Effect of biostimulation on the microbial community in PCB-contaminated sediments through periodic amendment of sediment with iron |
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Authors: | A Srinivasa Varadhan Amid P Khodadoust Richard C Brenner |
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Institution: | (1) Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA;(2) US Environmental Protection Agency, Cincinnati, OH 45268, USA; |
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Abstract: | Reductive dehalogenation of polychlorinated biphenyls (PCBs) by indigenous dehalorespiring microorganisms in contaminated
sediments may be enhanced via biostimulation by supplying hydrogen generated through the anaerobic corrosion of elemental
iron added to the sediment. In this study, the effect of periodic amendment of sediment with various dosages of iron on the
microbial community present in sediment was investigated using phospholipid fatty acid analysis (PLFA) over a period of 18 months.
Three PCB-contaminated sediments (two freshwater lake sediments and one marine sediment) were used. Signature biomarker analysis
of the microbial community present in all three sediments revealed the enrichment of Dehalococcoides species, the population of which was sustained for a longer period of time when the sediment microcosms were amended with
the lower dosage of iron (0.01 g iron per g dry sediment) every 6 months as compared to the blank system (without iron). Lower
microbial stress levels were reported for the system periodically amended with 0.01 g of iron per g dry sediment every 6 months,
thus reducing the competition from other hydrogen-utilizing microorganisms like methanogens, iron reducers, and sulfate reducers.
The concentration of hydrogen in the system was found to be an important factor influencing the shift in microbial communities
in all sediments with time. Periodic amendment of sediment with larger dosages of iron every 3 months resulted in the early
prevalence of Geobacteraceae and sulfate-reducing bacteria followed by methanogens. An average pH of 8.4 (range of 8.2–8.6) and an average hydrogen concentration
of 0.75% (range of 0.3–1.2%) observed between 6 and 15 months of the study were found to be conducive to sustaining the population
of Dehalococcoides species in the three sediments amended with 0.01 g iron per g dry sediment. Biostimulation of indigenous PCB dechlorinators
by the periodic amendment of contaminated sediments with low dosages of iron metal may therefore be an effective technology
for remediation of PCB-contaminated sediments. |
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