title: A swirling jet-induced cavitation to increase activated sludge solubilisation and aerobic sludge biodegradability.
abstract: In this work, a modified swirling jet induced hydrodynamic cavitation (HC) has been used for the pre-treatment of excess sludge. In order to both improve the HC treatment efficiencies and reduce the energy consumption, the effectiveness of the HC reactor on sludge disintegration and on aerobic biodegradability has been investigated at different operating conditions and parameters, such as temperature, inlet pressure, sludge total solid (TS) content and reactor geometry. The inlet pressure was related to the flow velocity and pressure drop. The best results in terms of sludge solubilisation were achieved after 2h of HC treatment, treating a 50.0gTSL-1and using the three heads Ecowirl system, at 35.0°C and 4.0bar. Chemical and respirometric tests proved that sludge solubilisation and aerobic biodegradability can be efficiently enhanced through HC pre-treatment technique. At the optimum operating conditions, the specific supplied energy has been varied from 3276 to 12,780kJkgTS-1in the HC treatment, by increasing the treatment time from 2 to 8 h, respectively. Low endogenous decay rates (bH) were measured on the excess sludge at low specific supplied energy, revealing that only an alteration in floc structure was responsible for the sludge solubilisation. On the contrary, higher bHvalues were measured at higher specific supplied energy, indicating that the sludge solubilisation was related to a decreasing biomass viability, as consequence of dead cells and/or disrupted cells (cell lysis).
authors.affiliation: Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123, Italy. Electronic address: giuseppe.mancuso@unitn.it.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mancuso
authors.affiliation: Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123, Italy. Electronic address: michela.langone@unitn.it.
authors.forename: Michela
authors.initials: M
authors.lastname: Langone
authors.affiliation: Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123, Italy. Electronic address: gianni.andreottola@unitn.it.
authors.forename: Gianni
authors.initials: G
authors.lastname: Andreottola
mesh_terms: D000332:Aerobiosis; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology; D057446:Hydrodynamics; D011312:Pressure; D012722:Sewage / Q000382:microbiology*; D012995:Solubility; D013696:Temperature; D000069453:Ultrasonic Waves; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*
chemical_list: D012722:Sewage
keywords: Aerobic biodegradability; Energy efficient; Sludge disintegration; Sludge solubilisation; Swirling jet-induced cavitation