title: Sludge reduction at low ozone doses: predictive effects and full-scale study.
abstract: The activated sludge process is the most widely used wastewater treatment. The main drawback of this technology is the excess sludge production (ESP). The ozonation of sludge of the recirculation line is used to reduce the ESP. In this study, ozonation was applied on a fraction of sludge of the recirculation line in a full-scale plant (50,000 population equivalent) at a lower-specific ozone dose (SOD) compared to previous studies. The results of batch tests to predict the main effect of the technology on the biomass activities are reported. Specifically, tests at 0.7-5 g O₃/kg MLVSS (mixed liquor volatile suspended solids) doses were made to evaluate the changes of the nitrification and denitrification rates, the population of phosphate-accumulating organisms and the gravitational properties. A certain reduction of the impact of ozonation on the kinetic parameters of sludge for values of SOD over 2 g O₃/kg MLVSS was found. The present study highlights also the use of the ratio of ozonated biomass to total biomass as an important operative parameter for ozonation in full-scale plants. Reduction in ESP in the wastewater treatment plant was equal to 10% as dry solids applying a SOD from 1.03 to 1.63 g O₃/kg MLVSS. An analysis of the economic cost of the technique is also reported.
authors: Department of Environmental Technology, Faculty of Marine and Environmental Sciences, Universidad de Cádiz, Poligono Rio San Pedro s/n, 11510 Puerto Real, Cadiz, Spain E-mail: pablo.romero@uca.es.
authors: P
authors: P
authors: Romero
authors: Department of Environmental Technology, Faculty of Marine and Environmental Sciences, Universidad de Cádiz, Poligono Rio San Pedro s/n, 11510 Puerto Real, Cadiz, Spain E-mail: pablo.romero@uca.es.
authors: M D
authors: MD
authors: Coello
authors: Foundation Centre for New Water Technologies (CENTA), Hwy Seville-Huelva (A-49), Km. 28. 41820 Carrión de los Céspedes, Seville, Spain.
authors: C A
authors: CA
authors: Aragón
authors: Department of Sciences and Engineering of Materials, Environment and Urban Planning, Marche Polytechnic University, Via Brecce Bianche, Ancona 60100, Italy.
authors: A L
authors: AL
authors: Eusebi
mesh_terms: D010126:Ozone / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D018505:Waste Management / Q000295:instrumentation / Q000379:methods*
chemical_list: D012722:Sewage; D010126:Ozone