Document Type

Dissertation - Open Access

Award Date

2019

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Guanghui Hua

Keywords

Advanced Oxidation Processes, Dehalogenation, Disinfection Byproducts, Iodinated Disinfection Byproducts, Natural Solar Photolysis, Trihalomethanes and Haloacetic acids

Abstract

Disinfection byproducts (DBPs) presence in wastewater effluents and receiving waters may impact the quality of drinking water during water reuse practices. Natural solar photolysis is one of the biogeochemical processes that may lead to decreased DBPs concentrations in water. The purpose of this dissertation is to determine the fate of chlorinated, brominated and iodinated DBPs in surface water by natural sunlight photolysis and investigate the use of solar-based advanced oxidation processes (AOPs) for removal of DBPs in water. Total organic halogen (TOX) was used to measure total chlorinated- (TOCl), brominated- (TOBr) and iodinated-DBPs (TOI) in water. The first objective was to determine the optimum protocol for TOX sample preservation conditions to ensure accurate TOX analysis throughout the following experiments. To achieve the highest TOX recovery, samples must be stored at pH 2 using nitric acid, 4 °C incubator and be analyzed within 14 days of storage. Overdosing of quenching agents such as sodium sulfite, sodium thiosulfate and ascorbic acid must be avoided to maintain stable TOX concentrations during storage. The second objective was to determine the fate of TOCl, TOBr, TOI and individual DBPs by natural sunlight in surface water. Iodinated DBPs were the most photodegradable specific halogenated DBPs, whereas chlorinated DBPs were the most resistant to sunlight photodegradation. The TOX degradation rates were generally in the order of TOI > TOBr TOCl(NH2Cl) > TOCl(Cl2) and the half-lives ranged between 2.6 and 10.7 h during solar photolysis. Typical concentrations of natural surface and wastewater containments including nitrate, nitrite and sulfite had little impact on enhancing DBPs photodegradation rates. However, natural organic matter and turbidity decreased photodegradation of DBPs by light screening. The third objective was to evaluate the use of solar-based AOPs for DBP removal in water. Both solar-TiO2 photocatalytic and solar photo-fenton processes increased DBPs photodegradation rates significantly in comparison to solar photolysis alone. TOX half-lives were reduced from hours to minutes by the two solar-based AOPs, and the rate of degradation were generally in the order of TOI > TOCl(NH2Cl) > TOBr > TOCl(Cl2). Oxidation by hydroxyl radicals is expected to be the main mechanism accountable for improved DBP degradation. Furthermore, several natural water constituents including chloride, sulfate, natural organic matter and bicarbonate decreased DBPs degradation efficiency by solar-based AOPs.

Format

application/pdf

Number of Pages

209

Publisher

South Dakota State University

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