Note: Descriptions are shown in the official language in which they were submitted.
CA 02481790 2004-09-16
1 °'SiIaTEM F~R oSAINIIT~ZINC ~1 SPA"
2
3 FIELD OF THE INVENTION
4 Embodiments of the invention relate to systems for treatment of
water in swimming pools, spas and the like and morE= particularly to
sanitizing
6 relatively small volume spas for residential use.
7
S BACKGR0~1ND ~F THE INVEN'T'ION
9 Halogens such as chlorine and bromine have long been used to
sanitize water. The chemistry is well known to those skilled in the art.
11 Hypochlorous or hypobromous acid are typically the most effective species
or
12 active free halide for sanitizing purposes Dissociation of these acids to
the
13 less effective hypochlorite or hypobromite is pH and temperature dependant.
14 For example, at a pH of 8.0 only about 20% hypochlorous acid is present
while at a pH of about ~.5 the amount of hypochlorous acid rises to about 50-
16 60%. Further, sunlight and organic load can also significantly affect
17 disinfection capability.
18 Chlorine or bromine for sanitizing can be provided in a tablet,
19 liquid or powdered format or can be generated on site using known
electrolytic
methods. Applicant is aware that electrolytic systems are commercially
21 available which provide sufficient quantities of chlorine or bromine to
22 effectively sanitize large volume swimming pools and the like having 15,000
to
23 in excess of 100,000 DS gallons of water. While electrolytic units have
been
24 successful in sanitizing commercial/municipal pools and spas having large
volumes of water, residential spas or whirlpools having volumes of about 200
26 to about 400 US gallons present significant dif~cultie~s. Current
electrolytic
CA 02481790 2004-09-16
1 systems are not reliably controllable to produce consistent and sufficiently
2 small volumes of halogen, particularly chlorine, to effectively sanitize
without
3 over or under-chlorination. The limited volume, high operating temperature,
4 aeration and large organic loading or demand , when in use, combine to
present challenges to keeping a constant pH and level of sanitizer.
6 Typically, prior art products and systems for sanitizing either
7 provide enough chlorine to satisfy needs when the spa is not in use or
enough
8 to sanitize when it is in use and the organic load increases significantly.
9 Applicant is not aware however, of products that are capable of effectively
handling both situations.
11 During use, organic materials such as hair oils, body oils,
12 sloughed skin and the like are added to the spa, causing the amount of
13 chlorine to begin to fail as the chlorine reacts with the organics, often
to levels
14 where the chlorine level is no longer sufficient to handle the total
dissolved
solids and organics. In conventional spa maintenance, a periodic "shock" is
16 required to clear or sanitize the spa. The term "shock" is typically used
to refer
17 to the addition of a high concentration of a sanitizer. Large amounts of
18 additional chlorine or products such as OXONE~ (available from Dupont~
19 Specialty Chemicals, Wilmington, Delaware 19898), a monopersulfate
compound, are used to either raise the chlorine levels sufficient to sanitize
the
21 increased level of organics or to oxidize the organics through the release
of
22 oxygen. It is not recommended that the spa be used for significant periods
of
23 time following a shock treatment as the pH is typicallly not optimum and
will
24 result in irritation to the eyes and skin and potentially result in
corrosion of
metal in the spa.
2
CA 02481790 2004-09-16
1 Typically, shocking of the spa is performed on a scheduled basis
2 which is determined by the spa owner when testing the water quality. As
3 bromine and chlorine levels drop over time or are used up during peak usage
4 periods, the user must continuously test and retest the water to determine
when treatment needs to be effected. As spa usage becomes more
6 infrequent, it becomes more diffcult to adjust levels of sanitizer to meet
the
7 demands of both low usage and the sporadic higher demand. ~ver-
8 chlorination during periods of low use or more frequent shocking in periods
of
9 high use may result in corrosion of metal parts within the tub.
Clearly what is required is a system for maintaining a level of
11 sanitizer that is responsive to handle both low and high organic demand
with
12 a minimum of testing and sanitizing procedures on the= part of the spa
owner.
3
CA 02481790 2004-09-16
1 ~UMMAf~Y C3F THE INVENTION
2 A sanitizing method and system utilizes electrolytic generation of
3 halide alone to sanitize spa water during periods of low-to-no use and is
4 augmented in anticipation of or in reaction to periods of high usage and
increased organic demand by the addition of a buffered oxidizer, which acts to
6 oxidize organics, generate active free halide from salt in the spa water and
to
7 buffer the pH of the war to a range that is more favorable for maintaining a
8 higher concentration of hypochlorous or hypobromous acid for sanitizing the
9 increased organics.. Accordingly, there is no need to maintain sanitizer
levels
sufficient to control organics at peak or near peak levels when the spa is not
11 being used. The method is particularly useful for sanitizing water in spas
12 having a volume of water of about 200 to about 400 US gallons.
13 fn a broad aspect, a method for sanitizing water in a spa
14 comprises: providing a halide salt in a range from about 2800 ppm to about
3500 ppm into the relatively low volume of water; and in periods of low to-no
16 use, exposing the relatively low volume of water to an electrolytic
apparatus
17 capable of generating a halide ion from the halide salt in the water at a
pH of
18 about 8.0 or greater, the generation of halide ion being sufficient to
maintain a
19 level of active free halide sufficient for sanitizing the relatively low
volume of
water during the periods of low to no organic demandi and in periods of
21 increased organic demand, providing a buffered oxidant at about pH 7.U to
22 oxidize at least a portion of the organics as a result c~f the increased
organic
23 demand, for oxidizing the free halide to produce free active halide and for
24 maintaining a pH in a range from about 7.2 to about ~'.8 in combination
with
the electrolytic apparatus so as to permit optimum levels of active free
halide.
4
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1 In another broad aspect, a system for sanitizing a residential spa
2 comprises: a halide salt dissolved in a relative ly low volume of water in
the
3 spa in a range of about 2500 ppm to about 3500 ppm per spa volume; an
4 electrolytic generator for generating a halide ion from the dissolved halide
salt
sufficient to maintain a level of active free halide optimum for sanitizing
the
6 relatively low volume of water during periods of low to-no organic demand
and
7 at a pH of about 8.0; and a buffered oxidizer, packaged for addition to the
8 water for periods of high organic demand, for oxidizing at least a portion
of the
9 organics in the water, for oxidizing free halide to produce free active
halide
and for maintaining the pH in a range from about 7.2 to about 7.8 in
11 combination with the electrolytic generator, so as to permit optimum levels
of
12 active free halide to be formed.
13 Preferably, the halide is either chloride or bromide and is
14 electrolyticaliy generated 'from sodium chloride or sodium bromide in water
to
produce hypochlorous acid or hypobromous acid. The pH following the
16 electrolytic generation is approximately pH 8Ø The dissociation of
17 hypochlorous acid to hypoclorite ion and hydrogen ion is particularly pH
18 dependant, white the dissociation of hypobromous acid is less so. At a pal
of
19 8.0 or higher, a smaller percentage of hypochiorous acid exists relative to
hypochiorite ion, however the electrolytic generation is relied upon only
during
21 periods of very lowto-no usage of the spa and therefore, with relatively
low to
22 non-existent levels of organics present, the amount of active free chlorine
23 (hypoclorous acid) or bromine (hypobromaus acid) is sufficient to sanitize
the
24 spa.
5
CA 02481790 2004-09-16
1 In anticipation of, or in reaction to, increased usage of the spa
2 and the increased organics caused therefrom, a buffered oxidizer is added to
3 the spa to oxidize at least a portion of the organics, the pH of the
buffered
4 oxidizer being such that in combination with the pH of the electrolytic
generation of halide ion being 8.0, the fine! pH of the spa water is in a
range
6 of pH 7.2 - 7.8 and preferably 7.4 - 7.6. At a pE-1 of about 7.2 to about
7.8, a
7 greater amount of hypochlorous or hypobromous acid is present and is
8 therefore capable of sanitizing the increased organics in the spa. Further,
the
9 buffered oxidizer acts to oxidize the free halide to increase levels of
active
free halide.
11 A generator cell in the electrolytic generator is preferably small
12 in size and capable of producing sufficient halide iorr from the salt and
water
13 to maintain a free available chlorine or bromine kevel of between 1 - 5
14 ppmlvoiume with no to very low organics present in tlhe spa water.
Preferably,
the free chlorine level is maintained in a range between 2.0 ~-- 3.0
ppmlvolume
16 and the free bromine level is maintained in a range between 2.0 - 4.0
17 ppm/volume.
18 Preferably, the oxidizer is a monopersLdfate such as OXONE~
19 (pH less than or about 3.0} buffered with an alkaline salt such as sodium
carbonate or sodium bicarbonate. The addition of the buffered oxidizer,
21 having a final pH of about 7.0, to the water containing electrolytically
22 generated halide at about pH 8.0, results in a final 19H of about pH 7.4-
7.6,
23 optimum for preventing dissociation of the hypochlorous acid or hypobromous
24 acid.
6
CA 02481790 2004-09-16
1 BRIEF DESCRIPTION OF THE DR,4WINCS
2 Figures 1 a-c are schematic views illustrating an embodiment of
3 the method and system of the Invention for sanitizing a residential spa
using a
4 retrofit electrolytic generator and the addition of a buffered oxidizer,
more
particularly
6 Figure 1 a is a schematic illustrating sanitizing during periods of
7 low to no usage;
8 Figure 1b is a schematic illustrating sanitizing before a high
9 organic demand; and
Figure 1c is a schematic illustrating sanitizing after use where
11 there is a high organic demand;
12 Figure 2 is a schematic of the retrofit electrolytic generator far
13 according to Fig. 1, for installation over a side wall of a spa; and
14 Figure 3 is a sectional view of a spa wall having the electrolytic
generator installed therein for use in the system according to Figs. 1 a-c.
16
7
CA 02481790 2004-09-16
1 DETAILED DESCRIPT14N ~F THE PREFERRED EP~B~DIIVIENT
2 As shown in Flgs. 1a-c, and in embodiments of the invention, an
3 electrolytic generator 10, capable of generating free active halide from a
4 halide salt, is installed in a spa 11, such as a residential spa, having a
volume
of approximately 200 -- 400 lJS gallons c750 -~ 1500 L) and typically
6 supporting from 1 - 10 bathers at the same time. "fhe active free halide is
7 most effective if it is in the acid form.
8 Preferably, the halide is either chloride or bromide and is
9 electrolytically generated from sodium chloride or sadium bromide in water
to
produce hypochlorous acid or hypobromous acid. The halide salt is added to
11 the spa water to maintain a concentration in the range oB about 2500 - 3500
12 ppmlspa volume and more preferably about 3000 ppm/spa volume. The pH
13 following the electrolytic generation is approximately pH 8Ø The
dissociation
14 of hypochlorous acid to hypoclorite ion and hydrogen ion is particularly pH
dependant, while the dissociation of hypobromous acid is less so.
16 During periods of !ow-to-no usage of the spa 11 where there is
17 minimal organic load, the electrolytic generator is capable of providing
18 sufficient active free halide to sanitize the spa 1. Typically, the
effective range
19 is approximately 1.0 - 5.0 ppm/spa volume. At a pH of 8.0 or higher, a
smaller
percentage of hypochlorous acid exists relative to hypochlorite ion than at
21 lower pH, however as the electrolytic generation is relied Lapon only
during
22 periods of very low to no usage of the spa, the amount of active free
chlorine
23 (hypochlorous acid) or bromine (hypobromous acid) is sufFcient to sanitize
the
24 spa.
8
CA 02481790 2004-09-16
1 As shown in Fig. 1 b, in anticipation of increased usage of the
2 spa 11 and the increased organics caused therefrom, a buffered oxidizer 12
is
3 added to the spa 11 to oxide at least a portion of the organics, the pH of
the
4 buffered oxidizer 12 being such that in combination with the pH of the
electrolytic generation of halide, the final pH of the spa water is in a range
of
6 about 7.2 to about 7.8 and preferably about 7.4 to about 7.6. At the pH of
7 about 7.2 to about 7.8, an increased amount of chlorine or bromi ne,
existing
8 as hypochlorous or hypobromous acid, is present for main~aining a relatively
9 constant level of chlorine or bromine in the water and is therefore capable
of
sanitizing the increased organics in the spa 11.
11 Further, the buffered oxidizer oxidizes the free halide present as
12 a result of the halide salt which in turn exists as hypochlorous or
13 hypobromous acid at a pH of about 7.2 to about 7.8. Thus, the addition of
the
14 buffered oxidizer also acts to increase the active free halide in the spa
water.
Preferably, an active free chlorine level is maintained in a range
16 between 2.0 - 3.0 ppmlvolume and an active free bromine level is maintained
17 in a range between 2.0-4.0 ppmlvolume.
18 Alternatively, as shown in Fig. 1 c, the buffered oxidizer 12 may
19 be added after the spa 11 has been used and the organic load 13 has
increased or the buffered oxidizer 12 can be added both immediately before
21 and after use. In each case the levels of chlorine and bromine remain
22 relatively consistently within the effective ranges of active free halide.
23 Advantageously, as a result, bathers can immediately use the spa as there
is
24 no large pH shift experienced with conventional sanitizing or shocking
regimes.
9
CA 02481790 2004-09-16
1 As shown in Figs 2 and 3, a generator cell 20 in the electrolytic
2 generator 10 is preferably small in size and capable of producing sufficient
3 active free halide from the salt and water to maintain the effective ranges
of
4 active free halide with no to very low organics present in the spa water. As
well known to those skilled in the art, the cell 20 comprises blades 21 of a
6 metal, such as, titanium preferably coated with a noble metal such as
7 platinum or iridium or preferably, ruthenium. The blades 21 are sandwiched
8 between end caps 22,23 and are housed in a perforated, transparent plastic
9 tube 24, such as polyvinyl chloride (PVC), to protect the blades 21 from
damage to the coating. The perforations in the tube 24 permit contact of the
11 blades 21 with the water.
12 In an embodiment of the invention, the electrolytic generator 10
13 has an output control dial 25 which is manually set to control the active
free
14 halide output relative to the spa volume. Set, for example at 100%, the
generator 10 is capable of producing the equivalent of approximately 15
16 grams of chlorine in a 24 hour period which would satisfy a spa having a
17 volume of 400 tJS gal (1500 L) during periods of low-to-no use.
18 As shown in Figs 1a-c and 2, the generator 10 is available as a
19 retrofit unit wherein the cel! 20 is suspended in the water over a wall 30
of the
spa 11 and a control module 31 is mounted on or adjacent an outside surface
21 32 of the spa 11.
22 Alternatively, as shown in Fig. 3, the generator 10 may be
23 installed within the wall 30 of the spa 11 at the factory, the control
module 31
24 being integrated into the spa controls (not shown).
CA 02481790 2004-09-16
1 Further, the generator 10 is programmed to reverse polarity at
2 regularly scheduled intervals which assists in cleaning of the ceA blades
21.
3 Preferably, the bufFered oxidizer is a monopersulfate such as
4 OXONE~ available from Dupont~ Specialty chemicals, Wilmington,
Delaware 19898) (pFl less than or about 3.0) buffered with an alkaline salt,
6 such as sodium carbonate or sodium bicarbonate. 'the addition of the
7 buffered oxidizer 12, having a final pH of about 7.0, to the water
containing
8 electrolytically generated halide at about pH 8.0, results in a final pH of
about
9 pH '7.4-7.6, optimum for preventing dissociation of the hypochlorous acid or
hypobromous acid and maintaining a constant, reproducible level of active
11 free halide within the spa during periods of peak usage.
12 Most preferably, the buffered oxidizer 12 is prepackaged in
13 convenient pouches 14 such as a gel capsule for addition to the spa 11. One
14 or more pouches 14 may be added depending upon the volume of the spa 11
or based ~n bather/organic loading.
16 For example in a 250 gal (1000L) spa containing 3000ppm
1? sodium chloride, the addition of about 15g of OXONE~ will produce
18 approximately 3ppm free chlorine in demand-free water. lr~ the presence of
an
19 organic demand, the amount of free chlorine produced will be less as a
portion of the OXONEC~ will act to oxidize the organics.
21 !n the case of a 250ga1 (1000L) spa containing 3000ppm halide
22 salt (97% sodium chloride and 3% sodium bromide), t:he halide will react
with
23 the OXONE~ and any free chlorine will also act to oxidize br~mide to
24 bromine, 'thus, virtually all of the halogen produced will be bromine. A
concentration of 15g of OXONEO will produce about 6.8ppm of free bromine
11
CA 02481790 2004-09-16
1 in demand-free water which is in excess of the normal amount of bromine
2 added to a spa.
3 As with conventional spa maintenance regimes in spas 11 using
4 chlorine as the active halide, Cyanuric acid may be added to the spa to
stabilize the chlorine, particularly if exposed direotly to tJV rays.
12
