Removal of Multiple Contaminants from Mining Waste Impoundment with SAMMS®

One of Steward’s Continuous Stirred Tank Reactor (CSTR) system was utilized at a Nevada mining facility for a field test to demonstrate the use of Thiol-SAMMS® for the removal of multiple contaminants from a mining waste impoundment.  The CSTR system is a flow-through system that uses Thiol-SAMMS sorbent to remove mercury and other related soft heavy metals from the aqueous waste.   Although the CSTR system is designed to utilize one or more reactors in series configuration, in this test the CSTR system was set-up to run in a batch type treatment mode.  A 5,000 gallon flexible tank (FT) was filled with over 4,000 gallons of barren solution.  Water from the FT was pumped through the 3 tank CSTR system and the effluent was returned to the FT.  The water was treated for approximately 72 hours.

The initial concentration of mercury in the barren solution was 1,110 ± 30 ppb.  During the test, samples were taken periodically after each stage of the CSTR system and in the FT.  After 24 hours the mercury concentration in the FT was reduced to 110 ppb.  The mercury concentration in the FT continued to drop during the test.  The concentration was reduced to about 20 ppb after 48 hours and about 6 ppb after 72 hours.  Samples from the three CSTR units showed even better performance.  The concentration of mercury from the first, second and the third CSTR units were 1.9 ± 0.5, 0.7 ± 0.2 and 0.4 ± 0.1 ppb respectively during the duration of the test.

FIGURE 1.  Mercury Concentration in the Flexible Tank.
In addition to the high level of mercury reduction during the test period, other heavy metals were analyzed to evaluate the effectiveness of SAMMS removing multiple contaminants at the same time.  The elements of interest that were tested included silver, cadmium and lead.  The reduction of these metal contaminants was evaluated by ICP-MS and is significant for all three.   The silver concentration in the FT was reduced from 1679 to 192 ppb.  The cadmium concentration in the FT began at 23 ppb and was reduced to 0.36 after 72 hours.  The lead concentration in the FT was reduced from 1.40 ppb to 0.20 ppb during the same time.

In this field trial a batch treatment test was used to compare to other SAMMS deployment technologies.  However, if faced with this waste stream for a permanent treatment solution it would probably be more desirable to have a single flow through treatment.

For more detail on this case watch this video.