Co-treatment of abandoned mine drainage and Marcellus Shale flowback water for use in hydraulic fracturing

Abstract

Flowback water generated during shale gas extraction in Pennsylvania is mostly reused for hydraulic fracturing operation. Abandoned mine drainage (AMD), one of the most widespread threats to water quality in Pennsylvania, can potentially serve as a make-up water source to enable flowback water reuse. This study demonstrated co-treatment of flowback water and AMD produced in northeastern Pennsylvania in a pilot-scale system consisting of rapid mix reactor, flocculation tank and sedimentation tank. Sulfate concentration in the finished water can be controlled at a desired level (i.e., below 100 mg/L) by adjusting the ratio of flowback water and AMD in the influent. Fe contained in the AMD can serve as a coagulant to enhance the removal of suspended solids, during which Fe is co-precipitated and the total iron is reduced to a desirable level. Solid waste generated in this process (i.e., barite) will incorporate over 99% of radium present in the flowback water, which offers the possibility to control the fate of naturally occurring radioactive materials (NORM) brought to the surface by unconventional gas extraction. Sludge recirculation in the treatment process can be used to increase the size of barite particles formed by mixing flowback water and AMD to meet specifications for use as a weighting agent in drilling fluid. This alternative management approach for NORM can be used to offset the treatment cost and promote flowback water reuse, reduce environmental impacts of AMD and reduce pressure on fresh water sources.

Variance in State Protection from Exposure to NORM and TENORM Wastes Generated During Unconventional Oil and Gas Operations: Where We Are and Where We Need to Go

“…54 Many studies suggest that TENORM waste from the oil and gas industry generates radiation exposure levels more than EPA's established limits for Ra-226 and Ra-228. 5,12,21,24,34,[37][38][39][40][41] These studies suggest that more careful monitoring of NORM and TENORM wastes may be necessary to protect the public and workers. For example, a recent study in Wyoming found that fracking waste had a negative impact on water supplies, with evidence of organic compounds and increased salinity in groundwater supplies, the latter of which is a conducive environment for radium migration.…”

“…37 These radionuclides may contaminate well sites, be present in the surface runoff, with the possibility of spreading into municipal water systems. 38 TENORM also includes scales, sludges, and contaminated equipment. Studies that evaluated TENORM waste generated during drilling found Ra-226 (speculated to be the most hazardous to human health) to be well over EPA's established limits for radium.…”

“…37 These radionuclides may contaminate well sites, be present in the surface runoff, with the possibility of spreading into municipal water systems. 38…”

Abatement of circumneutral mine drainage by Co-treatment with secondary municipal wastewater

“…Active AMD treatment utilizes addition of alkaline chemicals or oxidants (Goodwill et al, 2019;Singer and Stumm, 1970) and ongoing energy inputs for pumping, mixing, and/or aeration (Coulton et al, 2003;Mitsch and Wise, 1998). There are several additional options for co-treating AMD with other waste streams, including the use of organic solid waste substrates or flowback water produced from hydraulic fracturing (Chang et al, 2000;He et al, 2016). Although these co-treatment options improve water quality, disadvantages exist including the need for construction of treatment infrastructure (e.g.…”

Potential Implications of Acid Mine Drainage and Wastewater Cotreatment on Solids Handling: A Review

“…limestone dissolution, engineered wetlands) and active (e.g., chemical addition) treatment approaches (Hedin et al 1994;Johnson and Hallberg 2005;Watzlaf et al 2004). However, additional approaches can include co-treating AMD with other wastes such as organic solid waste substrates, agricultural slurry, fracking flowback water, or municipal wastewater (MWW) (Chang et al 2000;He et al 2016;Hughes and Gray 2013a;McDevitt et al 2020). Benefits of co-treating AMD with other wastewaters includes providing low cost AMD abatement, improving effluent quality from treatment systems, and mitigating AMD impacts on receiving bodies.…”