Matching Items (8)
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- All Subjects: environment
- All Subjects: Water
- Creators: Halden, Rolf
Description
Nitrate is the most prevalent water pollutant limiting the use of groundwater as a potable water source. The overarching goal of this dissertation was to leverage advances in nanotechnology to improve nitrate photocatalysis and transition treatment to the full-scale. The research objectives were to (1) examine commercial and synthesized photocatalysts, (2) determine the effect of water quality parameters (e.g., pH), (3) conduct responsible engineering by ensuring detection methods were in place for novel materials, and (4) develop a conceptual framework for designing nitrate-specific photocatalysts. The key issues for implementing photocatalysis for nitrate drinking water treatment were efficient nitrate removal at neutral pH and by-product selectivity toward nitrogen gases, rather than by-products that pose a human health concern (e.g., nitrite). Photocatalytic nitrate reduction was found to follow a series of proton-coupled electron transfers. The nitrate reduction rate was limited by the electron-hole recombination rate, and the addition of an electron donor (e.g., formate) was necessary to reduce the recombination rate and achieve efficient nitrate removal. Nano-sized photocatalysts with high surface areas mitigated the negative effects of competing aqueous anions. The key water quality parameter impacting by-product selectivity was pH. For pH < 4, the by-product selectivity was mostly N-gas with some NH4+, but this shifted to NO2- above pH = 4, which suggests the need for proton localization to move beyond NO2-. Co-catalysts that form a Schottky barrier, allowing for localization of electrons, were best for nitrate reduction. Silver was optimal in heterogeneous systems because of its ability to improve nitrate reduction activity and N-gas by-product selectivity, and graphene was optimal in two-electrode systems because of its ability to shuttle electrons to the working electrode. "Environmentally responsible use of nanomaterials" is to ensure that detection methods are in place for the nanomaterials tested. While methods exist for the metals and metal oxides examined, there are currently none for carbon nanotubes (CNTs) and graphene. Acknowledging that risk assessment encompasses dose-response and exposure, new analytical methods were developed for extracting and detecting CNTs and graphene in complex organic environmental (e.g., urban air) and biological matrices (e.g. rat lungs).
ContributorsDoudrick, Kyle (Author) / Westerhoff, Paul (Thesis advisor) / Halden, Rolf (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2013
Description
Plastics continue to benefit society in innumerable ways, even though recent public focus on plastics has centered mostly on human health and environmental concerns, including their endocrine-disrupting properties and the long-term pollution they represent. The benefits of plastics are particularly apparent in medicine and public health. Plastics are versatile, cost-effective, require less energy to produce than alternative materials like metal or glass, and can be manufactured to have many different properties. Due to these characteristics, polymers are used in diverse health applications like disposable syringes and intravenous bags, sterile packaging for medical instruments as well as in joint replacements, tissue engineering, etc. However, not all current uses of plastics are prudent and sustainable, as illustrated by the widespread, unwanted human exposure to endocrine-disrupting bisphenol A (BPA) and di-(2-ethylhexyl) phthalate (DEHP), problems arising from the large quantities of plastic being disposed of, and depletion of non-renewable petroleum resources as a result of the ever-increasing mass production of plastic consumer articles. Using the health-care sector as example, this review concentrates on the benefits and downsides of plastics and identifies opportunities to change the composition and disposal practices of these invaluable polymers for a more sustainable future consumption. It highlights ongoing efforts to phase out DEHP and BPA in the health-care and food industry and discusses biodegradable options for plastic packaging, opportunities for reducing plastic medical waste, and recycling in medical facilities in the quest to reap a maximum of benefits from polymers without compromising human health or the environment in the process.
ContributorsNorth, Emily Jean (Co-author) / Halden, Rolf (Co-author, Thesis director) / Mikhail, Chester (Committee member) / Hurlbut, Ben (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Chemical Engineering Program (Contributor)
Created2013-05
Description
Microplastics are defined as small pieces of plastics that are less than five millimeters in size. These microplastics can vary in their appearance, are known to be harmful to aquatic life and can threaten life cycles of marine organisms because of their chemical make-up and the toxic additives used in their manufacture. Although small in size, it is hypothesized that microplastics can serve as an example of how human activities can alter ecosystems near and far. To investigate the implications and determine the potential impact of microplastics on a protected atoll’s ecosystems, red-footed booby (Sula sula) guano samples from six locations on Palmyra Atoll were acquired from North Carolina State University via The Nature Conservancy and were inspected for the presence of microplastics. Each of the guano samples were weighed and prepared via wet oxidation. Microplastic fibers were detected via stereoscope microscopy and analyzed for chemical composition via Raman spectroscopy. All six sampling locations within Palmyra Atoll contained microplastic fibers identified as polyethylene terephthalate, with North-South Causeway and Eastern Island having the highest average number of microplastic fibers found per gram of guano sample (n = 0.611). These data provide evidence that seabirds can serve as vectors for the spread of microplastic pollution. This research lends context to the widespread impact of plastic pollution and states possible implications of its presence in delicate ecosystems.
ContributorsAnderson, Alyssa Cerise (Author) / Lisenbee, Cayle (Thesis director) / Halden, Rolf (Committee member) / Rolsky, Charles (Committee member) / College of Health Solutions (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
The production and incineration of single-use micropipette tips and disposable gloves, which are heavily used within laboratory facilities, generate large amounts of greenhouse gasses (GHGs) and accelerate climate change. Plastic waste that is not incinerated often is lost in the environment. The long degradation times associated with this waste exacerbates a variety of environmental problems such as substance runoff and ocean pollution. The objective of this study was to evaluate the efficacy of possible solutions for minimizing micropipette tip and disposable glove waste within laboratory spaces. It was hypothesized that simultaneously implementing the use of micropipette tip washers (MTWs) and energy-from-glove-waste programs (EGWs) would significantly reduce (p < 0.05) the average combined annual single-use plastic micropipette tip and nitrile glove waste (in kg) per square meter of laboratory space in the United States. ASU’s Biodesign Institute (BDI) was used as a case study to inform on the thousands of different laboratory facilities that exist all across the United States. Four separate research laboratories within the largest public university of the U.S. were sampled to assess the volume of plastic waste from single-use micropipette tips and gloves. Resultant data were used to represent the totality of single-use waste from the case study location and then extrapolated to all laboratory space in the United States. With the implementation of EGWs, annual BDI glove waste is reduced by 100% (0.47 ± 0.26 kg/m2; 35.5 ± 19.3 metric tons total) and annual BDI glove-related carbon emissions are reduced by ~5.01% (0.165 ± 0.09 kg/m2; 1.24 ± 0.68 metric tons total). With the implementation of MTWs, annual BDI micropipette tip waste is reduced by 92% (0.117 ± 0.03 kg/m2; 0.88 ± 0.25 metric tons total) and annual BDI tip-related carbon emissions are reduced by ~83.6% (4.04 ± 1.25 kg/m2; 30.5 ± 9.43 metric tons total). There was no significant difference (p = 0.06) observed between the mass of single-use waste (kg) in the sampled laboratory spaces before (x̄ = 47.1; σ = 43.3) and after (x̄ =0.070; σ = 0.033) the implementation of the solutions. When examining both solutions (MTWs & EGWs) implemented in conjunction with one another, the annual BDI financial savings (in regard to both purchasing and disposal costs) after the first year were determined to be ~$7.92 ± $9.31/m2 (7,500 m2 of total wet laboratory space) or ~$60,000 ± $70,000 total. These savings represent ~15.77% of annual BDI spending on micropipette tips and nitrile gloves. The large error margins in these financial estimates create high uncertainty for whether or not BDI would see net savings from implementing both solutions simultaneously. However, when examining the implementation of only MTWs, the annual BDI financial savings (in regard to both purchasing and disposal costs) after the first year were determined to be ~$12.01 ± $6.79 kg/m2 or ~$91,000 ± $51,200 total. These savings represent ~23.92% of annual BDI spending on micropipette tips and nitrile gloves. The lower error margins for this estimate create a much higher likelihood of net savings for BDI. Extrapolating to all laboratory space in the United States, the total annual amount of plastic waste avoided with the implementation of the MTWs was identified as 8,130 ± 2,290 tons or 0.023% of all solid plastic waste produced in the United States in 2018. The total amount of nitrile waste avoided with the implementation of the EGWs was identified as 32,800 ± 17,900 tons or 0.36% of all rubber solid waste produced in the United States in 2018. The total amount of carbon emissions avoided with the implementation of the MTWs was identified as 281,000 ± 87,000 tons CO2eq or 5.4*10-4 % of all CO2eq GHG emissions produced in the United States in 2020. Both the micropipette tip washer and the glove waste avoidance program solutions can be easily integrated into existing laboratories without compromising the integrity of the activities taking place. Implemented on larger scales, these solutions hold the potential for significant single-use waste reduction.
ContributorsZdrale, Gabriel (Author) / Mahant, Akhil (Co-author) / Halden, Rolf (Thesis director) / Biyani, Nivedita (Committee member) / Driver, Erin (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2022-05
Description
Arsenic (As) and chromium (Cr) occur naturally in AZ surface and groundwaters, pose different health impacts, and exhibit different treatment efficacies. Hexavalent chromium (Cr(VI)) has newly recognized human health concerns, and State and Federal agencies are evaluating a low Cr(VI)-specific maximum contaminant level (MCL) for drinking water. Occurrence of Cr and As in municipal drinking waters and industrial cooling tower waters was quantified by grab samples and compared with sampling results obtained from a new passive sampler developed specifically for Cr(VI). Cr(VI) and As concentrations in groundwater used for cooling tower make-up water concentrations were ~3 ppb and ~4 ppb, respectively, and were concentrated significantly in blowdown water (~20 ppb and ~40 ppb). Based upon pending Cr(VI), As, and other metal regulations, these blowdown waters will need routine monitoring and treatment. Cr(VI) concentrations in a water treatment plant (WTP) raw and finished water samples varied from 0.5 and 2 ppb for grab samples collected every 4 hours for 7 consecutive days using an ISCO sampler. The development of an ion exchange (IX) based passive sampler was validated in the field at the WTP and yielded an average exposure within 1 standard deviation of ISCO sampler grab data. Sampling at both the WTP and cooling towers suggested sources of Cr(III) from treatment chemicals or wood preservatives may exist. Since both facilities use chlorine oxidants, I quantified the apparent (pH=5) second-order rate constant for aqueous chlorine (HOCl/OCl-) with Cr(III) to form Cr(VI) as 0.7 M-1s-1. Under typical conditions (2 ppb Cr(III) ; 2 mg/L Cl2) the half-life for the conversion of Cr(III) to the more toxic form Cr(VI) is 4.7 hours. The occurrence studies in AZ and CA show the Cr(VI) and As treatment of groundwaters will be required to meet stringent Cr(VI) regulations. IX technologies, both strong base anion (SBA) and weak base anion (WBA) resin types were screened (and compared) for Cr removal. The SBA IX process for As removal was optimized by utilizing a reactive iron coagulation and filtration (RCF) process to treat spent IX brine, which was then reused to for SBA resin regeneration.
ContributorsBowen, Alexandra (Author) / Paul, Westerhoff K. (Thesis advisor) / Hristovski, Kiril (Committee member) / Halden, Rolf (Committee member) / Arizona State University (Publisher)
Created2014
Description
Six high-production-volume neonicotinoids were traced through a municipal wastewater treatment plant (WWTP) and engineered wetland located downstream, in a study motivated by reports on these insecticides posing threats to non-target invertebrate species and potentially playing a role in the global honeybee colony collapse disorder. An array of automated samplers was deployed in a five-day monitoring campaign and resultant flow-weighted samples were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) using the isotope dilution method. Concentrations in WWTP influent and effluent were 54.7 ± 2.9 and 48.6 ± 2.7 ng/L for imidacloprid, respectively, and 3.7 ± 0.3 and 1.8 ± 0.1 ng/L for acetamiprid, respectively. A mass balance over the WWTP showed no (p=0.09, CI = 95%) removal of imidacloprid, and 56 ± 6% aqueous removal of acetamiprid. In the constructed wetland downstream, a lack of removal was noted for both imidacloprid (from 54.4 ± 3.4 ng/L to 49.9 ± 14.6 ng/L) and acetamiprid (from 2.00 ± 0.03 ng/L to 2.30 ± 0.21 ng/L). Clothianidin was detected only inconsistently in the WWTP and wetland (>2 to 288 ng/L; 60% detection frequency), whereas thiamethoxam (<10 ng/L), thiacloprid (<2 ng/L), and dinotefuran (<180 ng/L) were not detected at all. Thus, imidacloprid and acetamiprid were identified as recalcitrant sewage constituents (estimated U.S. WWTP discharge of 1920- 4780 kg/y) that persist during conventional wastewater treatment to enter U.S. surface waters at potentially harmful concentrations.
ContributorsSadaria, Akash Mahendra (Author) / Halden, Rolf (Thesis advisor) / Fox, Peter (Committee member) / Popat, Sudeep (Committee member) / Arizona State University (Publisher)
Created2015
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 Future of Wastewater Sensing workshop is part of a collaboration between Arizona State University Center for Nanotechnology in Society in the School for the Future of Innovation in Society, the Biodesign Institute’s Center for Environmental Security, LC Nano, and the Nano-enabled Water Treatment (NEWT) Systems NSF Engineering Research Center. The Future of Wastewater Sensing workshop explores how technologies for studying, monitoring, and mining wastewater and sewage sludge might develop in the future, and what consequences may ensue for public health, law enforcement, private industry, regulations and society at large. The workshop pays particular attention to how wastewater sensing (and accompanying research, technologies, and applications) can be innovated, regulated, and used to maximize societal benefit and minimize the risk of adverse outcomes, when addressing critical social and environmental challenges.
ContributorsWithycombe Keeler, Lauren (Researcher) / Halden, Rolf (Researcher) / Selin, Cynthia (Researcher) / Center for Nanotechnology in Society (Contributor)
Created2015-11-01