Characterisation of Contaminated Soil by Crude Oil Associated with Produced Water
Figure 1: The Produced Water Disposing Pit at the Studied Oilfield
Figure 4: The Produced Water Associated with Crude Oil – Discharging Outlet into the Surface Pit at the Studied Oilfield
Figure 2: Contaminated Soil by Crude Oil at the Bank of the Produced Water Disposing Pit at the Studied Oilfield
two samples of crude oil were taken, the first from the crude oil storage tank and the second from the disposing pit, in order to prepare standard soil samples; the schematic shown in Figure 5 illustrates the studied area and the locations of the samples.
Experimental Procedures of Contaminant Characterisation
Figure 3: Crude Oil Contaminated Soil Around the Produced Water Disposal Pit
TPH was determined in soil and water samples by infrared, according to US Environmental Protection Agency (EPA) methods (413.2 and 418.1/600/4-79-020) that use Freon or other equivalent solvents. The instrument used was the Infracal TOG/TPH analyser, model CVH. Soil samples were air-dried and passed through a 10-mesh sieve. pH and electrical conductivity (EC) were determined in a 1:1 soil:water extraction by the ION450 Ion Analyzer, then anions and cations were determined as per American Society for Testing and Materials (ASTM) procedures D3561-96, D511-93 (re-approved 1998) and D4327-97. The sodium adsorption ratio (SAR) was calculated. Direct pH and EC were determined for produced water samples and cations and anions. The contaminant in terms of this work is the crude oil in soil samples, which is represented by TPH. Figure 6 shows the results of the determined TPH in the soil samples.
Evaluation of Bioremediation Process
constituents carried by it and its contribution in the contamination of the environment. In addition, 18 contaminated soil samples were collected from the topsoil around the disposal pit to be analysed in order to characterise the contaminants and assess the extent of impaction. Furthermore, two more samples of uncontaminated soil were taken to be used as a reference and prepare standard contaminated samples. Finally,
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The concentration of crude oil contaminants plays a significant role in the bioremediation process and determinination of the efficiency of the biodegradation of the crude oil contaminants. It is believed that the rate of biodegradation of oil contaminants corresponds to the concentration of contaminants due to the difference in the population count of hydrocarbon-utilising bacteria (HUB).11 Therefore, in such studies it is important to investigate the relationship between the concentration of oil contaminants and the overall biodegradation rate via the correlated HUB count. This relationship illustrates the extent of the effect of the concentration of the contaminants on the efficiency of the bioremediation process via the effects on the performance of HUB. For this purpose, four cells of contaminated soils were treated with four levels of crude oil – 10, 20, 30 and 40% (w/v) – and thoroughly mixed. One cell of soil with no crude oil addition served as a control. After the addition of the oil, all of the samples were incubated at the site of experimentation at the lab under the ambient temperature for 52 weeks (one year).
EXPLORATION & PRODUCTION – VOLUME 8 ISSUE 1
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