Wastewater from high volume hydraulic fracturing (HVHF) is highly saline and often contains elevated concentrations of barium (Ba) and radium (Ra). Previous studies suggest that both Ra and Ba are preferentially released from black shale under high ionic strength conditions. Sulfate precipitation of Ba and Ra is widely accepted as an effective method to remove these ions from wastewater. However, the speciation of Ra in solids from HVHF waste streams is not well understood. We conducted chemical sequential extractions on solids from two waste sources: 1) produced water sludge, and 2) solids produced by mixing produced water with acid mine drainage (AMD) water in the laboratory. Extractions were analyzed for Ra by gamma spectroscopy and other elements by ICP-OES. For the produced water sludge containing &lt; 1% barite in the solids, the ratio of 226Ra associated with the solids to the 226Ra present in liquid is ~0.005 L/Kg; the same ratio for Ba in solids versus liquid is ~2.6 L/Kg, indicating limited partitioning of 226Ra relative to Ba in the sludge solids. Radium and Ba in the solids are partitioned predominantly between operationally defined exchangeable, carbonate / iron oxide, organic, and silicate fractions. In the solids formed by mixing wastewater with AMD, approximately 80% of the total Ra is found in the barite fraction suggesting that a co-precipitated sulfate phase is the dominant uptake mechanism in this process. These results have implications for designing chemical treatment processes that remove Ra and Ba from wastewater, as well as the subsequent stability of co-precipitated solids to leaching in waste disposal environments.

Fate of radium and barium in waste solids from hydraulic fracturing

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.