Evaluation of biogas production rate and leachate treatment in Landfill through a water-energy nexus framework for integrated waste management

The aim of this study was to investigate the simultaneous biogas generation and leachate treatment using municipal waste and its polluted leachate at Mashhad landfill in northeast Iran. The research focused on examining the kinetic model of CH₄, CO₂, CO, H₂S and O₂ production with and without leachate recirculation (LR) through control/test wells. The findings from both wells showed an increase in logarithmic CH₄ production rate, with the coefficient related to the rate of increase in methane concentration ranging from 0/52-0/64 in the control well and 0/47-0/55 in the test well, respectively. Under LR conditions, it was observed that the CH₄ production rate was slower, taking an average of 120 minutes to reach 50% concentration, compared to just 15 minutes without LR. Using first-order equations, the CH₄ production coefficients were measured to be 2/17 h⁻¹ and 0/9 h⁻¹ for the control and test wells, respectively. The analysis of recirculated leachate revealed a significant decrease (∼30%) in the total volume of leachate with 72% COD removal, which could help manage overloaded leachate problems in the landfill. The COD removal coefficient was found to be 0/036 day⁻¹ in the control well, whereas the test well with leachate recirculation showed a more rapid decrease from 50 g.l⁻¹ to about 14 g.l⁻¹ with a removal coefficient of 0/012 day⁻¹, three times higher than the control well. Additionally, nitrogen content analysis indicated that although the amount of ammonia content increased with LR, the increase was relatively low in comparison to conditions without LR, equivalent to 1394 ppm and 1000 ppm in control and test wells, respectively. This study aligns with the water-energy-nexus concept by offering a sustainable solution for waste management and energy generation, while also addressing water management challenges associated with landfill operations.