Geothermal heat for remote acid mine drainage remediation: a laboratory and modelling study

Abstract

The growing problem of abandoned mine wastewater poses a threat to the environment and people living in drought prone areas. Many abandoned mines are located in remote regions, set apart from energy sources, population centers and infrastructure, rendering necessary remediation efforts in these areas slow-moving, and in many cases nonexistent. The primary demand from the industry and the government for these sites is a passive system that utilizes locally available and cheap material. Often the geothermal gradient available in mines, or the corresponding geothermal reservoir conditions proximal to the mine, is a viable heat energy source that can provide advantageous temperature conditions for established remediation techniques, namely bioremediation, which can run on diverse, inexpensive, and locally available material. Although geothermal direct use and bioremediation are proven technologies when practiced independently, the combination is not straight forward. The following thesis will address the chemical, thermal, hydrological and biological intricacies of this process and its promise for providing relevant remediation to abandoned metal mines in remote regions. The findings show that a modest 12°C increase in bioreactor temperature in mountainous area applications can double the contaminant removal rate, necessitating half the volume of reaction. A temperature control can provide a passive mixing system with convection which reinforces flow paths, preventing clogging. A temperature addition also corresponds to permeability fluctuations, corresponding to the growth of different organisms.