Journal
WATER RESEARCH
Volume 45, Issue 5, Pages 1995-2001Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2010.11.036
Keywords
Natural organic matter; Electrosteric hindrance; NZVI; Toxicity; Reactivity
Funding
- USEPA [R833326]
- Chinese government [NCET-07-0769, 2010ZD14, 2009ZX07424-002]
- China Scholarship Council
- EPA [909171, R833326] Funding Source: Federal RePORTER
- Direct For Biological Sciences
- Div Of Biological Infrastructure [830093] Funding Source: National Science Foundation
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Nano-scale zero-valent iron (NZVI) particles are increasingly used to remediate aquifers contaminated with hazardous oxidized pollutants such as trichloroethylene (TCE). However, the high reduction potential of NZVI can result in toxicity to indigenous bacteria and hinder their participation in the cleanup process. Here, we report on the mitigation of the bactericidal activity of NZVI towards gram-negative Escherichia coli and gram-positive Bacillus subtilis in the presence of Suwannee River humic acids (SRHA), which were used as a model for natural organic matter (NOM). B. subtilis was more tolerant to NZVI (1 g/L) than E. coli in aerobic bicarbonate-buffered medium. SRHA (10 mg/L) significantly mitigated toxicity, and survival rates after 4 h exposure increased to similar levels observed for controls not exposed to NZVI. TEM images showed that the surface of NZVI and E. coli was surrounded by a visible floccus. This decreased the zeta potential of NZVI from -30 to -45 mV and apparently exerted electrosteric hindrance to minimize direct contact with bacteria, which mitigated toxicity. H(2) production during anaerobic NZVI corrosion was not significantly hindered by SAHA (p > 0.05), However, NZVI reactivity towards TCE (20 mg/L), assessed by the first-order dechlorination rate coefficient, decreased by 23%. Overall, these results suggest that the presence of NOM offers a tradeoff for NZVI-based remediation, with higher potential for concurrent or sequential bioremediation at the expense of partially inhibited abiotic reactivity with the target contaminant (TCE). (C) 2010 Elsevier Ltd. All rights reserved.
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