Current Research in EEPS Seminar – Bingjie Ouyang – Earth Sciences Department, Dartmouth College
Title: Barium, Strontium, and Radium in Wastewater from Unconventional Oil & Gas Production – Distributions in Wastewater and Implications to Treatment
Wastewater from high volume hydraulic fracturing (HVHF) is highly saline and often contains elevated concentrations of strontium (Sr), barium (Ba) and radium (Ra). These elements are considered major contaminants during unconventional oil and gas production and may significantly reduce production efficiency if precipitated as scale minerals inside pipelines. Since such wastewater is often reused in HVHF, learning the distributions of Sr, Ba, and Ra in wastewater and removing these elements from liquid waste are important for contaminant assessment and waste treatment. Precipitation of Sr2+, Ba2+ and Ra2+ with SO42- is widely accepted as an effective method to remove these ions from wastewater. This work investigated the forms of Sr, Ba, and Ra in both untreated wastewater solids and treated materials by mixing wastewater with sulfate-rich fluids. Stemming from analysis of treated materials, the variance of Ra partitioning in precipitation was further examined under conditions with different solution chemistry. Sequential extraction was performed to study the distribution of Sr, Ba, and Ra in solids. Strontium, Ba, and Ra were present predominantly operationally defined soluble fraction in untreated solids, and were removed into sulfate fraction in treated materials. Titration and gel column experiments were conducted to evaluate the partitioning effects. High Sr:Ba ratios and freshwater conditions favored Ra partitioning into solids. The results of this study have implications for: understanding the fate of Sr, Ba, and Ra in HVHF waste, optimizing the chemical treatment methods that remove Sr, Ba, and Ra from wastewater, and evaluating the stability of co-precipitation in waste disposal sites.