Mining Wetlands | Acid Mine Drainage Treatment

In partnership with GEOENVIRON, Wetlands Construídos retrofitted a passive drainage water treatment system for a deactivated underground mine, aiming to meet the standards for Class II water (CONAMA 357/05), targeting pH (average influent concentration of 3.00), iron (average influent concentrations of 65 mg/L), manganese (average influent concentration of 1.24 mg/L), and sulfate (average influent concentrations of 526 mg/L).

The system's design addresses the specific geochemical signature of the water, combining several unit operations sequenced according to the removal route for each target parameter.

For this type of water, when Acid Mine Drainage (AMD) occurs, one of the biggest challenges is the high mobility of metals in an environment with very low pH (in this case, varying between 2 and 3). For this reason, the entire system arrangement was designed to create a geochemical environment, adjusting pH and redox potential patterns to ensure the precipitation of target metals.

In this project, the local topography was utilized so that all structures operate by gravity. The system flowchart consists of an alkalization stage, aeration, sedimentation basin, and surface and subsurface flow wetland systems.

The entire system operates passively, without continuous dosing of chemicals, without the use of electricity, with a low risk of vandalism and very low operational intensity and cost. Since this is a deactivated mine with no active industrial activities, these advantages are essential to the project's success and formed the basis of the entire design engineering.