From Pollution to Bioremediation: Tackling Arsenic-Rich Acid Mine Drainage

Acid mine drainage (AMD) is a persistent environmental issue arising from the oxidation of sulfide minerals present in mine wastes. This process generates acidic, metal-laden effluents, often containing high levels of arsenic (As) – a toxic metalloid commonly found in the exploited ores. Arsenic-rich AMD poses significant risks to ecosystems and human health. This chapter provides an overview of the biogeochemical processes responsible for the generation of As-rich AMD. It explores current advances and remaining challenges in biological treatment strategies, focusing on iron (Fe)- and As-oxidizing bacteria and sulfate-reducing bacteria (SRB), which promote As and metal immobilization via oxidation–precipitation and sulfide-driven processes, respectively. The chapter offers a global state-of-the-art review of bioremediation systems developed for As-rich AMD. A critical analysis of the main operational parameters influencing treatment performance is provided. Special attention is given to the case study of the Carnoulès mine (France), whose mine waste deposit generates one of the most As-rich AMD worldwide. Over three decades of interdisciplinary research at this site have deepened our understanding of biogeochemical processes controlling As dynamics in AMD and the downstream aquatic environment. In particular, understanding natural attenuation processes – based on Fe and As oxidation and subsequent precipitation – has proven especially important for guiding treatment design. This knowledge enabled the stepwise development of bioremediation strategies, from lab-scale to field pilot experiments. These systems harness naturally occurring microorganisms (Fe- and As-oxidizing and sulfate-reducing bacteria) for the sustainable remediation of As-rich effluents on mining sites.