CH619432A5 - Process for producing drinking water and apparatus for carrying out the process - Google Patents

Description

The invention relates to a method and a device for producing drinking water and in particular for producing biologically safe, natural drinking water.

Treatment of domestic drinking water by passing the water through a bed of activated carbon impregnated with or containing oligodynamic silver

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or contains other bactericides adsorbed is known, see. e.g. U.S. Patents 2,595,290; 3,242,073.3,268,444; 3,585,130; and the references therein.

In addition to the state of the art according to the above-mentioned patents, NASA (= United States National Aeronautics and Space Administration) carried out the experiments explained below and constructed devices for the purpose of killing biological material and water in space vehicles with silver ions of viruses, as explained below.

NASA's first report, “Biocidal Effects of Silver, Contract NAS 9-9300, Final Technical Report,” February 1971, by Dean O. Cliver, Phi D, University of Wisconsin, reports on the biological material and virus-killing effects of silver ions in a very pure distilled or deionized water, and the bacteria affected here are not pathogenic bacteria as they occur in natural water. These studies showed that increased levels of silver ions reduce the kill time and the inhibitory effect of chlorides is mentioned. However, this report does not say about procedures for introducing silver ions into natural water using silver salt and silver metal, adsorbed and impregnated in activated carbon to achieve high values of silver release at the seasonal, customary water temperatures, as is done according to the invention.

A second NASA report entitled "Potable Water Bäctericide Agent Development", Contract NAS 9-912 104, Final Report 3097, July 1972, Chemtric Inc., deals with the development of a silver ion cleaning system that is designed to be a by-product of fuel cells, to be used in the orbiter program to treat waste water produced. A specific water analysis was carried out. A specific sequence of units was built up for various purposes:

A. Biological filter containing AgCl particles. This filter was designed to do this; to remove particulate matter and biological contaminants that would otherwise quickly contaminate the following system.

B. A filter made of activated carbon. A common activated carbon filter was used to remove bad taste, smells, colors and other contaminants that had not been removed by the biological filter.

C. A silver chloride acid. A column composed of crystals of silver chloride, distributed among glass beads, was used to meter the water with silver ions. At natural concentrations of 1.35 X 10-3 g / 1, the silver ion content was far above the amount specified by Cliver (first NASA report).

D. A water storage container. A pair of water storage containers were next in line. No obvious grand was given for the order of the containers at this point in the order. Obviously, however, the supply flow rate of approximately 3.81 / h (1 gallon per hour) required an intermediate storage location to deliver the product water at approximately 26.5 1 / h (7 gallons per hour). It should be noted that two containers (of undefined size) were used that were connected in parallel and not in series. However, the system was able to bypass the containers completely, and then there is no longer any connection with the holding time for a possibility of completely killing biological material.

E. A deionizing device. A deionization column was used to remove silver ions because the content was above the allowable 50 ppb (ppb = parts per billion). Apparently, no other silver removal facility was provided. The disadvantages of deionized water were seen to be offset by the need for drinking water.

F. A silver bromide column. The 5 deionized water (with almost zero silver content) was found to be prone to further biological contamination prior to use. Therefore, it was considered necessary to add additional silver - within the 50 ppb limit - to the water as the final stage of the process, io. A temperature gradient plot was provided that indicated that the silver bromide crystals released silver in the 50 ppb range when released the water was at normal room temperature. However, when the water temperature rose, silver ions were released in an increased amount. 15 In this second report (Chemtric Report), the temperature effect was only related to the water temperature.

In summary, it can be seen that this report deals with a specific situation and that units have been put into a system to meet a specific condition. At no point in the report was the general problem of natural water considered.

The third NASA report, entitled "Advanced Prototype Silver Ion Water Bäctericide System", Contract NAS 9-13 718, Final Report 3104, December 1974, Chemtric, Inc., 25 deals with a highly modified system designed for the treatment of water which is generated by the fuel cells selected for the orbiter program.

The quality of the water released from the selected fuel cells is much better than that of the waste water according to report 3097. Therefore, the system consists of a single, outer container with a small, inner container. The active function of the unit is twofold:

A) A "pre-screen" or pre-filter is provided to remove all particulate matter and organisms above 0.35

Remove 35 microns and 98% of the particulate materials with such a small size of 0.15 microns.

B) A mixing column of activated carbon (80%) and Silberbro-midgranulen (20%) is provided in order to adsorb small amounts of organic substances and between 40 and

Release 40 85 ppb silver ions into the filtrate.

The report contains a repetition of the relationship between water temperature and the release of silver ions. The solution chosen here is to interpose a heat exchanger between the fuel tank of the fuel cell and the cleaning unit. In other words, the water temperature is controlled as a control of silver release.

No new data are given in the report.

None of the above patents and reports do not report the problem of chlorides in water, thereby inhibiting the ability of silver salts adsorbed and impregnated on activated carbon to release silver ions.

The prior art methods for treating natural water and the associated devices do not take into account the fact that chlorides in natural water combine with silver ions to either form a silver chloride deposit which is not as effective as a biological killer like silver ions seems, or 6o the chlorides limit the solubility of silver ions from silver salts and metallic silver, which are impregnated and adsorbed on media from activated carbon. Furthermore, it was the teaching of the prior art to change the media from silver activated carbon in order to change the desired silver release for the purposes of killing biological material. The purpose of the invention is to remedy the disadvantages mentioned.

The method according to the invention is therefore known

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records that the steps of treating water by introducing silver ions above 50 [ig / 1 to the water to be treated, holding the treated water containing such silver ions for a sufficient period of time for the silver ions to act as a bactericide, and then includes reducing the silver ions in the water to 50 µg / L or less.

The invention is explained in more detail by means of exemplary embodiments and the drawing; in the drawing are:

Fig. La to le is a schematic representation of the inventive method;

1 shows a schematic elevation of an embodiment of a water treatment unit for carrying out the method according to the invention according to FIGS.

FIG. 2 is a cross-sectional view of the unit 10 shown in FIG. 1;

3 shows a top view of a schematic illustration of a second embodiment of a device for carrying out the method according to the invention;

FIG. 4 shows a schematic side elevation of the device according to FIG. 3;

Fig. 5 is a cross-sectional view of the unit 1 shown in Figs. 3 and 4.

La to le, the inventive method is shown schematically to produce a biologically safe drinking water from a source of natural water at ambient temperature, i.e. Water intended for drinking purposes, such as tap water, the pipe being connected to a domestic well or a commercial well or private or urban household water sources, as well as surface water contained in lakes or streams. Natural waters exclude untreated wastewater and / or industrial wastewater or processed wastewater and saline water.

In Fig. La, the natural water is sent to a treatment station of unit A. In unit A, silver ions, Ag +, are introduced in the introduced water in large quantities compared to the value of 50 p.g / 1, which is approved by the "Environmental Protection Agency Standard for Drinking Water". The content of Ag +, which has been found to be effective, is in the order of 600 to 1000 p.g / 1, whereby this value can be fallen short of or exceeded. The high Ag + water from unit A is held for a period of the order of 6 minutes for water with a bacterial content of E. coli up to 10,000 colony forming units (CFU) per 100 ml. Laboratory studies have shown the need for high silver levels for the rapid killing of E. coli. Such investigations were carried out in connection with the development of the method according to the invention or the device according to the invention.

After the water, which contains 600 to 1000 (ig silver ions per liter, was held in unit B, it is then treated in unit C to reduce the silver ion content to 50 [ig / 1 or less in order to meet the legal norms for silver ions in Meet drinking water.

Fig. Lb explains schematically a modification of the method according to Fig. La. In Fig. Lb, the unit A of Fig. La is replaced by two treatment stations or units AI and A2. Unit AI removes or significantly reduces the chlorides (Cl ~) in the introduced water to prevent the complexation of silver ions entering Unit A2 for the same purpose as previously indicated in connection with the description of Figure la was introduced. Although this is not shown in FIG. 1b, it should be noted that the outflowing water from unit A2 is further treated in unit B and unit C, as described above. The modified procedure according to

Fig. Lb is used to carry out a partial water treatment, in which high silver ion contents are given to the raw water introduced.

The method according to the invention is modified in FIG. 1 c to treat the water introduced in unit D with a mixed resin bed in order to partially deionize the water introduced before treatment in unit A according to FIG. 1 a.

Part of the water introduced is passed past the unit D io of the mixed resin bed in order to obtain the natural minerals present in the water introduced, which are desirable for taste and for health reasons. The outflowing water from unit D is completely deionized.

However, as shown in FIG. 1d, in which the water introduced has a high mineral content, the method according to the invention is modified to completely deionize part of the water introduced in unit D, and the remaining water supplied is removed which treats chlorides, sulfates and nitrates, ie treated for selective removal of anions. The combined, outflowing water from the unit AI and the unit D are then sent through the unit A, which contains a medium of activated carbon, which is impregnated with silver-25 salt and metallic silver. Unit A of FIG. 1d is identical to unit A of FIG. 1b.

A further stage of the process according to FIG. 1 is explained in FIG. 1, in which water with a high content of silver ions is treated in order to reduce the silver ion content to 30 50 (ig / 1 or less). The unit C of FIG. le is identical to the unit C in Fig. la.

In Fig. 1, 10 denotes an open-topped container in which the first stage of the process is carried out. In zone 1 of the container there is a bed of ion exchange resin 35 for removing chlorides from the water to be treated. A suitable material for this purpose is a bed made of ion exchange resin, in which chloride ions are removed from the introduced water without the pH and the anion content of the water being significantly changed. One way to accomplish this removal of chloride ions is to use an anion exchange resin in the bicarbonate form. An anion exchange resin in the bicarbonate form exchanges all anions (Cl ~ SOJ NOg, etc.) until the equilibrium 45 between the concentrations of all anions (Cl ~ SOj, NOj, HCOf, etc.) bound to functional groups of the resin, and their concentrations are set in the imported water.

The effectiveness and the capacity of a given resin for Cr removal down to the desired Cf concentration is determined by the exchange equilibrium constants, the kinetics of the exchange, the flow rate through the resin bed, the concentration of ions supplied, the temperature, etc. Any anion exchange resin in any anionic form other than the chloride form can be used to remove chloride ions from the water introduced, although some anions may also be very inefficient and not very practical for 60 Cl removal .

Resins suitable for this purpose are commercially available, e.g. a styrene-divinylbenzene resin in the bicarbonate form (commercial product Amberlite IRA410 from Röhm & Haas).

In zone 2 of stage 1 (FIG. 1) there is a bed consisting of 65 a composition of silver salt / silver salts, adsorbed and / or impregnated on activated carbon. Any silver salt or any combination of silver salts whose solubility product is such that the silver concentration obtained

I tion over 50% silver per liter can be used. The silver salt (s) is / are present in amounts approximately equal to 1% by weight of the activated carbon.

Reference numeral 12 denotes a container which is arranged below the container 10 to collect and store water which has passed through the stage 1.

A container 14 is provided, and its structure can be the same as that of container 10. In the container 14 above the zone 3 there is an open space for the absorption of water from the container 12. The water from the container 12 passes through the zone 3, which can be a bed of conventional activated carbon (for example Calgon filtersorb 200 »), but it advantageously consists of a medium made of« self-protected »activated carbon. As already described above, a bed or medium made of “self-protected” activated carbon consists of a composition of activated carbon that contains silver salt / silver salts adsorbed or impregnated on the coal. The following treatment zone, Zone 4, contains a bed of ion exchange resin for the selective removal of the silver ions to a concentration below 50 (ig / 1, based on the silver ion concentration supplied by Zone 2 of stage 1, ie above 800 (ig / 1. A method of concentration is provided by zone 2 of stage 1, ie above 800 (ig / 1. A method of targeting the removal of silver ions is to use an anion exchange resin in the chloride form. It is believed that Silver combines with this resin in such a way that the silver concentration in the outflowing water is dominated by the solubility product of silver chloride.Other anionic forms, whose solubility product with silver is sufficiently small to reduce the concentration of silver in the treated water to less than 50 μg / 1 can also be used to remove silver, although it is not general one is known, the anion exchange shark can also remove silver by chelation, see I.M. Abrams, N.A.CE. Meeting - Houston, Texas, October 8, 1974: Selective Re-moval of Heavy Metals from Wash Waters by Ion Exchange and Adsorbent Resins.

Cation exchange resins can also be used to selectively remove silver. With both types of resins, their shapes must be such that they do not negatively change the treated water. Although water ionization can be negatively changed by ion exchange, ion exchange is also a possible method for removing silver.

A suitable ion exchange resin for removing silver ions from water is a commercially available resin made of styrene-DVB in the chloride form (product Amberlite IRA 410 from Röhm & Haas). A self-protected medium following the resin for silver removal requires a silver salt or silver salts which release residual silver ions to the water passing through in an amount of less than 50 μg / l.

With the method described above, it is also possible to achieve silver removal from the water in zone 3 through the anion exchange resin.

Stage II can also be constructed in reverse to the arrangement described above. This means that Zone 3 may contain the ion exchange resin for silver ion removal and Zone 4 the self-protected activated carbon.

In operation, a lot of raw water, e.g. poured a glass into the open top of the container 10, which has sufficient space above zone 1 to hold this amount. When the water passes through Zone 1 due to gravity, an ion exchange takes place, which removes chlorides and bicarbonate ions are released into the water.

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there, so that the natural character of the water is maintained. The water treated in this way then passes through the activated carbon impregnated with oligodynamic silver in zone 2. Here the activated carbon adsorbs organic materials that may be present in the water, and the silver releases silver ions into the water, which act as a bactericide and virucide. The concentration of silver ions generated in the water in zone 2 is 600 to 1000 micrograms per liter ((ig / I), which is considerably more than the permissible statutory standard for drinking water (EPA standard), the 50 (ig / I) 1. At this concentration, the silver ions act very rapidly to kill bacteria and they also appear to kill some viruses in the water, however the virus kill rate is lower than the bacterial kill rate.

After passing through zone 2, the water is collected in the container 12, where it is stored for a period of time, e.g. 6 minutes or more, and then poured into the container 14. When gravity flows down through the zone 3 bed, an ion exchange takes place, which removes silver ions from the water, so that the concentration thereof is brought below the permissible value of 50 (ig / 1).

The water then passes through a final bed of self-protected activated carbon in zone 4 for the further adsorption of organic material that has not been adsorbed in zone 2.

Alternatively, the zone 3 bed may contain the self-protected activated carbon for adsorbing organic material, and the water may then pass through an ion exchange resin in zone 4 to remove silver ions to a level below 50 μg / l.

An actual container 20 is shown in FIG. 2, which corresponds to the container 10 of FIG. 1. As shown in the figure, it consists of an upper section 22 with an open top. At the bottom of the department 22 there is a grid 24 over a sieve 26 which forms the upper part of zone 1. Under this screen and above the grid 28 is a bed of ion exchange resin for removing chlorides, as previously described in connection with FIG. 1. Zone 2, which contains the bed of coal impregnated with silver, is located between the grid 28 and the lower grid 30. A strainer 32 lies under the grid 30 and over an outlet opening 34 which is equipped with a normally closed, manually operated valve 36.

An actual container, which corresponds to container 14 of FIG. 1, is constructed identically to container 20 of FIG. 2, but of course it each has a bed in zones 3 and 4 as described in connection with FIG. 1.

The device shown schematically in FIGS. 3 and 4 is intended for a continuous flow of water to be treated. The container 40 corresponds to zone 1 in the container 10 (FIG. 1), in which water is supplied under pressure to the upper part. After flowing through the ion exchange bed in container 40, the water emerges from the lower part and into the lower end of container 42, which corresponds to zone 2. From here the water passes through a series of containers 44A-44F which, however, correspond to the collection container 12 of Fig. 1, are of a relatively larger capacity to provide sufficient time for the silver ions to act on the flowing water within the containers.

From the container 44F, the water enters the top of a container 46, which corresponds to zone 3 in FIG. 1. After passing through the ion exchange bed in container 46 where excess silver ions are removed, the water flows into the bottom of a container 48 which is from zone 4 of

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Fig. 1 corresponds to one, which contains the bed of self-protected activated carbon. The water emerges from this last container, either for direct consumption or for storage.

As previously described, containers 46 and 48 may be switched so that the water passes through an ion exchange resin to remove the silver ions and then through the bed of self-protected activated carbon, as described in more detail in connection with FIG. 1 has been.

An actual container 50 is shown in cross section in FIG. 5, which corresponds to any of the containers 40, 42, 46 and 48 of FIG. 4. It consists of a cylinder 52, with threads at both ends, on which threaded caps 54 and 56 can be removably attached.

At the upper inlet end, a cup-shaped felt pack 58 and a similarly shaped sieve 60 are pressed against the inside of the cylinder 52 by a tube 62, which is provided with notches 64 for the passage of water from an inlet attachment 66 in the cap 54. The construction on the bottom part is similar, except that the felt package 68 is not provided with a central opening and also serves as a filter. As shown in FIG. 5, the bottom of the container 50 is connected to the bottom of a similar container 70, which corresponds to the container 42 in FIG. 4. As previously described, the construction of the containers corresponding to 46 and 48 in Figs. 3 and 4 is the same as that of container 50 in Fig. 5. The actual containers corresponding to 44A-44F in Fig. 4 are just hollow tanks. To achieve a hold time of at least 6 minutes, the total volume of containers 44A-44F 5 itself should be 41 (3 gallons) if the flow rate is 1.891 / min (QA gallon per minute).

Laboratory studies have shown that viruses are killed by silver at concentrations according to the invention for type 1 polio virus and echo virus type 7. The same '10 laboratory tests showed the effectiveness of silver as a bactericide for E. coli, Salmonella typhimurium, Shigella son-nei, Candida albicans and Pseudomonas aeruginosa. Airborne bacteria that have contaminated water, such as Streptococcus Beta Haemolytus and Staphylococcus au-15 reus, appear to be killed by silver at the concentrations used according to the invention. However, a hold time of 12 to 24 hours is required for the above-mentioned bacteria introduced from the air, in contrast to the hold time of 6 minutes for the first-mentioned bacteria. However, the effectiveness of silver at high concentrations on any form of bacteria and virus can be determined by simple tests.

Examination methods and tests for killing bacteria and viruses have been e.g. by J. Melnick and C. Wal-25 Iis, Baylor University, School of Medicine, Department of Epidemiology and Virology.

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2 sheets of drawings

Claims (23)

619 432 2nd PATENT CLAIMS 1. A method for the production of biologically safe drinking water, characterized in that it has the stages of treating water by introducing silver ions above 50 (ig / 1 to the water to be treated, keeping the treated water containing such silver ions for sufficient Period of time for the silver ions to act as a bactericide, and thereafter includes reducing the silver ions in the water to 50 (ig / 1 or less). 2. The method according to claim 1, characterized in that the step of holding the treated water containing silver ions is extended for a sufficient period of time for the silver ions to act as a virus-killing substance. 3. The method according to claim 1, characterized in that chloride ions in the water are removed therefrom before the step of introducing silver ions. 4. The method according to claim 3, characterized in that the chloride ions are removed by sending natural water through a bed of a chloride-removing anion exchange shark. 5. The method according to claim 4, characterized in that the anion exchange resin is regenerated in the bicarbonate form and that it supplies bicarbonate ions to the treated water in order to maintain the character of the treated water. 6. The method according to claim 1, characterized in that silver ions are introduced into natural water by passing the water to be treated through a medium containing a silver salt whose solubility product gives a silver ion concentration above 50 (ig / 1. 7. The method according to claim 6, characterized in that the medium is activated carbon. 8. The method according to claim 6, characterized in that the silver salt adsorbed on the activated carbon does not significantly reduce the adsorption capacity of the activated carbon bed, and that the silver salts, metallic silver and silver ions protect the carbon bed by themselves. 9. The method according to claim 1, characterized in that silver ions of the order of magnitude of 300 (ig / 1 and above 300 p.g / 1 are introduced. 10. The method according to claim 1, characterized in that a part of natural water is deionized while the other part of it is not treated, and both the deionized and the untreated portion are combined before the introduction of silver ions. 11. The method according to claim 1, characterized in that part of the water is deionized while the other part of the water is freed from chloride ions and that both parts are brought together before the introduction of silver ions. 12. The method according to claim 1, characterized in that the step of reducing the silver ions is carried out by removing silver ions with an anion resin, which is regenerated with an anion that forms a silver salt of low solubility and that with the anion resin connected is. 13. The method according to claim 12, characterized in that the anion resin is in the chloride form. 14. The method according to claim 13, characterized in that the shark for removing chloride ions and the resin for removing silver ions are protected by washing with silver salt while being regenerated to the bicarbonate form and the chloride form, respectively. 15. The apparatus for performing the method according to claim 1, characterized in that it comprises: a Container, an inlet for introducing water into the container, a device in the container for adding silver ions to the water above 50 pg / l, a device in the container for removing organics from the water, a device in the container for removing Silver ions from the water to reduce the silver ion content below 50 pg / l, the silver ions cleaning the organic matter removal device and supplying residual silver ions to bacteria in the water between the organic matter removal device and the organic matter removal device Reduction in silver ions located to kill. 16. The apparatus according to claim 15, characterized in that the means for adding silver ions and the means for removing organic materials consist of a composition of activated carbon, which has silver salts adsorbed and impregnated on the activated carbon. 17. The apparatus according to claim 15, characterized by a device in the container for removing anions from this water. 18. The apparatus according to claim 17, characterized in that the device for removing anions has a higher exchange potential than bicarbonate anions at their relative concentrations in the water. 19. The apparatus according to claim 17, characterized in that the device for removing anions has a higher exchange potential than bicarbonate anions, that a further treatment zone is present in the container device, in which further treatment zone the device for adding silver ions to the water and for removing the organic substances from the water are arranged and that the device has a higher anion exchange potential than chloride anions, 20. The apparatus according to claim 19, characterized in that it additionally comprises a mechanical filter device for removing suspended solids from natural water before the water is introduced into the container devices. 21. The apparatus according to claim 19, characterized in that it additionally comprises a second device for removing organic substances in the container devices for removing organic substances from the water after the silver ions have been removed therefrom. 22. The apparatus according to claim 17, characterized in that the device for removing anions from the water removes the anions which form complexes with silver ions, that the device for adding silver ions to the water adds the silver ions after the removal of these anions that there is means for removing silver ions from the water after sufficient time for the silver ions to act as a bacteria and / or virus killing substance, and means for further removal of organics from the water. 23. The apparatus according to claim 21, characterized in that the means for removing anions and the means for removing silver ions are themselves protected by washing with silver salt while they are being regenerated into the bicarbonate or chloride form.