Available at: https://digitalcommons.calpoly.edu/theses/1786
Date of Award
MS in Civil and Environmental Engineering
Civil and Environmental Engineering
ABSTRACT Potential of Ozone and Hydroxyl Radicals to Degrade Emerging Organic Contaminants
Lisa Elaine Vance
Advanced water treatment processes are necessary for the treatment of emerging organic contaminants. Traditional treatment processes do not filter or treat these contaminants causing humans and animals to come into contact and ingest them, both causing illness. Advanced oxidation processes are a good alternative method, but are cost and time intensive.
Previous research on ozone and hydroxyl radicals leads to the conclusion that they might be a vial option for advanced water treatment processes. To test the effects of ozone and hydroxyl radicals on the destruction of algae, ozonated phosphate buffer was mixed with Anabaena and modified BG11 culture media and placed in a culturing apparatus to regrow the destructed Anabaena. The biomass density was measured via the optical density for five days and compared to controls. Exposure to ozone killed most of the algae in each batch, as expected. The higher the concentration of ozone, the higher amount of algal destruction. The Ozone Plus generator was more powerful at initial algal destruction than the Standard ozone generator, as indicated by the comparison between the results at 2 ppm ozone concentration. !
To test the effects of ozone and hydroxyl radicals on the treatment of carbamazepine (CMZ) and phenytoin (PHT) in controlled water systems, ozonated phosphate buffer was mixed with CMZ stock solution to make a 0.25 uM CMZ solution or PHT stock solution to form a 0.25 PHT solution.
The dissolved organic carbon was measured through a total organic carbon (TOC) analyzer to determine degradation of organic compounds after exposure to ozone. With the same goal in mind, other experiments were performed using ozonated carbon nanotubes to treat CMZ and PHT in a series of increasingly complex water systems. To test the effects of ozonated carbon nanotubes (CNTs) on the treatment of CMZ and PHT, mixtures of 5.0 mM CMZ or PHT and tert-butonal were treated with ozonated phosphate buffer or treated effluent wastewater and 10 ppm or 20 ppm carbon nanotube solid loading. A high-performance liquid chromatography analyzer was used to measure the treated CMZ and PHT in the mixtures and compared to controls.
The TOC test was used to determine the pharmaceutical destruction to ozone dose relationship was expected to be linear, but these results were inconclusive due to the maximum reduction of less than 10% for any level of ozone. In the simple media tests, CMZ was seemed to be completely when exposed to ozone, but a suspected breakdown product was measured. PHT had the most degradation with a CNT loading of 10 ppm and no ozone. This test suggests sorption had a greater effect on the pharmaceuticals than ozone or ·OH did. In more complex systems involving a mixture of the two pharmaceuticals in both a phosphate buffer, PHT with a CNT loading of 10 ppm had a degradation of 14% and 4% for a CNT loading of 20 ppm. The low degradation rate is most likely due to ozone reacting with other organic matter in the reactor and not the PHT. This was the same in the more complex systems involving a mixture of the two pharmaceuticals in both a phosphate buffer and a wastewater effluent system PHT with a CNT loading of 10 ppm had a degradation of 12% and 6% for a CNT loading of 20 ppm.
In all three Chapters, the ozone and hydroxyl radicals showed moderate reduction in emerging organic contaminants. These results suggest that ozone and hydroxyl radicals generated from ozonated CNTs have potential to be an effective alternative to current AOPs, and that further study to refine the process is merited.