USGS Patents Bioreactors that Treat Nitrate and Methyl Bromide Contamination

U.S. Geological Survey (USGS) scientists have developed and patented two bioreactor treatment systems. One is designed to remove dissolved nitrate from water supplies. The second is designed to remove gaseous methyl bromide from the exhaust that results from the fumigation of shipping containers. The systems are called bioreactors because they make use of specialized bacteria for efficient and cost-effective removal of the contaminants.

Nitrate Bioreactor Many households in the United States have ground water with elevated nitrate concentrations. High nitrate concentrations in drinking water are associated with adverse health effects, such as blue-baby syndrome. To help solve this problem, USGS scientist Richard L. Smith has designed, constructed, and patented (patent number 6,863,815 B1) a bioreactor that utilizes specialized microorganisms (hydrogen-oxidizing, denitrifying (HOD) bacteria) to remove excess nitrate from water supplies. The bacteria used in the reactor were originally isolated from sediments at the Toxic Substances Hydrology Program's research site on Cape Cod. The nitrate bioreactor is designed as a small-scale unit to treat single-well water supplies, which are typically affected by rural, non-point sources of nitrate contamination. The HOD bacteria in the bioreactor use hydrogen and nitrate to grow, and produce only water and nitrogen gas in the process, both of which are harmless end-products. The unit generates the hydrogen for the bacteria by the electrolysis of water. As a safety feature, the bioreactor is designed to contain only small amounts of hydrogen at any one time, and it produces the hydrogen only when needed. The inventor tested the bioreactor with ground water and surface water being used for home water supplies. He found the bioreactor to be functional and stable for long periods of time and capable of completely removing high levels of nitrate with only a 2-hour contact time. Laboratory-scale bioreactor for removing nitrate from water. Shown here is the bioreactor after 250 days of continuous bacterial growth. The purple pigmentation in the nitrate-free zone is created by the bacteria References Smith, R.L., Buckwalter, S.P., Repert, D.A., and Miller, D.N., 2005, Small-scale, hydrogen-oxidizing-denitrifying bioreactor for treatment of nitrate-contaminated drinking water: Water Research, v, 39, p. 2014-2023. Smith, R.L., 2005, Small-scale hydrogen-oxidizing-denitrifying bioreactor: Washington, D.C., U.S. Government Patent and Trademark Office, United States Patent No. 6,863,815 B1. More Information Microbial Biogeochemistry of Aquatic Environments More Information on Nitrate Nitrate Remediation, Massachusetts Military Reservation, Cape Cod, MA, USGS Toxics Program Remediation Activity Nitrogen Isotope Study Answers Questions about the Transport of Nutrients in Streams High Nitrate in the Desert? What’s Going On? A National Look at Nitrate Contamination of Ground Water Nutrients National Synthesis Project, USGS's National Water-Quality Assessment (NAWQA) Program Nutrients in the Nation's Waters--Too Much of a Good Thing?, USGS Circular 1136 Consumer Factsheet on: Nitrates/Nitrites, U.S. Environmental Protection Agency (USEPA) Technical Factsheet on: Nitrate/Nitrite, USEPA Nitrate, Integrated Risk Information System, USEPA Valuing Risk Reduction: The Example of Nitrates in Drinking Water (pdf 122 kb), Food Review, January-April 1997, U.S. Department of Agriculture

Methyl Bromide Bioreactor Seaports all along the coasts receive thousands of shipping containers each day that are routinely fumigated with methyl bromide to prevent non-native insects and other unwanted organisms from invading the country. The downside of this practice is that the methyl bromide (also know as bromomethane) exhausted to the atmosphere from fumigation operations has a negative impact on the Earth's ozone layer. In addition, methyl bromide is hazardous to human health. USGS scientists Larry Miller, Ron Oremland, and Shaun Baesman have received a patent (patent number 6,916,446) for a bioreactor that removes methyl bromide from the exhaust from fumigation operations. The bioreactor contains a culture of specialized microorganisms (methylotrophic bacteria) that removes methyl bromide from the exhaust by oxidizing it to carbon dioxide, hydrobromic acid, and water. A 1,000-liter bioreactor is capable of removing 10 kilograms (kg) of methyl bromide in 50 hours. The development of the bioreactor is a practical application of the extensive research by these scientists on microorganisms in the natural environment that degrade methyl bromide and other methyl halides (see text box). Laboratory-scale (10 liter) bioreactor for removing methyl bromide from the exhaust from fumigation operations. The fermenter contains 3 x 1012 cells of methylotrophic bacteria, Aminobacter ciceronei, capable of oxidizing 0.12 g of methyl bromide per hour References Miller, L.G., Oremland, R.S., and Baesman, S.M., 2005, A bioreactor for the oxidation of the fumigant methyl bromide: Washington, D.C., U.S. Government Patent and Trademark Office, United States Patent No. 6,916,446. Miller, L.G., Baesman, S.E., and Oremland, R.S., 2003, Bioreactors for removing methyl bromide following constrained fumigations: Environmental Science and Technology, v. 37, no. 8, p. 1698–1704. Oremland, R.S, Connell, T.L., and Miller, L.G., 2000, Method for enhancing oxidation of methyl bromide with strain IMB-1: Washington , D.C., U.S. Government Patent and Trademark Office, United States Patent No. 6,013,254. More Information Microbial Biogeochemistry of Aquatic Environments More Information on Methyl Bromide (Bromomethane) Methyl Bromide Phaseout , Ozone Depletion Rules and Regulations, U.S. Environmental Protection Agency (USEPA) Methyl Bromide , Topical and Chemical Fact Sheet, USEPA Bromomethane (Methyl Bromide), Integrated Risk Information System, USEPA Methyl Bromide (Bromomethane) Hazard Summary, Air Toxics Website, USEPA Bromomethane,ToxFAQs, Agency for Toxic Substances and Disease Registry Pesticides in the Atmosphere , USGS Fact Sheet FS-152-95 Alternatives to Methyl Bromide Soil Fumigation,1999 South Florida Restoration Science Forum Methyl Bromide Alternatives Newsletter, U.S. Department of Agriculture

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