JP2020081939A - Water treatment system - Google Patents

Abstract

To provide a water treatment system capable of easily balancing therein the content of sodium hypochlorite contained in feed water for biofilm suppression and the content of a stabilizer contained in feed water to prevent deterioration of a reverse osmosis membrane.SOLUTION: A water treatment system 1 comprises a filtration device 3 for filtering raw water W10 to produce feed water W21, a raw water line L1 for supplying the raw water W10 to the filtration device 3, a reverse osmosis membrane module 14 for separating feed water W22 produced by the filtration device 3 into permeated water W30 and concentrated water W40, a first chemical feeder 4 for injecting a stabilizer into the feed water W21, and a chemical injection control part 30 for adjusting the balance of the molar ratio of a chlorine-based oxidant and the stabilizer in the feed water W21 by adjusting the injection amount of the stabilizer.SELECTED DRAWING: Figure 1

Description

The present invention relates to water treatment systems.

In a water treatment system that performs a membrane filtration process using a reverse osmosis membrane, sodium hypochlorite should be used as a chlorine-based bactericide to remove microorganisms in order to suppress biofilms resulting from the growth of microorganisms. There is.
For example, Patent Document 1 is a water production method using a reverse osmosis membrane, in which sodium hypochlorite is allowed to flow into a reverse osmosis membrane in a water treatment system in order to suppress biofouling due to generation of biofilm. A method of making water is disclosed.

JP, 2016-190214, A

However, if the content of sodium hypochlorite in the feed water flowing through the water treatment system is too high, the reverse osmosis membrane will deteriorate. To prevent deterioration of the reverse osmosis membrane, a stabilizer may be added to the water treatment system, but if the amount of stabilizer added is too large, the degree of biofilm inhibition by sodium hypochlorite will drop too much. I will end up. Therefore, in order to prevent the deterioration of the reverse osmosis membrane while suppressing the biofilm, it is necessary to balance the content of sodium hypochlorite and the content of the stabilizer in the feed water.

The present invention, in the water treatment system, the content of sodium hypochlorite contained in the feed water for biofilm suppression, and the content of the stabilizer contained in the feed water to prevent deterioration of the reverse osmosis membrane. It is an object of the present invention to provide a water treatment system that can be easily balanced.

The present invention relates to a filtration device that filters raw water to generate feed water, a raw water line that supplies the raw water to the filtration device, and a reverse osmosis membrane that separates the feed water generated by the filtration device into permeated water and concentrated water. A module, a water supply line for supplying water to the reverse osmosis membrane module, a permeate line for sending out permeated water separated by the reverse osmosis membrane module, and a concentrated water separated by the reverse osmosis membrane module. Concentrated water line, concentrated drainage line that discharges all or part of the concentrated water as concentrated drainage to the outside of the system, first dosing device for dosing stabilizer with water supply, and dosing of stabilizer The present invention relates to a water treatment system comprising: a chemical injection control unit that adjusts the amount to adjust the balance of the molar ratio of the chlorine-based oxidizer and the stabilizer in the water supply.

Further, a first chlorine concentration measuring device for measuring the chlorine concentration at the outlet of the filtering device is further provided, and the first chemical injection device is a downstream of the first chlorine concentration measuring device, and a stabilizer is chemical-supplied to the water supply. However, it is preferable that the chemical injection control unit adjust the chemical injection amount of the stabilizer based on the chlorine concentration measured by the first chlorine concentration measuring device.

Further, downstream of the chlorine concentration measuring device, a second chemical dosing device for dosing a reducing agent into the water supply is further provided, and the chemical dosing control unit is based on the chlorine concentration measured by the first chlorine concentration measuring device. Therefore, it is preferable to control the dose of the reducing agent.

Further, the reducing agent is preferably any one or more of SBS (sodium bisulfite), sodium sulfite, sodium thiosulfate, and sulfurous acid gas.

Further, downstream of the first chlorine concentration measuring device, a third chemical dispensing device for chemical dosing the bromine compound in the water supply is further provided, and the chemical dispensing control unit is configured to measure the chlorine concentration measured by the first chlorine concentration measuring device. Based on the above, it is preferable to control the dose of the bromine compound.

Further, a fourth chemical injection device for chemical injection of a chlorine-based oxidant into the raw water and/or the feed water is further provided, and the chemical injection control unit is based on the chlorine concentration measured by the first chlorine concentration measuring device, And/or it is preferable to control the dosing of the chlorine-based oxidant to the water supply.

Further, a fifth chemical dosing device for chemical dosing of a stabilizer to raw water is further provided, and the chemical dosing control unit dispenses chemicals to raw water based on the chlorine concentration measured by the first chlorine concentration measuring device. It is preferred to control the dosing of both the stabilizing agent and the stabilizing agent dosed to the water supply.

It further comprises a second chlorine concentration measuring device for measuring the chlorine concentration in the concentrated water line or the concentrated drainage line, wherein the chemical injection control unit, in addition to the chlorine concentration measured by the first chlorine concentration measuring device, 2 It is preferable to control the chemical injection based on the chlorine concentration measured by the chlorine concentration measuring device.

The present invention also provides a filtration device for filtering raw water to generate feed water, a raw water line for supplying raw water to the filtration device, and reverse osmosis for separating the feed water generated by the filtration device into permeated water and concentrated water. Membrane module, water supply line for supplying water to the reverse osmosis membrane module, permeate line for sending permeate separated by the reverse osmosis membrane module, and concentrated water separated by the reverse osmosis membrane module Concentrated water line, a concentrated drainage line for discharging all or part of the concentrated water as concentrated drainage to the outside of the system, an outlet of the filtering device in the water supply line, and/or an oxidation-reduction potential in the concentrated drainage line. Based on the oxidation-reduction potential measured by the potential measuring device, and a first chemicals dispensing device that dispenses a stabilizing agent into the water supply downstream of the potential measuring device. And a chemical injection control unit that adjusts the balance of the molar ratio of the chlorine-based oxidant and the stabilizer in the water supply by controlling the chemical injection amount.

Further, downstream of the potential measuring device, a second chemical dispensing device for chemical dosing of a reducing agent into the water supply is further provided, and the chemical dispensing control unit reduces the redox potential based on the redox potential measured by the potential measuring device. It is preferable to control the dosing amount of the agent.

Further, the reducing agent is preferably any one or more of SBS (sodium bisulfite), sodium sulfite, sodium thiosulfate, and sulfurous acid gas.

Further, downstream of the potential measuring device, a third chemical dispensing device for chemical dosing of a bromine compound in the water supply is further provided, and the chemical dispensing control unit is based on the redox potential measured by the potential measuring device. It is preferable to control the dose of the compound.

Further, a fourth chemical injection device for chemical injection of a chlorine-based oxidant into the raw water and/or the feed water is further provided, and the chemical injection control unit is based on the redox potential measured by the potential measuring device. Alternatively, it is preferable to control the chemical injection of the chlorine-based oxidant into the water supply.

Further, a fifth chemical injection device for chemical dosing of a stabilizer to the raw water is further provided, and the chemical dosing control unit stabilizes the raw water by chemical dosing based on the redox potential measured by the potential measuring device. It is preferable to control the dosing of both the agent and the stabilizer dosed to the water supply.

Further, the reducing agent is preferably any one or more of SBS (sodium bisulfite), sodium sulfite, sodium thiosulfate, and sulfurous acid gas.

Further, further comprising water quality measuring means for measuring the water quality of the feed water, the chemical injection control unit, based on the water quality measured by the water quality measuring means, the molar ratio of the chlorine-based oxidizing agent and the stabilizer in the water supply. It is preferable to adjust the balance and the dosage of the drug.

In addition, it is preferable that the stabilizer contains a chelating component having a blocking action against metal ions, a dispersing action, and/or a polymer.

According to the present invention, in the water treatment system, the content of sodium hypochlorite contained in the feed water for biofilm suppression, and the stabilizer contained in the feed water to prevent deterioration of the reverse osmosis membrane. It becomes possible to easily balance with the content.

It is the whole water treatment system lineblock diagram concerning the embodiment of the present invention. It is a flowchart explaining operation|movement of the water treatment system which concerns on embodiment of this invention.

〔overall structure〕
Hereinafter, a water treatment system 1 which is an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a water treatment system 1 of the present invention.

As shown in FIG. 1, the water treatment system 1 includes a filtration device 3, a first chemical addition device 4, a second chemical addition device 5, a third chemical addition device 6, and a fourth chemical addition device 7, The fifth chemical addition device 8, the first chlorine concentration sensor 9, the second chlorine concentration sensor 10, the water quality sensor 11, the pressure pump 12, the inverter 13, the reverse osmosis membrane module (hereinafter referred to as “RO membrane module 14), a constant flow valve 15, a proportional control drain valve 16, and a control unit 30. Note that the illustration of the electrical connection line between the control unit 30 and the controlled device is omitted.

The water treatment system 1 includes, as lines, a raw water line L1, a water supply line L2, a permeate water line L3, a concentrated water line L4, a circulating water line L5, and a concentrated drainage line L6. The “line” is a general term for lines such as a flow path, a route, and a pipeline in which a fluid can flow. Further, regardless of its origin (source) or its water quality, the water flowing through the raw water line L1 is also referred to as "raw water", and the water flowing through the water supply line L2, the concentrated water line L4 or the circulating water line L5 is referred to as "water supply". The water flowing through the concentrated water line L4, the circulating water line L5, or the concentrated drainage line L6 is also referred to as “concentrated water”.

The raw water line L1 is a line that supplies the raw water W10 toward the filtration device 3. The upstream end of the raw water line L1 is connected to the water source 2 of the raw water W10. The downstream end of the raw water line L1 is connected to the filtration device 3. The raw water line L1 is provided with a fourth chemical addition device 7 and a fifth chemical addition device 8.

The fourth chemical addition device 7 is a device for adding the fourth chemical to the raw water line L1. The fourth drug addition device 7 is electrically connected to the control unit 30.
In the present embodiment, the fourth chemical addition device 7 adjusts the chlorine concentration in the raw water W10 by adding an oxidizing agent as the fourth chemical in order to suppress biofilm deposition in the reverse osmosis membrane module 14. .. In the reverse osmosis membrane module 14, since it is possible to effectively prevent the biofilm from adhering to the surface of the reverse osmosis membrane, examples of the fourth agent include a chlorine-based oxidizing agent such as sodium hypochlorite. .. When the fourth agent is sodium hypochlorite, the amount of sodium hypochlorite added is preferably such that the effective chlorine concentration in the water supply W21 described later is about 0.01 to ₅ mgCl2/L.
For simplicity of explanation, an example in which the fourth agent is sodium hypochlorite will be described below, but the present invention is not limited to this. As another chlorine-based oxidizing agent, for example, liquefied chlorine, bleaching powder, chlorinated isocyanuric acid, etc. may be used.

The fifth chemical addition device 8 is a device for adding the fifth chemical to the raw water line L1. The fifth drug adding device 8 is electrically connected to the control unit 30.
In the present embodiment, the fifth chemical addition device 8 adds a stabilizer as the fifth chemical in order to prevent deterioration of the reverse osmosis membrane provided in the reverse osmosis membrane module 14. By adding the stabilizer, for example, the hypochlorous acid contained in the raw water W10 or the feed water W21 described later becomes the stabilized hypochlorous acid. In the reverse osmosis membrane module 14, since deterioration of the reverse osmosis membrane can be effectively suppressed, examples of the fifth agent include amine compounds, for example, stabilizers such as sulfamic acid. When the fifth agent is sulfamic acid, the addition amount of sulfamic acid is preferably such that the molar ratio of available chlorine derived from hypochlorous acid in the water supply W21:sulfamic acid is about 1:1 to 20. , 1:1.5 to 10 is more preferable. This is because if the sulfamic acid is less than 1 with respect to 1 available chlorine, free chlorine is generated even if the reaction efficiency of both is 100%.
For simplicity of description, an example in which the fifth drug is sulfamic acid is described below, but the present invention is not limited to this.

Further, the stabilizer may contain a chelating component having a blocking action against metal ions, a dispersing action, and/or a polymer.
When a transition metal is present on the surface of the permeated water W30 or the reverse osmosis membrane, even if the substance has a low oxidizing power such as stabilized hypobromite, which will be described later, by coexisting with the oxidizing agent, There is a concern that the action will accelerate the film deterioration. Therefore, in order to suppress the deterioration of the film, a component having a chelating effect and a dispersing effect capable of sequestering a transition metal is compounded and added to the stabilizer.

The filtration device 3 is a device that preliminarily filters the raw water W10, and may be an iron removal/manganese removal device, a sand filtration device, or the like.

The water supply line L2 is a line that supplies the water supplies W21 to W22 toward the reverse osmosis membrane module 14. The water supply line L2 has a first water supply line L21 and a second water supply line L22 from the upstream side to the downstream side.

The upstream end of the first water supply line L21 is connected to the filtration device 3. The downstream end of the first water supply line L21 is connected to the second water supply line L22 and the circulating water line L5 at the connection portion J1. A first chlorine concentration sensor 9, a first chemical addition device 4, a second chemical addition device 5, and a third chemical addition device 6 are provided in the first water supply line L21. Especially, the first chlorine concentration sensor 9 is provided upstream of the first chemical addition device 4, the second chemical addition device 5, and the third chemical addition device 6.

The first chlorine concentration sensor 9 is a device that measures the concentration of free chlorine in the water supply W21 at the outlet of the filtration device 3. The first chlorine concentration sensor 9 is electrically connected to the control unit 30. The free chlorine concentration of the feed water W21 measured by the first chlorine concentration sensor 9 is transmitted to the control unit 30 as a detection signal.

The 1st chemical|medical agent addition apparatus 4 is an apparatus which adds a 1st chemical|medical agent to the water supply line L2. The first drug addition device 4 is electrically connected to the control unit 30.
In the present embodiment, the first chemical addition device 4 adds a stabilizer as the first chemical in order to prevent deterioration of the reverse osmosis membrane provided in the reverse osmosis membrane module 14. By adding the stabilizer, for example, hypochlorous acid contained in the water W21 becomes stabilized hypochlorous acid. In the reverse osmosis membrane module 14, since deterioration of the reverse osmosis membrane can be effectively suppressed, examples of the first drug include amine compounds, for example, stabilizers such as sulfamic acid. When the first agent is sulfamic acid, the addition amount of sulfamic acid is preferably such that the molar ratio of effective chlorine derived from hypochlorous acid in the water supply W21:sulfamic acid is about 1:1 to 20. , 1:1.5 to 10 is more preferable. This is because if the sulfamic acid is less than 1 with respect to 1 available chlorine, free chlorine is generated even if the reaction efficiency of both is 100%.
For simplicity of description, an example in which the first drug is sulfamic acid will be described below, but the present invention is not limited to this.

Further, the stabilizer may contain a chelating component having a blocking action against metal ions, a dispersing action, and/or a polymer.

The second chemical addition device 5 is a device that adds the second chemical to the water supply line L2. The second drug addition device 5 is electrically connected to the control unit 30.
In the present embodiment, the second chemical addition device 5 adds a reducing agent as the second chemical in order to prevent deterioration of the reverse osmosis membrane of the reverse osmosis membrane module 14. By adding the reducing agent, the chlorine concentration contained in the water supply W21 is reduced to an appropriate concentration. Examples of the second agent include reducing agents such as SBS (NaHSO ₃ : sodium bisulfite), sodium sulfite, sodium thiosulfate, and sulfurous acid gas. For simplicity of description, an example in which the second drug is SBS will be described below, but the present invention is not limited to this.

The third chemical addition device 6 is a device that adds the third chemical to the water supply line L2. The third drug adding device 6 is electrically connected to the control unit 30.
In the present embodiment, the third chemical addition device 6 adds a bromine compound in order to further reduce the damage given to the reverse osmosis membrane provided in the reverse osmosis membrane module 14. The addition of the bromine compound indirectly produces stabilized hypobromite, and the reaction of hypobromite and sulfamic acid finally produces the brominated sulfamic acid compound. Examples of the third agent include bromine compounds such as sodium bromide. The addition amount of the bromine compound is preferably such that the molar ratio of available chlorine derived from hypochlorous acid in the feed water W21:bromine compound is about 1:1 to 10, more preferably about 1:1 to 2. Good.
For simplicity of description, an example in which the third agent is sodium bromide will be described below, but the present invention is not limited to this.

The water quality sensor 11 measures the water quality of the water supply W21. The water quality sensor 11 is electrically connected to the control unit 30.
In the present embodiment, the water quality sensor 11 uses TOC (Total Organic Carbon), COD (Chemical Oxygen Demand), and BOD (Biochemical Oxygen Demand) as the water quality of the water supply W21. At least one of the amount of organic matter such as oxygen demand), AOC (Assimilable Organic Carbon), and the amount of microorganisms such as the number of bacteria and the number of ATP is measured. The control unit 30 receives these measured values from the water quality sensor 11, predicts the biofilm risk using the received measured values, and stabilizes the chlorine-based oxidizer in the water supply W21 with the oxidizer based on the predicted biofilm risk. In order to adjust the balance of the molar ratio of the agent and the drug dose, the drug doses of the first drug to the fifth drug to the water supply W21 are set.

Alternatively, the water quality sensor 11 may measure the concentration of the reducing substance contained in the water supply W21 as the water quality of the water supply W21. Specifically, the water quality sensor 11 is configured such that metal ions such as iron ions and manganese ions that are reducing substances, ion concentrations such as nitrite ions, the amount of ammoniacal nitrogen (nitrogen in ammonia ions), or SBS ( The concentration of sodium bisulfite: NaHSO ₃ ) or the like is measured. The control unit 30 receives the measured values of these reducing substance concentrations from the water quality sensor 11, and uses the received measured values to adjust the balance of the molar ratio of the chlorine-based oxidizing agent and the stabilizer in the water W21. , The amount of addition of the first to fifth chemicals to the water supply W21 is set.

The upstream end of the second water supply line L22 is connected to the connecting portion J1. The downstream end of the second water supply line L22 is connected to the primary inlet port of the reverse osmosis membrane module 14. The pressurizing pump 12 is provided in the second water supply line L22.

The pressurizing pump 12 is a device that sucks in the water W22 and feeds (discharges) it toward the reverse osmosis membrane module 14. The pressurizing pump 12 is supplied with drive power whose frequency is converted from the inverter 13. The pressurizing pump 12 is driven at a rotation speed according to the frequency (hereinafter, also referred to as “driving frequency”) of the supplied (input) driving power.

The inverter 13 is an electric circuit (or a device having the circuit) that supplies the pressurizing pump 12 with drive power whose frequency has been converted. The inverter 13 is electrically connected to the control unit 30. A command signal is input to the inverter 13 from the control unit 30. The inverter 13 outputs to the pressurizing pump 12 drive power having a drive frequency corresponding to the command signal (current value signal or voltage value signal) input by the control unit 30.

The water supply W22 is supplied to the reverse osmosis membrane module 14 via the pressure pump 12. The water supply W22 includes water supply W21 and circulating water W50 (described later).

The reverse osmosis membrane module 14 is equipment for separating the feed water W22 into permeated water W30 and concentrated water W40. More specifically, the reverse osmosis membrane module 14 performs a membrane separation process on the feed water W22 discharged from the pressurizing pump 12 into permeated water W30 from which dissolved salts have been removed and concentrated water W40 from which dissolved salts have been concentrated. Is. The reverse osmosis membrane module 14 includes a single or a plurality of reverse osmosis membrane elements (not shown). The reverse osmosis membrane module 14 membrane-separates the feed water W22 with these reverse osmosis membrane elements to produce permeated water W30 and concentrated water W40.

The permeated water line L3 is a line for sending out the permeated water W30 separated by the reverse osmosis membrane module 14. The upstream end of the permeate line L3 is connected to the secondary port of the reverse osmosis membrane module 14. The downstream end of the permeated water line L3 is connected to a storage tank (not shown).

The concentrated water line L4 is a line through which the concentrated water W40 separated by the reverse osmosis membrane module 14 flows. The upstream end of the concentrated water line L4 is connected to the secondary port of the reverse osmosis membrane module 14. Further, the downstream side of the concentrated water line L4 is branched into a circulating water line L5 and a concentrated drainage line L6 at the connection portion J2.

The circulating water line L5 is a line that is connected to the concentrated water line L4 and returns concentrated water (circulating water W50) as water supply to the water supply line L2. In the present embodiment, the circulating water line L5 is a line for returning (circulating) the concentrated water W40 flowing through the concentrated water line L4 to the upstream side of the pressure pump 12 in the water supply line L2 as the circulating water W50. The upstream end of the circulating water line L5 is connected to the concentrated water line L4 at the connection portion J2. Further, the downstream end of the circulating water line L5 is connected to the water supply line L2 at the connecting portion J1. A constant flow valve 15 is provided in the circulating water line L5.

The constant flow valve 15 is a device that adjusts the flow rate of the circulating water W50 flowing through the circulating water line L5 so as to maintain it at a predetermined constant flow rate value. The “constant flow rate value” held in the constant flow rate valve 15 is a concept having a range of constant flow rate values, and is not limited to the target flow rate value in the constant flow rate valve. For example, in consideration of the characteristics of the constant flow rate mechanism (for example, the temperature characteristics due to the material and structure), those having an adjustment error of about ±10% with respect to the target flow rate value of the constant flow rate valve are included. The constant flow rate valve 15 holds a constant flow rate value without requiring auxiliary power or external operation, and is, for example, one called by the name of water governor. The constant flow valve 15 may be operated by auxiliary power or an external operation to maintain a constant flow value.

The concentrated drainage line L6 is a line which is connected to the concentrated water line L4 and discharges the concentrated water as the concentrated drainage W60 out of the system. In the present embodiment, the concentrated drainage line L6 is connected to the concentrated water line L4 at the connection portion J2, and the concentrated water W40 separated by the reverse osmosis membrane module 14 is discharged outside the system (outside the system) as concentrated drainage W60. It is a line to do. The concentrated drainage line L6 is provided with the second chlorine concentration sensor 10 and the proportional control drainage valve 16.

The second chlorine concentration sensor 10 is a device that measures the combined chlorine concentration in the concentrated wastewater W60 in the concentrated wastewater line L6. The second chlorine concentration sensor 10 is electrically connected to the control unit 30. The combined chlorine concentration of the concentrated waste water W60 measured by the second chlorine concentration sensor 10 is transmitted to the control unit 30 as a detection signal.

The proportional control drainage valve 16 is a valve that adjusts the flow rate of the concentrated drainage W60 discharged from the concentrated drainage line L6 to the outside of the apparatus. The proportional control drain valve 16 is electrically connected to the control unit 30. The valve opening degree of the proportional control drain valve 16 is controlled by a drive signal transmitted from the control unit 30. By sending a current value signal (for example, 4 to 20 mA) from the control unit 30 to the proportional control drain valve 16 to control the valve opening, the drainage flow rate of the concentrated drainage W60 can be adjusted.

The control unit 30 is composed of a microprocessor (not shown) including a CPU and a memory. In the control unit 30, the CPU of the microprocessor executes various controls related to the water treatment system 1 according to a predetermined program read from the memory. Hereinafter, some of the functions of the control unit 30 will be described.

The control unit 30 is based on the chlorine concentration measured by the first chlorine concentration sensor 9 and/or the second chlorine concentration sensor 10, and the chemical injection amount of the stabilizer added by the first chemical addition device 4, 2 Dosing amount of the reducing agent added by the drug addition device 5, dosing amount of the bromine compound added by the third drug addition device 6, and dosing of the chlorine-based oxidizing agent added by the fourth drug addition device 7. As a chemical injection control unit which adjusts the balance of the molar ratio of the chlorine-based oxidizer and the stabilizer in the water supply W21 by adjusting the amount and the chemical injection amount of the stabilizer added by the fifth chemical addition device 8. Perform the function of. In the present specification, the "free chlorine concentration" measured by the first chlorine concentration sensor 9 and the "combined chlorine concentration" measured by the second chlorine concentration sensor are collectively referred to as "chlorine concentration".

When the control unit 30 uses both the chlorine concentration of the free chlorine measured by the first chlorine concentration sensor 9 and the combined chlorine concentration measured by the second chlorine concentration sensor 10, for example, both Of these chlorine concentrations, only the higher or lower chlorine concentration may be used.

In the present embodiment, for example, the chlorine concentration region measured by the first chlorine concentration sensor 9 and/or the second chlorine concentration sensor 10 is changed from the low concentration region to the high concentration region in order of the first region, When the chlorine concentration is in the first region when divided into the second region, the third region, and the fourth region, the control unit 30 controls the fourth chemical addition device 7 so that the water in the water supply W21. In order to raise the concentration of stabilized hypochlorous acid to an appropriate value, the chemical injection amount of chlorine-based oxidizer is increased, and the first chemical addition device 4 and the fifth chemical addition device 8 are controlled to supply water W21. The stabilizer may be adjusted in dosage so that no free chlorine remains in the solution.

When the chlorine concentration is in the second region, the control unit 30 controls the first chemical addition device 4 and the fifth chemical addition device 8 to stabilize the free water W21 so that no free chlorine remains in the water W21. The dosing amount of the agent may be adjusted.

Further, when the chlorine concentration is in the third region, the control unit 30 controls the third chemical addition device 6 to reduce damage to the reverse osmosis membrane of the reverse osmosis membrane module 14, so that the water supply W21. The amount of the bromine compound to the water is controlled and the first chemical addition device 4 and the fifth chemical addition device 8 are controlled to prevent the free chlorine from remaining in the water supply W21. May be adjusted.

Further, when the chlorine concentration is in the fourth region, the control unit 30 controls the second chemical addition device 5 to reduce the chlorine concentration in the water supply W21 to an appropriate value, so that the reducing agent for the water supply W21 is reduced. By controlling the first chemical addition device 4 and the fifth chemical addition device 8 together with the start of the chemical dosing, even if the dose of the stabilizer is adjusted so that free chlorine is not left in the water supply W21. Good.

Note that the above control contents are merely examples, and the present invention is not limited to this. For example, when the chlorine concentration is in any of the second to fourth regions, the control unit 30 may control the fourth chemical addition device 7 to reduce the chemical injection amount of the chlorine-based oxidant. ..

[Operation of the Invention]
Hereinafter, an operation example of the water treatment system 1 according to the embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a flowchart showing the operation of the water treatment system 1 of the present invention.
In the following, the first region is a region having a chlorine concentration of less than C ₁ , the second region is a region having a chlorine concentration of C ₁ or more and less than C ₂ , and the third region is a chlorine concentration of C ₁ or less. The region is ₂ or more and less than C ₃ , and the fourth region is a region having a chlorine concentration of C ₃ or more.

Table 1 below shows setting examples of C _{1 to} C ₃ . It is considered that the control concentration in the concentrated water is preferably 0.5 to 2.0 mg/L as the effective chlorine concentration. The concentration in the water supply is a value obtained by dividing this value by the concentration ratio, but assuming that the recovery rate is 50 to 80%, the concentration ratio is 2 to 5 times. This is based on the mathematical formula of concentration ratio=1/(1-recovery rate).

In step S1, if the chlorine concentration measured by the first chlorine concentration sensor 9 and/or the second chlorine concentration sensor 10 is less than C ₁ (S1: YES), the process proceeds to step S2. When the chlorine concentration measured by the first chlorine concentration sensor 9 or the second chlorine concentration sensor 10 is C ₁ or more (S1:NO), the process proceeds to step S3.

In step S2, the control unit 30 controls the fourth chemical addition device 7 to increase the chemical injection amount of the chlorine-based oxidant and controls the first chemical addition device 4 and the fifth chemical addition device 8. As a result, the dosage of the stabilizer is adjusted so that free chlorine does not remain in the water supply W21. Then, the process proceeds to step S1 (return).

In step S3, when the chlorine concentration measured by the first chlorine concentration sensor 9 or the second chlorine concentration sensor 10 is C ₁ or more and less than C ₂ (S3: YES), the process proceeds to step S4. When the chlorine concentration measured by the first chlorine concentration sensor 9 or the second chlorine concentration sensor 10 is C ₂ or more (S3: NO), the process proceeds to step S5.

In step S4, the control unit 30 controls the first chemical addition device 4 and the fifth chemical addition device 8 to adjust the chemical injection amount of the stabilizer so as not to leave free chlorine in the water supply W21. Then, the process proceeds to step S1 (return).

In step S5, when the chlorine concentration measured by the first chlorine concentration sensor 9 and/or the second chlorine concentration sensor 10 is C ₂ or more and less than C ₃ (S5: YES), the process proceeds to step S6. .. If chlorine concentration measured by the first chlorine concentration sensor 9 or the second chlorine concentration sensor 10 is C ₃ or more: in (S5 NO), the process proceeds to step S7.

In step S6, the control unit 30 controls the third chemical addition device 6 to increase the chemical injection amount of the bromine compound to the water supply W21, and at the same time, controls the first chemical addition device 4 and the fifth chemical addition device 8. By controlling, the chemical injection amount of the stabilizer is adjusted so that free chlorine is not left in the water supply W21. Then, the process proceeds to step S1 (return).

In step S7, the control unit 30 controls the second chemical addition device 5 to start the chemical dosing of the reducing agent to the water supply W21 and controls the first chemical addition device 4 and the fifth chemical addition device 8. By doing so, the chemical dosage of the stabilizer is adjusted so that free chlorine does not remain in the water supply W21. Then, the process proceeds to step S1 (return).

[Effects of this embodiment]
According to the water treatment system 1 of the present embodiment described above, for example, the following effects are achieved.
The water treatment system 1 of the present invention permeates the filtration device 3 that filters the raw water W10 to generate the feed water W21, the raw water line L1 that supplies the raw water W10 to the filtration device 3, and the feed water W21 generated by the filtration device 3. Reverse osmosis membrane module 14 for separating water W30 and concentrated water W40, water supply line L2 for supplying feed water W22 to the reverse osmosis membrane module, and permeate line for sending permeate W30 separated by reverse osmosis membrane module 14. L3, a concentrated water line L4 for sending the concentrated water W40 separated by the reverse osmosis membrane module 14, a concentrated drainage line L6 for discharging all or a part of the concentrated water W40 as concentrated drainage W60 to the outside of the system, and a water supply By adjusting the first chemical addition device 4 for injecting the stabilizer to W21 and the amount of the stabilizer to be injected, the balance of the molar ratio of the chlorine-based oxidant and the stabilizer in the water W21 is adjusted. And a control unit 30.

When the feed water filtered by the filtration device 3 is used as the feed water to the reverse osmosis membrane module, the fluctuation of the residual chlorine concentration in the feed water after filtration becomes large. The chlorine concentration in the preceding stage of the reverse osmosis membrane module can be adjusted to an appropriate value by adjusting the chemical injection of the stabilizer. Furthermore, in particular, compared to the method of removing free chlorine in a stage subsequent to the filtration device, it becomes possible to simplify chemical injection and reduce the amount of chemicals used in the entire system.

Further, the water treatment system 1 further includes a first chlorine concentration sensor 9 that measures the chlorine concentration at the outlet of the filtration device 3, and the first chemical addition device 4 is connected to the water supply W21 downstream of the first chlorine concentration sensor 9. The stabilizer is dosed, and the control unit 30 adjusts the dose of the stabilizer based on the chlorine concentration measured by the first chlorine concentration sensor 9.

By adjusting the chemical injection of the stabilizer based on the chlorine concentration at the outlet of the filtration device, the chlorine concentration in the preceding stage of the reverse osmosis membrane module can be set to an appropriate value.

The water treatment system 1 further includes a second chemical addition device 5 downstream of the first chlorine concentration sensor 9 for injecting a reducing agent into the water supply W21, and the control unit 30 measures with the first chlorine concentration sensor 9. The dosing amount of the reducing agent is controlled based on the chlorine concentration.

When the chlorine concentration at the outlet of the filtration device is too high, by adding a reducing agent to the feed water, it becomes possible to feed the feed water containing a predetermined concentration of residual chlorine to the reverse osmosis membrane module.

Further, the reducing agent is any one or more of SBS (sodium bisulfite), sodium sulfite, sodium thiosulfate, and sulfurous acid gas.

By using any one or more of SBS (sodium bisulfite), sodium sulfite, sodium thiosulfate, and sulfurous acid gas as a reducing agent, it is possible to supply the reverse osmosis membrane module with feed water containing residual chlorine at a predetermined concentration. It will be possible.

In addition, the water treatment system 1 further includes a third chemical addition device 6 for injecting a bromine compound into the water supply W21 downstream of the first chlorine concentration sensor 9, and the control unit 30 measures with the first chlorine concentration sensor 9. The dose of bromine compound is controlled based on the chlorine concentration.

By pouring a bromine compound and switching the stabilizer from chlorine to bromine, the oxidizing power of the feed water is weakened, and the degree of deterioration of the reverse osmosis membrane can be reduced.

In addition, the water treatment system 1 further includes a fourth chemical addition device 7 for chemical injection of a chlorine-based oxidant into the raw water W10, and the control unit 30 determines, based on the chlorine concentration measured by the first chlorine concentration sensor 9, Control the chemical injection of the chlorine-based oxidizer into the raw water W10.

If the chlorine concentration at the outlet of the filtration device is too high or too low, by controlling the chemical injection of the chlorine-based oxidizer based on the chlorine concentration at the outlet of the filtration device, the free chlorine in the preceding stage of the reverse osmosis membrane module It is possible to set the density to an appropriate value.

The water treatment system 1 further includes a fifth chemical addition device 8 for injecting a stabilizer into the raw water W10, and the control unit 30 controls the raw water based on the chlorine concentration measured by the first chlorine concentration sensor 9. Both the stabilizing agent dosed to W10 and the stabilizing agent dosed to the water supply W21 are controlled.

Since there are many pipes and tanks in the system, free chlorine volatilizes when the residence time of raw water is long. By using free chlorine as a bound substance such as stabilized hypochlorous acid, the inside of the system can be kept cleaner.

The water treatment system 1 further includes a second chlorine concentration sensor 10 for measuring the chlorine concentration in the concentrated water line L4 or the concentrated drainage line L6, and the control unit 30 controls the chlorine concentration measured by the first chlorine concentration sensor 9. In addition, the chemical injection is controlled based on the chlorine concentration measured by the second chlorine concentration sensor 10.

Not only the chlorine concentration measured by the first chlorine concentration sensor 9, but also the reducing agent/stabilizing agent/bromine compound chemical addition device, and further the concentrated water line L4 or the concentrated drainage line after the reverse osmosis membrane module 14. By controlling the chemical injection based on the chlorine concentration in L6 as well, it becomes possible to more appropriately adjust the balance of the chemical injection amount of each drug.

Further, the stabilizer may contain a chelating component having a blocking action against metal ions, a dispersing action, and/or a polymer.

It is considered that the film deterioration can be reduced by increasing the amount of the stabilizer added, but when the transition metal acts as a catalyst to accelerate the deterioration, this is not sufficient, and the chelate effect and the dispersion effect on the above metals are not sufficient. The addition of the component having γ can block the transition metal and further suppress the deterioration of the film. In particular, when it is added at the same ratio as the stabilizer, an increase in the addition amount can enhance the blocking effect on the transition metal, and the complementary effect can reduce the film deterioration.
Further, the chelating component having a sequestering and dispersing action for metal ions, besides having a sequestering action for the transition metal, also plays a role of preventing the metal from precipitating beyond its solubility. This makes it possible to suppress the biofilm and at the same time prevent the membrane from being clogged due to the generation of metal scale.
When a biofilm and scale are produced in a complex manner, the biofilm structure tends to be strengthened by using the scale component as a binder, but with the above scale inhibition effect, it prevents the formation of a strong biofilm. Further, by combining with the biofilm suppressing effect of stabilized hypobromite, a further biofilm suppressing effect is expected.
Furthermore, the chelating component itself has a bactericidal effect and an antiseptic effect by the action of depriving essential metals necessary for the habitation of bacteria and the action of disrupting cells by reacting with intracellular metals. It is expected that the storage stability of the biofilm will be improved, and at the time of addition to the water to be treated, it will act in a complementary manner with the stabilized hypobromite to further enhance the biofilm suppression effect.

[Modification]
Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be implemented in various forms.

[Modification 1]
The water treatment system 1 is provided with the first chlorine concentration sensor 9 and the second chlorine concentration sensor 10, and the control unit 30 as a chemical injection control unit performs chemical injection based on the chlorine concentration measured by these sensors. Controlled, but not limited to. For example, the water treatment system 1 includes a potential measuring device installed in the raw water line L1 instead of the first chlorine concentration sensor 9, and a potential installed in the concentrated drainage line L6 instead of the second chlorine concentration sensor 10. A measuring device may be provided. Further, the control unit 30 as the drug injection control unit may control the drug injection based on the redox potential measured by these potential measuring devices.

[Modification 2]
The water treatment system 1 may have a configuration different from that of the above embodiment. For example, although the circulating water line L5 is provided in the above, the configuration is not limited to this, and the circulating water line L5 may not be provided. In addition, the water treatment system 1 may be configured without the third chemical addition device 6 for chemical injection of a bromine compound. Further, the water treatment system 1 may be configured without the fifth chemical addition device 8 for chemical dosing of the stabilizer. In addition, in the water treatment system 1, the fourth chemical addition device 7 for injecting a chlorine-based oxidizing agent may be provided in the water supply line L2 instead of the raw water line L1. Further, the water treatment system 1 may be configured to have only one of the first chlorine concentration sensor 9 and the second chlorine concentration sensor 10.

[Modification 3]
Further, the water treatment systems 1 and 1A are more suitable when a chlorine-resistant film is used, because they are less susceptible to the influence of film deterioration. By using it together with the above-mentioned chemical injection adjustment method, the influence of deterioration can be further reduced. As the chlorine resistant film, for example, there is one manufactured using a polyamide-based material.

[Modification 4]
Further, in the water treatment systems 1 and 1A, it is preferable that the membrane cleaning step is also performed by using the water supply to which the chemical is added. The membrane cleaning step includes flushing and the like, but the concentrated water line may be connected to a water supply line to pass water.

[Modification 5]
Further, in the water treatment systems 1 and 1A, from the viewpoint of preventing deterioration, in order to reduce the amount of contact between chlorine and the membrane, the above-mentioned chemicals may be added intermittently only when the biofilm is generated.

[Modification 6]
In addition, in the water treatment systems 1 and 1A, in order to suppress microbial growth during suspension of the system, it is preferable to add the above-mentioned chemicals before suspension of the system.

1 water treatment system,
3 Filtration device 4 First chemical addition device (first chemical injection device)
5 Second chemical addition device (second chemical injection device)
6 Third chemical addition device (third chemical injection device)
7 4th chemical addition device (4th chemical injection device)
8 Fifth chemical addition device (fifth chemical injection device)
9 First chlorine concentration sensor (first chlorine concentration measuring device)
10 Second chlorine concentration sensor (second chlorine concentration measuring device)
11 Water quality sensor (water quality measuring means)
12 Pressurizing pump 14 Reverse osmosis membrane module 30 Control unit (medicine injection control unit)
L1 raw water line L2 water supply line,
L3 permeated water line L4 concentrated water line,
L5 circulating water line L6 concentrated drainage line,
L21 First water supply line L22 Second water supply line

Claims (16)

A filtration device that filters raw water to generate water supply,
A raw water line for supplying raw water to the filtration device,
A reverse osmosis membrane module that separates the feed water generated by the filtration device into permeated water and concentrated water,
A water supply line for supplying water to the reverse osmosis membrane module,
A permeate line for delivering permeate separated by the reverse osmosis membrane module;
A concentrated water line for delivering the concentrated water separated by the reverse osmosis membrane module,
A concentrated drainage line that discharges all or part of the concentrated water as concentrated drainage to the outside of the system,
A first dosing device for dosing a stabilizer to water supply;
A water treatment system comprising: a chemical injection control unit that adjusts the molar ratio of the chlorine-based oxidizing agent and the stabilizer in the water supply by adjusting the chemical injection amount of the stabilizer. Further comprising a first chlorine concentration measuring device for measuring the chlorine concentration at the outlet of the filtration device,
The first chemical injection device, in the downstream of the first chlorine concentration measurement device, chemicals a stabilizer to the water supply,
The water treatment system according to claim 1, wherein the chemical injection control unit adjusts the chemical injection amount of the stabilizer based on the chlorine concentration measured by the first chlorine concentration measuring device. Downstream of the first chlorine concentration measuring device, further comprising a second chemical dosing device for dosing a reducing agent into the water supply,
The water treatment system according to claim 2, wherein the chemical injection control unit controls the chemical injection amount of the reducing agent based on the chlorine concentration measured by the first chlorine concentration measuring device. The water treatment system according to claim 3, wherein the reducing agent is any one or more of SBS (sodium bisulfite), sodium sulfite, sodium thiosulfate, and sulfurous acid gas. Downstream of the first chlorine concentration measuring device, further comprises a third chemical injection device for chemical injection of bromine compound into the feed water,
The water treatment system according to claim 2, wherein the chemical injection control unit controls the chemical injection amount of the bromine compound based on the chlorine concentration measured by the first chlorine concentration measuring device. .. Further comprising a fourth chemical injection device for chemical injection of chlorine-based oxidant into raw water and/or feed water,
The chemical injection control unit controls chemical injection of a chlorine-based oxidant to raw water and/or feed water based on the chlorine concentration measured by the first chlorine concentration measuring device, any one of claims 2 to 5. The water treatment system according to item 1. Further comprising a fifth chemical dosing device for dosing a stabilizer into raw water,
The chemical-dose control unit, based on the chlorine concentration measured by the first chlorine-concentration measuring device, supplies both the stabilizer that is dosed to the raw water and the stabilizer that is dosed to the water supply. The water treatment system according to any one of claims 2 to 6, which controls water. Further comprising a second chlorine concentration measuring device for measuring the chlorine concentration in the concentrated water line or the concentrated drainage line,
The chemicals control unit controls chemicals based on the chlorine concentration measured by the second chlorine concentration measuring device in addition to the chlorine concentration measured by the first chlorine concentration measuring device, The water treatment system according to any one of 1. A filtration device that filters raw water to generate water supply,
A raw water line for supplying raw water to the filtration device,
A reverse osmosis membrane module that separates the feed water generated by the filtration device into permeated water and concentrated water,
A water supply line for supplying water to the reverse osmosis membrane module,
A permeate line for delivering permeate separated by the reverse osmosis membrane module;
A concentrated water line for delivering the concentrated water separated by the reverse osmosis membrane module,
A concentrated drainage line that discharges all or part of the concentrated water as concentrated drainage to the outside of the system,
An outlet for the filtering device in the water supply line, and/or a potential measuring device for measuring a redox potential in the concentrated drainage line,
A first dosing device for dosing a stabilizer to the water supply downstream of the potential measuring device;
Based on the oxidation-reduction potential measured by the potential measuring device, by controlling the dosage of the stabilizer, the chemical adjusting the balance of the molar ratio of the chlorine-based oxidizer and the stabilizer in the water supply. A water treatment system comprising: a controller. Downstream of the potential measuring device, a second chemical injection device for chemical injection of a reducing agent into the water supply is further provided,
The water treatment system according to claim 9, wherein the chemical injection control unit controls the chemical injection amount of the reducing agent based on the redox potential measured by the potential measuring device. The water treatment system according to claim 10, wherein the reducing agent is any one or more of SBS (sodium bisulfite), sodium sulfite, sodium thiosulfate, and sulfurous acid gas. Downstream of the potential measuring device, further comprises a third chemical dosing device for dosing a bromine compound into the water supply,
The water treatment system according to claim 9, wherein the chemical injection control unit controls the chemical injection amount of the bromine compound based on the oxidation-reduction potential measured by the potential measuring device. Further comprising a fourth chemical injection device for chemical injection of chlorine-based oxidant into raw water and/or feed water,
13. The chemical injection control unit controls chemical injection of a chlorine-based oxidant into raw water and/or feed water based on the oxidation-reduction potential measured by the electric potential measuring device, any one of claims 9 to 12. Water treatment system described in. Further comprising a fifth chemical dosing device for dosing a stabilizer into raw water,
The chemical injection control unit controls both chemical injection of a stabilizer that is dosed to raw water and a stabilizer that is dosed to water supply based on the redox potential measured by the potential measuring device. The water treatment system according to any one of claims 9 to 13. Further comprising water quality measuring means for measuring the water quality of the water supply,
The said chemical-feeding control part adjusts the balance of the molar ratio of the chlorine-based oxidizer and the stabilizer in the said water supply, and the chemical-dose amount based on the water quality measured by the said water-quality measuring means, 15. The water treatment system according to any one of 1. The water treatment system according to any one of claims 1 to 15, wherein the stabilizer contains a chelating component having a blocking action on metal ions, a dispersing action, and/or a polymer.

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