KR20200042437A - Method and apparatus for inspection of polymeric membrane aging in water treatment process - Google Patents

Abstract

The present invention relates to a method for diagnosing deterioration of a polymeric membrane for a water treatment process, to estimate structural deterioration of a polyamide layer of the polymeric membrane without disassembly of the polymeric membrane and additional analysis equipment, and a system thereof. According to the present invention, the method comprises the following steps of: performing chemical washing for the polymeric membrane; calculating a deterioration index from penetration performance measured in a membrane process after the chemical washing; and determining a replacement period of the polymeric membrane based on the deterioration index. The penetration performance includes at least one from a water penetration degree, a salt removal rate, and a salt penetration degree. The deterioration index includes at least one from variances in the water penetration degree, the salt removal rate, and the salt penetration degree. The replacement period is determined whether a critical condition set to the deterioration index is satisfied or not.

Description

METHOD AND APPARATUS FOR INSPECTION OF POLYMERIC MEMBRANE AGING IN WATER TREATMENT PROCESS}

The present invention relates to a method and apparatus for diagnosing aging of a polymer separation membrane for water treatment.

Recently, a water treatment process using a polyamide-based polymer separation membrane such as a reverse osmosis membrane has been spotlighted to overcome high-quality drinking water production and worldwide water shortage.

The polyamide layer present on the surface of the polymer separation membrane is formed in a dense structure through an interfacial polymerization reaction of m-Phenylenediamine and Trimesoyl chloride, and has a thickness of 50nm to 200nm Exists as.

In the water treatment process of the polymer membrane, the polyamide layer is responsible for the removal of ions, and the organic material of 200Da or more is separated according to the structure characteristics, and the salt rejection rate is 98% or more.

Oxidizing substances such as hypochlorous acid are frequently used in the pretreatment process of the water treatment process to reduce the biological membrane contamination of the polymer membrane. The oxidizing material remaining in this process can easily degrade the amide polymer in the polyamide structure even at a low concentration (0.1 mg / L), thereby reducing the salt separation performance of the polymer separator.

In addition, in the chemical cleaning process performed according to a certain period of time to remove the membrane contaminants, strong acids, strong bases, and other oxidizing agents contained in the chemicals may also damage the amide polymer on the surface of the polymer separator.

The rate of progress of the aging of the polymer membrane depends on the operating method of the water treatment process of the polymer membrane and the quality of the influent water. Therefore, it is difficult to accurately predict the expiration date of the polymer separation membrane for each water treatment process.

Conventionally, a method of directly confirming the aging degree of a polymer separator is to analyze a surface with high-level equipment such as X-ray photoelectron spectroscopy. In order to analyze the aging of the polymer membrane in this way, the polymer membrane used in the water treatment process must be dismantled. Therefore, since the process itself must be stopped, serious operational damage occurs.

In addition, conventionally, the replacement cycle of the polymer membrane is selected by monitoring the salt removal rate, which is an operating factor of the polymer membrane process, and the water permeability recovery rate by chemical cleaning. However, there is no method to directly measure the aging of the surface of the polymer membrane.

In addition, when the water treatment process of the polymer separator was operated, the indicator for predicting the aging of the polymer separator was not selected, so the aged polymer separator was entirely replaced by manufacturer's judgment.

However, timely replacement of the polymer membrane due to the aging of the polymer membrane is essential for smooth operation and cost reduction of the water treatment process of the polymer membrane. Therefore, there is a need for a technique capable of diagnosing the aging degree of the polymer separator.

The problem to be solved by the present invention is to provide a method and a system for diagnosing the aging degree of a polymer separation membrane by changing the permeate flux and salt flux according to exposure to a chemical cleaning agent during long-term operation of the water treatment separation membrane process. will be.

According to one feature of the present invention, the aging diagnosis method comprises performing chemical cleaning on a polymer membrane, calculating an aging index from permeation performance measured in a membrane process after the chemical cleaning, and based on the aging index. Furnace, comprising the step of determining the replacement time of the polymer separation membrane, the aging index, at least one of the amount of change in water permeability, the amount of change in salt removal rate and the amount of change in salt permeability, the replacement time, the aging index It is determined by whether or not the threshold condition set for is satisfied.

The chemical cleaning includes acid cleaning and base cleaning, and the aging index can be calculated from the permeation performance measured in the separation membrane process performed after the acid cleaning and the permeation performance measured in the separation membrane process performed after the base cleaning. have.

The step of performing the chemical cleaning is performed by performing a membrane process after base cleaning, measuring a first water permeability, a first salt removal rate and a first salt permeability of the polymer separator, and a membrane process after acid cleaning. And measuring the second water permeability, the second salt removal rate, and the second salt permeability of the polymer separation membrane, wherein the aging index is the amount of change in the first water permeability and the second water permeability, the second 1, the amount of change in the salt removal rate and the second salt removal rate, and may include a change in the first salt permeability and the second salt permeability.

The base washing may be performed before the acid washing.

The step of performing the chemical cleaning may include performing a first acid cleaning, performing a base cleaning after the first acid cleaning, and performing a separation membrane process after the base cleaning, and the first number of the polymer separation membrane. Measuring the permeability, the first salt removal rate and the first salt permeability, performing a second acid cleaning after the separation membrane process, and performing a separation membrane process after the second acid washing, and the second number of the polymer separation membrane And measuring the permeability, the second salt removal rate, and the second salt permeability, wherein the aging index is the amount of change in the first water permeability and the second water permeability, the first salt removal rate and the second salt removal rate. It may include a change amount, and a change amount of the first salt permeability and the second salt permeability.

The aging index may further include a boron removal rate change amount, and the boron removal rate change amount may be a change amount between the boron removal rate after base cleaning and the boron removal rate after acid washing.

According to another aspect of the invention, the water treatment process system is a membrane filtration tank equipped with a polymer separation membrane module, an acid cleaning liquid storage tank connected to the membrane filtration tank through a first pipe, a base cleaning liquid storage tank connected to the membrane filtration tank through a second pipe, the Raw water storage tank connected to a membrane filtration tank through a third pipe, flowmeter and pressure gauge installed in a fourth pipe connected to the membrane filtration tank to discharge filtered water processed by the polymer membrane module, and ion conductivity values before and after permeation of the polymer membrane module Based on the measured conductivity meter and the flow rate data of the filtered water measured from the flow meter, the pressure data of the filtered water measured from the pressure gauge, and the ion conductivity value, the water permeability and salt removal rate of the filtered water are calculated, and the water permeability and The aging index is calculated using the salt removal rate, and the mound is And a deterioration diagnostic device for determining a replacement time of a separation membrane module.

The aging diagnostic apparatus calculates the amount of change between the water permeability calculated after base cleaning and the water permeability calculated after acid cleaning, and the amount of change between the salt removal rate calculated after base cleaning and the salt removal rate calculated after acid cleaning as an aging index, When the change amount between the base water permeability and the change amount between the salt removal rate satisfies the critical condition, replacement of the polymer separation membrane module may be determined.

The aging diagnostic device is connected to the first valve installed in the first pipe, the second valve installed in the second pipe, and the third valve installed in the third pipe, respectively, the first valve, the second valve, and The aging index may be calculated after at least one base washing and at least one acid washing by selectively controlling the opening and closing of the third valve.

The aging diagnostic device opens only the first valve and closes the second valve and the third valve to perform acid cleaning, opens only the second valve, and closes the first valve and the third valve. Base cleaning is performed, only the third valve is opened, the first valve and the second valve are closed to perform a membrane process, the acid cleaning, the base cleaning and the acid cleaning are sequentially performed, and the base The aging index may be calculated based on data measured in a membrane process performed after washing and data measured in a membrane process after acid washing performed after the base washing.

The aging diagnostic device calculates a water permeability from the flow rate data of the filtered water received from the flow meter and the inter-membrane pressure difference of the filtered water received from the pressure gauge, and calculates a salt removal rate based on the conductivity value received from the basic conductivity meter. The salt permeability can be calculated based on the salt removal rate and the flow rate data.

The water treatment process system further includes a boron concentration measuring unit that measures boron concentrations before and after the separation membrane process in the membrane filtration tank, and the aging diagnostic device is from the boron concentration measuring unit after the base washing and after the acid washing, respectively. The boron removal rate calculated based on the received boron concentration may be added as the aging index.

According to an embodiment of the present invention, water permeability and salt permeability can be measured and quantified to diagnose the degree of aging of a polymer separation membrane (eg, polyamide-based) that is actually operated in the field.

In addition, it is possible to evaluate the structural aging of the polyamide layer of the polymer separator without dismantling the polymer separator and additional advanced analysis equipment in a manner that can evaluate the aging of the polymer separator during chemical cleaning performed according to a certain period of time.

In addition, since the degree of change in permeation performance during chemical cleaning is measured, additional analysis time is minimal and it is not necessary to dismantle the polymer separation membrane, so it is economical and efficient.

In addition, since the salt removal rate and water permeability, which are frequently measured in the polymer separation membrane process, are used, there is no need to install an additional analysis device and a required site.

In addition, acid cleaning is performed once more during chemical cleaning to reduce the reduction of salt removal rate of the polymer membrane by base cleaning.

1 is a schematic view showing a water treatment process system according to an embodiment of the present invention.
2 is a flow chart showing a method for diagnosing aging of a polymer separation membrane for water treatment according to an embodiment of the present invention.
3 is a graph showing changes in water permeability according to acid washing and base washing according to an embodiment of the present invention.
4 is a graph showing the change in the salt removal rate according to the acid washing and the base washing according to an embodiment of the present invention.
5 is a graph exemplarily showing the degree of aging of the polymer separator according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains may easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. In addition, in order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and like reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless otherwise stated.

The terms "first", "second", and the like are used herein to describe various features, members, and components, and such features, elements, and components should not be limited by the terms. In other words, the term is used for the purpose of distinguishing one feature or the like from another feature or the like. For example, within the scope of the scope of the present invention, the first component may also be referred to as the second component, and likewise the second component may also be referred to as the first component.

In addition, terms such as “… unit”, “… group”, and “… module” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. You can.

Now, with reference to the drawings, a method and system for diagnosing aging of a polymer separation membrane for water treatment according to an embodiment of the present invention will be described.

In the present specification, a membrane refers to a porous physical barrier capable of separating a mixture by selectively passing a specific component from two or more multi-component mixtures.

The separator has a myriad of micro-pores, namely membrane pores. The separation membrane filtration technology is a separation membrane process capable of separating and removing a target material present in water according to the pore size and surface charge of the separation membrane. The most important thing in the membrane process is the quantity and quality of the water produced through the membrane.

However, the membrane process may cause fouling depending on use. Membrane contamination is a phenomenon in which various foreign substances present in the influent are deposited or adsorbed on the surface of the membrane to reduce the water permeability of the membrane. When membrane contamination occurs, the surface of the separation membrane is covered with contaminant deposits during filtration, membrane pores are reduced or blocked, and the permeate flow rate and performance of raw water are deteriorated. Therefore, it is necessary to periodically clean the membrane during membrane filtration to restore the performance of the membrane. Chemical cleaning is repeatedly performed over a period of time in order to recover the membrane performance degradation (reduced water permeability) caused by membrane contaminants.

1 is a schematic view showing a water treatment process system according to an embodiment of the present invention.

Referring to Figure 1, the water treatment process system membrane filtration tank 100, acid cleaning liquid storage tank 200, base cleaning liquid growth tank 300, raw water storage tank 400, flow meter 500, pressure gauge 600, conductivity meter ( Conductivity Meter) (700), boron concentration measurement unit (800) and aging diagnostic device (900).

The membrane filtration tank 100 includes a separation membrane module M therein. A cleaning action and a membrane filtration action occur in the membrane filtration bath 100. The separation membrane module M desalinates the raw water by the reverse osmosis action and discharges the desalination filtered water and the remaining treated water.

The separation membrane module (M) is made of a polyamide layer. According to one embodiment, the microporous support is immersed in an aqueous solution of m-phenylenediamine (m-Phenylene Diamine, hereinafter, mPD) to form an mPD layer, and this is again trimesoyl chloride (TMC) organic The mPD layer may be contacted with TMC by immersion or coating in a solution to form a polyamide layer having a dense structure by an interfacial polymerization reaction. At this time, the polyamide layer may be 50 nm to 200 nm thick.

The polyamide layer is responsible for the actual removal of ions in the reverse osmosis membrane separation process, and can separate more than 200 Da organic materials according to the structure characteristics and show a salt rejection rate of 98% or more.

The acid cleaning solution storage tank 200 stores an acid cleaning solution, which is a chemical of pH 2 to pH 4. The acid cleaning solution functions as an oxidizing agent, and may be one or more selected from the group consisting of nitric acid (HNO3), phosphoric acid (H2PO4), hydrochloric acid (HCl), sulfuric acid (H2SO4), citric acid, citric acid, and oxalic acid, but is not limited thereto.

The acid cleaning liquid storage tank 200 supplies the acid cleaning liquid to the membrane filtration tank 100 through the first pipe L1. A first valve v1 is installed in the first pipe L1. The first valve v1 is connected to the aging diagnostic device 900. When the first valve v1 is opened, the acid cleaning solution is introduced into the membrane filtration tank 100 to cause a chemical reaction on the surface of the separation membrane module M to perform a cleaning action.

The base cleaning liquid storage tank 300 stores a base cleaning liquid, which is a chemical of pH 10 to pH 12. The base cleaning solution functions as a reducing agent, and may be one or more selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), and sodium carbonate (Na2CO3). It is not limited.

The base cleaning liquid storage tank 300 supplies the base cleaning liquid to the membrane filtration tank 100 through the second pipe L2. A second valve v2 is installed in the second pipe L2. The second valve v2 is connected to the aging diagnostic device 900. When the second valve v2 is opened, a base cleaning solution is introduced into the membrane filtration tank 100 to cause a chemical reaction on the surface of the separation membrane module M to perform a cleaning action.

The raw water storage tank 400 stores raw water that is a membrane filtration target. The raw water storage tank 400 supplies raw water to the membrane filtration tank 100 through the third pipe L3. A third valve v3 is installed in the third pipe L3. The third valve v3 is connected to the aging diagnostic device 900. When the third valve (v3) is opened, the raw water storage tank 400 is fed with raw water into the membrane filtration tank 100, and a membrane filtration action occurs in the separation membrane module M.

The membrane filtration tank 100 discharges the filtered water processed by the membrane filtration through the fourth pipe L4. At this time, a flowmeter 500 and a pressure gauge 600 are installed in the fourth pipe L4.

In addition, the membrane filtration tank 100 discharges treated water excluding filtered water from raw water to the outside through the fifth pipe L5.

The flow meter 500 measures the flow rate of the filtered water discharged through the fourth pipe L4 and outputs it to the aging diagnosis apparatus 900. For example, the flowmeter 500 may measure the amount of filtered water permeated in the membrane module M for a specific time.

The pressure gauge 600 measures the pressure of the filtered water and outputs it to the aging diagnosis apparatus 900.

The conductivity meter 700 measures the ion conductivity values before and after transmission of the membrane module M and outputs it to the aging diagnosis apparatus 900.

The boron concentration measurement unit 800 measures the boron concentration before and after transmission of the separation membrane module M and outputs it to the aging diagnosis apparatus 900. For example, the boron concentration measurement unit 800 may be an emission spectrophotometer (ICP emission spectrophotometer).

The aging diagnosis apparatus 900 is a computer device, and controls a cleaning process and a water treatment process (separation membrane process) and determines the replacement time of the polymer separation membrane according to the aging index.

The aging diagnosis apparatus 900 selectively opens and closes the first valve v1, the second valve v2, and the third valve v3 to perform a cleaning process and a water treatment process.

The aging diagnostic device 900 may sequentially open and close the first valve v1 and the second valve v2 to sequentially supply the acid cleaning solution and the base cleaning solution to sequentially perform acid cleaning and base cleaning. .

At this time, acid washing may be performed first, followed by base washing, and acid washing may be performed again. However, this order can be changed.

Since the base cleaning cannot remove the contamination generated on the outermost surface of the contaminated polymer membrane, only the cleaning effect by subsequent acid cleaning can be achieved. On the other hand, if the acid cleaning is performed first, the base cleaning acts while the contamination formed on the outermost surface of the contaminated polymer separation membrane is removed, thereby removing the contamination generated on or inside the polymer separation membrane. The synergistic effect of sequential application can be expected.

Accordingly, the aging diagnosis apparatus 900 compares the polymer permeation membrane by comparing the primary permeation performance measured after successively performing acid washing and base washing, and then the secondary permeation performance measured after performing acid washing once more. M) aging can be diagnosed. That is, after the final washing performed on the polymer membrane module M from which the contaminants have been removed, the aging of the polymer membrane can be diagnosed by changing the water permeability and salt removal rate by performing acid washing or base washing once more.

The aging diagnosis apparatus 900 can evaluate the degree of aging of the polymer separator by tracking the change in salt removal rate and water permeability due to chemical cleaning without an additional device.

According to one embodiment, the aging diagnosis apparatus 900 may measure salt rejection and permeate flux of the polymer separator after stabilization of the filtration process of the polymer separator with permeation performance.

According to another embodiment, the aging diagnosis apparatus 900 may measure boron rejection and salt permeability coefficient as permeation performance. When at about pH 8.0 in water, boron exists without charge. The separation membrane having a charge has a lower boron removal rate than a material having a different charge. Therefore, the boron removal rate is related to the change in the structural aging of the separator, such as the change in the pore size of the separator.

The aging diagnosis apparatus 900 measures the permeation performance of the membrane module M based on the measurement data received through the flowmeter 500, pressure gauge 600, conductivity meter 700, and boron concentration measurement unit 800, respectively. do. Permeability includes permeate flux, salt rejection, boron rejection and salt permeability coefficient.

The aging diagnostic apparatus 900 calculates the permeate flow rate based on the flow rate data transmitted from the flow meter 500. The aging diagnosis apparatus 900 calculates the inter-membrane pressure based on the pressure data transmitted from the pressure gauge 600. Then, the permeate flux is calculated from the inter-membrane differential pressure and permeation flow rate. For example, the water permeability can be calculated as the amount permeated per minute at a pressure of 1.0 bar. Since the water permeability calculation formula can use a known technique, a detailed description is omitted.

The aging diagnosis apparatus 900 calculates a salt rejection based on the conductivity value transmitted from the conductivity meter 700. At this time, the conductivity meter 700 may measure the salt concentration before and after permeation and transmit it to the aging diagnosis apparatus 900.

The salt removal rate is a value indicating the removal performance by measuring the ion conductivity value (TDS) of the filtered water. For example, the following formula can be used, but is not limited thereto.

The aging diagnosis apparatus 900 calculates the boron removal rate based on the measured value transmitted from the boron concentration measurement unit 800. The boron removal rate may be calculated using the following formula, but is not limited thereto.

Here, the undiluted solution means the raw water containing boron.

The aging diagnosis apparatus 900 calculates a salt permeability coefficient based on the salt removal rate calculated previously and the flow rate data transmitted from the flowmeter 500.

The aging diagnosis apparatus 900 calculates the aging index of the membrane module M based on the water permeability, salt removal rate, boron removal rate, and salt permeability, and uses this to determine the replacement timing of the membrane module M.

2 is a flow chart showing a method for diagnosing aging of a polymer separation membrane for water treatment according to an embodiment of the present invention.

Referring to FIG. 2, in order to remove a complex membrane contaminant of an inorganic substance and an organic substance, acid washing and base washing are carried out step by step. Chemical cleaning may be repeatedly performed over a period of time in order to recover the membrane performance degradation (reduced water permeability) caused by the membrane contaminant.

The first valve v1, the second valve v2, and the third valve v3 are all closed. First, the aging diagnosis apparatus 900 performs acid washing (S101). At this time, the aging diagnostic apparatus 100 opens only the first valve v1. Then, the acid cleaning solution is supplied from the acid cleaning solution storage tank 200 to the membrane filtration tank 100 through the first pipe L1 to generate the acid cleaning action on the separation membrane module M.

Subsequently, the aging diagnosis apparatus 900 performs base cleaning (S103). At this time, the aging diagnosis apparatus 100 closes the first valve v1 and opens only the second valve v2. Then, the base cleaning solution is supplied from the base cleaning solution storage tank 300 to the membrane filtration tank 100 through the second pipe L2 to generate the base cleaning action on the separation membrane module M.

Next, the aging diagnosis apparatus 900 performs a separation membrane process (S105) to measure the primary permeation performance (S107).

The aging diagnostic device 900 closes the second valve v2 and opens only the third valve v3. Then, the raw water, which is the membrane filtration target, is supplied from the raw water storage tank 400 to the membrane filtration tank 100 through the third pipe L3 to generate a membrane filtration action such as reverse osmosis in the separation membrane module M. As such, in the state in which the membrane filtration action occurs, the aging diagnosis apparatus 900 measures water permeability and salt removal rate based on the respective measurement data transmitted from the flowmeter 500 and the pressure gauge 600 (S107).

Then, the aging diagnostic device 900 closes the third valve v3 and opens only the first valve v1. Then, the acid washing described in step S101 is performed (S109).

The aging diagnosis apparatus 900 closes the first valve v1 and opens only the third valve v3 to perform a separation membrane process (S111). As described above, in the state in which the membrane filtration action occurs, the aging diagnosis apparatus 900 measures water permeability and salt removal rate based on the respective measurement data transmitted from the flowmeter 500 and the pressure gauge 600 (S113).

The aging diagnosis apparatus 900 calculates the aging index using the water permeability and salt removal rate measured in step S107 and the water permeability and salt removal rate measured in step S113 (S115). In an embodiment of the present invention, the aging index may be defined as in Table 1 below.

Aging indicators Arithmetic Change in water permeability (α)

Salt removal rate change (β)

Salt permeability change (γ)

In Table 1, J _a is the water permeability after acid washing. J _b is water permeability after base washing. R _a is the salt removal rate after acid washing. R _b is the salt removal rate after base washing.

는 염투과도 계수(Salt permeability coefficient)로서, 고분자 분리막에 염이 투과되는 정도를 계수로 나타낸 값이다.In addition,

Is a salt permeability coefficient, which is a value indicating the degree of salt permeation through the polymer membrane.

In addition, the aging index may further include a boron removal rate change amount. Although not shown in the formula, the amount of change in boron removal rate can be calculated by an arithmetic formula similar to the amount of salt removal rate change in Table 1. That is, it can be calculated as a ratio between the boron removal rate measured after acid cleaning and the boron removal rate measured after base cleaning.

The aging diagnosis apparatus 900 replaces the membrane module M at a time when the water permeability change (α), salt removal rate change (β), and salt permeability change (γ) defined in Table 1 satisfies a predefined threshold condition. It can be determined (S117).

Hereinafter, the configuration and operation of the present invention through a preferred embodiment of the present invention will be described in more detail. However, the following examples are intended to help the understanding of the present invention, and the scope of the present invention is not limited to the following examples. The contents not described here will be sufficiently technically inferred by those skilled in the art, and thus the description thereof will be omitted.

Figure 3 is a graph showing the change in water permeability according to the acid cleaning and base cleaning according to an embodiment of the present invention, Figure 4 is a graph showing the change of the salt removal rate according to the acid cleaning and base cleaning according to an embodiment of the present invention to be.

First, referring to FIG. 3, the water permeability after acid washing, followed by the water permeability after base washing, and then the water permeability after acid washing, and referring to FIG. 4, the salt removal ratio after acid washing, followed by salt removal after base washing, It shows the salt removal rate after acid washing.

 When the acid washing and the base washing are performed step by step, most of the contaminants formed on the polymer membrane are removed. Accordingly, water permeability and salt removal rate increase due to a decrease in membrane resistance due to membrane fouling and concentration polarization.

Referring to FIGS. 3 and 4, after acid washing is performed, when base washing is performed once more (acid washing → base washing), a phenomenon in which the functional groups on the surface of the polymer separator exhibit negative charge under the basic conditions (negatively charged) Occurs. Therefore, since the dense polymer layer present at 50 nm to 200 nm swells, the water permeability increases to the value of J _b and the salt removal rate increases to the value of R _b .

Referring to FIGS. 3 and 4, after base cleaning is performed, acid cleaning is performed once more (base cleaning → acid cleaning), whereby functional groups on the surface of the polymer membrane are not charged under acidic conditions (charge neutralization). This occurs, and the dense polymer layer existing from 50 nm to 200 nm shrinks. Therefore, the water permeability during acid washing is reduced by J _b -J _a . And the salt removal rate increases by R _a -R _b .

As described above, the phenomenon that the functional group of the polyamide layer becomes charged depending on the pH and thus the salt removal rate and water permeability change increases according to the degree of aging of the polymer membrane.

5 is a graph exemplarily showing the degree of aging of the polymer separator according to an embodiment of the present invention.

Here, the aging of the polymer membrane was accelerated using sodium hydroxide, which is a typical base cleaning agent, and acid cleaning was performed using hydrochloric acid (pH 2). As described in Table 1, the aging indicators are represented by α, β, and γ.

Referring to FIG. 5, as the total amount of chemical cleaning agent exposure (% · hr) increased, both α, β, and γ selected as aging indicators increased. Through this, the degree of change in permeation performance can be tracked to indicate the progress of aging of the polymer membrane.

At this time, according to one embodiment, the replacement time of the aging membrane module is based on the total amount of chemical cleaning agent exposed to about 20% / hr, α is 10% or more, β is 0.7% or more, and γ is 30% or more. You can.

However, the replacement time of the membrane module may be selected differently depending on the operation method of the membrane process, the type of the membrane, and the characteristics of the polymer. That is, the threshold values of α, β, and γ can be variously set.

The embodiment of the present invention described above is not implemented only through an apparatus and method, and may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium in which the program is recorded.

Although the embodiments of the present invention have been described in detail above, the scope of rights of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (12)

Performing chemical cleaning on the polymer membrane,
Calculating an aging index from the permeation performance measured in the membrane process after the chemical cleaning, and
Determining a replacement time of the polymer separator based on the aging index,
The transmission performance,
It includes at least one of water permeability, salt removal rate and salt permeability of the polymer membrane,
The aging indicator,
It includes at least one of a change amount of water permeability, a change amount of salt removal rate and a change amount of salt permeability,
The replacement time,
The aging diagnosis method is determined by whether or not a threshold condition set for the aging indicator is satisfied. In claim 1,
The chemical cleaning includes acid cleaning and base cleaning,
The aging index is calculated from the permeation performance measured in the separation membrane process performed after the acid cleaning and the permeation performance measured in the separation membrane process performed after the base cleaning. In claim 1,
The step of performing the chemical cleaning,
Performing a separation membrane process after base cleaning, measuring a first water permeability, a first salt removal rate and a first salt permeability of the polymer separation membrane, and
Comprising the step of performing a membrane process after the acid washing, measuring the second water permeability, the second salt removal rate and the second salt permeability of the polymer membrane,
The aging indicator,
The amount of change in the first water permeability and the second water permeability,
The amount of change in the first salt removal rate and the second salt removal rate, and
A method for diagnosing aging, comprising a change in the first salt permeability and the second salt permeability. In claim 3,
The base cleaning is performed before the acid cleaning, the aging diagnostic method. In claim 1,
The step of performing the chemical cleaning,
Performing a first acid cleaning,
Performing a base cleaning after the first acid washing,
Performing a separation membrane process after the base washing, and measuring a first water permeability, a first salt removal rate, and a first salt permeability of the polymer separation membrane,
Performing a second acid cleaning after the separation membrane process, and
And performing a separation membrane process after the second acid washing, and measuring a second water permeability, a second salt removal rate, and a second salt permeability of the polymer separation membrane,
The aging indicator,
The amount of change in the first water permeability and the second water permeability,
The amount of change in the first salt removal rate and the second salt removal rate, and
A method for diagnosing aging, comprising a change in the first salt permeability and the second salt permeability. In claim 1,
The aging indicator,
Boron removal rate additionally included,
The amount of change in the boron removal rate,
A method for diagnosing aging, which is the amount of change between the boron removal rate after base cleaning and the boron removal rate after acid washing. Membrane filtration tank equipped with a polymer separator module,
Acid cleaning solution storage tank connected to the membrane filtration tank through a first pipe,
Base cleaning solution storage tank connected to the membrane filtration tank through a second pipe,
Raw water storage tank connected to the membrane filtration tank through a third pipe,
Flowmeter and pressure gauge installed in a fourth pipe connected to the membrane filtration tank to discharge filtered water processed by the polymer separation membrane module,
Conductivity meter for measuring ion conductivity values before and after transmission of the polymer membrane module, and
Based on the flow rate data of the filtered water measured from the flow meter, the pressure data of the filtered water measured from the pressure gauge and the ion conductivity value, the water permeability and salt removal rate of the filtered water are calculated, and the water permeability and the salt removal rate are used. An aging diagnostic device that determines the replacement timing of the polymer separator module by calculating an aging index
Including, water treatment process system. In claim 7,
The aging diagnostic device,
The amount of change between the water permeability calculated after the base cleaning and the water permeability calculated after the acid washing, and the amount of change between the salt removal rate calculated after the base washing and the salt removal rate calculated after the acid washing is calculated as an aging index,
When the amount of change between the water permeability and the amount of change between the salt removal rate satisfies a critical condition, the replacement of the polymer membrane module is determined. In claim 7,
The aging diagnostic device,
The first valve installed in the first pipe, the second valve installed in the second pipe, and the third valve installed in the third pipe are respectively connected, and the opening of the first valve, the second valve, and the third valve And after the at least one base washing and at least one acid washing are performed by selectively controlling the closure, the aging index is calculated. In claim 9,
The aging diagnostic device,
Only the first valve is opened, and the second valve and the third valve are closed to perform acid cleaning,
Only the second valve is opened, and the first valve and the third valve are closed to perform base cleaning,
Only the third valve is opened, and the first valve and the second valve are closed to perform a separation membrane process.
The acid washing, the base washing and the acid washing are sequentially performed,
The data measured in the separation membrane process performed after the base cleaning and
A water treatment process system that calculates the aging index based on data measured in the separation membrane process after the acid washing performed after the base washing. In claim 10,
The aging diagnostic device,
The water permeability is calculated from the flow rate data of the filtered water received from the flowmeter and the inter-membrane pressure difference of the filtered water received from the pressure gauge,
The salt removal rate is calculated based on the conductivity value received from the conductivity meter,
A water treatment process system for calculating salt permeability based on the salt removal rate and the flow rate data. In claim 11,
Further comprising a boron concentration measuring unit for measuring the boron concentration before and after the separation membrane process in the membrane filtration tank,
The aging diagnostic device,
After the base cleaning and after the acid cleaning, the water treatment process system adds boron removal rate calculated based on the boron concentration received from the boron concentration measurement unit, respectively, as the aging index.

Images