JP2000084370A - Membrane separation device and its operation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evade to impose excess pressure on a separation membrane module in the rapid increase of the pressure difference of filtration or in the generation of the failure of a pressure sensor or a solenoid valve by giving a means for releasing water to be treated between a pressure liquid feed means and the separation membrane module. SOLUTION: The water to be treated is pressurized and supplied to the separation membrane module 5 from an original water treating tank 1 by the pressure liquid feed means 2 such as a pump, the whole or a part of the original water to be treated is permeated through the separation membrane and a clear treated water is stored in a treated water tank 7. In the case of rapid increase of the pressure difference of filtration or the failure of the pressure sensor 4, the solenoid valve 6b, or the like, and when the feed pressure of the original water to be treated is increased to reach a previously set value, the original water to be treated is returned to the original water treating tank 1 by detecting reaching equal to or above the previously set value and opening a valve by the means 3 such as a safety valve or a release valve for releasing the original water to be treated. As a result, even in the case of the rapid increase of the pressure difference of filtration or the failure of the pressure sensor 4, the solenoid valve 6, or the like, excess pressure is not imposed on the separation membrane module 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a membrane separation device and a method of operating the same. More specifically, the present invention relates to a membrane separation device that performs filtration using a pressure-type separation membrane module, and further includes a means for releasing raw water to be treated between a pressure liquid sending unit and the separation membrane module.

[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.

[0003] By using a separation membrane, it is possible to completely prevent pathogenic microorganisms such as cryptosporidium which are not killed by chlorination, which is a sterilization technique in the conventional water purification treatment, to obtain safe and high quality drinking water. This is because it becomes possible.

[0004] Microfiltration membranes and ultrafiltration membranes used in 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. When the filtration is continued and the dirt accumulates on the separation membrane surface and in the pores of the separation membrane, the filtration resistance 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, but in this case, filtration resistance increases due to accumulation of dirt on the membrane, and the filtration pressure difference rises sharply. There was a case.
In addition, in the case of constant pressure filtration, when the filtration resistance increases, the filtration flow rate decreases and the filtration differential pressure is kept constant.However, when the pressure sensor or the solenoid valve fails, excessive pressure is applied to the separation membrane module. There was sometimes.

[0005]

When an excessive pressure is applied to the separation membrane module, the separation membrane may be damaged, the separation membrane module may be damaged, or the piping of the membrane separation device may be ruptured. The disadvantage of the conventional technology is that the damage is small when the treatment scale is small, but when the membrane separation technology is introduced in a large-scale water purification plant in the future, the damage is immeasurable. It was an object of the prior art to provide a membrane separation apparatus and an operation method thereof in which an excessive pressure is not applied to a module.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem of the prior art. Even when the pressure difference in filtration suddenly rises, or when the pressure sensor, the electromagnetic valve or the like breaks down, the separation membrane module is not excessively charged. It is an object of the present invention to provide a membrane separation device in which pressure is not applied and a method of operating the same.

[0007]

That is, an object of the present invention is to provide a membrane separation apparatus for performing filtration using a pressurized separation membrane module, wherein a coating is provided between a pressurized liquid sending means and a separation membrane module. Membrane separation device characterized by having means for releasing treated raw water. "

[0008]

Embodiments of the present invention will be described below.

FIG. 2 shows a membrane separation apparatus using a conventional pressurized separation membrane module. The raw water to be processed is pressurized and supplied from the raw water tank 1 to the separation membrane module 5 using the pressurized liquid sending means 2 such as a pump, and the total amount (the electromagnetic valve 6a is closed)
Alternatively, part of the raw water to be processed (partially opened with the electromagnetic valve 6a) is allowed to permeate the separation membrane, and clear treated water is taken out and stored in the treated water tank 7. Part of the treated water is stored in the backwash water tank 8 via the electromagnetic valve 6e. Of the impurities contained in the raw water to be treated, those larger than the pores of the membrane are blocked by the separation membrane and accumulate on the surface of the separation membrane. For this reason, while removing impurities accumulated on the surface of the separation membrane by physical washing such as backwashing in which the treated water flows from the treated water side of the separation membrane toward the raw water to be treated from the backwash water tank 8 via the electromagnetic valve 6d. Continue filtration. The physical cleaning wastewater is discharged from the separation membrane module 5 via the electromagnetic valve 6c. In the conventional membrane separation device, even when the filtration differential pressure rises rapidly, or when the pressure sensor 4 or the electromagnetic valve 6b breaks down, excessive pressure is applied to the separation membrane module 5 to damage or separate the separation membrane. In some cases, the membrane module 5 was damaged, or the piping of the membrane separation device was ruptured.

FIG. 1 is a flowchart showing an example of a membrane separation apparatus using the pressurized separation membrane module of the present invention. The raw water to be processed is pressurized and supplied from the raw water tank 1 to the separation membrane module 5 by using a pressurized liquid sending means 2 such as a pump, and the whole or a part of the raw water to be processed is permeated through the separation membrane, thereby obtaining a clear treatment. The water is taken out and stored in the treated water tank 7. Here, when the supply pressure of the raw water to be treated becomes high, for example, when the filtration pressure difference rises rapidly, or when the pressure sensor 4 or the electromagnetic valve 6b breaks down, and reaches a preset pressure (P), the safety valve and the discharge valve are released. When it is detected that the means 3 for releasing the raw water to be treated such as a pressure valve or the like has become pressure (P) or more, the valve is opened and the raw water to be treated is returned to the raw water tank 1 so that excessive pressure is applied to the separation membrane module 5. A safe membrane separation device is provided which prevents such a phenomenon.

Here, the preset pressure (P) means the maximum operating pressure of the separation membrane module, the pressure resistance of the piping of the membrane separation device, the quality of the raw water to be treated and its fluctuation range, the operating pressure of the separation membrane module, and the like. Although it depends on the separation membrane module to be used, it is preferably about 50 kPa or more and 500 kPa or less, more preferably 100 kPa, in the case of a microfiltration membrane or an ultrafiltration membrane used for water treatment such as water production or wastewater treatment. It is about 300 kPa or less.

There are two types of operating methods of the membrane separation apparatus: 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 differential pressure is constant and the filtration flow rate changes. When the filtration is continued and the dirt accumulates on the surface of the separation membrane and in the pores of the separation membrane, the filtration resistance 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. The method of operating the membrane separation device of the present invention may be either constant flow filtration or constant pressure filtration. However, constant flow filtration is a general and preferred method because a constant throughput can be obtained.

[0013] The separation membrane used in the present invention is not particularly limited in view of the gist of the present invention, but 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 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 relations of equations (1) and (2).

J _v = L _p · ΔP (1) Equation L _p = (H / L) · {R _p ² / (8η)} (2) where (ΔP) is the transmembrane pressure difference, and (H) ) Is the moisture content of the membrane,
(L) is the film thickness, (R _p ) is the pore diameter, and (η) is the viscosity of water.

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. There is no particular limitation for the gist.

The shape of the separation membrane includes a hollow fiber membrane, a flat membrane, and a tubular 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 treated with extremely high turbidity in the raw water to be treated. It is preferable to use a flat film when the operation is difficult due to deposition of a flat film, 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 form having an outer diameter of 2 mm or more.

Further, in the manner of supplying the raw water to be treated to the separation membrane, a total amount filtering operation for filtering the entire raw water to be treated and a part of the raw water supplied to the separation membrane module are returned to the raw water tank to be treated. There is a cross-flow filtration operation. Although any filtration operation method may be used from the gist of the present invention,
The whole-volume filtration operation is simple and easy to operate, and all of the water to be treated that has been fed under pressure can be treated water.

When a hollow fiber membrane is used, the raw water to be treated flows from the outside to the inside of the hollow fiber membrane, that is, an external pressure type and the raw water to be treated flows from the inside to the outside of the hollow fiber membrane.
There is a so-called internal pressure type. From the point of the gist of the present invention, any method may be used. However, when river water or lake water having relatively poor water quality is used as raw water to be treated, the external pressure type is preferable because the physical cleaning recovery is better. The water to be treated according to the present invention is not particularly limited in view of the gist of the present invention. However, in the field of drinking water production, i.e., in the water purification process, water treatment use such as water production and wastewater treatment, river water or lake water is used. Alternatively, groundwater or the like is preferable.

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

[0021]

Example 1 Using a hollow fiber membrane module having a length of about 50 cm and an effective membrane area of 0.5 m2 in which a polyacrylonitrile hollow fiber membrane having an average pore diameter of 0.01 μm was bundled, the surface water of Chitose River, Hokkaido was used. A pressure-type constant flow total filtration was performed. The filtration linear velocity was 1 m / d. In addition, backwashing with clear water and empty washing by blowing air from below the separation membrane module were performed once an hour. On this occasion,
A safety valve is installed between the supply pump of raw water to be treated and the hollow fiber membrane module, and the supply pressure of raw water to be treated is 250 kP.
When the pressure became a, the safety valve was opened and the raw water to be treated was returned to the raw water tank to be treated so that a pressure of 250 kPa or more was not applied to the separation membrane module. Until about 500 hours after the start of operation, filtration was performed stably at a filtration pressure difference of about 30 to 50 kPa. Thereafter, the supply pressure starts to rise sharply, and about 18 hours after the supply pressure starts to rise, the supply pressure becomes 250.
When the pressure reached kPa, the safety valve was opened and the raw water to be treated was returned to the raw water tank to be treated. Even if the filtration pressure rises sharply,
No damage to the separation membrane, no damage to the separation membrane module, and no rupture of piping or the like occurred.

Comparative Example 1 Using the same hollow fiber membrane module as in Example 1, the external pressure type constant flow total filtration of the surface water of Chitosegawa, Hokkaido was performed at the same time.
The filtration linear velocity was 1 m / d. In addition, backwashing with clear water and empty washing by blowing air from below the separation membrane module were performed once an hour. At this time, no means for releasing the raw water to be treated such as a safety valve was provided between the supply pump of the raw water to be treated and the hollow fiber membrane module. Until about 500 hours after the start of operation, the filtration pressure difference is 30 to 50 kPa as in Example 1.
Filtration was performed stably at about the same level. Then the supply pressure began to rise sharply. About 28 hours after the start of the rapid rise in the supply pressure, the supply pressure reached 550 kPa, a part of the acrylic container of the separation membrane module was damaged, and the raw water to be treated leaked.

[0023]

According to the present invention, it is possible to prevent an excessive pressure from being applied to the separation membrane module even when the filtration differential pressure rises rapidly or when the pressure sensor or the electromagnetic valve breaks down.

[Brief description of the drawings]

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

FIG. 2 is a flowchart of a conventional membrane separation apparatus.

[Explanation of symbols]

 1: Raw water tank to be processed 2: Pressurized liquid sending means such as a pump 3: Means to release raw water to be processed such as a safety valve 4: Pressure sensor 5: Separation membrane module 6: Electromagnetic valve 7: Treated water tank 8: Backwash water tank

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 71/42 B01D 71/42 71/68 71/68 (72) Inventor Yoshiko Watanabe Nishioka, Toyohira-ku, Sapporo, Hokkaido 5-11-11-12-8 (72) Inventor Genzo Ozawa Hokkaido, Sapporo City, Kita-ku, Kita 33 Nishi 12-3-3-23 (72) Inventor Shinichi Minegishi 1-1-1, Sonoyama, Otsu City, Shiga Prefecture Toray F-term in Shiga Plant (reference) 4D006 GA06 GA07 HA01 HA21 HA41 JA14A JA59Z JA64Z JA65Z KC03 KE02Q KE07P KE07Q KE07R MA01 MA02 MA03 MC03 MC18 MC22 MC23 MC29 MC39 MC62 PA01 PB04 PB05 PB41 PCB11 PC11 PC11

Claims (13)

[Claims] 1. A membrane separation apparatus for filtering raw water to be treated using a pressurized type separation membrane module, comprising means for releasing the raw water to be treated between a pressurized liquid sending means and a separation membrane module. Membrane separation equipment. 2. The membrane separation device according to claim 1, wherein the means for releasing the raw water to be treated is selected from a safety valve and a pressure relief valve. 3. A means for returning the raw water to be treated to the raw water tank when the supply pressure of the raw water to be treated reaches a preset pressure (P). 5. The membrane separation device according to item 1. 4. The membrane separation apparatus according to claim 3, wherein the preset pressure (P) is not less than 50 kPa and not more than 500 kPa. 5. The membrane separation apparatus according to claim 1, wherein the membrane separation apparatus performs constant flow filtration. 6. The 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. 7. The material of the separation membrane is polyacrylonitrile,
Polysulfone, polyphenylene sulfone, polyphenylene sulfide sulfone, polyvinylidene fluoride,
The membrane separation device according to any one of claims 1 to 6, wherein the membrane separation device is selected from cellulose acetate, polyethylene, polypropylene, and ceramic. 8. The method for operating a membrane separation device and the membrane separation device according to claim 1, wherein the separation membrane is a hollow fiber membrane. 9. The method for operating a membrane separation apparatus and the membrane separation apparatus according to claim 1, wherein the separation membrane is a flat membrane or a tubular membrane. 10. The membrane separation device according to claim 1, wherein a total amount filtration operation is performed. 11. The membrane separation device according to claim 8, wherein an external pressure filtration operation is performed. 12. The membrane separation device according to claim 1, wherein the raw water to be treated is river water, lake water, or groundwater. 13. A method for operating a membrane separation apparatus, comprising filtering raw water to be treated using the membrane separation apparatus according to any one of claims 1 to 12.