Date

8-1-2018

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Environmental Engineering

First Adviser

SenGupta, Arup K.

Abstract

Hybrid ion exchange technology has been applied in many environmental aspects nowadays due to its high treatment efficiency, reusability, customizable selectivity, operational stability, and low cost. Under certain circumstances, ion exchange technology is a favorable substitute for traditional treatment process, and its applications in industries are continually growing.Water hardness is a concern for many industrial and municipal unit operations, which could result in surface scaling of heat transfer equipment or membranes. Sodium exchange softening, although commonly used, has caused serious pollution to local ecological and water environments due to its discharge of high salinity spent regenerant. Many arid areas are banning such softening processes as a result of the detection of increasing salinity in local water resources. The additional sodium ion introduced into the softened water also induces a health concern when the water is used for drinking or cooking. A more efficient hardness removal technology that does not add sodium ions to treated water is urgently inquired. Al3+ is an optimal regenerant considering its higher affinity to cation exchangers than calcium and magnesium at most water conditions. Furthermore, Al3+ will precipitate during the service cycle thus eliminating the addition of sodium or aluminum to the effluent. Experimental results indicated that calcium is persistently removed for multiple cycles using a stoichiometric amount of aluminum chloride as the regenerant. The process operates at nearly 100% thermodynamic efficiency, where one equivalent of Al3+ was consumed to remove one equivalent of Ca2+. Nevertheless, partial desalination is attained during hardness removal. The hardness removal capacity of the aluminum cycle process is slightly reduced from 1.4 meq/g to 1.2 meq/g compared with the sodium cycle process. However, at steady state, other contaminants, namely fluoride, phosphate, and silica, could be simultaneously removed as a consequence of Lewis acid and base reactions. It is noteworthy that the major components and setup are nearly the same as a traditional sodium cycle softening process, which eradicates the major difficulty to retrofit continuing softening systems.Wastewater produced from Marcellus Shale activities and acid mine drainage (AMD) are two major concerns of Pennsylvania for their environmental impact on surface and groundwater resources, aqueous ecosystems, and human health. Reuse of flowback and produced water represents one of the innovative technologies which could significantly reduce the environmental impacts of the activity. However, about 20% of injected water will return to the surface with high salinity. Both treatment techniques and makeup water resources are needed to fulfill this goal. Acid mine drainage (AMD) water, which is available in the vicinity of shale gas wells, could be utilized to alleviate the fresh water demand, reduce environmental impacts for both flowback and AMD, cut down the cost for transportation and leakage risk, trim the greenhouse gas emissions2, and diminish the cost and impact for wastewater treatment. Several researchers already inspected this possible technology genuinely. However, some issues remain unresolved such as the demand for large volume reactors and stirrers, long hydraulic retention time (HRT), haphazardly mixing, and uncertain mixing ratios. Radium, barium, and strontium, which induce precipitation on the piping and are regulated in water resources, are major concerns for either recycle or final disposal of flowback water. To remove these divalent ions, the addition of sulfate salt or mixing with sulfate-containing water are two widely studied processes. Huge amounts of salt addition could cause a TDS increase and a removal efficiency decrease. On the other hand, directly mixing with AMD water will cause significant volume increase of treated water. Ion exchange technology, which can selectively exchange sulfate with chloride, is an ideal process to treat flowback water without a TDS and final volume increase. Experimental data demonstrates that such technology can use sulfate ions in acid-mine drainage to treat Marcellus flow back waste water to remove radium, barium and strontium and without increasing the volume of waste water or adding excess sodium. Over 200 bed volumes of AMD water is treated and the effluent sulfate concentration is lower than 100 ppm, which is an ideal fresh water resource for hydrofracking. Moreover, there are no additional chemicals needed for such ion exchange processes to treat flowback water with AMD. Radium, barium, and strontium are removed over 90% in the treated flowback without any volume increase. The treated solids after evaporation are suitable for landfill disposal. Compared with current technology used at a flowback treatment factory, the reactor volume is reduced from 100 m3 to about 5 m3 to achieve the same treatment capacity.

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