JP2020082020A - Water treatment system - Google Patents

Abstract

To easily balance the injection amount of sodium hypochlorite injected for biofilm suppression and eventually the adjusted amount of free chlorine concentration in feed water, and the injection amount of a stabilizer added to prevent deterioration of a reverse osmosis membrane.SOLUTION: A water treatment system 1 comprises: a reverse osmosis membrane module 14 for separating feed water W11 into permeated water W20 and concentrated water W30, a stabilizer injection device 3 for injecting a stabilizer into the feed water W11, a potential measuring device 5 for measuring oxidation-reduction potential of a feed water line L1 or a concentrated waste water line L5, and a chemical concentration adjusting part 33 for adjusting the balance of the concentration of free chlorine and the concentration of the stabilizer in the feed water W11 by controlling the injection amount of the stabilizer into the feed water W11 based on the oxidation-reduction potential measured by the potential measuring device 5.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, chemical dosing of sodium hypochlorite into the water treatment system degrades the reverse osmosis membrane. 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 dosage of sodium hypochlorite and the dosage of stabilizer that are dosed to the water treatment system. There is.

The present invention, the dose of sodium hypochlorite dosed for biofilm suppression, and the balance of the dose of stabilizers dosed to prevent deterioration of the reverse osmosis membrane, It is an object to provide a water treatment system that can be easily taken.

The water treatment system according to the present invention comprises a reverse osmosis membrane module for separating feed water into permeated water and concentrated water, a water supply line for supplying feed water to the reverse osmosis membrane module, and a permeation separated by the reverse osmosis membrane module. A permeated water line for sending out water, a concentrated water line for sending out concentrated water separated by the reverse osmosis membrane module, and a concentrated drainage line for discharging a part or all of the concentrated water as concentrated drainage to the outside of the system. , A stabilizer dosing device for dosing a stabilizer in water supply, a potential measuring device for measuring the redox potential of the water supply line or the concentrated drainage line, and a redox potential measured by the potential measuring device. Based on the above, a drug concentration adjusting unit is provided for adjusting the balance between the concentration of free chlorine in the feed water and the concentration of the stabilizer by controlling the chemical injection amount of the stabilizer to the feed water.

The water treatment system further includes a target setting unit that sets a target potential that is a target value of the oxidation-reduction potential, and the measured value of the oxidation-reduction potential is equal to or higher than a first threshold value lower than the target potential, and If the second threshold value is higher than the target potential and is equal to or lower than the second threshold value, the drug concentration adjusting unit adjusts the balance by adjusting the chemical injection amount of the stabilizer, and the measured value of the redox potential is the first value. When it is less than the threshold value or exceeds the second threshold value, the drug concentration adjusting unit preferably adjusts the balance by adjusting the free chlorine concentration.

The water treatment system further includes a target setting unit that sets a target potential range including the target value of the oxidation-reduction potential, and the actually measured value of the oxidation-reduction potential is lower than the first threshold value. Above, and, when the lower limit value of the target potential range or less, the drug concentration adjusting unit adjusts the balance by adjusting the chemical injection amount of the stabilizer, the measured value of the redox potential, When in the target potential range, the drug concentration adjusting unit maintains the chemical injection amount and the free chlorine concentration of the stabilizer, the measured value of the redox potential is the upper limit value or more of the target potential range, And when it is less than or equal to the second threshold value higher than the target potential range, the drug concentration adjusting unit adjusts the balance by adjusting the chemical injection amount of the stabilizer, and the measured value of the redox potential is When it is less than the first threshold value or exceeds the second threshold value, it is preferable that the drug concentration adjusting unit adjusts the balance by adjusting the free chlorine concentration.

Further, the above water treatment system includes a pH measuring unit that measures the pH of the feed water or the concentrated waste water, and a redox potential correction unit that corrects the actual measurement value of the redox potential based on the pH measured by the pH measuring unit. Preferably, the drug concentration adjusting unit adjusts the balance between the adjusted amount of the free chlorine concentration and the dose of the stabilizer, based on the corrected redox potential.

Further, the water treatment system further comprises a free chlorine concentration adjusting means for adjusting the free chlorine concentration in the feed water, the drug concentration adjusting unit, based on the redox potential measured by the potential measuring device, Further, it is preferable to adjust the balance between the free chlorine concentration in the feed water and the concentration of the stabilizer by controlling the free chlorine concentration in the feed water.

Further, it is preferable that the water treatment system further includes, as the free chlorine concentration adjusting means, an oxidant chemical injection device for chemical injection of a chlorine-based oxidant into the feed water.

The water treatment system preferably further includes, as the free chlorine concentration adjusting means, a reducing agent dosing device for dosing a reducing agent into the feed water.

Further, the stabilizer preferably contains an amine compound.

Further, the amine compound is preferably a sulfamic acid compound.

Further, it is preferable that the stabilizer further contains a bromine compound.

Further, the water treatment system further comprises a silica concentration detection device for detecting the silica concentration in the permeate, when the silica concentration detected by the silica concentration detection device is a predetermined threshold or more, the drug concentration The adjusting unit preferably adjusts the concentration of the drug in the feed water so as to weaken the oxidizing power of the free chlorine and the stabilizer.

Further, it is preferable that the target setting unit sets the target value based on the silica concentration detected by the silica concentration detecting device.

Further, the water treatment system further comprises water quality measuring means for measuring the water quality of the feed water, wherein the drug concentration adjusting section is based on the water quality measured by the water quality measuring means, and is free in the feed water at the start of operation. It is preferable to set an adjustment amount of chlorine concentration and a chemical injection amount of a stabilizer to water supply.

According to the present invention, a balance between the dosage of sodium hypochlorite that is dosed for biofilm inhibition and the dosage of stabilizer that is dosed to prevent deterioration of the reverse osmosis membrane. Can be easily taken.

1 is an overall configuration diagram of a water treatment system according to a first embodiment of the present invention. It is a functional block diagram of a control part with which a water treatment system concerning a 1st embodiment of the present invention is equipped. It is a flowchart explaining operation|movement of the water treatment system which concerns on 1st Embodiment of this invention. It is a functional block diagram of a control part with which a water treatment system concerning a 2nd embodiment of the present invention is equipped. It is a flowchart explaining operation|movement of the water treatment system which concerns on 2nd Embodiment of this invention. It is a whole block diagram of the water treatment system which concerns on 3rd Embodiment of this invention.

[1st Embodiment]
Hereinafter, the water treatment system 1 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

[1.1 Structure of the Invention]
FIG. 1 is an overall configuration diagram of a water treatment system 1 according to this embodiment.
As shown in FIG. 1, the water treatment system 1 includes a first chemical addition device 3, a second chemical addition device 4, an ORP sensor 5, a pH sensor 6, a water quality sensor 7, a pressurizing pump 12, An inverter 13, a constant flow valve 15, a proportional control drainage valve 16, and a control unit 30 are provided. 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 water supply line L1, a permeate water line L2, a concentrated water line L3, a circulating water line L4, and a concentrated drainage line L5. The “line” is a general term for lines such as a flow path, a route, and a pipeline in which a fluid can flow. In addition, water that flows through the water supply line L1, the concentrated water line L3, or the circulating water line L4, regardless of its origin (source) and its water quality, is also referred to as "water supply", and the concentrated water line L3, the circulating water line L4, or the concentrated water The water flowing through the drainage line L5 is also referred to as “concentrated water”.

The water supply line L1 is a line that supplies the water supplies W11 to W12 toward the reverse osmosis membrane module 14. The water supply line L1 has a first water supply line L11 and a second water supply line L12 from the upstream side toward the downstream side.

The upstream end of the first water supply line L11 is connected to the water source 2 of the water supply W11. The downstream end of the first water supply line L11 is connected to the second water supply line L12 and the circulating water line L4 at the connection portion J1. In the first water supply line L11, the first chemical addition device 3, the second chemical addition device 4, the ORP sensor 5, the pH sensor 6, and the water quality sensor 7 are provided in this order from the upstream side to the downstream side.

The first chemical addition device 3 is a device that adds the first chemical to the water supply line L1. The first chemical addition device 3 is electrically connected to the control unit 30.
In the present embodiment, the first chemical addition device 3 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 W11 becomes stabilized hypochlorous acid. In the reverse osmosis membrane module 14, since the deterioration of the reverse osmosis membrane can be effectively suppressed, examples of the first drug include a stabilizer containing an amine compound such as a sulfamic acid compound. When the first 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 W11: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%.

The stabilizer as the first drug may further contain a bromine compound. The addition of the bromine compound indirectly produces hypobromous acid, and the reaction of hypobromous acid and sulfamic acid finally produces a sulfamic acid bromide compound. Examples of the bromine compound include sodium bromide and the like. The amount of the bromine compound added is preferably such that the molar ratio of available chlorine derived from hypochlorous acid in the water supply W11: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 first drug is sulfamic acid will be described below, but the present invention is not limited to this.

The second chemical addition device 4 is a device that adds the second chemical to the water supply line L1. The second drug addition device 4 is electrically connected to the control unit 30.
In the present embodiment, the second chemical addition device 4 adjusts the free chlorine concentration in the water supply W11 by adding an oxidant as the second chemical in order to suppress biofilm deposition in the reverse osmosis membrane module 14. To do. 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 second agent include a chlorine-based oxidizing agent such as sodium hypochlorite. .. When the second chemical is sodium hypochlorite, it is preferable that the amount of sodium hypochlorite added be such that the effective chlorine concentration in the water supply W11 is about 0.01 to 5 mgCl2/L.
For simplicity of explanation, an example in which the second 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 ORP sensor 5 is a device that detects the oxidation-reduction potential of the water supply W11 flowing through the first water supply line L11. The ORP sensor 5 is connected to the first water supply line L11. Further, the ORP sensor 5 is electrically connected to the control unit 30. The oxidation-reduction potential value ORP (hereinafter, also referred to as “detection ORP value”) of the water supply W11 detected by the ORP sensor 5 is transmitted to the control unit 30 as a detection signal. In the present embodiment, the ORP sensor 5 detects the redox potential value ORP in real time and transmits the redox potential value ORP to the control unit 30. Note that the “oxidation-reduction potential” has a positive value and a larger value as the oxidizing power (sterilizing action) of the water supply W11 becomes stronger.

The pH sensor 6 is a device that detects the pH of the water supply W11 flowing through the first water supply line L11. The pH sensor 6 is connected to the first water supply line L11. The pH sensor 6 is electrically connected to the control unit 30. The pH of the water supply W11 detected by the pH sensor 6 (hereinafter, also referred to as “detected pH value”) is transmitted to the control unit 30 as a detection signal.

The water quality sensor 7 measures the water quality of the water supply W11. The water quality sensor 7 is electrically connected to the control unit 30.
In this embodiment, the water quality sensor 7 uses TOC (Total Organic Carbon), COD (Chemical Oxygen Demand), and BOD (Biochemical Oxygen Demand) as the water quality of the water supply W11. 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 7, predicts a biofilm risk using the received measured values, and supplies water at the start of operation of the water treatment system 1 based on the predicted biofilm risk. The doses of the first drug and the second drug to W11 are set.

Alternatively, the water quality sensor 7 may measure the concentration of the reducing substance contained in the water supply W11 as the water quality of the water supply W11. Specifically, the water quality sensor 7 measures the concentration of reducing ions such as iron ions and manganese ions which are reducing substances, the concentration of ions such as nitrite ions, the amount of ammoniacal nitrogen (nitrogen in ammonia ions), or SBS ( The concentration of sodium bisulfite: NaHSO3) or the like is measured. The control unit 30 receives the measured values of these reducing substance concentrations from the water quality sensor 7 and adjusts the free chlorine concentration in the water supply W11 using the received measured values, so that when the operation of the water treatment system 1 is started. The doses of the first drug and the second drug to the water supply W11 are set.

The upstream end of the second water supply line L12 is connected to the connecting portion J1. The downstream end of the second water supply line L12 is connected to the primary inlet port of the reverse osmosis membrane module 14. A pressurizing pump 12 is provided in the second water supply line L12.

The pressurizing pump 12 is a device that sucks in the water supply W12 and pumps (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 W12 is supplied to the reverse osmosis membrane module 14 via the pressure pump 12. The water supply W12 includes water supply W11 and circulating water W40 (described later).

The reverse osmosis membrane module 14 is equipment for separating the feed water W12 into permeated water W20 and concentrated water W30. In detail, the reverse osmosis membrane module 14 performs a membrane separation process on the feed water W12 discharged from the pressure pump 12 into permeated water W20 from which dissolved salts have been removed and concentrated water W30 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 W12 with these reverse osmosis membrane elements to produce permeated water W20 and concentrated water W30.

The permeated water line L2 is a line for sending out the permeated water W20 separated by the reverse osmosis membrane module 14. The upstream end of the permeate line L2 is connected to the secondary port of the reverse osmosis membrane module 14. The downstream end of the permeated water line L2 is connected to a storage tank (not shown).

The concentrated water line L3 is a line through which the concentrated water W30 separated by the reverse osmosis membrane module 14 flows. The upstream end of the concentrated water line L3 is connected to the secondary port of the reverse osmosis membrane module 14. Further, the downstream side of the concentrated water line L3 branches into a circulating water line L4 and a concentrated drainage line L5 at a connection portion J2.

The circulating water line L4 is a line that is connected to the concentrated water line L3 and returns concentrated water (circulating water W40) as water supply to the water supply line L1. In the present embodiment, the circulating water line L4 is a line for returning (circulating) the concentrated water W30 flowing through the concentrated water line L3 to the upstream side of the pressure pump 12 in the water supply line L1 as the circulating water W40. The upstream end of the circulating water line L4 is connected to the concentrated water line L3 at the connection portion J2. Further, the downstream end of the circulating water line L4 is connected to the water supply line L1 at the connecting portion J1. A constant flow valve 15 is provided in the circulating water line L4.

The constant flow valve 15 is a device that adjusts the flow rate of the circulating water W40 flowing through the circulating water line L4 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 L5 is a line that is connected to the concentrated water line L3 and discharges the concentrated water as the concentrated drainage W50 out of the system. In the present embodiment, the concentrated drainage line L5 is connected to the concentrated water line L3 at the connection portion J2, and the concentrated water W30 separated by the reverse osmosis membrane module 14 is discharged outside the system (outside the system) as concentrated drainage W50. It is a line to do. A proportional control drain valve 16 is provided in the concentrated drain line L5.

The proportional control drainage valve 16 is a valve that adjusts the flow rate of the concentrated drainage W50 discharged from the concentrated drainage line L5 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 W50 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.

FIG. 2 is a functional block of the control unit 30. The control unit 30 includes a target setting unit 31, a redox potential correction unit 32, and a drug concentration adjustment unit 33.

The target setting unit 31 sets a target value of the redox potential measured by the ORP sensor 5. More specifically, the first chemical addition device 3 adds a stabilizer as the first chemical to the water supply line L1 so that the redox potential measured by the ORP sensor 5 becomes the target value, and thus the membrane is formed. The 2nd chemical|medical agent addition apparatus 4 performs biofilm suppression by adding the oxidizing agent as a 2nd chemical|medical agent to the water supply line L1, maintaining the range which does not become a deterioration tendency.

The oxidation-reduction potential correction unit 32 corrects the actual measurement value of the oxidation-reduction potential measured by the OPR sensor 5 to the oxidation-reduction potential at the reference pH around pH=8, based on the pH measured by the pH sensor 6. To do. As a result, the drug concentration adjusting unit 33, which will be described later, can adjust the drug concentration based on the more accurate value of the redox potential.

The chemical|medical agent density|concentration adjustment part 33 is based on the redox potential corrected by the redox potential correction|amendment part 32, and the chemical injection amount of the stabilizer to the water supply W11 by the 1st chemical addition device 3, and the 2nd chemical addition device 4 The balance between the two is adjusted by controlling the amount of the chlorine-based oxidizer to be injected into the water supply W11.

In particular, in the present embodiment, for example, the area of the value of the redox potential after correction is divided into the first area, the second area, and the third area in order from the area of the low value to the area of the high value, and The second region is set so as to include the target value of the redox potential set by the target setting unit 31.

When the corrected redox potential value is in the first region, the drug concentration adjusting unit 33 controls the second drug adding device 4 to increase the amount of the chlorine-based oxidizing agent added to the water supply W11. Thus, the concentration of free chlorine in the water supply W11 is adjusted to increase.

When the corrected redox potential is in the second region, the drug concentration adjusting unit 33 controls the first drug adding device 3 and adjusts the addition amount of the stabilizer to the water supply W11, thereby forming the membrane. The value of the redox potential after correction is lowered to a range that does not cause a deterioration tendency.

When the corrected redox potential is in the third region, the drug concentration adjusting unit 33 controls the second drug adding device 4 to reduce the addition amount of the chlorine oxidant to the water supply W11. The free chlorine concentration in the water supply W11 is adjusted to be low.

As a result, by adjusting the chemical injection amount of the chlorine-based oxidizer and the stabilizer based on the corrected redox potential, the concentration of the drug is controlled so as to suppress the degree of membrane deterioration while suppressing the production of biofilm. Can be adjusted.

It should be noted that the method of dividing the redox potential and the method of controlling the first drug adding device 3 and the second drug adding device 4 by the drug concentration adjusting unit 33 in each region are merely examples, and the present invention is not limited thereto. For example, the region of the measured value of the redox potential, not the corrected redox potential, is divided, and the drug concentration adjusting unit 33 determines the first drug addition device 3 according to which region the measured value of the redox potential belongs to. Also, the second drug addition device 4 may be controlled.

Further, the chemical concentration adjusting unit 33, based on the water quality measured by the water quality sensor 7, at the start of the operation of the water treatment system 1, the chemical injection amount of the chlorine-based oxidizer to the water supply line L1 and the chemical of the stabilizer. By initializing the injection amount and the chemical injection amount of the bromine compound, the balance of the content of the chlorine-based oxidant, the content of the stabilizer, and the content of the bromine compound in the water supply W11 may be adjusted. ..

[1.2 Operation of First Embodiment]
Hereinafter, the operation of the water treatment system 1 according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a flowchart showing the operation of the water treatment system 1 of the present invention.
In the following, the first region is defined as a region where the redox potential after correction is less than P ₁ , and the second region is defined as a region where the redox potential after correction is P ₁ or more and less than P ₂ . The third region is a region where the redox potential after correction is P ₂ or more. It is preferable that these P ₁ and P ₂ are numerical values arbitrarily set between 100 and 800 mV.

In step S11, if the corrected redox potential value is less than P ₁ (S11: YES), the process proceeds to step S12. When the value of the redox potential after correction is P ₁ or more (S11: NO), the process proceeds to step S13.

In step S12, the chemical concentration adjusting unit 33 controls the second chemical addition device 4 to increase the chemical injection amount of the chlorine-based oxidizer to the water supply W11 so that the concentration of free chlorine in the water supply W11 becomes high. adjust. Then, the process proceeds to step S11 (return).

When the value of the redox potential after correction is P ₁ or more and less than P ₂ in step S13 (S13: YES), the process proceeds to step S14. When the value of the redox potential after correction is P ₂ or more (S13: NO), the process proceeds to step S15.

In step S14, the chemical|medical agent concentration adjustment part 33 controls the 1st chemical|medical agent addition apparatus 3, and adjusts the chemical injection amount of the stabilizer to the water supply W11, and the oxidation after correction is carried out to the range which does not become a film deterioration tendency. Decrease the reduction potential value. Then, the process proceeds to step S11 (return).

In step S15, the chemical concentration adjustment unit 33 controls the second chemical addition device 4 to reduce the chemical injection amount of the chlorine-based oxidizer into the water supply W11 so that the concentration of free chlorine in the water supply W11 becomes low. adjust. Then, the process proceeds to step S11 (return).

[1.3 Effects of First 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 includes a first chemical addition device 3 for injecting a stabilizer into the water supply W11, an ORP sensor 5 for measuring the redox potential of the water supply line L1, and a redox potential measured by the ORP sensor 5. The chemical|medical agent density|concentration adjustment part 33 which adjusts the balance of the density|concentration of the free chlorine in the water supply W11 and the density|concentration of a stabilizer by controlling the chemical injection amount of the stabilizer to the water supply W11 based on this.
As a result, in the water treatment system 1 using the reverse osmosis membrane, in order to prevent the deterioration of the reverse osmosis membrane while suppressing the biofilm, the concentration of free chlorine in the water supply W11 and the stabilizer that is dosed to the water treatment system 1 It is possible to easily balance with the concentration of.

In addition, the water treatment system 1 further includes a target setting unit 31 that sets a target potential that is a target value of the redox potential, and the measured value of the redox potential is equal to or higher than a first threshold value lower than the target potential, and the target When the value is equal to or lower than the second threshold value which is higher than the potential, the drug concentration adjusting unit 33 adjusts the balance by adjusting the chemical injection amount of the stabilizer, and the measured value of the redox potential is less than the first threshold value. If there is, or exceeds the second threshold value, the drug concentration adjustment unit adjusts the balance by adjusting the free chlorine concentration.
If the oxidation-reduction potential is higher than the target value, damage to the reverse osmosis membrane may occur, but in this case, reducing the amount of chlorine-based oxidizer dosed may cause the free chlorine concentration to drop too much. There is. When the measured redox potential is in a range that is neither too high nor too low, controlling the stabilizer rather than the chlorine-based oxidizer maintains the free chlorine concentration to some extent to maintain the biofilm suppression effect. However, it becomes possible to balance the chlorine-based oxidizer and the stabilizer.

The water treatment system 1 further includes a pH sensor 6 that measures the pH of the water supply W11, and a redox potential correction unit 32 that corrects the actual measurement value of the redox potential based on the pH measured by the pH sensor 6. The drug concentration adjusting unit 33 adjusts the balance between the adjustment amount of the free chlorine concentration and the chemical injection amount of the stabilizer based on the corrected redox potential.
Since the redox potential changes greatly depending on the pH, it is possible to perform stable control by correcting the measured value of the redox potential to the redox potential at the reference pH and using the corrected redox potential.

The water treatment system 1 further includes free chlorine concentration adjusting means for adjusting the concentration of free chlorine in the water W11, and the chemical concentration adjusting unit 33 further supplies the water based on the redox potential measured by the ORP sensor 5. By adjusting the free chlorine concentration in W11, the balance between the free chlorine concentration in the feed water W11 and the concentration of the stabilizer is adjusted.
In the water treatment system 1 using the reverse osmosis membrane, by adjusting the free chlorine concentration in the water supply W11, in order to prevent the deterioration of the reverse osmosis membrane while suppressing the biofilm, the free chlorine concentration in the water supply W11 and the stabilization are stabilized. It becomes possible to easily balance with the concentration of the agent.

In addition, the water treatment system 1 further includes, as a free chlorine concentration adjusting means, a second chemical addition device 4 that chemical-feeds a chlorine-based oxidant to the feed water.
As a result, in the water treatment system 1 using the reverse osmosis membrane, in order to suppress the deterioration of the reverse osmosis membrane while suppressing the biofilm, the dosage and stabilization of the chlorine-based oxidant that is dosed to the water treatment system 1 are stabilized. It is possible to easily balance with the dose of the drug.

Further, the above stabilizer includes an amine compound.
Using an amine compound as a stabilizer and generating a stabilized chlorine component by reacting with a chlorine-based oxidant, it weakens the oxidizing power that leads to damage to the reverse osmosis membrane and functions as an effective component for slime control. To do.

Further, the amine compound is a sulfamic acid compound.
By using a sulfamic acid compound as a stabilizer and generating a stabilized chlorine component by reaction with a chlorine-based oxidant, it functions as an active ingredient for slime control while weakening the oxidizing power that leads to damage to the reverse osmosis membrane. To do.

In addition, the stabilizer includes a bromine compound.
By using the bromine-based stabilizer, it is possible to reduce the damage given to the reverse osmosis membrane as compared with the case of using the chlorine-based stabilizer.

In addition, the water treatment system 1 further includes a water quality sensor 7 that measures the water quality of the water supply W11, and the drug concentration adjusting unit 33 determines whether the water content of the water supply W11 at the start of operation is based on the water quality measured by the water quality sensor 7. The amount of chlorine concentration adjustment and the amount of stabilizer to be added to the water supply W11 are set.
By conducting a water supply water analysis in advance, it is possible to confirm the biofilm risk and then set the initial conditions of drug injection according to the biofilm risk.
[2 Second Embodiment]
Hereinafter, the water treatment system 1A which is 2nd Embodiment of this invention is demonstrated, referring FIGS. 4-5.

[2.1 Structure of the Invention]
The overall configuration of the water treatment system 1A according to the present embodiment is basically the same as the overall configuration of the water treatment system 1 according to the first embodiment illustrated in FIG. Further, in the following description, for simplification of the description, basically, the point that the water treatment system 1A is different from the water treatment system 1 will be described.

Unlike the water treatment system 1, the water treatment system 1A according to the present embodiment includes a control unit 30A instead of the control unit 30.
FIG. 4 is a functional block diagram of the control unit 30A. The control unit 30A includes a target setting unit 31A, a redox potential correction unit 32, and a drug concentration adjustment unit 33A.

The target setting unit 31A sets a target potential range including the target value of the redox potential measured by the ORP sensor 5. That is, in the first embodiment, the target setting unit 31 sets the target value itself of the oxidation-reduction potential. In the present embodiment, the target setting unit 31A sets the target potential range including this target value. .. More specifically, the first chemical addition device 3 adds the stabilizer as the first chemical to the water supply line L1 so that the redox potential measured by the ORP sensor 5 is included in this target potential range. The second chemical addition device 4 executes biofilm suppression by adding the oxidizing agent as the second chemical to the water supply line L1 while maintaining the range in which the tendency of film deterioration does not occur.

The drug concentration adjusting unit 33A, based on the redox potential corrected by the redox potential correcting unit 32, the amount of the stabilizer to be injected into the water supply W11 by the first drug adding device 3, and the second drug adding device 4 The balance between the two is adjusted by controlling the amount of the chlorine-based oxidizer to be injected into the water supply W11.

In particular, in the present embodiment, for example, the region of the value of the redox potential after correction is changed from the region of the low value to the region of the high value in the order of the first region, the second region, the third region, the fourth region, The target potential range of the redox potential set by the target setting unit 31A is set to be the third region while being divided into the fifth region.

When the corrected redox potential value is in the first region, the drug concentration adjusting unit 33A controls the second drug adding device 4 to increase the amount of the chlorine-based oxidizing agent added to the water supply W11. Thus, the concentration of free chlorine in the water supply W11 is adjusted to be high.

When the corrected redox potential is in the second region or the fourth region, the drug concentration adjusting unit 33A controls the first drug adding device 3 to adjust the amount of the stabilizer added to the water supply W11. As a result, the value of the redox potential after correction is increased or decreased to the range where the film deterioration tendency does not occur.

When the corrected redox potential is in the third region, the drug concentration adjusting unit 33A controls the first drug adding device 3 and the second drug adding device 4 to adjust the chlorine-based oxidant to the water supply W11 and the stability. By maintaining the added amount of the agent, the corrected redox potential remains within the third region.

When the corrected redox potential is in the fifth region, the drug concentration adjusting unit 33A controls the second drug adding device 4 to reduce the addition amount of the chlorine oxidant to the water supply W11. The free chlorine concentration in the water supply W11 is adjusted to be low.

The method of dividing the redox potential and the method of controlling the first drug adding device 3 and the second drug adding device 4 by the drug concentration adjusting unit 33A in each region are merely examples, and the invention is not limited thereto. For example, the region of the measured value of the redox potential, not the corrected redox potential, is divided, and the drug concentration adjusting unit 33A determines the first drug addition device 3 according to which region the measured value of the redox potential belongs to. Also, the second drug addition device 4 may be controlled.

[2.2 Operation of Second Embodiment]
Hereinafter, the operation of the water treatment system 1A according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a flowchart showing the operation of the water treatment system 1A of the present invention.
In the following, the above-mentioned first region is defined as a region where the redox potential after correction is less than P ₃ , and the above-mentioned second region is defined as a region where the redox potential after correction is P ₃ or more and less than P ₄ . third redox potential of the corrected region is an P ₄ or P ₅ the following areas, the redox potential of the corrected fourth region described above as the region of less than P ₆ exceed P _5, said fifth region Is a region where the corrected redox potential is P ₆ or more. It is preferable that these P ₃ , P ₄ , P _{5, and} P ₆ are numerical values arbitrarily set between 100 and 800 mV.

In step S21, when the corrected redox potential value is less than P ₃ (S21: YES), the process proceeds to step S22. When the value of the redox potential after correction is P ₃ or more (S21: NO), the process proceeds to step S23.

In step S22, the chemical concentration adjustment unit 33A controls the second chemical addition device 4 to increase the chemical injection amount of the chlorine-based oxidant to the water supply W11 so as to increase the concentration of free chlorine in the water supply W11. To do. Then, the process proceeds to step S21 (return).

When the value of the redox potential after correction is P ₃ or more and less than P ₄ or more than P ₅ and less than P ₆ in step S23 (S23: YES), the process proceeds to step S24. The value of the redox potential is less than _{P 4} or _{P 5} after correction, or is _{P 6} or more: in (S23 NO), the process proceeds to step S25.

In step S24, the chemical concentration adjustment unit 33A controls the first chemical addition device 3 to adjust the chemical injection amount of the stabilizer to the water supply W11, thereby performing the post-correction oxidation to the extent that the film does not tend to deteriorate. Increase or decrease the reduction potential value. Then, the process proceeds to step S21 (return).

In step S25, if the value of the redox potential of the corrected is _{P 4} or _{P 5} or less (S25: YES), the process proceeds to step S26. When the value of the redox potential after correction is P ₆ or more (S25: NO), the process proceeds to step S27.

In step S26, the chemical|medical agent concentration adjustment part 33A controls the 1st chemical|medical agent addition apparatus 3 and the 2nd chemical|medical agent addition apparatus 4, and corrects by maintaining the addition amount of the chlorine type oxidizing agent and the stabilizer to the water supply W11. The subsequent redox potential is allowed to remain in the third region.

In step S27, the chemical concentration adjusting unit 33A controls the second chemical addition device 4 to reduce the chemical injection amount of the chlorine-based oxidant into the water supply W11 so that the concentration of free chlorine in the water supply W11 becomes low. adjust. Then, the process proceeds to step S21 (return).

[2.3 Effects of Second Embodiment]
According to the above-described water treatment system 1A of the present embodiment, for example, the following effects are achieved.
The water treatment system 1A further includes a target setting unit 31A that sets a target potential range including a target value of the redox potential, and the measured value of the redox potential is equal to or higher than a first threshold value lower than the target potential range, and the target. When the value is less than the lower limit value of the potential range, the drug concentration adjusting unit 33A adjusts the balance by adjusting the amount of the stabilizer to be injected, and the measured value of the redox potential is within the target potential range. In addition, the drug concentration adjusting unit 33A maintains the dose of the stabilizer and the free chlorine concentration, and the measured value of the redox potential exceeds the upper limit of the target potential range and is higher than the target potential range. When it is less than the second threshold value, the drug concentration adjusting unit 33A adjusts the balance by adjusting the amount of the stabilizer to be injected, and whether the measured value of the redox potential is less than the first threshold value, When it is not less than the second threshold value, the drug concentration adjusting unit adjusts the balance by adjusting the free chlorine concentration.
If the oxidation-reduction potential is higher than the target value, damage to the reverse osmosis membrane is a concern, but in this case, reducing the amount of chlorine-based oxidizer dosed may result in too low a chlorine concentration. is there. When the measured redox potential is in a range that is neither too high nor too low, by controlling the stabilizer rather than the chlorine-based oxidant, the chlorine concentration for maintaining the biofilm inhibition effect can be maintained to some extent. It becomes possible to balance the chlorine-based oxidizer and the stabilizer.
In particular, in the range near the target value of the redox potential, neither the chlorine-based oxidizing agent nor the stabilizer is dosed, so that the dose can be saved.

[3 Third Embodiment]
Hereinafter, a water treatment system 1B according to a third embodiment of the present invention will be described with reference to FIG.

[3.1 Structure of the Invention]
FIG. 3 is an overall configuration diagram of the water treatment system 1B according to the present embodiment. In addition, below, for simplification of description, mainly the points that the water treatment system 1B differs from the water treatment system 1 according to the first embodiment will be described.

In the water treatment system 1B, in addition to the components of the water treatment system 1, a silica concentration sensor 10 is installed on the permeated water line L2 downstream of the reverse osmosis membrane module 14.

The silica concentration sensor 10 is a device that detects the silica concentration of the permeated water W20 flowing through the permeated water line L2. The silica concentration sensor 10 is connected to the permeated water line L2. The silica concentration sensor 10 is electrically connected to the control unit 30. The silica concentration value of the permeated water W20 detected by the silica concentration sensor 10 (hereinafter, also referred to as “detected silica concentration value”) is transmitted to the control unit 30 as a detection signal. As the silica concentration sensor 10, for example, a colorimetric sensor can be used.

[3.2 Operation of Third Embodiment]
In the present embodiment, when the silica concentration detected by the silica concentration sensor 10 is equal to or higher than a predetermined value, the chemical concentration adjusting unit 33 reduces the oxidizing power of free chlorine and the stabilizer in the water W11 so as to weaken the oxidizing power. Adjust the drug concentration inside. More specifically, when the silica concentration detected by the silica concentration sensor 10 is equal to or higher than a predetermined value, the target setting unit 31 determines the redox potential based on the width in which the detected silica concentration exceeds the predetermined value. The target value of is shifted downward. Further, the drug concentration adjusting unit 33, along with the shift of the target value of the oxidation-reduction potential, the values of P ₁ and P _{2 in} the above-mentioned second region including the target value, that is, the region of P ₁ or more and less than P _2. Shift down.
The drug concentration adjusting unit 33 shifts the second region downward and then executes the operation shown in the flowchart of FIG. 3.

[3.3 Effects of Third Embodiment]
According to the water treatment system 1B of the present embodiment described above, for example, the following effects are achieved.
The water treatment system 1B includes a silica concentration sensor 10 that detects the silica concentration in the permeated water W20. When the silica concentration detected by the silica concentration sensor 10 is equal to or higher than a predetermined threshold value, the drug concentration adjusting unit 33 , Adjust the drug concentration in the feed water so as to weaken the oxidizing power of free chlorine and stabilizer.
As a result, since silica leaked from the reverse osmosis membrane was detected, if it is assumed that the reverse osmosis membrane is damaged, it is generated in the reverse osmosis membrane by weakening the oxidizing power due to the chemical injection. It is possible to reduce the degree of damage.

The target setting unit 31 also sets a target value for the redox potential based on the silica concentration detected by the silica concentration sensor 10.
When the detection of silica is used as a trigger, the target value of the redox potential is lowered according to the silica concentration to weaken the oxidizing power due to chemical injection, thereby making it possible to tighten the management of the water treatment system.

[4 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.

[4.1 Modification 1]
For example, the second chemical addition device 4 adjusts the free chlorine concentration in the water supply W11 by adding an oxidizing agent as the second chemical, but the present invention is not limited to this. The 2nd chemical|medical agent addition apparatus 4 may add a reducing agent as a 2nd chemical|medical agent, and reduces the free chlorine concentration originally contained in the water supply W11 in this case. As the reducing agent, for example SBS: may be used (NaHSO ₃ sodium bisulfite).
Further, the water treatment systems 1 and 1A may not have the second chemical addition device 4 in the first place, and the free chlorine concentration may not be adjusted.

[4.2 Modification 2]
Further, when the water quality sensor 7 measures the concentration of the reducing agent contained in the water supply W11, the control unit adjusts the free chlorine concentration in the water supply W11 using the measurement value of the reducing substance concentration received from the water quality sensor 7. Therefore, the chemical injection amount of the first chemical agent and the second chemical agent to the water supply W11 at the start of the operation of the water treatment system 1 is set, but the present invention is not limited to this. For example, a reducing device may be used as the iron removing/manganese removing device to remove the reducing substance from the water supply W11 as a pretreatment.

[4.3 Modification 3]
In addition, the water treatment systems 1, 1A, and 1B may have a configuration different from that of the above-described embodiment. For example, although the circulating water line L4 is provided above, the present invention is not limited to this, and the circulating water line L4 may be omitted. Further, the ORP sensor 5 and/or the pH sensor 6 may be installed in the concentrated drainage line L5 instead of the first water supply line L11.

[4.4 Modification 4]
In addition, in the water treatment systems 1, 1A, and 1B, the control units 30 and 30A turn on the drug injection of the first drug by the first drug addition device 3 and the drug injection of the second drug by the second drug addition device 4. Although the /OFF control is performed, the invention is not limited to this. For example, the redox potential controlled by the above chemical injection, so that the target value, or so as to be included in the target potential range, the opening degree of the valve used by each chemical addition device for chemical injection, You may perform P control, PI control, or PID control.

[4.5 Modification 5]
The water treatment system 1B according to the third embodiment is the same as the water treatment system 1 according to the first embodiment except that a silica concentration sensor 10 is newly installed on the permeated water line L2 downstream of the reverse osmosis membrane module 14. However, it is not limited to this. For example, in the water treatment system 1A according to the second embodiment, the silica concentration sensor 10 may be newly installed on the permeated water line L2 downstream of the reverse osmosis membrane module 14.

[4.6 Modification 6]
In the water treatment system 1B according to the third embodiment, the silica concentration sensor 10 installed on the permeated water line L2 measures the silica concentration of the permeated water W20, and based on this silica concentration, the drug concentration adjusting unit 33 Although it has been stated that the drug concentration in the water supply W11 is adjusted, the present invention is not limited to this. For example, the recovery rate in the reverse osmosis membrane module 14 may be set based on the silica concentration of the permeated water W20, or the type of the drug added to the water supply line L1 by the second drug addition device 4 may be changed. Further, in addition to the silica concentration of the permeated water W20, the silica concentration of the concentrated water W30 is measured, and the drug concentration is calculated based on the silica rejection rate in the reverse osmosis membrane module 14 calculated based on both silica concentrations. The adjusting unit 33 may adjust the drug concentration in the water supply W11.

[4.7 Modification 7]
Further, the water treatment systems 1, 1A, and 1B 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.

[4.8 Modification 8]
In addition, in the water treatment systems 1, 1A, and 1B, it is preferable that the membrane cleaning step is also performed by using the water supply containing the above-mentioned chemicals. 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.

1, 1A, 1B water treatment system,
3 First chemical addition device (stabilizer chemical injection device)
4 Second chemical addition device (oxidizer chemical injection device)
5 ORP sensor 6 pH sensor 7 Water quality sensor (water quality measuring means)
12 pressurizing pump 14 reverse osmosis membrane module 30, 30A control unit 31, 31A target setting unit 32 redox potential correction unit 33, 33A drug concentration adjusting unit L1 water supply line, L2 permeate water line, L3 concentrated water line,
L4 circulating water line, L5 concentrated drainage line,
L11 first water supply line, L12 second water supply line

Claims (13)

A reverse osmosis membrane module that separates the feed water 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,
Concentrated drainage line for discharging a part or all of the concentrated water as concentrated drainage to the outside of the system,
A stabilizer dosing device for dosing a stabilizer for water supply;
A potential measuring device for measuring the oxidation-reduction potential of the water supply line or the concentrated drainage line,
A drug for adjusting the balance between the concentration of free chlorine in the feed water and the concentration of the stabilizer by controlling the amount of the stabilizer to be fed to the feed water based on the redox potential measured by the potential measuring device. A water treatment system comprising a concentration adjusting unit. Further comprising a target setting unit for setting a target potential which is a target value of the redox potential,
When the measured value of the oxidation-reduction potential is equal to or higher than the first threshold value lower than the target potential and equal to or lower than the second threshold value higher than the target potential, the drug concentration adjusting unit determines the dosage of the stabilizer. Adjust the balance by adjusting
When the measured value of the redox potential is less than the first threshold value or exceeds the second threshold value, the drug concentration adjusting unit adjusts the balance by adjusting the free chlorine concentration. Water treatment system described. Further comprising a target setting unit for setting a target potential range including a target value of the redox potential,
When the measured value of the oxidation-reduction potential is equal to or higher than the first threshold value lower than the target potential range and is equal to or lower than the lower limit value of the target potential range, the drug concentration adjusting unit determines the dosage of the stabilizer. Adjust the balance by adjusting
When the measured value of the redox potential is within the target potential range, the drug concentration adjusting unit maintains the dose of the stabilizer and the free chlorine concentration,
When the measured value of the oxidation-reduction potential is equal to or higher than the upper limit value of the target potential range and is equal to or lower than the second threshold value higher than the target potential range, the drug concentration adjusting unit determines the amount of stabilizer to be added. Adjust the balance by adjusting
The measured value of the redox potential is less than the first threshold value or exceeds the second threshold value, the drug concentration adjusting unit adjusts the balance by adjusting the free chlorine concentration. Water treatment system described. PH measuring means for measuring pH of water supply or concentrated wastewater,
Further comprising an oxidation-reduction potential correction unit that corrects an actual measurement value of the oxidation-reduction potential based on the pH measured by the pH measurement means,
The said chemical|medical agent concentration adjustment part adjusts the balance of the adjustment amount of a free chlorine concentration, and the chemical injection amount of a stabilizer based on the corrected oxidation-reduction potential. Water treatment system. Further comprising free chlorine concentration adjusting means for adjusting the free chlorine concentration in the feed water,
The drug concentration adjusting unit, based on the oxidation-reduction potential measured by the potential measuring device, by further controlling the free chlorine concentration in the feed water, between the free chlorine concentration in the feed water and the concentration of the stabilizer. The water treatment system according to any one of claims 1 to 4, which adjusts a balance. The water treatment system according to claim 5, further comprising, as the free chlorine concentration adjusting means, an oxidant chemical injection device for chemical injection of a chlorine-based oxidant into feed water. The water treatment system according to claim 5, further comprising, as the free chlorine concentration adjusting means, a reducing agent dosing device for dosing a reducing agent into the feed water. The water treatment system according to claim 1, wherein the stabilizer includes an amine compound. The water treatment system according to claim 8, wherein the amine compound is a sulfamic acid compound. The water treatment system according to claim 8 or 9, wherein the stabilizer further contains a bromine compound. Further comprising a silica concentration detection device for detecting the silica concentration in the permeate,
When the silica concentration detected by the silica concentration detection device is equal to or higher than a predetermined threshold value, the drug concentration adjusting unit adjusts the drug concentration in the feed water so as to weaken the oxidizing power of free chlorine and the stabilizer. The water treatment system according to any one of claims 1 to 10. The water treatment system according to claim 11, wherein the target setting unit sets the target value based on the silica concentration detected by the silica concentration detection device, directly or indirectly depending on claim 2 or 3. .. Further comprising water quality measuring means for measuring the water quality of the water supply,
The chemical concentration adjusting unit sets the adjustment amount of the free chlorine concentration in the feed water at the start of operation and the chemical injection amount of the stabilizer to the feed water based on the water quality measured by the water quality measuring means. The water treatment system according to any one of 1 to 12.

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