TABLE 2.2 Range of Total Dissolved Solids (TDS) in mg/L for CBM Produced Water from each Western Basin Compared to TDS for General Water Types and Water Quality Standards

 

TDS in mg/L

Western CBM basins

Powder River

250 to greater than 3,000

San Juan

10,000 to greater than 100,000

Raton

900 to 30,000

Uinta

6,350 to 42,700

Piceance

Greater than 10,000

General water types

Fresh water

Less than 1,000

Saline water

Greater than 1,000

Seawater

35,000

Water quality standards

U.S. Safe Drinking Water Act (secondary standard)

500

Wyoming agriculture standards (Class II)

2,000

Wyoming livestock standards (Class III)

5,000

NOTE: Both TDS and salinity can be used to measure water quality. TDS is a quantitative measure of all residual dissolved minerals after evaporation and is generally expressed as mg/L. Salinity measures the concentrations of dissolved salts in the water volume. Salinity may be measured by TDS, electrical conductivity, or osmotic pressure. Where sodium chloride and sodium bicarbonate are known to be the dominant minerals in a sample of water, such as in waters of the western basins, high TDS will often indicate high salinity.

SOURCES: ALL Consulting (2003); S.S. Papadopulos & Associates (2007); water.usgs.gov/watuse/wu-glossary.html (accessed July 6, 2010); www.watereuse.org/information-resources/about-desalination/glossaryd (accessed July 6, 2010); Wyoming DEQ (2005).

Generally, TDS concentration ranges from the hundreds to thousands of milligrams per liter in produced water in the basins where sodium bicarbonate dominates, such as in the Powder River Basin, whereas TDS concentrations can exceed tens of thousands to more than 100,000 mg/L where sodium chloride dominates the chemistry of the CBM water, such as in the San Juan Basin (Table 2.2). In the Powder River Basin, much of the geochemical signature of the produced water is derived from water-rock interactions (Box 2.3).

Jackson and Reddy (2007) report concentrations of trace elements and volatile organic compounds (Gas Research Institute, 1995; Rice et al., 2000) for produced water in the Powder River Basin (see also Jackson and Reddy, 2010). Some metals, such as barium, appear to have concentrations close to the solubility of controlling minerals (e.g., barite).



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