(8)Active treatment of tailings seepage with focus on sulfate and manganese removal

摘要

Mine operators are facing demanding water and wastewater treatmentchallenges due to supply scarcity and tightening regulatory dischargeconstraints. Water quality of collected tailings seepage is a significantproblem due to elevated metal and solute concentrations. Most metals canbe removed by conventional lime neutralization and solid/liquid separationprocesses, but manganese and sulfate are more difficult to remove due totheir solubility even at high pH values. Also, high reagent consumption andlong residence time can make their treatment unviable. This is a commonissue for compliance with environmental discharge limits and water qualityrequired for process reuse to reduce water make up.This paper presents a review of active treatment methods for: (i) Theremoval of manganese through aeration, chemical oxidation and filtering;and (ii) sulfate removal by its precipitation with limestone/lime, bariumsalts, ettringite generation, the use of membranes and biological sulfateremoval. Thermodynamic and kinetic issues will be discussed.The application of these technologies individually or in conjunctionwill depend on site specific conditions, economical constraints, effluentcharacteristics, technical feasibility and local standards. Finally, theselection of alternatives can be supported with treatability studies atlaboratory and pilot scale in order to determine critical and designprocess parameters.