The Microbial Degradation of a Diesel Oil in Multistage Continuous Culture Systems

Abstract

This project has dealt with the use of multistage continuous culture systems to model the fate of diesel oil in Lake Ontario. It has attempted to determine what happens to the oil after it is initially attacked by bacteria and subsequently dispersed into the water column. This study has successfully generated information which heretofore has not been obtainable in laboratory experiments. It has been shown that even under conditions which are more ideal than those in Lake Ontario (i.e. higher amounts of nitrogen and phosphorous) the oil is degraded very slowly. To date there has never been complete degradation in the systems, although it has been substantially modified by the bacterial activities. It was discovered that the degradation of oil by bacteria does not lead to its complete destruction but instead results in a transformation process in which the oil hydrocargons are converted into various end products. The chemical nature of these end products is as yet unknown but they appear to be more resistant to degradation and possibly more toxic than the original oil. Evidence is also presented indicating that oil droplets adhering to surfaces will undergo a more rapid and complete degradation than oil droplets which are freely suspended in the water column.