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Search Result from the February 2010 Issue

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OPERATION OF IN SITU BIOLOGICAL SYSTEM FOR TREATMENT OF HEXAVALENT CHROMIUM AT THE SELMA PRESSURE TREATING SUPERFUND SITE
Yurovsky, M., D. Cacciatore, L. Hudson, D.P. Leigh, C. Bhullar, and W. Shaheen. In Situ and On-Site Bioremediation 2009: Proceedings of the 10th International In Situ and On-Site Bioremediation Symposium, 5-8 May, Baltimore, Maryland. Battelle Press, ISBN: 9780981973012, CD-ROM, 2009

Groundwater at Selma Pressure Treating Superfund Site is affected by discharges of hexavalent chromium. A full-scale in situ bioremediation (ISB) recirculation system was implemented to convert soluble hexavalent chromium to trivalent in the extended plume. Treatment involved adding a biodegradable substrate (molasses) to the injected groundwater in a 450,000-square-ft treatment area where contamination extended vertically from the top of the groundwater at 45 feet to 120 feet below ground surface (bgs). Injection well biofouling was counteracted by delivering the substrate in pulses, by cleaning injection wells with a hydrogen peroxide solution and compressed air, and by daily injections of disinfectant solution containing chlorine dioxide (a biocide solution). In 21 months of continuous around-the-clock operation, 155 million gallons of groundwater was recirculated, and ~250 pounds of hexavalent chromium was converted. The concentration of hexavalent chromium has decreased from as much as 3,000 ug/L to less than 50 ug/L (MCL level).



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