Stability of water treatment sludge, Climax Mine, Colorado Part II: Leaching characteristics

Ponds have been used as reactors for lime neutralization water treatment at the Climax Molybdenum Mine since 1977, with sludge disposed of in two of the three tailings impoundments at the site. Proposed changes to the water treatment process resulted in a program to determine the long-term geochemical stability of sludge in the Mayflower impoundment. Sludge samples were collected from four locations in the Mayflower impoundment to evaluate the spatial variability of water treatment products throughout the water pool; two samples are sludgerich, two other samples have a significant tailings component. All samples were subjected to a sequential batch extraction (SBE) procedure at pH 7 and 9, allowing their behavior to be evaluated under conditions of increasing fluid-sludge ratios. The results of the SBE indicate that there is little potential for dissolution of metal-bearing phases under neutral to alkaline conditions.