Sustainable Remediation of Acidic and Metalliferous Mine Drainage Using an Adsorption-Constructed Wetland System: A Hybrid and Clean Approach

The efficacy of an engineered treatment wetland system was explored for the treatment of real acid mine drainage. Precisely, the treatment chain was a hybrid approach made up of two distinct stages comprising neutralization with magnesite (stage 1) and phytoremediation using a hydroponic floating wetland planted with Vetiver grass (stage 2). Both stages were operated in step-wise connection at the same flow rate of 1.6 L/d and with a hydraulic retention time of 40 days. Leachates were collected daily at the outlet of each wetland and the concentrations of inorganic pollutants were quantified. The findings revealed that pH increased from 2.8 to 8.4, demonstrating a significant attenuation of inorganic pollutants in the following order: Cu, Ni and Zn (100% each) > Fe (99.9%) > Al (99.7%) > Mn (96.41%) > SO42− (77.62%) and a moderate reduction in electrical conductivity (80.7%). Explicitly, a significant quantity of inorganic pollutants was attenuated in stage 1, while stage 2 further purified and polished the water to the desired standard. This, therefore, denotes the effective combination and complementary performance of the hybrid approach.