Self-Regenerating Hybrid Anion Exchange Process for Removing Radium, Barium, and Strontium from Marcellus-Produced Wastewater Using Only Acid Mine Drainage

• Published in: ACS ES&T water 2021-01, Vol.1 (1), p.195-204
• Main Authors: Li, Jinze, SenGupta, Arup K
• Format: Article
• Language: English
• ISSN: 2690-0637; 2690-0637
• DOI: 10.1021/acsestwater.0c00069

The advent of horizontal hydraulic fracturing and its implementation for unconventional shale gas development in the Marcellus Shale region in the northeastern United States have created a uniquely challenging wastewater stream, termed produced (or flowback) water. The salinity or the total dissolved solids (TDS) of this wastewater stream often exceeds that of seawater by 3–4-fold (i.e., >150000 mg/L), and in addition, the produced water stream also contains very high concentrations of dissolved barium and strontium and elevated levels of radioactivity due to the presence of radium (228Ra and 226Ra). Both deep well injection and evaporative crystallization with waste heat are major avenues for produced water disposal. However, the presence of radioactivity and a high concentration of barium render the disposal unacceptable from an environmental impact viewpoint. In the same region, naturally produced acid mine drainage (AMD) is pervasive and this impaired water stream is relatively high in sulfate. Previous studies used AMD to precipitate divalent cations in produced water as insoluble sulfates. Due to dilution, however, the disposable volume of the treated water is greatly increased, thus causing transport to be more involved and expensive. In this study, we present a novel self-regenerating anion exchange process for treating the produced water using AMD but without any increase in the treated water volume. No other chemical is needed in the process, and most importantly, the efficiency of the proposed process is not influenced by the sulfate content of the AMD. During our laboratory investigation, nearly complete removal of radioactivity and >95% removal of barium and strontium were achieved at a Marcellus site in Pennsylvania using only a local source of AMD water.