JP2012183483A - Water treatment method and water treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method of maintaining a high salt removal rate and a water permeate flow even in the case of hard water whose water quality is poor.SOLUTION: This water treatment method has a deionization step to be executed by reverse osmosis membrane separation, and includes: the softening process of raw water; a first reproduction process of reproducing a whole cation exchange resin floor; and a second reproduction process of reproducing a portion of the cation exchange resin floor. In the second reproduction process, a reproduction liquid amount whose reproduction level is 1 to 6eq/L-R is supplied to a hardness leak prevention floor, and in the softening process, raw water whose electric conductivity is equal to or less than 150 mS/m, and whose total hardness is equal to or less than 500 mgCaCO/L is supplied to this floor. Furthermore, an RO film module 5b includes a reverse osmosis membrane formed with a skin layer negatively charging of crosslinked wholly aromatic polyamide on a film surface, and has the reverse osmosis membrane which being configured such that when aqueous sodium chloride solution whose concentration is 500 mg/L of pH 7.0, and temperature of 25°C with an operating pressure of 0.7 MPa and recovery rate of 15% is supplied, a water permeation coefficient is equal to or more than 1.5×10mmsPa, and a salt removal rate is equal to or more than 99%.

Description

  The present invention relates to a water treatment method and a water treatment system using a reverse osmosis membrane separation device.

  Conventionally, high-purity pure water that does not contain impurities is used in semiconductor manufacturing processes, cleaning of electronic components, cleaning of medical instruments, and the like. This type of pure water is generally produced by treating raw water such as ground water or tap water with a reverse osmosis membrane (hereinafter also referred to as “RO membrane”).

  In a pure water production system using an RO membrane, a so-called fouling phenomenon occurs in which iron contained in the raw water (typically insoluble colloidal iron) is deposited on the membrane surface of the RO membrane. Thus, the salt removal rate and the amount of permeated water are reduced. For this reason, it is common to perform pre-processing with an iron removal device.

  The iron removal device is a facility that injects an oxidizing agent into raw water to insolubilize and remove iron. However, if the oxidant remains in the supply water to the RO membrane, the membrane itself deteriorates. Therefore, it is necessary to further provide an activated carbon filtration device after the iron removal device. Therefore, in the conventional pure water production system, the pretreatment for removing the oxidant remaining in the raw water is complicated, and it is inevitable that the cost of water production increases.

Therefore, the present applicant supplies soft water having a hardness of 5 mg CaCO ₃ / L or less to the RO membrane, thereby suppressing the oxidative deterioration of the RO membrane and increasing the salt removal rate to stably supply high-purity pure water. A method for producing pure water that can be used has been proposed (see Patent Document 1).

JP 2010-82610 A

  However, with conventional water softening devices, it is difficult to produce high-purity soft water with a sufficiently reduced hardness leak amount and to secure a practical water sampling amount for poor water quality hard water. there were. For example, in the countercurrent regeneration type water softening device disclosed in Patent Document 1, the ion exchange resin bed easily flows during the regeneration process. In addition, the split flow regeneration type water softening device disclosed in Patent Document 1 tends to cause a drift of the regeneration liquid in the vicinity of the intermediate liquid collection part. In other words, in the hard water soft water device adopting these regeneration methods, the regeneration rate of the ion exchange resin bed tends to be low due to the flow of the ion exchange resin bed and the drift of the regeneration liquid, which is higher than the RO membrane. It has been difficult to constantly supply pure soft water. Therefore, further improvement is desired in order to maintain a high salt removal rate in the RO membrane.

  Accordingly, an object of the present invention is to provide a water treatment method and a water treatment system that can maintain a high salt removal rate and a permeated water amount even when hard water having poor water quality is used.

The present invention includes a hard water softening process in which raw water is softened in a cation exchange resin bed tower to produce soft water, and a reverse process in which soft water produced in the hard water softening process is separated into permeated water and concentrated water by a reverse osmosis membrane module. A osmosis membrane separation step, and a deionization step of deionizing the permeated water obtained in the reverse osmosis membrane separation step with an electrodeionization module, an ion exchange resin mixed bed tower or a cation exchange resin single bed tower, A softening process for producing soft water by passing raw water in a downward flow with respect to a cation exchange resin bed having a depth of 300 to 1500 mm in the cation exchange resin bed tower; A first regeneration process for regenerating the entire cation exchange resin bed by generating a downward flow of the regenerated liquid by collecting at the bottom while distributing liquid to the top of the bed; and regenerating after the first regeneration process; Liquid before Including a second regeneration process for regenerating a part of the cation exchange resin bed by generating an upward flow of the regeneration liquid by collecting in the middle while distributing to the bottom of the cation exchange resin bed. In the second regeneration process, the amount of regenerated liquid with a regeneration level of 1 to 6 eq / LR with respect to the hardness leak prevention bed whose depth is set to 100 mm with the bottom of the cation exchange resin bed as the base point In the softening process after the second regeneration process, raw water having an electric conductivity of 150 mS / m or less and a total hardness of 500 mg CaCO ₃ / L or less is supplied, and the reverse osmosis membrane module is disposed on the membrane surface. A reverse osmosis membrane having a negatively charged skin layer made of a crosslinked wholly aromatic polyamide is formed. The reverse osmosis membrane is a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0, and a temperature of 25 ° C. When the pressure is 0.7 MPa and the recovery rate is 15%, the water permeability coefficient is 1.5 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ or more and the salt removal rate is 99% or more. It relates to a water treatment method.

The present invention also provides a hard water softening process in which raw water is softened in a cation exchange resin bed tower to produce soft water, and soft water produced in the hard water softening process is converted into permeated water and concentrated water by a first reverse osmosis membrane module. The first reverse osmosis membrane separation step that separates into two, and the second reverse osmosis membrane separation that further separates the permeate obtained in the first reverse osmosis membrane separation step into permeate and concentrated water in the second reverse osmosis membrane module A softening process for producing soft water by passing raw water in a downward flow through a cation exchange resin bed having a depth of 300 to 1500 mm in the cation exchange resin bed tower; A first regeneration process for regenerating the whole of the cation exchange resin bed by generating a downward flow of the regeneration liquid by collecting at the bottom while dispensing to the top of the cation exchange resin bed; and After the regeneration process, the regeneration solution is exchanged with the cation. While being distributed to the bottom of the resin bed, it is operated including a second regeneration process for regenerating a part of the cation exchange resin bed by generating an upward flow of the regeneration liquid by collecting at the middle part, In the second regeneration process, a regeneration liquid amount of 1 to 6 eq / LR is supplied to the hardness leak prevention bed whose depth is set to 100 mm with the bottom of the cation exchange resin bed as a base point. On the other hand, in the softening process after the second regeneration process, raw water having an electric conductivity of 150 mS / m or less and a total hardness of 500 mg CaCO ₃ / L or less is supplied, and the first and / or second reverse osmosis membrane module is And a reverse osmosis membrane having a negatively charged skin layer made of a crosslinked wholly aromatic polyamide formed on the membrane surface, the reverse osmosis membrane comprising a sodium chloride aqueous solution having a concentration of 500 mg / L, a pH of 7.0, and a temperature of 25 ° C. The The water permeability coefficient when supplied at an operating pressure of 0.7 MPa and a recovery rate of 15% is 1.5 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ or more and the salt removal rate is 99%. The above is a water treatment method.

  And a deionization treatment step of deionizing the permeated water obtained in the second reverse osmosis membrane separation step with an electrodeionization module, an ion exchange resin mixed bed tower or a cation exchange resin single bed tower. preferable.

  In the cation exchange resin bed tower, after the first regeneration process, the raw water is collected at the bottom while being distributed to the top of the cation exchange resin bed, thereby generating a downward flow of the raw water. A first extruding process for extruding the introduced regenerated liquid; and after the second regenerating process, the raw water is collected at the middle part while being distributed to the bottom of the cation exchange resin bed, thereby increasing the upward flow of the raw water. And is operated including a second extrusion process for extruding the introduced regenerated liquid, and in the first and second regenerated processes, the regenerated liquid is 0.7-2 m / h with respect to the cation exchange resin bed. In the first and second extrusion processes, the raw water is fed to the cation exchange resin bed at a linear velocity of 0.7 to 2 m / h and an extrusion rate of 0.4 to 2.5 BV. It is preferable to pass through.

The present invention also provides a hard water softening device that softens raw water using a cation exchange resin bed tower to produce soft water, and the soft water produced by the hard water softening device is converted into permeated water and concentrated water using a reverse osmosis membrane module. A reverse osmosis membrane separator for separation, an electrodeionization module, an ion exchange resin mixed bed tower or a cation exchange resin single bed tower for deionizing the permeated water obtained by the reverse osmosis membrane separator, A softening process for producing soft water by passing raw water in a downward flow with respect to a cation exchange resin bed having a depth of 300 to 1500 mm housed in an ion exchange resin bed tower; regenerating liquid of the cation exchange resin bed A first regeneration process for regenerating the whole of the cation exchange resin bed by generating a downward flow of the regeneration liquid by collecting at the bottom while collecting the liquid at the top; The cations A valve capable of switching to a second regeneration process for regenerating a part of the cation exchange resin bed by generating an upward flow of the regeneration liquid by collecting at the middle part while distributing liquid to the bottom of the exchange resin bed. In the second regeneration process, with respect to the hardness leak prevention bed whose depth is set to 100 mm with the bottom of the cation exchange resin bed as a base point, the amount of regenerated liquid at which the regeneration level is 1 to 6 eq / LR And a raw water supply means for supplying raw water having an electrical conductivity of 150 mS / m or less and a total hardness of 500 mgCaCO ₃ / L or less in the softening process after the second regeneration process, The reverse osmosis membrane module has a reverse osmosis membrane in which a negatively charged skin layer made of a crosslinked wholly aromatic polyamide is formed on the membrane surface, and the reverse osmosis membrane has a concentration of 500 mg / L, pH 7. The water permeation coefficient when an aqueous sodium chloride solution at 0 ° C. and a temperature of 25 ° C. is supplied at an operating pressure of 0.7 MPa and a recovery rate of 15% is 1.5 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ^{− The present invention} relates to a water treatment system having ¹ or more and a salt removal rate of 99% or more.

The present invention also provides a hard water softening device that softens raw water by a cation exchange resin bed tower to produce soft water, and the soft water produced by the hard water softening device is permeated and concentrated by a first reverse osmosis membrane module. A first reverse osmosis membrane separation device that separates the permeated water obtained by the first reverse osmosis membrane separation device into a second reverse osmosis membrane module and a second reverse osmosis membrane that separates the permeated water and concentrated water by a second reverse osmosis membrane module. A softening process for producing soft water by passing raw water in a downward flow through a membrane separation apparatus and a cation exchange resin bed having a depth of 300 to 1500 mm, which is accommodated in the cation exchange resin bed tower; A first regeneration process for regenerating the whole of the cation exchange resin bed by generating a downward flow of the regeneration liquid by collecting at the bottom while dispensing to the top of the cation exchange resin bed; and After one regeneration process, the regeneration solution is replaced with the cation A valve capable of switching to a second regeneration process for regenerating a part of the cation exchange resin bed by generating an upward flow of the regeneration liquid by collecting at the middle part while distributing liquid to the bottom of the exchange resin bed. In the second regeneration process, with respect to the hardness leak prevention bed whose depth is set to 100 mm with the bottom of the cation exchange resin bed as a base point, the amount of regenerated liquid at which the regeneration level is 1 to 6 eq / LR And a raw water supply means for supplying raw water having an electrical conductivity of 150 mS / m or less and a total hardness of 500 mgCaCO ₃ / L or less in the softening process after the second regeneration process, The first and / or second reverse osmosis membrane module has a reverse osmosis membrane having a negatively charged skin layer made of a crosslinked wholly aromatic polyamide formed on the membrane surface, and the reverse osmosis membrane has a concentration of 500. The water permeability coefficient when a sodium chloride aqueous solution of mg / L, pH 7.0, temperature 25 ° C. was supplied at an operating pressure of 0.7 MPa and a recovery rate of 15% was 1.5 × 10 ⁻¹¹ m ³ · m ⁻² · The present invention relates to a water treatment system having s ⁻¹ · Pa ⁻¹ or more and a salt removal rate of 99% or more.

  Moreover, it is preferable to provide the electrodeionization module, the ion exchange resin mixed bed tower, or the cation exchange resin single bed tower which deionizes the permeate obtained with the said 2nd reverse osmosis membrane separator.

  In addition, the valve means generates a downward flow of the raw water by collecting the raw water at the bottom while distributing the raw water to the top of the cation exchange resin bed after the first regeneration process. A first extrusion process for extruding the liquid; and after the second regeneration process, while collecting the raw water to the bottom of the cation exchange resin bed, collecting the middle water to produce an upward flow of the raw water, The regenerative liquid supply means is configured to be able to switch to a second extrusion process for extruding the introduced regenerant liquid, and the regenerant liquid supply means applies the regenerant liquid to the cation exchange resin bed in the first and second regeneration processes from 0.7 to 0.7. The raw water supply means is configured to pass the linear water at a linear velocity of 0.7 to 2 m / h with respect to the cation exchange resin bed in the first and second extrusion processes. And 0.4-2. It is preferably configured to pass at an extrusion amount of BV.

  According to the present invention, it is possible to provide a water treatment method and a water treatment system that can maintain a high salt removal rate and a permeated water amount even when hard water having poor water quality is used.

1 is an overall configuration diagram of a water treatment system 1 according to a first embodiment. It is a schematic sectional drawing of the water softening apparatus 3. 4 is a flowchart of a process executed by the control unit 10. (A)-(c) is explanatory drawing which shows the basic process performed by the control part 10. FIG. It is a whole block diagram of the water treatment system 1A which concerns on 2nd Embodiment.

(First embodiment)
First, the water treatment system 1 which concerns on 1st Embodiment of this invention is demonstrated, referring drawings. The water treatment system 1 is applied to, for example, a pure water production system that produces pure water from fresh water. FIG. 1 is an overall configuration diagram of a water treatment system 1 according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the water softening device 3. FIG. 3 is a flowchart of a process executed by the control unit 10. 4A to 4C are explanatory diagrams illustrating a basic process executed by the control unit 10.

As shown in FIG. 1, a water treatment system 1 according to this embodiment includes a raw water pump 2, a hard water softening device 3, a salt water tank 4, a reverse osmosis membrane separation device 5, and an electrodeionization module as an electrodeionization module. An ion device 6 and a control unit 10 are provided. The water treatment system 1 includes a raw water line L1, a soft water line L2, a salt water line L3, a drainage line L4, water flow lines L5 and L7, and concentrated water lines L6 and L8.
The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a radial path, and a pipeline.

  The upstream end of the raw water line L1 is connected to a supply source (not shown) of the raw water W1. On the other hand, the downstream end of the raw water line L1 is connected to a process control valve 32 (described later) of the water softening device 3.

  The raw water pump 2 is provided in the raw water line L1. The raw water pump 2 pumps raw water W1 such as tap water and groundwater supplied from a supply source toward the hard water softening device 3. The raw water pump 2 is electrically connected to a control unit 10 (described later) via a signal line (not shown). Operation (drive and stop) of the raw water pump 2 is controlled by the control unit 10.

  The raw water line L1 is provided with a raw water flow valve (not shown). The raw water flow valve opens and closes the raw water line L1. In the raw water flow valve, the valve body drive unit is electrically connected to the control unit 10 via a signal line (not shown). The opening and closing of the raw water flow valve is controlled by the control unit 10.

  The raw water line L1, the raw water pump 2, the raw water flow valve (not shown), and the raw water flow meter (or timer) (not shown) constitute raw water supply means in the present embodiment.

In addition, the raw water line L1, the raw water pump 2, and the raw water flow valve (not shown) have an electric conductivity of 150 mS / m or less and a total hardness of 500 mgCaCO ₃ / L in the softening process ST1 after the second regeneration process ST5 described later. It also functions as raw water supply means for supplying the following raw water W1 to the hard water softening device 3.

  The water softening device 3 is a facility for producing soft water W2 by replacing hardness components (calcium ions and magnesium ions) contained in the raw water W1 with sodium ions (or potassium ions) in a cation exchange resin bed 311 (described later). is there. As shown in FIG. 2, the water softening apparatus 3 is mainly configured by a pressure tank 31 as a cation exchange resin bed tower and a process control valve 32 as a valve means.

  The pressure tank 31 is a bottomed cylindrical body having an opening at the top, and the opening is sealed with a lid member. Inside the pressure tank 31, a cation exchange resin bed 311 made of cation exchange resin beads and a support bed 312 made of filtered gravel are accommodated.

  The cation exchange resin bed 311 functions as a treatment material that softens the raw water W1. The cation exchange resin bed 311 is stacked on the support bed 312 inside the pressure tank 31. The depth D1 of the cation exchange resin bed 311 is set in the range of 300 to 1500 mm.

  The support bed 312 functions as a fluid rectifying member for the cation exchange resin bed 311. The support floor 312 is accommodated on the bottom side of the pressure tank 31.

  In the pressure tank 31, a top screen 321 for preventing the cation exchange resin beads from flowing out is provided on the top of the cation exchange resin bed 311. The top screen 321 is connected to various lines constituting the process control valve 32 via a first flow path (not shown).

  The liquid distribution position and the liquid collection position by the top screen 321 are set near the top of the cation exchange resin bed 311. The top screen 321 functions as a top liquid distribution unit provided at the top of the cation exchange resin bed 311 and a top liquid collection unit provided at the top of the cation exchange resin bed 311.

  In the pressure tank 31, a bottom screen 322 for preventing the cation exchange resin beads from flowing out is provided at the bottom of the cation exchange resin bed 311. The bottom screen 322 is connected to various lines constituting the process control valve 32 through a second flow path (not shown).

  The liquid distribution position and the liquid collection position by the bottom screen 322 are set near the bottom of the cation exchange resin bed 311. The bottom screen 322 functions as a bottom liquid distribution unit provided at the bottom of the cation exchange resin bed 311 and a bottom liquid collection unit provided at the bottom of the cation exchange resin bed 311.

  In the pressure tank 31, an intermediate screen 323 for preventing the cation exchange resin beads from flowing out is provided above the hardness leak prevention floor 313 (described later) and in the intermediate portion in the depth direction of the cation exchange resin bed 311. Is provided. The intermediate screen 323 is connected to various lines constituting the process control valve 32 via a third flow path (not shown).

  The liquid collection position by the intermediate screen 323 is set near the intermediate part of the cation exchange resin bed 311. The intermediate part screen 323 functions as an intermediate part liquid collection part provided in the intermediate part of the cation exchange resin bed 311.

  The process control valve 32 includes various lines and valves therein. The process control valve 32 is a flow of the raw water W1 in the softening process ST1 for producing the soft water W2 by passing at least the raw water W1 in a downward flow with respect to the cation exchange resin bed 311; The flow of the salt water W3 in the first regeneration process ST3 in which the downward flow of the salt water W3 is generated by collecting at the bottom while liquid is distributed to the top of the exchange resin bed 311 and the entire cation exchange resin bed 311 is regenerated. And after the first regeneration process ST3, the salt water W3 is collected at the middle while the salt water W3 is distributed to the bottom of the cation exchange resin bed 311 to generate an upward flow of the salt water W3, and the cation exchange resin bed 311; The flow of the salt water W3 in the second regeneration process ST5 for regenerating a part of the water is switchable.

  The regeneration process in the present embodiment includes a first regeneration process ST3 and a second regeneration process ST5 performed after the end of the first regeneration process ST3. The first regeneration process ST3 is a cocurrent regeneration process in which the entire cation exchange resin bed 311 is regenerated. The second regeneration process ST5 is a partial countercurrent regeneration process in which a part of the cation exchange resin bed 311 is regenerated. The regeneration of the cation exchange resin bed 311 in this embodiment is operated by a two-stage regeneration process. Specifically, the operation is performed by executing the cocurrent regeneration process as the first regeneration process, and executing the partial countercurrent regeneration process as the second regeneration process after the completion of the first regeneration process.

  In the second regeneration process ST5 described later, as shown in FIG. 2, the hardness leak prevention floor 313 (described later) having a depth D2 set to 100 mm with the bottom (that is, the bottom) of the cation exchange resin bed 311 as a base point is used. On the other hand, salt water W3 is supplied in an amount such that the regeneration level is 1 to 6 eq / LR. Here, the regeneration level refers to the amount of the regenerant used for regenerating the unit volume ion exchange resin. Further, when sodium chloride is used as a regenerant, 1 eq corresponds to 58.5 g.

  The hardness leak prevention floor 313 is an area that needs to be sufficiently regenerated in the cation exchange resin bed 311 in order to prevent hardness leak in the softening process ST1 as much as possible. The depth of the hardness leak prevention floor 313 may be 100 mm, and hardness leak can be prevented as much as possible by regenerating at least the limited region at a predetermined reproduction level.

  Further, the process control valve 32 collects the raw water W1 with respect to the cation exchange resin bed 311 at the bottom while distributing the raw water W1 to the top of the cation exchange resin bed 311 after the first regeneration process ST3. The flow of the raw water W1 in the first extrusion process ST4 that generates a downward flow of the raw water W1 and pushes out the introduced salt water W3; and after the second regeneration process ST5, the raw water W1 is moved to the bottom of the cation exchange resin bed 311. While the liquid is being distributed, an upward flow of the raw water W1 is generated by collecting at the intermediate portion, and the flow of the raw water W1 in the second extrusion process ST6 for pushing out the introduced salt water W3 can be switched.

  The process control valve 32 is connected to the upstream end of the drain line L4. From the drainage line L4, salt water W3 and raw water W1 used in the regeneration process, extrusion process, and the like are discharged as drainage W4.

  Further, in the process control valve 32, the valve body drive section provided therein is electrically connected to the control section 10 via a signal line (not shown). Switching of the valve in the process control valve 32 is controlled by the control unit 10.

Here, each process implemented in the water softening apparatus 3 is demonstrated.
In the water treatment system 1 of the present embodiment, the control unit 10 to be described later performs the following processes ST1 to ST8 shown in FIG. 3 by switching the flow path of the process control valve 32.
(ST1) Softening process of passing raw water W1 from the top to the bottom with respect to the entire cation exchange resin bed 311 (ST2) Raw water W1 as washing water from the bottom to the top with respect to the entire cation exchange resin bed 311 First washing process (ST4) for passing salt water W3 as a regenerated liquid from the top to the bottom with respect to the entire cation exchange resin bed 311. Cation exchange resin for raw water W1 as extrusion water. The first extrusion process (ST5) for allowing the entire bed 311 to pass from the top to the bottom Salt water W3 as a regenerated liquid is passed from the bottom to the top of the cation exchange resin bed 311 mainly to the hardness leak prevention floor 313. Second regeneration process (ST6) A second extrusion process in which raw water W1 as extrusion water is passed from the bottom to the top of the cation exchange resin bed 311 mainly against the hardness leak prevention bed 313. Seth (ST7) rehydration process of supplying the raw water W1 as rinsing water rinsing process (ST8) to pass from top to bottom with respect to the cation exchange resin bed 311 raw water W1 as makeup water to the brine tank 4

  Next, an operation method of the softening process ST1, the first regeneration process ST3, and the second regeneration process ST5 which are main processes among the processes ST1 to ST8 will be described.

In the softening process ST1, as shown in FIG. 4A, the raw water W1 is distributed from the top screen 321, and the raw water W1 is allowed to pass through the entire cation exchange resin bed 311 in a downward flow. Manufacturing. The produced soft water W2 is collected from the bottom screen 322.
In a softening process ST1 after a second regeneration process ST5 described later, raw water W1 having an electric conductivity of 150 mS / m or less and a total hardness of 500 mgCaCO ₃ / L or less is supplied.

  In the first regeneration process ST3, as shown in FIG. 4 (b), salt water W3 is distributed from the top screen 321, and the salt water W3 is passed through the entire cation exchange resin bed 311 in a downward flow. The cation exchange resin bed 311 is regenerated. In the first regeneration process ST3, the salt water W3 is passed through the cation exchange resin bed 311 at a linear velocity of 0.7 to 2 m / h. The used salt water W3 obtained by regenerating the cation exchange resin bed 311 is collected from the bottom screen 322. In the first regeneration process ST3, the entire cation exchange resin bed 311 is regenerated by cocurrent regeneration.

  In 1st extrusion process ST4 implemented after completion | finish of 1st reproduction | regeneration process ST3, as shown in FIG.4 (b), raw water W1 is distributed from the top screen 321, and with respect to the whole cation exchange resin bed 311. Then, the raw water W1 is passed in a downward flow, and the salt water W3 introduced into the cation exchange resin bed 311 is pushed out. The raw water W1 that has passed through the cation exchange resin bed 311 is collected from the bottom screen 322. In the first extrusion process ST4, the raw water W1 is passed through the cation exchange resin bed 311 at a linear velocity of 0.7 to 2 m / h and an extrusion rate of 0.4 to 2.5 BV.

  In the first regeneration process ST3 and the first extrusion process ST4, cocurrent regeneration is performed on the entire cation exchange resin bed 311. Therefore, the entire amount of the cation exchange resin bed 311 is regenerated almost uniformly, so that in the softening process ST1, the sampled amount of the soft water W2 is increased to the maximum.

In the second regeneration process ST5, as shown in FIG. 4 (c), the salt water W3 is distributed from the bottom screen 322, and the salt water W3 is passed through the cation exchange resin bed 311 in an upward flow. The lower region including the hardness leak prevention floor 313 of the exchange resin floor 311 is regenerated. In the second regeneration process ST5, the salt water W3 is passed through the cation exchange resin bed 311 at a linear velocity of 0.7 to 2 m / h. The salt water W3 which has regenerated the lower region including the hardness leak prevention floor 313 of the cation exchange resin bed 311 is collected from the intermediate screen 323. In the second regeneration process ST5, salt water W3 is supplied in an amount such that the regeneration level is 1 to 6 eq / LR to the hardness leak prevention floor 313 set at the bottom of the cation exchange resin bed 311. In the second regeneration process ST5, the lower region including the hardness leak prevention bed 313 of the cation exchange resin bed 311 is mainly regenerated by partial countercurrent regeneration.
By performing this second regeneration process ST5, in the subsequent softening process ST1, when raw water W1 having an electric conductivity of 150 mS / m or less and a total hardness of 500 mg CaCO ₃ / L or less is supplied, the hardness leak amount is High-purity soft water W2 having a concentration of 0.8 mgCaCO ₃ / L or less can be produced.

  In the second extrusion process ST6 performed after the end of the second regeneration process ST5, as shown in FIG. 4C, the raw water W1 is distributed from the bottom screen 322, and the hardness of the cation exchange resin bed 311 is mainly increased. The raw water W1 is passed through the leak prevention floor 313 in an upward flow, and the salt water W3 introduced into the lower region of the cation exchange resin bed 311 including the hardness leak prevention floor 313 is pushed out. The raw water W <b> 1 that has passed through the hardness leak prevention floor 313 is collected from the intermediate screen 323. In the second extrusion process ST6, the raw water W1 is passed through the lower region of the cation exchange resin bed 311 at a linear velocity of 0.7 to 2 m / h and an extrusion rate of 0.4 to 2.5 BV.

  In the second regeneration process ST5 and the second extrusion process ST6, partial countercurrent regeneration is performed on the lower region of the cation exchange resin bed 311. Therefore, when the hardness leak prevention floor 313 is regenerated intensively, in the softening process ST1, the hardness leak amount of the soft water W2 is suppressed to the limit.

  Note that the illustration of the back cleaning process ST2, the rinsing process ST7, and the water replenishment process ST8 is omitted.

Again, the structure of the water treatment system 1 is demonstrated, referring FIG.
The salt water tank 4 stores salt water W3 for regenerating the cation exchange resin bed 311. The upstream end of the salt water line L3 is connected to the salt water tank 4. The downstream end of the salt water line L3 communicates with the process control valve 32 and is connected to various lines constituting the process control valve 32, respectively. The salt water line L3 is provided with a salt water valve (not shown). The salt water valve opens and closes the salt water line L3. The salt water valve is incorporated in the process control valve 32, and the drive unit of the valve body is electrically connected to the control unit 10 via a signal line (not shown). The opening and closing of the salt water valve is controlled by the control unit 10. The salt water tank 4 sends salt water W3 for regenerating the cation exchange resin bed 311 to the pressure tank 31 in the first regeneration process ST3 and the second regeneration process ST5.
The salt water tank 4, a salt water valve (not shown), an ejector (not shown), and a salt water flow meter constitute a regenerating liquid supply unit in the present embodiment.

  The reverse osmosis membrane separation device 5 concentrates the soft water W2 produced by the water softening device 3 into the permeated water W5 from which dissolved salts and the like are removed by the reverse osmosis membrane (the RO membrane module 5b described later) and the dissolved salts and the like. This is a facility for performing membrane separation treatment on the first concentrated water W6. The reverse osmosis membrane separation device 5 is connected to the downstream side of the water softening device 3 (process control valve 32) via the soft water line L2.

  The reverse osmosis membrane separation device 5 includes a pressure pump 5a and an RO membrane module 5b as a reverse osmosis membrane. The pressurizing pump 5a pressurizes the soft water W2 sent from the hard water softening device 3 and sends it to the RO membrane module 5b. The RO membrane module 5b includes a single or a plurality of RO membrane elements (not shown). The reverse osmosis membrane separation device 5 performs membrane separation treatment of the soft water W2 with these RO membrane elements to produce the permeated water W5 and the first concentrated water W6.

  The upstream end of the water flow line L5 is connected to the permeate outlet of the RO membrane module 5b. The permeated water W5 obtained by the reverse osmosis membrane separation device 5 is sent to the electrodeionization device 6 through the water passage line L5. The upstream end of the concentrated water line L6 is connected to the concentrated water outlet of the RO membrane module 5b. The first concentrated water W6 obtained by the reverse osmosis membrane separation device 5 is discharged to the outside through the concentrated water line L6. In order to keep the flow velocity on the membrane surface within a predetermined range, a part of the first concentrated water W6 is returned to the soft water line L2 on the upstream side of the reverse osmosis membrane separation device 5, and the other first concentrated water W6 is brought outside. You may comprise so that it may discharge | emit.

The RO membrane module 5b in this embodiment has a reverse osmosis membrane (not shown) in which a negatively charged skin layer made of a crosslinked wholly aromatic polyamide is formed on the membrane surface. The reverse osmosis membrane, concentration 500 mg / L, pH 7.0, sodium chloride aqueous solution temperature 25 ° C., the operating pressure 0.7 MPa, the water permeability coefficient when supplied at a recovery rate of 15%, 1.5 × 10 ^{- 11} m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ or more and a salt removal rate of 99% or more. In the reverse osmosis membrane set to such a performance, in the desalination treatment of fresh water, the lower the hardness of the feed water, the lower the salt removal rate (ie, (feed water EC− Permeated water EC) / feed water EC × 100) has a characteristic of increasing. Therefore, constantly supplying high-purity soft water W2 (actual value: 0.8 mgCaCO ₃ or less) produced by the water softening device 3 that performs a two-stage regeneration process consisting of cocurrent regeneration and partial countercurrent regeneration. Thus, it is possible to maintain a high salt removal rate (usually 98.5% or more).

Here, the operating pressure is an average operating pressure defined by JIS K3802-1995 “Membrane Term”. The operating pressure indicates an average value of the primary side inlet pressure and the primary side outlet pressure of the RO membrane module 5b.
Recovery and the feed water to the RO membrane module 5b (here, aqueous sodium chloride solution), the amount of the flow rate _{Q 2} of the permeate to the flow rate to _{Q 1 (i.e., Q 2 / Q 1 × 100} ) refers to.
The water permeation coefficient is a value obtained by dividing the permeated water amount [m ³ / s] by the membrane area [m ² ] and the effective pressure [Pa], and is an index indicating the water permeation performance of the reverse osmosis membrane. That is, the water permeation coefficient means the amount of water that permeates the unit area of the membrane per unit time when a unit effective pressure is applied. The effective pressure is defined by JIS K3802-1995 “Membrane Term” and is a pressure obtained by subtracting the osmotic pressure difference and the secondary pressure from the operating pressure (average operating pressure).
The salt removal rate is a value calculated from the concentration of specific salts before and after permeating the membrane (here, sodium chloride concentration), and is an index indicating the solute blocking performance of the reverse osmosis membrane. The salt removal rate is determined by (1−C ₂ / C ₁ ) × 100 from the inlet concentration (C ₁ ) to the RO membrane module 5 b and the permeated water concentration (C ₂ ).

  The reverse osmosis membrane that satisfies the conditions of the water permeability coefficient and the salt removal rate of this embodiment is commercially available as a reverse osmosis membrane element. As the reverse osmosis membrane element, for example, Toray Industries, Inc .: model name “TMG20-400”, Unjin Chemical, Inc .: model name “RE8040-BLF”, Nitto Denko Corporation: model name “ESPA1”, etc. may be used. it can.

The electrodeionization device 6 is a facility for performing a membrane separation process for separating the permeated water W5 obtained by the reverse osmosis membrane separation device 5 into deionized water W7 and second concentrated water W8 by an ion exchange membrane (not shown). It is.
Specifically, the electrodeionization apparatus 6 includes a demineralization chamber and a concentration chamber (both not shown). The desalting chamber and the concentration chamber are formed by alternately arranging a cation exchange membrane and an anion exchange membrane (both not shown) between a pair of electrodes. Among these, the cation exchange resin and the anion exchange resin are accommodated in the desalting chamber. The desalting chamber only needs to contain at least a cation exchange resin (the reason will be described later).

  The electrodeionization device 6 is electrically connected to a power supply device (not shown). In the electrodeionization device 6, when a DC voltage is applied between the pair of electrodes, the permeated water W5 that could not be removed by the reverse osmosis membrane separation device 5 due to the selective movement of ions through the ion exchange tree membrane. Residual ions contained in are removed in a desalting chamber. Thereby, deionized water (pure water) W7 is manufactured in the desalination chamber. Moreover, in the electrodeionization apparatus 6, the 2nd concentrated water W8 with high ion concentration is manufactured from the permeated water W5 in a concentration chamber.

  An upstream end portion of the water flow line L7 is connected to the demineralization chamber of the electrodeionization apparatus 6. The deionized water W7 produced by the electrodeionization device 6 is sent as pure water to the secondary purification device and the demand point through the water flow line L7. On the other hand, the upstream end of the concentrated water line L8 is connected to the concentration chamber of the electrodeionization apparatus 6. The second concentrated water W8 produced by the electrodeionization device 6 is discharged to the outside through the concentrated water line L8. The second concentrated water W8 can be returned to the soft water line L2 on the upstream side of the pressurizing pump 5a through the concentrated water line L8 without being discharged to the outside.

  The control unit 10 includes a microprocessor (not shown) including a CPU and a memory. The control unit 10 controls the operation of the process control valve 32 based on a detection signal or the like input from a raw water flow meter (not shown) or a salt water flow meter. The memory stores in advance a control program for performing the operation of the water softening device 3 of the present embodiment. The CPU controls the process control valve 32 so as to sequentially switch the softening process ST1 to the water replenishment process ST8 described above according to the control program stored in the memory. Further, the control unit 10 applies a predetermined DC voltage to the electrodeionization device 6 through a power supply circuit (not shown).

  In the water treatment system 1 configured as described above, the raw water W1 supplied from the supply source (not shown) of the raw water W1 through the raw water line L1 is supplied to the process control valve 32 of the hard water softening device 3 by the raw water pump 2. Sent out. The raw water W1 is softened by passing through the cation exchange resin bed 311 of the pressure tank 31 to produce soft water W2. The soft water W2 is further sent to the reverse osmosis membrane separation device 5 via the soft water line L2. In the reverse osmosis membrane separation device 5, the membrane separation process is performed in the RO membrane module 5b, and the permeated water W5 and the first concentrated water W6 are produced. Then, the obtained permeated water W5 is sent to the electrodeionization apparatus 6 through the water flow line L5. In the electrodeionization apparatus 6, membrane separation processing is performed in the ion exchange membrane, and deionized water W7 and second concentrated water W8 are produced. Among these, the deionized water W7 is sent as pure water to the secondary purification device or the demand point.

According to the water treatment system 1 which concerns on 1st Embodiment mentioned above, the following effects are show | played, for example.
In the water treatment system 1 of the present embodiment, the cation exchange resin bed 311 of the water softening device 3 collects the salt water W3 on the bottom screen 322 while distributing the salt water W3 to the top screen 321 of the cation exchange resin bed 311. To generate a downward flow of the salt water W3 to regenerate the entire cation exchange resin bed 311; and after the first regeneration process ST3, the salt water W3 is converted to the bottom screen 322 of the cation exchange resin bed 311. The second regeneration that regenerates a part of the cation exchange resin bed 311 (mainly the hardness leak prevention bed 313) by generating an upward flow of the salt water W3 by collecting the liquid at the intermediate screen 323 while distributing the liquid to the second screen. It is operated including the process ST5. Therefore, high-purity soft water W2 having a sufficiently reduced hardness leak amount can be obtained to the maximum within a practical water sampling range.

  In the water treatment system 1 of the present embodiment, in the second regeneration process ST5, the hardness leak prevention floor 313 having a depth D2 (see FIG. 2) set to 100 mm with the bottom of the cation exchange resin bed 311 as a base point is used. On the other hand, salt water W3 is supplied in an amount such that the regeneration level is 1 to 6 eq / LR. Therefore, in the cation exchange resin bed 311, the hardness leak prevention floor 313 that is an important region for preventing hardness leak can be almost completely regenerated. According to this, even when hard water of poor water quality with a high hardness level is used as the raw water W1, it is possible to obtain high-purity soft water W2 in which the amount of hardness leak is suppressed to the limit.

  Therefore, according to the water treatment system 1 of the present embodiment, even when hard water having poor water quality is used as the raw water W1, high-purity soft water W2 can be constantly supplied to the reverse osmosis membrane separation device 5. Therefore, not only the oxidative deterioration in the RO membrane module 5b but also scaling and fouling can be suppressed, and a high salt removal rate and permeated water amount can be maintained.

  Moreover, in the water treatment system 1 of this embodiment, the salt water W3 is 0.7-2 m / h with respect to the cation exchange resin bed 311 of the water softening device 3 in the first regeneration process ST3 and the second regeneration process ST5. It is driven to pass at a linear velocity of. Moreover, in 1st extrusion process ST4 and 2nd extrusion process ST6, with respect to the cation exchange resin bed 311 of the water softening apparatus 3, the raw | natural water W1 has a linear velocity of 0.7-2 m / h, and 0.4-2. Operated to pass at an extrusion rate of 5 BV. In this way, by regulating the linear velocity of the liquid flow in the regeneration process and the extrusion process to the above-described conditions, the regeneration efficiency of the cation exchange resin bed 311 can be increased, and the amount of water collected from the soft water W2 can be increased. Further, by limiting the extrusion amount of the extrusion process to the above-described conditions, even when hard water having poor water quality is used as the extrusion water, the contamination of the hardness leak prevention floor 313 due to the hardness component is suppressed, and the soft water W2 Purity can be increased.

  Furthermore, the water treatment system 1 of the present embodiment includes an electrodeionization device 6 on the downstream side of the reverse osmosis membrane separation device 5. Therefore, the ions contained in the permeate W5 that could not be removed by the reverse osmosis membrane separation device 5 can be further removed by the electrodeionization device 6. Therefore, deionized water W7 (pure water) with higher purity can be produced.

In addition, in this embodiment, although the structure provided with the electrodeionization apparatus 6 was demonstrated as an apparatus which implements a deionization process, it is not restricted to this, An ion exchange resin mixed bed tower or a cation exchange resin single bed tower It is good also as a structure provided with.
The ion exchange resin mixed bed tower is one in which a cation exchange resin and an anion exchange resin are mixed in one tower. In the ion exchange resin mixed bed tower, cations and anions contained in the permeated water W5 are simultaneously removed.

On the other hand, the cation exchange resin single-bed column contains only the cation exchange resin in one column (also called a cation polisher). The RO membrane module 5b of this embodiment includes a reverse osmosis membrane having a negatively charged skin layer formed thereon. For this reason, the RO membrane module 5b tends to remove anions, but tends to allow cations to pass therethrough (this tendency promotes ionization of weak acids such as carbonic acid, silicic acid (silica), boric acid and the like). Therefore, it becomes more remarkable when the pH of the soft water W2 is increased). In this case, the cation that has permeated through the reverse osmosis membrane separation device 5 is removed by a cation exchange resin single-bed column provided on the downstream side. Thus, when a cation exchange resin single bed column is used, anions and cations are removed stepwise.
In the electrodeionization apparatus 6 described above, even when only the cation exchange resin is accommodated in the demineralization chamber, the anion and the cation are stepped in the same manner as in the case of using a single cation exchange resin bed tower. Can be removed. That is, in the electrodeionization apparatus 6, cations that have permeated through the reverse osmosis membrane separation apparatus 5 are removed.

  As described above, the reverse osmosis membrane separation device 5 could not completely remove the deionization treatment even when the ion exchange resin mixed bed tower or the cation exchange resin single bed tower was used. Ions contained in the permeated water W5 can be further removed.

(Second Embodiment)
Next, a water treatment system 1A according to a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is an overall configuration diagram of a water treatment system 1A according to the second embodiment. In the second embodiment, differences from the first embodiment will be mainly described. For this reason, the same code | symbol is attached | subjected about the same (or equivalent) structure as 1st Embodiment, and detailed description is abbreviate | omitted. The description of the first embodiment is appropriately applied to points that are not particularly described in the second embodiment.

  As shown in FIG. 5, the water treatment system 1A according to the present embodiment includes a raw water pump 2, a hard water softening device 3, a salt water tank 4, a first reverse osmosis membrane separation device 5, and a second reverse osmosis membrane separation. The apparatus 8 and the control part 10 are provided. The water treatment system 1 includes a raw water line L1, a soft water line L2, a salt water line L3, a drainage line L4, water flow lines L5 and L7, and concentrated water lines L6 and L8.

  In the present embodiment, “reverse osmosis membrane separation device 5” in the first embodiment will be described as “first reverse osmosis membrane separation device 5”. The 1st reverse osmosis membrane separation apparatus 5 of this embodiment performs the membrane separation process of the soft water W2, and manufactures the 1st permeated water W9 and the 1st concentrated water W6.

  In the water treatment system 1 </ b> A according to the present embodiment, a second reverse osmosis membrane separation device 8 is provided on the downstream side of the first reverse osmosis membrane separation device 5. The configuration of the second reverse osmosis membrane separation device 8 is the same as that of the first reverse osmosis membrane separation device 5. That is, the pressure pump 8 a of the second reverse osmosis membrane separation device 8 is the same as the pressure pump 5 a of the first reverse osmosis membrane separation device 5. Further, the RO membrane module 8b of the second reverse osmosis membrane separation device 8 may have the same characteristics as the RO membrane module 5b of the first reverse osmosis membrane separation device 5, or may have different characteristics. As the RO membrane module 8b, for example, an NF membrane module having a nanofiltration membrane having pores looser than those of a normal reverse osmosis membrane can be used. The second reverse osmosis membrane separation device 8 performs membrane separation treatment on the first permeated water W9 obtained by the first reverse osmosis membrane separation device 5 with these RO membrane elements, and the second permeated water W10 and the second concentrated water W11. Manufacturing.

  The upstream end of the water flow line L7 is connected to the permeate outlet of the RO membrane module 8b. The 2nd permeated water W10 obtained with the 2nd reverse osmosis membrane separation apparatus 8 is sent to a secondary refinement | purification apparatus and a demand location as a pure water via the water flow line L7. The upstream end of the concentrated water line L8 is connected to the concentrated water outlet of the RO membrane module 8b. The second concentrated water W11 obtained by the second reverse osmosis membrane separation device 8 is discharged to the outside through the concentrated water line L8. The second concentrated water W11 can be returned to the soft water line L2 upstream of the pressurizing pump 5a via the concentrated water line L8 without being discharged to the outside.

  According to 1 A of water treatment systems of 2nd Embodiment mentioned above, the effect similar to the water treatment system 1 of 1st Embodiment is show | played. In particular, the water treatment system 1 </ b> A of the present embodiment further includes a second reverse osmosis membrane separation device 8 on the downstream side of the first reverse osmosis membrane separation device 5. Therefore, the ions contained in the permeated water W5 that could not be removed by the first reverse osmosis membrane separation device 5 can be further removed by the second reverse osmosis membrane separation device 8. Therefore, deionized water W7 (pure water) with higher purity can be produced.

  In addition, in this embodiment, it is good also as a structure provided with the electrodeionization apparatus 6 shown in 1st Embodiment as an apparatus which implements a deionization process in the downstream of the 2nd reverse osmosis membrane separation apparatus 8. FIG. Moreover, it is good also as a structure provided with the ion exchange resin mixed bed tower or the cation exchange resin single bed tower instead of the electrodeionization apparatus 6. FIG. In such a configuration, ions contained in the permeated water W5 that could not be removed by the first reverse osmosis membrane separation device 5 and the second reverse osmosis membrane separation device 8 can be further removed. Therefore, deionized water W7 (pure water) with higher purity can be produced.

  As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.

  For example, in the first and second embodiments, an alkaline agent addition device (not shown) is provided between the water softening device 3 and the reverse osmosis membrane separation device (first reverse osmosis membrane separation device) 5 to perform reverse osmosis membrane separation. It is good also as a structure which adds an alkaline agent to the soft water W2 supplied to the apparatus (1st reverse osmosis membrane separator) 5. FIG. Examples of the alkaline agent include sodium hydroxide and potassium hydroxide. When an alkaline agent is added to the soft water W2 produced by the hard water softening device 3 to raise the pH to 8 or more, free carbonic acid contained in the soft water W2 is ionized and changed to hydrogen carbonate ions or carbonate ions. For this reason, in the reverse osmosis membrane separation device (first reverse osmosis membrane separation device) 5 provided on the downstream side, ionized free carbonic acid (hydrogen carbonate ions or carbonate ions) can be removed. Therefore, deionized water W7 and second permeated water W10 with higher purity can be produced.

  Moreover, since the solubility of the silicic acid (silica) contained in the soft water W2 increases when an alkali agent is added to the soft water W2, it is possible to suppress the generation of silica-based scale, and as a result, the recovery rate of pure water is increased. Can be improved. Moreover, since the dissociation (ionization) of boric acid is accelerated | stimulated by adding an alkaline agent to soft water W2 and setting pH to 9 or more, the removal rate of boric acid can be improved.

  Further, in the second embodiment, when an ion exchange resin mixed bed tower is provided on the downstream side of the second reverse osmosis membrane separation device 8, by adding an alkali agent to the soft water W2, silicic acid (silica) is added. By promoting dissociation (ionization), the lifetime of the ion-exchange resin mixed bed tower can be extended. That is, when undissociated silicic acid remains in the second permeated water W10, the nonionic silicic acid is physically adsorbed and accumulated in the pores of the anion exchange resin. Therefore, it becomes difficult to recycle the anion exchange resin. On the other hand, when the dissociated silicic acid remains in the second permeated water W10, the ionic silicic acid is removed by ion exchange with the anion exchange resin. Is possible. For this reason, in the latter case, the load of the ion-exchange resin mixed bed tower is reduced, and the life can be extended.

Moreover, about the structure which provided the alkaline agent addition apparatus, there exist the following embodiments.
In the second embodiment, the quality of the first permeated water W9 produced by the second reverse osmosis membrane separation device 8 depends on the pH of the membrane surface of the RO membrane module 8b. Therefore, when the pH of the membrane surface of the RO membrane module 8b varies, the water quality of the first permeated water W9 produced by the second reverse osmosis membrane separation device 8 also becomes unstable.

  Therefore, in the second embodiment, a part of the second concentrated water W11 is returned to the soft water line L2 on the upstream side of the first reverse osmosis membrane separation device 5, and the other second concentrated water W11 is discharged to the outside. To do. And a pH detection means (not shown) is provided in the water flow line L5 (inlet side of the 2nd reverse osmosis membrane separation apparatus 8). An example of the pH detecting means is a pH sensor. This pH sensor is electrically connected to the control unit 10 through a signal line. The measurement value detected by the pH sensor is transmitted to the control unit 10.

  The control unit 10 controls addition or non-addition of the alkaline agent by the alkaline agent addition device based on the measured value detected by the pH sensor. Specifically, the control unit 10 determines that the pH of the first permeate W9 sent to the second reverse osmosis membrane separation device 8 is 7 to 8 based on the measurement value detected by the pH sensor, and the second The addition or non-addition of the alkaline agent is controlled so that the pH of the second concentrated water W11 discharged from the reverse osmosis membrane separation device 8 is 7 to 7.5.

  In this embodiment, the ionization of the free carbonic acid contained in the first permeate water W9 can be promoted by setting the pH of the first permeate water W9 to 7-8. Moreover, the purity of the pure water manufactured with the 2nd reverse osmosis membrane separation apparatus 8 can be improved by setting pH of the 2nd concentrated water W11 to 7-7.5. According to this, since the fluctuation of the pH of the membrane surface in the RO membrane module 8b can be suppressed and the membrane separation treatment can be performed in the optimum pH region, the first permeation manufactured by the second reverse osmosis membrane separation device 8 is possible. The water quality of the water W9 can be further stabilized. Moreover, since the addition amount of the alkaline agent can be optimized, the amount of the alkaline agent to be used can be minimized.

  Further, in the second regeneration process described in the first embodiment, an upward flow of the salt water W3 from the bottom screen 322 to the intermediate screen 323 is generated. Further, the salt water from the top screen 321 to the intermediate screen 323 is generated. A downward flow of W3 may be generated.

  Further, a raw water tank for supplying the raw water W1 to the raw water line L1 may be provided separately from the supply source of the raw water W1, and equipment including the raw water tank may be used as the raw water supply means. In this case, the raw water W1 stored in the raw water tank is supplied to the hard water softening device 3 as washing water, extrusion water, and rinsing water.

1, 1A Water treatment system 3 Hard water softening device 4 Salt water tank 5 Reverse osmosis membrane separation device (first reverse osmosis membrane separation device)
5b RO membrane module (reverse osmosis membrane)
6 Electrodeionization equipment (Electrodeionization module)
8 Second reverse osmosis membrane separation device 10 Control unit 31 Pressure tank (cation exchange resin bed tower)
32 Process control valve (valve means)
311 Cation exchange resin bed 313 Hardness leak prevention floor 321 Top screen 322 Bottom screen 323 Middle screen L1 Raw water line L2 Soft water line L3 Salt water line L4 Drainage lines L5, L7 Water flow lines L6, L8 Concentrated water line W1 Raw water W2 Soft water W3 Salt water (regenerated liquid)
W4 Wastewater W5 Permeated water W6 First concentrated water W7 Deionized water (pure water)
W8, W11 Second concentrated water W9 First permeated water W10 Second permeated water

Claims (8)

A water softening process in which raw water is softened in a cation exchange resin bed tower to produce soft water;
A reverse osmosis membrane separation step of separating soft water produced in the hard water softening step into permeated water and concentrated water with a reverse osmosis membrane module;
A deionization treatment step of deionizing the permeated water obtained in the reverse osmosis membrane separation step with an electrodeionization module, an ion exchange resin mixed bed tower or a cation exchange resin single bed tower,
In the cation exchange resin bed tower, a softening process for producing soft water by passing raw water in a downward flow with respect to a cation exchange resin bed having a depth of 300 to 1500 mm; A first regeneration process for regenerating the whole of the cation exchange resin bed by generating a downward flow of the regeneration liquid by collecting at the bottom while collecting the liquid at the top; A second regeneration process for regenerating a part of the cation exchange resin bed by generating an upward flow of the regeneration liquid by collecting at an intermediate portion while distributing liquid to the bottom of the cation exchange resin bed; Driven by,
In the second regeneration process, a regeneration liquid amount of 1 to 6 eq / LR is supplied to the hardness leak prevention bed whose depth is set to 100 mm with the bottom of the cation exchange resin bed as a base point. On the other hand, in the softening process after the second regeneration process, raw water having an electric conductivity of 150 mS / m or less and a total hardness of 500 mg CaCO ₃ / L or less is supplied.
The reverse osmosis membrane module has a reverse osmosis membrane in which a negatively charged skin layer made of a crosslinked wholly aromatic polyamide is formed on the membrane surface,
The reverse osmosis membrane has a water permeability coefficient of 1.5 × 10 ⁻¹¹ when a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0, and temperature of 25 ° C. is supplied at an operating pressure of 0.7 MPa and a recovery rate of 15%. m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ or more and the salt removal rate is 99% or more,
Water treatment method. A water softening process in which raw water is softened in a cation exchange resin bed tower to produce soft water;
A first reverse osmosis membrane separation step of separating soft water produced in the hard water softening step into permeated water and concentrated water by a first reverse osmosis membrane module;
A second reverse osmosis membrane separation step of further separating the permeated water obtained in the first reverse osmosis membrane separation step into permeated water and concentrated water in the second reverse osmosis membrane module,
In the cation exchange resin bed tower, a softening process for producing soft water by passing raw water in a downward flow with respect to a cation exchange resin bed having a depth of 300 to 1500 mm; A first regeneration process for regenerating the whole of the cation exchange resin bed by generating a downward flow of the regeneration liquid by collecting at the bottom while collecting the liquid at the top; A second regeneration process for regenerating a part of the cation exchange resin bed by generating an upward flow of the regeneration liquid by collecting at an intermediate portion while distributing liquid to the bottom of the cation exchange resin bed; Driven by,
In the second regeneration process, a regeneration liquid amount of 1 to 6 eq / LR is supplied to the hardness leak prevention bed whose depth is set to 100 mm with the bottom of the cation exchange resin bed as a base point. On the other hand, in the softening process after the second regeneration process, raw water having an electric conductivity of 150 mS / m or less and a total hardness of 500 mg CaCO ₃ / L or less is supplied.
The first and / or second reverse osmosis membrane module has a reverse osmosis membrane having a negatively charged skin layer made of a crosslinked wholly aromatic polyamide formed on the membrane surface,
The reverse osmosis membrane has a water permeability coefficient of 1.5 × 10 ⁻¹¹ when a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0, and temperature of 25 ° C. is supplied at an operating pressure of 0.7 MPa and a recovery rate of 15%. m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ or more and the salt removal rate is 99% or more,
Water treatment method. Including a deionization treatment step of deionizing the permeated water obtained in the second reverse osmosis membrane separation step with an electrodeionization module, an ion exchange resin mixed bed tower or a cation exchange resin single bed tower,
The water treatment method according to claim 2. In the cation exchange resin bed tower, after the first regeneration process, the raw water is distributed to the top of the cation exchange resin bed and collected at the bottom to produce a downward flow of the raw water. A first extrusion process for extruding the regenerated liquid; and after the second regeneration process, an upward flow of the raw water is generated by collecting the raw water at the middle while distributing the raw water to the bottom of the cation exchange resin bed. And operated including a second extrusion process for extruding the introduced regenerated liquid,
In the first and second regeneration processes, the regeneration solution is passed through the cation exchange resin bed at a linear velocity of 0.7 to 2 m / h, and in the first and second extrusion processes, the cation exchange resin The raw water is passed through the floor at a linear velocity of 0.7-2 m / h and an extrusion rate of 0.4-2.5 BV.
The water treatment method according to any one of claims 1 to 3. A water softening device for producing soft water by softening raw water in a cation exchange resin bed tower;
A reverse osmosis membrane separation device for separating soft water produced by the hard water softening device into permeated water and concentrated water by a reverse osmosis membrane module;
An electrodeionization module, an ion exchange resin mixed bed tower, or a cation exchange resin single bed tower for deionizing the permeated water obtained by the reverse osmosis membrane separator;
A softening process for producing soft water by passing raw water in a downward flow through a cation exchange resin bed having a depth of 300 to 1500 mm housed in the cation exchange resin bed tower; A first regeneration process for regenerating the entire cation exchange resin bed by generating a downward flow of the regenerated liquid by collecting at the bottom while distributing liquid to the top of the bed; and regenerating after the first regeneration process; A second regeneration process for regenerating a part of the cation exchange resin bed by generating an ascending flow of the regeneration liquid by collecting the liquid at the middle while distributing the liquid to the bottom of the cation exchange resin bed Valve means switchable to
In the second regeneration process, the amount of regeneration liquid that provides a regeneration level of 1 to 6 eq / LR is supplied to a hardness leak prevention bed whose depth is set to 100 mm with the bottom of the cation exchange resin bed as a base point. Regenerating liquid supply means;
In a softening process after the second regeneration process, raw water supply means for supplying raw water having an electric conductivity of 150 mS / m or less and a total hardness of 500 mg CaCO ₃ / L or less,
With
The reverse osmosis membrane module has a reverse osmosis membrane in which a negatively charged skin layer made of a crosslinked wholly aromatic polyamide is formed on the membrane surface,
The reverse osmosis membrane has a water permeability coefficient of 1.5 × 10 ⁻¹¹ when a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0, and temperature of 25 ° C. is supplied at an operating pressure of 0.7 MPa and a recovery rate of 15%. m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ or more and the salt removal rate is 99% or more,
Water treatment system. A water softening device for producing soft water by softening raw water in a cation exchange resin bed tower;
A first reverse osmosis membrane separation device for separating soft water produced by the hard water softening device into permeated water and concentrated water by a first reverse osmosis membrane module;
A second reverse osmosis membrane separation device for further separating the permeated water obtained by the first reverse osmosis membrane separation device into permeated water and concentrated water by a second reverse osmosis membrane module;
A softening process for producing soft water by passing raw water in a downward flow through a cation exchange resin bed having a depth of 300 to 1500 mm housed in the cation exchange resin bed tower; A first regeneration process for regenerating the entire cation exchange resin bed by generating a downward flow of the regenerated liquid by collecting at the bottom while distributing liquid to the top of the bed; and regenerating after the first regeneration process; A second regeneration process for regenerating a part of the cation exchange resin bed by generating an ascending flow of the regeneration liquid by collecting the liquid at the middle while distributing the liquid to the bottom of the cation exchange resin bed Valve means switchable to
In the second regeneration process, the amount of regeneration liquid that provides a regeneration level of 1 to 6 eq / LR is supplied to a hardness leak prevention bed whose depth is set to 100 mm with the bottom of the cation exchange resin bed as a base point. Regenerating liquid supply means;
In a softening process after the second regeneration process, raw water supply means for supplying raw water having an electric conductivity of 150 mS / m or less and a total hardness of 500 mg CaCO ₃ / L or less,
With
The first and / or second reverse osmosis membrane module has a reverse osmosis membrane having a negatively charged skin layer made of a crosslinked wholly aromatic polyamide formed on the membrane surface,
The reverse osmosis membrane has a water permeability coefficient of 1.5 × 10 ⁻¹¹ when a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0, and temperature of 25 ° C. is supplied at an operating pressure of 0.7 MPa and a recovery rate of 15%. m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ or more and the salt removal rate is 99% or more,
Water treatment system. Comprising an electrodeionization module, an ion exchange resin mixed bed tower or a cation exchange resin single bed tower for deionizing the permeated water obtained by the second reverse osmosis membrane separation device,
The water treatment system according to claim 6. The valve means generates a downward flow of the raw water by collecting the raw water at the bottom while distributing the raw water to the top of the cation exchange resin bed after the first regeneration process. After the first extrusion process of extruding; and after the second regeneration process, the raw water is distributed to the bottom of the cation exchange resin bed and collected in the middle part to generate an upward flow of the raw water and introduced. Configured to switch to a second extrusion process for extruding the regenerated liquid,
The regeneration liquid supply means is configured to pass the regeneration liquid through the cation exchange resin bed at a linear velocity of 0.7 to 2 m / h in the first and second regeneration processes.
In the first and second extrusion processes, the raw water supply means passes the raw water through the cation exchange resin bed at a linear velocity of 0.7 to 2 m / h and an extrusion amount of 0.4 to 2.5 BV. Configured to let the
The water treatment system according to any one of claims 5 to 7.

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