Oil Refinery

Oil Refineries take crude oil -- a mixture of many different organic hydrocarbons -- and change it into specific components such as gasoline, diesel fuel, jet fuel, kerosene, lubricating oils, tars and asphalt. The general procedure is to first remove water and other impurities from the crude oil, then distill the crude oil into its various fractions, and then, if necessary, further change these fractions through chemical reactions into their final products.

The type and concentration of pollutants in a given refinery's effluent depends on the chemical make-up of the crude oil and the processes used to make the final products. Many of these processes require heating the oil to high temperatures or pressures, as well as the use of chemicals called catalysts. Other chemicals are used to help create and purify the final products. Refineries use large amounts of water in the refining process and as a cooling agent. This water picks up waste oil and impurities from the refining process. Some impurities are in the crude oil itself -- such as heavy metals, sulfide, and phenols -- while others are created during the refining process -- such as cyanide, dioxins, and furans. All of these chemicals can be toxic to aquatic life at very low concentrations.