18 4 7 Pollution of Aquatic Systems: Pollution Through Eutrophication, Fecal Materials, and Oil Spills
present at the location during the time of the spill. The
method for the cleanup or remediation of oil spills may
be physical or biological.
- Physical methods of remediation
(a) Containment and recovery using booms and
skimmers
Containment and recovery are the earliest meth-
ods used to remediate and clean up an oil spill.
Long, floating plastic or rubber barriers or
booms are placed around the floating oil slick.
These act like fences, containing the oil and
preventing it from further spreading. In addi-
tion, booms may be used to divert and channel
oil slicks along desired paths, making them
easier to remove from the surface of the water.
Booms can be divided into several basic types.
They are not very effective in rough waters,
which flow over the barriers. Nonrigid or inflat-
able booms may be used; they are easy to clean
and store, and they perform well in rough seas.
They are, however, expensive, more complicated
to use, and may puncture and deflate easily.
After the oil is contained using booms, “skim-
mers” or boats that skim spilled oil from the water
surface are used. In calm waters, vacuum skim-
mers are used to suck the oil and put it into storage
tanks. In rough waters, floating disk and rope
skimmers can be passed through the oil. The
amount of oil recovered by booms and skimmers
is small, and if used for long periods, may hamper
the spread of oil, which helps its biodegradation.
(b) Absorption
Absorption is the technique employed in choppy
or fast-moving waters, when methods like con-
tainment and removal fail. In this method, sor-
bent materials such as talc, straw, sawdust, and
synthetic absorbents are added to the oil slick
and they are removed when they have soaked
up some of the oil. These sorbent materials act
like a big sponge, removing oil but contami-
nated absorbent materials must be treated as
toxic waste and present disposal problems.
Furthermore, straw and sawdust can become
waterlogged and difficult to remove.Fig. 7.7 Pathways for the breakdown of some oil components (From Harayama et al. 1999 )