United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-095 Aug. 1983
Project Summary
Measurement of Volatile
Chemical Emissions from
Wastewater Basins
Louis J. Thibodeaux, David G. Parker, and Howell H. Heck
Equipment and methodology were
developed for the measurement of vol-
atile organic carbon (VOC) emissions
from wastewater basins. Air samples,
wind velocities, and temperatures were
measured simultaneously at six vertical
positions above the water surface in
the aerodynamic boundary layer to yield
a single flux measurement The tech-
nique, known as the concentration pro-
file (CP) method, was used to measure
the emission rates of methanol, acetone
and total hydrocarbon (FID) from the
surface of four secondary wastewater
treatment lagoons of the pulp and paper
industry. The emission rate of meth-
anol was 1.4 to 3.8 ng/cm2 • sec (11 to
29 Ib/acre-day); acetone, 0.028 to
0.10 ng/cm2-sec(.22to0.77 Ib/acre-
day); and total hydrocarbon, 3.0 to 4.3
ng/cm2-sec (23 to 33 Ib/acre-day).
Methanol accounted for 6O to 8O per-
cent of the total hydrocarbon.
The CP method appears to be a versa-
tile technique that has a well-developed
theory and history of use, is ideally
suited for area sources, uses off-the-
shelf equipment is well adapted for
routine field use, and can be used with
a variety of air chemistry sample trapping
techniques (i.e., cryogenic, absorbents,
adsorbents, etc.) or direct analysis
techniques (i.e., total hydrocarbon
analysis, UV, etc.). It also has definite
limitations which make it applicable
only to basins or ground sources with
fairly large surface areas that have
minor up-wind disturbances and only
when sufficient wind is present
This report was submitted to fulfill
Grant No. R805534-O1 by the University
of Arkansas under the sponsorship of
the U.S. Environmental Protection
Agency. This report covers the period
September 26,1977 to December 31,
1980 and work was completed as of
December 31,1980
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory, Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The overall objective of this work was to
determine the magnitude of the flux rate of
organic compounds that are emitted into
the air from selected wastewater treatment
facilities forthe pulp and paper industry. In
order to make these measurements, it was
necessary to develop a field sampling
methodology, hereafter called the concen-
tration-profile (CP) technique, and labora-
tory analysis methodology to trap and
measure low molecular weight, volatile
organics in air.
Various organizations including the
chemical process industries and federal
and state agencies are concerned about
aspects of air emissions from wastewater
treatment basins. In some cases, efforts
are aimed at odor control. In others, there
is concern for the emission of hazardous
substances which originate from surface
impoundments. There is also a general
concern for the emission of vapor phase
organics and inorganics from wastewater
treatment basins. The placement of or-
ganic compounds (non-sulfurous) in these
basins gives rise to vapor phase organic
(non-methane) emissions that increase
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the quantity of hydrocarbons in the nearby
air mass. In this regard, attention has been
focused on wastewater treatment basins
as a source of potentially hazardous trace
contaminants to air.
As a result of interest generated during
an EPA demonstration project with Georgia
Kraft Company that evaluated the effective-
ness of cooling towers as a combined
wastewater cooling, biotreatment and
stripping operation, research was initiated
at the University of Arkansas to develop an
apparatus to quantify the air-strippable
organic fraction in industrial wastewater.
A mathematical simulation of air-stripping
and natural desorption from aerated stabili-
zation basins suggested that a significant
quantity of volatile organic material was
escaping treatment by the air route Further
studies of raw wastewaters from a broad
spectrum of industrial operations including
the wood products industry suggested
that a significant fraction of the discharged
organic material was volatile and easily
stripped by air. Gas chromatograph/mass
spectrometer analysis of organic com-
pounds in treated Kraft mill wastewater
indicated that many of these compounds
are known volatile chemicals.
Although it has been established that
chemicals are escaping through the air-
water interface of wastewater treatment
facilities, the question is how much of
what chemicals are desorbing. Due to
various chemical sinks in the facilities,
including water seepage, biochemical oxi-
dation, adsorption upon sediments and
paniculate matter, the only realistic approach
to quantifying the compounds emitted is
to perform measurements in the air bound-
ary layer immediately above the water
surface.
This report presents the results of the
research into mechanisms of volatilization
and the related emission measurement
procedures. The full report contains a
development of turbulent transport theory
for chemical flux measurement from water
surfaces; the methodology for performing
micrometeorological and chemical mea-
surements for using the concentration
profile (CP) technique; field results of the
emission rates of methanol, acetone, ace-
taldehyde, and total hydrocarbon (GC/FID)
from four pulp and paper wastewater
basins; and a model for predicting chemical
desorption rates.
Methodology and Final Working
Equations
This section summarizes the working
equations for the concentration profile
method and presents some details about
the theory upon which they are based. The
presentation is somewhat user oriented.
Details about the micrometeorology and
transport science basis of the final working
equations and the inherent limitations of
the method are presented in the full report
The method requires field measurement
of the concentration of the chemical in air,
PA1, wind speed, vx, and temperature T1(
within the turbulent boundary, no more
than two meters above the water surface.
Each variable should be measured at six
locations distributed logarithmically from
the water surface, and each measurement
should be taken well downwind of any
source of turbulence. Based on these
measurements. Equation 24 is used to
determine the vertical flux of the chemical
(i.e., species B, the chemical of interest)
from the water surface. Equation 24 is:
nB= - (DB1/ DA1) 2/3 8^2/02, scW
The components of each term in the
equation are described on following pages.
For introductory purposes, however, the
following identification of terms is provided:
nB = flux rate of chemical species
"B"
DB = molecular diffusivity of chemi-
cal species "B"
DA = molecular diffusivity of water
vapor
Sv = slope of line (as defined) rep-
resenting wind speed profile
Sp = slope of line (as defined) repre-
senting profile of chemical
concentration in air
k = von Karman constant (= 0.4)
= a correction factor term reflect-
ingstabilityoftheairboundary
layer. Value is estimated by a
term incorporating the Richard-
son Number, computed from
temperature and wind velocity
data.
Since the air is sampled close to the
water surface, only the vertical flux is
needed to assess the emission rate from
the water surface.
The flux rate, nB, is in grams of species B
per second per square centimeter (g/s.
cm2) of water surface. Sp is the slope of a
line from a graphical plot (or linear regres-
sion, computer generated) of Al (g/cm3)
vs. 1 n y, where y is the sample height
above the water surface in cm. Figure 1 is
an example of such a concentration profile.
For flux of chemical B from the water
surface, the slope should be a negative
number of units g/cm3. Sv is the slope of
a line from a similar relation between vx
(cm/s) vs. 1 n y. This slope should be a
A
positive number and have units of crrv/s
The combination of the units of Sp and S
is the units of flux (1 n denotes a nature
logarithm).
Only if the air boundary layer is neutrs
should the concentration and velocity vei
sus 1 n-height profiles be linear over th
entire range of the six observation heights
The profiles may be non- linear under stab!
and unstable micrometeorological condi
tions and display some curvature. In thi
case, the slopes of tangent lines drawn t
the profiles in the boundary layer regioi
nearest to the water surface should b
used for Sp and Sv
The stability category of the air boundar
layer is obtained by determining the Richard
son Number. The Richardson Numbe
(i.e., Ri) is computed from temperature
and wind velocities in the boundary laye
by Equation 1 8. The equation is:
(y2-y1)
(vx2-vxi)2
(18
g is the gravitational acceleration constan
(i.e., 980.7 cm/s2). T12 and Tn are
average dry bulbairtemperatures at sample
heights y2 andy-\ above the water surface
respectively. vx2andvx1 are average wine
speed at sample heights y2 and y1f re-
spectively. The sample heights (i.e., y-|
and y2) used in Equation 1 8 for the R
determination should be in the same regior
of the boundary as the Sp and_ Sy va]ues
used. The arithmetic average, TI 2 and T-j 1 ,
is usually sufficient for estimating T^ Ri is
dimensionless. A negative value of R
results if the air is unstable. If Ri = O, the
air is neutral and if Ri > 0, the air is stable,
The Richardson Number provides a means
of assessing the low-wind speed limitatior
of Equation 24 for the flux determinatior
and the application of the stability correc-
tion factor (0^ Sc^ )'1. If conditions
are stable , Equation 24 should be usec
only for |Ri| < 1.0. If conditions are
unstable. Equation 24 should be usec
only for | Ri| < 4.0. The correction factor is
then estimated by:
(02 Scjklj)-i=(1±50Ri)±J4 (25]
where -50 and +Yz apply for unstable
conditions and +50 and —Vt apply foi
stable conditions. The correction factor is
unity for neutral conditions.
Equation 25 is an empirical correlatior
factor that corrects the neutral condition,
concentration profile flux estimate for watei
vapor (i.e., nA = -SpSvk2) to the actua
water vapor flux from ground sources
under non-neutral conditions. This watei
vapor flux calibration factor and associatec
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750 25 1000
550
24
23
22
21
650 20
19
18
I
I
u
.g
5
450
300
10
100
500
Height (cm)
Figure 1.
Concentration—Profile field data from mill 2 sample trip 1 concentration In/1) vs.
height (cm) wind velocity (cm/sec) vs. height (cm).
\ K\\ values places limitations on the use of
Equation 24 for flux estimates since it has
not been verified outside the given Ri
range The % power ratio of the molecular
diffusivities of the chemical of interest to
that of water vapor (i.e., (DBi/DA1)%) cor-
rects the equation for the chemical in
which the flux is desired. Both the correc-
tion factor and the diffusivity ratio are
dimensionless.
The three equations presented above
are the working formulas of the concentra-
tion profile method. Appendix D of the full
report contains a sample calculation of the
flux rate illustrating the use of the above
three equations.
Field Emission Measurements
A field test program was performed
from February 18, 1980 through June
20,1980. Four aerated secondary waste-
water treatment basins adjacent to four
southern pulp and paper mills were sam-
pled Mill No. 1 was an integrated, 1400 ton
per day, bleached Kraft mill, processing
pine and hardwood. Mill No. 2 was also a
bleached Kraft mill with a production of
2000 tons per day. Mill No. 3 was a 350
ton per day, unbleached pulp and paper
Kraft mill, and Mill No. 4 was a 460 ton per
day facility for Kraft pulping. Table 1
contains information on the respective
treatment basins and summarizes the
emission measurements for each mill.
With very few exceptions, the maximum
concentrations of methanol, acetone, and
total hydrocarbon in air were observed at
the lowest sample point which was usually
a few centimeters above the water surface
Typical values at this height were 1000
ng/l methanol, 50 ng/l acetone and 2000
ng/l total hydrocarbon. Concentration of
the species decreased linearly with the
natural logarithm of height as shown by
example in Figure 1. At two meters above
the water surface, typical concentrations
were 200 ng/l methanol, 10 ng/l acetone
and 300 ng/l total hydrocarbon. This
variation with height reflects the general
characteristics of the 38 profiles obtained
in the field.
Conclusions
1. Air samples in a two meter region
above the water surface contained quanti-
ties of methanol, acetone and total hydro-
carbon in levels much higher than the
background. Concentrations in the layer
decreased significantly with height above
the water.
2. A field sampling method and associ-
ated apparatus referred to as the concen-
tration profile technique was developed
and tested. The technique is based on
obtaining samples of air, wind velocity and
temperature in a two meter boundary layer
region above the water surface. The flux
rates of methanol, acetone and total hydro-
carbon originating in aerated stabilization
basins were measured during field tests of
the technique. Flux rates were roughly 16,
0.46 and 23 pounds per acre per day
respectively.
Table 1. Volatile Organic Chemical Emissions and Aerated Basin Data
Mill
Parameter
Wastewater flow (mgd)
Detention time (days)
Depth (feet)
Surface area (acres)
Surface aerators (no.)
Power per aerator (hp.)
Water temperature range CC)
Air temperature range (°C)
Wind speed range (mi/h)
Methanol emission (tons/day)
Methanol flux (Ib/acre- day)*
Acetone emission (Ib/day)
Acetone flux (Ib/acre- day)*
Total hydrocarbon^ (tons/day)
Total hydrocarbon^ (Ib/acre -day)*
1
50
12.5
7.5
265
25
75
25-29
24-27
2.8-8.0
2.7
20
200
.77
4.4
33
2
30
13.8
10
85
32
75
28-34
20-25
13-16
1.2
29
39
.46
1.1
25
3
4
4
7
7
10
20
34-36
24-28
7.4-7.5
.011
3.2
2.5
.36
.042
12
4
10
25
10
110
8
100
35-36
27-30
6.2-12
0.61
11
24
.22
1.3
23
+GC/HD
Flux rate ng/crrf • sec = (Ib/acre day) •
7.70.
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3. A mathematical model was presented
to predict the emission rate of volatile
chemicals from surface impoundments.
Field flux measurements for methanol
were used to verify aspects of the mathe-
matical model. Interpretation of the model
results suggests that the emission of
methanol increases with increases in con-
centration of the species in water, and with
wind and water temperature.
Recommendations
1. The concentration profile (CP) tech-
nique should be tested f urtherto determine
the degree of reproducibility of the mea-
surements. This can best be done by
exhaustive sampling of a single lagoon at
one surface location.
2. The CP technique should be further
tested in measuring emissions from all
types of surface impoundments including
wastewater treatment basins of other in-
dustries, sludge basins, solvent dump pits,
land areas where sludges and wastewater
are applied, and landfills In this regard it
will be necessary to develop and test
alternative trapping and chemical analysis
techniques.
3. Other flux measuring techniques
should be developed for those impound-
ments for which the CP method is not
applicable because of up-wind disturbances,
short fetch, low or no wind, and other
reasons (See Section 5 of the full report).
4. The CP technique should be used to
measure the emission rate of a low solubility,
liquid-phase controlled species such as
benzene or toluene. This should provide
the necessary field data for final verification
of the predictive model.
Louis J. Thibodeaux. David G. Parker, and Howell H. Heck are with the University
of Arkansas, Fayetteville, AR.
Paul de Percin is the EPA Project Officer (see below).
The complete report, entitled "Measurement of Volatile Chemical Emissions from
Wastewater Basins," (Order No. PB 83-135 632; Cost: $10.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, v'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
*US. GOVERNMENT PRINTING OFFICE' 1983-659-017/7147
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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