ENHANCED DEGRADATION OF DISSOLVED BENZENE AND TOLUENE USING A SOLID OXYGEN-RELEASING COMPOUND

A field test to evaluate the applicability of an oxygen-releasing compound (ORC) to the remediation of ground water contaminated with benzene and toluene was conducted in the Borden Aquifer in Ontario, Canada. Benzene and toluene were injected as organic substrates to represent BTEX compounds, bromide was used as a tracer, and nitrate was added to avoid nitrate-limited conditions. The fate of the solutes was monitored along four lines of monitoring points and wells. Two lines studied the behavior of the solutes upgradient and downgradient of two large-diameter well screens filled with briquets containing ORC and briquets without ORC. One line was used to study the solute behavior upgradient and downgradient of columns of ORC powder placed directly in the saturated zone. The remaining line was a control. The results indicate that ORC in both briquet and powder form can release significant amounts of oxygen to contaminated ground water passing by it. In the formulation used in this work, oxygen release persisted for at least 10 weeks. Furthermore, the study indicates that the enhancement of the available dissolved oxygen content of at least 4 mg/L each of the ground water by ORC can support biodegradation of benzene and toluene dissolved in ground water. Such concentrations are typical of those encountered at sites contaminated with petroleum hydrocarbons; therefore, these results suggest that there is promise for ORC to enhance in situ biodegradation of BTEX contaminants at such sites using passive (nonpumping) systems to contact the contaminated ground water with the oxygen source.