title: Managing the interactions between sulfate- and perchlorate-reducing bacteria when using hydrogen-fed biofilms to treat a groundwater with a high perchlorate concentration.
abstract: A groundwater containing an unusually high concentration (∼4000 μg/L) of perchlorate (ClO4(-)) and significant (∼60 mg/L) sulfate (SO4(2-)) was treated with hydrogen (H2)-fed biofilms. The objective was to manage the interactions between sulfate-reducing bacteria (SRB) and perchlorate-reducing bacteria (PRB) by controlling the H2-delivery capacity to achieve ClO4(-) reduction to below the detection limit (4 μg/L). Complete ClO4(-) reduction with minimized SO4(2-) reduction was achieved by using two membrane biofilm reactors (MBfRs) in series. The lead MBfR removed >96% ClO4(-), and the lag MBfR further reduced ClO4(-) to below the detection limit. SO4(2-) reduction ranged from 10 to 60%, and lower SO4(2-) reduction corresponded to lower H2 availability (i.e., lower H2 pressure or membranes with lower H2-delivery capacity). Minimizing SO4(2-) reduction improved ClO4(-) removal by increasing the fraction of PRB in the biofilm. High SO4(2-) flux correlated with enrichment of Desulfovibrionales, autotrophic SRB that can compete strongly with denitrifying bacteria (DB) and PRB. Increased SO4(2-) reduction also led to enrichment of: 1) Ignavibacteriales and Thiobacteriales, sulfide-oxidizing bacteria that allow sulfur cycling in the biofilm; 2) Bacteroidales, heterotrophic microorganisms likely using organic sources of carbon (e.g., acetate); and 3) Spirochaetales, which potentially utilize soluble microbial products (SMPs) from autotrophic SRB to produce acetate.
authors.affiliation: Biodesign Institute, Swette Center for Environmental Biotechnology, Arizona State University, 1001 South McAllister Ave. Tempe, AZ 85287-5701, USA; School of Sustainability, Arizona State University, USA.
authors.forename: Aura
authors.initials: A
authors.lastname: Ontiveros-Valencia
authors.affiliation: Biodesign Institute, Swette Center for Environmental Biotechnology, Arizona State University, 1001 South McAllister Ave. Tempe, AZ 85287-5701, USA.
authors.forename: Youneng
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Biodesign Institute, Swette Center for Environmental Biotechnology, Arizona State University, 1001 South McAllister Ave. Tempe, AZ 85287-5701, USA; School of Sustainable Engineering and the Built Environment, Arizona State University, USA. Electronic address: dr.rosy@asu.edu.
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
authors.affiliation: Biodesign Institute, Swette Center for Environmental Biotechnology, Arizona State University, 1001 South McAllister Ave. Tempe, AZ 85287-5701, USA; School of Sustainable Engineering and the Built Environment, Arizona State University, USA. Electronic address: Rittmann@asu.edu.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D018441:Biofilms; D060587:Groundwater; D006859:Hydrogen / Q000378:metabolism*; D010472:Perchlorates / Q000378:metabolism*; D013431:Sulfates / Q000378:metabolism*; D014874:Water Pollutants, Chemical
chemical_list: D010472:Perchlorates; D013431:Sulfates; D014874:Water Pollutants, Chemical; D006859:Hydrogen; C494474:perchlorate
keywords: Biofilm; Hydrogen; Perchlorate-reducing bacteria; Pyrosequencing; Sulfate-reducing bacteria; qPCR