| Description |
Worldwide, anthropogenic contaminants emerge and enter into aquatic systems; their ubiquity in aquatic systems poses serious threats to both human health and ecological systems. As the demand for water continues to grow with population, treatment of wastewater and remediation of polluted aquatic systems are of critical concern. Ozonation and advanced oxidation processes (AOPs) are promising methods for removal of numerous waterborne contaminants. In this thesis, three groups of waterborne organic contaminants have been studied for degradation by uses of ozone and ozone in combination with hydrogen peroxide. Specifically, the study compounds are methyl tertiary-butyl ether (MTBE), six endocrine disruptor compounds (EDCs) and pharmaceutical and personal care products (PPCPs) chemicals that include dibutyl phthalate (DBP), diethyl phthalate (DEP), dimethyl phthalate (DMP), di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA), triclosan (TCS), and two naphthenic acids (NAs) including Cyclohexaneacetic acid and Cyclohexanebutyric acid. This study has also examined a pressure assisted ozonation (PAO) method that employs ozone microbubbles generated by repetitive compression-decompression cycles to treat the study compounds. Degradation has been investigated under different conditions. The results indicate that ozonation is very effective in removing these contaminants, and that PAO increases treatment efficiency by 10 to 40% for different chemicals. MTBE degradation by 90% was achieved in 36 min from an initial concentration of 12 mg/L. TCS and BPA iv disappeared completely within minutes of PAO treatment from an initial of 9 mg/L. The removals of four phthalate esters were between 45%~98% in 24 min from initial concentrations of 6.9 - 8.6 mg/L. For NAs, a high concentration of ozone (e.g., 15 mg/L) along with a proper dose of H2O2 (e.g., H2O2/O3 mole ratio 1/1) completely removed the study NAs from an initial concentration of 17 mg/L in 10 min. Varying treatment parameters significantly influenced treatment outcomes: e.g., addition of H2O2 increased removal percentage of different chemicals by 10 to 30%; increasing compression cycles improved removal of target compounds to a certain degree. Aqueous O3 concentration was an important factor, with increased removal at higher O3 concentration. The pH range between 7 and 10 was more suitable treatment condition than pH 3 for degradation of the target compounds. Initial target compound concentration, however, did not influence removal rate significantly. |
