JP2000140585A - Operation of membrane separation apparatus, and membrane separation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a separation membrane through which water to be treated is caused to pass to remove impurities by calculating the amount of impurities removed by the membrane per unit membrane area from the turbidity and membrane-permeating flux of water to be treated and physically cleaning the membrane every time when a specified amount of impurities is removed by the membrane. SOLUTION: In filtering with a membrane separation apparatus, the turbidity of water to be treated in an untreated-water tank 1 is measured with a turbidity meter 3; the amount of impurities removed by a separation membrane per unit membrane area is calculated from the turbidity and membrane-permeating flux of water to be treated; and every time when the amount of impurities removed by the membrane reaches 0.1 g/m2 or higher but not higher than 15 g/m2, the membrane is subjected to physical cleaning consisting of backward washing and air scrubbing. The backward washing is carried out by causing backward washing water in a backward washing water tank 8 to flow, via an electromagnetic valver 6d, from the treated water side to the untreated water side. The air scrubbing is done by introducing air from the lower part of a separation membrane module 5. After the completion of cleaning, an electromagnetic valve 6c is opened to discharge dirty water from the separation membrane module 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a membrane separation apparatus and a membrane separation apparatus suitably used in the food industry, medical field, drinking water production field, industrial process water production field, wastewater treatment field and the like.

[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. Particularly in recent years, separation membranes have been used in the field of drinking water production, that is, in the purification process. This is because by using a separation membrane, it is possible to prevent pathogenic microorganisms such as cryptosporidium that do not die in chlorination, which is a sterilization technique in conventional water purification treatment, and it is possible to obtain safe and good-quality drinking water. It is.

[0003] Microfiltration membranes and ultrafiltration membranes used in water treatment such as water production and wastewater treatment separate pressure differences into driving forces. 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 dirt accumulates on the surface of the separation membrane 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.

[0004] Therefore, the sediment on the separation membrane surface is peeled off,
As a means for recovering the processing ability by opening the pores of the closed separation membrane, a method of flushing the surface of the separation membrane (JP-A-5-138166) and a method of scrubbing with air (JP-A-61-1986) No. 263605), and a physical cleaning method (hereinafter referred to as physical cleaning) such as so-called backwashing, in which a gas such as air, a liquid such as treated water, or clear water is transmitted from the treated water side of the membrane to the treated water side. Have been. In the prior art, the filtration operation was continued while repeating the physical cleaning at regular intervals.

[0005] Further, film stains that cannot be removed only by physical cleaning include oxidizing agents such as acids, alkalis, surfactants, and chlorine.
Chemical solution washing with enzymes etc. is performed every few months to recover the performance of the separation membrane.However, there is no method to set the timing of chemical solution washing based on the basis, and it is implemented after a sudden rise in filtration differential pressure It was common to do.

It is necessary to carry out the physical cleaning to such an extent that a rapid rise in the filtration pressure difference does not occur. However, if the frequency is too high, the processing amount per unit time, that is, the recovery rate becomes small, which is disadvantageous. If the water quality is good and the rise in filtration resistance of the membrane is small, it is preferable that the physical cleaning be small.

In the case of water to be treated, such as river water or lake water, whose water quality fluctuates greatly due to rainfall or the like, high turbidity treated water containing a large amount of impurities is temporarily supplied to the membrane separation device. In this case, in this case, a sharp rise in the filtration differential pressure occurs, and the separation membrane module or the separation membrane is damaged, or the cleaning recovery is poor even if physical cleaning is performed,
Even when the operation is resumed, there have been problems such as the sudden rise in the filtration pressure difference. As a result, the life of the separation membrane is shortened, which is often disadvantageous in terms of processing cost.

[0008] In addition, it is difficult to set the timing of chemical cleaning, and it is often the case that the cleaning is performed after a sharp rise in the filtration pressure difference. However, even if chemical cleaning is performed after a rapid rise in the filtration pressure difference, the cleaning recovery is poor, and even when the operation is restarted, the filtration pressure difference rises rapidly again, and the life of the separation membrane is extremely short. This is disadvantageous in terms of processing cost. In addition, when the chemical solution is washed early and early, the recovery performance is good and the life of the separation membrane is long, but the frequency of the chemical solution is increased, so that the maintenance is complicated and the processing cost is reduced. Disadvantageous.

[0009]

When high turbidity treated water containing a large amount of impurities is temporarily supplied to a membrane separation apparatus, physical cleaning is simply repeated at regular time intervals.
It is not possible to prevent a sudden increase in the filtration pressure difference.If the separation membrane module or separation membrane is damaged, the cleaning recovery is poor even if physical cleaning is performed, or if the operation is restarted, the filtration pressure difference will be reduced again. However, in the prior art, there is no means for setting an optimum physical cleaning frequency other than time. As for chemical cleaning, there is no means for setting the optimal chemical cleaning execution time based on the basis.

The present invention has been made to solve the above-mentioned problems of the prior art. By performing washing every time a fixed amount (X ₀ ) of impurities is removed by a separation membrane, a rapid increase in filtration pressure difference can be prevented. An object of the present invention is to provide a method of operating a membrane separation device and a membrane separation device that are safe and extend the life of the separation membrane.

[0011]

The present invention relates to a membrane separation apparatus for removing impurities by passing the water to be treated through a separation membrane and separating the water from the turbidity of the water to be treated and the permeation flux (F). A film characterized by calculating an impurity amount (X) per unit film area removed by the film, and performing physical cleaning every time impurities of 0.1 g / m ² or more and 15 g / m ² or less are removed by the separation film. Operation method of separation device. "," In a membrane separation device for removing impurities by passing the water to be treated through the separation membrane, the water to be treated was removed from the water quality (A) and the permeate flux (F) by the separation membrane. The amount of impurities (X) per unit film area is calculated, and a certain amount (X
₀ ) A method for operating a membrane separation apparatus, wherein a chemical solution is washed each time impurities are removed by a separation membrane. And "means for measuring the water quality (A) of the water to be treated, and separating the water from the water (A) and the membrane permeation flux (F) in the membrane separation apparatus for removing impurities by passing the water to be treated through the separation membrane. A membrane separation comprising means for calculating the amount of impurities (X) per unit film area removed by the film, and means for washing each time a fixed amount (X ₀ ) of impurities is removed by the separation film. apparatus."
Is basically achieved by

[0012]

Embodiments of the present invention will be described below.

In the filtration operation of the membrane separation apparatus of the present invention, the pressure of the water to be treated is increased by using a pressurizing means such as a pump or a suction means on the side of the treated water so that the pressure of the water to be treated is increased. Water is supplied to the separation membrane module, and the whole or a part of the water to be treated is permeated to the treated water side of the separation membrane to obtain a clear permeate.

[0014] Of the impurities contained in the water to be treated, those that are larger than the pores of the membrane are blocked on the membrane surface and accumulate on the membrane surface. For this reason, backflow washing in which clear water or gas flows from the treated water side of the membrane toward the treated water side, or air that introduces a gas such as air near the separation membrane to shake the separation membrane and give a flow to the membrane surface Filtration is continued while removing impurities accumulated on the membrane surface by physical cleaning such as scrubbing cleaning.

In this case, in the prior art, the physical cleaning is generally repeated at regular intervals by controlling an automatic opening / closing valve such as a solenoid valve with a timer or the like. As a result of analyzing and examining various kinds of operation data of filtration in detail, it was found that when impurities of a certain amount or more were removed, the filtration differential pressure rapidly increased, and it became difficult to maintain stable operation. Until a certain amount or more of impurities are removed, the impurities accumulated on the separation membrane surface protect the separation membrane surface, and soluble organic substances such as humic substances enter, adsorb, and accumulate inside the separation membrane pores. In order to prevent this, it has been found that it is disadvantageous to increase the physical cleaning more than necessary because the rise in the filtration pressure difference is moderate and stable operation is possible.

Further, the present inventors have found from the analysis results of many operation data that the filtration pressure difference reaches a pressure at which the chemical solution should be washed after removing a certain amount of impurities in the chemical solution washing.

Therefore, the present invention uses the water quality (A _t ) of the water to be treated at time (t) and the membrane permeation flux (F _t ), which is the amount of filtration per unit time of the unit membrane area, from the previous washing. The amount of impurities per unit film area (X _t ) removed by the separation membrane by time (t) is calculated, and every time (X _t ) reaches a preset amount of impurities per unit film area (X ₀ ). Perform cleaning. The amount of impurities per unit film area (X _t ) removed by the separation membrane from the previous cleaning to the time (t) is calculated by, for example, the following equation (1), but is not particularly limited to this equation. In the above, the amount of impurities removed by the separation membrane may be integrated (integrated).

X _t = Σ (A _t · F _t · Δt) (1) where Δt is the measurement interval of A _t and F _t The water to be treated of the present invention can be said from the gist of the present invention. Although not particularly limited, river water, lake water, groundwater, and the like are preferable in the field of drinking water production, that is, water treatment applications such as water purification processes, water production and wastewater treatment. In recent years, reverse osmosis seawater desalination has been adopted in drinking water production as a permanent solution to water shortage, but the present invention is also applied to a membrane separation device used for pretreatment of a reverse osmosis membrane separation device. In this case, the water to be treated is preferably seawater. Further, activated sludge-containing water in the case of sewage treatment or human waste treatment is also preferable as the water to be treated in the present invention.

Here, the water quality (A) of the water to be treated is an index expressing the concentration of impurities in the water to be treated. For example, a microfiltration membrane having a pore diameter of 1 nm or more and 10 μm or less or an ultrafiltration membrane In the case of a membrane, turbidity, fine particle number concentration, SS concentration,
MLSS concentration and the like. When the raw water to be treated is relatively low turbidity water such as river water, lake water, groundwater or seawater, the turbidity and the concentration of fine particles are regarded as the quality of the water to be treated (A), and the raw water to be treated is used for wastewater treatment. In the case of high turbidity water such as activated sludge-containing water or powdered activated carbon-containing water, the SS concentration or the MLSS concentration is used as the quality (A) of the water to be treated.

Turbidity is an index that defines the turbidity of a kaolin 1 mg / l solution as 1 degree (= 1 mg / l). Although there is a certain degree, the measuring method should be appropriately selected and is not particularly limited.

The particle number concentration is an index indicating the number of particles having a size equal to or larger than a predetermined size per unit volume, and is generally measured by utilizing light scattering.

The SS concentration is a concentration of a suspended substance, and is expressed by a weight of a substance obtained by filtering water to be treated through a predetermined filter paper, usually at 105 to 110 ° C. for 2 hours. It is an indicator.

The MLSS concentration is an index representing the weight of the water to be treated on the evaporating dish after drying it at usually 105 to 110 ° C. for 2 hours, and is an index used when expressing the concentration of activated sludge-containing water and the like. is there.

In the present invention, it is preferable to use an apparatus capable of automatically measuring the water quality index as described above, and the water quality (A) of the water to be treated is constant in the water side line as close as possible to the separation membrane module. It is preferable to measure as much as possible every time and to automatically send data to the membrane separation device because the impurity amount (X) per unit membrane area can be accurately calculated. The quality of the water to be treated may be manually measured at irregular times, and the data may be input to the membrane separation device.

The physical cleaning according to the present invention is suitable for a separation membrane or a membrane module structure.
Although not particularly limited in the spirit of the present invention, flushing the separation membrane surface, a method of scrubbing with air, gas or treated water such as air, liquid or acid such as clear water,
So-called backwashing, in which a chemical solution such as an alkali, a surfactant, an oxidizing agent such as chlorine, or an enzyme is transmitted from the treated water side of the membrane to the treated water side, can be employed. It is appropriately selected according to the quality of the water.

The cleaning of the chemical solution in the present invention is also not particularly limited in view of the gist of the present invention, and may be appropriately selected depending on the material of the separation membrane and the type of dirt. Acid, alkali,
A surfactant, an oxidizing agent such as chlorine, and a chemical solution such as an enzyme are selected according to the situation.

The predetermined amount of impurities per unit membrane area (X ₀ ) is determined by the material of the separation membrane, the pore diameter, the material and size of the impurities to be separated and removed, the index of the measured water quality (A), and the like. different. For example, when the water quality (A) is turbidity, the physical cleaning is 0.1 g / m ² or more and 15 g / m ² or less,
It is preferably carried out each time impurities of an amount of impurities per unit film area of about 0.2 g / m ^{2 to} 12 g / m ² , more preferably about 0.5 g / m ^{2 to} 10 g / m ² are removed. . Here, if X ₀ is larger than 15 g / m ² , the filtration pressure difference will increase rapidly, and it will be difficult to continue stable operation. On the other hand, if X ₀ is less than 0.1 g / m ² , the protective effect of the membrane due to impurities accumulated on the surface of the separation membrane cannot be obtained, and soluble organic substances such as humic substances enter into the pores of the separation membrane, Adsorption and accumulation are not preferred.

Similarly, when the water quality (A) is turbid,
Washing is 300g / m^TwoMore than 10,000g / m^TwoThe following is good
Preferably, more preferably 500 g / m^TwoMore than 8000g
/ M ^TwoBelow, more preferably 800 g / m^TwoMore than 50
00g / m^TwoImpurity amount per unit film area (X
₀It is preferable to carry out each time the impurities are removed.

Further, if the filtration pressure difference is too high, impurities are pushed into the separation membrane and the physical cleaning recovery is deteriorated. Therefore, before the removal of a certain amount (X ₀ ) of impurities by the separation membrane, the filtration pressure difference is increased. When the set filtration pressure difference (P ₀ ) is reached,
Performing physical cleaning at this time can also be preferably employed.

Here, the preset filtration pressure difference (P ₀ ) varies depending on the material and pore size of the separation membrane, but is preferably 40 kPa or more and 200 kPa or less, more preferably 50 kPa or more and 180 kPa or less, and further preferably 60 kPa or less. It is about 150 kPa or less.

The separation membrane used in the present invention is not particularly limited in view of the gist of the present invention. However, the separation membrane is used in the field of drinking water production, that is, in a water treatment process such as a 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 (L _p ) of the separation membrane and the membrane permeation velocity (J _v ) of water using the relationship of the following equations (2) and (3).

J _v = L _p · ΔP (2) Expression L _p = (H / L) · {R _p ² / (8η)} (3) where ΔP is the transmembrane pressure. Difference, H is the film moisture content, L is the film thickness,
R _p 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, a flat membrane and the like, and any shape can be used in the present invention. It is preferable to use a hollow fiber membrane capable of increasing the effective membrane area per unit volume of the device for water treatment applications such as process and production of water. Here, the hollow fiber membrane has an outer diameter of 2 mm.
A tubular separation membrane having a diameter of less than 2 mm 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.

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. However, the constant flow filtration operation can obtain a constant throughput and is generally used. preferable.

[0036] Further, 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. In the case of total filtration, the amount of impurities removed by the separation membrane can be accurately calculated, so that this is a filtration method suitable for the present invention. On the other hand, cross-flow filtration is characterized by the ability to remove some of the dirt deposited on the membrane surface by the shear stress caused by the flow on the membrane surface, but from the gist of the present invention, the amount of impurities removed by the separation membrane can be accurately determined. It is not preferable because it cannot be calculated. Further, the total filtration operation 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. On the other hand, the cross-flow filtration is disadvantageous in terms of energy because the operation is complicated and the water to be treated must be flown in the module.

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

[0038]

EXAMPLE 1 Polyacrylonitrile hollow fiber membranes having an average pore diameter of 0.01 μm were bundled, about 50 cm long, and the effective membrane area was 0.55 m ^2.
A constant flow rate total filtration of Lake Biwa water was performed using a pressurized hollow fiber membrane module. FIG. 1 shows a membrane separation device.

The filtration operation is performed by pressurizing and supplying the water to be treated by the pressure pump 2 on the treated water side of the separation membrane module 5, closing the electromagnetic valve 6 a and storing the treated water in the treated water tank 7. Was. The membrane permeation flux (F) is 1 m ³ / m ² · d
And Treated water tank 1 with turbidity meter 3 of scattered light measurement method
The turbidity of the water to be treated (A) was measured every (Δt) = 5 minutes. Each time impurities of a fixed amount (X ₀ ) = 3 g / m ² were filtered, back washing was performed for 1 minute as physical washing, and air scrubbing washing with air was performed for 2 minutes. In the backwashing, a part of the treated water is flowed from the treated water side of the separation membrane module 5 to the treated water side through the electromagnetic valve 6d through the backwash water stored in the backwash water tank 8 via the electromagnetic valve 6d. This was performed by releasing from the electromagnetic valve 6a. The air scrubbing was performed by introducing air from below the separation membrane module 5 and shaking the hollow fiber membrane. After completion, the electromagnetic valve 6c was opened to drain the contaminated water in the separation membrane module. During the physical cleaning period, the electric valve 6b was closed.

FIG. 2 shows the change over time in the turbidity of the water to be treated. The turbidity of the water to be treated is from 2 mg / l to 100 The value fluctuated in the range of about mg / l, and the physical cleaning interval also changed accordingly. The amount of impurities (X) per unit film area removed by the film is calculated by the computer 9 according to the following equation, where (X) is (X ₀ ) = 3 g /
Physical cleaning was performed when the value became larger than m ² .

(X) = (X _i ) + (X _{i + 1} ) + (X _{i + 2} ) +... = (A _i · F · Δt) +... = (A _i × 1 × 5) / (24 × 60)) +... The time-dependent change in the filtration pressure difference immediately after the physical cleaning measured by the pressure sensor 4 is shown in FIG. Physical washing was performed 507 times during 1500 hours, and the filtration pressure difference after operation for 1500 hours was about 7
At 0 kPa, the increase in the filtration pressure difference was suppressed low. Comparative Example 1 Polyacrylonitrile hollow fiber membranes having an average pore diameter of 0.01 μm were bundled at the same time as in Example 1, and the length was about 50 cm.
Using a pressurized hollow fiber membrane module with an effective membrane area of 0.55 m ² , a constant flow rate total filtration of Lake Biwa water was performed. The filtration operation was performed by pressurizing and supplying the water to be treated with a pressure pump on the side of the water to be treated of the separation membrane. The filtration linear velocity was 1 m / d. The turbidity of the water to be treated was not measured, and backwashing with permeated water was carried out every 3 hours for 1 minute and air scrubbing with air was carried out for 2 minutes every 3 hours, regardless of the amount of impurities removed. FIG. 3 shows a temporal change of the filtration pressure difference immediately after the physical cleaning. In the operation for 1500 hours, the number of physical washings was 500 times, which is almost the same as in Example 1. However, the filtration pressure difference after the operation for 1500 hours was 300 kPa or more, making it difficult to continue the operation. Comparative Example 2 Polyacrylonitrile hollow fiber membranes having an average pore diameter of 0.01 μm were bundled at the same time as in Example 1, and the length was about 50 cm.
Using a pressurized hollow fiber membrane module with an effective membrane area of 0.55 m ² , a constant flow rate total filtration of Lake Biwa water was performed. The filtration operation was performed by pressurizing and supplying the water to be treated with a pressure pump on the side of the water to be treated of the separation membrane. The filtration linear velocity was 1 m / d. The turbidity of the water to be treated was not measured, and backwashing with permeated water was performed for 1 minute and air scrubbing with air was performed for 2 minutes every hour, regardless of the amount of impurities removed. FIG. 3 shows a temporal change of the filtration pressure difference immediately after the physical cleaning. The filtration pressure difference after the operation for 1500 hours was about 150 kPa, which was higher than that in Example 1. Also, 15
In the 00-hour operation, the number of times of physical cleaning was 1500 times, which was almost three times that of Example 1, and the recovery rate was low, which was disadvantageous. Example 2 Polyacrylonitrile hollow fiber membranes having an average pore diameter of 0.01 μm were bundled, about 50 cm in length, and the effective membrane area was 0.35 m ^2.
The constant flow rate total filtration of Lake Biwa water was performed using the hollow fiber membrane module of No. The membrane permeation flux (F) was 1 m ³ / m ² · d. The turbidity of the water to be treated (A) in the water tank to be treated was measured with a turbidity meter of a scattered light measurement method every (Δt) = 5 minutes. Each time an amount of impurities (X ₀ ) = 1500 g / m ² is filtered,
Chemical cleaning with hydrochloric acid, sodium hydroxide solution, and sodium hypochlorite solution was performed. The amount of impurities (X) per unit film area removed by the film was calculated by the computer 9 according to the following equation. When (X) became larger than (X ₀ ) = 1500 g / m ² , chemical cleaning was performed at the time. . (X) = (X _i ) + (X _{i + 1} ) + (X _{i + 2} ) +... = (A _i · F · Δt) +... = (A _i × 1 × 5 / (24) × 60)) +... The temporal change of the filtration pressure difference immediately after the physical cleaning measured by the pressure sensor 4 is shown in FIG. The filtration pressure difference after the washing with the chemical solution recovered to about 10 kPa, which was almost the same at the start of the operation, and the stable operation was continued thereafter. Comparative Example 3 Using a hollow fiber membrane module having a length of about 50 cm and an effective membrane area of 0.35 m ² , which was a bundle of polyacrylonitrile hollow fiber membranes having an average pore diameter of 0.01 μm as in Example 2, was used to determine the volume of Lake Biwa water. Flow rate total filtration was performed. The filtration linear velocity was 1 m / d. The turbidity of the water to be treated is not measured, and regardless of the amount of impurities removed, after the filtration pressure difference exceeds 100 kPa, the chemical solution is washed with hydrochloric acid, a sodium hydroxide solution, and a sodium hypochlorite solution as in Example 2. Was done. FIG. 5 shows the temporal change of the filtration pressure difference immediately after the physical cleaning. The filtration pressure difference after the cleaning with the chemical solution recovered only up to about 60 kPa. Comparative Example 4 In the same manner as in Example 2, a polyacrylonitrile-made hollow fiber membrane module having an average pore diameter of 0.01 μm was used to perform constant flow total filtration of Lake Biwa water. The filtration linear velocity was 1 m / d. FIG. 6 shows the change over time in the filtration pressure difference. The turbidity of the water to be treated was not measured, and the chemical was washed with hydrochloric acid, a sodium hydroxide solution, and a sodium hypochlorite solution every about 600 hours in the same manner as in Example 2 regardless of the amount of impurities removed. Although the cleaning recovery was good, the frequency of cleaning with the chemicals increased, which was disadvantageous in terms of maintenance and processing costs. Example 3 Using a pressurized hollow fiber membrane module having a length of about 50 cm and an effective membrane area of 0.4 m ² , in which polyacrylonitrile hollow fiber membranes having an average pore diameter of 0.01 μm were bundled, constant-flow total filtration of Lake Biwa water was performed. went.

In order to perform an accelerated test, the membrane permeation flux (F)
3m^Three/ M^Two・ It was d. With a turbidity meter that measures scattered light
The turbidity of the water to be treated was measured every (Δt) = 10 minutes. Fixed amount
(X ₀) = 0.2 g / m^TwoEach time impurities are filtered,
Air scrubbing with air for 1 minute for backwashing
Cleaning was performed for 1 minute. During the experiment, the turbidity of the treated water was 2
fluctuates in the range of about 15 mg / l to
Accordingly, the physical cleaning interval also changed. Separate as in Example 1.
The amount of impurities (X) per unit film area removed by the film
(X) = 0.2 g / m^TwoBigger
Physical cleaning was performed at the time when it became.

The filtration pressure difference 10 days after the start of the experiment only increased by 9 kPa from the filtration pressure difference at the start of the experiment. Table 1 shows the results. Example 4 Using a pressurized hollow fiber membrane module having a length of about 50 cm and an effective membrane area of 0.4 m ² , which is a bundle of polyacrylonitrile hollow fiber membranes having an average pore diameter of 0.01 μm, constant-flow total filtration of Lake Biwa water was performed. went. The experiment was performed in the same period as in Example 3.

In order to conduct an accelerated test, the membrane permeation flux (F)
3m^Three/ M^Two・ It was d. With a turbidity meter that measures scattered light
The turbidity of the water to be treated was measured every (Δt) = 10 minutes. Fixed amount
(X ₀) = 8 g / m^TwoEvery time impurities are filtered
1 minute of backwashing as clean, air scrubbing with air
Purification was performed for 1 minute. During the experiment, the turbidity of the water to be treated was 2 mg
/ L to 15mg / l range,
Physical wash intervals also changed. As in Example 1, the separation membrane
The amount of impurities (X) removed per unit film area is calculated by computer.
(X) = 8 g / m^TwoWhen it gets bigger
Physical cleaning was performed at the point.

The filtration pressure difference 10 days after the start of the experiment only increased by 13 kPa from the filtration pressure difference at the start of the experiment. Table 1 shows the results. Comparative Example 5 Using a pressurized hollow fiber membrane module having a length of about 50 cm and an effective membrane area of 0.4 m ² , which was formed by bundling polyacrylonitrile hollow fiber membranes having an average pore diameter of 0.01 μm, constant-flow total filtration of Lake Biwa water was performed. went. The experiment was performed in the same period as in Example 3.

In order to perform an accelerated test, the membrane permeation flux (F)
3m^Three/ M^Two・ It was d. With a turbidity meter that measures scattered light
The turbidity of the water to be treated was measured every (Δt) = 10 minutes. Fixed amount
(X ₀) = 0.05 g / m^TwoEach time impurities are filtered,
1 minute backwash as physical cleaning, air scrubbing with air
Cleaning was performed for 1 minute. During the experiment, the turbidity of the treated water was
It fluctuates in the range of about 2 mg / l to 15 mg / l.
As a result, the physical cleaning interval also changed. In the same manner as in Example 1,
The amount of impurities (X) per unit film area removed by film separation
(X) = 0.05 g / m^TwoGreater than
Physical washing was performed at the time when it became sharp.

The filtration pressure difference 10 days after the start of the experiment increased by 31 kPa from the filtration pressure difference at the start of the experiment. Table 1 shows the results. Comparative Example 6 Using a pressurized hollow fiber membrane module having a length of about 50 cm and an effective membrane area of 0.4 m ² , in which polyacrylonitrile hollow fiber membranes having an average pore size of 0.01 μm were bundled, constant-flow total filtration of Lake Biwa water was performed. went. The experiment was performed in the same period as in Example 3.

To perform an accelerated test, the permeation flux (F)
3m^Three/ M^Two・ It was d. With a turbidity meter that measures scattered light
The turbidity of the water to be treated was measured every (Δt) = 10 minutes. Fixed amount
(X ₀) = 20 g / m^TwoEach time impurities are filtered,
Air scrubbing with air for 1 minute backwashing as washing
Washing was performed for 1 minute. During the experiment, the turbidity of the treated water was 2 m
g / l to about 15 mg / l.
The physical cleaning interval also changed. Separation membrane as in Example 1
The amount of impurities (X) per unit film area removed by
(X) = 20 g / m^TwoGet bigger
At that time, physical cleaning was performed.

The filtration pressure difference 10 days after the start of the experiment increased by 55 kPa from the filtration pressure difference at the start of the experiment. Table 1 shows the results.

[0050]

[Table 1]

[0051]

According to the present invention, the amount (X) of impurities removed by the separation membrane is calculated from the water quality (A) of the water to be treated and the membrane permeation flux (F), and a certain amount (X ₀ ) of impurities is removed. The membrane separation device is characterized by performing washing every time it is removed by the separation membrane, and according to this method, the life of the separation membrane is prolonged, the recovery of the separation membrane is improved, and the optimal chemical cleaning is performed. An operation method of a membrane separation apparatus and a membrane separation apparatus which can set a time and are advantageous in terms of processing cost are provided.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an example of the membrane separation device of the present invention.

FIG. 2 is a graph showing the change over time in the turbidity of the water to be treated in Example 1.

FIG. 3 is a graph showing operation results of Example 1, Comparative Example 1, and Comparative Example 2.

FIG. 4 is a graph showing an example of operation results when a chemical solution cleaning is performed according to the present invention.

FIG. 5 is a graph showing an example of an operation result when a chemical cleaning is performed by a conventional method (when a chemical cleaning timing is delayed).

FIG. 6 is a graph showing an example of operation results when a chemical cleaning is performed by a conventional method (when a chemical cleaning is performed early and early).

[Description of Signs] 1: Raw water tank to be treated 2: Pressurized liquid sending means such as a pump 3: Measurement means for water quality (A) to be treated 4: Pressure sensor 5: Separation membrane module 6: Electromagnetic valve 7: Treated water tank 8: Backwash water tank 9: Means for calculating the amount (X) of impurities per membrane area removed by the separation membrane

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Claims (15)

[Claims] In a membrane separation apparatus for removing impurities by passing water to be treated through a separation membrane, impurities per unit membrane area removed by the separation membrane from the turbidity and the permeation flux (F) of the water to be treated. A method for operating a membrane separation apparatus, comprising calculating a quantity (X) and performing physical cleaning every time impurities in a range of 0.1 g / m ^{2 to} 15 g / m ² are removed by a separation membrane. 2. A membrane separation device for removing impurities by passing the water to be treated through a separation membrane, wherein the water quality (A) and the permeation flux (F) of the water to be treated are removed per unit membrane area by the separation membrane. A method of operating a membrane separation apparatus, comprising: calculating an impurity amount (X) of a solution and performing a chemical cleaning every time a fixed amount (X ₀ ) of the impurity is removed by the separation membrane. 3. The water quality (A) of the water to be treated is turbidity.
And a certain amount of impurities (X ₀ ) is 300 g / m ² or more and 1
3. The method for operating a membrane separation device according to claim 2, wherein the range is 0000 g / m ² or less. 4. The method for operating a membrane separation apparatus according to claim 2, wherein the quality (A) of the water to be treated is a concentration of fine particles, a concentration of SS, or a concentration of MLSS. 5. The method according to claim 1, wherein said water to be treated is river water, lake water, groundwater, or seawater. 6. The method for operating a membrane separation apparatus according to claim 1, wherein the water to be treated contains activated sludge. 7. The method for operating a membrane separation device according to claim 1, wherein a total filtration operation is performed. 8. The method for operating a membrane separation device according to claim 1, wherein a constant flow filtration operation is performed. 9. A membrane separation device for removing impurities by passing water to be treated through a separation membrane, wherein the water quality (A) of the water to be treated and the membrane flux (F) per unit membrane area removed by the separation membrane. Of impurities (X) of 0.1 g / m ² or more and 15 g /
operation of the membrane separation device, wherein the physical cleaning is performed at the earlier of the time when the impurities of m ² or less are removed by the separation membrane and the time when the filtration differential pressure reaches a preset filtration differential pressure (P ₀ ). Method. 10. The filtration pressure difference (P ₀ ) set in advance is 40
The method for operating a membrane separation device according to claim 9, wherein the pressure is not less than kPa and not more than 200 kPa. 11. The method for operating a membrane separation device according to claim 1, wherein the separation membrane is a microfiltration membrane or an ultrafiltration membrane having a pore diameter of 1 nm or more and 10 μm or less. 12. The material according to claim 1, wherein the material of the separation membrane is selected from the group consisting of polyacrylonitrile, cellulose acetate, polyphenylene sulfone, and polyphenylene sulfide sulfone. Method for operating the membrane separation device of the present invention. 13. The method for operating a membrane separation device according to claim 1, wherein the separation membrane is a hollow fiber membrane. 14. A membrane separation apparatus for removing impurities by passing water to be treated through a separation membrane, means for measuring the water quality (A) of the water to be treated, and water quality (A) and membrane permeation flux (F). Means for calculating the amount of impurities (X) per unit film area removed from the separation film from the substrate, and means for washing each time a fixed amount (X ₀ ) of impurities is removed by the separation film. Membrane separation device. 15. A fresh water producing method using the method for operating a membrane separation device according to any one of claims 1 to 12.