Assessment of an Advanced Oxidation System for the Generation of Oxidative Species and Effectiveness of Treating Synthetic and Real Stormwater
Date
2020-10-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
Stormwater (SW) is a type of wastewater that is of current concern for municipalities, especially in urban settings with large amounts of impervious areas. Stormwater contains high concentrations of contaminants that can cause large pollutant loading into receiving water bodies if left untreated. Many Best Management Practices (BMPs) in North America focus on minimizing the flood risk and pollution caused by SW, however, SW capture and beneficial reuse have become of increasing importance in areas and times of water scarcity. Stormwater treatment is usually needed to meet water quality targets required for beneficial reuse and for safe release of SW into receiving environments. Of recent interest are electrochemical Advanced Oxidation Processes (eAOPs) for SW treatment as they are cost effective, easy to operate and maintain, and have shown promise for SW treatment. An industry partner has developed an eAOP for treatment of wastewaters known as the Advanced Oxidation System (AOS) which was the technology used for research conducted in this thesis.
In Chapter 2, the AOS was shown to create iodide and chloride oxidative species that were used for operating parameter assessment and improved understanding of the system effectiveness and efficiency. Determining the optimum type and concentration of added salt, in addition to the optimal applied voltage is imperative to achieve the most effective treatment. The oxidative species were collected from the AOS anodes and cathodes and determined using a simple UV-vis spectrophotometric method. Iodate and periodate were determined for experiments using iodide addition and the optimal treatment parameters were 12 V and 10 ppm KI (potassium iodide). Chlorite and chlorate were measured for chloride with 6 V and 5 ppm NaCl (sodium chloride) were the optimal parameters. Iodate and chlorite were the dominant species created within the AOS, with oxidative species generally being created at reactor anodes and destroyed at cathodes.
The AOS treatment effectiveness for disinfection and decontamination was assessed for both synthetic (Chapter 2) and real (Chapter 3) stormwaters. Treatments included iodide addition, chloride addition, and no salt addition which were compared to determine the most effective SW treatment condition. Overall, the AOS performed well for the disinfection of Escherichia coli when iodide was used, showing 6 log removal for synthetic SW and 3.5 log removal for real SW. Organics removal was not as effective using the current AOS operation and design parameters. For example, the AOS was able to remove 50% of the chemical oxygen demand using iodide and 70% of the total organic carbon using chloride. For real SW, the pre-treatment of the SW via a coagulation/flocculation process using either alum or ferric chloride achieved reasonable solids removal.
Future work using the AOS could include investigating the creation of other oxidative species in the reactor beyond iodide and chloride species; further improvement of the organics removal through assessment of operating parameters; determination of the removal of other contaminants in SW such as heavy metals and polyaromatic hydrocarbons; testing different coagulants and pre-treatment technologies; assessing the creation of oxidative by-products in the treated SW effluent; and comparing the toxicity of the raw and treated SW.
Description
Keywords
stormwater treatment, advanced oxidation, electrochemical treatment
Citation
Degree
Master of Science (M.Sc.)
Department
Civil and Geological Engineering
Program
Civil Engineering