Effect of sonication on removal of petroleum hydrocarbon from contaminated soils by soil flushing method

Spilling of petroleum hydrocarbons from underground storage tanks is a major source of contamination to ground water and soils. In response to the need of developing an effective and economical cleanup technique, this research investigates the effectiveness of using sonication to enhance the soil flushing method.; The research involves both laboratory testing and theoretical analyses. The laboratory testing was conducted to determine the effect of sonication on seepage as well as on contaminant removal. The sonication was applied at 20 kHz frequency under different power levels. Test soils were Ottawa sand, a fine aggregate, and a natural soil; for each soil, the test specimens were prepared at two levels of density. Crisco Pure Vegetable Oil was used as a surrogate contaminant for soil flushing test.; Theoretical analyses involved the computer simulation of laboratory experiments using the commercial black-oil simulator named ECLIPSE 100. The program was used to find the relative permeabilities of water and oil for each soil flushing test. Utilizing the obtained the relative permeability data of each test, analyses were made for the effect of sonication on residual oil saturation, irreducible water saturation, and wettability of the test specimens.; The results of the investigation show that sonication can induce seepage in porous media, and also can enhance seepage flow rate when compared with no-sonication condition. Sonication enhanced the contaminant removal from soils significantly, and the degree of enhancement varied with soil type and hydraulic gradient. The computer analyses showed that sonication caused a shifting of the relative permeability curves of oil and water to a higher water saturation. As a result, the residual oil saturation decreased, and both the irreducible water saturation and wettability increased. These changes indicated the enhancement of oil removal due to sonication.; Based on the results of the study, it is concluded that the flushing method with sonication has a great potential to become an effective method for removing petroleum hydrocarbons from the contaminated ground. For effective applications of the method, various influence factors need to be taken into considerations.