Persistence and decontamination of surrogate radioisotopes in a model drinking water distribution system |
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Authors: | Jeffrey G Szabo Christopher A Impellitteri Shekar Govindaswamy John S Hall |
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Affiliation: | aUnited States Environmental Protection Agency, National Homeland Security Research Center, Water Infrastructure Protection Division (MS NG-16), Cincinnati, OH 45268, USA;bUnited States Environmental Protection Agency, National Risk Management Research Laboratory, Water Supply and Water Resources Division, Water Quality Management Branch, Cincinnati, OH, 45268, USA;cLakeshore Engineering Services, Inc., USA |
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Abstract: | Contamination of a model drinking water system with surrogate radioisotopes was examined with respect to persistence on and decontamination of infrastructure surfaces. Cesium and cobalt chloride salts were used as surrogates for cesium-137 and cobalt-60. Studies were conducted in biofilm annular reactors containing heavily corroded iron surfaces formed under shear and constantly submerged in drinking water. Cesium was not detected on the corroded iron surface after equilibration with 10 and 100 mg L−1 solutions of cesium chloride, but cobalt was detected on corroded iron coupons at both initial concentrations. The amount of adhered cobalt decreased over the next six weeks, but was still present when monitoring stopped. X-ray absorption near-edge spectroscopy (XANES) showed that adhered cobalt was in the III oxidation state. The adsorbed cobalt was strongly resistant to decontamination by various physicochemical methods. Simulated flushing, use of free chlorine and dilute ammonia were found to be ineffective whereas use of aggressive methods like 14.5 M ammonia and 0.36 M sulfuric acid removed 37 and 92% of the sorbed cobalt, respectively. |
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Keywords: | Decontamination Infrastructure Drinking water Persistence Cobalt Cesium Radioisotope Biofilm |
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