An innovative passive water treatment system, the world’s first full-scale vertical flow reactor (VFR), is becoming a reality at OceanaGold’s Reefton Restoration Project on the West Coast of New Zealand’s South Island. Scientists from Verum Group were instrumental in the design and installation of the system for the treatment of mine drainage.
The system removes heavy metals from water seepages before the water is gravity fed into Devil’s Creek. These metals, such as iron and arsenic, exist naturally inside the rock, but they could threaten the natural ecosystem if released at high levels into the environment.
Verum Group Senior Scientist Dave Trumm says the eyes of the mine-site environmental rehabilitation community around the world are now on New Zealand.
“In these systems, iron-rich water is oxygenated, which helps to precipitate the iron, then the iron particles are captured on a gravel filter bed contained in ponds with a small treatment footprint. The VFR system is the brainchild of Devin Sapsford of Cardiff University in Wales. Together with Devin, Verum Group installed trial VFRs in the USA, New Zealand, South Korea, and the UK in a range of mine drainage chemistries to understand exactly how these systems worked.
“A trial system installed at the Globe Progress Mine by Stephanie Hayton, as part of her Master’s thesis under the supervision of Verum Group, went one step further. Here, the contaminants consisted of both iron and arsenic. Iron naturally attracts other metals, and we found that the arsenic was adsorbed onto the captured iron in the reactor, resulting in clean discharge water.
“Based on these results and years of previous research, the full-scale system was designed, and installation is underway and due to be completed in late 2021.”
Over time, the metals will eventually be exhausted from the leachable area of the surrounding rock, and the ponds will continue to naturally spill into Devil’s Creek.