Assessment of Mine Drainage Management at Iron Ore Operations in Kogi State, North Central Nigeria

Mine drainage management at iron ore operations presents significant environmental and operational challenges, particularly in the context of Kogi State's humid tropical climate and complex hydrogeological setting. This study assesses mine drainage generation, characterisation, and management practices at iron ore mining operations in the Lokoja and Okene districts of Kogi State. Site water balances were established for three active operations using monitoring data including rainfall, evapotranspiration, runoff, and pit inflows. Drainage water samples collected monthly over one rainy season were analysed for pH, conductivity, total suspended solids, and dissolved metals including iron, manganese, and chromium. Drainage management infrastructure, including sedimentation ponds, pumping systems, and discharge points, was inspected and assessed for design adequacy. Findings reveal that sedimentation pond volumes are undersized at two operations, resulting in overflow during peak rainfall events and discharge of suspended-solid-laden water into adjacent streams. Iron and manganese concentrations in final effluents exceed NESREA discharge limits at all three sites during peak discharge periods. Effective passive treatment options including anaerobic wetlands and limestone drains are evaluated for technical feasibility. Recommendations include redesign of sedimentation systems, installation of automatic flow monitoring and early warning systems, and adoption of progressive pit backfilling to reduce long-term drainage volumes. Keywords: mine drainage, iron ore, Kogi State, water quality, management.