JPS603494B2 - Sterilization method for modules in reverse osmosis equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for sterilizing modules in a reverse osmosis device, more specifically, an absolute The present invention relates to a sterilization method that can extremely efficiently and safely eliminate bacterial contamination of modules, which is an unavoidable problem, and can ultimately improve concentration efficiency.

In recent years, the use of reverse osmosis to concentrate squeezed juice has attracted attention.

This is because concentrating squeezed juice by reverse osmosis does not involve phase transformation during concentration, so it is excellent in maintaining the original quality of the squeezed liquid (color, taste, aroma, etc.). A proposal has been made (Tokukan Sho 50-154494
, Tokukai Sho 52-25052, Tokukai Sho 52-105248
etc). By the way, when squeezed juice is continuously concentrated using a reverse osmosis device, various substances adhere to and accumulate on the pus surface of the module incorporated in the device, impairing its concentration efficiency, while the module gradually becomes infected with bacteria. As a result, this bacterial contamination increases rapidly, exceeding the permissible limit and having a serious adverse effect on the quality of the concentrate product. In other words, in the actual situation where squeezed juice is concentrated using a reverse osmosis device, after operating for a certain period of time, the device is temporarily stopped, and substances that have accumulated on the membrane surface of the module are removed to prevent bacterial contamination of the module. It is necessary to perform sterilization to eliminate this problem before restarting operation. Conventionally, a method using a sponge ball has been generally used to remove such adhered substances, but there are also methods that use the elastic action of a semipermeable membrane that utilizes a pressure difference to make it easier to peel off the adhered substances on the membrane surface, and then flushing. Method of combined use (Japanese Patent Application Laid-Open No. 51-79
686) has also been proposed, and in any case, the intended purpose of cleaning is maintained.

However, no new proposals have been made regarding the sterilization of modules, and the conventional method has generally been to pass an aqueous solution of a chemical sterilizer such as hypochlorous acid into the module.

However, conventional methods using chemical disinfectants have shown that the semi-permeable membrane materials of modules commonly used for concentrating juice, such as cellulose acetate membranes, cannot be used. In order not to impair functionality, it is not possible to use chemical disinfectants in high concentrations, and therefore chemical disinfectants in dilute concentrations must be used.
As a result, it takes an extremely long time to sterilize the module.
Moreover, there is a drawback that the degree of sterilization is not necessarily sufficient, etc., and there is a large variation. Of course, it is possible to disassemble and sterilize the module incorporated in the reverse osmosis device each time, but this is extremely impractical.
Therefore, in the actual situation where L juice is concentrated using a reverse osmosis device, there is a strong demand for a method to sterilize the L module efficiently and safely.

The present invention provides an improved method for sterilizing modules that meets such needs.

Hereinafter, the configuration of the present invention will be explained in detail based on the drawings.
FIG. 1 is a system diagram illustrating the sterilization procedure of the present invention, including a concentration procedure and a washing procedure.

The squeezed liquid in the supply tank is sent to the reverse osmosis device 3 by the pressure pump 2.
is pumped to. The reverse osmosis device 3 illustrated in the drawing is a one-time type device in which a large number of internal pressure type tubular modules 4 are connected. The squeezed liquid pumped as described above is concentrated while flowing under high pressure inside the internal pressure type tubular module 4, and the liquid mainly composed of water that has passed through the semipermeable membrane attached to the module is transferred to the receiving tank 5. from the terminal outlet of the module to which the concentrate is connected to the product tank 6.
will be collected. If such concentration is continued for a certain period of time, various substances will adhere to and accumulate on the membrane surface of the internal pressure type tubular module 4, and the module will gradually become contaminated with bacteria, which will impede the practical operation of the reverse osmosis device. or the quality of the resulting concentrate exceeds acceptable limits. Therefore, the sponge balls are passed through the internal pressure type tubular module 4 using sponge ball cleaning devices 7, 7', which are generally installed on the juice supply side, and the deposited substances on the membrane surface are peeled off and removed. Wash.

Then, the sterilization method according to the present invention is performed as follows. However, since it is not always the case that the accumulation of substances on the membrane surface and the bacterial contamination of the module exceed the permissible limit at the same time, in some cases, the cleaning described above may be omitted and only the next sterilization is performed. Sometimes. First, the connected internal pressure type tubular module W module 4 is sealed in the closed chamber 8 while being incorporated into the reverse osmosis device 3.

This closed chamber 8 is preferably one that can be assembled or disassembled or opened and closed as appropriate so as to be able to control the temperature, which is desired to be maintained at a relatively low temperature during concentration as described above, and the material thereof is not particularly limited. However, from the viewpoint of maintaining the heating temperature as described later, it is preferable to use a heat insulating material such as polyurethane foam. Heat.

Finally, while maintaining this heating state, the pressure pump 2 is used from the water storage tank 10 via the temperature-controllable heater il so that the entire membrane surface of the internal pressure type tubular module 4 has a temperature of 7000 or higher. to allow hot water to pass through the module.

Of course, if preheated hot water is used, the heater 1 can be omitted. During this sterilization operation, the temperature in the closed chamber 8 and the temperature of the hot water are controlled to such an extent that the membrane function of the semipermeable membrane attached to the internal pressure type tubular module 4 is not impaired.

For example, in the case of a cellulose acetate membrane that is normally used for concentrating squeezed juice using a reverse osmosis device, its membrane function will be impaired if the temperature exceeds 80 to 85 o0. The temperature shall be 80q0 or less. Therefore, in the same sense, it is recommended that the water vapor blown into the closed chamber 8 be blown into the closed chamber 8 gradually by interposing a separate shielding plate or the like, if necessary, so as not to locally overheat the internal pressure type tubular module 4. Preferable.According to the tests conducted by the present inventors, when the juice of tomatoes, carrots, apples, and other vegetables and fruits is concentrated using a reverse osmosis device, the built-in module is free from bacterial contamination that occurs during operation. ``It was discovered that the bacterial species that account for the majority of the causes die rapidly at temperatures above 7,000.

This is why, in the present invention, the entire surface area of the module is set to 7,000 or more, and the module is sealed in a closed chamber and the interior of the shielded chamber is heated with steam to allow hot water to pass into the module. In order not to impair the membrane function of the semipermeable membrane attached to the module, the above-mentioned 70 pm test should be carried out under as gentle conditions as possible and for a short period of time.
This is to ensure that temperature throughout the membrane surface of the module. According to the present invention, there is no chance of contamination by bacteria from the outside between the sterilization process and the restart of the concentration operation, and no special chemicals are used, so there is no risk that the quality of the product will change after the restart. FIG. 2 shows the sterilization time (minutes) and the outlet temperature ( 9 is a graph illustrating the relationship between the temperature and temperature (°C). Conditions: outside air temperature = 2000, hot water temperature = 8000,
Hot water supply rate = 300 pm/hour, semipermeable membrane = cellulose acetate membrane (manufactured by Daicel Corporation, DRS95), module length 14 side, module total length = 200 pm.

In FIG. 2, curve A (indicated by △ in the figure) represents the conventional common state in which the internal pressure type tubular module 4 is exposed to the outside air without being sealed in the closed chamber 8, and curve B represents the internal pressure type tubular module 4. When the sealed chamber 8 formed of a polyurethane foam heat insulating material is sealed and the sealed chamber 8 is left as it is without being heated, the curve C shows that in addition to the case of the curve B, the inside of the closed chamber 8 is heated. This is the case according to the present invention in which the temperature was heated to 70CO with water vapor. In each case, the axis time was set to 0 minutes when the supplied overflow water started to be discharged from the terminal outlet of the internal pressure type tubular module 4. From this second figure,
When the inlet overflow temperature is 80 oo, as shown by curve A, it is extremely difficult to secure the desired temperature of 7,000 or higher with a general equipment, and even with curve B, which is only provided with a closed room, it is difficult to maintain the desired temperature of 7,000 or higher. Although the effect is recognized, it is still insufficient, and in curve C according to the present invention, the desired temperature of 7000 or more is secured in a short time of only 2 minutes, and therefore the entire membrane surface of the internal pressure type tubular module 4 is It is clear that the temperature is sufficient for sterilization. As mentioned above, when the squeezed juice is concentrated using a reverse osmosis device, the bacterial species that contaminate the module rapidly become extinct when the number of bacteria exceeds 7,000.

However, to almost completely sterilize the module ~700
A certain amount of time is required even at temperatures above 0. This required time is in particular influenced by the degree of fin contamination of the module. According to the tests conducted by the present inventors, in such cases, for example, the number of viable bacteria in the concentrate obtained is 1 to 1.
What about modules that are bacterially contaminated to a level of 1? About 1 minute is enough. Therefore, a module that is bacterially contaminated to the above degree is almost completely sterilized in 30 minutes of sterilization time in curve C showing the case of the present invention in FIG. FIG. 3 shows a case in which the internal pressure type tubular module 4, which has been bacterially contaminated by continuously concentrating tomato juice according to the system diagram in FIG. (Curve E in the figure)
) is a graph illustrating the relationship between the continuous concentration time (hours) and the number of viable bacteria in the obtained concentrate (cells/night) when tomato juice is continuously concentrated again after that.

However, the conditions for continuous concentration are as follows. Conditions: Semipermeable membrane = cellulose acetate membrane (manufactured by Daicel, DRS95
), module diameter = 13 ribs ◇, total membrane area = 20mm, juice supply side pressure = 50-60k9/lump, juice sugar content = 4.
9% (Brix), juice temperature = 35°C, juice supply amount = 300 evenings/hour, concentration ratio = 3. Ear sounds (converted to basic temperature), outside temperature = 21℃.

As is clear from Fig. 3, if the viable cell count of the concentrate is 1 bacteria per night (normally, if the module is contaminated with bacteria beyond this limit) If the module is almost completely sterilized by the present invention as described above, continuous concentration can be performed again for about 3 hours ( Curve D), if the sterilization of the module is insufficient, subsequent continuous operation can only be performed for about one hour.

(Curve E). As explained above, the present invention provides an extremely efficient and safe way to eliminate bacterial contamination of the module, which is an absolutely unavoidable problem when concentrating squeezed juice using a reverse osmosis device. In the end, it has the effect of improving concentration efficiency.

[Brief explanation of drawings]

Figure 1 is a system diagram illustrating the sterilization procedure of the present invention, Figure 2 is a graph illustrating the relationship between sterilization time and outlet temperature of the water discharged from the end of the module, and Figure 3 is a graph illustrating the relationship between continuous concentration time and yield. 2 is a graph illustrating the relationship between the number of viable bacteria in the concentrate and Tortoise... Supply tank, 2... Pressure pump, 3
... Reverse osmosis device, 4 ... Internal pressure type tubular module, 5 ... Receiving tank, 6 ... Product tank,
7. Sponge ball cleaning device 8... Closed room 9... Piping, lo... Water storage tank. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 A method in which a reverse osmosis device is used to concentrate the juice of vegetables and/or fruits, and the module is sterilized for reuse after use, and the module incorporated in the reverse osmosis device is surrounded. forming a closed chamber, introducing steam into the closed chamber and introducing hot water into the module,
A method for sterilizing a module in a reverse osmosis device, the method comprising maintaining the entire reverse osmosis membrane surface of the module at 70°C or higher.