Water treatment method and water treatment apparatus

Abstract

The present invention provides a water treatment apparatus and a water treatment method capable of reliably reducing the PFAS concentration of treated water even after PFAS-containing water is purified for a long period of time and then a PFAS adsorbent is regenerated or replaced.SOLUTION: In one example, the water treatment device 1 includes an adsorption means 8 having an adsorbent that adsorbs PFAS, a membrane treatment means 10 having a filtration membrane for treating PFAS-treated water W3, a PFAS-treated water pipe L4 for supplying the PFAS-treated water W3 from the adsorption means 8 to the membrane treatment means 10, and a filtration membrane-treated water pipe L5 for supplying the filtration membrane-treated water W4 to the treated water tank 11, wherein materials of members included in the membrane treatment means 10, materials of the PFAS-treated water pipe L4, and materials of the filtration membrane-treated water pipe L5 are all non-fluorine materials.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water treatment device and a water treatment method. [Background technology]

[0002] Among organic fluorine compounds, there are concerns about the environmental impact of compounds called PFAS, a general term for perfluoroalkyl and polyfluoroalkyl compounds, and it is said that more than 10,000 substances fall into the PFAS category. The two most common examples of PFAS are PFOS (perfluorooctane sulfonate) and PFOA (perfluorooctanoic acid). PFOS and PFOA are particularly difficult to break down in nature and in the body, and are known to accumulate in the environment, such as soil.

[0003] While some PFAS are buried in landfills or released into the atmosphere, the majority are said to be released into the hydrosphere via wastewater. This raises concerns about the impact of PFAS, which are difficult to decompose, on the aquatic environment. PFAS regulatory standards vary from country to country. In April 2020, Japan established a provisional target value for the combined concentration of PFOS and PFOA in tap water of 50 ng / L or less. Each business operator is implementing water quality management and purification processes in compliance with this target value.

[0004] In conventional water treatment, fluorine-containing materials such as filtration membranes made of polyvinylidene fluoride are sometimes used (for example, Patent Document 1). In addition, fluorine-containing materials such as fluororesins are widely used for piping for permeated water that has passed through the filtration membranes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-062623 Summary of the Invention [Problem to be solved by the invention]

[0006] However, fluorine-containing materials have the property of adsorbing PFAS in water. Therefore, during the purification process of PFAS-containing water, PFAS gradually accumulates in the parts of the water treatment equipment where fluorine-containing materials are applied. The adsorbed PFAS gradually leaks into the treated water, even in small amounts within the standard range, and there is a risk that the PFAS concentration in the treated water will exceed the target value.

[0007] In particular, when fluorine-containing materials are present on the secondary side of adsorbents such as activated carbon or ion exchange resins, trace amounts of PFAS adsorbed on the fluorine-containing materials continue to leak out, even after the adsorbent is regenerated or replaced. As a result, when PFAS-containing water is purified over a long period of time, it becomes increasingly difficult to reduce the PFAS concentration in the treated water.

[0008] The present invention provides a water treatment device and a water treatment method that can reliably reduce the PFAS concentration in treated water, even after PFAS-containing water has been purified over a long period of time and the PFAS adsorbent has been regenerated or replaced. [Means for solving the problem]

[0009] The present invention has the following aspects. [1] A water treatment device for purifying water containing either or both of perfluoroalkyl compounds and polyfluoroalkyl compounds, an adsorption means having an adsorbent that adsorbs either or both of the perfluoroalkyl compound and the polyfluoroalkyl compound; a membrane treatment means having a filtration membrane for treating PFAS-treated water obtained by removing either or both of the perfluoroalkyl compounds and the polyfluoroalkyl compounds with the adsorbent; and a PFAS-treated water supply means for supplying the PFAS-treated water from the adsorption means to the membrane treatment means; a filtration membrane-treated water supply means for supplying filtration membrane-treated water, which is permeated water from the membrane treatment means, to a treated water tank; Equipped with the material of a member included in the PFAS-treated water supply means is a non-fluorine material, the material of the member included in the membrane treatment means is a non-fluorine material, The water treatment device, wherein the members included in the filtration membrane-treated water supply means are made of non-fluorine materials. [2] The water treatment device according to [1], wherein the PFAS-treated water supply means includes at least one selected from the group consisting of piping, sealing materials, pumps, valves, and meters. [3] The water treatment device according to [1] or [2], wherein the filtration membrane-treated water supply means includes at least one selected from the group consisting of piping, sealing materials, pumps, valves, and meters. [4] Further comprising a water-to-be-treated supply means for supplying the water-to-be-treated to the adsorption means, The water treatment device according to any one of [1] to [3], wherein the material of the members included in the untreated water supply means is also a non-fluorine material. [5] The water treatment device according to [4], wherein the untreated water supply means includes at least one selected from the group consisting of piping, sealing materials, pumps, valves, and meters. [6] The water treatment device according to any one of [1] to [5], further comprising a simulation means for predicting the timing of regeneration or replacement of the adsorbent based on the total concentration of the perfluoroalkyl compounds and the polyfluoroalkyl compounds in the raw water to be treated. [7] The simulation means a calculation means for calculating a total adsorption amount S1 based on the total concentration of the perfluoroalkyl compounds and the polyfluoroalkyl compounds in the raw water and the amount of water to be treated; a monitoring means for monitoring the total adsorption amount S1 by comparing it with the saturation amount S2 of the adsorbent; a prediction means for predicting a time to regenerate or replace the adsorbent based on the total adsorption amount S1, the saturation amount S2, and treatment conditions; a transmitting means for transmitting an instruction to regenerate or replace the adsorbent before the total adsorption amount S1 exceeds the saturation amount S2; The water treatment device according to [6], comprising: [8] A water treatment method using the water treatment device according to any one of [1] to [7].

[0010] [9] A water treatment method for purifying water containing either or both of a perfluoroalkyl compound and a polyfluoroalkyl compound, comprising: an adsorption step of obtaining PFAS-treated water using an adsorbent that adsorbs either or both of the perfluoroalkyl compounds and the polyfluoroalkyl compounds; a membrane treatment step of treating the PFAS-treated water using a filtration membrane to obtain filtration membrane-treated water; and the material of the member for supplying the PFAS-treated water to the filtration membrane is a non-fluorine material; the material of the member used in the membrane treatment step is a non-fluorine material, The water treatment method, wherein the material of the member for supplying the membrane-treated water to the treatment tank is a non-fluorine material.

[10] The method further includes a water-to-be-treated supply step of supplying the water-to-be-treated to the adsorbent; The water treatment method according to [9], wherein the materials used in the untreated water supply step are also non-fluorine materials.

[11] The water treatment method according to [9] or

[10] , further comprising a simulation step of predicting the timing of regeneration or replacement of the adsorbent based on the total concentration of the perfluoroalkyl compounds and the polyfluoroalkyl compounds in the raw water of the water to be treated.

[12] The simulation step a calculation step of calculating a total adsorption amount S1 based on the total concentration of the perfluoroalkyl compounds and the polyfluoroalkyl compounds in the raw water and the amount of water to be treated; a monitoring step of comparing and monitoring the total adsorption amount S1 with a saturation amount S2 of the adsorbent; a prediction step of predicting a time to regenerate or replace the adsorbent based on the total adsorption amount S1, the saturation amount S2, and treatment conditions; a transmitting step of issuing a regeneration instruction or a replacement instruction for the adsorbent before the total adsorption amount S1 exceeds the saturation amount S2; The water treatment method according to

[11] , comprising: [Effects of the Invention]

[0011] According to the present invention, a water treatment device and a water treatment method are provided that can reliably reduce the PFAS concentration in treated water, even after PFAS-containing water has been purified over a long period of time and the PFAS adsorbent has been regenerated or replaced. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of a water treatment device. DETAILED DESCRIPTION OF THE INVENTION

[0013] The meanings of the terms are as follows: "PFAS" refers to either or both perfluoroalkyl compounds and polyfluoroalkyl compounds, and is a general term for perfluoroalkyl compounds and polyfluoroalkyl compounds. "PFAS concentration" means the combined concentration of perfluoroalkyl and polyfluoroalkyl compounds.

[0014] The "primary side" refers to the upstream side in the direction of flow of the water to be treated and the treated water. The "secondary side" refers to the downstream side in the direction of flow of the water to be treated and the treated water. Therefore, the water to be treated and the treated water flow from the primary side to the secondary side. The symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0015] The treatment target of the water treatment device and water treatment method is not particularly limited as long as it contains PFAS. Examples of raw water include groundwater, surface water, industrial wastewater, and domestic wastewater. Other examples of raw water include concentrated water generated when PFAS-containing water is treated with a separation membrane (such as an ultrafiltration membrane or a reverse osmosis membrane), and reclaimed wastewater generated when PFAS-containing water is treated with an ion exchange resin and then the ion exchange resin is regenerated.

[0016] PFAS concentrations vary depending on the water source. The PFAS concentration in raw water is not particularly limited, but may be, for example, 0.5 ng / L or higher, 4 ng / L or higher, 50 ng / L or higher, 100 ng / L or higher, or 1000 ng / L or higher. In groundwater, PFAS concentrations are often between 4 and 2000 ng / L.

[0017] In addition to PFAS, the treated water may also contain impurities such as organic matter, ammonia nitrogen, anions such as bicarbonate ions, nitrate ions, sulfate ions, and chloride ions, cations such as iron ions, manganese ions, calcium ions, and magnesium ions, and bacteria.

[0018] Hereinafter, several embodiments of the present invention will be described with reference to the drawings. However, the following description is for representative examples, and the present invention is not limited to the following description. The dimensional ratios in the drawings are for the convenience of explanation and may differ from the actual ones. In the following drawings, the same components are indicated by the same reference numerals, and descriptions of overlapping components may be omitted.

[0019] [Water treatment equipment] The water treatment device 1 shown in Figure 1 is used to purify water to be treated that contains PFAS. The water treatment device 1 includes a pumping pipe L1 for pumping up well water W1 (an example of raw water) from a well 2, a raw water tank 4, a first oxidant addition means 5, a raw water tank pipe L2, a raw water pump 6, a sand filter tower 7, a sand filtration treated water pipe L3, an adsorption means 8, a PFAS treated water pipe L4, a second oxidant addition means 9, a membrane treatment means 10, a filtration membrane treated water pipe L5, and a treated water tank 11.

[0020] A first end of the pumping pipe L1 is connected to a pumping pump 3 installed in the well 2, and a second end of the pumping pipe L1 is connected to a raw water tank 4. Through the pumping pipe L1, well water W1 from the well 2 can be supplied to the raw water tank 4 by the action of the pumping pump 3.

[0021] The raw water tank 4 is for storing raw water (well water). The raw water tank 4 is provided with a first oxidizing agent adding means 5. An oxidizing agent such as sodium hypochlorite is supplied from the first oxidizing agent adding means 5 to the raw water in the raw water tank 4.

[0022] A first end of the raw water tank piping L2 is connected to the raw water tank 4, and a second end of the raw water tank piping L2 is connected to the sand filtration tower 7. A raw water pump 6 is provided in the raw water tank piping L2. Through the raw water tank piping L2, stored water W1' in the raw water tank 4 can be supplied to the sand filtration tower 7 by the action of the raw water pump 6.

[0023] The sand filter tower 7 is not particularly limited. Sand filter towers used in known water treatment devices can be used without any restrictions. One sand filter tower 7 may be used alone, or two or more sand filter towers 7 may be used in combination in parallel or in series.

[0024] When well water W1 contains metal ions such as iron ions and manganese ions, the metal ions can be oxidized and precipitated by mixing an oxidizing agent with first oxidizing agent adding means 5. These precipitates are filtered in a sand filter tower 7, and the filtered water, sand-filtered water W2, is obtained.

[0025] A first end of the sand filtration treated water pipe L3 is connected to the sand filtration tower 7, and a second end of the sand filtration treated water pipe L3 is connected to the adsorption means 8. The sand filtration treated water pipe L3 allows the sand filtration treated water W2 to be supplied to the adsorption means 8.

[0026] The adsorption means 8 is not particularly limited as long as it has an adsorbent that adsorbs PFAS. In the adsorption means 8, PFAS in the sand filtration treated water W2 is adsorbed by the adsorbent. The PFAS is removed by the adsorbent, thereby obtaining PFAS-treated water W3.

[0027] As the adsorption means 8, there can be used, without limitation, an activated carbon tower or an ion exchange resin tower used in a known water treatment device. One adsorption means 8 may be used alone, or two or more adsorption means 8 may be used in combination in parallel or in series.

[0028] Examples of adsorbents for the adsorption means 8 include organic ion exchangers, activated carbon, and inorganic ion exchangers. However, the adsorbents are not limited to these examples. Furthermore, one type of adsorbent may be used alone, or two or more types may be used in combination.

[0029] Only one ion exchange resin tower or activated carbon tower may be installed, or two or more towers may be installed. An ion exchange resin tower and an activated carbon tower may be used in combination. When two or more ion exchange resin towers are installed and different resins are used in each ion exchange resin tower, they may be regenerated with the same regenerating liquid, or they may be regenerated with different regenerating liquids depending on the characteristics of each type of resin.

[0030] Examples of backbone polymers for ion exchangers include styrene-based, (meth)acrylic, (meth)acrylamide-based, and cellulose-based polymers. From the viewpoint of non-electrostatic interaction-based adsorption of PFAS, highly hydrophobic styrene-based polymers are preferred. From the viewpoint of recyclability, weakly hydrophobic acrylic and acrylamide-based polymers are preferred.

[0031] Examples of ion exchangers include anion exchangers and cation exchangers. From the viewpoint of PFAS removal performance, it is preferable to use anion exchangers as the ion exchanger. The anion exchanger may be either weakly basic or strongly basic, but from the viewpoint of adsorption, a strongly basic anion exchanger is preferred because it is easily adsorbed by electrostatic interaction, and from the viewpoint of regeneration, a weakly basic anion exchanger is preferred. A strongly basic anion exchanger is an anion exchanger having, as an ion exchange group, a quaternary ammonium group that remains dissociated even in alkaline conditions. A weakly basic anion exchanger is an ion exchanger having a tertiary ammonium group as an ion exchange group.

[0032] Strongly basic anion exchangers include those having various ion exchange groups. Examples of the ion exchange groups include trimethylammonium groups, triethylammonium groups, tripropylammonium groups, tributylammonium groups, hydroxyethyldimethylammonium groups, and dihydroxyethylmethylammonium groups. Among these, trimethylammonium groups are preferred as the ion exchange group from the viewpoints of maximizing static exchange capacity, preventing an increase in the amount of organic matter due to leaching caused by the poor thermal stability of the ion exchange groups, the generation of odors due to the ion exchange groups, and the generation of formaldehyde due to the detachment and decomposition of the ion exchange groups over long-term use.

[0033] Examples of anion exchangers include anion exchange resins and anion exchange fibers. When a strongly basic anion exchange resin is used as the anion exchange resin, the strongly basic anion exchange resin may be either type I or type II.

[0034] The anion exchanger may be a commercially available product. Examples of commercially available ion exchange resins include Diaion HPA25M, HPA512L, SA10A, SA12A, SA20A, and PA308, as well as Relight JA810, JA800, and JA830 (Mitsubishi Chemical Corporation products), A860, A520E, and PFA694E (Purolite Corporation products), Lewatit A8071, Monoplus M500, M800, MP800, and TP-108 (Lanxess AG products). However, the ion exchange resin is not limited to these examples. One type of ion exchange resin may be used alone, or two or more types may be used in combination.

[0035] Activated carbon is made of carbon with micropores (10-200Å in diameter) that are created by reacting carbon materials such as coal and coconut shells with gases and chemicals at high temperatures. These micropores are formed in a mesh-like pattern inside the carbon. The walls of the micropores in activated carbon have a large surface area (500-2500m²). 2 / g) and adsorbs substances such as PFAS onto the surface of the micropores. Activated carbon is more than 90% carbon, some of which is in the form of compounds with oxygen and hydrogen. Ash is a component specific to the raw material and often contains Na, Si, K, Ca, Fe, etc.

[0036] Examples of activated carbon include powdered activated carbon smaller than 100 Mesh, granular activated carbon, fibrous activated carbon, and specially molded activated carbon (honeycomb, sheet, plate, etc.). Among these, granular activated carbon is preferred for water treatment applications. Examples of granular activated carbon include coconut shell charcoal, coal, and crushed charcoal.

[0037] Examples of commercially available activated carbon include Shirasagi WH2c, W2c, WH5c, W5c, LGK-100, and LGK-400 (products of Osaka Gas Chemicals Co., Ltd.), Kuraray Co., Ltd. GW, GW-H, GLC, and FILTRASORB400 (products of Kuraray Co., Ltd.), and PL-1S, PL-C1SK, PL-WPH, and PL-WPS (products of Dainen Co., Ltd.). However, activated carbon is not limited to these examples. One type of activated carbon may be used alone, or two or more types may be used in combination.

[0038] A first end of the PFAS-treated water pipe L4 is connected to the adsorption means 8, and a second end of the PFAS-treated water pipe L4 is connected to the membrane treatment means 10. A second oxidant addition means 9 is provided midway along the PFAS-treated water pipe L4. The PFAS-treated water pipe L4 can supply the PFAS-treated water W3 to which an oxidant such as sodium hypochlorite has been added to the membrane treatment means 10.

[0039] The water treatment device 1 includes a PFAS-treated water supply means that supplies PFAS-treated water W3 from the adsorption means 8 to the membrane treatment means 10. The PFAS-treated water supply means includes, in addition to a PFAS-treated water pipe L4, at least one selected from the group consisting of a sealant, a pump, a valve, and a meter. In the water treatment device 1, the components included in the PFAS-treated water supply means are made of non-fluorine materials. Therefore, even if the PFAS-treated water W3 flows through the PFAS-treated water supply means, adsorption and accumulation of PFAS on the components included in the PFAS-treated water supply means can be prevented.

[0040] Examples of materials for the PFAS-treated water piping L4 and pumps include metals such as iron, copper, steel, lead, stainless steel, aluminum, and titanium, as well as polyvinyl chloride, concrete, polyethylene, polybutene, polyurethane, nylon, polyamide, polyolefin, and silicone rubber. Examples of materials for pipe connecting members and resin members include polybutylene terephthalate, polyoxymethylene, polyphenylene sulfide, polycyclohexylene dimethylene terephthalate, polyethylene, polypropylene, acrylonitrile-butadiene-styrene, polyamide 6, polyether ether ketone, polycarbonate, polyvinyl chloride, and acrylic resin.

[0041] Contrary to these examples, fluorine-containing materials such as polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE) are not preferred materials for the PFAS-treated water piping L4.

[0042] Examples of the sealing material include O-rings, packings, and sealing materials. The material of the sealing material may be silicone-based, polysulfide-based, acrylic-based, SBR-based, butyl rubber-based, polyurethane-based, or oil-based.

[0043] Examples of materials for seals and valves include nitrile rubber (NBR), urethane rubber (U), silicone rubber (VMQ), ethylene propylene rubber (EPDM), hydrogenated nitrile rubber (HNBR), chloroprene rubber (CR), acrylic rubber (ACM), butyl rubber (IIR), chlorosulfonated polyethylene (CSM), epichlorohydrin rubber (CO, ECO), and natural rubber (NR).

[0044] The meters include water quality meters and water quantity meters, and it is preferable that the materials for these meters are also non-fluorine-containing materials as described above.

[0045] The membrane treatment means 10 is not particularly limited as long as it has a filtration membrane for treating the PFAS-treated water W3. Membrane treatment means used in known water treatment devices can be used without limitation. Examples of the filtration membrane of the membrane treatment means 10 include an ultrafiltration (UF) membrane, a microfiltration (MF) membrane, a nanofiltration (NF) membrane, and a reverse osmosis (RO) membrane. The membrane treatment means 10 may be used alone or in combination of two or more in parallel or series. Also, the membrane treatment means 10 may be used alone or in combination of two or more.

[0046] In the water treatment device 1, the components included in the membrane treatment means 10 are made of non-fluorine materials. Therefore, even if the PFAS-treated water W3 or the filtration membrane-treated water W4 flows through the membrane treatment means 10, adsorption and accumulation of PFAS on the components included in the membrane treatment means 10 can be prevented.

[0047] In one example, the materials of the components of the membrane treatment means 10 that come into contact with the PFAS-treated water W3 and the filtration membrane-treated water W4 are non-fluorine materials. For example, the housing, water flow path, and separation membrane of the membrane treatment means 10 are made of non-fluorine materials.

[0048] The material of the separation membrane is not particularly limited as long as it is a non-fluorinated material, and examples thereof include organic materials such as cellulose, polyolefin, polysulfone, polyethersulfone, polyvinyl alcohol, polyamide, cellulose acetate, polyester, polymethacrylate, polyacrylate, and soft polyvinyl chloride, and inorganic materials such as ceramics, glass, and metal. The separation membrane may be made of one material alone or two or more materials in combination.

[0049] Contrary to these examples, fluorine-containing materials such as PVDF and PTFE are not suitable as materials for the separation membrane.

[0050] A first end of the filtration membrane-treated water pipe L5 is connected to the membrane treatment means 10, and a second end of the filtration membrane-treated water pipe L5 is connected to the treated water tank 11. The filtration membrane-treated water pipe L5 allows the filtration membrane-treated water W4, which is the permeate of the membrane treatment means 10, to be supplied to the treated water tank 11.

[0051] The water treatment device 1 includes a filtration membrane-treated water supply means for supplying the filtration membrane-treated water W4 to the treated water tank 11. The filtration membrane-treated water supply means includes, in addition to the filtration membrane-treated water piping L5, at least one selected from the group consisting of a sealant, a pump, a valve, and a meter. In the water treatment device 1, the components included in the filtration membrane-treated water supply means are made of non-fluorine materials. Therefore, even if the filtration membrane-treated water W4 flows through the filtration membrane-treated water supply means, adsorption and accumulation of PFAS on the components included in the filtration membrane-treated water supply means can be prevented.

[0052] The details of the material of the filtration membrane-treated water pipe L5 are the same as those described for the material of the PFAS-treated water pipe L4. In addition, the details of the sealing material, etc. are the same as those described for the PFAS-treated water supply means.

[0053] The water treatment device 1 includes a water-to-be-treated supply means that supplies water-to-be-treated (such as sand-filtered water W2) to the adsorption means 8. The water-to-be-treated supply means includes a pumping pipe L1, a raw water tank pipe L2, and a sand-filtered water pipe L3, as well as at least one selected from the group consisting of a sealing material, a pump, a valve, and a meter.

[0054] In a preferred example, the materials of the components included in the PFAS-treated water supply means, membrane treatment means, and filtration membrane-treated water supply means, as well as the untreated water supply means, may be non-fluorine-containing materials. If the untreated water supply means located on the upstream side of the adsorption means 8 is also made of a non-fluorine-containing material, adsorption and accumulation of PFAS on the components included in the untreated water supply means can be prevented.

[0055] The use of a non-fluorine material for the water-to-be-treated supply means is effective in suppressing fluctuations in the PFAS concentration in the water-to-be-treated (sand filtration treated water W2, etc.) supplied to the adsorption means 8. The primary side of the adsorption means 8 has a significantly higher PFAS concentration than the secondary side of the adsorption means 8. This adsorption and accumulation of PFAS on the primary side of the adsorption means 8 can cause an overload of the PFAS treatment capacity in the adsorption means 8. For example, if a high load is placed on the adsorption means 8 in order to treat PFAS with a higher concentration than in the raw water, it is expected that it will be difficult to reduce the PFAS concentration on the secondary side of the adsorption means 8. It is believed that such problems can be solved by using a non-fluorine material for the water supply means disposed on the primary side of the adsorption means 8 as well.

[0056] In addition, the materials of the water pump 3, raw water tank 4, sand filter tower 7, and the packed container of the adsorption means 8 are also preferably non-fluorine materials.

[0057] In the preferred embodiment described here, the details of the materials of the pumping pipe L1, raw water tank pipe L2, and sand filtration treated water pipe L3 are the same as those described for the material of the PFAS-treated water pipe L4. In addition, the details of the sealing material of the treated water supply means are the same as those described for the PFAS-treated water supply means.

[0058] In a preferred example, the water treatment device 1 may further include a simulation means (not shown) that predicts when to regenerate or replace the adsorbent based on the PFAS concentration in the raw water to be treated. If the adsorbent of the adsorption means 8 is an ion exchanger, the simulation means predicts when to regenerate the ion exchanger. If the adsorbent of the adsorption means 8 is activated carbon, the simulation means predicts when to replace the activated carbon.

[0059] In a preferred example, the simulation means may include a calculation means for calculating a total adsorption amount S1 based on the PFAS concentration in the raw water to be treated and the amount of water to be treated; a monitoring means for comparing and monitoring the total adsorption amount S1 with the saturation amount S2 of the adsorbent; a prediction means for predicting the time to regenerate or replace the adsorbent based on the total adsorption amount S1, the saturation amount S2, and the treatment conditions; and a transmission means for issuing an instruction to regenerate or replace the adsorbent before the total adsorption amount S1 exceeds the saturation amount S2.

[0060] In the case of groundwater, fluctuations in water quality are minimal, so it is effective to monitor the quality of the treated water (filtration membrane treated water W4) by measuring the PFAS concentration in the raw water in advance. Because groundwater has little fluctuation in water quality, it is easy to predict when to regenerate or replace the adsorbent. For advance predictions, it is useful to obtain the relationship between the amount of raw water supplied and the PFAS concentration in the filtration membrane treated water W4 from the results of a column water flow test, or to perform simulations using the results of equilibrium adsorption tests. Water volume meters and water quality meters are also useful for monitoring water quality.

[0061] The simulation means may be installed on-site or remotely, and each function may be executed by a program. Furthermore, meters such as water quality meters and water flow meters required to execute the functions of the simulation means may be communicatively connected to the components of the water treatment device. For example, remote monitoring of the cumulative flow rate and PFAS concentration of each of the well water W1, sand filtration-treated water W2, and PFAS-treated water W3 is useful.

[0062] The treatment conditions in the prediction means include, for example, linear velocity, space velocity, water flow rate, and water temperature, but are not limited to these.

[0063] [Water treatment method] The water treatment method is a method for purifying water containing PFAS. The water treatment method includes an adsorption step of obtaining PFAS-treated water using an adsorbent that adsorbs PFASs, and a membrane treatment step of treating the PFAS-treated water using a filtration membrane to obtain filtration membrane-treated water. The water treatment method may further include a water-to-be-treated supply step of supplying the water-to-be-treated to the adsorbent.

[0064] An example of a water treatment method will be described with reference to FIG. First, well water W1 is collected from a well 2 and stored in a raw water tank 4 (treated water supply step). In the raw water tank 4, an oxidizing agent such as sodium hypochlorite is supplied to the well water W1 from a first oxidizing agent adding means 5. Precipitates in the stored water in the raw water tank 4 are filtered in a sand filter tower 7, and sand-filtered water W2 is obtained (treated water supply step).

[0065] Next, the sand filtration treated water W2 is supplied to the adsorbent of the adsorption means 8 (treated water supply process). The PFAS in the sand filtration treated water W2 is removed by adsorption in the adsorption means 8, and PFAS-treated water W3 is obtained (adsorption process). The PFAS-treated water W3 is additionally replenished with the required amount of oxidizing agent such as sodium hypochlorite from the second oxidizing agent addition means 9.

[0066] Next, the PFAS-treated water W3 is supplied to the filtration membrane of the membrane treatment means 10. The PFAS-treated water W3 is treated by the filtration membrane of the membrane treatment means 10 to obtain filtration membrane-treated water W4 (membrane treatment process). The filtration membrane-treated water W4 is stored in the treated water tank 11. The filtration membrane-treated water W4 in the treated water tank 11 can be used as drinking water, domestic water, industrial water, etc. In this specification, drinking water means water that meets the water quality standard items and standard values ​​(51 items) and has a total PFOS and PFOA concentration of 50 ng / L or less, which is the water quality management target setting item.

[0067] In a preferred embodiment, the water treatment method may further include a simulation step of predicting the timing of regeneration or replacement of the adsorbent based on the PFAS concentration in the raw water to be treated.

[0068] In a preferred example, the simulation process may include a calculation step of calculating a total adsorption amount S1 based on the PFAS concentration in the raw water and the amount of water to be treated; a monitoring step of comparing and monitoring the total adsorption amount S1 with a saturation amount S2 of the adsorbent; a prediction step of predicting the time to regenerate or replace the adsorbent based on the total adsorption amount S1, the saturation amount S2, and the treatment conditions; and a transmission step of issuing an instruction to regenerate or replace the adsorbent before the total adsorption amount S1 exceeds the saturation amount S2.

[0069] The total adsorption amount S1 is calculated as follows. Total adsorption amount S1 = raw water PFAS concentration × cumulative flow rate

[0070] The saturation amount S2 of the adsorbent is calculated using the following method 1 or method 2.

[0071] Method 1: Small-scale column test using actual raw water The water flow conditions are set to the same as those of the actual equipment. The water quality at the column outlet is measured over time. The water flow time at which the amount of PFAS can be detected is designated as T. Saturation amount S2 = Water flow rate × Water flow time T × PFAS concentration in actual raw water

[0072] Method 2: Calculation of equilibrium adsorption amount by equilibrium adsorption test using actual raw water Saturation amount S2 = Amount of adsorbent in actual equipment × Equilibrium adsorption amount

[0073] The timing of issuing a command to regenerate or replace the adsorbent is not particularly limited. For example, the command to regenerate or replace the adsorbent is issued when the total adsorption amount S1, which is the cumulative amount of adsorption onto the adsorbent, becomes 70% or more, preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more of the saturation amount S2.

[0074] The regenerating solution for the ion exchange resin is not particularly limited as long as it can desorb PFAS adsorbed by electrostatic interaction. Examples include solutions containing ionic substances and seawater. Examples of ionic substances include halide salts such as sodium chloride, potassium chloride, potassium iodide, sodium bromide, and ammonium chloride; oxoacid salts such as sodium sulfate, sodium nitrate, and ammonium sulfate; acids such as sulfuric acid and hydrochloric acid; and bases such as sodium hydroxide and ammonium hydroxide.

[0075] PFAS adsorbed by non-electrostatic interactions are preferably removed using a regeneration liquid containing a nonionic substance. Examples of nonionic substances include water-soluble organic solvents such as alcohols (e.g., methanol, ethanol, isopropyl alcohol) and acetone. However, the regeneration liquid is not limited to these examples. One regeneration liquid may be used alone, or two or more may be used in combination.

[0076] [Action and effect] In the water treatment method using the water treatment device 1 described above, the materials used for the components of the membrane treatment means 10 used in the membrane treatment step, the materials used for the components for supplying the PFAS-treated water W3 to the filtration membrane of the membrane treatment means 10, and the materials used for supplying the filtration membrane-treated water W4 to the treated water tank 11 are all non-fluorine materials. Non-fluorine materials have a low affinity for PFAS in water. Therefore, by suppressing the accumulation of PFAS in the secondary side of the adsorption means 8 in the water treatment device 1, leakage of PFAS can be prevented.

[0077] In this way, by selecting a material that adsorbs PFAS only to a specific area (adsorbent 8 of water treatment device 1) and prevents PFAS from being adsorbed on the secondary side of that specific area, it is possible to appropriately control the distribution of PFAS adsorption amounts. As a result, PFAS are less likely to be adsorbed or accumulated on the secondary side of PFAS adsorbents such as activated carbon and ion exchange resins, preventing PFAS from leaking into the treated water. Therefore, even after PFAS-containing water has been purified over a long period of time and the PFAS adsorbent has been regenerated or replaced, the PFAS concentration in the treated water can be reliably reduced.

[0078] Additionally, in a preferred embodiment, the materials used in the untreated water supply step may also be non-fluorine-containing materials. If the untreated water supply means disposed on the upstream side of the adsorption means 8 is also made of a non-fluorine-containing material, adsorption and accumulation of PFASs on the components included in the untreated water supply means can be prevented. This is effective in suppressing fluctuations in the PFAS concentration in the untreated water (such as sand filtration-treated water W2) supplied to the adsorption means 8.

[0079] Preventing adsorption and accumulation of PFAS on components included in the water supply means can prevent PFAS from leaking from components included in the water supply means into the water to be treated supplied to the adsorption means 8. This can suppress fluctuations in the PFAS concentration in the water to be treated between the well 2 and the adsorption means 8. Preventing an overload of the PFAS treatment amount in the adsorption means 8 makes it easier to reduce the PFAS concentration on the secondary side of the adsorption means 8. As a result, management and control of the PFAS purification process by the water treatment device 1 becomes easier.

[0080] [Other embodiment examples] Although the present invention has been described above by showing several exemplary embodiments, the present invention is not limited to the exemplary embodiments disclosed in this specification and can be appropriately modified and implemented without departing from the spirit of the invention. The embodiments disclosed in this specification can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. [Industrial Applicability]

[0081] According to the present invention, a water treatment device and a water treatment method are provided that can reliably reduce the PFAS concentration in treated water, even after PFAS-containing water has been purified over a long period of time and the PFAS adsorbent has been regenerated or replaced. [Explanation of symbols]

[0082] 1. Water treatment equipment 2. Well 3. Water pump 4 Raw Water Tank 5. First oxidizing agent adding means 6 Raw water pump 7 Sand filter tower 8 Adsorption means 9. Second oxidant adding means 10 Membrane treatment means 11 Treatment tank

Claims

1. A water treatment device for purifying water to be treated containing either or both of a perfluoroalkyl compound and a polyfluoroalkyl compound, an adsorption means having an adsorbent that adsorbs either or both of the perfluoroalkyl compound and the polyfluoroalkyl compound; a membrane treatment means having a filtration membrane for treating PFAS-treated water obtained by removing either or both of the perfluoroalkyl compounds and the polyfluoroalkyl compounds with the adsorbent; a PFAS-treated water supply means for supplying the PFAS-treated water from the adsorption means to the membrane treatment means; a filtration membrane-treated water supply means for supplying filtration membrane-treated water, which is permeated water from the membrane treatment means, to a treated water tank; Equipped with the PFAS-treated water supply means is made of a non-fluorine material; the material of the member included in the membrane treatment means is a non-fluorine material, The water treatment device, wherein the members included in the filtration membrane-treated water supply means are made of non-fluorine materials.

2. 2. The water treatment device according to claim 1, wherein the PFAS-treated water supply means includes at least one selected from the group consisting of piping, sealing materials, pumps, valves, and meters.

3. The water treatment device according to claim 1 , wherein the filtration membrane-treated water supply means includes at least one selected from the group consisting of piping, sealing materials, pumps, valves, and meters.

4. further comprising a water-to-be-treated supply means for supplying the water-to-be-treated to the adsorption means; 2. The water treatment device according to claim 1, wherein the material of the members included in the untreated water supply means is also a non-fluorine material.

5. 5. The water treatment device according to claim 4, wherein the untreated water supply means includes at least one selected from the group consisting of piping, a sealing material, a pump, a valve, and a meter.

6. The water treatment device according to claim 1 , further comprising a simulation means for predicting when to regenerate or replace the adsorbent based on the total concentration of the perfluoroalkyl compounds and the polyfluoroalkyl compounds in the raw water to be treated.

7. The simulation means a calculation means for calculating a total adsorption amount S1 based on the total concentration of the perfluoroalkyl compounds and the polyfluoroalkyl compounds in the raw water and the amount of water to be treated; a monitoring means for monitoring the total adsorption amount S1 and the saturation amount S2 of the adsorbent by comparing them; a prediction means for predicting a time to regenerate or replace the adsorbent based on the total adsorption amount S1, the saturation amount S2, and treatment conditions; a transmitting means for transmitting an instruction to regenerate or replace the adsorbent before the total adsorption amount S1 exceeds the saturation amount S2; The water treatment device of claim 6 , comprising:

8. A water treatment method using the water treatment device according to any one of claims 1 to 7.

9. A water treatment method for purifying water to be treated containing either or both of a perfluoroalkyl compound and a polyfluoroalkyl compound, comprising: an adsorption step of obtaining PFAS-treated water using an adsorbent that adsorbs either or both of the perfluoroalkyl compound and the polyfluoroalkyl compound; a membrane treatment step of treating the PFAS-treated water using a filtration membrane to obtain filtration membrane-treated water; and a member for supplying the PFAS-treated water to the filtration membrane is made of a non-fluorinated material; the material of the member used in the membrane treatment step is a non-fluorine material, The water treatment method, wherein the material of the member for supplying the membrane-treated water to the treatment tank is a non-fluorine material.

10. The method further includes a water-to-be-treated supply step of supplying the water-to-be-treated to the adsorbent, The water treatment method according to claim 9 , wherein the material of the member used in the untreated water supply step is also a non-fluorine material.

11. The water treatment method according to claim 9 or 10, further comprising a simulation step of predicting the timing of regeneration or replacement of the adsorbent based on the total concentration of the perfluoroalkyl compounds and the polyfluoroalkyl compounds in the raw water of the water to be treated.

12. The simulation step includes: a calculation step of calculating a total adsorption amount S1 based on the total concentration of the perfluoroalkyl compound and the polyfluoroalkyl compound in the raw water and the amount of water to be treated; a monitoring step of comparing and monitoring the total adsorption amount S1 with the saturation amount S2 of the adsorbent; a prediction step of predicting a time to regenerate or replace the adsorbent based on the total adsorption amount S1, the saturation amount S2, and treatment conditions; a transmitting step of issuing a regeneration instruction or a replacement instruction for the adsorbent before the total adsorption amount S1 exceeds the saturation amount S2; The water treatment method of claim 11 , comprising:

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