Portland State University. Department of Civil and Environmental Engineering
Date of Award
Master of Science (M.S.) in Civil & Environmental Engineering
Civil and Environmental Engineering
Titanium dioxide, Constructed wetlands -- Environmental aspects, Nanoparticles -- Environmental aspects -- Mathematical models, Cadmium, Sewage -- Purification -- Metals removal
Metallic nanoparticles are found in a variety of commercial products and industrial processes, and have become more common in the last few decades. As nanoparticles are toxic to biota and have the potential to spread other types of contamination, their increased use has become a concern. Research into the transport of nanoparticles in subsurface and surface waters shows a wide range in mobility, but that they are most likely to collect in systems with low linear velocities and high organic content. As a result, wetlands are the most vulnerable to nanoparticle contamination. Wetlands receiving and treating wastewater effluent have an even higher risk, both due to the increased loading of nanoparticles from wastewater, as well as the increased organic matter entering the system. A simple numerical model was designed to quantify the impact of nanoparticles on nutrient and contaminant reduction in wastewater treatment wetlands, with titanium dioxide (TiO2) nanoparticles and cadmium as the nanoparticle and contaminant of interest. Concentrations of nitrogen, phosphorus, BOD, NBOD, total suspended solids, phytoplankton, dissolved oxygen, cadmium and nanoparticles were modeled at a series of nodes along the length of the wetland across a span of 1000 days. Introduction of titanium dioxide nanoparticles at concentrations observed in wastewater effluent resulted in slower rates of nitrification, but otherwise had negligible impacts. Higher levels of nanoparticles saw slight variations in nitrogen, phytoplankton and dissolved oxygen dynamics with no change to steady state concentrations. Increasing nanoparticles also significantly enhanced the removal of dissolved and total cadmium. Nanoparticles could be incorporated into wastewater treatment to target cadmium and other contaminants, should the other impacts on the system and toxicity of the effluent due to remaining nanoparticles be low enough. While nanoparticles at low concentrations can likely be ignored in water quality models, higher concentrations warrant inclusion to give more accurate predictions.
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Hubbard, Madeline, "Impact of Titanium Dioxide Nanoparticles on Nutrient and Contaminant Reduction in Wastewater Treatment Wetlands" (2019). Civil and Environmental Engineering Master's Project Reports. 50.