Reducing emissions during gasoline bioremediation with a soil biofilter

One of the least expensive methods of treating petroleum contaminated soil is land treatment; however, current land treatment practices may do little more than transfer the pollutant from the soil to the atmosphere. The direction of this research was to modify current technology by maximizing soil retention and biological activity with a soil biofilter. The results clearly indicate a biofilter provides a barrier to volatile emissions while allowing hydrocarbon mineralization. Up to 73% of the gasoline was biodegraded. The rate and manner of VOC removal were strongly influenced by operating conditions.; Little data is currently available to evaluate gasoline removal in unsaturated soil. This research provides laboratory data on the sorption, volatilization and biodegradation pathways for 16 common gasoline constituents. It also considers the effect of variations in soil organic matter, contaminant concentration, soil moisture and depth of soil cover. Earthworm casts were used in evaluating the effect of increased organic matter. The influence of biofilter depth was evaluated by applying synthetic gasoline at different depths. An accounting of the gasoline removed by the various pathways was accomplished through a mass balance of total carbon.; Providing useful information in predicting gasoline removal from soil requires the kinetic constant be defined and the effect of environmental conditions quantified. Separate 35 to 50 point depletion curves were generated for total losses, volatilization, and biological removal using results from Tenax TM trap analysis and titrimetric CO2 determinations. This information was used to derive kinetic constants for the pathways considered and assess environmental effects. Biodegradation followed zero-order kinetics. A first order curve correctly describes total and volatile losses but does not provide insight into the mechanism of removal. A second model was developed that combines removal by zero and first order pathway kinetics.; Plots of the rate constants for volatilization and biological removal appear to represent a linear relationship with respect to organic matter and biofilter depth. The apparent relationship of soil organic matter with volatilization and mineralization is intriguing. Whether a relationship similar to that found for the sorption of organic compounds in saturated soils (Koc) exists can only be determined by additional research.