Naturally-occurring brines from Paradox Valley, Colorado, seep into the Dolores River and ultimately into the Colorado River, adding 200,000 tons of salt per year to the river. The Bureau of Reclamation had planned to reduce this contamination by pumping brine from shallow wells near the Dolores River into a deep injection well, thereby preventing movement of brine into the river. A USGS study, conducted in cooperation with the Bureau of Reclamation, indicated that the higher temperature of the deep well would cause the high concentrations of sulfate in the brine to react and clog the aquifer, soon making it unsuitable for future injections. Although the Paradox brine is about seven times more concentrated than sea water, USGS experiments showed that a membrane used by the petroleum industry to remove sulfate from sea water in the North Sea could be used to remove the sulfate from the brine and make it suitable for the deep-well injection. The USGS scientist, aware of the selenium problems from agricultural drainage and aware that some of the properties of selenium are similar to sulfur, then tested the membrane on selenium contaminated water from the San Joaquin Valley, California, and was able to remove 98% of the selenium from highly contaminated samples.

For additional information and references see the project description, Geochemistry of Water in Fine Grained Sediments, or contact: Yousif K. Kharaka
U.S. Geological Survey, 345 Middlefield Rd, MS472, Menlo Park, CA 94025
Internet: ykharaka@usgs.gov
Telephone: 415-329-4535