Electrochemical oxidation pretreatment for enhanced methane potential from landfill leachate in anaerobic co-digestion process: Performance, Gompertz model, and energy assessment

Abstract

• EO pretreatment was employed to improve the BMP from LL in anaerobic co-digestion process. • EO revealed an efficient technology to lower lag phase (3 days) in anaerobic co-digestion process. • A methane yield of 0.2925 NLH 4 /g sCOD removed in anaerobic co-digestion with feeding 35% volume LL. • The high R 2 (0.994–0.999) proved the reliable prediction accuracy of modified Gompertz model. • Energy yield in anaerobic co-digested reactors with EO showed increase of 5.88–16.55KJ/gVSremoved. Landfill leachate (LL) are well known with low biodegradability and bio-methane potential (BMP) due to recalcitrant compounds and limited potential microorganisms. In turn, pretreatment step and addition co-substrate seem mandatory to improve the biodegradation and enhance the energy output. The present study was developed to assess the electrochemical oxidation (EO) and electrochemical conversion in low current density to improve LL bioavailability in anaerobic co-digestion (LL + Sludge) process. The enhanced biodegradability index: soluble COD (sCOD) and total volatile fatty acid (TVFA) of LL using EO pretreatment process were optimized under operational parameters: current density (10–40 mA/cm 2 ), electrode gap (0.5–2 cm), and contact time (15–60 min). Specifically, the effects of EO pretreatment on anaerobic co-digestion reactors with high volume of LL under mesophilic temperature (37 ± 1 °C) in terms of operational performance, methane yield, Gompertz model and energy assessment were investigated in batch mode. An increase of sCOD (320–1165 mg/L) and TVFA (172–742 mg/L) were observed when the current density increased from 10 to 40 mA/cm 2 . The highest methane yield (0.2925 L/g sCOD removed ) was obtained in anaerobic co-digested reactor fed with 35% LL (in volume). The EO pretreatment showed a significant reduction in the lag phase period for anaerobic co-digested reactors with high volume of LL. Furthermore, the high R 2 proved the reliable prediction accuracy of modified Gompertz model to experimental data. Energy assessment showed an increase of 5.88–16.55 kJ/g VS removed in anaerobic co-digested reactors compared to controls. The EO and anaerobic co-digestion showed as feasible and cost efficient method to enhance BMP and energy output from landfill leachate.