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Title:Disinfection of wastewater for reuse using microchannel plasma ozone generator
Author(s):Dong, Shengkun
Director of Research:Nguyen, Thanh H.
Doctoral Committee Chair(s):Nguyen, Thanh H.
Doctoral Committee Member(s):Mariñas, Benito J.; Plewa, Michael J.; Guest, Jeremy S.
Department / Program:Civil & Environmental Eng
Discipline:Environ Engr in Civil Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
microchannel plasma
life cycle assessment
quantitative microbial risk assessment
disability adjusted life years
mammalian cell
Abstract:Waster reuse is increasing which alleviates pressure on water resources. However, successful reuse demands that the finished water be disinfected to prevent the spread of pathogens. One of the pathogens of potential public health concerns is Legionella pneumophila. This thesis investigated the performance of an energy efficient and compact microchannel plasma-based ozone generator to inactivate L. pneumophila for safer water reuse. Inactivation kinetics study quantified the inactivation. More than four Log10 of L. pneumophila inactivation was achieved within 1 minute at low energy consumption (< 0.022 kWh) by the microplasma ozonator, using only ambient air as the feedstock gas at a driving voltage of 120V. Contrary to previous studies, the CT (product of available disinfectant concentration and exposure duration) concept for wastewater disinfection using ozone appeared to be valid. A framework to derive wastewater-specific CT equations was therefore developed to predict ozone inactivation of L. pneumophila. Temperature was found to affect L. pneumophila inactivation only in the absence of wastewater organic matter (WOM). In the presence of WOM, inactivation was temperature-independent and controlled by the disinfection contact time, initial ozone concentration and initial WOM loading. An integrated life cycle assessment (LCA) and quantitative microbial risk assessment (QMRA) was used to compare microplasma ozonation versus chlorination to disinfect wastewater for landscape irrigational reuse. L. pneumophila, Giardia, and Cryptosporidium parvum were selected as the pathogens. Microplasma-based ozonation was significantly more competitive in environmental performance compared to chlorination for five of six impact categories, due to its low energy consumption and the high susceptibility of the pathogens to ozone. Across different electricity fuel sources in Florida, California, and Texas, the microplasma ozonation system consistently offset more disability adjusted life years values to provide greater human health protection as compared to the chlorination disinfection system. As such, from the point of view of reducing human health impact, the emerging microplasma ozonation technology is superior to chlorination (with dechlorination) for wastewater reuse disinfection. To reduce the overall human health impact, future design efforts should focus on a long hydraulic residence time (HRT) with low chlorine doses for the chlorination system, and a moderately high transferred ozone dose with long HRT for the microplasma ozonation system. In vitro mammalian cell cytotoxicity was evaluated before and after disinfection of two sources of wastewaters, using ozonation or chlorination. The swine farm wastewater was approximately 2000× more cytotoxic than the secondary effluent. Ozonation consistently reduced the mammalian cell cytotoxicity of the wastewaters by as much as 10×. Chlorination lowered the cytotoxicity only when followed by dechlorination. Based on mammalian cell cytotoxicity, secondary effluent is preferred for agricultural reuse over swine wastewater regardless of the disinfectants. Importantly, ozonation may hold the most promise in reducing the overall cytotoxicity of wastewater and this method may prove useful in agricultural reuse of wastewaters. The only significant correlation was observed between total haloacetonitriles and cytotoxicity in secondary effluent. Despite that the connection between reduced cytotoxicity and modification or reduction of certain compound(s) is not clear, regulated DBPs may not be the leading forcing agents. To summarize, the results from these studies demonstrated the promise of using the microchannel plasma-based ozonation technology as a sustainable and effective means for water reuse disinfection.
Issue Date:2016-08-31
Rights Information:Copyright 2016 Shengkun Dong
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12

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