Unpacking capabilities underlying design (thinking) process

Engineering graduates must know how to frame and solve non-routine problems. While design classes explicitly teach problem framing and solving, it is lacking throughout much of the rest of the engineering curriculum and is often relegated to capstone classes at the end of the students’ educational experience. This paper explores problem framing and solving through the lens of experiential learning theory. It captures core problem framing and solving approaches from critical, design and systems thinking and concludes with a table of learning outcomes that might be drawn upon in designing an engineering curriculum that more fully develops the problem framing and solving capabilities of its students

Use of Treated Municipal Wastewater as Power Plant Cooling System Makeup Water: Tertiary Treatment versus Expanded Chemical Regimen for Recirculating Water Quality Management

Treated municipal wastewater is a common, widely available alternative source of cooling water for thermoelectric power plants across the U.S. However, the biodegradable organic matter, ammonia-nitrogen, carbonate and phosphates in the treated wastewater pose challenges with respect to enhanced biofouling, corrosion, and scaling, respectively. The overall objective of this study was to evaluate the benefits and life cycle costs of implementing tertiary treatment of secondary treated municipal wastewater prior to use in recirculating cooling systems. The study comprised bench- and pilot-scale experimental studies with three different tertiary treated municipal wastewaters, and life cycle costing and environmental analyses of various tertiary treatment schemes. Sustainability factors and metrics for reuse of treated wastewater in power plant cooling systems were also evaluated. The three tertiary treated wastewaters studied were: secondary treated municipal wastewater subjected to acid addition for pH control (MWW_pH); secondary treated municipal wastewater subjected to nitrification and sand filtration (MWW_NF); and secondary treated municipal wastewater subjected nitrification, sand filtration, and GAC adsorption (MWW_NFG). Tertiary treatment was determined to be essential to achieve appropriate corrosion, scaling, and biofouling control for use of secondary treated municipal wastewater in power plant cooling systems. The ability to control scaling, in particular, was found to be significantly enhanced with tertiary treated wastewater compared to secondary treated wastewater. MWW_pH treated water (adjustment to pH 7.8) was effective in reducing scale formation, but increased corrosion and the amount of biocide required to achieve appropriate biofouling control. Corrosion could be adequately controlled with tolytriazole addition (4-5 ppm TTA), however, which was the case for all of the tertiary treated waters. For MWW_NF treated water, the removal of ammonia by nitrification helped to reduce the corrosivity and biocide demand. Also, the lower pH and alkalinity resulting from nitrification reduced the scaling to an acceptable level, without the addition of anti-scalant chemicals. Additional GAC adsorption treatment, MWW_NFG, yielded no net benefit. Removal of organic matter resulted in pitting corrosion in copper and cupronickel alloys. Negligible improvement was observed in scaling control and biofouling control. For all of the tertiary treatments, biofouling control was achievable, and most effectively with pre-formed monochloramine (2-3 ppm) in comparison with NaOCl and ClO2. Life cycle cost (LCC) analyses were performed for the tertiary treatment systems studied experimentally and for several other treatment options. A public domain conceptual costing tool (LC3 model) was developed for this purpose. MWW_SF (lime softening and sand filtration) and MWW_NF were the most cost-effective treatment options among the tertiary treatment alternatives considered because of the higher effluent quality with moderate infrastructure costs and the relatively low doses of conditioning chemicals required. Life cycle inventory (LCI) analysis along with integration of external costs of emissions with direct costs was performed to evaluate relative emissions to the environment and external costs associated with construction and operation of tertiary treatment alternatives. Integrated LCI and LCC analysis indicated that three-tiered treatment alternatives such as MWW_NSF and MWW_NFG, with regular chemical addition for treatment and conditioning and/or regeneration, tend to increase the impact costs and in turn the overall costs of tertiary treatment. River water supply and MWW_F alternatives with a single step of tertiary treatment were associated with lower impact costs, but the contribution of impact costs to overall annual costs was higher than all other treatment alternatives. MWW_NF and MWW_SF alternatives exhibited moderate external impact costs with moderate infrastructure and chemical conditioner dosing, which makes them (especially MWW_NF) better treatment alternatives from the environmental sustainability perspective since they exhibited minimal contribution to environmental damage from emissions

Geochemical Variability in Fossil Soils and Implications for Past Biogeochemical Cycling, Climates, and Atmospheres

The co-evolution of the terrestrial biogeochemical cycle, the atmosphere, and the marine biosphere remain relatively poorly understood, with outstanding questions surrounding terrestrial-marine links, climate, and tectonics. In particular, the terrestrial sediment source (i.e., soils) remains understudied relative to the marine sediment sink, with the source essentially defined by the record in the sediment sink rather than being considered equally important. Both the sediment source and sink need to be well-constrained in order to understand global biogeochemical changes. Additionally, interpretations of trends in paleosol (fossil soil) geochemistry are only loosely constrained by large-scale modern soil chemical variability, limiting our ability to assess potential changes in biogeochemical cycling through time. This dissertation focused on two primary goals: improving quantitative constraints on terrestrial biogeochemical cycling and weathering over geologic time, and improving our ability to accurately interpret those records by understanding both modern context and what the paleosol record actually represents. To address these goals, I analyzed the geochemical composition of soils and paleosols (fossil soils) over the past three billion years. Because soils form in the ‘critical zone’—the intersection of the biosphere, geosphere, and atmosphere at Earth’s surface—they record surficial conditions more directly than other geologic records, providing valuable insight into past climates, atmospheres, and ecosystems. After providing generalized, quantitative constraints on geochemical and weathering variability in modern soils (Chapter II), I used the paleosol record to test for state changes in soil P (Chapter III) and weathering intensity (Chapter IV) on land during key biogeochemical transitions. I also explored a variety of processes that could bias the distribution of paleosols through space and time (e.g., preservation, sampling), which needs to be better constrained in order to interpret paleosols accurately. In modern soils, I found weaker than expected relationships between soil P and Fe geochemistry and key environmental factors (climate, vegetation, parent material), but weathering intensity, the presence of vegetation, and P concentrations were related. The weak relationships could be due to the continental rather than localized scale of analysis. While the latter might have provided predictive relationships between soil chemistry and soil-forming factors, a highly-localized scale is often not considered in deep-time biogeochemical modeling. In paleosols, I found that both the P composition and weathering intensity have been stable through time. Discrete, state changes in P composition or weathering intensity—as have been hypothesized based upon marine records—were not recorded. A discrete change was present in the concentration of Ca in paleosols, which increased in the Phanerozoic, perhaps reflecting a shift in pedogenic processes as vascular, rooting plants evolved. Roots and vascularity allowed plants to colonize more arid environments and facilitated the formation of pedogenic carbonate—an important C sink. Therefore, while the advent of land plants may not have led to a global state change in either terrestrial P retention or weathering intensity, plants facilitated the growth of the soil C sink. Because weathering intensity is consistent through time, other factors (e.g., land area, erosion rates) would have been dominant controls on marine nutrient supply through time, with shorter-term perturbations in weathering intensity occurring before returning to the stable baseline. Finally, the distribution of paleosols through time is uneven, with more paleosols being more common (a) towards the present and (b) during peaks in zircon ages, suggesting a formation and/or preservation bias related to the supercontinent cycle.PHDEarth and Environmental SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/170021/1/rdzombak_1.pd

Plant tissue extraction method for complexed and free cyanide

A method for free cyanide and strongly-complexed cyanide measurement within plant tissue was developed to study uptake and movement of cyanide species separately from cyanide metabolism and metabolite movement by a willow plant (Salix eriocephala var. Michaux). Spike recoveries from solutions with and without plant tissue, using various solvent combinations, and background control tissue contributions were investigated to obtain an accurate and precise extraction method for measurement of complexed and free cyanide concentrations within plant tissue. The optimum extraction technique involved the freezing of plant tissue with liquid nitrogen to facilitate homogenization prior to extraction. Homogenized willow tissue samples, 1 to 1.5 g-fresh weight, were ground a second time under liquid nitrogen followed by grinding in slurry with 2.5 M NaOH. The slurry was brought to 100 mL volume, sonicated for 5 min, extracted in the dark for 16 h, and analyzed without filtration for total and free cyanide by acid distillation and microdiffusion respectively. Sample tissue extraction controls found recoveries of 89% and 100% for 100 µg L-1 CNT as KCN and K4Fe(CN)6 spiked in willow tissue slurries. Methanol, hexane, and 2-octanol inclusion in the solvent matrix with 2.5 M NaOH interfered with the cyanide analytical technique while chloroform reacted with NaOH and free cyanide in solution. Filtration was not included due to increased cyanide loss, and analysis of control tissue showed minimal release of cyanide or interference of plant tissue with the cyanide analytical method.Tissue cyanide concentrations from hydroponicallyexposed tissue using the optimal extraction method agreed with tissue cyanide stable isotope (15N) results

Assessment of end-of-life design in solid-state lighting

Consumers in the US market and across the globe are beginning to widely adopt light emitting diode (LED) lighting products while the technology continues to undergo significant changes. While LED products are evolving to consume less energy, they are also more complex than traditional lighting products with a higher number of parts and a larger number of electronic components. Enthusiasm around the efficiency and long expected life span of LED lighting products is valid, but research to optimize product characteristics and design is needed. This study seeks to address that gap by characterizing LED lighting products’ suitability for end of life (EOL) recycling and disposal. The authors disassembled and assessed 17 different lighting products to understand how designs differ between brands and manufacture year. Products were evaluated based on six parameters to quantify the design. The analysis indicates that while the efficiency of LED products has improved dramatically in the recent past, product designers and manufacturers could incorporate design strategies to improve environmental performance of lighting products at end-of-life

Weight‐of‐Evidence Approach for Assessing Removal of Metals from the Water Column for Chronic Environmental Hazard Classification

The United Nations and the European Union have developed guidelines for the assessment of long‐term (chronic) chemical environmental hazards. This approach recognizes that these hazards are often related to spillage of chemicals into freshwater environments. The goal of the present study was to examine the concept of metal ion removal from the water column in the context of hazard assessment and classification. We propose a weight‐of‐evidence approach that assesses several aspects of metals including the intrinsic properties of metals, the rate at which metals bind to particles in the water column and settle, the transformation of metals to nonavailable and nontoxic forms, and the potential for remobilization of metals from sediment. We developed a test method to quantify metal removal in aqueous systems: the extended transformation/dissolution protocol (T/DP‐E). The method is based on that of the Organisation for Economic Co‐operation and Development (OECD). The key element of the protocol extension is the addition of substrate particles (as found in nature), allowing the removal processes to occur. The present study focused on extending this test to support the assessment of metal removal from aqueous systems, equivalent to the concept of “degradability” for organic chemicals. Although the technical aspects of our proposed method are different from the OECD method for organics, its use for hazard classification is equivalent. Models were developed providing mechanistic insight into processes occurring during the T/DP‐E method. Some metals, such as copper, rapidly decreased (within 96 h) under the 70% threshold criterion, whereas others, such as strontium, did not. A variety of method variables were evaluated and optimized to allow for a reproducible, realistic hazard classification method that mimics reasonable worst‐case scenarios. We propose that this method be standardized for OECD hazard classification via round robin (ring) testing to ascertain its intra‐ and interlaboratory variability. Environ Toxicol Chem 2019;38:1839–1849. © 2019 SETAC.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151334/1/etc4470_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151334/2/etc4470.pd

Reactive transport simulations to study groundwater quality changes in response to CO2 leakage from deep geological storage

AbstractAs an effort to evaluate risks associated with geologic sequestration of CO2, this work assesses the potential effects of CO2 leakage on groundwater quality. Reactive transport simulations are performed to study the chemical evolution of aqueous Pb and As after the intrusion of CO2 from a storage reservoir into a shallow confined groundwater resource. The simulations use mineralogies representative of shallow potable aquifers in the USA; both 2D (depth-averaged) and 3D simulations are conducted. Sensitivity studies are also conducted for variation in hydrological and geochemical conditions, as well as several other critical parameters. Model results suggest that a significant increase of aqueous lead (Pb) and arsenic (As) may occur in response to CO2 intrusion, but in most sensitivity cases their concentrations remain below the EPA specified maximum contaminant levels (MCLs). Adsorption/desorption from mineral surfaces significantly impacts the mobilization of Pb and As. Results from the 3D model agree fairly well with the 2D model in cases where the rate of CO2 intrusion is relatively small (so that the majority of CO2 readily dissolves in the groundwater), whereas discrepancies between 2D and 3D models are observed when the CO2 intrusion rate is comparably large