How Alcoa is reducing discharges and contaminants at its aluminum facilities

Aluminum producer Alcoa implemented natural sustainable technologies to reduce the environmental footprint at three of its aluminum smelting, refining, and production facilities.

The innovative technologies, which Alcoa calls Engineered Natural Systems, use a variety of plants, soils, and microbes to reduce the volume of discharged stormwater and process water as well as the concentrations of pollutants in the discharged water. These passive "green" technologies are helping Alcoa to achieve environmental goals it set for itself in its "2020 Strategic Framework for Sustainability," which called for the company to reduce process water usage by 70% from 2000 to 2010 and achieve zero water discharge by 2020.

Alcoa retained the Engineered Natural Systems Group of environmental management and consulting firm, Roux Associates Inc., to provide professional expertise during the research, development, design, and installation of these natural systems at Alcoa's facilities in Mt. Holly, Lafayette and Iceland.

A pilot-scale constructed treatment wetlands system in conjunction with the development of a natural, sustainable, phytotechnology sprayfield at Alcoa's smelter facility in Mt. Holly succeeded in reducing process water discharges to a local publicly owned treatment works (POTW) by 60-70%. The cost to achieve this result was at least 50% less than conventional approaches, according to Alcoa.

Alcoa plans to expand the constructed treatment wetlands and sprayfield at Mt. Holly to further reduce stormwater and process water discharges at the entire site. The system is to be fully operational in 2007. The company also transferred knowledge it gained at Mt. Holly to construct a similar Engineered Natural System at its new smelting operations in Iceland. The Iceland smelter will begin operations in 2007.

The challenge at Alcoa's Lafayette Engineered Products Plant was different: remove PCBs from stormwater efficiently and at low cost. The sustainable solution selected to treat the water was an Engineered Natural System called natural media filtration.

Using natural leaves and mushroom compost, Alcoa built a pilot filtration system that enabled the Lafayette facility to reduce PCB levels in its stormwater by a factor of 10,000, from 1 part per million to less than 100 parts per trillion. According to Alcoa, this is the first demonstrated compost technology for PCB removal.

The Lafayette plant was able to achieve very stringent limits for PCB levels that were specified in its new operating permit. With the natural media filtration system, the facility now consistently achieves non-detect levels for PCBs using USEPA testing methods.

Total suspended solids in stormwater and aluminum levels in process water were also reduced by the natural media filtration technology.

Capital investment costs for the natural media filtration system at Lafayette were 60% less than a conventional sand filter carbon and membrane filtration system, according to Alcoa. Savings in operations and maintenance costs were more than 70%.

"We were excited to prove the cost-effectiveness of natural systems to Alcoa," said installer Roux Associates' principal, Walt Eifert. "Engineered Natural Systems are not applicable for all discharge problems, but they can be extremely effective and inexpensive under the right conditions."

For more information:

www.rouxinc.com