Removal of Radioactive Materials from Groundwater Using Iron Composite Media.

High levels of nitrate (NO₃) derived from agriculture and naturally occurring radioactive materials (NORM), primarily uranium (U) and natural decay chain products that have been mobilized by the influx of oxygenated, high-alkalinity water, are a threat to shallow groundwater resources in California. Iron Composite (IC) materials were evaluated as a water treatment option in a series of batch experiments. While the use of Zero Valent Iron (ZVI) to address groundwater contaminated with NO₃ or U has been demonstrated, the ability of ICs to chemically reduce and immobilize U and other associated contaminants in oxygenated alkaline groundwater where soluble uranyl-carbonate species dominate and high NO₃ levels may compete for reductive capacity remain a concern. Three different IC materials were evaluated in batch using an artificial groundwater surrogate containing NO₃ (89 ppm), 200 mg/L alkalinity, 100 µg/L U, 100 µg/L rhenium (Re), a non-radioactive surrogate for the fission product technetium-99, and 50 µg/L arsenic (As). Five gram samples of the three IC materials were reacted for seven days with 200 mL of artificial groundwater under two different atmospheric conditions to evaluate the impact of O₂. At specific time intervals, 5mL aliquots from each batch treatment were removed for chemical analysis (i.e., U, Re, As, Fe, NO₃, etc.) and the pH and ORP of the remaining suspension was measured.