High-rate activated sludge systems combined with dissolved air flotation enable effective organics removal and recovery

Cristina Cagnetta; Bart Saerens; Francis A Meerburg; Stijn O Decru; Eddie Broeders; Wilbert Menkveld; Tom G L Vandekerckhove; Jo De Vrieze; Siegfried E Vlaeminck; Arne R D Verliefde; Bart De Gusseme; Marjoleine Weemaes; Korneel Rabaey

doi:10.1016/j.biortech.2019.121833

High-rate activated sludge systems combined with dissolved air flotation enable effective organics removal and recovery

Bioresour Technol. 2019 Nov:291:121833. doi: 10.1016/j.biortech.2019.121833. Epub 2019 Jul 17.

Affiliations

¹ Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, Ghent 9000, Belgium.
² Aquafin NV, Dijkstraat 8, Aartselaar 2630, Belgium.
³ Nijhuis Water Technology, Innovatieweg 4, Doetinchem 7007, the Netherlands.
⁴ Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, Ghent 9000, Belgium; Research Group of Sustainable Energy, Air and Water Technology, University of Antwerp, Groenenborgerlaan 171, Antwerp 2020, Belgium.
⁵ Particle and Interfacial Technology Group (PaInT), Ghent University, Coupure Links 653, Ghent 9000, Belgium.
⁶ Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, Ghent 9000, Belgium. Electronic address: Korneel.Rabaey@UGent.be.

PMID: 31357043
DOI: 10.1016/j.biortech.2019.121833

Abstract

High-rate activated sludge (HRAS) systems typically generate diluted sludge which requires further thickening prior to anaerobic digestion (AD), besides the need to add considerable coagulant and flocculant for the solids separation. As an alternative to conventional gravitational settling, a dissolved air flotation (DAF) unit was coupled to a HRAS system or a high-rate contact stabilization (HiCS) system. The HRAS-DAF system allowed up to 78% removal of the influent solids, and the HiCS-DAF 67%. Both were within the range of values typically obtained for HRAS-settler systems, albeit at a lower chemical requirement. The separated sludge had a high concentration of up to 47 g COD L^-1, suppressing the need of further thickening before AD. Methanation tests showed a biogas yield of up to 68% on a COD basis. The use of a DAF separation system can thus enable direct organics removal at high sludge concentration and with low chemical needs.

Keywords: Adsorption/bio-oxidation system; Dissolved air flotation (DAF); High-rate activated sludge (HRAS) system; Sludge thickening; Waste activated sludge (WAS).

MeSH terms

Biofuels
Flocculation
Sewage*
Waste Disposal, Fluid

Substances

Biofuels
Sewage