Innovative processes to desulfate the Paradox Valley brine

Abstract

Nanofiltration (NF) was tested in a laboratory setup for the selective removal of sulfate from the Paradox Valley brine (PVB). However, the application of NF as a stand alone technology will be hampered by the limitation of the scale and hydraulic boundaries. The scale boundary mainly relates to sulfate scale accumulation at the membrane surface and in the concentrate stream whereas the hydraulic boundary relates to the differences between the osmotic pressures at the membrane surface and the product stream. A further limitation is the generation of a large sulfate-rich concentrate stream that demands a suitable disposal path, particularly for inland operation. Therefore, innovative processing approaches to desulfate the PVB must be centered on technologies that could: (1) withstand severe sulfate scale and high osmotic pressures; (2) provide a near-zero or a zero discharge; and if possible (3) extract some potable water from the treated PVB to supplement the Dolores River. An innovative processing approach based on the integration of NF with the liquid-phase precipitation (LPP) is developed for the selective removal of sulfate from the PVB. The LPP as an efficient pre-treatment step will permanently solve the NF inherent sulfate scale problems. Another innovative approach is also developed by integrating membrane distillation (MD) with LPP. In addition to operate MD in a scale-free manner and without the limitation of the PVB natural osmotic pressure, MD will provide ultra-pure water from the treated PVB to augment the Dolores River. The use of reasonable amounts of energy and additive, and the extraction of economic values from discarded inorganic materials and streams are the compelling advantages of the LPP–NF or MD–LPP technologies.