EVALUATION OF GROUNDWATER EXTRACTION FOR REMEDIATION OF PETROLEUM-CONTAMINATED AQUIFERS

Past experience has shown that restoration of an aquifer to drinking water quality by groundwater extraction and surface treatment may require many years of pumping. In this research, a mathematical model of hydrocarbon dissolution is developed to aid in the evaluation of groundwater remediation systems. The model assumes that residual hydrocarbon is distributed between two fractions: (1) a fast fraction in equilibrium with the aqueous phase and (2) a slow fraction in which mass transfer is limited. Relationships for simulating equilibrium partitioning are based on classical liquid-liquid equilibrium theory. Column experiments were performed to test the model and examine the kinetics of aromatic hydrocarbon dissolution as residual hydrocarbon ages. The hydrocarbon dissolution process included an initial equilibrium period during which dissolved hydrocarbon concentrations were high and roughly constant followed by a rapid drop-off period and an asymptotic period during which dissolved hydrocarbon concentrations were low and declined slowly. After passing more than 700 pore volumes of water through the column, between 8 and 10% of the original toluene and xylene isomers remained in the column. Model simulations were conducted to evaluate the effect of pulsed pumping on groundwater cleanup time.