Abstract

Crude oil is basically formed by anaerobic conversion of biomass under high pressure and temperature. It consists of many hydrocarbons consisting both light and heavy components. It can be divided basically into four fractions: The proportions of these fractions vary from site to site. Of these, lighter aromatics (Eg. BTEX) and the short chain alkanes are readily biodegradable. Currently, petroleum hydrocarbons are the most abundantly used chemicals in the world. Manufactured from crude oil, petroleum hydrocarbons are found in gasoline, kerosene, fuel oil, asphalt, and even some chemicals used in home or at work. Almost every person on this planet has once or more used a petroleum product or byproduct. Due to their wide demand, they are transported all over the world by ship, rail, trucks and pipelines. Unfortunately, because of the large volumes of petroleum hydrocarbons produced and their subsequent releases during transport, use and transport, petroleum hydrocarbons have become one of the most prevalent contaminants in the surface and subsurface environment. There are a number of incidents in which significant quantities of oil were accidently released into the environment causing environmental disasters of epic proportions. Exxon Valdez (1989) and Gulf War (1990) oil spills are possibly the most publicized and studied environmental tragedies in history.