Behaviors of nitrifiers in a novel biofilm reactor employing hanging sponge-cubes as attachment site

Nobuo Araki, Akiyoshi Ohashi, Izarul Machdar, Hideki Harada

Research output: Contribution to journalArticlepeer-review

87 Citations (Scopus)


Fluorescence in-situ hybridization (FISH) and DO microelectrodes were applied to biofilms developed in a novel reactor named DHS (downflow hanging sponge-cubes), to investigate the mechanisms of simultaneous carbon removal and nitrification. The DHS reactor was employed as an aerobic post-treatment process after an UASB anaerobic pre-treatment process receiving a municipal sewage. The presence ratio of Nitrosomonas and Nitrobacter cells to total cells of the DHS biomass was estimated by FISH technique to be 1.4% and 0.18%, respectively. Cell concentrations of both nitrifying bacteria were in good agreement with the magnitudes of ammonia-oxidizing and nitrite-oxidizing activities evaluated from batch tests. The habitats of both nitrifiers were the interior space of sponge-cubes, rather than within the biofilms attached onto sponge-cube surfaces. DO microelectrodes verify that the sponge-cubes insides were kept aerobically throughout the whole reactor height excluding the inlet vicinity portion.

Original languageEnglish
Pages (from-to)23-31
Number of pages9
JournalWater Science and Technology
Issue number7
Publication statusPublished - 1999
Externally publishedYes


  • Biofilm
  • DO microelectrodes
  • Fluorescent in situ hybridization
  • Municipal sewage
  • Nitrifying bacteria
  • Post-treatment process

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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