Title of Invention

A METHOD OF MONITORING MEMBERANE SEPARATION PROCESS IN AN INDUSTRIAL WATER SYSTEM

Abstract Methods and systems for monitoring and/or controlling membrane separation systems or processes are provided. The present invention utilizes measurable amounts of inert fluorescent tracer(s) added to a feed stream to evaluate and/or control the purification of such feed stream during membrane separation. The methods and systems of the present invention can be utilised in a variety ofdifferent industrial applications including raw wafer processing and waste water processing.
Full Text METHOD OF MONITORING MEMBRANE SEPARATION
PROCESSES
FIELD OF THE INVENTION
This invention relates generally to membrane separation and, more particularly,
to methods for monitoring and/or controlling membrane separation processes.
BACKGROUND OF THE INVENTION
Membrane separation, which uses a selective membrane, is a fairly recent
addition to the industrial separation technology for processing of liquid streams, such as
water purification. In membrane separation, constituents of the influent typically pass
through the membrane as a result of a driving force(s) in one effluent stream, thus
leaving behind some portion of the original constituents in a second stream. Membrane
separations commonly used for water purification or other liquid processing include
microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO),
electrodialysis, electrode ionization, pervaporation, membrane extraction, membrane
distillation, membrane stripping, membrane aeration, and other processes. The driving
force of the separation depends on the type of the membrane separation. Pressure-
driven membrane filtration, also known as membrane filtration, includes
microfiltration, ultrafiltration, nanofiltration and reverse osmosis, and uses pressure as a
driving force, whereas the electrical driving force is used in electrodialysis and
electrodeionization. Historically, membrane separation processes or systems were not
considered cost effective for water treatment due to the adverse impacts that membrane
scaling, membrane fouling, membrane degradation and the like had on the efficiency of
removing solutes from aqueous water streams. However, advancements in technology

have now made membrane separation a more commercially viable technology for
treating aqueous feed streams suitable for use in industrial processes.
Furthermore, membrane separation processes have also been made more
practical for industrial use, particularly for raw and wastewater purification. This has
been achieved through the use of improved diagnostic tools or techniques for
evaluating membrane separation performance. The performance of membrane
separation, such as efficiency (e.g. flux or membrane permeability) and effectiveness
(e.g. rejection or selectivity), are typically affected by various parameters concerning
the operating conditions of the process. Therefore, it is desirable to monitor these and
other types of process parameters specific to membrane separation to assess the
performance of the process and/or the operating conditions. In this regard, a variety of
different diagnostic techniques for monitoring membrane separation processes have
been routinely used and are now understood and accepted as essential to its practicality
and viability for industrial use.
However, monitoring is typically conducted on an intermittent basis, for
example, once a work shift or at times less frequently. Known employed monitoring
techniques can also be labor and time intensive. Thus, adjustments made to membrane
separation processes in order to enhance performance based on typical monitoring may
not be made in an expeditious manner. In addition, the presently available monitoring
techniques often do not provide optimal sensitivity and selectivity with respect to
monitoring a variety of process parameters that are generally relied on as indicators to
evaluate and/or control membrane separation processes.
For example, monitoring techniques typically applied to reverse osmosis and
nanofiltration include conductivity measurements and flow measurements.

Conductivity measurements are inherently less accurate in order to determine the
recovery of solutes which are substantially retained by the membrane. In this regard,
conductive salts, typically used as indicators during conductive measurements, can
pass through the membrane. Since salts generally pass through the membrane as a
percentage of the total salt concentration, changes in local concentration due to
concentration gradients or the like can change the conductivity of the product water
without necessarily indicating membrane damage. This is especially true in the last
stage of a multi-stage cross flow membrane system where salt concentrations (and,
therefore, passage of salts as a percentage of that concentration) reach their highest
. levels. In this regard, the salt passage/percent rejection parameter is generally
determined as an average value based on values measured during all stages of the
membrane system.
Further, flow meters generally employed in such systems are subject to
calibration inaccuracies, thus requiring frequent calibration. Moreover, typical
monitoring of reverse osmosis and other membrane separations can routinely require
the additional and/or combined use of a number of different techniques, thus increasing
the complexity and expense of monitoring.
Accordingly, a need exists to monitor and/or control membrane separation
processes winch can treat feed streams, such as aqueous feed streams, suitable for use
in industrial processes where conventional monitoring techniques are generally
complex and/or may lack the sensitivity and selectivity necessary to adequately monitor
one or more process parameters specific to membrane separation processes which are
important to the evaluation of the performance of membrane separation.

SUMMARY OF THE INVENTION
The present invention provides methods and systems for monitoring and/or
controlling membrane separation processes capable of treating feed streams suitable for
use in industrial processes. In this regard, the detection of inert fluorescent tracers is
utilized to evaluate and/or control a number of different process parameters unique to
membrane separation, such as operational parameters, chemical parameters, mechanical
parameters, and combinations thereof. The inert fluorescent tracer monitoring
technique of the present invention can be performed with a high degree of sensitivity
and selectivity with respect to the monitoring of process parameters specific to a
membrane separation. In this regard, the methods and systems of the present invention
can be effectively utilized to optimize the performance of membrane separation
processes. Examples of such optimized performance include longer times between
membrane cleanings, longer membrane life, verification of treatment chemical in the
system, ability to operate at optimal recovery, and decreased energy costs due to better
control of scaling, fouling
and other system parameters.
To this end, in an embodiment of the present invention, a method of monitoring
a membrane separation process including a membrane capable of separating a feed
stream into at least a first stream and a second stream is provided. The method includes
the steps of providing an inert fluorescent tracer; introducing the inert fluorescent tracer
into the feed stream; providing a fluorometer to detect the fluorescent signal of the
inert fluorescent tracer in at least one of the feed stream, the first stream and the second
stream; and using the fluorometer to determine an amount of the inert fluorescent tracer
in at least one of the feed stream, the first stream and the second stream.

In another embodiment, a method of monitoring a membrane separation system
including a membrane capable of removing solutes from a feed stream suitable for use
in an industrial process is provided. The method includes the steps of adding an inert
tracer to the feed stream; contacting the membrane with the feed stream; separating the
feed stream into a permeate stream and a concentrate stream to remove solutes from the
feed stream; providing a fluorometer to detect the fluorescent signal of the inert tracer
in at least one of the feed stream, the permeate stream and the concentrate stream; and
using the fluorometer to measure an amount of the inert tracer in at least one of the feed
stream, the permeate stream and the concentrate stream.
In yet another embodiment, a membrane separation system capable of purifying
an aqueous feed stream suitable for use in an industrial process is provided. The
membrane separation system includes a semi-permeable membrane capable of
separating the aqueous feed stream containing an inert tracer into a permeate stream
and a concentrate stream to remove one or more solutes from the aqueous feed stream;
a detection device capable of fluorometrically measuring an amount of the inert tracer
ranging from about 5 parts per trillion ("ppt") to about 1000 parts per million ("ppm")
in at least one of the aqueous feed stream, the permeate stream and the concentrate
stream wherein the detection device is capable of producing a signal indicative of the
amount of inert tracer that is measured; and a controller capable of processing the
signal to monitor and/or control the purification of the aqueous feed stream. Such
monitoring or control may include control of chemical dosing and checking the
accuracy/calibration of standard instruments (e.g. flow sensors).
In still another embodiment, a method of monitoring and controlling a
membrane separation process including a membrane capable of removing solutes from

a feed stream for use in an industrial process is provided. The method includes the
steps of adding an inert tracer to the feed stream; contacting the membrane with the
feed stream; separating the feed stream into a first effluent stream and a second effluent
stream to remove solutes from the feed stream; providing a fluorometer to detect the
fluorescent signal of the inert tracer in at least one of the feed stream, the first effluent
stream and the second effluent stream; using the fiuorometer to measure an amount of
the inert tracer ranging from about 5 ppt to about 1000 ppm in at least one of the feed
stream, the first effluent stream and the second effluent stream; and evaluating one or
more process parameters specific to membrane separation based on the measurable
amount of the inert tracer.
It is, therefore, an advantage of the present invention to provide methods and
systems that utilize inert fluorescent tracers to monitor and/or control membrane
separation processes or systems.
Another advantage of the present invention is to provide methods and systems
that utilize measurable amounts of inert tracers to improve the operational efficiency of
membrane separation processes or systems.
A further advantage of the present invention is to provide methods and systems
for monitoring parameters specific to membrane separation processes with selectivity
and specificity based on measurable amounts of inert tracers added to the membrane
separation system.
Yet another advantage of the present invention is to provide methods and
systems for monitoring and/or controlling membrane separation processes for purifying
aqueous feed streams suitable for use in industrial water systems.

Still further an advantage of the present invention is to provide an improved
performance specific to membrane separation processes or systems that utilize cross-
flow and/or dead-end flow separation to remove solutes from feed streams.
Additional features and advantages of the present invention are described in,
and will be apparent in, the detailed description of the presently preferred
embodiments.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED
EMBODIMENTS
The present invention provides methods and systems for monitoring and/or
controlling membrane separation processes that are capable of removing solutes from
feed streams, such as aqueous feed streams, which are suitable for use in a number of
different industrial applications. More specifically, the methods and systems of the
present invention can monitor and/or control membrane separation processes based on
measurable amounts of inert fluorescent tracers which have been added to the
membrane separation process. In this regard, a number of different process parameters
specific to membrane separation; including, for example, operational parameters,
chemical parameters, mechanical parameters, like parameters and combinations
thereof, can be evaluated with a high degree of selectivity, specificity and accuracy
such that the performance of the membrane separation process can be effectively
optimized.
The methods and systems of the present invention can include a variety of
different and suitable components, process steps, operating conditions and the like, for
monitoring and/or controlling membrane separation processes or systems. In an
embodiment, the membrane separation process of the present invention includes cross
flow and dead-end flow processes. During cross flow processes, the feed stream can be

treated in a flow direction that is substantially parallel to the membrane of the
separation system. With respect to dead-end flow separation processes, the feed stream
can be treated in a flow direction that is substantially perpendicular to the membrane of
the separation system.
In general, the membrane separation processes of the present invention are
capable of treating or purifying feed streams by dividing the feed stream into separate
streams. In an embodiment, the feed stream is separated into at least a first and second
stream, such as a permeate stream and a concentrate stream. The feed stream can
contain various solutes, such as dissolved organics, dissolved inorganics, dissolved
solids, suspended solids, the like or combinations thereof. Upon separation of the feed
stream into the permeate and the concentrate, in membrane filters for example, the
permeate stream essentially contains a substantially lower concentration of dissolved
and/or suspended solutes as compared to the aqueous feed stream. On the other hand,
the concentrate stream has a higher concentration of dissolved and/or suspended solutes
as compared to the aqueous stream. In this regard, the permeate represents a purified
feed stream, such as a purified aqueous feed stream.
It should be appreciated that the present invention can be utilized with respect to
a number of different types of membrane separation processes including, for example,
cross flow processes, dead-end flow processes, reverse osmosis, ultrafiltration,
microfiltration, nanofiltration, electrodialysis, electrodeionization, pervaporation,
membrane extraction, membrane distillation, membrane stripping, membrane aeration
and the like or combinations thereof. Reverse osmosis, ultrafiltration, microfiltration
and nanofiltration are the preferred membrane separation processes.

In reverse osmosis, the feed stream is typically processed under cross flow
conditions. In this regard, the feed stream flows substantially parallel to the membrane
surface such that only a portion of the feed stream diffuses through the membrane as
permeate. The cross flow rate is routinely high in order to provide a scouring action
that lessens membrane surface fouling. This can also decrease concentration
polarization effects (e.g., concentration of solutes in the reduced-turbulence boundary
layer at the membrane surface, which can increase the osmotic pressure at the
membrane and thus can reduce permeate flow). The concentration polarization effects
can inhibit the feed stream water from passing through the membrane as permeate, thus
decreasing the recovery ratio, e.g., the ratio of permeate to applied feed stream. A
recycle loop(s) may be employed to maintain a high flow rate across the membrane
surface.
Reverse osmosis processes can employ a variety of different types of
membranes. Such commercial membrane element types include, without limitation,
hollow fiber membrane elements, tubular membrane elements, spiral-wound membrane
elements, plate and frame membrane elements, and the like, some of which are
described in more detail in "The Nalco Water Handbook," Second Edition, Frank N.
Kemmer ed., McGraw-Hill Book Company, New York, N.Y., 1988, incorporated
hereinto, particularly Chapter 15 entitled "Membrane Separation". It should be
appreciated that a single membrane element may be used in a given membrane
filtration system, but a number of membrane elements can also be used depending on
the industrial application.
A typical reverse osmosis system is described as an example of membrane
filtration and more generally membrane separation. Reverse osmosis uses mainly spiral

wound elements or modules, which are constructed by winding layers of semi-porous
membranes with feed spacers and permeate water carriers around a central perforated
permeate collection tube. Typically, the modules are sealed with tape and/or fiberglass
over-wrap. The resulting construction has one channel which can receive an inlet flow.
The inlet stream flows longitudinally along the membrane module and exits the other
end as a concentrate stream. Within the module, water passes through the semi-porous
membrane and is trapped in a permeate channel which flows to a central collection
tube. From this tube it flows out of a designated channel and is collected.
In practice, membrane modules are stacked together, end to end, with inter-
connectors joining the permeate tubes of the first module to the permeate tube of the
second module, and so on. These membrane module stacks are housed in pressure
vessels. Within the pressure vessel feed water passes into the first module in the stack,
which removes a portion of the water as permeate water. The concentrate stream from
the first membrane becomes the feed stream of the second membrane and so on down
the stack. The permeate streams from all of the membranes in the stack are collected in
the joined permeate tubes. Only the feed stream entering the first module, the
combined permeate stream and the final concentrate stream from the last module in the
stack are commonly monitored.
Within most reverse osmosis systems, pressure vessels are arranged in either
"stages" or "passes." In a staged membrane system, the combined concentrate streams
from a bank of pressure vessels are directed to a second bank of pressure vessels where
they become the feed stream for the second stage. Commonly systems have 2 to 3
stages with successively fewer pressure vessels in each stage. For example, a system
may contain 4 pressure vessels in a first stage, the concentrate streams of which feed 2

pressure vessels in a second stage, the concentrate streams of which in turn feed 1
pressure vessel in the third stage. This is designated as a "4:2:1" array. In a staged
membrane configuration., the combined permeate streams from all pressure vessels in
all stages are collected and used without further membrane treatment. Multi-stage
systems are used when large volumes of purified water are required, for example for
boiler feed water. The permeate streams from the membrane system may be further
purified by ion exchange or other means.
In a multi-pass system, the permeate streams from each bank of pressure vessels
are collected and used as the feed to the subsequent banks of pressure vessels. The
concentrate streams from all pressure vessels are combined without further membrane
treatment of each individual stream. Multi-pass systems are used when very high
purity water is required, for example in the microelectronics or pharmaceutical
industries.
It should be clear from the above examples that the concentrate stream of one
stage of an RO system can be the feed stream of another stage. Likewise the permeate
stream of a single pass of a multi-pass system may be the feed stream of a subsequent
pass. A challenge in monitoring systems such as the reverse osmosis examples cited
above is that there are a limited number of places where sampling and monitoring can
occur, namely the feed, permeate and concentrate streams. In some, but not all,
systems "inter-stage" sampling points allow sampling/monitoring of the first stage
concentrate/second stage feed stream. Similar inter-pass sample points may be
available on multi-pass systems as well.
In practice it is possible to "probe" the permeate collection tube within a single
pressure vessel to sample the quality of the permeate from each of the membrane

elements in the stack. It is a time consuming, messy and inexact method and is not
routinely applied except in troubleshooting situations. There is no currently accepted
method of examining the feed/concentrate stream quality of individual membrane
elements within a single pressure vessel.
In contrast to cross-flow filtration membrane separation processes, conventional
filtration of suspended solids can be conducted by passing a feed fluid through a filter
media or membrane in a substantially perpendicular direction. This effectively creates
one exit stream during the service cycle. Periodically, the filter is backwashed by
passing a clean fluid in a direction opposite to the feed, generating a backwash effluent
containing species that have been retained by the filter. Thus conventional filtration
produces a feed stream, a purified stream and a backwash stream. This type of
membrane separation is typically referred to as dead-end flow separation and is
typically limited to the separation of suspended particles greater than about one micron
in size.
Cross-flow filtration techniques, on the other hand, can be used for removing
smaller particles (generally about one micron in size or less), colloids and dissolved
solutes. Such types of cross-flow membrane separation systems can include, for
example, reverse osmosis, microfiltration, ultrafiltration, nanofiltration, electrodialysis
or the like. Reverse osmosis can remove even low molecular weight dissolved species
that are at least about 0.0001 to about 0.001 microns in minimum diameter, including,
for example, ionic and nonionic species, low molecular weight molecules,
water-soluble macromolecules or polymers, suspended solids, colloids, and such
substances as bacteria and viruses.

In this regard, reverse osmosis is often used commercially to treat water that has
a moderate to high (e.g., 500 ppm or greater) total dissolved solids ("TDS") content.
Typically on order of from about 2 percent to about 5 percent of the TDS of a feed
stream will pass through the membrane. Thus, in general the permeate may not be
entirely free of solutes. In this regard, the TDS of reverse osmosis permeates may be
too high for some industrial applications, such as use as makeup water for high pressure
boilers. Therefore, reverse osmosis systems and other like membrane separation
systems are frequently used prior to and in combination with an ion exchange process
or other suitable process to reduce the TDS loading on the resin and to decrease the
amount of hazardous material used and stored for resin regeneration, such as acids and
sodium hydroxide.
As discussed above, the performance of membrane separation systems can vary
with respect to a number of different operational conditions specific to membrane
separation, such as temperature, pH, pressure, permeate flow, activity of treatment
and/or cleaning agents, fouling activity and the like. When developing and/or
implementing a monitoring and/or control program based on the detection of inert
fluorescent tracers, the effects of the operational conditions specific to membrane
separation must necessarily be taken into consideration. As previously discussed, the
operational conditions of water treatment processes can vary greatly from process to
process. In this regard, the monitoring techniques as applied to each process can vary
greatly.
Membrane separation processes and the monitoring thereof are unique because
of the following considerations.

1. Systems are constructed with limited flexibility in terms of where
monitoring may be done and/or where samples may be collected.
2. Membrane separation systems include a concentration polarization layer
that forms as water is permeated through the barrier. This is not present in other water
treatment systems, such as cooling water systems.
3. Membrane separation systems operate at significantly lower
temperatures than industrial processes where inverse solubility of solutes is a problem.
However, in the case of membrane separation systems such as reverse osmosis and
nanofiltration, this low temperature leads to scaling from salts that are less likely to be
problematic in higher temperature processes (such as silica and silicate salts). In this
regard, typical day-to-day membrane separation operations (for example RO and NF)
occur at about 75°F.
4. Because it is essential that the surface of the membrane remain clean, a
relatively small amount of fine precipitate can cause a significant performance loss.
The performance loss in a membrane is, thus, more sensitive to precipitate deposition
as compared to cooling water treatment. In this regard, performance loss in a
membrane can occur at a film thickness appreciably lower than that required for heat
transfer loss to occur in a cooling water system.
5. Water loss in membrane filtration is due to "permeation" or passage
through the membrane barrier. Damaged or otherwise imperfect membranes are
susceptible to undesirable leakage of solutes through the membrane. Thus it is critical
to monitor leakage through the membrane to keep it operating at maximum efficiency.
6. The thin, semi-permeable films (polymeric, organic or inorganic) are
sensitive to degradation by chemical species. Products which contact the membranes

surface must be compatible with the membrane chemistry to avoid damaging the
surface and thereby degrading performance.
7. Chemical treatments used in membrane systems must be demonstrated
to be compatible with the membrane material prior to use. Damage from incompatible
chemicals can result in immediate loss of performance and perhaps degradation of the
membrane surface. Such immediate, irreversible damages from a chemical treatment is
highly uncommon in cooling water systems.
Based on these differences, a number of different factors and considerations
must necessarily be taken into account when developing and/or implementing
monitoring and/or controlling programs with respect to membrane separation systems
as compared to other water treatment processes, such as cooling water treatment
processes.
For example, both the cost of the membrane and the energy consumed can be
significant operating cost factors specific to a membrane separation process. In this
regard, deposits of scale and foulants on the membrane, on a small scale, can adversely
impact the performance of membrane separation systems by, in membrane filtration for
example, decreasing the permeate flow for a given driving force, lowering the permeate
quality (purity), increasing energy consumed to maintain a given permeate flow,
causing membrane replacement and/or unscheduled downtime for membrane
replacement or cleaning/renovation, other like conditions and combinations thereof. In
this regard, the continuous monitoring of process parameters specific to membrane
filtration such as normalized permeate flow, driving force, differential pressure and
percent rejection are generally believed to be critical to the detection of fouling and/or
scaling and, thus, the implementation of remedial measures when such problems are

observed. In reverse osmosis, about a ten to fifteen percent change in any of these
parameters routinely signals a scaling/fouling problem requiring a responsive action,
such as the adjustment of the dosage of treatment agent. Thus, detection of these
problems at the earliest possible time can prevent, for example, undue energy
consumption, loss of product, premature membrane replacement and the like. Ideally,
when an unfavorable or questionable condition or change is detected in a system, some
means, such as an alarm, will be used to notify an operator of the condition or change.
Corrective action may then be taken as necessary or appropriate.
Applicants have uniquely discovered that the monitoring and/or controlling of
process parameters specific to membrane separation based on measuring an amount of
inert fluorescent tracer is faster, more sensitive, more comprehensive, more selective
and/or more reliable than conventional techniques presently available, particularly
when the monitoring methods of the present invention are employed on a substantially
continuous basis. The present invention has enhanced diagnostic capabilities such that,
for example, lack of chemical treatment, unplanned increases in percent recovery,
increased passage of solutes, flow irregularities and scaling and/or fouling problems
unique to membrane separation and/or membrane filtration can be detected with
reasonable certainty, with far greater sensitivity, and under a far less elapsed time than
the presently available methods. In this regard, temporary system upsets or other
short-lived variations can be detected during continuous monitoring as the transient
conditions that they are, rather than as incorrect warning signs as detected by sporadic
monitorings.
As previously discussed, the methods and systems of the present invention
employ inert fluorescent tracers to monitor and/or control the membrane separation

processes. By utilizing inert tracers, the present invention can evaluate a number of
different membrane separation process parameters with a greater selectivity and
sensitivity as compared to conventional monitoring techniques. In this regard, the
measurable amount of inert tracers can be effectively utilized to optimally maximize
the performance of such systems.
The term "inert," as used herein refers to an inert fluorescent tracer that is not
appreciably or significantly affected by any other chemistry in the system, or by the
other system parameters such as pH, temperature, ionic strength, redox potential,
microbiological activity or biocide concentration. To quantify what is meant by "not
appreciably or significantly affected", this statement means that an inert fluorescent
compound has no more than a 10% change in its fluorescent signal, under severe
conditions encountered in industrial water systems. Severe conditions normally
encountered in industrial water systems are known to people of ordinary skill in the art
of industrial water systems.
It should be appreciated that a variety of different and suitable inert tracers can
be utilized in any suitable amount, number and application. For example, a single tracer
can be used to evaluate a number of different membrane separation process parameters.
However, the present invention can include the use of a number of different tracers
each functioning as tracers for separate monitoring applications. In an embodiment,
inert fluorescent tracer monitoring of the present invention can be conducted on a
singular, intermittent or semi-continuous basis, and preferably the concentration
determination of the tracer in the stream is conducted on-site to provide a rapid real-
time determination.

An inert tracer must be transportable with the water of the membrane separation
system and thus substantially, if not wholly, water-soluble therein at the concentration
it is used, under the temperature and pressure conditions specific and unique to the
membrane separation system. In other words, an inert tracer displays properties similar
to a solute of the membrane separation process in which it is used. In an embodiment,
it is preferred that the inert tracer of the present invention meet the following criteria:
1. Not be adsorbed by the membrane in any appreciable amount;
2. Not degrade the membrane or otherwise hinder its performance or alter
its composition;

3. Be detectable on a continuous or semi-continuous basis and susceptible,
to concentration measurements that are accurate, repeatable and capable of being
performed on feedwater, concentrate water, permeate water or other suitable media or
combinations thereof;
4. Be substantially foreign to the chemical species that are normally
present in the water of the membrane separation systems in which the inert tracer(s)
may be used;
5. Be substantially impervious to interference from, or biasing by, the
chemical species that are normally present in the water of membrane separation
systems in winch the inert tracer(s) may be used;
6. Be substantially impervious to any of its own potential specific or
selective losses from the water of membrane separation systems, including selective
permeation of the membrane;

7. Be compatible with all treatment agents employed in the water of the
membrane separation systems in which the inert tracer(s) may be used, and thus in no
way reduce the efficacy thereof;
8. Be compatible with all components of its formulation; and
9. Be relatively nontoxic and environmentally safe, not only within the
environs of the water or the membrane separation process in which it may be used, but
also upon discharge therefrom.
It should be appreciated that the amount of inert tracer to be added to the
membrane separation process that is effective without being grossly excessive can vary
with respect to a variety of factors including, without limitation, the monitoring method
selected, the extent of background interference associated with the selected monitoring
method, the magnitude of the expected inert tracer(s) concentration in the feedwater
and/or concentrate, the monitoring mode (such as, an on-line continuous monitoring
mode), and other similar factors. In an embodiment, the dosage of an inert tracer added
to the membrane separation system includes an amount that is at least sufficient to
provide a measurable concentration in, for example, the concentrate stream, at steady
state of at least about 5 ppt, and preferably at least about 1 ppb or about 5 ppb or
higher, such as, up to about 100 ppm or about 200 ppm, or even as high as about 1000
ppm in the concentrate or other effluent stream. In an embodiment, the amount of
tracer ranges from about 5 ppt to about 1000 ppm, preferably from about 1 ppb to about
50 ppm, more preferably from about 5 ppb to about 50 ppb.
In an embodiment, the inert tracer can be added to a membrane separation
system as a component of a formulation, rather than as a separate component, such as a
dry solid or neat liquid. The inert tracer formulation or product may include an

aqueous solution or other substantially homogeneous mixture that disperses with
reasonable rapidity in the membrane separation system to which it is added. In this
regard, the inert tracer's concentration may be correlated to the concentration of a
product. In an embodiment, the product or formulation can include a treatment agent
which is added to treat scaling and/or fouling.
A variety of different and suitable types of compounds can be utilized as inert
fluorescent tracers. In an embodiment, the inert fluorescent compounds can include,
for example, the following compounds:
3,6-acridinediamine, N,N,N',N'-tetramethyl-, monohydrochloride, also known as
Acridine Orange (CAS Registry No. 65-61-2),
2-anthracenesulfonic acid sodium salt (CAS Registry No. 16106-40-4),
1,5-anthracenedisulfonic acid (CAS Registry No. 61736-91-2) and salts thereof,
2,6-anthracenedisulfonic acid (CAS Registry No. 61736-95-6) and salts thereof,
1,8-anthracenedisulfonic acid (CAS Registry No. 61736-92-3) and salts thereof,
anthra[9,1,2-cde]benzo[rst]pentaphene-5,10-diol, 16,17-dimethoxy-, bis(hydrogen
sulfate), disodium salt, also known as Anthrasol Green IBA (CAS Registry No. 2538-
84-3, aka Solubilized Vat Dye),
bathophenanthrolinedisulfonic acid disodium salt (CAS Registry No. 52746-49-3),
amino 2,5-benzene disulfonic acid (CAS Registry No. 41184-20-7),
2-(4-aminophenyl)-6-methylbenzothiazole (CAS Registry No. 92-36-4),
lH-benz[de]isoquinoline-5-sulfonic acid, 6~amino-2,3-dihydro-2-(4-methylphenyl)-
1,3-dioxo-, monosodium salt, also known as Brilliant Acid Yellow 8G (CAS Registry
No. 2391-30-2, aka Lissamine Yellow FF, Acid Yellow 7),
phenoxazin-5-ium, l-(aminocarbonyl)-7-(diethylamino)-3,4-dihydroxy-, chloride, also
known as Celestine Blue (CAS Registry No. 1562-90-9),
benzo[a]phenoxazin-7-ium, 5,9-diamino-, acetate, also known as cresyl violet acetate
(CAS Registry No. 10510-54-0),
4-dibenzofuransulfonic acid (CAS Registry No. 42137-76-8),

3-dibenzofuransulfonic acid (CAS Registry No. 215189-98-3),
1-ethylquinaldinium iodide (CAS Registry No. 606-53-3),
fluorescein (CAS Registry No. 2321-07-5),
fluorescein, sodium salt (CAS Registry No. 518-47-8, aka Acid Yellow 73, Uranine),
Keyfluor White ST (CAS Registry No. 144470-48-4, aka Flu. Bright 28),
benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-[[4-[bis(2-hydroxyethyl)amino]-6-[(4-
suIfophenyI)amino]-l,3,5-triazin-2-yl]amino]-, tetrasodium salt, also known as
Keyfluor White CN (CAS Registry No. 16470-24-9),
C.I. Fluorescent Brightener 230, also known as Leucophor BSB (CAS Registry No.
68444-86-0),
benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-[[4-[bis(2-hydroxyethyl)amino]-6-[(4-
sulfophenyl)amino]-l,3,5-triazin-2-yl]amino]-, tetrasodium salt, also known as
Leucophor BMB (CAS Registry No. 16470-24-9, aka Leucophor U, Flu. Bright. 290),
9,9'-biacridinium, 10,10'-dimethyl-, dinitrate, also known as Lucigenin (CAS Registry
No. 2315-97-1, aka bis-N-methylacridinium nitrate),
l-deoxy-l-(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)-D-ribitol,
also known as Riboflavin or Vitamin B2 (CAS Registry No. 83-88-5),
mono-, di-, or tri-sulfonated napthalenes, including but not limited to
1,5-naphthalenedisulfonic acid, disodium salt (hydrate) (CAS Registry
No. 1655-29-4, aka 1,5-NDSA hydrate),
2-amino-1-naphthalenesulfonic acid (CAS Registry No. 81-16-3),
5-amino-2-naphthalenesuIfonic acid (CAS Registry No. 119-79-9),
4-amino-3-hydroxy-1-naphthalenesulfonic acid (CAS Registry No. 90-
51-7),
6-amino-4-hydroxy-2-naphthalenesulfonic acid (CAS Registry No. 116-
63-2),
7-amino-l,3-naphthalenesulfonic acid, potassium salt (CAS Registry
No. 79873-35-1),
4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid (CAS Registry No.
90-20-0),
5-dimethylamino-1-naphthalenesulfonic acid (CAS Registry No. 4272-
77-9),

1-amino-4-naphthalene sulfonic acid (CAS Registry No. 84-86-6),
1-amiiio-7-naphthalene sulfonic acid (CAS Registry No. 119-28-8), and
2,6-naphthalenedicarboxylic acid, dipotassium salt (CAS Registry No.
2666-06-0),
3,4,94O-perylenetetracarboxylic acid (CAS Registry No. 81-32-3),
C.I. Fluorescent Brightener 191, also known as Phorwite CL (CAS Registry No.
12270-53-0),
C.I. Fluorescent Brightener 200, also known as Phorwite BKL (CAS Registry
No. 61968-72-7),
benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-(4-phenyl-2H-l,2,3-triazol-2-yl)-,
dipotassium salt, also known as Phorwite BHC 766 (CAS Registry No. 52237-03-3),
benzenesulfonic acid, 5-(2H-naphtho[l,2-d]triazol-2-yl)-2-(2-phenylethenyl)-, sodium
salt, also known as Pylaklor White S-15A (CAS Registry No. 6416-68-8),
1,3,6,8-pyrenetetrasulfonic acid, tetrasodium salt (CAS Registry No. 59572-10-
0),
pyranine, (CAS Registry No. 6358-69-6, aka 8-hydroxy-l, 3, 6-
pyrenetrisulfonic acid, trisodium salt),
quinoline (CAS Registry No. 91-22-5),
3H-phenoxazin-3-one, 7-hydroxy-, 10-oxide, also known as Rhodalux (CAS Registry
No. 550-82-3),
xanthylium, 9-(2,4-dicarboxyphenyl)-3,6-bis(diethylamino)-, chloride, disodium salt,
also known as Rhodamine WT (CAS Registry No. 37299-86-8),
phenazinium, 3,7-diamino-2,8-dimethyl-5-phenyl-, chloride, also known as Safranine O
(CAS Registry No. 477-73-6),
C.I. Fluorescent Brightener 235, also known as Sandoz CW (CAS Registry No.
56509-06-9),
benzenesulfonic acid, 2,2'-(1,2-ethenediyl)bis[5-[[4-[bis(2-hydroxyethyl)amino]-6-[(4-
sulfophenyl)amino]-l,3,5-triazin-2-yl]amino]-, tetrasodium salt, also known as Sandoz
CD (CAS Registry No. 16470-24-9, aka Flu. Bright. 220),
benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-[[4-[(2-hydroxypropyl)amino]-6-
(phenylamino)-l,3,5-triazin-2-yl]amino]-, disodium salt, also known as Sandoz TH-40
(CAS Registry No. 32694-95-4),

xanthylium, 3,6-bis(diethylamino)-9-(2,4-disulfophenyl)-, inner salt, sodium salt, also
known as Sulforhodamine B (CAS Registry No. 3520-42-1, aka Acid Red 52),
benzenesulfonic acid, 2,21-(l,2-ethenediyl)bis[5-[[4-[(aminomethyl)(2-
hydroxyethyl)amino]-6-(phenylamino)-1,3,5-triazin-2-yl]amino]-, disodium salt, also
known as Tinopal 5BM-GX (CAS Registry No. 169762-28-1),
Tinopol DCS (CAS Registry No. 205265-33-4),
benzenesulfonic acid, 2,2'-([1,1'-biphenyl]-4,4'-diyldi-2,l-ethenediyl)bis-, disodium salt
also known as Tinopal CBS-X (CAS Registry No. 27344-41-8),
benzenesulfonic acid, 5-(2H-naphtho[l,2-d]triazol-2-yl)-2-(2-phenylethenyl)-, sodium
salt, also known as Tinopal RBS 200, (CAS Registry No. 6416-68-8),
7-benzothiazolesulfonic acid, 2,2'-( 1 -triazene-1,3-diyldi-4,1 -phenylene)bis[6-methyl-,
disodium salt, also known as Titan Yellow (CAS Registry No. 1829-00-1, aka Thiazole
Yellow G), and
all ammonium, potassium and sodium salts thereof, and all like agents and suitable
mixtures thereof.
Preferred tracers include:
1 -deoxy-1 -(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin- 10(2H)-yl)-D- ribitol,
also known as Riboflavin or Vitamin B2 (CAS Registry No. 83-88-5),
fluorescein (CAS Registry No. 2321-07-5),
fluorescein, sodium salt (CAS Registry No. 518-47-8, aka Acid Yellow 73, Uranine),
2-anthracenesulfonic acid sodium salt (CAS Registry No. 16106-40-4),
1,5-anthracenedisulfonic acid (CAS Registry No. 61736-91-2) and salts thereof,
2,6-anthracenedisulfonic acid (CAS Registry No. 61736-95-6) and salts thereof,
1,8-anthracenedisulfonic acid (CAS Registry No. 61736-92-3) and salts thereof,
mono-, di-, or tri-sulfonated napthalene's, including but not limited to
1,5-naphthalenedisulfonic acid, disodium salt (hydrate) (CAS Registry
No. 1655-29-4, aka 1,5-NDSA hydrate),
2-amino-1-naphthalenesulfonic acid (CAS Registry No. 81-16-3),
5-amino-2-naphthalenesulfonic acid (CAS Registry No. 119-79-9),
4-amino-3-hydroxy-l-naphthalenesulfonic acid (CAS Registry No. 90-
51-7),

6-amino-4-hydroxy-2-naphthalenesuIfonic acid (CAS Registry No. 116-
63-2),
7-amino-l,3-naphthalenesulfonic acid, potassium salt (CAS Registry
No. 79873-35-1),
4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid (CAS Registry No.
90-20-0),
5-dimethylamino-l-naphthalenesulfonic acid (CAS Registry No. 4272-
77-9),
l-amino-4-naphthaIene sulfonic acid (CAS Registry No. 84-86-6),
l-amino-7-naphthalene sulfonic acid (CAS Registry No. 119-28-8), and
2,6-naphthalenedicarboxylic acid, dipotassium salt (CAS Registry No.
2666-06-0),
3,4,9,10-perylenetetracarboxylic acid (CAS Registry No. 81-32-3),
C.I. Fluorescent Brightener 191, also known as, Phorwite CL (CAS Registry
No. 12270-53-0),
C.I. Fluorescent Brightener 200, also known as Phorwite BKL (CAS Registry
No. 61968-72-7),
benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-(4-phenyl-2H-1,2,3-triazol-2-yl)-,
dipotassium salt, also known as Phorwite BHC 766 (CAS Registry No. 52237-03-3),
benzenesulfonic acid, 5-(2H-naphtho[l,2-d]triazol-2-yl)-2-(2-phenylethenyl)-, sodium
salt, also known as Pylaklor White S-15A (CAS Registry No. 6416-68-8),
1,3,6,8-pyrenetetrasulfonic acid, tetrasodium salt (CAS Registry No. 59572-10-
0),
pyranine, (CAS Registry No. 6358-69-6, aka 8-hydroxy-1, 3, 6-
pyrenetrisulfonic acid, trisodium salt),
quinoline (CAS Registry No. 91-22-5),
3H-phenoxazin-3-one, 7-hydroxy-, 10-oxide, also known as Rhodalux (CAS Registry
No. 550-82-3),
xanthylium, 9-(2,4-dicarboxyphenyl)-3,6-bis(diethylamino)-, chloride, disodium salt,
also known as Rhodamine WT (CAS Registry No. 37299-86-8),
phenazinium, 3,7-diamino-2,8-dimethyl-5-phenyl-, chloride, also known as SafranLne O
(CAS Registry No. 477-73-6),

CI. Fluorescent Brightener 235, also known as Sandoz CW (CAS Registry No.
56509-06-9),
benzenesulfonic acid, 2,2'-(l ,2-ethenediyl)bis[5-[[4-[bis(2-hydroxyethyl)aniino]-6-[(4-
sulfophenyl)amino]-l,3,5-triazin-2-yl]amino]-, tetrasodium salt, also known as Sandoz
CD (CAS Registry No. 16470-24-9, aka Flu. Bright. 220),
benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-[[4-[(2-hydroxypropyl)amino]-6-
(phenylamino)-l,3,5-triazin-2-yl]amino]-, disodium salt, also known as Sandoz TH-40
(CAS Registry No. 32694-95-4),
xanthylium, 3,6-bis(diethylamino)-9-(2,4-disulfophenyl)-, inner salt, sodium salt, also
known as Sulforhodamine B (CAS Registry No. 3520-42-1, aka Acid Red 52),
benzenesulfonic acid, 2,2'-(1,2-ethenediyl)bis[5-[[4-[(aminomethyl)(2-
hydroxyethyl)amino]-6-(phenylamino)-l,3,5-triazin-2-yl]amino]-, disodium salt, also
known as Tinopal 5BM-GX (CAS Registry No. 169762-28-1),
Tinopol DCS (CAS Registry No. 205265-33-4),
benzenesulfonic acid, 2,2'-([l,1'-biphenyl]-4,4'-diyldi-2,l-ethenediyl)bis-, disodium
salt, also known as Tinopal CBS-X (CAS Registry No. 27344-41-8),
benzenesulfonic acid, 5-(2H-naphtho[l,2-d]triazol-2-yl)-2-(2-phenyletheny!)-, sodium
salt, also known as Tinopal RBS 200, (CAS Registry No. 6416-68-8),
7-bcnzothiazolesulfonic acid, 2,2'-(l-triazene-l,3-diyldi-4,l-phenylene)bis[6-methyl-,
disodium salt, also known as Titan Yellow (CAS Registry No. 1829-00-1, aka Thiazole
Yellow G), and
all ammonium, potassium and sodium salts thereof, and all like agents and suitable
mixtures thereof.
The most preferred fluorescent inert tracers of the present invention include
1,3,6,8-pyrenetetiasulfonic acid tetrasodium salt (CAS Registry No. 59572-10-0); 1,5-
naphthalenedisulfonic acid disodium salt (hydrate) (CAS Registry No. 1655-29-4, aka
1,5 - NDSA hydrate); xanthylium, 9-(2,4-dicarboxyphenyl)-3,6-bis(diethylamino)-,
chloride, disodium salt, also known as Rhodamine WT (CAS Registry No. 37299-86-
8); l-deoxy-l-(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)-D-
ribitol, also known as Riboflavin or Vitamin B2 (CAS Registry No. 83-88-5);
fluorescein (CAS Registry No. 2321-07-5); fluorescein, sodium salt (CAS Registry No.

518-47-8, aka Acid Yellow 73, Uranine); 2-anthracenesulfonic acid sodium salt (CAS
Registry No. 16106-40-4); 1,5-anthracenedisulfonic acid (CAS Registry No. 61736-91-
2) and salts thereof; 2,6-anthracenedisulfonic acid (CAS Registry No. 61736-95-6) and
salts thereof; 1,8-anthracenedisulfonic acid (CAS Registry No. 61736-92-3) and salts
thereof; and mixtures thereof. The fluorescent tracers listed above are commercially
available from a variety of different chemical supply companies.
In addition to the tracers listed above, those skilled in the art will recognize that
salts using alternate counter ions may also be used. Thus, for example, anionic tracers
which have Na as a counter ion could also be used in forms where the counter ion is
chosen from the list of: K+, Li+, NH4+, Ca+2, Mg+2 or other appropriate counter ions. In
the same way, cationic tracers may have a variety of counter ions, for example: CI",
SO4-2, PO4-3, HPO4-2; H2P04; C03-2;
HCO3"; or other appropriate counter ions.
Modifications of these tracers to control molecular weight or physical size
within a desirable size range by, for example, affixing them to an inert polymeric
molecule, incorporating them into a fluorescent microsphere or adding additional
chemical moieties in the side chains of the molecules should be obvious to those skilled
in the art. Such modifications are included herein.
As previously discussed, the inert tracer(s) is measured or detected to evaluate
the performance of the membrane separation process. A determination of the presence
of an inert fluorescent tracer and the concentration thereof in the influent/feedwater
and/or other process stream of a membrane separation process can be made when the
concentration of the inert tracer in the influent/feedwater and/or other stream of a

membrane separation system is several parts per million or less, even as low as parts
per billion as previously discussed.
At times, it may be desired to employ a number of inert tracers. In this regard,
it may be desired to use a number of inert tracers to monitor, for example, inert
tracer-specific losses, variances, like conditions or combinations thereof. Such separate
and distinct inert tracers can each be detected and quantified in a single
influent/feedwater and/or other stream fraction despite both being inert fluorescent
tracers provided that their respective wavelengths of emission do not interfere with one
another. Thus, concurrent analyses for multiple inert tracers is possible by selection of
inert tracers that have appropriate spectral characteristics.
The inert tracers of the present invention can be detected by utilizing a variety
of different and suitable techniques. For example, fluorescence emission spectroscopy
on a substantially continuous basis, at least over a given time period, is one of the
preferred analytical techniques according to an embodiment of the present invention.
One method for the continuous on-stream measuring of chemical tracers by
fluorescence emission spectroscopy and other analysis methods is described in U.S.
Patent No. 4,992,380, B.E. Moriarty, JJ. Hickey, W.H. Hoy, J.E. Hoots and D.A.
Johnson, issued February 12, 1991, incorporated hereinto by reference.
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 tracer(s). Thus, there may be some degree of background
fluorescence in the influent/feedwater and/or concentrate on which the fluorescence
analysis is conducted. This background fluorescence may come from chemical
compounds in the membrane separation system (including the influent/feedwater

system thereof) that are unrelated to the membrane separation process of the present
invention.
In instances where the background fluorescence is low, the relative measurable
intensities (measured against a standard fluorescent compound at a standard
concentration and assigned a relative intensity, for instance 100) of the fluorescence of
the inert tracer versus the background can be very high, 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. Such ratios would be
representative of a "relative fluorescence" (under like conditions) of respectively 10 and
50. In an embodiment, the excitation/emission wavelengths and/or the amount of inert
tracer employed are selected to provide a relative fluorescence of at least about 5 or
about 10 for the given background fluorescence anticipated.
Examples of fluorometers that may be used in the practice of this invention
include the TRASAR® 3000 and TRASAR® 8000 fluorometers (available from Ondeo
Nalco Company of Naperville, IL); the Hitachi F-4500 fluorometer (available from
Hitachi through Hitachi Instruments Inc. of San Jose, CA); the JOBIN YvON
FluoroMax-3 "SPEX" fluorometer (available from JOBIN YVON Inc. of Edison, NJ);
and the Gilford Fluoro-IV spectrophotometer or the SFM 25 (available from Bio-tech
Kontron through Research Instruments International of San Diego, CA). It should be
appreciated that the fluorometer list is not comprehensive and is intended only to show
examples of fluorometers. Other commercially available fluorometers and
modifications thereof can also be used in this invention.
It should be appreciated that a variety of other suitable analytical techniques
may be utilized to measure the amount of inert tracers during the membrane separation

process. Examples of such techniques include combined HPLC-fluorescence analysis,
colorimetry analysis, ion selective electrode analysis, transition metal analysis and the
like.
For example, the combination of high-pressure liquid chromatography
("HPLC") and fluorescence analyses of inert fluorescent tracers can be utilized to detect
measurable amounts of the inert tracer within the membrane separation system of the
present invention, particularly when very low levels of the inert tracer are used or the
background fluorescence encountered would otherwise interfere with the efficacy of
fluorescence analysis. The HPLC-fluorescence analysis method allows the inert tracer
compound to be separated from the fluid matrix and then the inert tracer concentration
can be measured.
The HPLC method can also be effectively employed to separate an inert tracer
compound from a fluid matrix for the purposes of then employing an inert
tracer-detection method other than the fluorescence analysis. An example of this type
of chromatographic technique is described in "Techniques in Liquid Chromatography",
C.F. Simpson ed., John Wiley & Sons, New York, pp. 121-122, 1982, incorporated
herein by reference, and "Standard Method for the Examination of Water and
Wastewater", 17th Edition, American Public Health Association, pp. 6-9 to 6-10, 1989,
incorporated herein by reference.
With respect to colorimetry analysis, colorimetry and/or spectrophotometry may
be employed to detect and/or quantify an inert chemical tracer. Colorimetry is a
determination of a chemical specie from its ability to absorb ultraviolet or visible light.
Calorimetric analysis techniques and the equipment that may be employed therefor are

described in U.S. Patent No. 4,992,380, B.E. Moriarty, JJ. Hickey, W.H. Hoy, J.E.
Hoots and D.A. Johnson, issued February 12, 1991, incorporated herein by reference.
With respect to ion selective electrode analysis, an ion selective electrode may
be used to determine the concentration of an inert chemical tracer through the direct
potentiometric measurement of specific ionic tracers in aqueous systems. An example
of an ion selective electrode tracer monitoring technique is described in U.S. Patent No.
4,992,380, B.E. Moriarty, JJ. Hickey, W.H. Hoy, J.E. Hoots and D.A. Johnson, issued
February 12, 1991, incorporated herein by reference.
It should be appreciated that analytical techniques for detecting and/or
quantifying the presence and/or concentration of a chemical specie without isolation
thereof are within an evolving technology. In this regard, the above survey of
analytical techniques suitable for use in detecting measurable amounts of the inert
tracer during the membrane separation process of the present invention may presently
not be exhaustive. Thus, analytical techniques equivalent to the above for purposes of
the present invention may likely be developed in the future.
As previously discussed, the present invention can provide highly selective
and/or sensitive monitoring of a variety of process parameters unique and specific to
the membrane separation process. The monitoring is based on the measurable amounts
of an inert tracer analyzed during the membrane separation process. In this regard, the
inert tracer can be detected at any suitable location or locations within the membrane
separation process, such as any suitable position in a membrane filtration process along
the feedwater stream, the concentrate stream, the permeate stream, the like or
combinations thereof. This effectively corresponds to a concentration of the inert
tracer in each stream.

In an embodiment, the monitoring of the membrane filtration process of the
present invention can be based on a measurable amount of the inert tracer from at least
one of the feedwater stream, the permeate stream and the concentrate stream. For
example, when the parameter of interest is the percent rejection (discussed below), it is
believed that the most sensitive determinations are of the feedwater inert tracer
concentration and the permeate inert tracer concentration (which will be zero if the
percent rejection is 100 percent). The percent rejection parameter, that is, the percent
of solute that has been rejected or has not passed through the membrane, can be
determined by the following relationships:
Equation 1 CR = CB/CF = F/B
Equation 2 F = P[CR/(CR- 1)]
Equation 3 CR = [ 1 /(l - R)]
where CF is the concentration of solute in the feed stream (e.g., combined fresh feed
fluid and recycled feed fluid); Cp is the concentration of solute in the permeate as
discharged through; CB is the concentration of solute in the concentrate water as
discharged through; F is the feed stream flow rate in gal/min; P is the permeate
discharge flow rate in gal/min; B is the concentrate water flow rate; L is the recycle
rate; R is the recovery ratio (e.g., P/F); and CR is the concentration ratio, (e.g., CB/CF).
When there is less than complete rejection of a solute, for instance only SO
percent rejection (e.g., a 0.8 rejection factor), CR will be less than F/B as shown in
Equation 4:
Equation 4 CR = (F/B) x rejection factor

The rejection factor again is the measure of the extent of solute rejection by the
membrane, as calculated in Equation 5, wherein CF is the concentration of solute in the
feedwater and Cp is the concentration of solute in the permeate:
Equation 5 rejection factor = (CF - Cp) / CF
The same equations will apply in a traced stream (e.g., a stream that contains an
inert tracer(s)) wherein "tracer-C" (e.g., tracer-CF, tracer-Cp and tracer-CB) is
substituted for CF, CP and CB in equations 1-5. When there is less than complete
rejection of an inert tracer, for instance only 80 percent rejection (a 0.8 rejection
factor), tracer-CR will be less than F/B as shown in Equation 4. In this regard, the
determination of the rejection of the inert tracer in the membrane filtration system is at
least proportional to the rejection of the solute within same. In a preferred
embodiment, the percent rejection is determined and maintained at an amount ranging
from about 95 to about 100 percent.
In this regard, monitoring of an amount of the inert tracer as it may vary during
membrane filtration can be utilized to evaluate a number of process parameters specific
to membrane filtration such as a percent recovery, percent rejection, recovery ratio or
the like, with a high degree of sensitivity, selectivity and accuracy, as previously
discussed. The ability to evaluate these types of membrane separation process
parameters with such level of certainty, sensitivity and selectivity and on a continual
basis in accordance with the present invention can provide a better understanding, in
real time, of the performance of the membrane. Thus, adjustments to the membrane
separation process can be made more responsively and effectively based on the
measured amount of the inert tracer, if needed, to optimize membrane performance.
For example, adjustments can be made to increase the recovery ratio or percent

recovery of the membrane separation system. In this regard, increasing the recovery
ratio or percent recovery, for unit product, will reduce the feedwater required and thus
reduce feedwater costs, lower influent fluid pretreatment costs and chemical treatment
requirements. It should be appreciated that the optimal percent rejection value can vary
with respect to the type of membrane separation system. In addition, percent recovery
may be calculated in various ways. In membrane filtration the percent recovery
calculation can be based on ratios of the various streams or on concentrations of solutes
within those streams. In this regard, the amount of inert tracer in the various streams
can provide an accurate assessment of percent recovery as well as a method for
checking the calibration of the mechanical flow sensors in the system.
However, unless controlled or optimally minimized, scaling and/or fouling of
the membrane can adversely impact the performance of membrane separation. If
deposition on the membrane is neither prevented nor detected soon enough for effective
removal by cleaning methods, the normal life of the membrane, which can be about
three to five years for reverse osmosis, may be severely shortened and replacement
costs dramatically increased. As previously discussed, the membrane separation
systems are more sensitive to such scaling and/or fouling activity as compared to
cooling water systems. It should be appreciated that the membrane separation system of
the present invention can include any suitable type and amount of components in order
to effectively treat the scale and/or fouling conditions, such as, any suitable treatment
or pretreatment system including antiscalants and/or biofouling agents, filters,
treatment equipment, such as chemical agent delivery devices, suitable like components
or combinations thereof.

For example, suitable antiscalants that can be used in the membrane separation
system (especially reverse osmosis systems) of the present invention include suitable
polymers in aqueous solution which inhibit the formation and growth of alkaline earth
carbonate and sulfate scales, including calcium carbonate ("CaCO3"), calcium sulfate
("CaSO4') or the like. Antiscalant chemicals are generally fed continuously into the
feed stream wherein the optimum feed point is before a cartridge prefilter positioned
along the feedwater stream. The use of a continuous feed of antiscalants can minimize
or eliminate the need for acid to be fed into the system in order to control scale, and can
facilitate the suspension of solids and colloids in solution. This can minimize
membrane fouling, and inhibit the precipitation ofCaCO3 and CaSO4
In an embodiment, the present invention can monitor and/or control the
concentration of the scaling and/or fouling treatment agents within the membrane
separation process based on the measurable amounts of the inert fluorescent tracer in
the system. In an embodiment, the inert tracer is continuously fed to the feedwater
along with the treatment agents. It should be appreciated that the inert tracer can be
added separately or as a part of a formulation of the treatment agent to the feedwater.
In an embodiment, the inert tracer is fed to the feedwater in known proportion to the
scaling and/or biofouling agent. In this regard, the measure of the inert tracer
concentration corresponds to (is proportional to) the chemical concentration (under
zero-systcm-consumption conditions) at any suitable tracer monitoring point within the
membrane separation system.
The chemicals or treatment agents employed as antiscalants and/or anti-fouling
agents, and the mechanisms by which they inhibit scale deposition, may change as
improvements are made in antiscalant chemistry for membrane filtration systems, but

the need for a continuous feed of treatment agents will most likely continue despite the
improvements.
As previously discussed, inert tracers of the present invention can be utilized to
monitor a variety of different parameters specific to membrane separation such that the
performance of membrane separation processes can be effectively monitored and
controlled. In an embodiment, the parameters can include normalized permeate flow
and percent rejection (as discussed above). In this regard, the present invention can be
utilized to assess and/or control a variety of different process conditions that can impact
membrane performance, for example, scaling and/or fouling conditions, membrane
leakage, degradation and the like specific to the membrane separation process as
previously discussed.
It should be appreciated that the preferred inert tracers of the present invention,
substantially have a rejection factor of 1, and more preferably are employed in minute
concentrations. Thus, the use of the inert tracer of the present invention does not in any
significant manner add to the total dissolved solids ("TDS") of the permeate nor
detrimentally effect a downstream ion exchange process or other permeate polishing
process.
Normalized Permeate Flow Monitoring
The normalized permeate flow is typically considered a sensitive forecaster of
trouble in a membrane filtration process, such as reverse osmosis. In this regard, a
reduction of the permeate flow rate is a strong indicator of membrane fouling, whereas
its increase is a strong indicator of membrane degradation, for instance due to an
adverse operation condition. In reverse osmosis the actual permeate flow rate can vary
with respect to the feed stream temperature, driving force and feedstream TDS.

Normalized permeate flow is determined through a simple calculation which eliminates
the effect of actual system temperature and driving force variations and converts the
actual permeate flow readings to what they would be if the system were operating at
constant ("normal") driving force and temperature conditions, which are routinely the
start-up driving force and 25° C. The actual permeate flow rate is conventionally a
direct reading from a permeate flowmeter. The temperature conversion factor for a
given feedwater temperature is provided by the membrane manufacturer for each
specific membrane.
Normalized Permeate Flow Example
In reverse osmosis systems employing differential pressure as the driving force,
the feed pressure and permeate pressure variations are reduced to a differential pressure
conversion factor which includes the start-up net pressure divided by the actual net
differential pressure (e.g., a differential pressure calculated by subtracting the permeate
pressure from the feed pressure, which in turn can be measured from any suitable
pressure meters). The permeate flow rate is multiplied by the temperature conversion
factor and the driving pressure conversion factor. Applicants have discovered that the
monitoring of the inert tracer of the present invention can be used to enhance
normalized flow monitoring.
The monitoring of inert tracer concentrations in the feedwater and the
concentrate can provide a measure of actual permeate flow, which will be the
difference between total flow (e.g., the feedwater flow which an inert tracer measures)
and concentrate flow (which an inert tracer also measures). The inert tracer
monitorings of the present invention, thus, can provide a measure of actual permeate
flow in addition to the readings from the usual flow meter. With a combination of

normalized permeate flow determinations and driving force measures, several critical
trends can be readily detected. If the normalized permeate flow is dropping while the
driving force is increasing, this signals membrane fouling. If, instead, the normalized
permeate flow is dropping while the driving force remains the same there is a
forewarning to check the gauges and the like for accuracy.
As previously discussed, there exists a relationship between the flow rate and
the concentration of the inert tracer such that the water flow can be determined based
on the measurable amount of the inert tracer in the membrane separation system. The
flow rate of any membrane separation process stream is the volume that passes a given
point within a given time period. The monitoring of the concentration of an inert tracer
in a stream at a given point, thus, can provide a determination of flow rate by mass
balance of inert tracer ions in solution compared to inert tracer added. Alternatively,
since the mass flow rates of the discharge streams, in combination, must equal the mass
flow rate of the feed stream, and the mass of the inert tracer in the discharge streams, in
combination, must equal the mass of the inert tracer in the feedstream, flow rates and/or
inert tracer concentrations of one of such streams can be calculated from the others,
when known. Moreover, when an inert tracer is added to the feedwater at a known rate
(e.g., amount per unit time), the concentration of an inert tracer in the feedwater as it
passes the feedwater tracer monitoring point itself can determine the flow rate of the
feed stream.
Differential Pressure Monitoring
In membrane filtration, the differential pressure is the difference between the
feed pressure and the concentrate pressure. It is a measure of the hydraulic pressure
losses through the membrane-filtration membrane elements and the manifold piping.

When the feed stream flow channels become clogged, the driving force increases. The
differential pressure also depends upon the feedstream flow rate and the percent
recovery. An accurate comparison between differential pressure readings taken at
different times requires that the membrane filtration system is operating at the same
percent recovery and feed flow rate in each instance. In this regard, inert tracer
monitoring can be utilized to accurately assess the differential pressure of the
membrane separation system. It should be appreciated that the differential pressure at
any given point in time can be determined by conventional methods.
Percent Rejection Monitoring
The percent rejection is the percentage of solute(s) that is rejected by the
membrane separation process. In practice, a percent rejection is based on one or more
selected solutes rather than the entirety of solutes in the feedwater, and the percent
rejection value can include an accompanying identification of the reference solute(s).
The percent rejection often will change upon the onset of a membrane and/or system
problem, such as fouling, scaling, membrane hydrolysis, improper pH, too low of a
feed pressure, too high of a recovery rate, a change in the composition of the influent
fluid source, a leaking "O" ring and the like. Typically, a decrease in percent rejection
can indicate problems associated with membrane performance. However, the percent
rejection may increase upon membrane clogging by certain foulants. In membrane
filtration the percent rejection is the rejection factor (e.g., Equation 5) expressed as a
percentage (e.g., multiplied by 100). The present process permits the percent rejection
to be determined almost instantaneously, using Equation 6 as follows:
Equation 6 rejection factor = (tracer-Op - tracer-Cp)/tracer-CF

where the virtually instantaneous and continuous monitorings of the feedwater inert
tracer concentration and the permeate inert tracer concentration can be determined with
a high degree of selectivity, sensitivity and accuracy as previously discussed. Since the
feedwater inert tracer concentration (tracer-CF) effectively varies little in contrast to
other feedwater solutes (whose concentrations vary with feedwater quality
fluctuations), and since the inert tracer can be detected more accurately at low levels
than most all other solutes, less natural data variation (e.g., variations arising from
feedwater concentration variations) can exist with the method of the present invention
as compared to conventional percent recovery monitoring techniques that typically
measure the concentration of solutes to determine percent recovery. This reduction in .
natural data variation makes subtle trends easier to identify.
It should be appreciated that the present invention can be utilized to assess
and/or control a variety of different conditions that may have an impact on the
performance of the membrane separation process. For example, the present invention
can be utilized to monitor leaks in the membrane elements. This is very important to
the practical operation of a membrane separation system.
In this regard, leakage of concentrate through a membrane itself or a component
of the membrane element contaminates the permeate. Permeate contamination by
virtue of leakage may at times be so severe that the performance of the membrane
separation process is substantially impaired, and at best the quality of the permeate is
diminished. Upon such leakage there will be an increase in the normalized permeate
flow and permeate solute concentrations, but the increases may be minor and most
probably not be detected for at least a number of hours if conventional monitoring
techniques are utilized.

Applicants have discovered that the present invention can monitor membrane
leakage with a high degree of sensitivity, selectivity and/or accuracy and that can be
readily conducted on a continuous basis. For instance, if under normal conditions a
reverse osmosis system is producing a 75/25 ratio of parts by weight of permeate to
parts by weight of concentrate (e.g., the permeate having 40 ppm TDS and the
concentrate having 2000 ppm TDS) a leakage of 1 percent of the concentrate (e.g., 0.75
parts) into the permeate would increase the weight of the permeate by only 3 percent.
Such increase would be difficult to detect solely by conventional methods of
monitoring the normalized permeate flow. If undetected, such a leak would then
double the permeate TDS to about 97 ppm. When the inert fluorescent .tracer
monitoring of the present invention is utilized to monitor the permeate, particularly on a
continuous or substantially continuous basis, an increase in permeate inert tracer
concentration can be readily detected to signal that leakage is likely to be occurring. In
addition, the detection of an increase in the concentration of permeate inert tracer
would follow the onset of the leakage almost instantaneously.
When a reverse osmosis system employs a number of membrane elements, the
produced penneate from each are often combined before permeate quality screening.
An increase in permeate TDS from, a single membrane element is less detectable by a
determination of TDS with respect to the combined permeates because of the dilution
effects. In addition, the TDS increase in the combined permeates does not indicate the
site of the leakage. When the present process is employed to monitor permeate inert
tracer concentration, the separate permeates produced by each membrane element can
easily be monitored before the permeates are combined. Not only can the present

process detect the leakage, but it can also be utilized to determine the location of the
leak.
In addition to the monitoring capabilities of the present invention discussed
above, a number of different other process conditions of membrane separation systems
can also be monitored by the present invention on a regular or continuous basis to
provide a real-time assessment of membrane performance. These conditions can
include, for example, concentrate flow rate, percent recovery and biocide concentration.
In this regard, the SDI measures the quantity of particulate contamination in waters by
particles about 0.45 micron in diameter or greater. In an embodiment, the concentrate
flow rate and percent recovery can be monitored with a single inert tracer as discussed
above. In an embodiment, the biocide concentration can be most effectively monitored
using a separate inert tracer.
The methods of the present invention can include any suitable type, number and
combination of components, such as inert tracer compounds, inert tracer detection
devices (e.g., analytical techniques) or the like. In an embodiment, the chemical
compound(s) selected as the inert tracer(s) is soluble in the membrane separation
stream to which it is added to the concentration value desired and is substantially stable
in the environment thereof for the useful life expected of the inert tracer(s). In a
preferred embodiment, the combination of the chemical compound(s) selected as the
inert tracer(s) and the analytical technique selected for determining the presence of such
inert tracer(s), permits such determination without isolation of the inert tracer(s), and
more preferably should permit such determination on a continuous and/or on-line basis.
In an embodiment, the present invention includes a controller (not shown) to
monitor and/or control the operating conditions and the performance of the membrane

separation process based on the measurable amount of inert fluorescent tracer(s). The
controller can be configured and/or adjusted in a variety of different and suitable ways.
For example, the controller can be in contact with the detection device (not
shown) to process the detection signal (e.g., filter noise from the signal) in order to
enhance the detection of the inert tracer. Further, the controller can be adjusted to
communicate with other components of the membrane separation system. The
communication can be either hard wired (e.g., electrical communication cable), a
wireless communication (e.g., wireless RF interface), a pneumatic interface or the like.
In this regard, the controller can be utilized to control the performance of
membrane separation. For example, the controller can communicate with a feed device
(not shown) in order to control the dosage of treatment agents, such as antiscalants and
biocides, within the membrane separation process. In an embodiment, the controller is
capable of adjusting the feed rate of the feed stream based on the amount of inert tracer
that is measured.
It should be appreciated that pairs or groups of inert tracer monitoring points
that are to be compared should not be positioned across a flow-through site that has a
high concentration of solids, for instance a solids concentration of at least about 5 or
about 10 weight percent per unit volume based on a measured volume unit of about one
cubic inch. Such high solids concentration flow-through sites are found at the site of
filter cakes and the like. In this regard, these sites may absorb, or selectively absorb, at
least some amount of the inert tracer. This can distort the significance of monitoring
comparison. When an inert tracer is added upstream of, for instance, a cartridge filter,
in an embodiment, the first monitoring location of a monitoring pair should preferably
be downstream of such sites.

However, separate monitorings across a flow-through site of high solids
concentration may be conducted to determine the loss of an inert tracer from the fluid,
and if such loss is nonselective for the inert tracer, the loss of other solutes at that site.
For instance, when the flow-through site is a cartridge filter, such monitorings can
determine the loss of solutes, if any, attributable to that pretreatment location. Other
high solids concentration sites include without limitation sites of solids concentration(s)
created by the use of chemical additives such as coagulants, flocculants and the like.
In an embodiment, the inert tracer selected is not a visible dye, that is, the inert
tracer is a chemical specie that does not have a strong absorption of electromagnetic
radiation in the visible region, which extends from about 4000 Angstroms to about
7000 Angstroms (from about 400 nanometers ("ran") to about 700 nm). Preferably the
tracer is chosen from a class of materials which are excited by absorption of light and
product fluorescent light emission, where the excitation and emission light occurs at
any point within the far ultraviolet to near infrared spectral regions (wavelengths from
200 - 800 nm). The relative fluorescence intensity of the inert tracer must be such that
it is detectable in the amounts specified by product formulations (typically 2-10 ppb as
active fluorophore when dosed into the feed water stream of a device).
Alternatively, when the tracer dye does have strong adsorbtions in the visible
spectrum, it is used in concentrations such that it is not detectable to the naked eye.
Such embodiments may be preferred, for instance, when a membrane's percent
rejection of the tracer is less than 100 percent, and it is desirable to produce a permeate
free of color.

In some instances, it may be preferable to chose a fluorophore which emits
visible fluorescent light when excited by UV light. This may be preferred when visual
detection and/or photographic or other imaging of the system is desired.
Although membrane separation systems are often employed for the purification
of water, or the processing of aqueous streams, the systems of the present invention are
not limited to the use of an aqueous influent. In an embodiment, the influent may be
another fluid, or a combination of water and another fluid. The operational principles
of membrane separation systems and processes of the present invention are not so
governed by the nature of the influent that the present invention could not be employed
with influents otherwise suitable for water purification in a given membrane separation
system. The descriptions of the invention above that refer to aqueous systems are
applicable also to nonaqueous and mixed aqueous/nonaqueous systems.
In an embodiment, the inert fluorescent tracer monitoring methods of the
present invention can be utilized to monitor membranes which are subjected to
destructive (sacrificial) testing. This type of testing may include the sectioning or
division of an industrial membrane, for instance by cutting, into a number of separate
membrane pieces prior to testing so that a number of tests can be performed, each on a
different section of the membrane. In this regard, the inert fluorescent tracer
monitoring of the present invention can be utilized to monitor a number of different
parameters of destructive testing including, without limitation, the effects of excessive
pressure, contact with a membrane-destructive fluid and the like. The diagnostic
regime of the destructive testing would generally be focused on the membrane which
may be subjected to visual inspection of its surface, a membrane-surface
microbiological analysis by swabbing of its surface and analysis of water samples in

contact with membrane, surface analysis for inorganic deposits by SEM/EDS, surface
analysis for organic deposits by IR, electron microscopy, ICP and like surface analysis
techniques.
Although the membrane during destructive testing is not on-line, in an
embodiment of the present invention the inert tracer can be added to a fluid stream
which flows to the membrane and passes by or through it as a first effluent stream to
exit as a second effluent stream. The inert tracer can be added to the fluid upstream of
the membrane and the inert tracer in the fluid stream at least passes by the membrane as
a component of the first effluent stream and/or passes through the membrane to exit as
a component of the second effluent stream. The inert tracer is monitored in the fluid
stream at a point before the membrane to determine an influent inert concentration
value, and/or in at least one of the first and the second effluent streams to determine an
effluent inert tracer concentration. In this regard, the inert tracer is representative of a
solute of the fluid stream that can be added to the fluid in an amount sufficient for the
determinations of influent inert tracer concentration and effluent inert concentration.
Thus, the separation performance of the membrane can be determined prior to actual
use.
"Deposits" is meant herein to refer to material that forms and/or collects on
surfaces of a membrane. The "amount" or "concentration" of inert tracer is meant
herein to refer to the concentration of the inert tracer in the specified fluid in terms of
weight of the inert tracer per unit volume of the fluid, or weight of the inert tracer per

unit weight of the fluid, or some characteristic of the inert tracer that is proportional to
its concentration in the fluid and can be correlated to a numerical value of the inert
tracer concentration in the fluid (whether or not that correlation conversion is

calculated), and can be a value of zero or substantially zero. Thus, the process of the
present invention includes the detection of the absence of such chemical species, at
least to the limitations of the analytical method employed.
The foregoing descriptions of the present invention at times refer specifically to
aqueous influents and effluents, and the use of an aqueous system for describing a
membrane filtration system and the operation of the present invention therein is
exemplitive. A person of ordinary skill in the art, given the disclosures of the present
specification, would be aware of how to apply the foregoing descriptions to
nonaqueous membrane filtration systems.
"Treatment chemicals and/or agents" is 'meant herein without limitation to
include treatment chemicals that enhance membrane separation process performance,
antiscalants that retard/prevent membrane scale deposition, antifoulants that
retard/prevent membrane fouling, biodispersants, microbial-growth inhibiting agents,
such as biocides and cleaning chemicals that remove membrane deposits.
It should be appreciated that the present invention is applicable to all industries
that can employ membrane separation processes. For example, the different types of
industrial processes in which the method of the present invention can be applied
generally include raw water processes, waste water processes, industrial water
processes, municipal water treatment, food and beverage processes, pharmaceutical
processes, electronic manufacturing, utility operations, pulp and paper processes,
mining and mineral processes, transportation-related processes, textile processes,
plating and metal working processes, laundry and cleaning processes, leather and
tannine processes, and paint processes.

In particular, food and beverage processes can include, for example, dairy
processes relating to the production of cream, low-fat milk, cheese, specialty milk
products, protein isolates, lactose manufacture, whey, casein, fat separation, and brine
recovery from salting cheese. Uses relating to the beverage industry including, for
example, fruit juice clarification, concentration or deacidification, alcoholic beverage
clarification, alcohol removal for low-alcohol content beverages, process water; and
uses relating to sugar refining, vegetable protein processing, vegetable oil
production/processing, wet milling of grain, animal processing (e.g., red meat, eggs,
gelatin, fish and poultry), reclamation of wash waters, food processing waste and the
like.
Examples of industrial water uses as applied to the present invention include,
for example, boiler water production, process water purification and recycle/reuse,
softening of raw water, treatment of cooling water blow-down, reclamation of water
from papermaking processes, desalination of sea and brackish water for industrial and
municipal use, drinking/raw/surface water purification including, for example, the use
of membranes to exclude harmful micro-organisms from drinking water, polishing of
softened water, membrane bio-reactors, mining and mineral process waters.
Examples of waste water treatment applications with respect to the inert tracer
monitoring methods of the present invention include, for example, industrial waste
water treatment, biological waste treatment systems, removal of heavy metal
contaminants, polishing of tertiary effluent water, oily waste waters, transportation
related processes (e.g., tank car wash water), textile waste (e.g., dye, adhesives, size,
oils for wool scouring, fabric finishing oils), plating and metal working waste,
laundries, printing, leather and tanning, pulp and paper (e.g., color removal,

concentration of dilute spent sulfite liquor, lignon recovery, recovery of paper
coatings), chemicals (e.g., emulsions, latex, pigments, paints, chemical reaction by-
products), and municipal waste water treatment (e.g., sewage, industrial waste).
Other examples of industrial applications of the present invention include, for
example, semiconductor rinse water processes, production of water for injection,
pharmaceutical water including water used in enzyme production/recovery and product
formulation, and electro-coat paint processing.
Examples of diagnostics which can be determined by the use of inert tracers
include, but are not limited to, effective 'residence times" for species within the
membrane, system flow profiles, membrane damage detection, system recovery based
on mass balance, detection of scaling or fouling tendency (based on differences
between mass balance and flow based system parameters), system volume calculation,
chemical treatment product distribution and feed variability.
EXAMPLES
The following examples are intended 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.
Example 1
Tests were performed using a multi-stage reverse osmosis system. The system
utilized six pressure vessels, arranged in a 2:2:1:1 configuration with each pressure
vessel containing 3 spiral wound membrane elements. The membrane elements were a
polyamide based elements from several element manufacturers. Typical system
recovery, based on system flows, was 75 - 80%, with the feed flow ranging from about
100 to about 130 gpm.

The feed water included an inert fluorescent tracer (an aqueous solution of
1,3,6,8- pyrenetetrasulfonic acid tetrasodium salt (PTSA)), diluted with water to give a
final concentration of 0.20 to 0.25% as the active fluorophore in an aqueous solution.
The inert tracer was fed into the RO membrane system using a positive displacement
pump at a feed rate of approximately 2 milliliters/minute and at a concentration of
about 6 ppm into the feed stream described above.
The concentration of the inert tracer was fluorometrically measured (with a
TRASAR® 3000 and/or a TRASAR® 8000 fluorometer) in the RO membrane system in
both the feed stream and the concentrate stream over a select period of time, generally
one to three hours with data being collected at one second intervals. (Fluorometer
readings were expressed as "ppm of treatment product." The fluorometer was
programmed to read the concentration of the tracer and convert the reading into ppm of
treatment. In this case, the treatment was assumed to contain 0.2% active fluorophore.)
Periodic fluctuations in the concentration of the inert tracer in both of the concentrate
and feed streams were continuously detected. For example, the concentration of the
inert tracer in the concentrate stream varied from about 40 ppb of tracer (20 ppm as
treatment product) to as high as about 180 ppb of tracer (90 ppm as treatment product).
In general, the concentration of the inert tracer in the concentrate stream varied between
about 40 ppb of tracer (20 ppm as treatment product) and about 80 ppb of tracer (40
ppm as treatment product). In comparison, the concentration of the inert tracer in the
feed stream varied from about 10 ppb of tracer (5 ppm as treatment product) or less to
as high as about 130 ppb of tracer (65 ppm as treatment product). In general, the
concentration of the inert tracer in the feed stream varied from about 10 ppb of tracer (5

ppm as treatment product) or lower to about 20 ppb of tracer (10 ppm as treatment
product).
The ability of the present invention to detect fluctuations in the concentration of
the inert tracer added to the membrane separation system uniquely allows the present
invention to evaluate process parameters specific to a membrane separation with a high
degree of selectivity, sensitivity and/or accuracy such that the performance (e.g.,
operational, chemical, mechanical and/or the like) of membrane separation can be
effectively monitored. In this regard, suitable adjustments can be controllably and
responsively made to the membrane separation system such that performance is
optimized. For example, 'the detection of fluctuations in the concentration of the inert
fluorescent tracer during membrane separation (as discussed above) may necessarily
indicate that suitable and responsive adjustments to the membrane separation process
are necessary to decrease the fluctuations, and, thus enhance membrane separation
performance.
The test results also displayed spikes in the concentration of the inert tracer in
both of the feed stream and the concentrate stream. As previously discussed, the spike
in the amount of inert tracer in the feed stream occurred at about 120 ppb of tracer (60
ppm as treatment product) in comparison to that in the concentrate stream which
occurred at about 180 ppb of tracer (90 ppm as treatment product). By measuring the
elapsed time between the spikes in both of the feed and concentrate streams, the
effective residence time of solutes within the membrane separation system can be
calculated. This information can be useful, for example, in developing a treatment
strategy specific to membrane separation.

Furthermore, the tracer was used to calculate percent recovery as described
above. Whereas the percent recovery calculations based on flow measurements
indicate recoveries of about 35% to about 80%, recovery calculations based on mass
balance of the tracer shows significantly higher percent recovery values (89 - 92%).
Such information is useful in developing effective scale control strategies.
Example 2
Experiments were performed using thin film composites of a polyamide based
reverse osmosis membrane material in order to simulate process conditions utilizing a
reverse osmosis membrane separation system.
In this regard, a number of flat or planar sheets of the membrane were cut from
a roll of the polyamide material which is a commercially available product, for example
FT30 from FILMTEC of Minneapolis, MN.
Tests were performed in a SEPA CF, flat plate reverse osmosis cell which is
commercially available from the Osmonics Corporation of Minnetonka, MN. In
general, the test system included a feed water tank, a high pressure pump, and the flat
plate cell. The system was modified so that the change in pressure across the
membrane and the inlet pressure, as well as the feedwater, permeate water, and
concentrate water conductivities, and the permeate and concentrate water flows could
be continuously monitored. A data logger, available from the Yokogawa Corporation
of America of Newnan, GA, was used to continuously monitor and collect data.
Fluorometers (TRASAR® 3000, TRASAR® 8000 and Hitachi F-4500) were used to
measure the concentrations of tracers in the systems.


Permeate was sent to drain and concentrate returned to the feed water tank.
The test was designed to form scale on the membrane over time, thus decreasing permeate flow.
Tests were run to show monitoring of the reverse osmosis system with an
undamaged membrane. As shown by the calculated performance parameters in Table 2
below, the percent rejection of the tracer was 100%. This indicates that the tracer
molecule did not pass through an undamaged membrane. In contrast, a portion of the
dissolved salts (as measured by conductivity) did pass through the membrane.



Another sheet of polyamide membrane material was damaged by swabbing the
surface with a 0.05% hypochlorite solution. Using a feed solution of 1500 ppm NaCl,
rejection of the tracer molecule was monitored. All other experimental conditions were
the same as above. The results shown below in Table 4 indicate significant passage of
the tracer through the damaged membrane. Since conductive salts pass through both
undamaged (Table 2) and damaged (Table 3) membranes, the tracer only passes
through damaged membranes, making tracer measurement a more sensitive indicator of
membrane damage than conductivity measurements




While the present invention is described above in connection with preferred or
illustrative embodiments, these embodiments are not intended to be exhaustive or
limiting of the invention. Rather, the invention is intended to cover all alternatives,
modifications and equivalents included within its spirit and scope, as defined by the
appended claims.

WE CLAIM:
1. A method of monitoring a membrane separation process in an industrial
water system comprising the steps of:
(a) providing a membrane capable of removing solutes from a feed stream;
wherein the membrane separates the feed stream into a concentrate stream with a greater
amount of solutes in it and a permeate stream with a lesser amount of solutes in it;
wherein said membrane is suitable for use in an industrial water system;
(b) adding an inert fluorescent tracer to the feed stream wherein said fluorescent
tracer is not appreciably or significantly affected by the chemistry of the industrial water
system; wherein the concentration of the inert fluorescent tracer in the feed stream is
from 5 ppt to 1000 ppm;
(c) removing solutes from the feed stream by contacting the membrane with the
feed stream and having the membrane separate the feed stream into a permeate stream
and a concentrate stream;
(d) providing a fluorometer to detect the fluorescent signal of the inert tracer in at
least one of the permeate stream and the concentrate stream; and
(e) using the detected fluorescent signal of the inert tracer to determine the
amount of the inert fluorescent tracer in at least one of the permeate stream and the
concentrate stream.

2. The method of claim 1 further comprising the step of (f) evaluating a
process parameter of the membrane separation process based on the amount of the inert
fluorescent tracer that is measured.
3. The method of claim 2 further comprising the step of (g) adjusting the
operating conditions of the membrane separation process based on the evaluation of a
process parameter conducted in step (f).

4. The method of claim 2 wherein the process parameter evaluated is the
removal of solutes from the feed stream based on the amount of the inert tracer that is
detected and measured in the permeate stream and in the concentrate stream.
5. The method of claim 1 wherein the membrane separation process is
selected from the group consisting of a cross-flow membrane separation process and a
dead-end flow membrane separation process.
6. The method of claim 1 wherein the membrane separation process is
selected from the group consisting of reverse osmosis, ultrafiltration, microflltration,
nanofiltration, electrodialysis, electrodeionization, pervaporation, membrane extraction,
membrane distillation, membrane stripping, membrane aeration and combinations
thereof.
7. The method of claim 1 wherein the inert fluorescent tracer is selected from
the group consisting of 3,6-acridinediamine, N,N,N,'N'-tetramethyl, monohydrochloride;
2-anthracenesulfonic acid sodium salt; 1,5-anthracenedisulfonic acid; 2,6-
anthracenedisulfonic acid; 1,8-anthracenedisulfonic acid; anthra[9,l,2-
cde]benzo[rsf]pentaphene-5,10-diol, l6,17-dimethoxy-,bis(hydrogen sulfate), disodium
salt; bathophenanthrolinedisulfonic acid disodium salt; amino 2,5-benzene disulfonic
acid; 2-(4-aminophenyl)-6-methylbenzothiazole; 1 H-benz[de]isoquinoline-5-suIfonic
acid, 6-amino-2,3-dihydro-2-(4-methylphenyl)-l,3-dioxo-, monosodium salt;
phenoxazin-5-ium, laminoocarbonyl)-7-(diethylamino)3,4-dihydroxy-, chloride;
benzo[a]phenoxazin-7-ium, 5,9-diamino-, acetate; 4-dibenzofuransulfonic acid; 3-
dibenzofuransulfonic acid; 1-ethylquinaldinium iodide; fluorocein; fluorescein, sodium
salt; Keyfluor White ST; benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-[[4-[bis(2-
hydroxyethyl)amino]-6-[(4-sulfopheny l)amino]-l,3,5-triazin-2-yl]amino]-,tetrasodium
salt; C.I. Florescent Brightener 230; benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-[[4-
[bis(2-hydroxyethyl)amino]-6-[(4-sulfophenyl)amino]-l,3,5-triazin-2-yl]amino],
tetrasodium salt; 9,9'-biacridinium, 10,10-dimethyl-, dinitrate; l-deoxy-l-(3,4-dihydro-
7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)-r ibitol; mono-, di-, or tri-sulfonated
napthalenes selected from the group consisting of 1,5-naphthalenedisulfonic acid,
disodium salt (hydrate); 2-amino-1-napthalenesulfonic acid; 5-amino-2-

naphthalenesulfonic acid; 4amino-3-hydroxy-l-naphalenesuIfonic acid; 6-amino-4-
hydroxy-2-naphalenesulfonic acid; 7-arnino-l,3-naphthalenesuIfonic acid, potassium
salt; 4-amino-5-hydroxy-2,7-naphthalenedisuIfonic acid; 5-dimethylamino-1-
naphthalenesulfonic acid; l-amino-4-naphthalene sulfonic acid; 1 -amino-7-naphthalene
sulfonic acid; and 2,6-naphthalenedicarboxylic acid, dipotassium salt; 3,4,9,10-
perylenetetracarboxylic acid; C.I. Fluorescent Brightener 191; C.I. Fluorescent
Brightener 200; benzenesulfonic acid, 2,2'-(1,2-ethenediyl)bis[5-(4-phenyl-2H-l,2,3-
triazol-2-yl), dipotassium salt; benzenesulfonic acid, 5-(2H-naphtho[l,2-d]triazol-2-yl)-
2(2-phenylethenyI)-, sodium salt; 1,3,6,8-pyrenetetrasulfonic acid, tetrasodiun salt;
pyranine; quinoline; 3H-phenoxazin~3-one, 7-hydroxy-, 10-oxide; xanthylium, 9-(2,4-
dicarboxyphenyl)-3,6-bis(diethylamino)-, chloride, disodium salt; phenazinium, 3,7-
dianuno-2,8-dimethyl-5-phenyl-, chloride; C.I. Fluorescent Brightener 235;
benzenesulfonic acid, 2,2'-(1 ,2-ethenediyl)bis[5-[[4-[bis(2-hydroxyethyl)amino]-6-[(4-
sulfophenyl)amino]-l,3,5-triazin-2-yl]amino]-, tetrasodium salt; benzenesulfonic acid,
2,2'-(l ,2-ethenenediyl)bis[5-[[4-[(2-hydroxypropyl)amino]-6-(phenylamino)-1,3,5-triazin-
2-yl]amino]-, disodium 6alt; xanylium, 3,6-bis(diethylamino)-9-(2,4-disulfophenyl)-,
inner salt, sodium salt; benzenesulfonic acid, 2,2'-(l,2-ethenediyl)bis[5-[[4-
[(ammomemyl)(2-hydroxyemyl)amino]-6-(phe nylamino)-1 ,3,5-triazin-2-yl ]amino]-,
disodiun salt; Tinopol DCS; benzenesulfonic acid, 2,2'-([l,r-biphenyl]-4,4'-diyldi-2,l-
ethenediyl)bis, disodium salt; benzenesulfonic acid, 5-(2H-naphtho[l,2-d]triazol-2-yl)-2-
(2-phenylethenyl)-, sodium salt; 7-benzothiazolesulfonic acid, 2,2'-(l-triazene-l,3-diyldi-
4,l-phenylene)bis[6-methyl-, disodium salt; and all ammonium, potassium and sodium
salts thereof; and all mixtures thereof, wherein said components of said mixtures are
selected such that the fluorescent signals of the individual inert fluorescent tracers within
the mixture are capable of being detected.
8. The method of claim 1 wherein the inert fluorescent tracer is introduced
into the feed stream in an amount from 1 ppb to 50 ppm.
9. The method of claim 1 wherein the inert fluorescent tracer is introduced
into the feed stream in an amount from 5 ppb to 50 ppb.

10. The method of claim 1 wherein the inert fluorescent tracer is added to a
treatment chemical formulation in a known proportion to create a traced formulation and
it is this traced formulation that is subsequently added to the feed stream; wherein the
treatment chemical formulation is selected from the group consisting of antiscaling and
antibiofouling agents.
11. The method of claim I wherein the industrial water system is selected
from the group consisting of raw water processes, waste water processes, industrial water
processes, municipal water treatment, food and beverage processes, pharmaceutical
processes, electronic manufacturing, utility operations, pulp and paper processes, mining
and mineral processes, transportation-related processes, textile processes, plating and
metal working processes, laundry and cleaning processes, leather and tanning processes,
and paint processes.

Methods and systems for monitoring and/or controlling membrane separation systems or processes are provided.
The present invention utilizes measurable amounts of inert fluorescent tracer(s) added to a feed stream to evaluate and/or control the
purification of such feed stream during membrane separation. The methods and systems of the present invention can be utilised in a
variety ofdifferent industrial applications including raw wafer processing and waste water processing.

Documents:

1380-KOLNP-2004-FORM-27.pdf

1380-kolnp-2004-granted-abstract.pdf

1380-kolnp-2004-granted-assignment.pdf

1380-kolnp-2004-granted-claims.pdf

1380-kolnp-2004-granted-correspondence.pdf

1380-kolnp-2004-granted-description (complete).pdf

1380-kolnp-2004-granted-examination report.pdf

1380-kolnp-2004-granted-form 1.pdf

1380-kolnp-2004-granted-form 18.pdf

1380-kolnp-2004-granted-form 2.pdf

1380-kolnp-2004-granted-form 26.pdf

1380-kolnp-2004-granted-form 3.pdf

1380-kolnp-2004-granted-form 5.pdf

1380-kolnp-2004-granted-reply to examination report.pdf

1380-kolnp-2004-granted-specification.pdf


Patent Number 230176
Indian Patent Application Number 1380/KOLNP/2004
PG Journal Number 09/2009
Publication Date 27-Feb-2009
Grant Date 25-Feb-2009
Date of Filing 17-Sep-2004
Name of Patentee NALCO COMPANY
Applicant Address 1601 DIEHL ROAD, NAPERVILLE, ILLINOIS
Inventors:
# Inventor's Name Inventor's Address
1 GODFREY MARTIN R. 2 S 260 LOCUST COURT, ELBURN, IL 60119
2 ZEIHER E. H. KELLE 213 BENTON AVENUE, NAPERVILLE, IL 60540
3 HO BOSCO P 46 ROSSINI COURT, WHEATON, IL 60187
4 HOOTS JOHN E 1430 LANCASTER AVENUE, SAINT CHARLES, IL 60174
5 BEDFORD BINAIFER 2323 MOONLIGHT COURT, NAPERVILLE, IL 60565
PCT International Classification Number B01D 61/22
PCT International Application Number PCT/US03/01756
PCT International Filing date 2003-01-21
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/109,256 2002-03-28 U.S.A.