Biodegradation of Oil in Freshwaters

Abstract

There are a number of routes by which oil may reach freshwaters. Natural oil seeps reach the surface in many parts of the world (Wardley-Smith, 1976). At every stage of oil exploration, production, transportation, refining and use, oil products can escape into the environment. Spills of oil from tankers during transportation can potentially result in rapid and large scale pollution of rivers and lakes. On a smaller scale leaks or discharges from the fuel tanks of outboard motor boats and oil refinery discharges can represent a direct source of oil contamination in freshwaters. Oil spills on land from oil wells, road vehicles and leaking oil storage tanks or pipelines can potentially filter through soil and ultimately contaminate groundwater. Spills from onshore oilwells are relatively infrequent; discharge of a small amount of oil occurs only once for every thousand wells drilled in the USA (Wardley-Smith, 1976). Worldwide discharges of petroleum hydrocarbons into rivers was estimated in 1975 to be approaching 1.5 × 10⁶ kg per annum (Heitkamp and Johnson, 1984).