Date of Award

Spring 2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Mayer, Brooke K.

Second Advisor

McNamara, Patrick K.

Third Advisor

Nguyen, Thanh H.

Abstract

Waterborne viruses are ubiquitous in the environment and present a global threat to public health. Previous research has suggested that iron-based water treatment has promise as a low-cost, non-toxic means of virus mitigation. In particular, zero-valent and ferrous iron have shown evidence of inactivating bacteria and viruses. The purpose of this research was to elucidate the relationship between iron oxidation and virus inactivation and determine if iron-based inactivation can enhance two water treatment processes, electrocoagulation and electrooxidation, for virus mitigation. This research first investigated bacteriophage inactivation due to ferrous oxidation in batch tests using ferrous chloride salt. Ferrous iron oxidation correlated to bacteriophage inactivation, indicating that viruses can be inactivated as well as physically removed by ferrous iron coagulation. Greater inactivation was associated with both a higher ferrous iron dose and a slower rate of iron oxidation. Next, the importance of ferrous oxidation was determined for virus mitigation via iron electrocoagulation. Ferrous-based inactivation was an important fate of viruses in iron electrocoagulation. However, some bacteriophages showed far greater inactivation than human viruses. Physical removal was the dominant fate under most conditions for the three mammalian viruses tested, as well as bacteriophage ΦX174. This result casts doubt on the appropriateness of using common bacteriophages for research into iron-based water treatment technologies. However, most viruses did demonstrate some inactivation at low pH (pH 6).Finally, an electrocoagulation-electrooxidation treatment train was investigated to capitalize on the strengths of iron electrocoagulation. At typical coagulation doses (<30 mg/L Fe), ferrous iron did not enhance electrooxidation with boron-doped diamond electrodes. Nevertheless, the electrocoagulation-electrooxidation treatment train was beneficial in model surface waters, though electrocoagulation alone achieved equal or better mitigation in model groundwaters. The electrocoagulation-electrooxidation system also outperformed conventional treatment (ferric salt coagulant and free chlorine disinfection) in model groundwaters.

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