Date of Graduation

12-2018

Document Type

Thesis

Degree Name

Bachelor of Science in Chemical Engineering

Degree Level

Undergraduate

Department

Chemical Engineering

Advisor/Mentor

Ackerson, Michael

Committee Member/Reader

Penney, William R.

Abstract

Woo Pig Sulfate (WPS) has developed two methods for reducing levels of calcium sulfate in mine impacted waters, a “hot process” and a two-stage nanofiltration process. Both processes were designed to treat gypsum saturated water that is currently being pumped via interceptor wells to prevent the spread of a sulfate plume into a nearby community. Each solution was designed for Freeport McMoran’s Sierrita mine in Green Valley, Arizona, which was visited in order to gain insight about the problem. Below 250 ppm on the treated stream, nanofiltration and the hot process achieve overall recoveries of 84 and 99%, respectively. The waste, concentrated gypsum water, can be disposed of via evaporation ponds. Both processes are similar economically, but the hot process produces less waste, therefore requiring a smaller footprint for the evaporation pond, is less complex due to possessing fewer unit processes, and is less intensive maintenance-wise. However, since the hot process is more expensive than nanofiltration and is unused on an industrial scale, both processes are being presented as viable, with preference for either depending on whether the mine wants to maximize water recovery. A thorough evaluation of potential technologies to treat the impacted mine water was conducted by generating full-scale economic analyses for each process, taking note of the various advantages and disadvantages of each process. When conducting the research, the most important factors taken into account were capital and operating costs, complexity, frequency for maintenance and operator involvement, concentration of sulfate in water recovered, and percent recovery of water fed to the process.

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