Combining UASB and the "fourth generation" down-flow hanging sponge reactor for municipal wastewater treatment

M. Tandukar, S. Uemura, A. Ohashi, H. Harada

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


A "fourth generation" down-flow hanging sponge (DHS) Reactor has been developed and proposed as an improved variant of post-treatment system for UASB treating domestic wastewater. This paper evaluates the potential of the proposed combination of UASB and DHS as a sewage treatment system, especially for developing countries. A pilot-scale UASB (1.15 m3) and DHS (0.38 m3; volume of sponge) was installed in a municipal sewage treatment site and constantly monitored for 2 years. UASB was operated at an HRT of 6 h corresponding to an organic load of 2.15 kg-COD/m3 per day. Subsequently, the organic load in DHS was 2.35 kg-COD/m3 per day, operated at an HRT of 2 h. Organic removal by the whole system was satisfactory, accomplishing 96% of unfiltered BOD removal and 91% of unfiltered COD removal. However, nitrification decreased from 56% during the startup period to 28% afterwards. Investigation on DHS sludge was made by quantifying it and evaluating oxygen uptake rates with various substrates. Average concentration of trapped biomass was 26 g-VSS/L of sponge volume, increasing the SRT of the system to 100 - 125 d. Removal of coliforms obtained was 3 - 4log10 with the final count of 103 to 104 MPN/100 ml in DHS effluent.

Original languageEnglish
Pages (from-to)209-218
Number of pages10
JournalWater Science and Technology
Issue number3
Publication statusPublished - 2006


  • DHS reactor
  • Post-treatment
  • Sewage treatment
  • UASB reactor

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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