Bioaugmentation with Pseudomonas Stutzeri KC for Carbon Tetrachloride Remediation

Abstract

Bioaugmentation with denitrifying Pseudomonas stutzeri strain KC is a field-demonstrated strategy to treat groundwater contaminated with carbon tetrachloride (CT) to concentrations below current regulatory criteria. The key to this strategy is that strain KC secretes a compound (pyridine-2,6-bis-thiocarboxylate, or PDTC) that promotes chemical dechlorination of CT outside the cell. Strain KC is a highly motile (chemotactic toward nitrate) facultative aerobe capable of complete denitrification. Unlike other denitrifiers, however, strain KC degrades CT without producing chloroform (CF) and does so faster than competing microbial populations that produce CF, thus minimizing or avoiding CF formation. Because bioaugmentation with strain KC is accomplished with nitrate in a denitrifying environment and requires relatively low amounts of added organic carbon, it avoids side effects that result from biostimulation with large amounts of organic carbon, minimizing accumulation of volatile fatty acids, hydrogen sulfide (H2S), ferrous iron, carbon disulfide, ammonium, methane and biomass. This chapter summarizes the rationale behind this unique bioaugmentation strategy, and reviews the laboratory and field research that led to its development and validation.