LABORATORY SIMULATION OF THE 



MICROBIOLOGICAL DEGRADATION OF CRUDE OIL 



IN A MARINE ENVIRONMENT 



by 



D. Ballerini(l) , J. Ducreux(l) and J. Riviere(2) 



(1) Institut Francais du Petrole - Direction de Recherche 

 "Environnement et Biologie Petroliere" 



1 et 4 avenue de Bois-Preau - 92506 RUEIL-MALMAISON - FRANCE 



(2) Institut National Agronomique, Paris-Grignon 



16, rue Claude Bernard - 75231 PARIS 05 - FRANCE 



This study essentially intends to quantify the biodegradation 

 process of a crude oil in optimum conditions compatible with the 

 marine environment. 



Experiments were conducted in the Laboratory reactors (batch and 

 continuous cultures), with perfect monitoring of all physicochemical 

 parameters such as pH (pH 8.1), temperature at 20°C, mixing rate 

 600 rpm, and aeration velocity (1 liter of air/liter of medium 

 per hour) . 



The composition of the mineral medium was defined by taking the 



mean composition of salts in the Atlantic Ocean as a basis, and 



enriching it with nitrogen (235 mg.1-1), phosphorus (26.7 mg. 

 1-1) and iron (0.4 mg.1-1). 



In order to reproduce conditions prevailing at sea as closely 

 as possible, in which the evaporation of light products is not 

 negligible Arabian Light Crude was employed (ALC 240+) from which 

 all fractions distilling below 240°C were removed by low pressure 

 distillation. 



The analytical methodology employed to observe the crude oil biode- 

 gradation process is shown schematically in the following figure. 



The gas flow was passed through a trap containing CC14, which 

 retained the evaporated hydrocarbons, and then through a second 

 trap containing a known quantity of 1 N K0H, which retained the 

 carbon dioxide. The hydrocarbons were then determined by infrared 

 spectrometry. The C02 produced was determined by titrimetry. 



Liquid samples were taken during fermentation. 



The first sample was centrifuged to separate the hydrocarbon phase 

 from the aqueous phase, which was then filtered (filter pore diameter 

 0.22 jj) to eliminate fine particles in suspension. The following 

 were analyzed in this perfectly clarified aqueous phase: 



• total organic carbon (Dohrman DC. 50 instrument), 



• dissolved C02 using the Warburg equipment, 



27 



