Unconventional oil production from the Bakken region in North Dakota has been rising significantly since 2006 because of the development of the hydraulic fracturing and horizontal drilling technologies. The fracking produced water is typically injected back to underground disposal well, discharged to a nearby surface water body, discharged to municipal wastewater treatment/shallow groundwater, or reused for future fracking. The produced water is high in salinity and contains a number of toxic trace elements and naturally occurring radioactive material. Therefore, the direct discharge of the produced water to surface water/groundwater may cause the impairment of the water quality and be threatening to the local ecosystem and the public health. This project explored an alternative way of disposal of fracking-produced water. 38 elements in a couple of produced water samples collected from the North Dakota oilfield were measured by using a Thermo Scientific iCAP Qc ICP-MS equipped with a Teledyne CETAC ASX560 Autosampler. Nickel sampler and skimmer cones, a Microflow PFA-ST nebulizer, and a quartz cyclonic spray chamber were used for all experiments. Grade 5 helium was utilized as an inert gas in kinetic energy discrimination mode. It was found that the concentrations of certain elements were elevated in the produced water, especially some heavy metal ions. The concentrations of major elements were strongly correlated with each other, suggesting that these elements were from the same source(s). Caustic softening can efficiently reduce the concentrations of multivalent metal ions. The removal efficiency correlates well with the solubility product constants of metal hydroxides.