Volatile fatty acids (VFAs) production from waste-activated sludge affected by ultrasonic pretreatment

摘要

The effect of ultrasonic energy density from 0 to 4.0 kW/L on the hydrolysis and acidification of waste activated sludge (WAS) at pH 10.0 was investigated in this study. Experimental results showed that ultrasonic pretreatment caused significant enhancements of WAS hydrolysis and VFA accumulation. The study of ultrasonic energy density effect revealed that energy density influenced not only the total VFA accumulation but also the percentage of individual VFA. The maximal VFA accumulation occurred at ultrasonic energy density of 1.0 kW/L and fermentation time of 72 h, which was more than two times that without ultrasonic treatment. The analysis of VFA composition showed that the percentage of acetic acid ranked the first (more than 40%) and those of iso-valeric and propionic acids located at the second and third places, respectively. Thus, the suitable ultrasonic conditions for VFA accumulation from WAS were ultrasonic energy density of 1.0 kW/L and fermentation time of 72 h.