Sensitivity analysis of significant parameters affecting landfill leachate generation rate.

A landfill was designed to evaluate leachate quantity's governing factors using the HELP model. As a case study, the proposed methodology was tested in the Nazlou Landfill, Urmia, Iran. Indeed, the main objective was to illuminate the efficacy of executive parameters defined in the model. Lack of the final cover layer in the pre-closure period affects leachate generation as precipitation enters directly into the waste layers and changes their moisture constituents. Concerning the occurrence of the heaviest precipitation condition in the last 30 years in the pre-closure period, leachate leakage might increase to 0.23 m/tonne of waste. Due to changes in the layers' initial moisture, the effect of precipitation on leachate generation lasts till the landfill post-closure and would change the drained leachate from 0.083 to 0.089 m/year-tonne of waste (this amount is generally neglected in the leachate collection system design). During pre-closure, the heaviest precipitation causes an increased generated leachate by 37.59% in the first post-closure year, which is vital especially in landfills with limited capacity treatment plants. The impact of operating conditions involves the landfill leachate generation up to different years. However, over five years of averaging, the precipitation trend was consistent with the leachate leakage. Based on the different scenarios defined regarding the meteorological conditions and design parameters, if the geomembrane layer was removed from the final cover, the leachate quantity will be increased by 79.38%. Replacing 76 cm of dense clay can overcome this challenge.