| The purpose of this study was to demonstrate the in situ sequential degradation of nitrobenzene (NB) and 2,4-dinitrotoluene (2,4-DNT) using a granular iron permeable reactive barrier (PRB) followed by an aerobic biodegradation zone. To this end, a field study was conducted in a 24m long x 2m wide x 3m deep isolated section of the Borden aquifer (the "gate"). The gate is closed on three sides by sealable joint sheet piling keyed into the aquitard, and open to groundwater flow on the other, which, under natural conditions, is approximately parallel to the longest sides of the gate. The PRB was installed approximately 10 meters downgradient of the open end, and the oxygen injection system was installed approximately 18 meters into the gate. A hydraulic gradient was induced across the gate by pumping at the closed end via a fully-screened well, resulting in an average groundwater velocity of 56 cm/day. The first stage of treatment, involving the PRB, was expected to reduce nitrobenzene and 2,4-DNT to aniline and 2,4-diaminotoluene (2,4-DAT), respectively. Surprisingly, much of the nitrobenzene and 2,4-dinitrotoluene were transforming into their daughter products, aniline and 2,4-diaminotoluene, within 2 days of contaminant injection, and well before the contaminants encountered the zone of granular iron. (Abstract shortened by UMI.)... |
