Novel Treatment of Produced Waters from Shale Gas with Zero Liquid Discharge by Geothermal Heat

Vast amounts of impaired waters are produced in gas and oil wells. Energy-efficient desalination systems are needed to treat these waters to produce fresh water and concentrated brines. Mineral recovery systems can also yield valuable critical materials as byproducts. Savengy Technologies and University of Central Florida (UCF) will develop and commercialize an energy efficient system to treat shale gas produced waters through thermal desalination via a two-step multi-effect distillation (MED) system. The MED system uses thermal and electrical energy converted from geothermal sources. It will be integrated with mechanical vapor compression (MVC) and critical material recovery (CMR). This two-step MED process will result in near-zero liquid discharge. During the Phase I project, we will develop physics-based models to analyze our technology, build and evaluate a small prototype to confirm the feasibility. We will evaluate scalability to a large treatment system for study in Phase II. The Phase I effort project will also include a study of a two-step CMR process. MED with MVC combined with CMR can treat high-salinity shale gas produced water. According to the characteristics of different feed materials, CMR can flexibly select rare earth treatment mode by using specially designed filters. The pretreatment system is capable of removing benzene and other organics simultaneously. Our current capabilities can capture bulk groups of metals and then release individually or as a bulk group as well. We will program the filter system to capture and release bulk rare earth elements and selectively release other critical materials. We will show the system designed temperatures and flow rates for different operating conditions with a set of performance curves under the different conditions. We will compare our results on energy consumption with other desalination methods and demonstrate multifold reduction in energy consumption. Our proposed technologies and systems are able to produce fresh water (<500 ppm total dissolved solids) from highly salty water (>33,000 ppm total dissolved solids). The condensed water is re-useable water and the process will result in near-zero liquid discharge where CMR is more economical. In Phase II and beyond, we will collaborate with our partners to design and build a system for a 10,000 gal/day plant, with further investigations into scaling issues for a 100,000 gal/day target.