THWRC Awarded Proposal 515TAM0046H

Project Number:       515TAM0046H

Title:                           Boron Removal from Hydraulic Fracturing Wastewater by Aluminum

                                      Electrocoagulation:  Mechanisms and Process Optimization

Lead PI:                     Shankar Chellam

Awarded Amount:    $38,000

ABSTRACT

Produced water is the largest waste stream (on a volume basis) generated during oil and gas production. One increasingly popular method of developing unconventional petroleum resources is hydraulic fracturing wherein a mixture of water, sand, and other chemicals is pressurized and injected to form veins and fissures in the underground formation. This controversial technique of unlocking hydrocarbons uses large quantities of water, which in turn produces copious amounts of wastewater. This highly saline wastewater consists of a mixture of the injected chemicals and additives along with the groundwater and is very toxic. Concerns about environmental impacts associated with its discharge, consumption of large volumes of freshwater, and the desire to recover a valuable water resource have resulted in growing regulatory and technological interest in treating produced water from hydraulic fracturing operations. However, since the composition of the wastewater is highly variable both over time and location, purification of water co-produced from hydraulic fracturing operations presents significant challenges.

The overarching long-term goal of this research is to develop methods to reuse and recycle produced water to reduce the burden on existing fresh water supplies and to protect the environment where this high strength wastewater is discharged. Since produced waters contain a wide spectrum of organic, inorganic, microbiological, radiological, and physical contaminants, any research, by definition, has to focus on a specific subset. It is known that chronic exposure to low doses of boron causes testicular atrophy, suppressed growth, decreased survival, and other developmental and reproductive toxicity in animals. Further, boron can also be toxic to many crops and needs to be controlled to low levels in irrigation water. Additionally, it is necessary to remove boron in order to reuse produced water for additional well stimulation and development. In this context, we will exclusively target boron removal from hydraulic fracturing wastewater.

Limited information available to date suggests that electrocoagulation could be well-suited for boron removal from wastewaters. However, earlier experiments have been performed using synthetic waters with unrealistically low boron concentrations. This limits their applicability to real-world high strength wastewaters such as produced waters. It is emphasized that we have already obtained a produced water sample from the Eagle Ford formation in Southeast Texas after the water-flooding process employed in hydraulic fracturing. This black calcareous shale was chosen because it is located in Texas and a 50 mile wide and 250 feet thick play at depths between 4,000 and 14,000 feet is one of the most heavily drilled enhanced oil/gas recovery targets in the United States. Individual tasks to be completed include:

  • Comprehensively characterize the chemical composition of the produced water sample,
  • Implement D-Mannitol potentiometric titrations to accurately & precisely measure boron,
  • Calculate boron speciation diagrams at high background ionic strength values,
  • Perform aluminum electrocoagulation experiments to systematically evaluate the effects of operational parameters such as current density, pH, dosage, etc. on boron removal,
  • Rigorously analyze flocs for boron uptake mechanisms using a suite of interfacial tools such as attenuated total reflection – Fourier transform infra-red spectroscopy, X-ray photoelectron spectroscopy, electron microscopy, etc.

A 2-year project with a $40,000 budget is proposed. It is emphasized that the entire budget will be used to support a graduate student and no salary is requested for the principal investigator.