THE FRENCH RIVER - THE TRACER METHOD



      OF REAERATION MEASUREMENT

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OVERVIEW
1. PURPOSE
2. SUMMARY
3. SUMMARY OF FINDINGS
REAERATION KINETICS
1. INTRODUCTION
2 • OXYGEN TRANSFER
3. POLLUTANT AFFECTS ON REAERATION
THE TRACER METHOD OF REAERATION MEASUREMENT
1. INTRODUCTION
2. MATHEMATICAL RELATIONSHIPS
3’ STREAM HYDRAULICS AND REAERATION
4. TRACER METHOD
A) Dose
B) Dose Release
C) Sampling
D) Measurements
THE FRENCH RIVER STUDY

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PURPOSE OF STUDY
This report describes a new technique for direct field measurement
of stream gas exchange capacity, based upon the simultaneous use of
tracers for dispersion and for gas exchange.
The general purpose of the investigation was to provide a direct
measurement rather than a predictive model of the French River and to
investigate the model’s limitations and sources of error. It was
planned that this investigation provide useful and necessary reaeration
data to be of assistance in solving a real pollution problem and that
it would also provide a complete set of basic field data on reaeration
to be available to other investigators.

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OVERVIEW
As the French River meanders between Oxford and Webster, Massachusetts,
and Wilsonville, Connecticut, it receives numerous discharges of
untreated domestic and industrial wastewater. The treated effluent
from the Leicester, Dudley, and Webster water pollution control
facilities also enters the river. In general, the French River can
be considered polluted since it Is below the federally approved “C”
classification.
This river study area includes a wide variety of hydraulic
features and was divided into three reaches Including a total of
eleven sampling stations (see Figure 1). The flow during the study
ranged from 35 CFS to 50 CFS.
The gaseous radioactive tracer procedure for field observation
of stream reaeration capacity provides the necessary tool for charac-
terizing stream reaeration capacity. It consists of a direct measure-
ment of gas exchange capacity in a specific stream reach under existing
hydrodynamic conditions and does not depend upon Idealized theoretical
estimates that cannot be verified. Application of this measuring
technique is not limited to presently polluted stream reaches, as is
the case of the traditional indirect approach. Since the tracer
methOd measures the effects of turbulence and surface renewal on
gas exchange, its usefulness is not affected by the presence or
absence of sludge deposits, algae, zero dissolved oxygen levels, or
other similar conditions. The ability to accurately evaluate reaeration
capacity In presently unpolluted river reaches should prove to be
especially advantageous in electing sites and planning for pollution

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FRENCH RIVER BAS
CLASS IF I CATION
WATER QUALITY STANDARDS ® ® © ©
CHANGE OF cLA5s ’rlcATION
4
0,2345
LJ LJ L
h*ILES
ISLAND
FIGURE 1
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— —
4
UTN IN

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control for new industry, as well as in basin water quality and water
resource planning.
Although the tracer method permits highly accurate field evaluation
of reaeration capacity in specific stream sections, the field method
itself is not without certain limitations and disadvantages. Among
the limitations are the cost, availability of special equipment,
availability of specially trained personnel, and radiological safety;
consequently, the field tracer procedure is usually reserved for appli—
cation and situations where the highest degree of accuracy and depend-
ability is a necessity.
The field tracer method for reaeration capacity was utilized in
a full scale field study of gas exchange in the French River between
Oxford, Massachusetts, and Wilsonville, Connecticut. A total of three
separate tracer releases were made, involving totals of three curies
of krypton—85 and tritium.. A total of 15 subreach-determinations of the
reaeration coefficient (K 2 ) were made in the three separate reaches.
Each subreach averaged approximately one mile in length. This field
study demonstrated the practical feasibility of direct and independent
evaluation of the reaeration capacity of natural streams by the tracer
method.
The assumptions upon which the tracer method are based are: (1)
The tritiated water undergoes only dispersion and is not lost from the
stream in any significant amount; (2) the dissolved krypton undergoes
the same dispersion as the tritiated water and, in addition, is lost
to the atmosphere and is not otherwise lost in any significant amount;
(3) the ratio of gas transfer coefficients for dissolved krypton and
oxygen of 0.83 is not significantly affected by temperature, turbulence,
o the presence of pollutants.

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The supporting evidence of the validity of these ass .miptions is
presented in this report. No assumptions are made as to the uniformity
of the stream channel or of turbulent mixing, nor are assumptions as
to the frequency of mixing, mixing length, or the rate of surface
replacement required. Although results are expressed as values of K 2 ,
they are understood to be average values for the subreach, and no
assumption that reaeration took place as a single first order process
is necessary.
SUMMARY OF FINDINGS
The tracer technique for measurement of reaeration was used
successfully on the French River. The values of K2 ranged from 0.037
to 45.8 per day. As shown in Figures 9 to 11, much of the gas transfer
takes place in very short reaches. The wide range of values is consis—
tant with the variety of hydraulic features present in the river. The
effects of dilution on counting statistics and pollution on reaeration
were evident during the study. We have concluded, based on this study,
that the tracer method for reaeration measurement yields accurate and
reproducible results.
The tracer method for evaluating stream reaeration depends upon
a series of assumptions and the simultaneous use of three tracers: a
florescent dye, a dispersion tracer (tritium), and a gas transfer tracer
(krypton—85).
In any reach of the stream, the percent of dissolved tracer gas
that was lost was readily evaluated on the basis of the upstream and
downstream concentration ratios of krypton and tritium. Methods of
analysis for the water concentrations of both radiotracers that have
been developed were confirmed to be sensitive and accurate.

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REAERATION KINETICS

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INTRODUCTION
The ability of a stream to obtain oxygen from the atmosphere is
the fundamental process through which stream recovery occurs once its
dissolved oxygen resources have been reduced or depleted. Accurate
knowledge of the reaeration capacity of streams is a necessary component
in establishing their assimilative capacity. Proper understanding of
stream reaeration forms the basis for establishing wastewater treatment
needs to protect the natural aquatic life. Although attempts to evaluate
stream reaeration capacity date back to 1911, research on this subject
has been intensified in recent years.
OXYGEN TRANSFER (l)(2 )
General:
The physical reaeration process involves: (1) entry of oxygen
molecules from the atmosphere into the water at the air—water interface
(diffusion); and (2) subsequent distribution of this dissolved oxygen
throughout the volume and depth of water (dispersion). The driving
force for reaeration (or for the transfer of any other gas) is simply
the partial pressure difference of oxygen in the atmosphere and in
the water. When the partial pressure of dissolved oxygen in the water
is equal to the partial pressure of oxygen in the atmosphere, the water
is said to be saturated with oxygen, and there will be no further net
oxygen transfer.
Figure 2 illustrates the mechanics of gas transfer in a completely
quiescent water. Initially, there is no dissolved oxygen at all in
the water, so that initially oxygen molecules move only into the water
from the overlying atmosphere. As oxygen molecules diffuse through
.
the air—water interface, there will be available dissolved oxygen

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(C 1 - C 2 ) = AC = very small
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Q •r
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AGIJRE 2

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molecules in the upper water layer near the water surface. They are,
also, in constant random movement due to their kinetic energy. Oxygen
molecules are able to enter the surface layers of the water more
easily than to diffuse downward through the fluid medium. As a result,
the dissolved gas molecules accumulate fairly rapidly in the uppermost
water layers and those layers become “saturated”. The net rate of entry
(reaeration) soon becomes very small because of this relatively rapid
accumulation of gas molecules. Across an infinitesimal distance, the
dissolved oxygen concentration difference (L C) is very small. As at
any depth and at any time- the driving force for molecular diffusion,
the concentration gradient (L C/ Ah) is very small. The reaeration
process by diffusion is, therefore, very slow because of the blocking
action of molecular diffusion. -
In a naturally turbulent stream, mixing is imparted to the volume
of elements of water by the application of an external force. Volume
elements from the deeper regions of the fluid replace some of those at
the surface. Some of the liquid elements from the uppermost water layers
find thenselves adjacent to volume elements previously located at quite
deep regions in the fluid body. The gas concentration difference between
these neighboring volume elements of water is thus no longer infinitesimal,
and the net rate of movement of gas molecules from the richer to the
poorer volume elements is, therefore, relatively rapid. At the same
time, volume elements from the deeper regions of the fluid body appear
briefly at the surface and since they are oxygen deficient they can
take up oxygen from the atmosphere at a relatively rapid rate. It is
clear that the faster the water is mixed and the surface replaced the
faster will be the reaeration process.

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The term turbulence has a special meaning relating strictly to the
rate of water surface replacement and to the dispersion of volume elements
of water. Turbulent mixing of the water and consequent dispersion of
the dissolved gas molecules takes place due to the application of this
external force and, therefore, enhances molecular diffusion and reaeration,
Unfortunately, by its very nature, turbulence itself cannot be independently
or directly observed or measured even though it can be defined and treated
mathematically. As a result, although gas transfer is primarily a
function of turbulent mixing, the rate of gas transfer cannot be accurately
predicted in these terms.
Available procedures for estimating the reaeration capacity of natural
streams generally required the assumption of uniform mixing and turbulence
over relatively long stream reaches. They treated reaeration as a single
first order process over substantial distances as no other practical
alternative existed. The tracer method described in the following sections
of this report requires no such assumptions as to uniformity of mixing
or turbulence. It provides a direct and independent measure of gas
exchange capacity under existing conditions of mixing and surface water
replacement.
POLLUTANT AFFECTS ON REAERATION
Certain pollutants can alter the reaeration capacity of a stream.
This section describes some of the results of laboratory studies dealing
with the affects of pollutants on reaeration. This discussion has
applicability to the observed reaeration rates in selected reaches of
the French River.

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To recapitulate, aeration of water is a gas—liquid mass tjansfer
process that occurs as a result of the combined affects of molecular
diffusion of oxygen and physical mixing of the water.
The basic mathematical expression describing aeration of unpolluted
water is: dDt —= K2Dt (1)
dt
in which Dt is the dissolved oxygen concentration below the saturation
limit, in milligrams per liter at the time T, and K 2 is the gas transfer
rate coefficient for oxygen in unpolluted water, which may also be -
- written as: d(Cs—Ct ) = —K 2 (C 9 —Ct) (2)
dt
in which C 5 is the dissolved oxygen saturation limit for unpolluted
water, and C is the DO concentration at time T.
Equation (2) is an expression of oxygen transfer in an unpolluted
water system. Other complicating factors must be considered for
polluted water. A general expression may be written as:
d(BC —Ct ) = aK2(BCs—Ct)+r (3)
dt
in which B is the ratio of dissolved oxygen saturation for the polluted
water to that of unpolluted water, a is the ratio of the oxygen transfer
rate coefficient for the polluted water to that of the unpolluted water,
and r is the rate of dissolved oxygen utilization, with other terms as
previously defined,
The beta factor is a correction for the difference between the
actual and theoretical dissolved oxygen saturation concentration.
Generally, the beta factor is not readily predicted and must be determined
theoretically. The alpha factor is a correction that must be taken into
account since various pollutants can alter the ability of gas molecules

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to enter and escape water. This alteration causes the value of K 2 to
vary under the same conditions of turbulence depending upon whether clean
water or polluted water is being aerated. It has also been proven that
the alpha factor is not only related to the pollutant concentrations
but also to the turbulent mixing regime within the fluid.
Consider a dissolved tracer gas, krypton—85, which has been added
to the water. The expression for desorption of the tracer gas is:
Ct = COe t (3)
where Ct is the concentration of tracer gas remaining in the water at
time t, C 0 is the concentration at t=O, and K is the gas transfer rate
coefficient for krypton—85 in unpolluted water.
Equation (3) can be modified to describe the desorption of the
tracer gas in polluted water so that:
C = Coe < (4)
where alpha is the gas transfer rate coefficient correction factor for
the polluted water. -
It has been shown both experimentally and theoretically for the
same condition of turbulence:
= 0.83 (5)
al (2
and this is the basis for using krypton—85 as a tracer gas for oxygen
aeration studies. The numerical values 0.83, in equation (5) is inde-
pendent of the degree of turbulent mixing, independent of the directions
in which the two gases happen to be moving, and independent of temperature
within the normal range expected. This ratio has also been verified in
a biologically active wastewater.
.

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Laboratory studies on linear alkylate sulfonate (LAS) and mineral
oil and their affects on reaeration are typical examples of study of
pollutional affects.
Based upon various laboratory investigations with LAS, the following
conclusions have been reached: at a constant concentration of LAS, the
greater the degree of turbulent mixing, the greater the corresponding
reduction of gas transfer, or the less the gas transfer coefficient,
Much of the aeration takes place in short distances associated with rapids,
shoals, and waterfalls. It is, therefore, at just such hydraulic
features that the damaging affect of detergents will be at a maximum in
terms of reducing the magnitude of the- reaeration coefficient.
Other studies have shown, the presence of mineral oil enhances
the gas transfer capacity. The value of alpha diminishes as the rate
of mixing is increased and at relatively high mixing rates the mineral
oil was found to have no effect on the reaeration rate (alpha = 1).
It appears quite possible that the oil acted in some way as a lubricant,
modifying the surface tension of the water or increasing the rate of
surface water replacement.
SUMMARY
Having reviewed the basic concepts involved in oxygen transfer and
the affects of pollutants on thts transfer process, the following section
of this report details the tracer method of reaeration measurement.

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THE TRACER METHOD OF REAERAT ION MEASUREMENT

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INTRODUCT ION
The tracer method of stream reaeration measurement utilizes dye,
dissolved krypton—85 and tritiated water. These components are released
simultaneously in the stream at a known point. Subsequently, measurements
are made downstream and related to river characteristics. The dissolved
krypton—85 gas diffusion is used to evaluate the oxygen’absorption from
the atmosphere. The tritium, in the form of tritrated water, is used to
assess dispersion and dilution. The fluorescent dye serves two purposes:
it indicates when to sample for the two other traces, and it provides a
measure of the time of travel between sampling points. The mathematical
relationships governing this technique, the field and the analytical
procedures followed are outlined in subsequent sections of this report.
M&THEMATICAL RELATIONSHIPS
To understand the tracer method, it is essential that the
equivalence of two processes be clarified. These processes are (1)
absorption of oxygen from the atmosphere into the stream (reaeration),
and (2) desorption of a tracer gas from a stream into the atmosphere.
In both cases, the driving force is the concentration defecit, D. In
the reaeration process, the defecit is the difference between the
saturation concentration, C 6 , and the actual oxygen concentration C.
Dox = (C 9 — C)ox (6)
Similarly, the driving force of the tracer gas (radioactive
krypton—85) dissolved in the stream is the difference between the
tracer gas concentration in the stream and the atmosphere. Since the
atmospherictracer gas concentration is, for practical purposes, equal
to zero, the defecit is the stream concentration Ckr.
S
Dkr Ckr (7)

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If there exists an oxygen defecit in the stream, there will be a
net transfer of oxygen into the stream from the atmosphere. The net
movement of tracer gas will tend to decrease the tracer concentration in
the stream and thereby reduce the driving force. Both phenomena can
be represented by
= —i (8)
where K is a constant for the specific gas under consideration and
is dependent upon the intensity of turbulent mixing.
If only turbulent mixing affected the stream DO concentration,
Integration of (8) would yield a means of calculating the constant for
oxygen K 0
- D Doe_koxt (9)
where Do is the initial defecit (@ t=O); and D is the defecit at
time t. However, many other parameters affect the DO and therein
lies the need for the tracer method.
It has been shown experimentally that the ratio of Kox to that of
Kkr is constant as long as both gases are subjected to the same
conditions of turbulent mixing
( Kkr ) = constant = 0.83 (10)
Kox
This relationship of proportionality constants, along with the fact
that the tracer is chemically inert and, therefore, not subject to
extraction or degradation by aquatic biota, makes it possible to use
equation (9) to calculate Kkr and equation (4) to determine Kox.
Consider two points in a stream, A, the upstream point, and B,
the downstream point. If a specific quantity of krypton
gas was introduced at A, uniformly across the stream cross section,

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and assuming no vertical or horizontal velocity gradients in the stream
causing dispersion, and assuming no tributaries or other sources
causing dilution exited, the Kkr for the reach AB would be calculated
from equation (2)
e krt (11)
Cb
where Ca and Cb are krypton—8Y concentrations at A and B and t is the
time of travel from A to B. However, dispersion and dilution do exist
and, therefore, mustbe taken into account.
The direct measurement of dispersion and dilution is not necessary.
Equation (11) is modified by using an additional tracer, tritium,_in
the form of tritrated water. Tritrated water is released in the stream
simultaneously with the krypton—85 and provides a means of measuring
both dispersion and dilution. Because the tracers are released at the
same time, both undergo exactly the same dispersion and dilution.
Since tritium is not absorbed on the stream bed or otherwise lost,
the concentration decreases between sampling poitits only by dispersion
and dilution and, therefore, serves as an adjustment for said phenomena.
The decimal fraction of tracer gas remaining at point B is
( Ckr/CTr)B = eKkrt (12)
(Ckr/CTr)A
where (Ckr/CTr) A and B are concentrations ratios at time of peak
concentration, and t is the time of travel between A and B.
Fluorescent dye, the third component of the dose sample, serves two
purposes: (1) it indicates when to sample for the two tracers and (2)
provides a measure of the time of travel between sampling points.
Since the dye is absorbed 04 the stream bed, it cannot be used to

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determine dispersion and diffusion effects.
The three components of the dose solution are mixed and simultan—
eously injected into the stream. Samples are collected as the dye
peak passes and the krypton and tritium concentrations are analyzed
by simultaneous counting in a liquid scintillation counter. The
radioactive tracer ratios and the time of travel are plotted on semi—
log paper (see Figure 3). Equation (12) plots as a straight line and
the slope is equal to Kkr. From equation (10), the corresponding
value of K 0 x (or K 2 ) can be obtained.
The basic assumptions associated with this method are as follows:
(1) The nongaseous dispersion tracer (tritrated water) undergoes
only dispersion In the stream, and is not absorbed on the
stream bed or otherwise lost.
(2) The dissolved tracer gas (Krypton—85) undergoes dispersion
to the same degree as the nongaseous dispersion tracer and
is lost to the atmosphere only.
(3) The tracer gas and oxygen undergo gas transfer to the same
relative extent and the ratio of KKr/Kox is not significantly
affected by temperature, turbulence, or the presence of
contaminants.
It is not necessary, as it is with predictive methods, to assume
uniformity of cross section, depth, slope, roughness, etc. . . . and
no assumption is made as to uniformity of mixing or that reaeration
takes place as a simple first order reaction with a constant rate
coefficient (K 2 ).
With respect to assumption (1), tritium is no more subject to
absorption or other losses than water itself. It is water (in the form

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tritrated waterY and so constitutes an ideal dispersion indicator.
Any losses due to evaporation or seepage can be taken as negligible in
the small stream reaches under consideration. In any event, both
tritium and the krypton—85 tracer gas would be lost to the same extent
(i.e. tritium could not be selectively lost), and no effect upon the
observed concentration ratios would occur. Tritium is radioactive and,
therefore, very sensitive and accurate means of analysis are available.
The tracer gas, krypton.-85, meets the requirements of assumption
(2) in that it is a “noble” or chemically inert gas and is, theref öre,
lost only through gas transfer.
Assumption (3) has been the subject of considerable investigation
and is discussed elsewhere 3 . The relative exchange capacities of
krypton—85 and oxygen are functions of the molecular properties
(molecular diameters) and the ratio of 2 values is not significantly
affected by temperature, turbulence, or the presence of contaminants.
As shown in the 1967 FWPCA report, the ratio of 2 values for oxygen
and krypton—85 has been firmly established.
STR.EAN HYDRAULICS AND REAERATION
Consideration of the slope of the stream as the causitive property
of turbulence leads to the relationship
Z = (l_eC h) (13)
where Z is the decimal percent of dissolved gas lost between two points,
c is factor related to the molecular properties of the gas and the
proportionality constant in the surface replacement reaction, and . h is
change in elevation in feet. The equation (13) states that, at a given
temperature, the amount of tracer gas lost to the atmosphere or, conversely,
the amount of DO defecit satisfied in the reach AB can be related

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solely to the change in water surface elevation. Also, the value of
12 can be calculated on the basis of the elevation change and the time
of travel by the equation:
1 (2 c h) (14)
The value of C is determined, from a graphical interpretation of
percent gas remaining with respect to the change in stre in elevation
head.
THE TRACER METHOD
Dose Release
In the French River reaeration capacity study, the mixed doses of
three tracers (dye, dissolved krypton—85, and tritriated water) were
procured ready for immediate use from a vendor. The individual doses
ranged In size from one to two liters. This dose liquid volume was
essentially all florescent dye (20 percent aqueous solution), with
only a few milliliters of tritrated water and the dissolved krypton—85
added. In earlier studies conducted on much larger rivers, dose
solutions as large as nine liters in volume were used with proportionately
larger quantities of radioactive tracers.
Figure 4 shows the device used to release the dosing solution.
The base is a steel section with small bars welded underneath so as
to keep the dose above the stream bed. The dose bottle was taped to this
base section. The top section, or striker, with a four foot length of
one inch steel rod welded to it, was also taped to the base to complete
the assembly. The dosing rig was then carried by the rod to the river
and placed on the stream bed in mid channel. The submerged dose was
released by striking the steel rod to shatter the glass bottle.
S

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TRACER RELEASE
DEVICE
cMANUAL)
!IGURE 4
37
STRIKER
BOTTLE
BASE

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This device, because of its simplicity, proved to be very dependable
and satisfactory. Because of its weight, it can be held in place even
in strong currents. Complete shattering of glass and, thus, virtually
instantaneous tracer release is attained.
In rivers of much greater flow, where wading is impractical,
blasting caps have been shown effective in releasing the tracer dose.
A steel plate must be used when performing dosing by this method to
eliminate the possibility of splashing.
Sampling
The tracer release was usually accomplished in the early morning
hours. The procedure utilized in sampling the dosing solution consisted
of collecting samples by hand of the dye patch approximately 50 yards
below the release point. Several samples can be collected during
passage of the dye. Simultaneous to the dose release, the first
downstream sampling station was set up and placed in operation. After
completing the dosing operation, the crew proceeded to the first down-
stream station to provide any necessary assistance. Once the first
station was in operation, the dosing crew left.
The sampling consisted of placing a submersible pump in the main
stream flow. Garden hose was connected between the pump and the flow
through recording fluorometer located at the edge of the stream. The
pump and fluorometer were operated with power from a portable gasoline
generator. After passing through the fluorometer for dye concentration
measurement, the pump flow was split, the major portion going to waste
and the smaller flow being pumped into a 25 milliliter glass sampling
bottle via transparent flexible tygon tubing. This flow was delivered
.
at the bottom of the sample bottle at a slow rate so as to avoid any

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losses of the tracer gas. Al]. sample bottles were prenuinbered and
each was equipped with a pressure type screwon cap.
Prior to the approach of the leading edge of the dye, samples
were collected for analyses of background tracer concentrations.
Sampling for tracer concentration analysis began soon after the leading
dye edge passed the sampling point and was continued at increasing
frequency as the dye peak concentration approached the station. The
time and identification number of each of the 25 milliliter sample
bottles was noted. Each sample was pressure capped at once, sealed
f or shipment with black plastic tape, and placed in a plastic rack
for transportation to the laboratory. As the dye peak passes, the
frequency of sampling was decreased until the dye concentration diminished
to approximately half of the peak concentration. At this point, sampling
was discontinued, and the equipment was dismantled and moved to the
third sampling station.
The identical procedure was followed at all subsequent sampling
stations. The second crew placed station number two in operation well
in advance of the dye leading edge, followed the same sampling procedure,
and moved to the fourth station upon completion of sampling at station
two. The field sampling equipment is shown in Figure 5.
Laboratory Measurements and Procedures
Trutium is the heaviest isotope of hydrogen and has a mass of
three atomic units. It decays by beta emission to helium—3 with a
half life of 12.3 years. Its maximum beta energy is 18.6 key. Tritium
can exist In any physical or chemical state in which hydrogen can
manifest itself.

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FIELD SAMPUNG
ARRANGEMENT
GENERATOR
CONTINUOUS FLOW
RECORDI NG
FLUOROMETER
FIGURE • 5
I N F LOW
FROM
STREAM
PUMP
SAMPLE
BOTTLE
4
‘DISCHARGE
TO STREAM
69

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Krypton—85, an inert gas, decays by both beta and gamma emission.
The beta emissions occur 99.6 percent of the time with a maximum beta
energy of 670 key. The 0.4 percent abundant gamma emissions are
characterized by the 512 key photo peak.
Because of its extremely low energy, tritium cannot be measured
by the usual laboratory counting instruments. Gas counting of the
tritium gas, and liquid scintillation counting of tritiated water are
the only feasible methods of measurement. Tritium, when used in a
study of reaeration capacity, is in the chemical form of water and
hence liquid scintillation counting offers the best practical choice
from the standpoint of ease of sample preparation and counting efficiency.
Krypton—85 can be measured by both beta and gamma counting.
However, because of its low g mm abundance, the sensitivity of gaxmna
counting is poor since the concentration usually encountered in such
a reaeration procedure are usually low. Beta counting is, therefore,
the only alternative. Gas counting is impractical because of the un-
certainties involved with the loss of the krypton gas from solution.
Liquid scintillation counting, thus, becomes the only practical
choice and is suited well for measuring both radloisotopes simultaneously.
This technique becomes practical whenever the beta energies differ by
a factor of five or more (18.6 key for tritium vs. 670 key for krypton).
Great care must be exercised in the preparation of samples. Since
the krypton—85 is an inert gas dissolved in water, reasonable efforts
should be taken to prevent the loss of the gas from solution while
preparing the sample for counting.
This method provides for the direct simultaneous counting of
krypton—85 and tritium in replicate two millimeter portions using a

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three channel liquid scintillation counter (see Appendix for counting
data).
It should be noted that the presence of sample impurities such
as the dye causes some reduction of counting efficiency (by “quenching”),
and calibration curves must be utilized for the counting of both
mixed radioisotopes in the presence of dye. This procedure is
applicable when counting the initial dosing solution concentrations.
The liquid scintillation counter is calibrated against known
standards to provide counting efficiencies for both radiotracers.
Usual efficiencies are 25 to 28 percent for tritium and 86 to 90
percent for krypton—85. These efficiencies permit accurate counting
of river water samples having quite low tracer concentrations.

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SECTION VII
FRENCH RIVER
Figures 6, 7, and 8 are general maps of that portion of the French
River between Oxford and Webster, Massachusetts, and Wilsonville,
Connecticut, showing relevant features including dosing and sampling
stations used in the tracer study. The Leicester, Dudley, and Webster
Water Pollution Control facilities discharge their wastewater to the
French River. Untreated domestic and industrial wastes enter the
river from various locations. In general, the French River can be
considered polluted since it is below the federally approved tCI
classification.
The French River study reaches include a wide variety of hydraulic
features. The upper three miles studied are characterized by alternating
riffles and two shallow pools. At the downstream pooi, the flow spills
over a dam and falls approximately five feet high. Below the dam, the
river flows in a channel until it reaches a marshy :Linpoundinent above
Hodges Village Dam.
The middle reach included the length from Hodges Village Dam
downstream approximately four miles to the North Village impoundment.
The flow through this section was uniformly channeled except for the
impoundment immediately below Hodges Village Dam (approximately 30 feet
deep and well mixed) and the section just above the North Village
impoundment (where the flow meanders through a swamp). The dose point
was located immediately below Hodges Village Dam at a rapids section
of the river.
The lower study reach Included the length from Webster, Massachusetts,
downstream to Wilsonville, Connecticut, a distance of some 2.5 miles.

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D.se poin!
Station
StatIon 3
C.)
4
w
NORTH OXFORD
I
C)
xc
Station I
c L
IL l
>
VILLAGE
Figure 6

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Dose point
HODGES VILLAGE
CsJ
=
C)
4
I ii
Sf0 lion
•4
I
K
Station 3
NORTH VILLAGE
Fl ure 7

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I
C-)
.
MASSACHUSETTS
CONNECT ICUT
Station 5
3
4
DUDLEY
.9
Dose point
WEBSTER
w
Station I
— Station 2
‘Ash st.
ers Pond
NVILLE
Figure 8

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The subreach 3—4 included a 20 foot cascade dam. This reach receives
wastewater from various industries as well as both the Webster and
Dudley Water Pollution Control facilities. As a result, the stream
oxygen resources were completely exhausted.
The flow during the study averaged between 35 and 50 cfs. Table 1
gives the time of travel through the three reaches and Table 2 presents
the reaeration rate coefficients (K 2 )o determined by the study.
Reaeration Coefficients
As indicated, the French River incorporates a wide range of
hydraulic features within the ten miles studies, from waterfalls to
rapids, pools, and a swamp. As a result, a wide range of K 2 values
has been observed, ranging from 0.037 to 45.8 per day (a value of 2308
per day was measured at the cascade type dam). Reference is made to
Table 2 which should be regarded as containing highly reproducable
reaeration rates with the exception of the result that Involves Station 3
for Dump II. Since very little dissolved krypton—85 remained at this
station (because of dilution), counting statistics were poor. Also,
Dump I took place in a highly polluted section of the river. The
significance of the fact is discussed in a preceeding section; pollution
added to streams causes a variation of the reaeration capacity.
It is evident from the results that in a river such as the French,
much of the gas transfer takes place In very short reaches. Within
the entire reach for Dump I, most of the gas transfer occurred at the
waterfall (subreach 3—4). This and other similar effects are demonstrated
in Figures 9 to 11. These figures graphically show the gas transfer
of the respective reaches. The observed krypton: tritium ratios
.
(contained in the Appendix) have been plotted vs. the time of travel

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TABLE t
TINE OF PASSAGE
DUMP TINE OF TRAVEL (HOURS), .BETWEEN STATIONS
1 2 3 1 2 3 1 2 3 4 5
I 1.46 3.50 10.16 ——— ——— ——— ———
II ——— ——— ——— 7.34 7.66 15.00
III ——— ——— ——— ——— 0.30 050 4.15 0.02 4.90
TOTAL TIME 1.46 4.96 15.12 7.34 15.00 30.00 0.30 0.80 4.95 4.97 9.87
TABLE 2
OBSERVED REAERATION RATE COEFFICIENTS
DUMP (1(2) (per day), between stations
1 2 ox 1 2 3 1 2 3 4 5
i 45.8 4.4 0.9 ———
II ——— 2.6 0.7 (0.2) ——— ——— ——— ———
I I I ——— ——— ——— ——— 5.5 3.0 0.05 2308.6 0.04
CUMULATIVE 45.8 16.6 6.07 2.6 1.7 0.9 5.5 3.9 0.7 8.4. 4.2
(QUESTIONABLE VALUE)

-------
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-------
I
on semilog paper. The slope of the line between two points represents
the tracer gas transfer rate coefficient between those points (the
logarithmic scale shown refers to common logs or values of kKr, whereas
the values shown are to the base and are values of KKr). The values
reported are based on river temperatures at the time of sampling.
A more direct comparison can be.made in terms of the actual gas
loss in any specific reach. The decimal fraction of tracer gas remaining
at the downstream station is just the downstream krypton: tritium ratio
divided by the upstream ratio. For example, for Dump III, reach 1—2,
the observed ratios were 0.137 and 0.098 at stations 1 and 2, respectively.
Hence, at station 2 there remained
0.098 x 100 = 71.5 percent
0.137
of the tracer gas that was present earlier at station 1. Conversely,
28.5 percent (100—71.5) of the tracer gas was lost to the atmosphere
between stations 1 and 2. Similar calculations for Dump I, reach 3—4
show that 57 percent of the tracer gas present above the cascade type
waterfall was lost due to the dam.
Calculation of Gas Exchange Coefficient
The gas exchange coefficient for krypton—85 is customarily obtained
by the graphical procedure outlined previously. This is the most simple
and direct method. For purposes of showing the calculation, the
krypton and oxygen exchange coefficients will be determined here
analytically.
Using the previous example of Dump III, reach 12, 71.5 percent of
the quantity of krypton present at station 1 was still present at
station 2. Using equation 3, with a time of travel of 0.5 hours:

-------
.715 = e 0 .5KKr
Solving this equation yields K 1.59 per day for the subreach;
dividing by the krypton:oxygen ratio of 0.83 yields Kox = 1.91 per
day and converting this result to the common logarithm base, K 2 44
per day. This is the reaeration capacity coefficient for this sub—
reach under consideration at the prevailing river temperature and
flow rate.

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BIBLIOGRAPHY
1. Tsivoglov, E. C.; Tracer Measurement of Stream Reaeration; FWPCA,
Washington, DC; June, 1967
2. King, D. L.; Reaeration of Streams and Reservoirs; Bureau of
Reclamation; December, 1970
3. Tsivoglov, E. C.; Characterization of Stream Reaeration Capacity;
EPA, Washington, DC; October, 1972
4. Standard Methods for the Examination of Water and Wastewater; 13th
Edition; 1971
5. Symposium on the Direct Tracer Measurement of the Reaeration
Capacity of Streams and Estuaries; EPA; January, 1972

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APPENDIX

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Webster, Massachusetts, (Chase
A enue Bridge to Wilsonville,
Study No. 1 Connecticut
1st 2nd 3rd
Dose Count Count Count
0—3
0—4 0.269 0.257 0.249
0—5 0.251 0.240 0.233
0—6 0.248 0.239 0.233 0.254±0.004E— )
0—7 0.261 0.253 0.244
0—8 0.288 0.279 0.270
Station 1 Brandon Road Bridge
1—3 0.259 0.258 0.248
1—4 0.260 0.249 0.244
1—5 0.266 0.251 0.243
1—6 0.253 0.246 0.239
1—7 0.263 0.252 0.247
1—8 0.269 0.262 0.253
1—9 0.246 0.236 0.232 0.245+O.002(..- )
1—10 0.259 0.249 0.239 Average Ratio
1—11 0.254 0.246 0.243 at Station
1—12 0.246 0.236 0.231
1—13 0.235 0.227 0.233
1—14 0.245 0.237 0.227
1—15 0.255 0.248 0.231
1—16 0.246 0.240 0.240
1—17 0.248 0.233 0.215
Station 2 Dudley Sewage Treatment Plant
2—3 0.264 0.250 0.233
2—4 0.264 0.250 0.242
2—5 0.258 0.251 0.241
2 6 0.248 0.235 0.229
2—7 0.246 0.235 0.225
2—8 0.246 0.237 0.237
2—9 0.252 0.236 0.229 0.237+0.0O o- )
2—10 0.246 0.232 0.239 —
2—11 0.233 0.240 0.223
2—12 0.235 0.220 0.205
2—13 0.209 0.204 0.222
2—14 0.187
2—15 0.206

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Station 3
Carpenter Road Above Darn
3—8
0.282 0.273
0.235
0.224
3—9
0.276 0.253
0.235
0.232
3—10
0.236 0.239
0.233
0.227
3—11
0.240 0.245
0.220
0.233
3—12
0.238 0.201
0.209
0.192
3—13
0.271 0.249
0.249
0.246
3—14
0.258 0.246
0.227
0.236
3—15
0.246 0.236
0.224
0.207
3—16
0.225 0.250
0.243
0.216
3—17
0.256 0.250
0.234
0.238
3—18
0.250 0.242
0.225
0.234
3—19
0.228 0.233
0.213
0.200
3—20
0.242 0.239
0.226
0.242
3—21
0.239 0.239
0.218
0.209
3—22
0.241 0.254
0.230
0.225
3—23
0.239 0.255
0.205
——
Station 4
4—1
4—2
4—3
4—4
4—5
4—6
4—7
4—8
4—9
4—10
4—11
4—12
4—13
4—14
4—15
4—16
4—17
4—18
Carpenter Road
r
0.087 0.089
0.106 0.112
0.118 0.086
0.126 0.116
0.115 0.112
0.118 0.104
0.089 0.090
0.121 0.116
0.110 0.099
0.079 0.080
0.112 0.111
0.100 0.092
0.111 0.106
0.119 0.123
0.114 0.111
0.100 0.092
0.112 0.102
0.122 0.096
Below Dam
0.065
0.114
0.082
0.140
0.091
0.111
0.088
0.099
0.106
0.078
0.101
0.089
0.100
0.111
0.093
0.084
0.111
0.098
0.068
0.118
0.083
0.113
0.109
0.099
0.103
0.108
0.107
0.080
0.103
0.090
0.107
0.098
0.096
0.090
0.105
0.114
Station 5
Wilsonville
Above Dam
5—4
5—5
5—6
5—7
5—8
5—9
5—10
5—11
5—12
5—13
5—14
5—15
5—16
5—17
—— 0.106
0.709 0.122
0.086 0.130
0.105 0.112
0.097 9.105
0.112 0.140
0.109 0.098
0.120 0.122
0.114 0.121
0.120 0.112
0.113 0.109
0.114 0.133
0.108 0.088
0.096 0,139
0.095
0.132
0.085
0.092
0.092
0.103
0.093
0.105
0.115
0.085
0.079
0.087
0.090
0.079
0.086
0.089
0.087
0.094
0.098
0.080
0.091
0.114
0.084
0.081
0.115
0.083
0.066
0,083
0. 236±0 .002 ( x)
O.102±0.002(°ic)
(0.102055)
0.102+0. 002 & —x)
(0.10158)

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Hodges Village Below Corp of
Study No. 2 Engineer Dam to Upper End of
Dose 1st 2nd 3rd
Count Count Count
0—3 0.386 0.368 0.353
0—5 0.399 0.382 0.365
0—6 0.423 0.406 0.389 0.397+0.007( x)
0—7 0.459 0.440 0.418
0—8 0.405 0.387 0.371
Station 1 Chariton Road Bridge
1—5 0.229 0.267 0.254
1—6 0.273 0.310 0.265
1—7 0.249 0.237 0.272
1—8 0.225 0.283 0.241
1—9 0.303 0.289 0.304
1—10 0.192 0.212 0.265
1—11 0.288 0.253 0.272
1—12 0.234 0.253 0.279
1—13 0.256 0.238 0.240
1—14 0.268 0.254 0.298 0.216±0.004( —x)
1—15 0.255 0.233 0.299
1—16 0.265 0.243 0.335
1—17 0.248 0.227 0.307
1—18 0.297 0.224 0.217
1—19 0.276 0.269 0.232
1—20 0.274 0.275 0.272
1—21 0.255 0.210 0.259
1—22 0.278 0.255 0.276
Station 3 Harwood Road Bridge
3—9 0.158 0.306 0.268
3—10 0.195 0.243 0.230
3—11 0.186 0.242 0.248
3—12 0.243 0.233 0.248
3—13 0.183 0.206 0.226
3—14 0.211 0.16]. 0.225
3—15 0.305 0.242 0.245
3—16 0.234 0.191 0.249
3-17 0.211 0.197 0.250
3—18 0.330 0.175 0.285 —
3—20 0.238 0.234 0.186 0.230+0.005& x)
3—21 0.303 0.193 0.218
3—22 0.231 0.219 0.248
3—23 0.263 0.161 0.186
3—24 0.222 0.266 0.227
3—25 0.201 0.207 0.171
3—26 0.143 0.262 0.247
3—27 0.223 . 0.283 0.192
3—28 0.182 0.220 0.269
3—29 0.295 0.209 0.318
3 30 0.218 0.323 0.208

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Station 4 Large Impoundment -
4—1 0.126 0.118 0.279 0.077
4—2 0.151 0.339 0.280 0.228
4—3 0.278 0.159 0.283 0.220
4—4 0.246 0.369 0.444 0.093
4—5 0.182 0.208 0.225 0.231
4—6 0.203 0.187 0.211 0.211
4—7 0.158 0.208 0.195 0.240
4—8 0.301 0.226 0.155 0.268
4—9 0.183 0.159 0.154 0.215
4—10 0.309 0.219 0.184 0.169
4—11 0.272 0.197 0.201 0.147 0.213+0.007(c’ )
4—12 0.231 0.182 0.265 0.268
4—13 0.171 0.298 0.248 0.181
4—14 0.242 0.169 0.110 0.196
4—15 0.374 0.239 0.205 0.198
4—16 0.212 0.271 0.249 0.201
4—17 0.164 0.254 0.119 0.110
4—18 0.223 0.212 0.220 0.205
4—19 0.195 0.143 0.148 0.189
4—20 0.177 0.332 0.214 0.194
4—21 0.249 0.183 0.149 0.213

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Clara Barton Read Bridge to
Hodges Village Below Corp of
Study No. 3 Engineer Darn
Dose 1st 2nd 3rd
Count Count Count
0—2 0.610 0.597 0.577
0—3 0.519 0.505 0.486
0—4 0.669 0.655 0.629
0—5 0.586 0.571 0.546
0—6 0.960 0.949 0.924 ;0.593±0.0ll(e’ )
0—7 0.606 0.597 0.570 Average Ratio
0—8 0.719 0.705 0.688 at Station
0—9 0.574 0.558 0.544
-0—10 0.577 0.561 0.536
0—11 0.540 0.531 0.538
0—12 0,678 0.673 0.651
Foot Bridge Of f Dirt Road 0.9
Station 1 Miles Below Dose
1—2 0.169 0.170 0.122
1—3 0.156 0.156 0.147
1—4 0.141 0.140 0.137
1—5 0.142 0.143 0.135
1—6 0.131 0.132 0.129 0.137±0.003(i)
1—7 0.130 0.129 0.124
1—8 0.133 0.136 0.123
1—9 0.113 0.126 0.106
1—10 0.133 0.124 0.108
Foot Bridge Of f Dirt Road 1.8
Station 2 Miles Below Dose
2—5 0.107 0.097 0.130
2—6 0.102 0.094 0.089
2—7 0.096 0.101 0.092
2—8 0.107 0.105 0.104
2—9 0.100 0.102 0.094
2—10 0.099 0.099 0.095
2—11 0.103 0.100 0.101 O.O9 78 +0.00O8( x)
2—12 0.104 0.102 0.097 —
2—13 0.095 0.093 0.091
2—15 0.099 0.093 0.091
2—16 0.097 0.096 0.096
2—17 0.094 0.095 0.091

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Station 3
Hodges Village Below Corp of
Engineer Dam
3—9
0.084
0.089
0.085
3—10
0.082
0.085
0.083
3—11
0.087
0.073
0.079
3—12
0.076
0.077
0.077
3—13
0.077
0.075
0.076
3—14
0.088
0.077
0.083
3—15
0.089
0.076
0.080
3—16
0.085
0.077
0.081
3—17
0.082
0.072
0.081
3—18
0.075
0.076
0.080
3—19
0.081
0.078
0.072
0.0799±0. 0008 (° x)

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