title: The potential of oxygen to improve the stability of anaerobic reactors during unbalanced conditions: results from a pilot-scale digester treating sewage sludge.
abstract: A well-functioning pilot reactor treating sewage sludge at approximately 4.4 NL/m(3)/d of oxygen supply and 18d of hydraulic retention time (HRT) was subjected to a hydraulic overload to investigate whether oxygen benefits successful operation in stressful circumstances. Only a mild imbalance was caused, which was overcome without deterioration in the digestion performance. Volatile solids (VS) removal was 45% and 43% at 18 and 14 d of HRT, respectively. Biogas productivity remained around 546 NmL/gVS, but it was slightly higher during the period of imbalance. Thereafter, similar performances were achieved. Under anaerobic conditions, VS removal and biogas productivity were respectively 41% and 525 NmL/gVS, hydrogen partial pressure rose, and acetic acid formation became less favourable. Oxygen seemed to form a more stable digestion system, which meant increased ability to deal successfully with overloads. Additionally, it improved the biogas quality; methane concentration was negligibly lower, while hydrogen sulphide and oxygen remained around 0.02 and 0.03%v/v, respectively.
authors.affiliation: Department of Chemical Engineering and Environmental Technology, Escuela de Ingenierías Industriales, Sede Dr. Mergelina, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain. irisrc@iq.uva.es
authors.forename: I
authors.initials: I
authors.lastname: Ramos
authors.forename: M
authors.initials: M
authors.lastname: Fdz-Polanco
mesh_terms: D000693:Anaerobiosis / Q000187:drug effects; D056804:Biofuels / Q000032:analysis; D019149:Bioreactors / Q000382:microbiology*; D005232:Fatty Acids, Volatile / Q000032:analysis; D010100:Oxygen / Q000494:pharmacology*; D010865:Pilot Projects; D012722:Sewage / Q000382:microbiology*; D014835:Volatilization; D014865:Waste Disposal, Fluid / Q000295:instrumentation* / Q000379:methods*
chemical_list: D056804:Biofuels; D005232:Fatty Acids, Volatile; D012722:Sewage; D010100:Oxygen