Granulation and sludge retainment during start-up of a thermophilic UASB reactor

Kazuaki Syutsubo, Hideki Harada, Akiyoshi Ohashi

Research output: Contribution to journalConference articlepeer-review

29 Citations (Scopus)


A laboratory-scale UASB reactor was operated at 55°C over 600 days in order to investigate the granulation mechanism under thermophilic conditions. The reactor was seeded with a thermophilic digested sewage sludge, and fed with a synthetic wastewater composed of sucrose and volatile fatty acids. As a result of establishment of the whole granulated sludge bed, the reactor allowed ultimately a volumetric COD loading of 45 kgCOD m-3 d-1 with 90% COD removal. The maximum sludge loading achieved was 3.7 gCOD.gVSS-1 d-1, that is two to three times as large as that of mesophilically grown sludge. The behavior of SRT (sludge retention time) was closely correlated with the biogas evolution flux: excessive biogas evolution at the highest COD loading (45 kgCOD m-3 d-1) enhanced the sludge washout, and thus led to shortening of SRT into less than 7 days. Methanogenic activities of the retained sludge increased finally up to 110 times for acetate, 25 times for propionate, and 3.6 times for hydrogen as large as those of the seeded sludge.

Original languageEnglish
Pages (from-to)349-357
Number of pages9
JournalWater Science and Technology
Issue number8-9 -9 pt 7
Publication statusPublished - 1998
EventProceedings of the 1998 19th Biennial Conference of the International Association on Water Quality. Part 1 (of 9) - Vancouver, Can
Duration: 1998 Jun 211998 Jun 26


  • Biogas flux
  • Granulation
  • Methanogenic activity
  • Sludge retention time
  • Superficial velocity
  • Thermophilic UASB process

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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