The addition of ZVI to the traditional biological methods of wastewater treatment resulted in a significant improvement in pollutant levels, according to Ma, who directs the National Engineering Research Center for Urban Pollution Control in Tongji's College of Environmental Science and Engineering. The removal of biological oxygen demand (BOD) rose from 76 to 87 percent. Improvements were also recorded with the removals of nitrogen (13 to 85 percent), phosphorus (44 to 64 percent), and colors and dyes (52 to 80 percent).
"Before this project," says Ma, "few people believed scrap iron could work in a wastewater treatment plant. We have developed a copper-activated iron and used a systematic approach from benchtop to pilot to full-scale tests to show that ZVI-enhanced treatment can achieve dramatic improvements over biological processes used by themselves."
While biological methods, including biofilms and aerobic organisms, are effective at treating municipal wastewater, Zhang and Ma wrote in the ES&T article, they enjoy limited success in treating the less biodegradable and often toxic compounds in industrial wastewater, many of which are synthetic organic chemicals.
These chemicals are attracted to the surface of the iron, where they share electrons with the iron and are degraded and detoxified. The ZVI, which undergoes oxidation during this exchange, has a useful lifetime of about two years in the treatment process.
The ZVI scrap iron is chemically similar to iron-based nanoparticles invented by Zhang that are now widely used in North America to clean decontaminated soil and groundwater. The nanoparticles contain 99.9 percent iron and about .1 percent palladium or other Noble elements.
Zhang says the scrap iron's low cost gives it great potential to be used in developing cou
|Contact: Kurt Pfitzer|