Estimation of the unbiodegradable fraction of thickened waste activated sludge

Mohammad M.I. Chowdhury, George Nakhla, J. Zhu

Research output: Journal PublicationArticlepeer-review


The study investigated the unbiodegradable fraction of particulate chemical oxygen demand (PCOD) in thickened waste activated sludge (TWAS) using semicontinuous-flow completely-mixed anaerobic digesters. A laboratory-scale semicontinuous stirred tank reactor was used to investigate TWAS anaerobic biodegradability at hydraulic retention time of 16.7 d to 33.3 d and organic loading rate (OLR) of 1.21 kg COD/ md to 3.47 kg COD/m3·d. The COD and volatile suspended solids (VSS) removal for TWAS were 37% to 44% and 39% to 42% at an OLR of 1.27 and 3.47 kg COD/m3·d, respectively. Using a biomass yield (YAD) of 0.29 g COD biomass/g COD substrate, decay rate (bADÞof 0.015 d-1; and a solids retention time (SRT) of 16.7 d; two linear fits correlating the difference between effluent biomass; and effluent particulate COD with influent total COD, the unbiodegradable fractions of PCOD and VSS were estimated from the slopes of the linear fits to be in the range of 0.26 to 0.28.

Original languageEnglish
Pages (from-to)819-825
Number of pages7
JournalWater Environment Research
Issue number9
Publication statusPublished - 1 Sept 2018
Externally publishedYes


  • Anaerobic digestion
  • Thickened waste activated sludge
  • Unbiodegradable fraction

ASJC Scopus subject areas

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


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