The biogas upgrading from landfill leachate pretreated with low-frequency ultrasonic: anaerobic digestion performances and energy balance

Abstract

Abstract The efficient biogas production from landfill leachate (LL) is one of hot topics in anaerobic digestion systems. Higher bioavailability of LL can be achieved by application a feasible and promising pretreatment technologies in order to utilize as a substrate for anaerobic reactors. Here, the enhanced bioavailabity of LL using the low-frequency ultrasonic process and energy balance in anaerobic digestion process was estimated within incubation period of 24 days. The optimal performance of low-frequency ultrasonic for LL biodegradability index: sCOD and TVFA were estimated under influencing parameters: ultrasonic density (UD) (0.02–0.14 W/mL) and Ultrasonic time (UT) (0–12 min). Moreover, the effects of low-frequency ultrasonic pretreatment process on biogas production in batch mode anaerobic reactors operated at 37 ± 1 °C were surveyed for daily and cumulative methane production, operational performance and energy balance. An increased sCOD (820 mg/L) and TVFA (659 mg/L) were observed under optimum codition: UD (0.1 W/mL) and UT (10 min). The highest methane production (430 mL) was found in reactor 4, where %15 volume ratio of LL pretreated with low frequency ultrasonic were feed in. Energy balance assessment indicated that output energy for anaerobic reactors assissted with ultrasonic in range of + 6.99 and + 7.98 kJ/g VS removed. Therefore, incorporation the low-frequency ultrasonic and digestion process revealed a promising and economic technique to improve biomethane potential and energy balance from LL.