PERFORMANCE OF VERTICAL FLOW REACTOR FOR THE TREATMENT OF FERRUGINOUS MINE WATER

Ferruginous mine water contains varying concentrations of Fe(II) that quickly oxidizes to Fe(III) in the presence of oxygen. The hydrated Fe(III) precipitates rapidly during mine water treatment under net alkaline or neutral conditions. Thus, passive treatment technique has been applied for mine water treatment using an open containment area so as to allow simultaneous oxidation and precipitation of Fe(II), such as in a lagoon or an oxidation pond. Recently, a vertical flow reactor (VFR) was suggested to remediate ferruginous mine drainage passing down through an accreting bed of ochre [1]. However, VFR has a limited operation time until the system begins to overflow. It was also demonstrated that two-compartment VFR has a longer operation time than single compartment VFR of same size [2]. A mathematical model was also developed as a part of efforts to explore the operation of VFR, showing dynamic changes in head differences, ochre depth and Fe(II)/Fe(III) concentration in the effluent flow [3]. In this study, a VFR comprising two compartments was designed based on the mathematical model of the previous study and installed at abandoned coal mine to measure water parameters like pH, suspended solids, dissolved metals and head difference as time passed. The VFR is composed of two compartments with equal floor areas (1.5 m²), each of which had a flat sand bed as the bottom floor. The apparent hydraulic conductivity of the sand bed was identified to be 30 - 50 m/day from head difference data and the mathematical model. The data obtained from the VFR operation were compared to the simulation results of the mathematical model under various conditions, which enabled us to identify the hydraulic conductivity of ochre bed and the kinetic constants for Fe(II) oxidation and ochre formation. We evaluated the performance of a pilot scale VFR (3 m³) for the treatment of ferrouginous mine water from an abandoned mine. Mathematical model was used to analyze VFR operation data to identify Fe(II) oxidation and ochre formation rate laws and ochre accretion that should be balanced with permeability of ochre bed to maximize VFR operation time and minimize residual Fe(II) in the effluent.