The detection of perchlorate in several surface waters and ground water wells used to supply drinking water created an unforeseen water contamination crisis in the many Western states in the United States and problems are likely to emerge at other sites where perchlorate is used. In March of 1997, the California Department of Health Services (CDHS) developed a method that reduced the detection limit of perchlorate from 400 ppb to 4 ppb. Based on EPA work, they established a provisional action level of 18 ppb for drinking water. Perchlorate is a health concern due to its interference with iodine in the production of hormones in the thyroid. Subsequent monitoring of 232 groundwater wells by the CDHS indicated perchlorate was in 69 wells (30%) and at concentrations above the action level in 20 wells (9%) (AWWARF 1997). Perchlorate concentrations in surface and groundwater range from detectable to 0.37%, and endanger the extensive use of Colorado River water in the western states. Samples taken from the Las Vegas Wash, which feeds Lake Mead and then the Colorado River, contained 1,500 to 1,680 ppb (Urbansky 1998). The Los Angeles Metropolitan Water District measured 8 ppb in water at its intake in Lake Mead, and the Southern Nevada Water Authority found 11 ppb in its tap water.
Perchlorate contamination arises from the generation and disposal of ammonium perchlorate (AP), a highly energetic compound produced for use in solid rocket propellant. It is extremely soluble and stable in water, and is not easily removed from water. It was the consensus of a team of experts that met at a special workshop on perchlorate that “at this time there is no proven removal process available at the low concentrations being found in drinking water” (AWWARF, 1997). Typical water treatment technologies such as ion exchange, air stripping, carbon adsorption and advanced oxidation, have so far not been shown to be economical for treating perchlorate, which is extemely stable in water and does not adsorb well to activated carbon. Despite its use in rocket propellant, perchlorate is stable in water even under highly reducing conditions. For example, merely lowering the Eh of the water to the range below -200 mV does not produce abiotic perchlorate reduction (Bliven 1996).
Penn State Research on Perchlorate
Research at Penn State on perchlorate and chlorate has been funded by a variety of sources, including the National Science Foundation (NSF), the Water Research Foundation (at that time it was called the American Water Works Association Research Foundation (AWWARF), Regenesis, and the Stan and Flora Kappe endowment. These projects cover both laboratory experiments and pilot scale testing of reactors. Our engineering collaborators on perchlorate removal technologies include CDM SMith (at that time it was Camp, Dresser and McKee, CDM), and EnSafe.
In 1998, Penn State filed a patent application for the concept of using fixed bed reactor technologies, and this patent was granted in 2000 (US Patent No. 6214607). These reactors can be fueled with organic substrates, such as acetate or acetic acid, or only inorganic substrates, using hydrogen gas. The process is called the PSU-O4 system (where O4 is our shorthand notation for perchlorate). In the summer of 2001, the PSU-O4 system was field tested at the Redlands Texas Well Street facility in Redlands, California. It was demonstrated that with proper backwashing and feed loads, the system could remove perchlorate to below the detection limit (4 ppb).
Selected Publications on Perchlorate
[For all publications, go to the publications page]
Steinberg, L., J. Trimble, and B.E. Logan. 2005. Enzymes responsible for chlorate reduction by Pseudomonas sp. are different from those used for perchlorate reduction by Azospira sp. FEMS Microb. Lett. 247:153-159.
Zhang, H, B.E. Logan, J.M. Regan, L.A. Achenbach, and M.A. Bruns. 2005. Molecular assessment of inoculated and indigenous bacteria in biofilms from a pilot-scale perchlorate-reducing bioreactor. Microb. Ecol. 49(3):388-398.
Xu, J., Trimble, J.J., Steinberg, L. and Logan, B.E. 2004. Chlorate and nitrate reduction pathways are separately induced in the perchlorate-respiring bacterium Dechlorosoma sp. KJ and the chlorate-respiring bacterium Pseudomonas sp. PDA. Wat Res., 38(3):673-680.
Song, Y. and B.E. Logan. 2004. Effect of O2 exposure on perchlorate reduction by Dechlorosoma sp. KJ. Wat. Res., 38(6):1626-1632.
Min, B., P.J. Evans, A. Chu, and B.E. Logan. 2004. Perchlorate removal in sand and plastic media bioreactors. Wat. Res., 38(1):47-60.
Song, Y. and B.E. Logan. 2004. Inhibition of aerobic respiration and dissimilatory perchlorate reduction using cyanide. FEMS Microbiol. Lett. 239:229-234.
Xu, J., Y. Song, B. Min, L. Steinberg, and B.E. Logan. 2003. Microbial degradation of perchlorate: principles and applications. Environ. Engin. Sci, 20(5): 405-422.
Xu, J. and B.E. Logan. 2003. Measurement of chlorite dismutase activities in perchlorate respiring bacteria. J. Micro. Methods 54:239-247.
Logan, B.E. and D. LaPoint. 2002. Treatment of perchlorate-contaminated groundwater in an autotrophic, gas phase, packed bed bioreactor. Wat. Res. 36(14):3647-3653.
Zhang H., M.A. Bruns, and B.E. Logan. 2002. Perchlorate reduction by a novel chemolithoautotrophic hydrogen-oxidizing bacterium. Environ. Microbiol., 4(10):570-576.
Logan, B.E. and J. Wu. 2002. Enhanced toluene degradation under chlorate-reducing conditions by bioaugmentation of sand columns with chlorate- and toluene-degrading enrichments. Bioremed. J., 6(2):87-95.
Logan, B.E. 2001. Assessing the outlook for perchlorate remediation. Environ. Sci. Technol. 35(23): 482A-487A. [Color, 13 mB]
Logan, B.E., J. Wu and R.F. Unz. 2001. Biological perchlorate reduction in high salinity solutions. Wat. Res. 35(12):3034-3038
Logan, B.E., H. Zhang, P. Mulvaney, M.G. Milner, I.M. Head, and R.F. Unz. 2001. Kinetics of perchlorate- and chlorate- respiring bacteria. Appl. Environ. Microbiol. 67(6): 2499-2506
Wu, J., R. Unz, H. Zhang and B.E. Logan. 2001. Persistence of perchlorate and the relative numbers of perchlorate- and chlorate-respiring microorganisms in natural waters, soils and wastewater. Bioremed. J. 5(2):119-130
Logan, B.E. 2001. Analysis of overall perchlorate removal rates in packed-bed reactors. J. Environ. Engng. 127(5):469-471
Miller, J.P. and B.E. Logan. 2000. Sustained perchlorate degradation in a gas phase hydrogen-oxidizing packed bed bioreactor. Environ. Sci. Technol. 34(14):3018-3022.
Kim, K. and B.E. Logan. 2000. Fixed-bed bioreactor treating perchlorate-contaminated waters. Environ. Engin. & Sci. 17(5):257-265.
Logan, B.E. 1998. A review of chlorate and perchlorate respiring microorganisms. Bioremediation J. 2(2):69-79.
Logan, B.E., A.R. Bliven, S.R. Olsen, and R. Patnaik. 1998. Growth Kinetics of Mixed Cultures under Chlorate-Reducing Conditions. J. Env. Engrg., 124(10):1008-1011.
Chapters in Books
Evans, P., A. Chu, S. Liao, S. Price. B. Min and B.E. Logan. 2002. Pilot testing of bioreactor for perchlorate-contaminated groundwater treatment. In: Remediation of of Chlorinated and Recalcitrant Compounds, A.R. Gavaskar and A.S.C. Chen. Battell Press. (ISBN 1-57477). Published on CD-ROM, 5 pages
Logan, B.E., K. Kim and S. Price. 2001. Perchlorate degradation in bench- and pilot-scale ex-situ bioreactors. In: Bioremediation of Inorganic Compounds, A. Leeson, B. M. Peyton, J.L. Means, and V.S. Magar, eds. Battelle Press, Columbus, OH. 6(9):303-308.
Logan, B.E., H. Zhang, J. Wu, R. Unz and S.S. Koenigsberg. 2000. The potential for in situ perchlorate degradation.In: Accelerated bioremediation of chlorinated compounds in groundwater. S.S. Koenigsberg and C.H. Ward, eds.Regenesis, San Juan Capistrano, CA. pp. 85-90.
Logan, B.E. 2000. Evaluation of biological reactors to degrade perchlorate to levels suitable for drinking water. In Perchlorate in the Environment, E.T. Urbansky Ed. Plenum, 189-197.
Logan, B.E., H. Zhang, J. Wu, R. Unz and S.S. Koenigsberg. 2000. The potential for in situ perchlorate degradation.In: Case studies in the remediation of chlorinated and recalcitrant compounds.G.B. Wickramanayake, A.R. Gavaskar, J.T. Gibbs and J.L. Means, eds.Battelle Press, Columbus, OH. pp. 87-92.
Logan, B.E., K. Kim, P. Mulvaney, J. Miller, and R. Unz. 1999. Biological treatment of perchlorate contaminated waters. In: Bioremediation of Metals and Inorganic Compounds. A. Leeson and B.C. Alleman, Eds.Proc. Fifth International Symposium of In-situ and On-site Bioremediation, April 19-22, San Diego, CA. 5(4):147-151.