Self-Seeding of a Field-Scale MTBE-Degrading Bioreactor by Native Aquifer BacteriaEPA Grant Number: FP916429
Title: Self-Seeding of a Field-Scale MTBE-Degrading Bioreactor by Native Aquifer Bacteria
Investigators: Hicks, Kristin A.
Institution: University of California - Davis
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $104,933
RFA: STAR Graduate Fellowships (2004) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Biochemistry
The objective of this research project is to evaluate methyl tertiary-butyl ether (MTBE) biodegradation and self-seeding by native microbial populations in an aboveground granular activated carbon (GAC)-based fluidized bed reactor. The bioreactor (BIO-GAC) contains granular activated carbon as both an MTBE sorptive and a biofilm carrier material and typically employs a patented microbial inoculum (Shell Global Solutions) of MTBE-degrading bacteria.
In the current study, the bioreactor was used to treat an MTBE-contaminated aquifer (14 mg/ml) in North Hollywood, CA, without initial seeding of the bioreactor by ex situ MTBE-degrading organisms. Increases in total biomass colonizing the bioreactor were measured over an 8-week period by viable plate counts and by DNA extraction coupled with quantitative Taqman polymerase chain reaction (PCR). In addition, q-PCR using 16s rRNA specific primers was used to detect and quantify a known MTBE-degrading bacteria, Rubrivivax gelatinos PM1. Self-seeding of the bioreactor by native aquifer bacteria occurred rapidly, with colonization reaching 106 cells/g GAC within 7 days of system startup. Strain PM1 was detected in all samples at a concentration of two orders of magnitude below total bacteria and increased in conjunction with total bacteria. Effluent MTBE concentrations correlated well with bacterial densities, with concentrations at the time of predicted breakthrough below detection (0.5 μg/L). This study demonstrates that bioaugmentation of biological treatment systems, and the subsequent added costs and regulatory approval processes associated with bioaugmentation, may not be necessary in some situations and that self-seeding of bioreactors by in situ microbial populations may be a rapid and effective MTBE treatment option.