Nitrate enhancement of in‐situ bioremediation of monoaromatic compounds in groundwater

Abstract

Abstract Removal of benzene, toluene, and the isomers of xylene (BTX) from gasoline‐contaminated groundwater under denitrifying conditions was investigated. In laboratory microcosms, benzene removal was found to be significantly stimulated by phosphorus addition. For total xylenes, removal followed a similar response, but toluene disappearance was unaffected by phosphorus enrichment. An in‐situ bioremediation project was conducted to extend this laboratory work to an actual field‐scale cleanup of gasoline‐contaminated groundwater. The flow of groundwater from two extraction wells to an infiltration gallery created a mostly closed loop to recycle the groundwater enriched with added nutrients and the electron acceptor (nitrate). The coincident occurrence of BTX loss (greater than 90 percent) in situ, nitrate (as well as phosphorus and ammonia) appearance, and increased levels of denitrifying bacteria at a downgradient well all suggested that denitrification may play a significant role in BTX remediation at this site.