Date of Award
Master of Science (MS)
Environmental Engineering and Science
Dr. Sudeep Popat
Dr. David Freedman
Dr. David Ladner
Source separation and urine treatment present the opportunity to significantly reduce influent concentrations of nitrogen and phosphorus in wastewater treatment plants and to capture those minerals for reuse. This study aims to use electrochemical cells with a sacrificial iron electrode to produce hydrogen peroxide in situ for the stabilization of urea while dissolving ferrous iron ions to promote the precipitation of phosphate into compounds such as vivianite (Fe3 (PO4)2 ∙ 8 H2O), a precipitate with potential uses in agriculture and manufacturing. Synthetic urine samples were treated as anolyte, then were given time to form precipitate before being fed to the cathode. The concentrations of iron, phosphate, H2O2, and total ammonia nitrogen (TAN), as well as pH, were monitored over the course of experimentation. Simultaneously, the effects of total charge and current density on urea stabilization and precipitate formation were analyzed. Across the ranges of charges and current densities examined, iron dissolved into the urine in accordance with the total charge applied, and dissolved phosphate was reduced by higher concentrations of iron. After 48 hours of precipitation in experiments where total charge was increased over same treatment time, phosphate decreased by approximately 72% for 90 Coulombs of charge, 98% for 180 coulombs, and 100% for 360 coulombs, or 0.71, 1.43, and 2.86 A/L, respectively, for one hour. With increasing total charge, hydrogen peroxide concentration and pH in the catholyte increased. In contrast to changing the total charge, current density had little to no effect on the treatment efficacy, but higher current density caused more power consumption. In the experiments where current density was varied, increasing ammonia concentrations in the urine after treatment indicated that the urine was partially stabilized, resulting from the high iron levels during cathode treatment, which likely degraded hydrogen peroxide. These results suggest that electrochemical cells with an iron anode could effectively dissolve iron and remove phosphate. Still, more research is required to determine the stability of urea following treatment.
Voisin, Skyler, "The Potential of Iron Electrodes in Electrochemical Cells for the Stabilization of Synthetic Urine" (2023). All Theses. 4113.