Evaluation of the use of acid mine drainage (AMD) sludge as soil amendment

Abstract

The treatment of acid mine drainage (AMD) involves chemical additives to raise pH and precipitate solubilized metals. The byproduct of this process is an AMD sludge precipitate, and its management and disposal are a continuous environmental legacy.  This study evaluated the application of AMD sludge as a soil amendment to support vegetation establishment. A small-scale growth study was completed with six treatments composed of different proportions of topsoil and AMD sludge as follows:  i) 100% topsoil, ii) 10% sludge, and 90% topsoil, iii) 20% sludge and 80% topsoil, iv) 30% sludge and 70% topsoil), v) 40% sludge and 60% topsoil), and vi) 50% sludge and 50% topsoil. Four replications of each treatment were considered.  Ground cover was monitored weekly for nine weeks (September 29, 2021 – December 2, 2021). Stem length and biomass were measured. Groundcover varied from 14.6% to 70.1% among all treatments throughout the study; all treatments were determined as statistically similar to the 100% topsoil treatment. Biomass ranged from 1.41 to 6.22 g, and average stem length varied from 3.6 to 4.6 cm.  Toxicity did not exceed minimum levels for one representative sludge sample. This preliminary study provides support for the further advancing AMD sludge as a soil amendment.