civil and environmental engineering Use of Abandoned Mine Drainage for Hydraulic Fracturing in Marcellus Shale Radisav D. Vidic Department of Civil and Environmental Engineering University of Pittsburgh, Pittsburgh, PA 15261

civil and environmental engineering Why AMD? Well permits AMD Reclaimed AMD Proximity of AMD to Marcellus wells Significantly lower transportation costs (reduce truck traffic) Environmental benefit (if every Marcellus well is fracked with AMD, discharge to PA rivers could be reduced by about 30%)

civil and environmental engineering 3 Hydraulic fracturing Abandoned mine drainage (AMD) Flowback water Co-treatment of Flowback Water and AMD Barium, Strontium, CalciumSulfate Enables the reuse of flowback water for hydraulic fracturing with limited treatment => decreases the treatment and transport cost of flowback water Finished water should meet industry limit of ppm of sulfate

civil and environmental engineering 4 AMD and Flowback Water Chemistry Site ASite BSite CSite D pH Alkalinity SO Fe TDS FB 1FB 2 Cl104,30029,000 Na38,37011,860 Ca15,0212,224 Mg1, Sr1, Ba AMD Flowback AMD from sites a and B are available in the vicinity of FB1 while C and D are found close to FB2 Selected actual AMD that are available in the vicinity of well sites in Washington and Westmoreland Counties in Southwest Pennsylvania for experiments aimed at understanding relevant chemical reactions, kinetics and solids generation to enable the design of realistic treatment process.

civil and environmental engineering Adjusting the Mixing Ratio to Achieve Desired Effluent Sulfate Limit Depending on the initial quality of flowback and AMD, adjustment of the mixing ratio is needed to achieve desired finished water quality in terms of sulfate concentration ( ppm) to allow unrestricted use for fracking

civil and environmental engineering 6 Crystal Characteristics SO 4 ≈ 250 mg/LSO 4 ≈ 600 mg/L Ba = 35 mg/L Sr = 270 mg/L I ≈ 0.5 M Ba 0.78 Sr 0.22 SO 4 Ba 0.68 Sr 0.32 SO 4 Ba = 75.9 mg/L Sr = 36 mg/L I ≈ 0.1 M Ba 0.9 Sr 0.1 SO 4 Ba 0.84 Sr 0.16 SO 4 Predicting the Finished Water Quality TCLP tests revealed no leaching of Ba or Sr Sludge generated in this process is non-hazardous

civil and environmental engineering 7 Optimizing Coagulation/Flocculation Process Optimum coagulant dose: 20 mg/L Optimum pH: 6.0 Slow mixing time: 30 min Settling time: 30 min

civil and environmental engineering 8 Sulfate Removal is Governed by the Ba 2+ /SO 4 2- ratio Very low turbidity of the finished water

civil and environmental engineering Process Design for 1 MGD Plant Simple, conventional process with sludge recycle Sludge passes TCLP test for Ba, Sr and Ra Capital cost for 1 MGD plant: $1.5 million Cost of treatment estimated at $1.5/1,000 gal ($0.063/bbl) Q = 0.4 MGD C o = 1,000 ppm Q = 0.15 MGD C = 70,000 ppm Q = 0.6 MGD C o = 1,000 ppm Q = 1.15 MGD C = 9,625 ppm Q = 1 MGD C < 5 ppm