PNNL

Abstract

A series of conventional saturated and pressurized unsaturated flow (PUF) column experiments were conducted to evaluate the effects of utilizing soluble polyphosphate amendments for in situ, subsurface remediation of uranium. Experiments were conducted under mildly alkaline, calcareous conditions, representative of conditions commonly encountered at sites across the arid western United States. Results presented here illustrate that application of a soluble polyphosphate amendment to sediment contaminated with uranium will rapidly reduce the concentration of uranium to near or below drinking water limits under water saturated and unsaturated conditions. Column experiment conducted in the absence of polyphosphate illustrate sustained release of aqueous uranium at concentrations well above drinking water standards in excess of over 25 pore volumes under saturated conditions and over 50 pore volumes under water unsaturated conditions. However, in the presence of tripolyphosphate the concentration of aqueous uranium released from sediment was near or below drinking water limits within 10 to 35 pore volumes under saturated and unsaturated conditions, respectively. Moreover, results indicate the necessity of conducting site specific dynamic tests in order to tailor phosphate remediation technology based relevant geochemical and hydrological conditions.