High Recovery Reverse Osmosis Process Defies Silica Scaling Standards

DesaliTec™ announced recently that its SOAR (previously ReFlex) reverse osmosis (RO) process successfully purified groundwater at the Kay Bailey Hutchison (KBH) Desalination plant in El Paso, Texas, at record high water recovery rates. The announcement was made upon completion of tests conducted by the University of Texas’ Center for Inland Desalination Systems (CIDS) over a period of eight months. The tests successfully demonstrated brackish water desalination operation at 94% recovery without silica (and other) scaling, far exceeding the recovery rates possible with traditional RO technology. The demonstration establishes a new standard for water efficiency in reverse osmosis processes with significant global financial and environmental implications.

Silica is a natural contaminant present in ground water around the world that is notorious for precipitating in desalination and other membrane processes, producing a dense coating that is nearly impossible to remove. Accordingly, the water recovery rate at which a reverse osmosis system can operate is limited by the presence of silica and other sparingly soluble constituents. Low-recovery operation results in a high-volume waste stream that requires difficult and expensive treatment or disposal. The prospect of sustainable inland RO operation at recovery rates that exceed the saturation concentrations of these salts represents a technological breakthrough for industrial and municipal water purification.

The 27.5 million gallon per day KBH plant was commissioned in 2007 to supply drinking water to El Paso. The plant assures public water supply despite drought conditions, emergency situations, population growth and salt water intrusion into fresh water aquifers. The plant pumps groundwater from an onsite nearby wellfield to treatment works that include sand strainers, cartridge filters and reverse osmosis equipment. The plant is currently operating at 82.5% recovery, limited by the traditional multi-stage RO design along with the high silica concentrations, resulting in a wastewater stream that is sent to disposal wells.

CIDS installed a mobile containerized DesaliTec™ RO pilot unit at the KBH plant in June of 2015. The pilot unit was equipped with standard reverse osmosis membranes, pumps and other components, which operated at typical membrane flux and crossflow rates. Recovery rates above 90% were sustained for days of continuous testing. The highest recovery achieved without scale formation was 94%, corresponding to silica supersaturation of 273%. For context, traditional reverse osmosis and distillation systems are generally limited to a maximum of 100% silica saturation. Detailed results of the tests are expected to be published by CIDS.

About The Center for Inland Desalination Systems
The Center for Inland Desalination Systems (CIDS) builds on a strong foundation of related research already being done by faculty members in geological sciences, chemistry, and civil engineering at The University of Texas at El Paso (UTEP). CIDS researchers are primarily focused on inland desalination issues such as researching and developing high recovery desalination processes and recovering useful products from desalination waste streams. For more information, visit http://cids.utep.edu.