New Horizons (March 03, 2008)

For centuries, some of the greatest scholars believed in alchemy — the ability to turn base metals into gold. While none ever succeeded, there are echoes of alchemy in today’s technological advances that are allowing mine operators to turn the metals and byproducts found in wastewater into a viable, revenue-generating product, while at the same time helping them to reduce their impact on the environment.

Mine operators are competing in a market where environmental regulations are becoming increasingly stringent. Reducing the environmental impact of operations has become especially critical in an industry that is experiencing growth at twice the rate of the Canadian economy.

At the same time, operators need to scrutinize the economic viability of adopting new technologies to address these needs.

Mining companies have always maintained a focus on water treatment, since it demands considerable investment over a long time. Historically, miners have treated acid and metal contaminated mine water by adding lime (calcium oxide or hydroxide), or sometimes caustic soda, to precipitate metals as hydroxides to form sludge.

Simply put, lime treatment transfers heavy metal contaminants from one medium (water) to another (sludge). Because the sludge winds up containing the heavy metals, it must be stored and managed, often in perpetuity, to prevent the contained metals from re-dissolving and entering the environment.

To put the challenge in perspective, it is estimated that 70% of the world’s mine sites experience acid mine drainage. This naturally occurring process leads to contamination of water, and is a result of water and oxygen reacting with exposed sulphide minerals in waste rock, tailings, rock cuts and underground workings.

In the process, the water picks up a variety of heavy metals, including copper, lead, zinc, cadmium, nickel, cobalt and arsenic. The resulting water is often toxic to plants and animals.

The treatment of acid mine drainage is fully regulated, and therefore can create an ongoing environmental liability long after a mine has closed. In fact, environmental regulations surrounding the treatment of contaminated water can represent the single greatest liability for mine operators.

Lime treatment technology is widely used, easily engineered and relatively simple to operate. For the most part, it has been successful in meeting water quality discharge standards in most jurisdictions.

But this will not continue to be the case, as a growing number of jurisdictions are adopting stricter regulations for water treatment and are more closely scrutinizing sludge management.

Furthermore, newly introduced regulatory requirements for the reduction of sulphate concentrations that are always present in acid mine drainage, demand a performance well beyond the capabilities of existing lime plants.

Even after a closure, mine operators and/or government agencies are faced with absorbing the ongoing

cleanup costs, which can last for years.

As a result, mining companies have to allot a significant portion of their planning budgets to ongoing remediation and cleanup activities relating to wastewater before, during and after production. Regulators are also requiring miners to post bonds that guarantee long-term remediation costs.

Clearly, given these circumstances, lime treatment alone is becoming an increasingly unrealistic solution. That is why many operators are seeking an entirely new approach to treating effluents from mines.

Looking to the future

The issues surrounding wastewater treatment and environmental stewardship are certainly not exclusive to mining companies that operate in Canada. Companies around the world are aggressively pursuing more efficient, cost-effective, alternative technologies to help them address these increasingly stringent environmental regulations.

Today’s consensus is that it is far more prudent and cost-effective to invest in future requirements from the outset, than to wait for legislation to be passed. In many cases, mining firms have realized that a reactive or “make-do” approach inevitably will lead to more costly retrofits and sizable penalties.

So, rather than addressing only the here and now, most are ensuring that what they invest in today will address potential liabilities and regulatory changes down the road.

Newer, advanced technologies in wastewater treatment are now available that allow operators to meet regulatory requirements, minimize environmental impact, and reduce the penalties associated with long-term remediation activities.

At the same time, they can also deliver a reasonable return on investment through the sale of recovered byproducts.

For example, two proprietary processes that we have developed in Canada and deployed worldwide selectively recover metals from acidic mine wastewater, and produce clean water that can be safely discharged to the environment or recycled. Metals such as copper, zinc, cobalt and nickel can be recovered and sold to generate revenues and offset the cost of the water treatment process. Toxic metals such as arsenic, antimony, cadmium, lead, molybdenum and manganese are also removed from the water.

Another new treatment technology we have developed and deployed removes sulphate from contaminated water to produce a saleable gypsum coproduct and clean water that meets new sulphate regulations that are being adopted in many jurisdictions around the world. It is an ion-exchange technology that can replace the more costly alternative of reverse osmosis and other competing technologies.

These processes do not produce a toxic sludge, thereby eliminating the associated long-term environmental liability.

The processes also cost less over the long term because of the reduced liability and the revenues generated from the sale of recovered metals and some byproducts.

Given Canada’s exceptional prospects for the mining industry and our global reputation for environmental leadership, we now have a unique opportunity to lead the world in addressing water treatment challenges at mine sites. –The author is CEO of Vancouver-based BioteQ Environmental Technologies, which builds, owns and operates water treatment plants that remove metals and sulphate from contaminated water (www.bioteq.ca). He is a specialist in mineral processing and biohydrometallurgy, and has 25 years of experience in plant operations, process consulting, business development and management, working in the mining industry around the world.