Population dynamics and biofilm composition in a new three-phase circulating bed reactor

Valentina Lazarova, Danièle Bellahcen, Danièle Rybacki, Bruce Rittmann, Jacques Manem

Research output: Contribution to journalConference articlepeer-review

15 Scopus citations


The biofilm characteristics of a novel three-phase reactor, the circulating bed reactor (CBR), were studied using industrial prototype fed with primary and secondary settled effluent in conditions of tertiary N and secondary C+N nitrification. The results showed a high nitrification rate close to the intrinsic values for N and C+N conditions: up to 2 and 0.6 kgN-NH4 m-3 d-1, or 1.88 ± 0.26 and 0.22 ± 0.07 gN g-1 PR d-1, respectively. The application of an integrated approach for biofilm analysis enabled the better understanding of biofilm dynamics. The biofilm remained relatively thin, below 100 μm, indicating an effective control of the biofilm development. Protein, measured by the conventional colometric method and pyrolysis-GC-MS, was the major fraction accounting for up to 35% of the biomass dry weight and 58% of the biopolymer content. The polysaccharide's fraction remained very low (< 3%). The ribosomal RNA probes analysis confirmed the predominance of bacterial cells in the CBR biofilm (80-86% of bacteria versus the universal probe) showing a high proportion of nitrifying bacteria accounting for up to 50% and 27% in the N and C+N removal respectively. Nitrosomonas predominated in tertiary nitrification whereas carbon input led to the appearance of other ammonia oxidizers. This particular composition was characterized by a high state of oxidation of the biomass, expressed by the low COD/DW ratio of about 0.85. In conclusion, it can be stated that this new three-phase bioreactor ensures a high nitrification rate through an effective biofilm control promoting the development of bacterial cells, especially nitrifying bacteria, and minimizing exopolysaccharides production.

Original languageEnglish (US)
Pages (from-to)149-158
Number of pages10
JournalWater Science and Technology
Issue number4-5
StatePublished - 1998
Externally publishedYes
EventProceedings of the 1997 2nd International Conference on Microorganisms in Activated Sludge and Biofilm Processes - Berkeley, CA, USA
Duration: Jul 21 1997Jul 23 1997


  • Biofilm
  • Biofilm activity
  • Biofilm composition
  • Circulating bed reactor
  • Kinetics
  • Nitrification
  • Population dynamics
  • Respirometry
  • Ribosomal RNA probes
  • Secondary treatment
  • Tertiary treatment

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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