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ASTM Selected Technical Papers
Oil Dispersants: New Ecological Approaches
By
LM Flaherty
LM Flaherty
1
U.S. Environmental Protection Agency
(retired),
10332 Democracy Lane, Potomac, MD
;
symposium chairman and editor
Search for other works by this author on:
ISBN-10:
0-8031-1194-0
ISBN:
978-0-8031-1194-3
No. of Pages:
308
Publisher:
ASTM International
Publication date:
1989

A small-scale model sewer was constructed to determine the behavior of dispersed and nondispersed fuel flushed or spilled into sewers. The system included a headbox containing a concrete pad with a drain in the middle. The drain fed into a sewer pipe. Six vapor sensors were positioned in ports or simulated manholes at intervals along the pipe length. The vapor sensors were connected to a computer which generated a continuous data record of vapor concentrations at each port. Liquid samples were also taken at different intervals under the vapor sensor ports.

Vapors in a sewer system have two distinct origins: the first is vapor evaporating from the liquid fuel as it is transported with the water and the remainder is vapor that formed upstream and is in the process of moving downstream at a slower rate than the underlying liquid. The latter movement is caused by the pumping action of the water flow, but is slower than the liquid flow as a result of the drag of the walls and the low gas-to-liquid friction coefficient. Gasoline, whether treated with dispersant or not, produces two sharply different vapor peaks at the sensor ports because it evaporates rapidly upon entering the sewer and thus produces a slowly moving vapor cloud. Diesel fuel does not evaporate as rapidly and produces only a single vapor peak at the ports.

The use of dispersants at the beginning of the sewer increases the volatilization rate of the smaller fuel molecules and thus increases the amount of vapor present in the sewer system. This occurs irrespective of the amount or brand of dispersant employed. When dispersants are applied, the vapor concentration and duration is increased at each subsequent port. An increasing amount of dispersant or dispersant/water mixture increases this effect. If dispersants are mixed with the fuel in a very vigorous manner the vapor concentration may not be increased in the first ports, but it will not be decreased and the concentrations are increased 5 min downstream. In no case is the vapor concentration at any port reduced by the use of dispersants.

The results from the small-scale model show that dispersants do not reduce the explosion risk of fuels in sewers. In fact, the use of dispersants will in most cases greatly increase the potential for explosions and their magnitude. Dispersants increase the rate of volatilization of small fuel molecules and increase the total amount of those released. This is consistent with the results obtained by other authors who have conducted static experiments of similar nature.

1.
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,
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, “
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,” in
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,
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,
L. T.
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, and
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American Society for Testing and Materials
,
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,
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2.
Kaufmann
,
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, “
Treatment of Oil Spill Fire Hazards with Chemical Dispersants: A Case History
,” in
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, ASTM STP 840,
Allen
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, Ed.,
American Society for Testing and Materials
,
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,
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, pp. 166–174.
3.
Breslin
,
M. K.
and
Royer
,
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, “
Use of Selected Sorbents and an Aqueous Film Forming Foam on Floating Hazardous Materials
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U.S. Environmental Protection Agency
, Cincinnati,
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4.
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,
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,
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,
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,
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,
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,
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, and
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,
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,
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,
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,
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6.
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and
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U.S. Environmental Protection Agency
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,
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,” in
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,
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,
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,
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8.
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,
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,
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,
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,
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, and
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,
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, “
Foam Agent to Mitigate the Vapors from Hazardous Material Spills
,” in
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,
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,
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,
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, pp. 366–372.
9.
Halman
,
R.
,
Lockwood
,
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, and
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,
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, “
Development of a Person-Portable Analytical System for Environmental Emergencies
,” Manuscript Report EE-52,
Environment Canada
, Ottawa,
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Wilson
,
M. P.
, et al
, “
Assessment of Treated Versus Untreated Oil Spills: Final Technical Report
,” Report DOE/EV/04047-T3,
Department of Energy
, Washington, DC,
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.
11.
Bowler
,
B.
,
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,
A.
,
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,
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, and
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,
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, “
Laboratory Studies on the Effect of Oil Dispersant on Evaporation and Dissolution
,” SINTEF Report,
Center for Industrial Research
, Trondheim, Norway,
1985
.
12.
McAuliffe
,
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, “
Dispersal and Alteration of Oil Discharged on a Water Surface
,” in
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,
Pergamon Press
,
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,
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, pp. 19–35.
13.
Johnson
,
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,
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,
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, and
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,
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, “
Physical and Chemical Behaviour of Small Crude Oil Slicks on the Ocean
,” in
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, ASTM STP 659,
McCarthy
,
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,
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, and
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, Eds.,
American Society for Testing and Materials
,
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,
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, pp. 141–158.
14.
Harrison
,
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,
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,
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,
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,
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, and
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,
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, “
Crude Oil Spills: Disappearance of Aromatic and Aliphatic Components from Small Sea-Surface Slicks
,”
Environmental Science and Technology
 0013-936X, Vol.
9
,
1975
, pp. 231–234.
15.
Mackay
,
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,
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,
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, and
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A Study of the Mechanism of Chemical Dispersion of Oil Spills
,” Manuscript Report EE-76,
Environment Canada
, Ottawa,
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.
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