Enhanced Toluene Degradation Under Chlorate-Reducing Conditions by Bioaugmentation of Sand Columns with Chlorate- and Toluene-Degrading Enrichments

Abstract

Chlorate was examined as a potential electron acceptor for enhancing toluene degradation. Most chlorate respiring bacteria (CRB) use nitrate as an electron acceptor, and toluene is known to be degraded under denitrifying conditions. Therefore, it was hypothesized that there would be bacteria that could degrade toluene using chlorate as an electron acceptor, and that chlorate could be used to stimulate toluene degradation. Repeated tests and different approaches in batch tests failed to produce an enrichment capable of toluene degradation supported by chlorate reduction. However, the addition of chlorate increased the overall rate of toluene degradation in bioaugmented columns that were fed chlorate vs. a control column. Toluene removal at an influent toluene concentration of 11 mg/L was 93±5%, which was larger by a factor of 1.95 than toluene removal in a nonbioaugmented control column. Following the discontinued feed of chlorate, toluene removal decreased to 69±4%, demonstrating that chlorate could be used to produce a 1.36-fold increase in toluene removal.