JP7579439B2 - Method and apparatus for analyzing membrane blocking substances, and method and apparatus for controlling chemical injection into separation membrane - Google Patents

Description

The present invention relates to a method and apparatus for analyzing membrane blocking substances that block separation membranes, as well as a method and apparatus for controlling chemical injection into separation membranes.

In water treatment systems that use separation membranes to treat water to be treated, it is known that the separation membrane gradually becomes clogged due to membrane-blocking substances contained in the water to be treated. As the clogging of the separation membrane progresses, the efficiency of water treatment decreases, so generally, a cleaning solution such as an acid or alkali is used to dissolve and remove the membrane-blocking substances and restore the separation membrane to its initial state. The cleaning conditions for the separation membrane using a cleaning solution (type, concentration, cleaning flow rate, water temperature, etc. of the cleaning solution) are determined according to the degree of membrane clogging and the type of membrane-blocking substances, etc.

One possible method for determining the degree of membrane blockage and the type of membrane-blocking substance is to stop operation of the water treatment system, remove the blocked separation membrane or replace it with an unused separation membrane, and then analyze the blocked separation membrane. However, such methods have issues in that they require the time and effort of removing the separation membrane, reinstalling it after cleaning, or replacing it, and they also require a long time to obtain analysis results. Therefore, technologies for estimating the degree of membrane blockage and technologies for identifying the type of membrane-blocking substance are being developed.

For example, Patent Document 1 describes a technology in which a portion of the concentrated water separated by a separation membrane is sent to a monitoring separation membrane, and the degree of membrane blockage of the separation membrane is estimated based on the absolute value or rate of change of the amount of concentrated water permeated through the monitoring separation membrane, the absolute value or rate of change of the pressure difference of the concentrated water before and after permeation through the monitoring separation membrane, etc.

Furthermore, Patent Document 2 describes a membrane separation device equipped with a separation membrane that is made of a transparent resin or the like, and the type of membrane-blocking substance adhering to the membrane surface is identified by observing the membrane surface over time with a color sensor.

The above-mentioned Patent Document 1 proposes a technology for estimating the degree of membrane blockage, but does not identify the type of membrane-blocking substance attached to the membrane surface of the separation membrane. Therefore, the technology described in Patent Document 1 has the problem that it is not possible to select an appropriate chemical solution depending on the type of membrane-blocking substance.

On the other hand, the water treatment system described in Patent Document 2 identifies membrane-blocking substances from the color of the membrane surface observed by a color sensor, which has the problem that the types of membrane-blocking substances that can be identified are limited.

JP 2012-130823 A JP 2019-166463 A

The present invention has been made to solve the problems associated with the background art as described above, and aims to provide an analytical method and apparatus for membrane blocking substances that are capable of identifying a greater number of types of membrane blocking substances, as well as a method and apparatus for controlling chemical injection into a separation membrane that uses the analytical method and analytical apparatus.

In order to achieve the above object, the present invention provides a method for analyzing membrane blocking substances, comprising: irradiating a monitoring separation membrane through which test water has been passed with visible light;
measuring the reflection intensity of the visible light reflected by the monitoring separation membrane with a visible light spectrophotometer;
identifying an obstructing substance in the membrane based on the measured reflected intensity of the visible light;
The step of identifying a membrane obstructing substance comprises:
Measure the reflection intensity of an unused membrane, which is the unused monitoring separation membrane, and an assumed substance, which is an assumed clogging substance of the membrane;
Calculating a first slope, which is a difference in reflection intensity with respect to a difference in wavelength of visible light in the unused film and the assumed substance, respectively;
storing the first gradient of the unused film and the assumed substance, and the reflection intensity of the unused film at a wavelength of 400 to 450 nm or 700 to 800 nm;
measuring the reflection intensity of the visible light from the monitored membrane, which is the monitoring separation membrane through which the test water is passed;
determining that the monitored film is clogged when the reflection intensity of the monitored film is smaller than the reflection intensity of the unused film for the light of the wavelength of 400 to 450 nm or 700 to 800 nm;
calculating a second gradient, which is a difference in reflection intensity with respect to a difference in wavelength of the visible light in the monitored film;
The method identifies a membrane occluding substance that is occluding the monitored membrane by comparing the first gradient with the second gradient.

The apparatus for analyzing membrane-blocking substances of the present invention comprises a monitoring separation membrane through which test water is passed,
a visible light spectrophotometer that irradiates the monitoring separation membrane with visible light and measures the reflection intensity of the visible light reflected by the monitoring separation membrane;
a computing device for identifying an obstructing substance in the membrane based on the measured reflection intensity of the visible light;
having
The computing device includes:
A first slope, which is a difference in reflection intensity with respect to a difference in wavelength light of the visible light in the unused membrane and the assumed substance, is calculated from the reflection intensity of the unused membrane, which is the unused monitoring separation membrane, measured by the visible light spectrophotometer, and the assumed substance, which is an assumed clogging substance of the membrane, and the first slope of the unused membrane and the assumed substance, and the reflection intensity of the unused membrane in the wavelength light of 400 to 450 nm or 700 to 800 nm are stored;
Based on the reflection intensity of the visible light of the monitored membrane, which is the monitoring separation membrane through which the test water has been passed, measured by the visible light spectrophotometer, it is determined that the monitored membrane is clogged when the reflection intensity of the monitored membrane at wavelengths of 400 to 450 nm or 700 to 800 nm is smaller than the reflection intensity of the unused membrane, and a second slope, which is the difference in reflection intensity versus the difference in wavelengths of the visible light in the monitored membrane, is calculated, and the first slope and the second slope are compared to identify the blocking substance in the membrane that is blocking the monitored membrane.

The chemical injection control method for a separation membrane of the present invention separates water to be treated into permeate and concentrated water by a separation membrane;
A part of the concentrated water is passed through a monitoring separation membrane as test water,
Irradiating the monitoring separation membrane through which the test water has passed with visible light;
measuring the reflection intensity of the visible light reflected by the monitoring separation membrane with a visible light spectrophotometer;
identifying a membrane blocking substance that blocks the separation membrane based on the measured reflection intensity of the visible light;
The step of identifying the membrane-occluding substance comprises:
Measure the reflection intensity of an unused membrane, which is the unused monitoring separation membrane, and an assumed substance, which is the assumed membrane blocking substance;
Calculating a first slope, which is a difference in reflection intensity with respect to a difference in wavelength of visible light in the unused film and the assumed substance, respectively;
storing the first gradient of the unused film and the assumed substance, and the reflection intensity of the unused film at a wavelength of 400 to 450 nm or 700 to 800 nm;
measuring the reflection intensity of the visible light from the monitored membrane, which is the monitoring separation membrane through which the test water is passed;
determining that the monitored film is clogged when the reflection intensity of the monitored film is smaller than the reflection intensity of the unused film for the light of the wavelength of 400 to 450 nm or 700 to 800 nm;
calculating a second gradient, which is a difference in reflection intensity with respect to a difference in wavelength of the visible light in the monitored film;
identifying the membrane blocking substance blocking the monitored membrane by comparing the first gradient with the second gradient;
The method comprises injecting a chemical solution for dissolving and removing the identified membrane-clogging substance, or a chemical solution for suppressing membrane clogging due to the identified membrane-clogging substance, into a water flow line of the separation membrane.

The chemical injection control device for a separation membrane of the present invention comprises: a membrane separation device having a separation membrane that separates water to be treated into permeate and concentrated water;
A monitoring separation membrane through which a portion of the concentrated water is passed as test water;
a visible light spectrophotometer for irradiating visible light onto the monitoring separation membrane through which the test water has passed and measuring the reflection intensity of the visible light reflected by the monitoring separation membrane;
a calculation device that identifies a membrane clogging substance that causes the separation membrane to be clogged based on the measured reflection intensity of the visible light;
A control device that injects a chemical solution for dissolving and removing the identified membrane blocking substance or a chemical solution for suppressing membrane blocking due to the identified membrane blocking substance into a water flow line of the separation membrane;
having
The computing device includes:
A first slope, which is a difference in reflection intensity with respect to a difference in wavelength light of the visible light in the unused membrane and the assumed substance, is calculated from the reflection intensity of the unused membrane, which is the unused monitoring separation membrane, and the assumed substance, which is the assumed membrane blocking substance, measured by the visible light spectrophotometer, and the first slope of the unused membrane and the assumed substance and the reflection intensity of the unused membrane in the wavelength light of 400 to 450 nm or 700 to 800 nm are stored;
Based on the reflection intensity of the visible light of the monitored membrane, which is the monitoring separation membrane through which the test water has been passed, measured by the visible light spectrophotometer, it is determined that the monitored membrane is clogged when the reflection intensity of the monitored membrane at wavelengths of 400 to 450 nm or 700 to 800 nm is smaller than the reflection intensity of the unused membrane, and a second slope, which is the difference in reflection intensity relative to the difference in wavelengths of the visible light in the monitored membrane, is calculated, and the first slope and the second slope are compared to identify the membrane blocking substance that is blocking the monitored membrane.

1 is a block diagram showing one configuration example of a chemical injection control device for a separation membrane according to the present invention; FIG. 2 is a side cross-sectional view showing one configuration example of the analysis device shown in FIG. 1 . FIG. 13 is a block diagram showing a modified example of the chemical injection control device for the separation membrane of the present invention. 1 is a graph showing an example of a change in the spectrum of a membrane occluding substance. 1 is a graph showing an example of a change in the spectrum of a membrane occluding substance. 6 is a table showing an example of spectral data of the assumed substances shown in FIGS. 4 and 5. 6 is a table showing parameters used in the method for analyzing membrane-blocking substances of the embodiment, determined from the spectral data shown in FIGS. 4 and 5. 1 is a flowchart illustrating an example of a processing procedure according to an embodiment. 6 is a table showing parameters used in a comparative example of an analytical method for membrane-blocking substances, determined from the spectral data shown in FIGS. 4 and 5 .

Next, the present invention will be explained with reference to the drawings.

In the present invention, the occurrence of "membrane blockage" refers to a state in which a membrane-blocking substance is attached to at least a portion of the membrane surface, and does not limit the degree of membrane blockage. The degree to which membrane blockage must progress before cleaning of the separation membrane can be determined according to the purpose of water treatment, the type of water to be treated, the components contained in the water to be treated, the purity of the permeate, etc. Examples of separation membranes to which the present invention can be applied include reverse osmosis membranes, microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, forward osmosis membranes, degassing membranes, and decarbonation membranes.

Figure 1 is a block diagram showing one configuration example of a separation membrane chemical injection control device of the present invention, and Figure 2 is a side cross-sectional view showing one configuration example of the analysis device shown in Figure 1. Figure 3 is a block diagram showing a modified example of the separation membrane chemical injection control device of the present invention. The separation membrane chemical injection control device of the present invention shown in Figures 1 to 3 constitutes part of a water treatment system that treats the water to be treated using a separation membrane.

As shown in FIG. 1, the chemical injection control device for separation membranes of the present invention includes a raw water tank 1 for storing water to be treated, a membrane separation device 2 equipped with a separation membrane for separating the water to be treated supplied from the raw water tank 1 into concentrated water and permeate water, an analyzer 3 for identifying the type of membrane blocking substance attached to the separation membrane, a part of the concentrated water separated by the membrane separation device 2 being supplied as test water, a chemical tank 4 for storing cleaning chemicals for cleaning the separation membrane, and a control device 5 for controlling the operation of the entire chemical injection control device for separation membranes. In FIG. 1, a configuration example in which the chemical injection control device for separation membranes has one chemical tank 4 is shown, but the chemical injection control device for separation membranes may have a configuration having multiple chemical tanks 4. In that case, different types of chemicals may be stored in the multiple chemical tanks 4.

In addition to the above configuration, the chemical injection control device for the separation membrane shown in FIG. 1 includes a raw water pump 11 for supplying treated water from the raw water tank 1 to the membrane separation device 2, a chemical injection pump 12 for injecting chemical liquid from the chemical liquid tank 4 into the water treatment system, and a plurality of valves 13 arranged in a water supply line for discharging concentrated water separated by the membrane separation device 2 to the outside. When the chemical injection control device for the separation membrane has a plurality of chemical liquid tanks 4, the chemical injection control device for the separation membrane may include a plurality of chemical injection pumps 12 according to the number of chemical liquid tanks 4. FIG. 1 shows an example of a configuration including a first valve 13A arranged in a water supply line between the membrane separation device 2 and the analysis device 3, a second valve 13B arranged in a water supply line between the analysis device 3 and the raw water tank 1, and a third valve 13C for discharging concentrated water separated by the membrane separation device 2 that is not sent to the analysis device 3 to the outside. The second valve 13B is provided to return the chemical solution to the raw water tank 1 through the concentrated water flow line of the concentrated water separated by the membrane separation device 2 during injection (chemical injection). The second valve 13B may also be used to return the concentrated water to the raw water tank 1 during normal operation. The chemical injection control device for the separation membrane of the present invention does not need to be configured to return the concentrated water or the chemical solution to the raw water tank 1. The multiple valves 13 may be provided as appropriate depending on the configuration and operation of the chemical injection control device for the separation membrane. Similarly, the multiple pumps are not limited to the raw water pump 11 and the chemical injection pump 12, and may be provided as appropriate depending on the configuration and operation of the chemical injection control device for the separation membrane.

The water to be treated stored in the raw water tank 1 is supplied to the membrane separation device 2 by the raw water pump 11. The membrane separation device 2 separates the water to be treated into permeate containing substances that permeate the separation membrane and concentrated water containing substances that do not permeate the separation membrane. The permeate is discharged as treated water. Alternatively, the permeate is further treated in another membrane separation device or ion exchange device, etc. and discharged as treated water. The concentrated water is discharged as wastewater. Alternatively, the concentrated water is further treated in another membrane separation device, or biological treatment device, solid-liquid separation device, etc. and discharged.

As shown in FIG. 1, the chemical solution stored in the chemical solution tank 4 is injected into the water flow line of the separation membrane equipped in the membrane separation device 2. The chemical solution may be, for example, injected into the raw water tank 1, into the water flow line of the water to be treated between the raw water pump 11 and the membrane separation device 2, or into the water flow line of the concentrated water between the membrane separation device 2 and the analysis device 3. The chemical solution stored in the chemical solution tank 4 is selected based on the type of water to be treated, the components contained in the water to be treated, and the like, according to the type and properties of the membrane blocking substances expected to occur. Types of chemical solutions include acidic chemical solutions, alkaline chemical solutions, surfactants, etc., which are used to dissolve and remove membrane blocking substances and wash the separation membrane. The chemical solution may be a slime control agent, a scale dispersant, etc., which are used to suppress membrane blocking due to membrane blocking substances (to delay membrane blocking).

The control device 5 controls the operation of the entire chemical injection control device for the separation membrane of the present invention by controlling the raw water pump 11, the chemical injection pump 12, and the multiple valves 13. The control device 5 also injects the chemical liquid stored in the chemical liquid tank 4 into the water flow line of the separation membrane based on the analysis results of the analysis device 3. When the chemical injection control device for the separation membrane has multiple chemical liquid tanks 4, the control device 5 may inject a chemical liquid selected from multiple types of chemical liquids stored in the multiple chemical liquid tanks 4 into the water flow line of the separation membrane according to the type of membrane blocking substance identified by the analysis device 3. When injecting chemicals into the water flow line of the separation membrane, the control device 5 may circulate the chemical liquid by opening the first valve 13A and the second valve 13B and closing the third valve 13C. The control device 5 can be realized, for example, by a well-known PLC (Programmable Logic Controller). The control device 5 may be realized by a well-known information processing device (computer) equipped with a CPU (Central Processing Unit), a storage device, an I/O interface, a communication device, etc.

1 and 2, the analysis device 3 includes a raw water chamber 31, a permeated water chamber 32, a monitoring separation membrane 33, a visible light spectrophotometer 34, and a computing device 35, with the monitoring separation membrane 33 separating the raw water chamber 31 and the permeated water chamber 32. The raw water chamber 31, the permeated water chamber 32, and the monitoring separation membrane 33 constitute a monitoring cell 30.

A portion of the concentrated water separated by the membrane separation device 2 is supplied as test water to the monitoring separation membrane 33, which further separates the test water into concentrated water and permeate water. It is preferable to use the same type of separation membrane as the separation membrane provided in the membrane separation device 2 for the monitoring separation membrane 33. Furthermore, it is more preferable to use a membrane made by the same manufacturer as the separation membrane provided in the membrane separation device 2 for the monitoring separation membrane 33.

The raw water chamber 31 is supplied with the test water and discharges concentrated water containing substances that do not permeate the monitoring separation membrane 33. Permeated water containing substances that have permeated the monitoring separation membrane 33 is discharged from the permeated water chamber 32. The raw water chamber 31 and the permeated water chamber 32 are each made of a material that transmits visible light, and a visible light spectrophotometer 34 is disposed on the outer wall surface of the raw water chamber 31 that faces the membrane surface of the monitoring separation membrane 33. The raw water chamber 31 and the permeated water chamber 32 may be made of any material that transmits visible light, such as an acrylic plate, a glass plate, quartz, or plastic. The raw water chamber 31 and the permeated water chamber 32 may be formed individually or integrally.

The visible light spectrophotometer 34 includes an illumination unit that irradiates visible light and a measurement unit that measures the reflection intensity of each wavelength of visible light. The illumination unit irradiates the membrane surface of the monitoring separation membrane 33 with visible light, and the measurement unit measures the reflection intensity of each wavelength of visible light reflected from the membrane surface. The measurement unit of the visible light spectrophotometer 34 may measure the reflection intensity of at least four or more wavelengths of light in the visible light range of 400 to 800 nm. For example, the measurement unit may measure the reflection intensity of at least one or more wavelengths of light from the wavelength light ranges of 400 to 450 nm, 450 to 500 nm, 600 to 700 nm, and 700 to 800 nm. The illumination unit may have any known configuration as long as it can irradiate wavelength light in the visible light range. The visible light spectrophotometer 34 measures the reflection intensity of visible light reflected from the membrane surface of the monitoring separation membrane 33 at a predetermined period set in advance, and transmits the measurement data to the calculation device 35.

When the calculation device 35 receives the measurement data of the reflection intensity from the visible light spectrophotometer 34, it estimates the type of substance attached to the membrane surface of the monitoring separation membrane 33 based on the measurement data, and notifies the control device 5 of the estimated substance as a membrane blocking substance of the separation membrane. At this time, the calculation device 35 may estimate the progress of membrane blocking of the monitoring separation membrane 33 and transmit the estimation result to the control device 5 as well. The calculation device 35 or the control device 5 may notify the manager of the water treatment system including the separation membrane chemical injection control device of the present invention of the estimated result of the membrane blocking substance or the estimated result of the progress of membrane blocking, etc., using an output device such as a display device.

1 and 2 show an example of a configuration in which a portion of the concentrated water separated by the membrane separation device 2 is supplied to the monitoring cell 30 as test water. The separation membrane chemical injection control device of the present invention may also be configured to supply a portion of the water to be treated stored in the raw water tank 1 to the monitoring cell 30 as test water, as shown in Figure 3. In that case, the first valve 13A may be moved, for example, to the water flow line between the raw water pump 11 and the analysis device 3, as shown in Figure 3.

In the present invention, one or more membrane blocking substances (hereinafter referred to as assumed substances) that are expected (assumed) to occur in the separation membrane are selected based on the purpose of the water treatment system, the type of water to be treated, the components contained in the water to be treated, etc., and data on the reflection intensity in visible light (spectral data) for each assumed substance is measured in advance. In addition, data on the reflection intensity in visible light of an unused monitoring separation membrane (= separation membrane, hereinafter referred to as unused membrane) is also measured in advance. Then, the slope (first slope) which is the difference in reflection intensity with respect to the difference in wavelength light for the unused membrane and each assumed substance, calculated from the spectral data, and the value of the reflection intensity at a specific wavelength light are each stored in the memory device of the calculation device 35.

The computing device 35 identifies membrane blocking substances by comparing the previously measured data of reflection intensity for each wavelength of light of the unused membrane and the assumed substance with the data of reflection intensity for each wavelength of light of the monitoring separation membrane (hereinafter referred to as the monitored membrane) through which the test water is passed by operating the water treatment system. More specifically, the computing device 35 measures the reflection intensity data for four or more wavelengths of light in the visible light range for the unused membrane and the assumed substance, and stores the reflection intensity and the above-mentioned slope for each unused membrane and assumed substance obtained from the measurement data. In addition, the computing device 35 stores the discrimination conditions for discriminating membrane blocking substances, which are set based on the reflection intensity and slope for each unused membrane and assumed substance. Then, when the reflection intensity for each wavelength of light of the monitored membrane is measured by the visible light spectrophotometer 34, the discrimination conditions are used to identify membrane blocking substances from the measurement data of the monitored membrane.

In addition, when estimating the degree of membrane blockage, the calculation device 35 may use a method for estimating the degree of membrane blockage of the separation membrane based on, for example, the absolute value or rate of change of the amount of concentrated water permeated through the monitoring separation membrane 33, the absolute value or rate of change of the pressure difference of the concentrated water before and after permeation through the monitoring separation membrane 33, etc., as described in the above Patent Document 1.

It is desirable to always include light with wavelengths of 400 to 450 nm or 700 to 800 nm in the visible light range when measuring reflection intensity. The inventors have confirmed through experiments that when membrane blocking substances are attached to the membrane surface of the separation membrane (monitoring separation membrane 33), the reflection intensity in these wavelength light ranges is lower than that of an unused membrane. Therefore, by including light with wavelengths of 400 to 450 nm or 700 to 800 nm in the reflection intensity measurement, it is possible to determine whether membrane blocking has occurred in the monitored membrane.

The arithmetic unit 35 may be realized, for example, by an information processing device (computer) equipped with a CPU, a storage device, an I/O interface, a communication device, etc. When the control device 5 is realized by an information processing device (computer), the functions of the arithmetic unit 35 may be realized by the control device 5. In that case, the visible light spectrophotometer 34 may transmit measurement data of the reflection intensity for each wavelength of light to the control device 5. The communication means between the visible light spectrophotometer 34 and the arithmetic unit 35 (or the control device 5), and the communication means between the arithmetic unit 35 and the control device 5 may be either well-known wired communication means or wireless communication means, and the communication standard may be any well-known standard.

As described above, the control device 5 injects the chemical solution stored in the chemical solution tank 4 into the water flow line of the separation membrane based on the membrane blocking substance identified by the analysis device 3. For example, if the membrane blocking substance is identified as calcium scale, an acidic chemical solution is injected, and if the membrane blocking substance is identified as silica or biofouling, an alkaline chemical solution is injected. In this way, by cleaning the separation membrane with an appropriate cleaning chemical solution depending on the type of membrane blocking substance, the function of the separation membrane can be restored. Before injecting the chemical solution, the control device 5 may flush each water flow line provided in the separation membrane chemical injection control device of the present invention with pure water or the like.

The control device 5 may also inject a chemical solution intended to suppress (delay) the occurrence of membrane clogging into the water line of the separation membrane. For example, if the membrane clogging substance is identified as slime caused by biofouling, a slime control agent may be injected, and if the membrane clogging substance is identified as an inorganic substance such as calcium fluoride (CaF ₂ ) or silica, a scale dispersant may be injected. If the membrane clogging substance is a substance that can suppress the occurrence of membrane clogging by controlling the pH, such as calcium carbonate (CaCO ₃ ), the occurrence of membrane clogging may be suppressed by injecting an acidic or alkaline chemical solution.

In this way, by injecting appropriate chemicals during operation of the water treatment system to prevent clogging of the separation membrane, the water treatment system can be operated stably for a relatively long period of time. Furthermore, if it is confirmed that the generation of membrane-clogging substances is being suppressed, it is also possible to reduce the running costs of the water treatment system by reducing the injection amounts of slime control agents, scale dispersants, etc.

According to the present invention, data on the reflection intensity of an unused film and an assumed substance for four or more wavelengths of light in the visible light region is measured, and the reflection intensity and the above-mentioned slope for each unused film and assumed substance obtained from the measurement data are stored. In addition, discrimination conditions for discriminating between film blocking substances, which are preset based on the reflection intensity and slope for each unused film and assumed substance, are stored. Then, when the reflection intensity data for each wavelength of light of the monitored film is measured by the visible light spectrophotometer 34, the discrimination conditions are used to identify the film blocking substance from the measurement data of the monitored film. This makes it possible to identify a greater number of types of film blocking substances.

Next, an embodiment of the present invention will be described with reference to the drawings.

Figures 4 and 5 are graphs showing an example of the change in the spectrum of a hypothetical substance.

In this example, multiple separation membranes (= monitoring separation membranes 33, hereafter referred to as blocked membranes) to which the assumed substance was intentionally attached and the unused membrane were prepared, and the reflection intensity of each wavelength of light of the unused membrane and the blocked membrane was measured using a visible light spectrophotometer 34. A hyperspectral camera (Pika L, manufactured by RESONON) with a measurement wavelength range of 400 to 1000 nm was used as the visible light spectrophotometer 34.

The blocking membranes were prepared by attaching calcium carbonate (CaCO3), calcium fluoride ( _CaF2 ), and silica ( _SiO2 ) to the separation membrane, as well as by biofouling. An unused membrane and a number of blocking membranes were placed on the operating stage, and visible light was irradiated onto the unused membrane and the blocking membrane, and the reflection intensity of each wavelength of light reflected from the membrane surface was measured using the hyperspectral camera.

For the blocked membranes with calcium carbonate, calcium fluoride, and silica attached, the reflection intensity was measured in the range of 450 to 600 nm wavelength light, along with the unused membrane. The graph in Figure 4 shows the reflection intensity (spectrum) for each wavelength light of these separation membranes. For the blocked membranes that were biofouled, the reflection intensity was measured in the range of 400 to 1000 nm wavelength light, along with the unused membrane. The graph in Figure 5 shows the reflection intensity (spectrum) for each wavelength light of these separation membranes. Here, the measurement range of wavelength light is different for the blocked membranes with calcium carbonate, calcium fluoride, and silica attached and the blocked membranes that were biofouled, but the measurement range of wavelength light should be set so that the spectrum of the unused membrane and each assumed substance can be distinguished, and should be set appropriately within the visible light region of 400 to 800 nm depending on the properties of the unused membrane and the assumed substance.

Next, we will explain an analytical method for identifying membrane blocking substances based on the measurement data (spectral data) of the reflection intensity of the unused membrane and blocked membrane.

Figure 6 is a table showing an example of spectral data for the assumed substance shown in Figures 4 and 5, and Figure 7 is a table showing parameters used in the analytical method for membrane-blocking substances of the embodiment, determined from the spectral data shown in Figures 4 and 5.

Figure 6 shows the measurement data (spectral data) of the reflection intensity of the unused film and blocked film shown in Figures 4 and 5, extracted from the measurement data of light with five wavelengths of 400 nm, 450 nm, 600 nm, 700 nm, and 800 nm.

Figure 7 shows the sum of the reflection intensities at wavelengths of 400 and 450 nm, the slopes at wavelengths of 400 and 450 nm, and the slopes at wavelengths of 600 and 800 nm for an unused film and an assumed substance, calculated from the measurement data of the reflection intensities of the unused film and blocked film shown in Figures 4 and 5, respectively.

As described above, whether or not film blockage has occurred in the monitored film can be determined by comparing the reflection intensity of the unused film at wavelengths of 400-450 nm or 700-800 nm with the reflection intensity of the monitored film. However, the difference may be small and difficult to determine using only one wavelength of light. Therefore, in this embodiment, the sum of the reflection intensities of the two wavelengths of light, 400 and 450 nm, shown in Figure 7, is used to determine whether or not film blockage has occurred in the monitored film.

The slope (first slope) for the unused film and the assumed material can be calculated by dividing the difference in the reflection intensity of the wavelength light relative to the difference in the wavelength light, i.e., the difference in the reflection intensity of the two wavelength lights by the difference in the wavelength light. For example, the slope for wavelengths of 600 and 800 nm can be calculated using the following formula:

Tilt (600 nm, 800 nm)
=(Reflection intensity 800nm-Reflection intensity 600nm)/(800nm-600nm)
Next, the method for analyzing membrane-blocking substances in this embodiment will be described with reference to a flow chart.

Figure 8 is a flowchart showing an example of the processing procedure of the embodiment. The calculation device 35 stores the sum of the reflection intensity and the slope value calculated from the measurement data of the reflection intensity for each unused film and assumed substance (see Figure 7). The calculation device 35 also stores the discrimination conditions for identifying the film blocking substance. As described later, the discrimination conditions include, for example, whether the slope of the monitored film at wavelengths of 600 and 800 nm is more than twice the slope of the unused film, whether the slope of the monitored film at wavelengths of 400 and 450 nm is more than 1.5 times the slope of the unused film, whether the slope of the monitored film at wavelengths of 400 and 450 nm is less than 0.5 times the slope of the unused film, etc. The discrimination conditions are not limited to these, and may be set in advance based on the slope (first slope) at each wavelength of the unused film and each assumed substance so that the substance (film blocking substance) attached to the monitored film can be identified.

8, when the calculation device 35 receives measurement data of the reflection intensity of the monitored film from the visible light spectrophotometer 34, it calculates the sum of the reflection intensities of the monitored film at wavelengths of 400 and 450 nm (step S1) and determines whether or not film blockage has occurred in the monitored film (step S2). As described above, the calculation device 35 may determine that film blockage has occurred in the monitored film when the sum of the reflection intensities of the monitored film at wavelengths of 400 and 450 nm is smaller than the sum of the reflection intensities of an unused film.

If it is determined that no film blockage has occurred in the monitored film, the calculation device 35 returns to step S1 and repeats the process from step S1. On the other hand, if it is determined that a film blockage has occurred in the monitored film, the calculation device 35 proceeds to step S3 and calculates the slope of the monitored film at wavelengths of 600 and 800 nm.

Next, the calculation device 35 determines whether the inclination of the monitored film at wavelengths of 600 and 800 nm is larger (e.g., more than twice as large) than the inclination of the unused film (step S4).

If the slope of the monitored membrane at wavelengths of 600 and 800 nm is more than twice the slope of the unused membrane, the membrane blocking substance is likely to be biofouling, as shown in Figure 7. In this case, the calculation device 35 transmits information to notify the control device 5 that the membrane blocking substance is biofouling (step S5), and the process returns to step S1 and repeats the process from step S1.

When the control device 5 is notified by the computing device 35 that the membrane blocking substance is biofouling, if the separation membrane is to be cleaned, an alkaline chemical solution is injected to clean the separation membrane (monitoring separation membrane 33). If the occurrence of membrane blockage is to be suppressed, the amount of slime control agent injected is increased.

On the other hand, in step S4, if the slope of the monitored film at wavelengths of 600 and 800 nm is less than twice the slope of the unused film, the film blocking substance is likely to be calcium carbonate, silica, or calcium fluoride, as shown in Figure 7. In this case, the calculation device 35 proceeds to the process of step S6 and calculates the slope of the monitored film at wavelengths of 400 and 450 nm.

Next, the calculation device 35 determines whether the inclination of the monitored film at wavelengths of 400 and 450 nm is larger than the inclination of the unused film (e.g., 1.5 times or more) (step S7).

If the slope of the monitored film at wavelengths of 400 and 450 nm is 1.5 times or more the slope of the unused film, the film blocking substance is likely to be calcium carbonate, as shown in Figure 7. In this case, the calculation device 35 transmits information to notify the control device 5 that the film blocking substance is calcium carbonate (step S8), and the process returns to step S1 and repeats the process from step S1.

When the control device 5 is notified by the computing device 35 that the membrane blocking substance is calcium carbonate, in case of cleaning the separation membrane, it injects an acidic chemical solution to clean the separation membrane (monitoring separation membrane). In addition, in case of suppressing the occurrence of membrane blockage, it suppresses the occurrence of membrane blockage by injecting an acidic or alkaline chemical solution to control the pH.

In step S7, if the slope of the monitored film at wavelengths of 400 and 450 nm is less than 1.5 times the slope of the unused film, the film blocking substance is likely to be silica or calcium fluoride, as shown in Figure 7. In this case, the computing device 35 proceeds to the process of step S9 and determines whether the slope of the monitored film at wavelengths of 400 and 450 nm is smaller (e.g., 0.5 times or less) than the slope of the unused film.

If the slope of the monitored film at wavelengths of 400 and 450 nm is less than 0.5 times the slope of the unused film, the film blocking substance is likely to be silica, as shown in Figure 7. In this case, the calculation device 35 transmits information to notify the control device 5 that the film blocking substance is silica (step S10), and the process returns to step S1 and repeats the process from step S1.

When the control device 5 is notified by the computing device 35 that the membrane blocking substance is silica, if the separation membrane is to be cleaned, an alkaline chemical solution is injected to clean the separation membrane (monitoring separation membrane 33). If membrane blockage is to be suppressed, the amount of scale dispersant injected is increased. The control device 5 may also suppress the occurrence of membrane blockage by injecting an acidic or alkaline chemical solution to control the pH.

On the other hand, if the slope of the monitored film at wavelengths of 400 and 450 nm is greater than 0.5 times the slope of the unused film, the film blocking substance is likely to be calcium fluoride, as shown in Figure 7. In this case, the calculation device 35 transmits information to the control device 5 notifying that the film blocking substance is calcium fluoride (step S11), and the process returns to step S1 and repeats the process from step S1.

When the control device 5 is notified by the computing device 35 that the membrane blocking substance is calcium fluoride, if the separation membrane is to be cleaned, an acidic chemical solution is injected to clean the separation membrane (monitoring separation membrane). If membrane blockage is to be suppressed, the amount of scale dispersant injected is increased. The control device 5 may suppress membrane blockage by injecting an acidic or alkaline chemical solution to control the pH.

In this embodiment, an example for identifying membrane blocking substances when the assumed substances are calcium carbonate, calcium fluoride, silica, and biofouling is shown. If the assumed substances are other than those mentioned above, the reflection intensity of four or more wavelengths of light for each substance can be measured in advance, and the total value of the reflection intensity for each substance and the slope at a specific wavelength of light can be obtained as shown in FIG. 7, and used to identify membrane blocking substances. For example, if barium salts, calcium salts, magnesium salts, metal complexes, etc. are considered as assumed substances, the reflection intensity of four or more wavelengths of light in visible light for each substance can be measured in advance, and the total value of the reflection intensity for each substance and the slope at a specific wavelength of light can be obtained as shown in FIG. 7, and used to identify membrane blocking substances.

Comparative Example

In this comparative example, we explain the results of comparing the method for identifying membrane-blocking substances shown in the above examples with the method for identifying membrane-blocking substances shown in Patent Document 2 above.

Figure 9 is a table showing the parameters used in the comparative example analysis method for membrane-blocking substances, determined from the spectral data shown in Figures 4 and 5.

Figure 9 shows the slopes obtained from the measurement data for each of the assumed substances shown in the above examples for red (R: wavelength of light 466 nm), green (G: wavelength of light 532 nm), and blue (B: wavelength of light 630 nm), which are the three primary colors of light that can be measured by the color sensor used in Patent Document 2.

As shown in Figure 9, when comparing the slopes of the unused membrane and each assumed substance at wavelengths of 466 nm, 532 nm, and 630 nm, it can be seen that the slopes of the unused membrane and calcium fluoride are almost the same. It can also be seen that the slopes of calcium carbonate, silica, and biofouling are almost the same.

Therefore, when calcium carbonate, calcium fluoride, silica, and biofouling are considered to be the assumed substances, it is difficult to distinguish between an unused membrane and calcium fluoride, and it is difficult to distinguish between calcium carbonate, silica, and biofouling, using the method for identifying membrane blocking substances shown in Patent Document 2. In other words, when calcium carbonate, calcium fluoride, silica, and biofouling are considered to be the assumed substances, it is clear that the method for identifying membrane blocking substances shown in Patent Document 2 cannot identify membrane blocking substances.

In contrast, in the present invention, as shown in the above examples, it is possible to distinguish between these substances, and by selecting an appropriate chemical solution based on the identified membrane-blocking substance, it is possible to clean the separation membrane or suppress the occurrence of membrane blockage.

The present invention has been described above with reference to the embodiments and examples, but the present invention is not limited to the above embodiments. Various modifications that can be understood by a person skilled in the art are possible in the configuration and details of the present invention within the scope of the present invention.

Claims (8)

Visible light is irradiated onto the monitoring separation membrane through which the test water has been passed,
measuring the reflection intensity of the visible light reflected by the monitoring separation membrane with a visible light spectrophotometer;
identifying an obstructing substance in the membrane based on the measured reflected intensity of the visible light;
The step of identifying a membrane obstructing substance comprises:
Measure the reflection intensity of an unused membrane, which is the unused monitoring separation membrane, and an assumed substance, which is an assumed clogging substance of the membrane;
Calculating a first slope, which is a difference in reflection intensity with respect to a difference in wavelength of visible light in the unused film and the assumed substance, respectively;
storing the first gradient of the unused film and the assumed substance, and the reflection intensity of the unused film at a wavelength of 400 to 450 nm or 700 to 800 nm;
measuring the reflection intensity of the visible light from the monitored membrane, which is the monitoring separation membrane through which the test water is passed;
determining that the monitored film is clogged when the reflection intensity of the monitored film is smaller than the reflection intensity of the unused film for the light of the wavelength of 400 to 450 nm or 700 to 800 nm;
calculating a second gradient, which is a difference in reflection intensity with respect to a difference in wavelength of the visible light in the monitored film;
The method for analyzing a membrane clogging substance includes comparing the first gradient with the second gradient to identify a membrane clogging substance that is clogging the monitored membrane. The method for analyzing membrane blocking substances according to claim 1, which identifies the membrane blocking substances based on the reflection intensity of four or more wavelengths of light in the visible light region of 400 nm to 800 nm. The method for analyzing membrane blocking substances according to claim 2, wherein the membrane blocking substances are identified based on the reflection intensity of at least one or more wavelengths of light measured in each of the visible light ranges of 400 nm to 450 nm, 450 nm to 500 nm, 600 nm to 700 nm, and 700 nm to 800 nm. A monitoring separation membrane through which test water is passed;
a visible light spectrophotometer that irradiates the monitoring separation membrane with visible light and measures the reflection intensity of the visible light reflected by the monitoring separation membrane;
a computing device for identifying an obstructing substance in the membrane based on the measured reflection intensity of the visible light;
having
The computing device includes:
A first slope, which is a difference in reflection intensity with respect to a difference in wavelength light of the visible light in the unused membrane and the assumed substance, is calculated from the reflection intensity of the unused membrane, which is the unused monitoring separation membrane, measured by the visible light spectrophotometer, and the assumed substance, which is an assumed clogging substance of the membrane, and the first slope of the unused membrane and the assumed substance, and the reflection intensity of the unused membrane in the wavelength light of 400 to 450 nm or 700 to 800 nm are stored;
This membrane blocking substance analysis device determines that the monitored membrane is blocked when the reflection intensity of the monitored membrane, which is the monitoring separation membrane through which the test water has been passed, is smaller than the reflection intensity of the unused membrane at the 400 to 450 nm or 700 to 800 nm wavelength light based on the reflection intensity of the visible light reflected by the monitored membrane measured by the visible light spectrophotometer, calculates a second slope which is the difference in reflection intensity relative to the difference in wavelength light of the visible light in the monitored membrane, and compares the first slope with the second slope to identify the blocking substance in the membrane that is blocking the monitored membrane. The computing device includes:
5. The apparatus for analyzing membrane clogging substances according to claim 4, wherein the membrane clogging substances are identified based on the reflection intensities of four or more wavelengths of light in the visible light region of 400 nm to 800 nm. The computing device includes:
The apparatus for analyzing membrane blocking substances according to claim 5, wherein the membrane blocking substances are identified based on the reflection intensity of at least one or more wavelengths of light measured in each of the visible light ranges of 400 nm to 450 nm, 450 nm to 500 nm, 600 nm to 700 nm, and 700 nm to 800 nm. The water to be treated is separated into permeate and concentrated water by a separation membrane;
A part of the concentrated water is passed through a monitoring separation membrane as test water,
Irradiating the monitoring separation membrane through which the test water has passed with visible light;
measuring the reflection intensity of the visible light reflected by the monitoring separation membrane with a visible light spectrophotometer;
identifying a membrane blocking substance that blocks the separation membrane based on the measured reflection intensity of the visible light;
The step of identifying the membrane-occluding substance comprises:
Measure the reflection intensity of an unused membrane, which is the unused monitoring separation membrane, and an assumed substance, which is the assumed membrane blocking substance;
Calculating a first slope, which is a difference in reflection intensity with respect to a difference in wavelength of visible light in the unused film and the assumed substance, respectively;
storing the first gradient of the unused film and the assumed substance, and the reflection intensity of the unused film at a wavelength of 400 to 450 nm or 700 to 800 nm;
measuring the reflection intensity of the visible light from the monitored membrane, which is the monitoring separation membrane through which the test water is passed;
determining that the monitored film is clogged when the reflection intensity of the monitored film is smaller than the reflection intensity of the unused film for the light of the wavelength of 400 to 450 nm or 700 to 800 nm;
calculating a second gradient, which is a difference in reflection intensity with respect to a difference in wavelength of the visible light in the monitored film;
identifying the membrane blocking substance blocking the monitored membrane by comparing the first gradient with the second gradient;
A chemical injection control method for a separation membrane, comprising injecting a chemical solution for dissolving and removing the identified membrane-clogging substance, or a chemical solution for suppressing membrane clogging due to the identified membrane-clogging substance, into a water flow line of the separation membrane. A membrane separation device having a separation membrane that separates the water to be treated into permeate and concentrated water;
A monitoring separation membrane through which a portion of the concentrated water is passed as test water;
a visible light spectrophotometer for irradiating visible light onto the monitoring separation membrane through which the test water has passed and measuring the reflection intensity of the visible light reflected by the monitoring separation membrane;
a calculation device that identifies a membrane clogging substance that causes the separation membrane to be clogged based on the measured reflection intensity of the visible light;
A control device that injects a chemical solution for dissolving and removing the identified membrane blocking substance or a chemical solution for suppressing membrane blocking due to the identified membrane blocking substance into a water flow line of the separation membrane;
having
The computing device includes:
A first slope, which is a difference in reflection intensity with respect to a difference in wavelength light of the visible light in the unused membrane and the assumed substance, is calculated from the reflection intensity of the unused membrane, which is the unused monitoring separation membrane, and the assumed substance, which is the assumed membrane blocking substance, measured by the visible light spectrophotometer, and the first slope of the unused membrane and the assumed substance and the reflection intensity of the unused membrane in the wavelength light of 400 to 450 nm or 700 to 800 nm are stored;
A separation membrane drug injection control device that determines that the monitored membrane is clogged when the reflection intensity of the monitored membrane at wavelengths of 400 to 450 nm or 700 to 800 nm is smaller than the reflection intensity of the unused membrane based on the reflection intensity of the visible light of the monitored membrane, which is the monitoring separation membrane through which the test water has been passed, measured by the visible light spectrophotometer, calculates a second slope, which is the difference in reflection intensity relative to the difference in wavelengths of the visible light in the monitored membrane, and identifies the membrane blocking substance that is blocking the monitored membrane by comparing the first slope with the second slope.

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