High levels of bromide have been reported in surface water receiving wastewater discharges from the energy industry, including flowback water and produced water from hydraulic fracturing of shale gas, and wet flue gas desulfurization (FGD) scrubber purge water from coal-fired power plants. Bromide can lead to the formation of precursor of brominated disinfection byproducts during water treatment process, and removing bromide from the wastewater instead of discharging it to natural water body protects the drinking water source of downstream communities. Conventional treatment processes for bromide removal is costly and not specific. Selective bromide removal is technically challenging due to the competition of other ions. For example, flowback water from the Marcellus Shale contains chloride concentration two orders of magnitudes higher than that of bromide. To achieve feasible selective bromide removal from energy wastewater, this study evaluated electrochemical bromide oxidation using solid graphite electrodes in flowback water and produced water from a shale gas operation in Southwestern PA. Bromide was selectively oxidized into bromine, and bromine can be outgassed from the aqueous phase and recovered separately as a valuable commodity. No side reaction of oxygen or chlorine generation was observed. Results of this study suggested that bromide can be effectively removed from oil and gas brines (~10 h-1m-2 for produced water and ~60 h-1m-2 for flowback water). The electrolysis occurred with a current efficiency between 60 and 90%, and the estimated energy cost was ~6 kJ/g Br. Although the presence of chloride and other brine components decreased the bromide removal rate, the overall process still suggests that bromide removal from energy wastewater is feasible utilizing mature technologies used in the chlor-alkali process (the industrial process of chlorine gas and sodium hydroxide production). The electrochemical selective bromide oxidation technique also has the potential to treat power plant FGD wastewater directly, or other waste streams containing high bromide levels from FGD wastewater treatment, such as ion exchange resin regenerant.

Electrochemical selective bromide removal from energy wastewater

252nd National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.