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The National Research Council 2011 report lists quantifying the extent of de facto (or unplanned) potable reuse in the U.S. as the top research need associated with assessing the potential for expanding the nations water supply through reuse of municipal wastewater. Efforts to identify the significance and potential health impacts

The National Research Council 2011 report lists quantifying the extent of de facto (or unplanned) potable reuse in the U.S. as the top research need associated with assessing the potential for expanding the nations water supply through reuse of municipal wastewater. Efforts to identify the significance and potential health impacts of de facto water reuse are impeded by out dated information regarding the contribution of municipal wastewater effluent to potable water supplies. This project aims to answer this research need. The overall goal of the this project is to quantify the extent of de facto reuse by developing a model that estimates the amount of wastewater effluent that is present within drinking water treatment plants; and to use the model in conjunction with a survey to help assess public perceptions. The four-step approach to accomplish this goal includes: (1) creating a GIS-based model coupled with Python programming; (2) validating the model with field studies by analyzing sucralose as a wastewater tracer; (3) estimating the percentage of wastewater in raw drinking water sources under varying streamflow conditions; (4) and assessing through a social survey the perceptions of the general public relating to acceptance and occurrence of de facto reuse. The resulting De Facto Reuse in our Nations Consumable Supply (DRINCS) Model, estimates that treated municipal wastewater is present at nearly 50% of drinking water treatment plant intake sites serving greater than 10,000 people (N=2,056). Contrary to the high frequency of occurrence, the magnitude of occurrence is relatively low with 50% of impacted intakes yielding less than 1% de facto reuse under average streamflow conditions. Model estimates increase under low flow conditions (modeled by Q95), in several cases treated wastewater makes up 100% of the water supply. De facto reuse occurs at levels that surpass what is publically perceived in the three cities of Atlanta, GA, Philadelphia, PA, and Phoenix, AZ. Respondents with knowledge of de facto reuse occurrence are 10 times more likely to have a high acceptance (greater than 75%) of treated wastewater at their home tap.
ContributorsRice, Jacelyn (Author) / Westerhoff, Paul (Thesis advisor) / Abbaszadegan, Morteza (Committee member) / Vivoni, Enrique (Committee member) / Wutich, Amber (Committee member) / Arizona State University (Publisher)
Created2014
Description
Filtration for microfluidic sample-collection devices is desirable for sample selection, concentration, preprocessing, and downstream manipulation, but microfabricating the required sub-micrometer filtration structure is an elaborate process. This thesis presents a simple method to fabricate polydimethylsiloxane (PDMS) devices with an integrated membrane filter that will sample, lyse, and extract the DNA

Filtration for microfluidic sample-collection devices is desirable for sample selection, concentration, preprocessing, and downstream manipulation, but microfabricating the required sub-micrometer filtration structure is an elaborate process. This thesis presents a simple method to fabricate polydimethylsiloxane (PDMS) devices with an integrated membrane filter that will sample, lyse, and extract the DNA from microorganisms in aqueous environments. An off-the-shelf membrane filter disc was embedded in a PDMS layer and sequentially bound with other PDMS channel layers. No leakage was observed during filtration. This device was validated by concentrating a large amount of cyanobacterium Synechocystis in simulated sample water with consistent performance across devices. After accumulating sufficient biomass on the filter, a sequential electrochemical lysing process was performed by applying 5VDC across the filter. This device was further evaluated by delivering several samples of differing concentrations of cyanobacterium Synechocystis then quantifying the DNA using real-time PCR. Lastly, an environmental sample was run through the device and the amount of photosynthetic microorganisms present in the water was determined. The major breakthroughs in this design are low energy demand, cheap materials, simple design, straightforward fabrication, and robust performance, together enabling wide-utility of similar chip-based devices for field-deployable operations in environmental micro-biotechnology.
ContributorsLecluse, Aurelie (Author) / Meldrum, Deirdre (Thesis advisor) / Chao, Joseph (Thesis advisor) / Westerhoff, Paul (Committee member) / Arizona State University (Publisher)
Created2011
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Contamination of drinking water supplies from oxo-anion pollutants necessitates treatment prior to potable use. This dissertation aims to inform and improve light delivery (emission spectra, radiant intensity, reactor configuration) in order to enhance the photocatalytic reduction of hexavalent chromium (Cr(VI)) and nitrate, two common oxo-anions in drinking water, and photocatalytic

Contamination of drinking water supplies from oxo-anion pollutants necessitates treatment prior to potable use. This dissertation aims to inform and improve light delivery (emission spectra, radiant intensity, reactor configuration) in order to enhance the photocatalytic reduction of hexavalent chromium (Cr(VI)) and nitrate, two common oxo-anions in drinking water, and photocatalytic oxidation of two model organic pollutants (methylene blue, (MB) and para-chlorobenzoic acid (pCBA)). By varying the photon fluence dose, two metrics (contaminant quantum yield (Φ), and electrical energy per order (EEO)) were used to assess photocatalytic reactor performance. A detailed literature review and experimental results demonstrated how different irradiance sources with variable intensity and emission spectra synergistically enhanced contaminant removal by a coupled photolytic/photocatalytic reaction mechanism. Cr(VI) was photocatalytically reduced on TiO2 and formed Cr(OH)3(s) in a large-scale slurry reactor, but Cr(III) was then photolyzed and reformed Cr(VI). UV light also led to photo-aggregation of TiO2 which improved its recovery by the ceramic membrane within the reactor. For nitrate reduction, light source emission spectra and fluence dose delineate the preferred pathways as intermediates were reduced via wavelength-dependent mechanisms. HONO was identified as a key nitrate reduction intermediate, which was reduced photocatalytically (UV wavelengths) and/or readily photolyzed at 365nm, to yield nitrogen gases. Photocatalytic nitrate reduction efficiency was higher for discrete wavelength irradiation than polychromatic irradiation. Light delivery through aqueous media to the catalyst surface limits efficiency of slurry-based photocatalysts because absorption and scattering of light in nanomaterial slurries decreases effective photon transmittance and minimizes photolytic reactions. The use of optical fibers coupled to light emitting diodes (OF-LED) with immobilized catalyst demonstrated higher performance compared to slurry systems. OF-LED increased Φ for MB degradation by increasing direct photon delivery to the photocatalyst. Design of OF-LED reactors using bundled optical fibers demonstrated photocatalytic pCBA removal with high Φ and reduced EEO due to increased surface area and catalytic sites compared to single OF/LED couples. This work advances light delivery as well as the suspension and attachment of nanoparticles in photocatalytic water treatment for selective transformation of oxo-anions and organic compounds to innocuous species.
ContributorsTugaoen, Heather O'Neal (Author) / Westerhoff, Paul (Thesis advisor) / Hristovski, Kiril (Thesis advisor) / Chan, Candace (Committee member) / Arizona State University (Publisher)
Created2017
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Description
Ion exchange sorbents embedded with metal oxide nanoparticles can have high affinity and high capacity to simultaneously remove multiple oxygenated anion contaminants from drinking water. This research pursued answering the question, “Can synthesis methods of nano-composite sorbents be improved to increase sustainability and feasibility to remove hexavalent chromium and arsenic

Ion exchange sorbents embedded with metal oxide nanoparticles can have high affinity and high capacity to simultaneously remove multiple oxygenated anion contaminants from drinking water. This research pursued answering the question, “Can synthesis methods of nano-composite sorbents be improved to increase sustainability and feasibility to remove hexavalent chromium and arsenic simultaneously from groundwater compared to existing sorbents?” Preliminary nano-composite sorbents outperformed existing sorbents in equilibrium tests, but struggled in packed bed applications and at low influent concentrations. The synthesis process was then tailored for weak base anion exchange (WBAX) while comparing titanium dioxide against iron hydroxide nanoparticles (Ti-WBAX and Fe-WBAX, respectively). Increasing metal precursor concentration increased the metal content of the created sorbents, but pollutant removal performance and usable surface area declined due to pore blockage and nanoparticle agglomeration. An acid-post rinse was required for Fe-WBAX to restore chromium removal capacity. Anticipatory life cycle assessment identified critical design constraints to improve environmental and human health performance like minimizing oven heating time, improving pollutant removal capacity, and efficiently reusing metal precursor solution. The life cycle environmental impact of Ti-WBAX was lower than Fe-WBAX as well as a mixed bed of WBAX and granular ferric hydroxide for all studied categories. A separate life cycle assessment found the total number of cancer and non-cancer cases prevented by drinking safer water outweighed those created by manufacture and use of water treatment materials and energy. However, treatment relocated who bore the health risk, concentrated it in a sub-population, and changed the primary manifestation from cancer to non-cancer disease. This tradeoff was partially mitigated by avoiding use of pH control chemicals. When properly synthesized, Fe-WBAX and Ti-WBAX sorbents maintained chromium removal capacity while significantly increasing arsenic removal capacity compared to the parent resin. The hybrid sorbent performance was demonstrated in packed beds using a challenging water matrix and low pollutant influent conditions. Breakthrough curves hint that the hexavalent chromium is removed by anion exchange and the arsenic is removed by metal oxide sorption. Overall, the hybrid nano-sorbent synthesis methods increased sustainability, improved sorbent characteristics, and increased simultaneous removal of chromium and arsenic for drinking water.
ContributorsGifford, James McKay (Author) / Westerhoff, Paul (Thesis advisor) / Hristovski, Kiril (Thesis advisor) / Chester, Mikhail (Committee member) / Arizona State University (Publisher)
Created2016