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Description
Advanced oxidation processes (AOP’s) are water/wastewater treatment processes simultaneously providing disinfection and potential oxidation of contaminants that may cause long-term adverse health effects in humans. One AOP involves injecting peracetic acid (PAA) upstream of an ultraviolet (UV) irradiation reactor. Two studies were conducted, one in pilot-scale field conditions and another under laboratory conditions. A pilot-scale NeoTech UV reactor (rated for 375 GPM) was used in the pilot study, where a smaller version of this unit was used in the laboratory study (20 to 35 GPM). The pilot study analyzed coliform disinfection and also monitored water quality parameters including UV transmittance (UVT), pH and chlorine residual. Pilot study UV experiments indicate the unit is effectively treating flow streams (>6 logs total coliforms) twice the 95% UVT unit capacity (750 GPM or 17 mJ/cm2 UV Dose). The results were inconclusive on PAA/UV inactivation due to high data variability and field operation conditions creating low inlet concentrations.Escherichia coli (E. coli) bacteria and the enterobacteria phage P22—a surrogate for enteric viruses—were analyzed. UV inactivated >7.9 and 4 logs of E. coli and P22 respectively at a 16.8 mJ/cm2 UV dose in test water containing a significant organics concentration. When PAA doses of 0.25 and 0.5 mg/L were injected upstream of UV at approximately the same UV Dose, the average E.coli log inactivation increased to >8.9 and >9 logs respectively, but P22 inactivation decreased to 2.9 and 3.0 logs, respectively. A bench-scale study with PAA was also conducted for 5, 10 and 30 minutes of contact time, where 0.25 and 0.5 mg/L had <1 log inactivation of E. coli and P22 after 30 minutes of contact time. In addition, degradation of the chemical N-Nitrosodimethylamine (NDMA) in tap water was analyzed, where UV degraded NDMA by 48 to 97% for 4 and 0.5 GPM flowrates, respectively. Adding 0.5 mg/L PAA upstream of UV did not significantly improve NDMA degradation.
The results under laboratory conditions indicate that PAA/UV have synergy in the inactivation of bacteria, but decrease virus inactivation. In addition, the pilot study demonstrates the applicability of the technology for full scale operation.
The results under laboratory conditions indicate that PAA/UV have synergy in the inactivation of bacteria, but decrease virus inactivation. In addition, the pilot study demonstrates the applicability of the technology for full scale operation.
ContributorsCooper, Samantha (Author) / Abbaszadegan, Morteza (Thesis advisor) / Alum, Absar (Committee member) / Fox, Peter (Committee member) / Arizona State University (Publisher)
Created2017
Description
Acetylcholinesterase (AChE) inhibition by chemical toxicants such as organophosphates, nerve agents, and carbamates can lead to a series of adverse health outcomes including seizures, coma, and death. An adverse outcome pathway (AOP) is a framework that describes a series of biologically measurable key events (KEs) leading from some molecular initiating event (MIE) to an adverse outcome (AO) of regulatory significance, all developed and hosted in the AOP Wiki. A quantitative AOP (qAOP) is a mathematical model that predicts how perturbations in the MIE affect KEs based on the key event relationships (KERs) that define the AOP. The purpose of this thesis was to expand upon the KERs that define the AOP for AChE inhibition leading to neurodegeneration in order to better understand the effects of AChE inhibitors and the risks they pose to ecosystems, wildlife, and human health. In order to reduce the resources and time spent for chemical toxicity testing, a qAOP was developed based on the available quantitative data and models that supported the AOP. A literature review for the collection of qualitative evidence and quantitative data in support of the AOP was performed resulting in further expansion of the relationships between key events (KERs) through construction of additional KER description pages. A model evaluation was performed by comparing the qAOP model predictions with experimental data, with a subsequent sensitivity analysis of unknown parameters. The qAOP model simulates the MIE through its fifth KE (KE 5) and KE 7. Model predictions compared to experimentally measured data either under- or overpredicting multiple KEs warranting additional refinement such as a formal parameter optimization. Overall, more data amenable to qAOP model development are needed. To aid qAOP model development, the presentation of data in the AOPWiki may be improved by presenting the quantitative data in the AOP Wiki in a tabular format and allowing for the hosting of mathematical models or raw data. With these recommendations in mind, and through continued AOP construction in the AOP Wiki, new qAOP models will be developed, ultimately supporting chemical risk assessment and the mitigation of effects upon exposed individuals and wildlife populations.
ContributorsSinitsyn, Dennis (Author) / Watanabe, Karen (Thesis advisor) / Vinas, Natalia (Committee member) / Wirkus, Stephen (Committee member) / Arizona State University (Publisher)
Created2023