Chapter 8ENVIRONMENTAL POLLUTION
debris-free waters, and with thick oil layers. They
are not extensively used for Navy spills.
5. Sorbent Surface Skimmers. These units use
an endless belt, hose, or rotating drum, the sur-
face of which absorbs the spilled oil from the
water surfaces. The concept is applied in large,
craft-mounted units for large spills and in smaller
units using an endless, hose-width belt. The ab-
sorbed oil is conveyed to temporary storage tanks
where it is squeezed from the belt or wiped from
the drum or disc.
6. Manual Methods. Occasionally, manual
removal methods are used in the Navy. Manual
removal processes involve the physical pickup of
the oil from shoreline areas with the use of sor-
bent materials, pitchforks, and/or shovels. They
also include in water removal operations such
as that mounted for small shipside spills in which
the Mark I Spill Control Kit is employed. In this
instance, herder chemicals may be used to retard
spreading of the spill, and hand-held polyurethane
absorbent pads or mops are used to sorb
and remove the oil. The pads are squeezed out
with conventional mop wringers.
Chemical Removal Methods.Chemicals
should not be used to emulsify, disperse,
solubilize, or precipitate oil whenever the protec-
tion or preservation of freshwater supply sources,
major shellfish or finfish nurseries, harvesting,
grounds, passage areas, or 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 preser-
vation may make the use of such materials a
necessary alternative. When chemical compounds
are used in connection with oil cleanup, only those
compounds exhibiting minimum toxicity toward
aquatic flora and fauna should be used. The EPA
is now developing, and will soon issue, a standard
procedure for determining the toxicity of such
chemicals.
Now lets describe some of the chemical
removal methods used.
1. Dispersants. Dispersants (emulsifiers) are
surface active agents which foster the development
of oil/water emulsion. They may be ionic or non-
ionic in nature and are typically mixed with
stabilizers, to preserve the emulsion formed, and
solvents for cold weather use when surfactant
viscosity is reduced. A typical dispersant is about
70-80% solvent, 10-15% surfactant and 10-15%
stabilizer.
The use of dispersants exposes a great surface
area for microbiological attack. However, many
Figure 8-4.Principle of Operation of Dynamic Inclined Plane (DIP) Skimmer.
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