title: Laboratory-scale assessment of vacuum-degassed activated sludge for improved settling properties.
abstract: 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.
authors.affiliation: a Department of Chemical Engineering, Water and Environmental Engineering, Lund University , Lund , Sweden.
authors.forename: Salar
authors.identifier: http://orcid.org/0000-0002-8640-2769
authors.initials: S
authors.lastname: Haghighatafshar
authors.affiliation: b Department of Civil and Environmental Engineering, Water Environment Technology , Chalmers University of Technology , Gothenburg , Sweden.
authors.forename: Britt-Marie
authors.identifier: http://orcid.org/0000-0001-6155-7759
authors.initials: BM
authors.lastname: Wilén
authors.affiliation: c Käppala Wastewater Treatment Plant , Lidingö, Stockholm , Sweden.
authors.forename: Andreas
authors.initials: A
authors.lastname: Thunberg
authors.affiliation: a Department of Chemical Engineering, Water and Environmental Engineering, Lund University , Lund , Sweden.|d NSVA, Nordvästra Skånes Vatten och Avlopp , Helsingborg , Sweden.
authors.forename: Marinette
authors.initials: M
authors.lastname: Hagman
authors.affiliation: e VA SYD , Malmö , Sweden.
authors.forename: Annika
authors.initials: A
authors.lastname: Nyberg
authors.affiliation: f Stockholm Vatten , Stockholm , Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Grundestam
authors.affiliation: g SWECO , Malmö , Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Mases
authors.affiliation: a Department of Chemical Engineering, Water and Environmental Engineering, Lund University , Lund , Sweden.
authors.forename: Jes
authors.identifier: http://orcid.org/0000-0002-3336-9416
authors.initials: J
authors.lastname: la Cour Jansen
mesh_terms: D019149:Bioreactors; D058440:Denitrification; D058465:Nitrification; D009584:Nitrogen; D012722:Sewage; D014618:Vacuum; D014865:Waste Disposal, Fluid
chemical_list: D012722:Sewage; D009584:Nitrogen
keywords: Activated sludge; biological nitrogen removal; settling properties; sludge volume index; vacuum degassing