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Title: Final Project Report, DE-SC0001280, Characterizing the Combined Roles of Iron and Transverse Mixing on Uranium Bioremediation in Groundwater using Microfluidic Devices

In situ bioremediation of U(VI) involves amending groundwater with an appropriate electron donor and limiting nutrients to promote biological reduction to the less soluble and mobile U(IV) oxidation state. Groundwater flow is laminar; mixing is controlled by hydrodynamic dispersion. Recent studies indicate that transverse dispersion along plume margins can limit mixing of the amended electron donor and accepter (such as U(VI) in remediation applications). As a result, microbial growth, and subsequently contaminant reaction, may be limited to these transverse mixing zones during bioremediation. The primary objective of this work was to characterize the combined effects of hydrology, geochemistry, and biology on the (bio)remediation of U(VI). Our underlying hypothesis was that U(VI) reaction in groundwater is controlled by transverse mixing with an electron donor along plume margins, and that iron bioavailability in these zones affects U(VI) reduction kinetics and U(IV) re-oxidation. Our specific objectives were to a) quantify reaction kinetics mediated by biological versus geochemical reactions leading to U(VI) reduction and U(IV) re-oxidation, b) understand the influence of bioavailable iron on U(VI) reduction and U(IV) re-oxidation along the transverse mixing zones, c) determine how transverse mixing limitations and the presence of biomass in pores affects these reactions, and d) identify howmore » microbial populations that develop along transverse mixing zones are influenced by the presence of iron and the concentration of electron donor. In the completed work, transverse mixing zones along plume margins were re-created in microfluidic pore networks, referred to as micromodels. We conducted a series of experiments that allowed us to distinguish among the hydraulic, biological, and geochemical mechanisms that contribute to U(VI) reduction, U(IV) re-oxidation, and U(VI) abiotic reaction with the limiting biological nutrient HP042-. This systematic approach may lead to a better understanding of U(VI) remediation, and better strategies for groundwater amendments to maximize remediation efficiency.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Clemson Univ., SC (United States)
  2. Univ. of Texas, Austin, TX (United States)
  3. Univ. of Illinois, Urbana-Champaign, IL (United States)
Publication Date:
OSTI Identifier:
1167119
Report Number(s):
Final Technical Report (DE-SC0001280)
DOE Contract Number:
SC0001280
Resource Type:
Technical Report
Research Org:
Univ. of Illinois, Urbana-Champaign, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 58 GEOSCIENCES Bioremediation; uranium; groundwater; transverse mixing