Phosphate-Induced Immobilization of Uranium in Hanford Sediments.

Phosphate can be added to subsurface environments to immobilize U(VI) contamination. The efficacy of immobilization depends on the site-specific groundwater chemistry and aquifer sediment properties. Batch and column experiments were performed with sediments from the Hanford 300 Area in Washington State and artificial groundwater prepared to emulate the conditions at the site.

Effect of Reaction Pathway on the Extent and Mechanism of Uranium(VI) Immobilization with Calcium and Phosphate.

Phosphate addition to subsurface environments contaminated with uranium can be used as an in situ remediation approach. Batch experiments were conducted to evaluate the dependence of the extent and mechanism of uranium uptake on the pathway for reaction with calcium phosphates. At pH 4.

Transport of U(VI) through sediments amended with phosphate to induce in situ uranium immobilization.

Phosphate amendments can be added to U(VI)-contaminated subsurface environments to promote in situ remediation. The primary objective of this study was to evaluate the impacts of phosphate addition on the transport of U(VI) through contaminated sediments. In batch experiments using sediments (<2 mm size fraction) from a site in Rifle, Colorado, U(VI) only weakly adsorbed due to the dominance of the aqueous speciation by Ca-U(VI)-carbonate complexes.

Effect of diffusive transport limitations on UO2 dissolution.

The effects of diffusive transport limitations on the dissolution of UO(2) were investigated using an artificial groundwater prepared to simulate the conditions at the Old Rifle aquifer site in Colorado, USA. Controlled batch, continuously-stirred tank (CSTR), and plug flow reactors were used to study UO(2) dissolution in the absence and presence of diffusive limitations exerted by permeable sample cells. The net rate of uranium release following oxidative UO(2) dissolution obtained from diffusion-limited batch experiments was ten times lower than that obtained for UO(2) dissolution with no permeable sample cells.

Impact of galvanic corrosion on lead release from aged lead service lines.

Partial lead service line replacement (PLSLR) may be performed when tap water lead concentrations exceed the action level and in association with water main replacement or other maintenance. Partially replacing lead pipes with copper tubing can create a galvanic couple if the lead and copper are connected by a metal coupling, which can potentially enhance lead release by galvanic corrosion. The effect of two types of couplings, brass and plastic, on lead release after a simulated PLSLR was investigated in a set of laboratory-scale experiments.