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Title:Advancing biocatalytic technologies for degradation of micropollutants in drinking water
Author(s):Hutchison, Justin M.
Director of Research:Zilles, Julie L.
Doctoral Committee Chair(s):Zilles, Julie L.
Doctoral Committee Member(s):Werth, Charles J.; Strathmann, Timothy J.; Guest, Jeremy S.; Brown, Jess C.
Department / Program:Civil & Environmental Eng
Discipline:Environ Engr in Civil Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Azospira oryzae
Paracoccus denitrificans
Haloferax denitrificans
Contaminants of Emerging Concern, Endocrine Disrupting Compounds
Ion Exchange
Perchlorate Reductase
Chlorite Dismutase
Abstract:Biological enzymes, referred in this dissertation as biocatalysts, offer targeted and rapid destruction of micropollutants such as perchlorate. This targeted destruction of perchlorate even in the presence of orders of magnitude higher concentrations of co-competing compounds offers a distinct advantage over traditional and emerging perchlorate treatment technologies. In this work, the bacterial biocatalysts perchlorate reductase and chlorite dismutase from Azospira oryzae had 3 to 4 orders of magnitude faster activity than catalytic technologies while maintaining activity in the presence of oxygen and nitrate. Activity was retained even when molar concentrations of nitrate were 500 times greater than perchlorate. The biocatalysts are active in a range of water quality conditions relevant to groundwater, including operation in hard water conditions, temperatures from 5ºC to 30ºC, and pH from 6.0 to 9.0. The robustness of this activity was further confirmed using two real-world groundwaters where the biocatalysts had no statistically significant difference in activity compared to laboratory-buffered conditions. However, perceptions of the costs and environmental impacts of biocatalytic drinking water treatment have hindered implementation. To overcome these perceptions, a detailed economic and environmental assessment was performed. In the analysis, the conservative, baseline biocatalytic scenario (single-use in batch reactors) was found to have median costs of $1.92 and global warming potential of 3.72 kg CO2 eq per m3 of drinking water treated. These values are more than current drinking water treatment price and emissions. To accelerate the advancement and bring down costs and environmental impacts of biocatalytic technologies, several critical improvements were evaluated. These improvements include achieving biocatalytic reuse and implementing alternative electron donors. Upon realization of these goals, biocatalytic technologies are projected to have comparable costs and emissions to an idealized, highly selective ion-exchange technology. Realizing these improvements requires development of the biocatalysts. To achieve reuse, two methods were tested. The biocatalysts were encapsulated in nanoreactors and modified to include a tag that allows for attachment to larger resin beads. The nanoreactors demonstrated full perchlorate reduction; however, the reactors are still relatively small, approximately 100nm, and were activity limited. Tagged forms of chlorite dismutase showed activity in free, attached, and column-packed formats. Attached and column-packed biocatalysts were mass transfer limited over a range of environmental chlorite concentrations. To understand the limitations of mass transfer, a model including kinetic and mass transfer parameters was developed. This model better fit the activity data of the attached biocatalysts. To gain acceptance for biocatalytic drinking water treatment, the biocatalysts were tested for potential use in a hybrid system, one step removed from direct drinking water treatment. Using an ion-exchange waste brine, the biocatalytic treatment system treated the contaminants, nitrate and perchlorate. The perchlorate biocatalytic system, as well as a novel nitrate biocatalytic system, were employed to treat the waste brine. The treatment would prevent the reintroduction of the contaminants into the environment. Biocatalysts reduced perchlorate into chloride and oxygen in synthetic, 12% sodium chloride and real-world waste brine. Nitrate biocatalysts from Paracoccus denitrificans and Haloferax denitrificans reduced nitrate. Tracking dinitrogen formation using stable isotopes in the 12% sodium chloride solution, the combined P. denitrificans and H. denitrificans biocatalysts reduced nitrate into a mixture of nitrous oxide and dinitrogen. Overall, this work demonstrates the potential application of biocatalysts to treat both micropollutants and traditional contaminants in drinking water as well as the integration of biocatalysts in hybrid treatment systems. Using sustainability analysis, critical technology advancements were identified and explored experimentally. Biocatalytic technologies represent the next generation of treatment, breaking the current cycle of moving contaminants between environmental matrixes and assuring access to safe drinking water treatment for all.
Issue Date:2018-07-10
Rights Information:Copyright 2018 Justin Hutchison
Date Available in IDEALS:2018-09-27
Date Deposited:2018-08

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