Hydraulic fracturing wastewater analysis Reagent-Free Ion Chromatography

Significance of the Topic

The environmental and regulatory implications of hydraulic fracturing wastewater necessitate robust analytical methods. Ion chromatography offers sensitive, reproducible quantification of key anions, cations and organic acids mobilized during fracking operations, supporting water treatment, reuse strategies and discharge compliance.

Study Objectives and Overview

This work demonstrates the application of reagent-free ion chromatography to characterize wastewater from hydraulic fracturing. Two wastewater types are examined: flowback water rich in injection fluid additives and produced water containing formation brines. The goals include:

• Quantifying major anions (chloride, sulfate, bromide, etc.) and cations (sodium, calcium, magnesium, etc.).
• Measuring low-level organic acids (formate, acetate) relevant to microbial activity and treatment impacts.
• Employing automated dilution and conductivity/pH monitoring to extend dynamic range and streamline workflows.

Methodology and Instrumentation Used

Samples were filtered (0.2 µm) and diluted (50–1000×) using autosampler-driven protocols. Instrumentation includes:

• Thermo Scientific Dionex ICS systems (ICS-2100, ICS-4000 HPIC, ICS-5000+ HPIC) with reagent-free eluent generation (RFIC).
• Ionic separation columns: Dionex IonPac AG18/AS18 for anions, CG16/CS16 for cations, and specialized concentrator columns for 2D-IC.
• Dionex AS-AP autosampler with AutoDilution and in-line conductivity/pH accessory.
• OnGuard II and InGuard cartridges for matrix cleanup.

Main Results and Discussion

Flowback samples exhibited extremely high ionic strength, with chloride and sodium exceeding 90 g/L and 30 g/L, respectively. Calcium, magnesium, strontium and barium were detected at gram-per-liter to milligram-per-liter levels. Formate and acetate were quantified at sub-ppm concentrations (<5 mg/L). Produced waters showed broader variability: bromide at 0.1–1.7 mg/L, sulfate at 0.4 mg/L, and trace nitrate and fluoride. 2D-IC enabled low-µg/L determination of disinfection byproducts (chlorite, bromate) by diverting high-salt matrix in the first dimension and focusing analytes onto capillary columns.

Benefits and Practical Applications

• Automated dilution and conductivity/pH triggers ensure results within calibrated ranges without reruns.
• Reagent-free gradient eluent generation reduces handling of corrosive reagents and improves reproducibility.
• High-capacity separations and 2D-IC approaches overcome matrix interferences for trace analytes.
• Method supports screening for treatment optimization, reuse decisions and regulatory compliance.

Future Trends and Opportunities

Advancements in capillary and microbore IC promise reduced solvent consumption and continuous operation. Integration with high-resolution detection (e.g., mass spectrometry) and data analytics will further enhance selectivity and throughput. On-line sample preparation and multidimensional separations are poised to address evolving regulatory and environmental monitoring needs.

Conclusion

Reagent-free ion chromatography, coupled with automated sample handling and advanced column chemistries, provides a comprehensive solution for the analysis of high-matrix hydraulic fracturing wastewaters. The approach delivers robust quantification of major and trace ionic species, facilitating environmental protection and process optimization.

Reference

• Technical Note 139: Determination of Anions in Fracking Flowback Water Using Automated Dilution and Ion Chromatography.
• Technical Note 138: Automated Dilution and In-line Conductivity Measurement Prior to IC Analysis.
• Application Note 1094: Determination of Cations in Hydraulic Fracturing Flowback Water.