WATER POLLUTION CONTROL RESEARCH SERIES • ORD-3
Chemical Treatment of Oil Slicks
U.S. DEPARTMENT OF THE INTERIOR • FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
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CHEMICAL TREATMENT OF
OIL SLICKS
A STATUS REPORT
ON THE USE OF CHEMICALS AND OTHER
MATERIALS TO TREAT OIL SPILLED ON WATER
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
DEPARTMENT OF THE INTERIOR
BY
WATER QUALITY LABORATORY
NORTHEAST REGION
EDISON, NEW JERSEY 08817
MAHCH 1969
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ABSTRACT
The effectiveness and potential pollutional effects of chemicals and other
materials used to disperse, sink,.burn or otherwise dissipate oil slicks
are discussed.
Agents considered are classed as; dispersants, floating sorbents, sinking
agents, gelling agents and burning agents.
Since many dispersants are presently available, much experience has
been gained with the use of dispersants. However, dispersants should
not be used indiscriminately, they may have deleterious effects on the
ecology. It is necessary to determine the toxicity and the effectiveness
of dispersants viz-a-viz the same characteristics of the oil -without
dispersants. Practical experience', with gelling burning, floating and
sinking agents is limited;"
Some of the many commercial' products' and".natural materials used in
connection with recent large-Soil spills'-'are reported.
KEY WORDS: Oil spills, oil spills-chemical treatment, dispersants,
detergents, sorbents, floating sorbents, burning agents,
sinking agents, gelling agents, dispersant toxicity,
dispersant effectiveness chemical use, effects.
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CONTENTS
I. Introduction 11
II. Summary 1
III. Sections
Dispersants 5
Floating Sorbents 10
Sinking Agents 14
Gelling Agents 17
Burning Agents 18
ill
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INTRODUCTION
The disastrous effects of significant oil spills into the water environ-
ment, together with required remedial measures, are described in "Gil
Pollution: A Report to the Presidentt" submitted early in 1968. Chemical
compounds are intended to assist in the control of oil on the water and
facilitate cleanup operation. Basically, chemicals are employed to dis-
perse, gel, sink, absorb, and facilitate the burning of oil. Present
knowledge has resulted primarily from experience with the major spills
from the tankers TORREY CANYON and OCEAN EAGLE and the offshore oil
platform at Santa Barbara, California. In addition, the FWPCA is gaining
valuable experience through giving technical assistance on actual spill
incidents and is conducting broad research and development programs
relating to the cleanup and control of oil in the water environment.
With the exceptidn of gelling agents, chemicals have been used during
the three major incidents, singly and in combination, with varying
results. Each major incident differed as to causes and immediate control
of the sources of oil, the type and use of the water environment, and
the nature and proximity of the shoreface. The resulting damage has
been waterfowl fatalities, deposition of oil upon recreational beaches,
and adverse effects to marine life.
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SUMMARY
This report provides a statement by the Research Program of the FWPCA
on the use of various chemicals to treat oil on water. Basically,
methods employed are designed to disperse, absorb, sink, gel, and
facilitate burning of oil on the water surface and affected shorelines.
A number of factors must be carefully evaluated in the use of chemicals
most important of which are toxicity and overall effects upon the water
environment, effectiveness of the methods utilized, and cost of obtain-
ing and applying chemicals together with recovery and disposal operations.
Dispersants theoretically serve to increase the surface area of an oil
slick and disperse oil globules throughout the larger volume of water
thereby aiding in accelerated degradation of oils by microbiological
means. The chemical dispersants do not themselves destroy oil. They vary
considerably in toxicity, effectiveness and ability to stabilize the oil
after extended periods of time. Technology for proper application of
dispersants over large oil slicks with necessary mixing is currently
lacking. Use appears far more critical in harbor and estuary areas and
in proximity to shore. Particular care must be exercised where water supply
might be affected. The desirability of employing dispersants in the open
sea remains doubtful although their use here is potentially more promising
pending additional field data. After widespread dispersant use, reports
led to the conclusion that dispersants on the dispersant-oil mixture cause
much more damage to aquatic life than oil alone. For beaches, they actually
compound the problem by adding to the amount of pollutants present, by
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causing the oil to penetrate more deeply into the sand, and by disturbing
the sand's compactness, so as to increase beach erosion through tidal and
wave action.
Floating absorbents include a wide range of materials with oil-attracting
and water-repelling characteristics. Absorbents have unique advantages
over other methods of oil cleanup, such as limiting the rate of slick
spreading or facilitating cleanup, but it also has a number of disadvan-
tages including delivery and application of the material, and collection
and disposal of the oil-absorbent mass. Straw is extensively used as an
absorbent because of availability, cheapness and accepted effectiveness;
large investment in equipment and manual labor for removal of oil soaked
straw is however required. Natural products or those modified by heat and
chemical treatment are currently used as absorbents. An additional group
of absorbent products, which hold potential promise, are those derived
from the synthetic or plastic manufacturing field; of these, polyurethane
and polypropylene are in greatest use. Considerable mixing or interac-
tion between the oil and the absorbent is very desirable for maximum
uptake of oil. Absorbent application and their overall use become
increasingly complex with the larger oil spills. Collection and disposal
of the oily mass poses greater problems than disposal of oil-water
emulsions due to the relatively large bulk and due to the lack of disposal
techniques that can handle the conglomerate.
Sinking agents properly applied onto an oil slick adhere to the oil, and
there is subsequent absorption and sinking of the oily mass. Sinking
absorbents should be evenly mixed with the slick and allowed time to react
before the mass eventually sinks. For optimum effectiveness, there should
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also be little or no tendency for release of the oils back to the water
environment. Care should be exercised in its use as the oil mass can form
a layer 'or "blanket" on the bottom causing adverse effects on fixed shell-
fish beds and bottom feeding organisms. The only large-scale use of
sinkants was that made by the French following the TORREY CANYON. Opinion
is still divided as to efficency, cost, application, and possible environ-
mental effects. It appears the utilization of sinking agents would be
most advantageous in deeper ocean waters outside the heavier fishing zones
minimum
and where there will be /adverse effects to productive biological life in
the coastal zones.
Gelling agents applied over the surface or periphery of an oil slick show
promise as another approach for containing and cleaning up oil spills.
The gelled mass would still require removal from the water surface perhaps
with specialized equipment developed for that purpose. Further development
is necessary for this class of chemicals.
Burning agents offer an attractive and inexpensive means of disposing of
large amounts of oil over the water surface. This course of action is
inadvisable except in situations where the oil is sufficiently distant
from the shoreline or other property subject to fire damage. Past attempts
to burn oil have been largely unsuccessful due to the fact that the light
ends of the oil usually are no longer present, raising the flame temperature,
plus the ability of the water to remove the heat faster than it can be
created. Because of the potential value of this method, however, further
consideration should be given for improving and refining these procedures.
In considering the use of chemicals with oil spills, a number of factors
muse be carefully borne in mind. Of prime importance is the effect of
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the chemical or oil-chemical mixture on the water environment. The intro-
cution of toxic chemicals in the water or on the shoreface can destroy the
delicate balance of aquatic ecology and result in long-lasting damage or
destruction of valuable species intended to be protected by the removal of
the oil. The ability of the chemicals to accomplish the assigned task is
a critical factor. The type of oil involved, the physical and chemical
nature of the water body, and the particular products used will relate to
the effectiveness of the method. In major incidents involving spills of
oil, the cost of obtaining and applying chemicals may range into millions
of dollars.
The purpose of oil removal is not to eliminate its visibility but to mini-
mize its effects upon water shore and near shore resources. The most
effective means for eliminating visible oil could destroy the very resources
intended to be protected; conversely, the most visible and tedious means
for removal can be the most effective in resource protection. The objective
of adequate oil pollution control is to minimize the removal and minimize
the short and long range adverse effect.
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DISPERSANTS
Scores of products are sold in this country for the purpose of emulsify-
ing oils. Many have been developed for such us is as clearing residual
oil from cargo tanks before loading of fresh cargo. Of these, at least
70 have been claimed useful for dispersing oil from the surface of water.
These products are known by a variety of names: emulsifiers, detergents,
degreasers, dispersants, etc. For consistency, they will be referred to
as dispersants since this term describes what they are intended to
accomplish - the dispersion of oil from the surface into and throughout
the body of water.
The primary components in most dispersants are surfactants, solvents, and
stabilizers. Surfactants, by their affinity for both oil and water, alter
the interaction between oil and water so the oil tends to spread and can
be more easily dispersed into small globules - or what is commonly called
an emulsion. Soap does the same thing to oil on our hands, allowing it
to b.e emulsified or dispersed and washed away in water.
Solvents enable the active agent or surfactant, to mix with and penetrate
into the oil slick and thusly form the emulsion. The solvent usually
comprises the bulk of the dispersant product and may range from petroleum
solvents such as kerosene to water solvents. Petroleum based and
chlorinated hydrocarbon solvents represent the most toxic component in
the dispersant product but also dissipate rapidly in the\ater environment.
Stabilizers,which are the third major component in most dispersants,
fix the emulation once it is formed.
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The use of dispersants in oil pollution incidents is intended to separate
the slick into miniscule particles and thus provide a means of accelerat-
ing the rate of natural degradation of oil. We know that oil is degraded
naturally at sea at a rate depending upon the surface area of the oil
available to the microorganism populations. Increasing the surface area
of the oil by dispersion is thought to accelerate this biological degra-
dation.
Dispersants have been used for a number of years, for dispersing small
oil slicks in several harbors in this country and abroad. Because of the
small quantities involved, the environmental effects were minimal and the
complaints limited. Few alternatives exist.for handling oil spills and
dispersants are easily obtained, transported and applied. They further-
more offer visible evidence of "doing something" about pollution incidents.
Their first major test came during the TORREY CANYON incident where 15,000
tons of dispersants were used to treat 75,000 tons of oil. Two-thirds of
this amount was used for cleaning oil from contaminated shores and resulted
in severe adverse effects on the aquatic life. The areas of the shore
where dispersants were not used, but heavily polluted with oil alone,
showed very minor damage according to J. E. Smith, Director of the
Plymouth Laboratory of the Marine Biological Association of the United
Kingdom, who studied the biological effects of the TORREY CANYON spill.
These observations led to the conclusion that dispersants cause much more
damage to aquatic life than oil alone.
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The dispersants used during the TORREY CANYON incident were mostly solvent-
based and highly toxic, killing marine organisms at concentrations around
10 parts per million.
The biological damage during the TORREY CANYON appeared to be limited to
the shore areas. In the open sea where they were also used, there were
no detectable effects on. marine life. Officials from the United Kingdom
took samples by trawling directly beneath slicks treated with emulsifiers
and observed no deaths and no tainting of the flavor of commercial species.
Procedures for this type of sampling are not notably precise, however.
Current information indicates that dispersants vary considerably in
toxicity. Various reports state that dispersants used during the TORREY
CANYON incident were highly toxic. Since then, other less toxic dis-
persants have been developed. Fifty percent of marine test fish are
killed within 24 hours by exposure to concentrations as low as 4 parts per
million of one product, and as high as 10,000 parts per million of another.
Moreover, the combination of oil and dispersant may conceivably increase
the toxicity of either the oil, the dispersant chemical, or both. The
possibility of this "synergistic" action must be carefully examined before
wholesale and widespread use of dispersants is permitted. Dispersing the
oil (which is toxic) may also compound the damage.
But toxicity is not the only consideration in the use of dispersants. Of
equal significance is their effectiveness. Experience at San Juan, Puerto
Rico, and field tests conducted by research personnel at Edison, N.Y.,
indicate that they are generally ineffective for cleaning oil from beach
sand of the ty.pe found along our east coast. They actually compound the
problem by adding to the amount of pollutants present and by causing the
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oil to prenetrate more deeply Into the sand. The "TORREY CANYON Pollution
and Marine Life" report also noted that "quicksand," occurred as the result
of using these materials, resulting in beach erosion from tidal and wave
action.
Evaluation of the effectiveness of dispersants on water is much more
difficult in cases of accidental spills. Lack of adequate methods for
measuring the amount of oil on water and the rate of natural dispersion
make precise evaluation difficult. Their effectiveness during the TORREY
CANYON is still being debated. Subsequent incidents which are claimed to
have demonstrated their effectiveness have been at remote locations and
without'impartial, qualified observers. Application methods of disper-
sants and subsequent agitation, which are critical for effective performance,
have not always been optimal.
The cost of dispersants ranges from two to four dollars per gallon.
Using recommended doses, the cost of chemicals for dispersing a relatively
small 500 barrel spill would be about $20,000. The cost for chemicals
used on the TORREY CANYON oil exceeded $5 million. Adequate technology
for their massive application to major spills is lacking. Slicks from
large spills spread in micro-thin layers over hundreds of square miles .
Efficient use of dispersants to treat a complete slick would require
proper density application and agitation of large areas of the sea surface.
Sbch methods and the required scale of equipment have not been developed.
Thus, the desirability of using dispersants on the open sea remains
unresolved. The FWPCA is conducting research to help provide the
answers. As an initial step an interim standard procedure has been
developed for measuring 'Che comparative acute tbxicity of dispersants
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to selected aquatic organisms. This will allow the assessment of
relative toxicity among equally effective dispersants. We are continu-
ing Nto refine this procedure and refine our capability for predicting
the effect of dispersants on the water and near shore environment. Our
research personnel are also developing a standard tes't for measuring the
effectiveness of dispersants, so they may be rated on. a common basis.
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DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
POLICY ON THE USE OF
CHEMICALS TO TREAT FLOATING OILS
1. Chemicals should not be used to emulsify, disperse, solubillze, or
precipitate oil whenever the'protection or preservation of (a) fresh
water supply sources, (b) major shellfish or fin fish nurseries,
harvesting grounds or passage areas, or (c) beaches is a prime concern.
Such chemicals should only be used in those surface water areas and
under those circumstances where preservation and protection of water
related natural resources is judged not to be the highest priority or
where a choice as to resource preservation may make the use of such
materials a necessary alternative.
2. Examples of areas and circumstances where the use of such chemicals
might be acceptable are:
a. where fire or safety hazards are presented by the spill of a
petroleiw product;
b, where large numbers of waterfowl may perish because of the
proximity of floating oil;
c. under certain conditions, as a "polishing" or final clean-up of
light slicks of oil following mechanical removal of floating oils.
3. Chemicals that emulsify, disperse, solubilize or precipitate oil
should be used only unrler the immediate supervision of the Federal
Water Pollution Control Administration except where it is judged
that fire or safety hazards require the immediate application of such
chemicals.
4. When chemical compounds are used in connection with oil clean-up* only
those compounds exhibiting minimum toxicity toward the aquatic flora
and fauna should be used. The Federal Water Pollution Control
Administration 1s now developing and will soon issue a standard
procedure for determining the toxicity of such chemicals.
5. Materials which aid in the collection of floating oils such as sorbents,
gel1 ants and viscosity control additives are considered to be generally
acceptable providing that these materials do not in themselves or in
combination with the oil increase the pollution hazard.
6. Research and development to improve chemicals which emulsify, disperse*
solubillze or precipitate oil 1s encouraged. Whenever it is demon-
strated to the complete satisfaction of the Federal Water Pollution
Control Administration, that such a chemical, by itself and in combina-
tion with oil 1s non-toxic its use may be approved in the areas where
the protection or preservation of a) fresh water supply sources, or
b) major shellfish or fin fish nurseries, harvesting grounds or passage
areas 1s a prime concern.
July 5, 1968
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FLOATING SORBENTS
Absorbent is a broad term defining in this report a type of material
used in oil pollution control and clean-up. Most absorbents are de-
scribed as oil-attracting (oleophilic) and water-repelling (hydrophobia).
The use of absorbents requires placement in the oil slick, attraction
of the oil to this material, and subsequent removal and disposal of the
resulting oily materials. Such materials include straw, hay, sawdust,
rope, sisal, tree bark, peat moss, perlite, vermiculite, talc, pumice,
various clays, sea weed, kelp, chrome leather wastes, rock wool sheets,
glass wool, rayon floss, polymer beads and copolymers, polyurethane and
polypropylene sheets, fibers and foam, rubber or latex, and cotton or
textile wastes. Any of the above materials may also be specially
treated in one or more ways to improve its absorbtive properties and
handling characteristics. Furthermore, these materials may be used
as integrallpart of oil recovery-pickup devices, booming systems, beach
clean-up methods and other.
Absorbents are advantageous in that they generally do not add materials
in solution and thereby contribute to the existing problem. They are
also capable of picking up oils in large ratio to the amount of absorbent
usedo Major difficulties, particularly for large-scale spills, are in
calculating and delivering sufficient absorbent in the proper form at
the proper place and time, applying the materials over the water body,
adequately collecting and transporting the oil-soaked mass to shore,
recovering the oil and securing ultimate disposal of the mass. Fire
hazard may also be increased by use of many of these materials in
confined places if ignition sources are present.
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Many absorbents have performed quite well, particularly in small-scale
spills, and may have high potential for moderate and even large-scale
spills. Toxicity is far less a problem than with dispersants since
the absorbent material generally remains in solid state; however,
certain absorbent products may need further evaluation in this respect.
Comparison of the relative effectiveness between various products
together with relative cost is presently lacking. Evaluation must be
conducted both within the laboratory and under realistic field conditions.
The FWPCA Research facility has initiated limited studies in this direction.
Straw is widely used as an oil absorbent because of ready availability,
cheapness and accepted effectiveness. It can be distributed manually
or mechanically with or without shredding. Straw is most effective
when used on shore or close to shore. Although straw can be effective
in clean-up it must be adequately worked into the oil and its retrieval
and disposal is a dirty, slow and tedious job, requiring equipment and
considerable manual labor. In certain areas, soaked straw may not be
burned because of air pollution codes and may not be buried because of
potential groundwater pollution.
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Far less use has been made of other absorbents compared to straw. Con-
cerning natural absorbents, sea weed, kelp and indigenous grasses have
been capable of absorbing apprecialble oil in the TORREY CANYON, OCEAN
EAGLE and Santa Barbara incidents. Production of powdered pine bark
has been initiated by a Swedish pulp and papei mill. It is reported
that two pounds of bark will absorb about one gallon of oil with in-
dicated costs around |5 per 33 pound bag of powdered bark. Pre-
liminary data received from Sweden on peat moss show about two pounds
of absorbent required per gallon of oil.
Natural products can be heated or chemically treated to provide modified
materials for oil pollution control. Perlite, a naturally occurring
volcanic rock receiving subsequent pulverization and thermal expansion,
has received favorable reports in aiding oil recovery on San Juan beaches;
however, its action was less certain in Santa Barbara and in FWPCA
research studies conducted on New Jersey beaches in 1968. Cost is
approximately $75.00 per 100 cubic feet of absorbent. Vermiculite after
treatment to render it expandable and hydrophobic has received mixed
reports in its ability to absorb oil. Certain vermiculite products
are reported to rapidly absorb floating oils whereas others do not have
the required affinity.
Absorbents derived from synthetics or plastics represent an additional
group of products with potential promise. These materials are generally
high-molecular weight polymers or polyethylene, polystyrene, polypropylene
and polyurethane. These agents may be applied as a light foam or plastic
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network by spraying, as a solid-state in. the form of pillows, sausage
shapes, or otherwise shredded and distributed over the oil slick. It
is reported in theoretical terms that polyurethane foam can ultimately
absorb over 90 percent of its own volume of oil or 100 times its own
weight. Polypropylene is also reported as abjorbing six times its weight
in oil with one cubic yard capable of retaining 100 pounds of oil. These
data represent extremely low cost to clean-up large volumes of oil but
such figures likely reflect laboratory conditions which can be far
different from those experienced in the field. Difficulties have been
experienced with absorbing heavy and weathered oils. Effectiveness
appears dependent upon prolonged time interaction, temperature, and other
factors which must be better understood before many of the observed
limitations can be overcome.
No absorbent appears truly effective when merely distributed over the
oil slick. Agitation and increased interaction between the oil and the
absorbent is necessary whether induced by natural wind, wave or tidal
forces or by mechanical means. Absorbent application becomes increasingly
complex with the larger oil spills. In massive oil spills, the logistics
and equipment required to acquire and properly apply sufficient amounts
of absorbents and the consequent collection and disposal of the resultant
oily mass, become enormous due to the sheer bulk of the conglomerate and
the lack of adequate methods for handling and disposal.
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SINKING AGENTS
Sinking agents are granular solids of high density and generally of fine
structure. When applied over the surface of a slick, they adhere to the
oil, absorb it and ultimately sink. Typical oil-sinking agents include
sand, brick dust, fly ash, slaked lime, stucco, cement, china dust, omya
clay, vlocanic ash, chalk, crushed stone, coal dust and specially-produced
materials such as carbonized-siliconized-waxed sands and fly ash.
Sinking agents can be efficiently employed on thick heavy or weathered oil
slicks. If the oil is widely dispersed on the surface in disassociated
masses, quantities of materials required are prohibitive. It is doubtful
that sinkants may be profitably used with thin films and light crudes.
The absorbent must be evenly mixed with the slick and have proper time
for interaction before the ensuing mass eventually sinks. Furthermore,
bonding of the agent with the oil must be nearly permanent; or else
there will be eventual release of the entrapped and sunken oils back
to the water environment.
The single known large-scale application of sinking agents was undertaken
by the French during the TOKREY CANYON incident. Some 3,000 tons of
calcium carbonate with about one percent of sodium stearate added were
reportedly used to treat and sink about 20,000 tons of oil found in
the Bay of Biscay and originating from the TORREY CANYON. Although good
scientific data are generally lacking particularly as to the precise
amount of oil acutally treated, the oils were reported sunk in 60-70
fathoms and coastal pollution was minimized. The French success was
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attributed to good spreading and mixing of the chalk into the oil body
and the high density of the weathered slick, thereby requiring considerably
less absorbent as compared to fresher oils. Subsequent reports state
that 14 months after the incident no sign of oil was found over the water
surface. On the basis of French 'experiences above, oil-sinking agents
have subsequently become more attractive and promising.
Opinions on the use of oil sinkants still remain divided as to efficiency,
cost, application and detrimental environmental effects. Advantages of
this type of treatment are that it tends to confine the spilled oil and
the concommitant damage to a fixed place on the sea and probably minimizes
toxicity to free floating plants and animals. Opposition to these agents
are ascribed to the potential damage to sea bottom life, the problems
associated with transporting and properly applying large amounts of the
agents to the oil slicks plus the possibility of the oil resurfacing
following biological degradation of the conglomerate.
Economics of this treatment method varies widely because practically all
data have been obtained from laboratory testing rather than from application
under field conditions. Early Department of Interior studies suggest three
pounds of carbonized sand are required to sink one pound of oil whereas
other studies indicate ratios of one or less of sinker weight to oil weight,
depending upon density of oil slick and other factors. Large-scale
application generally envisions spraying a slurry of sand or other mixture
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over the slick from a large vessel, hopper dredge, or equivalent. The
cost of sinking agents is generally in the range of §20 to $80 per ton,
depending upon quantity purchased, and location and type of material
required.
The use of sinking agents would be most advantageous in deeper ocean
waters outside the heavy-fishing zones. If resurfacing of the oils
does occur, it should be gradual and far less objectionable in the
event weathered oils were washed ashore at a later time.
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GELLING AGENTS.
The use of special gelling or congealing materials applied over the sur-
face or periphery of an oil slick is another approach for containing and
cleaning up oil spills. The gelling concept is also in the process of
development for stabilizing liquid cargo aboard a stranded or heavily-
damaged vessel at sea.
One patented product when applied in spray form, is reported to form a
stiff gel with oil on water. When placed around the perimeter of an oil
slick, the gel is said to form an effective chemical boom which prevents
the oil from further spreading. The oil contained within the inner circle
may be removed by mechanical means or the total slick may be gelled to
facilitate removal. The developers also claimed that the oils recovered in
this manner may be profitably reclaimed. For example, the gelled mass
may be mixed with fuel oil and burned as replacement bunker fuel.
Possible toxicity of this class of chemical is unknown but under current
evaluation. Data from the manufacturer indicate approximately one part
chemical is necessary per part of oil to be gelled, thereby givijag an esti-
mated cost of about $1.50 per gallon oil treated. However, these costs
very likely reflect laboratory testing and assuredly would be lower then
for field application.
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BURNING AGENTS
The concept of setting afire oils which have spilled and spread over the
surface of a-water body is potentially attractive principally because
this appears to offer an inexpensive means of disposing of the problem.
Past attempts to burn oils upon the sea have been almost completely unsuc-
cessful, especially in the case of the TOEREY CANYON. There, addition of
thousands of gallons of aviation fuel, Napalm and sodium chlorate, to-
gether with aerial bombing of the vessel, failed to produce sustained
burning. Spilled oil may possibly be burned by using catalytic or com-
bustible agents or inducing "wicking" action between the oil and water.
The "wick" theory, assumes that capillary action is induced in the oil
slick and a portion of the oil is drawn up to air (oxygen) interface to
promote burning. Concurrently, the surface oil is partially insulated
from the cooling effect of the sea water underneath. Wood, debris and
flotsam enmeshed with the spilled oil apparently also insulates this
layer from the colder water body and sustains burning. Since freshly
spilled crude oil contains a relatively high proportion of volatile
components, its ignition is more feasible than for weathered crude where
the volatiles have already evaporated. Besides potential materials such
as felting and asbestos-like agents, two commercial products are known
which promote the burning of oils on water. One employs both a liquid
and powder. The other is reported to consist of a specially-treated
fine silica which increases capillary action aiding in sustained and
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controlled burning. Neither product, so far as is known, has been applied
in large-scale, and therefore factors of logistics, application and amount
of residue are unknown.
Controlling the burning oil mass, ensuing air pollution and disposal of
residue would appear to preclude the use of this course of action except
in those situations where the oil mass is sufficiently distant from the
•shore face and off shore facilities. The possible loss of the vessel or
drill platform that is the source of the spill, is another factor which
must be recognized. Because of the potential value of burning, additional
and refined procedures should be further investigated.
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