An Introduction to Multiphase Extraction for Contaminated Soils Professional Engineers

This discussion presents an overview and general description of the overlying physics associated with any Multiphase Extraction (MPE) technology. The remediation of NAPL requires an understanding first of NAPL distribution and movement in the subsurface. Based on this, understanding three strategies for applying MPE (source mass recovery, source mass control, and source phase change) is discussed. This chapter describes each of these strategies as they relate to multiphase fluid (air, water, and NAPL) flow in porous media (such as unconsolidated soils) and an assessment of the limitations of the strategies. Multi-Phase Extraction (MPE) comprises a generic category of in situ remediation technologies that simultaneously extract multiple fluid phases from the subsurface through wells or trenches via induction of hydraulic gradients. These phases generally include air (gaseous phase including organic vapor) and water (such as aqueous phase including dissolved constituents) and may include NAPL. The actual engineering controls used to induce hydraulic gradients and designs used to manage the recovered fluid phase are described in subsequent chapters of this manual. The terminology presented by the Environmental Protection Agency (EPA) distinguishes between DPE and TPE technologies (USEPA 1997).