NZ331893A - Water treatment method comprising adding hydrogen peroxide, a polyquaternary ammonium compound and intermittently chlorine or the like - Google Patents

Abstract

This method of treating water is 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 5 treating water with hydrogen peroxide, polyguaternary 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 10 acquires a variety <$"£"-micsqojrganisms 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 15 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, 20 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 25 to maintain its efficacy, and readily forms irritating Printed from Mimosa chlorammes 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 C^), periodic superchlorination 5 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 10 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 15 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 20 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 Hencp, an additional stabilizer is 25 needed to protect and enhance the peroxide, post-application As to other sanitizers, polyquaternary 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 30 biocides However, when monomenc quaternary ammonium compounds are used as primary sanitizers high concentrations (25-75 ppm) are necessary. Unlike polyquats, monomenc quats tend to produce substantial foam even at low concentrations . 5 ppm). Foaming will only be Printed from Mimosa WO 97/34835 PCT/US97/04200 exacerbated at levels of 25 to 75 ppm.

When regulated waters are treated with H202, the system can only remain biocidally effective as long as H202 remains available for disinfection If levels of 5 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 10 sanitizers such as hydrogen peroxide and a polyquaternary ammonium compounds, with and without the additional use of chlorine. The present invention addresses this need Printed from Mimosa SUMMARY OF THE INVENTION 331893 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 c!, ebloroisocyarmrate, trichloroisocyanurate, sodium hypochlorite, potassium peroxymonopersulfate, etc. to shock regulated waters treated with hydrogen peroxide (^02) and polyquaternary ammonium compounds (polyquats) Periodic 10 superchlormation or superoxygentation can assist these regulated waters m maintaining acceptable water duality In particular, the present invention provides a method j£ treating water, comprising the steps of (a) providing hydrogen peroxide and at least one polyquaternary ammonium compound to a recirculating water system, and (b) intermittently adding to said water system an oxidizing a^ent selected from the group consisting of chlorine-, bromne- and oxygen-releasing compounds One object of the invention is to provide a method of enhancing the quality of regulated waters using polyquaternary amomum compounds, hydrogen peroxide and regular shocks with dry or liquid oxidizers Further objects and advantages o£ the present invention will be apparent from the following description INTELLECTUAL ^PROPERTY 1 3 jan 2000 received.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph of the half-lifa estimations of H2^2 an^ without PDED.

FIG. 2 is a graph of the half-life estimations of 5 ^2^2 W1*-k ant* without Q6/6.

Printed from Mimosa 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 5 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 tne principles of the invention as described herein being 10 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 15 dichloroisocyanurate, tnchloroisocyanurate, sodium hypochlorite, potassium peroxymonopersulfate, etc. are used to regenerate regulated waters treated with hydrogen peroxide (H202) and polyquaternary ammonium compounds (polyquats). The addition of these materials destroys 20 organic materials and restores H202 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-25 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 H202 and a polyquat) or polyquats) is added to a body of water to give 30 concentrations of H202 ranging from 1-100 ppm and a polyquat concentration ranging from 0 1-30 ppm Preferably, the H20^ level ranges from 10-30 ppm and the polyquat level ranges from 1-5 ppm. The solution is preferably Printed from Mimosa PCT US97/04200 applied at specified intervals (weekly, bi-weekly or monthly). At certain intervals (weekly, bi-weekly or monthly), superchlormation or superoxygenating shock treatment is applied prior to adding the P°ly9uat solutions. After several hours (if using unstabilized shock treatments), it is preferred to resume the treatment program with another H202 polyquat application.

Unstabilized chlorine products such as calcium hypochlorite, lithium hypochlorite are the preferred 10 shocking agents because the resulting chlorine residuals will quickly be degraded by Ultraviolet radiation from the sun Hence, although periodic superchlormation may be necessary for the system to maintain optimal performance, active chlorine will actually be present for relatively 15 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 20 surprising Stabilized chlorinating agents using a cyanunc 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 23 chlorine might cause irritation to swimmers or might degrade H^O^. Potassium monopenoxytsulf ate is a non-chlorine alternative for persons desiring to avoid the use of halogens.

Another aspect of the present invention uses dilute 30 hydrogen peroxide as a sanitizer along with a polyquaternary 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 Printed from Mimosa 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 5 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 polyquaternary ammonium compounds may be used in the various aspects of the present invention, 10 including poly(hexamethylammonium) chloride ("Q6/6"), poly[oxyethvlene-(dimethylimmo) ethylene-(dimethylimino) ethylene dichloride] ("PDED"), dodecamethylenedimathylimino chloride ("Q6/12") and 1,J-diazo-2,4-cyclopentadiene with l-chloro-2,3-epoxypropane ("IPCP") These and other polyquaternary ammonium compounds are available from common commercial sources Preferably the hydrogen peroxide and the polyquaternary ammonium compound are added independently so that appropriate concentrations of each composition may be 20 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 25 In regular use, the water should contain between 5 and 40 ppm H2°2 amJ a Poly<3uaternary 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 30 pei• me gallon container. When applied as separate products, the relative concentrations of H202 and polyquat should remain the same, using either gallon or half gallon containers.

As previously suggested, the various aspects of the 35 present invention provide simple, albeit novel, improvements Printed from Mimosa 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 5 can be packaged as a shelf stable blend or in separate containers Third, the schedule o£ 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 10 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 monomenc 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 polybiquanide system in that the components can be blended in one container.

In one aspect of the invention the polyquaternary 20 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. 25 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 105 per milliliter. Despite high bacterial populations, water clarity remained excellent Table 1 30 displays a brief excerpt from the m-use pool study.

Printed from Mimosa WO 97/34835 PCT/US97/04200 Table 1 Bacterial Densities Versus Water Clarity.

Q6/6 CONCENTRATION (PPM} BACTERIAL DENSITY PER ML TURBIDITY1 ( NTU^ S 12.350 0.22 126.000 0.25 24.300 0.17 3 4.130 0. 19 3 8.500 0.29 1 NTU - Nephelometric 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 15 clear At 0.32 NTU or higher water is ha^y or cloudy.

Based on literature and on our corroborating observations, it appears that the bacteri, remained completely viable, but in tight aggregates This would explain the excellent clarity and the high bacterial 20 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 more accessible to critical areas of the cell membrane. In essence, the polyquat acts as an adjuvant or potentiator for H202 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 30 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 Printed from Mimosa 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 8 9 suspension (about 10 to 10 organisms) containing £ aeruginosa. E qoil, and fi. aureus These are some of the 15 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 20 nutrient agar to determine the number of viable bacteria.

Table 2. H2O2 as a Stand Alone Sanitizer.

DAY H2O2 PPM TPC1 1 34 .350 2 11.9 692 . 000 3 4.25 752.000 42 1.7 1.776.000 .4 91.000 6 7.65 2.080.000 7 1.7 2.24B.OOO 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.

Printed from Mimosa Table 3. Effect of PDED on H2O2 Stability and Efficacy DAY H202 PPM TPC 1 28.9 40 2 12. b 109 3 .95 970 4 3.4 500 24.7 220 6 11.9 3. 000 7 8.5 4,950 Table 4 Effect of IPCP on H202 Stability and Efficacy.

DAY H20? PPM TPC 1 32.3 0 2 n i 0 3 6 0 4 2.6 1 24.7 2 6 17.85 3 7 7.65 38 Table 5 Effect of Q6/12 on K202 Stability and Efficacy DAY H202 PPM TPC 1 32.3 0 2 12.b 0 3 7.7 0 4 3.4 11 27.2 0 6 22 . 1 7 .2 7 Printed trom Mimosa Table 6. Effect of Q6/6 on H2O2 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 19.6 23 6 16.2 2.000 7 6.B 4.800 The data presented in Tables 2-6 strongly suggests that the class of molecules known as polyquaternary ammonium compounds has the ability to stabilize and increase the efficacy of hydrogen peroxide. That is to say, R202 was more persistent in the presence of either of the polyquats 15 (stability enhanced) and bacterial counts were greatly reduced (efficacy enhanced) EXAMPLE 2 Since surprising trends were observed during the 1 aquarium trials, further experiments were performed m 20 outdoor pools The efficacy of a combination of H with PDED and H202 a*one 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 25 microbial inoculations from the environment, each pool was treated with bacterial suspensions (about 1010 to 1011 organisms) containing E. aeruginosa. E col1. 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 H202 to control bacterial growth, even at high concentrations. In addition, previous research has demonstrated that PDED like H202, is not an Printed from Mimosa PCT7US97/04200 -Ineffective sanitizer when used alone (data not shown) . By-contrast, Table 8 demonstrates the ability of polyquats to enhance H2°2' ren^er3-n9 lfc n101,0 efficacious While PDED has deraonstrated antimicrobial synergy with oxidizers, these 5 data indicate that polyquats can also stabilize and extend peroxide half life in the use dilutions.

Table 7. H2°2 as a Stand Alone Sanitizer DAY H2O2 PDED PM CFU/ML 1 26.35 2 23.8 330 3 23.0 900 A 17.0 _ 4 . 900 7 .1 _ 51.000 8 0 47.000 Table 8. Stabilization of H202 With PDED.

DAY h2o2 PDED PM CFU/ML 1 26.35 0 2 24. 65 0 3 23.8 3 4 18.7 7 0 7 11.9 4 445 8 .2 3 205 The data in Tables 7 and 8 were graphed to show the trends of H2°2 dlsaPPearance (FIG 1). In addition, the 25 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 H202, even when the PDED concentration was as low as 3 ppm Using the data, we can extrapolate that 30 H2°2 a^one last approximately 10.7 days, but would last 14.2 when stabilized with PDED.

Printed from Mimosa Table 9. Half Life of H2O2 with and without PDED STATISTICS H2C>2 H202 + PDED Y-INTERCEPT 31.04 28.7 SLOPE -3,34 -2.3,9 R2 0.978 0.961 -ii2Q2 HALF LIFE (PAYS) ^15 LU example 3 The experiment summarized in Example 3 is identical to Example 2, except that Q6/6 was substituted for PDED (Tables 10 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 H2C>2 Hydrogen peroxide alone had a shorter half life and was not an effective bactericide even at the highest 15 levels tested.

Linear regression is compiled in Table 12 FIG 2 grapnically 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 20 almos4- 16 days when stabilized with Q6/6.

Table 10. H202 as a Stand Alone Sanitizer day h202 ppm q6/6 ppm cfu/ml 1 31.5 555 2 29.fi _, 19.350 3 — 36. 100 4 13.6 7 0.7 .8 0.7 - 1.950 Printed from Mimosa Table 11. Stabilization of H2O2 with Q6/6.

DAY h2o2 ppm Q6/6 PPM CFU/ML 1 33.15 7 1 2 29.8 4 9 3 27.2 4 38 4 .5 2 17 1 6 14 1 4 ft Table 12.

Half Life of H202 with and without PDED STATISTICS H2<>2 H202 + PDED Y-INTERCEPT 33.58 34.7 SLOPE -3.95 -2.3 0 96 0-99 -J&2.QZ HALF LIFE (PftYS) 4.52 7^3.

The data clearly show that a water treatment system based solely on ^2^2 an°' a P°1Y<3uafcernary 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 20 constitutes a vast improvement over the existing polybiguamde 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 25 14 daysy 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 30 one (blended) or two (separate) products are used instead of three.

Furthermore, since the method disclosed precludes the Printed from Mimosa 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 5 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 ^2^2 an^ a P°ly^uat (Q6/12) weekly. The pool was challenged daily with an artificial insult containing synthetic sweat and a bacterial 9 — 10 inoculum consisting of P. aeruginosa (10 cells) In addition, the pool received natural inoculations from the I5 environment In some cases, H202 was not measured due to intervening weekends.

As the data in Table 13 indicate, a chlorine shock allowed H202 to remain active in the pool for a longer period of time Without a chlorine shock, H202 remained 20 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%.

Printed from Mimosa WO 97/34835 PCT/US97/04200 TABLE 13 Effect of Chlorine on K2°2 and DATE »2°2 PPM CHEMICALS ADDED /18/94 — PPM H2°2 /19/94 B.5 — /20/94 .1 — /21/94 0 — /26/94 0 Calcium Hypochlorite /27/94 — PPM H202 /28/94 7.7 /29/94 — /30/94 — /31/94 3.4 11/01/94 0 11/16/94 — PPM H202 11/17/94 6 — U/1B/94 0 — EXAMPLE 5 In another experiment, a 5,000 gallon, above ground pool 20 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^mocula 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 25 person per week in this particular pool The data presented m Table 14 demonstrates the ability of a strong shock treatment to extend the life of H202. By using chlorine prior to adding peroxide, H202 remained at detectable levels for 6 days Without chlorine, 30 peroxide lasted only for a maximum of 4 days. In this case, chlorine increased the life of H202 by at least 33%. Moreover, H202 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). 35 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.

Printed from Mimosa TABLE 14 Effect of Chlorine on H2O2 and Q6/6.

DATE H202 PPM CHEMICALS ADDED 6/1/94 — Lithium Hypochlorite 6/2/94 27.5 PPM H202 6/3/94 — — 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 PPM H202 6/11/94 — 6/12/94 — 6/13/34 0 The data in Tables 13 and 14 clearly demonstrate the surprising benefits of shock chlorination on hydrogen 20 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 H2°2 (30%) containing Q6/6 (0 5%) 25 and PDED (1.5%). The maintenance application rate was 1 5 gallons per week and delivered 22.5 ppm H^02 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 30 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 ppra 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 Printed from Mimosa trial, H202 applications resulted in theoretical (or near theoretical) levels of H202 m the pool (6/28-7/9) As the trial progressed, subsequent H202 applications were substantially less productive (7/9-7/13). 5 in order to restore H2D2 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 H202PPM 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 H_0_ 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 H,0, 7/12 10 7/13 0 37.5 PPM H202 Printed from Mimosa 7/14 25 7/27 0 7/28 15 7/29 10 7/30 5 7/31 3 8/1 2 8/2 1 8/3 0 8/4 10 8/5 10 8/6 5 8/7 2 8/8 1 8/9 0 8/10 0 8/11 0 8/12 15 8/13 10 22.5 PPM H202 22.5 PPM H202 Lithium Hypochlorite 22 5 PPM H202 As time elapsed, the H202 maintenance applications again failed to yield theoretical levels (7/2-8/9). Furthermore, the u«se of slow eroding chlorine sticks did not effectively prevent the conditions that were responsible for the decrease in the theoretical levels However, the 25 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 H202 addition, the pool still contained 2 ppm of free chlorine (8/11) Free 30 chlorine readily neutralizes H202 and was probably responsible for a lower than expected H202 concentration. Nonetheless, superchlormation increased the H202 level by 33% over the previous initial Printed from Mimosa concentration (8/4 and 8/12).

It is to be appreciated that the methods described above axe particularly applicable for use in treating swimming pool water, as shown in the foregoing examples. The methods 5 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 10 illustrative and not restrictive m 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.

Printed from Mimosa

Claims (3)

WO 97/34835 PCT/US97/042G0 -23- 331893 WHAT W£ CLAIM IS

1 A method of treating water, comprising the steps of (a) providing hydrogen peroxide and at least one polyquaternary 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- and oxygen-releasing compounds

2 The method of claim 1 wherein said hydrogen peroxide and said polyquaternary ammonium compound are provided by providing to the water a shelf-stable composition comprising hydrogen peroxide and at least one polyquaternary 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, tnchloroisocyanurate, sodium hypochlorite and potassium pero/yrnonopersu±£ate INTELLECTUAL PROPERTY OFFICE OF NZ 13 jan 2000 received