title: Dissimilatory iron reduction and odor indicator abatement by biofilm communities in swine manure microcosms.
abstract: Animal waste odors arising from products of anaerobic microbial metabolism create community relations problems for livestock producers. We investigated a novel approach to swine waste odor reduction: the addition of FeCl(3), a commonly used coagulant in municipal wastewater treatment, to stimulate degradation of odorous compounds by dissimilatory iron-reducing bacteria (DIRB). Two hypotheses were tested: (i) FeCl(3) is an effective source of redox-active ferric iron (Fe(3+)) for dissimilatory reduction by bacteria indigenous to swine manure, and (ii) dissimilatory iron reduction results in significant degradation of odorous compounds within 7 days. Our results demonstrated that Fe(3+) from FeCl(3) was reduced biologically as well as chemically in laboratory microcosms prepared with prefiltered swine manure slurry and limestone gravel, which provided pH buffering and a substrate for microbial biofilm development. Addition of a 1-g liter(-1) equivalent concentration of Fe(3+) from FeCl(3), but not from presynthesized ferrihydrite, caused initial, rapid solids flocculation, chemical Fe(3+) reduction, and E(h) increase, followed by a 2-day lag period. Between 2 and 6 days of incubation, increases in Fe(2+) concentrations were accompanied by significant reductions in concentrations of volatile fatty acids used as odor indicators. Increases in Fe(2+) concentrations between 2 and 6 days did not occur in FeCl(3)-treated microcosms that were sterilized by gamma irradiation or amended with NaN(3), a respiratory inhibitor. DNA sequences obtained from rRNA gene amplicons of bacterial communities in FeCl(3)-treated microcosms were closely related to Desulfitobacterium spp., which are known representatives of DIRB. Use of iron respiration to abate wastewater odors warrants further investigation.
authors.affiliation: Department of Crop and Soil Sciences, 116 ASI Building, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Castillo-Gonzalez
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Bruns
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D002712:Chlorides; D017753:Ecosystem; D005232:Fatty Acids, Volatile / Q000032:analysis; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D008372:Manure / Q000382:microbiology*; D008969:Molecular Sequence Data; D009812:Odorants / Q000032:analysis*; D010084:Oxidation-Reduction; D017422:Sequence Analysis, DNA; D013552:Swine
chemical_list: D002712:Chlorides; D005232:Fatty Acids, Volatile; D005290:Ferric Compounds; D008372:Manure; D007501:Iron; C024555:ferric chloride