title: Microbial community composition of a household sand filter used for arsenic, iron, and manganese removal from groundwater in Vietnam.
abstract: Household sand filters are used in rural areas of Vietnam to remove As, Fe, and Mn from groundwater for drinking water purposes. Currently, it is unknown what role microbial processes play in mineral oxide formation and As removal during water filtration. We performed most probable number counts to quantify the abundance of physiological groups of microorganisms capable of catalyzing Fe- and Mn-redox transformation processes in a household sand filter. We found up to 10(4) cells g(-1) dry sand of nitrate-reducing Fe(II)-oxidizing bacteria and Fe(III)-reducing bacteria, and no microaerophilic Fe(II)-oxidizing bacteria, but up to 10(6) cells g(-1) dry sand Mn-oxidizing bacteria. 16S rRNA gene amplicon sequencing confirmed MPN counts insofar as only low abundances of known taxa capable of performing Fe- and Mn-redox transformations were detected. Instead the microbial community on the sand filter was dominated by nitrifying microorganisms, e.g. Nitrospira, Nitrosomonadales, and an archaeal OTU affiliated to Candidatus Nitrososphaera. Quantitative PCR for Nitrospira and ammonia monooxygenase genes agreed with DNA sequencing results underlining the numerical importance of nitrifiers in the sand filter. Based on our analysis of the microbial community composition and previous studies on the solid phase chemistry of sand filters we conclude that abiotic Fe(II) oxidation processes prevail over biotic Fe(II) oxidation on the filter. Yet, Mn-oxidizing bacteria play an important role for Mn(II) oxidation and Mn(III/IV) oxide precipitation in a distinct layer of the sand filter. The formation of Mn(III/IV) oxides contributes to abiotic As(III) oxidation and immobilization of As(V) by sorption to Fe(III) (oxyhydr)oxides.
authors.affiliation: Geomicrobiology/Microbial Ecology, Center for Applied Geoscience, Eberhard Karls University Tübingen, Germany.
authors.forename: Katja Sonja
authors.initials: KS
authors.lastname: Nitzsche
authors.affiliation: Geomicrobiology/Microbial Ecology, Center for Applied Geoscience, Eberhard Karls University Tübingen, Germany.
authors.forename: Pascal
authors.initials: P
authors.lastname: Weigold
authors.affiliation: Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, USA.
authors.forename: Tina
authors.initials: T
authors.lastname: Lösekann-Behrens
authors.affiliation: Geomicrobiology/Microbial Ecology, Center for Applied Geoscience, Eberhard Karls University Tübingen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kappler
authors.affiliation: Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, USA. Electronic address: sbehrens@umn.edu.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Behrens
mesh_terms: D001105:Archaea / Q000235:genetics / Q000254:growth & development; D001151:Arsenic / Q000032:analysis / Q000302:isolation & purification*; D018533:Biomass; D060766:Drinking Water / Q000032:analysis / Q000592:standards; D005191:Family Characteristics; D005290:Ferric Compounds / Q000737:chemistry; D005374:Filtration / Q000295:instrumentation*; D060587:Groundwater / Q000737:chemistry / Q000382:microbiology; D007501:Iron / Q000032:analysis / Q000302:isolation & purification*; D008345:Manganese / Q000032:analysis / Q000302:isolation & purification*; D043369:Nitrosomonadaceae / Q000235:genetics / Q000254:growth & development; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012822:Silicon Dioxide / Q000737:chemistry; D014744:Vietnam; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000302:isolation & purification*
chemical_list: D060766:Drinking Water; D005290:Ferric Compounds; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D008345:Manganese; D012822:Silicon Dioxide; D007501:Iron; D001151:Arsenic
keywords: Ammonia oxidation; Arsenite oxidation; Drinking water; Iron oxidation; Manganese oxidation; Water filtration