PARENT SESSION
MA5 - Selenium and Phosphate mining: Sources, Pathways, Receptors
Chair: Moller, Greg¹, ¹ University of Idaho, Dept. of Food Science and Toxicology, Moscow, ID
8:00 AM to 12:00 PM - Monday, 18 November 2002
Room Ballroom D

(208) Natural and Engineered Systems for Selenium Remediation, Sequestration and Control.

Moller, Gregory^*,1,2, Baier, Charles¹, Brackney, Kevin¹, Munkers, John¹, ¹ Environmental Research Institute, University of Idaho, Moscow, Idaho, US² Department of Food Science and Toxicology, University of Idaho, Moscow, Idaho, US

ABSTRACT- In our continuing field and laboratory work examining natural and engineered selenium control approaches in the phosphate mining areas of southeastern Idaho, we have found that amendments using iron metal combined with organic materials such as cheese whey, potato waste and composted manure can significantly sequester Se mobilized by natural weathering processes in the waste rock impoundments. Our experimental field removal efficiency in vadose zone soil-water, seeps, and even small creeks has been demonstrated at > 90% for various time periods. In most applications, Se concentrations in discharge have been lowered to below drinking water levels (50 g/L) or below aquatic biota criteria levels (5 g/L). We have observed that the application of iron metal and organic matter yields a significant increase in microbe catalyzed Se reduction, Se sorption on iron oxides and selenium mineralization. The field approaches explored include subsurface amendment horizons, infiltration gallery, surface amendment, and development of a passive subsurface reactor. We show the performance and dosing sequence of the subsurface wetland reactor. Inlet seep selenium concentrations were approximately 2000 g Se/L and demonstrated a decline over the next five months with an apparent late summer plateau of approximately 500 g Se/L. We demonstrate a 97% removal rate with the reactor effluent concentration of 24 g/L for this subsurface, passive reactor system.

Key words: selenium, remediation, control, treatment