JP4954543B2 - Water treatment system - Google Patents

Description

  The present invention relates to a water treatment technique that efficiently removes oxides using electrolytic treatment, and more particularly to a water treatment system that can make treated water suitable for reuse as cleaning water, hydrophilic water, or the like.

Various types of wastewater discharged from ordinary households and various factories are subjected to water treatment according to their water quality. For example, as shown in FIG. 10, N, P, COD, BOD, and SS are contained in daily wastewater such as human waste, kitchen wastewater, and bath wastewater, so that they are discharged after biological treatment in the septic tank 50. The discharged septic tank sludge was treated with sludge treatment equipment. In addition, as shown in FIG. 11, in the case of car wash wastewater generated by car wash using clean water, since it contains sand, mud, DS, and SS, the sand and mud are separated by the pressure levitation device 51, and coagulation sedimentation is performed. A flocculant such as PAC (polyaluminum chloride) or sulfuric acid band was added to the apparatus 52 to cause coagulation sedimentation, the coagulation separation liquid was discharged, and sand, mud or coagulation sedimentation sludge was treated in a sludge treatment facility or the like. .
Thus, in the water treatment technology, treatment is selectively performed according to the removal target contained in the water to be treated.

  In recent years, water pollution of rivers, lakes, and seawater has become a problem, and in order to reuse wastewater as much as possible to reduce the amount of water released, and for effective use of water resources, new large-scale water resource development There is a need to reuse water after removing pollutants from water as a measure that can reduce the water supply-demand gap and reduce the effects of drought to some extent, without the need for facility development. .

  As one of water treatment technologies, treatment using an electrolytic method has been proposed and put into practical use. The treatment of pollutants by the electrolytic method is to generate hypochlorous acid from chlorine in waste water or externally added chlorine by electrolytic reaction, and decompose the pollutants using the oxidizing power of the hypochlorous acid. . The treatment using such an electrolytic method is a technology that has been attracting attention in recent years because it has a high processing speed and can easily decompose oxides by simply passing electricity.

Patent Document 1 (Japanese Patent Laid-Open No. 2004-330182) discloses a method of performing an electrolytic treatment on waste water containing a nitrogen compound and then performing a biological treatment at a subsequent stage to remove a nitrogen component. However, in order to perform efficient electrolysis, it is necessary to add a chloride ion source according to the flow rate, and there is a disadvantage that the processing cost increases.
Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-218983) discloses a method for removing nitrogen compounds and organic substances provided with an electrolysis facility and a concentrating device. However, it is necessary to transfer from the anode side to the cathode side after the treatment is completed. There is a disadvantage that the number of devices increases. In addition, the nitrogen component can be removed in the electrolytic cell only in the anode region, so the amount that can be charged is small relative to the scale of the device, and the number of transfers increases, so the operating time must be reduced, and the equipment must be increased in size. There is a problem.

JP 2004-330182 A Japanese Patent Application Laid-Open No. 2005-218983

  Therefore, in view of the above-mentioned problems of the prior art, the present invention is a water treatment system that can perform treatment with high electrolysis efficiency and can make the treated water after electrolytic treatment suitable for reuse. The purpose is to provide.

Therefore, in order to solve this problem, the present invention provides:
A reduction device for reducing chlorine by adding a reducing agent to the water containing oxide, and a biological treatment device for introducing biological treatment by biological denitrification or anaerobic treatment, into which treated water discharged from the reduction device is introduced And pretreatment for performing at least one treatment selected from a coagulation filtration facility, a sand filtration facility, a pressurized flotation separation tank, an MF membrane or UF membrane, and a pH adjustment facility on the water to be treated discharged from the biological treatment apparatus An apparatus and a concentrating device for introducing the pretreated water after the pretreatment and concentrating chloride ions in the treated water after the reduction , comprising at least one of a reverse osmosis membrane device and an electrodialysis device Concentration apparatus , electrolyzed concentrated water obtained by the concentration to produce hypochlorous acid, and oxidative decomposition of the oxide by the hypochlorous acid, and electrolytic treatment solution after the electrolysis A circulation line that circulates through the reduction device. When, with a chloride ion concentration of the treated water discharged from the reducing device is to be equal to or less than 8000 mg / L, and wherein the withdrawing sludge from the pre-processing unit.

In the present invention, by installing an electrolytic device in the latter stage of the concentration device, the concentrated solution having a high chloride ion concentration is subjected to electrolytic treatment, so that the electrolytic efficiency can be kept high and the control of the electrolysis becomes easy. Therefore, it is not necessary to apply an excessive voltage. Further, by providing a reduction device on the downstream side of the electrolysis device, residual chlorine that adversely affects the concentration device can be treated, and the life of the concentration device can be improved. Moreover, by allowing the oxide-containing water to flow between the electrolyzer and the reducing device, residual chlorine discharged from the electrolyzer can be consumed, the amount of reducing agent injected can be reduced, and nitrogen in the oxide-containing water can be reduced. The components can be decomposed. Furthermore, control of the residual chlorine concentration in an electrolysis apparatus can be simplified by installing a storage device and providing a certain residence time.
In the present invention, the oxides to be removed include alcohols, phenols, hydrocarbons, aldehydes, ketones, fatty acids, esters, amines, nitrogen oxides, ammonia, and chromaticity components. It is a substance represented by odor components.

Moreover, it is possible to improve the separation efficiency in a concentration apparatus by providing a pre- processing apparatus in this way.
Further, by providing a biological treatment apparatus, nitrate nitrogen in the oxide-containing water can be removed, and improvement in water quality can be expected.
In addition, by setting the chloride ion in the electrolytic treatment cycle to 8000 mg / L or less as described above, the biological treatment in the biological treatment apparatus can be processed without impeding, and a high concentration of chloride in the electrolytic apparatus is possible. Since ions can be maintained without external addition, high-efficiency processing is possible.

Further, the concentrating device is a device for obtaining concentrated water having a plurality of concentrations with a plurality of stages of reverse osmosis membrane devices, and at least a part of the concentrated water having a high concentration obtained by the concentrating device is supplied to the reducing device. It is characterized by returning. The multi-stage arrangement configuration preferably employs a cross-free system.
Thereby, the amount of inflow water to the electrolysis equipment can be reduced. That is, it becomes possible to obtain concentrated water having a higher concentration. In addition, when there is a change in the waste water state, by adjusting the circulation amount of the return concentrated water, it is possible to always supply the concentrated water having a constant water quality to the electrolysis equipment, and the electrolysis equipment can be stably operated.

Moreover, the concentrator is a reverse osmosis unit, in the case of reusing the permeate obtained in the reverse osmosis membrane apparatus as washing water, sludge is withdrawn from the pre-processing unit with washing waste liquid after washing It is provided with a coagulation sedimentation apparatus for coagulation sedimentation. Thereby, the electrolytic treatment cycle and the coagulation sedimentation apparatus in the washing wastewater treatment system can be unified, and the entire system can be miniaturized .
Also of et, characterized in that the heat generated from the electrolysis device equipped with heat exchange means for supplying water to be treated at the previous stage of the reverse osmosis unit. In this way, by controlling the temperature of the water flowing into the concentrating device by the heat exchange means so as to be a constant temperature, it is possible to ensure a constant amount of permeated water without changing the pressure.

In addition, a means for collecting the hardness component deposited in the electrolytic device by at least one of gravity sedimentation, dissolution by acid addition, and water washing is provided, and the collected hardness component is added to the permeated water obtained by the concentrator. It is characterized by adding.
In this way, the hardness component is deposited in the electrolytic equipment and recovered by dissolving with hydrochloric acid. By adding the recovered hardness component to the permeated water of the concentrator and using it as hydrophilic water, the hardness component that adversely affects electrolytic performance degradation and electrode life is recovered and added to the permeated water. Necessary hardness components can be produced in-house.

Furthermore, the electrolyzer is configured to perform electrolysis up to a free chlorine concentration of 2000 to 2500 mg / L by being supplied with chlorine-containing water, and a reaction vessel is provided in the previous stage of the reduction device, and the reaction vessel is provided with the electrolyzer from the electrolyzer. The electrolytic treatment solution is introduced, and at least a part of the concentrated water obtained by the concentrator is returned to the electrolyzer.
Thus, efficient electrolysis can be performed by setting the free chlorine concentration to 2500 mg / L or less. Moreover, the usage-amount of chlorine containing water can be reduced by selectively returning high concentration salt water. Furthermore, since it is difficult for organic substances or the like that adversely affect the electrodes of the electrolysis apparatus to flow in, the life of the electrolysis equipment can be extended.

Furthermore, it is preferable that the oxide-containing water is subjected to membrane pretreatment with a membrane pretreatment device, and the membrane pretreatment water is concentrated with a concentrating device and then flowed into the electrolysis device for electrolytic treatment.
Thereby, since the separation process is performed by the concentrator on the front side, the equipment on the rear side can be made compact. By reducing the flow rate, the amount of chemical injection such as a chloride ion source can be reduced. Further, the permeated water can be used for dilution before the discharge. Furthermore, the density | concentration of a process target object can be increased and control in an electrolysis installation becomes easy.

  As described above, according to the present invention, by providing a concentrating device on the upstream side of the electrolyzer, the electrolysis efficiency can be maintained high, so that the removal efficiency of the oxide can be improved, and the electrolysis reaction can be improved. Control can be facilitated. In addition, by providing a reducing device in front of the concentrating device, residual chlorine that adversely affects the concentrating device can be treated, and the life of the concentrating device can be improved. Moreover, it is possible to improve the separation efficiency in a concentration apparatus by providing a pre-processing apparatus. Furthermore, the amount of water flowing into the electrolysis equipment can be reduced by using a concentration device in which reverse osmosis membrane devices are arranged in multiple stages.

  In addition, by setting the chloride ion in the electrolytic treatment cycle to 8000 mg / L or less, high-concentration treatment can be performed because high-concentration chloride ions can be maintained in the electrolytic apparatus without external addition. Further, the electrolytic treatment cycle and the coagulation sedimentation apparatus in the washing wastewater treatment system can be unified, and the entire system can be reduced in size. Furthermore, by providing a biological treatment apparatus or an ion exchange membrane treatment apparatus, nitrate nitrogen in the oxide-containing water can be removed, and improvement in water quality can be expected. Furthermore, by controlling the temperature of the water flowing into the concentrating device by the heat exchange means, it is possible to ensure a constant amount of permeated water without changing the pressure by making the temperature constant.

  Moreover, it collect | recovers by depositing a mineral component in an electrolysis installation and dissolving with hydrochloric acid. The collected mineral components are added to the permeated water of the concentrator and reused as water for containing hardness components such as water for hydrophilicity, thereby recovering hardness components that adversely affect electrolytic performance and electrode life and add them to the permeated water. In this way, the hardness component necessary for producing water for hydrophilicity can be produced in-house. Moreover, efficient electrolysis can be performed by making the free chlorine density | concentration after a reducing device into 2500 mg / L or less. Furthermore, the equipment on the rear stage can be made compact by performing the separation treatment with the concentrator on the front stage of the electrolyzer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
1 is a view showing a water treatment flow according to Embodiment 1 of the present invention, FIG. 2 is a view showing an application example of Embodiment 1, and FIG. 3 is a view showing a water treatment flow according to Embodiment 2 of the present invention. 6 is a diagram showing a water treatment flow according to Example 3 of the present invention, FIG. 7 is a diagram showing a water treatment flow according to Example 4 of the present invention, and FIG. 8 is a water treatment flow according to Example 5 of the present invention. FIG. 9 shows a water treatment flow according to Embodiment 6 of the present invention.

  In this embodiment, the oxide in the oxide-containing water is oxidized and decomposed by the oxidizing power of hypochlorous acid generated by electrolyzing the chlorine-containing water. Substances to be removed are represented by alcohols, phenols, hydrocarbons, aldehydes, ketones, fatty acids, esters, amines, nitrogen oxides, ammonia, chromaticity components, and odor components. It is an oxide.

1 and 2 show a water treatment flow according to the first embodiment. The present Example 1 can treat the oxide as described above, but is particularly suitable for removing nitrogen compounds. The oxide-containing water has a relatively high concentration of the oxide to be contained, and can be treated up to several tens of ppm. Moreover, the treatment amount of the oxide-containing water can be treated up to about several tens m ³ / day.
In Example 1, as shown in FIG. 1, the reducing device 1 into which the oxide-containing water 10 flows, the membrane pretreatment device 2 into which the reduced treated water flows, and the membrane pretreated membrane pretreated water. Is constituted by a concentrating device 3 for concentrating the water by membrane separation, an electrolyzing device 4 for electrolyzing the concentrated water 15 obtained by the concentrating device 3, and a circulation line for circulating the electrolytic treatment liquid 17 to the reducing device 1. A cycle is formed.

The reducing device 1 is a device that has a supply means for the reducing agent 11 such as sodium thiosulfate and reduces residual chlorine in the electrolytic treatment liquid 17 flowing from the electrolytic device 4 described later with a reducing agent. The reduction reaction formula is as follows.
4HClO + 2Na ⁺ + S ₂ O ₃ ²⁻ + 6OH ⁻ → 2Na ⁺ + 2SO ₄ ²⁻ + 4Cl ⁻ + 5H ₂ O
Na ₂ S ₂ O ₃ + 4Cl ₂ + 5H ₂ O → 2NaCl + 2H ₂ SO ₄ + 6HCl

The membrane pretreatment device 2 is a device that adjusts the water quality before flowing into the concentration device 3, and is at least one selected from a coagulation filtration facility, a sand filtration facility, a pressurized flotation separation tank, an MF membrane or UF membrane, and a pH adjustment facility. Perform the process. Examples include (1) coagulation filtration equipment + sand filtration equipment, (2) pressurized flotation separation tank + sand filtration equipment, (3) coagulation sedimentation tank + sand filtration equipment, (4) MF membrane or UF membrane, (5) Examples include pH adjusting equipment.
The concentrating device 3 is composed of at least one of a reverse osmosis membrane device and an electrodialysis device. The membrane pretreated water 12 is subjected to membrane pretreatment into concentrated water 15 enriched with chloride ions and permeated water 14. To separate. In the concentrating device 3, the oxide is concentrated together with chloride ions.

The electrolyzer 4 is an apparatus that has at least a pair of electrodes, generates hypochlorous acid by electrolysis, and oxidizes and decomposes the oxide by the oxidizing power of the hypochlorous acid.
As a method for electrolyzing the oxide, as shown in FIG. 1, concentrated water 15 containing chloride ions at a high concentration is directly flowed into the electrolytic cell 4 to generate hypochlorous acid by electrolysis, 4 in which the hypochlorous acid and the oxide are brought into contact with each other to oxidize and decompose, and as shown in FIG. There is a method in which the electrolytic treatment liquid 17 containing hypochlorous acid is introduced into the reaction tank 5 to oxidatively decompose the oxide contained in the oxide-containing water 10 and the electrolytic treatment liquid 17. When the reaction tank 5 is provided, electrolysis may be performed excessively in the electrolysis apparatus 4 and may be introduced as an electrolytic treatment solution having a high free chlorine concentration.

The flow of water treatment will be described with reference to FIG. First, the oxide-containing water 10 flows into the reduction facility 1, and the reduction facility 1 reduces residual chlorine contained in the electrolytic treatment liquid 17 flowing from the downstream electrolyzer 4. At this time, since the oxide-containing water 10 flows into the reducing device 1, residual chlorine contained in the electrolytic treatment liquid 17 can be consumed, the amount of the reducing agent 11 injected can be reduced, and the oxide-containing water can be reduced. The oxide in 10 can be decomposed.
The reduced treated water discharged from the reducing device 1 flows into the membrane pretreatment device 2, where water quality adjustment is mainly performed. The membrane pretreatment water 12 discharged from the membrane pretreatment device 2 flows into the concentration device 3, and chloride ions in the treatment water are concentrated by reverse osmosis membrane and / or electrodialysis. At this time, the oxide to be removed is also concentrated. The permeated water 14 permeated through the concentrating device 3 is obtained with water quality suitable for reuse.

On the other hand, the whole or part of the concentrated water 15 enriched with chloride ions flows into the electrolysis apparatus 4, and hypochlorous acid having strong oxidizing power is generated by electrolysis in the electrolysis apparatus 4. In the electrolytic reaction for producing hypochlorous acid, the reaction proceeds with higher efficiency when the chloride ion concentration is higher, but in this embodiment, the concentrated water 15 in which the chloride ions are concentrated in the concentrating device 3 is electrolyzed. Hypochlorous acid can be generated with high efficiency. Further, since the oxide that is oxidatively decomposed by hypochlorous acid is also concentrated, the decomposition efficiency is improved.
Alternatively, the electrolyte solution 13 containing hypochlorous acid may be extracted from the membrane pretreatment device 2 and reused for the purpose of disinfecting water or the like.

As described above, according to the present embodiment, by installing the electrolysis device 4 at the subsequent stage of the concentration device 3, the concentrated water 15 having a high chloride ion concentration is subjected to electrolysis treatment, and the electrolysis efficiency can be maintained high. In addition, since it is easy to control the electrolysis, it is not necessary to apply an excessive voltage.
In addition, by providing the reduction device 1 on the downstream side of the electrolysis device 4, residual chlorine that adversely affects the concentration device 3 can be treated, and the life of the concentration device 3 can be improved.
Moreover, by allowing the oxide-containing water 10 to flow between the electrolysis apparatus 4 and the reduction apparatus 1, residual chlorine discharged from the electrolysis apparatus 4 can be consumed, the amount of the reducing agent 11 injected can be reduced, and the oxidation target can be reduced. The nitrogen component of the product-containing water 10 can be decomposed.
Furthermore, control of the residual chlorine concentration in the electrolyzer 4 can be simplified by installing the storage device 5 and providing a certain residence time.

FIG. 3 shows a water treatment flow according to the second embodiment. In Example 2, the oxide-containing water has a relatively high concentration of the oxide to be contained, and can be processed to several tens ppm to several hundred ppm. Moreover, the treatment amount of the oxide-containing water can be treated up to about 100 m ³ / day, and is also suitable for the oxide-containing water having temperature fluctuation.
In the following second to sixth embodiments, the detailed description of the configuration is omitted as in the first embodiment.
As shown in FIG. 3, the second embodiment includes a reducing device 1 into which the oxide-containing water 10 flows, a biological treatment device 5 that biologically treats the reduced treated water after reduction, and a membrane before the biological treatment solution flows. The treatment device 2, the concentration device 3 for concentrating the membrane pretreated water subjected to membrane pretreatment by membrane separation, the electrolysis device 4 for electrolyzing the concentrated water 15 obtained by the concentration device 3, and the electrolytic treatment solution 17 for the reduction device 1 And an electrolytic treatment cycle is formed by these.
Further, in this embodiment, the permeated water 14 obtained from the concentrating device 3 is reused as washing water, and the pressurized flotation device 22 for separating mud, sand 24 and the like from the washing waste water 21 used for the washing 20. And a coagulating sedimentation device 25 that coagulates and precipitates the separation liquid 23. The coagulation sedimentation device 25 is configured to coagulate and separate the liquid from the electrolytic treatment cycle of the membrane pretreatment device 2 and the like.

The biological treatment apparatus 5 is an apparatus that performs biological treatment by biological denitrification or anaerobic treatment. Further, instead of the biological treatment device 5, an ion exchange device for removing nitrate nitrogen may be installed.
In Example 2, the membrane pretreatment device 2 is provided with sludge extraction means, and the reduction device 1 is oxidized so that the chloride ion concentration of the reduction treatment liquid flowing into the biological treatment device 5 is 8000 mg / L or less. The inflow amount of the material-containing water 10 and the sludge extraction amount from the membrane pretreatment device 2 are adjusted.
As described above, by setting the chloride ion in the electrolytic treatment cycle to 8000 mg / L or less, the biological treatment in the biological treatment device 5 can be performed without impeding the biological treatment, and the chloride ion is removed in the electrolytic device 4. Since it can maintain without attaching, a highly efficient process is attained. In general, the chloride ion concentration required for electrolytic treatment is at least 2000 mg / L or more, and the higher the concentration, preferably 5000 mg / L or more, the more efficient the treatment can be achieved. Although chloride ion is reduced to 8000 mg / L or less, chloride ion concentration sufficient for electrolytic treatment remains in the circulation system (especially in the electrolyzer 4 after concentration). This makes it possible to eliminate or reduce the external addition.

Further, as a characteristic configuration of the second embodiment, the permeated water 14 obtained by the concentrating device 3 is used for washing, and the sludge discharged from the electrolytic treatment cycle in the coagulating sedimentation device 25 in the treatment system of the washing waste water 21 is used. In addition, it is configured to agglomerate.
The treatment system for the washing waste water 21 is to add makeup water to the permeated water 14 as necessary, and use this for washing 20 as washing water for equipment, vehicles, etc., and treat the washing waste water 21 after washing. , A pressure levitation device 22 and a coagulation sedimentation device 25. The washing waste water 21 is subjected to pressure levitation device 22 to remove solids such as sand and mud 24 by pressure levitation, and the separated liquid 23 from which the solid has been separated and removed is introduced into a coagulation sedimentation device 25. Further, the sludge extracted from the membrane pretreatment device 2 in the electrolytic treatment cycle is put into the coagulation sedimentation device 25, and a coagulant is added to these to perform the coagulation sedimentation treatment. The sludge 27 separated by the coagulation sedimentation device 25 is discharged, and the separation liquid 26 is discharged after other water treatment is performed as necessary.
In this way, by making the sludge discharged from the electrolytic treatment cycle flow into the treatment system of the cleaning wastewater 21, the facilities can be unified, and the entire system can be downsized and the running cost can be reduced.

Further, as a characteristic configuration of the second embodiment, when the concentrating device 3 is a reverse osmosis membrane device, a heat exchange is performed between the upstream stage of the reverse osmosis membrane device and the electrolysis device 4.
Specifically, the apparatus includes a cooling device 1 that supplies cooling water to the electrolysis device 4 and a heat exchanger 6 that heats the membrane pretreatment water 12 in the previous stage of the concentration device 3, and generates heat generated from the electrolysis device 4. It is supplied to the membrane pretreatment water 12 in the preceding stage of the concentrator 3 by heat exchange (* 2). On the other hand, the water cooled by exchanging heat with the membrane pretreatment water 12 is circulated to the cooling device 7 (* 1) and used for cooling the electrolysis device 4. At this time, it is preferable that the makeup water for cooling the electrolytic device 4 is the permeated water 14 from the concentrating device 3 (* 3).

  The application temperature of the reverse osmosis membrane provided in the concentration device 3 is, for example, 0 to 35 ° C. in the case of a cellulose acetate membrane (CA / CTA membrane), and 0 to 45 ° C. in the case of a synthetic thin film film (TFC membrane). . Accordingly, it is desirable to set the heat exchanger 6 to a value that does not exceed these application temperatures. Thus, by controlling the temperature of the water flowing into the concentrating device 3 by the heat exchanger 6 so as to be a constant temperature, it is possible to ensure a constant amount of permeated water without changing the pressure.

The reverse osmosis membrane, as shown in the graph showing the relationship between the water temperature and the amount of permeated water in the RO membrane in FIG. 4, has a permeated water amount change of 2-3% / ° C. (under the same operating pressure) due to the water temperature. The amount of permeate increases as the temperature of the water increases. On the other hand, as shown in the graph showing the relationship between the water temperature and the blocking rate in the RO membrane of FIG. 5, the blocking rate decreases as the temperature is raised. As a preferable condition of the present embodiment, the concentration rate of the concentrating device 3 can be reduced by securing a blocking rate so that the obtained permeated water has the target water quality within the application temperature of the RO membrane, and increasing the permeated water amount as much as possible. It is preferable to make it easier. When the reuse destination is not required to have high water quality such as washing, the blocking rate is not particularly problematic. Therefore, it is preferable to keep the temperature as high as possible within the application temperature.
In addition, this structure can also be used as a flow-correcting use when the temperature of the liquid flowing into the concentrating device 3 occurs, such as in winter.

FIG. 6 shows a water treatment flow according to the third embodiment. In the present Example 3, the oxide-containing water can be treated up to a concentration of the contained oxide of several ppm to several tens of ppm. Moreover, the treatment amount of the oxide-containing water can be treated up to about several tens m ³ / day.
As shown in FIG. 6, the third embodiment has a configuration in which reverse osmosis membrane devices are arranged in multiple stages in the configuration of the first embodiment. FIG. 6 shows, by way of example, reverse osmosis membrane devices 30a to 30c, 31a to 31b, and 32a that are configured in a cross-flow Christmas tree shape.
The membrane pretreatment water 12 discharged from the membrane pretreatment device 2 flows into the first-stage reverse osmosis membrane devices 30a to 30c, and the permeated water 14 and the concentrated water 15 are obtained from the respective devices. At least a part of the concentrated water 15 flows into the second-stage reverse osmosis membrane devices 31a to 31b, and similarly, the permeated water 14 and the concentrated water 15 are obtained. Furthermore, at least a part of the concentrated water 15 discharged from the second-stage reverse osmosis membrane devices 31a to 31b flows into the third-stage reverse osmosis membrane device 32a.
In the third embodiment, when the ion concentration of the membrane pretreatment water 12 is low, a part of the intermediate concentrated water in the reverse osmosis membrane device is extracted and returned to the reducing device 1 as the return concentrated water 15 ′. Yes.
Thereby, the amount of inflow water to the electrolysis equipment 4 can be reduced. That is, it becomes possible to obtain concentrated water having a higher concentration. Further, when there is a change in the properties of the oxide-containing water, by adjusting the circulation amount of the return concentrated water 15 ′, it is possible to always supply the concentrated water 15 having a constant water quality to the electrolysis equipment 4, and to stabilize the electrolysis equipment 4. Driving is possible.

FIG. 7 shows a water treatment flow according to the fourth embodiment. In Example 4, the oxide-containing water can be treated until the concentration of the contained oxide is about several tens of ppm. Moreover, the treatment amount of the oxide-containing water can be treated up to about several tens m ³ / day.
The present Example 5 is suitable when the permeated water 17 is reused as hydrophilic water, and the hardness component precipitated in the electrolysis apparatus 4 is recovered by at least one of gravitational precipitation, dissolution by acid addition, and water washing. In addition, it is configured to be added to the permeated water from the concentration device 3.
Specifically, a Langeria coefficient measuring means 30 for measuring the Langeria coefficient of the permeated water 14 obtained by the concentrating device 3 is provided, and the hardness component-containing water 31 separated from the electrolytic treatment liquid 17 based on the Langeria coefficient of the permeated water 14 is obtained. The permeated water 14 is supplied.
Separation of the hardness component from the electrolytic treatment liquid 17 includes a method of recovering the hardness component by depositing the hardness component in the electrolysis apparatus 4 and adding hydrochloric acid. A mineral precipitation tank 8 for introducing the electrolytic treatment liquid 17 and separating it from the hardness component is provided at the subsequent stage of the electrolysis apparatus 4, and the hardness component-containing water 31 including the hardness component settled and separated here is supplied to the permeated water 14.
Thus, by collecting the hardness component of the electrolytic treatment liquid 17, the hardness component is not deposited in the electrolytic treatment cycle, and it is possible to prevent the electrodes and the like from being adversely affected. Further, by collecting the hardness component and supplying it to the permeated water 14, it is possible to perform reuse suitable for biotope formation, equipment cleaning, etc., including hydrophilic water.

  As another method for stabilizing other hardness components, there is a method for preventing the precipitation of calcium carbonate by supplying a sufficient amount of carbon dioxide gas to the electrolysis apparatus 4 and performing a re-carbonization treatment. This is because by supplying carbon dioxide and re-carbonizing, the pH of the water decreases and calcium carbonate becomes calcium hydrogen carbonate. However, if sufficient free carbonic acid remains in the water, the calcium hydrogen carbonate becomes stable. Therefore, it is possible to prevent the hardness component from being precipitated in the electrolytic treatment cycle. In this configuration, by supplying a part of the electrolytic treatment liquid 17 as the hardness component-containing water to the permeated water 14, hardness component-containing water such as hydrophilic water can be obtained.

Here, the Langeria coefficient is obtained from the pH of water, the calcium ion concentration, the total alkalinity, and the soluble substance (used for correction value calculation) by the following equation.
Langeria coefficient (LI) = pH-pHs
= PH-8.313 + log [Ca ⁺⁺ ] + log [A] -S
Here, pH: actual pH value of water, pHs: pH value when in equilibrium, log [Ca ⁺⁺ ]: logarithm of calcium ion concentration, log [A]: logarithm of total alkalinity, S: correction value It can be.
The larger the value of the Langelia coefficient, the greater the value. The tendency to corrode water increases as the absolute value increases.
Therefore, by obtaining the Langeria coefficient from the pH, calcium ion concentration, total alkalinity and soluble substance of the water and supplying the hardness component-containing water 31 to the permeated water 14 based on the Langeria coefficient, high-quality recycled water can be obtained. It becomes possible to provide.

  As described above, according to the present embodiment, the hardness component is precipitated in the electrolysis apparatus 4 and recovered by dissolving with hydrochloric acid. The collected hardness component is added to the permeated water 14 of the concentrator and used as hydrophilic water, etc., and the hardness component that adversely affects electrolytic performance degradation and electrode life is collected and added to the permeated water 14 to make the hydrophilic Hardness components required when reusing water such as irrigation water can be produced in-house.

FIG. 8 shows a water treatment flow according to the fifth embodiment. In Example 5, the amount of the oxide-containing water can be treated from several tens m ³ / day to several thousand m ³ / day.
In Example 5, in addition to the configuration of the application example of Example 1 shown in FIG. 2, chloride ion-containing water is electrolyzed to a free chlorine concentration of 2000 to 2500 mg / L and added to the oxide-containing water 10. In addition, at least a part of the processing liquid is returned.
In the electrolyzer 4, 2000 to 2500 mg / L of free chlorine is generated by electrolysis of the chlorine-containing water 18, and the electrolytic solution is supplied to the reaction vessel 5 and mixed with the oxide-containing water 10. The chlorine-containing water 18 is water containing chloride ions such as seawater that hardly contains organic matter and nitrogen.
Further, the concentrated water from the concentrating device 3 is selectively returned to the electrolysis equipment 4 according to the concentration of the chlorine-containing water 18. This uses the multi-stage reverse osmosis membrane device shown in Example 3, and does not circulate the low-concentration concentrated water 15 ″ obtained from the previous-stage reverse osmosis membrane device to the electrolysis device 4 but the latter-stage reverse osmosis membrane. This can be implemented by circulating only the high-concentration concentrated water 15 obtained from the apparatus to the electrolysis apparatus 4.

  According to the fifth embodiment, efficient electrolysis can be achieved by setting the free chlorine concentration to 2500 mg / L or less. Moreover, the usage-amount of the chlorine containing water 18 can be reduced by selectively returning high concentration salt water. Furthermore, since it is difficult for an organic substance or the like that adversely affects the electrodes of the electrolysis apparatus 4 to flow in, the life of the electrolysis apparatus 4 can be extended.

FIG. 9 shows a water treatment flow according to the sixth embodiment. In Example 6, the oxide-containing water has a relatively high concentration of the oxide to be contained, and can be processed up to about several tens of ppm. Moreover, the treatment amount of the oxide-containing water can be treated up to about several tens m ³ / day.
In the sixth embodiment, the oxide-containing water 10 is subjected to membrane pretreatment by the membrane pretreatment device 2, and the membrane pretreatment water 12 is concentrated by the concentration device 3 and then flowed into the electrolysis device 4 for electrolytic treatment. It has become. At this time, a chloride ion source may be added to the upstream side of the concentration device 3 in order to ensure the differential pressure in the concentration device 3.
According to the sixth embodiment, since the separation process is performed by the concentrating device 3 on the front stage side, the equipment on the rear stage side can be made compact. By reducing the flow rate, the amount of chemical injection such as a chloride ion source can be reduced. Further, the permeated water 14 can be used for dilution before the discharge. Furthermore, the density | concentration of a process target object can be increased and control in the electrolysis installation 4 becomes easy.

It is a figure which shows the water treatment flow which concerns on Example 1 of this invention. It is a figure which shows the application example of Example 1 shown in FIG. It is a figure which shows the water treatment flow which concerns on Example 2 of this invention. It is a graph which shows the relationship between the water temperature in RO membrane, and the amount of permeate. It is a graph which shows the relationship between the water temperature in a RO membrane, and the rejection. It is a figure which shows the water treatment flow which concerns on Example 3 of this invention. It is a figure which shows the water treatment flow which concerns on Example 4 of this invention. It is a figure which shows the water treatment flow which concerns on Example 5 of this invention. It is a figure which shows the water treatment flow which concerns on Example 6 of this invention. It is a figure which shows the processing flow of the conventional domestic wastewater. It is a figure which shows the processing flow of the conventional car wash wastewater.

Explanation of symbols

1 Reduction device 2 Membrane pretreatment device (Pretreatment device)
DESCRIPTION OF SYMBOLS 3 Concentrator 4 Electrolyzer 5 Biological treatment device 6 Heat exchanger 7 Cooling device 8 Mineral precipitation tank 13 Electrolyte 14 Permeated water 15 Concentrated water 17 Electrolyzed solution 18 Chlorine-containing water 21 Washing waste liquid 22 Pressure floating device 30 Langeria coefficient measurement means

Claims (6)

A reducing device for reducing chlorine by adding a reducing agent to the water containing oxide;
A biological treatment device into which treated water discharged from the reduction device is introduced, and performs biological treatment by biological denitrification or anaerobic treatment;
A pretreatment device that performs at least one treatment selected from a coagulation filtration facility, a sand filtration facility, a pressurized flotation separation tank, an MF membrane or a UF membrane, and a pH adjustment facility on the water to be treated discharged from the biological treatment device; ,
A concentrating device which introduces the pretreated water after the pretreatment and concentrates chloride ions in the treated water after the reduction, and is a concentrating device comprising at least one of a reverse osmosis membrane device and an electrodialysis device Equipment ,
An electrolyzer that electrolyzes the concentrated water obtained by the concentration to produce hypochlorous acid, and oxidatively decomposes the oxide with the hypochlorous acid;
A circulation line for circulating the electrolytic treatment solution after the electrolysis to the reduction device;
Equipped with a,
A water treatment system , wherein sludge is extracted from the pretreatment device so that a chloride ion concentration of water to be treated discharged from the reduction device is 8000 mg / L or less .   The concentrating device is a device for obtaining concentrated water having a plurality of concentrations with a reverse osmosis membrane device arranged in multiple stages, and at least a part of the concentrated water obtained with the concentrating device is returned to the reducing device. The water treatment system according to claim 1. The concentration device is a reverse osmosis membrane device;
And wherein when the permeate obtained in the reverse osmosis unit for reuse as washing water, along with cleaning waste water after washing was withdrawn from the pretreatment device sludge with a coagulating sedimentation apparatus for coagulating sedimentation The water treatment system according to claim 1 . The concentration device is a reverse osmosis membrane device;
The water treatment system according to claim 1, further comprising heat exchange means for supplying heat generated from the electrolyzer to the water to be treated before the reverse osmosis membrane device . The concentration device is a reverse osmosis membrane device;
A means for recovering the hardness component precipitated in the electrolysis apparatus by at least one of gravity sedimentation, dissolution by acid addition, and water washing is provided, and the recovered hardness component is converted into permeated water obtained by the reverse osmosis membrane apparatus . The water treatment system according to claim 1, wherein the water treatment system is added.   The electrolysis apparatus is configured to perform electrolysis up to a free chlorine concentration of 2000 to 2500 mg / L by being supplied with chlorine-containing water, and a reaction tank is provided in front of the reduction apparatus, and electrolysis from the electrolysis apparatus is provided in the reaction tank. The water treatment system according to claim 1, wherein a treatment liquid is introduced and at least a part of the concentrated water obtained by the concentrator is returned to the electrolyzer.

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