The artesian groundwater being considered by Sandoval County, NM, contains 12,000 milligrams per liter of TDS with extremely high levels of calcium, magnesium, arsenic and boron, in addition to radionuclides and a temperature of 150 degrees Fahrenheit.
In “Marketability and Selective Recovery Methods for Concentrate Brine and Salts from Brackish Water Desalination,” a discussion of the six sparingly soluble and recoverable salts generated from brackish water supplies using reverse osmosis (RO) will be presented, including calcium carbonate, calcium sulfate, sodium sulfate, sodium carbonate, sodium chloride and calcium chloride. The characteristics and possible uses of the recoverable salts for a utility operating a desalination plant will be explored.
The presentation will include market analysis of the six salts identified, including product information and market trends, purity requirements and obstacles to using these salts produced from RO concentrate. Treatment processes that have the potential for selectively recovering salts from RO concentrate and research being conducted by the University of New Mexico on a possible ion exchange process for selective salt recovery will also be discussed.
Treatment and Usable Byproducts – A Pilot Study
A second presentation addressing salt recovery is “Salt Production from a Potable Water Supply – Pilot Study Results,” a summary of a pilot study conducted for Sandoval County Water Department (New Mexico) to investigate treatment of a saline groundwater for potable water use. The pilot testing also considered possible production of usable byproducts from the waste streams to reduce disposal costs and offset operating costs of the proposed desalination facility.
The artesian groundwater being considered by Sandoval County contains 12,000 milligrams per liter of total dissolved solids with extremely high levels of calcium, magnesium, arsenic and boron, in addition to radionuclides and a temperature of 150 degrees Fahrenheit. To remove these contaminants, a process treatment approach was developed using a combination of coagulation, chemical softening, media filtration, ion exchange and reverse osmosis to produce potable water. It also created three distinct waste streams, two of which could produce saleable byproducts.
Pilot testing confirmed that calcium can be effectively removed, maintaining a relatively pure calcium carbonate waste stream that can potentially be recovered, recalcinated and reused in the treatment process. RO waste streams were found to contain primarily sodium chloride and sodium sulfate, which can be separated from each other using nanofiltration to produce high purity salt product streams. The presentation will explore how the successful pilot testing—which achieved 80-percent RO recovery—is now guiding the county as it plans to produce a new water supply by treating saline groundwater.
