EPA 670/2-73-098
December 1973
Environmental Protection Technology Series
Odors Emitted From Raw
And Digested Sewage Sludge
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC 20460
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
Environmental Protection Agency have been grouped into five
series. These five broad categories were established to facili-
tate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface
in related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to
develop and demonstrate instrumentation, equipment and method-
ology to repair or prevent environmental degradation from point
and non-point sources of pollution. This work provides the new
or improved technology required for the control and treatment of
pollution sources to meet environmental quality standards.
-------
EPA-670/2-73-098
December 1973
ODORS EMITTED FROM
RAW AND DIGESTED SEWAGE SLUDGE
by
Bernard A. Rains
Mario J. DePrimo
I. L. Groseclose
Grant No. WPRD 23-01-68
Project No. 11010 EZQ
Program Element 1BB033
Project Officer
Dr. William Garner
Region VII
U.S. Environmental Protection Agency
Kansas City, Missouri 64108
816/374-5736
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D. C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.15
-------
EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication.
Approval does not signify that the contents
necessarily reflect the views and policies of the
Environmental Protection Agency, nor does mention
of trade names or commercial products constitute
endorsement or recommendation for use.
ii
-------
ABSTRACT
Odors emitted during' thickening of raw and secondary sludge
have been responsible for adverse criticism at many sewage
treatment plants. This study was undertaken to identify
typical odor causing substances and evaluate selected con-
ventional methods for controlling or eliminating these
substances. A styrofoam dome covering a sludge thickener
was utilized to control atmospheric conditions and concen-
trate odors.
Field collected vapor samples were analyzed using gas
chromatography techniques. Analyses using both polar and
nonpolar column material indicated that the major odor
causing compounds were mercaptans and amines. Other
compounds which were minor contributors to odor were
aldehydes, alcohols, and organic acids.
Odor control methods selected for study included air
dilution, activated carbon adsorption, and chlorine
oxidation. Air dilution using cyclic operation of an
exhaust fan was found to be an effective means of odor
control when outside atmospheric conditions were conducive
to odor dissipation. Passing vapors through activated
carbon filters was not completely effective in odor control
since a detectible residual odor remained. A 1.5 mg/1
solution of chlorine was effective in removing all odors
from vapor samples bubbled through the solution.
This report was submitted in fulfillment of Project Number 11010 EZQ,
Grant Number WPRD 23-01-68, by the Metropolitan St. Louis Sewer
District under the partial sponsorship of the Environmental Protection
Agency.
i ii
-------
CONTENTS
Conclusions
Summary and Recommendation 3
Synopsis 3
Future Work 4
Introduction 5
General Statement 5
Objective and Scope of Study 5
Odor Causing Substances 6
Description of Field Equipment and Procedures 9
Sludge Thickener and Dome 9
Gas Sampling Procedure 9
Odor Threshold Sampling and Evaluation 16
Odor Treatment Techniques 17
Inorganic Gas Determinations 20
Description of Laboratory Equipment and Procedures 24
Gas Chromatograph Column Selection 24
Selected Column Evaluation Using Standards 24
Chromatogram Comparison Procedure 29
Column Temperature Effects 29
Infrared Analyses 35
Results of Odor Identification Study 37
Relative Retention Time Determinations 37
Odor-Retention Time Comparisons 46
Compound Concentration Evaluation 50
Threshold Evaluation and Odor Treatment Results 54
General Statement 54
Selection of Odor Panel 54
Treatment by Air Dilution 54
Carbon Adsorption of Odors 57
Chlorine Treatment of Odors 59
Acknowledgements 63
References 65
Appendix 67
-------
LIST OF FIGURES
No. Page
1. PLACEMENT OF FABRICATED DOME ON THE THICKENER 10
WALL.
2. THICKENER WITH DOME INSTALLATION COMPLETE. 11
3. SCHEMATIC FLOW DIAGRAM OF COLDWATER CREEK 12
TREATMENT PLANT.
4. SCHEMATIC FLOW DIAGRAM OF THE GAS SAMPLING 14
EQUIPMENT.
5. STAINLESS STEEL CONDENSATION TRAP USED IN 15
INSULATED DEWAR FLASK.
6. GAS SAMPLING TRAIN. 15
7. THRESHOLD ODOR TESTING APPARATUS. 18
8. ADSORPTION COLUMN AND SAMPLING APPARATUS FOR 18
ACTIVATED CARBON ODOR TREATMENT EVALUATION.
9. SCHEMATIC FLOW DIAGRAM FOR ACTIVATED CARBON 19
TREATMENT EVALUATION.
10. CROSS SECTION OF LAB APPARATUS USED FOR 21
CHLORINE TREATMENT EVALUATION.
11. SCHEMATIC FLOW DIAGRAM OF THE AMMONIA ABSORPTION 23
EQUIPMENT.
12. CHROMATOGRAPHIC SEPARATIONS OF A DOME-GAS 30
GRAB AND CONDENSATE SAMPLE FROM THE SAME DAY.
13. CHROMATOGRAPHIC SEPARATIONS OF DOME-GAS 32
CONDENSATE SAMPLES ON CARBOWAX 20M AT
VARIOUS TEMPERATURES.
14. CHROMATOGRAPHIC SEPARATIONS OF DOME-GAS CON- 33
DENSATE SAMPLES ON SE-30 AT VARIOUS TEMPERA-
TURES.
15. CHROMATOGRAPHIC SEPARATIONS OF DOME-GAS CON- 36
DENSATE SAMPLES ON PORAPAK Q AT VARIOUS TEM-
PERATURES.
vi
-------
LIST OF FIGURES
No. Pag
16. RELATIVE RETENTION TIME OF DOME COMPOUNDS ON 41
CARBOWAX 20M AT 55°C AND 5 X 10~1Z AMP.
17. RELATIVE RETENTION TIME OF DOME COMPOUNDS ON SE- 41
30 AT 90°C and 5 X 10"'^ AMP.
18. RELATIVE RETENTION TIME OF VARIOUS STANDARDS ON 44
CARBOWAX 20M AT 55°C.
19. RELATIVE RETENTION TIME OF VARIOUS STANDARDS ON 45
SE-30 AT 90°C.
VI 1
-------
LIST OF TABLES
No. Page
1. Retention Time of Selected Standards Using 26
Various Columns.
2. Peak Elutions (Minutes) Observed for Bag 28
And Condensate Samples Using Designated Columns
And Temperatures.
3. Relative Retention Times of Dome Compounds on 38
Carbowax 20M at 55°C.
4. Relative Retention Times of Dome Compounds on 39&40
SE-30 at 90°C.
5. Comparison of Relative Retention Times of 42
Standards and Condensate Peaks.
6. Retention Time of Organic Acids and Dome 48
Compounds on Carbowax 20M.
7. Odor Thresholds of Several Organic 49
Compounds. (17,18)
8. Comparison of Odor Types with Operational 51
Measurements.
9. Maximum and Minimum Concentrations Recorded 52
for Identified Odor Compounds.
10. Sensitivity of Personnel to Triangle Test. 55
11. Threshold Levels and Air Dilution Requirements 58
for Dome Atmosphere.
12. Carbon Adsorption of Dome Odors. 60
13. Typical Chlorine Treatment Results For 62
Dome Odor Removal.
viii
-------
CONCLUSIONS
1} The compounds identified in the vapors emitted from
the sludge thickener were: ethyl, propyl, tert-butyl,
tert-amyl, amyl mercaptans; diallylsulfide, isopropanol,
propanol, butanol; acetaldehyde, propionaldehyde;
ethylamine, butylamine, hexylamine, diisopropylamine,
dibutylamine, diisobutylamine, triethylamine; acetic,
propionic, and isobutyric acids; ammonia; hydrogen
sulfide; and methane.
2) The discernible odors, which were a function of the
type and amount of waste present in the thickener, could
be typified as being either rancid, fecal, cabbage-like,
skunk-like, or sour.
3) A correlation between the blanket depth, peaks eluted
on the gas chromatograph, and the various odor types
was found to exist.
4) Propyl mercaptan (cabbage-like odor) and ethylamine
(rancid) were the only compounds identified in the dome
that were present in concentrations above their thres-
hold levels.
5) The inorganic gases, hydrogen sulfide and ammonia, and
the organic gas, methane, were present in the dome
atmosphere but could not be quantitated.
6) Threshold odor levels varied depending upon quantity
of sludge being thickened.
7) Odor control by air dilution of the dome atmosphere
can be accomplished by operation of an exhaust system
during optimum atmospheric conditions.
8) Carbon adsorption removes offensive type odors from
vapors emitted during sludge thickening but some
discernible odors are not affected.
9) Oxidation of sludge thickener odors by scrubbing
with a water solution containing 1.5 mg/1 of
residual chlorine is effective in reducing the odors
below detectible limits.
-------
SUMMARY AND RECOMMENDATIONS
SYNOPSIS
Vaporous compounds emitted from a sludge thickener were
identified using gas chromatography as mercaptans, alcohols,
amines, organic acids, and aldehydes. Samples were col-
lected in the field by pumping quantities of the atmosphere
within a styrofoam dome covering a sludge thickener through
a sampling tube to a condensate trap supported in a Dry Ice-
alcohol bath. The relative retention times of the sample
components and laboratory standards, as determined by gas
chromatography from eluted peaks on a Carbowax 20M and an
SE-30 column, were compared. Flame-ionization was used as
the detector system.
The quantity of odorous compounds emitted by the sludge
thickening process was found to be a function of the quan-
tity of waste sludge present. A correlation between the
blanket depth, peaks eluted on the gas chromatograph, and
the various odor types was found to exist. The discernible
odors could be typified as being either rancid, fecal,
cabbage-like, skunk-like, or sour. The cabbage-like odor
was noted on days when a large concentration of propyl mer-
captan was present. A pungent, rancid odor was detected
when a large amount of ethylamine was present. The other
noticeable odors could not be correlated with any one iden-
tified compound. Methane, hydrogen sulfide, and ammonia
were qualitatively identified by gas chromatography and/or
wet test methods. Their concentrations, however, were below
the detectible limits of Orstat or Tutweiler gas analyzers.
The dome vapors were not concentrated sufficiently to yield
absorption information except for water and carbon dioxide
bands on an infrared spectrophotometer using a 10-meter cell
An odor panel was selected to determine the threshold level
which could be utilized as a base-line value for evaluating
treatment of the odors within the dome atmosphere. It was
found that the threshold levels varied from day to day
complicating efficiency evaluations using air dissipation
as an odor control technique . Cyclic operation of the
exhaust system was considered to be an effective odor con-
trol method during optimum atmospheric conditions.
Activated carbon adsorbed most of the detectible odors from
the dome, however, some of the odor causing organic com-
pounds were not removed by the carbon. Samples of the gas
taken after passage through a carbon filter had a slight,
detectible odor resembling lard.
-------
The treatment method that was found to be the most efficient
as far as complete removal of the odor was chlorine
oxidation. It was found that bubbling the dome vapors
through a chlorinated water solution containing 1.5 mg/1
of residual chlorine could effectively remove all obnoxious
odors present.
FUTURE WORK
Because of the numerous compounds that were eluted during
the study by the gas chromatograph and not identified, fur-
ther investigation is needed. Selected absorbents could be
used to collect a particular class of organic compound con-
sidered, based on previous results, to be present. Such
collected compounds could be released under controlled
laboratory conditions and identified by using a gas chroma-
tograph equipped with a column particularly suited for
separation of that class of compound. Temperature program-
ming and other detector systems could be utilized effectively
Research on the threshold levels of the compounds should be
made to determine their effect individually and together on
olfactory perception.
Treatment methods using chlorinated water or effluent as a
scrubber solution should be evaluated on a large scale.
Laboratory evaluation of the chlorine oxidation products
would also be necessary.
Further studies concerning the effects of climatic changes
and type of waste being treated upon odor formation and its
control are advisable.
-------
INTRODUCTION
General Statement
Numerous complaints from the residential community
surrounding the Metropolitan St. Louis Sewer District's
Coldwater Creek Sewage Treatment Plant were part of
the initiating force that led to a study of odors
emitted by the sludge thickening process at the plant.
This process was considered the major source of objec-
tionable odors due to its retention of actively decom-
posing organic sludge from primary and secondary treat-
ment units.
A dome constructed of styrofoam and an exhaust system
were installed on the thickener to control the emission
of odorous gases from the surface of the decomposing
sludge as well as concentrate vapors for purposes of
identification. Initial study indicated that it was
not feasible to catalog the odor emissions from the thick-
ener before dome installation, because there was no
means of segregating effects of odors from industrial
and agricultural sources in the surrounding region.
Covering the thickener prior to research presented a
more controlled environment for odor studies without
the influence of climatic changes, wind current, and
interferences from other adjacent odor sources within
the plant such as grit and primary basins. Elimination
of the odors was the ultimate goal of the study and a
controlled atmosphere above the thickener provided a
convenient means of confining the odors for any
treatment considered necessary.
This report presents in total all data collected,
analyses performed, and conclusions formulated as a
result of the study.
Objective and Scope of Study
The primary objective of the study was to utilize
instrumentation and gas concentration techniques to
identify and evaluate quantitatively the odors emitted
from the sludge thickener, Guided by the identification
and concentration results, selected treatment methods
were conducted to determine their effectiveness in odor
reduction and control.
-------
The project proceeded in five phases which were as follows:
1) Construction of dome and installation of
exhaust system.
2) Startup of thickener unit and stabilization
of operation.
3) Sampling and identification of odor components.
4) Determination of odor thresholds.
5) Evaluation of odor reduction by air dilution,
activated carbon adsorption and chlorine
oxidation.
Observations relative to thickener operation and dome
atmospheric conditions were recorded for daily and bi-
weekly grab and condensate samples collected through a
period covering spring -and late summer months. Data
were obtained by gas chromatography utilizing the several
columns which gave best recovery and separation of peaks
and by infrared spectrophotometry. Wet chemistry methods
were used to determine the non-organic dome atmosphere
constituents. The effect of sampling time, moisture re-
moval, cold trap configuration, and condensation time
were evaluated in order to optimize and standardize
sampling conditions.
Odor Causing Substances
Odors emitted from decomposing organic wastes can be
highly disagreeable. The odor causing compounds are
bacterial breakdown products of fats and nitrogen
and/or sulfur-containing organics such as proteins (1).
Odors are not caused entirely by inorganic gases such
as NH3 and H«S, but rather a wide assortment of vola-
tile organic compounds.(2) (3) In his studies of odors
emitted from various locations in a sewage treatment
plant, Glaser (1) was able to absorb specific volatile
gases and correlate their formulation with sewage influent
characteristics and time of day. He measured sulfides
by first passing the gas through a cadmium sulfate-
sodium hydroxide absorption solution, and then adding this
solution to a mixture of ferric chloride and p-aminodi-
methylaniline to form methylene blue. In a similar
-------
manner he determined the presence of mercaptans by first
absorbing the gas in a solution of mercuric nitrate and
nitric acid and' then developing color in the solution
with N, N-dimethyl-p-phenylenediamine and Reissner
solution. The presence of aldehydes was determined by
forming an aldehyde complex with sodium bisulfite and
then later titrating the complex with iodine. Of the
compounds he found the most odorous and obnoxious were
the mercaptans and sulfides.
Miner and Hazen (^indicated that the odor in a swine
building could not be attributable only to ammonia and
further work revealed the presence of three amines in
addition to the ammonia. These compounds were identified
using gas chromatography as methyl amine, ethylamine,
and triethylamine.
Burnett ^)conc]uded from his work on poultry wastes that
the odors emitted therefrom contained acetic, propionic,
isobutyric, n-butyric, isovaleric, and n-valeric acids.
These compounds all have sour type odors with the most
disagreeable being isobutyric, n-butyric, isovaleric, and
n-valeric acids. The heterocyclic compounds, indole and
skatole, were also found to be present in the liquid
portion of the waste. Both these compounds have extremely
obnoxious odors even in dilute concentrations and they
both tend to persist for long periods on clothing and
other fabrics. Other odorous compounds detected by
gas chromatography were methyl mercaptan, ethyl mercaptan,
methyl sulfide, diacetyl , n-propyl mercaptan, acetoin,
n-butyl mercaptan, and methyl disulfide. He did not
study the amines, but he did state that when his extracts
were made alkaline the strong characteristic fish type
odor of amines was emitted.
Such research leads to speculation concerning the com-
ponents causing odors at a domestic wastewater treatment
plant. Complex mixtures of volatile organics could
certainly create some of the odors noticeable at such
plants.
Yet to be studied are the synergistic effects of malodors.
We are aware that a variety of essences are carefully
compounded to produce the pleasant odor of perfumes.
It is highly probable that individual compounds that have
unpleasant odors also enhance and modify the pure odors of
each other. Such interaction of odorous materials makes
-------
it quite difficult to identify specific odor causing com-
pounds and the causative source. The development of
methods to control odor emissions may be more effective
once such relationships are understood.
8
-------
DESCRIPTION OF FIELD EQUIPMENT AND PROCEDURES
Sludge Thickener and Dome
A dome was constructed from styrofoam by the Dow Chemical
Company and positioned as shown in Figures 1 and 2 on the
65-ft. diameter sludge thickener at the Coldwater Creek
Plant. The air space which is bounded by the dome's
inner surface, the liquid level and the effluent channel
has a volume of 31,370 cu. ft. The air exhaust and duct
system installed by a local contractor has a capacity
of 16,600 cu. ft./min., which theoretically allows a
complete air exchange of the dome every two minutes.
Different operating depths of sludge in the thickener
were evaluated to determine effects on the subsequent
digestion of the sludge. Residence time in the thickener
is thus directly related to sludge blanket depth. The
liquid surface to sludge depth chosen as the most effec-
tive operating level was six (6) feet. That is, the dis-
tance measured from the water surface to the sludge inter-
face was maintained at about six feet. The depth of
sludge then at the center of the tank was about ten
feet due to the conical bottom. One sludge pump operated
continuously and another pump was put in service between
the noon to midnight hours. This second pump would be
turned off when the sludge level in the thickener dropped
below nine (9) feet. For further sludge thickener
operational details refer to Appendix A of this report.
Dilution water from the final clarifier is piped into the
dome each day from 8:00 a.m. until 4:00 p.m. as indicated
in Figure 3 which presents the operational flow pattern
for the Coldwater Creek Plant. This maintenance procedure
to freshen the contents of the thickener is maintained
unless primary sludge has to be bypassed directly into
the digesters during periods of high solids loadings.
Gas Sampling Procedure
Vapor samples were collected from the dome atmosphere by
filling a Hamilton 1-liter gas-tight syringe at the center
of the dome and injecting it through a septum into a 1-1/3
liter Saran bag. Water and air temperatures were recorded
at the same location as well as the interior relative
humidi ty.
-------
FIGURE 1.
Placement of fabricated dome on the thickener wall,
-------
FIGURE 2.
Thickener with dome installation complete. Note exhaust motor and
effluent duct to left and sampling compartment to right of entrance.
-------
(Sludge Lagoons)
1 ^
CMorim
'
Plant
Effluent
z.
—Digested
Sludge
Secondary
By Pass-
Digesters
(6)
Prim (4)
Sec. (2)
»kmt Influent
FIGURE 3. Schematic flow diagram of Coldwater Creek
Treatment Plant.
12
-------
Concentration of vapors was accomplished by using a poly-
ethylene tube that extended from the center of the dome to
the sampling train shown in Figure 4. The train consisted
of two insulated glass wells equipped with a thermometer
to measure the gas temperature before and after passage
through the condensation trap, a gas flow meter to record
the volume of gas that passed through the sampling line,
and a carbonvane pump with a 2 cu. ft./min. pumping rate.
Plastic quick disconnects were used to join the poly-
ethylene tube sections, and Swagelok fittings were used
to join the metal and polyethylene tubes.
In order to prevent damage to the gas meter from the cold
gas, a 20-ft. coil of aluminum tubing was installed in the
line to bring the influent gas back to ambient temperature
prior to entering the flow meter. The condensation trap
shown in Figure 5 is a 5-ft. x 1/4-in. o.d. coiled stain-
less steel tube that was fitted with Whitney valves. The
coiled configuration of the trap gave the vapors an extended
contact time in the cold bath.
Initially a 1-inch glass fiber filter was placed inside
of the dome at the head of the sampling tube but its
use was discontinued for two reasons: 1) the dome was
devoid of large quantities of atmospheric particulate
matter and it was therefore not necessary to filter the
vapors and 2) the filter tended to adsorb and restrict
the free -flow of the vapors.
The sampling train with condensation trap as shown in
Figure 6 was purged for 5 min. to dislodge the stale gases
and condition the apparatus for the next sample. The
trap valves were closed and the trap placed in the dry
ice-alcohol bath for several moments to cool the stainless
steel coils prior to the sampling run. The temperature
of the ice bath was maintained at minus 78°C during each
run. Sampling was terminated when the flow through the
coil was reduced as noted by a temperature rise of the
exit thermometer. This occurred after 15 to 20 minutes
into the run. The trap was then disconnected from the
vacuum line, sealed, and the pump shut off. During
the 15-20 minute sampling time normally 20-40 cu. ft.
of vapor passed through the sampling train. The
quantity of sample collected was highly dependent upon
the relative humidity and concentration of odorants
inside the dome. While the sample was condensing, the
temperature and relative humidity in the interior of the
13
-------
Gas Influent
Insulated
Temperature
Well
r—XI
Insulated
Temperature
Well
Dry Ice Alcohol
Bath
Carbon Vane
Vacuum Pump
Coiled
Aluminum
Tubing
»
Gas Effluent
Gas Flow Meter
FIGURE 4. Schematic flow diagram of the gas sampling
equipment.
14
-------
FIGURE 5-
Stainless steel condensation trap used in
insulated Dewar flask.
FIGURE 6.
Gas sampling train. Gas enters tubing at
left and flows through insulated thermometer
wells and condensation trap. Flow meter and
vacuum pump are on right.
15
-------
dome were recorded as well as the temperature of the
entrance and exit thermometer wells in the sampling train.
The sample was transported to the laboratory and warmed
slightly using hot water for 15 minutes to facilitate
vaporization of the gases. The sample coil was then cooled
to room temperature. The condenser was connected to a
mercury manometer for determining pressure within the coil.
Samples of vapor were removed by putting a rubber septum on
the gas condenser, inserting a Hamilton 5-ml gas-tight
syringe, and opening the valve. The syringe was flushed
several times prior to final withdrawal from the septum.
The trap was cleaned prior to another run by first blowing
air through the coils and then washing with acetone. The
acetone was evaporated from inside the coils by placing
them in hot water and purging with air. The coils were then
cooled and pressurized to check for leaks by attaching a
laboratory air line and sealing while under pressure. A
soap solution was applied to detect the presence of any leaks
around connections. If no leak was found, the system was
left pressurized until the collection of the next sample.
During the cleaning process there was from 3.5 to 4.0 ml
of condensate water removed from the trap.
A comparison of condensate peaks eluted on a gas chroma-
tograph was made to determine the trapping efficiency
of: l) a vapor sample with water removed prior to entry
into the coiled trap and 2) a vapor sample without water
removed. Anhydrous potassium carbonate with a few pieces
of indicating Drierite was chosen as the drying agent
because of its nonreactivity with most compounds. (5)
material was placed in a drying tube ahead (upstream) of
the cold trap. The samples, those that were desiccated as
well as those that were not dryed, had similar chromatograms.
The collection time, however, of the desiccated samples was
inconsistent from run to run while the undesiccated samples
had a more consistent collection time (15-20 min.) prior to
a rise in effluent gas temperature.
Odor Threshold Sampling and Evaluation
Odor threshold levels.were determined by following the
procedure of ASTM-19.l°) Saran bags were used to collect
the vapor samples as shown in Figure 7. Fresh samples
were collected daily as indicated previously at the center
of the dome by using a Hamilton 1-liter gas-tight syringe and
injecting into a Saran bag. The temperature and relative
16
-------
humidity inside the dome were recorded. All syringes
(gas transfer and odor panel) were cleaned in odor free
soap, rinsed thoroughly with distilled water, and allowed
to dry. Syringes were considered dirty when panel members
detected a residual greasy odor inside the syringe even
after successive purging with odor free air.
Successive dilutions of the gas sample being evaluated
were given to the individual panel members until the
threshold odor level was reached. For example, if a
panelist required a 0.001 dilution, a master syringe was
used to make a 0.01 dilution of the gas and then 10 ml
of this was transferred to the panelist's syringe which
was then filled with odor free air to the required volume
for final dilution. Odor free dilution air was obtained
by passing compressed air through a carbon filter equipped
with a teflon tube into a collection bottle where syringes
could be inserted.
Odor Treatment Techniques
Treatment of odors by air dispersion or simple dilution
was evaluated by collecting samples of the dome atmosphere
and preparing several dilutions in the laboratory using
odor free air. The dilutions were prepared by injecting
known volumes of dome atmosphere and odor free air into
Saran bags using the techniques described earlier for
threshold odor evaluations. These diluted samples were
then compared by the odor panel to determine odor
intensity.
A system developed to filter out odor constituents using
activated carbon as shown in Figure 8. The apparatus
consisted of a glass tube that had a quick disconnect
on one end connected to the main line of the sampling
train. The other end was attached to a 250 ml glass
sampling bulb that contained a rubber septum where a
syringe could be inserted and treated gas samples removed
at selected time intervals. The sampling bulb was hooked
to the flow meter and vacuum pump of the main sampling
line as shown schematically in Figure 9. A 10-gram
sample of 4 to 10 mesh activated carbon was packed
into the glass tube and glass wool was used to hold the
charcoal firmly inside the tube. ('*
Initially, a sample of untreated gas was collected from
inside the dome for an odor threshold level determination
using the method described previously for odor sampling.
17
-------
FIGURE 7. Threshold odor testing apparatus with Saran sample
bag above and transfer syringes with special
adaptor for odor dilution below.
FIGURE 8. Adsorption column and sampling apparatus for
activated carbon odor treatment evaluation.
18
-------
Gas Influent
Sample Tap
Carbon Filter
Glass Bulb
Gas Effluent
Carbon Vane
Vacuum Pump
Gas Flow
Meter
FIGURE 9.
Schematic flow diagram for activated carbon
treatment evaluation.
19
-------
The pump was then started and gas allowed to flow through
the activated carbon and sampling bulb. At 5 minute in-
tervals (about 10 cu. ft. gas volume) the pump was stopped
and a sample of treated gas was collected by inserting
the 1-liter syringe into the septum of the sampling bulb
and withdrawing a 1-liter sample. The sample was then
transferred to a 1-1/3. liter Saran bag. The total volume
of gas that had passed through the filter was also recorded
and the pumping was continued. A 100ml sample was also
withdrawn from the sampling bulb and tested immediately
for presence of odor in the treated gas. If odor was
noted, the sampling run was terminated since it was con-
sidered the carbon had become saturated.
The bag samples for the sampling run were brought back
to the laboratory and odor panel members were given suc-
cessive dilutions from each bag collected following'the
procedure for odor threshold sampling. At the first
sign of an odor breakthrough a threshold odor was
determined on that sample. This threshold odor was then
compared with the odor threshold from the sample taken
at the start of the run from inside the dome.
To determine the effectiveness of chlorine on oxidation
of odor components, samples of dome gas were bubbled through
distilled water containing a known concentration of
chlorine. Figure 10 shows the apparatus used during the
chlorine evaluation. Two cylindrical containers were
filled with a fixed volume of chlorinated water. A
septum in the bottom of the inverted cylinder was used
as the port to withdraw a treated sample. The thres-
hold of this treated gas was determined and compared
with the threshold level of the untreated gas using
odor free air as the diluting component. Both treated
and untreated samples were originally collected at the
center of the dome.
Inorganic Gas Determinations
Since inorganic gases such as HgS, 03, C0£» N£» NH3
and CO cannot be detected by flame-ionization gas chromato-
graphy, it was necessary to use Orstat and Tutweiler gas
analyzers and other techniques to attempt to identify
and quantitate these gases. The Orstat analyzer also
detects the organic illuminants, methane and other com-
bustible hydrocarbons and is sensitive down to the
20
-------
Collection
container
guides
r
Septum for treated gas sample
, .
f
*
t
1
ft
Chlorinated
water
L_ ^1
°0
00
00°
o
°0
o o
0
o
o o
00
0°
00
0°
°0
o_
o
°o
o
o
o
o
0
o
o
o
o
o
o r
O a>
4
3
w
V
\.
ireaiea air sampi
Constant 6 -in.
reaction distance
i — n IL
4 h
^-m-"
V
Septum for dome
gas introduction
FIGURE 10. Cross section of lab apparatus used for
chlorine treatment evaluation.
21
-------
0.8% level for C02, 02, N2, CO and methane. Samples were
collected in the same manner as other grab samples and
brought back to the laboratory for inorganic gas evalua-
tion. Each sample was injected into the two gas analyzers
by means of water displacement until a specific volume
of gas had entered the collection chamber. Each specific
analysis was conducted according to standard procedures.
Initially, qualitative tests for the presence of ^S and
NH3 were made according to the method of Day, Hansen and
Anderson. * ' An open vial of hydrochloric acid inside
the dome noticeably fumed white vapors which indicated
the presence of NH3 and/or amines. The darkening of
moist lead acetate paper placed inside the dome showed
the presence of I^S gas, which was also indicated by the
metal sulfide reaction of copper wire used to fasten the
sampling line inside of the dome.
Ammonia»was determined by the apparatus shown in Figure
1 1 . ^' An aerator pump placed inside the dome forced
vapor first through a 2% boric acid absorption solution
and then through a flow meter. After 24 to 48 hours of
operation, the pump was disconnected from the absorption
bottle and the volume of gas that passed through the solution
during that time interval was recorded. The bottle was then
sealed and returned to the laboratory. Nessler's reagent
was used to determine the concentration of ammonia pre-
sent in the solution. '*' Dome vapors were allowed to
percolate through the absorption solution for a minimum
of one day to a maximum of three days. Even after the
three day time interval, there was no development of
color in the solution upon the addition of the Nessler's
reagent. There was, however, a clouding of the solution
which indicated that aldehydes and/or amines had been
absorbed. Because of the lack of sensitivity of the methods
utilized for quantitative analysis of inorganic odor causing
'gases present within the dome, more effort in this area
was considered unjustified. The inorganic odorous gases
such as H2S and NHg obviously were not major contributors
to odors emitted by the thickening sludge.
22
-------
Gas Influent
Gas flow
meter
CX-
Aerator
pump
Gas
effluent
Boric acid
absorption trap
FIGURE II. Schematic flow diagram of the ammonia absorption
equipment.
23
-------
DESCRIPTION OF LABORATORY EQUIPMENT AND PROCEDURES
Gas Chromatograph Column Selection
A Beckman GC-4 gas chromatograph, equipped with a dual-flame
ionization detector, was the major instrument used in the
laboratory for analysis of dome gas samples.
A 10-ft. x 0.125-in. o.d. stainless steel column with
10% SE-30 on 100 to 120 mesh Chromosorb 6 was the column
chosen to identify indole, skatole, amines, and sulfur
compounds that might be present in the dome atmosphere.
(2,4,10,11) For the analysis of organic acids a 10-ft.
x 0.125-in. o.d, stainless steel column packed with
18% Carbowax 2QM +2% H3P04 on 60 to 80 mesh C-22 Firebrick
was selected.(2,12) jne alcohols and carbonyls if present
could be detected by using a 5-ft. x 0.125-in. o.d.,
stainless steel, 100 to 120 mesh, Porapak Q, P, or QS
column although the other columns could also be used in
identification of these and sulfur compounds.(2,13)
All columns were purchased with the above specifications
from the Beckman Company.
The Carbowax column was conditioned according to the
procedure of Andrews, Thomas, and Pearson(12) at a
helium flow rate of 25 ml/min and a column temperature of
185°C for 4 hours. A conditioning solution of 0.05 M
propionic and acetic acids was prepared of which
10-jul samples were injected at ten minute intervals for
2 hours into the column using a Hamilton syringe. The
SE-30 column was conditioned at 250°C overnight without
any helium flow. Further conditioning was necessary
at a column temperature of 230°C and a helium flow rate
of 40 ml/min for 2 hours.(14) The individual Porapak
columns were conditioned at a column temperature of 230°C
and a helium flow rate of 50 ml/min for 4 hours.(15)
Selected Column Evaluation Using Standards
To determine whether compounds that might be present in
the dome environment would separate and elute on selected
columns, a series of liquid and vaporous standards were
prepared for injection into the columns. A column com-
parison of such standards would also enable determination
of the optimum temperatures at which the columns would
give maximum separation without excessive elution time.
The following standard compounds were injected at various
temperatures on the selected columns: acetone, propionic
24
-------
and butyric acids, diethylsulfide, butyl- and ethyl-amines,
isopropanol, and diacetyl.
The sample size used for the liquids was between 0.1 and l->il
The procedure followed was to increase the injected sample
size until peak elution was noted. The lowest sample size
was then injected to ascertain whether this quantity gave
a detectable response. The different size sample injections
were selected to condition the column so no adsorption of
these types of compounds whether from standards or dome
samples would take place on the column. All standard
injections were made with a Hamilton 1-jul sampling syringe.
The compounds used for the column evaluation and for the
comparison of standard retention times with dome components
were purchased as kits from the Polyscience Company. The
SE-30 column eluted symmetrical peaks for amines, ketones,
alcohols, and sulfur compounds without any tailing. However,
organic acids tailed on this column. There was tailing of
the organic acids on the Porapak P and QS columns at three
column oven temperatures. Other materials were eluted in a
short time. Both the Carbowax 20M and Porapak Q columns
eluted the standard compounds at the selected oven tempera-
tures except for amines which were held up on the Carbowax
20M column. The elution time of the standards on the vari-
ous columns at selected temperatures are shown in Table 1.
After column response and retention time of the individual
standards were determined, a mixture of isopropanol,
acetone, diacetyl, butylamine, and propionic acid was
prepared by injecting a l-^il sample of each of these
standards into a 125-ml glass container fitted with a rubber
septum. The bottle was placed in water at 65°C to hasten
the vaporization of the volatile materials. A portion
(1-ml) of the vaporized mixture was then withdrawn and .
injected into the column with a Hamilton 5-ml gas-tight
syringe. The mixture for the Carbowax 20M column did not
contain the amine nor the diketone but contained instead
butyric acid. The mixture for the SE-30 column did not
contain the propionic acid; The purpose of injecting the
standard mixture was to determine whether the columns would
separate these compounds in mixed vapor form.
The SE-30 column separated the mixture at a temperature
of 97°C. The mixture of acetone, isopropanol, and pro-
pionic and butyric acids was separated on the Carbowax
25
-------
TABLE 1
RETENTION TIME OF SELECTED STANDARDS USING VARIOUS COLUMNS
Column
Carbowax
20M
ii
ii
Porapak
QS
H
M
Porapak
P
ii
n
Porapak
Q
n
SE-30
Temp
(•c)
124
90
70
166
150
143
170
166
152
170
148
97
Acetone
(min)
.4
—
1.2
2.8
3.6
_ . _
2.0
2.3
3.1
4.2
6.7
1.9
Propionic
Acid
(min)
1.2
5.6
16.9
9.0
14.4
14.8
7.2
9.6
17.5
40.5
T
Butyric
Acid
(min)
1.5
8.8
30.1
T
...
T
- _ -
41,0
_ _ _
T
Diethyl -
sulfide
(min)
...
...
1.57
...
16.0
...
_ - _
8.7
8.6
_ —
4.2
Isopro-
panol
(mi n)
...
—
2.4
2.9
4.6
4,7
2.1
2.1
2.7
4.2
7.7
4.2
Butyl-
ami ne
(min)
NR
—
—
9.8
15.1
_ _ _
6.2
9,8
8.8
14.2
1.8
Diacetyl
(min)
__ _
—
—
...
8.8
9.9
- _ _
4.4
6.6
8.9
16.1
3.5
Ethyl -
amine
(min)
NR
...
— _
1 .8
1 .6
2.4
- - -
ro
Notes: NR
T
no response from the compound
tailing of the component.
-------
20M column at an oven temperature of 70°C. At temperatures
of 166°C and 150°C the Porapak P column would not separate
the mixture into separate components and it only eluted two
peaks in both cases. The mixture on the Porapak QS column
at a temperature of 150°C tailed considerably and could not
be separated. The Porapak Q column did not resolve the
acetone, isopropanol, butylamine, and diacetyl at 170°C,
but the mixture was totally resolved at a column temperature
of 148°C. Tailing was the major cause of poor separation
on the columns that would not resolve the mixture. Helium
flows were maintained at 30 ml/min.
While the column evaluation with selected standards was
being conducted, periodic injections of dome grab and
condensate samples were made. Oven temperatures used were
those that gave the best separation of the standards. The
average peak retention times recorded for 5 ml vapor sample
injections are presented in Table 2. Observations made from
these results were: 1) that the Carbowax and SE-30 columns
separated the many peaks of the condensate sample at a much
lower oven temperature than the Porapak columns and 2) that
the bag (grab) sample did not have a sufficient concentra-
tion of organic vapors for detection upon elution from the
Carbowax and SE-30 columns. The Porapak columns did not
resolve the condensate sample at either a high or low oven
temperature. This suggests that the components were either
being held on the columns or that the compounds were all
eluting at the same time from the column. Further experi-
mentation with these columns at different oven temperatures
did not remedy the situation. All aforementioned preliminary
work was conducted at a helium flow rate of 30 ml/min.
The decision was made to utilize the Carbowax 20M and SE-30
columns primarily with Porapak Q as a backup for detailed
chromatographic identification since good standard separa-
tion was achieved by this column. The volume of dome vapor
sample selected for injection into the gas chromatograph
throughout the study was 5 ml. The temperatures of the
SE-30 and Carbowax 20M columns chosen were 90°C and 55°C,
respectively. Other column oven temperatures were necessary,
however, for Carbowax 20M (75° and 90°C) and SE-30 (110°
and 130°C) for the acid and the indole analyses.
27
-------
TABLE 2
PEAK ELUTIONS (MINUTES) OBSERVED FOR BAG ANO CQNDENSATE SAMPLES USING DESIGNATED COLUMNS AND TEMPERATURES.
SE-30
«97°C
(Bag)
.8
1 .3
1 .9
2.6
8.4
SE-30
»97"C
(Condensate)
.8
.1
.2
.2
.5
.6
2.6
8.4
3.6
4.2
6.3
7.8
10.0
10.9
11.5
13.3
14.2
16.0
16.9
17.8
19.1
20.1
21.2
22.4
23.5
24.6
26.7
29.3
31.4
34.8
38.6
40.8
Carbowax
20M9
70°C
(Baa)
.7
.9
1.1
2.9
6.2
14.1
Carbowax
20M9
70°C
(Condensate)
.8
1.0
1.1
1.3
1.9
2.1
2.6
2.8
3.6
3.9
4.4
4.8
5.2
5.8
6.4
7.5
8.4
9.3
10.4
11.1
12.6
13.5
14.4
15.7
16.3
17.1
17.7
18.7
19.8
21.1
22.0
24.0
25.6
26.9
29.4
32.0
33.8
36.9
40.1
Porapak QS
9143°C
(Bag)
.2
.7
7.7
16.6
24.8
Porapak QS
§143°C
(Condensate)
.4
.8
2.4
3.9
15.9
Porapak P
ei52"C
(Bag)
.1
.6
1.2
Porapak P
0152"C
(Condensate)
.2
.6
1.3
2.6
7.8
Porapak Q
0148°C
(Bag)
.2
.6
1 .1
2.3
4.8
Porapak Q
P148°C
(Condensate)
.4
. 7
1 .3
2.4
3.8
7.6
25.5
ro
oo
-------
Chromatogram Comparison Procedure
Sampling by the bag method as previously mentioned failed
to concentrate the dome components in sufficient quantity
for detector response. The chromatograms reproduced in
Figure 12 show the elution of a number of peaks from a
condensate sample while that of a grab sample collected the
same day does not elute peaks even at a relatively low
attenuation. The initial peak on both the grab and conden-
sate chromatograms on the Carbowax 20M and SE-30 columns
at 55°C and 90°C is due to the presence of methane inside
of the dome. The retention time (0.7 minutes) of this
peak and that of a methane gas standard were similar on
both columns. The retention time of methane was sub-
tracted from each of the retention times of the various
eluted peaks to compute the adjusted retention time
for each component. Methane was injected with the stan-
dards to also compute their adjusted retention times.
The major portion of the chromatographic evaluation of
the dome vapors was performed with condensate samples
whose chromatograms were compared to standards run on the
same day as the sample was collected. It was noted that
a standard of diallylsulfide injected on the Carbowax 20M
column and a standard of diisobutylamine injected on the
SE-30 column consistently eluted at the same time as
peaks that were distinguishable and well separated on
chromatograms of dome samples injected on both columns.
These peaks were therefore used as internal standards
on the dome sample chromatograms, and a sample of either
diallylsulfide or diisobutylamine was injected as an
internal standard with each known compound. These in-
ternal standards were not utilized with the condensate
samples because of the risk of addition of extraneous
peaks from impurities and possible masking of the large
number of peaks eluted from the condensate.
Column Temperature Effects
A column temperature was selected for each column which
would enable the complete resolution of the condensate
peaks without excessively long retention times. Conden-
sate samples were injected into the chromatographic
columns at several column oven temperatures, and print-
outs of the corresponding peak separations were compared.
Carbowax 20M at an oven temperature of 55°C proved to be
the column packing that gave maximum separation of the
29
-------
A) Grab sample at 5XIO"12
amp.
u»
o
B) Condensate sample at 5XIO"12 amp.
8
16
32
36
40
44
FIGURE
20 24
Time, minutes
12. Chromatographic separations of a dome - gas grab and condensate sample from the same
day. Conditions1 10-ft X 1/8 - in stainless steel column, 18% Carbowax 20M f 2%
on 20 - to 50 - mesh C - 22 Firebrick at 57°C with 5.0-ml volume samples.
48
-------
condensate sample into its individual peaks. The column
oven temperatures and the resulting chromatograms shown
in Figure 13 were used initially during the Carbowax
20M column evaluation. Temperatures below that of 55°C
failed to yield well defined elution peaks. As indicated
in Figure 13 (A) the peaks were resolved and had a sym-
metrical shape, however, sufficient separation between
the peaks was not achieved. Figure 13 (B) and (C) show
the effects of a twenty degree increase of the column
temperature on peak elution and separation. The peaks
tended to merge together at 75°C and 90°C and eluted
within a very short retention time.
Vaporized standards were also injected on the column at
these various oven temperatures in order to determine
the effect of temperature on peak elution and geometry
of these reference compounds. Indications were that
the optimum oven temperature was 55°C for comparison of
the reference compounds with the components of the dome
condensate mixture.
The organic acid standards presented a special problem.
At the lowest oven temperature, they tended to tail and
have excessively long retention times. Many of these
organic acid standards and some condensate materials
(14 in number) had retention times greater than the 48
minute limit of Figure 13 (A). This fact along with the
excessive retention times of the acids at the low oven
temperature made it necessary to utilize the higher oven
temperatures when comparing condensate compounds with orga-
nic acid reference compounds on the Carbowax 20M column.
The returning and stabilization of the recorder zero
to baseline after elution of the condensate peaks shown
in Figure 13 (B) and (C) indicated that all the major
components in the dome vapor had been eluted within
the selected time interval. At the higher oven temper-
ature there was no further elution of new peaks that
might have been held on the column.
Peaks were not eluted from the SE-30 column at the 55°C
temperature utilized for evaluation of the Carbowax
20M Column. Figure 14 (A) shows the results of an injec-
tion of a condensate sample on the SE-30 column at the
oven temperature of 55°C. The retention of most conden-
sate compounds at the low oven temperature made it impos-
sible to operate the gas chromatograph as a dual-flame
ionization system with the Carbowax 20M column hooked to
31
-------
C) at 90° C and 25X10-12 amp.
20 24 28
Time, minutes
FIGURE 13. Chromotographic separations of dome - gas condensate samples
on Carbowax 20M at various temperatures. Conditions: 10-ft. X
l/8-m. stainless steel column, 18% Carbowax 20M t 2%
on 30-to 50 - mesh C-22 Firebrick with 5.0-ml. sample
volumes.
32
-------
A) At 55°C and 5X12-12 amp.
B) At 90° C and 5XIO'12 amp
C) At I25°C and 10X10-12 Gmp
20 24 28
Time, minutes
FIGURE 14. Chromatographic separations of dome - gas condensate samples
on SE - 30 at various temperatures. Conditions1 10-ft X 1/8-in
stainless steel column, 10% SE - 30 on 100 - to 120 - mesh
Chromosorb G with 5.0-ml sample volumes.
33
-------
one detector and the SE-30 column hooked to the other
detector. An Injection of a specific condensate sample
could not be made on both liquid columns in one day,
however, since there was insufficient time during the
day to change the oven temperature and rerun the sample.
It was therefore decided to analyze the condensate
mixture on the SE-30 column after several days of evalu-
ating samples on the Carbowax 20M column. The oven tem-
perature of 55°C utilized initially with the SE-30
column was near the minimum temperature limit of the sub-
strate material.v16) This temperature probably did not
make the material fluid enough on the support phase to
permit an adequate separation and diffusion of the
dome materials through it. A further temperature increase
to 90°C (Figure 14 (B)) caused elution of the components
of the condensate sample as shown by the resolution and
symmetrical peaks. A further increase of the oven
temperature (Figure 14 (C)) produced merged peaks at
a reduced retention time. The temperature of 125°C
however, did present a stable baseline which indicated
that there were no additional materials retained on the
column.
The standards also failed to elute with reasonable reten-
tion times from the SE-30 column at a temperature of
55°C. The temperature of 125°C also ran the standards
together, so their retention times could not be deter-
mined. The relative retention times of the standard
reference compounds and condensate samples were compared
on both the Carbowax 20M and SE-30 columns at the optimum
separation temperature of 55°C and 90°C, respectively. A
column helium flow rate of 30 ml/min was used throughout
the study with a hydrogen flow rate of 30 ml/min and an
air flow rate of 300 ml/min.
Porapak Q when used presented a special problem because
of the nature of the column material. The column packing
is not a liquid substrate coated on a solid support as
is the Carbowax 20M and SE-30 columns. The media is
actually a solid material that is able to separate
organic materials because of the special properties and
structure of the porous polymer beads used as packing
material. Such column material necessitates the injection
of organic mixtures at higher temperatures than are gener-
ally used with liquid columns in order to elute the organic
components within a reasonable time.
34
-------
Since the Porapak Q column was able to separate a mixture
of standard reference compounds as mentioned in a previous
section, condensate samples were injected at various
oven temperatures to determine the effects of temperature
upon peak separation and elution. As shown in Figure 15 (C)
the lower oven temperature of 60°C did not elute any
peaks from the condensate sample injections as did the
Carbowax 20M column at this temperature. The column
temperature was therefore increased. As is indicated in
Figure 15 (B) and (C) more peaks were eluted at the higher
temperatures, but the column performance never did match
that of the Carbowax 20M and SE-30 columns. The Porapak Q
at the higher temperatures was either retaining the
compounds or failing to resolve the individual components
into their respective peaks by allowing elution of many
of the peaks at one time. The oven temperature could
not be increased above 200°C because the pressure drop
became too great across the column and the pressure
regulator at its maximum capacity could not maintain
a column helium flow rate of 30 ml/min. Due to the
high oven temperature necessary to elute peaks using
Porapak Q column material and the poor separation of
these peaks at such temperatures, the column was not
used in subsequent evaluation of the dome condensate
compounds.
Infrared Analyses
A Beckman IR-10 spectrophotometer and a Beckman 10-meter
gas cell were also used for odor component identification.
The 10-meter gas cell was used to analyze the vapors
collected by both grab and condensate sampling methods.
Both condensate and bag samples were scanned using the
cell's 10-meter pathlength. Attenuation was necessary
at times to adjust printout of some minimal absorption
bands detected. Results obtained were not encouraging
and more detailed infrared analysis was considered
impracti cal .
35
-------
A) At 60° C and IOXIO'12 amp.
B) At 145° C and IOXIO-|2amp.
C) At 193° C and tOXIO'12 amp.
8
16
18
20
22 24
FIGURE 15.
10 12 14
Time, minutes
Chromatographic separations of dome - gas condensate samples on
Porapak Q at various temperatures. Conditions: 5-ft. X 1/8 -in.
stainless steel column, 100 - to 120- mesh packing and 5.0-ml
samples.
36
-------
RESULTS OF ODOR IDENTIFICATION STUDY
Relative Retention Time Determinations
A total of 25 condensate samples were collected between the
months of April through July, 1971. Fourteen condensate
samples were run on the Carbowax 20M column and 11 were
run on the SE-30 column utilizing the procedures described
previously. Tables 3 and 4 present relative retention
times of those peaks separated on the Carbowax 20M and
the SE-30 columns for all sampling days. Certain peaks
were always present in the condensate sample while others
appeared only occasionally. Typical separations on the
Carbowax 20M and SE-30 columns of some of the numbered
peaks in Tables 3 and 4 are shown in Figures 16 and 17.
These chromatograms represent those condensate samples that
were run at the optimum separation temperature on both
columns, i.e., 55°C on Carbowax 20M and 90°C on SE-30. Peak
number 12 on Figure 16 and peak number 23 on Figure 17 had
retention times similar to the laboratory standards of
diallylsulfide and diisobutylamine, respectively. Since
these peaks were always easily distinguishable and well sepa-
rated on the daily chromatograms from the condensate samples,
as stated previously, they were made the reference compounds
in the condensate mixture for the basis of relative retention
time calculations.
From the reproductions of the chromatograms (Figures 16 and
17) it is noted that some peak numbers present in Tables
3 and 4 are absent. These missing peaks appeared only on
certain sampling occasions as trace components or they were
not well resolved on most sampling days.
When the relative retention times of standards that were
eluted on both columns were compared with the relative
retention times of the condensate peaks under similar
chromatographic conditions, a number of the standard and
condensate peaks eluted at the same time.
The relative retention times of both the standards and num-
bered condensate peaks are compared in LaJilAjL- Tne com~
pounds whose retention times on both columns matched with
laboratory standards are as follows:
37
-------
TABLE 5
RELATIVE RETENTION TlfES OF DOME COMPOUNDS OH CAPBOWAX20H AT 55'C
Month
Day
4-6
4-7
4-8
4-13
4-15
4-16
4-19
4-20
4-21
4-27
4-30
5-4
5-3
5-12
AVE,
1234567
.03 .06 .11 .26 .31 .52
.06 .10 .26 .32 .41 .52
.06 .11 .32 .42 .53
.03 .08 .12 ,27 .32
.03 .07 .12 .26 .31 .42 .53
.03 .07 .12 .31 .43 ,54
.07 .12 .31 .41 .52
.08 ,51
.07 .41
.08
,03 .08 .10 .42 .53
.07 .11 .26 .30 .46 .53
.08 .10 .31 .42 .50
.06 ,10 .30 .41 .52
.03 .07 .11 .26 .31 .42 .52
8 9 10
.78
.70 .76
.68 .77
.76
.75
.76
.69 ,74
.70 .74
.74
.60 .75
.59 ,70 .76
,74
.71 .75
.57 .70 .76
.58 .69 .75
11
.86
.84
.65
.82
.84
.85
.84
.84
.84
.87
.84
.83
.84
.86
.84
PEAK
1?
1.00
1.00
1.00
1 .00
1 .00
1 .00
1.00
1 .00
1.00
1,00
1.00
1 .00
1 .00
1 .00
1 .00
NUMBER
13
1.15
1.11
1.10
1.12
1.10
1.11
1.10
1 .10
1.10
1.12
1.11
1.09
1 .10
1 .10
1.10
DESIGNATION
14
1 .20
'.19
.23
1.19
1.19
1.1B
1 .19
1 .18
1.22
1.20
1.17
1 .20
1 .20
1.19
15 16
1.45
1.42 1.77
1.41 1.75
1.41
1.40 1.72
1.41 1,74
1.40
1.41 1.72
1.40 1.74
1.43 1.77
1.41 1.76
1.39 1.72
1 .41 1 .75
1.42 1.78
1.41 1 .74
17 18 10 20 21 22 23 24 25 26 27
2.06 2.31 2.59 2.78 3.18 3.85
1.88 1.99 2.06 2.28 2.52 2.72 2.96 3.11 3.30 3.75
'•86 2.03 2.24 2.51 2.69 2.90 3.05 3.23 3.68
1.96 2.21 2.50 2.70 3.12 3.71
1.88 1.94 2. IB 2.26 2.48 2.68 3.04 3.18 3.78
1.86 1.94 2.17 2.24 2.48 2.65 2.90 3.16 3.70
1.84 1.94 2.02 2.17 2.24 2.48 2.68 2.93 3.22 3.68
1.84 1.97 2.06 2.14 2.30 2.52 2.74 2.84 3.00 3.28 3.81
1.87 1.94 2,01 2.24 2.46 2.65 2.89 3.17 3.65
1.90 1.98 2.06 2.28 2.52 2.72 2.95 3.10 3.23 3.72
1.86 1.95 2.02 2.17 2.25 2.48 2.67 2.95 3.19 3.68
1 .89 1 .98 2.10 2.20 2.40 3.68
1.85 1.93 2.02 2.12 2.24 2.46 2.67 2.94 3,67
1.89 2.00 2.08 2.30 2.57 2.78 3.02 3.28 3.82
1.87 1.96 2.04 2,15 2.26 2.50 2.70 2.92 3.06 3.22 3.73
* Peak No. 12 (Diallylsulflde) internal standard.
-------
TABLE 4
RELATIVE RETENTION TIMES OF DOME COMPOUNDS ON SE-30 AT 9Q°C
Month
Day
5-W
5-18
5-19
5-20
5-25
5-26
6-1
6-2
6-4
6-8
6-16
AVE,
PEAK NUMBER DESIGNATION
1
.04
.03
.04
.04
.03
.04
.03
.04
.03
.04
2 3
.06
.05
.05
.05
.05
.05
.05
.05
.05
.07
.05 .07
.05 .07
4
.08
.09
.09
.09
.09
.08
.09
.09
.09
.09
.09
5 6
.16
.11 .16
.15
.16
.16
.16
.11 .16
.16
.16
.15
.15
.11 .16
7
.19
.18
.19
.19
.19
.19
.19
.18
.18
.19
.19
.19
8
.25
.24
.24
.25
.25
.25
.25
.25
.26
.26
.25
.25
9 10 11 12 13
.32 .35 .41 .46
.32 .46
.32 .45
.31 .34 .46
.32 .36 .46
.31 .33 .35 .46
.33
.33 .38 .45
.33 .35
.30 .33 .45
.32 .35
.31 .33 .35 .39 .46
w
.50
.50
.49
.50
.50
.50
.50
.50
.50
.50
.50
.50
15 16
.54 .61
.58
.60
.60
.61
.60
.60
.61
.61
.60
.54 .60
17 18
.64 .68
.67
.67
,68
.64 .68
.68
.67
.68
.68
.68
.64 .68
19 20
.73 .79
.79
.72
,73
.74
.74
.74
.74
.73
.78
.79
.73 .79
00
ID
Table IV (Cont'd on next
page)
-------
TABLE 1 (continued)
RELATIVE RETENTION TIMES OF DOME COMPOUNDS ON SE-50 AT 90°C
Month
Day
5-11
5-18
5-19
5-20
5-25
5-26
6-1
6-2
6-1
6-8
6-16
AVE.
21 22
.84 .95
.94
.84 .96
.86 .95
.85 .94
.94
.84 .95
.84 .94
.94
.85 .94
.84 .94
23*
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1 .00
1.00
21
1.06
1.06
1.06
1.05
1.06
1.05
1.04
1.06
1.06
1.05
25
1.17
1.17
1.16
1.17
1.16
1.17
1.18
1.17
1.17
1.17
1.17
1.17
1
1
1
1
1
1
1
1
1
1
1
1
26 27
.28 1.40
.28
.27
.28 1.39
.28
.28 1.40
.30
.28 1.40
.28 1.36
.28 1.37
.28 1.40
.28 1.39
PEAK NUMBER
28 29
1.47 1.52 1
1.47 1.52 1
1
1.52 1
1.48 1.58 1
1.46 1.54 1
1
1.47 1.53 1
1 .46 1
1.46 1.53 1
1.53 1
1.47 1.53 1
DESIGNATION
30
.64
.63
.62
.63
.64
.65
.66
.64
.63
.65
.64
.64
31
1.73 1
1.74 1
1.73 1
1.73 1
1 .74 1
1.75 1
1 .74 1
1.73 1
1.74 1
1 .74 1
1 .74 1
32
.85
.86
.88
.86
.85
.86
.86
.85
.85
.87
.86
33
1.97
1.98
1 .98
1.98
1.98
1.99
1.98
1 .98
1.98
1 .98
1.98
31 35 36
2.08 2.16 2.28
2.09 2.28
2.08 2.28
2.08 2.28
2.08 2.29
2.30
2.08 2.29
2.16 2.27
2.16 2.29
2.08 2.29
2.08 2.16 2.28
37
2.54
2.53
2.53
2.53
2.54
2.55
2.54
2.52
2.55
2.54
2.54
38
2.75 2
2.80 2
2
2.76 2
2.76 2
3
2.76 3
3
2.74 2
2.78 3
2.76 3
39
.97
.99
.98
.98
.99
.01
.00
.09
.99
.07
.01
10
3.32
3.32
3.32
3.32
3.34
3.34
3.31
3.34
3.34
3.33
* Peak No. 23 (Diisobutylamine) internal standard.
-------
.50
I.OO 1.50 2.00 2.50 3.00 3.50 4.00
Relative Retention Time
FIGURE 16, Relative retention time of dome compounds on Carbowax
20M at 55°C and 5XIO'12 amp.
.50
.00 1.50 2.00 2.50
Relative Retention Time
3.00 3.50 4.00
FIGURE 17. Relative retention time of dome compounds on SE - 30 at
90° C and 5XIO~12 amp.
41
-------
TABLE 5
COMPARISON OF RELATIVE RETENTION TItfES OF STANDARDS AND CONDENSATE PEAKS
COMPOUND
Ethyl mercaptan
Propyl mercaptan
tert-Butyl mercaptan
sec-Butyl mercaptan
Isobutyl mercaptan
Butyl mercaptan
tert-Amyl nercaptan
sec-Isoamyl mercaptan
Amyl mercaptan
Nexyl mercaptan
Heptyl mercaptan
Diethyl sulfide
Di-n-propyl sulfide
Di-n-butyl sulfide
Diallyl suHide (1)
Methyl disulfide
Isopropanol
Propanol
Butanol
Isopentanol
Acetaldehyde
Propional dehyde
Butyraldehyde
Valeraldehyde
Acetone
Diacetyl
Acetic acid
Propionic acid
Ethyl ami ne
Propylamine
Butyl ami ne
Hexylamine
Diethyl ami ne
Di Propylamine
Di isopropylamine
Dibutylamine
Diisobutylaroine (2)
Triethylamine
Tripropylamine
COLUMN
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20H
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
SE-30
C-20M
C-20M
SE-30
SE-30
SE-30
SE-30
SE-30
SE-30
SE-30
SE-30
SE-30
SE-30
SE-30
OVEN
TEMP. °C
55
90
55
90
55
90
55
90-
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
90
55
' 90
55
90
55
90
55
90
55
90
55
90
55
55
90
90
90
90
90
90
90
90
90
90
90
RELATIVE RETENTION
TIME (STANDARD)
.03
.08
.08
.16
.10
.15
.14
.24
.16
.26
.21
.33
.26
.36
.37
.46
.54
.68
K4T(4)
2.97
T
.17
.31
1.12
1.12
2.46
T
1 .00
T
.22
.41
.52
.07
.87
.15
2.16
.31
4.37
.45
.04
.06
.06
.12
.14
.16
.38
.33
.01
.12
.14
.15
3.22
4.20
.09
.23
.39
1 .28
.13
.48
.24
1 .88
1 .00
.31
1.57
DOME
PEAK NO.
1
4
2
6
3
6
8
8
10
4
11
13
7
18
9
13
22
12
12
7
3
11
6
20
9
13
1
2
2
5
6
10
5
6
26
4
12
26
8
32
23
9
RELATIVE RETENTION
TIME (CONDENSATE)
.03
.09
.07
.15
.11
.15
.25
.25
.33
.26
.35
.45
.52
.68
.31
1.10
2.49
1 .00
.39
.52
.07
.84
.15
2.15
.31
.45
.03
.05
.07
.11
.15
.33
.11
.15
3.22
.09
.39
1 .28
.25
1 .86
1 .00
.31
NOTES:
(1) Diallylsulfide-internal standard
(2) Diisobuty1 amine-internal standard
(3) (C-20M) signifies Carbowax 20M
(4) Totalling of the component
42
-------
1. ethyl mercaptan
2. propyl mercaptan
3. tert-butyl mercaptan
4. tert-amyl mercaptan
5. amyl mercaptan
6. isopropanol
7. propanol
8. butanol
9. acetaldehyde
10. propionaldehyde
The compounds that
dome atmosphere by
the following:
were identified as being present in the
using the Carbowax 20M column alone were
1. diallylsulfide
2. acetic acid
The following amines were identified in the dome atmosphere
using the SE-30 column:
1. ethyl amine
2. butylamine
3. hexylamine
4. diisopropylamine
5. dibutylamine
6. diisobutylamine
7. triethylamine
The mercaptans (ethyl, propyl, tert-butyl, tert-amyl, amyl)
and dial lylsulfide all have strong, offensive odors which
were particularly noticeable as being present inside the dome
on certain sampling days. The alcohols (isopropanol, pro-
panol, and butanol) and the aldehydes (acetaldehyde and
propionaldehyde) were judged unimportant as far as major
odor contributors, however, they might have a synergistic
effect on the composite odor in the dome atmosphere.
The acetic acid standard and a comparative condensate peak
had large relative retention times at 55°C and further
analysis for specific organic acids was considered necessary
The amines would contribute a very pungent odor to the
dome atmosphere, but most amines do not have as low a
threshold odor level as the sulfur compounds (17). Amines
therefore must be present in large amounts before a dis-
tinct amine odor can be detected in the presence of sulfur
compounds.
The relative retention times of the standards on the Car-
bowax 20M and the SE-30 columns are shown diagramatical ly
in Figures 18 and 19. It is noted from these figures
that most of the standards eluted rapidly on both columns
43
-------
V
9
3
e
4
16 ' '
11 ? » .7
"V
19
•
,. 21
22 2? 24
i i i
i i
2
1 1
5 2
i i
i i i i
.200 .400 .600 .800 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20
Relative Retention Time
KEY 1. Acetone
RRT
.01
Z. Ethyl mercaptan .03
3. Acetaldehyde
4. Propionaldehyde
.04
.06
5. Propyl mercaptan .08
6. tert - Butyl mercaptan ,10
7 sec - Butyl mercaptan .14
8. Diacetyl
9. Butyraldehyde
H
.14
FIGURE 18. Relative retention time of
10. Isobutyl mercoptan
II. Di ethyl sulfide
12. Butyl mercaptan
13. Methyl disulfide
RRT
RRT
.16 19. Propanol .87
.17 20. Diallyl sulfide 1.00
.21 2
1. Di -n-propyl sulfide 1.12
.22 22 Hexyl mercaptan 1.47
14. tert-Amyl mercaptan .26 23 Butanol 2.16
15. sec'-lsoamyl
mercapton .37 24 Di-n- butyl sulfide 2.46
16. Valeraldehyde
17. Isopropanol
.38 25 Heptyl mercapton 2.97
.52 26 Acetic acid 3.22
18. Amyl mercaptan
.54 27. Propionic acid 4.20
various standards on Carbowax 20M at 55° C.
-------
V
3 5T
a
r
4
s
17,18
II 14 19
a a
12 If
13
1
16
22
20
a
•t
I
23
2
1
20
a
28
4
29
2
' 28
1 1
1 1 1
33
32
30 31
I
1 1 1
1 1 1
.100 .200 .300.400.500 .600 .700 .800 .9001.000 1.100 1.200 1.300 1.400 1.500 1.600 1.700 1800 1.900 2.000
cn
KEY: |, Acetoldehyde
2. Isopropanol
3. Ethyl mercaptan
4. Ethylamine
5, Acetone
6. Propionaldehyde
7 Diethylamine
8. tert- Butyl mercaptan
9. Diacetyl
10. Propanol
II Propyl mercaptan
12. Butyraldehyde
FIGURE 19. Relative retention time
Relative Retention Time
RRT RRT
Propylamine ,23
Diisopropylamme .24
sec - Butyl mercaptan .24
Isobutyl mercaptan 26
Butanol .31
Dtethyl sulfide .31
Triethylamine .31
Valeraldehyde 33
Butyl mercaptan .33
tert - Amyl mercaptan .36
Butylamine .39
Methyl disulfide .41
standards on SE - 30 at 90° C.
.06
.07
08
.09
.12
.12
.13
.15
.15
.15
.16
.16
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
RRT
25. Isopentanol .45
26. sec - Isoamyl mercaptan .46
27. Dipropylamine .48
28. Amyl mercaptan .68
29. Oiisobutylamine 1.00
30. Di-n-propyl sulfide 1.12
31. Hexylamine 1,28
32. Tripropylamine 1.57
33 Dibutylamme 1.88
of various
-------
with the exception of the acids on Carbowax 20M and the
amines on SE-30. The acids at the 55°C temperature on the
Carbowax 20M column did not give a symmetrical peak but
tended to tail with a resultant inconsistent retention time
It was therefore necessary to reinject these standards at
a higher temperature on the Carbowax 20M column in order
to obtain consistent retention times and sharp peaks. For
comparison, dome condensate samples were also run at the
higher temperature. The amines on the SE-30 column and
especially the diamines and triamines tended to elute
much later from the column at the 90°C temperature. How-
ever, the peaks were symmetrical and did not tail. It is
interesting to note that a major portion of the peaks in
the dome atmosphere elute much later than many of the low
boiling vaporized standards that were used for comparison.
This suggests that the dome compounds that were not identi-
fied are probably rather high boiling materials that have
large vapor pressures, and possibly complex materials
such as sulfur or nitrogen compounds with nonsimiiar
alkyl groups attached to the sulfur or nitrogen atom.
Further investigation would be necessary to confirm this
premise.
Confirmation could be obtained by first finding the
amount of sulfurous or nitrogenous compounds Present in
a fixed gas volume, and then selectively absorbing these
materials by specific functional group reactions. '£"*. ^
absorbed materials could later be analyzed cnr?1™^ Separ_
cally by using a column that is known to eTteci J . g
ate a mixture of such compounds. TcmP«r?J"reap^e SssSrt-
would probably be warranted to separate such a wide
ment o? materials with.f different bo.lngpont^^^ ^
Detection systems specific for these rype u. p
also be of great assistance.
Since the organic acids tailed considerably on the Carbo-
wax 20M column at a I'V^nnlc ac?2s e uted much
dard peaks of acetic and Pr°P10"^^ condensate samples
later than comparative dome comp?^^ied at higher tempera-
and standard organic acids were inje chromatogram was
tures into the Carbowax 20M column J cnroma y
developed as Presented previous y in ^ur^A
comparison of these retention times.
Odor-Retention Time Comparisons
Samples were collected from the dome on days that a very
46
-------
noticeable sour-acid odor was detected in the atmosphere.
Portions of these samples were injected into the Carbowax
20M column with a helium flow rate of 30 ml/min. A compar-
ison of the retention times of organic acids and peaks from
dome samples is presented in Table 6. Acetic, propionic,
and isobutyric acids (as identified in the dome mixture from
Table 6) all have very disagreeable odors that were
especially noticeable on certain days inside the dome.
The pH of the waste liquid inside the sludge thickener was
always between 5.8 and 6.9 during the study. This pH
range would enable the acids to be in a nonionized form and
therefore volatilization of the acids into the atmosphere
would be highly possible.
The water that was collected as condensate in the collection
trap had a very distinct sickening-sweet odor which was
not detected inside the dome. This odor smelled much like
that of the skatole standard used in the laboratory. The
odor became more intense upon heating the material.
Standard solutions of skatole and its homolog, indole,
were prepared by dissolving 25 mg of the material in 5 mg of
isopropanol. One-microliter portions of the skatole and
indole solutions were injected into the SE-30 column at
oven temperatures of 110°C and 130°C. The isopropanol
eluted from the column as expected. There was no elution
however of the skatole or indole in a half-hour period.
Comparison of retention times with the dome materials could
not be made. This indicates that there was either adsorp-
tion or large retention times of the indole and skatole on
the SE-30 column.
The threshold odor level in air for mercaptans, sulfides,
and amines has been measured in the very low parts per
billion range.(17) Aldehydes and alcohols have a level
that is in the parts per million range, while the organic
acids represent a wide range of threshold concentrations.
(17) Threshold values of several odorous compounds with
their characteristic odors are listed in Table 7. (17, 18)
It is noted from Table 7 that molecules with the same func-
tional group all exhibit the same characteristic odor.
The sulfur containing organics are detected in very minute
quantities and have a very unpleasant odor. The alcohols
are detected only in much greater concentrations and
elicit a pleasant odor. The alcohol response would probably
be less offensive to humans and therefore quantities which
were present in excess of threshold would not be disagree-
able. In the case of the sulfur compounds anything above
47
-------
TABLE 6
RETENTION TIME OF ORGANIC ACIDS AND
DOME COMPOUNDS ON CARBOWAX 20M
COMPOUND
I
i
•Acetic
Propionic
Isobutyric
Butyric
Isovaleric
Valeric
Temp. (°C)
75
75
90
75
90
75
90
75
90
75
90
Retention time
of standards
(min)
8.23
10.88
6.45
12.95
7.30
18.40
10.00
27.50
13.70
37.90
18.70
Retention time
of dome compounds
(min)
8.70
10.70
6.20
12.40
7.20
9.50
18.60
48
-------
TABLE 7
ODOR THRESHOLDS OF SEVERAL ORGANIC COMPOUNDS (17,18)
CHEMICAL
Odor
threshold
(ppm)
Characteristic
odor
Formaldehyde
Acetaldehyde
Acetic acid
Butyric acid
Methylamine
Dimethylamine
Trimethylamine
Methanol
Ethanol
Hydrogen sulfide
Ammonia
Diallyl sulfide
Dimethyl sulfide
Diethyl sulfide
Dipropyl sulfide
Dibutyl sulfide
Methyl mercaptan
Ethyl mercaptan
Propyl mercaptan
Butyl mercaptan
t-Butyl mercaptan
1
1
0
066
0
.001
.021
.047
.0002
100.0
10.0
.00047
8
,00014
,0037
,0028
,011
,015
,0021
,00026
,0016
,0010
,00008
46
Straw-!i ke
Green sweet
Sour
Sour
Fishy
Fishy
Fishy
Sweet
Sweet
Rotten Eggs
Pungent
Garlic
Decayed vegetables
Garlic-1i ke
Foul
Unpleasant
Decayed cabbage
Decayed cabbage
Unpleasant
Unpleasant
Unpleasant
49
-------
threshold would be highly offensive. The odorous organic
compounds such as the amines, acids, and aldehydes have
increasing obnoxious odors as the molecular weights increase
up to a certain weight. Further increase beyond this
weight results in decreasing odor perception.('/ Charac-
teristic odor types inside the dome were recorded by
laboratory personnel on sampling days. These odors can
be classified into fecal, rancid, cabbage-like, sour, and
skunk-like. Table 8 lists the odor types for the sampling
days along with the temperatures of the wastewater and dome
atmosphere, relative humidity inside the dome, wastewater
pH, and blanket depth in the sludge thickener.
The water and atmospheric temperatures are seasonally depen-
dent and they increased slightly as the weather became
warmer. The odor types observed appear to be dependent
on the depth of the sludge in the thickener. The fecal
and rancid odors are typical of low sludge levels (greater
blanket depth) with the cabbage-like and sour odors
associated with a high sludge level. The skunk-like odor
appears to be a transition odor between high and low levels
of sludge in the thickener.
On the days that a descriptive odor was noted inside the
dome, there was a noticeable increase in concentration
or appearance of certain peaks on the chromatogram of that
day's condensate sample. Peak numbers shown on Figures
16 and 17 are compared with identified dome compounds in
Table 9. Peak number 2 on the Carbowax 20M column (see
Figure 16 and Table 9) was more concentrated when the
cabbage odor was noticed (propyl mercaptan). Peak number
3 was higher when the sour odor prevailed (tert-Butyl
mercaptan). On the days when rancid and fecal odors were
prevalent no significant change in any peaks on the
chromatograms was observed. On the SE-30 column,(see
Figure 17 and Table 9), peak number 4 was more concentrated
for the rancid and fecal odor days (ethylamine). Peak
number 2 on the SE-30 column appeared on both the sour
and skunk odor days (acetaldehyde).
Compound Concentration Evaluation
The quantisation of identified materials from the dome was
accomplished by comparing under similar conditions the peak
heights of the compounds from the dome chromatogram and the
peak heights of vaporous standards that were injected
into the gas chromatograph. Standards were prepared by
first injecting with a Hamilton syringe a l-/ul liquid
50
-------
TABLE 8
COMPARISON OF ODOR TYPES WITH OPERATIONAL MEASUREMENTS
Month
Day
4-6
4-7
4-8
4-13
4-15
4-16
4-19
4-20
4-21
4-27
4-30
5-4
5-5
5-7
5-10
5-12
5-14
5-18
5-19
5-20
5-25
5-26
6-1
6-2
6-4
6-8
6-16
6-21
6-25
6-29
7-14
Temp. (°C)
Water Atmosphere
56
56
58
60
62
60
62
64
62
62
63
62
64
64
64
64
64
66
66
66
62
62
66
66
68
68
64
64
64
64
64
48
55
61
55
63
66
69
71
64
63
60
63
64
65
69
56
65
70
67
67
62
62
69
73
74
72
72
75
80
79
74
Relative Characteristic Blanket
humidity odor-type pH depth(ft)
86
66
51
82
60
55
57
54
75
74
69
57
80
90
90
71
67
65
64
68
70
84
72
67
79
86
86
71
76
69
91
fecal
fecal
fecal
rancid
fecal
fecal
fecal
cabbage-1 i ke
cabbage-1 i ke
cabbage-1 i ke
cabbage-like
cabbage-1 i ke
cabbage-1 i ke
cabbage-1 i ke
sour
sour
rancid
fecal
rancid
rancid
ran-ci d
rancid
fecal
ranci d
skunk-1 ike
skunk-1 i ke
sour
sour
sour
sour
sour
6.1
6.1
6.0
6.1
6.1
6.1
6.2
5.8
6.0
6.1
6.0
6.3
6.0
6.0
5.9
6.1
5.9
6.0
6.0
6.8
6.8
6.9
6.6
6.0
6.2
5.9
6.0
6.1
6.0
8.5
8.5
8.5
8.5
8.0
8.0
7.5
7.5
7.5
5.5
5.5
6.0
5.2
2.2
1.0
6.0
5.2
9.0
8.5
8.2
8.5
8.5
8.5
9.0
7.5
7.2
3.2
3.0
5.5
5.5
5.5
51
-------
TABLE 9
MAXIMUM AND MINIMUM CONCENTRATIONS RECORDED FOR IDENTIFIED ODOR COMPOUNDS
COMPOUND
Acetaldehyde
Isopropanol
Propanol
Butanol
Ethylamine
Butyl ami ne
Diisopropylamine
Dlisobutylamine
Dibutylamine
Triethylamlne
D1allylsulf1de
Ethyl mercaptan
Propyl mercaptan
tert-Butyl mercaptan
tert-Amyl mercaptan
Amy! mercaptan
Dome
Maximum
(xlO ppm)
78
1.4
20
82
270
,0014
,066
.99
.14
.21
48
.38
26000
5.1
.58
.14
Dome
Minimum
(xlO"%Dm)
1.6
.26
4
2.4
1.5
.0005
.0035
.07
.016
.08
.09
.16
.05
.023
.23
.023
Col umn
SE-30
SE-30
C-20M
C-20M
SE-30
SE-30
SE-30
SE-30
SE-30
SE-30
C-20M
C-20M
C-20M
C-20M
SE-30
SE-30
Dome
Peak
No.*
2
3
11
20
4
12
8
23
32
9
12
1
2
3
11
18
en
no
* refer to Figures 16 and 17
-------
sample into a 125-ml sampling bottle capped with a septum
containing cap. This bottle was then placed in warm water
to volatilize the material completely. A specific volume
of the sample as a vapor was withdrawn with a 1-ml Hamilton
gas-tight syringe and the vapor was injected into the column
Gaseous volumes were chosen such that the comparison
of the standard and the dome peak were both recorded at
the same attenuation. Further dilution of the standard
vapor was necessary in some cases to keep the peak from
going offscale.
The experimentally determined maximum and minimum concen-
trations of some odorants in the dome atmosphere are pre-
sented in Table 9. Comparing these values with threshold
values for some of the compounds as presented previously
in Table 7 reveals that many of the compounds are below
their threshold levels except for the mercaptans and
ethylamine. Propyl mercaptan and ethylamine appeared to
be the only identified compounds present in concentrations
above their threshold levels.
Those compounds with concentrations below the threshold
level listed for compounds with a similar functional
group, although not major odor contributors, may have a
synergistic effect on odor perception. Obviously, no one
compound detected on a given day can be considered totally
responsible for the perceived odor.
53
-------
THRESHOLD EVALUATION AND ODOR TREATMENT RESULTS
General Statement
This section presents the results from various tests con-
ducted to evaluate treatment methods for dome odor control.
These tests included: (1) dilution of the odors with air,
(2) adsorption of odors by activated carbon, and (3) oxi-
dation of odor compounds with chlorine. The effectiveness
of each method was determined through a threshold odor
evaluation by a selected group of individuals.
Selection of Odor Panel
Laboratory personnel assigned to the Industrial Waste
Division of MSD and working at the Bissell Point Sewage
Treatment Plant were asked to serve on the odor panel.
Eight people were initially screened, with four of these
chosen for the panel. Selection of the four panel members
was based on results of the screening tests with those
individuals having the most sensitive sense of smell
used for detailed odor detection. The most sensitive
individuals were used so that efficiency evaluations of
odor treatment methods would be stringent.
The panel members were screened'uti1izing the "triangle
test".(19) This test allowed each person to evaluate
three odor flasks for similarity of odors. Two flasks
contained one per cent vanillin solution in benzyl benzoate
while the third contained a one per cent methyl salicylate
solution in benzyl benzoate. Starting with these one
per cent solutions, personnel were asked to determine the
control odor (i.e., methyl salicylate) in increasingly
dilute solutions from a random arrangement of the flasks.
At low concentrations vanillin and methyl salicylate smelled
similar and only the most sensitive individuals were able
to distinguish the control odor as indicated in Table 10.
The plus mark indicates that the individual had chosen the
control odor correctly from a set of three flasks while
a zero shows no response. Personnel with reference numbers
1, 2, 4 and 8 were chosen to serve on the panel.
Treatment by Air Dilution
The simplest form of treatment is the dilution of an odor
to a level where it is undetectable, that is, below the
54
-------
TABLE 10
SENSITIVITY OF PERSONNEL TO TRIANGLE TEST
Standard Odoran
(X w/w)
1
0.1
0.05
0.01
0.0025
0.000125
Key: + =
0 =
ts
12345
+ + + + +
+ + + + 0
+ + + + 0
+ + 0 + 0
+ 0000
0 0 0 0 0
odor difference detected
no difference detected
678
+ + +
+
+ + +
00 +
00 +
00 +
55
-------
threshold level. The threshold level is defined according
to ASTM(6) as the amount of dilution required to make
the odors barely perceptible to 50 per cent of the popula-
tion. During the study since very sensitive individuals
were used on the odor panel this percentage would be
reduced considerably and is therefore referred to as
"odor threshold for 50% of the panel members."
Grab samples collected at the center of the dome around
9:30 a.m. in the morning were given a threshold level
evaluation by 2:00 p.m. the same day. Odor samples collected
from the dome each morning were diluted with various volumes
of odor free air in the laboratory prior to panel evaluation.
Table 11 presents the results from the threshold level
determination on individual samples taken during the months
of June and July, 1971. Each threshold level is given as
a per cent concentration on a volume per volume basis.
The threshold value that would be detected by 50 per cent
of the panel members shown in Table 11 was determined by
finding a midpoint between the value of maximum per cent
odor concentration perceptible to all panel members and
the minimum per cent odor concentration perceptible to none
of the panel members on each sampling day. For example,
on June 21st the maximum detectable concentration by all
panel members was 0,3 per cent since at a concentration
just below this level, Panel Member "A" could not sense
the odor. However, Panel Member "C" could detect the
odor at 0.05 per cent concentration, but not at the next
dilution which was 0.04 per cent. The threshold level for
50 per cent of the panel members was therefore calculated
to be:
0.3 + 0.04 = 0.17
2
In order to give meaning to the concentration of daily
odors inside the dome, the odor concentration was defined
^6'
in terms of a predetermined threshold level
defines this level as the number of cubic feet that one
cubic foot of odorant will occupy when it is diluted to
the odor threshold. The formula for calculating odor
concentration is:
C = V [1] where, C is the odor
56
-------
concentration in odor units/cu. ft., Vs is the volume in
milliters of original sample that is contained in the most
dilute sample in which odor was detected, and V is the volume
of the syringe used. In this study the syringe volume
was 100 ml.
An odor unit is defined as one cubic foot of air at the
odor threshold. The odor concentration (C) on June 21st
was therefore calculated to be:
c = 100 = 588 odor units/cu. ft.
0.17
Table 11 lists these odor concentrations as determined
from panel results. From the definition of odor concentra-
tion, these values in Table 11 represent the number of
cubic feet (or any other conveniently measurable unit)
by which one cubic foot of dome air must be diluted in
order to produce the threshold level concentration. In
the example one cubic foot of dome air would have to be
diluted with 588 cubic feet of odor free air to reduce
the odor below detectible levels. The sludge thickener
dome at the Coldwater Creek Plant has a volume of 31,370
cu. ft. Therefore, the amount of air needed to dilute the
entire dome atmosphere to the threshold level is found by
multiplying the odor concentration by the dome volume.
Further investigation of the meterological effects in and
around the treatment plant which was beyond the scope of
the study is necessary before a procedure involving out-
side air dilution can be adequately adopted.
Carbon Adsorption of Odors
Another method investigated for treatment of dome odors
was adsorption using activated carbon. The use of acti-
vated carbon can be economical if regeneration is feasible.
It is a good adsorbant for most organic compounds and its
efficiency is not affected by moisture.(^1.22) jne pro_
cedure for carbon treatment evaluations has been described
previously.
Table 12 lists the results for one week of concentrated
sampling and adsorption testing during the month of July.
The threshold values before and after treatment are com-
pared with the quantity of carbon used to treat a specific
57
-------
TABLE 11
THRESHOLD LEVELS AND AIR DILUTION REQUIREMENTS FOR DOME ATMOSPHERE
MONTH
DAY
6-21
6-22
6-23
6-24
6-25
6-28
6-29
6-30
7-1
7-14
7-15
7-16
7-19
7-20
Odor threshold level for
each panel member
A B C D
.3 .2 .05 .1
.4 .05 .2 .3
.08 .07 .04 .01
.3 .2 .2 .5
.01 .09 .01 .08
.1 .3 .3 .3
.1 .05 .03 .1
,3 .3 .3 ,03
.05 .05 .1 .2
.2 .2 .03 .03
.3 .1 .1 .1
.04 .1 .04 ND(2)
.2 .6 .2 ND
.3 .4 .4 ND
Odor threshold
for 502 of the
panel members
.17
.22
.04
.30
.05
.20
.06
.16
.12
.11
.54
.06
.35
.30
Odor Concen-( 1 )
tration (odor
un1ts/cu ft)
588
454
2500
332
2000
500
1666
625
833
909
185
1666
286
333
Air volume needed
to reach threshold
(cu ft)
18,446,000
14,242,000
78,425,000
10,415,000
62,740,000
15,685,000
52,262,000
19,606,000
26,131 ,000
28^515,000
5,803,000
52,262,000
8,971 ,820
10,446,000
CO
NOTES:
Average odor concentration 873
ND signifies not detected
-------
volume of air from the dome. The efficiency of activated
carbon treatment was calculated using the following formula
% Efficiency = cone, of entering gas - cone, of effl . gas
cone, of entering gas X 100
At the breakthrough point (the time at which odors were
first noticed in the discharge from the filter), the efficiency
of the activated carbon treatment was calculated for the study
period, efficiencies for carbon adsorption were between 97%
and 99%.
The efficiency of the process depends greatly on the type of
organics being adsorbed. Some organics were observed to pass
through the filter without being adsorbed. A typical odor
that did not appear to be adsorbed by the carbon was similar
to the odor of lard. Even though most dome odors were ad-
sorbed by the carbon, the odor panel noticed the greasy lard-
type odor in samples taken from the filter discharge even
before the breakthrough point was reached. This odor was
totally dissimilar to the characteristic odors present inside
the dome.
Panel members were instructed to compare a sample of diluted
and untreated dome gas with samples of filter discharge to
determine the breakthrough time. An evaluation was not made
of the increase in odor intensity after the breakthrough
point. The carbon filter could probably have been operated
for a longer time until the odors emitted reached a level of
around 200 odor units which was determined by previous
studies as the point where the odors became objectionable.
The quantity of dome atmosphere that can be treated with a
known weight of carbon is represented in Table 12. These
values represent the amount of carbon needed for a 98%
efficient treatment of odors. The average is 0.102 gram of
carbon per cu. ft. of dome air.
Chlorine Treatment of Odors
A number of laboratory techniques were investigated to
evaluate treatment of odors with chlorine. In the first
method studied a chlorine scrubber solution was attached
to the carbon adsorption system, with the carbon filter
removed, and connected to the sampling train at the dome.
59
-------
TABLE 12
CARBON* ADSORPTION OP DOME ODORS
Month
Day
7-1
7-2
7-6
7-7
7-8
Before
treatment
odor units/
cu ft
835
760
910
715
835
After
treatment
odor units/
cu ft
10
10
25
15
15
Efficiency
99
99
97
98
98
Weight of
carbon
(grams)
10.5
10.6
9.6
10.3
10.0
Gas
volume
(cu ft)
109
100
80
130
90
C'arbon/gas volume
grams/cu ft
.096
.106
.120
.079
.111
Average
.102
* Activated carbon used was 4-to 10-mesh as manufactured by the Cliff-Dow
Chemical Company.
-------
However, as the dome gas was bubbled through the solution
most of the chlorine was lost by volatilization rather
than chemical oxidation of the odorous compounds. An
identical solution was similarly stripped of chlorine
when odor free air was passed through it using the same
flow conditions as that of the dome gas.
The second method studied utilized treatment of the
odors by injecting air diluted chlorine gas into a Saran
bag containing a known concentration of dome gas. It
was very difficult to determine accurately the amount
of chlorine injected into the sample bag and therefore
the method was not used for treatment evaluation.
The method selected for chlorine treatment evaluation has
been described earlier (see Figure 10). The results from
this method are presented in Tab!e 13. The most signi-
ficant point made during these chlorine evaluations was
that water alone is an effective reducer for most of the
odors. There was a 10 to 100 fold reduction in odor by
merely bubbling the dome gas through water. The optimum
chlorine concentration for treatment of dome odors was
found to be 1.5 mg/1 . At this concentration in the
chlorine solution, all odors were effectively removed.
This was proven when the odor panel members could detect
a very faint dome odor in a bag sample that was passed
through the chlorine solution. At concentrations greater
than the 1.5 mg/1 level only the odor of chlorine was
detected.
The combination of water and chlorine appears to provide
effective treatment of the odors. On a practical scale
the dome atmosphere can be bubbled through a large scrubber
tank which has a chlorine concentration maintained at
1.5 mg/1. If post chlorination is practiced, as it is
at the Coldwater Creek Plant, odorous gases could possibly
be bubbled through the final effluent at the discharge
of the chlorine contact basin (see Figure 3). The
residual chlorine concentration in the effluent must be
controlled to insure adequate odor reductions.
61
-------
TABLE 13
TYPICAL CHLORINE TREATMENT RESULTS FOR DOME ODOR REMOVAL
Initial Odor Final Odor
Chlorine Concentration Concentration
Concentration (odor units/ (odor units/
(mg/1) cu ft) cu ft) Odor Type
1.15 2000 25 Dome-like
1.50 " 1 Very fai nt
odor
2.20 " 2-10 Chlorine
H20 blank " 33 Dome-like
62
-------
ACKNOWLEDGEMENTS
Appreciation is expressed to the Environmental Protection
Agency (EPA) for the financial assistance which in part
allowed this study to be undertaken. Recognition is made
also to Mr. Otmar 0. Olson and Dr. William Garner of the
EPA for their guidance during implementation of the study
and review of project results.
Special thanks is given to Mr. Thomas Wydrzynski for
analytical assistance provided during laboratory evalu-
ations and to Mr. Stan Lamb whose drawings appear through-
out this report.
63
-------
REFERENCES
1. Glaser, J. R., "Air Pollution From Sewage Treatment",
Ph.D. thesis, University of Texas, Austin, Texas, (l 969).
2. Burnett, W. E., "Air Pollution From Animal Wastes
Determination of Malodors by Gas Chromatographic and
Organoleptic Techniques", Environ. Sci. Techno!.. 3,
No. 8, p. 744 (August, 19697::
3. Lebeda, D. L., Day, D.L., Hayakavva, I., "Air Pollutants
in Swine Buildings with Fluid Waste Handling", Paper
presented at the National Meeting of the American Society
of Agricultural Engineers, New Orleans, Louisiana,
(December 8, 1964) .
4. Miner, J. R. , Hazen,T.E., "Ammonia and Amines: Components
of Swine-Building Odor", Trans. Am. Soc. Agr. Engrs.,12.
p. 772 (1969)
5. Farrington, P.S., Pecsok, R. L., Meeker, R. L., Olson,
T. J., "Detection of Trace Constituents by Gas Chroma-
tography Analysis of Polluted Atmosphere", Anal. Chem. ,
3_1, No. 9, p. 1512 (September, T959).
6. "Measurement of Odors in Atmospheres (Dilution Method)",
ASTM Designation: D1391-57 (1957).
7. Jacobs, M. B., "The Analytical Chemistry of Industrial
Poisons, Hazards, and Solvents" Interscience. New York
p. 96, (1949).
8. Day, D. L., Hansen, E. L., Anderson, S., "Gases and Odors
in Confinement Swine Buildings", Trans. Am. Soc. Agr.
Engrs. , 8, p. 118, (1965).
9. American Public Health Association, Standard Methods for
the Examination of Water and Wastewater, p. 226,
Thirteenth Edition, New York, APHA, (1971).
10. Dedio, W. , Zalik, S., "Gas Chromatography of Indole
Auxins", Anal. Biochem. , 16, p. 36 (1966).
11. Bednas, M. E, Russell, D.S., "Determination of Natural
Gas Leakage via Gas Chromatography of Drill Core Samples",
Journal of Gas Chromatography, 5, p. 592 (November, 1967).
65
-------
12, Andrews, G. F., Thomas, J. F., Pearson, E. A.,
"Determination of Volatile Acids by Gas Chromatography",
Hater and Sewage Works, 4, (1964).
13. Mahadevan, V., Stenroos, L., "Quantitative Analysis of
Volatile Fatty Acids in Aqueous Solution by Gas Chroma-
tography", Anal. Chem., 39, No. 13, p. 1652 (November,
1967).
14. McNair, H.M., Bonelli, E. J., Basic Gas Chromatography,
Consolidated Printers, Berkeley, p. 67 (1969).
15. Thompson, B., "GC Column Conditioning" Technical Bulletin
801A, Beckman.
16. "Chromatography/Lipids", Catalog 1970, Supelco, p. 7.
17. Leonardos, G. , Kendall, D., Barnard, N., "Odor
Threshold Determinations of 5«3 Odorant Chemicals",
Journal of the Air Pollution Control Association,
19, No. 2, p. 91 (February, 1969).
18. Stern, A.C., Air Pollution, Academic Press, New York, p.
509, (1962).
19. Benforado, D.M., Rotella, W.J., Horton, D. L., "Develop-
ment of an Odor Panel for Evaluation of Odor Control
Equipment", Journal of the Air Pollution Control Associa-
tion, 19, No. 2, p. 101 (February, 1969).
20. Daniels, F., Alberty, R.A., Physical Chemistry, John Wily
and Sons, New York, p. 327, (1966).
21. Turk, A., "Industrial Odor Control and Its Problems",
Chem. Eng. , 76, No. 24, p. 70 (November, 1969).
22. Yocom, J.E., Duffee, R.A. , "Controlling Industrial Odors".
Chem. Eng. , 77, No. 13, p. 160 (June, 1970).
23. Culp, G., Slechta, A., "Plant Scale Reactivation and Reuse
of Carbon in Wastewater Reclamation", Water and Sewage
Works, 113, No. 11, p. 425 (November, 1966).
66
-------
APPENDIX A
.kener Onpr
Creek Plant
Sludge^Thickener Operational Instructions for the Coldwater
The operation of the sludge thickener during the project
is summarized by the following:
1. "Depth of Blanket" (D.O.B.) shall be interpreted to
mean the measured distance from the water surface
of the thickener down to the point that the blanket-
finder light goes out. This reading will provide
the basis for routine operations which are very
slow moving trends in most cases.
2. The No. 1 thickened sludge pump shall be operated
as the "lead" pump, twenty-four hours per day for
normal service, and No. 3 thickened sludge pump shall
be operated from twelve noon until twelve midnight
each day unless a blanket depth reading below 9 ft.
is indicated at which time this pump shall be shut
down. Until the first D.O.B. reading of 8 ft. is
recorded, this second level pump is to remain off.
If the first 8 ft. D.O.B. reading falls into the
normal twelve noon to twelve midnight operating
period for No. 3 thickened sludge pump, it shall be
turned on to complete the pump schedule and def-
initely be turned on the following day.
3. The dilution water pump shall be operated each day
from 8 a.m. until 4 p.m. (approximately) unless special
orders are issued cancelling this operation for the
day due to weather conditions, or other reasons.
4. Thickener bypassing, thereby pumping raw sludge
directly to the primary digesters, requires special
considerations and interpretations. Whenever the
indicated raw sludge density reading doubles from
the normal trend and establishes that trend for one
(1) hour, the raw sludge shall be bypassed directly
to the digesters. During the intervening bypass
period only No. 3 thickened sludge pump shall be
used until the first thickened sludge sample indi-
cates dilute (watery) sludge or the raw sludge flow is
returned to the thickener when a drop in density
to 150 per cent of the original normal rate is noted.
This method of control is necessary to allow for
drifting sludge density meter trends.
67
-------
5. If dilute sludge is noted in a sample of thickened
sludge while raw sludge is being routed direct to the
primary digesters for an extended period, the following
actions shall be taken.
A. The thickener sweep mechanism is to be shut
off.
B. The thickened sludge pump (No. 3) is to be
shut off.
C. The daily dilution water pumping schedule is
to be maintained.
D. Once daily on the4-p.m. to 12 a.m. shift the
thickener drain valve shall be opened for 2-3
min.
Steps C and D shall be completed daily until the
thickener is restored to normal service. When
switching raw sludge feedback to the thickener, the
normal pumping schedule with thickened sludge pumps
is to be resumed.
6. The key to overall control will be the D.O.B. reading.
The lowest D.O.B. trends occur Sunday, Monday, and
Tuesday with much higher levels of D.O.B. occurring
toward the latter part of the week which is in part
due to a heavier waste activated sludge disposal
program.
«U& GOVERNMENT HUNTING OFFICE:1974 546-316/257 1-3
68
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1: Report No.
W
7' ="* ?.-
Odors Emitted from Raw and Digested Sewage Sludge
Bernard A. Rains, Mario j. DePrimo & I. L. Groseclose
Metropolitan St. Louis Sewer District
10 East Grand Avenue
St. Louis, Missouri 63U7
5. Report Datt
V"; . .
8. "P,iformis ^
• Report Ho*
11010EZQ.
Grant WPD123-01-68
Typf if Reps, * ajtd
Period Covered
Protection Agency
Program Element 1BB033
ROAP 21-ASD
EPA-670/3-73-098
Odors emitted during thickening of raw and secondary sludge have been responsible for
adverse criticism at many sewage treatment plants . This study was undertaken to
identify typical odor causing substances and evaluate selected conventional methods for
controlling or eliminating these substances. A styrofoam dome covering a sludge
thickener was utilized to control atmospheric conditions and concentrate odors.
Field collected vapor samples were analyzed using gas chromatography techniques.
Analyses using both polar and nonpolar column material indicated that the major odor
eauaing compounds were mercaptans and. nines. Other compounds which were minor contri-
butors to odor were aldehydes, alcohols, and organic acids.
Odor control methods selected for study included air dilution, activated carbon
adsorption, and chlorine oxidation. Air dilution using cyclic operation of an exhaust
fan was found to be an effective means of odor control when outside atmospheric condi-
tions were conducive to odor dissipation. Passing vapors through activated carbon
filters was not completely effective in odor control since a detectible residual odor
remained. A 1.5 mg/1 solution of chlorine was effective in removing all odors from
vapor samples bubbled through the solution.
17a. Descriptors
odor
odor abatement
17b. Identifiers
odor control
malodors
I7c. COWRR Field £ Gro-:p
sewage
sludge
sludge treatment
Q5D
From EPA
30,' Sec .rityC??
(fag*)
ffo. at
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 2O24O
Bernard A. Rains
Metropolitan St. Louis Sewer District
------- |