title: Two-step upflow anaerobic sludge bed system for sewage treatment under subtropical conditions with posttreatment in waste stabilization ponds.
abstract: A pilot-scale sewage treatment system consisting of two upflow anaerobic sludge bed (UASB) reactors followed by five waste stabilization ponds (WSPs) in series was studied under subtropical conditions. The first UASB reactor started up in only 1 mo (stable operation, high chemical oxygen demand [COD] removal efficiency, low volatile fatty acids concentration in the effluent, alkalinity ratio above 0.7, biogas production above 0.1 Nm3/kg of CODremoved). Removal efficiencies up to 90% were obtained in the anaerobic steps at a hydraulic retention time of 6 + 4 h (80% removal in the first step). Fecal coliform removal in the whole system was 99.9999% (99.94% in anaerobic steps and 99.98% in WSPs). COD balances over UASB reactors are provided. A minimum set of data necessary to build COD balances is proposed. Intermittent sludge washout was detected in the reactors with the COD balances. Sludge washout from single-step UASB reactors should be monitored and minimized in order to ensure constant compliance with discharge standards, especially when no posttreatment is provided. The system combined high COD and fecal coliform removal efficiency with an extremely low effluent concentration, complying with discharge standards, and making it an attractive option for sewage treatment in subtropical regions.
authors.affiliation: Universidad Nacional de Salta, Laboratorio de Estudios Ambientales (CIUNSa-INENCO), Buenos Aires 177, A4402FDC Salta, Argentina. lucas@unsa.edu.ar
authors.forename: Lucas
authors.initials: L
authors.lastname: Seghezzo
authors.forename: Aníbal P
authors.initials: AP
authors.lastname: Trupiano
authors.forename: Viviana
authors.initials: V
authors.lastname: Liberal
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Todd
authors.forename: María E
authors.initials: ME
authors.lastname: Figueroa
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Gutiérrez
authors.forename: Ana C
authors.initials: AC
authors.lastname: Da Silva Wilches
authors.forename: Martín
authors.initials: M
authors.lastname: Iribarnegaray
authors.forename: Raquel G
authors.initials: RG
authors.lastname: Guerra
authors.forename: Angélica
authors.initials: A
authors.lastname: Arena
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Cuevas
authors.forename: Grietje
authors.initials: G
authors.lastname: Zeeman
authors.forename: Gatze
authors.initials: G
authors.lastname: Lettinga
mesh_terms: D001421:Bacteria, Anaerobic / Q000254:growth & development* / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D018929:Cell Culture Techniques / Q000295:instrumentation / Q000379:methods; D019544:Equipment Failure Analysis; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D007220:Industrial Waste / Q000517:prevention & control; D008697:Methane / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D010865:Pilot Projects; D012037:Refuse Disposal / Q000379:methods*; D012722:Sewage / Q000382:microbiology*; D014329:Tropical Climate; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*
chemical_list: D005232:Fatty Acids, Volatile; D007220:Industrial Waste; D012722:Sewage; D014874:Water Pollutants, Chemical; D008697:Methane