The Wellington Oro treatment plant behind heaps of dredge rock: a reminder of Breckenridge`s mining past
Since last November, a water treatment facility designed by BioteQ Environmental Technologies and operated by the Town of Breckenridge in Colorado has been treating up to 35 cubic metres of contaminated water per hour from the former Wellington Oro mine. During that time, the stockpiles of zinc-cadmium concentrate — a byproduct of the treatment process (along with clean water) — has been growing at the treatment plant. Far from a nuisance to be rid of, however, creation of the concentrate had been a valuable feature of BioteQ’s design. In fact, it had been instrumental in helping the company beat out international competitors for the Environmental Protection Agency-vetted contract to provide the technology to treat the drainage from an old mine a few miles upstream from the mountain resort town.
This past summer, the Colorado Department of Public Health and Environment confirmed what BioteQ had always maintained: the contents in the collection of pallets filled with zinc-cadmium sulphide, collecting in the bay of the plant, was not waste. The high-grade concentrate can, instead, be sold to a metal refiner and trucked away to be turned into anything from batteries to paint. This not only eliminates the need for sludge-filled catchment ponds and the disposal cost when that sludge has to be removed, but mines value from what once was simply waste.
The ChemSulphide™ Process
BioteQ applies its proprietary ChemSulphide™ water treatment technology to recover saleable metals that are otherwise lost through acid mine drainage or during processing. To extract the metals, sulphide is mixed into a tank containing mine drainage or waste from metallurgical processing. The chemical conditions of the sulphide reagent are tuned to target a specific metal in a contactor tank. The soluble metal precipitates, forming solid metal particles. The metal and water are then sent to a clarifying tank where the solid is filtered out and condensed. This process, put into operation last year at Jiangxi Copper Company’s Dexing Mine, yielded 120,000 tonnes of copper processed from waste and low-grade stockpile drainage. The treatment plant, owned in a joint venture with Jiangxi Copper and operated by BioteQ, sells the recovered copper back to the company for refining. At a similar operation in Queensland, Australia, a series of contactor tanks — each adjusted for a specific metal — and clarifying tanks together allows the reclamation of copper, nickel and cobalt.
Traditionally, lime treatment has been the most widely applied approach to cleaning up acid mine drainage. Relatively cheap, lime made into slurry, then added to the drainage raises the pH of the water to the point where metals in it become insoluble, form particles and sink. Over time, innovation has made lime treatment more efficient, but the process inevitably generates metal-heavy sludge that remains an environmental and financial liability. Added is the problem that, as the standards for effluent rise, lime-treated water may not always meet them. The BioteQ process smooths out both of these wrinkles.
“Our technology can’t solve all water treatment problems,” explains BioteQ CEO Brad Marchant. “We can’t do desalination. In some cases a simple lime plant can work just fine.” Those cases, however, will likely become fewer as regulations tighten. For Breckenridge, the mining town-turned-recreational tourism destination, BioteQ’s chemical sulphide plant was the right fit. Breckenridge’s water department operates the plant with the help of BioteQ, whose technical team can monitor all stages of the operating process from its company headquarters in Vancouver. “Putting a lime plant in there would have been a bad idea. It would have created a tremendous amount of sludge with nowhere for it to go,” says Marchant.
There is, he says, no typical site where BioteQ simply “cuts and pastes” its technology. Each operation is designed to fit the needs of their customers and settings. “We work at both old and operational sites — base metal mines, gold mines, coal mines, and different geographical and geological settings.”