Note: Descriptions are shown in the official language in which they were submitted.
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
METHODS OF SIMULTANEOUSLY CLEANING AND
DISINFECTING INDUSTRIAL WATER SYSTEMS
Field of the Invention
This invention is in the field of industrial water systems. Specifically, this
invention is in the field of cleaning and disinfection of industrial water
systems.
Background of the Invention
Throughout the world, there are many different types of industrial water
systems. Industrial water systems exist so that necessary chemical, mechanical
and
biological processes can be conducted to reach the desired outcome. Fouling
can occur
even in industrial water systems treated with the best water treatment
programs
currently available. For purposes of this patent application "fouling" is
defined as "the
deposition of any organic or inorganic material on a surface".
If these industrial water systems are not periodically cleaned, then they will
become heavily fouled. Fouling has a negative impact on the industrial water
system.
For example, severe mineral scale (inorganic material) will buildup on the
water
contact surfaces and anywhere there is scale, there is an ideal environment
for the
growth of microorganisms.
Evaporative cooling water systems are particularly prone to fouling. This
fouling occurs by a variety of mechanisms including deposition of air-borne
and water-
borne and water-formed contaminants, water stagnation, process leales, and
other
factors. If allowed to progress, the system can suffer from decreased
operational
efficiency, premature equipment failure, and increased health-related risks
associated
with microbial fouling.
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
Fouling can also occur due to microbiological contamination. Sources of
microbial contamination in industrial water systems are numerous and may
include, but
are not limited to, air-borne contamination, water make-up, process leaks and
improperly cleaned equipment. These microorganisms can establish microbial
communities on any wetable or semi-wetable surface of the water system. Once
these
microbial populations are present in the bulk water more than 99% of the
microbes
present in the water will be present on all surfaces.
Exopolymeric substance secreted by microorganisms aid in the formation of
biofilins as the microbial communities develop on the surface. These biofilins
are
complex ecosystems that establish a means for concentrating nutrients and
offer
protection for growth, and biofilins can accelerate scale, corrosion, and
other fouling
processes. Not only do biofilms contribute to reduction of system
efficiencies, but they
also provide an excellent environment for microbial proliferation that can
include
Legioaella bacteria. It is therefore important that biofihns and other fouling
processes
be reduced to the greatest extent possible to minimize the health-related risk
associated
with Legiohella and other water-borne pathogens.
There are several different cleaning or disinfection methods for cooling water
systems. For example, mechanical cleaning, hyperhalogenation with and without
surfactants or dispersants, and acid cleaning, are amongst the cleaning
methods most
commonly used.
A simple mechanical cleaning program consists of "power washing" and
"scrubbing". Power washing refers to the use of high-pressure water directed
at
equipment surfaces such that the impact of the water on the surface removes
deposits
from those surfaces that can be reached. Mechanical cleaning strategies do not
always
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
remove all heavily adhering deposits such as deposited scale and biological
slime from
equipment surfaces. Further limitations on the use of mechanical cleaning
include the
fact that such methods are effective at removing only loose deposits, and not
for
removing deposits from within the fill (in the case of a cooling tower). For
systems
such as domestic water distribution pipes, power washing is completely
ineffective.
Mechanical cleaning methods also do not provide a means of disinfection, which
is
crucial to maintaining clean and safe equipment.
One standard procedure that uses hyperhalogenation and surfactant is
commonly known as the "Wisconsin Protocol", see "CONTROL OF LEGIONELLA
IN COOLING TOWERS", Summary Guidelines, Section of Acute and Communicable
Disease Epidemiology, Bureau of Community Health and Prevention, Division of
Health, Wisconsin Department of Health and Social Services, August 1987. The
Wisconsin Protocol is used to disinfect an industrial water system following a
Legionellosis outbreak. Even in the absence of an outbreak, hyperhalogenation
is
commonly used to reduce microbial fouling in water systems. Hyperhalogenation
protocols do not remove mineral scale, thereby limiting their ability to
remove or
reduce biological foulants. In addition, the hyperhalogenation procedures that
require a
biodispersant have limited effectiveness within the period the protocol is
implemented.
The use of certain acids, such as sulfuric acid, in combination with high
halogen doses,
as specified in the Wisconsin Protocol, can form copper sulfate and other
deposits that
are subsequently difficult to remove. Finally, because the hyperhalogenation
methods
do not remove scale and other deposits sufficiently, microbial populations re-
establish
rapidly in the systems.
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
An "acid cleaning procedure" is designed to remove mineral scale. Acid is
capable of removing alkaline scale from virtually all wetable surfaces. Acid
cleaning
procedures offer limited disinfection because of the lowered pH, but do not
adequately
penetrate biological deposits (biofilms) that remain associated with system
surfaces.
Operators of industrial water systems use chlorine dioxide to kill
microorganisms. Chlorine dioxide is a well-known biocide, but does not have
the
ability to remove mineral scale. Chlorine dioxide must be generated on-site
where it is
applied. There are several methods for generating and delivering chlorine
dioxide.
One of these methods uses acid in combination with sodium chlorite (acid
activation).
For example, the chlorine dioxide is generated using sodium chlorite and
hydrochloric
acid as follows:
5 NaC102 + 4 HCl = 4 C102 + 5 NaCI + 2 HZO
Typically, the reactants (sodium chlorite and hydrochloric acid) are mixed and
allowed
to react to form chlorine dioxide. Following this reaction, the products
(chlorine
dioxide, sodium chloride, water, some remaining unreacted sodium chlorite, and
hydrochloric acid) are added directly into the water of the industrial water
system. Once
this externally-generated chlorine dioxide solution is applied to the water
system, the
chlorine dioxide is diluted and either lost through volatility or is reduced
by substances
within the water system. Using this method, chlorine dioxide must be
constantly
generated outside the water system, and injected into the system to maintain a
chlorine
dioxide residual.
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
Patent Cooperation Treaty Patent Application WO 02112130 A1 describes and
claims a method of treating water in a water distribution system, comprising:
admixing a sodium chlorite solution with a second solution containing an acid
to make a reacted mixture; and
introducing a predetermined amount of the reacted mixture into a water system.
As described in this Patent Cooperation Treaty Patent Application, the
preferred
method of treating water includes the addition of a catalyst, wherein the
catalyst is
sodium molybdate.
United Kingdom Patent Application No. 2,313,369 describes and claims an
aqueous composition having a pH of more than 9 consists of a stabilized
chlorine
dioxide precursor, an alkali metal polyphosphate and an alkali metal
hydroxide. It also
describes and claims a method of treating water in a water distribution system
comprising the addition of an acid activator to the aqueous composition to
reduce the
pH to less than 7 and injecting the aqueous solution in to the water system.
It would be desirable to have a method for simultaneously cleaning and
disinfecting an industrial water system.
Summary of the Invention
The first aspect of the instant claimed invention is a method of
simultaneously
cleaning and disinfecting an industrial water system comprising the steps of
a) providing an industrial water system;
b) adding to the water of said industrial water system
i) a Compound, wherein said Compound is selected from the group
consisting of the alkali salts of chlorite and chlorate, or a mixture
thereof; and
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
ii) an acid;
wherein said acid is added before the Compound is added; and
c) allowing the water to circulate through the industrial water system for at
least from
about one to about 72 hours; and
d) draining the water from the industrial water system.
The second aspect of the instant claimed invention is a method of
simultaneously cleaning and disinfecting an industrial water system comprising
the
steps of
a) providing an industrial water system;
b) adding to the water of said industrial water system
i) a Compound, wherein said Compound is selected from the group
consisting of the alkali salts of chlorite and chlorate, or a mixture
thereof; and
ii) an acid;
wherein said Compound is added before the acid is added; and
c) allowing the water to circulate through the industrial water system for at
least from
about one to about 72 hours; and
d) draining the water from the industrial water system.
The third aspect of the instant claimed invention is an on-line method of
simultaneously cleaning and disinfecting an industrial water system comprising
the
steps of
6
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
a) providing an industrial water system; wherein said industrial water system
is
selected from the group consisting of cooling water systems and boiler water
systems;
b) optionally reducing the cycles of said industrial water system to single
cycles
and halting the feeding of the routine water maintenance chemicals to the
water
of the industrial water system;
c) adding a Compound selected from the group consisting of the alkali salts of
chlorite and chlorate, or a mixture thereof, and optionally adding a corrosion
inhibitor and optionally adding a dispersant to the water of said industrial
water
system; wherein enough Compound is added to reach a concentration of from
about 1 ppm to about 1000 ppm; wherein if a corrosion inhibitor is added
enough corrosion inhibitor is added to reach a concentration of from about 50
ppm to about 500 ppm and wherein if a dispersant is added enough dispersant is
added to reach a concentration of from about 1 ppm to about 500 ppm;
d) lowering the pH of the water in the industrial water system to about 4.0 by
adding an acid to the water of said industrial water system and maintaining
the
pH of the water in the industrial water system at about 4'.0 for from about 1
to
about 4 hours;
e) adding a chelating agent to the water of the industrial water system,
wherein
enough chelating agent is added to maintain the concentration of the chelating
agent at from about 10 ppm to about 500 ppm in the water of the industrial
water system; wherein said chelating agent is added either before or after the
next step of raising the pH;
7
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
f) optionally raising the pH of the water in the industrial water system from
about
5.5 to about 11 by either adding caustic or stopping the addition of acid or
by a
combination of both of these methods;
g) adding a biocide to the water of the industrial water system; wherein if
the
chelating agent is added after the optional step of raising the pH, then the
chelating agent and the biocide from step g) may be added simultaneously to
the water or the chelating agent may be added first followed by the biocide or
the biocide may be added first, followed by the chelating agent; wherein the
amount of biocide added is that amount sufficient to have a concentration of
from about 1 ppm to about 500 ppm in the water of the industrial water system;
h) allowing the water in the industrial water system to circulate for an
additional
time period of from about 1 hour to about 120 hours; and
i) concluding the cleaning and disinfecting method when the desired cleaning
efficiency has been achieved; wherein, if feeding of the routine water
treatment
maintenance chemicals was stopped during the process, then now resuming the
feeding of the routine water treatment maintenance chemicals to the water of
the
industrial water system; and wherein if feeding of the routine water treatment
maintenance chemicals was not stopped during the procedure, then now
bringing the industrial water system back to normal operation by stopping
cleaning chemical feed, blowing down the water to reduce system cycles to a
single cycle, and then proceeding under normal operating conditions.
The fourth aspect of the instant claimed invention is:
an on-line method of simultaneously cleaning and disinfecting an industrial
water
system comprising the steps of
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
a) providing an industrial water system; wherein said industrial water system
is
selected from the group consisting of cooling water systems and boiler water
systems;
b) optionally reducing the cycles of said industrial water system to single
cycles
and halting the feeding of the routine water maintenance chemicals to the
water
of the industrial water system.
c) adding a chelating agent to the water of the industrial water system,
wherein
enough chelating agent is added to maintain the concentration of the chelating
agent at from about 10 ppm to about 500 ppm in the water of the industrial
water system; wherein said chelating agent is added either before or after the
optional next step of maintaining the pH;
d) optionally maintaining the pH of the water in the industrial water system
from
about S.5 to about 11 by either adding caustic or stopping the addition of
acid or
by a combination of both of these methods;
e) adding a biocide to the water of the industrial water system; wherein if
the
chelating agent is added after the optional step of maintaining the pH, then
the
chelating agent and the biocide from step e) may be added simultaneously to
the water or the chelating agent may be added first followed by the biocide or
the biocide may be added first, followed by the chelating agent; wherein the
amount of biocide added is that amount sufficient to have a concentration of
from about 1 ppm to about 500 ppm in the water of the industrial water system;
f) allowing the water in the industrial water system to circulate for an
additional
time period of from about 1 hour to about 120 hours; and
9
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
g) concluding the cleaning and disinfecting method when the desired cleaning
efficiency has been achieved; wherein, if feeding of the routine water
treatment maintenance chemicals was stopped during the process, then now
resuming the feeding of the routine water treatment maintenance chemicals to
the water of the industrial water system; and wherein if feeding of the
routine
water treatment maintenance chemicals was not stopped during the procedure,
then now bringing the industrial water system back to normal operation by
stopping cleaning chemical feed, blowing down the water to reduce system
cycles to a single cycle, and then proceeding under normal operating
conditions.
Detailed Description of the Invention
Throughout this patent application, the following terms have the stated
meaning
"Fouling" refers to the deposition of any organic or inorganic material on a
surface. These deposits impede water flow and/or heat transfer, and harbor
microorganisms that cause increased deposition, enhance corrosion and increase
health-
related risks.
"Cleaning" means reducing the overall quantity of deposits, which is desirable
because reducing the overall quantity of deposits improves the overall
efficiency of the
industrial water system.
"Disinfection" is typically used to describe a method for killing
microorganisms. As used herein, the goal of disinfection is to cause an
overall
significant reduction in the number or viability of microorganisms within the
water
system.
l0
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
"ONC" refers to Ondeo Nalco Company, Ondeo Nalco Center, 1601 W. Diehl
Road, Naperville, IL 60563, telephone (630) 305-1000.
The first and second aspects of the instant claimed invention are a method of
simultaneously cleaning and disinfecting an industrial water system comprising
the
steps of
a) providing an industrial water system;
b) adding to the water of said industrial water system
i) a Compound selected from the group consisting of the alkali salts of
chlorite and chlorate or a mixture thereof; and
ii) an acid; and
wherein said acid is added before the Compound is added, or the acid is
added after the Compound is added;
c) allowing the water to circulate through the industrial water system for at
least from
about one to about 72 hours ; and
d) draining the water from the industrial water system.
The method of the instant claimed invention can be used to simultaneously
clean and disinfect industrial water systems that are being installed, those
that are
currently in operation, are temporarily not operating, or have been inactive
for extended
periods and are being restored to service.
The method of the instant claimed invention can be used to clean and disinfect
many industrial water systems. These industrial water systems include, but are
not
limited to cooling water systems, including open recirculating, closed and
once-through
cooling water systems; boilers and boiler water systems; petroleum wells,
downhole
formations, geothermal wells and other oil field applications; mineral process
waters
n
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
including mineral washing, flotation and benefaction; paper mill digesters,
washers,
bleach plants, stock chests, and white water systems, and paper machine
surfaces; black
liquor evaporators in the pulp industry; gas scrubbers and air washers;
continuous
casting processes in the metallurgical industry; air conditioning and
refrigeration
systems; industrial and petroleum process water; indirect contact cooling and
heating
water, such as pasteurization water; water reclamation systems, water
purification
systems; membrane filtration water systems; food processing streams (meat,
vegetable,
sugar beets, sugar cane, grain, poultry, fruit and soybean); and waste
treatment systems
as well as in clarifiers, liquid-solid applications, municipal sewage
treatment, municipal
water systems, potable water systems, aquifers, water tanks, sprinkler systems
and
water heaters. The preferred industrial water systems to be simultaneously
cleaned and
disinfected by the method of the instant claimed invention are cooling water
systems,
including open recirculating, closed and once-through cooling water systems,
paper
machine surfaces, food processing streams, waste treatment systems and potable
water
systems. The most preferred industrial water systems to be simultaneously
cleaned and
disinfected by the method of the instant claimed invention are cooling water
systems,
including open recirculating, closed and once-through cooling water systems.
Prior to conducting the method of the instant claimed invention it is
typically
recommended, though not required, that the addition of any chemical or
biological
treatment chemicals to the water be discontinued. It is also recommended to
stop all
energy transfer within the system so that prior to addition of the Compound
and acid,
the water of the industrial water system is circulating through the industrial
water
system without being chemically or biologically treated and without having
heat
transfer occurring.
12
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
The Compound is selected from the alkali salts of chlorite and chlorate and
mixtures thereof. These alkali salts include sodium chlorite, potassium
chlorite, sodium
chlorate and potassium chlorate. The preferred alkali salts are sodium
chlorite and
sodium chlorate. The most preferred alkali salt is sodium chlorite.
The alkali salts of chlorite and chlorate are commodity chemicals that can be
obtained from most chemical supply companies. Sodium chlorite can be obtained
either at its normal pH or in its colloquially referred to "stabilized form"
at an elevated
pH. The preferred sodium chlorite is a 25% solution of sodium chlorite in
water. This
material is available as HYG-25 from ONC.
Sodium chlorate is a commodity chemical that can be obtained from most
chemical supply companies. The preferred sodium chlorate is from about a 20 to
about a 50 Wt/Wt % solution of sodium chlorate in water. This preferred sodium
chlorate is available from Eka Chemicals, Inc., 1775 West Oak Commons Court,
Marietta, GA 30062-2254 USA, telephone number 1-770-578-0858.
Potassium chlorite and potassium chlorate are both available from most
chemical supply companies.
The amount of sodium chlorite or potassium chlorite added to the water of the
industrial water system depends upon what type of industrial water system is
being
cleaned and disinfected. If the method of the instant claimed invention is
applied to a
cooling water system, then the amount of sodium chlorite or potassium chlorite
added
is from about 1 ppm to about 1000 ppm, preferably from about 10 ppm to about
500
ppm and most preferably from about 50 ppm to about 250 ppm.
The amount of sodium chlorate or potassium chlorate added to the water of the
industrial water system depends upon what type of industrial water system is
being
13
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
cleaned and disinfected. If the method of the instant claimed invention is
applied to a
cooling water system, then the amount of sodium chlorate added is from about 1
ppm to
about 1000 ppm, preferably from about 10 ppm to about 500 ppm and most
preferably
from about 50 ppm to about 250 ppm.
If sodium chlorite or potassium chlorite and sodium chlorate or potassium
chlorate are both used then the ratio of chlorite to chlorate, expressed in
weight percent,
is from about 1:99 to about 99:1, preferably from about 10:90 to about 90:10,
and most
preferably about 50:50. The total amount of both chlorite and chlorate
together is the
same as that for either chlorite or chlorate used separately.
The acid is selected from the group consisting of mineral acids and organic
acids wherein said mineral acids are selected from the group consisting of
hydrochloric acid, sulfuric acid, amido sulfuric acid (98%), nitric acid,
phosphoric acid,
hydrofluoric acid and sulfamic acid; and said organic acids are selected from
the group
consisting of citric acid and its salts, formic acid, acetic acid, peracids
including
peracetic acid, peroxyacetic acid and peroxyformic acid, glycolic acid
(hydroxyacetic
acid), oxalic acid, propionic acid, lactic acid (hydroxypropionic acid) and
butyric acid.
The choice of acid depends primarily upon metallurgy within the system. For
metals
such as carbon steel, copper or yellow metal alloys the preferred acids are
hydrochloric
acid, sulfamic acid, formic acid and glycolic acid. The most preferred acid,
for most
metals, is hydrochloric acid.
These acids are commercial chemicals available from a chemical supply
company. These acids can be purchased in dry or in liquid form or in
formulations that
contain other functional chemicals which also can be in dry or liquid form.
For
instance, most of these acids can be obtained in formulation with corrosion
inhibitors.
14
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
Hydrochloric acid formulated with a corrosion inhibitor made of diethyl urea
is sold as
Nalco~2560 Inhibited HCl by ONC.
The amount of acid added to the water of the industrial water system depends
upon what type of industrial water system is being cleaned and disinfected. If
the
method of the instant claimed invention is applied to a cooling water system,
then the
amount of acid added is that required to achieve and maintain a pH from about
1 to
about 5, preferably from about 1 to about 3 and most preferably from about 2
to about
2.5. People of ordinary skill in the art know how to calculate how much of
each acid
would be required in order to achieve the desired pH by taking into account
the system
volume and the alkalinity within the system.
The Compound that is selected from the group consisting of the alkali salts of
chlorite and chlorate and mixtures thereof and the acid are added directly to
the water
of the industrial water system, without being premixed prior to addition.
Either the acid
is added before the Compound or the Compound is added before the acid. It is
possible, although not preferred, to add the acid and Compound simultaneously
to the
water.
The advantage of the instant claimed method is that it is possible to obtain
continuous generation of chlorine dioxide disinfectant throughout the water
system
while also achieving simultaneous acid cleaning. Adding the Compound and the
acid
separately allows a certain amount of circulation of the Compound and acid
prior to
their reaction to create chlorine dioxide. This means more chlorine dioxide is
created
farther away from the point of addition of the Compound and the acid.
After the Compound and acid are added to the water, the water is allowed to
circulate throughout the industrial water system. This circulation of water
allows the
IS
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
cleaning and disinfection of the "water-contact" surfaces of equipment in the
industrial
water system. In addition to the cleaning and disinfection of the water
contact surfaces,
volatile chlorine dioxide is also capable of reaching surfaces that are not
continuously
in contact with water.
The water in the industrial water system is allowed to circulate for a time
period
of from about 1 hour to about 72 hours, preferably from about 1 hour to about
24 hours
and most preferably from about 1 hour to about 8 hours.
During these time periods it is possible, though not required, to monitor the
progress of the cleaning and f indirectly monitor} disinfection by using
standard
techniques to determine the amount of ions present in the water due to the
breaking up
and detachment of inorganic deposits. The inorganic deposits are typically
calcium
salts, magnesium salts, iron oxide, copper oxide and manganese salts. For
instance, it
is known that it is typical for the amount of calcium ion in the water to rise
steadily as
the cleaning progresses and scale, known to contain calcium, is detached from
the
surfaces of the equipment. When the amount of calcium in the water plateaus it
indicates that the cleaning is complete because no new calcium scale is being
dissolved.
After the cleaning and disinfection is finished, the water in the industrial
water
system must be drained and sent for appropriate treatment so that it can be
discharged
in compliance with state and local regulations. Of course, once the water is
drained, it
may be necessary to conduct additional mechanical cleaning of the water
contact
surfaces. This mechanical cleaning is recommended when the cleaning and
disinfection has worked so well that there is an accumulation of loose dirt
and other
undesired material collected in the nooks and crannys of the industrial water
system.
These nooks and crannys can include the fill used in most cooling towers.
After
16
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
mechanical cleaning is over, it is possible to refill the water and begin
operation of the
industrial water system. For heavily contaminated industrial water systems it
is also
possible to fill the industrial water system with water and conduct the method
of the
instant claimed invention again.
In addition to the chemicals named, it is possible to conduct the method of
the
instant claimed invention by adding additional functional chemicals. These
additional
functional chemicals include additional biocides, corrosion inhibitors,
dispersants,
surfactants, reducing agents and chemicals added for pH adjustment.
Additional biocides can be added when microbial contamination is severe.
Biocides suitable for use in the instant claimed invention are selected from
the group
consisting of oxidizing or non-oxidizing biocides. Oxidizing biocides include,
but are
not limited to, chlorine bleach, chlorine, bromine and materials capable of
releasing
chlorine and bromine. The preferred oxidizing biocide is chlorine bleach. Non-
oxidizing biocides include, but are not limited to, glutaraldehyde,
isothiazolin, 2,2-
dibromo-3-nitrilopropionamide, 2-bromo-2-nitropropane-1,3 diol, 1-bromo-1-
(bromomethyl)-1,3-propanedicarbonitrile, tetrachloroisophthalonitrile,
alkyldimethylbenzylammonium chloride, dimethyl dialkyl ammonium chloride,
didecyl
dimethyl ammonium chloride,
poly(oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride,
methylene bisthiocyanate, 2-decylthioethanamine, tetrakishydroxymethyl
phosphonium
sulfate, dithiocarbamate, cyanodithioimidocarbonate, 2-methyl-5-nitroimidazole-
1-
ethanol, 2-(2-bromo-2-nitroethenyl)furan, beta-bromo-beta-nitrostyrene, beta-
nitrostyrene, beta-nitrovinyl furan, 2-bromo-2-bromomethyl glutaronitrile,
bis(trichloromethyl) sulfone, S-(2-hydroxypropyl)thiomethanesulfonate,
tetrahydro-3,5-
1~
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
dimethyl-2H-1,3,5-hydrazine-2-thione, 2-(thiocyanomethylthio)benzothiazole, 2-
bromo-4'-hydroxyacetophenone, 1,4-bis(bromoacetoxy)-2-butene,
bis(tributyltin)oxide,
2-(tert-butylamino)-4-chloro-6-(ethylarnino)-s-triazine, dodecylguanidine
acetate,
dodecylguanidine hydrochloride, coco allcyldimethylamine oxide, n-coco
alkyltrimethylenediamine, tetra-alkyl phosphonium chloride, 7-
oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid, 4,5-dichloro-2-n-octyl-4-
isothiazoline-
3-one, 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-
one. The
preferred non-oxidizing biocide is 2,2-dibromo-3-nitrilopropionarnide and is
available
from ONC.
If the method of the instant claimed invention is applied to a cooling water
system, then the amount of oxidizing biocide added is from about 0.1 ppm to
about 200
ppm, preferably from about 1 ppm to about 100 ppm, more preferably from about
5 to
about 50 ppm and most preferably from about 5 ppm to about 20 ppm.
Corrosion inhibitors can be added when needed to reduce corrosion of the metal
in the industrial water system. Corrosion inhibitors for mufti-metal
protection are
typically triazoles, such as, but not limited to, benzotriazole, halogenated
triazoles,
nitro-substituted azoles, and other triazoles as listed in United States
Patent No.
5,874,026, which is incorporated by reference in its entirety. The preferred
triazole is
benzotriazole.
Triazoles are commercially available from most chemical supply companies.
The preferred benzotriazole is Nalco ~ 73199, which is available from Ondeo
Nalco
Company.
Whether a corrosion inhibitor is used depends upon the industrial water system
and the composition of the water contact surfaces in the industrial water
system. For
~8
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
example, if all the water contact surfaces in the industrial water system are
wood, noble
metals, glass, titanium or plastic, then the use of corrosion inhibitor in
those systems is
not indicated. However, when the water contact surfaces are non-titanium
metal, such
as, but not limited to, stainless steel, carbon steel, galvanized steel, and
yellow metals
such as copper, admiralty and brass, then the use of a corrosion inhibitor is
preferred.
The amount of corrosion inhibitor added to the water of the industrial water
system depends upon what type of industrial water system is being cleaned and
disinfected. If the method of the instant claimed invention is applied to a
cooling water
system, then the amount of corrosion inhibitor added is from about 1 ppm to
about
2000 ppm, preferably from about 10 ppm to about 1000 ppm and most preferably
from
about 50 ppm to about 600 ppm.
The corrosion inhibitor may be added before, after or during the addition of
the
Compound and the acid. The corrosion inhibitor is preferably added prior to
the
addition of acid. The corrosion inhibitor can be added immediately before the
acid and
Compound are added. However, it is preferred that the corrosion inhibitor be
added
sufficiently in advance of the addition of acid that the corrosion inhibitor
can circulate
throughout the system. Thus it is preferred that the corrosion inhibitor be
added from
about 1 hour to about 24 hours prior to addition of the Compound and acid.
The corrosion inhibitor could also be preformulated with other ingredients
being
added to the water. As mentioned previously, corrosion inhibitor can be
formulated
with acid to create an "inhibited acid".
Dispersants are added when needed to keep particulate matter present in the
water of an industrial water system dispersed, so that it does not agglomerate
and cause
fouling during the cleaning and disinfecting process. Dispersants are
typically low
19
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
molecular weight anionic polymers, with "low" referring to a weight average
molecular
weight of from about 500 to about 20,000. These polymers are typically, but
not
limited to acrylic acid, polymaleic acid, copolymers of acrylic acid with
sulfonated
monomers and alkyl esters thereof. These polymers can include terpolymers of
acrylic
acid, acrylamide and sulfonated monomers. These polymers can also include quad-
polymers consisting of acrylic acid and three other monomers.
Dispersant polymers are commercially available from most chemical supply
companies. The preferred dispersant polymer is a High Stress Polymer such as
High
Stress Polymer PR 4832 which is available from Ondeo Nalco Company.
Whether a dispersant is used depends upon the industrial water system, the
deposits present in the system and the foulants present in the water and the
composition
of the water contact surfaces in the industrial water system.
The amount of dispersant added to the water of the industrial water system
depends upon what type of industrial water system is being cleaned and
disinfected. If
the method of the instant claimed invention is applied to a cooling water
system then
the amount of dispersant added is from about 1 ppm to about 500 ppm,
preferably from
about 5 ppm to about 200 ppm and most preferably from about 10 ppm to about
100
ppm.
The dispersant may be added before, after or during the addition of the
Compound and the acid. The dispersant could also be preformulated with other
ingredients being added to the water.
One or more surfactants may be added when and where needed to enhance the
cleaning and disinfection process. Surfactants useful in industrial water
systems
include, but are not limited to, ethylene oxide propylene oxide copolymers,
linear
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
alkylbenzene sulfonates ("LAS"), ethoxylated phosphate esters, and alkyl
polyglycosides, and other surfactants described in United States Patent No.
6,139,830,
U.S. Patent No. 5,670,055 and U.S. Patent No. 6,080,323, which are all
incorporated
by reference.
Surfactants are commercially available from most chemical supply companies.
The preferred surfactants are ethylene oxide propylene oxide copolymers and
alkyl
polyglycosides. These surfactants CL-103, CL-361, CL-362, Nalco~73550, and
Nalco~7348 are available from ONC.
Whether a surfactant is used depends upon the industrial water system, the
deposit or foulant, and the composition of the water contact surfaces in the
industrial
water system.
The amount of surfactant added to the water of the industrial water system
depends upon what type of industrial water system is being cleaned and
disinfected. If
the method of the instant claimed invention is applied to a cooling water
system, then
the amount of surfactant added is from about 0.1 ppm to about 1000 ppm,
preferably
from about 1 ppm to about 500 ppm and most preferably from about 5 ppm to
about
100 ppm.
Surfactant could be added at any time during the method of simultaneous
cleaning and disinfection, but surfactant would preferably be added after
chlorine
dioxide generation has started f in order to reduce any potential
aerosolization of viable
microbial foulants~.
One or more reducing agents may be added when and where needed to react
with oxidants present in order to prepare the water for discharge in
compliance with
state and local environmental regulations. Reducing agents suitable for use in
the
21
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
method of the instant claimed invention include, but are not limited to,
sodium
thiosulfate, sodium bisulfate, sodium metabisulfite and sodium sulfite.
Reducing agents such as these are commercially available from most chemical
supply companies. The preferred reducing agent is sodium bisulfate which is
available
from Ondeo Nalco Company.
Whether a reducing agent is used depends upon the industrial water system and
the amount of oxidants present therein. The amount of reducing agent added to
the
water of the industrial water system depends upon what type of industrial
water system
is being cleaned and disinfected. If the method of the instant claimed
invention is
applied to a cooling water system, then the amount of reducing agent added is
equimolar to the amount of oxidant present. Another way of determining the
amount of
reducing agent that is required is to add reducing agent until there is no
residual
halogen present.
The reducing agent is typically added at the conclusion of the cleaning and
disinfection process just before the water is to be discharged or may be added
to the
discharge pipe or reservoir.
A pH adjusting chemical may be added when needed to adjust the pH of the
water being discharged from the industrial water system. Typical pH adjusting
chemicals include, but are not limited to, NaOH (aka "caustic"), KOH, Ca(OH)Z,
Na2CO3 and KZC03. The preferred pH adjusting chemical is caustic, specifically
a 50%
solution of NaOH in water. Caustic is commercially available from most
chemical
supply companies.
The amount of pH adjusting chemical added to the water of the industrial water
system depends upon what type of industrial water system is being cleaned and
22
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
disinfected, what the pH of the water typically is and what are the pH
requirements for
the water being discharged from the industrial water system.
If the method of the instant claimed invention is applied to a cooling water
system, then the amount of pH adjusting chemical added is that required to
achieve a
pH from about 2 to about 8, preferably from about 3 to about 7 and most
preferably
from about 4 to about 6. The pH adjusting chemical is typically added at the
conclusion of the cleaning and disinfection process just before the water is
to be
discharged or it may be added to the discharge pipe or reservoir.
In practicing the method of the instant claimed invention all of the chemicals
may be added separately. Aside from the Compound and acid being added
separately,
the other chemicals may be formulated together.
A preferred formulation would include corrosion inhibitor, dispersant and
surfactant blended together in a single product.
At the conclusion of the process, the water containing the cleaning and
disinfection chemicals and residual material removed from the water is drained
from
the industrial water system. Then, the system can be refilled with water and
returned to
service right away or not, depending on the needs of the system operators. It
is of
course possible to fill the tower with fresh water and conduct the method of
the instant
claimed invention again, in order to clean heavily contaminated industrial
water
systems.
If a cooling tower has been cleaned and disinfected by the method of the
instant
claimed invention, any of the following actions can tales place at the
conclusion of the
method.
23
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
1) fill the cooling tower using fresh make-up water, and begin dosing a
"normal"
treatment program of inhibitors and biocides;
2) fill the cooling tower using fresh make-up water, and begin dosing a
program of
inhibitors and/or biocides at elevated doses, to achieve passivation of any
exposed
metals and kill off any remaining organisms, followed by resumption of a
"normal"
treatment program;
3) leave the cooling tower dry during a period in which cooling is not
required; or
fill the system with fresh make-up water, and slug dose inhibitors and/or
biocide at
elevated doses, then drain the system (without ever having resumed normal
function)
and leave dry during a period in which cooling is not required.
4) fill the cooling tower with fresh make-up water, drain the system and
refill, slug
dose inhibitors and/or biocide at elevated or normal doses, then return to
service.
The advantages of the first and second aspects of the instant claimed
invention
include the fact that this cleaning and disinfection procedure removes
deposits from
virtually all wetable surfaces, and simultaneously disinfects bulk water and
all wetable
surfaces, and some surfaces not continually in contact with the water, by in-
situ
generation of Cl~2. The method of the instant claimed invention is designed to
minimize corrosion while cleaning and disinfection are taking place, can be
completed
. in less than eight hours, effectively removes microbial deposits and
significantly
extends the period for microbial re-colonization. The procedure works well to
clean
heavily fouled industrial water systems.
The third aspect of the instant claimed invention is an on-line method of
simultaneously cleaning and disinfecting an industrial water system comprising
the
steps of
24
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
a) providing an industrial water system; wherein said industrial water system
is
selected from the group consisting of cooling water systems and boiler water
systems;
b) optionally reducing the cycles of said industrial water system to single
cycles
and halting the feeding of the routine water maintenance chemicals to the
water
of the industrial water system;
c) adding a Compound selected from the group consisting of the alkali salts of
chlorite and chlorate, or a mixture thereof, and optionally adding a corrosion
inlubitor and optionally adding a dispersant to the water of said industrial
water
system; wherein enough Compound is added to reach a concentration of from
about 1 ppm to about 1000 ppm; wherein if a corrosion inhibitor is added
enough corrosion inhibitor is added to reach a concentration of from about 50
ppm to about 500 ppm and wherein if a dispersant is added enough dispersant
is added to reach a concentration of from about 1 ppm to about 500 ppm,;
d) lowering the pH of the water in the industrial water system to about
4.0 by adding an acid to the water of said industrial water system and
maintaining the pH of the water in the industrial water system at about 4.0
for
from about 1 to about 4 hours;
e) adding a chelating agent to the water of the industrial water system,
wherein
enough chelating agent is added to maintain the concentration of the chelating
agent at from about lOppm to about SOOppm in the water of the industrial water
system; wherein said chelating agent is added either before or after the next
step
of raising the pH;
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
f) optionally raising the pH of the water in the industrial water system from
about
5.5 to about 11 by either adding caustic or stopping the addition of acid or
by a
combination of both of these methods;
g) adding a biocide to the water of the industrial water system; wherein if
the
chelating agent is added after the step of raising the pH, then the chelating
agent
and the biocide from step g) may be added simultaneously to the water or the
chelating agent may be added first followed by the biocide or the biocide may
be added first, followed by the chelating agent; wherein the amount of biocide
added is that amount sufficient to have a concentration of from about 1 ppm to
about 500 ppm in the water of the industrial water system;
h) allowing the water in the industrial water system to circulate for an
additional
time period of from about 1 hour to about 120 hours; and
i) concluding the cleaning and disinfecting method when the desired cleaning
efficiency has been achieved; wherein, if feeding of the routine water
treatment
maintenance chemicals was stopped during the process, then now resuming the
feeding of the routine water treatment maintenance chemicals to the water of
the
industrial water system; and wherein if feeding of the routine water treatment
maintenance chemicals was not stopped during the procedure, then now
bringing the industrial water system back to normal operation by stopping the
cleaning chemical feed, blowing down the water to reduce system cycles to a
single cycle, and then proceeding under normal operating conditions.
The third aspect of the instant claimed invention is a method applicable to
cooling water systems and boiler water systems. These industrial water systems
consist
of evaporative cooling towers, open re-circulating, closed and once-through
cooling
26
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
water systems; boilers and boiler water systems and industrial water systems
including
cooling water equipment and boiler equipment.
The Compound is selected from the alkali salts of chlorite and chlorate and
mixtures thereof. These alkali salts include sodium chlorite, potassium
chlorite, sodium
chlorate and potassium chlorate. The preferred alkali salts are sodium
chlorite and
sodium chlorate. The most preferred alleali salt is sodium chlorite.
The alkali salts of chlorite and chlorate are commodity chemicals that can be
obtained from most chemical supply companies. Sodium chlorite can be obtained
either at its normal pH or in its colloquially referred to "stabilized form"
at an elevated
pH. The preferred sodium chlorite is a 25% solution of sodium chlorite in
water. This
material is available as HYG-25 from ONC.
Sodium chlorate is a commodity chemical that can be obtained from most
chemical supply companies. The preferred sodium chlorate is from about a 20 to
about a 50 Wt/Wt % solution of sodium chlorate in water. This preferred sodium
chlorate is available from Eka Chemicals, Inc., 1775 West Oak Commons Court,
Marietta, GA 30062-2254 USA, telephone number 1-770-578-0858.
Potassium chlorite and potassium chlorate are both available from most
chemical supply companies.
The amount of sodium chlorite or potassium chlorite added to the water of the
industrial water system depends upon what type of industrial water system is
being
cleaned and disinfected. If the method of the instant claimed invention is
applied to a
cooling water system, then the amount of sodium chlorite or potassium chlorite
added
is from about 1 ppm to about 1000 ppm, preferably from about 10 ppm to about
500
27
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
ppm, most preferably from about 50 ppm to about 250 ppm and most highly
preferably
about 100 ppm.
If sodium chlorite or potassium chlorite and sodium chlorate or potassium
chlorate are both used then the ratio of chlorite to chlorate, expressed in
weight percent,
is from about 1:99 to about 99:1, preferably from about 10:90 to about 90:10,
and most
preferably about 50:50. The total amount of both chlorite and chlorate
together is the
same as that for either chlorite or chlorate used separately.
The corrosion inhibitor optionally used in the third aspect of the instant
claimed
invention is selected from the group consisting of benzotriazole, halogenated
triazoles,
nitro-substituted azole, and the triazoles listed in United States Patent No.
5,874,026,
which is incorporated by reference in its entirety. The preferred triazole is
benzotriazole. Benzotriazole is available from ONC as Nalco 73199. The amount
of
azole added is that amount sufficient to reach a concentration of about 50 to
about 500
ppm in the water of the industrial water system. The preferred concentration
of azole is
about 100 ppm in the water of the industrial water system.
The dispersant optionally used in the third aspect of the instant claimed
invention is selected from the group consisting of, but not limited to, High
Stress
Polymer (as previously described), acrylic acid, polymaleic acid, copolymers
of acrylic
acid with sulfonated monomers and alkyl esters thereof. These polymeric
dispersants
can include terpolymers of acrylic acid, acrylamide and sulfonated monomers.
These
polymeric dispersants can also include quad-polymers consisting of acrylic
acid and
three other monomers. The preferred dispersant is a terpolymer comprising from
about
30-70 mol % acrylic acid, from about 10-30 mol % Acrylamide and from about 20-
40
28
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
mol % aminomethylsulfonic acid. A terpolymer with such composition is
available
from ONC as High Stress Polymer PR 4382.
The amount of dispersant added is that amount sufficient to reach a
concentration of from about 1 ppm to about SOOppm. The preferred amount of
dispersant is about 100 ppm.
The acid used in the third aspect of the instant claimed invention is either a
mineral acid or an organic acid selected from the group consisting of
hydrochloric acid,
sulfuric acid, amido sulfuric acid (98%), nitric acid, phosphoric acid,
hydrofluoric acid
and sulfamic acid; and said organic acids are selected from the group
consisting of
citric acid and its salts, formic acid, acetic acid, peracids including
peracetic acid,
peroxyacetic acid and peroxyformic acid, glycolic acid (hydroxyacetic acid),
oxalic
acid, propionic acid, lactic acid (hydroxypropionic acid) and butyric acid.
The
preferred acid is glycolic acid, which is available as Nalco 83076 from ONC.
The
amount of acid added is that amount sufficient to lower the pH of the water to
about 4.0
and subsequently to maintain the pH at about 4Ø
The chelating agent useful in the third aspect of the instant claimed
invention is
selected from the group consisting of sodium hexametaphosphate, sodium
polyphosphate, phosphonates, and polycarboxylates (homopolymers and
copolymers).
The preferred chelating agent is sodium hexametaphosphate. It is available as
Glassy
Calgon from ONC. Sufficient chelating agent is added such that the
concentration of
the chelating agent at from about 10 ppm to about 500 ppm in the water of the
industrial water system.
The biocide useful in the third aspect of the instant claimed invention can be
an
oxidizing biocide or a non-oxidizing biocide. Oxidizing biocides are selected
from the
29
28
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
group consisting of chlorine bleach, chlorine, bromine and materials capable
of
releasing chlorine and bromine. The preferred oxidizing biocide is chlorine
bleach..
Non-oxidizing biocides are selected from the group consisting of
glutaraldehyde,
isothiazolin, 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-nitropropane-1,3
diol, 1-
bromo-1-(bromomethyl)-1,3-propanedicarbonitrile, tetrachloroisophthalonitrile,
alkyldimethylbenzylammonium chloride, dimethyl dialkyl ammonium chloride,
didecyl
dimethyl ammonium chloride,
poly(oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride,
methylene bisthiocyanate, 2-decylthioethanamine, tetrakishydroxymethyl
phosphonium
sulfate, dithiocarbamate, cyanodithioimidocarbonate, 2-methyl-5-nitroimidazole-
1-
ethanol, 2-(2-bromo-2-nitroethenyl)furan, beta-bromo-beta-nitrostyrene, beta-
nitrostyrene, beta-nitrovinyl furan, 2-bromo-2-bromomethyl glutaronitrile,
bis(trichloromethyl) sulfone, S-(2-hydroxypropyl)thiomethanesulfonate,
tetrahydro-3,5-
dimethyl-2H-1,3,5-hydrazine-2-thione, 2-(thiocyanomethylthio)benzothiazole, 2-
bromo-4'-hydroxyacetophenone, 1,4-bis(bromoacetoxy)-2-butene,
bis(tributyltin)oxide,
2-(tert-butylamino)-4-chloro-6-(ethylamino)-s-triazine, dodecylguanidine
acetate,
dodecylguanidine hydrochloride, coco alkyldimethylamine oxide, n-coco
alkyltrimethylenediamine, tetra-alkyl phosphonium chloride, 7-
oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid, 4,5-dichloro-2-n-octyl-4-
isothiazoline-
3-one, 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-
one, The
preferred non-oxidizing biocide is 2,2-dibromo-3-nitrilopropionamide, which is
available as Nalco N7649 from ONC. The amount of biocide added is that amount
sufficient to have a concentration of from about 1 ppm to about 20 ppm in the
water of
the industrial water system.
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
In the third aspect of the instant claimed invention, the on-line method of
cleaning and disinfection of industrial water systems allows for cleaning of
inorganic
and organic deposits initially through lowered pH, using an acid for a short
period of
time and subsequently for a prolonged period of time using a chelating agent
at a near
neutral pH. The disinfection talees place initially through the in-situ
generation of
chlorine dioxide when the pH is about 4.0, followed by addition of a chelating
agent
and a biocide when the pH is near neutral.
The fourth aspect of the instant claimed invention is:
an on-line method of simultaneously cleaning and disinfecting an industrial
water
system comprising the steps of
a) providing an industrial water system; wherein said industrial water system
is
selected from the group consisting of cooling water systems and boiler water
systems;
b) optionally reducing the cycles of said industrial water system to single
cycles
and halting the feeding of the routine water maintenance chemicals to the
water
of the industrial water system.
c) adding a chelating agent to the water of the industrial water system,
wherein
enough chelating agent is added to maintain the concentration of the chelating
agent at from about 10 ppm to about 500 ppm in the water of the industrial
water system; wherein said chelating agent is added either before or after the
optional next step of maintaining the pH;
d) optionally maintaining the pH of the water in the industrial water system
from
about 5.5 to about 11 by either adding caustic or stopping the addition of
acid or
by a combination of both of these methods;
31
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
e) adding a biocide to the water of the industrial water system; wherein if
the
chelating agent is added after the optional step of maintaining the pH, then
the
chelating agent and the biocide from step e) may be added simultaneously to
the water or the chelating agent may be added first followed by the biocide or
the biocide may be added first, followed by the chelating agent; wherein the
amount of biocide added is that amount sufficient to have a concentration of
from about 1 ppm to about 500 ppm in the water of the industrial water system;
f) allowing the water in the industrial water system to circulate for an
additional
time period of from about 1 hour to about 120 hours; and
g) concluding the cleaning and disinfecting method when the desired cleaning
efficiency has been achieved; wherein, if feeding of the routine water
treatment maintenance chemicals was stopped during the process, then now
resuming the feeding of the routine water treatment maintenance chemicals to
the water of the industrial water system; and wherein if feeding of the
routine
water treatment maintenance chemicals was not stopped during the procedure,
then now bringing the industrial water system back to normal operation by
stopping cleaning chemical feed, blowing down the water to reduce system
cycles to a single cycle, and then proceeding under normal operating
conditions.
In the fourth aspect of the instant claimed invention, cleaning is attributed
to
chelation by the chelating agent and the disinfection occurs as a function of
the added
biocide.
The chelating agent useful in the fourth aspect of the instant claimed
invention
is selected from the group consisting of sodium hexametaphosphate, sodium
polyphosphate, phosphonates, and polycarboxylates (homopolymers and
copolymers).
32
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
The preferred chelating agent is sodium hexametaphosphate. It is available as
Glassy
Calgon from ONC. Sufficient chelating agent is added such that the
concentration of
the chelating agent at from about 10 ppm to about 500 ppm in the water of the
industrial water system.
The biocide useful in the fourth aspect of the instant claimed invention can
be
an oxidizing biocide or a non-oxidizing biocide. Oxidizing biocides are
selected from
the group consisting of chlorine bleach, chlorine, bromine and materials
capable of
releasing chlorine and bromine. The preferred oxidizing biocide is chlorine
bleach..
Non-oxidizing biocides are selected from the group consisting of
glutaraldehyde, isothiazolin, 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-
nitropropane-1,3 diol, 1-bromo-1-(bromomethyl)-1,3-propanedicarbonitrile,
tetrachloroisophthalonitrile, alkyldimethylbenzylammonium chloride, dimethyl
dialkyl
ammonium chloride, didecyl dimethyl ammonium chloride,
poly(oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride,
methylene bisthiocyanate, 2-decylthioethanamine, tetrakishydroxymethyl
phosphonium
sulfate, dithiocarbamate, cyanodithioimidocarbonate, 2-methyl-5-nitroimidazole-
1-
ethanol, 2-(2-bromo-2-nitroethenyl)furan, beta-bromo-beta-nitrostyrene, beta-
nitrostyrene, beta-nitrovinyl furan, 2-bromo-2-bromomethyl glutaronitrile,
bis(trichloromethyl) sulfone, S-(2-hydroxypropyl)thiomethanesulfonate,
tetrahydro-3,5-
dimethyl-2H-1,3,5-hydrazine-2-thione, 2-(thiocyanomethylthio)benzothiazole, 2-
bromo-4'-hydroxyacetophenone, 1,4-bis(bromoacetoxy)-2-butene,
bis(tributyltin)oxide,
2-(tert-butylamino)-4-chloro-6-(ethylamino)-s-triazine, dodecylguanidine
acetate,
dodecylguanidine hydrochloride, coco allcyldimethylamine oxide, n-coco
alkyltrimethylenediamine, tetra-alkyl phosphonium chloride, 7-
33
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid, 4,5-dichloro-2-n-octyl-4-
isothiazoline-
3-one, 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-
one, The
preferred non-oxidizing biocide is 2,2-dibromo-3-nitrilopropionamide, which is
available as Nalco N7649 from ONC. The amount of biocide added is that amount
sufficient to have a concentration of from about 1 ppm to about 500 ppm in the
water of
the industrial water system.
34
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
The following examples are presented to be illustrative of the present
invention
and to teach one of ordinary skill how to make and use the invention. These
examples
are not intended to limit the invention or its protection in any way.
Examples
A plastic Pilot Cooling Tower with titanium metal heat exchangers and a
plastic
sump is chosen as a test site for the method of the second aspect of the
instant claimed
invention. The Pilot Cooling Tower is in almost continuous use for over one
year so
there is severe contamination present. The contamination is believed to be
both
inorganic scale as well as microbiological sessile populations. There is
visible fouling
on most of the water contact surfaces as well as visible particulate matter
present in the
water that is circulating.
To conduct the method of the instant claimed invention it is necessary to take
the Pilot Cooling Tower out of service for 24 hours.
To prepare for the cleaning and disinfection of the Pilot Cooling Tower, the
cooling system heat load is removed. The cooling system fans are turned-off
and the
blowdown valve is closed. The addition of water treatment program chemicals
are
discontinued, such that the water circulating through the Pilot Cooling Tower
has only
residual water treatment chemicals present.
Throughout the cleaning and disinfection program, Pilot Cooling Tower water
recirculation remains on. Benzotriazole and the dispersant, which is High
Stress
Polymer PR 4832 from ONC are added to the water of the Pilot Cooling Tower.
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
Enough benzotriazole is added to achieve a concentration of about 100 ppm.
Enough
High Stress Polymer is added to achieve a concentration of about 100 ppm.
Sufficient sodium chlorite (NaC102), taken from the chemical stockroom, is
added to the system water such that its concentration in the water is 100 ppm.
The
sodium chlorite is circulated in the system for 30 minutes.
Inhibited hydrochloric acid is then added to the water. Sufficient
hydrochloric
acid is added such that the pH of the water is from about 2.0 to about 3.0,
preferably
about 2.5. The water is circulated for 6 hours while continuing to add
whatever acid is
required in order to maintain a pH of from about 2.0 to about 2.5. During
cleaning and
disinfection, samples are periodically collected and monitored for chlorine
dioxide
using standard analytical technique to determine chlorine dioxide {such as the
diethyl-
p-phenylene diamine test ("the DPD test") for free residual chlorine dioxide,
expressed
"as chlorine") as well as determining the level of hardness present by
complexometric
titration.
During this six hour time period, chlorine dioxide concentrations are found to
be in the range of from about 0.5 to about 1.0 ppm, expressed as free
chlorine.
Hardness values increase from 600 to 2000 ppm over a S hour period. After 5
hours,
the hardness value increases are minimal and acid addition is stopped. The
system
water is recirculated for one additional hour. The system is drained. The
system is
flushed with fresh makeup water and drained a second time.
A visual inspection of the water contact surfaces shows clean surfaces with no
contamination. The method of simultaneous cleaning and disinfection is deemed
to be
a success.
36
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
After the second drainage, the Pilot Cooling Tower is refilled with fresh make-
up water and returned to normal service.
Example 2
This is an example of the third aspect of the instant claimed invention.
A plastic Pilot Cooling Tower with titanium metal heat exchangers and a
plastic
sump is chosen as a test site for the method of the third aspect of the
instant claimed
invention. The Pilot Cooling Tower is in almost continuous use so there is
severe
contamination present. The contamination is believed to be both inorganic
scale as
well as microbiological sessile populations. There is visible fouling on most
of the
water contact surfaces as well as visible particulate matter present in the
water that is
circulating.
To prepare for the cleaning and disinfection of the Pilot Cooling Tower, the
cooling system water is blown-down to reduce system water to single cycle. The
heat
load and the cooling system fans is maintained in operation. For this example,
the
addition of water treatment program chemicals is discontinued, such that the
water
circulating through the Pilot Cooling Tower has only residual water treatment
chemicals present.
Throughout the cleaning and disinfection program, Pilot Cooling Tower water
re-circulation remains on. Benzotriazole and the dispersant, which is High
Stress
Polymer PR 4832 from ~NC are added to the water of the Pilot Cooling Tower.
Enough benzotriazole is added to achieve a concentration of about 100 ppm.
Enough
High Stress Polymer is added to achieve a concentration of about 100 ppm.
37
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
Sufficient sodium chlorite (NaC102), taken from the chemical stockroom, is
added to the system water such that its concentration in the water is 100 ppm.
The
sodium chlorite is circulated in the system for 30 minutes.
Glycolic acid is then added to the water. Sufficient glycolic acid is added
such
that the pH of the water is from about 3.5 to about 5.5, preferably about 4Ø
The water
is circulated for about 1.0 to about 4.0 hours, preferably about 2.0, while
continuing to
add whatever acid is required in order to maintain a pH of from about 4.0 to
about 4.25.
During cleaning and disinfection, samples are periodically collected and
monitored for
chlorine dioxide using standard analytical technique to determine chlorine
dioxide
{such as the diethyl-p-phenylene diamine test ("the DPD test") for free
residual
chlorine dioxide, expressed "as chlorine"} as well as determining the level of
hardness
present by complexometric titration.
During this two hour time period, chlorine dioxide concentrations are found to
be in the range of from about 0.5 to about 1.0 ppm, expressed as free
chlorine.
Hardness values increase from 400 to 1600 ppm over a 2 hour period. After 2
hours,
the acid feed is stopped and the system water pH is allowed to rise due to the
increasing
alkalinity within the system. A rapid rise in the pH is also achieved by the
addition of
enough caustic solution to bring the pH to about 5.0 to 6.5, preferably 5.5.
Sufficient sodium hexametaphosphate, used as a chelating agent, taken from the
Ondeo Nalco chemical stockroom, is added to the system water such that its
concentration in the water is from about lOppm to about SOOppm, preferably 200
ppm.
Sufficient quantities of a non-oxidizing biocide 2,2-dibromo-3-
nitrilopropionamide, taken from the Ondeo Nalco chemical stockroom, is added
to the
38
CA 02484029 2004-10-20
WO 03/092919 PCT/US03/13219
system water such that its concentration in the water is from about 1 ppm to
about 20
ppm.
The system water pH is maintained at 5.5 with intermittent addition of
glycolic
acid, as needed. The system water blow-down was maintained per normal
operational
program and loss of chemical (sodium hexametaphosphate and 2,2-dibromo-3-
nitrilopropionamide) following blow down was replenished by slug doses of the
chemicals. The system water is recirculated for a period of about 48 hours.
The total
hardness levels.are monitored periodically and when hardness level increases
are
minimal, the acid and biocide feed is stopped and the cleaning process is
deemed
completed. The system water is blown down to single cycles, and the routine
water
treatment program is reinstated. The industrial water system is returned to
normal
service.
A visual inspection of the water contact surfaces shows clean surfaces with no
contamination. The method of on-line simultaneous cleaning and disinfection is
deemed to be a success.
39
