Date of Award
Summer 7-8-2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Civil, Construction, and Environmental Engineering
First Advisor
Daniel Zitomer
Second Advisor
Brooke Mayer
Third Advisor
Patrick McNamara
Abstract
Ozonation and membrane treatment have been widely used in drinking water treatment all around the world; however, they are far less common in wastewater treatment. Typically, secondary wastewater treatment involves a biological process known as conventional activated sludge (CAS) to remove chemical oxygen demand (COD), nutrients, and other contaminants. CAS comes with an array of challenges, including long retention times, formation of waste activated sludge (WAS) and a need to dispose of it, potential sludge settling issues, and inability to easily adapt to changing wastewater composition. Most studies using ozonation for wastewater treatment involve using the process as tertiary treatment, usually in combination with other processes such as membrane filtration or biological treatment. The goal of this study was to evaluate ozonation and reverse osmosis (RO) as an alternative secondary treatment for municipal wastewater. Primary effluent from a local water resource recovery facility was ozonated for 180 minutes with samples taken every 30 minutes and analyzed for nutrient concentrations. Two applied ozone doses, 28.1 and 229 mg O3/L-min and three temperatures, 7, 22, and 34°C, were used to evaluate how temperature and ozone dose affect transformation and removal of nutrients during ozonation. The total nitrogen concentration did not change through ozonation, but ammonia was converted to nitrate during most tests. The higher ozone dose had more nitrification occur than the lower ozone dose. Additionally, as the temperature increased, nitrification increased as well. There was no significant phosphorus removal at 7°C, but there was removal at the other two temperatures. Total phosphorus was removed through precipitation, ostensibly due to a rise in pH from air stripping of CO2. The phosphorus likely precipitated out as calcium phosphate or other phosphate solids. Finally, the fate of nitrogen and phosphorus through an ozonation and RO process was evaluated and compared to CAS and RO. CAS/RO removed nitrogen and phosphorus better than ozone/RO. Both processes had total phosphorus concentrations of less than 0.05 mg/L P and total nitrogen concentrations below 2 mg/L after RO. Depending on nutrient permit limits, the ozone/RO process could be applicable in place of CAS for secondary treatment of municipal wastewater.