Enhanced biogas production from anaerobic digestion of wastewater from the fruit juice industry by sonolysis: experiments and modelling

The aim of this study is to investigate the use of ultrasound pretreatment as potential technique to solubilize organic matter and fermentation of fruit juice effluents in anaerobic batch reactor. The efficacy of ultrasound pretreatment has been assessed at low frequency of 20 kHz and at different sonication times (20, 40 and 60 min). Compared with control, the amount of biogas produced increased by 47, 57 and 60% for sonication times of 20, 40 and 60 min, respectively. Methane content of the produced biogas was about 59% in the control and 64% in the case of effluent subjected to ultrasonication for 60 min. After 20 days of anaerobic digestion of the fruit juice effluents, the efficiency of chemical oxygen demand (COD) increased by 9, 31 and 35% with respect to control for sonication times of 20, 40 and 60 min, respectively, corresponding to total sugars uptake efficiency of about 35, 51 and 54%, respectively. The modified Gompertz equation was used to describe the cumulative biogas production. A good agreement was found between simulated and experimental data. HIGHLIGHTS Biogas production from fruit juice processing industry.; Ultrasound pretreatment to improve biogas production.; High methane content is obtained for prolonged sonication time.; The COD removal increased by 35% for sonication time of 60 min.;