Molecular and modeling analyses of the structure and function of nitrifying activated sludge

Bruce E. Rittmann, Chrysi S. Laspidou, Jodi Flax, David A. Stahl, Vincent Urbain, Hervé Harduin, Jaap J. Van Der Waarde, Bert Geurkink, Maurice J.C. Henssen, Harry Brouwer, Abraham Klapwijk, Maarten Wetterauw

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


Activated sludge community structure was assessed directly by oligonucleotide probes for seven treatment plants in France and two treatment plants in The Netherlands. Routine operating data also were obtained for these plants. Mathematical modeling was employed to translate the operating data into parameters that reflect community function and structure. These model-translated measures were compared to the direct probing measures of community structure. Extraction of RNA and subsequent slot-blot hybridization with probes Nso1225 (for active ammonium oxidizers) and Eub338 (for all active bacteria) confirmed that the ratio of active nitrifiers to active heterotrophs was mainly explained by the ratio of TKN:BOD(L) removed and that probe Nso1225 provided a quantitative measure of ammonium oxidizers easily distinguishable from background. Fluorescent in situ hybridization (FISH) followed similar trends. The ratio of active nitrifiers to total VSS depended on the TKN/BOD(L) removal ratio and the sludge age. Finally, the ng rRNA/mg VSS hybridized by probe Eub338 was strongly and inversely correlated to the sludge age and suggests that specific rRNA contents of about 11,000 ng rRNA/mg VSS(active) for heterotrophic bacteria and 14,000 ng rRNA/mg VSS(active) for ammonium oxidizers can be used to estimate active VSS from probing results targeted to rRNA.

Original languageEnglish (US)
Pages (from-to)51-59
Number of pages9
JournalWater Science and Technology
Issue number1
StatePublished - Feb 3 1999
Externally publishedYes


  • Active biomass
  • Biological treatment
  • Heterotrophs
  • Microbial ecology
  • Modeling
  • Molecular analyses
  • Nitrifiers
  • Oligonucleotide probes

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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