Abstract
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
Effluents generated by juice fruit industries include high concentrations of organic matter as well as high chemical oxygen demand (COD)
It can be seen that the biogas production increases with the increase of time for selected tests
The juice effluents pretreated by ultrasound provide higher biogas production compared to untreated effluent; the values reached are about 409 and 162 NmLbiogas/gVS, respectively
Summary
Effluents generated by juice fruit industries include high concentrations of organic matter as well as high chemical oxygen demand (COD) These effluents have different characteristics depending on the specific types of fruit processing operations, including wastewater from washing, rinsing and sanitizing operations during the fruit crushing and cleaning of tanks (Noronha et al 2002), and sustainable management of these wastes has become a major concern (Kaparaju & Rintala 2006). They can be a source of smell generation, toxic gas emissions, insects’ attraction, and pathogen increase, which may lead to contamination of groundwater or surface water. To improve the anaerobic digestibility of substrate by making it more readily accessible to anaerobic biodegradation, the disintegration techniques and their combinations are often employed
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