REMEDIATION OF DISSOLVED BTEX THROUGH SURFACE APPLICATION - A PROTOTYPE FIELD INVESTIGATION

The feasibility of surface application for remediating monoaromatic hy drocarbons (benzene, toluene, ethylbenzene, and xylenes - termed BTEX as a group) dissolved in ground water under field conditions was inves tigated at a site within Canadian Forces Base, Borden, Ontario. The su rface area was 25 m(2) and underlain by 3 to 3.5 m of unsaturated sand y soil. For periods of at least 216 hours, between 43 and 72 cm/d of w ater containing BTEX at concentrations that averaged between 8 and 11 mg/L were continuously applied by drip irrigation. Nitrogen was added to the soil as a nutrient for the final third of the investigation. Be fore the applied water reached the water table, BTEX mass losses range d from 65 to essentially 100 percent. Less that 6 percent of the BTEX mass losses could be attributed to volatilization from the unsaturated soil. The remaining BTEX losses were attributed to biodegradation, mo stly in the top 50 cm of the soil, which contained more inorganic nitr ogen and organic carbon than the deeper soil. Biodegradation rates inc reased with applied concentration, nitrogen addition, and exposure to BTEX. Benzene concentrations in ground water attained compliance with Canadian and American drinking water standards only after nitrogen app lication.