JP2020054969A - Water treatment system - Google Patents

Abstract

To provide a system of effectively suppressing biofouling, while preventing a generation of resistant bacteria, and suppressing a deterioration of a reverse osmosis membrane as much as possible.SOLUTION: There is provided a water treatment system 1, including: injection means 6, 7 for injecting a stabilizer and a bromine compound into a water supply W11; and a chemical concentration adjustment unit that switches a chemical concentration adjustment step in water supply performed by the chemical injection means, between a first chemical concentration adjustment step of injecting the stabilizer into the water supply W11, and a second chemical concentration adjustment step of injecting the chemical of the stabilizer and the bromine compound to the water supply W11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment system.

In a water treatment system that performs a membrane filtration process using a reverse osmosis membrane, sodium hypochlorite is used as a chlorine-based disinfectant to remove microorganisms in order to control biofilms derived from the growth of microorganisms. There is.
For example, Patent Literature 1 discloses a method for producing fresh water using a reverse osmosis membrane, in which sodium hypochlorite flows into a reverse osmosis membrane in a water treatment system in order to suppress biofouling due to generation of a biofilm. A method for producing fresh water is disclosed.

JP-A-2006-190214

However, the reverse osmosis membrane deteriorates due to the chemical injection of sodium hypochlorite into the water treatment system. Stabilizers may be added to the water treatment system to prevent degradation of the reverse osmosis membrane.However, depending on the type of stabilizer added, the risk of damage to the reverse osmosis membrane and the degree of suppression of biofouling can be reduced. different.
In addition, by continuously injecting the same drug, resistant bacteria are generated as microorganisms from which the biofilm is derived, and the effect of suppressing biofouling decreases as time elapses from the start of drug injection. Sometimes.

  An object of the present invention is to provide a water treatment system capable of effectively suppressing biofouling while preventing the occurrence of resistant bacteria and minimizing membrane degradation of a reverse osmosis membrane.

  A first water treatment system according to the present invention includes a reverse osmosis membrane module for separating feedwater into permeated water and concentrated water, a water supply line for supplying feedwater to the reverse osmosis membrane module, and a separation by the reverse osmosis membrane module. A permeated water line for delivering concentrated water, a concentrated water line for delivering concentrated water separated by the reverse osmosis membrane module, and a concentrate for discharging part or all of the concentrated water as concentrated wastewater to the outside of the system. A drain line, a chemical injecting means for injecting a stabilizer and a bromine compound into the water supply, and a chemical concentration adjusting step in the water supply performed by the chemical injecting means. The present invention relates to a water treatment system including a drug concentration adjusting step and a drug concentration adjusting unit that switches between a stabilizer and a second drug concentration adjusting step of injecting a bromine compound into water supply.

  Further, the first water treatment system further includes free chlorine concentration adjusting means for adjusting the free chlorine concentration in the feed water, and the chemical concentration adjusting unit adjusts the free chlorine concentration in the feed water and stabilizes the feed water. Switching between a first drug concentration adjusting step of injecting the agent and a second drug concentration adjusting step of adjusting the free chlorine concentration in the feed water and injecting the stabilizer and the bromine compound into the feed water. Is preferred.

  In addition, it is preferable that the drug concentration adjusting unit switches a drug concentration adjusting step performed by the chemical dosing unit and the free chlorine concentration adjusting unit based on an operation time of the water treatment system.

  Further, the first water treatment system may include a transmembrane pressure measuring means for measuring a transmembrane pressure difference, which is an input / output differential pressure of a path through which the concentrated water flows in the reverse osmosis membrane module, or a permeate flow in the reverse osmosis membrane module. Further comprising a permeation flux value calculating means for calculating a flux value, wherein the value of the transmembrane pressure measured by the transmembrane pressure measuring means exceeds a first threshold, or the permeation flux value calculating means When the permeation flux value calculated by the above is equal to or less than a second threshold value, the drug concentration adjustment unit switches to the first drug concentration adjustment step, and the value of the transmembrane pressure is changed to the first threshold value. In the following cases, or when the permeation flux value exceeds the second threshold value, it is preferable that the drug concentration adjustment unit switch to the second drug concentration adjustment step.

  Further, when the value of the transmembrane pressure measured by the transmembrane pressure measuring means exceeds a third threshold value higher than the first threshold value, or the value calculated by the permeation flux value calculating means. When the permeation flux value is equal to or less than a fourth threshold value lower than the second threshold value, it is preferable that the drug concentration adjusting unit decreases the amount of the stabilizer injected.

  Further, when the value of the transmembrane pressure measured by the transmembrane pressure measuring means exceeds a fifth threshold value higher than the third threshold value, or the value calculated by the permeation flux value calculating means. When the permeation flux value is equal to or less than a sixth threshold value lower than the fourth threshold value, it is preferable that the drug concentration adjusting unit increases the free chlorine concentration.

  Further, it is preferable that the free chlorine concentration adjusting means is a second chemical injecting means for injecting a reducing agent into the water supply.

  Further, the first water treatment system further includes water quality measuring means for measuring the water quality of the feed water, and the chemical concentration adjusting section is configured to determine the free chlorine concentration at the start of operation based on the water quality measured by the water quality measuring means. It is preferable to set the amount of adjustment and the injection amount of the stabilizer and the bromine compound.

  Further, the second water treatment system according to the present invention includes 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; A permeate line for delivering the permeated water separated by the above, a concentrated water line for delivering the concentrated water separated by the reverse osmosis membrane module, and discharging part or all of the concentrated water as concentrated wastewater to the outside of the system. A concentrated drainage line to be supplied, a chemical injection means for injecting isothiazoline and / or DBNPA and / or a stabilizing agent and / or a bromine compound into the feed water, a free chlorine concentration adjusting means for adjusting the free chlorine concentration in the feed water, The step of adjusting the concentration of the drug in the water supplied by the chemical injecting means includes the step of adjusting the concentration of free chlorine in the water supplied and the first agent for adjusting the concentration of the drug in the water supplied by isothiazoline and / or DBNPA. If, while adjusting the concentration of free chlorine in the feed water, and a drug concentration adjusting unit for switching between a second drug concentration adjusting step dispenses drugs stabilizers and / or bromine compounds to the water.

  ADVANTAGE OF THE INVENTION According to this invention, while preventing generation | occurrence | production of resistant bacteria, it becomes possible to suppress biofouling effectively, suppressing the membrane deterioration of a reverse osmosis membrane as much as possible.

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 provided. It is a flow chart explaining operation of a water treatment system concerning a 1st embodiment of the present 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 provided. It is a flow chart explaining operation of a water treatment system concerning a 2nd embodiment of the present invention.

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

[1.1 Overall configuration]
FIG. 1 is an overall configuration diagram of a water treatment system 1 of the present embodiment.
As shown in FIG. 1, the water treatment system 1 includes a first drug adding device 5, a second drug adding device 6, a third drug adding device 7, a water quality sensor 8, a pressurizing pump 10, an inverter 11 , A first pressure sensor 13, a reverse osmosis membrane module (hereinafter also referred to as an “RO membrane module”) 14, a second pressure sensor 15, a flow sensor FM, a third pressure sensor 17, and a constant flow valve 18 , A proportional control drain valve 19, and a control unit 30. The illustration of the electrical connection lines between the control unit 30 and the controlled device is omitted.

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

  The water supply line L1 is a line that supplies the water supply 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 to 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 a connection portion J1. In the first water supply line L11, a first medicine adding device 5, a second medicine adding device 6, a third medicine adding device 7, and a water quality sensor 8 are provided in this order from the upstream side to the downstream side.

The first drug adding device 5 is a device that adds a first drug to the water supply line L1. The first medicine adding device 5 is electrically connected to the control unit 30.
In the present embodiment, the first chemical addition device 5 adjusts the free chlorine concentration in the feed water W11 by adding an oxidizing agent as a first chemical in order to suppress the deposition of the biofilm in the reverse osmosis membrane module 14. I do. In the reverse osmosis membrane module 14, since a biofilm can be effectively prevented from adhering to the surface of the reverse osmosis membrane, a chlorine-based oxidizing agent such as sodium hypochlorite is given as an example of the first agent. . When the first chemical is sodium hypochlorite, the amount of sodium hypochlorite to be added is preferably such that the effective chlorine concentration in the feed water W11 is about 0.01 to 5 mgCl2 / L.
Hereinafter, for the sake of simplicity, an example in which the first agent is sodium hypochlorite will be described, but the present invention is not limited to this. As other chlorine-based oxidizing agents, for example, liquefied chlorine, bleached powder, chlorinated isocyanuric acid, and the like may be used.

The second drug adding device 6 is a device for adding a second drug to the water supply line L1. The second medicine adding device 6 is electrically connected to the control unit 30.
In the present embodiment, the second drug addition device 6 adds a stabilizer as a second drug in order to prevent the reverse osmosis membrane provided in the reverse osmosis membrane module 14 from deteriorating. By the addition of the stabilizer, for example, hypochlorous acid contained in the feed water W11 becomes stabilized hypochlorous acid. In the reverse osmosis membrane module 14, since the degradation of the reverse osmosis membrane can be effectively suppressed, examples of the second agent include a stabilizer such as sulfamic acid. In addition, when a 2nd chemical | medical agent is a sulfamic acid, it is preferable that the molar amount ratio of the effective chlorine derived from the hypochlorous acid in the feed water W11: sulfamic acid becomes about 1: 1-20 about sulfamic acid. , 1: 1.5-10. This is because, if the sulfamic acid falls below 1 with respect to the available chlorine 1, free chlorine is generated even if the reaction efficiency of both is 100%.
Hereinafter, an example in which the second drug is sulfamic acid will be described for simplification of description, but the present invention is not limited to this.

The third drug addition device 7 is a device that adds a third drug to the water supply line L1. The third drug addition device 7 is electrically connected to the control unit 30.
In the present embodiment, the third chemical addition device 7 adds a bromine compound in order to further reduce damage to the reverse osmosis membrane provided in the reverse osmosis membrane module 14. By the addition of the bromine compound, hypobromite is generated indirectly, and the reaction between hypobromite and sulfamic acid eventually generates a brominated sulfamic acid compound. Examples of the third agent include a bromine compound such as sodium bromide. The amount of the bromine compound added is preferably such that the molar ratio of available chlorine derived from hypochlorous acid in the feed water W11 to the bromine compound is about 1: 1 to 10, and more preferably about 1: 1 to 2. Good.
Hereinafter, for the sake of simplicity, an example in which the third agent is sodium bromide will be described, but the present invention is not limited to this.

The water quality sensor 8 measures the water quality of the water supply W11. The water quality sensor 8 is electrically connected to the control unit 30.
In the present embodiment, the water quality sensor 8 includes TOC (Total Organic Carbon: total organic carbon amount), COD (Chemical Oxygen Demand: chemical oxygen demand), BOD (Biochemical Oxygen Demand: biochemical One or more of the amount of organic substances such as oxygen demand) and AOC (Assimilable Organic Carbon) and the amount of microorganisms such as bacteria and ATP are measured. The control unit 30 receives these measured values from the water quality sensor 8, 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 injection amount of the first medicine and the second medicine into W11 is set.

Alternatively, the water quality sensor 8 may measure the concentration of a reducing substance contained in the feed water W11 as the water quality of the feed water W11. Specifically, the water quality sensor 8 is configured to control the concentration of metal ions such as iron ions and manganese ions as reducing substances, the concentration of ions such as nitrite ions, the amount of ammonia nitrogen (nitrogen in ammonia ions), or SBS ( The concentration of sodium bisulfite: NaHSO ₃ ) is measured. The control unit 30 receives the measured values of these reducing substance concentrations from the water quality sensor 8 and adjusts the free chlorine concentration in the feed water W11 using the received measured values. The medicine injection amounts of the first medicine and the second medicine into the water supply W11 are set.

  The upstream end of the second water supply line L12 is connected to the connection 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. In the second water supply line L12, the pressurizing pump 10 and the first pressure sensor 13 are provided in this order from the upstream side to the downstream side.

  The pressurizing pump 10 is a device that sucks in the feed water W11 and pressure-feeds (discharges) it to the reverse osmosis membrane module 14. The driving power whose frequency has been converted is supplied from the inverter 11 to the pressurizing pump 10. The pressurizing pump 10 is driven at a rotational speed according to the frequency of the supplied (input) drive power (hereinafter, also referred to as “drive frequency”).

  The inverter 11 is an electric circuit (or a device having the circuit) for supplying the frequency-converted drive power to the pressure pump 10. The inverter 11 is electrically connected to the control unit 30. A command signal is input from the control unit 30 to the inverter 11. The inverter 11 outputs to the pressurizing pump 10 driving power having a driving 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 10. Further, the water supply W12 includes a water supply W11 and a circulating water W40 (described later).

  The first pressure sensor 13 is a device that detects the pressure of the water supply W12 at the primary inlet of the reverse osmosis membrane module 14. The first pressure sensor 13 is arranged on the discharge side of the pressure pump 10. The pressure of the feed water W12 detected by the first pressure sensor 13 (hereinafter, also referred to as “first detected pressure value”) is transmitted to the control unit 30 as a detection signal.

  The reverse osmosis membrane module 14 is a facility for separating the feed water W12 into the permeated water W20 and the concentrated water W30. Specifically, the reverse osmosis membrane module 14 performs a membrane separation process on the feed water W12 discharged from the pressure pump 10 into a permeated water W20 from which dissolved salts have been removed and a concentrated water W30 in which dissolved salts have been concentrated. It is. Reverse osmosis membrane module 14 includes one or more reverse osmosis membrane elements (not shown). The reverse osmosis membrane module 14 performs a membrane separation process on the feed water W12 using these reverse osmosis membrane elements to produce a permeate W20 and a 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 permeated water 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). In the permeated water line L2, the second pressure sensor 15 and the flow rate sensor FM are provided in this order from the upstream side to the downstream side.

  The second pressure sensor 15 is a device that detects the pressure of the permeated water W20 discharged from the secondary side of the reverse osmosis membrane module 14. The pressure of the permeated water W20 detected by the second pressure sensor 15 (hereinafter, also referred to as “second detected pressure value”) is transmitted to the control unit 30 as a detection signal.

  The flow sensor FM is a device that detects the flow rate of the permeated water W20 flowing through the permeated water line L2. The flow sensor FM is electrically connected to the control unit 30. The flow rate of the permeated water W20 detected by the flow rate sensor FM (hereinafter, also referred to as “detected flow rate value”) is transmitted to the control unit 30 as a detection signal.

  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 is branched into a circulating water line L4 and a concentrated drainage line L5 at a connection portion J2. A third pressure sensor 17 is provided in the concentrated water line L3.

  The third pressure sensor 17 is a device that detects the pressure of the concentrated water W30 discharged from the secondary side of the reverse osmosis membrane module 14. The pressure of the concentrated water W30 detected by the third pressure sensor 17 (hereinafter, also referred to as “third detected pressure value”) is transmitted to the control unit 30 as a detection signal.

  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 pressurizing pump 10 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 a connection J2. Further, a downstream end of the circulating water line L4 is connected to the water supply line L1 at a connection portion J1. A constant flow valve 18 is provided in the circulating water line L4.

  The constant flow valve 18 is a device that adjusts the flow rate of the circulating water W40 flowing through the circulating water line L4 to a predetermined constant flow value. The “constant flow value” held in the constant flow valve 18 is a concept that has a range in the constant flow value, and is not limited to the target flow value in the constant flow valve. For example, in consideration of the characteristics of the constant flow mechanism (for example, temperature characteristics due to the material and structure), those having an adjustment error of about ± 10% with respect to the target flow value of the constant flow valve are included. The constant flow valve 18 maintains a constant flow value without requiring any auxiliary power or external operation, and includes, for example, a valve called a water governor. The constant flow valve 18 may be operated by auxiliary power or external operation to maintain a constant flow value.

  The concentrated drainage line L5 is a line that is connected to the concentrated drainage line L3 and discharges the concentrated water as the concentrated drainage W50 to the outside of the system. In the present embodiment, the concentrated drainage line L5 is connected to the concentrated water line L3 at the connection part J2, and discharges the concentrated water W30 separated by the reverse osmosis membrane module 14 to the outside of the apparatus (outside the system) as the concentrated wastewater W50. It is a line to do. A proportional control drain valve 19 is provided in the concentrated drain line L5.

  The proportional control drain valve 19 is a valve for adjusting the flow rate of the concentrated drain water W50 discharged from the concentrated drain line L5 to the outside of the device. The proportional control drain valve 19 is electrically connected to the control unit 30. The valve opening of the proportional control drain valve 19 is controlled by a drive signal transmitted from the control unit 30. By transmitting a current value signal (for example, 4 to 20 mA) from the control unit 30 to the proportional control drain valve 19 and controlling the valve opening, the drain flow rate of the concentrated drain water W50 can be adjusted.

  The control unit 30 is configured by 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 diagram of the control unit 30. The control unit 30 includes a medicine concentration adjusting unit 31 and a time counting unit 32.

The drug concentration adjusting unit 31 adjusts the drug concentration in the water supply W11.
Particularly in the present embodiment, the concentration of free chlorine in the feed water W11 is adjusted by adding sodium hypochlorite to the feed water W11 by the first chemical adding device 5, and the feed water W11 is added to the feed water W11 by the second chemical adding device 6. Similarly to the "first drug concentration adjusting step" in which the stabilizer is added, the concentration of free chlorine in the feed water W11 is adjusted by adding sodium hypochlorite to the feed water W11 by the first drug adding device 5 in the same manner. And a “second drug concentration adjusting step” in which a stabilizer is added to the feed water W11 by the second drug addition device 6 and a bromide compound is added to the feed water W11 by the third drug addition device 7. Execute while switching at time intervals.

  The drug concentration adjusting unit 31 switches the type of drug added to the feed water W11 at predetermined time intervals, thereby preventing the occurrence of resistant bacteria and preventing the biodegradation of the reverse osmosis membrane as much as possible. It is possible to effectively suppress the generation of a film.

The chemical concentration adjusting unit 31 further includes sodium hypochlorite to the feed water W11 at the start of the operation of the water treatment system 1 based on the amount of organic matter, the amount of microorganisms, or the concentration of the reducing agent measured by the water quality sensor 8. Set the dosage of stabilizer.
Thereby, it becomes possible to set the initial condition of the chemical injection according to the biofilm risk.

  The timer 32 measures a predetermined time interval for switching between the “first drug concentration adjusting step” and the “second drug concentration adjusting step”.

[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 step S11, the drug concentration adjusting section 31 executes the above-mentioned "first drug concentration adjusting step". More specifically, the drug concentration adjusting unit 31 controls the first drug addition device 5 to adjust the free chlorine concentration in the feed water W11 by adding sodium hypochlorite to the feed water W11, By controlling the second chemical addition device 6, a stabilizer is added to the feed water W11.

  In step S12, when the timer 32 measures that a predetermined time has elapsed (S12: YES), the process proceeds to step S13. If the timer 32 has not counted the elapse of the predetermined time (S12: NO), the process proceeds to step S11.

  In step S13, the drug concentration adjusting section 31 executes the above-mentioned "second drug concentration adjusting step". More specifically, the drug concentration adjusting unit 31 controls the first drug addition device 5 to adjust the free chlorine concentration in the feed water W11 by adding sodium hypochlorite to the feed water W11, The stabilizer is added to the feed water W11 by controlling the second drug addition device 6, and the bromide compound is added to the feed water W11 by controlling the third drug addition device 7.

  In step S14, when the timer 32 measures that the predetermined time has elapsed (S14: YES), the process proceeds to step S13. If the timer 32 has not counted the elapse of the predetermined time (S14: NO), the process proceeds to step S11 (return).

[1.3 Effect of First Embodiment]
According to the water treatment system 1 according to the above-described embodiment, for example, the following effects can be obtained.
The water treatment system 1 according to the first embodiment includes a reverse osmosis membrane module 14 that separates the feedwater W12 into a permeated water W20 and a concentrated water W30, a water supply line L1 that supplies the feedwater W12 to the reverse osmosis membrane module 14, A permeated water line L2 for delivering the permeated water W20 separated by the osmosis membrane module 14, a concentrated water line L3 for delivering the concentrated water W30 separated by the reverse osmosis membrane module 14, and a part or all of the concentrated water W30. The concentrated wastewater W50 is a concentrated wastewater line L5 discharged to the outside of the system, the feedwater W11 is supplied with a stabilizing agent and a chemical injection means 6 and 7 for injecting a bromine compound, and the free chlorine is used to adjust the concentration of free chlorine in the feedwater W11. The concentration adjusting means 5 and the drug concentration adjusting step in the feed water performed by the chemical injection means 6 and 7 and the free chlorine concentration adjusting means 5 adjust the free chlorine concentration in the feed water W11, A first chemical concentration adjusting step of injecting a stabilizer into the water W11, and a second chemical concentration adjusting the free chlorine concentration in the feed water W11 and injecting a stabilizer and a bromine compound into the feed water W11. A drug concentration adjusting unit 31 that switches between the adjusting step and the adjusting step.

  Biofilms are generated from the overgrowth of microorganisms.However, if the same biofilm inhibitor is continuously injected to suppress biofilms, the degree of suppression of biofilms will increase due to the emergence of resistant bacteria. Stop lowering. By appropriately switching the type of the biofilm inhibitor, it becomes possible to prevent the occurrence of resistant bacteria. In addition, since the degree of damage to the reverse osmosis membrane and the degree of biofilm suppression differ depending on the type of biofilm inhibitor, by appropriately switching the type of biofilm inhibitor, the degradation of the reverse osmosis membrane is minimized, Can be effectively suppressed.

  In addition, the drug concentration adjusting unit 31 switches the drug concentration adjusting process performed by the chemical dosing units 6 and 7 and the free chlorine concentration adjusting unit 5 based on the operation time of the water treatment system 1.

  Biofilms are generated from the overgrowth of microorganisms.However, if the same biofilm inhibitor is continuously injected to suppress biofilms, the degree of suppression of biofilms will increase due to the emergence of resistant bacteria. Stop lowering. By switching the type of the biofilm inhibitor based on the operation time of the water treatment system, it becomes possible to easily prevent the generation of resistant bacteria.

  Further, the water treatment system 1 further includes a water quality measuring unit 8 for measuring the quality of the supplied water, and the chemical concentration adjusting unit 31 determines the free chlorine concentration at the start of operation based on the water quality measured by the water quality measuring unit 8. The adjustment amount, the amount of the stabilizer and the amount of the bromine compound to be injected are set.

  By conducting the water analysis in advance, the biofilm risk can be confirmed, and then the initial conditions for chemical injection can be set according to the biofilm risk.

[2 Second Embodiment]
Hereinafter, a water treatment system 1A according to a second embodiment of the present invention will be described with reference to FIGS. Note that the following mainly describes differences between the water treatment system 1A according to the second embodiment and the water treatment system 1 according to the first embodiment.

[2.1 Overall configuration]
The water treatment system 1A is different from the water treatment system 1 in that a control unit 30A is provided instead of the control unit 30.
FIG. 4 is a functional block diagram of the control unit 30A. The control unit 30A differs from the control unit 30 in that the control unit 30A does not include the timer unit 32, but instead includes a differential pressure measurement unit 33 and a permeation flux value calculation unit. Further, the control unit 30A includes a medicine concentration adjusting unit 31A instead of the medicine concentration adjusting unit 31.

  The differential pressure measuring unit 33 is configured to measure the pressure of the feedwater W12 at the primary inlet of the reverse osmosis membrane module 14 measured by the first pressure sensor 13 and the two pressures of the reverse osmosis membrane module 14 measured by the third pressure sensor 17. Based on the pressure of the concentrated water W30 on the next side, a transmembrane pressure, which is an input / output differential pressure of a path through which the concentrated water flows in the reverse osmosis membrane module 14, is measured.

The transmembrane pressure difference of the reverse osmosis membrane module 14 can be expressed by the following equation (1).
Transmembrane pressure [MPa] = pressure at the primary inlet port of the reverse osmosis membrane module 14−pressure at the secondary port of the reverse osmosis membrane module 14 (1)
In the present embodiment, “the pressure at the inlet port on the primary side of the reverse osmosis membrane module 14” is obtained by the first detected pressure value [MPa] measured by the first sensor 13, and “the pressure of the reverse osmosis membrane module 14 The “pressure of the secondary port” is obtained from the third detected pressure value [MPa] measured by the third pressure sensor 17.

The permeation flux value calculation unit 34 calculates the pressure of the feed water W12 at the primary inlet of the reverse osmosis membrane module 14 measured by the third pressure sensor 17, and the two of the reverse osmosis membrane module 14 measured by the second pressure sensor 15. The permeate flux value in the reverse osmosis membrane module 14 is calculated based on the pressure of the permeate W20 on the next side and the flow rate of the permeate W20 flowing through the permeate line L2 measured by the flow rate sensor FM.
Here, the permeation flux is an index indicating the state of clogging of the membrane of the reverse osmosis membrane module 14, and the amount of water passing through a unit membrane area per unit time is converted under a standard temperature condition as a unit membrane differential pressure. It was done. When this is expressed by a mathematical expression, it can be expressed by the following expression (2), for example, as described in JP-A-2008-55336.
Permeate flux [L / m ² · h · MPa] = treated water instantaneous flow rate / [{inlet operating pressure-(device differential pressure / 2)-outlet back pressure-osmotic pressure] x temperature correction coefficient x membrane area] (2 )

  In the present embodiment, for each value used in the calculation of the permeation flux, the “processed water instantaneous flow rate” is obtained by the detected flow rate value [L / h] measured by the flow rate sensor FM, and the “inlet operating pressure” is , The first detected pressure value [MPa] measured by the first pressure sensor 13. The “device differential pressure” is a set value [MPa], and the “outlet back pressure” is obtained from a second detected pressure value [MPa] measured by the second pressure sensor 15. The “osmotic pressure” is a set value [MPa], the temperature correction coefficient is a function of a temperature detected by a water temperature sensor (not shown), and the “membrane area” is a set value [m2].

  The drug concentration adjusting unit 31A adjusts the drug concentration in the feed water W11 based on the transmembrane pressure value measured by the differential pressure measuring unit 33 or the permeation flux value calculated by the permeation flux value calculation unit 34. adjust.

  Particularly, in the present embodiment, for example, the region of the transmembrane pressure value is divided into a first region, a second region, a third region, and a fourth region in order from a low-pressure region to a high-pressure region, and transmission is performed. When the flux value area is divided into a fifth area, a sixth area, a seventh area, and an eighth area in order from a low value area to a high value area, the value of the transmembrane pressure becomes the first area. Or the value of the permeation flux value is in the eighth region, the drug concentration adjusting unit 31A executes the above-mentioned "second drug concentration adjusting step". Specifically, the drug concentration adjustment unit 31A controls the first drug addition device 5 to adjust the free chlorine concentration in the feed water W11 by adding sodium hypochlorite to the feed water W11, The stabilizer is added to the feed water W11 by controlling the second drug addition device 6, and the bromide compound is added to the feed water W11 by controlling the third drug addition device 7.

  When the value of the transmembrane pressure is in the second region or the permeation flux value is in the seventh region, the drug concentration adjusting unit 31A executes the “first drug concentration adjusting step”. . Specifically, the drug concentration adjustment unit 31A controls the first drug addition device 5 to adjust the free chlorine concentration in the feed water W11 by adding sodium hypochlorite to the feed water W11, By controlling the second chemical addition device 6, a stabilizer is added to the feed water W11.

  When the value of the transmembrane pressure is in the third region or the permeation flux value is in the sixth region, the drug concentration adjusting unit 31A controls the second drug addition device 6 to supply the water W11. Decrease the amount of stabilizer to be injected.

  When the value of the transmembrane pressure is in the fourth region or the permeation flux value is in the fifth region, the drug concentration adjusting unit 31A controls the first drug addition device 5 to supply the water W11. To increase the amount of free chlorine in the feed water W11.

  Thereby, based on the production amount of the biofilm estimated from the value of the transmembrane pressure or the permeation flux value, by switching whether or not to inject the bromine compound, the degradation of the membrane while suppressing the production of the biofilm is suppressed. It is possible to adjust the drug concentration so as to minimize the degree of the drug concentration.

  It should be noted that the region dividing method of the transmembrane pressure and the permeation flux value, and the medicine concentration adjusting unit 31A in each region, the first medicine adding device 5, the second medicine adding device 6, and the third medicine adding device 7 are used. The control method is merely an example, and is not limited to this.

[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 1 of the present invention.
In the following, the transmembrane pressure difference of the first region described above and P ₁ than the region, the transmembrane pressure difference of the second region of the above and P ₁ or P ₂ less than the region, the third region of the transmembrane pressure difference is set to P ₂ or P ₃ less area, transmembrane pressure the fourth region described above and P ₃ or more regions. Preferably, P ₁ , P ₂ , and P ₃ are numerical values arbitrarily set between 0.03 and 0.1 MPa.
Similarly, a fifth region of the flux values and F ₃ following areas, the sixth region of the flux value is the F ₂ following areas exceed F _3, transmitted through the seventh region of the flux value and F ₁ the following areas beyond the F _2, an eighth region of the above flux value and a region of more than F _1. It is preferable that these F ₁ , F ₂ , and F ₃ be numerical values arbitrarily set between 70% and 100% as the initial ratio of the permeation flux.

In step S21, if either the transmembrane pressure difference measured by the differential pressure measuring part 33 is less than P _1, or flux value calculated by the flux value calculating unit 34 exceeds F ₁ (S21: If (YES), the process proceeds to step S22. If either the transmembrane pressure difference measured by the differential pressure measuring part 33 is P ₁ or more, or flux value calculated by the flux value calculating section 34 is F ₁ or less (S21: NO) in The process proceeds to the step S23.

  In step S22, the medicine concentration adjusting unit 31A executes the above-mentioned "second medicine concentration adjusting step". Specifically, the drug concentration adjusting unit 31A adjusts the free chlorine concentration in the feedwater W11 by adding sodium hypochlorite to the feedwater W11 by controlling the first drug addition device 5, The stabilizer is added to the feed water W11 by controlling the second drug addition device 6, and the bromide compound is added to the feed water W11 by controlling the third drug addition device 7. Thereafter, the processing shifts to step S21 (return).

In step S23, whether the transmembrane pressure difference measured by the differential pressure measuring part 33 is less than P ₁ or P _2, or F flux value exceeds the F ₂ calculated by flux value calculating section 34 If it is ₁ or less (S23: YES), the process proceeds to step S24. If either the transmembrane pressure difference measured by the differential pressure measuring part 33 is P ₂ or more, or flux value calculated by the flux value calculating section 34 is F ₂ less (S23: NO) in The process shifts to the step S25.

  In step S24, the medicine concentration adjusting unit 31A executes the above-described "first medicine concentration adjusting step". Specifically, the drug concentration adjustment unit 31A controls the first drug addition device 5 to adjust the free chlorine concentration in the feed water W11 by adding sodium hypochlorite to the feed water W11, By controlling the second chemical addition device 6, a stabilizer is added to the feed water W11. Thereafter, the processing shifts to step S21 (return).

In step S25, F or transmembrane pressure measured by the pressure measuring part 33 is smaller than P ₂ or P _3, or flux value calculated by the flux value calculating unit 34 exceeds F ₃ If it is ₂ or less (S25: YES), the process proceeds to step S26. If either the transmembrane pressure difference measured by the differential pressure measuring part 33 is P ₃ or more, or flux value calculated by the flux value calculating section 34 is F ₃ or less (S25: NO) in The process proceeds to the step S27.

  In step S26, the drug concentration adjusting unit 31A controls the second drug addition device 6 to reduce the amount of the stabilizer injected into the water supply W11. Thereafter, the processing shifts to step S21 (return).

  In step S27, the drug concentration adjusting unit 31A controls the first drug adding device 5 to increase the amount of sodium hypochlorite injected into the water supply W11 and increase the amount of free chlorine in the water supply W11. . Thereafter, the processing shifts to step S21 (return).

[2.3 Effect of Second Embodiment]
According to the water treatment system 1A according to the present embodiment described above, for example, the following effects can be obtained.
The water treatment system 1A includes a transmembrane pressure measurement unit 33 that measures a transmembrane pressure difference, which is an input / output pressure difference of a path through which the concentrated water W30 flows in the reverse osmosis membrane module 14, or a permeation flux value in the reverse osmosis membrane module 14. Is further provided, and the value of the transmembrane pressure measured by the transmembrane pressure measuring means 33 exceeds the first threshold value, or the permeation flux value calculating means 34 When the calculated permeation flux value is equal to or less than the second threshold value, the chemical dosing means 6 and 7 and the free chlorine concentration adjusting means 5 execute the first chemical concentration adjusting step, and the value of the transmembrane pressure is reduced to the second value. When the value is equal to or smaller than the threshold value of 1, or when the permeation flux value exceeds the second threshold value, the chemical injecting means 6 and 7 and the free chlorine concentration adjusting means 5 perform the second chemical concentration adjusting step so as to execute the second chemical concentration adjusting step. The concentration adjusting unit 31A adjusts the chemical injection means 6 and 7 and the free chlorine concentration. Switching the drug concentration adjusting process executed by the stage 5.

  Because the value of the differential pressure and the permeation flux value in the reverse osmosis membrane module reflect the biofilm production amount, based on the biofilm production amount estimated from the transmembrane pressure difference value or the permeation flux value, By switching between injecting and not injecting the bromine compound, it is possible to adjust the drug concentration so as to minimize the degree of membrane degradation while suppressing the formation of a biofilm. In particular, at normal times, by making the form of stabilized hypoxia a bromine type, it is possible to reduce damage to the reverse osmosis membrane, and when the value of the differential pressure exceeds the first threshold When the flux value is equal to or less than the second threshold value, the chlorine-based oxidizing agent and the stabilizer are stopped by stopping the chemical injection of the bromine compound, instead of suddenly changing the molar ratio between the chlorine-based oxidizing agent and the stabilizer. The damage to the reverse osmosis membrane can be reduced as compared with the case where the molar ratio is changed.

  Further, when the value of the transmembrane pressure measured by the transmembrane pressure measuring means 33 exceeds a third threshold higher than the first threshold, or when the permeate flow calculated by the permeate flux value calculating means 34 is used. When the bundle value is equal to or less than a fourth threshold value lower than the second threshold value, the drug concentration adjusting unit 31A decreases the amount of the stabilizer injected.

  When the value of the transmembrane pressure exceeds the third threshold value or when the permeation flux value is equal to or less than the fourth threshold value, the injection amount of the stabilizer is reduced, and the amount of the chlorine-based oxidizing agent and the stabilizing agent is reduced. By changing the molar ratio, it is possible to reduce the amount of biofilm produced.

  Further, when the value of the transmembrane pressure measured by the transmembrane pressure measuring means 33 exceeds a fifth threshold value higher than the third threshold value, or when the permeate flow calculated by the permeate flux value calculating means 34 is used. When the bundle value is equal to or less than a sixth threshold value lower than the fourth threshold value, the drug concentration adjusting unit 31A increases the free chlorine concentration.

  When the value of the transmembrane pressure exceeds the fifth threshold value or when the permeation flux value is equal to or less than the sixth threshold value, the amount of the chlorine-based oxidizing agent is increased, and the chlorine-based oxidizing agent and the stabilizer are increased. By changing the molar ratio of, it is possible to reduce the amount of biofilm produced. In particular, the risk of membrane degradation of the reverse osmosis membrane increases when the chemical injection amount of the chlorine-based oxidant is increased, but only when the value of the transmembrane pressure exceeds the fifth threshold value, By increasing the chemical injection amount, it is possible to remove the biofilm while limiting the risk of membrane deterioration.

(Modification)
Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be implemented in various forms.

[Modification 1]
For example, the first chemical addition device 5 adjusts the free chlorine concentration in the feed water W11 by adding an oxidizing agent as the first chemical, but is not limited to this. The first chemical addition device 5 may add a reducing agent as the first chemical, and in this case, the concentration of free chlorine originally contained in the feed water W11 is reduced by the filtration process in the preceding stage or the like. As this reducing agent, for example, SBS (NaHSO ₃ : sodium bisulfite) may be used.
Further, the water treatment systems 1 and 1A may not be provided with the first chemical addition device 5 in the first place, and may be configured not to adjust the free chlorine concentration.

[Modification 2]
When the water quality sensor 8 measures the concentration of the reducing agent contained in the feed water W11, the control unit adjusts the free chlorine concentration in the feed water W11 by using the measured value of the reducing substance concentration received from the water quality sensor 8. In order to do so, the amount of the first medicine and the second medicine injected into 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 removed from the feedwater W11 as a pretreatment by using a filtering device as an iron removing / manganese removing device.

[Modification 3]
Further, in the above embodiment, when the first chemical adding device 5 adds an oxidizing agent such as sodium hypochlorite to the water supply line L1, and the second chemical adding device 6 adds a stabilizer to the water supply line L1. However, the present invention is not limited to this. For example, in addition to the oxidizing agent and the stabilizing agent, a bactericide such as isothiazoline and / or DBNPA may be injected. In addition, the drug concentration adjusting unit 31 or 31A performs a drug concentration adjusting step for the water supply line L1 performed by the drug injecting unit, and a first drug concentration adjusting step for dispensing isothiazoline and / or DBNPA to the water supply W11. The process may be switched between a second chemical concentration adjusting step of injecting a stabilizer and / or a bromine compound into the feed water W11.

  In this case, more specifically, when residual chlorine is present in the feed water W11, there is a concern that the reverse osmosis membrane module 14 may be deteriorated. Therefore, after removing residual chlorine, isothiazoline and / or DBNPA are used as a chemical. Note. On the other hand, as for the bromine compound, the chemical is injected in a state where the residual chlorine is present in the feed water W11.

[Modification 4]
Further, the water treatment systems 1 and 1A may have a configuration different from the above embodiment. For example, in the above description, the circulating water line L4 is provided. However, the configuration is not limited thereto, and a configuration without the circulating water line L4 may be employed. Further, in particular, in the first embodiment, for example, the first pressure sensor 13, the second pressure sensor 15, the third pressure sensor 17, and the flow rate sensor FM do not have to be essential components.

[Modification 5]
Further, in the water treatment systems 1 and 1A, it is more preferable to use a chlorine-resistant film because the water treatment systems 1 and 1A are less likely to be affected by the film deterioration. The combined use with the above-described chemical injection adjustment technique can further reduce the influence of deterioration. As the chlorine-resistant film, there is a film manufactured using, for example, a polyamide-based material.

[Modification 6]
In addition, in the water treatment systems 1 and 1A, it is preferable that the membrane cleaning step is also performed using the water supplied with the chemical. The membrane washing step includes flushing and the like, but a water supply line may be connected to the concentrated water line to flow water.

1 water treatment system,
5 First chemical addition device (free chlorine concentration adjusting means)
6 Second drug addition device (drug injection means)
7 Third drug addition device (drug injection means)
8 water quality sensor (water quality measurement means)
10 pressure pump 13 first pressure sensor, 15 second pressure sensor, 17 third pressure sensor,
14 reverse osmosis membrane module 30 30A control unit 31 31A drug concentration adjustment unit 32 clock unit 33 differential pressure measurement unit 34 permeation flux value calculation unit L1 water supply line, L2 permeate line, L3 concentrated water line,
L4 circulating water line, L5 concentrated drainage line,
L11 1st water supply line, L12 2nd water supply line

Claims (9)

A reverse osmosis membrane module that separates feedwater into permeate and concentrated water,
A water supply line for supplying water to the reverse osmosis membrane module;
A permeate line for delivering the 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 part or all of the concentrated water as concentrated wastewater to the outside of the system,
Stabilizing agent for water supply, and a chemical injection means for injecting a bromine compound,
The chemical concentration adjusting step in the water supply executed by the chemical injecting means includes a first chemical concentration adjusting step of injecting a stabilizer into the water supply, and a second chemical concentration adjusting step of injecting the stabilizer and the bromine compound into the water supply. A water treatment system, comprising: a medicine concentration adjusting unit that switches between a medicine concentration adjusting step and a medicine concentration adjusting step. Further provided with a free chlorine concentration adjusting means for adjusting the free chlorine concentration in the feed water,
The chemical concentration adjusting section adjusts the free chlorine concentration in the feed water, adjusts the free chlorine concentration in the feed water, and adjusts the free chlorine concentration in the feed water. The water treatment system according to claim 1, wherein the water treatment system switches between a second agent concentration adjusting step of injecting an agent and a bromine compound.   The water treatment system according to claim 1, wherein the drug concentration adjustment unit switches a drug concentration adjustment step performed by the chemical dosing unit and the free chlorine concentration adjustment unit based on an operation time of the water treatment system. . In the reverse osmosis membrane module, a transmembrane pressure difference measuring means for measuring a transmembrane pressure difference which is an input / output pressure difference of a path through which concentrated water flows, or a permeation flux value calculation for calculating a permeation flux value in the reverse osmosis membrane module Further comprising means,
When the value of the transmembrane pressure measured by the transmembrane pressure measurement means exceeds a first threshold value, or the permeation flux value calculated by the permeation flux value calculation means is equal to or less than a second threshold value. In the case of, the drug concentration adjusting unit switches to the first drug concentration adjusting step, and when the value of the transmembrane pressure is equal to or less than the first threshold, or when the permeation flux value is the second The water treatment system according to claim 1, wherein the medicine concentration adjustment unit switches to the second medicine concentration adjustment step when a threshold value is exceeded.   When the value of the transmembrane pressure measured by the transmembrane pressure measurement means exceeds a third threshold value higher than the first threshold value, or when the permeation flow calculated by the permeation flux value calculation means is used. 5. The water treatment system according to claim 4, wherein when the bundle value is equal to or less than a fourth threshold value lower than the second threshold value, the drug concentration adjustment unit decreases the amount of the stabilizer to be injected.   When the value of the transmembrane pressure measured by the transmembrane pressure measurement means exceeds a fifth threshold value higher than the third threshold value, or when the permeation flow calculated by the permeation flux value calculation means is used. The water treatment system according to claim 5, wherein the drug concentration adjusting unit increases the free chlorine concentration when the bundle value is equal to or less than a sixth threshold lower than the fourth threshold.   The water treatment system according to any one of claims 1 to 6, wherein the free chlorine concentration adjusting means is a second chemical injecting means for injecting a reducing agent into the water supply. Further provided is a water quality measuring means for measuring the quality of the supply water,
The said chemical | medical-concentration adjustment part sets the adjustment amount of the free chlorine concentration at the time of an operation start, the stabilizer, and the chemical | medical injection amount of a bromine compound based on the water quality measured by the said water quality measuring means. The water treatment system according to claim 7.
A reverse osmosis membrane module that separates feedwater into permeate and concentrated water,
A water supply line for supplying water to the reverse osmosis membrane module;
A permeate line for delivering the 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 part or all of the concentrated water as concentrated wastewater to the outside of the system,
Injection means for injecting isothiazoline and / or DBNPA and / or a stabilizer and / or a bromine compound into water supply;
Free chlorine concentration adjusting means for adjusting the free chlorine concentration in the feed water,
The step of adjusting the concentration of the drug in the water supplied by the chemical injecting means includes the first step of adjusting the concentration of free chlorine in the water and the first step of adjusting the concentration of the drug in the water by isothiazoline and / or DBNPA. A water concentration system that adjusts the free chlorine concentration and switches between a second drug concentration adjusting step of injecting a stabilizer and / or a bromine compound into the water supply.

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