Palladium-doped nanoscale zero valent iron (NZVI-Pd) particles are widely used as reactive agents for remediation of sites contaminated with chlorinated solvents such as trichloroethylene (TCE). NZVI-Pd rapidly reductively transforms TCE to benign end products. In groundwater environments, TCE may also be degraded to benign end products by Dehalococcoides anaerobic bacteria. The overall objective of this study is to identify and evaluate the combined effects of using stabilized NZVI-Pd and KB-1, a competent dechlorinating microbial consortium containing Dehalococcoides, on 1,2 DCA degradation rates, intermediates, and endpoints. 1,2 DCA was selected as a target compound as it is degraded by KB-1 but not by NZVI-Pd. An associated objective was to determine the potential for polymeric, colloidal stabilizers for NZVI-Pd such as carboxymethylcellulose (CMC) to act as a primary source of carbon and electrons for KB-1. Parallel microcosms were setup as follows with CMC and KB-1 alone, as well as with bare NZVI-Pd and KB-1 or CMC NZVI-Pd and KB1 together. Experiments were carried out under a strict anaerobic environment. Periodic measurements of 1,2 DCA, and end products were made using gas chromatography. Results indicate that the systems with CMC alone as a sole carbon source and electron donor were capable of degrading 1,2 DCA. The microcosms with KB-1 and CMC-coated NZVI-Pd degraded 1,2 DCA at a higher rate compared to those with KB-1 and CMC only systems. This study also shows CMC NZVI-Pd concentrations of (350 mg/L) did not inhibit the growth of dechlorinating bacteria and there was enhancement observed. In addition bacterial systems supplemented with NZVI-Pd only degraded 1,2 DCA, suggesting NZVI-Pd used as an electron donor by Dehalococcoides.  This is the first study to demonstrate stabilizing polymers for NZVI/NZVI-Pd can be used as a carbon source and electron donor by competent dechlorinating bacteria.

Degradation of trichloroethylene by nanoscale zerovalent iron particles and dechlorinating bacteria: A combined approach

248th National Meeting (2014)

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