title: Successful treatment of an MTBE-impacted aquifer using a bioreactor self-colonized by native aquifer bacteria.
abstract: A field-scale fixed bed bioreactor was used to successfully treat an MTBE-contaminated aquifer in North Hollywood, CA without requiring inoculation with introduced bacteria. Native bacteria from the MTBE-impacted aquifer rapidly colonized the bioreactor, entering the bioreactor in the contaminated groundwater pumped from the site, and biodegraded MTBE with greater than 99 % removal efficiency. DNA sequencing of the 16S rRNA gene identified MTBE-degrading bacteria Methylibium petroleiphilum in the bioreactor. Quantitative PCR showed M. petroleiphilum enriched by three orders of magnitude in the bioreactor above densities pre-existing in the groundwater. Because treatment was carried out by indigenous rather than introduced organisms, regulatory approval was obtained for implementation of a full-scale bioreactor to continue treatment of the aquifer. In addition, after confirmation of MTBE removal in the bioreactor to below maximum contaminant limit levels (MCL; MTBE = 5 μg L(-1)), treated water was approved for reinjection back into the aquifer rather than requiring discharge to a water treatment system. This is the first treatment system in California to be approved for reinjection of biologically treated effluent into a drinking water aquifer. This study demonstrated the potential for using native microbial communities already present in the aquifer as an inoculum for ex-situ bioreactors, circumventing the need to establish non-native, non-acclimated and potentially costly inoculants. Understanding and harnessing the metabolic potential of native organisms circumvents some of the issues associated with introducing non-native organisms into drinking water aquifers, and can provide a low-cost and efficient remediation technology that can streamline future bioremediation approval processes.
authors.affiliation: Department of Land, Air and Water Resources, University of California, One Shields Ave, Davis, CA, 95616, USA.
authors.forename: Kristin A
authors.initials: KA
authors.lastname: Hicks
authors.forename: Radomir
authors.initials: R
authors.lastname: Schmidt
authors.forename: Michael G
authors.initials: MG
authors.lastname: Nickelsen
authors.forename: Susan L
authors.initials: SL
authors.lastname: Boyle
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Baker
authors.forename: Paul M
authors.initials: PM
authors.lastname: Tornatore
authors.forename: Krassimira R
authors.initials: KR
authors.lastname: Hristova
authors.forename: Kate M
authors.initials: KM
authors.lastname: Scow
mesh_terms: D058491:Bacterial Load; D020562:Betaproteobacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors; D002140:California; D060587:Groundwater / Q000737:chemistry / Q000382:microbiology; D008738:Methyl Ethers / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000302:isolation & purification*; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*
chemical_list: D008738:Methyl Ethers; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; C043243:methyl tert-butyl ether