Sonolytic And Sono-Fenton Pretreatment of Waste Activated Sludge

The pretreatment of waste activated sludge (WAS) to facilitate solubilization and biodegradability is most common using thermal mechanical (e.g. ultrasound high pressure homogenization) chemical (oxidation) and alkali methods. Ultrasonic disintegration is one of the most effective one owing to the capacity of ultrasound to break-up microbial cells and extract the intracellular material. The mechanism involves deagglomeration of biological flocs and disruption of large organic particles via the shear forces produced by high pressure waves during the implosion of cavitation bubbles. A less common method of WAS pretreatment is the Fenton process in which the production and diffusion of hydroxyl radicals through the microbial cell membrane lead to the oxidative decomposition of the cell wall. Moreover hydroxyl radicals are highly effective in oxidation of recalcitrant compounds in the sludge the biodegradable products of which are further subject to biochemical treatment.