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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 biodegradation
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,
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