title: Characterization, morphology and composition of biofilm and precipitates from a sulphate-reducing fixed-bed reactor.
abstract: The characteristics of the biofilm and the solids formed during the operation of a sulphate-reducing fixed-bed reactor, fed with a moderately acidic synthetic effluent containing zinc and iron, are presented. A diverse population of delta-Proteobacteria SRB, affiliated to four distinct genera, colonized the system. The morphology, mineralogy and surface chemistry of the precipitates were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The XRD patterns observed are characteristic of amorphous solid phases. Peaks corresponding to crystalline iron sulphide, marcasite, sphalerite and wurtzite were also identified. SEM-EDX results confirm the predominance of amorphous phases appearing as a cloudy haze. EDX spectra of spots on the surface of these amorphous phases reveal the predominance of iron, zinc and sulphur indicating the formation of iron and zinc sulphides. The predominance of these amorphous phases and the formation of very fine particles, during the operation of the SRB column, are in agreement and can be explained by the formation pathways of metal sulphides at ambient temperature, alkaline pH and reducing conditions. Solids are precipitated either as (i) amorphous phases deposited on the bed material, as well as on surface of crystals, e.g. Mg(3)(PO(4))(2) and (ii) as rod-shaped solids characterized by a rough hazy surface, indicating the encapsulation of bacterial cells by amorphous metal sulphides.
authors.affiliation: National Technical University of Athens, School of Mining and Metallurgical Engineering, Laboratory of Environmental Science and Engineering, Heroon Polytechniou 9, Athens, Greece. remound@metal.ntua.gr
authors.forename: Emmanouela
authors.initials: E
authors.lastname: Remoundaki
authors.forename: Pavlina
authors.initials: P
authors.lastname: Kousi
authors.forename: Catherine
authors.initials: C
authors.lastname: Joulian
authors.forename: Fabienne
authors.initials: F
authors.lastname: Battaglia-Brunet
authors.forename: Artin
authors.initials: A
authors.lastname: Hatzikioseyian
authors.forename: Marios
authors.initials: M
authors.lastname: Tsezos
mesh_terms: D000595:Amino Acid Sequence; D018441:Biofilms; D019149:Bioreactors / Q000382:microbiology*; D011232:Chemical Precipitation; D005296:Ferrous Compounds / Q000737:chemistry*; D005798:Genes, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013431:Sulfates / Q000378:metabolism*; D013440:Sulfides / Q000737:chemistry*; D016999:Sulfur-Reducing Bacteria / Q000235:genetics / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D005296:Ferrous Compounds; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D013440:Sulfides; D014874:Water Pollutants, Chemical; D017967:Zinc Compounds; C031238:zinc sulfide; C022597:ferrous sulfide