In situ biotransformation of BTEX compounds under methanogenic conditions

In situ biotransformation of BTEX (benzene, toluene, ethylbenzene, o-, m-, and p-xylenes) was investigated for a gasoline spill at Seal Beach Naval Weapons Station (Schroeder 1991) under methanogenic conditions in three controlled-release push-pull experiments. To create methanogenic conditions, anaerobic ground water (710 to 1365 L) was extracted from the anaerobic test zone, treated by deionization to remove nitrate and sulfate, and helium-purged to remove any traces of oxygen. Prior to release through the multiport injection/extraction well, the injection water was amended with BTEX compounds (160 to 367 micrograms/L) and bromide tracer. Contaminant transformation was observed in three consecutive experiments by withdrawing samples at regular intervals for periods of 73 to 159 d. BTEX removal rates were rapid for toluene and o- and m-xylenes (