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SPATIALLY-DISTINCT REDOX CONDITIONS AND DEGRADATION RATES FOLLOWING FIELD-SCALE BIOAUGMENTATION FOR RDX-CONTAMINATED GROUNDWATER REMEDIATION
Michalsen, M.M., A.S. King, J.D. Istok, F.H. Crocker, M.E. Fuller, K.H. Kucharzyk, et al.
Journal of Hazardous Materials 387:121529(2020)
A recent pilot study demonstrated successful remediation of a hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) plume by bioaugmenting groundwater with Gordonia sp. KTR9 and Pseudomonas fluorescens strain I-C cells. A cell transport test showed the strains were transported 13 m downgradient over one month. Abundances indicators genes (xplA and xenB) of KTR9 and Strain I-C approached injection well cell densities at 6 m downgradient. Gene abundances (and conservative tracer) had begun to increase at 13 m downgradient at test conclusion. Subsequent in situ push-pull tests measured RDX degradation rates in the bioaugmented wells under ambient gradient conditions. Time-series monitoring of RDX, RDX endproducts, conservative tracer, (xplA and xenB gene copy numbers, and XplA and XenB protein abundance were used to assess the efficacy of bioaugmentation and to estimate the apparent first-order RDX degradation rates during each test. A collective evaluation of redox conditions, RDX end-products, varied RDX degradation kinetics, and biomarkers indicated that Strain I-C and KTR9 rapidly degraded RDX. Results showed bioaugmentation was a viable technology to accelerate RDX cleanup and may apply to other sites. Full-scale implementation considerations are discussed.
Journal of Hazardous Materials 387:121529(2020)
A recent pilot study demonstrated successful remediation of a hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) plume by bioaugmenting groundwater with Gordonia sp. KTR9 and Pseudomonas fluorescens strain I-C cells. A cell transport test showed the strains were transported 13 m downgradient over one month. Abundances indicators genes (xplA and xenB) of KTR9 and Strain I-C approached injection well cell densities at 6 m downgradient. Gene abundances (and conservative tracer) had begun to increase at 13 m downgradient at test conclusion. Subsequent in situ push-pull tests measured RDX degradation rates in the bioaugmented wells under ambient gradient conditions. Time-series monitoring of RDX, RDX endproducts, conservative tracer, (xplA and xenB gene copy numbers, and XplA and XenB protein abundance were used to assess the efficacy of bioaugmentation and to estimate the apparent first-order RDX degradation rates during each test. A collective evaluation of redox conditions, RDX end-products, varied RDX degradation kinetics, and biomarkers indicated that Strain I-C and KTR9 rapidly degraded RDX. Results showed bioaugmentation was a viable technology to accelerate RDX cleanup and may apply to other sites. Full-scale implementation considerations are discussed.
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