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the central United States, PW disposal occurs through deep well injection, which can increase seismic activity. The treatment of PW for use in agriculture is an alternative to current disposal practices that can also provide supplemental water in regions where limited freshwater sources can affect agricultural production. This paper assesses the potential for developing PW as a water source for agriculture in the Anadarko basin, a major oil and gas field spanning parts of Kansas, Oklahoma, Colorado, and Texas. From 2011 to 2019, assessment of state oil and gas databases indicated that PW generation in the Anadarko Basin averaged 428 million m3/yr. A technoeconomic analysis of PW treatment was combined with geographical information on PW availability and composition to assess the costs and energy requirements to recover this PW as a non-conventional water resource for agriculture. The volume of freshwater economically extractable from PW was estimated to be between 58 million m3 per year using reverse osmosis (RO) treatment only and 82 million m3 per year using a combination of RO and mechanical vapor compression to treat higher salinity waters. These volumes could meet 1–2 % and 49–70 % of the irrigation and livestock water demands in the basin, respectively. PW recovery could also modestly contribute to mitigating the decline of the Ogallala aquifer by ~2 %. RO treatment costs and energy requirements, 0.3–1.5 $/m3 and 1.01–2.65 kWh/m3, respectively, are similar to those for deep well injection. Treatment of higher salinity waters increases costs and energy requirements substantially and is likely not economically feasible in most cases. The approach presented here provides a valuable framework for assessing PW as a supplemental water source in regions facing similar challenges. 

The formation of precipitates (scales) during reinjection limits the reuse of oil and gas production water (produced water) for additional oil recovery. Selective removal strategies that target Ba and Sr, the primary scale-forming cations, would limit produced water treatment costs, reduce waste generation, and increase produced water reuse. A novel treatment technique for targeted Ba and Sr removal, complexation with polyelectrolyte polymers, is compared with chemical precipitation (sulfate addition and precipitative softening) for the removal of Ba and Sr from Kansas oil field brines. Four polymers were examined for cation removal, both with and without ultrafiltration: poly-vinyl sulfonate (PVS), poly(4-styrenesulfonate) (PSS), polyacrylic acid (PAA), and poly(4-styrenesulfonic acid- co -maleic acid) (PSSM). PSSM and PSS were effective for Ba and Sr removal from the lower salinity brine (TDS of 31 000 mg L −1 ), but exhibited limited Sr removal in the absence of Ba in the high salinity brine (TDS of 92 000 mg l −1 ). Similar results were achieved in both brines using sulfate addition. PSSM used in conjunction with ultrafiltration removed >99% of initial Sr and Ba from the lower salinity brine, while removing only 65% and 78% of Mg and Ca, respectively. These results compare favorably to precipitative softening, which removed >90% of all divalent cations from the same brine but was less selective for Ba and Sr. PAA plus ultrafiltration removed 58% of Sr (and 68% of Ca) from the high-salinity brine at pH 9. While increased Sr removal can be achieved by polymer-assisted ultrafiltration, further development of this process, including methods for polymer recovery and regeneration, will be needed to improve its performance compared to precipitative softening.