Water treatment system

Abstract

This water treatment system purifies water under treatment that contains an organic substance by removing the organic substance from the water under treatment, and includes a separation membrane device and an organic substance treatment device. The separation membrane device includes a separation membrane. The water under treatment is passed through the separation membrane, whereby the separation membrane separates the water under treatment into permeated water, from which at least a portion of the organic substance has been removed, and non-permeated water, which did not permeate through the separation membrane. The organic substance treatment device includes an adsorption element. By coming into contact with the non-permeated water and adsorbing the organic substance, the adsorption element discharges the non-permeated water as adsorption treated water. By coming into contact with a heating gas and desorbing the organic substance, the adsorption element discharges a desorption gas containing the heating gas and the organic substance.

Description

Water Treatment Systems

[0001] The present invention relates to a water treatment system.

[0002] Conventionally, organic fluorine compounds such as polytetrafluoroethylene (hereinafter also referred to as "PTFE") have been used to impart various functions, such as lubricity, to both industrial and consumer goods. Among these organic fluorine compounds, perfluoroalkyl compounds and polyfluoroalkyl compounds are collectively referred to as "PFAS." Among PFAS, perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are particularly persistent, highly accumulating, and highly mobile, and are known to persist widely on a global scale. If the above-mentioned PFAS continue to be released into the environment, there is a risk of further accumulation, which could have adverse effects on human health, the habitat and growth of plants and animals, etc., through the environment and food chain.

[0003] JP 2015-150519 A

[0004] The PFAS may also be contained in industrial wastewater and domestic wastewater (hereinafter, also referred to simply as "wastewater"). Japanese Patent Application Laid-Open No. 2015-150519 (Patent Document 1) relates to a wastewater treatment system that purifies wastewater by removing organic substances from wastewater containing the organic substances, and can remove organic substances such as the PFAS from a water system by incorporating them into wastewater. However, Patent Document 1 has the potential to generate a large amount of wastewater, leaving room for improvement in the treatment of the wastewater.

[0005] In view of the above circumstances, an object of the present invention is to provide a water treatment system that can reduce the amount of waste liquid.

[0006] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. The present inventors discovered that by appropriately combining elements capable of removing organic substances from liquids such as wastewater, it is possible to reduce the amount of wastewater discharged from a water treatment system. This discovery led to the completion of the present invention. The present invention relates to a water treatment system as described below.

[0007] [1] The present invention relates to a water treatment system that purifies water to be treated by removing organic substances from the water to be treated, the system comprising: a separation membrane device; and an organic substance treatment device. The separation membrane device comprises a separation membrane. The separation membrane separates the water to be treated into permeate from which at least a portion of the organic substances have been removed and non-permeate that has not passed through the separation membrane by passing the water to be treated. The organic substance treatment device comprises an adsorption element. The adsorption element contacts the non-permeate and adsorbs the organic substances, thereby discharging the non-permeate as adsorption-treated water. The adsorption element contacts a heated gas and desorbs the organic substances, thereby discharging a desorbed gas containing the heated gas and the organic substances. [2] The present invention relates to a water treatment system that purifies water to be treated by removing organic substances from the water to be treated, the system comprising: a separation membrane device; and an organic substance treatment device. The organic substance treatment device comprises an adsorption element. The adsorption element contacts the water to be treated and adsorbs the organic substances, thereby discharging the water to be treated as adsorption-treated water. The adsorption element contacts a heated gas and desorbs the organic substances, thereby discharging a desorbed gas containing the heated gas and the organic substances. The separation membrane device includes a separation membrane. The separation membrane is passed through the adsorption-treated water to separate the adsorption-treated water into permeated water from which at least a portion of the organic substances has been removed and non-permeated water that did not pass through the separation membrane. [3] The water treatment system according to [1] or [2], which includes a condenser that liquefies the desorbed gas. [4] The water treatment system according to [1], which returns the adsorption-treated water to the water to be treated. [5] The water treatment system according to [2], which returns the non-permeated water to the water to be treated. [6] The water treatment system according to any one of [1] to [5], which includes an ion exchange device equipped with an ion exchange resin, and which passes the adsorption-treated water through the ion exchange resin. [7] The water treatment system according to any one of [1] to [6], further comprising an ion exchange device equipped with an ion exchange resin, through which the permeate is passed.[8] The water treatment system according to any one of [1] to [7], wherein the separation membrane comprises at least one member selected from the group consisting of a reverse osmosis membrane, a forward osmosis membrane, an ion exchange membrane, and a nanofiltration membrane. [9] The water treatment system according to any one of [1] to [8], wherein the adsorption element comprises at least one member selected from the group consisting of activated carbon, activated carbon fiber, zeolite, silica gel, activated alumina, and a metal-organic framework.

[10] The water treatment system according to any one of [1] to [9], wherein the organic substance treatment device has a means for repeatedly transferring a portion of the adsorption element where desorption treatment has been completed to a portion where adsorption treatment will be performed, and transferring a portion of the adsorption element where adsorption treatment has been completed to a portion where desorption treatment will be performed.

[0008] According to the present invention, there is provided a water treatment system that can reduce the amount of the waste liquid.

[0009] Fig. 1 is a system configuration diagram of a water treatment system according to a first embodiment. Fig. 2 is a system configuration diagram of a water treatment system according to a second embodiment. Fig. 3 is a system configuration diagram of a water treatment system according to a third embodiment. Fig. 4 is a system configuration diagram of a water treatment system according to a fourth embodiment. Fig. 5 is a system configuration diagram of a water treatment system according to a fifth embodiment. Fig. 6 is a system configuration diagram of a water treatment system according to a sixth embodiment. Fig. 7 is a system configuration diagram of a water treatment system according to a seventh embodiment.

[0010] Hereinafter, several embodiments of the present invention will be described in more detail with reference to the drawings. The present invention is not limited to these embodiments. In the drawings, the same reference symbols represent the same or corresponding parts. In this specification, an expression in the form of "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and only a unit is specified for B, the unit of A and the unit of B are the same.

[0011] [Water Treatment System] The water treatment system according to the present invention purifies water to be treated by removing organic substances from the water. The water treatment system includes a separation membrane device and an organic substance treatment device. The separation membrane device includes a separation membrane. The separation membrane is passed through the water to be treated, separating the water into permeated water from which at least a portion of the organic substances have been removed and non-permeated water that did not pass through the separation membrane. The organic substance treatment device includes an adsorption element. The adsorption element comes into contact with the non-permeated water and adsorbs the organic substances, thereby discharging the water to be treated or the non-permeated water as the adsorption-treated water. The adsorption element comes into contact with a heated gas and desorbs the organic substances, thereby discharging a desorbed gas containing the heated gas and the organic substances.

[0012] Another water treatment system according to the present invention is a water treatment system that purifies water to be treated by removing organic substances from the water containing the organic substances. The water treatment system includes a separation membrane device and an organic substance treatment device. The organic substance treatment device includes an adsorption element. The adsorption element comes into contact with the water to be treated and adsorbs the organic substances, thereby discharging the water to be treated as adsorption-treated water. The adsorption element comes into contact with a heated gas and desorbs the organic substances, thereby discharging a desorbed gas containing the heated gas and the organic substances. The separation membrane device includes a separation membrane. The separation membrane is passed through the adsorption-treated water to separate the adsorption-treated water into permeate from which at least a portion of the organic substances have been removed and non-permeate that has not passed through the separation membrane.

[0013] In the water treatment system having such characteristics, when the desorbed gas discharged to the outside of the system is liquefied, the resulting liquid can contain high concentrations of organic substances. In other words, the amount of waste liquid discharged from the water treatment system can be reduced. The water treatment system preferably includes a condenser that liquefies the desorbed gas.

[0014] As used herein, the "organic substances" contained in the treated water are not particularly limited, but may include, for example, so-called PFAS. As used herein, "PFAS" refers to the general term for perfluoroalkyl compounds and polyfluoroalkyl compounds, as described above. In particular, the compounds listed in the "non-exhaustive list" published by the U.S. Environmental Protection Agency (EPA) on January 25, 2024 are defined as "PFAS." The "non-exhaustive list" refers to the list of compounds that meet the definition of "per / polyfluoroalkyl substances or PFAS" as defined in "§705.3 Definitions" of 40 CFR Part 705, a regulation enacted on November 13, 2023, pursuant to Section 8(a)(7) of the U.S. Toxic Substances Control Act (TSCA). In this specification, "PFAS" may also include perfluoroalkyl compounds and polyfluoroalkyl compounds that have become newly subject to regulation as a result of being included in the above-mentioned non-exhaustive list due to a change in definition or the like after the date of filing of the patent application for this invention.

[0015] Alternatively, the "organic substances" contained in the water to be treated may be aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and acrolein; ketones such as methyl ethyl ketone, diacetyl, methyl isobutyl ketone, and acetone; esters such as 1,4-dioxane, 2-methyl-1,3-dioxolane, 1,3-dioxolane, tetrahydrofuran, methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; alcohols such as ethanol, n-propyl alcohol, isopropyl alcohol, and butanol; glycols such as ethylene glycol, propylene glycol, diethylene glycol, and triethylene glycol; organic acids such as acetic acid and propionic acid; aromatic organic compounds such as phenols, toluene, xylene, and cyclohexane; ethers such as diethyl ether and allyl glycidyl ether; and diesters such as acrylonitrile. tolyls, dichloromethane, 1,2-dichloroethane, trichloroethylene, epichlorohydrin and other chlorinated organic substances; organic substances such as N-methyl-2-pyrrolidone, dimethylacetamide, N,N-dimethylformamide; dioxins such as polychlorinated dibenzoparadioxins (PCDD), polychlorinated dibenzofurans (PCDF), dioxin-like polychlorinated biphenyls (DL-PCB); antibiotics such as tetracycline, oseltamivir, oseltamivir phosphate, bezafibrate, triclosan and other antilipidemic ingredients; antipyretic analgesic ingredients such as diclofenac, salicylic acid, acetaminophen and other antiepileptic ingredients; humic substances such as humic acid, fulvic acid and other humic substances;

[0016] Additionally, the term "water to be treated" in this specification refers to, for example, wastewater from factories or homes, river water, seawater, drinking water, industrial water, etc. Hereinafter, details of several embodiments illustrating the present invention will be described with reference to the drawings.

[0017] First Embodiment FIG. 1 is a system configuration diagram of a water treatment system according to a first embodiment. The water treatment system according to the first embodiment purifies water A to be treated by removing organic substances from the water A. As shown in FIG. 1 , the water treatment system includes a separation membrane device 10 and an organic substance treatment device 20. The separation membrane device 10 includes a separation membrane 110. The separation membrane 110 is passed through the water A to be treated, separating the water A into a permeate B from which at least some or all of the organic substances have been removed and a non-permeate B that did not pass through the separation membrane 110. The organic substance treatment device 20 includes adsorption elements 211 and 221. The adsorption elements 211 and 221 contact the non-permeate and adsorb the organic substances, thereby discharging the non-permeate as adsorption-treated water. The adsorption elements 211 and 221 contact a heated gas C and desorb the organic substances, thereby discharging a desorbed gas containing the heated gas C and the organic substances. That is, in the wastewater treatment system according to the first embodiment, water to be treated A is passed through the separation membrane 110. The adsorption elements 211, 221 come into contact with non-permeated water. The adsorption-treated water is returned to the water to be treated A. The water treatment system according to the first embodiment includes a condenser 24 that liquefies the desorbed gas. The desorbed gas is liquefied into condensed water D by the condenser 24. The condensed water D is discharged outside the water treatment system.

[0018] The water treatment system includes a supply tank T1 for supplying water A to be treated introduced from outside the system to the separation membrane device 10, and an intermediate tank T2 for receiving non-permeated water separated by the separation membrane device 10 and supplying the non-permeated water to the organic substance treatment device 20. The supply tank T1 and the separation membrane device 10, the separation membrane device 10 and the intermediate tank T2, the intermediate tank T2 and the organic substance treatment device 20, and the organic substance treatment device 20 and the supply tank T1 are each connected by piping. A more specific structure of the water treatment system will be described below.

[0019] (Separation membrane device) As described above, the separation membrane device 10 includes the separation membrane 110. The separation membrane 110 is provided in a separation membrane module 11 that forms the separation membrane device 10. The separation membrane module 11 includes the separation membrane 110 and a first chamber 111 and a second chamber 112 that are separated by the separation membrane 110. The separation membrane device 10 includes, as a component thereof, a liquid feed pump 12 for supplying the water to be treated A in the supply tank T1 to the separation membrane module 11.

[0020] The separation membrane 110 preferably includes at least one member selected from the group consisting of a reverse osmosis membrane (RO membrane), a forward osmosis membrane (FO membrane), an ion exchange membrane (IE membrane), and a nanofiltration membrane (NF membrane). In particular, the separation membrane 110 is preferably an RO membrane or an NF membrane. For example, RO membranes are known for their high efficiency in separating substances that ionize in water, such as NaCl. On the other hand, for organic substances that do not ionize, RO membranes allow the membrane material to be selected based on the properties of the organic substance to be separated, in terms of molecular size and affinity with the membrane material. Generally, organic substances with larger molecular size and lower affinity with the membrane material tend to be less permeable through RO membranes and tend to be concentrated (contained in the non-permeated water).

[0021] The material of the separation membrane 110 is preferably at least one selected from the group consisting of a polymer membrane, a carbon membrane, a ceramic membrane, a zeolite membrane, and an alumina membrane. For example, the material of the RO membrane is not particularly limited, but examples include polymer membranes made of aromatic polyamide, cellulose acetate, and polyvinyl alcohol. The separation performance of the RO membrane is not particularly limited, but preferably has an NaCl rejection of 99% by mass or more. This significantly reduces the possibility of organic substances being contained in the permeate B.

[0022] The pressure of the liquid feed pump 12 is not particularly limited, but when the separation membrane 110 is an RO membrane, it is preferably set to a pressure of 50% or more of the pressure limit value. This makes it possible to ensure the amount of water passing through the separation membrane 110 while significantly reducing the possibility of organic substances being contained in the permeate B. A conventionally known pump can be used as the liquid feed pump 12.

[0023] In the separation membrane device 10, first, water to be treated A introduced into a supply tank T1 from outside the system is supplied to the first chamber 111 of the separation membrane module 11 by the action of the liquid feed pump 12. Next, the water to be treated A in the first chamber 111 is passed through the separation membrane 110 by the pressure of the liquid feed pump 12. As described above, the separation membrane 110 separates the water to be treated A into permeated water B, from which at least some or all of the organic substances have been removed, and non-permeated water, which did not pass through the separation membrane 110. As a result, the permeated water B moves to the second chamber 112 and is then discharged from the separation membrane device 10. The non-permeated water is discharged from the separation membrane device 10 from the first chamber 111 by the pressure of the liquid feed pump 12 and sent to the intermediate tank T2.

[0024] (Organic substance treatment device) As described above, the organic substance treatment device 20 includes the adsorption elements 211, 221. The adsorption elements 211, 221 are provided in the first treatment tank 21 and the second treatment tank 22 that form the organic substance treatment device 20. The organic substance treatment device 20 includes, as a component thereof, a liquid feed pump 23 for supplying the non-permeated water in the intermediate tank T2 to the first treatment tank 21 and the second treatment tank 22.

[0025] As will be described later, the organic substance treatment device 20 is provided with valves V201 to V210 that adjust the flow of non-permeated water or heated gas C toward the first treatment tank 21 and the second treatment tank 22, so that the first treatment tank 21 and the second treatment tank 22 alternately function as adsorption tanks and desorption tanks for organic substances.

[0026] As described above, the adsorption elements 211 and 221 come into contact with the non-permeated water and adsorb the organic substances, thereby discharging the non-permeated water as adsorbed-treated water from which at least some or all of the organic substances have been removed from the organic substance treatment device 20. The adsorption elements 211 and 221 come into contact with the heated gas C and desorb the organic substances from the adsorption elements 211 and 221, thereby discharging a desorbed gas containing the heated gas C and the organic substances from the organic substance treatment device 20.

[0027] The adsorption elements 211 and 221 preferably contain at least one member selected from the group consisting of activated carbon, activated carbon fiber, zeolite, silica gel, activated alumina, and metal-organic frameworks. The adsorption elements 211 and 221 may use one of these members alone or a combination of two or more. For example, the adsorption upstream side may be made of activated carbon (crushed carbon), and the adsorption downstream side may be filled with a member made of activated carbon fiber, forming the adsorption elements 211 and 221. The "metal-organic framework" refers to, for example, MOF (metal-organic framework) or PCP (porous coordination polymer).

[0028] For example, granular, particulate, honeycomb-shaped activated carbon, activated carbon fiber, zeolite, silica gel, activated alumina, and metal-organic structures can be used for the adsorption elements 211 and 221. Activated carbon fiber is more preferably used for the adsorption elements 211 and 221. Activated carbon fiber has a fibrous structure with micropores on the surface, which allows for high contact efficiency with water and a particularly fast adsorption rate of organic substances in water, thereby achieving extremely high adsorption efficiency compared to other adsorption materials.

[0029] For example, the physical properties of the activated carbon fiber used as the adsorption elements 211 and 221 are not particularly limited, but the BET specific surface area is preferably 700 to 3000 m ２ / g, pore volume of 0.4 to 1.35 cm ３ / g and an average pore diameter of 14 to 27 Å (angstroms). By providing these physical properties, the cost of the adsorption elements 211 and 221 can be reduced while efficiently increasing the amount of organic substances adsorbed.

[0030] The heating gas C is not particularly limited, but examples thereof include water vapor, heated air, and heated nitrogen. It is preferable that the heating gas C is water vapor at, for example, 100°C or higher, since this facilitates liquefaction by the condenser 24 described below. Examples of heating methods for raising the heating gas C to a predetermined temperature (for example, 100°C or higher) include, but are not particularly limited to, indirect heating, heating by an electric heater, and heating by microwaves.

[0031] The organic substance treatment apparatus 20 may have a means for repeatedly transferring the portions of the adsorption elements 211, 221 for which desorption treatment has been completed to the portion for adsorption treatment, and transferring the portions of the adsorption elements 211, 221 for which adsorption treatment has been completed to the portion for desorption treatment. Specifically, the first treatment tank 21 and the second treatment tank 22 containing the adsorption elements 211, 221 alternately function as an adsorption tank and a desorption tank by operating the opening and closing of valves V201 to V208. By operating the opening and closing of valves V201 to V208, for example, when the first treatment tank 21 functions as an adsorption tank, the second treatment tank 22 functions as a desorption tank. When the first treatment tank 21 functions as a desorption tank, the second treatment tank 22 functions as an adsorption tank.

[0032] When functioning as desorption tanks, the first treatment tank 21 and the second treatment tank 22 are preferably purged. Purging refers to passing a purge gas through the adsorption elements 211, 221 before passing the heated gas C through them to purge and remove non-permeated water adhering to the adsorption elements 211, 221. This increases the desorption efficiency of the adsorption elements 211, 221. The purged non-permeated water is preferably returned to the intermediate tank T2 by opening and closing V209 and V210, for example. This is because the non-permeated water adhering to the adsorption elements 211, 221 may simply be water from which organic substances have not been sufficiently removed.

[0033] The pressure of the liquid feed pump 23 is not particularly limited, but is preferably set so as to ensure the amount of non-permeated water that contacts the adsorption elements 211, 221 in accordance with the physical properties of the adsorption elements 211, 221. This allows the adsorption elements 211, 221 to efficiently adsorb organic substances, thereby reducing the concentration of organic substances in the adsorption-treated water discharged from the organic substance treatment apparatus 20. A conventionally known pump may be used as the liquid feed pump 23.

[0034] In the organic substance treatment device 20, the non-permeated water introduced into the intermediate tank T2 is first supplied to the first treatment tank 21 or the second treatment tank 22, which functions as an adsorption tank, by the action of the liquid feed pump 23 and the opening and closing of valves V201 to V208. The non-permeated water supplied to the first treatment tank 21 or the second treatment tank 22 then comes into contact with the adsorption elements 211 and 221. As described above, the adsorption elements 211 and 221 adsorb organic substances in the non-permeated water by contacting the non-permeated water. The non-permeated water from which the organic substances have been removed is then discharged from the organic substance treatment device 20 as adsorption-treated water. The adsorption-treated water is then returned to the water to be treated A in the supply tank T1 by the pressure of the liquid feed pump 23. In this way, in the water treatment system according to the first embodiment, the adsorption-treated water can be passed through the separation membrane 110 by supplying the adsorption-treated water from the supply tank T1 by the pressure of the liquid feed pump 12. Therefore, a greater amount of organic substances can be removed from the water to be treated A.

[0035] (Condenser) The water treatment system according to the first embodiment includes a condenser 24 that liquefies the desorbed gas as described above. The condenser 24 liquefies the desorbed gas discharged from the first treatment tank 21 and the second treatment tank 22, which function as desorption tanks, and discharges the desorbed gas as condensed water D containing concentrated organic substances outside the system. A known heat exchanger may be used as the condenser 24. The desorbed gas is introduced into the condenser 24 and heat-exchanged to liquefy the desorbed gas, forming condensed water D containing concentrated organic substances. The condensed water D is then discharged outside the water treatment system. Because the condensed water D contains concentrated organic substances, its volume is significantly smaller than that of the water to be treated A containing the same amount of organic substances. This reduces the amount of wastewater discharged from the water treatment system. The cooling method for the desorbed gas in the condenser includes, but is not limited to, indirect cooling using cooling water, groundwater, or the like, and cooling using a chiller (cold water).

[0036] (Effects) According to the wastewater treatment system of the first embodiment, permeate B is obtained from water to be treated A, from which organic substances have been removed through the separation membrane 110 of the separation membrane device 10. Meanwhile, organic substances in the non-permeate water that did not pass through the separation membrane 110 are adsorbed by the adsorption elements 211, 221 of the organic substance treatment device 20, then desorbed from the adsorption elements 211, 221 by a desorption gas, and subsequently liquefied by the desorption gas to form condensed water D in which the organic substances are concentrated, which is then discharged outside the system. As a result, the amount of waste liquid discharged from the water treatment system can be reduced.

[0037] Second Embodiment Fig. 2 is a system configuration diagram of a water treatment system according to a second embodiment. The water treatment system according to the second embodiment has the same structure as the water treatment system according to the first embodiment, except that it includes an ion exchange device 30 into which adsorption-treated water is introduced. That is, the water treatment system according to the second embodiment has an aspect in which the water treatment system according to the first embodiment further includes an ion exchange device 30 equipped with ion exchange resin 311. Specifically, the ion exchange device 30 is disposed midway through the piping connecting the organic substance treatment device 20 and the supply tank T1. Therefore, the adsorption-treated water is passed through the ion exchange resin 311. The ion exchange device 30 includes an ion exchange column 31 and ion exchange resin 311 packed in the ion exchange column 31.

[0038] In the water treatment system according to the second embodiment, the adsorption-treated water discharged from the organic substance treatment device 20 is introduced into the ion exchange device 30 and passes through the ion exchange resin 311. As described above, the adsorption-treated water may contain the organic substances. In this case, the organic substances are adsorbed by the ion exchange resin 311, thereby further reducing the concentration of the organic substances in the adsorption-treated water. A known ion exchange resin may be used as the ion exchange resin 311. The ion exchange resin 311 may be in any of the following forms: granular, particulate, fibrous, and membrane-like. Other than the ion exchange device 30, the aspects of the water treatment system according to the second embodiment are the same as those of the first embodiment, and therefore, redundant description will not be repeated.

[0039] <Third Embodiment> Figure 3 is a system configuration diagram of a water treatment system according to a third embodiment. The water treatment system according to the third embodiment has the same structure as the water treatment system according to the first embodiment, except that it includes an ion exchange device 30 into which permeate B is introduced. In other words, the water treatment system according to the third embodiment has an aspect in which the water treatment system according to the first embodiment further includes an ion exchange device 30 equipped with ion exchange resins 311. Specifically, the ion exchange device 30 is disposed midway through a pipe through which permeate B discharged from the separation membrane device 10 flows toward the outside of the system. Therefore, permeate B is passed through the ion exchange resins 311. The structure of the ion exchange device 30 may be the same as the ion exchange device 30 described in the second embodiment.

[0040] In the water treatment system according to the third embodiment, permeate B separated by the separation membrane 110 of the separation membrane device 10 is introduced into the ion exchange device 30 and passes through the ion exchange resin 311. In this case, organic substances in the permeate B can be further removed. Since aspects of the water treatment system according to the third embodiment other than the ion exchange device 30 are the same as those according to the first embodiment, redundant description will not be repeated.

[0041] <Fourth Embodiment> Figure 4 is a system configuration diagram of a water treatment system according to a fourth embodiment. The water treatment system according to the fourth embodiment has the same configuration as the water treatment system according to the first embodiment, except that it does not include an intermediate tank into which non-permeated water separated by the separation membrane device 10 is introduced, and a liquid feed pump that generates pressure to supply the non-permeated water to the organic substance treatment device 20. In this case, in the water treatment system, the non-permeated water discharged from the separation membrane device 10 is supplied to the first treatment tank 21 and the second treatment tank 22 of the organic substance treatment device 20 by the pressure of the liquid feed pump 12. The water treatment system may be provided with a pressure regulating valve NV201 for the purpose of regulating the amount of non-permeated water supplied to the first treatment tank 21 and the second treatment tank 22.

[0042] The manner in which the water to be treated A in the water treatment system according to the fourth embodiment is treated is the same as that in the first embodiment, except that the non-permeated water is supplied directly to the organic substance treatment device 20 without passing through the intermediate tank, and therefore redundant explanations will not be repeated. The water treatment system according to the fourth embodiment can omit the intermediate tank and the liquid feed pump, which may reduce installation costs, etc.

[0043] Fifth Embodiment FIG. 5 is a system configuration diagram of a water treatment system according to a fifth embodiment. The water treatment system according to the fifth embodiment differs from the water treatment system according to the first embodiment, in that the water to be treated A is supplied to an organic substance treatment device 20. That is, the water treatment system according to the fifth embodiment purifies the water to be treated A by removing organic substances from the water to be treated A containing organic substances. As shown in FIG. 5 , the water treatment system includes a separation membrane device 10 and an organic substance treatment device 20. The organic substance treatment device 20 includes adsorption elements 211 and 221. The adsorption elements 211 and 221 contact the water to be treated A and adsorb the organic substances, thereby discharging the water to be treated A as adsorption-treated water. The adsorption elements 211 and 221 contact a heated gas C and desorb the organic substances, thereby discharging a desorbed gas containing the heated gas C and the organic substances. The separation membrane device 10 includes a separation membrane 110. The separation membrane 110 separates the adsorption-treated water into permeated water B, from which at least some or all of the organic substances have been removed, and non-permeated water that has not passed through the separation membrane 110, by passing the adsorption-treated water through it. That is, in the wastewater treatment system according to the fifth embodiment, the separation membrane 110 passes the adsorption-treated water through it. The adsorption elements 211, 221 come into contact with the water to be treated A. The non-permeated water is returned to the water to be treated A. The water treatment system according to the fifth embodiment includes a condenser 24 that liquefies the desorbed gas. The desorbed gas is liquefied into condensed water D by the condenser 24. The condensed water D is discharged outside the water treatment system.

[0044] The water treatment system includes a supply tank T1 for supplying water to be treated A introduced from outside the system to the organic substance treatment device 20, and an intermediate tank T2 for receiving adsorption-treated water separated in the organic substance treatment device 20 and supplying the adsorption-treated water to the separation membrane device 10. The supply tank T1 and the organic substance treatment device 20, the organic substance treatment device 20 and the intermediate tank T2, the intermediate tank T2 and the separation membrane device 10, and the separation membrane device 10 and the supply tank T1 are each connected by piping.

[0045] The structures of the separation membrane device 10 itself and the organic substance treatment device 20 itself in the water treatment system according to the fifth embodiment are the same as those in the water treatment systems according to the first to fourth embodiments, respectively, and therefore redundant descriptions will not be repeated. Furthermore, the water treatment system according to the fifth embodiment includes a condenser 24 that liquefies the desorbed gas as described above, but the structure of the condenser 24 is also the same as those in the water treatment systems according to the first to fourth embodiments, and therefore redundant descriptions will not be repeated.

[0046] In the water treatment system according to the fifth embodiment, the water to be treated A is treated as follows. First, the water to be treated A is introduced into the supply tank T1, and is supplied to the first treatment tank 21 or the second treatment tank 22, which functions as an adsorption tank of the organic substance treatment device 20, by the action of the liquid feed pump 23 and the opening and closing of valves V201 to V208. The water to be treated A supplied to the first treatment tank 21 or the second treatment tank 22 then comes into contact with the adsorption elements 211 and 221. The adsorption elements 211 and 221 adsorb organic substances in the water to be treated A by contacting the water to be treated A. The water to be treated A from which the organic substances have been removed is then discharged from the organic substance treatment device 20 as adsorption-treated water. The adsorption-treated water is then sent to the intermediate tank T2 by the pressure of the liquid feed pump 23.

[0047] The adsorption-treated water introduced into the intermediate tank T2 is then supplied to the first chamber 111 of the separation membrane module 11 in the separation membrane device 10 by the action of the liquid feed pump 12. The adsorption-treated water in the first chamber 111 is then passed through the separation membrane 110 by the pressure of the liquid feed pump 12. The separation membrane 110 separates the adsorption-treated water into permeated water B, from which at least a portion of the organic substances have been removed, and non-permeated water that did not pass through the separation membrane 110. The permeated water B moves to the second chamber 112 and is then discharged from the separation membrane device 10. The non-permeated water is discharged from the separation membrane device 10 from the first chamber 111 by the pressure of the liquid feed pump 12 and returned to the water to be treated A in the supply tank T1. As a result, in the water treatment system according to the fifth embodiment, the adsorption elements 211 and 22 come into contact with the non-permeated water as it is supplied from the supply tank T1 by the pressure of the liquid feed pump 23. Therefore, a larger amount of organic matter in the water A to be treated can be removed.

[0048] Sixth Embodiment Fig. 6 is a system configuration diagram of a water treatment system according to a sixth embodiment. The water treatment system according to the sixth embodiment has the same structure as the water treatment system according to the fifth embodiment, except that it includes an ion exchange device 30 into which adsorption-treated water is introduced. That is, the water treatment system according to the sixth embodiment has an aspect in which the water treatment system according to the fifth embodiment further includes an ion exchange device 30 equipped with ion exchange resin 311. Specifically, the ion exchange device 30 is disposed midway through the piping connecting the organic substance treatment device 20 and the intermediate tank T2. Therefore, the adsorption-treated water is passed through the ion exchange resin 311. The structure of the ion exchange device 30 may be the same as the ion exchange device 30 described in the second and third embodiments.

[0049] In the water treatment system according to the sixth embodiment, the adsorption-treated water discharged from the organic substance treatment device 20 is introduced into the ion exchange device 30 and passes through the ion exchange resin 311. In this case, the concentration of organic substances in the adsorption-treated water can be further reduced. Other than the ion exchange device 30, the aspects of the water treatment system according to the sixth embodiment are the same as those of the fifth embodiment, and therefore, redundant description will not be repeated.

[0050] Seventh Embodiment Fig. 7 is a system configuration diagram of a water treatment system according to a seventh embodiment. The water treatment system according to the seventh embodiment has the same structure as the water treatment system according to the fifth embodiment, except that it includes an ion exchange device 30 into which permeate B is introduced. That is, the water treatment system according to the seventh embodiment has an aspect in which the water treatment system according to the fifth embodiment further includes an ion exchange device 30 equipped with ion exchange resin 311. Specifically, the ion exchange device 30 is disposed midway through a pipe through which permeate B discharged from the separation membrane device 10 flows toward the outside of the system. Therefore, permeate B is passed through the ion exchange resin 311. The structure of the ion exchange device 30 may be the same as the ion exchange device 30 described in the sixth embodiment.

[0051] According to the water treatment system of the seventh embodiment, permeate B separated by the separation membrane 110 of the separation membrane device 10 is introduced into the ion exchange device 30 and passes through the ion exchange resin 311. In this case, organic substances in the permeate B can be further removed. Since aspects of the water treatment system of the seventh embodiment other than the ion exchange device 30 are the same as those of the fifth embodiment, redundant description will not be repeated.

[0052] Other Embodiments The water treatment system according to the present invention may include other embodiments in addition to the embodiments illustrated in the drawings as the first to seventh embodiments. For example, the water treatment system according to the first or fifth embodiment may include an ion exchange device equipped with an ion exchange resin, and the non-permeated water may be passed through the ion exchange resin. That is, in the water treatment system according to this embodiment, when described with reference to FIG. 1, the ion exchange device may be disposed midway in the piping connecting the separation membrane device 10 and the intermediate tank T2. Even in this embodiment, the water treatment system can remove a greater amount of organic matter from the water to be treated.

[0053] Furthermore, the water treatment system may include a plurality of ion exchange devices. That is, the ion exchange devices may be disposed in the pipe through which the adsorption-treated water flows, the pipe through which the permeated water flows, and the pipe through which the non-permeated water flows, in order to remove organic substances from the adsorption-treated water, the permeated water, and the non-permeated water, respectively. In the water treatment system, the ion exchange devices may be disposed in the pipe through which the adsorption-treated water flows and the pipe through which the permeated water flows, or in the pipe through which the adsorption-treated water flows and the pipe through which the non-permeated water flows, or in the pipe through which the non-permeated water flows and the pipe through which the permeated water flows.

[0054] The water treatment system may be provided with an aeration tank capable of blowing air or other gas into the water to be treated or the non-permeated water, which is located before the separation membrane device or between the separation membrane device and the organic substance treatment device. In this case, it may be possible to reduce the treatment load of the separation membrane device and the organic substance treatment device.

[0055] The water treatment system may include a pretreatment facility in front of the separation membrane device or organic substance treatment device to remove impurities that may cause deterioration of the separation membrane or adsorption element. The specific pretreatment facility may be selected appropriately depending on the properties of the impurities to be removed.

[0056] Furthermore, in the water treatment system, a fluid transport means such as a pump can be disposed at an appropriate position as required.

[0057] Although the embodiments of the present invention have been described above, it is also planned from the beginning that the configurations of the above-described embodiments may be appropriately combined.

[0058] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0059] A water to be treated, B permeate water, C heated gas, D condensed water, 10 separation membrane device, 11 separation membrane module, 110 separation membrane, 111 first chamber, 112 second chamber, 12 liquid feed pump, 20 organic substance treatment device, 21 first treatment tank, 211 adsorption element, 22 second treatment tank, 221 adsorption element, 23 liquid feed pump, 24 condenser, 30 ion exchange device, 31 ion exchange column, 311 ion exchange resin, T1 supply tank, T2 intermediate tank, V201 to V210 valves, NV201 pressure regulating valve.

Claims

1. A water treatment system that purifies water to be treated by removing organic substances from the water to be treated, the water treatment system comprising: a separation membrane device; and an organic substance treatment device; the separation membrane device includes a separation membrane; the separation membrane is passed through the water to separate the water to be treated into permeated water from which at least a portion of the organic substances have been removed and non-permeated water that has not passed through the separation membrane; the organic substance treatment device includes an adsorption element; the adsorption element comes into contact with the non-permeated water and adsorbs the organic substances, thereby discharging the non-permeated water as adsorption-treated water; and the adsorption element comes into contact with a heated gas and desorbs the organic substances, thereby discharging a desorbed gas containing the heated gas and the organic substances.

2. A water treatment system that purifies water to be treated by removing organic substances from the water to be treated, the water treatment system comprising: a separation membrane device; and an organic substance treatment device; the organic substance treatment device comprising an adsorption element; the adsorption element contacting the water to be treated and adsorbing the organic substances, thereby discharging the water to be treated as adsorption-treated water; the adsorption element contacting a heated gas and desorbing the organic substances, thereby discharging a desorbed gas containing the heated gas and the organic substances; the separation membrane device comprising a separation membrane; the separation membrane passing through the adsorption-treated water, thereby separating the adsorption-treated water into permeate from which at least a portion of the organic substances has been removed, and non-permeate that has not passed through the separation membrane.

3. The water treatment system according to claim 1 or 2, further comprising a condenser for liquefying the desorbed gas.

4. The water treatment system according to claim 1, wherein the adsorption-treated water is returned to the water to be treated.

5. The water treatment system according to claim 2, wherein the non-permeate water is returned to the water to be treated.

6. A water treatment system according to any one of claims 1 to 5, comprising an ion exchange device equipped with an ion exchange resin, the adsorption-treated water being passed through the ion exchange resin.

7. The water treatment system according to any one of claims 1 to 6, further comprising an ion exchange device equipped with an ion exchange resin, wherein the permeate is passed through the ion exchange resin.

8. The water treatment system according to any one of claims 1 to 7, wherein the separation membrane comprises at least one member selected from the group consisting of a reverse osmosis membrane, a forward osmosis membrane, an ion exchange membrane, and a nanofiltration membrane.

9. The water treatment system according to any one of claims 1 to 8, wherein the adsorption element includes at least one member selected from the group consisting of activated carbon, activated carbon fiber, zeolite, silica gel, activated alumina, and organic metal frameworks.

10. A water treatment system as described in any one of claims 1 to 9, wherein the organic substance treatment device has a means for repeatedly transferring the portion of the adsorption element where desorption processing has been completed to the portion where adsorption processing will be performed, and transferring the portion of the adsorption element where adsorption processing has been completed to the portion where desorption processing will be performed.

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