Conditions for partial nitrification in biofilm reactors and a kinetic explanation

J Pérez, E Costa, Jan-Ulrich Kreft

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44 Citations (Scopus)


Nitrification is a two-step process in which ammonia is incompletely oxidized by ammonia-oxidizing bacteria or archaea (AOB) to nitrite, which is then further oxidized to nitrate by nitrite-oxidizing bacteria (NOB). Literature reports show that segregation of initially coexisting ammonia and nitrite oxidizing populations co-immobilized in gel cubes and Cultured in a set-up with three reactors in series (without recirculation) is attained. In those studies NOB were present and nitrite was oxidized mainly in the last reactor, We developed a mathematical model for immobilized biomass that allows for one-dimensional gradients of metabolites and changes of porosity within the gel due to growth. The model reproduced the experimentally observed compartmentalization under the conditions used by Noto et al. (Noto et al., 1998. Water Res 32(3): 769773), using standard kinetic parameters of nitrifying bacteria including free ammonia inhibition of AOB and NOB. The model predicted compartmentalization when the ammonium load was sufficiently high and liquid phase mixing sufficiently limited (close to plug-flow). Modeling results demonstrated that inhibition of NOB by free ammonia-did not Substantially contribute to the compartmentalization in biofilm reactors. Additional simulations identified the higher oxygen affinity of AOB as the key parameter leading to compartmentalization (i.e., partial nitrification) in artificial and natural biofilms since they enable the formation of oxygen gradients. As a result, a tendency for compartmentalization was found even at equal competitiveness. Biotechnol. Bioeng. 2009;103: 282-295. (C) 2009 Wiley Periodicals, Inc.
Original languageEnglish
Pages (from-to)282-295
Number of pages14
JournalBiotechnology and Bioengineering
Early online date6 Jan 2009
Publication statusPublished - 6 Jan 2009


  • incomplete nitrification
  • compartmentalization
  • nitrite oxidizing bacteria
  • mathematical model
  • ammonia oxidizing bacteria
  • ammonia inhibition
  • liquid phase mixing


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