Water management is core to the mining industry, could natural processes ensure a more sustainable water system? A new project in Saudi Arabia hopes so.
Most of the water used in aluminum refining and smelting is treated in a system that involves networks of pipes and tonnes of steel. The water is "cleaned" in tanks using chemicals, monitors, mechanical filters, and man-power to assess purity levels. When it's clean enough, the water is returned and reused for industrial use.
A new joint project between Alcoa and the Saudi Arabian Mining Company (Ma'aden) wants to change all that. By constructing wetlands that naturally act as a bio-filter for sanitary and industrial wastewater from the world's largest integrated mine for aluminum, natural vegetation stimulates growth of microorganisms and natural chemical processes to remove nitrogen, metals, and other impurities from the water.
The engineered wetlands also add efficiency and competitiveness to the value chain. It's expected that the system will avoid the purchase of 1,000 tonnes of steel and reduce water demand by 2m gallons (7.5m litres) per day, a saving of US$7m annually that would otherwise be used to purchase water.
Engineered wetlands systems are not new, but getting such a large scale, three-step system to mimic the physical, chemical, and biological processes of natural wetlands to purify wastewater in the aluminum industry is innovative.
First built and tested at an Alcoa facility in Pittsburgh four years ago, the Ma'aden natural infrastructure uses common reeds, a native grass species. Already the wetlands are attracting birds to the area, and could potentially provide an important habitat for migratory birds. The size of seven football fields, the engineered wetland was chosen because it saved money and its effectiveness was proven. It was also built six months faster than a conventional tank-based system.
Ken Wisnoski, president of global primary products growth at Alcoa, said the Ma'aden project sought balance between using the newest innovations and avoiding risky systems that were not yet tested. "We have seen the engineered wetlands work for over four years and we knew the project could be easily transferred to Saudi Arabia, to the largest engineered wetlands of its kind in the world," he said. "If it had not been proven to work, we would have shied away from it."
For Ma'aden's location in the desert, water is a precious commodity and comes from a desalination plant. The closed-loop system holds water underground, so it doesn't evaporate. Managing this resource in a water-intensive industry and using it wisely is core to the business, said Abdulaziz A Al Harbi, president of Ma'aden Aluminum. "In Saudi Arabia, water is a very important resource and the wetlands technology helps to make sure the industry is competitive, has very good efficiency, and reduces the impact on the environment."
Ray Kilmer, executive vice president and chief technology officer at Alcoa, said the natural system is more effective than mechanical filters that require sophisticated controls and human intervention to target certain chemicals that are expected to pass through the system. Kilmer said the wetlands bacteria cleans whatever passes through, whether it's pharmaceuticals and hair conditioner from residential wastewater or industrial wastewater. "The wetlands provide a better mechanism for cleaning the water, helping the earth use its own processes to heal itself, and don't require sophisticated controls," he says. "Its also less cost, more effective and more robust." Kilmer said the Ma'aden system, which was scaled up from the Pittsburgh test site, is being considered for other mining and industrial applications throughout Saudi Arabia.
Smelting and mining processes are energy intensive. Power sources and industrial processing require so much water that they're usually located near abundant natural water sources. As the world's largest integrated mine for aluminum, the Alcoa-Ma'aden project in a desert location seems counter-intuitive. Still, Marielle Canter Weikel, senior director of responsible mining and energy at Conservation International, said she is seeing greater use of green infrastructure with companies that handle large volumes of water because it makes good business sense.
"This whole idea of natural infrastructure is catching on with corporate goals over the past three to five years, to add value and to achieve their corporate commitment of sustainable water management," she says. Dow is now using wastewater treatment in Texas, and DuPont is also doing work on this, she said.
Weikel points to one of the best examples of natural filtration — New York State, which relies on water filtered naturally. It comes from upstream in the Catskill, Delaware and Croton watersheds to provide 1.1bn gallons of drinking water per day. By paying $1.5bn to protect the watersheds and forested lands, New York City has avoided $10bn in costs to build an expensive water treatment facility.
The scarcity of water and management of natural resources is still a very big business concern. Corporations that put value on natural systems is one of the major emerging trends in water management. Understanding and innovating around high risk areas, such as water resource management, can help businesses target sustainability investments.