A Penn State environmental engineer has developed the first successful microbiological process for treating drinking water contaminated by perchlorate, a rocket fuel ingredient detected in 14 states where rocket, munitions, fireworks and match manufacturers are located.
Dr. Bruce E. Logan, the Stan and Flora Kappe Professor of Environmental Engineering, recently filed a patent disclosure on the process which relies on a mixture of several kinds of live bacteria to remove the pollutant. He presented a paper on the process at the National Groundwater Association meeting June 3 and 4 in Anaheim, Calif.
Logan says, "Recent improvements in the detection of perchlorate have shown that it has become a widespread contaminant of water in the western U.S. The California Department of Health Services found 30 percent of 232 wells sampled were contaminated. The Southern Nevada Water Authority found perchlorate in its tap water in just under action level. Perchlorate has also been found in the Las Vegas Wash, the Colorado River and Lake Mead."
High doses of perchlorate interfere with the absorption of iodine by the thyroid and is a serious human health concern when present in drinking water. Until Logan demonstrated his process, however, there was no proven removal technique available for the relatively low concentrations being found in the water supply.
Logan says that it had been known for over 40 years that certain bacteria found naturally in the environment could remove chlorate from water when there was no oxygen present. More recently, he and his research group, as well as other researchers, showed that the same bacteria could remove perchlorate under similar conditions.
The Penn State researchers packed glass tubes with sandy soil, added a mixture of naturally occurring bacteria that had been shown to remove chlorate and perchlorate, and waited until the bacteria, through normal growth processes, coated the soil grains by forming a biofilm and used up the oxygen in the tube. They then pumped perchlorate-contaminated water and nutrients through the soil-packed tubes. The filtered water emerged with perchlorate concentrations below 18 parts per billion, the action level, and even below the detectable level, 4 parts per billion, depending on the flow rate.
Logan says these preliminary experiments also suggest that the chlorate and perchlorate-destroying bacteria might be added directly to contaminated soil.
Early tests on soil samples from the Nevada Wash areas indicate that chlorate and perchlorate-destroying microorganisms are already growing there. However, he says, "We need to conduct additional tests to determine their abundance and ecological roles at perchlorate sites."
Logan's co-author on the paper to be presented at the National Groundwater Association (NGA) meeting is Kijung Kim, a master's degree candidate in the Department of Civil and Environmental Engineering. Their paper, Microbiological Treatment of Perchlorate Contaminated Ground Waters, was presented at the NGA Southwest Focused Ground Water Conference: Discussing the Issue of MTBE and Perchlorate in Ground Water.
EDITORS: Dr. Logan is available by phone at 814-863-7908 or by e-mail at blogan@psu.edu.