title: Comparing the influence of low power ultrasonic and microwave pre-treatments on the solubilisation and semi-continuous anaerobic digestion of waste activated sludge.
abstract: Anaerobic digestion is a well-known technique for the recovery of energy from waste sludge. Pre-treatment methods are useful tools to improve the biodegradability of the sludge and to enhance the digestion efficiency. In this study, an ultrasound (US) and a microwave (MW) pre-treatment were compared in a long-term digestion experiment, using 3 small pilot scale semi-continuous digesters (SRT=20 days). A specific energy of 96 kJ/kg sludge was applied, hence enabling to compare the effectiveness of both pre-treatment methods towards sludge solubilisation and biogas production enhancement. Total and volatile solids (TS and VS), COD, carbohydrates and proteins were monitored throughout the digestion experiment. It was seen that US was most effective in COD solubilisation. The average biogas increment was 20% for the microwave pre-treatment and 27% for the ultrasonic pre-treatment. However, this additional biogas production did not outweigh the energy consumed by the pre-treatment, leading to a negative energy balance.
authors.affiliation: KU Leuven, Department of Chemical Engineering, Process and Environmental Technology Lab, Campus De Nayer, J. De Nayerlaan 5, B-2860 Sint-Katelijne-Waver, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Houtmeyers
authors.affiliation: KU Leuven, Department of Chemical Engineering, Chemical and Biochemical Process Technology and Control Division, Willem de Croylaan 46, B-3001 Heverlee, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Degrève
authors.affiliation: KU Leuven, Department of Microbial and Molecular Systems, Cluster of Bioengineering Technology, Technology Campus De Nayer, J. De Nayerlaan 5, B-2860 Sint-Katelijne-Waver, Belgium; Scientia Terrae Research Institute, B-2860 Sint-Katelijne-Waver, Belgium.
authors.forename: Kris
authors.initials: K
authors.lastname: Willems
authors.affiliation: KU Leuven, Department of Chemical Engineering, Process and Environmental Technology Lab, Campus De Nayer, J. De Nayerlaan 5, B-2860 Sint-Katelijne-Waver, Belgium.
authors.forename: Raf
authors.initials: R
authors.lastname: Dewil
authors.affiliation: KU Leuven, Department of Chemical Engineering, Process and Environmental Technology Lab, Campus De Nayer, J. De Nayerlaan 5, B-2860 Sint-Katelijne-Waver, Belgium. Electronic address: lise.appels@cit.kuleuven.be.
authors.forename: Lise
authors.initials: L
authors.lastname: Appels
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D008872:Microwaves; D012722:Sewage / Q000382:microbiology*; D012995:Solubility; D014465:Ultrasonics / Q000379:methods*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage
keywords: Anaerobic digestion; Microwave pre-treatment; Pilot scale; Ultrasound pre-treatment; Waste activated sludge