DE3243817C2 - Process for the production of low-germ pure water - Google Patents

Abstract

A vacuum degasser is used to generate low-germ pure water, which reduces the germs contained in the water to be treated to a minimum. In order to maintain the sterility, care must be taken to maintain the sterility of the water in cases of low withdrawal or standstill or when larger amounts of own water are required, for example by downstream connection of a continuously flowed storage tank which is under negative pressure. Conventional treatment systems, which are operated with ion exchangers or reverse osmosis units, can be converted to produce low-germ pure water by using a vacuum degasser. The pure water treated in this way meets the highest requirements, for example in the pharmaceutical or electronic industry.

Description

The invention relates to a method for producing low-germ pure water, in particular for use in the pharmaceutical and electronic field, by removing oxygen by means of negative pressure, the pure water is kept constantly flowing. . ~. ·,

Whereas in earlier years the water demand came from high-quality groundwater resources surface water has to be used today to meet demand Quality is severely impaired by environmental pollution and which must therefore be processed. Therefore certain applications, e.g. B. in electronics, the chemical-pharmaceutical and cosmetic industries as well as high quality is required for laboratories and food companies as well as for public drinking water supply companies, expensive and often complicated procedures have to be 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 B. floating, floating and sinking material. fe ·.

These particles are no longer visible to the eye; the particle size is 10 ⁴ to 10-'cm:

c) Molecularly disperse substances:

Ions, organic molecules, real solutions; particle size <10 " ⁷ cm;

d) gases:

O ₂ , N ₂ , CO ₂ , which can be dissolved in the liquid. The problem of eliminating ionogenic substances, e.g. B. of salts, can now be regarded as solved

are used during the elimination of colloids, of high molecular weight and low molecular weight substances

Nutrients, etc., still poses a problem for many uses. The use of Surface water for the water supply brings with it that increased organic residues in the water

are included, the elimination of which meets with great difficulty.

Pure and ultrapure water is mainly required in the following areas:

a) In the electronics industry for the production of microprocess controls, b) in the pharmaceutical and cosmetic industry for the production of aqua purificata and aqua pro

iji injectione,

jif c) for hospitals, dialysis stations and laboratories,

for drinking water. Water for the beverage industry as well as water for the food industry.

43 817

For the aforementioned types of use, it is very important that the water is largely free of germs. That Drinking water must be free from pathogens. These requirements do not apply according to the ^ hthmeaals fulfilled if there are coliforms in 100 ml of drinking water. The number of colonies should be the »» htmrt of'JOO do not exceed per ml. In disinfected drinking water, the guide value for the Koloruen ^ hl should be after completion the treatment of the water are below 20 per ml. In the electronics industry there are typically 100 germs per 100 ml, in special cases only 19 germs per 199 ml required ^ riurin

The water for pharmaceutical purposes, especially for injection purposes, must pyroeenfta ™ J «« J? ^ · It is known to use ion exchange systems with ™ ***? »^ * ^^ _t for the production of ultrapure water. To the proportion of organic substances. To keep colloids * bacteria and germs ^ one tries to reduce these substances in flocculation reactors by adding flocculants ^ des ^ ektionsmitteta. The addition of the precipitating agents made the co-organic ^substances . "However, the results in the downstream systems were very negative. Sludge contact reactors were used to reduce organic residues. However, the success was not satisfactory, so precoat filters were still used by which a higher removal rate could be achieved. The operating and maintenance costs of such systems are extraordinarily high. To remove the colloidal particles, precoat filters in the acidic area were precoated in several layers and combined with a complete desalination process, through which organic substances, such as humic acids, in particular, could be removed ^ The acquisition ^ - * and operating costs of such a system are also extremely high.This type of system also has the disadvantage that the number of germs in the treated water is still too high 70% possible (TOC = Tota l Organic Carbon = hlffX

The use of ion exchangers to generate water has been found to be particularly disadvantageous. Although ion exchangers are capable of largely removing ionic substances from the treated water, they can only partially absorb organic substances. These can lead to irreversible blocking of the exchangers It was also observed that, depending on the loading condition of the exchangers, organic substances were given off again by the exchangers, so that higher values were present in the treated refined water than in the raw water. The risk of germs from ion exchangers is also very high Because of its large surface, the exchanger material is a good breeding ground for germ growth. ^ especially after periods of downtime, such as at the weekend Ion exchanges The number of germs can be kept constant. The use of ion exchangers for the production of germ-free and pyrogen-free water is therefore extremely problematic. . n, «. hHi *.

It is also known to use reverse osmosis membranes for the production of ultrapure water. Through reverse osmosis, large-molecular substances such as humic acids, bacteria, germs, viruses, etc., are better protected. In reverse osmosis, the membrane must be protected from scaling (precipitation of substances) and from standing fouling. For water with a high carbonate hardness, cmc Sauredoaenmg is necessary. The addition of acid releases carbonic acid, so that the water has a W * ™ * ™ * ™ ^ ** . The released carbonic acid is then expelled to a value of <10 mg / 1 in a counter-current in an atmospheric serial carbonic acid degasser. Phosphate has to be added to the residual stabilization of the carbonate hardness. If the carbonic acid boiler was not installed, the disadvantage arises that the carbonic acid permeates through the reverse osmosis membranes so that the Ca content then had to be eliminated by ion exchangers connected downstream, which a high chemical and equipment expense would result. The use of such ion exchangers and the associated operating speeds promote the growth of germs. _orn n _pn lwh

Investigations have shown, however, that the use of a carbonic acid degasser with grudge iNacn sharing is afflicted By blowing air in countercurrent, germs and particles are introduced, so that SeriShteiSmvShrung occurs Furthermore, trickle deaerator forms in the exhaust air pipe! Condensation water, i.e. S run back the carbonic acid sprinkler and encourage the growth of germs. This is also done by d.e high air humidity * n carbonic acid diesel deaerator promoted The fact that this is particularly disadvantageous is also a disadvantage If the air blower in the carbonic acid sprinkler was used, large amounts of oxygen would be introduced Create living conditions for bacteria, germs and viruses. The addition of phosphate to stabilize

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UV radiation or ozone treatments would be used let air supply to the Riesler via sterile air filter ipparauvc effort only had moderate success or that additional chemicals must be accepted. In addition, the germ growth could not

It is also known from DE-PS 67 924, oxygen and other gases by boiling at atmospheric pressure desorb from water. However, this method is very energy-intensive and for larger amounts of liquid not suitable

The invention is based on the object of providing a method for producing pure water with a low germ content create, in which the sterile water freed of oxygen in the negative pressure is in a sterile state is held in order to be able to feed it to the point of use with low germs.

This object is achieved according to the invention in that the pure water at a speed of at least 1 m / sec in a ring line. Experience has shown that with such Flow rate of the recirculated water prevents new nucleation.

IQ By degassing in the vacuum process, the growth of the pyrogenic Microorganisms such as bacteria, fungi and viruses are significantly reduced. The increase in the number of germs will effectively counteracted because for aerobes there is a lack of oxygen, while for anaerobes there is a lack of oxygen Is deprived of carbonic acid.

Depending on the intended use, the operating temperatures and thus the suction performance of the vacuum degasser are set. B. above 50 ⁰ C, used as this /. B. is the case in the electronics industry, then it is useful if the degassed water before removal.

is preferably recooled in countercurrent. To increase the economic efficiency of the process preferably the raw water is warmed up by heat exchange with the pure water.

To maintain a required carbonate hardness or to prevent the precipitation of carbonate compounds the degassing is expediently adjusted so that a residual carbonic acid remains. Through this it is ensured that precipitates in downstream ion exchangers and reverse osmosis systems are avoided will.

In such treatment circuits, in which larger amounts of own water are necessary, z. B. in operation with ion exchangers in the batch process, it is useful to maintain the sterility of the water, downstream of the vacuum degassing is a continuously flowing storage tank which is under negative pressure. This counteracts the proliferation of germs. The water flowing to the vacuum degasser can be used to to prevent any further multiplication of germs, additionally irradiated with UV lamps or with ozone be treated.

The inventive method has compared to the previously known method for processing Pure water has considerable advantages. On the one hand, as stated, germ multiplication is avoided. When a Post-treatment of the treated water with ion exchangers is required, this can be done with the low-germ, degassed water can be operated in negative pressure. On the other hand, there is the advantage that the Use of chemicals and thus environmental pollution are avoided because, in addition to the conditioning chemicals, such as hydrochloric acid or sulfuric acid, no chemicals used for ongoing disinfection Need to become. The carbonic acid is removed mechanically by the degassing, without a Use of chemicals is required

The invention is based on various possible uses, which are shown schematically in the drawing are reproduced, explained in more detail Herein shows

F i g. 1 shows a plant for the production of pure water according to the invention, shown schematically in a flow diagram,

F i g. 2 a variant in which only one desalination system is connected downstream of the vacuum degasser,
F i g. 3 the schematic representation of a system in which the desalination system is connected upstream of the vacuum degasser and in which the degassed water is further treated in a subsequent desalination stage,

4 shows a system schematically in which the vacuum degasser is in front of a mixed bed desalination system is switched and further mixed-bed systems are connected downstream, with the pure water possibly via a Ultrafiltration stage is performed,

F i g. 5 a processing plant according to FIG. 4, which is followed by an entire ion exchange system and in which an ultrafiltration system is switched on in a downstream circuit.

With the in F i g. 1 schematically illustrated plant according to the invention low-germ pure water produces the raw water flows via a line 12 to a preheater 14, in which it is heated to a temperature of about 20 'C ³ O ^0. To condition the raw water, acid is then fed in via line 16 and the raw water is then filtered using a filter iS.A high-pressure pump 20 pumps the conditioned raw water into a reverse osmosis unit 22 at a pressure of either 28 bar or 70 bar. The permeate is extracted from the reverse osmosis unit 22 The concentrate from the reverse osmosis unit 22 is fed via a line 26 to the vacuum pump 28 of the vacuum degasser 24 and serves as sealing water for the vacuum pump. The water then flows through a line 30 to the sewer

So that the vacuum degasser 24 is closed to the outside air, the withdrawn air is drawn off in a container 32 Air 33 released to the atmosphere. A storage container (storage) 24a is attached to the vacuum degasser 24 in which the degassed water is temporarily stored. From the vacuum degasser 24 is via a Pressure booster pump 34 transfers the degassed water via line 23 to a second reverse osmosis system 36 The operating pressure of this unit 36 is either 28 bar or 70 bar. The interpretation of the Vacuum degasser 24 is expediently chosen so that a certain residual COr concentration is present in order to avoid a failure of carbonate hardness in the reverse osmosis unit 36.

The concentrate from the reverse osmosis unit 36 is fed into the raw water inlet 12 via a line 40 returned because it has a better quality than the raw water and thus improves the feed water quality This circuit is particularly economical, as the following example shows:

In an experiment carried out, the concentrate from the reverse osmosis unit had 36 (amount: 4911)

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. The admixing of the concentrate from the reverse osmosis unit 36 of the raw water salinity / reduced by approximately '4, wherein the salt passage connected thereto can be set lower also by this value. This means that there is no waste water.

The permeate (pure water) generated in this way is fed to the consumers via a ring line 42.

For a better understanding of this system, measurement results are given below which were taken from points A - G (cf.Fig. 1) as follows:

F permeate

Pressure (bar) 2 2 max. 3 22nd vacuum max. 3 max. 60 Water volume (l / h) 1171 1662 1247 415 1246 755 491 Salinity (mg / kg) 708 581.6 76.6 2100 76.6 4.2 167.9

The experiments were carried out at temperatures of 20 or 3O ⁰ C. It can be seen from the above list that in point B an increase in the acid dosage Sai / .gciiä! I5 takes place.

As a result of the admixture of the raw water with the concentrate from the reverse osmosis unit 36, there is an inflow rate of 1662 l / h in point B. From point C one can see that the salt content has been reduced to only 76.6 mg / kg. The amount of permeate is 1247 l / h, which corresponds to the difference between 415 l / h in point B and the amount of permeate in point C + inflow in point D. The composition at D shows a considerable increase in the salt content due to the concentration in the reverse osmosis stage 22. The concentrate is also under a pressure of approx. 22 bar or approx. 60 bar. depending on the inlet pressure. The water behind the vacuum degasser 24 at point E has the same composition as the permeate. The remaining CO2 quantity after the vacuum degasser is approx. 5–30 mg / 1, depending on the existing carbonate hardness. The water is practically oxygen-free.

The measurement results in point F relate to the permeate downstream of the reverse osmosis unit 36. The particularly low salt content of 4.2 mg / kg is noticeable here, compared to the salt content of the raw water of 708 mg / kg at point A or the mixed water in point B. of 581.6 mg / kg. The permeate in point F corresponds to the requirements of the pharmaceutical industry with regard to the residual ion concentration.

A considerable decrease in the number of germs has also been measured in the permeate. While with a assumed germ count in the feed to the reverse osmosis unit 22 of approx. 1430 germs per 100 ml the number of germs in pure water is only about 10 germs per 100 ml. The same behavior is shown in the TOC value, which is reduced from 43 mg / kg to 1.5 mg / kg.

The example shown shows that chemicals could largely be dispensed with. This has on the one hand, the advantage of considerable cost savings and a lower amount of coverage. Except an electrical power consumption practically no further resources are required. The repatriation of the concentrate from the reverse osmosis unit 36 or the use of the concentrate from the reverse osmosis unit 22 as sealing water in the vacuum pump 28 completes the overall system in such a way that no waste water is produced.

The system described above can, depending on the intended use and the composition of the raw water, with various post-cleaning and pre-cleaning stages can be combined, as the further exemplary embodiments show.

In the embodiment according to FIG. 2, a vacuum degasser 50 is connected upstream of a desalination stage labeled 62. The desalination stage can either consist of a reverse osmosis system or an ion exchange system. For economic or operational reasons, the vacuum degasser can with can be operated at higher temperatures of up to 60 °. This hot water is particularly useful in establishments Electronics desired The raw water fed in via line 53 is fed to a preheating stage 54 and thereby cools the warm, degassed water down to approx. 20 ° C. If the temperature of the feed water supplied to the vacuum degasser via line 51 is insufficient, heating steam is supplied via line 56 and via steam regulator 58 Condensate drains off via line 57. The cooled, degassed water from the vacuum degasser 50 is over a line 59 is fed to a desalination stage 62, in the event that it is a reverse osmosis unit if a high-pressure pump 61 is connected upstream, it is optionally available with a pressure of 28 or 70 bar operated.

If it is an ion exchange system, the operating pressure of the pressure _{booster pump 61 is only} 3_4 bar. The permeate (pure water) is taken from the ring line 63. The gases flowing out of the vacuum degasser 50 via the line 48, namely CO ₂ and O ₂ , are discharged via a vacuum pump 49

In FIG. 3 shows a Remwasseranlage in which the vacuum degasser is a desalination plant is connected upstream and in which the degassed water then in a post-desalination stage, which consists of a Reverse osmosis unit or ion exchangers can be treated further.

According to FIG. 3, the fed raw water through line 71 is initially in a reverse osmosis unit _{prior to} go jw _e; is _"e booster pump 68, vorentsalzt and then passes into a heat exchanger 77/79. In a heating stage 77, the water is warmed up in the manner described above, in that the water flowing in from the vacuum degasser 70 through the line 73 is re-cooled (at 79). By supplying heating steam via line 76 and steam control 74, the water to be treated is transferred to the operating temperature

20th 25th 30th 35 40 45 50 55 60

65

temperature for the vacuum degasser warmed up. Any condensate is discharged via line 75.

The water preheated in the heating stage 77 reaches the vacuum degasser 70 via the line 80. This stores degassed water 70a up to a certain degree of filling. It is provided that by means of a supply control via a line 81 and a control valve 82 maintain a certain degree of filling

The degassed water is fed via a pressure increasing pump 84 from the vacuum degasser 70 via a line 73 and the recooling stage 79 via a line 83 to a post-desalination stage 86. This can consist of a reverse osmosis unit or ion exchangers. The pressure booster pump 67 generates either 28 or 70 bar for a reverse osmosis unit, and an operating pressure ίο of 3-4 bar for the ion exchanger. If ion exchangers are used, the temperature of the degassed water in line 83 must not expediently ^{exceed 20 °} C., since the ion exchange is otherwise impaired. If reverse osmosis systems are used, the operating temperature is set to a maximum of 40 ° C. This results in a higher flux in the reverse osmosis system, which means that smaller membrane surfaces are required.

The water coming from the post-desalination stage 86 is schematically indicated at 89 via line 88 reproduced consumer points supplied. The delivery rate in the ring line 88 is fed via a Pressure holding valve 66 controlled so that a certain flow rate is always maintained in the ring line will. This flow rate is at least 1 m / s, so that no deposits and nucleation are formed can occur in the ring main.

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

returned. To prevent nucleation, the Nachenisaizuiigssiüic can still with a UUrafiUra-

system can be added. The gases flowing out of the vacuum degasser 70, namely COj and O2,

are discharged via a line 65 by means of a vacuum pump 78. With this circuit, too, how

indicated, be provided that the concentrate from the reverse osmosis unit 69 as a sealing water via a

Line 63 is passed into the vacuum pump 78 and discharged via an expansion tank 64.

In FIG. 4 shows a further advantageous circuit in which a vacuum degasser 102 is included

a complete demineralization system, which consists of cation and anion exchange stages, is that

Raw water entering through line 90 is passed through a UV irradiation system 91 and a

Cation and anion exchangers 92, 93 supplied. The water degassed in the vacuum degasser 102 is over

a pressure increasing pump 105 is fed to a mixed-bed ion exchange stage 104. The deionized water

From there, water enters a ring line 106, in which an ultrafiltration system 107 can also be switched on again. The pure water is supplied to consumer points 95.

The unused pure water is returned to the storage tank 102a of the vacuum degasser 10Z via the ring line 106. Pressure control is carried out via the valve 108 depending on the withdrawal.

With this circuit, too, a minimum value of the speed in the ring line 106 of approx. 1 m / s must be prescribed, which must not be undercut in order to maintain the sterility of the water.

This circuit can then be used to advantage when the DOC value in the inflow is low, e.g. B. S1 mg / kg The water therefore has only a low content of nutrients for the formation of nuclei. Existing systems of this type can be easily retrofitted by replacing the previously existing carbon dioxide trickle degasser with the vacuum degasser 102 described, so that the production of sterile pure water of the best quality is now possible with the existing systems. The use of disinfecting chemicals , combined with disruptive operational 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 plant.

The pure water degassed in the vacuum degasser 120 reaches the consumer points via a line 124

126, wherein an ultrafiltration stage 125 can be switched on in the ring line to remove residual particles from

Ion exchangers could be released. In the ring line 127 there is a control valve 128 which regulates the flow rate in such a way that it does not drop below the predetermined value of approx. 1 m / s

The unused pure water is returned to the receiver 120a of the vacuum degasser 120 I via the line 127. There is thus a constant circulation which counteracts a possible germ build-up

In this case, too, existing systems in which ion exchangers are in operation can easily be Way by connecting a vacuum degasser in an advantageous manner to be expanded as possible to get sterile water.

In addition 5 sheets of drawings

Claims (1)

Patent claims: is used. nenspeicner is cached. !, characterized in that the pure water is circulated to the Vaauument- gaserreturn.unnwnj ^ ^ ^^^ _{claims characterized by the fact} that the pure water A ^ sp'cÄ b venanren na ^ Ans ^ rach 1, characterized in that the degassing is adjusted so that a residual _{carbonic acid remains in order to maintain the carbonate hardness} 7. The method according to any one of the preceding claims, characterized in that the 'κ «» «**' for rinsing and regeneration of the ion exchangers upstream and / or downstream of the vacuum degasser "TvShref according to one of the preceding claims, characterized in that the raw water in one! «smbrantrennstufe desalinated and the concentrate of the vacuum pump of the vacuum degasser as ^ 'method according to one of the preceding claims, characterized in that the raw water in pre-desalinated in a first membrane separation stage, degassed, further desalinated in a second membrane separation stage as well as the concentrate of the first membrane separation stage of the vacuum pump of the vacuum degasser and the concentrate of the second membrane separation stage is returned to the feed of the first membrane separation stage ^TO ? 0. Ve ^ Xen according to one of the preceding claims, characterized in that the raw water is UV-irradiated and the pure water is ultrafiltered.