Correlation model to predict residual immiscible organic contaminants in sandy soils

Abstract

Researchers in both environmental and petroleum engineering have conducted studies in one-dimensional columns to quantify the amount of residual nonaqueous phase liquids (NAPL) trapped in the porous media as a function of capillary, viscous and buoyancy forces. From these previous studies, it is proven that significant amounts of the original NAPL spill remain as a trapped residual. The objective of this research was to extend this body of work and to develop a correlation model that could predict residual NAPL saturation as a function of common soil characteristics and fluid properties. These properties include parameters derived from sieve analysis, namely, the uniformity coefficient ( C u), the coefficient of gradation ( C c), as well as fluid properties (interfacial tension, viscosity and density). Over 100 column experiments were conducted across a range of nine different soil gradations. The data produced by these tests, along with measured soil and fluid properties, were used to generate correlation models to predict residual NAPL saturation ( S rn). The first correlation model predicts S rn for the region where residual NAPL saturation is independent of the capillary number, and dependent on C u, C c and the Bond number. The second correlation model predicts S rn for the region where residual NAPL saturation is dependent on capillary number, as well as C u, C c and the Bond number. The third correlation model predicts S rn over the entire region as a function of C u, C c and the total trapping number. The correlation models have a R 2 value of 0.972, 0.934 and 0.825, respectively. Hence, the models may potentially be integrated into site characterization approaches.