Treatment strategies of hydraulic fracturing wastes are needed due to concerns over disposal practices and increased demand for recycled water. These wastes are challenging to treat: they contain chemicals additives, formation minerals and gases, and by-products of reactions occurring within fractured formations. The waste streams have undesirable characteristics: high organic carbon content from broken gels and friction-reducing compounds, excessive salinity, toxic organic chemicals (e.g., biocides), naturally occurring radioactive materials (NORM), and heavy metals. To develop treatment strategies, we collected data on chemical additive use in California as well as physical, chemical, and toxicological data on the chemicals used. We next developed screening criteria for candidate treatment technologies and applied the criteria in evaluating potential removal of hydraulic fracturing chemicals. The results indicate that 80% of chemical additives used were organic and that at least 37% of these are biodegradable (more than half are missing biodegradability data). Since the biodegradable chemical additives are used frequently and in large quantities, biological treatment is a candidate treatment technology as long as microbial inhibition can be controlled. Only approximately one-third of chemical additives have characteristics that would suggest adsorption-based treatment. Air/gas stripping was also not a good candidate for treatment as only 10% of chemical additives are volatile enough to suggest this approach. Advanced oxidation and electrocoagulation appear to be candidate technologies based on the organic nature of 80% of the chemical additives used; however, verification of these technologies is needed. Desalination—accomplished using NF/RO or evaporation technologies—is likely needed to reduce salinity. Salts were added in 87% of treatments examined and salts are also present in waste streams due to their presence in fractured formations. Success of desalination is impingent on reduction of oxygen demand and scale-forming minerals in upstream treatment processes. The following chemicals were identified as those posing concern due to their pervasive use, toxicity, and current lack of data: propargyl alcohol, 2-mercaptoethyl alcohol, tetrakis hydroxymethyl-phosphonium sulfate, thioglycolic acid, 2-bromo-3-nitrilopropionamide, formaldehyde polymers, polymers of acrylic acid, quaternary ammonium compounds, and surfactants (e.g. ethoxylated alcohols).

Use of physical/chemical data as a tool for screening potential treatment approaches for hydraulic fracturing waste streams

251st National Meeting (2016)

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