Chapter 8—ENVIRONMENTAL POLLUTIONdebris-free waters, and with thick oil layers. Theyare not extensively used for Navy spills.5. Sorbent Surface Skimmers. These units usean endless belt, hose, or rotating drum, the sur-face of which absorbs the spilled oil from thewater surfaces. The concept is applied in large,craft-mounted units for large spills and in smallerunits using an endless, hose-width belt. The ab-sorbed oil is conveyed to temporary storage tankswhere it is squeezed from the belt or wiped fromthe drum or disc.6. Manual Methods. Occasionally, manualremoval methods are used in the Navy. Manualremoval processes involve the physical pickup ofthe oil from shoreline areas with the use of sor-bent materials, pitchforks, and/or shovels. Theyalso include “in water” removal operations suchas that mounted for small shipside spills in whichthe Mark I Spill Control Kit is employed. In thisinstance, herder chemicals may be used to retardspreading of the spill, and hand-held polyurethaneabsorbent pads or “mops” are used to “sorb”and remove the oil. The pads are squeezed outwith conventional mop wringers.Chemical Removal Methods.—Chemicalsshould 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 primeconcern.Such chemicals should only be used in thosesurface water areas and under those circumstanceswhere preservation and protection of water relatednatural resources is judged not to be the highestpriority or where a choice as to resource preser-vation may make the use of such materials anecessary alternative. When chemical compoundsare used in connection with oil cleanup, only thosecompounds exhibiting minimum toxicity towardaquatic flora and fauna should be used. The EPAis now developing, and will soon issue, a standardprocedure for determining the toxicity of suchchemicals.Now let’s describe some of the chemicalremoval methods used.1. Dispersants. Dispersants (emulsifiers) aresurface active agents which foster the developmentof oil/water emulsion. They may be ionic or non-ionic in nature and are typically mixed withstabilizers, to preserve the emulsion formed, andsolvents for cold weather use when surfactantviscosity is reduced. A typical dispersant is about70-80% solvent, 10-15% surfactant and 10-15%stabilizer.The use of dispersants exposes a great surfacearea for microbiological attack. However, manyFigure 8-4.—Principle of Operation of Dynamic Inclined Plane (DIP) Skimmer.8-9
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