From: Cornell University News Service
Water Treatment Cleans Pesticides On-Site
ANAHEIM, Calif. -- A new Cornell University invention can clean up waste water from pesticides and textile processing on-site efficiently, inexpensively and without some of the problems of current technologies, say two Cornell University environmental chemists.
This major improvement of the commonly used pesticide rinse water treatment processes was reported by David Saltmiras, a Cornell doctoral student in environmental toxicology, at the American Chemical Society's (ACS) national meeting at the Anaheim Disneyland Hotel today (March 23). His research, which won the 1999 ACS Agrochemicals Division Young Scientist Predoctoral Research Award, was conducted with water-quality expert Ann Lemley, Cornell professor in the College of Human Ecology.
The new cleanup system, called Anodic Fenton Treatment (AFT), is relatively fast, taking just two to three minutes to clean up a glass of water contaminated with atrazine, the most widely used herbicide in the United States. In contrast, the commonly used technology used worldwide, called the Classic Fenton Treatment (CFT), takes about 30 seconds but it has certain drawbacks that the new system corrects. A basic electrochemical version of CFT takes about 25 minutes. Using their new system, the researchers also have successfully degraded the contaminants trifluralin and ETU (ethylene thiourea).
The researchers noted that AFT has the promise of a much faster cleanup, and also has the capability of being used as an on-site flow-through system, allowing contaminated water to be pumped in and emerge clean. "We believe that because of its flow-through capabilities, it has the potential to be an on-site treatment and disposal system for farmers and industries and perhaps even for Superfund and other hazardous waste sites," said Saltmiras.
Many waste water cleanup systems generate hydroxyl radicals because they are very reactive and degrade contaminants in waste water, such as dyes and pesticides. One common way to generate hydroxyl radicals is with the Fenton reaction as in AFT and CFT. "Using the Fenton reaction has become increasingly popular worldwide in recent years to degrade pesticide wastes because it is cheap and easy," says Saltmiras who expects to receive his doctorate next year.
In the CFT, iron salts deliver the needed iron to trigger the Fenton chemistry. However, these salts absorb water from the air, making them more difficult to handle and weigh accurately.
In a variation of this treatment, the electrochemical Fenton system, iron salts aren't used. Instead, an electrode delivers the needed iron via an electrical current to achieve the Fenton reaction. However, the hydroxide ions produced as the water gets broken down raise the pH of the water. This system, which is much slower than the classic Fenton method, produces water with a neutral pH -- not acidic enough for the Fenton reaction to proceed efficiently.
To improve on these Fenton systems, Saltmiras and Lemley developed the AFT process, for which they hold a provisional patent. AFT involves using two electrochemical half-cells. In the first half-cell, iron is delivered by an iron anode which triggers the Fenton reaction and produces the pesticide-chewing hydroxyl radicals; in this cell, the hydroxyl radicals break down the unwanted chemicals in the waste water. The pH remains low and keeps the Fenton reaction working efficiently.
The other half-cell has the cathode needed for an electrical current. It contains tap water, which gets broken down and produces hydroxide ions; the ions raise the pH of the water. Finally, waters from both cells are combined, one with a low pH and one with a higher pH, to produce water with a neutral pH. This water can then be safely discarded.
Although AFT is still not as fast as the classic Fenton treatment, AFT has tremendous potential, Saltmiras and Lemley believe.
The research, which also was presented at the Ninth International Pesticide Chemistry Congress in London last August, is funded by the U.S. Department of Agriculture.
Related World Wide Web sites: The following sites provide additional information on this news release. Some might not be part of the Cornell University community, and Cornell has no control over their content or availability.
-- For information on Ann Lemley, see http://www.human.cor nell.edu/txa/faculty/lemley.html
-- For information on the Department of Textiles and Apparel at Cornell University, see http://www.human.cornell.ed u/txa/txahome.html
-- 217th ACS national meeting, Anaheim: http://www.acs.org/meetings/anaheim/welcome.htm