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

Abstract

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 ( 228 Ra and 226 Ra). 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 selfregenerating 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.

Use of a Novel Bio-Nano-IX Process to Remove SeO42– or Se(VI) from Contaminated Water in the Presence of Competing Sulfate (SO42–)

“…Its removal from the contaminated water in the presence of a much higher concentration of sulfate, with a chemical makeup similar to that of selenate, poses a formidable challenge. Many previous studies devoted to the selective sorption of trace ions by polymeric sorbents were devoted to the characterization and effects of functional groups, matrix composition, aqueous-phase ionic strength, the Donnan effect, and pore structures. − Hybrid ion exchangers have also demonstrated selective removal of trace amounts of naturally occurring arsenic from groundwater and barium and radioactive radium from the Marcellus-produced wastewater from gas wells in Pennsylvania. , Nevertheless, selective separation of selenate or SeO 4 2– in the presence of competing sulfate ions has remained elusive and unattainable to date. Experimental results of the study presented here validate that a synergistic combination of an anoxic biological process in tandem with HAIX-NanoFe sorption offers a new avenue for addressing the challenge.…”

“…49−53 Hybrid ion exchangers have also demonstrated selective removal of trace amounts of naturally occurring arsenic from groundwater and barium and radioactive radium from the Marcellusproduced wastewater from gas wells in Pennsylvania. 54,55 Nevertheless, selective separation of selenate or SeO 4 2− in the presence of competing sulfate ions has remained elusive and unattainable to date. Experimental results of the study presented here validate that a synergistic combination of an anoxic biological process in tandem with HAIX-NanoFe sorption offers a new avenue for addressing the challenge.…”

Progress of Ultrafiltration-Based Technology in Ion Removal and Recovery: Enhanced Membranes and Integrated Processes

“…Different technologies, such as precipitation–coagulation–flocculation (Figure a), adsorption (Figure b), ion exchange (Figure c), flotation (Figure d), and membrane-based separation have been developed for ion removal from wastewater. − Precipitation combined with coagulation, flocculation, and flotation has been widely applied for the removal of ions from wastewater due to their low cost. However, several major problems, such as the large volumes of generated sludge and the additional of extra chemicals limit their further application .…”