초록
<P>Fe<SUP>0</SUP> is a powerful chemical reductant with applications for remediation of chlorinated solvents, including tetrachloroethene and trichloroethene. Its utilization efficiency at contaminated sites is limited because most of the electrons from Fe<SUP>0</SUP> are channeled to the reduction of water to H<SUB>2</SUB> rather than to the reduction of the contaminants. Coupling Fe<SUP>0</SUP> with H<SUB>2</SUB>-utilizing organohalide-respiring bacteria (i.e., <I>Dehalococcoides mccartyi</I>) could enhance trichloroethene conversion to ethene while maximizing Fe<SUP>0</SUP> utilization efficiency. Columns packed with aquifer materials have been used to assess the efficacy of a treatment combining in space and time Fe<SUP>0</SUP> and a<I>D. mccartyi</I>-containing culture (bioaugmentation). To date, most column studies documented only partial conversion of the solvents to chlorinated byproducts, calling into question the feasibility of Fe<SUP>0</SUP> to promote complete microbial reductive dechlorination. In this study, we decoupled the application of Fe<SUP>0</SUP> in space and time from the addition of organic substrates and<I>D. mccartyi</I>-containing cultures. We used a column containing soil and Fe<SUP>0</SUP> (at 15 g L<SUP>-1</SUP> in porewater) and fed it with groundwater as a proxy for an upstream Fe<SUP>0</SUP> injection zone dominated by abiotic reactions and biostimulated/bioaugmented soil columns (Bio-columns) as proxies for downstream microbiological zones. Results showed that Bio-columns receiving reduced groundwater from the Fe<SUP>0</SUP>-column supported microbial reductive dechlorination, yielding up to 98% trichloroethene conversion to ethene. The microbial community in the Bio-columns established with Fe<SUP>0</SUP>-reduced groundwater also sustained trichloroethene reduction to ethene (up to 100%) when challenged with aerobic groundwater. This study supports a conceptual model where decoupling the application of Fe<SUP>0</SUP> and biostimulation/bioaugmentation in space and/or time could augment microbial trichloroethene reductive dechlorination, particularly under oxic conditions.</P><P>Decoupling the application of Fe<SUP>0</SUP> and bioaugmentation in space and/or time augments microbial reductive dechlorination and overall treatment of chlorinated ethenes in groundwater.</P><BR>[FIG OMISSION]</BR>