Model-Based Feasibility Assessment of a Sequenced Anaerobic Limestone Drain and Sulfate-Reducing Bacteria System for Passive Acid Mine Drainage Treatment

Acid Mine Drainage (AMD) poses global threats to ecosystems and has compelled the optimization of passive treatment systems via the understanding of internal hydrochemical and biological kinetics. This study systematically analyzed the performance of an integrated treatment scheme combining Anaerobic Limestone Drains (ALD) and Sulfate-Reducing Bacteria (SRB) through a multi-scale experimental and modeling approach. At the laboratory scale, the ALD reactor effectively neutralized highly acidic AMD (pH < 3.0) and favored the precipitation of Al- and Fe-hydroxides. However, the ALD exhibited lower efficiency for Zn 2+ and Mn 2+ removal, due to pH oscillations that altered the adsorption kinetics, as testified by reactive transport modeling in porous media. The encouraging ALD results prompted the construction of a pilot-scale ALD-SRB coupling system. Experimental results were complemented with a second numerical model to evaluate the sulfate removal performance. In the mature phase, observed and simulated results indicated a sulfate removal rate of 1.22 × 10 -4 mol m -3 s -1 ( R 2 > 0.92), which aligned with the stabilization of the Desulfovibrio -dominated syntrophic network. This integrated strategy confirmed the tight coupling between chemical and biological reaction kinetics, providing theoretical foundations and alternative approaches for optimizing upscaled passive AMD remediation.