Date

2015

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Environmental Engineering

First Adviser

SenGupta, Arup K.

Other advisers/committee members

Brown, Derick G.; Jellison, Kristen; Roberts, James E.; Snyder, Mark A.

Abstract

For inland desalination plants, managing and discarding produced brine leftover from the production of pure drinking water can be a significant operating cost. By increasing the recovery of the desalination process, brine volume and disposal costs will be reduced. Achieving high recovery is not immediately possible as when the recovery is increased, there is a higher potential for the precipitation of calcium sulfate which, for reverse osmosis (RO) processes, can foul and damage the RO membrane. Ion exchange may be used as a pretreatment method to selectively remove and replace sulfate by chloride which does not pose any threat to fouling. The RO process can then be operated at higher recoveries without any threat of sulfate scaling due to its removal by the ion exchange column. After RO the leftover concentrate, highly concentrated chloride brine, can be used as a regenerant for the ion exchange column without requiring the purchase of additional chemical regenerant. By changing the type and/or mixing together characteristically different ion exchange resins, the selectivity of the ion exchange column can be precisely tuned to remove sulfate regardless of feedwater composition. Results demonstrate that a properly designed Hybrid Ion Exchange-Reverse Osmosis (HIX-RO) system can effectively eliminate the potential for CaSO4 scaling sustainably without requiring external regenerant. The selectivity of the ion exchange resin has a significant role in controlling sulfate removal, and it is possible to precisely predict how resin selectivity changes depending on solution composition or mixing ratio with another resin.

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