Excutive review of hydrostatic pressure effects on sludge pretreament by sonication

Abstract

Related to ultrasonic {US) pretreatment of sludge, changing the hydrostatic pressure will change tihe resonance condition of cavitation bubbles and then may drive the system toward resonance conditions, consequently increase the rate and yield of reactions. Nevertheless, nearly all the US experiments had been carried out at atmospheric pressure. Only a few studies had been focusing on how increasing static pressure affects cavitation. The effect of hydrostatic pressure on sludge disintegration was studied for the first time in the last few years. This work aimed at reviewing the effect of pressure on sludge ultrasonic pretteatment efficiency in different conditions. The major result was that the optimum pressure depends on power input - Pụs, intensity -Ivs (or probe size), and temperature -T, but not on specific energy mput -ES, frequency -Fs, nor sludge type. In general, sludge disintegration efficacy was significantly improved by sonication at the optimum pressure, especially at low ES, leading to a potential of energy input savings in sludge sonication prefreatment, but also in most of ultrasound assisted processes.