Anaerobic Biodegradation of Vegetable Oil Spills

Abstract

ABSTRACT Vegetable oil spills are common in the United States and Canada. Although vegetable oils usually are not toxic in the classic sense, at least not to the extent normally associated with crude oil and refined petroleum products, they can cause severe harmful effects in contaminated ecosystems. Since most of the adverse environmental effects of vegetable oils appear to be a result of the presence of the oil on the water surface, on shoreline sediments, or (in emulsified form) in the water column, a prudent spill response is to remove floating and suspended oil from the contaminated water body as quickly as possible. The goal of this research is to investigate a response alternative that is based on sedimentation of floating and suspended oil followed by anaerobic biodegradation in the sediments. The authors' research demonstrates that sedimentation of floating oil by formation of oil-mineral aggregates (OMAs) is possible, and that the interaction between oil and dry clay is crucial to the successful formation of negatively buoyant floes. The rate and extent of vegetable oil biodegradation under methanogenic and iron-reducing conditions in freshwater sediments have also been investigated. Anaerobic biodegradation of vegetable oil occurred in all sediments that were examined, including sediments from a river, a lake, and a wetland. Carbon and electron balances indicate that anaerobic mineralization of the added vegetable oil was complete.