Alcoa Develops 'Engineered Natural Systems' to Reduce Discharges
The innovative technologies, called 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 stated in its "2020 Strategic Framework for Sustainability," which calls 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 ENR 200 environmental management and consulting firm, Roux Associates Inc., to provide professional expertise during the research, development, design, and installation of these natural systems at three of Alcoa's facilities -- in Mt. Holly, Lafayette, and Iceland.
"Roux was hired not only because of our experience in this area, but also because of our ability to work with Alcoa in coming up with innovative approaches," said Walt Eifert, Principal Hydrologist of Roux Associates and Director of its Engineered Natural Systems Group. "We were willing and able to work closely with Alcoa to push these technologies further than ever before."
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 to reduce 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.
Due to the success of the project, the development team was bestowed with Alcoa's coveted Environmental Health and Safety Achievement Award. The project was selected for the award by an independent panel of experts from renowned international organizations, including the World Environment Center, the Conference Board, the Center of Study for Corporate Sustainability in Argentina, and the Center for Environmental Education and Communications in China.
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 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%. The technology development team for the natural media filtration system was awarded the prestigious Alcoa Environmental Health and Safety Achievement Award for sustainable water treatment of PCBs.
Partnership with Roux Associates. "We were excited to prove the cost-effectiveness of natural systems to Alcoa," said Roux's 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."
Roux and Alcoa are currently developing a full-scale ENS system to handle process wastewater generated at Mt. Holly. The system will be fully operational in 2007.
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