DE3243817A1 - Process for producing aseptic pure 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

Process for the production of low-germ pure water

The invention relates to a method for producing low-germ pure water.

While in earlier years the water requirement was of high quality Could cover groundwater resources, surface water now has to be increased to meet demand are used, the quality of which is severely affected by environmental pollution and which must therefore be processed. As for certain applications, e.g. in the Electronics, chemical-pharmaceutical and cosmetic Industry as well as for laboratories and food companies as well as for public ones High quality drinking water supply companies are required Elaborate and often complicated procedures are used to produce pure and ultrapure water with the required properties.

The impurities in the water are divided into the following groups: a) Coarsely dispersed substances: particle size> 10 4 cm, such as floating, floating and suspended matter; b) Colloidal substances: These particles are no longer visible to the eye visible; the particle size is 10 to 10 7 cm; c) Molecularly disperse substances: ions, organic molecules, real solutions; Particle size 4 × 10 7 cm; d) gases: 02, N2 CO2, which can be dissolved in the liquid.

The problem of eliminating ionogenic substances, e.g.

of salts, today, can be considered dissolved while eliminating of colloids, of high molecular weight and low molecular weight substances, of nutrients etc., still poses a problem for many purposes. The one required today Use of surface water for water supply bring it with it that more organic residues are contained in the water, their elimination encounters great difficulties.

Pure and ultrapure water is mainly required in the following areas: a) In the electronics industry for the production of microprocess controls, b) In of the pharmaceutical and cosmetic industry for the production of aqua purificata and aqua pro injectione, c) For hospitals, dialysis stations and laboratories, d) For drinking water, water for the beverage industry and water for the food industry.

For the aforementioned types of use, it is very important that the Water is largely sterile. The drinking water must be free from pathogens be. According to the guidelines, these requirements are deemed not to have been met if in 100 ml of drinking water Ecoli are included. The number of colonies of coliforms should not exceed the guideline value of 100 ml. In disinfected drinking water the value of the treated water should be below 20 per ml. In the electronics industry usually 100 germs per 100 ml, in special cases only 10 germs per 100 ml required.

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

It is known for the production of ultrapure water ion exchange systems to be used with downstream fine filters.

To the percentage of organic substances, colloids, bacteria and Attempts have been made to keep germs small in flocculation reactors by adding flocculants and disinfectants. By adding The colloidal substances were reduced by precipitants, they had an effect however, in the downstream systems it is very negative. To reduce organic Substances have been used in sludge contact reactors. However, the success was not satisfactory, so that precoat filters were still used, through which a higher one Elimination rate was achievable. The operation and maintenance costs of such systems is extraordinarily high. Precoat filters were used to remove the colloidal particles in the acidic area washed ashore in several layers and with a demineralisation system combined, through which in particular organic substances such as humic acids are eliminated could become. The acquisition and operating costs of such a system are also extremely high. These systems also have the disadvantage that the number of germs in the treated water is still too high. A reduction in the TOC value is only possible up to approx. 50 to 70% with such systems (TOC = Total Organic Carb # on = total carbon).

The use of ion exchangers has proven to be particularly disadvantageous highlighted for the production of sterile water. The ion exchangers are capable of Although largely removing ionic substances from the treated water, they however, organic substances are only partially capable of doing this to record. These can lead to irreversible blocking of the exchanger. It was also observed that, depending on the loading condition of the exchanger, organic substances from the exchangers were released again, so that higher values were present in the treated pure water than in raw water.

The risk of contamination from ion exchangers is also very high. In particular the number of germs increases sharply after downtimes, because the exchange material is a good breeding ground for germ growth due to its large surface.

Especially after downtimes, such as the weekend, the germ count increases, which are e.g. 10 ml / l in the raw water, up to 500,000 germs on Monday. at continuously operating ion exchangers can keep the germ count constant will. Thus, the use of ion exchangers for the generation of germs and pyrogen-free water extremely problematic.

It is also known for the production of ultrapure water reverse osmosis membranes to use. Reverse osmosis removes large-molecule substances such as humic acids, Bacteria, germs, viruses etc. are better retained than salts. With reverse osmosis the membrane has to protect itself from scaling (failure of substances) and from biological fouling to be protected.

Acid dosing is necessary for water with high carbonate hardness. By adding acid, carbonic acid is released, so that the water has a negative effect Has saturation index.

The released carbon dioxide is then degassed in an atmospheric carbon dioxide steam generator expelled in countercurrent to a value of 4 10 mg / l. To stabilize the residual Carbonate hardness must be added to phosphate. One would use the carbon dioxide drier do not install, there is the disadvantage that the carbonic acid through the reverse osmosis membranes permeated, so that the CO content is then reduced through large-dimensioned downstream ion exchangers would have to be eliminated, which means a high expenditure on chemicals and equipment Consequence would have. The use of such ion exchangers and the associated low Operating speeds favor germ growth.

Investigations have shown, however, that the use of a carbonic acid drip degasser is fraught with major disadvantages. By blowing air in countercurrent germs and particles are introduced, so that an increased multiplication of germs occurs. Furthermore, condensation water forms in the exhaust pipe of the trickle deaerator, which in the carbonic acid trickle deaerator run back and favor the germ growth.

This is also due to the high air humidity in the carbonic acid diesel deaerator promoted. Another disadvantage is the fact that over the air blower Large amounts of oxygen are introduced into the carbon dioxide gas aerator, which are good Create living conditions for bacteria, germs and viruses. Also the dosing of phosphate to stabilize the residual carbonate hardness acts for nucleation cheap.

In order to reduce the formation of nuclei in such systems, UV radiation is used, Ozone treatments or ongoing disinfection carried out. Also was the air supply fed to the Riesler via a sterile air filter. However, it has been shown that this high expenditure on equipment had only very moderate success or that such high side effects, e.g. by using additional chemicals, had to be accepted, that an economical operation is not guaranteed. In addition, could germ growth cannot be effectively prevented.

The invention is based on the aforementioned disadvantages to eliminate and to create a process for the production of low-germ ultrapure water, which is used without the disadvantages mentioned, such as the use of chemicals.

This object is achieved according to the invention in that the, if necessary pre-cleaned water is subjected to degassing in negative pressure and when it falls below this a predetermined minimum withdrawal value or returned to a milieu in the event of a standstill which counteracts nucleation.

It has been found that when the water to be treated is degassed The carbonic acid trickled out in the negative pressure and the oxygen content was considerably reduced thereby worsening the microbial living conditions. The rise the germ count is effectively counteracted because there is no oxygen for aerobes, while for anaerobes the vital carbonic acid is withdrawn. By degassing in the vacuum process, the microorganisms present in the water, such as bacteria, Fungi, viruses, yrogenic and organic substances with a high molecular weight of over 200 to 300 and also colloids decreased. Depending on the intended use, the operating temperatures and thus the suction performance of the vacuum degasser is determined. Will be a relative high operating temperature, e.g. above 590 C, used, e.g. in the electronics industry is the case, then it is advisable if the degassed water, before it is withdrawn, is preferably recooled in countercurrent. To increase profitability Of the process, it is preferred that one by means of the degassed under pressure water warms up the raw water to be treated through heat exchange.

To maintain the required carbonate hardness or

to prevent the precipitation of carbonate compounds is expedient the degassing is adjusted so that a residual carbonic acid remains. This is ensures that precipitates on downstream ion exchangers and reverse osmosis systems be avoided.

In such treatment circuits, in which larger amounts of water are necessary, e.g. when operating with ion exchangers in a batch process, it is To maintain the sterility of the water, it is advisable to use vacuum degassing to connect a continuously flowed storage tank which is under negative pressure. This counteracts an increase in germs. The flowing to the vacuum degasser In order to prevent any further multiplication of germs, water can also be used with UV lamps irradiated or treated with ozone.

The inventive method has compared to the previously known Process for the treatment of pure water significant advantages. On the one hand, as stated, a germ proliferation avoided. If a follow-up treatment of the processed Water with ion exchangers is required, this can be done with the low-germ, can be operated in negative pressure degassed water. On the other hand, the following results Advantage: The use of chemicals and thus environmental pollution are avoided, because apart from the conditioning chemicals such as hydrochloric acid or sulfuric acid, none Chemicals must be used for ongoing disinfection. The carbonic acid is removed mechanically by degassing without the use of chemicals is required.

The degassing in a vacuum also largely removes oleic acid with the exception of the remainder that is required to maintain the carbonate hardness will. The low proportion of carbonic acid has the advantage that there is no carbonate hardness fails, which can lead to caking in downstream ion exchangers. This also applies to the downstream installation of reverse osmosis systems caused by the precipitation be subjected to irreversible scaling.

The degassing of liquids in negative pressure is for other purposes known. This is how we know the treatment of drinking water and boiler feed water using vacuum degassers to remove hydrogen sulfide and methane. It is also known as the "stripping" of gases, that is, the expulsion of volatile substances Substances according to their vapor pressure at normal or higher temperature with the help a carrier gas or a simultaneous shift in the partial pressure.

A method for degassing F1js' activities is also known subsequent centrifugation for the purpose of expelling gas bubbles in photographic Procedure. The aim is to create a bubble-free liquid. These However, types of use could not provide any suggestions for the present process because this is based on a completely different task and so far has taken completely different paths to solve the aforementioned problem.

The invention is based on various possible uses, which are shown schematically in the accompanying drawing, explained in more detail. Show here: Figure 1 shows a complete plant for the production of Pure water according to the invention, shown schematically in the flow diagram; Figure 2 the schematic representation of a plant for the treatment of pure water, in which the vacuum degasser is connected upstream of a desalination plant; Figure 3 the schematic Reproduction of a plant for the treatment of pure water, in which the desalination plant the vacuum degasser is connected upstream and in which the degassed water in a Post-desalination stage is further treated; Figure 4 shows a system schematically, at which of the vacuum degassers is connected upstream of a mixed-bed desalination system and further mixed bed systems are connected downstream, with the treated water in the circuit driven and possibly passed through an ultrafiltration stage; Figure 5 a Processing system according to FIG. 4, which is connected as a whole downstream of an ion exchange system and an ultrafiltration system is switched on in a downstream circuit is.

in Fig. 1 schematically reproduced system is according to ner Invention of low-germ pure water produced The walking water flows via a line 12 to a preheating - @@@@ 14, in which it is heated to a temperature of approx. 20-30 ° C.

is heated to the conditioning of the raw water is then under the Line 16 is supplied with acid and anzenliessend the raw water. by means of a filter 18 filtered. A high pressure pump 20 delivers at a pressure of optionally 28 bar under 70 bar the conditioned raw water in a reverse smose unit 22. The permeate is from the reverse osmosis unit 22 via a line 23 and a valve 25 a gekumentgaser 24 supplied and degassed in this. The concentrate from the reverse osmosis unit 22 is fed via a 26 to the vacuum pump 28 of the vacuum degasser 2a and is used as sealing water for the vacuum pump. The sC then flows through a pipe 30 to the Kanaj is completed with the vacuum degasser 24 to the outside air, n n one Container 32 deliver the extracted air 33 to the gosoherence. The vacuum degasser 24 is a voriace; he (memory) 24a affiliated, in which the ent - !? sser is cached is. From the vacuum degasser 24 via the L via a booster pump 34 the degassed Water, e2r? he second reverse osmosis system 36 is fed. The operational: 0 of these Unit 36 is optionally 28 bar or 70 bar - design of the vacuum degasser 24 is expedient so that a certain residual C02 concentration is available Avoid carbonate hardness precipitates in the reverse-36.

concentrate from the reverse osmosis unit 36 is supplied via a line I returned to the raw water inlet 12) as it is of better quality than the raw water has and thus to an improvement in the feed water quality leads. This circuit is particularly economical, like the following example shows: In an experiment carried out, the concentrate from the reverse osmosis unit had 36 (amount: 491 1) has a salt content of 167.9 mg / kg, the raw water a salt content of 708 mg / kg with a raw water volume of 1171 l / h. By adding the concentrate from the reverse osmosis unit 36 the raw water salt content is reduced by approx. 1/4, whereby the associated salt passage is also set lower by this value can be. As a result, no wastewater is produced The permeate (pure water) generated in this way can be fed to the consumers via a line 42, conveniently in a ring line will.

For a better understanding of this system, measurement results are given below that were taken from points A - G (see Fig. 1) as follows: ABCDEFG Permeate Pressure 2 2 max 3 22 ~ vacuum | max 3 max 60 (bar) Amount of water 1171; 1662 1247 415 j 1246, 755 491 (l / h) Salinity 708 581.6 76.6 2100 i 76.6 ', 4.2! 167.9 (mg / kg) The tests were carried out at temperatures of 20 or 30 ° C.

It follows from the above list that in point B by the acid dosage increases the salt content.

If it is an ion exchange system, the operating pressure is of the pressure booster pump 61 only 3 - 4 bar.

The permeate (pure water) is withdrawn from line 63.

The gases flowing out of the vacuum degasser 50 via the line 48, namely CO2 and ° 2 are removed via a vacuum pump 49.

In Fig. 3, a pure water system is shown in which the Vacuum degasser a desalination plant is connected upstream and in which the degassed Water then in a post-desalination stage, which comes from a reverse osmosis unit or can consist of ion exchangers, is further transformed.

3, the raw water fed in through line 71 is first in a reverse osmosis unit 69, in front of which a booster pump 68 is located, pre-desalinated and - # elapses then in a heat exchanger Z.7tn a heat level 77 ird the water is warmed up in the manner described above by removing the from the vacuum Mentgaser 70 by the water flowing in at 79 line 73 / is re-cooled. Means The conduction of heating steam via the line 76 and the steam control 74 is what is to be treated Water warmed up to the operating temperature for the vacuum degasser.

Two condensate is discharged via line 75.

The water preheated in the heating stage 77 reaches the pipe 80 in the vacuum degasser 70. This stores e; #tgased water 70a up to one certain degree of filling.

It is provided that by means of an inflow control via a Line 81 and a control valve 82 a certain Füilungsgrad is maintained.

The degassed water is a booster pump 84 from the Vacuum degasser 70 via a line 73 and the recooling stage 79 via a line 83 is fed to a post-desalination stage 86. This can come from a reverse osmosis unit or consist of ion exchangers. The booster pump 67 generates at a reverse osmosis unit optionally 28 or 70 bar, for the ion exchanger one Operating pressure of 3 - 4 bar. If ion exchangers are used, the temperature may of the degassed water in line 83 should not exceed 200 -C, otherwise the ion exchange will be impaired. If reverse osmosis systems are used, the operating temperature is set to a maximum of 400 C. This becomes a higher flux achieved in the reverse osmosis system, resulting in smaller membrane areas required are.

The water coming from the post-desalination stage 86 is via the Line 88 is supplied to the consumer points shown schematically at 89. In this case, the delivery rate in the ring line 88 is set via a pressure holding valve 66 regulated that a certain flow rate is always maintained in the ring main will. This flow velocity should be at least 1 m / s, so that none Deposits and nucleation can occur in the ring main.

The unused pure water is fed into the receiver via a line 88a 70a of the vacuum degasser 70 returned.

The post-desalination stage can also be used to prevent nucleation can be supplemented with an ultrafiltration system.

The gases flowing out of the vacuum degasser 70, namely CO2 and ° 2 'are discharged via a line 65 by means of a vacuum pump 78. Also at this circuit can, as indicated, be provided that the concentrate from the reverse osmosis unit 69 as sealing water via a line 63 passed into the vacuum pump 78 and discharged via an expansion tank 64 will.

In Fig. 4 a further advantageous circuit is shown, in which a vacuum degasser 102 with a demineralization system, which consists of cation and anion exchange stages is combined. That through line 90 incoming raw water is passed through a UV irradiation system and a cation and anion exchanger 92,93 supplied. The water degassed in the vacuum degasser 102 becomes a mixed-bed ion exchange stage 104 via a pressure increasing pump 105 fed. The deionized water passes from there into a ring line 106, in which can also be switched on again an ultrafiltration system 107.

The pure water is supplied to consumer points 95.

The unused pure water arrives via the ring line 106 back into the storage container 102a of the vacuum degasser 102. Via the valve 108 a pressure control is carried out depending on the withdrawal.

With this circuit, too, there is a minimum value for the speed in the ring line 106 of about 1 m / s to prescribe the purpose of maintaining the sterility of the water must not be undercut.

This circuit can then be used to advantage when the DOC value in the feed is low, e.g. <- 1 mg / kg.

The water thus has only a low content of nutrients for nucleation. Existing systems of this type can easily be converted by the previously existing carbon dioxide trickle deaerator through the described Vacuum degasser 102 is replaced so that with the existing systems Now the production of sterile pure water of the best quality is possible. Of the Use of disinfection chemicals combined with disruptive business interruptions during disinfection, are avoided.

Another advantageous system according to FIG. 5 shows a vacuum degasser 120, which is connected downstream of a desalination stage designated as a whole with 121. The desalination plant 121 can, depending on the raw water conditions, consist of a cation or Anion or mixed bed system exist.

The pure water degassed in the vacuum degasser 120 passes through a pipe 124 to the consumer points 126, with an ultrafiltration stage in the ring line 125 can be switched to residual particles given off by ion exchangers could be to eliminate. A control valve is located in the ring line 127 128, which regulates the flow rate in such a way that it does not fall below the specified Value of approx. 1 m / s # drops.

The unused pure water is via line 127 into the Original 120a of the vacuum degasser 120 returned.

There is thus a constant cycle, that of a possible one Counteracts nucleation.

In this case, too, can existing systems in which ion exchangers are in operation, simply by connecting a vacuum degasser in can advantageously be expanded in order to obtain the most germ-free water possible.

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Claims (11)

Process for the production of low-germ pure water Patent claims 1. Process for the production of low-germ pure water, in particular for use in the pharmaceutical and electronic sector c h n e t that the optionally pre-cleaned water degassing under negative pressure subject and when falling below a specified minimum withdrawal value or at standstill is returned to an environment which counteracts the formation of nuclei. 2. The method according to claim 1, characterized in that the underpressure degassed water warms up the raw water to be treated by heat exchange, or the warm degassed water is cooled back by the raw water. 3. The method according to claim 1, characterized in that the degassing is adjusted so that a residual alcoholic acid to maintain the carbonate hardness remains. 4. The method according to claim 1, characterized in that the in the negative pressure degassed unused water in a standing, continuously flowing storage tank is cached. 5. The method according to any one of the preceding claims, characterized in, that the degassed water is recycled to the vacuum degasser. 6. The method according to any one of the preceding claims, characterized in, that the degassed water of a salt-free disinfection (by means of UV or ozone treatment) is subjected. 7. The method according to any one of the preceding claims, characterized in, that the water degassed in the vacuum is used for rinsing and regeneration of the vacuum degasser upstream and / or downstream ion exchanger is used. 8. The method according to any one of the preceding claims, characterized in, that the water to be treated is desalinated in a membrane separation stage and their The concentrate feeds the vacuum pump of the vacuum degasser as sealing water. 9. The method according to any one of the preceding claims, characterized in, that the water to be treated is desalinated in a first membrane separation stage, degassed in a subsequent vacuum degasser, in a second membrane separation stage further desalinated the concentrate of the first membrane separation stage of the vacuum pump Vacuum degasser and the concentrate of the second membrane separation stage Feed of the first membrane separation stage supplies again. 10. The method according to any one of the preceding claims, characterized in, that the vacuum degasser before a desalination stage or, if necessary, also switches between desalination stages. 11.Methods for treating liquids, especially water, with degassing of the liquid in negative pressure to generate low-germ ultrapure water.