Hixon Center Study Reveals Chemicals of Concern in Fracking Wastewater

A new study authored by Tanja Srebotnjak (director of the Hixon Center) and Emily Chittick (POM-’17), and published in the Journal of Environmental Management, examines the chemical make-up of California’s fracking wastewater. Fracking, or high-volume hydraulic fracturing, involves pumping large volumes of water mixed with a proppant and dozens of chemicals at high pressures underground to create and prop open fissures in the rock so that oil and gas bubbles trapped in it can flow to the wellbore.

As Srebotnjak and Chittick emphasize in the study, fracking wastewater is a problem because California is the country’s 4th largest oil-producing state, and the oil and gas industry generates an average of 15 barrels of wastewater for each barrel of crude oil. This adds up to approximately 21 billion barrels of contaminated wastewater (also called oilfield produced water) every year. However, the magnitude of wastewater produced is not the sole issue. In addition to containing high levels of dissolved solids, the produced water also often contains hydrocarbons, polycyclic aromatic hydrocarbons (PAH), alkylphenols, naturally occurring radioactive material (NORM), metals, and other organic and inorganic substances. Fracking adds additional chemical compounds to this mix, such as friction reducers, scale inhibitors, and biocides – many of which are known to cause serious health effects.

In their study, Srebotnjak and Chittick provide a first aggregate chemical analysis of wastewater from 630 fracked wells – made possible by a 2013 California law that increased data collection and transparency requirements for fracking in the oil and gas sector. The findings raise concerns about the safe management and disposal of this waste stream. For example, wastewater from 95% of the tested wells contained measurable, and in some cases elevated, concentrations of BTEX (benzene, toluene, ethylbenzene, and xylenes) and PAH. The wastewater from nearly 500 wells (79% of wells) contained lead, uranium, and/or other metals. In addition, the majority of harmful chemicals known to be used in fracking, including formaldehyde and acetone, are not even tested for in the published reports.

The prevalent methods for dealing with produced water in California – underground injection and open evaporation ponds – are inadequate due to risks from induced seismicity, well integrity failure, well upsets, accidents and spills. The potentially beneficial reuse of produced water, for example, in agricultural crop irrigation in the Central Valley, are so far not adequately tested with respect to their safety for consumers and agricultural workers.

The authors conclude that (i) reporting of produced water chemical composition should be expanded in frequency and cover a wider range of fracking chemicals, and that (ii) wastewater management practices should be reoriented towards safer and more sustainable options such as reuse and recycling and with adequate controls in place to ensure their safety and reliability.

The newly published study can be viewed online. For more information about the study or about the Hixon Center’s research, send an e-mail to hixoncenter@hmc.edu. Tanja Srebotnjak can also be reached directly at tsrebotnjak@g.hmc.edu.