Water treatment and recovery system and method

Abstract

To provide a water treatment and recovery system capable of efficiently treating fluorine-containing treated water and prevent clogging of the reverse osmosis membrane.SOLUTION: A water treatment and recovery system 10 for treating and recovering raw water containing fluorine, includes: a fluorine adsorption tower 16 that reduces the fluorine concentration by adsorbing fluorine contained in the raw water in a state in which the pH of raw water containing fluorine is adjusted to an acidic level; a caustic addition part 17 that precipitates calcium hydroxide by adding caustic 62 to the raw water with the fluorine concentration reduced in the fluorine adsorption tower 16; an UF membrane filtration part 20 that removes the precipitated calcium hydroxide with an UF membrane; and a RO membrane treatment part 26 that treats the raw water after filtration by the UF membrane filtration part 20 to remove at least ion content in the raw water.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, water treatment devices for treating wastewater containing fluorine have been proposed. For example, Patent Document 1 discloses a water treatment device for recovering water from fluorine-containing water to be treated that contains fluorine. This water treatment device includes a first flocculation / separation device that adds a calcium agent to the water to be treated that contains fluorine to perform a first flocculation / separation treatment, a second flocculation / separation device that adds a carbonate-containing agent to the first flocculation / separation-treated water that has been subjected to the first flocculation / separation treatment to perform a second flocculation / separation treatment, a fluorine adsorption treatment device that brings the second flocculation / separation-treated water that has been subjected to the second flocculation / separation treatment into contact with a fluorine adsorbent to perform a fluorine adsorption treatment, and a reverse osmosis membrane treatment device that treats the fluorine adsorption-treated water that has been subjected to the fluorine adsorption treatment with a reverse osmosis membrane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-82546 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the water treatment device described in Patent Document 1, a calcium agent such as slaked lime (i.e., calcium hydroxide) is added to the water to be treated in the first flocculation / separation device. Since calcium hydroxide reacts slowly with fluoride ions, a large amount of calcium hydroxide must be added to perform the first flocculation / separation treatment, and the content of unreacted calcium hydroxide is likely to be high. For this reason, when water to be treated with a high concentration of calcium hydroxide is treated with a reverse osmosis membrane, the reverse osmosis membrane is likely to be clogged. To explain in more detail, when the fluorine-containing water concentration is high, fluorine reacts with calcium in the concentration step to produce calcium fluoride. Calcium fluoride is a substance that inhibits recovery during regeneration, and is difficult to remove even by washing. When the above-mentioned scale is generated in the concentration step, the reverse osmosis membrane is clogged. In addition, the frequency of regeneration of the reverse osmosis membrane increases, which is not efficient.

[0005] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a water treatment and recovery system and a water treatment and recovery method that can efficiently treat fluorine-containing water to be treated and suppress clogging of a reverse osmosis membrane. [Means for solving the problem]

[0006] The water treatment and recovery system according to a first aspect is a water treatment and recovery system that treats and recovers fluorine-containing water to be treated, and includes a fluorine adsorption section that adsorbs fluorine contained in the fluorine-containing water to be treated to reduce the fluorine concentration in the water to be treated while the pH of the water to be treated is adjusted to be acidic; an alkali addition section that adds an alkali to the water to be treated, the fluorine concentration of which has been reduced by the fluorine adsorption section, to thereby precipitate calcium hydroxide; a UF membrane filtration section that removes the calcium hydroxide precipitated by adding the alkali to the water to be treated, using a UF membrane which is an ultrafiltration membrane; and a reverse osmosis membrane treatment section that treats the water to be treated after filtration by the UF membrane filtration section, using a reverse osmosis membrane, to remove at least ions in the water to be treated.

[0007] In the above water treatment recovery system, it is preferable that the fluorine adsorption section includes a fluorine adsorbent containing a lanthanoid, and the alkali addition section adds the alkali to cause the lanthanoid eluted from the fluorine adsorbent into the water to precipitate as hydroxide, and the hydroxide is removed in the UF membrane filtration section.

[0008] The above water treatment and recovery system preferably further comprises a sterilization treatment section disposed between the fluorine adsorption section and the UF membrane filtration section for adding a bactericide to the water to be treated and sterilizing the water to be treated.

[0009] In the above-mentioned water treatment recovery system, it is preferable that the bactericide is hypochlorous acid, and that the system has an activated carbon adsorption section that is arranged between the UF membrane filtration section and the reverse osmosis membrane treatment section and adsorbs and removes residual chlorine contained in the treated water onto activated carbon.

[0010] The above water treatment and recovery system preferably further comprises a sand filtration section which is disposed before the treatment of the to-be-treated water by the fluorine adsorption section and which removes fine particles contained in the to-be-treated water by filtering the to-be-treated water to which a coagulant has been added.

[0011] In the above-mentioned water treatment recovery system, it is preferable that the system comprises at least one processor, a first pressure measurement unit that measures the pressure on the inlet side of the UF membrane filtration unit, and a second pressure measurement unit that measures the pressure on the outlet side of the UF membrane filtration unit, and the processor outputs information regarding the timing of cleaning the UF membrane before the UF membrane of the UF membrane filtration unit becomes clogged, based on the inlet side pressure measured by the first pressure measurement unit and the outlet side pressure measured by the second pressure measurement unit.

[0012] In the above-mentioned water treatment recovery system, it is preferable that the system comprises at least one processor, a third pressure measurement unit that measures the pressure on the inlet side of the reverse osmosis membrane processing unit, and a fourth pressure measurement unit that measures the pressure on the outlet side of the reverse osmosis membrane processing unit, and that the processor outputs information regarding the timing of cleaning the reverse osmosis membrane before the reverse osmosis membrane of the reverse osmosis membrane processing unit becomes clogged, based on the inlet side pressure measured by the third pressure measurement unit and the outlet side pressure measured by the fourth pressure measurement unit.

[0013] In the above-mentioned water treatment recovery system, it is preferable that the system further comprises at least one processor, which calculates a permeation flux of the reverse osmosis membrane processing unit and outputs information regarding the timing of cleaning the reverse osmosis membrane before the reverse osmosis membrane of the reverse osmosis membrane processing unit becomes clogged, based on the permeation flux.

[0014] In the above-mentioned water treatment recovery system, it is preferable that the system comprises at least one processor and a terminal device that monitors at least the status of the UF membrane filtration unit at a location isolated from the UF membrane filtration unit, and the processor transmits information regarding the UF membrane filtration unit to the terminal device directly or via a relay unit, and the terminal device monitors the status of the UF membrane filtration unit based on the information regarding the UF membrane filtration unit.

[0015] In the above-mentioned water treatment recovery system, it is preferable that the system comprises at least one processor and a terminal device that monitors at least the status of the reverse osmosis membrane processing unit at a location isolated from the reverse osmosis membrane processing unit, the processor transmits information related to the reverse osmosis membrane processing unit to the terminal device directly or via a relay unit, and the terminal device monitors the status of the reverse osmosis membrane processing unit based on the information related to the reverse osmosis membrane processing unit.

[0016] The water treatment and recovery method according to the second aspect is a water treatment and recovery method for treating and recovering fluorine-containing water to be treated, and includes a fluorine adsorption step of adsorbing fluorine contained in the fluorine-containing water to be treated to reduce the fluorine concentration in the water to be treated, with the pH of the water to be treated being adjusted to be acidic; a precipitation step of precipitating calcium hydroxide by adding an alkali to the water to be treated, the fluorine concentration of which has been reduced in the fluorine adsorption step; a UF membrane filtration step of removing the calcium hydroxide precipitated by adding the alkali to the water to be treated, using a UF membrane which is an ultrafiltration membrane; and a reverse osmosis membrane treatment step of treating the water to be treated after the filtration in the UF membrane filtration step with a reverse osmosis membrane to remove at least ions in the water to be treated. Effect of the Invention

[0017] According to the present disclosure, it is possible to efficiently treat fluorine-containing water to be treated and to suppress clogging of the reverse osmosis membrane. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic configuration diagram showing a water treatment and recovery system according to a first embodiment. [Diagram 2] 2 is a block diagram showing a hardware configuration of a user terminal used in the water treatment and recovery system according to the first embodiment. FIG. [Diagram 3] 4 is a graph showing the results of measuring fluctuations in RO membrane permeation flux versus operation time in the water treatment and recovery system according to the first embodiment. [Figure 4] FIG. 1 is a schematic configuration diagram showing a water treatment and recovery system of a first comparative example. [Diagram 5] 1 is a graph showing the results of measuring fluctuations in RO membrane permeation flux versus operation time in the water treatment and recovery system of the first comparative example. [Figure 6] FIG. 11 is a schematic configuration diagram showing a water treatment and recovery system of a second comparative example. [Figure 7] 13 is a graph showing the results of measuring fluctuations in RO membrane permeation flux versus operation time in the water treatment and recovery system of the second comparative example. [Figure 8] 1 is a graph showing the results of measuring the variation in RO membrane permeation flux versus operating time in an example water treatment and recovery system that has been replaced with a new RO membrane. [Figure 9] FIG. 11 is a block diagram showing a hardware configuration of a monitoring system used in a water treatment and recovery system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0020] [First embodiment] A water treatment and recovery system according to a first embodiment will be described.

[0021] <Overall configuration of water treatment and recovery system> 1 shows a water treatment and recovery system 10 according to a first embodiment. The water treatment and recovery system 10 is a system that treats and recovers raw water, which is an example of water to be treated that contains fluorine. More specifically, the water treatment and recovery system 10 is a system that treats raw water that contains fluorine and recovers it as water that can be reused in a factory or the like, or as water that can be discharged outside the factory.

[0022] As shown in Fig. 1, the water treatment and recovery system 10 includes a treatment device 11 equipped with each treatment section described below. The treatment device 11 is provided with piping 32 that connects each treatment section and allows raw water to flow. The piping 32 is provided with a plurality of (e.g., four) pumps 30A, 30B, 30C, and 30D, and the raw water in the piping 32 is sent (i.e., pumped) in the direction of arrow A by driving the plurality of pumps 30A, 30B, 30C, and 30D. The water treatment and recovery system 10 (treatment device 11) sends the raw water through the piping 32 to each treatment section described below, and performs a predetermined treatment in each treatment section.

[0023] More specifically, the treatment device 11 is provided with, in order from the upstream side to the downstream side in the raw water transport direction (arrow A direction), a raw water tank 12, a sand filtration tower 14, an acid addition section 15, a fluorine adsorption tower 16, a caustic addition section 17, and a filtered water tank 18 as each processing section. The treatment device 11 is also provided with, in order from the filtered water tank 18 to the downstream side in the raw water transport direction (arrow A direction), a UF membrane filtration section 20 equipped with a UF membrane which is an ultrafiltration membrane, a pretreatment water tank 22, an activated carbon tower 24, and an RO membrane treatment section 26 equipped with an RO membrane which is a reverse osmosis membrane as each processing section.

[0024] In the water treatment and recovery system 10, the treatment device 11 and a user terminal 80 can be connected online via a computer network. The user terminal 80 is, for example, a personal computer (PC). The user terminal 80 includes a control unit 90 that controls each processing unit of the treatment device 11, and a display unit 82 that displays the processing status of each processing unit of the treatment device 11. For example, the user terminal 80 is connected to the treatment device 11 wirelessly, but may be connected to the treatment device 11 by wire.

[0025] (Raw water tank) As shown in Fig. 1, the raw water tank 12 is a container in which raw water is supplied and stored. The raw water includes fluorine-containing wastewater discharged from a factory, and fluorine-containing wastewater discharged from a factory that has been pretreated to reduce fluorine. Examples of pretreatment include a primary treatment in which calcium hydroxide is added to fluorine-containing wastewater to perform neutralization treatment, and calcium fluoride is converted into calcium fluoride, which is then separated by sedimentation.

[0026] The raw water tank 12 is provided with a number of measuring units for measuring various items of the raw water inside the raw water tank 12, including a pH measuring unit 41A, a turbidity measuring unit 42, a SS measuring unit 43A for measuring the suspended solids (SS), a temperature measuring unit 44A, an EC measuring unit 45A for measuring the electrical conductivity (EC), and an ORP measuring unit 71 for measuring the oxidation-reduction potential (ORP). The pH measuring unit 41A measures the pH of the raw water. The turbidity measuring unit 42 measures the turbidity of the raw water. The suspended solids (SS) is an index of the turbidity of the water quality. The suspended solids are small particles with a diameter of 2 mm or less that are not completely dissolved in the water. The SS measuring unit 43A measures the suspended solids (SS) in the raw water. The temperature measuring unit 44A estimates the temperature of the raw water. The electrical conductivity (EC) is the ability of water to conduct electricity. The EC measuring unit 45A measures the electrical conductivity (EC) of the raw water. The oxidation-reduction potential (ORP) is a numerical value (unit: mV) that indicates the oxidation-reduction state of a solution. In other words, the oxidation-reduction potential (ORP) is an index that indicates the oxidation or reduction of a solution. The ORP measuring unit 71 measures the oxidation-reduction potential of the raw water. The measured values ​​measured by the pH measuring unit 41A, the turbidity measuring unit 42, the SS measuring unit 43A, the temperature measuring unit 44A, the EC measuring unit 45A, and the ORP measuring unit 71 are transmitted to the control unit 90.

[0027] In the raw water tank 12, a flocculant 60 is added to the raw water as an example of a chemical. As a result, fine particles contained in the raw water are flocculated by the flocculant 60. Examples of the flocculant 60 include cationic flocculants, anionic flocculants, iron-based flocculants, and aluminum-based flocculants. In the first embodiment, a cationic flocculant is used as the flocculant 60. The flocculant 60 breaks fine particles in the raw water into larger clumps of fine particles (i.e., flocculated substances) for removal in the sand filter tower 14.

[0028] A pump 30A is provided in the pipe 32 connecting the raw water tank 12 and the sand filtration tower 14, and raw water is sent (ie, pumped) from the raw water tank 12 to the sand filtration tower 14 by driving the pump 30A.

[0029] (Sand filter tower) As shown in Fig. 1, the sand filter tower 14 is a filtering facility that uses sand as a filter medium. The sand filter tower 14 is an example of a sand filtration section. The sand filter tower 14 removes fine particles (e.g., flocculated substances flocculated by a flocculant 60) contained in the raw water. As an example, the sand filter tower 14 has a sand layer (not shown) inside a vertically long tower, and removes fine particles by filtering the raw water by passing it through the sand layer at a set flow rate.

[0030] The sand filtration tower 14 is disposed in the raw water sending direction (the direction of the arrow A) before the raw water is treated in the fluorine adsorption tower 16.

[0031] The sand filter tower 14 is provided with an SS measuring unit 43B, an inlet side pressure measuring unit 47A, an outlet side pressure measuring unit 48A, and a flow rate measuring unit 49A. The SS measuring unit 43B measures the amount of suspended solids (SS) in the raw water. The inlet side pressure measuring unit 47A measures the pressure on the inlet side where the raw water flows into the sand filter tower 14 through the piping 32. The outlet side pressure measuring unit 48A measures the pressure on the outlet side where the raw water flows out from the sand filter tower 14 to the piping 32. The flow rate measuring unit 49A measures the flow rate of the raw water passing through the sand filter tower 14.

[0032] The measured values ​​respectively measured by the SS measuring unit 43B, the pressure measuring unit 47A, the pressure measuring unit 48A, and the flow rate measuring unit 49A are transmitted to the control unit 90. A CPU 91 (described later) of the control unit 90 calculates a differential pressure 101 based on the inlet side pressure measured by the pressure measuring unit 47A and the outlet side pressure measured by the pressure measuring unit 48A.

[0033] (Acid addition section) In the water treatment and recovery system 10, raw water is sent from the sand filtration tower 14 to the fluorine adsorption tower 16 through a pipe 32 connecting the sand filtration tower 14 and the fluorine adsorption tower 16. The acid addition unit 15 is provided in the middle of the pipe 32 connecting the sand filtration tower 14 and the fluorine adsorption tower 16. In the acid addition unit 15, an acid 61, which is an example of a chemical, is added to the raw water. Examples of the acid 61 include hydrochloric acid, sulfuric acid, dilute hydrochloric acid, dilute sulfuric acid, and citric acid. In the first embodiment, hydrochloric acid is used as the acid 61.

[0034] The pH of the raw water is adjusted to be acidic by adding the acid 61 to the raw water. For example, since the fluorine adsorption tower 16 has a tendency to have higher fluorine adsorption performance as the acidic range increases, the pH of the raw water is adjusted to be in the acidic range before being introduced into the fluorine adsorption tower 16. The pH of the raw water immediately before being introduced into the fluorine adsorption tower 16 is preferably 2.0 or more and 5.0 or less, more preferably 2.5 or more and 4.5 or less, and more preferably 3.0 or more and 3.5 or less.

[0035] (Fluorine adsorption tower) In the water treatment and recovery system 10, raw water to which acid 61 has been added in the acid adding section 15 is sent to the fluorine adsorption tower 16 through a pipe 32. The fluorine adsorption tower 16 is an example of a fluorine adsorption section.

[0036] As an example, the fluorine adsorption tower 16 is filled with a fluorine adsorbent inside the tower, and the raw water is passed so as to come into contact with the fluorine adsorbent. For example, a fluorine adsorbent containing lanthanoids can be used as the fluorine adsorbent. Here, lanthanoids are a collective term for 15 elements with atomic numbers from 57 to 71, that is, lanthanum (La) to lutetium (Lu). In addition, as the fluorine adsorbent, an adsorbent made of a composite granulation product of hydrated iron oxide particles containing one or more metals selected from lanthanoids or zirconium (Zr), hafnium (Hf), and yttrium (Y) and one or more organic polymer resins may be used. Examples of the organic polymer resin include ethylene-vinyl alcohol copolymer resin and polyvinyl acetal resin. In the first embodiment, a fluorine adsorbent containing cerium (Ce) with atomic number 58 is used as the lanthanoid.

[0037] In the fluorine adsorption tower 16, while the pH of the raw water is adjusted to be acidic, fluorine contained in the raw water is adsorbed by a fluorine adsorbent to reduce the fluorine concentration (i.e., fluorine content) of the raw water. The fluorine concentration of the raw water before being introduced into the fluorine adsorption tower 16 is preferably 4 mg / L to 30 mg / L, more preferably 4 mg / L to 8 mg / L, and even more preferably 4 mg / L to 5 mg / L. For example, when the fluorine concentration of the raw water before being introduced into the fluorine adsorption tower 16 is 4 mg / L to 8 mg / L, the fluorine concentration of the raw water after passing through the fluorine adsorption tower 16 will be, for example, 0.2 mg / L or less.

[0038] A pH measuring unit 41B is provided at the inlet side of the fluorine adsorption tower 16. The pH measuring unit 41B measures the pH of the raw water at the inlet side of the fluorine adsorption tower 16. The pH of the raw water at the inlet side of the fluorine adsorption tower 16 is adjusted to, for example, 3.0 or more and 3.5 or less by injecting an acid 61 into the raw water before the raw water is introduced into the fluorine adsorption tower 16. The measured value measured by the pH measuring unit 41B is transmitted to the control unit 90.

[0039] An ORP measuring unit 53 for measuring the oxidation-reduction potential (ORP) of the raw water is provided on the inlet side of the fluorine adsorption tower 16. The oxidation-reduction potential (ORP) is a numerical value (unit: mV) that represents the oxidation-reduction state of a solution. The measured value measured by the ORP measuring unit 53 is transmitted to the control unit 90.

[0040] (caustic addition section) In the water treatment and recovery system 10, raw water is sent from the fluorine adsorption tower 16 to the filtered water tank 18 through a pipe 32 connecting the fluorine adsorption tower 16 and the filtered water tank 18. The caustic addition unit 17 is provided in the middle of the pipe 32 connecting the fluorine adsorption tower 16 and the filtered water tank 18. In the caustic addition unit 17, caustic 62 (sometimes called caustic alkali) as an example of an alkali is added to the raw water after treatment in the fluorine adsorption tower 16. The caustic addition unit 17 is an example of an alkali addition unit. Examples of the caustic 62 include caustic soda (sodium hydroxide) and sodium carbonate. In the first embodiment, caustic soda (sodium hydroxide) is used as the caustic 62. By adding the caustic 62 to the raw water, unreacted calcium hydroxide (Ca(OH) 2 In addition, when a fluorine adsorbent containing cerium is used in the fluorine adsorption tower 16, the cerium eluted from the fluorine adsorbent is converted into cerium hydroxide (Ce(OH) 2 Cerium hydroxide is an example of a hydroxide.

[0041] A pH measuring unit 41C is provided on the inlet side of the filtration water tank 18 after the caustic 62 is added to the raw water. The pH measuring unit 41C measures the pH of the raw water after the caustic 62 is added. The pH of the raw water after the caustic 62 is injected is adjusted to about 7 (for example, near neutral, 5.8 to 8.6). In other words, in the first embodiment, when adjusting the raw water to about pH 7, the caustic 62 is added to the raw water. The reason for adjusting the pH of the raw water to about 7 is to enable reuse of the water or discharge of the water outside the factory after the fluorine contained in the raw water is removed by the water treatment recovery system 10. The measured value measured by the pH measuring unit 41C is transmitted to the control unit 90.

[0042] (Filtration tank) In the filtered water tank 18, a bactericide 63 is added as an example of a chemical to the raw water after the caustic 62 has been added. The raw water is sterilized by the bactericide 63. The filtered water tank 18 is an example of a sterilization treatment section. Examples of the bactericide 63 include chloramine-based chemicals (chlorine-based and bromine-based), peracetic acid, and hydrogen peroxide. In the first embodiment, hypochlorous acid encapsulated in a chloramine-based chemical is used as the bactericide 63. The filtered water tank 18 is disposed between the fluorine adsorption tower 16 and the UF membrane filtration section 20.

[0043] The filtration tank 18 is a tank that stores filtered water, and serves as a buffer for adjusting the pH and for applying the effects of the bactericide 63. The raw water is stored in the filtration tank 18 so that the pH adjustment can be performed well. The raw water is also stored in the filtration tank 18 so that the effects of the bactericide 63 can be applied evenly. Since the filtration tank 18 is a tank that stores filtered water as described above, no filtration is performed.

[0044] (UF membrane filtration section) In the water treatment recovery system 10, a pump 30B is provided in a pipe 32 connecting the filtered water tank 18 and the UF membrane filtration section 20, and by driving the pump 30B, raw water is sent from the filtered water tank 18 through the pipe 32 to the UF membrane filtration section 20.

[0045] The UF membrane filtration section 20 is equipped with a UF membrane inside, and is used to filter calcium hydroxide (Ca(OH) 2 ), cerium hydroxide (Ce(OH) 2 ), and other substances are removed by the UF membrane. Here, the UF membrane is also called an ultrafiltration membrane as described above, and is a filtration membrane that separates suspended solids (SS), bacteria, and polymeric substances from water, ionic substances, and low molecular weight substances. The pore size of the UF membrane is generally 0.001 μm or more and 0.01 μm or less, which is larger than that of the RO membrane (reverse osmosis membrane). Here, SS (suspended solids) refers to insoluble substances suspended in water, and is also called suspended matter or floating matter.

[0046] The UF membrane is made of, for example, PVDF (polyvinylidene fluoride), which has excellent mechanical strength and chemical durability such as resistance to chlorine and oxidation.

[0047] The UF membrane filtration section 20 is provided with an inlet pressure measuring section 47B, an outlet pressure measuring section 48B, and a flow rate measuring section 49B. The inlet pressure measuring section 47B is an example of a first pressure measuring section, and the outlet pressure measuring section 48B is an example of a second pressure measuring section. The inlet pressure measuring section 47B measures the pressure on the inlet side where the raw water flows into the UF membrane filtration section 20 through the piping 32. The outlet pressure measuring section 48B measures the pressure on the outlet side where the raw water flows out from the UF membrane filtration section 20 to the piping 32. The flow rate measuring section 49B measures the flow rate of the raw water passing through the UF membrane filtration section 20. The measured values ​​measured by the pressure measuring section 47B, the pressure measuring section 48B, and the flow rate measuring section 49B are transmitted to the control section 90. A CPU 91 (to be described later) of the control unit 90 calculates a differential pressure 102 based on the inlet pressure measured by the pressure measuring unit 47B and the outlet pressure measured by the pressure measuring unit 48B.

[0048] (Pre-treatment tank) In the water treatment and recovery system 10, a pipe 32 is provided that connects the UF membrane filtration unit 20 and the pretreated water tank 22, and raw water is sent from the UF membrane filtration unit 20 through the pipe 32 to the pretreated water tank 22.

[0049] A pH measuring unit 41D is provided at the inlet side of the pretreatment water tank 22, and the pH of the raw water is measured by the pH measuring unit 41D at the inlet side of the pretreatment water tank 22. In addition, an EC measuring unit 45B is provided inside the pretreatment water tank 22, and the electrical conductivity (EC) of the raw water is measured by the EC measuring unit 45B.

[0050] (activated carbon tower) In the water treatment and recovery system 10, a pump 30C is provided in a pipe 32 connecting the pretreatment water tank 22 and the activated carbon tower 24, and by driving the pump 30C, raw water is sent from the pretreatment water tank 22 through the pipe 32 to the activated carbon tower 24. The activated carbon tower 24 is an example of an activated carbon adsorption section. The activated carbon tower 24 is provided downstream of the UF membrane filtration section 20 and upstream of the RO membrane treatment section 26 in the raw water sending direction (direction of arrow A). In other words, the activated carbon tower 24 is disposed between the UF membrane filtration section 20 and the RO membrane treatment section 26.

[0051] As an example, the activated carbon tower 24 is filled with activated carbon, and raw water is passed through the tower so as to come into contact with the activated carbon. In the filtered water tank 18, hypochlorous acid, which is an example of a bactericide 63, is added to the raw water, so that the raw water contains residual chlorine. In the activated carbon tower 24, the residual chlorine contained in the raw water is adsorbed by the activated carbon and removed.

[0052] The activated carbon tower 24 is provided with an inlet-side pressure measuring unit 47C and an outlet-side pressure measuring unit 48C. The inlet-side pressure measuring unit 47C measures the pressure on the inlet side where raw water flows into the activated carbon tower 24 through the piping 32. The outlet-side pressure measuring unit 48C measures the pressure on the outlet side where raw water flows out from the activated carbon tower 24 to the piping 32. The measured values ​​respectively measured by the pressure measuring unit 47C and the pressure measuring unit 48C are transmitted to the control unit 90. A CPU 91 of the control unit 90, which will be described later, calculates a differential pressure 103 based on the inlet-side pressure measured by the pressure measuring unit 47C and the outlet-side pressure measured by the pressure measuring unit 48C.

[0053] (RO membrane processing section) In the water treatment and recovery system 10, a pump 30D is provided in a pipe 32 connecting the activated carbon tower 24 and the RO membrane treatment unit 26, and by driving the pump 30D, raw water is sent from the activated carbon tower 24 through the pipe 32 to the RO membrane treatment unit 26. A sterilizing agent 64 and a dispersing agent 65, as examples of chemicals, are added to the raw water in the pipe 32 connecting the activated carbon tower 24 and the RO membrane treatment unit 26.

[0054] An example of the sterilizing agent 64 is combined chlorine. For example, a chloramine-based chemical is used as combined chlorine. The raw water is sterilized by adding the sterilizing agent 64 to the raw water. In addition, when hypochlorous acid, an example of the sterilizing agent 63, is added to the raw water, the hypochlorous acid breaks through the RO membrane of the RO membrane processing unit 26. For this reason, adding combined chlorine makes it possible to sterilize the water without causing it to break through the RO membrane.

[0055] For example, a scale dispersant, a scale inhibitor, etc. are used as the dispersant 65. By adding the dispersant 65 to the raw water, adhesion of scale to the RO membrane of the RO membrane treatment unit 26 is suppressed.

[0056] The RO membrane treatment unit 26 is provided downstream of the UF membrane filtration unit 20 in the raw water flow direction (direction of arrow A), and the raw water after filtration in the UF membrane filtration unit 20 is treated in the RO membrane treatment unit 26.

[0057] An RO membrane (reverse osmosis membrane) is disposed inside the RO membrane processing unit 26, and the raw water is brought into contact with the RO membrane. Here, the RO membrane (reverse osmosis membrane) is a type of filtration membrane that allows water to pass through but does not allow impurities other than water molecules, such as ions and salts, to pass through. The pore size of the RO membrane (reverse osmosis membrane) is approximately 2 nm or less, which is smaller than that of a UF membrane (ultrafiltration membrane). By bringing the raw water into contact with the RO membrane (reverse osmosis membrane) and taking out the permeated water that has permeated the RO membrane, at least the ions contained in the raw water can be removed.

[0058] As the RO membrane, for example, a polyamide-based composite membrane is used.

[0059] In the RO membrane treatment unit 26, when the raw water is treated with the RO membrane, the permeated water that has permeated the RO membrane is discharged into a pipe 33 connected to the RO membrane treatment unit 26. The permeated water is water that has been recovered by the water treatment and recovery system 10 after treating the raw water.

[0060] Furthermore, when the raw water is treated with the RO membrane, concentrated water that does not permeate the RO membrane is discharged to a pipe 34 connected to the RO membrane treatment section 26. The pipe 34 is branched into a first pipe 35A and a second pipe 35B. A part of the concentrated water is discharged from the first pipe 35A.

[0061] The downstream end of the second pipe 35B is connected to an upstream portion (a portion before the sterilizing agent 64 and the dispersing agent 65 are added) of the pipe 32 that connects the activated carbon tower 24 and the RO membrane processing unit 26. As a result, a portion of the concentrated water is returned to the pipe 32 as circulating water through the second pipe 35B.

[0062] The RO membrane treatment unit 26 is provided with an inlet pressure measurement unit 47D, an outlet pressure measurement unit 48D, an inlet pH measurement unit 41F, a temperature measurement unit 44B, an EC measurement unit 45C, an EC measurement unit 45D on the permeate side, and a flow rate measurement unit 49C. The inlet pressure measurement unit 47D is an example of a third pressure measurement unit, and the outlet pressure measurement unit 48D is an example of a fourth pressure measurement unit. The inlet pressure measurement unit 47D measures the pressure on the inlet side where the raw water flows into the RO membrane treatment unit 26 through the piping 32. The outlet pressure measurement unit 48D measures the pressure on the outlet side where the raw water flows out from the RO membrane treatment unit 26 to the piping 33.

[0063] The pH measurement unit 41F measures the pH of the raw water. The temperature measurement unit 44B measures the temperature of the raw water. The EC measurement unit 45C measures the electrical conductivity (EC) of the raw water flowing into the RO membrane treatment unit 26 through the piping 32. The EC measurement unit 45D measures the electrical conductivity (EC) of the permeate water flowing out from the RO membrane treatment unit 26 to the piping 33. The flow rate measurement unit 49C measures the flow rate of the raw water passing through the RO membrane treatment unit 26.

[0064] The measured values ​​measured by the pressure measuring unit 47D, the pressure measuring unit 48D, the pH measuring unit 41F, the temperature measuring unit 44B, the EC measuring unit 45C, the EC measuring unit 45D, and the flow rate measuring unit 49C are transmitted to the control unit 90. A CPU 91 of the control unit 90, which will be described later, calculates a differential pressure 104 based on the inlet side pressure measured by the pressure measuring unit 47D and the outlet side pressure measured by the pressure measuring unit 48D. Furthermore, the CPU 91 of the control unit 90 calculates the permeation flux of the RO membrane processing unit 26. The permeation flux is used to determine the membrane clogging tendency of the RO membrane, and is a value calculated taking into account the electrical conductivity (EC), temperature, flow rate, pressure, membrane area, and the like. For example, the permeation flux can be calculated by dividing the permeation speed of the permeated liquid through the RO membrane by the membrane area, and can also be referred to as the amount of permeated liquid per unit membrane area and unit time.

[0065] The first pipe 35A is provided with an EC measuring unit 45E, a flow rate measuring unit 49C, and a pH measuring unit 41E. The EC measuring unit 45E measures the electrical conductivity (EC) of the concentrated water. The flow rate measuring unit 49D measures the flow rate of the concentrated water flowing through the first pipe 35A. The pH measuring unit 41E measures the pH of the concentrated water. The measured values ​​respectively measured by the EC measuring unit 45E, the flow rate measuring unit 49C, and the pH measuring unit 41E are transmitted to the control unit 90.

[0066] (User terminal) Fig. 2 is a block diagram showing a hardware configuration of the user terminal 80. As shown in Fig. 2, the user terminal 80 includes a control unit 90, a display unit 82, and a notification unit 84. The control unit 90 includes a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, a storage 94, and an input / output interface 95. Each component is connected to each other via a bus 99 so as to be able to communicate with each other.

[0067] The CPU 91 is a central processing unit that executes various programs and controls each part. The CPU 91 is an example of a processor. That is, the CPU 91 reads a program from the ROM 92 or the storage 94, and executes the program using the RAM 93 as a working area. The CPU 91 performs control processing of each of the above components according to the program recorded in the ROM 92 or the storage 94. In the first embodiment, the ROM 92 or the storage 94 stores a control program that controls the treatment device 11 of the water treatment recovery system 10.

[0068] The ROM 92 stores various programs and various data. The RAM 93 temporarily stores programs or data as a working area. The storage 94 is configured with an HDD (Hard Disk Drive) or an SSD (Solid State Drive) and stores various programs including an operating system and various data.

[0069] The input / output interface 95 is an interface for communicating with the treatment device 11 mounted on the water treatment and recovery system 10. The control unit 90 is connected to the raw water tank 12, the sand filtration tower 14, the acid addition unit 15, the fluorine adsorption tower 16, the caustic addition unit 17, the filtered water tank 18, the UF membrane filtration unit 20, the pretreated water tank 22, the activated carbon tower 24, the RO membrane treatment unit 26, and the like of the treatment device 11 via the input / output interface 95. The raw water tank 12, the sand filtration tower 14, the acid addition unit 15, the fluorine adsorption tower 16, the caustic addition unit 17, the filtered water tank 18, the UF membrane filtration unit 20, the pretreated water tank 22, the activated carbon tower 24, the RO membrane treatment unit 26, and the like of the treatment device 11 may be directly connected via a bus 99.

[0070] In the control unit 90, a CPU 91 controls the raw water tank 12, sand filtration tower 14, acid addition section 15, fluorine adsorption tower 16, caustic addition section 17, filtered water tank 18, UF membrane filtration section 20, pretreated water tank 22, activated carbon tower 24, RO membrane treatment section 26, etc. of the treatment device 11.

[0071] The display unit 82 displays the treatment status of the raw water tank 12, sand filtration tower 14, acid addition unit 15, fluorine adsorption tower 16, caustic addition unit 17, filtered water tank 18, UF membrane filtration unit 20, pretreated water tank 22, activated carbon tower 24, RO membrane treatment unit 26, etc. of the treatment device 11. This allows the user terminal 80 to monitor the treatment status of the raw water tank 12, sand filtration tower 14, acid addition unit 15, fluorine adsorption tower 16, caustic addition unit 17, filtered water tank 18, UF membrane filtration unit 20, pretreated water tank 22, activated carbon tower 24, RO membrane treatment unit 26, etc. online.

[0072] In the user terminal 80, the control unit 90 continuously monitors the inlet pressure, differential pressure, and flow rate, particularly those caused by clogging of the UF membrane of the UF membrane filtration unit 20. In addition, in the user terminal 80, the control unit 90 continuously monitors the inlet pressure, differential pressure, electrical conductivity (EC), flow rate, temperature, and permeation flux, particularly those caused by clogging of the RO membrane of the RO membrane processing unit 26. This allows the CPU 91 of the control unit 90 to predict in advance the timing of clogging of the UF membrane of the UF membrane filtration unit 20 and calculate the timing of cleaning the UF membrane. In addition, the CPU 91 of the control unit 90 predicts in advance the timing of clogging of the RO membrane of the RO membrane processing unit 26 and calculates the timing of cleaning the RO membrane.

[0073] The notification unit 84 notifies the user of information relating to the timing of cleaning the UF membrane via the user terminal 80. The notification unit 84 also notifies the user of information relating to the timing of cleaning the RO membrane via the user terminal 80. The notification unit 84 may output an audio warning sound from a speaker (not shown) of the user terminal 80 as information relating to the cleaning timing, or may display information relating to the cleaning timing as warning information such as text on the display unit 82, or may both output a warning sound and display warning information.

[0074] The CPU 91 outputs information regarding the timing of cleaning the UF membrane before the UF membrane of the UF membrane filtration section 20 becomes clogged to the alarm section 84 based on the pressure on the inlet side of the UF membrane filtration section 20 measured by the pressure measurement section 47B and the pressure on the outlet side of the UF membrane filtration section 20 measured by the pressure measurement section 48B.

[0075] As an example, when the pressure on the inlet side of the UF membrane filtration unit 20 is greater than a first threshold value and the pressure difference 102 between the pressure on the inlet side and the pressure on the outlet side is greater than a second threshold value, the CPU 91 determines that it is time to clean the UF membrane of the UF membrane filtration unit 20. In this case, the CPU 91 outputs information on the timing of cleaning the UF membrane to the notification unit 84, and the notification unit 84 notifies the user of the information on the timing of cleaning the UF membrane via the user terminal 80. Examples of methods for cleaning the UF membrane include backwashing, air backwashing, and cleaning with hypochlorous acid. Here, backwashing is a method in which treated water is made to flow in the opposite direction to the water flow to remove accumulated dirt. Air backwashing is a method in which air is introduced into the above-mentioned backwash to make it easier to float sediments.

[0076] The CPU 91 outputs to the alarm unit 84 information regarding the timing of cleaning the RO membrane before the RO membrane of the RO membrane treatment unit 26 becomes blocked, based on the pressure on the inlet side of the RO membrane treatment unit 26 measured by the pressure measurement unit 47D and the pressure on the outlet side of the RO membrane treatment unit 26 measured by the pressure measurement unit 48D.

[0077] As an example, when the pressure on the inlet side of the RO membrane processing unit 26 is greater than a third threshold value and the pressure difference 104 between the pressure on the inlet side and the pressure on the outlet side is greater than a fourth threshold value, the CPU 91 determines that it is time to clean the RO membrane of the RO membrane processing unit 26. Similarly, when the permeation flux of the RO membrane processing unit 26 is smaller than the threshold value, the CPU 91 determines that it is time to clean the RO membrane of the RO membrane processing unit 26. In the above case, the CPU 91 outputs information regarding the timing of cleaning the RO membrane to the notification unit 84, and the notification unit 84 notifies the user of the information regarding the timing of cleaning the RO membrane via the user terminal 80. That is, in the water treatment recovery system 10 of the first embodiment, the RO membrane is monitored by double-checking the permeation flux and the pressure difference of the RO membrane in the RO membrane processing unit 26.

[0078] <Action and Effects> Next, the operation and effects of the first embodiment will be described.

[0079] The water treatment recovery system 10 comprises, from upstream to downstream in the raw water transport direction (direction of arrow A), a raw water tank 12, a sand filtration tower 14, an acid addition section 15, a fluorine adsorption tower 16, a caustic addition section 17, a filtered water tank 18, a UF membrane filtration section 20, a pretreated water tank 22, an activated carbon tower 24, and an RO membrane treatment section 26.

[0080] In the acid addition section 15, an acid 61 is added to the raw water to adjust the pH of the raw water to be acidic. In the fluorine adsorption tower 16, while the pH of the raw water is adjusted to be acidic, the fluorine contained in the raw water is adsorbed by a fluorine adsorbent to reduce the fluorine concentration of the raw water (fluorine adsorption step). For example, when the fluorine concentration of the raw water before being sent to the fluorine adsorption tower 16 is 4 mg / L or more and 5 mg / L or less, the fluorine contained in the raw water is adsorbed in the fluorine adsorption tower 16, so that the fluorine concentration of the raw water becomes 0.2 mg / L or less.

[0081] In the caustic addition section 17, caustic 62 is added to the raw water whose fluorine concentration has been reduced in the fluorine adsorption tower 16, thereby precipitating calcium hydroxide (precipitating step).

[0082] In the UF membrane filtration section 20, calcium hydroxide precipitated by adding caustic 62 to the raw water is removed by a UF membrane (ultrafiltration membrane) (UF membrane filtration process).

[0083] In the RO membrane processing section 26, the raw water after filtration in the UF membrane filtration section 20 is treated with an RO membrane (reverse osmosis membrane) to remove at least ions from the raw water (RO membrane treatment process). Because the RO membrane does not allow impurities other than water molecules, such as ions and salts, to pass through, it is possible to remove ions such as calcium ions by extracting the permeated water that has passed through the RO membrane.

[0084] Furthermore, in the water treatment and recovery system 10, the fluorine adsorption tower 16 adsorbs fluorine contained in the raw water to reduce the fluorine concentration of the raw water. As a result, after the fluorine concentration of the raw water is reduced, the raw water is sent to the RO membrane treatment unit 26. This prevents raw water with a fluorine concentration of 2 mg / L or more from being sent to the RO membrane treatment unit 26. For example, when the fluorine concentration is 2 mg / L or more, fluorine and unreacted calcium hydroxide react with each other during concentration in the RO membrane treatment to generate calcium fluoride, which may clog the RO membrane. In contrast, in the water treatment and recovery system 10, the generation of calcium fluoride due to the reaction between fluorine and unreacted calcium hydroxide is suppressed, and clogging of the RO membrane is suppressed.

[0085] Therefore, in the water treatment and recovery system 10, it is possible to efficiently treat raw water containing fluorine and to prevent clogging of the RO membrane (reverse osmosis membrane).

[0086] In the water treatment and recovery system 10, the fluorine adsorption tower 16 is provided with a fluorine adsorbent containing cerium. In the caustic addition unit 17, caustic 62 is added to precipitate cerium that has dissolved from the fluorine adsorbent containing cerium into the raw water as cerium hydroxide. The precipitated cerium hydroxide is then removed in the UF membrane filtration unit 20.

[0087] Therefore, in the water treatment and recovery system 10, when a fluorine adsorbent containing cerium is used in the fluorine adsorption tower 16, the raw water into which cerium has eluted is prevented from being sent to the RO membrane treatment unit 26. This makes it possible to more effectively prevent clogging of the RO membrane (reverse osmosis membrane).

[0088] Furthermore, in the water treatment and recovery system 10, a filtered water tank 18 is disposed between the fluorine adsorption tower 16 and the UF membrane filtration section 20 in the raw water transport direction (the direction of arrow A). In the filtered water tank 18, a bactericide 63 is added to the raw water to sterilize the raw water.

[0089] Therefore, in the water treatment and recovery system 10, the bactericide 63 added to the raw water can sterilize microorganisms and the like contained in the raw water.

[0090] In the water treatment and recovery system 10, the disinfectant 63 is hypochlorous acid. An activated carbon tower 24 is disposed between the UF membrane filtration unit 20 and the RO membrane treatment unit 26 in the raw water transport direction (direction of arrow A), and in the activated carbon tower 24, residual chlorine contained in the raw water is adsorbed by the activated carbon and removed.

[0091] As a result, in the water treatment and recovery system 10, when hypochlorous acid is used as the bactericide 63, the activated carbon tower 24 can remove residual chlorine contained in the raw water. For example, when raw water containing hypochlorous acid is sent to the RO membrane treatment unit 26, the hypochlorous acid may break through the RO membrane. Therefore, in the water treatment and recovery system 10, the activated carbon tower 24 removes residual chlorine contained in the raw water, thereby preventing raw water containing hypochlorous acid from being sent to the RO membrane treatment unit 26.

[0092] Furthermore, in the water treatment and recovery system 10, a sand filtration tower 14 is disposed before the treatment of raw water in the fluorine adsorption tower 16. In the sand filtration tower 14, the raw water to which a coagulant 60 has been added is filtered to remove fine particles contained in the raw water.

[0093] Therefore, in the water treatment and recovery system 10, before the raw water is treated in the fluorine adsorption tower 16, fine particles contained in the raw water can be removed.

[0094] The water treatment recovery system 10 also includes at least one CPU 91, a pressure measuring unit 47B that measures the pressure on the inlet side of the UF membrane filtration unit 20, and a pressure measuring unit 48B that measures the pressure on the outlet side of the UF membrane filtration unit. The CPU 91 outputs information regarding the timing of cleaning the UF membrane before the UF membrane of the UF membrane filtration unit 20 becomes clogged, based on the inlet side pressure measured by the pressure measuring unit 47B and the outlet side pressure measured by the pressure measuring unit 48B.

[0095] This allows the water treatment and recovery system 10 to check information regarding the timing of cleaning the UF membrane before the UF membrane of the UF membrane filtration unit 20 becomes clogged. Therefore, the water treatment and recovery system 10 can stably treat and recover raw water containing fluorine while avoiding clogging of the UF membrane of the UF membrane filtration unit 20.

[0096] The water treatment recovery system 10 also includes at least one CPU 91, a pressure measurement unit 47D that measures the pressure on the inlet side of the RO membrane treatment unit 26, and a pressure measurement unit 48D that measures the pressure on the outlet side of the RO membrane treatment unit 26. The CPU 91 outputs information regarding the timing of cleaning the RO membrane before the RO membrane of the RO membrane treatment unit 26 becomes clogged, based on the inlet side pressure measured by the pressure measurement unit 47D and the outlet side pressure measured by the pressure measurement unit 48D. The CPU 91 also outputs information regarding the timing of cleaning the RO membrane before the RO membrane of the RO membrane treatment unit 26 becomes clogged, according to the permeation flux of the RO membrane treatment unit 26.

[0097] This allows the water treatment and recovery system 10 to check information regarding the timing of cleaning the RO membrane before the RO membrane of the RO membrane treatment unit 26 becomes clogged. Therefore, the water treatment and recovery system 10 can stably treat and recover raw water containing fluorine while avoiding clogging of the RO membrane of the RO membrane treatment unit 26.

[0098] The water treatment and recovery method also includes a fluorine adsorption step of adsorbing fluorine contained in raw water to reduce the fluorine concentration in the fluorine-containing raw water in a state in which the pH of the raw water is adjusted to be acidic. The water treatment and recovery method also includes a precipitation step of precipitating calcium hydroxide by adding caustic 62 to the raw water whose fluorine concentration has been reduced in the fluorine adsorption step, and a UF membrane filtration step of removing the calcium hydroxide precipitated by adding caustic 62 to the raw water with a UF membrane. The water treatment and recovery method also includes a reverse osmosis membrane treatment step of treating the raw water after filtration in the UF membrane filtration step with an RO membrane to remove at least ions in the raw water.

[0099] Therefore, the water treatment and recovery method can efficiently treat raw water containing fluorine and suppress clogging of the RO membrane.

[0100] For example, the general method of treating fluorine-containing wastewater discharged from factories is to add calcium hydroxide as a primary treatment to neutralize it, turn it into calcium fluoride, and separate it by settling, then perform secondary treatment using coagulation sedimentation or an adsorption tower to reduce the fluorine concentration to below the regulated concentration before discharging it. However, because calcium hydroxide reacts slowly with fluoride ions, a large amount of calcium hydroxide must be added to carry out the primary treatment, which poses the problem of a very high content of unreacted calcium hydroxide.

[0101] Another method of treating fluoride-containing wastewater is to use an RO membrane, but it is difficult to reduce the fluoride concentration by simply treating fluoride-containing wastewater with an RO membrane. In particular, when the fluoride concentration is 2 mg / L or more, the fluoride reacts with unreacted calcium hydroxide during concentration in the RO membrane process, producing calcium fluoride, which blocks the RO membrane. Generally, when an RO membrane becomes clogged, it is cleaned with chemicals in order to restore the membrane's permeability, but calcium fluoride has high chemical resistance and is difficult to clean.

[0102] In contrast, the water treatment and recovery system 10 and the water treatment and recovery method suppress the generation of calcium fluoride during concentration in the RO membrane treatment, making it possible to suppress clogging of the RO membrane.

[0103] [Example] Next, an embodiment of the water treatment and recovery system 10 will be described. In the embodiment, the water treatment and recovery system 10 was used to continuously treat raw water containing fluorine and recover the treated water as permeate that had permeated the RO membrane of the RO membrane treatment unit 26. During this process, each treatment unit of the water treatment and recovery system 10 was monitored online by the user terminal 80.

[0104] 3 is a graph showing the relationship between the operation time of the water treatment and recovery system 10 and the permeation flux of the RO membrane of the RO membrane processor 26. As described above, the permeation flux is a value calculated taking into consideration the electrical conductivity (EC), temperature, flow rate, pressure, membrane area, etc. As shown in FIG. 3, it was confirmed that the permeation flux of the RO membrane was stable, as shown by line 120.

[0105] [First Comparative Example] Here, a water treatment and recovery system 200 of a first comparative example shown in FIG. 4 will be described.

[0106] As shown in FIG. 4, the water treatment recovery system 200 of the first comparative example includes, in order from the upstream side to the downstream side in the flow direction (direction of arrow B) of wastewater, which is an example of the water to be treated, a sand filtration tower 14, a UF membrane filtration section 204, an activated carbon tower 206, a fluorine adsorption tower 208, and an RO membrane treatment section 210.

[0107] In the sand filter tower 14, the wastewater to which the flocculant 60 has been added is subjected to sand filtration, thereby removing fine particles contained in the wastewater.

[0108] Next, hypochlorous acid 221 is added to the wastewater, and the wastewater is then sent to the UF membrane filtration section 204. The addition of hypochlorous acid 221 to the wastewater sterilizes the wastewater. In the UF membrane filtration section 204, calcium fluoride and other substances contained in the wastewater are removed by the UF membrane. The wastewater is neutralized in advance as a primary treatment by adding calcium hydroxide, at which time calcium fluoride precipitates. This calcium fluoride and other substances are removed by the UF membrane.

[0109] Next, the wastewater is sent to an activated carbon tower 206, where the residual chlorine is adsorbed by the activated carbon in the activated carbon tower 206 and removed.

[0110] Next, hydrochloric acid 222 is added to the wastewater, and the wastewater is then sent to the fluorine adsorption tower 208. By adding hydrochloric acid 222 to the wastewater, the pH of the wastewater is adjusted to an acidic range (for example, about pH 3). In the fluorine adsorption tower 208, fluorine contained in the wastewater is adsorbed by a fluorine adsorbent, thereby reducing the fluorine concentration of the wastewater.

[0111] Next, caustic 223 is added to the wastewater, and further, a scale dispersant 224 and combined chlorine 225 are added to the wastewater, and the wastewater is then sent to the RO membrane treatment unit 210.

[0112] Caustic 223 is added to the wastewater to adjust the pH of the wastewater to about 7. Combined chlorine 225 is added to the wastewater to prevent hypochlorous acid 221 and the like from entering the RO membrane treatment unit 210. A scale dispersant 224 is added to the wastewater to reduce adhesion of scale to the RO membrane. In the RO membrane treatment unit 210, ions contained in the wastewater are removed by the RO membrane.

[0113] An experiment was conducted using the water treatment and recovery system 200 of the first comparative example to continuously treat wastewater containing fluorine and recover the permeate that permeated the RO membrane of the RO membrane treatment unit 210. During the experiment, each treatment unit of the water treatment and recovery system 200 was monitored online by a user terminal (not shown).

[0114] 5 is a graph showing the relationship between the operation time of the water treatment and recovery system 200 of the first comparative example and the permeation flux of the RO membrane of the RO membrane treatment unit 210. As shown in FIG 5, in the water treatment and recovery system 200 of the first comparative example, scale adhered to the RO membrane of the RO membrane treatment unit 210, and a decrease in the permeation flux was confirmed as shown by line 230.

[0115] This is because the caustic 223 is added to the wastewater between the fluorine adsorption tower 208 and the RO membrane treatment unit 210, and calcium hydroxide (Ca(OH) 2 ) precipitated, which is thought to have led to clogging of the RO membrane. For this reason, it is possible to consider stopping the addition of caustic 223 and treating the wastewater while it is still in the acidic range.

[0116] [Second Comparative Example] Next, a water treatment and recovery system 250 of a second comparative example shown in FIG. 6 will be described.

[0117] 6, the water treatment recovery system 250 of the second comparative example, like the water treatment recovery system 200 of the first comparative example, is equipped with, in this order from the upstream side to the downstream side in the wastewater transport direction (the direction of arrow B), a sand filtration tower 14, a UF membrane filtration section 204, an activated carbon tower 206, a fluorine adsorption tower 208, and an RO membrane treatment section 210. The water treatment recovery system 250 of the second comparative example is different from the water treatment recovery system 200 of the first comparative example in that caustic 223 (see FIG. 4) is not added to the wastewater between the fluorine adsorption tower 208 and the RO membrane treatment section 210, and the wastewater is transported to the RO membrane treatment section 210 while remaining in the acidic range (for example, about pH 3).

[0118] An experiment was conducted using the water treatment and recovery system 250 of the second comparative example to continuously treat wastewater containing fluorine and recover the permeate that permeated the RO membrane of the RO membrane treatment unit 210. During the experiment, each treatment unit of the water treatment and recovery system 250 was monitored online by a user terminal (not shown).

[0119] Fig. 7 is a graph showing the relationship between the operation time of the water treatment and recovery system 250 of the second comparative example and the permeation flux of the RO membrane of the RO membrane processor 210. As shown in Fig. 7, in the water treatment and recovery system 250 of the second comparative example, scale adhered to the RO membrane of the RO membrane processor 210, and a decrease in the permeation flux was confirmed as shown by line 270. The decrease in the permeation flux was more gradual than the decrease in the permeation flux of the water treatment and recovery system 200 of the first comparative example.

[0120] In the water treatment and recovery system 250 of the second comparative example, it was found that cerium was dissolved into the wastewater under acidic conditions (e.g., about pH 3) by using a fluorine adsorbent containing cerium in the fluorine adsorption tower 208. This cerium was converted into cerium hydroxide (Ce(OH) 2 ) which is thought to have led to clogging of the RO membrane in the RO membrane treatment section 210.

[0121] 8 is a graph showing the relationship between the operation time and the RO membrane permeation flux of the RO membrane processor 210 in an example of a water treatment and recovery system in which the RO membrane was replaced with a new one. As shown in FIG. 8, the decrease in the RO membrane permeation flux is gradual, as indicated by line 280.

[0122] In the water treatment and recovery system 10 of the first embodiment, as a countermeasure to the problem of the water treatment and recovery system 250 of the second comparative example, the UF membrane filtration section 20 is disposed upstream of the RO membrane treatment section 26 in the raw water sending direction (arrow A direction). As a result, when a fluorine adsorbent containing cerium is used in the fluorine adsorption tower 16, the cerium dissolved in the raw water is converted to cerium hydroxide (Ce(OH) 2 ), and the cerium hydroxide is removed by the UF membrane of the UF membrane filtration unit 20. Therefore, in the water treatment and recovery system 10, clogging of the RO membrane (reverse osmosis membrane) can be suppressed.

[0123] Second Embodiment Next, a water treatment and recovery system according to a second embodiment will be described. Note that the same components as those in the first embodiment described above are given the same reference numerals and the description thereof will be omitted.

[0124] Fig. 9 is a block diagram showing a hardware configuration of a monitoring system used in the water treatment and recovery system according to the second embodiment. As shown in Fig. 9, the water treatment and recovery system 130 according to the second embodiment has a monitoring system 131 that monitors the treatment status of the treatment device 11 online. The monitoring system 131 includes a control panel 132 that controls each part of the treatment device 11, a data center 140 as an example of a relay unit to which information related to the treatment device 11 is transmitted from the control panel 132, and a monitoring terminal 150 to which information related to the treatment device 11 is transmitted from the data center 140. The monitoring terminal 150 is an example of a terminal device. The configuration of each part of the treatment device 11 is similar to that of the treatment device 11 according to the first embodiment.

[0125] The control panel 132 includes a PLC (Programmable Logic Controller) 133 and a communication interface 134. The PLC 132 is a control device for controlling each part of the processing device 11. Although not shown, the PLC 132 includes an input unit, an output unit, a calculation unit (CPU), a storage unit, a power supply unit, etc. The PLC 132 is an example of a processor.

[0126] The communication interface 134 is an interface for communicating with the data center 140. The control panel 132 transmits information about the processing device 11 (e.g., data such as various measurement values) to the data center 140 via the communication interface 134 by wireless communication. As an example, the communication interface 134 transmits information about the UF membrane filtration unit 20 (see FIG. 1) (e.g., data such as various measurement values ​​of the UF membrane filtration unit 20) and information about the RO membrane processing unit 26 (see FIG. 1) (e.g., data such as various measurement values ​​of the RO membrane processing unit 26) to the data center 140.

[0127] Although not shown, the data center 140 includes a CPU, a storage unit, and a communication unit. The data center 140 receives information about the processing device 11 from the control panel 132 via wireless communication, and transmits information about the processing device 11 to the monitoring terminal 150 via wireless communication. The dashed lines connecting the various parts in Fig. 9 indicate wireless, and the solid lines connecting the various parts in Fig. 9 indicate wired. The data center 140 may transmit and receive data using a cloud that provides services to users via a network such as the Internet.

[0128] The monitoring terminal 150 monitors the processing status of the processing device 11 online based on the information about the processing device 11 received from the data center 140. The monitoring terminal 150 is, for example, a PC or a tablet. As an example, the monitoring terminal 150 has a display unit (not shown) on which the processing status of the processing device 11 is displayed. For example, the monitoring terminal 150 monitors the processing status of the processing device 11 in a location isolated from the processing device 11 and the control panel 132 (for example, a room or building different from the location where the processing device 11 is installed). Other configurations of the water treatment recovery system 130 of the second embodiment are similar to those of the water treatment recovery system 10 of the first embodiment.

[0129] In the water treatment recovery system 130, the monitoring terminal 150 monitors the state of the UF membrane filtration unit 20 based on information related to the UF membrane filtration unit 20 (see FIG. 1). This allows the monitoring terminal 150 to obtain information related to the timing of cleaning the UF membrane before the UF membrane of the UF membrane filtration unit 20 becomes clogged, based on the inlet pressure measured by the pressure measurement unit 47B (see FIG. 1) and the outlet pressure measured by the pressure measurement unit 48B (see FIG. 1). Therefore, in the water treatment recovery system 130, the monitoring terminal 150 can monitor the state of the UF membrane filtration unit 20 online at a location separated from the treatment device 11, and know the timing of cleaning the UF membrane of the UF membrane filtration unit 20.

[0130] In addition, in the water treatment recovery system 130, the monitoring terminal 150 monitors the state of the RO membrane processing unit 26 based on information related to the RO membrane processing unit 26 (see FIG. 1). As a result, the monitoring terminal 150 can obtain information related to the timing of cleaning the RO membrane before the RO membrane of the RO membrane processing unit 26 becomes clogged, based on the inlet side pressure measured by the pressure measurement unit 47D (see FIG. 1) and the outlet side pressure measured by the pressure measurement unit 48D (see FIG. 1). In addition, the monitoring terminal 150 can obtain information related to the timing of cleaning the RO membrane before the RO membrane of the RO membrane processing unit 26 becomes clogged, according to the permeation flux of the RO membrane processing unit 26. Therefore, in the water treatment recovery system 130, the monitoring terminal 150 can monitor the state of the RO membrane processing unit 26 online at a location separated from the treatment device 11, and know the timing of cleaning the RO membrane of the RO membrane processing unit 26.

[0131] In the second embodiment, the control board 132 transmits information about the processing device 11 to the monitoring terminal 150 via the data center 140 by wireless communication, but the present disclosure is not limited to this configuration. For example, the control board of the processing device 11 may be configured to directly transmit information about the processing device 11 to the monitoring terminal by wireless communication.

[0132] 〔supplementary explanation〕 In the water treatment and recovery systems 10 and 130 of the first and second embodiments, the type of acid 61 and the level of the acidic range in which the raw water is acidified by adding the acid 61 can be changed. Also, the caustic 62 can be changed to another substance as long as it is alkaline. Also, the types of the sterilizing agent 64 and dispersing agent 65 can be changed.

[0133] In the water treatment recovery systems 10 and 130 of the first and second embodiments, the CPU 91 outputs information regarding the timing of cleaning the RO membrane before the RO membrane of the RO membrane processor 26 becomes clogged, based on the inlet pressure measured by the pressure measuring unit 47D and the outlet pressure measured by the pressure measuring unit 48D, or based on the permeation flux of the RO membrane processor 26, but the present disclosure is not limited to this configuration. For example, the CPU 91 may calculate the timing of cleaning the RO membrane according to other measurement items (e.g., temperature, electrical conductivity, etc.).

[0134] Furthermore, the CPU 91 outputs information regarding the timing of cleaning the UF membrane before the UF membrane of the UF membrane filtration unit 20 becomes clogged based on the inlet pressure measured by the pressure measurement unit 47B and the outlet pressure measured by the pressure measurement unit 48B, but the present disclosure is not limited to this configuration. For example, the CPU 91 may calculate the timing of cleaning the UF membrane according to other measurement items (e.g., temperature, electrical conductivity, etc.) in addition to the inlet pressure measured by the pressure measurement unit 47B and the outlet pressure measured by the pressure measurement unit 48B.

[0135] The water treatment and recovery systems 10 and 130 of the first and second embodiments described above can also be realized by a dedicated hardware circuit. In this case, the water treatment and recovery systems may be implemented by a single piece of hardware or multiple pieces of hardware.

[0136] Furthermore, the programs for operating the water treatment and recovery systems 10, 130 of the first and second embodiments may be provided by a computer-readable recording medium such as a Universal Serial Bus (USB) memory, a flexible disk, or a Compact Disc Read Only Memory (CD-ROM), or may be provided online via a network such as the Internet. In this case, the programs recorded on the computer-readable recording medium are usually transferred to and stored in a memory or storage. Furthermore, the programs may be provided, for example, as standalone application software, or may be incorporated into the software of each device of the water treatment and recovery system as one function of the system.

[0137] Although the embodiments of the present disclosure have been described above, these embodiments are merely examples and can be modified in various ways without departing from the spirit of the present disclosure. Furthermore, it goes without saying that the scope of the rights of the present disclosure is not limited to these embodiments and can be embodied in various forms without departing from the spirit of the present disclosure.

[0138] [Preferred embodiment of the present disclosure] Preferred aspects of the present disclosure will be described below.

[0139] [Additional note 1] A water treatment and recovery system for treating and recovering fluorine-containing water to be treated, comprising: a fluorine adsorption section that adsorbs fluorine contained in the water to be treated to reduce the fluorine concentration in the water to be treated, while the pH of the water to be treated is adjusted to be acidic; an alkali adding section that adds an alkali to the water to be treated whose fluorine concentration has been reduced by the fluorine adsorption section, thereby precipitating calcium hydroxide; a UF membrane filtration section that removes calcium hydroxide precipitated by adding the alkali to the water to be treated using a UF membrane that is an ultrafiltration membrane; a reverse osmosis membrane treatment unit that treats the water to be treated after filtering in the UF membrane filtration unit with a reverse osmosis membrane to remove at least ions from the water to be treated; A water treatment and recovery system having:

[0140] [Additional note 2] the fluorine adsorption portion includes a fluorine adsorbent containing a lanthanoid; In the alkali adding section, the alkali is added to precipitate lanthanoids eluted from the fluorine adsorbent into the water to be treated as hydroxides, The water treatment and recovery system according to claim 1, wherein the hydroxide is removed by the UF membrane filtration section.

[0141] [Additional note 3] 3. The water treatment and recovery system according to claim 1 or 2, further comprising a disinfection treatment unit disposed between the fluorine adsorption unit and the UF membrane filtration unit, which adds a disinfectant to the water to be treated and disinfects the water to be treated.

[0142] [Additional note 4] The disinfectant is hypochlorous acid, 4. The water treatment and recovery system according to claim 3, further comprising an activated carbon adsorption section disposed between the UF membrane filtration section and the reverse osmosis membrane treatment section, which adsorbs residual chlorine contained in the water to be treated onto activated carbon and removes it.

[0143] [Additional note 5] 5. The water treatment and recovery system according to claim 1, further comprising a sand filtration section that is disposed before the treatment of the water to be treated by the fluorine adsorption section and removes fine particles contained in the water to be treated by filtering the water to which a coagulant has been added.

[0144] [Additional note 6] At least one processor; A first pressure measuring unit that measures the pressure on the inlet side of the UF membrane filtration unit; A second pressure measuring unit that measures the pressure on the outlet side of the UF membrane filtration unit, The water treatment recovery system according to any one of appendix 1 to appendix 5, wherein the processor outputs information regarding the timing of cleaning the UF membrane before the UF membrane of the UF membrane filtration unit becomes clogged, based on the inlet side pressure measured by the first pressure measuring unit and the outlet side pressure measured by the second pressure measuring unit.

[0145] [Additional note 7] At least one processor; a third pressure measuring unit that measures the pressure on the inlet side of the reverse osmosis membrane processing unit; a fourth pressure measuring unit that measures the pressure on the outlet side of the reverse osmosis membrane processing unit, The water treatment recovery system according to any one of appendix 1 to appendix 6, wherein the processor outputs information regarding the timing of cleaning the reverse osmosis membrane before the reverse osmosis membrane of the reverse osmosis membrane processing unit becomes clogged, based on the inlet pressure measured by the third pressure measuring unit and the outlet pressure measured by the fourth pressure measuring unit.

[0146] [Additional note 8] at least one processor; The water treatment and recovery system according to any one of claims 1 to 7, wherein the processor calculates a permeation flux of the reverse osmosis membrane processing unit and outputs information regarding the timing of cleaning the reverse osmosis membrane before the reverse osmosis membrane of the reverse osmosis membrane processing unit becomes clogged, based on the permeation flux.

[0147] [Additional note 9] At least one processor; and a terminal device that monitors at least the state of the UF membrane filtration unit at a location separated from the UF membrane filtration unit, The processor transmits information about the UF membrane filtration unit to the terminal device directly or via a relay unit, 9. The water treatment and recovery system according to any one of claims 1 to 8, wherein the terminal device monitors a state of the UF membrane filtration unit based on information about the UF membrane filtration unit.

[0148] [Additional Note 10] At least one processor; and a terminal device that monitors at least the state of the reverse osmosis membrane processing section at a location separated from the reverse osmosis membrane processing section, The processor transmits information about the reverse osmosis membrane processing unit to the terminal device directly or via a relay unit, 10. The water treatment and recovery system according to any one of claims 1 to 9, wherein the terminal device monitors a state of the reverse osmosis membrane processing unit based on information related to the reverse osmosis membrane processing unit.

[0149] [Additional Note 11] A water treatment and recovery method for treating and recovering fluorine-containing water to be treated, comprising the steps of: a fluorine adsorption step of adsorbing fluorine contained in the fluorine-containing water to be treated in a state in which the pH of the fluorine-containing water to be treated is adjusted to an acidic state, thereby reducing the fluorine concentration in the water to be treated; a precipitating step of precipitating calcium hydroxide by adding an alkali to the water to be treated whose fluorine concentration has been reduced in the fluorine adsorption step; a UF membrane filtration step of removing calcium hydroxide precipitated by adding the alkali to the water to be treated using a UF membrane which is an ultrafiltration membrane; a reverse osmosis membrane treatment step in which the treated water after the filtration in the UF membrane filtration step is treated with a reverse osmosis membrane to remove at least ions from the treated water; The water treatment and recovery method according to claim 1, [Explanation of symbols]

[0150] 10...water treatment recovery system, 14...sand filtration tower, 16...fluorine adsorption tower (fluorine adsorption section), 17...caustic addition section (alkali addition section), 18...filtered water tank (sterilization processing section), 20...UF membrane filtration section, 24...activated carbon tower (activated carbon adsorption section), 26...RO membrane processing section (reverse osmosis membrane processing section), 47B...pressure measurement section (first pressure measurement section), 47D...pressure measurement section (third pressure measurement section), 48B...pressure measurement section (second pressure measurement section), 48D...pressure measurement section (fourth pressure measurement section), 60...coagulant, 62...caustic (alkali), 63...sterilizing agent, 91...CPU (processor), 130...water treatment recovery system, 132...PLC (processor), 140...data center (relay section), 150...monitoring terminal (terminal device)

Claims

1. A water treatment and recovery system for treating and recovering fluorine-containing water to be treated, comprising: a fluorine adsorption section that adsorbs fluorine contained in the water to be treated in a state in which the pH of the water to be treated containing fluorine is adjusted to be acidic, thereby reducing the fluorine concentration; an alkali adding section that adds an alkali to the water to be treated whose fluorine concentration has been reduced by the fluorine adsorption section, thereby precipitating calcium hydroxide; a UF membrane filtration section that removes calcium hydroxide precipitated by adding the alkali to the water to be treated using a UF membrane that is an ultrafiltration membrane; a reverse osmosis membrane treatment unit that treats the water to be treated after filtering in the UF membrane filtration unit with a reverse osmosis membrane to remove at least ions from the water to be treated; A water treatment and recovery system having:

2. the fluorine adsorption portion includes a fluorine adsorbent containing a lanthanoid; In the alkali adding section, the alkali is added to precipitate lanthanoids eluted from the fluorine adsorbent into the water to be treated as hydroxides, The water treatment and recovery system according to claim 1 , wherein the hydroxide is removed in the UF membrane filtration section.

3. 2. The water treatment and recovery system according to claim 1, further comprising a disinfection treatment section disposed between the fluorine adsorption section and the UF membrane filtration section, which adds a disinfectant to the water to be treated and disinfects the water to be treated.

4. The disinfectant is hypochlorous acid, 4. The water treatment and recovery system according to claim 3, further comprising an activated carbon adsorption section disposed between the UF membrane filtration section and the reverse osmosis membrane treatment section, which adsorbs residual chlorine contained in the water to activated carbon and removes it.

5. 2. The water treatment and recovery system according to claim 1, further comprising a sand filtration section that is disposed before the treatment of the water to be treated by the fluorine adsorption section and removes fine particles contained in the water to be treated by filtering the water to which a coagulant has been added.

6. At least one processor; A first pressure measuring unit that measures the pressure on the inlet side of the UF membrane filtration unit; A second pressure measuring unit that measures the pressure on the outlet side of the UF membrane filtration unit, 2. The water treatment recovery system according to claim 1, wherein the processor outputs information regarding the timing of cleaning the UF membrane before the UF membrane of the UF membrane filtration unit becomes clogged, based on the inlet side pressure measured by the first pressure measuring unit and the outlet side pressure measured by the second pressure measuring unit.

7. At least one processor; a third pressure measuring unit that measures the pressure on the inlet side of the reverse osmosis membrane processing unit; a fourth pressure measuring unit that measures the pressure on the outlet side of the reverse osmosis membrane processing unit, The water treatment and recovery system of claim 1, wherein the processor outputs information regarding the timing of cleaning the reverse osmosis membrane before the reverse osmosis membrane of the reverse osmosis membrane processing unit becomes clogged, based on the inlet side pressure measured by the third pressure measuring unit and the outlet side pressure measured by the fourth pressure measuring unit.

8. At least one processor; The water treatment and recovery system according to claim 1, wherein the processor calculates a permeation flux of the reverse osmosis membrane processing section and outputs information regarding the timing of cleaning the reverse osmosis membrane before the reverse osmosis membrane of the reverse osmosis membrane processing section becomes clogged, in accordance with the permeation flux.

9. At least one processor; a terminal device that monitors at least the state of the UF membrane filtration unit at a location isolated from the UF membrane filtration unit, The processor transmits information about the UF membrane filtration unit to the terminal device directly or via a relay unit, The water treatment and recovery system according to claim 1 , wherein the terminal device monitors a state of the UF membrane filtration unit based on information about the UF membrane filtration unit.

10. At least one processor; and a terminal device that monitors at least the state of the reverse osmosis membrane processing section at a location separated from the reverse osmosis membrane processing section, The processor transmits information about the reverse osmosis membrane processing unit to the terminal device directly or via a relay unit, The water treatment and recovery system according to claim 1 , wherein the terminal device monitors a state of the reverse osmosis membrane processing unit based on information about the reverse osmosis membrane processing unit.

11. A water treatment and recovery method for treating and recovering fluorine-containing water to be treated, comprising the steps of: a fluorine adsorption step of adsorbing fluorine contained in the fluorine-containing water to be treated in a state in which the pH of the fluorine-containing water to be treated is adjusted to an acidic state, thereby reducing the fluorine concentration in the water to be treated; a precipitating step of precipitating calcium hydroxide by adding an alkali to the water to be treated whose fluorine concentration has been reduced in the fluorine adsorption step; a UF membrane filtration step of removing calcium hydroxide precipitated by adding the alkali to the water to be treated using a UF membrane which is an ultrafiltration membrane; a reverse osmosis membrane treatment step of treating the treated water after the filtration in the UF membrane filtration step with a reverse osmosis membrane to remove at least ions from the treated water; The water treatment and recovery method according to claim 1,

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