INTRODUCTION

Several methods exist for containing and cleaning up oil spills in the aquatic environment. Mechanical equipment, such as booms and skimmers, is often used to block the spread of oil, concentrate it into one area, and remove it from the water. Chemical and biological treatment of oil can be used in place of, or in addition to, mechanical methods, especially in areas where untreated oil may reach shorelines and sensitive habitats in which cleanup becomes difficult and expensive. This document describes some of the chemical and biological methods that are used by response personnel to contain and clean up oil spills in the aquatic environment.

TYPES OF SUBSTANCES USED

Three types of substances commonly used to contain or clean up an oil spill are (1) dispersing agents, (2) biological agents, and (3) gelling agents.

Dispersing agents

Dispersing agents, also called

dispersants, are chemicals that contain surfactants, or compounds that act to break liquid substances such as oil into small

droplets. In an oil spill, these droplets disperse

into the water column where they are subjected to natural processes -- such as wind, waves, and currents -- that help to break them down further. This helps to clear oil from the water surface, making it less likely that the oil slick will reach the shoreline.

The effectiveness of a dispersant is determined by the composition of the oil it is being used to treat, and the method and rate at which the dispersant is applied. Heavy crude oils do not disperse as well as light- to medium-weight oils. Dispersants are most effective when applied immediately following a