Environmental Engineering Reference
In-Depth Information
consumers may suffer from eating contaminated
fish and shellfish (ITOPF
2013
).
contained in the MOCB can be collected and re-
cycled (Wang et al.
2014
).
Skimmers
Oil skimmers are devices that separate oil float-
ing on water. Skimmers are of three types—weir,
oleophilic, and suction skimmers. Weir skimmers
allow oil floating on water to spill over the weir,
which can be then entrapped in a well. They tend
to get jammed and clogged by floating debris and
need to be monitored. Oleophilic skimmers use
mop, belts, drums, and discs made of oleophilic
material to attract oil, which then can be scrapped
off or squeezed out into a recovery tank for fur-
ther processing. Oleophilic skimmers are effec-
tive against oil layers of varying thickness (Broje
and Keller
2006
). Suction skimmer is quite simi-
lar to the household vacuum cleaner and operates
on the same principle: it sucks the oil floating on
water, which is then pumped into storage tanks.
Suction skimmers often suffer from clogging by
debris and work best in scenarios where oil has
been already contained against a boom.
9.4
Approaches for Cleanup of Oil
Spills
Containment and recovery of oil are major con-
cerns in the event of an oil spill. Containment
aims at minimizing the area of oil spill, thus cur-
tailing its adverse effects on lives of animals and
plants, economics of surrounding area, and en-
vironment. Containment is the preliminary step
that allows recovery or dispersal of oil at later
stages. The following are the approaches for
cleanup of oil spills.
9.4.1
Mechanical Approaches
Careful selection and proper use of equipment
for combating oil spill is the key to successful oil
spill cleanup. Booms, skimmers, and varieties of
sorbents are utilized for such cleanup operations,
which are often used in conjunction with one an-
other. Type of oil spilled, weather conditions, and
topography of the surrounding area need to be
considered while choosing the method of cleanup
(EPA
1999c
).
Sorbents
Natural and synthetic sorbents are used to recover
oil. Sorbents are materials that tend to absorb or
adsorb liquids. Peat, corn cobs, hay, and saw dust
are some examples of natural organic sorbents,
which tend to absorb 3-15 times their weight in
oil. These are relatively inexpensive and readily
available. They tend to absorb oil as well as water
causing them to sink; moreover, they tend to be
loose, hence they need to be packaged for their
easy disposal (EPA
1999c
).
Inorganic natural sorbents include clay, glass,
vermiculite, volcanic ash, and wool. They absorb
4-20 times their weight in oil and, like natural
organic sorbents, are relatively inexpensive and
readily available. Synthetic sorbents like poly-
urethane, nylon, and polyethylene can absorb 70
times their weight in oil and can be cleaned and
reused several times. Factors like rate of absorp-
tion, ease of application, and oil retention are
considered while choosing sorbents for oil spill
cleanup. Heavy oils have slower rate of absorp-
tion than light oils. Rate of absorption also var-
ies with the thickness of oil. Oil may be released
from the pores of sorbents while recovering from
Containment booms
Containment booms and skimmers are utilized to
block spreading of oil, concentrating and recov-
ering it. They are temporary floatation devices
used to contain oil spills. Containment booms are
most successful in gentle seas. In choppy waters,
booms are prone to failure due to environmen-
tal constraints. Oil entrapped in the area under
the containment boom can be scooped and col-
lected by ships, which then return to the shore
for its proper disposal and recycling (Castro et al.
2010
). Wang et al. made a superhydrophobic and
superoleophilic miniature oil containment boom
(MOCB) based on Cu
2
O film-coated stainless
steel (SS) mesh. MOCB has high efficiency in
excluding oil from the water surface (it repels
water absolutely), is reusable, and has good
water pressure and corrosion resistance. The oil
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