title: Optimisation of sludge pretreatment by low frequency sonication under pressure.
abstract: This work aims at optimizing sludge pretreatment by non-isothermal sonication, varying frequency, US power (PUS) and intensity (IUS varied through probe size), as well as hydrostatic pressure and operation mode (continuous vs. sequential - or pulsed - process). Under non isothermal sonication sludge solubilization results from both ultrasound disintegration and thermal hydrolysis which are conversely depending on temperature. As found in isothermal operation: - For a given specific energy input, higher sludge disintegration is still achieved at higher PUS and lower sonication time. - US effects can be highly improved by applying a convenient pressure. - 12 kHz always performs better than 20 kHz. Nevertheless the optimum pressure depends not only on PUS and IUS, but also on temperature evolution during sonication. Under adiabatic mode, a sequential sonication using 5 min US-on at 360 W, 12 kHz, and 3.25 bar and 30 min US-off gives the best sludge disintegration, while maintaining temperature in a convenient range to prevent US damping.
authors.affiliation: Université de Toulouse, Laboratoire de Génie Chimique, INP-ENSIACET, 31030 Toulouse, France; University of Science, Vietnam National University, Ho Chi Minh City, Viet Nam.
authors.forename: Ngoc Tuan
authors.initials: NT
authors.lastname: Le
authors.affiliation: Université de Toulouse, Laboratoire de Génie Chimique, INP-ENSIACET, 31030 Toulouse, France.
authors.forename: Carine
authors.initials: C
authors.lastname: Julcour-Lebigue
authors.affiliation: Université de Toulouse, Laboratoire de Génie Chimique, INP-ENSIACET, 31030 Toulouse, France.
authors.forename: Laurie
authors.initials: L
authors.lastname: Barthe
authors.affiliation: Université de Toulouse, Laboratoire de Génie Chimique, INP-ENSIACET, 31030 Toulouse, France. Electronic address: henri.delmas@ensiacet.fr.
authors.forename: Henri
authors.initials: H
authors.lastname: Delmas
mesh_terms: D010316:Particle Size; D011312:Pressure; D012722:Sewage / Q000737:chemistry*; D013010:Sonication; D013696:Temperature; D018508:Water Purification / Q000379:methods*
chemical_list: D012722:Sewage
keywords: Audible frequency; Hydrostatic pressure; Pulsed ultrasound; Sequential process; Sludge disintegration