Effects of Ultrasonic and Acid Pretreatment on Food Waste Disintegration and Volatile Fatty Acid Production

This study aims at investigating the effects of ultrasonic and acid pretreatment on food waste （FW） disintegration and volatile fatty acid （VFA） production. Single-factor experiments are carried out to obtain optimal conditions of individual ultrasonic and acid pretreatment, and response surface method （ RSM ） is applied to optimize the conditions of the combination of ultrasonic and acid （UA） pretreatment. Results show that the optimal acid, ultrasonic and UA pretreatments conditions are individual pH 2, individual ultrasonic energy density of 1.0 W/mL and the combination of ultrasonic energy densityl. 11 W/mL and pH 1.43, respectively. Correspondingly, the maximum disintegration degrees （DD） of 46. 90%, 57.38% and68.83%are obtained by acid, ultrasonic and UA pretreatments, respectively. After optimizing pretreatment conditions, batch experiments are operated to produce VFA from raw and pretreated FW under anaerobic fermentation process. Both the maximum VFA production （976. 17 mg COD/gVS） and VFA/SCOD （72. 89%） are obtained with ultrasonic pretreatment, followed by UA pretreatment, non-pretreatment and acid pretreatment, respectively. This observation demonstrates that a higher acidity on acid and UA pretreatments inhibits the generation of VFA. Results suggest that ultrasonic pretreatment is preferable to promote the disintegration degree of FW and VFA production.