Laboratory-scale assessment of vacuum-degassed activated sludge for improved settling properties

Research output: Contribution to journalArticle


Vacuum degassing of activated sludge was tested at eight different Swedish wastewater treatment plants with laboratory-scale equipment in batch mode in order to evaluate its efficiency on improvement of sludge compaction and settling properties. The results show that the efficiency of the degassing technique is mainly dependent on the initial sludge volume index (SVI) of the target sludge which was found to be related to its process configuration. Facilities with full activated sludge-based nitrogen removal processes, including both nitrification and denitrification, had high SVIs (>300 mL g-1) and were strongly affected by vacuum degassing with reduction of SVI up to 30%. Nitrogen removal facilities also including biological phosphorus removal showed better compaction and settling properties with relatively lower SVIs and were affected to a lesser extent by degassing with SVI reduction of 10–20%. Wastewater treatment plants without full biological nitrogen removal, lacking either nitrification or denitrification (or both) processes in the activated sludge had the lowest SVIs observed with almost no effect of vacuum degassing.


External organisations
  • Chalmers University of Technology
  • VA Syd
  • Stockholm Vatten
  • Sweco
  • Käppala Association
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Water Treatment
  • Water Engineering
Original languageEnglish
Pages (from-to)2193-2201
Number of pages9
JournalEnvironmental Technology
Issue number17
Publication statusPublished - 2017
Publication categoryResearch