JP6617071B2 - Pure water production method and apparatus - Google Patents

Description

  The present invention relates to a pure water production method and apparatus used for supplying pure water whose dissolved oxygen concentration is reduced by deaeration treatment.

  A pure water production apparatus that produces pure water used in an analyzer such as an automatic blood analyzer temporarily stores primary pure water generated by, for example, ion exchange treatment or reverse osmosis treatment in a pure water tank that is open to the atmosphere. And it is the structure which supplies the primary pure water in a pure water tank to a use point with a pump as needed. Depending on the analysis item in the analyzer, pure water with a reduced amount of dissolved oxygen may be required. In such a case, as described in Patent Document 1, etc., from a pure water tank to a use point. A membrane deaerator is installed in the water supply line. The membrane deaerator removes oxygen and the like from pure water by flowing pure water on one side (liquid phase side) of the deaeration membrane and reducing the pressure on the other side (gas phase side).

  In such a pure water production system that supplies pure water with a reduced dissolved oxygen concentration to the point of use, the membrane deaerator stops operating at times when the point of use does not use pure water, such as at night or on holidays. It is common to make it. When a membrane deaerator having a hollow fiber membrane is used, water is condensed in the hollow fiber membrane when the vacuum pump is stopped and the membrane deaerator is stopped. Since the effective area of the device decreases, the start-up of the device may be delayed when the membrane degassing device is restarted. In Patent Document 2, in order to prevent water from condensing in the hollow fiber membrane used in the membrane degassing device, after the operation of the membrane degassing device is stopped, an inert gas is provided on the gas phase side of the degassing membrane. Is disclosed.

Japanese Utility Model Publication 1-167385 JP 2000-185203 A

EIC Net Environmental Glossary “Dissolved Oxygen”, [online], October 14, 2009, Environmental Innovation Information Organization, [Search March 17, 2016], Internet <URL: http: //www.eic .or.jp / ecoterm /? act = view & serial = 2623>

In a pure water production system that reduces the amount of dissolved oxygen by degassing primary pure water from a pure water tank released to the atmosphere in a membrane deaeration device, and supplying pure water with a reduced amount of dissolved oxygen to the point of use In particular, there is a problem that so-called slime is formed by viable bacteria generated in the water supply line to the use point and the pure water tank when the operation is stopped, the degassing membrane is blocked, and the water supply flow rate after the operation is restarted is reduced. When the blockage of the deaeration membrane proceeds, it is necessary to replace the deaeration membrane. Although it is conceivable to suppress the growth of viable bacteria with an ultraviolet (UV) sterilizer, ozone (O ₃ ) and the like are generated by ultraviolet sterilization, so that the meaning of reducing the amount of dissolved oxygen is lost. As described in Patent Document 2, it is conceivable to suppress the generation of aerobic bacteria by supplying an inert gas to the decompression side of the membrane deaerator when the operation is stopped. Equipment is expensive.

  The objective of this invention is providing the pure water manufacturing method and apparatus which can prevent obstruction | occlusion of the deaeration membrane by a living microbe with a simple structure.

  In the pure water production method of the present invention, primary pure water stored in a pure water tank is passed through a membrane deaerator equipped with a deaeration membrane to perform deaeration treatment, and the pure water after deaeration treatment is used as a point of use. In the deionized membrane manufacturing method, the degassing membrane is kept in a state where pure water is present on the liquid phase side of the degassing membrane within the interruption period in which the supply of pure water to the use point is interrupted. The vacuum pump connected to the membrane deaerator is operated intermittently on the gas phase side.

  A first deionized water production apparatus of the present invention includes a deionized water tank that stores primary deionized water and a degassing membrane, and a membrane deaerator that performs degassing by passing primary deionized water in the deionized water tank. In addition, there is pure water on the liquid phase side of the degassing membrane in the vacuum pump connected to the membrane degassing device on the gas phase side of the degassing membrane and the interruption period in which the supply of pure water to the use point is interrupted A control device that intermittently operates the vacuum pump while maintaining the state, and supplies pure water deaerated by the membrane deaerator to the use point.

  A second deionized water production apparatus of the present invention includes a deionized water tank that stores primary deionized water and a degassing membrane, and a membrane degassing apparatus that performs degassing by passing primary deionized water in the deionized water tank. And a filter provided on a water supply line between the outlet of the pure water tank and the membrane deaerator, and supplies pure water deaerated in the membrane deaerator to the use point.

  In the present invention, the activity of aerobic microorganisms is suppressed at the position of the membrane deaerator, thereby preventing the deaeration membrane from being blocked by viable bacteria.

It is a figure which shows the structure of the pure water manufacturing apparatus of one Embodiment of this invention. It is a graph which shows the relationship between the elapsed time after a vacuum pump stop, and dissolved oxygen concentration. It is a figure which shows the structure of the pure water manufacturing apparatus of another embodiment of this invention.

  Next, a preferred embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a pure water producing apparatus according to an embodiment of the present invention. The pure water production apparatus shown in FIG. 1 accepts primary pure water obtained by ion exchange treatment or reverse osmosis treatment, performs membrane deaeration to reduce the amount of dissolved oxygen, etc., and analyzes the pure water after membrane deaeration. It is supplied to use points such as equipment. The pure water production apparatus includes a pure water tank 11 opened to the atmosphere for receiving primary pure water, a valve 12 provided at the outlet of the pure water tank 11, a membrane deaerator 14, and pure water flowing out from the valve 12. Is supplied to the membrane deaerator 14, and a valve 15 provided at the outlet of the membrane deaerator 14 is provided. The membrane deaerator 14 includes, for example, a hollow fiber membrane as a deaeration membrane, and pure water from the liquid feed pump 13 is caused to flow toward the outlet on one side of the deaeration membrane. . The other side of the degassing membrane is a gas phase side, and the gas phase side of the membrane degassing device 14 is connected to a vacuum pump 17 via a pipe 16 in order to bring the gas phase side into a reduced pressure state. One end of a valve 18 is connected to the pipe 16 and the other end of the valve 18 is open to the atmosphere. Further, the pure water production apparatus is provided with a control device 20 that controls the driving of the liquid feed pump 13 and the vacuum pump 17 and controls the opening and closing of the valves 15 and 18. The valve 18 is provided to prevent the vacuum pump 18 from being overloaded when the vacuum pump 17 is started. When the vacuum pump 17 is started, the valve 18 is opened for a certain period of time (for example, several seconds) and the pipe 18 is opened. It is controlled so that a small amount of air is introduced into the tank and kept closed otherwise.

  Next, the pure water manufacturing method using this pure water manufacturing apparatus is demonstrated. This pure water production device supplies pure water whose dissolved oxygen concentration has been reduced by deaeration treatment. However, since it is assumed that an analyzer such as an automatic blood analyzer is used as a point of use, it is always at a constant flow rate. Instead of supplying pure water, the required amount of pure water is supplied each time pure water is needed, and the supply of pure water is interrupted when the analyzer is not in operation. Therefore, the operation of this pure water production system is as follows: during working hours on working days, the supply period for supplying pure water immediately to the use point whenever there is a demand for pure water at the use point, Since the demand for pure water cannot be expected, it can be divided into two periods: an interruption period in which the supply of pure water is interrupted. The supply period is not necessarily a period for supplying pure water continuously, but is a period in which demand for pure water is expected to occur within a few tens of minutes at the longest. On the other hand, the interruption period is a period in which the operation of the pure water production apparatus is minimized because it is expected that pure water to the use point does not have to be performed for several tens of minutes to several hours or more.

  When pure water is supplied to the use point by the pure water production apparatus shown in FIG. 1, first, primary pure water is stored in the pure water tank 11 and the valve 12 is opened. Then, at the start of the supply period such as the start time, the vacuum pump 17 is started in a state where pure water is present on the liquid phase side of the deaeration membrane of the membrane deaerator 14 and the valve 15 is closed, and the membrane deaerator The gas phase side of 14 is in a reduced pressure state. When the demand for pure water at the use point is generated, the valve 15 is opened at the same time as the liquid feed pump 13 is operated according to the demand. As a result, deionized water having passed through the membrane deaerator 14 and pure water with a reduced dissolved oxygen concentration are supplied to the use point. Assuming that the demand for pure water is intermittently generated at the use point, when one supply is finished, the valve 15 is closed and the liquid feed pump 13 is stopped simultaneously. During the supply period, it is expected that the next demand for pure water will occur within, for example, several tens of minutes. Therefore, the vacuum pump 17 is kept operating, and the reduced pressure state on the gas phase side of the membrane deaerator 14 is maintained. At this time, pure water still exists on the liquid phase side of the degassing membrane. The control device 20 performs control so that the operation and stop of the liquid feed pump 13 and the opening and closing of the valve 15 are synchronized.

  For example, at the end time, the pure water production apparatus is switched from the supply period to the interruption period. During the interruption period, the vacuum pump 17 is also stopped to stop the operation of the membrane deaerator 14. Even in this state, pure water still exists on the liquid phase side of the degassing membrane. When the operation of the membrane deaerator 14 is stopped for a long time, the pure water tank 11 may be open to the atmosphere as described in the “Background Art” section. Viable bacteria propagate in the line from the water tank 11 to the membrane degassing device 14, and as a result, the degassing membrane in the membrane degassing device 14 may be blocked by the living bacteria. These live bacteria are mainly aerobic microorganisms. In general, aerobic microorganisms are considered to be active actively under conditions where the dissolved oxygen concentration (DO) in water is 2 mg / L or more. Therefore, in the pure water production apparatus of the present embodiment, the dissolved oxygen concentration in the pure water in or near the membrane degassing apparatus 14 is lower than the dissolved oxygen concentration necessary for active aerobic microorganisms. Try to continue. Specifically, when the supply of pure water is interrupted for several tens of minutes to several hours or more, the vacuum pump 17 is operated intermittently during the interruption period. Although it is conceivable that the vacuum pump 17 is always operated, the life of the vacuum pump is shortened according to the operation time, and the running cost is increased. Therefore, in the present embodiment, the vacuum pump 17 is intermittently provided during the interruption period. Is supposed to work. The control device 20 controls the vacuum pump 17 and the valve 18 in order to operate the vacuum pump 17 intermittently during the interruption period.

  Next, the results of experiments conducted by the present inventors regarding the operating conditions of the vacuum pump 17 during the interruption period will be described.

[Experimental Example 1]
The pure water production apparatus shown in FIG. 1 was assembled, and primary pure water was supplied to the pure water tank 11. As the membrane deaerator 14, Sterapore (registered trademark) 2000 series product number 20M0060A, which is a membrane module for deaeration and supply from Mitsubishi Rayon Co., Ltd., was used. This membrane module for deaeration and supply uses a hollow fiber membrane that is a three-layer composite membrane as a deaeration membrane. When the number of general bacteria contained in the pure water in the pure water tank 11 was measured, it was 8200 / mL.

  Next, pure water in the pure water tank 11 was introduced from the liquid feed pump 13 to the membrane deaerator 14, and the vacuum pump 17 was continuously operated for 50 hours with the valve 15 closed. When the pure water in the vicinity of the membrane deaerator 14 was collected after 50 hours of continuous operation and the number of general bacteria contained in the pure water was measured, it was 2200 / mL. This indicates that the number of bacteria is reduced by operating the membrane deaerator 14 to reduce the dissolved oxygen concentration in the pure water, and the membrane deaerator is also used during the operation period. 14 shows that reducing the dissolved oxygen concentration of pure water in the vicinity of 14 can prevent clogging of the deaeration membrane by viable bacteria.

[Experiment 2]
Next, using the same apparatus as in Experimental Example 1, the vacuum pump 17 was operated with the valve 15 being closed from the liquid feed pump 13 through the membrane deaerator 14. At this time, the pressure of the pipe 16 was 11.3 kPa in absolute pressure. The vacuum pump 17 was stopped, the dissolved oxygen concentration in the pure water near the membrane deaerator 14 was measured, and the change in the dissolved oxygen concentration according to the elapsed time from the stop of the vacuum pump 17 was examined. For measurement of dissolved oxygen, DO30A manufactured by Toa DKK was used. The results are shown in FIG. The vacuum degree of the piping 16 decreased with time from the stop of the vacuum pump 17, and the pressure of the piping 16 after 45 minutes was 41.3 kPa in absolute pressure.

  As described above, the active activity of the aerobic microorganism requires that the dissolved oxygen concentration be 2 mg / L or more. Therefore, in order to suppress the activity of the aerobic microorganism and prevent clogging of the deaeration membrane, The dissolved oxygen concentration in or near the deaerator 14 may be kept below 2.0 mg / L. In the results shown in FIG. 2, the dissolved oxygen concentration gradually increases when the vacuum pump 17 is stopped, but the dissolved oxygen concentration is 1.5 mg / L or less within 30 minutes from the stop of the vacuum pump 17. If it is within 45 minutes from the stop, the dissolved oxygen concentration is 1.6 mg / L or less. When the results shown in FIG. 2 were extrapolated, the dissolved oxygen concentration exceeded 2.0 mg / L after 100 minutes from the stop of the vacuum pump 17. Therefore, if the vacuum pump 17 is operated intermittently, for example, once every 30 minutes, the dissolved oxygen concentration in or near the membrane deaerator 14 is kept below 1.5 mg / L. Therefore, it is possible to more reliably prevent occlusion of the deaeration membrane by viable bacteria. In one intermittent operation, the vacuum pump 17 is operated for 1 minute, for example. The control device 20 is configured so that the dissolved oxygen concentration of pure water existing in or near the membrane deaerator 14 is kept below 2 mg / L (for example, once every 100 minutes) Set the operating conditions (for example, once every 45 minutes, operate for 1 minute or more), more preferably 1.5 mg / L or less. The operating conditions (for example, once every 30 minutes, for one minute or more) are set.

  Next, the pure water manufacturing apparatus of another embodiment of this invention is demonstrated. It is considered that aerobic microorganisms that cause clogging of the deaeration membrane of the membrane deaerator during the interruption period of the pure water production apparatus are mainly derived from the pure water tank that is open to the atmosphere. Therefore, if a filter is provided in the water supply line between the pure water tank and the membrane deaerator, and this filter prevents the aerobic microorganisms from reaching the membrane deaerator, the deaeration membrane is blocked by the aerobic microorganisms. It can be prevented more effectively.

  The pure water producing apparatus according to another embodiment of the present invention shown in FIG. 3 has the same configuration as that shown in FIG. 1, but between the outlet of the liquid feed pump 13 and the inlet of the membrane deaerator 14. 1 is different from that shown in FIG. 1 in that a filter 21 is provided in the water supply line. As the filter 21, it is preferable to use a microfiltration membrane having a pore size that does not allow aerobic microorganisms to pass through. The pore diameter of the microfiltration membrane is, for example, 1 μm or less. In the pure water production apparatus shown in FIG. 3, the filter 21 is provided in front of the entrance of the membrane deaerator 14 in the water supply line from the pure water tank 11 to the membrane deaerator 14. Even if aerobic microorganisms are mixed in, the aerobic microorganisms are removed from the pure water in the filter 21 and do not reach the membrane deaerator 14. Therefore, in the pure water manufacturing apparatus shown in FIG. 3, it is possible to prevent the deaeration membrane of the membrane deaeration device 14 from being blocked by aerobic microorganisms during the interruption period. However, since there may be aerobic microorganisms already attached to the member at the time of assembling the pure water production apparatus and aerobic microorganisms that have passed through the filter 21, the pure water production apparatus shown in FIG. Similarly to the pure water production apparatus shown in FIG. 1, it is desirable to operate the vacuum pump 17 intermittently (for example, every 30 minutes for 1 minute) during interruption periods such as nighttime and holidays. When the presence of aerobic microorganisms existing from the beginning or aerobic microorganisms that pass through the filter 21 can be ignored, the pure water production apparatus shown in FIG. 3 does not require the vacuum pump 17 to be intermittently driven during the interruption period. Good.

11 Pure water tank 12, 15, 18 Valve 13 Liquid feed pump 14 Membrane deaerator 16 Piping 17 Vacuum pump 20 Controller 21 Filter

Claims (5)

This is a pure water production method in which primary pure water stored in a pure water tank is passed through a membrane deaerator equipped with a deaeration membrane for deaeration treatment, and the deionized water is supplied to the point of use. And
Within the interruption period in which the supply of pure water to the use point is interrupted, the membrane degassing is performed on the gas phase side of the degassing membrane while maintaining the state where pure water is present on the liquid phase side of the degassing membrane. have intermittently operated to process a vacuum pump connected via a pipe for the device,
Setting the operation interval of the vacuum pump within the interruption period so that the dissolved oxygen concentration of pure water existing in or near the membrane deaerator is kept below 2 mg / L,
A method for producing pure water , wherein air is introduced into the pipe for a certain period of time when the vacuum pump is started . Each time the demand occurs while continuously operating the vacuum pump in a supply period for supplying the use point with pure water after the deaeration treatment according to the demand at the use point outside the interruption period. The pure water manufacturing method according to claim 1, wherein a liquid feed pump for feeding the primary pure water to the membrane deaerator is operated. A pure water tank for storing primary pure water;
A membrane deaeration device comprising a deaeration membrane, wherein primary deionized water in the pure water tank is passed to perform membrane deaeration;
A vacuum pump connected via a pipe for the membrane degasifier in the gas phase side of the degassing membrane,
A valve having one end connected to the pipe and the other end open to the atmosphere;
A control device that intermittently operates the vacuum pump while maintaining a state in which pure water is present on the liquid phase side of the degassing membrane within an interruption period in which the supply of pure water to the use point is interrupted,
Have
Supply pure water deaerated by the membrane deaerator to the point of use ,
The control device sets the operation interval of the vacuum pump within the interruption period so that the dissolved oxygen concentration of pure water existing in or near the membrane deaerator is kept below 2 mg / L,
The said control apparatus is a pure water manufacturing apparatus which controls the said valve to open only for the fixed time at the time of starting of the said vacuum pump . A liquid feed pump connected to an outlet of the pure water tank and feeding the primary pure water to the membrane deaerator;
The control device is configured to supply the demand while continuously operating the vacuum pump in a supply period in which the membrane-degassed pure water is supplied to the use point according to the demand at the use point outside the interruption period. The pure water manufacturing apparatus according to claim 3 , wherein the liquid feed pump is operated each time the water is generated. The pure water manufacturing apparatus of Claim 3 or 4 further provided with the filter provided on the water supply line between the exit of the said pure water tank, and the said membrane deaeration apparatus.

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