Capping agent test for tailings

Four mining companies and the federal government have invested $100,000 to see if ultramicrobacteria, or UMBs, can successfully and cheaply replace clay as a capping agent for tailing ponds.

If successful, it could reduce the capping costs by one-sixth, to $25,000 per hectare from $150,000 per hectare.

It has yet to pass one of its most crucial tests: whether or not it can withstand harsh Canadian winters.

Licence holder Continental Amelioration Research Environmentalists (CARE) International of Calgary is putting the agent through its paces this winter, first in a controlled lab environment, then in the field.

Among the research and development investors are Noranda Technologies, Inco (TSE), Teck (TSE) and Denison Mines (TSE). CANMET (Canada Centre for Mineral and Energy Technology) is also a contributor, through the federal government’s Ministry of Energy, Mines and Resources.

The tiny bacteria create a thick gelatin-like cap over the waste, and are self-perpetuating. With the use of a specially formulated nutrient and buffer solution, the UMBs are injected beneath the surface of the tailing pond. It takes about a month for the organisms to grow and secrete an exopolysaccharide gum that seals the top of the tailing pond, preventing acid-producing oxidation and binding toxic elements in place. “The basic idea behind using this ultramicrobacteria initially was establishment of a sub-strate biological barrier to isolate a pollutant,” said Paul Bercier, CARE International president. “If you think of this concept for a moment, what you’re doing is permeability reduction. The idea then of applying it to mine capping just evolved from there.” The basic science behind the UMBs is well known from natural occurrences. For example, lost water flow in water wells is often attributable to a biological plug around the well bore.

Research into UMBs as a capping agent is investigating whether this process can be controlled.

And it has an indefinite lifespan because of its self-perpetuating biological nature.

“The first idea is to get the surface capped so that you can exclude the oxygen,” Bercier said. “That is followed with the natural vegetation cap on it. Once the natural vegetation cap takes hold, then the roots provide the nutrients required to sustain and maintain the barrier.”

Bercier feels confident that a relatively inexpensive process can be fielded in 18 months.

Canada currently has more than 15,000 hectares of tailing ponds across the country.

This process has major significance for mining companies which are being asked to foot the bill for waste management costs long after mining projects have been abandoned.

As mining companies are expected to spend $3 billion in mine reclamation during the next 20 years, cost-cutting methods such as using UMBs as tailing pond caps instead of clay could figure greatly in those reclamation plans.