Integrated Accelerated Precipitation Softening (APS) – Microfiltration (MF) Assembly and Process Development to Maximize Water Recovery During Energy Production and CO2 Sequestration

The development of hydrocarbon resources such as crude oil, coalbed methane, conventional gas, and tight-shale gas unvaryingly results in the generation of brackish wastewaters. Brackish wastewater is characterized by salt content, often expressed as total dissolved solids (TDS). In the United States, over 21 billion barrels of produced water are generated every year. The disposal of this produced water has major economic and environmental implications. Current reverse osmosis (RO) treatment methods yield clean water recovery rates ranging from 50-75%, commonly limited by the presence of mineral scalants such as CaCO₃ and CaSO₄.

To address the suboptimal water recovery rate, we have developed an integrated system that treats the primary RO concentrate via Accelerated Precipitate Softening (APS) to remove scale-forming ions from the RO concentrate in the form of precipitate and subsequently utilizes microfiltration (MF) membrane modules to remove any suspended solids, prior to passing the permeate to a secondary RO. The integrated system allows water recovery ratios to approach or even exceed 90%. In addition, advanced anti-fouling membrane materials will be explored and their effect on the integrated APS-MF system will be evaluated. The combined process and membrane materials development platform provides a feasible pathway for beneficial reuse of produced water, such as irrigation of crops or hydrofracturing reuse.