Performance and granule characteristics of UASB process treating wastewater with hydrolyzed proteins

H. H.P. Fang, H. K. Chui, Y. Y. Li, T. Chen

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64 Citations (Scopus)


UASB process consistently removed 84% of COD in wastewater with hydrolyzed proteins for loading rates up to 32 g-COD/L/day, corresponding to a food-to-microorganism ratio of 0.81 g-COD/g-VSS/day, at 37°C and a hydraulic retention time of 9 hours. Of all the COD in the wastewater, about 74% was converted to methane, 16% was unhydrolyzed proteins which remained refractory to degradation, and 10% converted to biomass. The average sludge yield was 0.079 g-VSS/g-COD. There was no noticeable foaming and sludge flotation. The maximum specific methane production rate in the reactor was 0.60 g-methane-COD/g-VSS/day, which was comparable to the specific methanogenic activity (SMA) of 0.59 g-methane-COD/g-VSS/day observed by the serum vial test using hydrolyzed proteins as substrate. The SMA using acetate as substrate was 0.89 g-methane-COD/g-VSS/day, higher than those (0.39-0.59 g-methane-COD/g-VSS/day) using formate, propionate and butyrate, individually, as substrate. The granules did not have a layered structure nor a predominant type of bacteria. Instead, it had a densely packed structure with interwined bacteria of diverse morphologies with scattered microcolonies of Methanothrix, Methanosarcina, and juxtapositioned syntrophic associations.

Original languageEnglish
Pages (from-to)55-63
Number of pages9
JournalWater Science and Technology
Issue number8 pt 8
Publication statusPublished - 1994
EventProceedings of the 17th Biennial Conference of the International Association on Water Quality. Part 8 - Budapest, Hung
Duration: 1994 Jul 241994 Jul 30


  • Anaerobic
  • Granules
  • Methanogenic activity
  • Microbial structure
  • Protein
  • Syntrophic association
  • UASB


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