JP2000033241A - Operation of membrane separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the stable operation of a membrane separator which is characterized by good washing recovery of a separation membrane, long service life of the separation membrane, easy maintenance, and cost merits. SOLUTION: In a method for operating a membrane separator which allows raw water to pass through a separation membrane to remove impurities, the total amount of filtrate until the necessity of chemical cleaning is generated is calculated by using the relationship between the quantity of soluble components contained in the raw water and the turbidity, the time of chemical cleaning is determined on the basis of the calculation results, and the chemical cleaning is carried out at the time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separation device and a method for operating the same, and further relates to a method for producing permeated water. In detail, the change in filtration resistance with time is predicted from the quality of the water to be treated in the membrane separation apparatus, the total filtered water amount V until the necessity of performing the chemical cleaning is calculated, and the treated water having the total filtered water amount V is treated. The present invention relates to a membrane separation apparatus which is excellent in terms of washing and recovery properties of a separation membrane, has a long life of the separation membrane, is easy to maintain and manage, and is advantageous in terms of cost by performing chemical cleaning at a point in time, and an operation method thereof.

[0002]

2. Description of the Related Art Separation membranes such as microfiltration membranes and ultrafiltration membranes are used in various fields including the food industry, the medical field, water production, and wastewater treatment. Especially in recent years,
Separation membranes have been used in the field of drinking water production, that is, in the purification process.

[0003] Microfiltration membranes and ultrafiltration membranes used for water treatment such as water production and wastewater treatment separate pressure difference into driving force. There are two types of filtration: constant-flow filtration in which the filtration flow rate is constant and the filtration differential pressure changes, and constant-pressure filtration in which the filtration pressure is constant and the filtration flow rate changes. As the filtration is continued and the dirt accumulates on the separation membrane surface and in the pores of the separation membrane, the filtration resistance R of the separation membrane increases. Generally, in a real process, a fixed amount of water is often treated because a fixed amount of water is treated.In this case, in order to obtain a fixed amount of filtered water, the filtration differential pressure is controlled. There must be. In the case of constant-pressure filtration, the filtration flow rate decreases as the filtration continues.

Therefore, as a means for recovering the processing ability by peeling off the deposits on the surface of the separation membrane or opening the pores of the separation membrane which is closed, a method of flushing the surface of the separation membrane (JP-A-5-138166) Publication) and a physical cleaning method such as a method of scrubbing with air (Japanese Patent Application Laid-Open No. 61-263605) have been proposed. However, physical cleaning alone cannot remove dirt in the pores of the separation membrane, so it is necessary to periodically perform chemical cleaning with a chemical such as citric acid, oxalic acid, hypochlorite, or sodium hydroxide. is there. Also,
As a method of removing dirt in the pores of the separation membrane by physical washing using a chemical solution and suppressing the growth of bacteria and the like, a method of back-pressure washing with an aqueous solution of hypochlorite, sodium hydroxide, etc. No. 5-168873) has been proposed.

[0005]

It is difficult to set the timing of chemical cleaning, and it is often the case that chemical cleaning is performed after a sharp rise in the filtration differential pressure. However, even if chemical cleaning is performed after a rapid rise in the filtration differential pressure, the cleaning recovery is poor, and even when the operation is resumed, the filtration differential pressure sharply increases again, and the life of the separation membrane becomes extremely short. This is disadvantageous in terms of processing cost. In addition, when the chemical solution is washed early, the recoverability of the cleaning solution is good and the life of the separation membrane is long.However, since the frequency of the chemical solution washing is increased, the maintenance and management becomes complicated, which is disadvantageous in terms of processing cost. Become. The method of contaminating the separation membrane differs depending on the quality of the raw water, that is, the type and concentration of impurities contained in the raw water.Even when the same separation membrane is used, the optimal chemical solution cleaning time differs in each case. There was no means to set the timing for performing the chemical cleaning based on the grounds.

[0006]

According to the present invention, there is provided a method for operating a membrane separation apparatus for removing impurities by passing the water to be treated through a separation membrane. Using the relationship between the amount A of the sexual component and the turbidity B, the total filtered water amount V until it is necessary to perform the chemical solution washing is calculated,
The method is characterized in that the time for performing the chemical cleaning is determined based on the calculation result, and the operation method of the membrane separation apparatus that performs the chemical cleaning at that time.

At this time, it is preferable to calculate the operation elapsed time (t + T) at which the chemical cleaning needs to be performed in the following procedure, and to perform the chemical cleaning at the time of the operation elapsed time (t + T). (1) Using the time-dependent change of the filtration resistance R obtained from the filtration data of three or more different types of water to be treated, the filtration mechanism constant n is calculated based on the amount A of the soluble component and the turbidity B contained in the water to be treated. Ratio x
= A / B function n = f (x). (2) Filtration mechanism constant n calculated from x of the water to be treated using function n = f (x) and resistance (R ₀ ) of the separation membrane itself,
From the total filtered water amount V (t) and the filtration resistance R (t) at the operation elapsed time t, the filtration coefficient α is calculated as a function α = g (n,
R ₀ , V (t), R (t)). (3) Filtration resistance R (t +
T) is the product of the resistance R ₀ of the separation membrane itself and a constant k (k · R ₀ )
= R (t + T). (4) Filtration resistance R (t) at operation elapsed time (t + T)
+ T), filtration coefficient α, filtration mechanism constant n, and resistance R ₀ of the separation membrane itself, the inverse function V (t + T) = g ⁻¹ (n, R ₀ , α,
R (t + T)) to calculate the total filtered water amount V (t + T) during the operation elapsed time (t + T). (5) Elapsed operation time (t + T) from total filtered water amount V (t + T)
T) is obtained by dividing the total amount of filtered water by the filtration flow rate in the case of constant flow filtration, and by integration in the case of constant pressure filtration.

Further, a function α = g (n, R ₀ , V (t),
R (t)) is the expression (1), the constant k is 1.5 or more and 15 or less, and the function n = f (x) is
Expression (2) using constants a and m, and it is preferable that the constant a is 1 or more and 10 or less and the constant m is 0.1 or more and 1 or less. R ¹⁻ⁿ / (1−n) = αV + R ₀ ¹⁻ⁿ / (1−n) Formula (1) n = ax ^m Formula (2) Further, the solubility component is represented by humic substances, It is also preferable that the amount A of the component is the ultraviolet absorbance at a wavelength of 260 nm or the total amount of organic carbon.

Also, a preferred embodiment is a method for producing water, in which the water to be treated is passed through a separation membrane after the chemical solution washing is performed by any of the methods described above.

In order to achieve the above object, the present invention provides a separation membrane for removing impurities by passing water to be treated;
Means for calculating the total filtered water amount V until the necessity of performing the chemical cleaning using the relationship between the amount A of the soluble component contained in the water to be treated and the turbidity B, and cleaning the chemical based on the calculation result The present invention is also characterized by a membrane separation device comprising means for determining when to perform the cleaning and means for performing the chemical cleaning.

Here, the means for determining when it is necessary to perform the chemical cleaning preferably includes means for calculating the operation elapsed time (t + T) in the following procedure, and displays the operation elapsed time (t + T). It is more preferred to have means. (1) Using the time-dependent change of the filtration resistance R obtained from the filtration data of three or more different types of water to be treated, the filtration mechanism constant n is calculated based on the amount A of the soluble component and the turbidity B contained in the water to be treated. Ratio x
= A / B function n = f (x). (2) Filtration mechanism constant n calculated from x of the water to be treated using function n = f (x), resistance R ₀ of the separation membrane itself, total filtered water amount V (t) and filtration resistance R at operation elapsed time t From (t), the filtration coefficient α is calculated by the function α = g (n, R ₀ , V
(T), R (t)). (3) Filtration resistance R (t +
T) is calculated by multiplying the resistance R ₀ of the separation membrane itself by a constant k (k · R ₀ ).
= R (t + T). (4) Filtration resistance R (t) at operation elapsed time (t + T)
+ T), filtration coefficient α, filtration mechanism constant n, and resistance R ₀ of the separation membrane itself, the inverse function V (t + T) = g ⁻¹ (n, R ₀ , α,
R (t + T)) to calculate the total filtered water amount V (t + T) during the operation elapsed time (t + T). (5) Elapsed operation time (t + T) from total filtered water amount V (t + T)
T) is obtained by dividing the total amount of filtered water by the filtration flow rate in the case of constant flow filtration, and by integration in the case of constant pressure filtration.

The separation membrane has a pore diameter of 1 nm or more and 10 nm or more.
It is preferable that the membrane is a microfiltration membrane or an ultrafiltration membrane of μm or less, and furthermore, the material of the separation membrane is any one of polyacrylonitrile, cellulose acetate, polyphenylene sulfone, and polyphenylene sulfide sulfone.

[0013]

Embodiments of the present invention will be described below.

The change in the manner of fouling of the separation membrane can be represented by the change in filtration resistance R, which is the reciprocal of the membrane permeability coefficient. According to the method of the present invention, it is possible to predict in advance how the separation membrane is contaminated, that is, a change with time in the filtration resistance R, so that it is possible to set an optimum chemical cleaning time based on the basis, and as a result, the life of the separation membrane becomes longer, An operation method of a membrane separation device which is advantageous in terms of cost is provided.

That is, the present invention relates to a method for operating a membrane separation apparatus for removing impurities by passing water to be treated through a separation membrane, wherein the amount A of the soluble component contained in the water to be treated and the turbidity B
Is used to calculate the total filtered water amount V until the necessity of performing the chemical cleaning, determine when to perform the chemical cleaning based on the calculation result, and perform the chemical cleaning at that time. In the present invention, the point of time when the chemical cleaning is performed,
In addition to the point in time when the chemical cleaning is performed based on the calculation result, the period includes one month before and after the time based on the calculation result. Preferably,
The range is within two weeks before and after the time based on the calculation result.

The setting of the optimum chemical cleaning time is performed as follows.

As a result of analyzing and examining various kinds of operation data of filtration in detail, it was found that the constant n and the value x = A / B of the ratio of the amount A of soluble components contained in the water to be treated to the turbidity B were obtained. And the function n =
The present inventors have found that there is a relationship that can be expressed by f (x). Therefore, using a temporal change of filtration resistance R obtained from filtration data of three or more different types of water to be treated in a certain separation membrane, the filtration mechanism constant n is determined by the amount A of the soluble component contained in the water to be treated and the turbidity. Function of n = f of ratio x = A / B of degree B
(X). Here, the soluble component refers to the total amount of humic substances, iron, manganese, aluminum, silica, etc., and the solubility component and the adsorptivity of the separation membrane material and the amount of each soluble component relative to the total soluble component amount. One or a plurality of components may be selected from the ratio and the like, and the total amount may be selected. However, since humic substances are often a factor that increases filtration resistance, soluble components can be represented by humic substances. is there. With the amount A of the soluble component, in the case of humic substances, several kinds of standard solutions having a known concentration of a commercially available humic acid reagent dissolved in pure water are adjusted, and the ultraviolet absorbance of the standard solution at a wavelength of 260 nm is measured. A calibration curve of humic acid concentration and ultraviolet absorbance at a wavelength of 260 nm was created, and the wavelength of the water to be treated was 260 n.
m is converted to the amount of humic substance using a calibration curve. Its unit is mg / l. Amount of soluble component A
Is preferably an ultraviolet absorbance at a wavelength of 260 nm, which is simple and preferable. Further, it is also convenient and preferable to measure the total amount of organic carbon in the water to be treated and determine the amount A of the soluble component. In addition,
Iron, manganese, aluminum, silica, etc. are the amounts measured by the measurement method specified in tap water standards, and the unit is mg / l.
It is. Turbidity B is an index that defines the turbidity of a kaolin 1 mg / l solution as 1 degree. There are transmitted turbidity, scattered light turbidity, and integrated light turbidity due to differences in the measurement principle. It should be appropriately selected and is not particularly limited. As the function n = f (x), for example, equation (2) is given. n = ax ^m (2) where a and m are constants and are values determined by the material of the separation membrane and the pore diameter, and differ in each case.
Approximately constant a is 1 or more and 10 or less and constant m is 0.1
It is 1 or less.

Next, the filtration mechanism constant n calculated from x of the water to be treated using the function n = f (x), the resistance R ₀ of the separation membrane itself, the total filtered water amount V (t) at the operation elapsed time t, the filtration From the resistance R (t), the filtration coefficient α is calculated as a function α = g (n, R
₀ , V (t), R (t)). here,
When the operation elapsed time t is short, it is advantageous to calculate the operation elapsed time when it is necessary to perform the chemical cleaning with a small amount of data, but there is a problem that the prediction accuracy is low. In addition, as the operation elapsed time t increases, the prediction accuracy improves, which is preferable. The time t for making the first prediction differs in each case, but is about 1 hour or more, preferably about 24 hours or more.

The function α = g (n, R ₀ , V (t), R
For (t)), for example, it has been found that the Hermans equation shown in the equation (1) known in the filtration theory of chemical engineering can be applied. R (t) ¹⁻ⁿ / (1−n) = αV (t) + R ₀ ¹⁻ⁿ / (1−n) (1) Next, the filtration resistance R (t + T) for performing chemical cleaning is the separation membrane itself. Of the resistance R ₀ and the constant k (k · R ₀ ) = R (t + T). The constant k should be appropriately selected depending on characteristics such as the washing recovery property of the separation membrane, the filtration linear velocity, and the like.
It is about 8 or more and 10 or less, more preferably about 2 or more and 7 or less.

The filtration resistance R (t +
T), the total amount of filtered water V (t + T) is calculated as: filtration resistance R (t + T), filtration coefficient α, filtration mechanism constant n,
From the resistance R ₀ of the separation membrane itself, the inverse function V (t + T) = g ⁻¹
It is calculated using (n, R ₀ , α, R (t + T)).

Finally, the operation elapsed time (t + T) is obtained from the total filtered water amount V (t + T). In the case of constant flow filtration, it is obtained by dividing the total amount of filtered water by the filtration flow rate, and in the case of constant pressure filtration, it is obtained by integration.

The present invention is a method for operating a membrane separation apparatus, characterized in that a chemical solution is washed during the elapsed operation time (t + T) obtained as described above. Here, the operation elapsed time (t + T) for performing the chemical cleaning is different in each case depending on the material of the separation membrane, the pore diameter, the quality of the water to be treated, the filtration linear velocity, and the like. , Approximately 1 month to 3 years, preferably 3 months to 2 years 6
It is about 6 months or less, more preferably about 6 months or more and about 2 years or less.

The operation elapsed time (t + T) is calculated,
The present invention also includes a membrane separation device provided with a means for automatically or manually cleaning the chemical solution during the elapsed operation time (t + T). Further, it is preferable that the membrane separation device has a means for displaying the operation elapsed time (t + T) since the chemical solution cleaning time can always be known.

The chemical cleaning performed in the present invention is not particularly limited in view of the gist of the present invention, and should be determined according to the material of the separation membrane and the type of dirt. For example, in the case of an inorganic substance such as iron or manganese, an acid such as hydrochloric acid, citric acid, or oxalic acid is used, and in the case of an organic substance such as a protein, a microorganism, or a bacterium, an alkali such as sodium hydroxide or sodium hypochlorite is used. It is common.

The separation membrane used in the present invention is not particularly limited in terms of the gist of the present invention. However, the separation membrane is used in the field of drinking water production, that is, in the water treatment process such as water purification process, water production and wastewater treatment. It is preferable that the separation membrane is classified into a so-called microfiltration membrane or an ultrafiltration membrane having a pore diameter of 1 nm or more and 10 μm or less. Here, the pore diameter of the separation membrane is
It is measured by the method described below. That is, it is calculated from the water permeability Lp of the separation membrane and the water membrane permeation velocity Jv using the relations of the equations (3) and (4). Jv = Lp · ΔP Equation (3) Lp = (H / L) · [Rp ² / (8η)] (4) where ΔP is the transmembrane pressure difference, H is the membrane water content, L is the film thickness,
Rp is the pore size and η is the viscosity of water.

The shape of the separation membrane includes a hollow fiber membrane, a tubular membrane, and a flat membrane, and any shape can be used in the present invention. For water treatment applications such as process, water production and wastewater treatment, hollow fiber membranes that can increase the effective membrane area per unit volume of the equipment are required to have extremely high turbidity in the water to be treated and turbidity in the hollow fiber membrane bundle. It is preferable to use a flat film when the operation is difficult after deposition, and a tubular film when the inorganic film or the like is difficult to form. Here, the hollow fiber membrane is a tubular separation membrane having an outer diameter of less than 2 mm, and the tubular membrane is a tubular separation membrane having an outer diameter of 2 mm or more.

Further, examples of the material of the separation membrane include inorganic materials such as polyacrylonitrile, polysulfone, polyphenylene sulfone, polyphenylene sulfide sulfone, polyvinylidene fluoride, cellulose acetate, polyethylene, polypropylene, and ceramics. Polyacrylonitrile, which is not particularly limited but hydrophilic material from the gist of cellulose, cellulose acetate,
Polyphenylene sulphone and polyphenylene sulfide sulphone are preferable because they are hardly contaminated and have good cleaning recoverability.

The water to be treated according to the present invention is not particularly limited in view of the gist of the present invention, but is preferably river water, lake water, or groundwater for producing drinking water or producing water for use. Further, the present invention can be applied to wastewater treatment and the like, in which case the water to be treated is wastewater.

As described above, the operation of the membrane separation apparatus includes the constant flow filtration and the constant pressure filtration. Either one may be used, but the constant flow filtration operation can obtain a constant throughput and is generally used. preferable.

In addition, in the manner of supplying the water to be treated to the separation membrane, a total amount filtering operation for filtering the entire amount of the water to be treated and a cross-section for returning a part of the water to be treated supplied to the separation membrane module to the water to be treated. There is a flow filtration operation. Although any filtration operation method may be used from the gist of the present invention, the total amount filtration operation is advantageous because it is simple and easy to operate and can be operated at a low pressure, which leads to a reduction in energy cost and is advantageous and preferable.

[0031]

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.

Example 1 A polyacrylonitrile hollow fiber membrane having an average pore diameter of 0.01 μm was bundled, about 50 cm in length, and an effective membrane area of 0.35 m ^2.
Using the hollow fiber membrane module of No. 1, constant flow total filtration of surface water in Chitosegawa, Hokkaido was performed. The filtration linear velocity was 1 m / d.
The time-dependent change of the filtration pressure difference is shown by a white circle in FIG. River A
Surface water and the polyacrylonitrile hollow fiber membrane,
There is a relationship of n = 3.9 × ^{0.76, and} n = 1.3 from x = (amount of humic substance) / (turbidity) = 3.5 / 15 = 0.233. By substituting n = 1.3 into the Hermans equation and obtaining α to match the initial operation data, α = 8.
It becomes 8 × 10 ^-5 . The time-dependent change of the filtration pressure difference obtained from the Hermans equation in which the constant is determined is shown by a solid line in FIG. Operation started at a preset filtration pressure difference of 100 kPa 14
Since it was predicted to reach 60 hours later, about 1 day after the start of operation about 4 days before, a chemical solution washing was performed with citric acid and sodium hypochlorite, and the filtration pressure difference recovered to approximately 10 kPa at the start of the operation. Continued stable operation.

Comparative Example 1 In the same manner as in Example 1, a polyacrylonitrile hollow fiber membrane module having an average pore size of 0.01 μm was used to perform constant flow total filtration of the surface water of Chitosegawa, Hokkaido. Filtration linear velocity is 1m / d
And The time-dependent change of the filtration pressure difference is shown by a white circle in FIG. After exceeding a preset filtration pressure difference of 100 kPa,
Chemical cleaning was performed with citric acid and sodium hypochlorite in the same manner as in Example 1, but the filtration pressure difference did not recover much.

Comparative Example 2 In the same manner as in Example 1, a polyacrylonitrile hollow fiber membrane module having an average pore diameter of 0.01 μm was used to perform constant flow total filtration of surface water of Chitosegawa, Hokkaido. Filtration linear velocity is 1m / d
And The time-dependent change of the filtration pressure difference is shown by a white circle in FIG. Chemical cleaning with citric acid and sodium hypochlorite was performed every 500 hours in the same manner as in Example 1. As a result, stable operation was possible and cleaning recovery was good, but the frequency of chemical cleaning increased, and maintenance, treatment, and treatment were performed. It was disadvantageous in terms of cost.

[0035]

According to the present invention, the total filtered water amount V until the necessity of chemical cleaning is calculated from the ratio x = A / B of the amount A of the soluble component contained in the water to be treated and the turbidity B. Then, the chemical cleaning of the membrane separation device is performed when the water to be treated having the total filtered water amount V is treated, so that the optimal chemical cleaning time can be set, the cleaning recovery of the separation membrane is good, and the life of the separation membrane is extended. It is possible to provide a membrane separation apparatus which is easy to maintain and is advantageous in terms of cost, an operation method thereof, and a method for producing permeated water.

[Brief description of the drawings]

FIG. 1 is a diagram showing data of an operation result example using the operation method of the present invention.

FIG. 2 is a diagram showing data of an operation result example (when a chemical solution cleaning timing is delayed) according to a conventional method.

FIG. 3 is a diagram showing data of an operation result example (in the case of performing a chemical cleaning at an early stage) according to a conventional method.

Claims (14)

[Claims] 1. A method for operating a membrane separation apparatus for removing impurities by passing water to be treated through a separation membrane, wherein a relationship between the amount A of a soluble component contained in the water to be treated and the turbidity B is used. Calculate the total filtered water volume V until it is necessary to perform chemical cleaning,
A method for operating a membrane separation device, wherein a time when chemical cleaning is performed is determined based on the calculation result, and the chemical cleaning is performed at that time. 2. An operation elapsed time (t + T) at which the chemical solution needs to be cleaned is calculated in the following procedure, and the operation elapsed time (t + T) is calculated.
The operation method of the membrane separation device according to claim 1, wherein the chemical solution cleaning is performed at the time of T). (1) Using the time-dependent change of the filtration resistance R obtained from the filtration data of three or more different types of water to be treated, the filtration mechanism constant n is calculated based on the amount A of the soluble component and the turbidity B contained in the water to be treated. Ratio x
= A / B function n = f (x). (2) Filtration mechanism constant n calculated from x of the water to be treated using function n = f (x), resistance R ₀ of the separation membrane itself, total filtered water amount V (t) and filtration resistance R at operation elapsed time t From (t), the filtration coefficient α is calculated by the function α = g (n, R ₀ , V
(T), R (t)). (3) Filtration resistance R (t +
T) is calculated by multiplying the resistance R ₀ of the separation membrane itself by a constant k (k · R ₀ ).
= R (t + T). (4) Filtration resistance R (t) at operation elapsed time (t + T)
+ T), filtration coefficient α, filtration mechanism constant n, and resistance R ₀ of the separation membrane itself, the inverse function V (t + T) = g ⁻¹ (n, R ₀ , α,
R (t + T)) to calculate the total filtered water amount V (t + T) during the operation elapsed time (t + T). (5) Elapsed operation time (t + T) from total filtered water amount V (t + T)
T) is obtained by dividing the total amount of filtered water by the filtration flow rate in the case of constant flow filtration, and by integration in the case of constant pressure filtration. 3. The function α = g (n, R ₀ , V (t), R
The method according to claim 2, wherein (t)) is the expression (1). ^{R 1-n / (1-} n) = αV + R 0 1-n / (1-n) (1) formula 4. The method according to claim 2, wherein the constant k is 1.5 or more and 15 or less. 5. The method for operating a membrane separation apparatus according to claim 2, wherein the function n = f (x) is the equation (2) using constants a and m. n = ax ^m (2) 6. The method according to claim 5, wherein the constant a is 1 or more and 10 or less and the constant m is 0.1 or more and 1 or less. 7. The method according to claim 1, wherein the soluble component is represented by humic substances. 8. The method for operating a membrane separation apparatus according to claim 7, wherein the amount A of the soluble component is the ultraviolet absorbance at a wavelength of 260 nm or the total organic carbon amount. 9. A method for producing water, comprising washing a chemical solution by the method according to any one of claims 1 to 8, and further passing treated water through a separation membrane. 10. It is necessary to perform chemical cleaning using a separation membrane for removing impurities by passing water to be treated and a relationship between the amount A of soluble components contained in the water to be treated and the turbidity B. A membrane separation device comprising: means for calculating the total filtered water amount V up to the above, means for determining when to perform chemical cleaning based on the calculation result, and means for performing chemical cleaning. 11. The membrane separation apparatus according to claim 10, wherein the means for determining when it is necessary to perform the chemical cleaning includes a means for calculating the operation elapsed time (t + T) according to the following procedure. (1) Using the time-dependent change of the filtration resistance R obtained from the filtration data of three or more different types of water to be treated, the filtration mechanism constant n is calculated based on the amount A of the soluble component and the turbidity B contained in the water to be treated. Ratio x
= A / B function n = f (x). (2) Filtration mechanism constant n calculated from x of the water to be treated using function n = f (x), resistance R ₀ of the separation membrane itself, total filtered water amount V (t) and filtration resistance R at operation elapsed time t From (t), the filtration coefficient α is calculated by the function α = g (n, R ₀ , V
(T), R (t)). (3) Filtration resistance R (t +
T) is calculated by multiplying the resistance R ₀ of the separation membrane itself by a constant k (k · R ₀ ).
= R (t + T). (4) Filtration resistance R (t) at operation elapsed time (t + T)
+ T), filtration coefficient α, filtration mechanism constant n, and resistance R ₀ of the separation membrane itself, the inverse function V (t + T) = g ⁻¹ (n, R ₀ , α,
R (t + T)) to calculate the total filtered water amount V (t + T) during the operation elapsed time (t + T). (5) Elapsed operation time (t + T) from total filtered water amount V (t + T)
T) is obtained by dividing the total amount of filtered water by the filtration flow rate in the case of constant flow filtration, and by integration in the case of constant pressure filtration. 12. The membrane separation apparatus according to claim 11, further comprising means for displaying the operation elapsed time (t + T). 13. The separation membrane having a pore diameter of 1 nm or more and 10 μm.
The following microfiltration membrane or ultrafiltration membrane:
13. The membrane separation device according to any one of claims to 12. 14. The membrane separation device according to claim 10, wherein the material of the separation membrane is any one of polyacrylonitrile, cellulose acetate, polyphenylene sulfone, and polyphenylene sulfide sulfone.