Note: Descriptions are shown in the official language in which they were submitted.
~1~975;~
BFN 6770 ~1~
DISINFECTANT CHLOR~N~TE~ CyA~u~ATE CONTA~ G
_ COMPOSITIONS ~ND METHOD O~ USE
........ .... .... .... ...
Back round o~ 't~e Invention
g ~
Thi~ lnvention relates ~o disinfectant
compositions, and more particularly to a pelletized
disinfectan~ salt composition for use in water
softening systems.
Dls~nfection of domestic water supplies in
the United States b~ chlorination has been practiced
since the late 1800's Early methods utilized chlorinated
lime, ~odium and calcium hypochlorite, or chlorine
gas added to water systems at a central location. The
use of chIorinated cyanurates as a convenient source
of available chlorine for bleaching and disinfectant
purposes has also been ~opular for several years.
These organic compounds, genexally classified as
chloxamines, contain chloxine bearing nitrogen atoms
located ketween a pair of carbonyl (C=O) groups and
have been found to exhibit good stability as well as
bactexicidal properties in water.
In recent years, the increasing numbers of
backyaxd swimming pools has created a need for
disinfecting compositions which are added directly
to the ~ater b~ the individual consumer. Both
hypoc~lorite and chlorinated cyanurate compounds have
found use in swimming pools as disinfectants~ See,
for example, Hilton, "The Chlorinated Cyanurates"~
'SWi~n~i'ng Pool Age, Nov. 1961~
In European countries, there has been a
recognition of the problem of possible bacterial growth
in brine solutions used to regenerate water conditioning
sx~stems, Bacterial growth in such solutions could
contamlnate domestic drinking water supplies if
b~cteria remained in the ion exchange resin column
~ter ~ xegeneration c~cle Efforts have
'~
752
BFN 6770 ~-
been made in Europe to combat this problem by txeating
the ion exchange columns after each regeneration cycle
with chemicals or in some cases with silver impregnated
resins that have been dispersed into such columns.
However, chloramine compounds, one of the chemicals
u$ed~ do not react rapidly and require contact times
o~ at leas~ two hours to disinfect effectiv~ely a water
$uppl~, See, W. Hardenbergh, Water Supply and
Purification 413 ~1952). Such long contact times are
impractical for domestic water conditioning systems
since the ion exchange resin would be unavailable to
perform its softening function for extended time periods.
Use of silver impregnated ion exchange resins in the
xe$in column likewise is impractical because of the high
cost of such resins and the ineffectiveness of silver
compounds in disinfecting water supplies. Id. at 416.
Accordingly, the need exists in the field
o~ domestic water conditioning for a means to disinfect
e~ectively brine solutions used for regeneration of
ion exchange resins thus avoiding contamination of such
~esins and resulting in a minimum of time for which the
~ater conditioning unit is unavailable to perform its
softening function.
. .
Su-mmary of the Invention
In accordance with the present invention, a
di~infectant composition is compounded with sodium
Chloride~ and the mixture is formed into pellets.
The disinfectant pellets can then be added to the
brine storage tank o a conventional domestic water
3~ conditioning system. As brine solution is formed at
the bottom of the storage tank by dissolving the
pellets in water, chlorine disinfectant is released
fxom the pellets to control effectively any bacterial
growth in the solution. There is, therefore, no
dan~er of bacterial contamination of the ion exchange
column during regeneration with such brine solutions.
:~L2~7~iZ
BFN 6770 ~3-
~ the dlsinfectant agentr yaxiou~
chloramlne compounds can ~e utilized. Des~rable
properties ~or such compounds include high available
chlorine content, solid cr~stalline orm for ease of
pelletizing, rapid solubility in water, stability in
dry formulation, nontoxlc to humans at low
cancentrations, and no calcium ion ccntamination.
It h~s ~een found that chlorinated cyanurate compounds
such as potassium dichloroisocyanurate ~l-potassium,
3,5~dichloro-s-triazine-2,4,6-t~ione) and sodium
dichloroisocyanurate (l-sodium9 3,5-dichloro-s-triazine-
2~4~6-trlone) are particularly useful and possess all
of the above properties.
The disinfectant pellets are for~ed by mixing
~ small, predetermined amount of a dry powdered cyanurate
com~ound with fine grain crystalline salt (i.e.,
soaium chloride or other regenerant salt). The
mixture may then be compressed into pellets using
a conventional pill press. It has been found that by
using a xatio in the range of 6.5 x 10 3 grams of
potassium dichloroisocyanurate to about one gram of salt,
sufficient residual chlorine will be released into the
brine solution to insure bactericidal effectiveness
oyer extended periods of time.
~ccordir.glv, it is an object of this invention
to provide an inexpensive, convenient to use, and
effective means of disinfecting brine solutions in
domestic water conditioning svstems and thereby avcid
contamination of the ion exchange column during
regeneration, This and other objects and advan~ages
of the invention Will become apparent from the
following description and appended claims.
~L25975;2
BFN 6770 -~
Descri~tion of the Preferred ~m~odimen~s
Chlorinated cyanurates have been used safely
as sources of available chlorine for bleaching and
disinfectant purposes for several years. They are,
therefore/ known to be effective in controlling the
growth of bacteria Their use in swimming pools as
a source of chlorine has also shown them to present
no toxicological problems to humans. The preferred
chlorinated cyanurates for use in this invention are
lQ potassium dichloroisocyanurate (l-potassium~3,5-
dichloro-s-triazine-2, 4, 6-trione) and sodium
dichloroisocyanurate (l-sodium-3, 5-dichloro-s-triazine-2,
4, 6-trione). They are availa~le from Monsanto
Chemical Company, St. Louis, Missouri, under the
trademarks ACL-59 and ACL-60, respectively. It has
been found that these compounds exhibit the physical
properties required for use as disinfectants in brine
stoxage tanks. The compounds have a high percentage
of available chlorine, they have a solid crystalline
form and rapidly dissolve in water, and they are stable
when dry mixed with sodium chloride.
The chIorinated cyanurates can be mixed
easily with fine grain sodium chloride and then
pelletized by using a conventional pellet mill or
pill press. It was found that moderate pressures
(up to 50,000 psi~ were sufficient to ~rm the granular
m1xture into compact pellets. The size and shape of
the pellets are not critical, with the major consideration
being the ease of handling of the pellets. Pellets
3a having diameters of from 1/4" to 1/2" and having
generally spherical or flattened pill shapes are preferred.
It has been found that the addition of as
little as 1 to 3 ppm tmg/ll of dichloroisocyanurate
compound produces a very high initial kill rate of
bacteria which greatly reduced the bacteria even after
96 hours. Addition of 3 ppm and above of dichloro-
isocyanurate to a water system should provide both a
~ 2~33752
BFN ~77a -5-
high initial kill rate as well as sufficient residualchlorine to maintain an essentiall~ bacteria-free
environment.
}Iowever, to establish the effectiveness of such
known disinfectants in term of the present invention,
a series of tests were run to check the effect of brine
solution and moist air on the residual levels of
chlorine produced with the disinfectant chemicals
and the ability of the pelletized composition to
maintain a sufficient level of residual chlorine in
a brine storage tank environment~ The results were
as reported in the ~ollowing examples.
EXample I
The ef~ects of brine solution and humidity
on residual chlorine produced by cyanurate compounds
~5 were tested. Deionized water was saturated with sodium
chloride at room temperature. Potassium dichloro-
isocyanurate was then added to the saturated solution
at a ratio of 100 mg cyanurate to one liter of
solution. The starch-iodide method was used to
determine residual chlorine content. Samples were
taken and tested at several intervals. The results
are xeported in Table I below~
.. ....
''Tab'le I
Rasidual
'Chlorine tm~ '~ime '
446 0 (at mixing~
465 30 minutes
436 1 hour
195 815 days
The results show that the maximum level of
residual chlorine occurred shortly after mixing and that
the level then dropped ovex a period of several days.
:
;2
BFN 6770 ~6- ,
significant level of residual chlorine remained in ~he
test solution even after 8.5 days, indicating that brine
has no drastic effect on the residual chlorir~e level
produced by cyanurate compounds.
Fresh, dry potassium dichloroisocyanurate was
tested against cyanurate which'had been exposed to the
ambient air for three days to determine if moisture in
the air significantly affected the stability or ability
of the compound to release free chlorine. To test this~
2000 mg/1 of potassium dichloroisocyanurate ~both fresh
and a~ed 3 daysl was added to one liter of deionized water.
Samples were taken at 30 minute intervals. The results
are reported in Table II below.
... ... ..
' Tab'l'e 'II
Residual Chlorine
Time Fresh Aged
(mln.) (m~/l) ' tmg/l)
0 844 864
gog 896
~0 866 905
The results indicate that the cyanurate-
compound remains stable upon exposure to the ambient
atmosphere and that moisture in the air has no
significant effect on the ability of the compound to
release free chlorine in solution.
E~ le II
The tests in this example were designed to
determine the disinfection potential o~ salt and
potassium dichloroisocyanurate pellets in a simulated
brine storage tank environment. The experiment was
carried out over a three-month period to insure that
the pellets would not be degraded over a reasonable
period of time such as would be required for a given
BFN 6770 ~7- ~29752
charge of pellets to be used by a domestic water
conditioning system.
Fine grain crystalline sodium chloride and
powdered potassium dichloroisocyanurate were mixed
together in a ratio of about 6.5 x 10 3 grams of
cyanurate to one gram of salt. The mixture was fed
to a three-eighths inch diameter pill press where it
was formed into pellets.
Two 4.4 cm diameter ylass columns were
constructed and sealed at the bottom with one hole
~ubber stoppers. Tubing from the stoppers was clamped
shut ~hen water was not being added to or removed from
the column. Disinfectant pellets we~e added to the
columns maintaininy a ratio of 36" of pellets for every
6" to 8" of water. Brine solution ~as removed every
third day for testing of the level of residual chlorine
by the starch iodide method. Fresh deionized water
~as introduced to replace the brine. The tops of the
column5 were loosely covered to keep out contaminants
2Q but permit air circulation. The results are reported
in Tables III and IV below.
Table III
Water
Column Inches of No. of Height
No. Pellet's 'Pellets ' (in.)
1 30 690 5.84
2 23 530 4.50
~Z~75~
BFN 6770 -8~
~able IV
,
:
~esiduaL Chlorine
... ............ ............
Column #l Column # 2 Ti~e Elapsed_ . -
mg~l mg~l days
53880.0 3150 3
85~.0 990 6
1870.0 801
970.0 801 . 12
100.0 826 lS
10 800.0 . 740 40
130 D 170 43
25.3 2~7 46 ~:
14.4 1280 ~9
400.0 485 52
15 885.0 362 55
312,0 668 59
550.0 20 62
296.0 366 65 ~ .
866.0 1188 68
2Q 5~4.0 1184 72
322,0 868 75
595.0 616 78
154.0 275 81
1120.0 482 8~
25 380.0 790 87
121,0 1015 ~0
1036.0 504 ~3
Ayera~e 658.0 my~1 777 mg/l
As can be seen from Table IV, there was
30 substantial variation in the measured residual chIorine
levels. This can be explained partly by the visually
observed phenomenon of hanging up of the pellets in the
small diameter columns above the water level. This
BFN 6770 ~9~ ~ ~297Sz
problem would not be present in a large diameter brine
storage tank such as those used in domestic water
conditioning systems. Additionally, when fresh water
was added to the colum~ the pellets under water would
dissolve and new pellets would slide down the column
to replace them. Water would be displaced upwardly,
wetting even more pellets and causing high residual
chlorine levels for a short tîme.
However, even after g3 days, the pellets in
both columns were producing significant residual
chlorine levels. The dry pellets remaining in the
columns had not degraded, and the long-term exposure
to ambient air and humidity had not adversely affected
their disinfecting potential.
While the compositions and methods herein
descxibed constitute preferred embodiments of the
in~ention, it is to be understood that the invention
is not limited to these precise compositions and methods,
and that changes may be made in either without departing
from the scope of the invention, which is defined in
the appended claims.
