Reliability Assessment of Bioreactor Landfill Performance Using Coupled Thermo-Hydro-Bio-Mechanical Model

This study presents a reliability-based analysis performed using a coupled thermo-hydro-bio-mechanical model to assess the long-term performance of a typical landfill cell geometry under simulated bioreactor landfill conditions. Several Monte-Carlo simulations were carried out by considering randomly generated lognormally distributed fields of different properties of waste to represent the waste heterogeneity. The long-term performance of the simulated bioreactor landfill cell was evaluated in terms of wetted area ($W_A$), cumulative methane (${\mathrm{CH}}_4$) gas generated ($W_{{\mathrm{CH}}_4}$), maximum surface settlement ($S{S}_{\max }$), and maximum temperature of the waste ($T_{\max }$), at different intervals of time during the operation of the simulated bioreactor landfill cell. A deterministic analysis was also conducted using the mean values for the different properties of waste. The results show that the deterministic analysis overpredicts the maximum value for $W_A$, $W_{{\mathrm{CH}}_4}$, $S{S}_{\max }$, and $T_{\max }$ obtained from the stochastic analysis by approximately 10%, 17%, 25%, and 14%, respectively. The most likely values estimated for the four performance metrics from the stochastic analysis were approximately 44%, $\mathrm{88,000}{\mathrm{m}}^3$, 5.5 m, and 62.5°C, respectively. It was also determined that the waste’s anisotropy with regard to its hydraulic conductivity and the biodegradation-induced void change parameter had the most influence on $W_A$ and the $S{S}_{\max }$ in the landfill cell, respectively.