Combined electrochemical conversion and micro-scale ZVI for enhanced energy production from anaerobic digestion of landfill leachate: Microorganisms survival and operational performance

A comprehensive study is reported on biogas upgradation as a green and renewable energy from the landfill leachate (LL) using combined electrochemical conversion (EC) pretreatment and micro-scale ZVI supplementation in anaerobic co-digested reactors. Enhanced biodegradability index (sCOD and TVFA) of LL are assessed through EC technique at lower current density (10–40 mA/cm²), electrode gap (0.5–2 cm), and contact time (15–60 min). The effects of different dosages of micro-scale ZVI (4, 10 and 20 g/L) on enhanced syntrophic activity between acid-producing bacteria and methanogens, methane yield and energy production in mesophilic anaerobic reactors are evaluated. The low current density (30 mA/cm²) for EC enhanced biodegradability index of LL before the injection to anaerobic reactors. Flucytometry analysis indicated that EC pretreatment had a negligible detrimental effects on living microorganism (reduction by 6.2 %). The highest biomethane potential (BMP) (0.2805 NL/g sCOD removed) and methane yield (70.12 %) were achieved in anaerobic co-digested reactor supplemented with 10 g/L of micro-scale ZVI. Energy analysis showed an increase of 2.45–10.93 kJ/gVSremoved in anaerobic co-digested reactors compared to the control. The combined EC and micro-scale ZVI can be considered as a feasible and promising technology to offer enhanced methane production and renewable energy from LL.