BIOCIDE

Abstract: A biocidal composition for the treatment of water comprises a cationic polyquaternary ammonium biocide, e.g. an ionene halide, or a quaternary ammonium biocide or a quaternary ammonium biocide comprising a long chain alkyl group and three other groups selected from lower alkyl and aralkyl groups, together with a source of transition metal cations e.g. copper II cations and/or a biocide of the type containing a gem. bromonitro­ methylene group e.g. 2- bromo-2-nitropropane-1,3-diol.

Description: This invention relates to biocidal compositions for the treatment of water, and to methods for preventing microbial growth in water. When water is used or retained in an open environment where it is subject to contamination by microorganisms, maintaining a suitable degree of sterility can be a problem. For example, recirculating water in cooling towers tends to become fouled by algal growths and bacterial slimes. Swimming pools become contaminated with algae and then by potentially dangerous bacteria. Similarly, industrial and agricultural lagoons, process water from various industrial applications such as paper milling, and other recycled water, need to be treated to control microbiological growths. Various agents have been proposed, and are commonly used, for the control of algae. The most frequently used today are oxidative substances such as hydrogen peroxide, sodium hypo-chlorite, and quaternary ammonium compounds such as n-alkyl dimethylbenzylammonium chlorides and n-alkyl dimethyl ethylbenzylammonium chlorides and analogous compounds. These substances are used to prevent microbial growth: that is to say they are added to water which has already been cleaned and sterilized (e.g by filtration and chlorination), in order to maintain sterility. They are effective, typically at levels in the water of 10-100 ppm, although they do not necessarily provide a particularly wide spectrum of antimicrobial activity. It is also well known that cations of transition metals such as copper and cobalt have algaecidal properties. Copper is particularly noted in this respect but has little, if any, activity against bacteria. One problem with the use of copper salts is that they tend to break down under neutral or slightly basic conditions to yield a precipitate of hydrated copper II hydroxide. We have now discovered that a combination of transition metal cations, especially copper II cations, with a cationic polyquaternary ammonium biocidal compound or a quaternary ammonium biocide comprising one long chain alkyl group and three other groups selected from lower alkyl and aralkyl groups, has advantageous properties. In particular, the combination of the quaternary compound and the metal ions in a concentrated aqueous system provides a stabilized metal ion solution which does not precipitate on dilution in the water to be treated. It may be theorized that the combination comprises some form of complex, since characteristic colour changes occur, e.g. the formation of an intense deep blue colour in dilute aqueous solutions of the copper II complex. The result is a distinct stabilization of the metal ions. Thus, if copper sulphate (the blue pentahydrate) is dissolved in a concentrated aqueous solution of the quaternary ammonium compound, a clear common solution is formed. This solution can be added to the water, typically to give a quaternary compound level of 40 ppm and a copper level of 2.4 ppm without any precipitation of copper hydroxides or salts on dilution. The quaternary compound is a halide, especially a chloride, of the type comprising polymers based on quaternised imines. The compounds of choice are poly[hydroxyethylene(dimethylimino)β'-hydroxypropyl(dimethylimino)methylene-dichloride], hereinafter referred to as PHE, such as the product sold by ABM Chemicals Limited of Woodley, Stockport, Cheshire SK6 1PQ ; poly[2-hydroxyethylene(dimethylimino)ethylene-(dimethylimino)methylene dichloride]; and poly[oxyethylene(dimethylimino)ethylene(dimethylimino)ethylene dichloride]. Typically, the transition metal ion content in the mixture should be sufficient to give a level of about 0.5 to 3 ppm in the treated water when the quaternary compound is present in the water at about 30 to 50 ppm. The metal is advantageously copper, but may for example be zinc, chromium or tin. The concentrated mixture for addition to water can contain upto 50 or 60% of the quaternary compound and an equivalent amount of copper or other transition metal ions. We have found that the bactericidal activity of quaternary biocides in the presence of copper etc. can be enhanced by formulation with a biocide of the type comprising a carbon atom substituted by a halogen atom and a nitro group, e.g. cyclic compounds and also 2-bromo-2-nitropropane-1,3-diol, supplied under the brand names Myacide (regd. Trade Mark) by Boots Pure Drug Co., Nottingham and Bronopol and Bronidox by Henkel & Cie. These biocides have activity against a wider range of bacteria than quaternaries, and especially are active against pseudomonads. Myacide is usually used at a level of about 50-100 ppm. Surprisingly, we have now found that if Myacide or the like is formulated with a quaternary such as PHE so that at a dilution in water of the quaternary of about 20-30 ppm, the Myacide etc is present at about 0.5 to 5 ppm, the formulation is active against pseudomonads as well, even though the Myacide is present at levels far below those normally considered necessary. The two substances are mutually compatible, forming a stable co-solution concentrate and provide a powerful biocidal action in all water environments, especially pools and cooling towers. We therefore provide a biocidal composition for the treatment of water comprising a cationic polyquaternary ammonium biocide which is a polymer based on a quaternised imine halide, together with a source of transition metal cations and a biocide of the type containing a gem. halonitromethylene group, selected from 2-bromo-2-nitro-propane-1,3-diol and 5-bromo-5-nitro-1,3-dioxane and also a method of controlling microorganisms in water, using such a composition. Preferably the ratio by weight of the first biocide to the second biocide is from 50:1 to 10:1. Example 1 Microbiological Activity (1) Three samples were compared: Sample 1: % by weight PHE 83.0 2-bromo-2-nitro-propan-1, 3-diol (BNP) 2.5 CuS0₄ 7.0 4N HCl 0.5 Mains water 7.0 Sample 2: As Sample 1, but omitting the BNP Sample 3: As Sample 1, but omitting the copper salt Sample 4: As Sample 1, but replacing the BNP by 5-bromo-5-nitro-1,3-dioxan. Methods 1. Culture Preparation A 24 hour Tryptone Soya Agar (TSA) sloped culture of Pseudomonas aeruginosa NCTC 6750 was washed off using sterile distilled water (SDW) and diluted in SDW to approx. 10⁸ organisms per ml. 2. Kill Tests A range of dilutions of the test solutions were prepared in sterile standard World Health Organisation (WHO) Hard Water (see Appendix 1). At zero time P. aeruginosa inoculum was added to each dilution of each test solution to give approx. 10⁶ organisms per ml. A control of sterile standard WHO hard water was also included. The tests were stored at 22°C and sampled at 0 hours (control only), 24 hours, 48 hours and 72 hours. The number of viable bacteria was estimated using a pour plate technique (0.1% peptone water as diluent and TSA as growth medium). The pour plates were incubated at 30°C for 3 days, surviving colonies counted and the dilution giving a 99.99% reduction in the bacterial population for each contact time calculated. The test was carried out on two separate occasions. Results The number of surviving organisms for each test sample at each dilution and sampling time are shown in Tables 1 to 8. TEST 1 - Preliminary range finding test TEST 2 Calculations Linear regression was used to plot graphs of the log of number of colony forming units per ml. versus ppm of product. From these graphs the concentration of each product required, at each sampling time, to give 99.99% reduction in the bacterial population was determined. The values thus obtained for Test 1 and Test 2, and the corresponding dilution factors, are depicted in Tables 9 and 10. TEST 1 Product Contact time in hours Product required to give 99.99% reduction in bacterial numbers pm dilution Sample 1 24 6.3 1:158,730 48 7.6 1:132,450 72 10.1 1: 99,009 Sample 2 24 5.5 1:183,486 48 6.6 1:151,515 72 7.4 1:134,589 Sample 3 24 6.3 1:159,235 48 approx 12.0 1: 83,333 72 approx 15.5 1: 64,516 Sample 4 24 6.1 1:163,934 48 5.9 1:169,491 72 9.0 1:111,111 TEST 2 Product Contact time in hours Product required to give 99.99% reduction in bacterial numbers ppm dilution Sample 1 24 105.2 1: 9,505 48 44.5 1:22,471 72 24.0 1:41,666 Sample 2 24 60.5 1:16,528 48 40.5 1:24,691 72 37.5 1:26,666 Sample 3 24 74.5 1:13,422 48 46.0 1:21,739 72 28.0 1:35,714 Sample 4 24 28.5 1:35,087 48 31 .5 1:31 ,746 72 28.5 1:35,087

Claims: A biocidal composition for the treatment of water comprising a cationic polyquaternary ammonium biocide which is a polymer based on a quaternised imine halide, together with a source of transition metal cations and a biocide of the type containing a gem. halonitromethylene group, selected from 2-bromo-2-nitro-propane-1,3-diol and 5-bromo-5-nitro-1,3-dioxane. A biocidal composition according to claim 1, in which the transition metal is copper II. A biocidal composition according to claim 1 or 2 in which the quaternary compound is poly[hydroxethylene (dimethylimino) β'-hydroxypropyl(dimethylimino)-methylene dichloride]. A biocidal composition accoridng to any of claims 1 to 3 in which the ratio by weight of the first biocide to the second biocide is from 50:1 to 10:1. A method of controlling microorganisms in water by application thereto of a composition according to any of claims 1 to 4.

Inventors: STAINER, PHILIP JOHN
Applicants: ADVANCED CHEMICAL PRODUCTS LIMITED
Application year: 1988
Main classification: A01N33
IPC codes: A01N59, A01N33, C02F1