From neutralization to resource recovery: Option studies for sulfate removal and acid valorization in acid mine drainage

Acid mine drainage (AMD) with high sulfate requires treatment trains that balance discharge compliance, cost, and resource recovery. Using a consistent design basis of 100 m 3 ·h −1 (pH 3.5; 14 g·L −1 SO₄ 2− ), we quantify the feasibility and economics of precipitation, reverse osmosis (RO) concentration, sulfate-reducing bacteria (SRB) wetland polishing, and bipolar-membrane electrodialysis (BMED). Order-of-magnitude Faradaic sizing shows full-flow electrodialysis (ED)/BMED is infeasible, demanding more than 10 6 A and more than 10 3 m 2 membranes; by contrast, 0.1–1 m 3 ·h −1 side stream BMED is practical, producing acids/bases at specific energies near 6.8 MWh·t −1 H₂SO₄. For 1 m 3 ·h −1 of AMD flow, precipitation followed by BMED hybrid reduces the BMED area to 65 m 2 as opposed to the large area required for full-flow treatment. Energy price dominates operational expenditures (OPEX); at less than $0.05 kWh −1 and with on-site substitution of recovered chemicals, pilot BMED approaches breakeven. We provide consistent mass/cost bases, product-quality targets, and sludge-management pathways, offering a decision framework for AMD sulfate control with credible circular-economy value. • Precipitation treats acidity and metals effectively but with high costs. • RO polishing lowers TDS after pretreatment but does not enable sulfate valorization. • ED/BMED is infeasible at 100 m 3 h −1 ; side stream BMED is viable for recovery. • Wetlands and SRB suit partial treatment but sidestream avoids excessive land use. • Energy dominates costs; internal acid–base reuse and renewables reduce OPEX by ~58%. • Hybrid trains (precipitation–RO–BMED) best balance performance, cost, circularity.