title: Impact of microbial activities on the mineralogy and performance of column-scale permeable reactive iron barriers operated under two different redox conditions.
abstract: The present study focuses on the impact of microbial activities on the performance of various long-term operated laboratory-scale permeable reactive barriers. The barriers contained both aquifer and Fe0 compartments and had received either sulfate or iron(III)-EDTA to promote sulfate-reducing and iron(III)-reducing bacteria, respectively. After dismantlement of the compartments after almost 3 years of operation, DNA-based PCR-DGGE analysis revealed the presence of methanogenic, sulfate-reducing, metal-reducing, and denitrifying bacteria within as well as up- and downgradient of the Fe0 matrix. Under all imposed conditions, the main secondary phases were vivianite, siderite, ferrous hydroxy carbonate, and carbonate green rust as found by scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). Under sulfate-reduction promoting conditions, iron sulfides were formed in addition, resulting in 7 and 10 times higher degradation rates for PCE and TCE, respectively, compared to unreacted iron. These results indicate that the presence of sulfate-reducing bacteria in or around iron barriers and the subsequent formation of iron sulfides might increase the barrier reactivity.
authors.affiliation: Flemish Institute for Technological Research (VITO), Environmental and Process Technology, Boeretang 200, 2400 Mol, Belgium.
authors.forename: Thomas
authors.initials: T
authors.lastname: Van Nooten
authors.forename: François
authors.initials: F
authors.lastname: Lieben
authors.forename: Jan
authors.initials: J
authors.lastname: Dries
authors.forename: Eric
authors.initials: E
authors.lastname: Pirard
authors.forename: Dirk
authors.initials: D
authors.lastname: Springael
authors.forename: Leen
authors.initials: L
authors.lastname: Bastiaens
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001673:Biodegradation, Environmental; D006207:Half-Life; D007501:Iron / Q000737:chemistry*; D008903:Minerals / Q000378:metabolism*; D010084:Oxidation-Reduction; D010539:Permeability; D010865:Pilot Projects; D013431:Sulfates / Q000737:chemistry
chemical_list: D008903:Minerals; D013431:Sulfates; D007501:Iron