KR20190133596A - Photo-electro-dialysis water treatment apparatus and water treatment method for simultaneous desalination and pollutants oxidation - Google Patents

Abstract

The present invention relates to a photo-electrodialysis water treating device and a water treating method using the same capable of stably performing electrodialysis water treating, electrochemical advanced oxidation water treating, and photochemical water treating. The present invention removes an ion pollutant by using an ion exchanging film in an electric field generated through applied voltage applied to a positive pole and a negative pole by using the photo-electrodialysis water treating device. The present invention performs oxidative removal of a nonionic pollutant by using an action of free chlorine species produced through oxidation of chlorine ions and radical species produced through an additional reaction with ultraviolet light. The water treating method facilitates a stable operation of the photo-electrodialysis water treating device, minimizes damage to an ion exchanging film of an electrooxidation-dialysis module, and economically performs desalination and advanced oxidation at the same time without injecting an external oxidant from the outside.

Description

Photo-electro-dialysis water treatment apparatus and water treatment method for simultaneous desalination and pollutants oxidation}

The present invention relates to a photoelectrodialysis water treatment apparatus and a water treatment method in which desalination and contaminant oxidation are simultaneously performed, and more particularly, chlorine ions in concentrated water generated during electrodialysis desalination are oxidized through an anode (anode). By generating chlorine species and injecting them into a treatment tank equipped with an ultraviolet lamp, it is possible to generate chlorine-based radicals and hydroxide radicals, which are powerful oxidants, to remove ions and to highly oxidize organic and inorganic pollutants in water, and to a water treatment method using the same. It is about.

Recently, water management has emerged as an important issue in the international community. The background is the global water shortage caused by 'climate change' and 'continuous population growth' accompanied by rapid changes. As of 2004, the water shortage was about 700 million of the world's population of about 6.5 billion, but by 2025, the water shortage is expected to be about 2.8 billion. As an alternative to such water shortages, the need for water conservation, environment-friendly and stable water supply, and proper water resource management are urgently needed. According to the <Long-term Long-term Comprehensive Plan Report> established by the Ministry of Land, Transport and Maritime Affairs, the water shortage problem in Korea is serious enough that the annual water shortage is expected to be 400 million tons by 2020. To cope with this water shortage problem, the government intends to shift the water resource management policy to demand management by establishing and promoting mid- and long-term measures, including supplying alternative water resources such as groundwater and sewage reuse.

Effluents treated in environmental basic facilities such as sewage and wastewater treatment plants are very stable alternative water resources in terms of water quality and quantity. Clean treated effluent can serve as dilution water of contaminated streams upstream during the drainage period, can also be used as high quality industrial water, and can be supplied as ecological flow to urban streams, which are dry due to urbanization. It has been reported that securing sewage / wastewater as an alternative water resource ultimately reduces the cost of society as a result of reducing tap water usage and dam construction demand. Therefore, the Ministry of Environment has established and implemented a sewage treatment plant effluent reuse plan by revising the sewage law in 2001, and has been steadily increasing the reuse rate of sewage treatment plant effluents. The foundation for reuse of water resources was established. In particular, the 2nd Basic Plan for Water Environment Management, established by the Ministry of Environment in 2017, emphasizes the need for technology to treat and recycle wastewater treatment plant effluents at the level of industrial water.

As reverse osmosis, nano-filtration, and electrodialysis are continuously developed and improved for desalination, they are applied to industrial water, wastewater, and sewage. Much research is being conducted on reuse and sewage reuse. Nanofiltration and reverse osmosis is a method of obtaining low concentration fresh water by applying pressure to the treated water containing high concentration of salt and removing salt dissolved in the water as it passes through the membrane. Reverse osmosis can reduce monovalent and divalent ions simultaneously, whereas nanofiltration can only remove bivalent or more ions. Electrodialysis is a technology that produces pure fresh water as treated water by increasing the rate of ion separation (desalting) through the ion exchange membrane by alternately arranging ion exchange membranes that selectively pass cations and anions, and removing all kinds of ions. can do. The three techniques are the same in the use of membranes, but the driving force is pressure in reverse osmosis and nanofiltration, while electrodialysis uses electrostatic attraction. When treating low-concentration brine such as wastewater effluent, electrodialysis is relatively economical in terms of energy consumption and can be operated at room temperature and atmospheric pressure, resulting in less corrosion problems than reverse osmosis and nanofiltration. In addition, since it is an environmentally friendly process that is simple and does not produce by-products such as waste, it is recently used in various fields such as salt removal in fermentation media, protein concentration, separation and purification, organic acid purification, industrial wastewater treatment, and sewage reuse processes. Is adding. However, the process efficiency of the electrodialysis process greatly depends on the membrane performance, and nanofiltration and reverse osmosis have the disadvantage that the removal of trace organic matter and disinfection by-products is impossible.

In order to recycle recycled water to industrial water, suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), and nutrients must be removed. . Electrodialysis has high ion removal rate and ease of operation, but trace organic matter and disinfection by-products cannot be removed, so additional treatment is required when reused treated water. Existing wastewater recycling facilities remove residual organic matter and nutrients through physicochemical treatment such as activated carbon and flocculation sedimentation. However, problems such as economic burden due to the use of a large amount of oxidant, deactivation of microorganisms, secondary treatment of the adsorbent, and the like have been pointed out.

In addition, pharmaceuticals, personal hygiene products, and endocrine disruptors have recently been detected in trace concentrations in water systems around the world, and even some trace contaminants have been detected in sewage treatment plants and in drinking water treatment plants that people consume daily. These substances are present in trace concentrations, but continuous exposure can have adverse effects on the environment and ecosystems. Against this background, advanced oxidation treatments that produce strong oxidizing radicals can be a solution to the removal of hardly degradable organics. Advanced oxidation process is divided into various kinds according to the method of generating hydroxyl radical by oxidizing the material to be treated by using radical hydroxide (· OH) which has strong oxidizing power and finally inorganicizing it into the form of CO ₂ or H ₂ O. . Types of AOPs include electrochemical advanced oxidation, UV / Chlorine, UV / H ₂ O ₂ , UV / TiO ₂ , Fenton, Photo-Fenton, photocatalyst, and ultrasonic.

Existing methods for treating wastewater through electrodialysis have been designed to improve the efficiency of wastewater treatment by solving concentration polarization and membrane contamination caused by organic matter and inorganic ions that cause precipitation during membrane separation. Specifically, the membrane resistance is measured in real time, and accordingly, appropriate chemical cleaning is automatically performed to continuously treat wastewater (Korean Patent Publication No. 10-1046776), and a spacer through hole between a cation exchange membrane and an anion exchange membrane is provided. As the area decreases toward the outflow area of the treated water, there is a method of increasing the recovery rate of ions in the treated water by alleviating the concentration polarization formed around the ion exchange membrane (Korean Patent Publication No. 10-1235887). However, previous studies have only dealt with water at the desalination (deionization) level, so that organic and other nonionic contaminants cannot be removed and remain in the treated water. There has also been reported a method of removing the organic matter that has not been removed in the electrodialysis treatment by the post-treatment process (Korean Patent Publication No. 10-0687095), in which case there is a disadvantage in that additional injection of an external drug is required.

Korea Patent Registration 100687095 Korea Patent Registration 101046776 Korea Patent Registration 101235887

 Kyeong-Ho Yeon et al., Integrating electrochemical processes with electrodialysis reversal and electro-oxidation to minimize COD and T-N at wastewater treatment facilities of power plants, Desalination, 202, 400-410.

The present invention has been made to solve the above problems, an object of the present invention is to enable the simultaneous removal of ionic contaminants and oxidizable nonionic contaminants contained in the waste water in a single water treatment device, It is to provide an opto-dialysis water treatment apparatus that increases the efficiency of the process and energy by eliminating the addition of additional chemicals (oxidants) or a separate post-treatment process. It is also an object of the present invention to provide a water treatment method in which desalination and contaminant oxidation are simultaneously performed using a photoelectrodialysis water treatment apparatus.

The limitation of electrodialysis water treatment method is that the purpose of applying DC power is basically limited to the improvement of ion resolution through the generation of electric field. In the process, the water decomposition (oxygen and hydrogen generation) reaction occurring at the anode and cathode is treated with water. It will not be used for. On the other hand, the electrochemical highly oxidized water treatment method is capable of oxidizing contaminants such as organic matter in wastewater by using an oxidation reaction occurring after flowing an electric current by installing an anode (anode) and a cathode (cathode) in the sewage water having high electrical conductivity. For example, chlorine ions present in sewage water can generate free chlorine species as oxidants without chemical injection from the outside through oxidation reaction on the anode surface, and this principle can be applied to existing electrodialysis equipment. In addition, the electrochemical highly oxidized water treatment method described above is not efficient when the concentration of chlorine ions in the raw water is low, but the efficiency of the electrochemical highly oxidized water treatment can be increased by increasing the concentration of chlorine ions in the electrodialysis process. In other words, the combination of electrodialysis and electrochemical highly oxidized water treatment is complementary. On the other hand, free chlorine species used in electrochemical highly oxidized water treatment can produce highly toxic disinfection by-products such as trihalomethane, which, when combined with ultraviolet light, generates chlorine-based radicals and hydroxide radicals, which are more powerful oxidants, In addition to improving oxidation efficiency, it is possible to suppress the generation of disinfection by-products.

The inventors of the present invention simultaneously applied electrodialysis and photo / electrochemical advanced oxidation principles for the reuse of sewage, wastewater or wastewater treatment effluents, resulting in the removal of ionic contaminants contained in the wastewater in a single water treatment device. The present invention was completed by confirming that oxidizable nonionic contaminants can be removed at the same time, and additional chemicals (oxidizing agents) added or separate post-treatment steps are omitted, thereby increasing the efficiency of the process and energy.

In the present invention, high chlorine ions in the concentrated water generated during electrodialysis desalination are oxidized to the anode in the same apparatus to generate free chlorine species by itself. Of generating the hydroxide radicals that can not be processed in conventional electrodialysis water treatment recalcitrant organic matter ^- then, by injecting a free-chlorine species generated in the process water tank with UV irradiation chlorine radical (· / Cl · such as Cl ₂₎ It can be removed. Since chlorine radicals and hydroxyl radicals have higher oxidizing power and reaction rate than free chlorine species such as hypochlorous acid and less generation of disinfection by-products, higher water treatment efficiency can be achieved with the same energy supply through a water treatment device capable of generating radicals. have.

The present invention includes an apparatus and method for stably implementing the above principles in a single device without remaining in a simple combination of an electrodialysis water treatment method, an electrochemical advanced oxidation water treatment method, and a photochemical water treatment method.

Photoelectrodialysis water treatment apparatus according to an embodiment of the present invention includes an electrooxidation-dialysis module, a power supply, a concentrated water tank, an electrolyte tank, a treatment tank equipped with an ultraviolet lamp and a control unit.

In the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the electrooxidation-dialysis module includes an anode (electrode) and a cathode (reduction electrode) installed to face each other; A plurality of cation exchange membranes and a plurality of anion exchange membranes alternately disposed between the anode and the cathode; And a spacer interposed between the anode and the ion exchange membrane, between the cathode and the ion exchange membrane, and between the ion exchange membrane. The electrooxidation-dialysis module has a positive electrode, a negative electrode, and a plurality of cation exchange membranes and a plurality of anion exchange membranes are alternately arranged, and a spacer having a predetermined thickness is installed between the membranes and between the membranes and the electrodes. Provide space. The anode provides a attraction force for attracting anions present in the wastewater according to the application of current and at the same time serves to oxidize chlorine ions (Cl ⁻ ) contained in the concentrated water to free chlorine species. In addition, the cathode serves to reduce the water by providing a attraction force to attract the cation of the waste water according to the application of the current.

In the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the power supply device serves to apply a constant power to the positive electrode and the negative electrode of the electrooxidation-dialysis module and is preferably a DC power supply device.

In the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the concentrated water tank serves to provide a space in which the concentrated water circulating the electrooxidation-dialysis module is stored. Provide a brine reservoir for supplying brine and for the brine exiting the electrooxidation-dialysis module.

In the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the electrolyte tank serves to provide a space in which the electrolyte circulating in the electrooxidation-dialysis module is stored in contact with the positive electrode and the negative electrode, and specifically, the anode of the electrooxidation-dialysis module And an electrolyte storage space for supplying an electrolyte to the cathode and containing an electrolyte flowing out of the electrooxidation-dialysis module.

In the photovoltaic dialysis water treatment apparatus according to an embodiment of the present invention, the treated water is stored in the treated water circulating the electrooxidation-dialysis module, and when free chlorine species are introduced, chlorine radicals are caused by photooxidation of free chlorine species due to the immersed UV lamp. And it serves to provide a space for the generation of hydroxide radicals and advanced oxidation of the treated water, specifically the treatment to supply the treated water to the cathode of the electrooxidation-dialysis module and to receive the treated water flowing out of the electrooxidation-dialysis module At the same time, it provides a water storage space, accommodates oxidized concentrated water flowing out of the electrooxidation-dialysis module, and generates chlorine-based radicals and hydroxyl radicals from free chlorine species contained in the oxidized concentrated water by ultraviolet lamps, and advances the oxidation of the treated water. Provide space to become.

In the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the controller controls the flow rate of the concentrated water, the electrolyte, the treated water, or the oxidized concentrated water, the supply timing, or the blocking of the supply. To this end, the control unit is connected to the pump, valve, sensors provided in the opto-dialysis water treatment apparatus to be described later.

In the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the oxidized concentrated water is chlorine ion-containing concentrated water supplied between the anode and the ion exchange membrane of the electrooxidation-dialysis module, and the oxidized reaction is discharged after the oxidation reaction on the surface of the anode. It includes free chlorine species converted from chlorine ions by means of the oxidized brine outlet and the oxidized brine outlet pipe which fluidly connects the electrooxidation-dialysis module with the treatment tank.

The term 'concentrated water' used in the present invention is raw water contained in a concentrated tank; And a solution in which the chlorine ion concentration is increased by the electrooxidation-dialysis module treatment as a solution supplied to the electrooxidation-dialysis module and alternately circulated between the ion exchange membranes and then recovered by the concentration bath.

The term 'treated water' used in the present invention refers to raw water contained in a treated water tank; And a solution that is supplied to the electrooxidation-dialysis module and alternately circulated between the ion exchange membranes, and then recovered to the treatment tank, and includes a solution in which the chlorine ion concentration is reduced or the chlorine ion is removed by the electrooxidation-dialysis module treatment. .

In the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the anode of the electrooxidation-dialysis module is preferably in fluid communication with the brine tank through a brine inlet, a brine inlet, a brine outlet and a brine outlet. The cathode of the electrooxidation-dialysis module is preferably in fluid communication with the treatment tank through the treatment water inlet tube, the treatment water inlet, the treatment water outlet, and the treatment water outlet tube. The positive electrode and the negative electrode of the dialysis module are preferably in fluid communication with the electrolyte bath through the electrolyte inlet tube, the electrolyte inlet, the electrolyte outlet and the electrolyte outlet tube.

In addition, in the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the electrooxidation-dialysis module may further include a first body plate and a second body plate disposed to face each other. An anode is attached to the inside of the first body plate and a cathode is attached to the inside of the second body plate. The first body plate is connected in fluid communication with the anode through the brine inlet, the brine outlet, the electrolyte inlet and the electrolyte outlet. In addition, the second body plate is connected in fluid communication with the negative electrode through the treatment water inlet, the treatment water outlet, the electrolyte inlet, and the electrolyte outlet.

In addition, in the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the concentrated tank is preferably provided with an electrical conductivity sensor for measuring the electrical conductivity of the concentrated water. The electrical conductivity sensor is preferably immersed in a concentrated tank to measure the electrical conductivity of the concentrated water.

In addition, in the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the oxidized concentrated water outlet pipe is preferably provided with a free chlorine sensor for measuring the concentration of free chlorine species of the oxidized concentrated water. The free chlorine sensor is provided in the outlet pipe of the oxidation-treated concentrated water, and measures the free chlorine species concentration of the oxidation-treated concentrated water to determine whether anodization is further progressed and whether the oxidation-treated concentrated water flows into the treatment tank. Provide the baseline data to determine.

In addition, in the photovoltaic dialysis water treatment apparatus according to an embodiment of the present invention, the concentrated water inflow pipe, the electrolyte inflow pipe and the treated water inflow pipe are preferably pumps for controlling the flow rate of the concentrated water, the electrolyte and the treated water or blocking the inflow. Or a valve is provided. Specifically, when the electrical conductivity of the concentrated water measured by the electrical conductivity sensor immersed in the concentrated water tank reaches a preset reference value (the electrical conductivity of the electrolyte), the flow rate of the electrolyte and the concentrated water flowing around the anode is measured. A valve to control; When the free chlorine species concentration in the concentrated water measured by the free chlorine sensor exceeds a predetermined reference value, there is a valve for blocking the flow rate of the concentrated water flowing around the anode.

In addition, in the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, preferably between the anode and the concentrated tank of the electrooxidation-dialysis module, a first concentrated water inlet pipe and a second concentrated water inlet pipe are installed, and electrooxidation- The dialysis module is preferably formed with a first brine inlet and a second brine inlet. The first concentrated water inlet pipe and the second concentrated water inlet pipe are used to supply the concentrated water to the electrooxidation-dialysis module in the concentrated tank in the desalting step described later, and the second concentrated water inlet pipe and the second concentrated water The inlet is used to prepare the oxidized concentrated water by supplying the concentrated water to the electrooxidation-dialysis module in the concentrated tank in the free chlorine generation step described below. Specifically, the concentrated water supplied from the thickening tank through the second concentrated water inlet tube and the second concentrated water inlet to the electrooxidation-dialysis module is oxidized at the surface of the anode while flowing between the anode and the ion exchange membrane of the electrooxidation-dialysis module. After passing through the oxidized concentrated water outlet, it is discharged from the electrooxidation-dialysis module.

In addition, in the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the anode is made of a conductive metal material, preferably at least one material selected from IrO ₂ , RuO ₂ , SnO ₂ , Ta ₂ O _5, or TiO ₂ . Is made of. In addition, the cathode is made of a conductive metal material, preferably made of a material selected from Ti or stainless steel.

In addition, in the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the ion exchange membrane is made of a known divorce exchange resin, preferably made of a commercially available ion exchange resin. The commercialized ion exchange resin is crosslinked polystyrene, and specifically, there is a styrene-divinylbenzene-based ion exchange resin prepared by copolymerizing styrene and some divinylbenzene.

In addition, in the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the type of ultraviolet lamp is not particularly limited as long as the free chlorine species can emit ultraviolet rays of an absorbable wavelength, and preferably, UV-B lamp or UV-C It may be at least one selected from the lamps.

In addition, in the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention, the free chlorine species is preferably composed of one or more selected from hypochlorous acid (HOCl) or chlorine monoxide (OCl ⁻ ), and the chlorine-based radical is preferably dihydrochloride bovine radical ion (Cl ₂ ^- ·), chlorine radical (Cl ·) or may be composed of at least one element selected from among chlorine monoxide radicals (ClO˙).

The water treatment method according to an embodiment of the present invention uses the above-mentioned photoelectrodialysis water treatment apparatus. Water treatment method according to an embodiment of the present invention (a) to supply the raw water containing chlorine ions to the concentrated tank to prepare the concentrated water, the raw water containing chlorine ions to the treated tank to prepare the treated water, the electrolyte The tank comprises an operation preparation step consisting of supplying the electrolyte to prepare the electrolyte; (b) After the operation preparation step, a predetermined voltage is applied to the electrooxidation-dialysis module, and the electrolyte is supplied from the electrolytic bath to the electrooxidation-dialysis module, between the anode (anode) and the ion exchange membrane, and between the cathode and the ion exchange membrane. Circulating and supplying the concentrated water and the treated water from the concentrated tank and the treated tank to the electrooxidation-dialysis module, and circulating alternately between the ion exchange membranes, to recover the concentrated water having an increased chlorine ion concentration into the concentrated tank, and Desalination of raw water, comprising reducing or recovering the treated water without chlorine ions to the treated water tank; (c) After the desalting step, a portion of the concentrated water having an increased chlorine ion concentration from the concentrated bath is supplied to the electrooxidation-dialysis module, and the electrolyte is supplied from the electrolyte bath to the electrooxidation-dialysis module to supply the concentrated water and the electrolyte to the anode (oxide electrode). Free chlorine generation step comprising circulating between the ion exchange membrane and oxidized concentrated water containing free chlorine species converted from chlorine ions by oxidation reaction on the surface of the anode, and supplying the oxidized concentrated water to the treatment tank; And (d) after generating the free chlorine species, driving an ultraviolet lamp provided in the treatment tank to generate chlorine-based radicals and hydroxide radicals from the free chlorine species contained in the oxidized concentrated water and reacting with the non-ionic contaminants. And a highly oxidized treatment step consisting in oxidizing. In addition, the water treatment method according to an embodiment of the present invention preferably (e) after the advanced oxidation treatment step, when the content of residual non-ionic contaminants in the treatment tank is less than a predetermined reference value to empty the solution in the treatment tank and the raw water It may further comprise the step of ending the water treatment consisting of the inflow.

In the water treatment method according to an embodiment of the present invention, the desalting step supplies raw water or at least one desalted brine to an electrooxidation-dialysis module and is treated in a conventional electrodialysis mode, where the concentrated water and chlorine are relatively rich in chlorine ions. The ions are separated into treated water with relatively low or removed ions and recovered into concentrated tanks and treated water, respectively. The voltage applied to the electrooxidation-dialysis module in the desalting step is preferably 1 to 2.5 V / cm, and the circulation rates of the electrolyte, concentrated water and treated water are preferably 70 to 100 cm / h. In addition, the electrolyte serves to facilitate the generation of a current when the voltage is applied to the electrooxidation-dialysis module, it may be selected from known electrolytes used in the electrochemical field, preferably sodium nitrate solution of 1M concentration or less Or sodium perchlorate solution at a concentration of up to 1 M. In addition, in the desalting step, the electrical conductivity sensor of the concentrated water tank is measured in real time and compared with the electrical conductivity of the electrolyte in real time, and when a predetermined standard is reached, a free chlorine generation step is performed. desirable. Specifically, the free chlorine species generation step is preferably carried out when the electrical conductivity of the concentrated water is similar to or the same as the electrical conductivity of the electrolyte.

In the water treatment method according to an embodiment of the present invention, the free chlorine generation step is to supply chlorine ion with an increased concentration of chlorine ions through a desalting step to the anode surface of the electrooxidation-dialysis module and to oxidize to convert the chlorine ions into free chlorine species. This is the step. In the free chlorine species generation step, the free chlorine species concentration of the oxidized concentrated water is measured in real time through a free chlorine sensor provided in the oxidized concentrated water outlet pipe and the free chlorine species concentration of the oxidized concentrated water exceeds 10 mg / L. It is preferable to block the inflow of the concentrated water to the anode (anode) through the control unit. The flow of treated water in the free chlorine generation step is the same as the desalting step.

In the water treatment method according to an embodiment of the present invention, the advanced oxidation treatment step may be performed by irradiating oxidized concentrated water containing free chlorine species with ultraviolet light to generate chlorine radicals and hydroxide radicals from the free chlorine species, and using chlorine radicals and hydroxide radicals. Decomposing ionic contaminants, especially organic contaminants. At the beginning of the advanced oxidation step, the stream of concentrated water is recovered in the same way as the desalting step.

Photoelectrodialysis water treatment apparatus according to the present invention and the water treatment method using the desalination and pollutant oxidation at the same time has the following effects.

In addition to the removal of ionic contaminants using ion exchange membranes under the electric field generated by the applied voltage applied to the anode and cathode, the action of radical species generated through the additional reaction of free chlorine species generated through the oxidation of chlorine ions with ultraviolet rays. Oxidative removal of nonionic contaminants is possible.

During the electrodialysis desalination process, the conductivity of the concentrate is monitored by monitoring the conductivity of the concentrate in real time so that the voltage and current between the oxidation and reduction electrodes can be maintained in a steady state even when the concentrate is injected around the anode. Condensed water is injected at the same time to ensure stable operation.

Self-generated free chlorine concentration is monitored by a free chlorine sensor located at the outlet of the oxidized concentrated water, and when free chlorine concentration exceeds the standard concentration that can damage the ion exchange membrane, injection of concentrated water to the anode Stopping and stopping the oxidation of chlorine ions can minimize ion exchange membrane damage of the electrooxidation-dialysis module.

The generated free chlorine species flows into the treatment tank (or treated water reactor) in which the UV lamp is immersed through the oxidized concentrated water outlet pipe, and chlorine-based radicals and hydroxide radicals are generated, resulting in more efficient oxidation of the treated water and ) By-products can be reduced.

In summary, it maintains stable operation condition of a single device, and it can economically perform desalination and advanced oxidation because there is no external oxidant injection by producing its own oxidant.

1 is a block diagram of a photoelectrodialysis water treatment apparatus combining electrodialysis and photoelectrochemical processes according to an embodiment of the present invention.
Figure 2 is a schematic diagram showing the electrooxidation-dialysis process of the electrooxidation-dialysis module.
Figure 3 is a schematic diagram showing the oxidation reaction and the reduction reaction of the cathode of the electrooxidation-dialysis module.
Figure 4 is a result of measuring the change in conductivity of the treated water according to the voltage and recovery rate, flow rate applied to the positive electrode according to an embodiment of the present invention over time.
5 is a result of measuring the change in conductivity of the concentrated water according to the voltage and recovery rate, flow rate applied to the positive electrode according to an embodiment of the present invention over time.
Figure 6 is the result of measuring the amount of free chlorine generated according to the chlorine ion concentration according to an embodiment of the present invention.
7 is an experimental result comparing the removal efficiency of organic matter when treated with free chlorine species according to an embodiment of the present invention by irradiating UV light.

Electrodialysis is a membrane separation process in which an ionic substance is separated using a plurality of ion exchange membranes and an electric field formed by DC power supplied to electrodes provided at both ends thereof as a driving force. In the electrodialysis, an anode and a cathode are provided on both sides, and a membrane in which only a cation permeates selectively (hereinafter cation exchange membrane) and a membrane in which only an anion permeates selectively (hereinafter anion exchange membrane) are alternately provided. A spacer having a constant thickness is installed between the membranes to allow the solution to flow between the membranes, and when a proper amount of direct current is applied, the cations and anions in the solution move in opposite directions by electric force. In this case, ion selective separation occurs according to the type of ions by the selective membrane, whereby raw water can be separated into concentrated water and treated water. Therefore, the electrodialysis method has the disadvantage that the electrically charged material, that is, only the ionic component is removed and the non-charged organic material is not processed.

In order to increase the completeness of the wastewater treatment function of the electrodialysis process, the organic matter should be removed by post-treatment. In view of the above, the present invention provides a photoelectrodialysis apparatus that generates a chlorine-based oxidant and radicals in concentrated water by using an oxidation electrode capable of oxidizing chlorine ions and an ultraviolet lamp, thereby eliminating a separate post-treatment process. . In detail, some of the concentrated water containing high concentration of chlorine ions is injected from the surface of the powered anode to oxidize the chlorine ions into free chlorine species through oxidation, and the free chlorine species is treated as a treatment tank (or treated water reactor). It is then sent to produce a powerful oxidizing agent, chlorine-based radicals and hydroxyl radicals. Radicals oxidize nonionic contaminants, such as organic matter, that are not removed by conventional electrodialysis methods.

At this time, if the electrical conductivity of the concentrated water injected for the generation of free chlorine species and the electrolyte contacted by the anode at the start of operation of the device is greatly different, the generation of current under the same voltage may cause damage to the voltage supply device. There is a possibility. Therefore, by measuring the electrical conductivity of the concentrated water in real time, we propose an operation method of injecting the concentrated water at the time when the electrical conductivity similar to the existing electrolyte is reached.

In addition, the main component that determines the overall performance of electrodialysis is the ion exchange membrane, which, when contacted with high concentrations of free chlorine, causes damage to the ion exchange resin, impairs water quality of the treated water, reduces system run time, and increases the amount of regeneration. Cause. Therefore, in order to prevent chemical damage of the ion exchange resin due to the generation of free chlorine species, the concentration of free chlorine species generated at the anode is monitored in real time. Inflow is blocked. This ensures the stability of the process and improves the quality of the treated water without external oxidant injection and additional post-treatment.

Hereinafter, a photoelectrodialysis water treatment apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2, the photoelectrodialysis water treatment apparatus according to the embodiment of the present invention includes an electrooxidation-dialysis module. The electrooxidation-dialysis module separates raw water into concentrated water and treated water through desalination, and provides a space for the oxidation reaction of chlorine ions contained in the concentrated water.

The electrooxidation-dialysis module is provided with a positive electrode immersed in an electrolyte or concentrated water or a mixed solution of the two and a negative electrode immersed in the electrolyte, the DC power supply for applying power to the positive electrode and the negative electrode on one side of the electrooxidation-dialysis module Feeding device is provided. The positive electrode and the negative electrode have a flat plate shape and are attached to a plate of the module main body, and are connected to the concentrated water inlet / outlet, the treated water inlet / outlet, and the electrolyte inlet / outlet.

In the electrooxidation-dialysis module, a plurality of cation exchange membranes and a plurality of anion exchange membranes are alternately arranged, and a spacer is disposed between the anode and the ion exchange membrane, the cathode and the ion exchange membrane, and each ion exchange membrane to form a flow path. In the desalting process, electrolyte flows between the anode and the ion exchange membrane, and between the cathode and the ion exchange membrane, and the concentrated water and the treated water alternately flow between each ion exchange membrane. The anion in the raw water moves in the direction of the oxidizing electrode, the cation moves in the opposite direction, and a current is formed, and it is preferable that the value does not have a sudden change for the stability of the voltage supply device. That is, for stable electrodialysis operation, the electrical conductivity of the electrode surface electrolyte must be kept constant.

The raw water means the target water to be treated for the purpose of removing ionic and oxidizable nonionic contaminants, and the electrical conductivity is preferably within 5 mS / cm.

The electrolyte is supplied around the anode and cathode, respectively, to facilitate the generation of current when voltage is applied, and has higher electrical conductivity than the raw water, such as NaNO ₃ and NaClO ₄ solutions of 1 M or less, and the oxidation of the cathode and anode. It is desirable to have a component which is not affected by the reduction reaction.

In the present invention, the conductivity of the concentrated water is monitored by immersing the conductivity sensor in the concentrated water tank to prevent a sudden change in the electrical conductivity of the electrolyte due to the inflow of the concentrated water into the anode and thereby overloading the voltage supply device. Specifically, the conductivity of the concentrated water is continuously monitored, and when the conductivity of the concentrated water is similar to that of the electrolyte, the concentrated water is injected into the surface of the anode through the control unit to minimize the change in the current and voltage of the process. It is to maintain the driving conditions.

The anode should have excellent electrical conductivity and corrosion resistance, and may be formed by mixing oxides such as Ir and Ru with oxides such as Sn, Ti and Ta in order to satisfy these conditions. The higher the ratio of the transition metals Ir and Ru to the surface of the anode, the greater the amount of current generated. The cathode may be stainless steel, Ti, or the like.

When the ion exchange resin, which is a material of the ion exchange membrane, is exposed to an oxidizing agent such as free chlorine species, the divinylbenzene linkage is broken and permanent damage of the ion exchange resin occurs. Because of this, the concentration of free chlorine species produced electrochemically must be kept below the oxidizer resistance strength of the ion exchange resin so that the electrodialysis process can be operated in the long term. Commercially available styrene-divinylbenzene-based ion exchange resins are resistant to oxidants. It can operate for about 1000 hours at 10 mg / L free chlorine concentration, and it can operate for about 4000 hours because it can minimize membrane damage and prevent biological membrane fouling in the 0.3 ~ 0.5 mg / L free chlorine species concentration range. It has been reported to be the most efficient condition possible. It is desirable to maintain free chlorine species concentrations in the range of 10 mg / L or less in order to minimize membrane damage and at the same time induce effective UV interaction in the treated water bath.

The concentration of free chlorine species generated at the anode is influenced by the performance of free chlorine species generation at the anode, the concentration of chlorine ions in the concentrated water, the supply amount of the concentrated water, the applied voltage, and the residence time. Therefore, it is possible to control the free chlorine species concentration by controlling the flow rate of the concentrated water flowing into the anode based on the evaluation of the free chlorine species generation performance of the positive electrode according to the chlorine ion concentration and the desalination performance of the raw water. More actively, the concentration of free chlorine species can be controlled by monitoring with free chlorine sensors.

Hereinafter, a water treatment method in which desalination and contaminant oxidation are simultaneously performed using the photoelectrodialysis water treatment apparatus according to an embodiment of the present invention will be described in detail.

In the operation preparation stage, raw water is supplied to the concentrate tank and the treatment tank, and electrolyte is supplied to the electrolyte tank.

In the desalting step of raw water, a constant voltage is applied to the electrooxidation-dialysis module, and the electrolyte circulates around the anode and the cathode (between the ion exchange membranes), and the concentrated water and the treated water are alternated between the ion exchange membranes. Circulate In the process, the conductivity of chlorine water (chlorine ion concentration) continuously increases, and the conductivity of treated water (chlorine ion concentration) decreases continuously. In addition, since the components of the electrolyte are not affected by the redox reaction, water decomposition reactions (oxygen generation and hydrogen generation) occur on the surfaces of the anode and the cathode, respectively. At this time, the applied voltage can be selected in the range of 1 ~ 2.5 V / cm (the total applied voltage divided by the distance between the anode and the cathode) according to the properties of the raw water. The circulation rate of the electrolyte, the concentrated water and the treated water can be selected in the range of 70 to 100 cm / h (the flow rate divided by the total area of the positive ion exchange membrane).

The free chlorine generation step begins at a point similar to the electrical conductivity of the concentrated water and the electrical conductivity of the electrolyte, wherein the concentrated water containing a certain amount of high concentration of chlorine ions with the electrolyte moves around the anode (between the anode and the ion exchange membrane). Supplied. At this time, oxidation of chlorine ions (Cl ⁻ ) occurs on the surface of the anode, and the reduction of water due to electron acceptance continues on the cathode. More specifically, at the anode, chlorine ions (Cl ⁻ ) are oxidized to free chlorine species such as chlorine (Cl ₂ ), hypochlorous acid (HOCl), or chlorine monoxide (OCl ⁻ ), depending on the power applied (Equation 1, 2 and Equation 3), the cathode recovers the electrons (e ⁻ ) generated at the anode and transfers them to water, which is an electron acceptor, inducing a reduction reaction of water and generating hydroxide ions (OH ⁻ ) (see Equation 8).

(Equation _{^{1) 2Cl - → Cl 2 +}} 2e -

(Equation ^{_{2) Cl 2 - + H 2}} O → HOCl + H + + Cl -

(Equation ^{3) HOCl ↔ ClO - + H} +

(Equation ^{_{8) 2H 2 O + 2e -}} → H 2 + 2OH -

At this time, the concentrated water that has undergone oxidation on the surface of the anode is introduced into the treatment tank instead of the concentrated tank.

The advanced oxidation treatment step starts when the free chlorine species concentration in the oxidized reaction reaches 10 mg / L, and at this time recovers the flow of the concentrated water in the same way as the desalting step and simultaneously immerses the UV in the treatment tank. The lamp is driven. Combining free chlorine species and ultraviolet rays, which are mainly used in the disinfection process aimed at sterilizing and disinfecting waterborne pathogens, it is known that oxidation of hardly degradable organic pollutants is possible through the generation of strong oxidants. Free chlorine species undergo photolysis when absorbing a light source with a wavelength of 511 nm or less, producing hydroxyl and chlorine radicals, which are powerful oxidants. Free chlorine species in the 250 ~ 350 nm wavelength range absorbs the light source to the maximum, the most effective photolysis occurs. Therefore, UV-B (280 ~ 315nm) lamp is immersed in the treated water reactor to advance the oxidation. (See equations 4 to 11).

(Equation ^{4) HOCl / ClO - + +} hv → · OH / O˙ - + Cl˙

(Equation ^{5) · OH ↔ O˙ - +} H +

(Formula ^{6) Cl˙ + Cl - → Cl} 2 ˙ -

OH + HOCl-> ClO '+ H ₂ O

(Equation ^{8) · OH + ClO - →} ClO˙ + OH -

(Equation ^{9) Cl˙ + HOCl → H +} + Cl - + ClO˙

(Formula ^{10) Cl˙ + OCl - → Cl} - + ClO˙

(Formula ^{11) Cl˙ + OH - → ClOH˙} -

Chlorine radicals and hydroxide radicals generated through the reactions of Equations 4 to 11 are known to bring organic pollutants and disinfection effects at a faster rate than free chlorine species, and trihalomethane (THM) generated when free chlorine species are used. It has the additional advantage of less generation of disinfection by-products such as haloacetic acids (HAAs).

The end of the water treatment process starts when the residual organic matter in the treated water tank is below a predetermined standard value, and refers to a process of emptying the water in the concentrated water tank and the treated water tank and introducing raw water for the next step.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings. In this embodiment, one Ti / IrO ₂ anode, 10 cation exchange membranes, 11 anion exchange membranes, and 1 Ti cathode were used to implement an electrooxidation-dialysis module, each having a space of 64 cm ² . Fixed at 0.8 cm. The raw water to be treated was artificial wastewater containing 1400 ppm (about 40 mM) of chlorine ion, 1200 ppm of sulfate ion, and 10 μM of methylene blue as organic matter.

4 and 5 are the results of measuring the change in conductivity of the concentrated water and the treated water during the electrodialysis desalination process of the raw water by using the voltage, the recovery rate, the flow rate as variables. As the time of capacitive desalination increases, the conductivity (ion concentration) of the concentrated water increases and the conductivity (ion concentration) of the treated water decreases clearly. Through these experiments, it is possible to determine the optimal operating conditions to minimize the concentration of ions in the treated water according to the characteristics of the raw water, and to determine the point of time when the concentrated water is injected around the anode through monitoring the conductivity of the concentrated water. At this time, the current flowing in the anode and cathode was found to be in the range of 30 to 200 A / m ² .

FIG. 6 shows the amount of free chlorine generation at 200 A / m ² current density when the concentration of chlorine ions is 50, 100 and 150 mM for Ti / IrO ₂ anode and Ti cathode. As the concentration of chlorine ions increases or the oxidation time increases, the amount of free chlorine generation increases. In addition, as the applied current density increases, the amount of free chlorine species is also known to increase. Therefore, when some of the concentrated water flows around the anode during the generation of free chlorine species, the concentration of chlorine ion around the anode (between the anode and the ion exchange membrane) can be adjusted according to the concentration of the water injection and the electrolyte circulation rate. Therefore, in theory, it is possible to control the concentration of free chlorine species by adjusting the ratio of the concentration of the concentrated water injection and the electrolyte circulation rate, the residence time around the electrode (2.8 to 4 seconds in this embodiment), and the applied current. However, more aggressively concentrated at a point where the free chlorine species becomes 5-15 mgCl ₂ / L, preferably 8-12 mgCl ₂ / L, more preferably 10 mgCl ₂ / L, through the free chlorine species sensor. It is desirable to stop the anodic injection of water and begin the advanced oxidation step.

7 is an organic material under UV (UV) irradiation conditions, free chlorine species injection conditions of 10 mgCl ₂ / L, and UV and free chlorine species injection simultaneously for Methylene blue 10 μM solution, a kind of organic material The decomposition rate is shown. It can be seen that UV / Cl ₂ complex treatment shows significantly higher organic removal efficiency than UV alone or Cl ₂ (free chlorine species) alone.

Although the present invention has been described in detail through the embodiments as described above, the protection scope of the present invention is not necessarily limited thereto, and various modifications may be made without departing from the scope and spirit of the present invention. Therefore, the protection scope of the present invention should not be limited to the specific embodiments disclosed as the best mode, but should be construed as including all embodiments falling within the scope of the claims appended to the present invention.

Claims (16)

An electro-dialysis dialysis module comprising an electro-oxidation-dialysis module, a power supply device, a concentrated water tank, an electrolyte tank, a treatment tank equipped with an ultraviolet lamp, and a control unit,
The electro-oxidation-dialysis module includes an anode (electrode) and a cathode (reduction electrode) installed to face each other; A plurality of cation exchange membranes and a plurality of anion exchange membranes alternately disposed between the anode and the cathode; And a spacer interposed between the anode and the ion exchange membrane, between the cathode and the ion exchange membrane, and between the ion exchange membrane,
The power supply device applies power to the positive electrode and the negative electrode of the electrooxidation-dialysis module,
The brine tank provides a brine reservoir for supplying brine to the anode of the electro-dialysis dialysis module and receiving the brine flowed out of the electro-dialysis dialysis module,
The electrolyte tank provides an electrolyte storage space for supplying the electrolyte to the positive electrode and the negative electrode of the electrooxidation-dialysis module and for receiving the electrolyte flowing out of the electrooxidation-dialysis module,
The treatment tank supplies treated water to the cathode of the electrooxidation-dialysis module and provides a treated water storage space for receiving the treated water flowing out of the electrooxidation-dialysis module, and at the same time, receives the oxidized concentrated water flowing out of the electrooxidation-dialysis module. Chlorine radicals and hydroxide radicals are generated from free chlorine species contained in the oxidized concentrated water by ultraviolet lamps, and provide a space for advanced oxidation of the treated water,
The control unit controls the flow rate of the concentrated water, the electrolyte, the treated water or the oxidized concentrated water, the time of supply or whether the supply is blocked.
The oxidized concentrated water includes chlorine ion-containing concentrated water supplied between the anode and the ion exchange membrane of the electrooxidation-dialysis module after being oxidized at the surface of the anode, and includes free chlorine species converted from chlorine ions by the oxidation reaction. And an electrolytic dialysis module and an oxidized concentrated water outlet and an oxidized concentrated water outlet that connect the electrolytic dialysis module to the treated tank in fluid communication.
The method of claim 1, wherein the anode of the electrooxidation-dialysis module is connected in fluid communication with the brine tank through a brine inlet, a brine inlet, a brine outlet and a brine outlet, The cathode of the module is connected in fluid communication with the treatment tank through the treatment water inlet, the treatment water inlet, the treatment water outlet, and the treatment water outlet, and the anode and cathode of the electrooxidation-dialysis module are the electrolyte inlet tube, the electrolyte. A photoelectrodialysis water treatment apparatus, which is connected in fluid communication with an electrolyte tank through an inlet, an electrolyte outlet, and an electrolyte outlet tube.
The method of claim 1, wherein the electrooxidation-dialysis module further comprises a first body plate and a second body plate disposed opposite each other,
An anode is attached to the inside of the first body plate and a cathode is attached to the inside of the second body plate,
The first body plate is connected in fluid communication with the positive electrode through the concentrated water inlet, the concentrated water outlet, the electrolyte inlet and the electrolyte outlet,
The second body plate is a photoelectrodialysis water treatment apparatus, characterized in that in fluid communication with the negative electrode through the treated water inlet, the treated water outlet, the electrolyte inlet and the electrolyte outlet.
The apparatus of claim 1, wherein the concentrated water tank is provided with an electrical conductivity sensor for measuring the electrical conductivity of the concentrated water.
The apparatus of claim 1, wherein the oxidized concentrated water outlet pipe is provided with a free chlorine sensor for measuring the concentration of free chlorine species in the oxidized concentrated water.
3. The photoelectrodialysis of claim 2, wherein each of the concentrated water inflow pipe, the electrolyte inflow pipe, and the treated water inflow pipe is provided with a pump or a valve for controlling the flow rate of the concentrated water, the electrolyte, and the treated water or blocking the inflow. Water treatment device.
According to claim 2, wherein the first concentrated water inlet pipe and the second concentrated water inlet pipe is installed between the anode and the concentrated tank of the electrooxidation-dialysis module, the electrolytic-dialysis module is the first concentrated water inlet and the second concentrated A water inlet is formed,
The concentrated water supplied to the electrooxidation-dialysis module from the concentrate tank through the second concentrated water inlet tube and the second concentrated water inlet is subjected to oxidation reaction on the surface of the anode while flowing between the anode and the ion exchange membrane of the electrooxidation-dialysis module. Photoelectrodialysis water treatment apparatus, characterized in that flow out from the electrooxidation-dialysis module through the oxidation concentrate outlet.
The method of claim 1, wherein the anode is made of at least one material selected from IrO ₂ , RuO ₂ , SnO ₂ , Ta ₂ O ₅ or TiO ₂ , the cathode is made of a material selected from Ti or stainless steel. Photoelectrodialysis water treatment apparatus.
The apparatus of claim 1, wherein the ultraviolet lamp is at least one selected from a UV-B lamp or a UV-C lamp.
The method of claim 1 wherein said free chlorine species difference acid (HOCl) or monoxide chlorine (OCl ^-) are composed of at least one element selected from the chlorine radicals are dibasic bovine radical ion (Cl ₂ ^- ·), chlorine radical Optodialysis water treatment apparatus, characterized in that it is composed of one or more selected from (Cl ·) or chlorine monoxide radical (ClO ').
Using the photoelectrodialysis water treatment apparatus of any one of claims 1 to 10, the water treatment method comprising the following steps:
(a) supplying raw water containing chlorine ions to the concentrated tank to prepare concentrated water, supplying raw water containing chlorine ions to the treated tank to prepare the treated water, and supplying electrolyte to the electrolyte tank to prepare the electrolyte. An operation preparation step consisting of;
(b) After the operation preparation step, a predetermined voltage is applied to the electrooxidation-dialysis module, and the electrolyte is supplied from the electrolytic bath to the electrooxidation-dialysis module, between the anode (anode) and the ion exchange membrane, and between the cathode and the ion exchange membrane. The concentrated water and the treated water are supplied to the electrooxidation-dialysis module and alternately circulated between the ion exchange membranes from the concentrated water tank and the treated water tank to recover the concentrated water having increased chlorine ion concentration into the concentrated water tank, and the chlorine ion concentration is increased. Desalination of raw water consisting of recovering the treated water which is reduced or does not contain chlorine ions to the treated water tank;
(c) After the desalting step, a portion of the concentrated water having an increased chlorine ion concentration from the concentrated tank is supplied to the electrooxidation-dialysis module, and the electrolyte is supplied from the electrolyte tank to the electrooxidation-dialysis module to supply the concentrated water and the electrolyte to the anode (oxide electrode). A free chlorine species generation step comprising circulating between the ion exchange membrane and an oxidized concentrated water containing free chlorine species converted from chlorine ions by an oxidation reaction on the surface of the anode, and supplying the oxidized concentrated water to a treatment tank; And
(d) After the step of generating free chlorine species, the UV lamp provided in the treatment tank is operated to generate chlorine radicals and hydroxide radicals from free chlorine species contained in the oxidized concentrated water and react with the non-ionic contaminants to remove the non-ionic contaminants. Advanced oxidation treatment step consisting in oxidizing.
The water treatment method according to claim 11, wherein the applied voltage in the desalting step is 1 to 2.5 V / cm, and the circulation rates of the electrolyte, the concentrated water and the treated water are 70 to 100 cm / h.
The free chlorine species generation step according to claim 11, wherein the electrical conductivity sensor of the concentrated water is measured in real time through an electrical conductivity sensor provided in the concentrated tank in the desalting step, and compared with the electrical conductivity of the electrolyte. Water treatment method characterized in that to carry out.
The method of claim 13, wherein the electrolyte is selected from sodium nitrate solution at a concentration of 1 M or less or sodium perchlorate solution at a concentration of 1 M or less.
The free chlorine species concentration of the oxidized concentrated water is measured in real time through a free chlorine sensor provided in the oxidized concentrated water outlet in the free chlorine species generation step, the free chlorine species concentration of 10 mg When the water exceeds / L water treatment method characterized in that the inlet of the concentrated water to the anode (anode) through the control unit.
12. The method of claim 11, wherein at the beginning of the advanced oxidation step, the stream of concentrated water is recovered in the same way as the desalting step.

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