Produced water is generated during the production of coal bed natural gas (CBNG) from the Big George coal at Anadarko Petroleum Company’s (APC) County Line field, near Gillette, Wyoming. The produced water contains dissolved solids that typically meet drinking water standards. But, the total barium limit of 1.8 mg/L, established by the Wyoming Department of Environmental Quality (WDEQ) for discharge to draws leading to the Powder River, was often exceeded for produced water discharging into multiple tire tanks, draws and ultimately into the Powder River. Originally, gypsum was used in the field to reduce the barium levels, but the monthly monitoring results were sporadic. This study was performed to (a) investigate reliable methods for reduction/removal of total barium from the discharge water, in order to meet the limit, and (b) design and construct cost effective treatment systems. The removal mechanisms tested were; (a) precipitation as an insoluble sulfate, or (b) adsorption on zeolite. Precipitation chemicals tested were: sulfuric acid, magnesium sulfate solution, and magnesium sulfate crystals. Even though soluble barium was decreased as a result of sulfate addition, the precipitation mechanisms were not successful in reliably reducing/removing total barium. However, total barium was dramatically and reliably removed by adsorption/filtration in direct, flow-through beds of zeolite, with flow rates of over 500 bbl/day/ton of zeolite. The designed zeolite beds (tinhorn tanks), at each outfall will maintain total barium in the discharge water below the established limit for four to eight weeks before renewal or burial as a non-hazardous waste.

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