Optimisation of sludge pretreatment by low frequency sonication under pressure

Ngoc Tuan Le (1, 2) , Carine Julcour-Lebigue (1) , Laurie Barthe (1) , Henri Delmas (1)

1 LGC - Laboratoire de Génie Chimique
2 HCMUS - Ho Chi Minh City University of Science

This work aims at optimizing sludge pretreatment by non-isothermal sonication, varying frequency, US power (P-US) and intensity (I-US 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 P-US and I-US, 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.

Mots clés: Audible frequency; Hydrostatic pressure; Sequential process; Pulsed ultrasound; Sludge disintegration

Domaines: Génie chimique; Génie des procédés

Ngoc Tuan Le, Carine Julcour-Lebigue, Laurie Barthe, Henri Delmas. Optimisation of sludge pretreatment by low frequency sonication under pressure. Journal of Environmental Management, 2016, 165, pp.206-212. ⟨10.1016/j.jenvman.2015.09.015⟩. ⟨hal-01264379⟩