Correlation model to predict residual immiscible organic contaminants in sandy soils

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.