Biofilters as an eco-efficient technology for the removal of iron and copper from acid mine drainage

Abstract

The present research aims to evaluate the efficiency of copper and iron removal using a biofilter composed of vegetable ash, dried guinea pig manure, and cattle manure applied to acid mine drainage (AMD). Real AMD samples with an initial pH between 2.70 and 2.72 were collected and treated through three biofilter configurations with different biomass dosages: Treatment 1 with 50 g of vegetable ash, 30 g of guinea pig manure, and 20 g of cattle manure; Treatment 2 with 40 g of ash, 40 g of guinea pig manure, and 20 g of cattle manure; and Treatment 3 with 20 g of ash, 60 g of guinea pig manure, and 30 g of cattle manure. Contact times of 5, 10, and 15 minutes were evaluated, showing a rapid increase in pH to values between 7.2 and 8.9. Residual concentrations of Fe and Cu were determined using a colorimetric method with a digital colorimeter and specific reagent kits. The results showed that Treatment 3 achieved the best performance, reaching a maximum removal of 89.84 % for iron and 97.85 % for copper at 15 minutes, while formulations with higher ash content produced higher alkalinity but lower stability in metal retention. It is concluded that pH increase alone does not guarantee effective remediation and that the contribution of organic matter plays a fundamental role in metal immobilization, demonstrating that the proposed system constitutes an eco-efficient and viable alternative for passive AMD treatment in rural contexts.