The objective of this study was to evaluate the significance of heterotrophic growth in nitrifying biofilm reactors fed only with ammonium as an energy source. The diversity, abundance and spatial distribution of nitrifying bacteria were studied using a combination of molecular tools and mathematical modeling, in two biofilm reactors operated with different hydraulic retention times. The composition and distribution of nitrifying consortia in biofilms were quantified by fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes combined with confocal laser scanning microscopy (CLSM) and digital image analysis. Autotrophic and heterotrophic biofilm fractions determined by FISH were compared to the output from a multispecies model that incorporates soluble microbial products (SMP) production/consumption. In reactor R1 (short retention time) nearly 100% of the total bacteria could be identified as either ammonia- or nitrite-oxidizing bacteria by quantitative FISH analyses, while in reactor R2 (long retention time) the identification rate was only 73%, with the rest probably consisting of heterotrophs. Mathematical simulations were performed to evaluate the influence of the hydraulic retention time (HRT), biofilm thickness, and substrate utilization associated SMP production on the growth of heterotrophic bacteria. The model predicts that low HRTs resulted in a lower availability of SMPs leading to purely autotrophic biofilms. These model predictions are consistent with experimental observations. At HRTs that are about an order of magnitude larger than the reciprocal of the net maximum growth rate the majority of the active biomass will grow suspended in the bulk phase rather than in the biofilm.
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Research Article|
October 01 2005
Evaluating heterotrophic growth in a nitrifying biofilm reactor using fluorescence in situ hybridization and mathematical modeling
R. Nogueira;
*Centro de Engenharia Biológica, Universidade do Minho, Campus de Gualtar, 4700-057 Braga, Portugal, (E-mail: [email protected]; [email protected])
E-mail: [email protected]
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D. Elenter;
D. Elenter
**Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA, (E-mail: [email protected])
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A. Brito;
A. Brito
*Centro de Engenharia Biológica, Universidade do Minho, Campus de Gualtar, 4700-057 Braga, Portugal, (E-mail: [email protected]; [email protected])
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L.F. Melo;
L.F. Melo
****Departamento de Engenharia Química, Faculdade de Engenharia of Porto, 4200-465 Porto, Portugal, (E-mail: [email protected])
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M. Wagner;
M. Wagner
*****Institut für Ökologie und Naturschutz, Universität Wien, Althanstr. 14, A-1090 Wien, Austria, (E-mail: [email protected])
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E. Morgenroth
E. Morgenroth
**Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA, (E-mail: [email protected])
***Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA, (E-mail: [email protected])
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Water Sci Technol (2005) 52 (7): 135–141.
Citation
R. Nogueira, D. Elenter, A. Brito, L.F. Melo, M. Wagner, E. Morgenroth; Evaluating heterotrophic growth in a nitrifying biofilm reactor using fluorescence in situ hybridization and mathematical modeling. Water Sci Technol 1 October 2005; 52 (7): 135–141. doi: https://doi.org/10.2166/wst.2005.0192
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