CS257768B2 - Method of germs growth suppression in purified water - Google Patents

Abstract

To produce aseptic pure water, a vacuum degasifier is used which reduces to a minimum the microbes contained in the water which is to be treated. To maintain the aseptic state, in cases where there is a low consumption or during shutdown or if there is a relatively large requirement for internal water quantities, care must be taken to maintain the aseptic state of the water, for example by providing downstream a reservoir under reduced pressure through which the water continuously flows. Conventional treatment plants which are operated with ion exchangers or reverse osmosis units can be converted for the production of aseptic pure water by the use of a vacuum degasifier. The pure water treated in such a manner satisfies the highest requirements, for example of the pharmaceutical or electronic industry.

Description

The invention relates to a method for suppressing the growth of germs in purified water, in particular water for use in the field of pharmacy and electronics, by depleting oxygen under reduced pressure, while keeping the clean water in constant motion.

While in previous years water consumption could be covered from high-quality basic water sources, surface water has to be increasingly used today to cover consumption. The quality of this water is strongly affected by environmental damage and must therefore be treated.

Given that high water quality is required for certain areas of use, such as the electronics, chemical-pharmaceutical and cosmetics industries, as well as for laboratories and food processing plants, as well as for drinking water supply companies, costly and often complicated ways to produce pure and highly pure water with the desired properties.

Impurities in water can be divided into the following groups:

(a) Coarse dispersants:

The particle size of greater than 10 ^-4 cm, such as floating particles, suspended particles and sedimenting particles;

(b) Colloidal substances:

The particles are no longer visible; particle size is 10 * ⁴ to 10 ^-7 cm;

(c) Molecular dispersants:

Ions, organic molecules, true solutions; the particle size is less than 10 ^-7 cm;

(d) Gases:

Oxygen, nitrogen, carbon dioxide, which can be dissolved in the liquid.

The problem of removing ionic substances, such as salts, can currently be considered to be solved, while the removal of colloids, high and low molecular weight substances, nutrients, and the like is still a considerable problem for many fields of application.

The presently needed use of surface water for supply brings with it the problem that water contains increasingly contained organic residual substances, the removal of which encounters great difficulties.

Pure and high purity water is needed mainly in the following areas:

(a) in the electronics industry in the manufacture of microprocessor devices;

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(b) in the pharmaceutical and cosmetic industry for the production of water for injection and aqua purlflcata;

(c) for hospitals, dialysis stations and laboratories;

dj for drinking water, water for the beverage industry as well as water for the food industry.

It is very important for the above-mentioned fields of application that the water is as germ-free as possible. Drinking water must not contain the causative agent of the disease. These requirements are not fulfilled in a straight line when 100 ml of drinking water contain Escherichia coli. The number of conformal germ colonies should not exceed the guide number in 100 ml. In disinfected drinking water, the guide water number must lie below 20 per milliliter. In the electronics industry, 100 germs per 100 ml are usually required, in special cases only 10 germs per 100 ml.

Water for pharmaceutical purposes, especially for injection, must be pyrogen-free and sterile.

It is known that ion exchange equipment is used to produce high purity water, followed by fine filtration. In order to achieve a low proportion of organic substances, colloids, bacteria and germs, it was tested to reduce their content in the flocculation reactor with the addition of flocculants and disinfectants. The addition of coagulants reduced the content of colloidal substances, however, they had a very negative effect in the downstream facilities.

Sludge contact reactors were included to reduce the organic matter content. However, the results obtained were not satisfactory, so that an alluvial filter was also included, with which a high degree of removal of the substances is achievable. The costs of operation and downtime of such equipment are extremely high.

In order to remove colloidal particles, the leaching filter in the acidic area is deposited in several layers and combined with a complete desalination plant, in particular organic substances such as humic acids can be removed. The cost and operating costs of such equipment are also extremely high.

Furthermore, said devices have the disadvantage that the number of germs in the treated water is still too high. The reduction of the total carbon content (TOC value = Total Organic Carbon) is only possible in the said apparatuses at about 50-70%.

The use of ion exchangers for the production of germ-free water has proven to be particularly disadvantageous. Although ion exchangers allow virtually complete removal of ionic substances from the water to be treated, they allow only partial removal of organic substances. However, this leads to irreversible blocking of the capacity of the ion exchanger. It has also been observed that each time the ion exchanger capacity is exhausted, the organic substances are released again from the ion exchanger so that their content in the treated pure water is higher than in the raw water. There is also a very high risk of infection with germs. In particular, the number of embryos increases strongly after the rest periods, because the ion exchanger material is a good nutrient medium for the growth of embryos due to its large surface area. Particularly after resting periods, such as Saturday and Sunday, the number of germs in the raw water is, for example, 10 ml / l, on Monday up to 500 000. In continuously operating ion-exchange devices, the number of germs can remain constant. For these reasons, the use of ion exchangers for the production of pyrogen-free and germ-free water is very problematic.

It is further known that reverse osmosis membranes can be used to produce high purity water. By inverting osmosis, large molecules such as humic acids, bacteria, germs, viruses and the like are removed better than salts. In reverse osmosis, the membrane must be protected by scaling (scaling) and biological precipitation (Fouling). When water is treated with high carbonate hardness, acid addition is required.

Dosing the acid releases free carbonic acid so that the water shows a negative saturation index. The released carbonic acid is then desorbed in a countercurrent atmospheric carbon dioxide shower to a value of less than 10 mg / liter. For residual stabilization of carbonate hardness, phosphate must be added.

If the carbonic acid spray separator is not installed, the disadvantage is that the carbonic acid passes through the reverse osmosis, so that the carbon dioxide content must be removed by means of a downstream high-ion ion exchanger, resulting in high chemical costs and a.par. equipment. The inclusion of such an ion exchanger and the associated lower (the cleaning speed favoring the growth of the seeds).

Attempts have been found that the inclusion of a carbonic acid shower separator is associated with major disadvantages. By supplying air in countercurrent, germs and particles are introduced into the water, thus increasing the number of germs. Further, condensation water is formed in the off-pipe of the separator shower device, which is fed back into the carbonic acid separator and allows the growth of the seeds. This is also due to the high humidity in the carbonic acid separator.

Also of particular importance is the fact that the supply of air to the carbonic acid scavenger carries a large amount of oxygen, which causes good welfare for bacteria, germs and viruses. Also, the addition of phosphate to stabilize the residual hardness of the carbonate acts well to form the seed.

In order to limit the formation of nucleation in these facilities, water must be subjected to ultraviolet rays, ozone treatment or continuous disinfection. Air must also be supplied to the spray washer through a sterile air filter. However, it has been shown that these high apparatus costs only lead to little improvement, or that such high side effects, for example due to the use of additional chemicals, must be taken into account that economical operation is not guaranteed. In addition, the growth of the germs cannot be effectively suppressed.

A device for separating air from liquids, in particular from seawater, is known from DOS No. 2,427,320. The water is removed from the air in the tank using an air separator. The water to be treated is fed to an evaporator or irrigation system and can be converted to clean water with little consumption. Further details on the dewatering of the germs are not given in this file.

It is apparent from DOS No. 3,038,940 that absorbed oxygen in water can lead to undesirable growth of aerophilic microorganisms. Due to this fact, the treated water is freed of air under vacuum. However, such a measure is inadequate, since in the continuous operation of the process or in the case of prolonged standstill of clean water in the plant, the growth of the germs immediately occurs again.

Further, it is known from German Patent No. 67 924 to desorb oxygen and other gases from water by boiling at atmospheric pressure. However, this process is too energy intensive and therefore unsuitable for larger quantities of liquids.

It is therefore an object of the present invention to provide a method for inhibiting the growth of germs in pure water, in which the reduced-germ-depleted water, depleted of oxygen under pressure, optionally with heating, is maintained in this reduced-germ-depleted state.

The above object has been solved by providing a process according to the present invention, the principle being that the pure water is continuously circulated at a rate of at least 1 m / s, whereby the raw water is optionally heated by heat exchange with pure water. Experience has shown that at such a rate of recirculated water flow, new germ formation is suppressed.

By degassing in a vacuum process, the content of the microorganisms present, such as fungi, bacteria and viruses, pyrogenic substances, high molecular weight organic substances over 200-300 and, moreover, colloids, is substantially reduced in water. The growth of germ counts is effectively suppressed because oxygen is lacking for aerobes, while carbonic acid is missing for anaerobes.

N 7 7 8 8

Depending on the purpose of use, the operating temperature - and thus also the suction power of the vacuum system - is determined. If a relatively high operating temperature is used, for example above 50 ° C, as is the case with water in the electronics industry, then it is expedient for the degassed water to be cooled again, preferably countercurrently, before withdrawal. In order to increase the economy of the process, it is advantageous if the treated water is heated using heat exchange with clean water.

In order to guarantee the necessary carbonate hardness, possibly avoiding the possibility of precipitation of carbonate compounds, it is expedient to adjust the degassing so as to leave a residual carbonic acid content. This ensures that precipitate formation in the downstream ion exchanger and reverse osmosis device is avoided.

In such treatment plants where larger amounts of inherent water are required, for example when operating with ion exchangers in a discontinuous process, it is expedient to maintain germ-free clean water to maintain a vacuum flow degassing system that is maintained under vacuum. This measure prevents germ reproduction. The water flowing into the vacuum degasser can be additionally irradiated with an ultraviolet lamp or treated with ozone to prevent any further growth of the germs.

The process of the present invention has considerable advantages over the prior art methods of treating pure water.

Firstly, as has been stated, the reproduction of germs is excluded. If subsequent treatment of the treated water with ion exchangers is required, they can work with water of lower seed content, which has been degassed under vacuum.

Secondly, the advantage of the process according to the invention is that the addition of chemicals and thus also environmental pollution is avoided, since no chemicals for continuous disinfection need to be used in addition to conditioning chemicals such as hydrochloric acid or sulfuric acid. Carbonic acid is drawn off mechanically in the degassing process, so that no chemicals are required.

Also, virtually the carbonic acid is removed by vacuum degassing except for the residual fraction required to maintain the carbonate hardness. The low proportion of carbonic acid has the advantage that no carbonates are precipitated by precipitation, which could lead to deposits in the downstream ion exchanger. This also applies to downstream osmosis equipment, where precipitation would cause irreversible scale formation.

The invention is explained in more detail below with reference to the various operating options, which are schematically illustrated in the accompanying figures.

Giant. 1 is a flow diagram of a complete device for producing pure water according to the present invention;

Giant. 2 - A variant in which only one desalination plant is installed upstream of the vacuum degasser;

Giant. 3 - A schematic representation of a plant in which a desalination plant is downstream of the vacuum degasser and in which the degassed water is further treated in a downstream desalination stage;

Giant. 4 is a schematic representation of an apparatus in which a vacuum degasser is installed upstream of a mixed bed desalination plant and another mixed bed apparatus is downstream of it, wherein pure water is passed through an ultrafiltration stage;

Giant. 5 - The water treatment device according to FIG. 4, which is downstream of the ion exchange device and in which an ultrafiltration device is arranged in the downstream circulation stream.

With the aid of the apparatus schematically shown in FIG. 1, pure water with reduced nucleation content is produced according to the invention. The raw water flows through line 12 to a preheating stage 14 in which it is preheated to a temperature of about 20-30 ° C. The acid is then fed to the raw water to be cured via line 16, and the raw water is then filtered using a filter 18. A high-pressure pump is then used to introduce conditioned water into the inverted osmosis unit at a pressure of either 2.8 MPa or 7.0 MPa. 22nd

The permeate is discharged from the inverted osmosis unit 22 via line 23 and valve 25 to the vacuum degasser 24 and degassed in the degasser. The concentrate from the inverted osmosis unit 22 with line 28 is fed to the vacuum pump 28 of the vacuum degasser 24 where it serves as barrier water for the vacuum pump 28. This water is then discharged via line 30 to waste.

In order to close the vacuum degasser 24 to ambient air, the exhausted air is discharged via line 33 from the tank 32 to the atmosphere. A vacuum tank 24a (reservoir) is assigned to the vacuum degasser 24 in which the degassed water is stored. From the vacuum degasser 24, gas-free water 34 is fed via line 35 to a second inverted osmosis unit 36.

The operating pressure of the second inverted osmosis unit 36 may optionally be 2.8 or 7.0 MPa, preferably selected to provide some residual carbon dioxide concentration, thereby avoiding precipitation of carbonate hardness in the inverted osmosis unit 36.

2 7 7 β 8

The concentrate from the second inverted osmosis unit 36 is passed through line 40 to the raw water line 12, since it has a better quality than the raw water and thus leads to an improvement in the quality of the feed water. This measure is particularly cost-effective, as the following example shows:

In the experiment, the concentrate of the second inverted osmosis unit 33 (491 liters) had a salt content of 167.9 mg / kg, the raw water containing 708 mg / kg of salts at a raw water amount of 1171 liters / hour. By mixing the concentrate from the second inverted osmosis unit 36, the salt content of the raw water is reduced by approximately one quarter, and the associated salt passage can also be determined by this value. This leaves no waste water.

The permeate (pure water) obtained in this way can be discharged via a conduit 42 to consumers, preferably via a conduit.

In the following table, the results obtained at locations A to G of the apparatus are shown for better clarity (see FIG. 1).

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AND В C D E F permeate G Pressure 0.2 0.2 max 0.3 2.2 vacuum max 0.3 max 6.0 (MPa) Amount of water 1 171 1662 1 247 415 1246 755 491 ^! U / h) Salt content 708 581.6 76.6 2 100 76.6 4.2 167.9

(mg / kg)

The experiment was carried out at temperatures of 20 to 30 ° C.

The above table shows that the product at the V site increases the salt content after acidification. Due to the mixing of the raw water with the concentrate from the second inverted osmosis unit 36, a feed rate of 1662 liters per hour results. From the composition of the product at point C, it was seen that the salt content was reduced to only 76.6 mg / kg.

The amount of permeate here is 1,247 liters per hour, which corresponds to the difference between the amount of raw water at site V and the amount of concentrate at 415 liters per hour at site D. The concentrate composition at site D shows a significant increase in salt content by concentration in the inverted osmosis unit. depending on the inlet pressure, the concentrate pressure is about 2.2 MPa or about 6.0 MPa. The water downstream of the vacuum degasser 24 at E has the same composition as the permeate. The residual amount of carbon dioxide after the vacuum degasser 24 is 5 to 30 mg / liter, depending on the original carbonate hardness. The water is practically free of oxygen.

The measured results at point F refer to the permeate after the second inverted osmosis unit 36. There is a particularly low salt content of 4.2 mg / kg compared to the salt content in the raw water at site A 708 mg / kg or in mixed water at site V 581.6 mg / kg. The composition of the permeate at site F meets the requirements of the pharmaceutical industry in relation to the residual ion concentration. *

A significant decrease in the number of embryos was found in the permeate. While the number of germs in the feed to the inverted osmosis unit 22 was about 1430 germs per 100 ml, the number of germs in purified water is only about 10 germs per 100 ml. The total organic carbon (TOC) will also be reduced from 4.8 mg / kg to 1.5 mg / kg.

This example shows that chemicals are excluded during the entire process. On the one hand, this has the advantage of substantial cost savings as well as slight damage to the environment. In addition to the power consumption, virtually no other operating means are required. The return of the concentrate from the second inverted osmosis unit 36 or the use of the concentrate from the inverted osmosis unit 22 as a barrier water in the vacuum pump 28 favors the overall system in the sense that no waste water is discharged.

The above-described apparatus can be combined with various pretreatment stages as required, i.e. the purpose of using purified water and the composition of the starting raw water, as shown in other embodiments.

In the exemplary embodiment shown in FIG. 2, a vacuum degasser 50 is preceded by the desalination stage 62. The desalination stage 62 may be a reverse osmosis device and an ion exchange device.

From an economic and operational point of view, the vacuum degasser 50 can operate at higher temperatures up to 60 ° C. This hot water * is required in particular in the electronics industry. The raw water supplied by the conduit is fed to the preheating stage 54, cooling the degassed water from the vacuum degasser 50 supplied by the pump 52 through the conduit 55 to a temperature of about 20 ° C.

If the temperature of the water supplied to the vacuum degasser 50 via line 51 is insufficient, then it is supplied to the preheating stage via line 56 via a steam regulator.

Гв 7 7 6 8 heating steam. Condensate is discharged via line 57.

The degassed and cooled water from the vacuum degasser 50 is then fed via line 59 to desalination stage 62, which is preceded by a high pressure pump 61 in the case of a reverse osmosis unit. 0 MPa.

When it is an ion exchange device, the operating pressure of the high pressure pump 61 is only 0.3 to 0.4 MPa. The permeate (pure water) is taken through line 63.

The gases coming from the vacuum degasser 50 via line 48, namely carbon dioxide and oxygen, are discharged through the vacuum pump 49.

Fig. 3 shows a water purification plant in which a desalination plant is connected upstream of the vacuum degasser and in which the de-gassed water is led to a second desalination plant, which may consist of an inverted osmosis unit or ion exchange device for further processing . ·

Referring to FIG. 3, the raw water supplied via line 71 is first fed to an inverted osmosis unit 69, upstream of which a high pressure pump 68 is placed, where it is pre-dried and then fed to heat exchanger 77, 79. In the heat stage of heat exchanger 77 For example, the water is heated as previously described by cooling the water flowing from the vacuum degasser 70 through line 73 in the cooling stage of the heat exchanger 79 by heat exchange. By supplying hot steam through line 76 through a steam regulator 74, the process water is heated to an operating temperature for vacuum degassing. The resulting condensate is then removed via line 75.

The water preheated in the heat exchanger 77 is fed via line 80 to the vacuum degasser 70. In this, the degassed water is retained in the tank 70a up to a certain degree of filling. It can be seen here that by means of the inflow control of the line 81 and the control valve 82 a predetermined flow rate is guaranteed.

The de-gassed water is discharged from the vacuum degasser 70 via line 73 via heat exchanger 79 and line 83 to the second desalination stage 86. The second desalination stage may be a reverse osmosis device or an ion exchange device. When the reverse osmosis is engaged, the high pressure pump 67 operates at a pressure of 2.8 or 7.0 MPa, while the ion exchange device operates at an operating pressure of 0.3 to 0.4 MPa.

When using an ion exchange device, the temperature of the degassed water in line 83 should not expediently exceed 20 ^° C, since the ion exchange is then adversely affected. When a reverse osmosis device is used, the operating temperature shall be set to a maximum of ^ς Ό. This results in a higher flow in the reverse osmosis device, so that a smaller membrane area is required.

The water coming from the second desalination stage 86 is discharged via line 88 to the consumption point 89. In this case, the required amount in line 88 is controlled by means of a pressure valve 66 so that a certain flow rate is always maintained in the return line. This rotation speed should be at least 1 m / s to prevent deposits and germs in the line.

Unused clean water is fed via line 88a to the receiver tank 70a of the vacuum degasser 70. In order to prevent the formation of germs, an ultrafiltration device can be added downstream of the second desalination stage.

The gases coming out of the vacuum degasser 70, namely carbon dioxide and oxygen, are removed by the vacuum pump 78 through line 65. Also in this embodiment, the concentrate from the inverted osmosis unit 69 can be used as barrier water for the vacuum pump 78 supplied from the inverted unit. The axis 64 is then discharged from the system via the expansion vessel 64.

Referring to Figure 4, another preferred embodiment of the process of the invention is shown in which the vacuum degasser 102 is combined with a complete desalination plant comprising a cation exchange and anion exchange stages. The raw water supplied through line 90 is passed through the ultraviolet irradiation device 91 and fed to cation exchanger 92 and anion exchanger 93. The de-gassed water in the vacuum degasser 102 is fed to a mixed bed ion exchanger 104 via a system pressure boost pump 105. The deionized water flows out of the circulation duct 106, in which the ultrafiltration device 107 is also optionally connected again.

Unused clean water is passed through the recirculation line 106 back to the receiver tank 102a of the vacuum degasser 102. Pressure control is performed by the valve 108 depending on consumption.

Also in this process arrangement, the prescribed minimum velocity in the recirculation line is 106 1 m / s. This value should not be lower in order to maintain the microbiological purity of the water.

This arrangement can advantageously be used when the total organic carbon content of the feed is small, for example less than or equal to 1 mg per kilogram. Water thus contains only a small proportion of nutrients for the formation of germs. Existing devices of this kind can be easily converted by replacing the existing carbonic acid scrubber with the vacuum degasser described above. This allows the use of existing equipment to produce clean water with a lower seed content and better quality. Excluded is the addition of chemicals for disinfection, associated with interfering with the cleaning operation.

Another preferred arrangement is shown in Figure 5. Here, the vacuum degasser 120 is downstream of the desalination stage 121. Depending on the quality of the raw water supplied, the desalination stage 121 may be a cation exchange, anion exchange or mixed bed apparatus.

In the vacuum degasser 120, the degassed clean water is discharged via line 124 to the consumption point 126, and an ultrafiltration stage 125 may be included in the recirculation line 127 to remove particles that may be discharged from the ion exchangers. In the circulation line 127 there is a control valve 128, by means of which the flow velocity is controlled so that it does not fall below 1 m / s.

Unused clean water is passed through the recirculation line 127 to the vacuum degasser 120a pattern 120a. This ensures a constant recirculation flow to prevent the possible formation of germs.

In this case too, the existing ion exchange equipment can be adapted in a simple manner by incorporating a vacuum degasser in order to obtain as germ-free water as possible.

Claims (5)

1. A method for suppressing the growth of germs in purified water by removing oxygen under reduced pressure, optionally under heating, wherein degassing is directed such that a residual carbonic acid content is maintained in order to maintain carbonate hardness, wherein pure water is allowed to flow continuously, The pure water is circulated at a rate of at least 1 m / s, optionally the raw water being heated by heat exchange with pure water. Method according to claim 1, characterized in that the clean water which has not been consumed is stored in a static, continuously flowing container. 3. The process according to claim 1, wherein the recirculated clean water is recycled through vacuum degassing. 4. The method according to claim 1, wherein after degassing the clean water is subjected to ultraviolet or ozone treatment. 5. A process according to claims 1 to 4, characterized in that the degassed water is subjected to ultrafiltration.