Mohajeri, Leila
(2010)
Process Parameters Optimization For Bioremediation Of Crude Oil In Contaminated Coastal Sediments.
Engineering Doctorate thesis, Universiti Sains Malaysia.
Abstract
Crude oil causes a variety of risks when released into the environment. Biodegradation
of hydrocarbon compounds is one of the most important processes for clean-up of the
environment. One of the current knowledge gaps is the suitable concentration of
weathered crude oil (WCO) in coastal sediment for selection of bioremediation as a
clean-up option. In the first layout of this study, biodegradation of three different
concentrations of synthetic weathered crude oil was investigated at laboratory scale.
Natural attenuation, biostimulation and bioaugmentation were determined and compared
at 3, 30, 60 g oil per kg dry sediment. Samples were collected from the Butterworth
channel and acclimatized indigenous microorganisms were used. Total petroleum
hydrocarbons (TPHs) were measured by gravimetric method on days 0, 7, 14, 28, 50, 70
and 90. Highest removal of 73.8 % was observed in bioaugmentation experiments for
oil concentration of 30 g/kg dry soil while natural attenuation process removed 15.5 %
of TPHs in 90 days. Removal by natural attenuation was slow; however, addition of
nutrient increased its removal compared to non-stimulated reactors in all three oil
concentrations. Bioremediation during 70 days reached the maximum value and no
significant further decrease was observed up to 90 days. In the second part, TPHs and
selected n-alkanes were measured at 0, 6, 14, 25, 40 and 60 days after introducing WCO
to coastal sediment samples by gravimetric method and gas chromatography.
Experiments were designed by response surface methodology (RSM) and central
composite design (CCD). Initial oil concentration, microorganism, nitrogen and
phosphorus concentrations were used as independent variables (factors). TPHs removal
and n-alkanes removal were investigated separately as dependent variables (response).
For each test a quadratic polynomial model was generated.
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