Effective partial nitrification to nitrite by down-flow hanging sponge reactor under limited oxygen condition

Hui Ping Chuang, Akiyoshi Ohashi, Hiroyuki Imachi, Madan Tandukar, Hideki Harada

Research output: Contribution to journalArticlepeer-review

143 Citations (Scopus)


Combining the processes of partial nitrification and anaerobic ammonium oxidation (ANAMMOX) is an attractive wastewater-treatment technology for nitrogen removal. In this study we investigated partial nitrification by implementing a closed down-flow hanging sponge (DHS) reactor operated at controlled oxygen concentrations. Basic concept of DHS process is similar to that of trickling filter, in which oxygen concentration can be easily manipulated by controlling airflow to the reactor. The closed reactor was fed with artificial wastewater containing NH4Cl and operated with an HRT of 1.5 h at 30 °C. Oxygen inside the reactor was maintained below 3% (1.2 mg DO·L-1) (DO-dissolved oxygen) except during the startup periods. Five months of continuous operation showed that there was a strong relationship between oxygen concentration and nitrite production. The ratio of nitrite produced relative to ammonium oxidized increased by decreasing oxygen concentration. Partial nitrification was satisfactorily accomplished under oxygen limitation at around 0.5% in the gas phase (0.2 mg DO L-1). The system showed a high ammonium-removal rate, at a maximum of 1.46 kg NH4+-N m-3 day-1, even at limited oxygen concentration. We also found that oxygen concentration played an important role in the production of nitrous oxide, which increased with decreasing oxygen concentration.

Original languageEnglish
Pages (from-to)295-302
Number of pages8
JournalWater Research
Issue number2
Publication statusPublished - 2007 Jan


  • Down-flow hanging sponge (DHS) reactor
  • Nitrite
  • Nitrous oxide
  • Oxygen concentration
  • Partial nitrification

ASJC Scopus subject areas

  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution


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