International Case Studies of Acid Mine Drainage: Environmental Impacts, Treatment Performance, and Transferable Lessons for Global Mine-Water Management — A Critical Review (2020–2026)
Abstract
Acid mine drainage (AMD), acid rock drainage (ARD), and related acidic or metalliferous mine waters remain among the most persistent liabilities of sulfide-bearing mining because oxidation, hydrologic transport, secondary-mineral reactions, and legacy infrastructure can sustain contaminant release for decades after extraction ceases. This critical review synthesizes international case studies published from 2020 through September 2026, emphasizing the causal links among mineralogy, climate, hydrology, mine-waste architecture, hydrochemistry, treatment design, residuals management, and long-term field performance. The evidence shows that treatment success cannot be judged solely by short-term pH correction or dissolved-metal removal. Robust performance requires controlling acidity generation and flux, recognizing seasonal and multi-decadal variability, managing sulfate and salinity, preventing secondary reacidification, and establishing defensible routes for sludge, brine, and spent reactive media. Case studies from North America, Latin America, Europe, Africa, Asia, and Oceania demonstrate that source control, active neutralization, passive systems, and hybrid treatment trains each occupy distinct operating windows. Long-duration field evidence supports passive dispersed alkaline substrates and engineered covers in selected settings, whereas high-flow or highly variable systems often still require active treatment. Emerging approaches increasingly couple AMD control with water reclamation, critical-metal recovery, remote sensing, machine learning, reactive-transport modeling, and life-cycle assessment. The central conclusion is that AMD management should move from technology-by-technology selection toward adaptive, site-specific treatment trains evaluated across water quality, residual stability, carbon intensity, operational resilience, and life-cycle cost.