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Iron Works! Innovative Technology to Clean Water
Article Posted On 10/23/2009
Iron has been used by mankind for thousands of years and is the most widely used metal nowadays. Researchers at Lehigh University believe they have identified yet another use for iron - particularly scrap iron - which could not only help minimize the waste that scrap iron creates but also help clean up contaminated water.
Associate Professor Wei-xian Zhang and colleagues at Lehigh University and Tongji University in China recently completed one of the largest projects in the world to assess iron in environmental remediation. Rather than use the conventional iron powders that have become the norm in such water treatment techniques, Zhang turned to iron shavings obtained from local metal-processing shops, which are available in abundance at a relatively low cost.
The six-year project set out to explore the technical and economic feasibility of using iron shavings, which may have otherwise ended up in the scrap heap, for the enhanced treatment of industrial waste water. A bench-scale experiment was carried out for six months during 2003-2004 at an industrial park in Shanghai. The treatment plant received waste water from more than 50 small to medium sized factories, many of which produced dyes, pigments, petrochemicals, and pharmaceuticals, and proved effective at removing most of the contaminants from the water supply.
The project graduated in 2005 to a pilot test in which 2000kg of iron shavings were used to treat 12,600 gallons of water per day. The proven success of the addition of iron shavings to the water treatment process led to the Shanghai city government approving a full-scale treatment reactor in the Taopu district of the city, capable of processing almost 16 million gallons of water every day. The iron reactor contains almost one million kilograms of iron shavings and has been in continuous use since first connected in August 2006.
Professor Zhang states, "The addition of the iron reactor improved immediately and substantially the quality of water in the treatment plant. Following the success of the project, we have been invited by several municipalities to assess the feasibility of the combined iron-bio process for treatment of wastewaters from a variety of industrial processes. We may have opened up a new chapter in industrial waste treatment."
As well as iron shavings, Lehigh researchers have also pioneered the use of nano-sized iron particles in comparable water treatment techniques, which are now widely used in many parts of the world. Due to their greater surface area, nano-particles have been shown to have greater reactivity than more granular sizes and are, therefore, potentially more efficient at removing contaminants from water. Nano-iron reaction rates can be also as much as 10,000 times higher than conventional iron particles and, when suspended in solution, are easily injected into underground water sources without the need for extensive underground work.
"This opens the potential for portable water treatment systems that can be easily implemented at low cost," Professor Koel explains: "Research at Lehigh shows that nano-iron can degrade a wide variety of environmental contaminants including PCBs, chlorinated hydrocarbons, chlorinated pesticides and perchlorate. Degradation of a widely used pesticide, lindane, which has been shown to have harmful side effects in animals, for example, was found be over 95 percent following treatment with iron nano-particles for 24 hours." A field experiment in New Jersey has further highlighted the potential of the technology.
Funding from the Pennsylvania Infrastructure Technology Alliance has enabled the Lehigh researchers to examine the applications and potential implications of iron in the environment while collaborating with PA industry. These researchers have partnered with Lehigh Nanotech LLC, a knowledge-driven firm in Bethlehem, PA, focused on the development of new and value-added nanomaterials for environmental remediation and wastewater treatment. Lehigh Nanotech is conducting several pilot scale field projects using nano-iron to remediate contaminated groundwater, while working with Keystone Innovation Zones and the City of Bethlehem to improve the city's wastewater treatment plant.
