JPS60197206A - Washing method of permeable membrane module - Google Patents

Abstract

PURPOSE:To prevent the contamination of a permeate side by a pyrogen by enabling backwashing using a permeate, by hermetically closing the permeate side in a gas preliminarily filled state while raising raw water pressure in a raw water side for a predetermined time and subsequently falling the same. CONSTITUTION:If circumferential sterilized gas is naturally substituted with a sterilized liquid after a permeable membrane module 7 is sterilized, the gas in the permeate side of the permeable membrane module 7 can be filled. At the time of washing, a permeate take-out valve 3 is closed. Raw water transmits a membrane 9 from an open raw water inflow valve 1 and is gradually accumulated in the permeate side while compresses gas to raise the pressure in the permeate side. Next, when a raw water discharge valve 2 is opened, the pressure in the raw water side is lowered at a stroke. The permeate 15 accumulated in the permeate side is flowed to the raw water side by the expansion force of the compressed gas to perform backwashing. The fine suspended substance accumulated on the surface of the membrane 9 is released and discharged out of the system while goes with the flow in the raw water side. This operation is repeated several times by the opening and closing of the raw water discharge valve 2.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for cleaning a permeable membrane module, in particular city water, ion-exchanged water, slurry aqueous solution containing fine particles, etc. as raw water, and fine particles are removed by membrane permeation. , permeated water that does not contain live bacteria, pyrogen, etc.
The present invention relates to a method for cleaning a permeable membrane module to obtain purified water.

(Prior art) City tap water, ion-exchanged water, distilled water, etc. are water that has undergone appropriate purification treatment depending on the purpose of use, such as household or industrial use. It is not completely removed, but it is used in the electronic industry, pharmaceutical industry,
It is unsuitable for medical purposes.

In order to produce water that has completely removed particulates, viable bacteria, and pyrogenes (hereinafter referred to as sterile water), membrane separation methods are generally more appropriate than dropless methods. Water of extremely high purity can be produced. However, in order to secure such high-purity sterile water at a high flow rate, large equipment is required, complicated pressure adjustment equipment is required, and furthermore, the equipment up to the terminal where it is used is
There are many opportunities for recontamination, and it is extremely difficult to control this.

In contrast, recently, on the premise that high-quality raw water can be used, very compact and simple equipment has been developed that can be installed near the user terminal, and - allows all of the supplied raw water to pass through to obtain sterile water. There is a need for something that can be easily managed.

For example, microfiltration grade membranes are currently commonly used to supply sterile water in hospitals and the like. Specifically, in JP-A No. 57-17407, it is believed that if a microfiltration membrane with a network structure made by stretching polyolefin is used as a membrane, its theoretical pore diameter will be larger than the size of bacteria or pyrodiene. Nevertheless, it has been shown that surface permeate of bacteria and pyrogens can be obtained. Although the mechanism is not fully clear, it is thought that bacteria and pyrogens are trapped inside the membrane and blocked from passing through.

However, in reality, when sterile water is produced using a micro-siltation grade membrane using city water as raw water, the amount of permeated water (total amount of water permeated up to that point, cumulative amount of water) ), the water permeability rate (
When the amount of permeated water decreases and exceeds a certain amount of permeated water, pyrogen begins to leak, and the concentration of pyrogen in the permeated water increases with the amount of permeated water.

This phenomenon is thought to be because fine suspended matter in the raw water is trapped in the membrane pores and become trapped, and also because there is a certain limit to the amount of pyrogen that can be trapped.

Next, in the case of a sterile water supply module that uses an ultrafiltration membrane rather than a microfiltration grade membrane, its theoretical pore diameter is much smaller, and its pyrogens are also smaller. Therefore, of course, bacterial spores can be completely removed, but in the case of pyrodiene, it is thought that the transmittance is extremely low (estimated to be on the order of, for example, 10-9 to 10-18). The inhibition mechanism of ultrafiltration membranes is believed to be inhibition on the membrane surface. However, when sterile water is produced using urban tap water as raw water and through total permeation using an ultrafiltration membrane, the water permeation rate decreases rapidly with the amount of permeated water, and when the amount of permeated water exceeds a certain level, the initial use of sterile water occurs. pyrogen leaks out, and its concentration also increases. This phenomenon is caused by microscopic suspended matter in the raw water depositing on the membrane surface and resisting water permeation, and also because pyrogen accumulates at a high concentration on the membrane surface, causing pyrogen to pass through the membrane. It is thought that a very large difference in concentration occurs, and this concentration difference is used as a driving force to diffuse pyrogen from the raw water side to the permeate side while the equipment is stopped, and this is released at the beginning of use.

Conventionally, it has been known that if such a membrane is backwashed, the water permeability of the membrane can be restored and dirt on the membrane surface can be removed. However, when Tore is used in a device for producing sterile water,
There are the following problems.

1) When raw water is used for backwashing, the permeate side becomes contaminated with fine particles, viable bacteria, pyrogen, etc.

2) Of course, it would be good if backwashing could be performed with permeate water, but in order to use permeate water for backwashing, it is necessary to expand it, use a permeate storage tank, a pressure pump for backwashing, or a compressor. Huge equipment is required, including an air source and ancillary equipment to keep it sterile.

(Objective of the Invention) One of the main objects of the present invention is to prevent the accumulation of high concentration of dirt on the raw water side of the permeable membrane module by reducing the accumulation of fine particles and dirt on the permeated water side.
It is an object of the present invention to provide a method for cleaning a permeable membrane module that can minimize and easily prevent contamination by viable bacteria, pyrodiene, and the like.

(Structure of the Invention) The structure of the present invention is to fill the permeated water side of the permeable membrane module with a gas in advance and seal it, to increase the raw water pressure on the raw water side for a predetermined period of time, and then to increase the raw water pressure on the raw water side. This method of cleaning a permeable membrane module is characterized by lowering the pressure of raw water and peeling off accumulated material on the permeable membrane to the raw water side.

That is, in the present invention, the permeated water side of the permeable membrane module is filled with a gas body in advance, and the raw water pressure on the universal water side is increased and then lowered, thereby reversing the pressure relationship between the gas body and the raw water. This enables backwashing with permeated water.

In the present invention, the permeated water side of the permeable membrane module is filled with a gas body in advance. As the gas, a gas having low solubility in water, such as air or nitrogen gas, can be used, and air is particularly preferred because it can be easily used. For example, if the permeable membrane module is sterilized with a sterilizing liquid and then the surrounding sterilizing gas and the sterilizing liquid are naturally replaced, the permeated water side of the permeable membrane module can be filled with the gas. Furthermore, a sterilizing gas tank may be provided at the permeable wood outlet of the permeable membrane module, and sterilizing gas may be pumped in when taking out and replacing the permeated water. In this case, in order to seal the permeated water side of the permeable membrane module filled with sterilizing gas, the connecting port between the permeable wood outlet and the sterilizing gas tank is closed.

In the present invention, after the permeated water side of the permeable membrane Modineal is filled with a gas and sealed, the raw water pressure on the raw water side is increased for a predetermined period of time. Specifically, for example, the raw water pressure is raised to the same level as when using a normal permeable membrane (1 to 3/I gauge). Next, lower the pressure on the raw water side (for example, 0 to 0.5 Kg/d
gauge).

Next, the configuration of the present invention will be explained in more detail using specific examples.

In this invention, means for backwashing is used by controlling the pressure using the water pressure on the raw water side. As a specific example of this pressure control, an example of time control using a solenoid valve, relay, timer, etc. is shown below, but other examples include direct pressure control on the permeate side, or Examples include liquid level control.

Next, as a specific example of a combination, an example of time control will be shown using the configuration shown in FIG. Urban water supply with constant pressure (
2) and a sterile water supply device which is an example of the present invention.

By pressing the foot switch (2), the solenoid valve for raw water inflow (1) and the solenoid valve for removing permeated ice at the permeated ice outlet provided at the bottom of the permeated water passage ( 3) is opened, and sterile water is supplied from the permeated ice extraction pipe αa under sterile air. When it is no longer necessary to supply sterile water, by stepping on the foot switch (2) again, the solenoid valve (3) will be immediately closed via the control section, and the raw water discharge solenoid valve (2) will be closed at an arbitrary interval. Press to open and close. At this time, the membrane surface on the raw water side is cleaned. After a certain period of time has passed after entering the cleaning mode, the solenoid valve for raw water inflow (1) and the solenoid valve for raw water discharge (2) are closed via a timer on the control unit side (not shown), and a stop message is issued. The state during cleaning will be explained in detail with reference to FIG. Immediately after the foot switch is stepped on for the second time, the solenoid valve (3) for removing the transparent wood is closed. At this time, raw water flows from the open raw water inflow solenoid valve (1) to the permeable membrane module (9).
) flows on the raw water side and permeates the membrane, compressing the gas and accumulating on the permeate side (<0) Therefore, the water level on the permeate side rises and the pressure increases.

If this state is maintained as it is, the pressure on the raw water side and the pressure on the permeate side will be balanced to be equal. If the raw water discharge solenoid valve (2) opens after or before the pressure on the raw water side and the pressure on the permeate side are balanced, the pressure on the raw water side will drop at once, and the pressure on the permeate side will be lower than that on the raw water side. becomes higher. Due to this pressure difference, the permeated water accumulated on the permeated water side flows from the permeated side to the raw water side, and backwashing is performed by the expansion force of the gas body compressed on the permeated side. As the gas body expands, the pressure on the permeate side gradually decreases, and eventually the pressures on the raw water side and the permeate side match approximately 9.

At this time, the gas does not pass through the membrane surface and remains on the permeate side. The reason for this is that a permeable membrane wet with water will not allow the gas to pass through unless a pressure difference greater than the bubble point acts. This is because they will not be allowed to pass. During backwashing at this time, the fine suspended particles that had accumulated on the membrane surface are lifted up (peeled off) from the membrane surface.
, and is discharged out of the system along with the flow of raw water, and the membrane surface is cleaned. After repeating this operation several times to open and close the raw water discharge solenoid valve (2), the solenoid valve for raw water inflow (1) and the solenoid valve for raw water discharge (2)
) is closed and becomes in a stopped state C. In this explanation, cleaning was performed after supplying sterile water, but cleaning may be performed before supplying sterile water. Furthermore, in this explanation, raw water was flowed to the raw water side during backwashing, but backwashing can also be performed by stopping the flow of raw water. Also, during backwashing, it may be generally thought that permeated water from only the area below the water surface is used for backwashing, but even above the water surface, there is water attached to the outside of the permeable membrane. Since this adhered water is thought to flow from the permeate side to the raw water side in the early stage of backwashing, backwashing is thought to extend over the entire length of the permeable membrane. Of course, sometimes the effect of backwashing can be ensured by turning the permeable membrane module upside down and changing the part below the water surface.

Furthermore, if an accumulator (air chamber) is installed in the permeate water line upstream of the permeate ice extraction solenoid valve (3), the volume of the usable gas body will be large and the amount of backwash of permeate water will be increased.

Although the main reason for the effectiveness of this cleaning method is the backwashing of permeated water, another cause is the solenoid valve for raw water discharge (
The pressure shock (rapid pressure change) caused by the opening and closing of 2) causes the permeable membrane to sway, and the permeable membrane may be subject to both internal and external pressure, and this shock causes contaminants to float away from the permeable membrane. It is also possible to raise it.

When the above cleaning method is applied to a microfiltration membrane module, minute suspended matter is removed from the membrane, and the water permeation rate is maintained at a high level over a long period of time.

In addition, if the same cleaning method is applied to an ultrafiltration membrane module, pyrogens and minute suspended substances are removed from the membrane surface, and by cleaning regularly, the water permeation rate remains constant. It can supply very large quantities of sterile water.

(Example) The present invention will be explained below with reference to Examples and Comparative Examples.

Example 1 Using 5,900 polyethersulfone hollow fiber ultrafiltration M (hollow fiber inner diameter 600 μm, outer diameter 800 μm) with a pure water permeation rate of 4 t/(min/d/atm), the length was 32 and the effective length was 27. an, shell inner diameter 92+w.

Effective membrane area 3tt? , a module with a permeated water side volume of 994- was created, and an apparatus having the configuration shown in FIG. 1 was assembled.

This device is directly connected to the Himeji city water supply and operated to supply sterilized water for 9 hours a day at a water supply pressure of 1 atm.
Washing was performed for minutes. Cleaning was performed at the same raw water flow rate as when sterile water was supplied. This cleaning was carried out for 1 minute by repeating the cycle of closing the raw water discharge solenoid valve (2) for 3 seconds and opening it for 12 seconds four times. This operation was carried out for a long period of time for 5 days a week.

Comparative Example 1 A module with the same hollow fibers and the same dimensions as the module used in Example 1 was created, and this was directly connected to the Himeji city water supply, and the entire amount was allowed to permeate for 9 hours a day at a water pressure of 1 atm.
The exercise was carried out for a long period of time, five days a week.

Comparative Example 2 A commercially available micro-sillage system for supplying sterilized water was directly connected to the Himeji City water supply, operated for 9 hours a day at an inlet pressure of 1 atm, and operated for a long period of time 5 days a week. carried out. What a shame this Mike.

Lofiltration equipment internal diameter 270 Jim outer diameter 3
Two modules using 90 μm polyethylene microfilter hollow fiber membranes are connected in a row 4, and both modules are used for total permeation, and the permeated water from the second module is used as sterilized water.

Regarding the three Examples and Comparative Example 1, which were conducted in parallel as described above, tests were conducted to detect the water permeation rate for each amount of permeated water, the number of viable bacteria in the permeated water, and the detection of pyrogen. Sample water was collected 1 minute and 3 minutes after the start of operation on the day.

To measure viable bacterial water, collect the collected water 1- and tryptonya agar■
After the mixture was mixed with a medium and cultured at 37°C for 48 hours, the number of colonies was counted.

Measurement of Pyrodiene: A predetermined amount of Rim 2 Test Wako-■ was added to the sampled water, allowed to stand at 37°C for 1 hour, and then optically calibrated.

Display 1io, , 1 + 1 gram (ng)/d or more +, 0.01 to 0. l n17-100.01 n
&− and below were designated as −.

Approximately 10 n of Hiropyrogien is present in the Himeji City water source.
Table 1 shows the results of 0 or more, which were lowered by about g/-.

Table 1 Comparative Example 1 Comparative Example 2 Thus, from Table 1, the following can be seen.
In Comparative Example 1, leakage occurred from around 30-, and in Comparative Example 2, leak #1 started around 20- even though the two modules were connected in series.

(2) In the case of cleaning using an ultrafiltration membrane (Example 1), the permeation rate stabilizes around 20 m and maintains a pressure of 5t7H-atm or higher and over 100-. Pyrogen a100/
-1 keeps it negative.

■ Regarding bacteria, sterility is maintained in both the actual example and the comparative example.

From the above, by cleaning the hollow fiber type ultrafiltration module with the method of the present invention, the accumulation of high concentrations of micro-suspended particles and pyrodiene is prevented, the water permeation rate is constant, and the sterile and pile-free diene is maintained. Water can now be produced in large quantities at low cost (Effects of the invention) The present invention mainly utilizes the gas body on the permeated water side of the permeable membrane module and the pressure change on the raw water side to generate water by permeated water. This enables backwashing, thereby making it possible to obtain inexpensive permeate water that does not contain pyrogens or the like over a long period of time.

[Brief explanation of the drawing]

The line in FIG. 1 is a functional explanatory diagram showing an example of an apparatus for carrying out the method of cleaning a permeable membrane module according to the present invention, and FIG. 2 is a graph showing changes in pressure at each part of the apparatus. (Foundation)... Sterile water supply equipment, (1)...
・・・・・・Solenoid valve for raw water inflow, (2)・・・・・・
... Solenoid valve for raw water discharge, (3) ... Solenoid valve for removing permeated ice, (4) ... Raw water inlet, (5) ...・・・・・・Raw water outlet, (6)・
...... Permeated ice removal port, (7) -...
...Permeable membrane module, (8)--Gas body retention section, (9)......Permeable membrane,
・・・・・・・・・Control section,■・・・・・・・・・
・Electrical wiring, @...7...Foot switch, (
2)・・・・・・Urban water supply, αΦ・・・・・・
...Sterilized water outlet, (to) - ... Permeated water.

Claims (1)

[Scope of Claims] l The permeated water side of the permeable membrane module is sealed by filling the permeated water side with a gas in advance, increasing the raw water pressure on the raw water side for a predetermined period of time, and then decreasing the raw water pressure on the raw water side. A method for cleaning a permeable membrane module, characterized in that the accumulated material on the permeable membrane is peeled off to the raw water side. The method described in Scope No. 1. 3. The method according to claim 1 or 2, wherein the gas body is sterilized air. The method according to claim 1 or 2, wherein the permeable membrane module is an ultrafiltration membrane module. 5. The method according to claim 1 or claim 2, wherein the permeable membrane module is a hollow fiber membrane module.