Optimal treatment technology selection for acid mine drainage via spherical fuzzy analytic hierarchy process

The Philippines is endowed with large deposits of mineral resources, but mining operations have the potential to negatively impact the environment. For example, acid mine drainage (AMD) is a problem that occurs when sulfide minerals are exposed to air, water, and microbial activity, releasing hazardous elements. Many treatment options have been proposed to date to address these negative impacts of AMD. However, little effort has been made over the years to develop a generalized framework for the selection of the optimum technology for AMD treatment. This study thus proposes the spherical fuzzy analytic hierarchy process (SFAHP) as a multi-criteria decision analysis tool to select the best treatment technology for the treatment of AMD. The use of SFAHP is novel in this context as it addresses uncertainty due to indeterminacy by incorporating a "hesitancy parameter" in the decision-making process. Three treatment options were evaluated using a set of criteria such as technical, economical, and environmental aspects. The results showed that the combination of the two-step neutralization ferrite formation and sulfidogenic bioreactor (TSNFF + SB) was considered the most sustainable, with the environmental aspect being the most important factor. The second most preferred option is the high-density sludge (HDS) process while the least preferred is the combination of the conventional lime neutralization and sulfidogenic bioreactor (CLN + SB). A sensitivity analysis was also done, and a comparison with traditional AHP was conducted, which also found TSNFF + SB to be the best option. This illustrative case study demonstrates the robust framework built from SFAHP for selecting the best technology to manage AMD and addresses uncertainty in the decision-making process.