Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- All Subjects: Environmental engineering
Description
Drinking water filtration using reverse osmosis (RO) membranes effectively removes salts and most other inorganic, organic, and microbial pollutants. RO technologies are utilized at both the municipal and residential scale. The formation of biofilms on RO membranes reduces water flux and increases energy consumption. The research conducted for this thesis involves In-Situ coating of silver, a known biocide, on the surface of RO membranes. This research was adapted from a protocol developed for coating flat sheet membranes with silver nanoparticles, and scaled up into spiral-wound membranes that are commonly used at the residential scale in point-of-use (POU) filtration systems. Performance analyses of the silver-coated spiral-wound were conducted in a mobile drinking water treatment system fitted with two POU units for comparison. Five month-long analyses were performed, including a deployment of the mobile system. In addition to flux, salt rejection, and other water quality analyses, additional membrane characterization tests were conducted on pristine and silver-coated membranes.
For flat sheet membranes coated with silver, the surface charge remained negative and contact angle remained below 90. Scaling up to spiral-wound RO membrane configuration was successful, with an average silver-loading of 1.93 g-Ag/cm2. Results showed the flux of water through the membrane ranged from 8 to 13 liters/m2*hr. (LMH) operating at 25% recovery during long-term of operation. The flux was initially decreased due to the silver coating, but no statistically significant differences were observed after 14 days of operation (P < 0.05). The salt rejection was also not effected due to the silver coating (P < 0.05). While 98% of silver was released during long-term studies, the silver release from the spiral-wound membrane was consistently below the secondary MCL of 100 ppb established by the EPA, and was consistently below 5 ppb after two hours of operation. Microbial assays in the form of heterotrophic plate counts suggested there was no statistically significant difference in the prevention of biofouling formation due to the silver coating (P < 0.05). In addition to performance tests and membrane characterizations, a remote data acquisition system was configured to remotely monitor performance and water quality parameters in the mobile system.
For flat sheet membranes coated with silver, the surface charge remained negative and contact angle remained below 90. Scaling up to spiral-wound RO membrane configuration was successful, with an average silver-loading of 1.93 g-Ag/cm2. Results showed the flux of water through the membrane ranged from 8 to 13 liters/m2*hr. (LMH) operating at 25% recovery during long-term of operation. The flux was initially decreased due to the silver coating, but no statistically significant differences were observed after 14 days of operation (P < 0.05). The salt rejection was also not effected due to the silver coating (P < 0.05). While 98% of silver was released during long-term studies, the silver release from the spiral-wound membrane was consistently below the secondary MCL of 100 ppb established by the EPA, and was consistently below 5 ppb after two hours of operation. Microbial assays in the form of heterotrophic plate counts suggested there was no statistically significant difference in the prevention of biofouling formation due to the silver coating (P < 0.05). In addition to performance tests and membrane characterizations, a remote data acquisition system was configured to remotely monitor performance and water quality parameters in the mobile system.
ContributorsZimmerman, Sean (Author) / Westerhoff, Paul K (Thesis advisor) / Sinha, Shahnawaz (Committee member) / Perreault, Francois (Committee member) / Arizona State University (Publisher)
Created2017
Description
With the application of reverse osmosis (RO) membranes in the wastewater treatment and seawater desalination, the limitation of flux and fouling problems of RO have gained more attention from researchers. Because of the tunable structure and physicochemical properties of nanomaterials, it is a suitable material that can be used to incorporate with RO to change the membrane performances. Silver is biocidal, which has been used in a variety of consumer products. Recent studies showed that fabricating silver nanoparticles (AgNPs) on membrane surfaces can mitigate the biofouling problem on the membrane. Studies have shown that Ag released from the membrane in the form of either Ag ions or AgNP will accelerate the antimicrobial activity of the membrane. However, the silver release from the membrane will lower the silver loading on the membrane, which will eventually shorten the antimicrobial activity lifetime of the membrane. Therefore, the silver leaching amount is a crucial parameter that needs to be determined for every type of Ag composite membrane.
This study is attempting to compare four different silver leaching test methods, to study the silver leaching potential of the silver impregnated membranes, conducting the advantages and disadvantages of the leaching methods. An In-situ reduction Ag loaded RO membrane was examined in this study. A custom waterjet test was established to create a high-velocity water flow to test the silver leaching from the nanocomposite membrane in a relative extreme environment. The batch leaching test was examined as the most common leaching test method for the silver composite membrane. The cross-flow filtration and dead-end test were also examined to compare the silver leaching amounts.
The silver coated membrane used in this experiment has an initial silver loading of 2.0± 0.51 ug/cm2. The mass balance was conducted for all of the leaching tests. For the batch test, water jet test, and dead-end filtration, the mass balances are all within 100±25%, which is acceptable in this experiment because of the variance of the initial silver loading on the membranes. A bad silver mass balance was observed at cross-flow filtration. Both of AgNP and Ag ions leached in the solution was examined in this experiment. The concentration of total silver leaching into solutions from the four leaching tests are all below the Secondary Drinking Water Standard for silver which is 100 ppb. The cross-flow test is the most aggressive leaching method, which has more than 80% of silver leached from the membrane after 50 hours of the test. The water jet (54 ± 6.9% of silver remaining) can cause higher silver leaching than batch test (85 ± 1.2% of silver remaining) in one-hour, and it can also cause both AgNP and Ag ions leaching from the membrane, which is closer to the leaching condition in the cross-flow test.
This study is attempting to compare four different silver leaching test methods, to study the silver leaching potential of the silver impregnated membranes, conducting the advantages and disadvantages of the leaching methods. An In-situ reduction Ag loaded RO membrane was examined in this study. A custom waterjet test was established to create a high-velocity water flow to test the silver leaching from the nanocomposite membrane in a relative extreme environment. The batch leaching test was examined as the most common leaching test method for the silver composite membrane. The cross-flow filtration and dead-end test were also examined to compare the silver leaching amounts.
The silver coated membrane used in this experiment has an initial silver loading of 2.0± 0.51 ug/cm2. The mass balance was conducted for all of the leaching tests. For the batch test, water jet test, and dead-end filtration, the mass balances are all within 100±25%, which is acceptable in this experiment because of the variance of the initial silver loading on the membranes. A bad silver mass balance was observed at cross-flow filtration. Both of AgNP and Ag ions leached in the solution was examined in this experiment. The concentration of total silver leaching into solutions from the four leaching tests are all below the Secondary Drinking Water Standard for silver which is 100 ppb. The cross-flow test is the most aggressive leaching method, which has more than 80% of silver leached from the membrane after 50 hours of the test. The water jet (54 ± 6.9% of silver remaining) can cause higher silver leaching than batch test (85 ± 1.2% of silver remaining) in one-hour, and it can also cause both AgNP and Ag ions leaching from the membrane, which is closer to the leaching condition in the cross-flow test.
ContributorsHan, Bingru (Author) / Westerhoff, Paul (Thesis advisor) / Perreault, Francois (Committee member) / Sinha, Shahnawaz (Committee member) / Arizona State University (Publisher)
Created2017
Description
Electrospinning is a means of fabricating micron-scale diameter fiber networks with enmeshed nanomaterials. Polymeric nanocomposites for water treatment require the manipulation of fiber morphology to expose nanomaterial surface area while anchoring the nanomaterials and maintaining fiber integrity; that is the overarching goal of this dissertation. The first investigation studied the effect of metal oxide nanomaterial loadings on electrospinning process parameters such as critical voltage, viscosity, fiber diameter, and nanomaterial distribution. Increases in nanomaterial loading below 5% (w/v) were not found to affect critical voltage or fiber diameter. Nanomaterial dispersion was conserved throughout the process. Arsenic adsorption tests determined that the fibers were non-porous. Next, the morphologies of fibers made with carbonaceous materials and the effect of final fiber assembly on adsorption kinetics of a model organic contaminant (phenanthrene, PNT) was investigated. Superfine powdered activated carbon (SPAC), C60 fullerenes, multi-walled carbon nanotubes, and graphene platelets were added to PS and electrospun. SPAC maintained its internal pore structure and created porous fibers which had 30% greater PNT sorption than PS alone and a sevenfold increase in surface area. Carbon-based nanomaterial-PS fibers were thicker but less capacious than neat polystyrene electrospun fibers. The surface areas of the carbonaceous nanomaterial-polystyrene composites decreased compared to neat PS, and PNT adsorption experiments yielded decreased capacity for two out of three carbonaceous nanomaterials. Finally, the morphology and arsenic adsorption capacity of a porous TiO2-PS porous fiber was investigated. Porous fiber was made using polyvinylpyrrolidone (PVP) as a porogen. PVP, PS, and TiO2 were co-spun and the PVP was subsequently eliminated, leaving behind a porous fiber morphology which increased the surface area of the fiber sevenfold and exposed the nanoscale TiO2 enmeshed inside the PS. TiO2-PS fibers had comparable arsenic adsorption performance to non-embedded TiO2 despite containing less TiO2 mass. The use of a sacrificial polymer as a porogen facilitates the creation of a fiber morphology which provides access points between the target pollutant in an aqueous matrix and the sorptive nanomaterials enmeshed inside the fiber while anchoring the nanomaterials, thus preventing release.
ContributorsHoogesteijn von Reitzenstein, Natalia Virginia (Author) / Westerhoff, Paul (Thesis advisor) / Hristovski, Kiril (Committee member) / Perreault, Francois (Committee member) / Herckes, Pierre (Committee member) / Arizona State University (Publisher)
Created2018
Description
C.C. Cragin Reservoir’s location in the Coconino National Forest, Arizona makes it prone to wild fire. This study focused on the potential impacts of such a wild fire on the reservoir’s annual thermal stratification cycle impacts and water quality. The annual thermal stratification cycle impacted the reservoir’s water quality by increasing hypolimnion concentrations of magnesium, iron, turbidity, and specific ultraviolet absorbance (SUVA) values, as well as resulting in the hypolimnion having decreased dissolved oxygen concentrations during stratified months. The scarification process did not affect the dissolved organic carbon (DOC) concentrations in the reservoir or the total/dissolved nitrogen and phosphorous concentrations. Some general water quality trends that emerged were that phosphorous was the limiting nutrient, secchi disk depth and chlorophyll a concentration are inversely related, and no metals were found to be in concentrations that would violate an EPA drinking water maximum contaminant level (MCL). A carbon mass model was developed and parameterized using DOC measurements, and then using historic reservoir storage and weather data, the model simulated DOC concentrations in the reservoir following four hypothetical wild fire events. The model simulated varying initial reservoir storage volumes, initial flush volumes, and flush DOC concentrations, resulting in reservoir DOC concentrations varying from 17.41 mg/L to 8.82 mg/L.
ContributorsFlatebo, Theodore (Author) / Westerhoff, Paul K (Thesis advisor) / Fox, Peter (Committee member) / Perreault, Francois (Committee member) / Arizona State University (Publisher)
Created2018
Description
This report analyzes the potential for accumulation of boron in direct potable reuse. Direct potable reuse treats water through desalination processes such as reverse osmosis or nanofiltration which can achieve rejection rates of salts sometimes above 90%. However, boron achieves much lower rejection rates near 40%. Because of this low rejection rate, there is potential for boron to accumulate in the system to levels that are not recommended for potable human consumption of water. To analyze this issue a code was created that runs a steady state system that tracks the internal concentration, permeate concentration, wastewater concentration and reject concentration at various rejection rates, as well as all the flows. A series of flow and mass balances were performed through five different control volumes that denoted different stages in the water use. First was mixing of clean water with permeate; second, consumptive uses; third, addition of contaminant; fourth, wastewater treatment; fifth, advanced water treatments. The system cycled through each of these a number of times until steady state was reached. Utilities or cities considering employing direct potable reuse could utilize this model by estimating their consumption levels and input of contamination, and then seeing what percent rejection or inflow of makeup water they would need to obtain to keep boron levels at a low enough concentration to be fit for consumption. This code also provides options for analyzing spikes and recovery in the system due to spills, and evaporative uses such as cooling towers and their impact on the system.
ContributorsDoidge, Sydney (Author) / Fox, Peter (Thesis director) / Perreault, Francois (Committee member) / Civil, Environmental and Sustainable Engineering Program (Contributor) / School of International Letters and Cultures (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
Description
As selenium is toxic at low levels, treatment methods to remove selenium from industrial waste waters are needed. In this work, three groups of sorbent materials were investigated in detail for their effectiveness for selenium and arsenic removal from water: 1) nanostructured carbon-based materials, 2) layered double hydroxide (LDH)-based materials, and 3) biopolymer-based sorbents. The materials were investigated in spiked de-ionized water and waters collected from different locations at Salt River Project’s (SRP) Santan Generating Station in Gilbert, AZ. The results show that nanostructured carbon-based materials removed ~80% and up to 100% selenium and arsenic, respectively in spiked DI water. Heat treated layered double hydroxides removed close to 100% removal in selenium and arsenic spiked DI water. Isotherms conducted in spiked DI water fit the Langmuir model and showed a maximum selenate adsorption capacity of 67 mg/g for the calcined LDH powder. Results from SRP waters showed that certain LDH sorbents were effective for removing the selenium, but that higher pH and existence of competing ions affected the removal efficiencies. The functionalized biopolymer sorbent from Crystal Clear Technologies: CCT-149/OCI-B showed good removal efficiencies for both selenate and selenite in DI water. Isotherms conducted in spiked DI water for CCT-149 fit the Langmuir model and showed a maximum selenate adsorption capacity of 90.9 mg/g. Column tests using spiked DI water and waters obtained from SRP wells were investigated using both LDH and CCT-149/OCI-B. Removal of sulfate using chemical pre-treatment of the water with barium chloride resulted in about three times higher selenate loading onto the granular LDH and doubled the water volume that can be treated using CCT-149/OCI-B. The results from the column tests are being used to guide the pilot testing investigating the implementation of LDH sorbents at pilot scale at the Santan plant. The good results in the cooling tower #5 blowdown water and combined discharge waste water of SRP provide valuable information about the efficacy and efficiency of adsorptive media for the removal of selenium. Composites comprising LDH nanosheets with different substrates were successfully synthesized that were able to retain the performance in removing selenate of nanosheet LDH.
ContributorsLi, Man (Author) / Chan, Candace (Thesis advisor) / Lind, Mary Laura (Committee member) / Perreault, Francois (Committee member) / Arizona State University (Publisher)
Created2017
Environmental releases of neonicotinoid and fipronil insecticides via U.S. wastewater infrastructure
Description
This dissertation is focused on environmental releases from U.S. wastewater infrastructure of recently introduced, mass-produced insecticides, namely neonicotinoids as well as fipronil and its major degradates (sulfone, sulfide, amide, and desulfinyl derivatives), jointly known as fiproles. Both groups of compounds recently have caught the attention of regulatory agencies worldwide due to their toxic effects on pollinators and on aquatic invertebrates at very low, part-per-trillion levels (Chapter 1). Mass balance studies conducted for 13 U.S. wastewater treatment plants (WWTPs) showed ubiquitous occurrence (3-666 ng/L) and persistence of neonicotinoids (Chapter 2). For the years 2001 through 2016, a longitudinal nationwide study was conducted on the occurrence of fiproles, via analysis of sludge as well as raw and treated wastewater samples. Sludge analysis revealed ubiquitous fiprole occurrence since 2001 (0.2-385 µg/kg dry weight) and a significant increase (2.4±0.3-fold; p<0.005) to elevated levels found both in 2006/7 and 2015/6. This study established a marked persistence of fiproles during both wastewater and sludge treatment, while also identifying non-agricultural uses as a major source of fiprole loading to wastewater (Chapter 3). Eight WWTPs were monitored in Northern California to assess pesticide inputs into San Francisco Bay from wastewater discharge. Per-capita-contaminant-loading calculations identified flea and tick control agents for use on pets as a previously underappreciated source term dominating the mass loading of insecticides to WWTPs in sewage and to the Bay in treated wastewater (Chapter 4). A nationwide assessment of fipronil emissions revealed that pet products, while representing only 22±7% of total fipronil usage (2011-2015), accounted for 86±5% of the mass loading to U.S. surface waters (Chapter 5). In summary, the root cause for considerable annual discharges into U.S. surface waters of the neonicotinoid imidacloprid (3,700-5,500 kg/y) and of fipronil related compounds (1,600-2,400 kg/y) is domestic rather than agricultural insecticide use. Reclaimed effluent from U.S. WWTPs contained insecticide levels that exceed toxicity benchmarks for sensitive aquatic invertebrates in 83% of cases for imidacloprid and in 67% of cases for fipronil. Recommendations are provided on how to limit toxic inputs in the future.
ContributorsSadaria, Akash Mahendra (Author) / Halden, Rolf (Thesis advisor) / Fraser, Matthew (Committee member) / Perreault, Francois (Committee member) / Mascaro, Giuseppe (Committee member) / Arizona State University (Publisher)
Created2017
Description
The waterways in the United States are polluted by agricultural, mining, and industrial activities. Recovery of valuable materials, such as energy and nutrients, from these waste streams can improve the economic and environmental sustainability of wastewater treatment. A number of state-of-the-art anaerobic bioreactors have promise for intensified anaerobic biological treatment and energy recovery, but they have drawbacks. The drawbacks should be overcome with a novel anaerobic biological wastewater treatment process: the anaerobic biofilm membrane bioreactor (AnBfMBR). This research works aims to advance key components of the AnBfMBR. The AnBfMBR is a hybrid suspended growth and biofilm reactor. The two main components of an AnBfMBR are plastic biofilm carriers and membranes. The plastic biofilm carriers provide the surface onto which the biofilms grow. Membranes provide liquid-solid separation, retention of suspended biomass, and a solids-free effluent. Introducing sufficient surface area promotes the biofilm accumulation of slow-growing methanogens that convert volatile fatty acids into methane gas. Biofilms growing on these surfaces will have a mixed culture that primarily consists of methanogens and inert particulate solids, but also includes some acetogens. Biomass that detaches from biofilms become a component of the suspended growth. A bench-scale AnBfMBR was designed by the AnBfMBR project team and constructed by SafBon Water Technology (SWT). The primary objective of this thesis project was to evaluate the ability of plastic biofilm carriers to minimize ceramic-membrane fouling in the AnBfMBR setting. A systematic analysis of mixing for the bench-scale AnBfMBR was also conducted with the plastic biofilm carriers. Experiments were conducted following a ‘run to failure’ method, in which the ceramic membranes provide filtration, and the time it takes to reach a ‘failure transmembrane pressure (TMP)’ was recorded. The experiments revealed two distinct trends. First, the time to failure TMP decreased as mixed liquor suspended solids concentration (MLSS) concentration increased. Second, increasing the carrier fill extend the time to failure, particularly for higher MLSS concentrations. Taken together, the experiments identified an optimized “sweet spot” for the AnBfMBR: an operating flux of 0.25-m/d, a failure TMP of 0.3-atm pressure, MLSS of 5,000 – 7,500 mg/L, and 40% carrier fill.
ContributorsRoman, Brian Aaron (Author) / Rittmann, Bruce (Thesis advisor) / Boltz, Joshua (Committee member) / Perreault, Francois (Committee member) / Fox, Peter (Committee member) / Arizona State University (Publisher)
Created2021
Description
Engineered nanomaterials (ENMs) are added to numerous consumer products to enhance their effectiveness, whether it be for environmental remediation, mechanical properties, or as dietary supplements. Uses of ENMs include adding to enhance products, carbon for strength or dielectric properties, silver for antimicrobial properties, zinc oxide for UV sun-blocking properties, titanium dioxide for photocatalysis, or silica for desiccant properties. However, concerns arise from ENM functional properties that can impact the environment and a lack of regulation regarding ENMs leads to potential public exposure to ENMs and results in ill-informed public or manufacturer perceptions of ENMs. My dissertation evaluates the environmental, human health, and societal impacts of using ENMs, with a focus on ionic silver and nanosilver, in consumer and industrial products. Reproducible experiments served as functional assays to assess ENM distributions among various environmental matrices. Functional assay results were visualized using radar plots and aid in a framework to estimate likely ENM disposition in the environment. To assess beneficial uses of ENMs, bromide ion removal from drinking waters to limit disinfection by-product formation was studied. Silver-enabled graphene oxide materials were capable of removing bromide from water, and exhibited less competition from background solutes (e.g. natural organic matter) when compared against solely ionic silver addition to water for bromide removal. To assess complex interactions of ENMs with the microbiome, batch experiments were performed using fecal samples spiked with ionic silver or commercial dietary silver nanoparticles. Dietary nanosilver and ionic silver exposures to the fecal microbiome for 24 hours reduce short chain fatty acid (SCFA) production and changes the relative abundance of the microbiota. To understand the social perceptions of ENMS, statistically rigorous surveys were conducted to assess related perceptions related to the use of ENMs in drinking water treatment devices the general public and, separately, industrial manufacturers. These stakeholders are influenced by costs and efficiency of the technologies, consumer concerns of the safety of technologies, and environmental health and safety of the technologies. This dissertation represents novel research that took an interdisciplinary approach, spanning from wet-lab engineering bench scale testing to social science survey assessments to better understand the environmental, human health, and societal impacts of using ENMs such as nanosilver and ionic silver in industrial processes and consumer products.
ContributorsKidd, Justin (Author) / Westerhoff, Paul (Thesis advisor) / Krajmalnik-Brown, Rosa (Committee member) / Perreault, Francois (Committee member) / Maynard, Andrew (Committee member) / Arizona State University (Publisher)
Created2020
Description
This dissertation investigated the use of membrane processes to selectively separate and concentrate nitrogen in human urine. The targeted nitrogen species to be recovered were urea from fresh human urine and unionized ammonia from hydrolyzed human urine. Chapter 1 investigated a novel two-step process of forward osmosis (FO) and membrane distillation (MD) to recover the urea in fresh human urine. Specifically, FO was used to selectively separate urea from the other components in urine and MD was used to concentrate the separated urea. The combined process was able to produce a product solution that had an average urea concentration that is 45–68% of the urea concentration found in the fresh urine with greater than 90% rejection of total organic carbon (TOC).Chapter 2 determined the transport behavior of low molecular weight neutral nitrogen compounds in order to maximize ammonia recovery from real hydrolyzed human urine by FO. Novel strategic pH manipulation between the feed and the draw solution allowed for up to 86% recovery of ammonia by keeping the draw solution pH <6.5 and the feed solution pH >11. An economic analysis showed that ammonia recovery by FO has the potential to be much more economically favorable compared to ammonia air stripping or ion exchange if the proper draw solute is chosen.
Chapter 3 investigated the dead-end rejection of urea in fresh urine at varying pH and the rejection of unionized ammonia and the ammonium ion in hydrolyzed urine by reverse osmosis (RO), nanofiltration (NF), and microfiltration (MF). When these different membrane separation processes were compared, NF is found to be a promising technology to recover up to 90% of ammonia from hydrolyzed urine with a high rejection of salts and organics.
Chapter 4 investigated the use of the RO and NF to recover ammonia from hydrolyzed human urine in a cross-flow system where both rejection and fouling experiments were performed. For both RO and NF, ammonia rejection was found to be 0% while still achieving high rejection of TOC and salts, and MF pretreatment greatly reduced the extent of fouling on the membrane surface.
ContributorsRay, Hannah (Author) / Boyer, Treavor H (Thesis advisor) / Perreault, Francois (Committee member) / Sinha, Shahnawaz (Committee member) / Arizona State University (Publisher)
Created2020