Chemical Composition of Rock Salt Brine Compared with Brine from Oil and Gas Wells

The overall mass of sodium chloride salt used to treat icy roads can be significantly reduced by pretreating roads or prewetting dry rock salt with concentrated brine solutions. Brine solutions can be made from rock salt; however, an alternative source of brine for some communities is brine that is a waste product of oil and gas extraction. This study compares contaminant chemistry of brine made from rock salt with literature data on oil and gas well brine from conventional and unconventional wells. In addition to reviewing existing literature, this paper analyzes four rock salt samples for a suite of chemical constituents. Maximum reported levels of some harmful contaminants are higher for well brines than for rock salt brines and are higher for unconventional than for conventional well brines. Because the regulatory structure for using well brines varies among states, the authors recommend a consistent approval process for permitting the use of waste brines that includes specific maximum allowable limits for potentially harmful contaminants, and that each batch of solution be tested before use. Although the use of brine, including waste brine, can reduce the overall amount of salt needed for snow and ice control, adequate steps should be taken to ensure the safety of the brine solutions before they are used.