EP1018874A1

EP1018874A1 - Water treatment with hydrogen peroxide and a polyquaternary ammonium stabilizer

Info

Publication number: EP1018874A1
Application number: EP96921228A
Authority: EP
Inventors: Geaffrey A. Brown; Mary L. Lines; James J. Miller
Original assignee: Bio Lab Inc
Current assignee: Bio Lab Inc
Priority date: 1995-06-07
Filing date: 1996-05-30
Publication date: 2000-07-19
Also published as: ZA964767B; AR002397A1; AU6249996A; EP1018874A4; JP2001519706A; CA2223704A1; BR9612623A; WO1996039825A1

Abstract

A method of treating water by adding hydrogen peroxide and a polyquaternary ammonium compound to the water. The hydrogen peroxide and the polyquaternary ammonium compound are independently added to the water so that the appropriate concentration of each component may be maintained in the water.

Description

WATER TREATMENT WITH HYDROGEN PEROXIDE AND A POLYQUATERNARY AMMONIUM STABILIZER

FIELD OF THE INVENTION

The present invention relates generally to methods of treating water, and more particularly to a method of treating water with hydrogen peroxide and a polyquatemary ammonium stabilizer.

BACKGROUND TO THE INVENTION

It is well established that the water used in swimming pools, spas, hot tubs, cooling towers, etc., rapidly acquires a variety of microorganisms that may be harmful to human health. In addition, these microbes may damage the structural materials, equipment, etc., which contact the water, and may compromise industrial processes which use the water. Accordingly, biological fouling is a significant problem to the regulated water industry, resulting in much attention being paid to the development of agents to control microbial growth in aqueous milieu.

Biocides traditionally used to control microbial growth include chlorine, bromine, biguanide salts, peroxy compounds, ozone and quaternary ammonium compositions. Of these, chlorine has long been the dominant disinfectant, although the disadvantages of chlorine have led to a continued search for other disinfecting products. For example, although chlorine is highly effective it must be applied frequently to maintain its efficacy, and readily forms irritating chloramines and/or trihalomethanes . At high levels, chlorine can harm pool surfaces and equipment.

Although chlorine and bromine levels must be maintained at levels of 1-3 pp (as Cl_), periodic superchlorination is often required to assure microbiological control and adequate water quality. The environmental hazards associated with chlorine and the shortcomings associated with mechanical feeders underscores the need for a simplified, non-halogen alternative for water treatment.

As previously indicated, peroxy compounds are known to be effective sanitizers under certain conditions. One problem associated with the use of these compounds however, is that peroxides such as hydrogen peroxide are not effective as a stand alone sanitizers except when used at relatively high concentrations (e.g . , 200 ppm or higher) . Unfortunately, as the peroxide concentration increases so does the likelihood of injury or discomfort to swimmers and spa bathers. When used in recreational waters, hydrogen peroxide suppliers usually treat their products with compounds such as phosphates in order to stabilize the concentrated solutions. However, these stabilizers are not designed to affect * stability once the product has been applied to a body of water and diluted. Hence, an additional stabilizer is needed to protect and enhance the peroxide, post-application.

As to other sanitizers, polyquatemary ammonium compounds have been used in water treatment with some success. Monomeric quaternary ammonium compounds have also been used in water treatment, and generally are effective biocides. However, when monomeric quaternary ammonium compounds are used as primary sanitizers high concentrations (25-75 ppm) are necessary. Unlike polyquats, monomeric quats tend to produce substantial foam even at low concentrations (e_..g., ^r> PPm) • Foaming will only be exacerbated at levels of 25 to 75 ppm.

It can be seen from the foregoing that a need continues to exist for methods of treating water with non-halogen sanitizers such as hydrogen peroxide and a polyquatemary ammonium compounds. The present invention addresses this need. SUMMARY OF THE INVENTION

Briefly describing the present invention there is provided a method of treating water by adding hydrogen peroxide and a polyquate ary ammonium compound to the water. The hydrogen peroxide and the polyquate ary ammonium compound are independently added to the water in amounts effective to maintain in the water a balanced sanitizing solution.

One object of the present invention is to provide an improved method of sanitizing water with dilute hydrogen peroxide.

Another object of the present invention is to provide a method of adding flocculant and clarifying properties to dilute hydrogen peroxide solutions. Another object of the present invention is to provide a method of reducing the amount of hydrogen peroxide necessary to sanitize recreational waters.

Another object of the present invention is to provide a method of increasing the half-life of hydrogen peroxide used to sanitize recreational waters.

Further objects and advantages of the present invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of the half-life estimations of H O with and without PDED.

FIG. 2 is a graph of the half-life estimations of H_0- with and without Q6/6.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to preferred embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the preferred embodiments, and such further applications of the principles of the invention as described herein being contemplated as would normally occur to one skilled in the art to which the invention pertains.

The present invention uses dilute hydrogen peroxide as a sanitizer along with a polyquatemary ammonium stabilizer for treating regulated waters. The stabilizer allows ^H _o ^{0 to} remain biocidally active for longer periods of time and enhances its overall efficacy. The sanitizer and stabilizer can be added separately or blended together for a single, slug application. The ideal dose would comprise 1-2 gallons of the active ingredients (blended or separate) to maintain 20,000 gallons of regulated water every two weeks. The ability to effectively treat such a large volume of water without mechanical feeders and with such an infrequent dosing schedule is an unexpected advantage of the invention.

A variety of polyquatemary ammonium compounds may be used in the present invention, including poly(hexamethylarnmoniu ) chloride ("Q6/6"), poly[oxyethylene-(dimethylimino) ethylene-(dimethylimino) ethylene dichloride] ("PDED"), dodecamethylenedimethylimino chloride ("Q6/12") and 1,3-diazo-2 , -cyclopentadiene with l-chloro-2,3-epoxypropane ("IPCP"). These and other polyquatemary ammonium compounds are available from common commercial sources.

Preferably the hydrogen peroxide and the polyquatemary ammonium compound are added independently so that appropriate concentrations of each composition may be maintained in the water. Appropriate concentrations are generally determined by testing the treated water. Then, the appropriate amount of either composition may be added. This technique provides the additional benefit of allowing the two components to be stored and handled separately.

In regular use, the water should contain between 5 and 40 ppm H„0_ and a polyquatemary ammonium stabilizer concentration between 1 and 20 ppm. In order to treat 20,000 gallons, a concentrated, blended product should contain between 10% and 80% H O and 2% to 40% polyquat per one gallon container. When applied as separate products, the relative concentrations of H„0_ and polyquat should remain the same, using either gallon or half gallon containers.

As previously suggested, the present invention provides simple, albeit novel, improvements to the existing art. First, the invention precludes the need to purchase a mechanical device to apply the products. The cost of equipment and upkeep is thereby eliminated. Second, the invention is flexible in that the ingredients can be packaged as a shelf stable blend or in separate containers. Third, the schedule of product additions can be tailored to meet the needs of individual pool owners. For example, more or less stabilizer may be required in certain cases and can be added without adding unnecessary quantities of the other composition. Fourth, abandoning the mechanical device will make the technology more practical for consumers treating regulated waters. Fifth, this system melds the antimicrobial and aesthetic benefits of monomeric and polymeric quaternary ammonium compounds. That is, a biocidally efficacious system that produces only small amounts of foam, if any. Sixth, the invention is superior to the polybiguanide system in that the components can be blended in one container.

In one aspect of the invention the polyquatemary ammonium compounds act as flocculants. Flocculants are chemicals that are used to aggregate suspended solids from liquids, thereby facilitating their separation via precipitation or filtration. Consistent with this ability, polyquats are capable of cell adhesion and aggregation.

Studies performed in pools with swimmers have shown that polyquats such as Q6/6 are unable to sanitize water when used alone. In such cases bacterial densities were as high as 1 x 10 5 per milliliter. Despite high bacterial populations, water clarity remained excellent. Table 1 displays a brief excerpt from the in-use pool study.

Table 1. Bacterial Densities Versus Water Clarity.

¹ NTU - Nephelo etric Turbidity Units.

A priori, one might expect the relationship between turbidity and bacterial density to be directly proportional. However, in the case where the bacterial population was as high as 126,000/ml water clarity remained excellent. A turbidity value below 0.32 NTU is considered clear. At 0.32 NTU or higher water is hazy or cloudy.

Based on literature and on our corroborating observations, it appears that the bacteria remained completely viable, but in tight aggregates. This would explain the excellent clarity and the high bacterial densities . Significant, non-lethal alterations of the bacterial membrane might occur during the adhesion/aggregation process. These modifications could conceivably make an oxidizer such as H_0_ more accessible to critical areas of the cell membrane. In essence, the polyquat acts as an adjuvant or potentiator for H_0_ . As a result, the kinetics of bacterial kill would be improved as well as the overall efficiency. This would lead to significantly faster kill rates and a decrease in the amount of H_0„ needed to sanitize the water.

Reference will now be made to specific examples using the processes described above. It is to be understood that the examples are provided to more completely describe preferred embodiments, and that no limitation to the scope of the invention is intended thereby.

EXAMPLE 1 In order to test the ability of various polyquats to stabilize H_0_ , five, 10 gallon aquariums were filled with water and adjusted to the following parameters: about 200 ppm calcium hardness, 120 ppm alkalinity and pH 7.4.

Each aquarium was dosed with 10 ppm of a different polyquat consisting of Q6/6, PDED, Q6/12 or IPCP. Hydrogen peroxide was added (27.5 ppm) to the tanks containing the polyquats and to a control tank that contained no polyquat. Each tank was challenged daily with 25 ml of bacterial suspension (about 10 8 to 109 organisms) containing P. aeruqinosa. E. coli , and S. aureus . These are some of the major bacteria which can be recovered from recreational and industrial waters. Peroxide and polyquat concentrations were monitored after about 24 hours and recorded in Tables 2-6.

Moreover, samples were removed 30 minutes after inoculation, treated with a neutralizer and plated onto nutrient agar to determine the number of viable bacteria. Table 2. H2O2 as a Stand Alone Sanitizer

TPC - Total heterotrophic Plate Count (viable aerobic bacteria) expressed as colony forming units per ml. Hydrogen Peroxide (about 27.5 ppm) was added to each tank at the end of Day 4.

Table 3. Effect of PDED on H2O2 Stability and Efficacy.

Table 4. Effect of IPCP on H₂0₂ Stability and Efficacy.

Table 5. Effect of Q6/12 on H₂0₂ Stability and Efficacy.

Table 6. Effect of Q6/6 on H₂0 Stability and Efficacy.

The data presented in Tables 2-6 strongly suggests that the class of molecules known as polyquate ary ammonium compounds has the ability to stabilize and increase the efficacy of hydrogen peroxide. That is to say, H_0„ was more persistent in the presence of either of the polyquats (stability enhanced) and bacterial counts were greatly reduced (efficacy enhanced) .

EXAMPLE 2 Since surprising trends were observed during the aquarium trials, further experiments were performed in outdoor pools. The efficacy of a combination of H_0_ with PDED and ^H ₂°₂ ^{alone was} tested in 5,000 pools with Hayward S-166T sand filters. Using standard pool chemicals, each pool was adjusted to about 120 ppm alkalinity, 200 ppm calcium hardness and pH 7.4. In addition to receiving microbial inoculations from the environment, each pool was treated with bacterial suspensions (about 10 to 10 organisms) containing P. aeruginosa, E. coli , and S. aureus . Unlike the aquarium studies, the pools were subject to UV radiation from the sun.

Tables 7 and 8 summarize the results. Table 7 demonstrates the inability of H_0- to control bacterial growth, even at high concentrations. In addition, previous research has demonstrated that PDED like H„0_ , is not an effective sanitizer when used alone (data not shown) . By contrast, Table 8 demonstrates the ability of polyquats to enhance H_0_, rendering it more efficacious. While PDED has demonstrated antimicrobial synergy with oxidizers, these data indicate that polyquats can also stabilize and extend peroxide half life in the use dilutions.

Table 7. H2O2 as a Stand Alone Sanitizer

Table 8. Stabilization of H2O2 with PDED,

The data in Tables 7 and 8 were graphed to show the trends of H O- disappearance (FIG. 1). In addition, the data were subjected to linear regression analysis. Table 9 was prepared using the statistics generated during linear regression and shows that PDED was able to extend the half life of H-O- , even when the PDED concentration was as low as 3 ppm. Using the data, we can extrapolate that H_0_ alone would last approximately 10.7 days, but would last 14.2 when stabilized with PDED.

Table 9. Half Life of H₂0₂ with and without PDED,

H₂Q₂ HALF LIFE (DAYS) _5_._35 7.1

EXAMPLE 3 The experiment summarized in Example 3 is identical to Example 2, except that Q6/6 was substituted for PDED (Tables 10 and 11) . Q6/6 alone is not an effective sanitizer in regulated waters (data not shown) . As was the case with PDED, Q6/6 stabilized and enhanced the efficacy of H„0- . Hydrogen peroxide alone had a shorter half life and was not an effective bactericide even at the highest levels ^"tested. Linear regression is compiled in Table 12. FIG. 2 graphically shows the difference in half life. Based on the regression, we can extrapolate that H_0_ alone would have lasted for about 9 days, but would have lasted for almor.t 1 f, days when stabilized with Q6/6. Table 10. H2O2 as a Stand Alone Sanitizer,

Table 11. Stabilization of II₂0₂ with Q6/6

Table 12. Half Life of H₂0₂ with and without PDED.

The data clearly show that a water treatment system based solely on H_0- and a polyquatemary ammonium compound can achieve and maintain acceptable water quality. The fact t ai one gallon of blended material miqht be used to treat up tυ 20,000 gallons for up to two weeks constitutes a vast improvement over the existing polybiguanide technology. Recreational waters sanitized with biguanide usually require the staggered addition of three distinct products:

Biguanide, hydrogen peroxide and ancillary algicides. Biguanide is usually added every 10 to 14 days, peroxide is added about every 20 to 30 days and algicides are added weekly or as needed. The present method greatly simplifies the biguanide art in that the products are added at the same time and may be combined into one bottle. In essence, product application is synchronized and one (blended) or two (separate) products are used instead of three.

Furthermore, since the method disclosed precludes the use of mechanized feeders, it offers tenable benefits for individuals involved in treating regulated waters. This method allows for a substantial cost savings, the elimination of feeder problems and maintenance and improved efficacy due to the inherent flexibility of applying bottled products. While the invention has been described in detail in the foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

Claims

CLAIMSWhat is claimed is:

1. A method of treating water, comprising adding to the water:

(a) a first composition comprising hydrogen peroxide; and (b) a second composition comprising a polyquatemary ammonium compound; wherein said first and second compositions are independently added to the water so that the appropriate concentration of each component may be maintained in the water.

2. The method of claim 1 wherein said first composition consists essentially of hydrogen peroxide.

3. The method of claim 1 wherein said second composition consists essentially of a polyquatemary ammonium compound.

4. The method of claim 1 wherein said second composition comprises poly(hexamethylammonium) chloride ("Q6/6").

5. The method of claim 1 wherein said second composition comprises poly[oxyethylene-(dimethylimino) ethylene-(dimethylimino) ethylene dichloride] ("PDED").

6. The method of claim 1 wherein said second composition comprises dodecarnethylenedimethylimino chloride ("Q6/12") .

7. The method of claim 1 wherein said second composition comprises 1,3-diazo-2,4-cyclopentadiene with l-chloro-2 ,3-epoxypropane ("IPCP") .

8. The method of claim 1 wherein said second composition comprises two or more polyquatemary ammonium compounds .

9. The method of claim 1 wherein said first composition and said second composition are added separately to the water.

10. The method of claim 1 wherein said first composition and said second composition are added to water which is essentially free of other sanitizing agents.

11. The method of claim 1 wherein said first composition and said second composition are added to the water in biweekly additions.

12. The method of claim 1 wherein said first composition and said second composition are added to the water in weekly additions.

13. The method of claim 1 wherein said first composition and said second composition are added to the water in monthly additions .