title: Modelling of the temperature-phased batch anaerobic digestion of raw sludge from an urban wastewater treatment plant.
abstract: The disposal of excess sludge from wastewater treatment plants is a serious problem that needs to be addressed. Temperature-phased anaerobic digestion (TPAD) which combines thermophilic and mesophilic processes in one, brings together the advantages of both systems. The aim of the present work was to develop a simple kinetic model to describe the TPAD of sewage sludge in batch completely stirred tank reactors (CSTRs) and to determine the kinetic parameters of both thermophilic and mesophilic stages. A zero-order kinetic equation described the thermophilic step after 2, 4 and 6 days of digestion time (experiment 1, 2 and 3, respectively), yet a first-order equation was found to be adequate to correlate the methane gas accumulated with time in the mesophilic step, the kinetic constant being 0.21 days(-1). The methane yield coefficient obtained was found to be almost proportional to the digestion time used in the thermophilic step with values of 0.067, 0.132 and 0.193 L CH(4) STP/g VS(added) for experiments 1, 2 and 3, respectively. By contrast, the kinetic constant of the mesophilic stage was not influenced by the digestion time used in the thermophilic phase.
authors.affiliation: Department of Environmental Technologies, Faculty of Sea and Environmental Sciences, University of Cádiz, Cádiz, Spain.
authors.forename: Víctor
authors.initials: V
authors.lastname: Riau
authors.forename: M Angeles
authors.initials: MA
authors.lastname: De la Rubia
authors.forename: Montserrat
authors.initials: M
authors.lastname: Pérez
authors.forename: Antonio
authors.initials: A
authors.lastname: Martín
authors.forename: Rafael
authors.initials: R
authors.lastname: Borja
mesh_terms: D001421:Bacteria, Anaerobic; D019149:Bioreactors; D007700:Kinetics; D008697:Methane; D008962:Models, Theoretical; D012722:Sewage; D013696:Temperature; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage; D008697:Methane