title: Wet oxidation of activated sludge: transformations and mechanisms.
abstract: Wet oxidation (WO) is an interesting alternative for the solubilization and mineralization of activated sludge. The effects of different temperatures (160-200 °C) and pressures (4-8 MPa), on the evolution of chemical composition and rheological characteristics of a thickened activated sludge during WO are analyzed in this work. Soluble COD increases initially to a maximum and then diminishes, while the apparent viscosity of the mixture falls continuously throughout the experiment. Based on the experimental evolution of the compositions and rheological characteristics of the sludge, a mechanism consisting of two stages in series is proposed. Initially, the solid organic compounds are solubilized following a pseudo-second order kinetic model with respect to solid COD. After that, the solubilized COD was oxidized, showing a pseudofirst kinetic order, by two parallel pathways: the complete mineralization of the organic matter and the formation of highly refractory COD. Kinetic parameters of the model, including the activation energies are mentioned, with good global fitting to the experiments described.
authors.affiliation: Department of Chemical and Environmental Engineering, University of Oviedo, C/ Julián Clavería s/n., E-33071 Oviedo, Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Urrea
authors.affiliation: Department of Chemical and Environmental Engineering, University of Oviedo, C/ Julián Clavería s/n., E-33071 Oviedo, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Collado
authors.affiliation: Scientist-Technical Services, University of Oviedo, C/ Fernando Bonguera s/n, E-33071 Oviedo, Spain.
authors.forename: Amanda
authors.initials: A
authors.lastname: Laca
authors.affiliation: Department of Chemical and Environmental Engineering, University of Oviedo, C/ Julián Clavería s/n., E-33071 Oviedo, Spain. Electronic address: mariodiaz@uniovi.es.
authors.forename: Mario
authors.initials: M
authors.lastname: Díaz
mesh_terms: D019149:Bioreactors; D006801:Humans; D007700:Kinetics; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage
keywords: Activated sludge; Kinetic; Rheology; Wet oxidation