Determination of Anions and Cations in Produced Water from Hydraulic Fracturing

Significance of the Topic

The management and reuse of hydraulic fracturing produced water is a critical environmental and operational concern. Detailed knowledge of dissolved ion composition enables optimized treatment, minimizes scale formation, and reduces risks such as bromate formation during disinfection.

Objectives and Study Overview

This application note demonstrates rapid and reliable quantification of both anions and cations in produced water from hydraulic fracturing sites in Texas (Eagle Ford Shale), California (Monterey Shale), and North Dakota (Bakken Shale). Two ion chromatography configurations—a microbore RFIC system for anions and a capillary HPIC system for cations—were evaluated to resolve key ions within 35 minutes.

Instrumentation

• Dionex ICS-2100 Integrated Reagent-Free IC system with IonPac AS18 microbore column for anion analysis
• Dionex ICS-5000+ Reagent-Free HPIC capillary system with IonPac CS16 capillary column for cation analysis
• Eluent generator cartridges (EGC III KOH and EGC-MSA)
• Continuously regenerated suppressors (AERS 500 and CCES 300)
• Dionex AS-AP autosampler and Chromeleon CDS software

Methodology

Produced water samples were filtered (0.2 µm) and diluted to match calibration ranges. Anion separations employed a KOH gradient (15–29 mM) at 0.25 mL/min on a 2 mm AS18 column with suppressed conductivity detection. Cation separations used an MSA gradient (20–55 mM) at 0.01 mL/min on a 0.5 mm CS16 column. Calibration standards covered low-to-high concentrations with coefficients of determination (r2) ≥0.999, except ammonium which followed a quadratic fit.

Results and Discussion

Anion analysis revealed chloride concentrations of 8 000 mg/L (TX), 52 000 mg/L (CA), and 190 000 mg/L (ND), with proportional levels of bromide and sulfate. Organic acids and fluoride appeared at tens of mg/L or lower. Cation profiles showed sodium as the most abundant (4 300–92 000 mg/L), followed by calcium, magnesium, potassium, and ammonium; lithium and strontium were detected at ≤530 mg/L, and barium was below detection. Comparison to Marcellus flowback water highlighted the influence of formation brine and geological variability on ion content, underscoring treatment challenges related to scale and by-product formation.

Benefits and Practical Applications

The described IC methods provide robust, high-throughput analysis of a broad ion concentration range with minimal reagent usage and waste. Accurate ion profiling supports water treatment design, recycling strategies, and regulatory compliance in fracking operations and subsequent water reuse or discharge.

Future Trends and Potential Applications

Emerging compact IC systems and enhanced automation will facilitate on-site monitoring. Integration with real-time analytics may allow dynamic adjustment of fracturing fluid composition, optimized reagent consumption, and improved environmental risk management. Future applications include in-field speciation analysis and coupling with mass spectrometry for expanded contaminant screening.

Conclusion

The combination of microbore RFIC and capillary HPIC systems enables comprehensive, sensitive, and efficient ion analysis of hydraulic fracturing produced water. These validated methods facilitate informed water management decisions, mitigate environmental impacts, and support sustainable resource utilization.

Reference

• Spegele B.; Scheck J. Energy-Hungry China Struggles to Join Shale-Gas Revolution. Wall Street Journal, 2013.
• Trotman A. UK Needs 40 Fracking Wells to See if Shale Gas is Viable, Says Lord Browne. The Telegraph, 2014.
• FracFocus Chemical Disclosure Registry. What Chemicals Are Used. (Accessed 2014).
• Bomgardner M. Cleaner Fracking. C&EN, 2012, 90(142), 13–16.
• Thermo Fisher Scientific. Technical Note 139: Anion Determination in Marcellus Shale Flowback Water, 2013.
• Thermo Fisher Scientific. Application Note 1094: Cation Determination in Marcellus Flowback Water, 2014.
• Barbot E.; Vidic N.S.; Gregory K.B.; Vidic R.D. Spatial and Temporal Correlation of Water Quality Parameters of Produced Waters from Devonian-Age Shale after Hydraulic Fracturing. Environ. Sci. Technol., 2013, 47, 2562–2569.
• Vengosh A.; Jackson R.B.; Warner N.; Darrah T.H.; Kondash A. Risks to Water Resources from Unconventional Shale Gas Development and Hydraulic Fracturing in the United States. Environ. Sci. Technol., 2014.