Note: Descriptions are shown in the official language in which they were submitted.
2189948
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Technical Field of the Invention
The present invention is in the technical field of microbioreactive compositionsand methods for monitoring and controlling the level of microbioactivity in fluid systems.
Description of the Prior Art
Microbiocides are added to aqueous systems in a variety of industrial and
recreational applications. Some of these applications include the addition of
microbiocides to control the growth of algae, bacteria, fungi and protozoa in industrial
cooling water systems, recreational water systems such as pools and spas, the addition of
microbiocides to control bacteria in the manufacture of paper, the use of microbiocides to
control bacterial growth during the processing of raw sugar, and the like. Using various
methods, the amount of a microbiocide in a system is monitored and controlled,
balancing economic and environmental impacts against the effectiveness of the biocide.
While particularly applicable to aqueous systems, the invention may also find utility in
nonaqueous systems. As used herein, the terms "microbiocide" and biocide" are used
interchangeably and are meant to include chemicals used to control.
Current methods for the direct determination of the amounts of biological activity
and the need for the addition of microbiocide in a fluid system tend to be time consuming
2189948
measurements of the amount of bacterial growth in the system or wet-chemical analysis
of samples for active microbiocide. These methods include culturing a sample taken
from the fluid in the system to determine bacterial growth. If excessive bacterial growth
is present, more microbiocide is generally fed into the system until a culture shows a
steady or decreasing amount of microbiological growth. However, this method requires a
culturing time of at least a day. Therefore, the ability to respond to microbiological
problems in real time is not available with this method. Wet chemical analysis methods
are time consuming, labor intensive and maybe subject to significant error when
conducted in the field rather than a well equipped laboratory and do not give any
information as to the level of microbiological conkol in the system.
Pending U.S. Patent Application, Serial No. 08/236,945 is directed to
microbiocide compositions or systems cont~ining microbiocide having added thereto a
small quantity of inert fluorescent tracer material in an amount proportional to the
quantity of microbiocide so that the amount of microbiocide added to the system can be
measured and controlled on a continuous real-time basis by detennining the level of
fluorescence of the tracer added to the microbiocide. While this application teaches
measurement of biological activity through system consumption, it does not teach or
suggest the measurement of the biological activity in a fluid system by the direct reaction
of the kacer with bacteria in the system. The term consumption, as used herein, does not
2189948
include consumption of the bioreactive reagent due to excessive halogenation or
corrosion within the fluid system.
The present invention is directed to compositions and methods using bioreactive
reagents for on-line real-time determination of microbiological activity in an industrial
system. The amount of bioreactive reagent added to the system and therefore, itsexpected concentration should no biodegradation occur in the system, is determined
precisely. The actual concentration of the bioreactive reagent in the system is measured
on-line. The extent of biological activity in the system is calculated as the difference
between the two measurements. Based on the level of biological activity that is detected,
the dosage of a microbiocide necessary to control the biological activity can bedetermined and controlled.
The use of inert tracer materials to monitor and control the concentration of
treatment chemical products (e.g., those cont~ining corrosion and scale inhibitors) in
industrial water systems is well-known. Hoots (U.S. Patent No. 4,783,314) discloses the
use of inert tracer materials for monitoring and controlling the concentration of treatment
chemical products, corrosion and scale inhibitors, using fluorometry. Hoots et al. (U.S.
Patent Nos. 4,966,711 and 5,041,386) teaches the use of inert fluorescent additives which
are added in direct proportion to the arnount of a corrosion and/or scale inhibitor to
monitor the concentration of a corrosion and/or scale inhibitor in a given industrial water
- 4 -
21899~8
_
system. U.S. Patent Nos. 4,992,380, 5,006,311 and 5,132,096 disclose methods and- equipment to monitor fluorescent tracers used in industrial water treatment applications.
Japanese Patent No. 55003668 (1980) discloses an atomic adsorption
spectroscopy method for monitoring biocide concentrations by adding and measuring
lithium salt materials to indirectly determine the concentration of microbiocides added to
the system. This method requires the separate addition of tracer material and requires the
use of atomic adsorption spectroscopy to obtain results. Atomic adsorption spectroscopy
is expensive compared to fluorometry and has the disadvantage that atomic adsorption
spectroscopy is not readily adaptable to field use for continuous monitoring and/or
1 0 control of treatment dosage due to the complex equipment involved, as well as open
flame and fl~mm~ble gas supplies. In addition, this patent does not teach nor does it
suggest the measurement of the biological activity or the level of the active biocide in a
fluid system.
U.S. Patent No. 4,242,602 discloses an ultraviolet spectroscopy technique to
1 5 monitor multiple water treatment components. The method involves the use of expensive
analytical equipment along with computer hardware having specially written software. In
addition, equipment must be calibrated on a site specific basis over a period of weeks or
months and recalibration may be necessary if conditions in the water change. European
Patent Application 466303 discloses a method involving the addition of a substance to
treated water and how it reacts with the microbiocide, not the microbiological agents
218g9~8
within the system. The substance reacting with the microbiocide is continuously
measured and the concentration of the microbiocide is determined by loss of the
substance. The method is cumbersome, requires special equipment, and two séparate
chemical feeds. The method is used to calculate the level of biocide in a system at a
given time, but it does not measure the microbiological activity in the system.
Ideally, a bioreactive reagent composition and method would exist by which the
level of microbiological activity in a system could be easily monitored, and in certain
situations, by which an industrial microbiocide could be fed to the system in response to
decreasing concentration or increasing consumption of the bioreactive reagent. The
present invention solves many of the problems detailed above by providing an easy to
use, continuous method for the detçrmin~tion and control of microbiological activity in
fluid systems, particularly in~ tri~l water systems.
Summaly of the Invention
The invention provides to the art novel bioreactive reagent compositions, the
concentrations of which can be conveniently and continuously measured. The invention
is a method for monitoring the level of microbiological activity of a fluid system. The
method comprises adding a known amount of at least one bioreactive reagent of from
about l 0 ppb to about l 00 ppm to the system. The bioreactive reagent is added at a level
to provide a system having a bioreactive reagent concentration at or greater than the
2189948
minimum detection concentration for the bioreactive reagent in the system. The actual
concentration of the bioreactive reagent in the system is measured on-line continuously
by any known means. The difference between the expected and measured concentration
of the bioreactive reagent, the consumption of the bioreactive reagent, is a measure of the
microbiological activity in the system. Using the difference, the level of microbiological
activity in the fluid system can be determined.
In the prerelled embodiment, the invention is also a method for monitoring and
controlling the microbiological activity in an aqueous system. The method comprises
adding to the system a formulation consisting of two components, namely, a fluorescent
bioreactive reagent and an inert fluorescent compound. The bioreactive reagent and the
inert fluorescent compound are added at a level to provide a system having
concentrations at or greater than the minimum detection concentrations for the
bioreactive reagent and the inert fluorescent compound in the system. The amount of the
fluorescent bioreactive reagent added to the system is determined accurately by
measuring the concentration of the inert compound in the system. The actual
concentration of the fluorescent bioreactive reagent in the system is also measured on-line
continuously. The difference between the expected and measured concentration (i.e.,
consumption) of the bioreactive reagent is a measure of the microbiological activity at a
desired level. A microbiocide is then added to the system to control the microbiological
activity at a desired level.
2189948
Brief Desc- ;I,lion of the Drawin~
FIG. l graphically represents the biodegradation of the 5-methylbenzot~iazole
isomer after tolyltriazole spike.
FIG. 2 graphically represents the results from a Pilot Cooling Tower test showing
the effect of bioreactive reagent consumption on microbiological population.
FIG. 3 graphically represents bacterial populations as a function of dosage of the
5-methylbenzotriazole isomer, the 4-methylbenzotriazole isomer and distilled water.
FIG. 4 graphically represents the data obtained from a respirometry experiment
demonstrating the aerobic biodegradation of the 5-methylbenzotriazole isomer.
Description of the Preferred Embodiments
The present invention provides a method of monitoring and controlling
microbiological activity in fluid systems. Although the invention is not limited to any
particular source of water, preferably, cooling water systems, such as cooling towers,
once-through cooling systems, cooling lake or pond systems, and spray ponds, are treated
by the method and compositions of the invention. These cooling water systems aredescribed in detail in the Nalco Water Handbook, 2nd ed., Ch. 34 (1988).
The present invention is a method for monitoring the level of microbiological
activity of a fluid system which comprises the following steps.
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(Step a) Adding to the system a known amount of at least one bioreactive reagent of
from about 10 ppb to about 100 ppm. The bioreactive reagent is added at a level to
provide a system having a concentration of the bioreactive reagent at or greater than
minimum detection concentration for such a bioreactive reagent in the system.
(Step b) The concentration of the bioreactive reagent is continuously measured by any
known means.
(Step c) The concentration of bioreactive reagent present as measured in (Step b) is
subtracted from the concentration of bioreactive reagent added in (Step a). The difference
is used to calculate the level of consumption of the bioreactive reagent.
(Step d) The level of microbiological activity in the fluid system is calculated using the
level of consumption of the bioreactive reagent.
A bioreactive reagent feed pump may be activated in response to concentration
losses of bioreactive reagent below a pre-determined level and deactivated in response to
concentrations of bioreactive reagent at or above the pre-determined level as determined
by blowdown measurements, mass flow measurements of water loss, or any other known
means used in measuring hydraulic losses in the fluid system. The concentration of the
bioreactive reagent in the system can be measured by fluorescence. The concentration of
the bioreactive reagent may be measured on an intermittent basis. The bioreactive
reagent may be delivered to the system as a neat product or mixed with other treatment
additives.
2189948
In addition to the dynamic operating conditions of a cooling water system, othersignificant variables and unknown factors are commonly encountered. For example,blowdown water (B) can be removed from the cooling system through a variety of ways
(see equation l ), which unfortunately tend to be variable and ill-defined in nature. The
rate at which water is specifically pumped from the cooling water system is defined as
"recirculating water blowdown" (BR)~ and even that rate is not always accurately known
due to practical difficulties in measuring large volumes of water. In addition, ill-defined
amounts of recirculating water (un-accounted system losses) are commonly removedfrom the cooling water system to be used in other areas of the industrial plant, defined as
"plant blowdown" (Bp). Leakage of recirculating water (BL) and drift of liquid droplets
from cooling tower (BD) also add to unaccounted system losses. A similar situation can
occur with the makeup water, where the total makeup water rate (M) is the combined rate
at which makeup water is specifically pumped into the recirculating system (MR) and
liquid origin~ting from other sources (M'), (see equation 2). The complexity of the
situation can be appreciated by considering equations l and 2.
B=BR+Bp+BL+BD (eq l)
M=MR+M' (eq2)
The feed rate of chemical treatment into the cooling water system is commonly
based on estimated values for MR or BR~ which means there can be considerable
uncertainty regarding the concentration of the chemical treatment. When operating
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2~89948
-
conditions of the cooling water system change, the feed rate of the chemical treatment
should be adjusted. Those adjustments may or may not be made, depending on how
carefully the cooling water system is monitored and controlled. Even when feed rates are
adjusted, the concentration of chemical treatment within a cooling water system generally
may respond slowly to the change (see equation 3).
t = (VT/B) ln (2) (eq 3)
where t = response time for 50% of concentration increase to occur.
The fluid system to which the present invention may find applicability includes
various aqueous systems such as a cooling water system or a waste treatment system. In
addition, the fluid system may be a mixed organic/aqueous fluid system or a non-aqueous
fluid system.
The method may comprise a further step of adding to the system an effective
amount of microbiocide necessary to control the microbiological activity as calculated in
(Step d). The required dosage level of microbiocide is based on the results determined in
(Step d).
The microbiocide used in the present invention may be an oxidizing biocide
selected from the group consisting of chlorine, bromine, iodine, hypochlorous acid,
hypobromous acid, hypoiodous acid, stabilized hypochlorous acid, stabilized
hypobromous acid, stabilized hypoiodous acid, and salts thereof. Alternatively, the
microbiocide may be a non-oxidizing biocide selected from the group consisting of
21899~8
glutaraldehyde, isothiazolone, dibromonitrilopropionaminde, metronidazole,
dodecylguanidine, triazine, tributyltinoxide, cocodiamine, quaternary ammonium salt,
carbamates, and copper sulfate. A microbiocidal chemical feed pump may be activated in
response to levels of bioreactive reagent consumption at or above a pre-determined level
of consumption and deactivated in response to levels of bioreactive reagent consumption
which is below a pre-determined level of consumption.
The data obtained from the system consumption measurement may be used to
quantitatively determine real-time system consumption of the bioreactive reagent. This
data can be used to determine the extent to which undesirable system consumption has
been reduced or elimin~ted by the addition of a microbiocide to the system.
Another embodiment is a method for monitoring and controlling the
microbiological activity of a fluid system which comprises the following steps.
(Step a) Adding to the system a known amount of a bioreactive reagent of from about 10
ppb to about 100 ppm. The bioreactive reagent is added at a level to provide a system
having a concentration of the bioreactive reagent at or greater than minimum detection
concentration for such a bioreactive reagent in the system.
(Step b) Adding a substantially inert compound in a known ratio of bioreactive reagent to
the inert compound. The ratio of bioreactive reagent to inert compound can range from
about 100:1 to about 1:100. The substantially inert compound is added at a level to
21899A8
provide a system having the concentration of the inert compound at or greater than
minimum detection concentrations for such a inert compound in the system.
(Step c) The concentration of the inert compound in the system is m~int~ined at a
constant predetermined level by adding inert compound and the bioreactive reagent in the
initial ratio as required.
(Step d) The concentration of the inert compound is continuously measured by anyknown means.
(Step e) The concentration of the bioreactive reagent is continuously measured by any
known means.
(Step f) The concentration of bioreactive reagent present as measured in step e) is
subtracted from the concentration of inert compound present as measured in step d). The
difference is used to calculate the level of consumption of the bioreactive reagent. Where
the concentration of the inert compound is m~int~ined at a pre-determined level, the
amount of consumption of the bioreactive reagent is a measure of the difference between
the amount of the reagent added to the system and the amount of the reagent measured in
the system.
(Step g) The level of microbiological activity in the fluid system is calculated using the
level of consumption of the bioreactive reagent.
By the terms "substantially inert" and "inert", it is meant that the compound
(tracer) is not appreciably or significantly affected by any other chemistry in the system,
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~189948
or by other system parameters such as metallurgical composition, heat changes or heat
content. Such compounds are not degraded by or deposited within the fluid system. This
is termed an inert compound, inert to the system equipment and all chemistry i~ the
system, so that the inert compound moves through the system unscathed and not altered
to any significant or meaningful extent. The inert compounds used herein subscribe to
the practical analytical chemistry requirement of loss equal to or less than l 0%.
Both an inert compound feed pump and a bioreactive reagent feed pump may be
activated in response to concentrations of inert compound below the pre-determined level
and deactivated in response to concentrations of inert compound at or above the pre-
determined level. In addition, the inert compound and bioreactive reagent can be added
concurrently or as a mixture, using one feed pump. The concentrations of the inert
compound and bioreactive reagents may be measured on an intermittent basis. The
concentrations of the inert compound and the bioreactive reagent in the system may be
measured by fluorescence. The bioreactive reagent and the inert compound can be added
to the system as a mixture.
The fluid system to which the present invention may find applicability includes
various aqueous systems, such as a cooling water system or a waste treatment system. In
addition, the fluid system may be a mixed organic/aqueous fluid system or a non-aqueous
fluid system.
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21~9998
The method may comprise a further step of adding to the system an effective
amount of microbiocide necessary to control the microbiological activity calculated in
(Step g).
The microbiocide used in the present invention may be an oxidizing biocide
selected from the group consisting of chlorine, bromine, iodine, hypochlorous acid,
hypobromous acid, hypoiodous acid, stabilized hypochlorous acid, stabilized
hypobromous acid, stabilized hypoiodous acid, and salts thereof. Alternatively, the
microbiocide may be a non-oxidizing biocide selected from the group consisting of
glutaraldehyde, isothiazolone, dibromonitrilopropion~min(le, metronidazole,
dodecylguanidine, triazine, tributyltinoxide, coco~ mine, quaternary ammonium salt,
carbamates, and copper sulfate. A microbiocidal chemical feed pump may be activated in
response to levels of bioreactive reagent consumption at or above a pre-determined level
of consumption and deactivated in response to levels of bioreactive reagent consumption
below a pre-determined level of consumption.
The data obtained from system consumption measurement is used to
quantitatively determine real-time system consumption of the bioreactive reagent. This
data can be used to deterrnine the extent to which undesirable system consumption has
been reduced or elimin~ted by the addition of a microbiocide to the system.
A preferred embodiment is a method for monitoring and controlling the
microbiological activity of a fluid system which comprises the following steps:
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2l899~8
(Step a) Adding to the system a known amount of a bioreactive reagent of from about 10
ppb to about 100 ppm. The bioreactive reagent is added to a level to provide a system
having a concentration of the bioreactive reagent at or greater than minimum détection
concentration for such a bioreactive reagent in the system.
(Step b) Adding a substantially inert compound in a known ratio of bioreactive reagent to
the inert compound. The ratio of bioreactive reagent to inert compound can range from
about 100:1 to about 1:100. The substantially inert compound is added at a level to
provide a system having the concentration of the inert compound at or greater than
minimum detection concentrations for such inert compound in the system.
(Step c) The concentration of the bioreactive reagent in the system is m~int~ined at a
constant predetermined level by adding inert compound and the bioreactive reagent in the
initial ratio as required.
(Step d) The concentration of the inert compound is continuously measured by anyknown means.
(Step e) The concentration of the bioreactive reagent is continuously measured by any
known means.
(Step f) The concentration of bioreactive reagent present as measured in step e) is
subtracted from the concentration of inert compound present as measured in step d). The
difference is used calculate the level of consumption of the bioreactive reagent.
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21 899~8
(Step g) The level of microbiological activity in the fluid system is calculated using the
level of consumption of the bioreactive reagent.
An inert compound feed pump and bioreactive reagent feed pump may be
activated in response to concentrations of inert compound below the pre-determined level
and deactivated in response to concentrations of inert compound at or above the pre-
determined level. In addition, the inert compound and bioreactive reagent can be added
concurrently or as a mixture, using one feed pump. The concentrations of the inert
compound and the bioreactive reagent may be measured on an intermittent basis. The
concentrations of the inert compound and the bioreactive reagent in the system may be
measured by fluorescence. The bioreactive reagent and the inert compound can be added
to the system as a mixture.
The fluid system to which the present invention may find applicability includes
various aqueous systems, such as a cooling water system or a waste treatment system. In
addition, the fluid system may be a mixed organic/aqueous fluid system or a non-aqueous
fluid system.
The method may comprise a further step of adding to the system an effective
amount of microbiocide necessary to control the microbiological activity calculated in
(Step g).
The microbiocide used in the present invention may be an oxidizing biocide
selected from the group consisting of chlorine, bromine, iodine, hypochlorous acid,
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hypobromous acid, hypoiodous acid, stabilized hypochlorous acid, stabilized
hypobromous acid, stabilized hypoiodous acid, and salts thereof. Alternatively, the
microbiocide may be a non-oxidizing biocide selected from the group consisting of
glutaraldehyde, isothiazolone, dibromonitrilopropionaminde, metronidazole,
dodecylguanidine, triazine, tributyltinoxide, coco~i~mine, qu~tçrn~ry ammonium salt,
carbamates, and copper sulfate. A microbiocidal chemical feed pump may be activated in
response to levels of bioreactive reagent consumption at or above a pre-determined level
of consumption and deactivated in response to levels of bioreactive reagent consumption
below a pre-determined level of consumption.
The data obtained from system consumption measurement is used to
quantitatively determine real-time system consumption of the bioreactive reagent. This
data can be used to determine the extent to which undesirable system consumption has
been reduced or elimin~ted by the addition of a microbiocide to the system.
In the present invention, a bioreactive composition, the concentration of which
when added to a fluid system is capable of being measured by known means in suchsystem, is comprised of a diluent, one or more bioreactive reagents, and at least one
substantially inert compound, wherein the bioreactive reagents and the substantially inert
compound is present in a ratio of from about 100:1 to about 1:100. More preferably, the
ratio of bioreactive reagent to substantially inert compound is from about 100:1 to about
2:1, and most preferably from about 20:1 to about 2:1. The diluent may be water.
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The inert compound may be soluble or evenly dispersible in the diluent. The inert
compound may be selected from a group consisting of mono-, di-, and tri- sulfonated
naphthalenes, including their water soluble salts, particularly the various naphthalene
mono- and di- sulfonic acid isomers, which are preferred inert compounds for use in the
present invention. The naphthalene mono- and di- sulfonic acid isomers are water-
soluble, generally available commercially and are easily detectable and quantifiable by
know fluorescence analysis techniques. Preferred naphthalene mono- and di- sulfonic
acid isomers are the water-soluble salts of naphthalene sulfonic acid (NSA), such as 1-
NSA and 2-NSA, and naphthalene disulfonic acid (NDSA or NDA), for instance 1,2-
NDSA, 1,3-NDSA, 1,4-NDSA, 1,5-NDSA, 1,6-NDSA, 1,7-NDSA, 1,8-NDSA, 2,3-
NDSA, 2,4-NDSA, and so forth. In addition, methyl naphthalene sulfonates and water-
soluble salts thereof, and naphthalene sulfonate-formaldehyde polymers are also useful as
inert compounds in the present invention. Many of these inert compounds (mono-, di-,
and tri- sulfonated naphthalene and mixtures thereof) are generally compatible with the
environments of most aqueous systems employing industrial microbiocides.
Another group of inert fluorescent compounds that are preferred for usein the
process of the present invention are the various sulfonated derivatives of pyrene, such as
1,3,6,8 pyrenetetrasulfonic acid, and the various water-soluble salts of such sulfonated
pyrene derivatives. The composition of the present invention contains at least one inert
compound that is selected from a group con~i~ting of monosulfonated naphthalenes and
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- 2189948
water-soluble salts thereof, disulfonated naphthalenes and water-soluble salts thereof,
trisulfonated naphthalenes and water-soluble salts thereof, methyl naphthalene sulfonates
and water-soluble salts thereof, naphthalene sulfonate-formaldehyde polymers, sulfonated
derivatives of pyrene and water-soluble salts thereof, and mixtures thereof. Many other
water soluble tracer materials that fluoresce will be appalell~ to those skilled in the art.
As a general rule, inert tracers should be:
1. Thermally stable and not decompose at the temperature within the given system;
2. Detectable on a continuous or semicontinuous basis and susceptible to
concentration measurements that are accurate, repeatable, and capable of being
performed on the system;
3. Substantially foreign to the chemical species that are normally present in the
water;
4. Substantially impervious to any of its own potential specific losses from the water
of the system;
5. Substantially impervious to interference from, or biasing by, the chemical species
that are normally present in the water;
6. Compatible with all treatment agents employed in the system in which the inert
tracer may be used, and thus in no way reduce the efficacy thereof;
7. Compatible with all mechanical components of the system, and be stable in any
storage and transportation conditions encountered; and,
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21 899g8
8. Reasonably nontoxic and environmentally safe.
The bioreactive reagent may be selected from a group consisting of S-
methylbenzotriazole, benzotriazole-5-carboxylic acid, and butylbenzotriazole.
As stated above, a preferred embodiment of the invention is a method for
controlling the feed of an aqueous biocide into an aqueous system. The method
comprises adding the system a formulation consisting of two components, namely, a
fluorescent bioreactive reagent and an inert fluorescent reagent. The bioreactive reagent
and the inert fluorescent reagent are added at a level to provide a system having a
bioreactive reagent concentration at or greater than the minimum detection concentration
of these reagents in the system. The amount of the fluorescent bioreactive reagent added
to the system is determined accurately by measuring the concentration of the inert
fluorescent reagent in the system. The actual concentration of the fluorescent bioreactive
reagent in the system is also measured on-line continuously. The difference between the
expected and measured concentration of the bioreactive reagent is a measure of the
microbiological activity of the system. A microbiocide is then added to the system to
control the microbiological activity at a desired level.
According to one embodiment of the invention, a known amount of a bioreactive
reagent composition is added to an industrial or commercial cooling system to monitor
microbiological activity. The bioreactive reagent is preferably added in a dosage of from
0.01 to 100 parts per million (ppm). More preferably, the bioreactive reagent is added to
_. 21899~8
the cooling water in a final concentration of from O.Ol to about 20 ppm. A most
preferred bioreactive reagent final concentration is from O.Ol to about 5 ppm. In one
embodiment of the invention, bioreactive reagent is added to the cooling water
continuously at a controlled rate to target or m~int~in a concentration of from O.Ol to lO0
ppm. The bioreactive reagent, may also be added intermittently to achieve a
concentration of bioreactive reagent in the water from O.Ol to about l 00 ppm. The
cooling water may also contain corrosion inhibitors, such as biocides, phosphates,
benzotriazole, napthalenetriazole, molybdates, zinc, phosphonates, and polymer treatment
programs. These corrosion inhibitors may be added with the bioreactive reagent or
1 0 separately.
Several different methods by which the bioreactive reagent concentration can be
measured are described below.
Fluorescence Emission Spectroscopy
The detection and quantification of specific substances by fluorescence emissionspectroscopy is founded upon the proportionality between the amount of emitted light
and the amount of a fluoresced substance present. When energy in the form of light,
including ultra violet and visible light, is directed into a sample cell, fluorescent
substances therein will absorb the energy and then emit that energy as light having a
longer wavelength than the absorbed light. The amount of emitted light is determined by
_ 21899~
a photodetector. In practice, the light is directed into the sample cell through an optical
light filter so that the light transmitted is of a known wavelength, which is referred to as
the excitation wavelength and generally reported in nanometers ("nm"). The emitted
light is similarly screened through a filter so that the amount of emitted light is measured
at a known wavelength or a spectrum of wavelengths, which is referred to as the emission
wavelength and generally also reported in nanometers. When the measurement of
specific substances or categories of substances at low concentrations is desired or
required, such as often is the case for the process of the present invention, the filters are
set for a specific combination of excitation and emission wavelengths, selected for
substantially optimum low-level measurements.
Fluorescence emission spectroscopy is one of the preferred analysis techniques for
the process of the present invention. Some naturally fluorescent compounds are also
water treatment agents, and thus may be among the normal components of cooling water,
such as aromatic organic corrosion inhibitors, such as aromatic (thio)(tri)azoles.
In general for most fluorescence emission spectroscopy methods having a
reasonable degree of practicality, it is preferable to perform the analysis without isolating
in any manner the fluorescent tracer. Thus, there may be some degree of background
fluorescence. In instances where the background fluorescence is low, the relative
intensities (measured against a standard fluorescent compound at a standard concentration
and assigned a relative intensity for instance l 00) of the fluorescence of the tracer or
_ . 21899g8
compound of interest is very high versus the background, for instance a ratio of 100/10 or
500/10 when certain combinations of excitation and emission wavelengths are employed
even at low fluorescent compound concentrations, and such ratios would be
representative of relative performance (under like conditions) of respectively l O and 50.
For most cooling water backgrounds, a compound that has a relative performance
(fluorescence of tracer or compound of interest versus background) of at least about 5 at a
reasonable concentration is very suitable as a fluorescent tracer itself or as a tagging agent
for water treatment polymers and the like when such compounds contain an ~plo~liate
reactive group for the tagging reaction. When there is or may be a specific chemical
specie of reasonably high fluorescence in the background, the tracer and the excitation
and/or emission wavelengths often can be selected to nullify or at least minimi7:~ any
interference of the tracer measurements(s) caused by the presence of such specie.
Continuous on-stream monitoring of chemical tracers by fluorescence emission
spectroscopy and other analysis methods is described in U. S. Patent No. 4,992,380, B. E.
Moriarity, J. J. Hickey, W. H. Hoy, J. E. Hoots and D. A. Johnson, issued February 12,
1991, incorporated herein by reference.
Combined HPLC-Fluorescence Analysis
The combination of high-performance liquid chromatograph ("HPLC") and
fluorescence analyses of fluorescent tracers is a powerful measurement tool with the
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21899~8
present invention, particularly when very low levels of the fluorescent tracer are used or
the background fluorescence encountered would otherwise interfere with the efficacy of
the fluorescence analysis. The HPLC-fluorescence analysis method allows thetracer
compound and/or bioreactive reagent to be separated from the fluid matrix and then the
tracer concentration can be measured. The combination of HPLC-fluorescence analysis
is particularly effective for measuring minute levels of tracer compound and/or
bioreactive reagent in highly cont~min~ted fluids.
The HPLC method can also be effectively employed to separate a tracer
compound and/or bioreactive reagent from a fluid matrix for the purposes of thenemploying a tracer-detection method other than fluorescence analysis, and such other
tracer-detection methods include without limitation light absorbance, post-column
derivatization, conductivity and the like.
Colorimetry And Spectrophotometry Analysis
Colorimetry or spectrophotometry may be employed to detect and/or quantify a
chemical tracer. Colorimetry is a determination of a chemical specie from its ability to
absorb ultraviolet or visible light. One colorimetric analysis technique is a visual
comparison of a blank or standard solution (containing a known concentration of the
tracer specie) with that of a sample of the fluid being monitored. Another colorimetric
method is the spectrophotometric method wherein the ratio of the intensities of the
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2189948
incident and the transmitted beams of light are measured at a specified wavelength by
means of a detector such as a photocell or photomultiplier tube. Using a colorimetric
probe, a fiber optic (dual) probe, such as a Brinkman PC-80 probe (570 nm filtér), a
sample solution is admitted to a flowcell in which the probe is immersed. One fiber optic
cable shines incident light through the sample liquid onto a mirror inside the cell and
reflected light is transmitted back through the sample liquid into a fiber optic cable and
then to the colorimetric analyzer unit, which contains a colorimeter, by the other cable.
The colorimeter has a transducer that develops an electrical analog signal of the reflected
light characteristic of the tracer concentration. The voltage emitted by the transducer
activates a dial indicator and a continuous line recorder printout unit. A set point voltage
monitor may be employed to constantly sense or monitor the voltage analog generated by
the colorimeter, and upon detection of a tracer signal (discussed below), a responsive
signal may be transmitted to a responsive treatment agent feed line to commence or alter
the rate of feed. Such a colorimetric analysis technique and the equipment that may be
employed therefor are described in U. S. Patent No. 4,992,380, B. E. Moriarity, J. J.
Hickey, W. H. Hoy, J. E. Hoots and D. A. Johnson, issued February 12, 1991,
incorporated hereinto by reference. Chemical tracers suitable for use in conjunction with
a colorimetric technique include transition metals (discussed below) and substances
which show light absorbance which is detectable from that of other species present in the
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- 21899q8
system fluid or substances which react with color-forming reagents to produce light
absorbance which is detectable from that of other species present in the system fluids.
Transition Metal Analysis
A transition metal compound (transition metal ions, oxy-anions, cations and
associated complexes) can be quantitatively measured by one or more of known
techniques. Preferred techniques include colorimetry and fluorescence analysis. Another
technique is molecular absorption. Molecular absorption in the ultra violet and visible
region depends on the electronic structure of the molecule. The energy absorbed elevates
electrons from orbitals in a lower-energy state to orbitals in a higher-energy state. A
given molecule can absorb only certain frequencies because only certain states are
possible in any molecule and the energy difference between any ground and excited state
must be equal to the energy added. At a frequency that is absorbed by a molecule, the
intensity of the incident energy is greater than the intensity of the emergent energy, and is
a measure of the absorbance. A sample of the fluid being monitored may be compared to
a calibration curve (absorbance versus concentration) prepared from standard solutions
cont~ining known concentrations of the transition metal (or other suitable tracer specie) to
detect and determine the concentration of the tracer. A molecular absorption technique
for transition metal tracers is described in U. S. Patent No. 4,992,380, B. E. Moriarity, J.
2t8~9q8
J. Hickey, W. H. Hoy, J. E. Hoots and D. A. Johnson, issued February 12, 1991,
incorporated hereinto by reference.
Analytical techniques for detecting the presence and/or concentration of a
chemical specie without isolation thereof are within an evolving technology, and the
above survey of reasonable analytical techniques for use in the process of the present
invention may presently not even be exhaustive, and most likely techniques equivalent to
the above for the purposes of the present invention will be developed in the future.
A chemical specie may be selected for a given process based on a preference for
one or more analytical techniques, or an analytical technique may be selected for a given
process based on a ple~elellce for one or more chemical tracers. In preferred
embodiments, the chemical compound(s) selected as the tracer should be soluble in at
least one, and more preferably in both, of the temperature-conditioning fluid and process
fluid of the industrial process, at least at the concentration level(s) expected in the
respective fluid.
The compositions and methods of this invention are applicable to both so-called
non-oxidizing and oxidizing microbiocides. Examples of commonly available oxidizing
biocides to which this invention may find utility include but are not limited to the
following: hypochlorite bleach, hydrogen peroxide, peracetic acid, potassium
monopersulfate, bromochlorodimethylhydantoin, dichloromethylethylhydantoin, and
chloroisocyanurate. The compositions and methods of this invention are also applicable
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- 2189948
to ingredients that later react to form biocidal compositions. Examples of materials of
this type include the reaction of sodium bromide with chlorine to produce hypobromite
bleach.
Examples of commonly available non-oxidizing biocides to which this invention
may find applicability include but are not limited to the following:
dibromonitrilopropionamide, thiocyanomethylbenzothiazole, methyldithiocarbamate,tetrahydrodimethylthiodiazonethione, tributyltin oxide, bromonitropropanediol,
bromonitrostyrene, methylene bisthiocyanate, chloromethyl/methylisothiazolone,
bensiosthiazolone, dodecylguanidine hydrochloride, polyhexamethylene biguanide,
tetrakishydroxymethyl phosphonium sulfate, glutaraldehyde, alkyldimethylbenzyl
ammonium chloride, didecyldimethylammonium chloride,
poly[oxyethylene(dimethyliminio) dichloride], decylthioeth:~n~mine, and terbuthylazine.
By utili7.ing compositions of this invention, along with ~plopl;ate fluorescent
measuring devices, an accurate and continuous method for determining the levels of
microbiological activity such as, but not limited to, industrial water treatment and
paperm~king is achieved.
Most importantly, the method allows the on-line measurement of microbiological
activity in the system and makes it possible to respond to system changes and upsets in a
timely fashion. Since biocide is fed based on measured microbiological activity, the
invention also provides a means to minimi7P the dosage of biocide required to achieve
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21899 18
microbiological control by elimin~ting excess feed. The invention also provides a means
to control the treatment regime, e.g. the frequency and arnplitude of microbiocide dosage
in order to improve the antimicrobial performance of the treatment. One way that the
tracer compositions of the subject invention are monitored, however, not limited to, is
much the same way as disclosed in U.S. Patent Nos. 4,992,380 and 4,783,314, both of
which are hereinafter incorporated by reference into the specification.
The invention may also be employed to automatically add microbiocide into a
system, thereby keeping the biocide at a level at or greater than its minimum inhibitory
concentration or to automatically add tracer material into a system, thereby keeping the
tracer at a level at or greater than its minimum detection concentration. In this
embodiment of the invention, a forrnulation consisting of a mixture of a bioreactive
reagent and an inert compound in a known ratio are added to the system. The
concentration of the bioreactive reagent and inert reagent are continuously determined
by fluorescence measurement. The concentration of the inert fluorescent compound is
maintained at a constant value by feeding additional formulation as needed to
compensate for water losses (blowdown, drift, et.) from the system. In the event the
fluorescence level of the bioreactive reagent decreases from a present known value, the
fluorometer sends a signal to a controller, or to a pump to feed additional biocide until
the level of the bioreactive reagent (or consumption of bioreactive reagent) reached a
predetermined set point. Means for allowing a fluorometer to send a signal to a pump,
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2I 89948
alarm device, or modem are generally known in the art, and will not be discussed herein.
This method can be used to keep the biocide level in a system at or slightly above the
specified minimum inhibitory concentration of the biocide in the system. In another
embodiment of the invention, a formulation consisting of a mixture of a bioreactive
reagent and an inert compound in a known ratio are added to the system. In the event
the fluorescence level of the bioreactive reagent decreases from a present known value,
the fluorometer sends a signal to a controller, or to a pump to feed additional formulation
and/or biocide until the level of the bioreactive reagent reached a pre-set value. The
difference between the inert fluorescent compound and the bioreactive reagent
concentrations is a measure of the microbiological activity.
The compositions of this invention are measured preferably by fluorometry. In
this method, a sample of the system co~ i l-g the tracer material is excited by passing a
light wave of known wave length into the sample. The wavelength utilized is
determined by the frequency at which the sample fluoresces, and if other constituents in
the system also fluoresce at a known wave length after excitation at this frequency.
After excitation of the sample, the emission caused by the excitation is measured.
Fluorometers for this purpose are commercially available from a variety of sources.
Preferred fluorometers for this purpose are available from the Nalco Chemical
Company, Naperville, Illinois under the trade name TRASAR(g).
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218g948
-
The following examples are presented to describe ~ f~ d embodiments and
utilities of the invention and are not meant to limit the invention unless otherwise stated
in the claims appended hereto.
Example l
A field sample of discharge water from a utility treated with a mixed tolyltriazole
preparation (TT), cont~ining 40% of the 4-MeBT isomer and 60% of the 5-MeBT isomer,
was analyzed for 4-MeBT and 5-MeBT using HPLC and found to contain only 4-MeBT.
This sample was spiked with 2 ppm. of a mixed isomer tolyltriazole preparation (l . l 6
ppm 5-MeBT and 0.84 ppm 4-MeBT). The sample was periodically assayed for 4-MeBT
and 5-MeBT. It was found that the 5-MeBT levels had not changed in about l 0 hours.
When measured at the end of 40 hours, the 5-MeBT had disappeared completely (Figure
l ). This type of degradation, following an initial acclimation period is very typical of
microbial degradation. Sulfuric acid was added to the sample in order to lyse any
bacteria. The sample was analyzed directly using fluorescence as well as HPLC. 5-
MeBT was not observed in either assay.
Example 2
A field sample of discharge water from a utility was analyzed for TT by HLPC
and found to contain only 4-MeBT. The sample was split into 8 fractions. One fraction
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2~899~8
'_
was left as is and spiked with 2 ppm TT as in Example l. The other seven fractions were
subjected to one of the following processes and then spiked with 2 ppm TT:
Sample # Treatment
None
The following samples were treated to elimin~te microbiol agents from the water sample:
2 Filtration through 0.211 filter
3 Treatment with 200 ppm glutaraldehyde
4 Ozonation for 5 minutes
Autoclaving for l5 min~ltes
6 Acidification to reduce pH < l with H2SO4
7 Addition of CH3CN to get final concentration of 20%
Additionally, sample 8 was spiked with 2 ppm TT and chilled in a refrigerator. It
was found that in sample l with no treatment, 5-MeBT disappeared in approximately 2
days. In samples 2 through 8, 5-MeBT was stable for up to one month, analysis was not
performed after this time. Since all the treatments listed in samples nos. 2 through 8
either were treated with a bactericide or a treatment in inhibit bacterial metabolism,
preservation of the 5-MeBT in these samples demonstrates a microbiological mode of
degradation. When sample no. 8, the chilled sample, was kept at room temperature, the
5-MeBT disappeared in about 2 days. This provides evidence of a microbiological
degradation mechanism for 5-MeBT.
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21899~8
Example 3
A Pilot Cooling test (PCT) was conducted using a mixed isomer tolyltriazole
product at a 75 ppm maintenance TT dosage level. The product was fed continuously in
order to m:~int~in the level. Samples were collected daily and TT levels were analyzed
using HPLC. No chlorination was used for the first 13 days. During this period, the 5-
MeBT to 4-MeBT ratio stayed constant at approximately 1.5 to 1 for the first 8 days and
began to drop thereafter. The drop in the S-MeBT to 4-MeBT ratio coincided with a
precipitous rise in the microbiological counts. The ratio dropped to 0.29 to 1 on the 1 3th
day of the test, at which time the basin was slugged with bleach to achieve a 0.1 ppm
residual and then fed bleach continually to m~int~in 0.1 - 0.2 ppm residuals. The 5-
MeBT to 4-MeBT ratio began to climb back up, reaching 1.5 to 1 in approximately 3
days. The total microbiological counts, in the mean time dropped to <100 CFU/ml. On
the 1 9th day of the test, the chlorine feed was shut off again. The 5-MeBT to 4-MeBT
ratio started to decrease again, reaching approximately 0.27 to 1 in about 9 days and
staying constant thereafter. The decrease in 5-MeBT to 4-MeBT ratio once again
coincided with the increase in microbiological counts. Results are summarized in Figure
2. This example simulates the degradation of 5-MeBT due to microbiological activity in
a cooling tower.
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218g948
-
Example 4
A field water sample from the PCT test in Examples l and 2 was split into three
portions. To the first portion, 5-MeBT was repeatedly spiked after the previous spike
disappeared to achieve a total concentration of l l 50 ppm. To the second portion, l l 50
ppm of 4-MeBT was added in an analogous manner. The third portion was spiked with
distilled water. Samples were withdrawn at various intervals and assayed for total
aerobic counts. The results are shown in Figure 3. It can be clearly seen that the
degradation of the 5-MeBT isomer results in a significant increase in total cell counts.
No such increase was found for the 4-MeBT isomer and control sample.
At the end of the experiment, the samples were filtered through a 0.2,u filter and
submitted for Dissolved Organic Carbon (DOC) analysis. It was found that the DOC of
the sample with 5-MeBT addition had increased by 60 ppm over the control. If no
degradation or As~imilAtion into cell mass occurred, the DOC should have increased by
726 ppm over the control sample. In contrast, the DOC of the sample with 4-MeBT
addition increased by 770 ppm over the control sample. Addition of l 5% sulfuric acid to
the 5-MeBT spiked solutions to lyse the cells does not increase the 5-MeBT
concentration, ruling out adsorption effects. This example illuskates that most of the
organic carbon was ~imilAted into cell mass or degraded substantially.
Example 5
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21899A~
Three liters of a solution cont~ining 1 ml/L of heavy metals, 1 g/L of NH4Cl, 0.5
g/L of K2HPO4 and 0.1 g/L of MgSO4 was prepared. The pH was adjusted to 7 with
H3PO4. The solution was then split into three parts. To the first part, 50 ppm of 5-MeBT
was spiked. To the second part, 50 ppm of 4-MeBT was spiked. To the third part,
distilled water was spiked. To each of the parts, 10 ml of an inoculum cont~ining bacteria
acclimated with 5-MeBT (from 5-MeBT spiked sample in Examples 1 and 2) was added.
The three solutions were then transferred to respirometry bottles and the oxygenconsumption by the bacteria in the bottles was measured as a function of time. It was
found that the 5-MeBT spiked samples showed a significantly higher oxygen
consumption (55 mg per 50 mg of 5-MeBT), than the 4-MeBT and distilled water spiked
samples. The 5-MeBT spiked sample was additionally spiked with 100, 150 and 200
ppm of 5-MeBT, each time waiting for the oxygen consumption from the previous spike
to level off. The results are shown in Figure 4. This example illustrates an aerobic
oxidation mechanism for the microbial degradation of the 5-MeBT isomer, however, the
invention is not limited to aerobic mech~ni~m~ only.
Example 6
Additional respirometry experiments were carried out as described in Example 8.
To the first part, distilled water was spiked. To the second part, 25 ppm of 5-MeBT was
spiked. To the third part, 165 ppm of benzotriazole-5-carboxylic (BZT-5-C) was spiked.
- 36 -
21899~8
To each of the parts, 300 of an inoculum cont~ining bacteria acclimated with 5-MeBT
was added. The three solutions were then transferred to respirometry bottles and the
oxygen consumption by the bacteria in the bottles was measured as a function of time. It
was found that the 5-MeBT and BZT-5-C spiked samples showed significantly higheroxygen consumptions than the distilled water spiked sample. The 5-MeBT spiked sample
was additionally spiked with 50, 120 and 240 ppm of 5-MeBT, each time waiting for the
oxygen consumption from the previous spike to level off. The BZT-5-C spike sample
was additionally spiked with 165, 165 and 250 ppm of BZT-5-C, each time waiting for
the oxygen consumption from the previous spike to level off. Samples were drawn
before each spike and assayed for the spiked compound by HPLC, for DOC and for total
viable aerobic counts. The results showed that each spike of 5-MeBT and BZT-5-C was
accompanied by a proportional amount of oxygen uptake. It was seen that approximately
95% of the spiked DOC disappeared. In addition of 5-MeBT and BZT-5-C resulted in an
increase of approximately three orders of magnitude in the total viable aerobic counts.
This example illustrates an aerobic oxidation mechanism for the microbial degradation of
both 5-MeBT and BZT-5-C.
Changes can be made in the composition, operation and arrangement of the
method of the present invention described herein without departing from the concept and
scope of the invention as defined in the following claims:
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