LU85532A1 - WATER DISINFECTION PROCESS - Google Patents

Description

WATER DISINFECTION PROCESS

The present invention relates to a method for disinfecting water.

It is applicable, on the one hand, to treat water which must or can be recirculated such as, for example, swimming pool or swimming pool water and, on the other hand, to treat waste water, or even effluents, which must not or cannot be recirculated and which are intended in particular for uses such as: air conditioning, water for domestic use, drinking water, etc.

The sterilization of swimming pool water is currently carried out almost exclusively using halogens or halogen compounds with an oxidizing character. Their role is twofold: they make it possible, on the one hand, to destroy the bacterial cells by oxidation and, on the other hand, to destroy the organic materials which can be used as food for bacteria. The power of a halogen or halogen compound can be expressed by its redox potential; the higher this is, the more energetic the halogen or halogen compound will be.

The halogens used are mainly chlorine and bromine or derivatives thereof.

In the particular case of sterilization of swimming pool water, the doses of halogen required vary between 0.5 to 3 PP® and are generally more than 1 ppm. j i - c. “

Lower halogen concentrations result in either a too slow bactericidal effect, or a bactericidal effect linked to a narrower spectrum of microorganisms, or both.

5 The use of these halogens or their derivatives encounters many problems on the technical and physiological plan, a) Technical problems: - Halogens are very volatile compounds. In the case of their use in an indoor swimming pool, these compounds cause rapid corrosion of the installations. In the case of their use in an open-air swimming pool, the losses in sterilizing product are very high and due in particular to their decomposition in sunlight and / or heat.

- The use of these products sometimes requires, moreover, a correction of the pK of the water (case of chlorine). The addition of a mineral acid is often required.

B) Physiological problems for humans:

These products, halogens in particular, give water uncomfortable organoleptic properties for humans by forming compounds that irritate the skin and mucous membranes. In particular, for chlorine and bromine, this discomfort begins to appear for concentrations of the order of 0.3 ppm.

Furthermore, a sterilization method is known which differs radically from conventional methods in that it does not use any chemical compound with an oxidizing effect.

- 3 -

In this other process, the sterilizing agent used consists of metallic ions of copper and · of silver introduced into the liquid aqueous phase by electrolysis. The elimination of the bare organic matter contained in said phase is ensured by the formation, upstream of a sand filter, of a copper microfloculate which traps the organic matter in solution and / or in suspension, and which promotes its retention and / or its adsorption on the sand filter.

The main advantages of this process are, on the one hand, that it does not give the treated water uncomfortable organoleptic properties for humans in the range of concentrations of sterilizing products used (copper: 0.5 to 1 , 5 ppm; silver: 1 to 10 ppb) 15 and, on the other hand, that it makes it possible to maintain a particularly clear and limpid water thanks to the process of elimination of the organic matter based on the formation of a microfloculate.

However, this process does not always make it possible to achieve a rate of decay of microorganisms as rapid as that obtained with chlorine (1 ppm) for concentrations of ions situated in the ranges of concentrations specified above. An increase in the concentration of silver ions makes it possible to obtain a rate of decay of germs identical to, or even greater than, that obtained with chlorine (1 ppm), but technical and physicochemical problems can, in certain cases cause use of the process, prevent or limit this increase.

The present invention relates to a process for disinfecting water making it possible to obtain a bactericidal effect equal to or even very much greater than that exerted by chlorine (element taken with reference to the concentration of 1 ppm), while using halogen concentrations 35 or derivatives thereof as low as 0.05 ppm or 50 ppb, or more than 20 times lower than the doses conventionally used. If

II

- k -

The water disinfection process according to the invention, in which copper and / or silver is added to the water to be treated, is essentially characterized by the fact that a halogen or a halogenated compound with oxidizing character in an amount less than that necessary to cause, alone, the desired bactericidal effect.

In a particular embodiment of the invention, an amount of halogen or a halogenated compound is used such that the water contains, more particularly, from about half to about one-fiftieth of the amount of halogen or halogenated compound necessary to cause, alone, the desired bactericidal effect.

As for the amounts of copper and / or silver added to the water in electrolytic form or in the form of water-soluble salts, advantageously 0 to 3 ppm of copper in ionic form and 0 to 100 ppb of silver are used.

The process according to the invention uses a remarkable synergistic effect between, on the one hand, metals such as copper and / or silver and, on the other hand, one or more conventional halogens or their derivatives, present at trace in the liquids to be treated.

In the process according to the invention, the bactericidal agents are copper and / or silver. These elements exert a bactericidal effect by irreversibly blocking vital sites located on the membrane and / or in the cytoplasm of microorganisms. The use of a halogen or derivative thereof, at very low concentrations,. 30 allows the membrane of microorganisms to be sufficiently disorganized and oxidized to cause an increase in the bactericidal effect of copper and / or silver by a factor of up to several tens of times, compared with the single use of these ions. The low concentrations of halogen or derivative thereof which it is necessary to use have no effect on microorganisms, if they are applied alone.

As halogens, chlorine, bromine, iodine, fluorine or mixtures thereof can be used in the process according to the invention.

As halogen derivatives, chlorinated, brominated, iodinated, fluorinated derivatives or derivatives containing several different halogen atoms can be used in the process according to the invention.

In the present specification, the expression "halogen derivatives" designates any mineral or organic halogenated derivative liberating, in aqueous medium, halogens or halogen derivatives of oxidizing nature.

As specific examples of chlorinated derivatives which can be used for the sterilization of water, there may be mentioned: 1) chlorine dioxide: CIO ^ 2) hypochlorous acid: HC10 3) sodium hypochlorites: KaOCl 20 of lithium: LiOCl calcium: Ca (0Cl) 2 4) chlorinated organic compounds: - chloramine T (formed by reaction of Cl ^ with toluene) 25 - chloramine D (formed by reaction of Cl ^ with ______ sulfonated paratoluene) CH ^ Cgl · ^ S02 NC12 - di- and tri-chloroisocyanurates.

In these compounds, chlorine can be replaced by the other halogens with the exception of halogen oxides, where several forms are often encountered.

There are of course many other halogenated compounds having an oxidizing power which can be used in the context of the present invention. Thus, the reaction of the halogens with ammonia, amines or proteins gives compounds which still exhibit oxidizing power. For example, monobromamine retains a high oxidizing power and a bactericidal activity equal to that of hypobromous acid.

EXAMPLES

5 1. Experimental protocol

The examples described below were carried out under the following conditions:

A strain of Streptococcus faecalis was used in these examples, because it appeared, in previous trials, that this microorganism is more resistant to the combined action of copper and silver ions than others microorganisms encountered in swimming pool waters, such as, for example, Echerischia coli, Staphylococcus aureus and Pseudomonas aeruginosa.

The microorganism strain used for all the examples, Streptococcus faecalis ATCC 6569, was cultivated in an inclined tube on a selective culture medium (Kanamycin Aesculin Azide Agar, OXOID CM 481) and subcultured for at least three consecutive days. once a day before being used for the experiment. One hour before the start of the experiment, the compound mineral solutions to be studied were prepared in sterile polypropylene bottles with a total volume of 500 ml, from the following aqueous mineral solutions: 1) CuSO4 5H20: 0, 1 mg Cu ++ ml "1 2) AgN03: 1 ug Ag + ml" 1 3) NaHCO ^: 30.5 mg HCO "ml" 1 4) Cl2 ï NaCIO solution at a concentration, 30 of 8 + 2% 5) I2 ! 0.1 mg I2 ml "(as KI ^).

The final volume of each compound solution was 250 ml. In each bottle, the concentration of buffer 3 bicarbonate was constant and equal to 10 M. This concentration makes it possible to maintain the pK of each solution - 7 - 8 ± 0.1 for the entire duration of the tests.

The bacterial cells contained in one or more culture tubes were then suspended in distilled water (25 to 50 ml) and stirred for 45 minutes on a shaking table (2 shakes per second) at 26 ° C. A given volume of this bacterial suspension was then added to each bottle of mineral solution.

These flasks were then incubated at 26 ° C with shaking (2 shakes per second) for the duration of the tests.

The count of the germs was carried out on each flask, after 0, 2, 4, 6 and 8 hours of incubation, by the method of successive dilution in test tube and incubation in Petri dish for 24 hours at 37 ° C. (Medium: 0X0ID CK 481).

2. Results

The experiments clearly demonstrate the synergy between copper and silver, a much greater synergy between copper and / or silver and elements of the class of halogens, such as chlorine and iodine.

The results of these experiments are presented in Table I.

25 For each experiment, we have included in this table the number of the experiment, the mineral composition of the solution, the concentration of microorganisms at time zero of the experiment, the decimal mortality rate, Λ K, (expressed in min) corresponding to the slope of the right line of a graph on which the time in minutes is placed on the abscissa and the percentage of germs remaining alive is placed on the ordinate on a logarithmic scale. Finally, for each experiment, we compared the mortality rate obtained with that achieved in the presence of a chlorine concentration of 1 ppm (Kn ^), rtci · - ί -

Table I: Declared mortality rate of the streptococcus strain ATCC 6569 as a function of the mineral composition of medium A. Elements taken separately

Composition no Conc. in E

in the middle / .____ germs E - (ppm) - a t = o EPé (10 ^ ml ') (10 J min') - Cl2 = 1 EXP AL 1,760 16.7 1.00 - Cl2 = 0.5 EXP AL 2 765 10.5 0.62 - Cl2 = 0.05 EXP AL 5 660 0.0 0.00 - Cu = 1 EXP AL A 265 1.6 0.09 - Cu = 2 EXP AL 5 755 2.0 0.12 - Ag = 0.01 EXP AL 6 127 1.4 0.08 - Ag = 0.04 EXP AL 7 612 6.3 0.50 - I2 = 1 EXP AL 8 2.8 11.1 0, 66 B. Items taken simultaneously

Composition d.j0 Conc. in K

eXüé; ience? e ™ eE „K - (ppm) * a t - o Kp r„ _ (10? ml'1) (IP "3 min" 1) - Cu = 1 EXP AL 5 360 4, 0 0.24

Ag = 0.01 - Cu = 1 EXP AL 10 882 4.0 0.24

Ag = 0.01 - Cu = 1 EXP AL 11 105 * 33.3 1.99

Ag = 0.05 Κπ, - = mortality rate in the presence of 1 ppm of chlorine.

lté x · \

Table I: Tarn: decimal this mortality of the StrsrjtOCO ^ U ^ E ATCC strain t θ ’"; "^ C ^ iCÎi-Or1 1b mineral composition of the medium (continued! B. Elements taken simultaneously (continued)

Composition T, 0 Conc. in K

medium K - (ppm) exp „_c„ a t = o KRf ^ (10 ^ ml ‘) (10 ^ min ') - Cu = 1 EXP AL 12 375 20.0 1.20

Cl2 = 0.10 * - Cu = 1 EXP AL 13 860 20.0 1.20

Cl2 = 0.10 - Ag = 0.01 EXP AL 14 140 33.3 1.99

Cl2 = 0.10 - Cu = 1 EXP AL 15 52 40.0 2.39 - 1 - Cu = 1 EXP AL 16 300 16.7 1.00 I2 = 0.5 - Cu = 1 EXP AL 17 395 9, 0 0.54

Ag = 0.01

Cl2 = 0.01 - Cu = 1 EXP AL 18 345 12.0 0.72

Ag = 0.01

Cl2 = 0.03 - Cu = 1 EXP AL 19 220 16.7 1.00

Ag = 0.01

Cl2 = 0.05 - Cu = 1 EXP AL 20 214 25.0 1.50

Ag = 0.01

Cl2 = 0.07 - Cu = 1 EXP AL 21 677 50.0 2.99

Ag = 0.01

Cl2 = 0.10 - Cu = 1 EXP AL 22 870 33.3 1.99

Ag = 0.01 i2 = 1 K Ref = mortality rate in the presence of 1 ppm of chlorine. i

Table IB compared to Table IA clearly shows a remarkable synergy between the use of metal ions and a halogen compared to the separate use of any of these elements or the use of these ions alone.

In other words, the process according to the invention makes it possible to obtain such a synergy, by using copper and / or silver with a very reduced amount of halogen. In the particular case where 10 chlorine is used as halogen, this quantity can be 20 times less than that commonly used.

3. Remarkable advantages of the process according to the invention - This process makes it possible to very greatly limit the use of halogens and conventional halogenated compounds, and to keep their concentration very clearly below the threshold at which organoleptic problems begin. to appear (0.3 ppm C ^).

- This process uses metal ions of copper and / or silver within the concentration limits accepted in European legislation applicable to drinking water or food.

At these levels, these elements are harmless to humans and do not cause any organoleptic discomfort. These metallic elements can be provided in the form of soluble salts or by an electrolysis process.

- As halogens and halogen derivatives are used at very low concentrations, the corrosion problems of installations are no longer present.

• - All halogenated products can be used in this process in synergy with copper and / or silver.

These oxidizing products are: halogens (chlorine, bromine, iodine, fluorine) and their derivatives.

- In the particular case of chlorine, the concentration range that can be used ranges from 0.01 to 0.5 ppm of 35 Cl2.

Claims (12)

1. A method of disinfecting water, in which copper and / or silver is added to the water to be treated, characterized in that a halogen or a halogenated compound having an oxidizing nature is also added thereto. amount less than that necessary to cause, alone, the desired bactericidal effect. 2. Method according to claim 1, characterized in that the water to be treated is water to be used in a swimming pool or swimming pool. 3. Method according to either of claims 1 and 2, characterized in that an amount of halogen or of a halogenated compound is used such that the water contains from approximately half to approximately one fiftieth of the amount of halogen or halogenated compound necessary to cause, alone, the desired bactericidal effect. 4. Method according to claim 3, characterized in that, in the case of swimming pool or swimming pool water, an amount of halogen or of a halogenated compound is used such that the water contains about 0.05 to 0.4 ppm halogen. 5. Method according to any one of the preceding claims, characterized in that approximately 0 to 3 ppm of copper in ionic form is used. . "6. Method according to any one of the preceding claims, characterized in that approximately 0 to 100 ppb of silver is used in ionic form. 7. Method according to any one of the preceding claims, characterized in that copper and / or silver are added in electrolytic form. 8. Method according to any one of claims 1 to 7, characterized in that copper and / or silver are added in the form of a water-soluble salt. 35 9, Process according to any one of the preceding claims, characterized in that approximately 1 ppm of copper and 0.10 ppm of chlorine are used. 1 "" φ - ΊΟ I £ _ - 10. Method according to any one of claims 1 to 6, characterized in that approximately 0.010 ppm of silver and 0.10 ppm of chlorine are used. 11. Method according to any one of claims 118, characterized in that approximately 1 pnm of copper, 0.01 ppm of silver and 0.05 to 0.10 ppm of chlorine are used. 12. Method according to any one of claims 1 to 8, characterized in that approximately 1 ppm Λ * of copper is used, from 0 to 0.01 ppm of silver and from 0.5 to 1 ppm of iodine . A • - * w