resistance can be reduced, power saving can be achieved. In addition, when the electrode water is circulated, for example, calcium ions that have flowed into the cathode chamber may precipitate as hydroxides and block the flow path. Since the solubility of the compound increases and scale generation can be prevented, stable continuous operation becomes possible. In addition, by adding a scale generation inhibitor, the scale can be dispersed by charge repulsion due to micelle formation or stabilized by chelation. Moreover, in the desalination waste water treatment apparatus 10b of 2nd Embodiment, installation of the chemical | medical agent addition means 8 may be abbreviate | omitted.
[0025]
Next, a third embodiment will be described with reference to FIG. FIG. 5 is a flow chart showing a different form of the portion 90 in the frame of the two-dot chain line in FIG. 1, and showing another form of FIG. 4. The same components as in FIG. The description will be omitted, and different points will be mainly described. That is, FIG. 5 is different from FIG. 4 in that a part of the circulating electrode water is used as the concentrated water of the polarity switching electrodialysis apparatus and the supply of the electrode water to the wastewater treatment apparatus is stopped. That is, the desalination wastewater treatment apparatus 10c is provided with a pipe 211 that connects the electrode water circulation pipe 21 and the desalination drainage supply pipe 14 (concentrated water supply pipe 14) of the polarity change type electrodialysis apparatus 1, and the electrode water circulation pipe 21 and the waste water. The pipe connecting the pipe 191 is omitted.
[0026]
The desalination waste water treatment apparatus 10c of the third embodiment also has the same effects as the desalination waste water treatment apparatus 10a of the first embodiment and the desalination waste water treatment apparatus 10b of the second embodiment. Since the electrode water with high conductivity to which scale generation prevention ability is imparted is used as the concentrated water, the generation of scale in the concentration chamber of the polarity conversion electrodialysis apparatus can be prevented. Moreover, in the desalinization waste water treatment equipment 10b of 3rd Embodiment, installation of the chemical | medical agent addition means 8 may be abbreviate | omitted.
[0027]
The desalination waste water treatment apparatus of the present invention is provided with a pipe for allowing the concentrated water of the reverse osmosis membrane apparatus to flow into the electrode chamber of the polarity switching type electrodialysis apparatus. This pipe is the first embodiment. In this way, even the branch pipe 171 of the concentrated water pipe 17 or the pipe constituted by the branch pipe 171 and the circulation pipe 21 as in the second and third embodiments may be used. Good. Moreover, in the polarity conversion type electrodialysis apparatus used in the desalinization waste water treatment apparatus of the present invention, the supply pressure of the electrode water is set to be equal to or higher than, for example, about 0.01 to 0.02 MPa. Is preferable in that it is possible to prevent leakage of fluoride and chloride contained in the concentrated water into the electrode chamber.
[0028]
【The invention's effect】
According to the present invention (1), conventionally, desalted waste water containing a large amount of low-solubility salt that can be directly treated by a wastewater treatment device can be further desalted by a polarity-changing electrodialyzer. The polarity conversion type electrodialyzer has a low removal rate of silica and organic substances, but these can be removed by the reverse osmosis membrane device, so the permeated water of the reverse osmosis membrane device can be recovered as the raw water of the desalination device, increasing the water utilization rate be able to. Further, since the concentrated water of the reverse osmosis membrane apparatus from which fluoride ions and chloride ions have been almost removed is used as electrode water, the positive electrode is not corroded and chlorine gas is not generated in the positive electrode chamber.
[0029]
In addition, according to the present invention (2), in addition to the same effects as the above invention, the water utilization rate is increased, the electrical conductivity of the electrode water is improved, and the electrical resistance of the electrode chamber can be reduced, thereby saving power. I can plan. Moreover, according to this invention (3), besides having the same effect as the said invention, the electrical resistance of an electrode chamber can further be reduced. In addition, according to the present invention (4), the conductivity of the electrode water is improved by the circulation use of the electrode water. On the other hand, there is a possibility that scales are deposited in the electrode chamber and block the flow path. Since the scale generation of the compound can be prevented or dispersed and removed by the addition of the scale generation inhibitor, stable continuous operation is possible. According to the present invention (5), since electrode water with high conductivity to which scale generation prevention ability is imparted is used as concentrated water, generation of scale in the concentration chamber of the polarity conversion electrodialyzer can be prevented. Moreover, according to this invention (6), it can apply to the conventional ultrapure water manufacturing apparatus, and the invention of the said desalination method of the waste_water | drain can be implemented reliably.
[Brief description of the drawings]
FIG. 1 is a flow diagram of a desalinating wastewater treatment apparatus according to a first embodiment.
FIG. 2 is a diagram for explaining the principle of desalting in a reverse phase state of a polarity switching type electrodialysis apparatus.
FIG. 3 is a diagram for explaining the principle of desalting in the normal phase state of the polarity switching type electrodialysis apparatus.
FIG. 4 is a flowchart of a desalinating waste water treatment apparatus in a second embodiment.
FIG. 5 is a flowchart of a desalinating waste water treatment apparatus in a third embodiment.
FIG. 6 is a flowchart of a desalinating wastewater treatment apparatus in a conventional example.
[Explanation of symbols]
1 Polarization switching type electrodialysis machine
2 Reverse osmosis membrane device
3, 30 Raw water storage tank
4, 40 Demineralizer
5, 50 Use place
6, 70 Wastewater treatment equipment
7 Salt addition means
8 Drug addition means
9, 11-20, 51, 52, 171, 172, 191, 211 Piping
10a-10c Desalination waste water treatment equipment
21 Circulation piping
100 Ultrapure water production system

Claims (6)

The desalted waste water having a calcium ion concentration of 10 to 800 mg / l and a fluoride ion concentration of 10 to 300 mg / l discharged from the desalting apparatus is treated with a polar conversion type electrodialyzer, and then the treated water is treated with a reverse osmosis membrane apparatus. In the method for treating desalted waste water, the permeated water and the concentrated water are obtained by treating with the reverse water, and the permeated water of the reverse osmosis membrane device is returned to the raw water supply side of the desalting device. A method for treating desalinated wastewater, characterized by using concentrated water obtained from the reverse osmosis membrane device. 2. The method for treating desalinated waste water according to claim 1, wherein the electrode water is circulated and used. The method for treating desalted wastewater according to claim 1 or 2, wherein the electrode water is adjusted to have a conductivity equal to or higher than that of the desalted wastewater by adding salts. The deionized wastewater according to any one of claims 1 to 3, wherein the electrode water is adjusted to pH 4 or less by adding an acid or added with a scale generation inhibitor. Processing method. The circulating electrode water according to claim 2 is adjusted to pH 4 or less by adding an acid or to which a scale generation inhibitor is added, and a part of the circulating electrode water is converted into the polarity-changing electricity. A method for treating desalinated waste water, which is used as concentrated water for a dialysis machine. A polarity conversion method for removing ionic impurities in the desalted wastewater, using desalted wastewater having a calcium ion concentration of 10 to 800 mg / l and a fluoride ion concentration of 10 to 300 mg / l discharged from the desalting apparatus as treated water. An electrodialysis apparatus, a reverse osmosis membrane apparatus using treated water of the polarity conversion type electrodialysis apparatus as treated water, and at least the concentrated water of the polarity conversion type electrodialysis apparatus and the concentrated water of the reverse osmosis membrane apparatus are treated. An apparatus for treating desalinated wastewater, comprising a wastewater treatment apparatus, wherein piping for allowing the concentrated water of the reverse osmosis membrane apparatus to flow into the electrode chamber of the polarity switching electrodialysis apparatus is disposed.

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