EP0888250A4

EP0888250A4 - Water treatment method

Info

Publication number: EP0888250A4
Application number: EP97916788A
Authority: EP
Inventors: Geoffrey A Brown; Mary L Lines; James J Miller
Original assignee: Bio Lab Inc
Current assignee: Bio Lab Inc
Priority date: 1996-03-18
Filing date: 1997-03-18
Publication date: 1999-07-21
Also published as: AR009944A1; NZ331893A; CA2249701A1; WO1997034835A1; EP0888250A1; ZA972298B; AU2531997A; BR9708098A

Abstract

A method of treating water by adding to the water a shelf-stable composition of hydrogen peroxide and a polyquaternary ammonium compound, followed by intermittent treatment with chlorine-, bromine- or oxygen-releasing compounds.

Description

WATER TREATMENT METHOD

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, polyquatemary ammonium compounds and chlorine.

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 ppm (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.α. , 5 ppm). Foaming will only be exacerbated at levels of 25 to 75 ppm.

When regulated waters are treated with H₂0_, the system can only remain biocidally effective as long as H_0₂ remains available for disinfection. If levels of organic materials accumulate, the half life of peroxide decreases with a corresponding decrease in antimicrobial efficacy.

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, with and without the additional use of chlorine. The present invention addresses this need.

SUMMARY OF THE INVENTION

Briefly describing the present invention there is provided a method of treating water by using strong oxidizing agents such as calcium hypochlorite, lithium hypochlorite, activated sodium bromide, sodium dichloroisocyanurate, trichloroisocyanurate, sodium hypochlorite, potassium peroxymonopersulfate, etc. to shock regulated waters treated with hydrogen peroxide (H-,0-) and polyquatemary ammonium compounds (polyquats) . Periodic superchlorination or superoxygentation can assist these regulated waters in maintaining acceptable water quality.

In another aspect of the 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 polyquatemary ammonium compound are independently added to the water in amounts effective to maintain in the water a balanced sanitizing solution.

One object of the invention is to provide a method of enhancing the quality of regulated waters using polyquatemary amonium compounds, hydrogen peroxide and regular shocks with dry or liquid oxidizers.

Another 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 with and without PDED. FIG. 2 is a graph of the half-life estimations of

H-O 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.

In one preferred embodiment of the present invention strong oxidizing agents such as calcium hypochlorite, lithium hypochlorite, activated sodium bromide, sodium dichloroisocyanurate, trichloroisocyanurate, sodium hypochlorite, potassium peroxymonopersulfate, etc. are used to regenerate regulated waters treated with hydrogen peroxide (H_0_?) and polyquatemary ammonium compounds (polyquats) . The addition of these materials destroys organic materials and restores H_0_ half life to near its original level, effectively renewing the system to its original potency.

As to the specifics of the claimed method, only small amounts of unstabilized chlorine-, bromine- or oxygen- releasing compounds are needed. Moreover, the chlorine-, bromine- or oxygen- releasing compounds need only be applied on an intermittent basis in order to regenerate the water.

Preferably, a stable solution of H„0„ and a polyquat) or polyquats) is added to a body of water to give concentrations of H₂0₂ ranging from 1-100 ppm and a polyquat concentration ranging from 0.1-30 ppm. Preferably, the H O level ranges from 10-30 ppm and the polyquat level ranges from 1-5 ppm. The solution is preferably applied at specified intervals (weekly, bi-weekly or monthly) . At certain intervals (weekly, bi-weekly or monthly), superchlorination or superoxygenating shock treatment is applied prior to adding the H₂0₂ polyquat solutions. After several hours (if using unstabilized shock treatments), it is preferred to resume the treatment program with another H O polyquat application.

Unstabilized chlorine products such as calcium hypochlorite, lithium hypochlorite are the preferred shocking agents because the resulting chlorine residuals will quickly be degraded by Ultraviolet radiation from the sun. Hence, although periodic superchlorination may be necessary for the system to maintain optimal performance, active chlorine will actually be present for relatively brief periods of time. The same would be true for activated sodium bromine. Bromine (as sodium bromide) can be activated by hypochlorous acid generated from bleach or dry oxidizers in water. Maintaining excellent water quality with such infrequent use of a halogen shock treatment is surprising.

Stabilized chlorinating agents using a cyanuric acid carrier (UV stabilizer) would be as effective as unstabilized chlorine, but oxidizing chlorine would remain active for longer periods of time. Residual levels of chlorine might cause irritation to swimmers or might degrade H₂0_. Potassium onoperioxytsulfate is a non-chlorine alternative for persons desiring to avoid the use of halogens.

Another aspect of the present invention uses dilute hydrogen peroxide as a sanitizer along with a polyquatemary ammonium stabilizer for treating regulated waters. The stabilizer allows H₂0₂ 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 various aspects of the present invention, including poly(hexamethylammoniu ) chloride ("Q6/6"), pol [oxyethylene-(dimethylimino) ethylene-(dimethylimino) ethylene dichloride] ("PDED"), dodecamethylenedimethylimino chloride ("Q6/12") and 1,3-diazo-2, -cyclopentadiene with l-chloro-2, 3-epoxyproρane ("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% H₂0₂ and 2% to 40% polyquat per' >ne gallon container. When applied as separate products, the relative concentrations of H₂0_ and polyquat should remain the same, using either gallon or half gallon containers.

As previously suggested, the various aspects of the present invention provide 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

5 as 1 x 10 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.

Q6/6 CONCENTRATION BACTERIAL DENSITY TURBIDITY¹ fPPM) PER ML (NTU)

6 12.350 0.22

5 126.000 0.25

5 24.300 0.17

3 4.130 0.19

3 8.500 0.29

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 H₂0 . 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 H₂0₂ 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 H₂0₂, 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

Q Q suspension (about 10 to 10 organisms) containing £. aeruginosa. E. coli . and £. 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.

DAY H₂0₂ PPM TPC¹

1 34 20.350

2 11.9 692.000

3 4.25 752.000

₄2 1.7 1 .776.000

5 20.4 91.000

6 7.65 2. .080.000

1.7 2,246,QQQ 1 TPC - Total heterotrophic Plate Count (viable aerobic bacteria) expressed as colony forming units per ml.

² 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,

DAY H₂0 PPM TPC

1 28.9 40

2 12.8 109

3 5.95 970

4 3.4 500

5 24.7 220

6 11.9 3.000

7 8.5 4,950

Table 4. Effect of IPCP on H 0₂ Stability and Efficacy.

DAY H₂0₂ PPM TPC

1 32.3 0

2 13.6 0

3 6.8 0

4 2.6 1

5 24.7 2

6 17.85 3

7 7.65 38

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

DAY H₂0₂ PPM TPC

1 32.3 0

2 12.8 0

3 7.7 0

4 3.4 11

5 27.2 0

6 22.1 5

7 10.2 7 Table 6. Effect of Q6/6 on H₂0 Stability and Efficacy

DAY H₂0₂ PPM TPC

1 31.5 3.040

2 12.8 475

3 6.0 1.070

4 2.6 11.750

5 19.6 23

6 16.2 2.000

7 6.8 4,800

The data presented in Tables 2-6 strongly suggests that the class of molecules known as polyquatemary ammonium compounds has the ability to stabilize and increase the efficacy of hydrogen peroxide. That is to say, H_0₂ 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 H₂0₂ 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 £. aeruginosa . E. coli . and £>. 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 H₂0₂ to control bacterial growth, even at high concentrations. In addition, previous research has demonstrated that PDED like H O , 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.

DAY H₂0₂ PDED PM CFU/ML

1 26.35 _

2 23.8 —. 330

3 23.0 — 900

4 17.0 _ 4.900

7 5.1 _ 51.000

8 0 _ 47,000

Table 8. Stabilization of H₂O2 with PDED.

DAY H₂0₂ PDED PM CFU/ML

1 26.35 10 0

2 24.65 10 0

3 23.8 10 3

4 18.7 7 0

7 11.9 4 445

8 10.2 3 205

The data in Tables 7 and 8 were graphed to show the trends of H_0₂ 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_0„, even when the PDED concentration was as low as 3 ppm. Using the data, we can extrapolate that ^HH₂₂00_? aalloonnee wwoouulldd llaasstt aapppprrooxxiimmaatteellyy 10.7 days, but would last 14.2 when stabilized with PDED, Table 9. Half Life of H 0₂ with and without PDED,

STATISTICS H₂0₂ H₂0₂ + PDED

Y-INTERCEPT 31.04 28.7

SLOPE -3.34 -2.19

R2 0.978 0.961

HoOo HALF LIFE (PAYS) 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 io 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 H₂0₂ alone would have lasted for about 9 days, but would have lasted for almost 16 days when stabilized with Q6/6.

Table 10. H 02 as a Stand Alone Sanitizer.

DAY H₂0₂ PPM Q6/6 PPM CFU/ML

1 31.5 _., 555

2 29.8 _ 19.350

3 21.3 _ 36.100

4 13.6 —

7 0.7 _ _

8 0.7 _ 1,950 Table 11. Stabilization of H₂0₂ with Q6/6

DAY H₂0₂ PPM Q6/6 PPM CFU/ML

1 33.15 7 1

2 29.8 4 9

3 27.2 4 38

4 25.5 2

5 17 1 _

6 14 1 46

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

STATISTICS H₂0₂ H₂0₂ + PDED

Y-INTERCEPT 33.58 34.7

SLOPE -3.95 -2.3

R 0.96 0.99

H₂0₂ HALF LIFE (DAYS) 4.52 7.9 The data clearly show that a water treatment system based solely on H„0₂ and a polyquatemary ammonium compound can achieve and maintain acceptable water quality. The fact that one gallon of blended material might be used to treat up to 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.

EXAMPLE 4 Table 13 shows the surprising effect that a chlorine shock has on peroxide half life. A 5,000 above ground pool was maintained on 10 ppm H_?0„ and 5 ppm of a polyquat (Q6/12) weekly. The pool was challenged daily with an artificial insult containing synthetic sweat and a bacterial inoculum consisting of P. aeruginosa (10 9-10 cells). In addition, the pool received natural inoculations from the environment. In some cases, H₂0₂ was not measured due to intervening weekends.

As the data in Table 13 indicate, a chlorine shock allowed H„0_ to remain active in the pool for a longer period of time. Without a chlorine shock, H_0_ remained in the pools for only 3 days. Chlorine extended the presence of peroxide for an additional 2 days. Expressed differently, a single chlorine shock extended the life of

H₂0₂ by 67%.

TABLE 13 Effect of Chlorine on H O and Q6/12.

DATE H2O2 PPM CHEMICALS ADDED

10/18/94 — 10 PPM H₂0₂ 10/19/94 8.5

10/20/94 5.1

10/21/94 0

10/26/94 0 Calcium Hypochlorite

10/27/94 — 10 PPM H₂0₂ 10/28/94 7.7

10/29/94

10/30/94

10/31/94 3.4

11/01/94 0 11/16/94 — 10 PPM H₂0₂

11/17/94 6

11/18/94 Q —

EXAMPLE 5 In another experiment, a 5,000 gallon, above ground pool was treated with 27.5 ppm H₂0₂ and 10 ppm of a polyquat (Q6/6) on a weekly basis. Neither synthetic insult nor prepared bacterial inocula were added since human swimmers contributed natural flora and secretions whenever they were in the pool. These swimmers (4) averaged between 2-4 hr per person per week in this particular pool.

The data presented in Table 14 demonstrates the ability of a strong shock treatment to extend the life of H-0-,. By using chlorine prior to adding peroxide, H₂0₂ remained at detectable levels for 6 days. Without chlorine, peroxide lasted only for a maximum of 4 days. In this case, chlorine increased the life of H O y at least 33%. Moreover, H-0- remained active for a longer period of time even though a larger amount of H₂0₂ was added during the subsequent addition (Table 14; 6/9-6/10). Similar results could be expected with strong oxidizers such as activated NaBr (or other forms of oxidizing bromine), leach, ozone, potassium peroxymonopersulfate, dichloroisocyanurates or trichloroisocyanurates. TABLE 14 Effect of Chlorine on H₂0₂ and Q6/6,

DATE H₂0₂ PPM CHEMICALS ADDED

6/1/94 Lithium Hypochlorite

6/2/94 20 27.5 PPM H₂0₂

6/3/94

6/4/94

6/5/94

6/6/94 6

6/7/94 2

6/8/94 0

6/9/94 19 27.5 PPM H₂0₂

6/10/94 16 10 PPM H₂0₂

6/11/94

6/12/94

6/13/94 _0

The data in Tables 13 and 14 clearly demonstrate the surprising benefits of shock chlorination on hydrogen peroxide half life. Example 6, including Table 15, corroborates and expands further on these findings.

EXAMPLE 6

A 23,000 gallon in-ground, gunite pool was treated with weekly applications of H₂0₂ (30%) containing Q6/6 (0.5%) and PDED (1.5%). The maintenance application rate was 1.5 gallons per week and delivered 22.5 ppm H_0_ and 2.25 ppm polyquat. In addition, 3 slow dissolving chlorine sticks were added every two weeks. At no time was a free chlorine residual observed using the slow dissolving chlorine sticks. As a comparison, typical chlorine sticks are^' used at a rate of 1 per 10,000 gallons and a free chlorine residual of 1-3 ppm should be maintained at all times. Moreover, these sticks may completely dissolve within three to five days. Table 15 shows the beneficial effects of shock chlorination upon this system. At the beginning of this trial, H_0 applications resulted in theoretical (or near theoretical) levels of H₂0₂ in the pool (6/28-7/9). As the trial progressed, subsequent H„0_? applications were substantially less productive (7/9-7/13). In order to restore H₂0₂ half life to its original length, 6 gallons of H₂0₂ were needed within a four day period even though the maintenance application rate was only 1.5 gallons per seven days.

TABLE 15

Effect of Chlorine on H₂0₂ Q6/6 and PDED

DATE H 0₂PPM CHEMICALS ADDED

6/28 0 30 PPM H₂0₂

6/29 25

6/30 20

7/1

7/2 15

7/3 5

7/4 2 22.5 PPM H₂0₂

7/5 20

7/6 10

7/7 5

7/8 2

7/9 0 22.5 PPM H₂0₂

7/10 5

7/11 2.5 30 PPM H₂0₂

7/12 10

7/13 0 37.5 PPM H₂0₂ 7/14 25

7/27 0 22.5 PPM H₂0₂

7/28 15

7/29 10

7/30 5

7/31 3

8/1 2

8/2 1

8/3 0 22.5 PPM H₂0₂

8/4 10

8/5 10

8/6 5

8/7 2

8/8 1

8/9 0 Lithium Hypochlorite

8/10 0

8/11 0 22.5 PPM H₂0₂

8/12 15

8/13 10

As time elapsed, the H₂0₂ maintenance applications again failed to yield theoretical levels (7/2-8/9) . Furthermore, the use of slow eroding chlorine sticks did not effectively prevent the conditions that were responsible for the decrease in the theoretical levels. However, the addition of 5 lbs. of lithium hypochlorite successfully allowed hydrogen peroxide applications to yield concentrations that approached their expected levels (8/9-8/13). At the time of ϋ₂ °2 addition, the pool still contained 2 ppm of free chlorine (8/11) . Free chlorine readily neutralizes H₂0₂ and was probably responsible for a lower than expected H₂0₂ concentration. Nonetheless, superchlorination increased the H_^0_ level by 33% over the previous initial concentration (8/4 and 8/12).

It is to be appreciated that the methods described above are particularly applicable for use in treating swimming pool water, as shown in the foregoing examples. The methods may also be used, however, to treat spa water or other recirculating recreational water systems, as well as to treat cooling tower water, etc.

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

What is claimed is:

1. A method of treating water, comprising the steps of:

(a) providing hydrogen peroxide and at least one polyquatemary ammonium compound to a recirculating water system; and

(b) intermittently adding to said water system an oxidizing agent selected from the group consisting of chlorine-, bromine- or oxygen-releasing compounds.

2. The method of claim 1 wherein said hydrogen peroxide and said polyquatemary ammonium compound are provided by providing to the water a shelf-stable composition comprising hydrogen peroxide and at least one polyquatemary ammonium compound.

3. The method of claim 1 wherein said chlorine-, bromine- or oxygen-releasing compound is a member selected from the group consisting of calcium hypochlorite, lithium hypochlorite, activated sodium bromide, sodium dichloroisocyanurate, trichloroisocyanurate, sodium hypochlorite, potassium peroxymonopersulfate.