Conference Agenda

The concept of passive treatment of AMD was conceived in the early 1980 based on the observations of scientists in Ohio and West Virginia. They noted that the quality of AMD was improved after passing through a natural aerobic wetland and they postulated that oxidation reactions and settling of sludge particles caused the improvement. Among the first to construct and report on constructed wetlands were researchers at the US Bureau of Mines (Kleinmann, Hedin, Nairn, Watzlaf) but many others reported designs and results. By 1989, more than 150 wetlands had been constructed for mine drainage treatment.

This paper documents the application of a reducing and alkalinity producing system (RAPS) named CaroRap implemented for coal mine water remediation in South Africa. RAPS combines the mechanisms of anaerobic treatment wetlands and anoxic limestone drains. These systems improve water quality by processes, amongst others, of calcite dissolution and sulfate reduction through sulfate-reducing bacteria (SRB). Results from the system, which became operational in January 2021, show an increase in pH from an average of 2.9 to that of 5.6 coupled with an increase by 35.8 mg/L in alkalinity .

Drainages from mining operations frequently contain elevated levels of contaminants of concern (CoC). The unique adapted bacterial communities are characterized and their ability to reduce many CoC are showcased. Each contaminated site consists of a distinct prokaryotic community that in turn requires a specific C:N:P balanced environments to contribute to site remediation. This balanced bioremedial strategy are managed both for in situ or fix-filmed bioreactors, using hydraulic retention times, electron donor selection and ratios, and redox potential. These communities can effectively treat elevated levels of hexavalent chromium (10 mg/L), nitrate (110 mg/L), and sulfate (1 250 mg/L) in a one-pot balanced.

Real-time and on-site analysis of metals in waters is not routinely carried out for environmental monitoring. Laboratory analyses are used instead, which require sampling on-site, shipping to a laboratory and analysis making them expensive and slow. A novel analytical technique based on nanotechnology enhanced preconcentration and portable X-ray fluorescence was developed in this study. The analysis system was calibrated for Mn, Ni, Cu and Zn between concentrations of 50 µg/l and 10 mg/l and fast on-site analysis was demonstrated for two mining related sites.

Diffuse impacts to surface waters are a critical issue facing mining industries, given rigorous environmental quality standards. Many conventional treatment technologies are expensive and difficult to comply with discharge criteria. Gravel Bed Reactors (GBR™) are a versatile semi-passive treatment technology capable of addressing a variety of water quality issues through altering the geochemistry of extracted mine water. GBRs™ offer simpler, cost-effective alternatives to water treatment facilities, packed or fluidized bed reactors and the possibility to re-use waste rock as packing media. GBRs™ allow installation of smaller systems in remote, challenging environments and the potential to treat mine water at source.