TRACING BROMIDE IN A NATURAL LABORATORY: IMPLICATIONS FOR WATER TREATMENT

Bromide is a highly soluble halogen introduced into water by the dissolution of evaporite minerals and rocks, or via human contamination. Recent environmental monitoring by the Cincinnati Water Works has shown an increase in brominated-methane compounds in post-treatment city water and it has been suggested that these compounds are the result of treatment of hydraulic-fracturing produced brines in city treatment facilities. Due to its high solubility, toxicity at high concentrations and propensity to form toxic and carcinogenic halo-methane compounds upon mixture with organic matter and exposure to UV light, bromide is of particular concern to public water treatment facilities and ultimately public health.

Identification of the bromide contamination source and an understanding of contaminant behavior are necessary when addressing public health concerns. Although it is difficult to study produced waste water brines from fracturing wells due to limited access at extraction and disposal sites, naturally occurring brine seeps may offer a proxy for these anthropogenic sources. Big Bone Lick State Park in northern Kentucky is well known for its brine fed salt springs that flow directly into a freshwater stream running nearby. Geochemical analyses suggest a Paleozoic source for these brines and a similarity in age and composition to brines from natural gas containing rock formations that are actively being hydraulically fractured. Through further determination of geochemistry and stable isotopic composition, our research aims to determine the age and origin of Big Bone Lick’s bromine-containing brines. By doing so, we will establish their utility as a proxy for hydraulic-fracturing produced brines. Understanding the fate of these brines, specifically the transport and bioavailability of bromide in a simplified system, will provide insight into determining the fate and the potential for environmental and human impacts of treatment and disposal of brines in an urban setting.