Changes in bacterial community structure correlate with initial operating conditions of a field-scale denitrifying fluidized bed reactor
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High levels of nitrate are present in groundwater migrating from the former waste disposal ponds at the Y-12 National Security Complex in Oak Ridge, TN. A field-scale denitrifying fluidized bed reactor (FBR) was designed, constructed, and operated with ethanol as an electron donor for the removal of nitrate. After inoculation, biofilms developed on the granular activated carbon particles. Changes in the bacterial community of the FBR were evaluated with clone libraries (n=500 partial sequences) of the small-subunit rRNA gene for samples taken over a 4-month start-up period. Early phases of start-up operation were characterized by a period of selection, followed by low diversity and predominance by Azoarcus-like sequences. Possible explanations were high pH and nutrient limitations. After amelioration of these conditions, diversification increased rapidly, with the appearance of Dechloromonas, Pseudomonas, and Hydrogenophaga sequences. Changes in NO3, SO4, and pH also likely contributed to shifts in community composition. The detection of sulfate-reducing-bacteria-like sequences closely related to Desulfovibrio and Desulfuromonas in the FBR have important implications for downstream applications at the field site.
KeywordsDenitrification Chemical Oxygen Demand Clone Library Granular Activate Carbon Azoarcus
This research was supported by The US Department of Energy under the Natural and Accelerated Bioremediation Research program. The authors especially thank Dr. Raj Rajan and Mr. Daniel W. Wagner, Ecovation, Inc., Victor, NY, for their great contribution to the design, fabrication, and start-up of the FBR system and Ms. Tonia Mehlhorn for her support of the field work. We also appreciate Ms. Hui Yang, Mr. Kenneth Lowe, and Dr. Bobette Nourse for assistance in sample analysis.
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