Development of an electrical conductivity screening test for mine waste assessments

• Leaching characteristics of a waste stream from a coal processing plant were evaluated.
• The key factors impacting electrical conductivity of leachate were evaluated using statistical analyses.
• Leachant volume to particles surface area ratio and oxidant were the most significant parameters.
• A conductivity screening test was developed for assessing environmental impacts of waste streams.

An environmental concern at mining operations is the potential leaching of trace elements from overburden and byproduct streams of processing plants. To provide a timely assessment of this concern, electrical conductivity of the leachate emanating from the plant waste streams can be measured as an indicator of the trace element content levels using the USGS Field Leach Test (FLT). However, the research reported in this publication revealed the need to modify the FLT procedure to improve the precision of the test results. The primary issue involved the importance of leachant volume-to-particle surface area ratio in the assessment of the leaching potential for a given source. To determine the key factors impacting leachability of a given material, a statistically-designed parametric study was performed. The experimental program evaluated the effects of particle surface area, the leachant volume-to-surface area ratio, and the amount of oxidant used to expedite the leaching rate during the test. The results revealed that the significant parameters are leachant volume-to-solid surface area ratio and the amount of oxidant. The findings were used to recommend a modification to the conductivity screening test.