Many companies have historically used carbon based adsorbents to reduce the mercury concentration in well water but are unable to utilize carbon to achieve the low levels of mercury that are now desired. Steward has conducted successful field tests at locations where new stringent mercury adsorbent targets could not be met with carbon adsorbents.

For the process described below, Steward first demonstrated that Thiol-SAMMS® was able to reduce mercury in well water down to ~14 ppt from a starting concentration of about 25,000 ppt in a static batch kinetics test with a very small amount of SAMMS applied. Steward then conducted several trials demonstrating that SAMMS was able to reduce the mercury level below ~12 ppt and lower using a series of lab scale fixed bed filters.

Steward then conducted field tests applying a series of contactor tanks with separation systems that retained the SAMMS in the series of tanks. The field system is designed for a nominal 10 gallons per minute flow but can be scaled up or down. The results of the field test are shown in Figure 1. Some data during startup has been smoothed to remove testing inconsistencies. In the tests SAMMS was able to reduce the mercury concentration in the well water from its input levels of 20,000 - 30,000 ppt down below the detection limit of EPA Method 245.7 (shown as 5 ppt in the figure), well below the 12 ppt mercury reduction goal. The field test ran for 1,300 hours and processed over 450,000 gallons of well water.

FIGURE 1. Mercury Concentration.

The field test also verified the high mercury adsorption capacity of SAMMS (about 40 pounds of SAMMS is typically used in the 10gpm system). In addition, mercury laden SAMMS from the field test passed the United States Environmental Protection Agency land disposal requirements, Toxicity Characteristic Leaching Procedure (TCLP). This enables used adsorbents to be disposed of in a non-hazardous landfill where compliance with local regulations are permitted and also minimizes generating the larger volume of secondary waste from spent carbon.