Mobile NAPL recovery: Conceptual, field, and mathematical considerations

Recovery of mobile Nonaqueous Phase Liquids (NAPLs), referred to as ''oil recovery,'' is one of the most common remedial technologies currently being implemented at sites where NAPLs have been released. The rationale for oil recovery typically includes resource recovery, mitigation of further NAPL migration, and compliance with regulatory mandates for source reduction. Efficient oil recovery can be achieved by optimizing conditions within the oil flow path. This concept is referred to as flow path management. Building on this concept, a waterflood oil recovery technique utilizing dual recovery and parallel delivery drainlines has been developed for recovery of creosote-based wood-treating oil, a Dense Nonaqueous Phase Liquid (DNAPL). Full-scale application of this technique at a contaminated site has yielded 1.5 million gallons of DNAPL. Furthermore, an operational endpoint of 95 percent recovery of the mobile oil is being achieved. Building on the concept of flow path management and the observed performance of the waterflood oil recovery system, a first-order analytical solution for DNAPL flow to a drainline has been derived and validated using field data. This solution leads to a set of useful design equations and further insight into the factors that control oil recovery.