Microbially-mediated transformations of chlorinated solvents and engineered nanomaterials in the subsurface: Implications for bioremediation, natural attenuation, fate and transport
Duhl, Tiffany.
2020
-
Thesis
(Ph.D.)--Tufts University, 2020.
Submitted to the Dept. of Civil Engineering.
Advisor: Natalie Cápiro.
Committee: Kurt Pennell, John Fortner, C. Andrew Ramsburg, and Albert Jr. Robbat.
Keywords: Environmental engineering, Microbiology, and Nanotechnology.
Ubiquitous subsurface microorganisms, including organohalide-respiring, iron- and ... read moresulfate-reducing, and biofilm-forming bacteria can impact the fate and transport of chlorinated organic contaminants and engineered nanoparticles released into the subsurface. Bioremediation via microbial reductive dechlorination (MRD) is a common treatment remedy for chlorinated solvents such as tetrachloroethene (PCE). The delivery of fermentable electron donor (ED) substrates to stimulate MRD in chlorinated solvent groundwater plumes and source zones is impeded by ED consumption by non-target microbes, preventing sustained MRD and leading to formation of undesirable byproducts such as sulfide. The effect of iron reduction on the MRD of PCE alone and in the presence of sulfate reduction was evaluated in 1-dimensional column studies; increased dechlorination was observed in the presence of iron-reducing bacteria (IRB), possibly because conditions were more reduced compared to IRB-free conditions. Under both iron- and sulfate-reducing conditions, MRD proceeded under higher (10.8 mM) sulfide levels compared to concentrations previously reported (5 mM) to inhibit MRD, presumably due to removal of sulfide from solution via reaction with reduced iron. In another column study, the partitioning electron donor (PED) n-butyl acetate (nBA) was evaluated against a conventional water-soluble electron donor (lactate) for its ability to partition into a mixed PCE non-aqueous-phase liquid (NAPL), sustain PCE MRD, and support bioenhanced NAPL dissolution. In abiotic systems, nBA persisted longer and exhibited higher NAPL partitioning compared to lactate. Bioenhanced dissolution of PCE-NAPL and PCE dechlorination performance by nBA were superior or comparable to that of lactate in biotic columns, suggesting that PEDs are promising EDs for use in NAPL source zones. Iron oxide nanoparticles (IONPs) are an important class of nanoparticles that may enter the subsurface intentionally or unintentionally, with potential but unknown impacts from IRB or biofilm-forming bacteria. The susceptibility of oleic acid (OA)-stabilized IONPs to iron reduction by a model IRB was quantified in batch reactor experiments, and the impacts of Pseudomonas fluorescens biofilm on IONP transport were measured in column experiments. The OA coating reduced but did not eliminate reduction of the IONPs, while IONP transport was completely inhibited by P. fluorescens biofilm at seepage velocities of 0.4 and 4 m/d.read less - ID:
- 0r967j25n
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