The interacting effects of Focused Pulsed (FP) treatment and solids retention time (SRT) were evaluated in laboratory-scale digesters operated at SRTs of 2-20days. Anaerobic digestion and methanogenesis of waste activated sludge (WAS) were stable for SRT≥5days, but the effluent soluble organic compounds increased significantly for SRT=2days due to a combination of faster hydrolysis kinetics and washout of methanogens. FP treatment increased the CH4 production rate and TCOD removal efficiency by up to 33% and 18%, respectively, at a SRT of 20days. These effects were the result of an increase in the hydrolysis rate, since the concentrations of soluble components remained low for SRT≥5days. Alternately, FP pre-treatment of WAS allowed the same conversion of TCOD to CH4 with a smaller SRT and digester size: e.g., 40% size savings with a CH4 conversion of 0.23g CH4-COD/g CODin.

Original languageEnglish (US)
Pages (from-to)2542-2548
Number of pages7
JournalBioresource Technology
Issue number3
StatePublished - Feb 1 2011


  • Focused Pulsed (FP)
  • Hydrolysis
  • Methanogenesis
  • Pre-treatment
  • SRT

ASJC Scopus subject areas

  • Bioengineering
  • Environmental Engineering
  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal


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