A physical model was used to study effects of gravity on areal recovery of a dense nonaqueous phase liquid (DNAPL) contaminant by alcohol pre-flooding and co-solvent flooding in dipping aquifers. Experimental results demonstrate a decrease in PCE recovery with increasing dip angle attributed to DNAPL swelling and migration, flood front instabilities, and bypassing of the source zone. Results demonstrate that alcohol pre-flooding can improve DNAPL recovery in the absence of a dip angle (horizontal orientation), but has negative effects when a dip angle exists. Electrokinetic experiments were conducted to examine effects of DC voltage gradient, pH, surfactants, ionic strength, and porous media on DNAPL movement in an electrical field. DNAPL movement was proportional to the applied voltage gradient and attributed to electroosmosis and electrophoresis. DNAPL droplets moved toward the cathodes under neutral and low pH conditions, and movement reversals were observed in high pH and ionic solutions
