No abstract

For several decades, high-salinity water brought to the surface during oil and gas (O&G) production has been treated and discharged to waterways under National Pollutant Discharge Elimination System (NPDES) permits. In Pennsylvania, USA, a portion of the treated O&G wastewater discharged to streams from 2008 to 2011 originated from unconventional (Marcellus) wells. We collected freshwater mussels, Elliptio dilatata and Elliptio complanata, both upstream and downstream of a NPDES-permitted facility, and for comparison, we also collected mussels from the Juniata and Delaware Rivers that have no reported O&G discharge. We observed changes in both the Sr/Ca and Sr/Sr in shell samples collected downstream of the facility that corresponded to the time period of greatest Marcellus wastewater disposal (2009-2011). Importantly, the changes in Sr/Ca and Sr/Sr shifted toward values characteristic of O&G wastewater produced from the Marcellus Formation. Conversely, shells collected upstream of the discharge and from waterways without treatment facilities showed lower variability and no trend in either Sr/Ca or Sr/Sr with time (2008-2015). These findings suggest that (1) freshwater mussels may be used to monitor changes in water chemistry through time and help identify specific pollutant sources and (2) O&G contaminants likely bioaccumulated in areas of surface water disposal.

No abstract

In the western U.S., produced water from oil and gas wells discharged to surface water augments downstream supplies used for irrigation and livestock watering.

Oil and gas extraction generates large volumes of produced water (PW) in regions that are water-stressed. PW can be passively treated in retention ponds prior to beneficial use. Oxic conditions lead to sequestration and lower bioavailability of Ra.

No abstract

Mixing of acid mine drainage (AMD) and hydraulic fracturing flowback fluids (HFFF) could represent an efficient management practice to simultaneously manage two complex energy wastewater streams while reducing freshwater resource consumption. AMD discharges offer generally high sulfate concentrations, especially from the bituminous coal region of Pennsylvania; unconventional Marcellus shale gas wells generally yield HFFF enriched in alkaline earth metals such as Sr and Ba, known to cause scaling issues in oil and gas (O&G) production. Mixing the two waters can precipitate HFFF-Ba and -Sr with AMD-SO 4 , therefore removing them from solution. Four AMD discharges and HFFF from two unconventional Marcellus shale gas wells were characterized and mixed in batch reactors for 14 days. Ba could be completely removed from solution within 1 day of mixing in the form Ba x Sr 1−x SO 4 and no further significant precipitation occurred after 2 days. Total removal efficiencies of Ba + Sr + SO 4 and the proportion of Ba and Sr in Ba x Sr 1−x SO 4 depended upon the Ba/Sr ratio in the initial HFFF. A geochemical model was calibrated from batch reactor data and used to identify optimum AMD−HFFF mixing ratios that maximize total removal efficiencies (Ba + Sr + SO 4 ) for reuse in O&G development. Increasing Ba/Sr ratios can enhance total removal efficiency but decrease the efficiency of Ra removal. Thus, treatment objectives and intended beneficial reuse need to be identified prior to optimizing the treatment of HFFF with AMD.

Hydraulic fracturing is often criticized due in part to the potential degradation of ground and surface water quality by high-salinity produced water generated during well stimulation and production. This preliminary study evaluated the response of the freshwater mussel, Elliptio complanata, after exposure to produced water. A limited number of adult mussels were grown over an 8-week period in tanks dosed with produced water collected from a hydraulically fractured well. The fatty tissue and carbonate shells were assessed for accumulation of both inorganic and organic pollutants. Ba, Sr, and cyclic hydrocarbons indicated the potential to accumulate in the soft tissue of freshwater mussels following exposure to diluted oil and gas produced water. Exposed mussels showed accumulation of Ba in the soft tissue several hundred times above background water concentrations and increased concentrations of Sr. Cyclic hydrocarbons were detected in dosed mussels and principle component analysis of gas chromatograph time-of-flight mass spectrometer results could be a novel tool to help identify areas where aquatic organisms are impacted by oil and gas produced water, but larger studies with greater replication are necessary to confirm these results.