Graduation Year

2021

Document Type

Thesis

Degree

M.S.C.E.

Degree Name

MS in Civil Engineering (M.S.C.E.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Jeff Cunningham, Ph.D.

Committee Member

Sarina Ergas, Ph.D.

Committee Member

Karloren Guzman, Ph.D.

Keywords

Arsenic, Arsenopyrite, Uninoculated, Microcosm, Oxidation

Abstract

Aquifer storage and recovery technology is used to sustain water resources and to prevent saltwater intrusion. The injected water can come from various resources, including treated wastewater. In pilot ASR studies in the Tampa Bay region, researchers found high As concentrations in the recovered water from the oxidation of the arsenopyrite that is embedded in the aquifers. The presence of dissolved O2 in the injected water is a major factor in the arsenopyrite oxidation during ASR, however the effects of NO3- on the arsenopyrite has not been studied yet. This is an important knowledge gap because injected water may contain appreciable levels of NO3-. I conducted a microcosms study to understand how NO3- reacted with the arsenopyrite biotically and abiotically under anaerobic conditions. The results showed that even low NO3- concentrations can mobilize As, and that high NO3- concentration contributed to even greater mobilization of the As under anaerobic conditions. The oxidation of the mineral was accompanied with NH4+ production in the biologically active environments. The biotic oxidation of the mineral released high concentration of SO42- in the water. I concluded that NO3- residual in the wastewater can have negative impacts on the recovered water during ASR, and that treating the wastewater to have an NO3- residual close to 0 mg/L is essential to have a successful ASR.

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