Use of UV and Fluorescence Spectra as Surrogate Measures for Contaminant Oxidation and Disinfection in the Ozone/H202 Advanced Oxidation Process
Year Released: 2013
Funding Partner: Bureau of Reclamation, Water Research Foundation
Total Investment: $256,627.98 (Cash: $145,021.60, In-Kind: $111,606.38)
Principal Investigators: Shane A. Snyder, Ph.D., University of Arizona, Gregory Korshin, Ph.D., University of Washington, Daniel Gerrity, Ph.D., Southern Nevada Water Authority and Trussell Technologies, Inc., and Eric Wert, P.E., Southern Nevada Water Authority
The performance of advanced oxidation processes depends largely on water quality and the ability to form hydroxyl radicals to meet disinfection or contaminant destruction objectives. However, there are no direct methods to measure hydroxyl radical exposure, and frequent monitoring for trace organic contaminants and pathogenic microorganisms is a costly and difficult proposition.
Goals and Objectives
The project develops differential UV absorbance and fluorescence models to estimate hydroxyl radical exposure, contaminant oxidation, and disinfection efficacy with ozone, ozone/H2O2, and UV/H2O2.
In order to facilitate this effort, this project included a series of bench-scale experiments on five secondary effluents with varying water quality. The bench-scale experiments consisted of spiking samples with approximately 20 different trace organic and microbial contaminants prior to advanced oxidation with ozone, ozone/H2O2, or UV/H2O2. The samples were then analyzed for the surrogate microbes and target compounds, including a number of pharmaceuticals and potential endocrine disrupting compounds (EDCs); several disinfection byproducts (DBPs); and a variety of bulk organic parameters, including UV absorbance and total fluorescence (TF). Advanced oxidation experiments were also performed with multiple pilot-scale reactors to validate the data collected during the bench-scale phase.
Findings and Conclusions
This project addresses the need to develop alternative monitoring strategies for AOPs in IPR applications. Specifically, the project indicates that the correlation models for differential absorbance or fluorescence, contaminant oxidation, and microbial inactivation were consistent regardless of secondary effluent water quality and scale of the oxidation process. Separate regression models were required for the various contaminants because of their respective oxidation rate constants, and separate models were also required for ozone- versus UV-based oxidation processes. Although the correlations were quite strong for the TOrCs, the microbial data were characterized by greater variability. The linear correlations between bulk organic matter and microbial inactivation were still evident, particularly for the bacteriophage MS2, despite the increased variability. This concept has tremendous promise for full-scale implementation, which will provide opportunities for process optimization, further redundancy in ensuring the integrity of unit process performance, and, most important, additional safeguards for public health.
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