Kinetics of the Sequential Microbial Reductive Dechlorination of Hexachlorobenzene

Abstract

The reductive dechlorination kinetics of hexachlorobenzene and all other chlorinated benzene congeners (CBs) were evaluated using a mixed enrichment culture derived from a contaminated estuarine sediment. The predominant, sequential hexachlorobenzene dechlorination pathway was hexachlorobenzene → pentachlorobenzene → 1,2,3,5-tetrachlorobenzene → 1,3,5-trichlorobenzene → 1,3-dichlorobenzene. Very low levels of 1,2,4,5-tetrachlorobenzene, 1,2,4-trichlorobenzene, and 1,4-dichlorobenzene were also detected. Batch dechlorination assays were performed separately for all CBs with an initial biomass concentration of 330 mg/L as volatile suspended solids, initial concentrations of CBs of 180 nM, and electron donor in excess. The maximum dechlorination rate (k‘) and the half-saturation coefficient (KS) as well as the pseudo-first-order rate constant (kobs) for eight dechlorination reactions were estimated by nonlinear regression of CBs progress curves data based on a Michaelis−Menten-type and the pseudo-first-order...