Now showing items 21-40 of 106

    • Modeling Biosorption Of Cadmium, Zinc And Lead Onto Native And Immobilized Citrus Peels In Batch And Fixed Bed Reactors

      Chatterjee, Abhijit; Schiewer, Silke; Barnes, Dave; Johnson, Ron; Tainor, Tom (2012)
      Biosorption, i.e., the passive uptake of pollutants (heavy metals, dyes) from aqueous phase by biosorbents, obtained cheaply from natural sources or industrial/agricultural waste, can be a cost-effective alternative to conventional metal removal methods. Conventional methods such as chemical precipitation, membrane filtration or ion exchange are not suitable to treat large volumes of dilute discharge, such as mining effluent. This study is a continuation of previous research utilizing citrus peels for metal removal in batch reactors. Since fixed bed reactors feature better mass transfer and are typically used in water or waste water treatment using ion-exchange resins, this thesis focuses on packed bed columns. A number of fixed bed experiments were conducted by varying Cd inlet concentration (5-15 mg/L), bed height (24-75 cm) and flow rate (2-15.5 ml/min). Breakthrough and saturation uptake ranged between 14-29 mg/g and 42-45 mg/g respectively. An empty bed contact time of 10 minutes was required for optimum column operation. Breakthrough curves were described by mathematical models, whereby three popular models were shown to be mathematically identical. Citrus peels were immobilized within an alginate matrix to produce uniform granules with higher uptake capacity than raw peels. All breakthrough curves of native and immobilized peels were predicted using external and intra-particle mass transfer resistances from correlations and batch experiments, respectively. Several analogous mathematical models were identified; other frequently used models were shown to be the approximate derivatives of a single parent model. To determine the influence of competing metals, batch and fixed bed experiments were conducted in different binary combinations of Pb, Cd, Zn and Ca. Equilibrium data were analyzed by applying competitive, uncompetitive and partially competitive models. In column applications, high affinity Pb replaced previously bound Zn and Cd in Pb-Zn and Pb-Cd systems, respectively. However, the Cd-Zn system did not show any overshoot. Calcium, which is weakly bound, did not affect target metal binding as much as other metals. Saturated columns were desorbed with 0.1 N nitric acid to recover the metal, achieving concentration factors of 34-129. Finally, 5 g of citrus peels purified 5.40 L mining wastewater.
    • Permafrost Settlement Caused By Climate Warming In Alaska And The Estimation Of Its Damage Costs For Public Infrastructure

      Hong, Eunkyoung; Trainor, Sarah; Colt, Stephen; Perkins, Robert; Walsh, John (2012)
      Climate models and studies indicate that the changes in the northern latitudes will be serious and accelerated. Climate warming may impact structures in the northern latitudes through permafrost settlement affecting the performance of infrastructure and increasing costs for maintenance. The material presented is organized in three main chapters. Chapter 1 describes the motivation for the research. Chapter 2 addresses the permafrost settlement hazard in Alaska. I developed the Permafrost Settlement Hazard Index, which considered anticipated climate warming and ecological characteristics which regulate permafrost settlement. I found that the discontinuous permafrost region is at more risk due to permafrost settlement than other regions of Alaska. I also found that the correlation that the areas with high settlement hazard value have higher road maintenance costs. Chapter 3 is an estimate of damage cost caused by permafrost settlement related to climate warming in the field of public infrastructure. I concluded that climate warming may add about $106 million annually from 2010 to 2050 to annual costs for public infrastructure in Alaska. This amount of damage cost is the relative size of damage cost that is caused by climate warming. In order to understand the broader idea of adaptation methods, a case study of Alaska roads for discontinuous permafrost regions is presented in Chapter 4. Some alternative construction methods were chosen as adaptation methods. Then, the comparison of the cost effectiveness of each adaptation method was shown to identify the most economical option when the cost estimation includes the effect of the additional permafrost settlement caused by climate warming. I concluded that pre-thaw method was the most cost effective method. I also recommended Air-Cooled Embankment on a condition that coarse rocks are available to create a convection cell. Chapter 5 summarizes the research and indicates possibilities for future research directions. I employed an interdisciplinary approach combining engineering knowledge with environmental impact assessments, utilizing economic tools in estimating damage costs, and analyzing the cost effectiveness of adaptation options to climate induced permafrost settlement. Nevertheless, this interdisciplinary analysis was not intended as a civil engineer design but intended for these economic estimates.
    • Detecting Methane Ebullition In Winter From Alaskan Lakes Using Synthetic Aperture Radar Remote Sensing

      Engram, Melanie J.; Walter, Katey (2012)
      Methane (CH4) is a greenhouse gas with a high radiative forcing attribute, yet large uncertainties remain in constraining atmospheric CH4 sources and sinks. While freshwater lakes are known atmospheric CH4 sources, flux through ebullition (bubbling) is difficult to quantify in situ due to uneven spatial distribution and temporally irregular gas eruptions. This heterogeneous distribution of CH4 ebullition also creates error when scaling up field measurements for flux estimations. This thesis reviews estimates of CH4 contribution to the atmosphere by freshwater lakes presented in current literature and identifies knowledge gaps and the logistical difficulties in sampling CH 4 flux via ebullition (bubbling). My research investigates various imaging parameters of space-borne synthetic aperture radar (SAR) to constrain current CH4 emissions from northern lakes. In a GIS spatial analysis of lakes on the northern Seward Peninsula, Alaska, comparing field data of ebullition to SAR, I found that SAR L-band backscatter from lake ice was high from lakes with CH4 bubbles trapped by lake ice and low from lakes with low ebullition activity. The 'roughness' component of a Pauli polarimetric decomposition of quad-pol SAR showed a significant correlation with the percentage of lake ice area containing CH4 bubbles and with CH4 ebullition flux. This indicates that the mechanism of SAR scattering from ebullition bubbles trapped by lake ice is single bounce. I conclude that SAR remote sensing could improve our ability to quantify lake ebullition at larger spatial scales than field measurements alone, could offer between-lake comparison of CH 4 ebullition activity, and is a potential tool for developing regional estimations of lake-source CH4.
    • Multi-Dimensional Frost Heave Modeling With Sp Porosity Growth Function

      Kim, Koui; Huang, Scott L. (2011)
      This dissertation presents a multi-dimensional frost-heave modeling with coupled heat transfer, moisture transfer, and mechanical analysis. A series of laboratory frost-heave tests was conducted to determine segregation potential (SP) values using the effect of cooling rate and overburden pressure in two different freezing modes. Regardless of the freezing mode, consistent SP values were obtained at the formation of the final ice lens. Continuous heave and water-intake measurements made it possible to determine the time at the formation of the final ice lens. The SP porosity growth function was developed using simulations of the growing ice lens and frozen fringe. The developed frost-heave model was verified by laboratory frost-heave tests in one dimension. The simulated temperature distribution and amount of heave were in good agreement with experimental values. The SP porosity growth function was then expanded to two dimensions to simulate the soil-pipeline interaction of an experimental buried chilled pipeline constructed in Fairbanks, Alaska in the early 2000s. A two-dimensional frost-heave simulation was conducted at the free-field area, where the influence of pipeline resistance in frozen ground was negligible. This model, which considers the effect of frozen soil creep on stress distribution due to temperature variation, analyzed the influence of stress fields on soil frost-heave susceptibility and deformation. Simulations of pipe displacement were conducted for two cases, with and without the use of the long-term creep characteristics of frozen soils. Using the long-term creep characteristics, the simulated result agreed well with the observed value, differing by only a few percentage points. However, without using long-term creep characteristics, the simulated pipe heave was approximately 75% of the observed heave because of an unrealistic stress buildup. Finally, the SP porosity growth function was expanded to predict soil-pipeline interaction around a frozen-unfrozen boundary. Temperature distribution was successfully predicted in both the pre-frozen soil and the unfrozen zones, as well as at the time when differential pipeline movement started. The developed three-dimensional frost-heave model could predict pipe movement and induced bending due to differential frost heave for a 20-year period.
    • The Hydrologic Regime At Sub-Arctic And Arctic Watersheds: Present And Projected

      Liljedahl, Anna K.; Hinzman, Larry (2011)
      The wetlands in the Arctic Coastal Plain, Northern Alaska, support a multitude of wildlife and natural resources that depend upon the abundance of water. Observations and climate model simulations show that surface air temperature over the Alaskan arctic coast has risen in recent history. Thus a growing need exists to assess how the hydrology of these arctic wetlands will respond to the warming climate. A synthesis study was conducted combining the analysis of an extensive field campaign, which includes direct measurements of all components of the water balance, with a physically-based hydrologic model forced by downscaled climate projections. Currently, these wetlands exist despite a desert-like annual precipitation and a negative net summer water balance. Although evapotranspiration is the major pathway of water loss, there are multiple non-linear controls that moderate the evapotranspiration rates. At the primary study site within the Barrow Environmental Observatory, shallow ponding of snowmelt water occurs for nearly a month at the vegetated drained thaw lake basin. Modeling studies revealed that the duration and depth of the ponding are only replicated faithfully if the rims of low-centered polygons are represented. Simple model experiments suggest that the polygon type (low- or high-centered) controls watershed-scale runoff, evapotranspiration, and near-surface soil moisture. High-centered polygons increase runoff, while reducing near-surface soil moisture and evapotranspiration. Soil drying was not projected by the end-of-the century but differential ground subsidence could potentially dominate the direct effects of climate warming resulting in a drying of the Arctic Coastal Plain wetlands. A drier surface would increase the susceptibility to fire, which currently is a major part of the Alaskan sub-arctic but not the arctic landscape. High quality pre- and postfire data were collected in the same location in central Seward Peninsula, uniquely documenting short-term soil warming and wettening following a severe tundra fire. Overall, this research concludes that arctic and sub-arctic watershed-scale hydrology is affected by changes in climate, surface cover, and microtopographic structures. It is therefore crucial to merge hydrology, permafrost, vegetation, and geomorphology models and measurements at the appropriate scales to further refine the response of the Arctic Coastal Plain wetlands to climate warming.
    • Impact Of Freeze -Thaw On Liquefaction Potential And Dynamic Properties Of Mabel Creek Silt

      Zhang, Yu (2009)
      In the early winter of 2002 (November), the Alaska Denali earthquake (Mw=-7.9) caused significant damage in partially frozen fine-grained soil and extensive liquefaction was observed in glacial fine-grained saturated soil surface deposits near Tok, Alaska. It illustrated that there was a need to evaluate the seismic response and liquefaction potential of fine-grain soil in cold regions; however, until now most of the research on the liquefaction phenomenon and seismic response were mainly about soil in non-cold regions. The seismic response and liquefaction potential of soils in cold regions, especially those of fine-grained nature, has not been studied thoroughly and therefore is not well-understood. This document presents a laboratory study on liquefaction potential and cyclic response of fine-grained soil in cold regions. As the main features of the soil in the ground of cold regions, temperature change at below freezing temperatures or near-freezing temperatures, and the seasonal climate change were evaluated on liquefaction potential, dynamic properties, and post-cyclic-loading settlement of fine-grained soils. Increasing temperatures from near freezing to the completely thawed temperature (i.e., 24�C, 5�C, 1�C, and 0.5�C) were used to thaw the frozen Mabel Creek silt to simulate temperature change on it, or the Mabel Creek silt experienced several freezing and thawing alternating processes (i.e., 1, 2, and 4 freeze-thaw cycles) to simulate seasonal climate change. Triaxial strain-controlled cyclic tests were conducted to evaluate liquefaction potential, dynamic properties, and post-cyclic-loading settlement. Based on this limited laboratory effort, results show that in most cases, temperature rise and freeze-thaw cycles can impact: (a) liquefaction potential, (b) dynamic properties and (c) post-cyclic-loading settlement of fine-grained soils. However, there was one case exception and this is decribed in the following sentence. When a fine-grained soil was conditioned in a partially frozen state, the possibility and threat of liquefaction significantly increased.
    • Biodegradation Of Petroleum And Alternative Fuel Hydrocarbons In Moderate To Cold Climate

      Horel, Agota Anna (2009)
      Microbial degradation of hydrocarbon fuels contaminating soil in the Arctic and subarctic environment is a relatively slow process. Nevertheless, due to transportation and logistical limitations in rural Alaska, biodegradation might be the best and cheapest contaminant removal option. The aim of this thesis was to investigate the environmental effects on biodegradation by naturally occurring microorganisms for some innovative hydrocarbon fuels and to determine the overall fate of hydrocarbons in soil, including degradation by fungi and bacteria, volatilization, and transport in the soil. Three major types of fuels were investigated in small scale microcosms and larger soil columns: conventional diesel as a control substance, synthetic diesel (arctic grade Syntroleum) and different types of fish oil based biodiesel. The environmental conditions investigated included different soil types (sand and gravel), different temperatures (constant 6�C, 20�C, and fluctuating between 6 and 20�C), moisture levels (from 2% to 12% GWC), fuel concentrations (from 500 to 20,000 mg fuel/kg soil) and nutrient dosages (0 or 300 mg N/kg soil). Microbial response times and growth phases were also investigated for different inoculum types. Conditions of 20�C, 300 mg N/kg soil, sand, ?4000 mg of fuel/kg soil and ?4% GWC were favorable for bioremediation, with a short lag phase lasting from one day to less than a week, and pronounced peaks of daily CO 2 production between week 2 and 3. At suboptimal conditions, all phases were extended and slow, however at low temperatures steady metabolization continued over a longer time. The relative importance of fungal and bacterial remediation varied between fuel types. Diesel fuel degradation was mainly due to bacterial activities while fish biodiesel degradation occurred largely by mycoremediation. For Syntroleum both bacterial and fungal remediation played key roles. Volatilization contributed up to 13% to overall contaminant removal. In soil columns, degradation was slower than in microcosms, due to an uneven concentration profile of contaminants, nutrients and oxygen with depth. In general, biodegradation showed promising results for soil remediation and the alternate fuel types were more biodegradable compared with conventional diesel fuel.
    • The Influence Of Soil Cryostructure On The Creep And Long Term Strength Properties Of Frozen Soils

      Bray, Matthew Thomas (2008)
      The time dependent mechanical properties of ice-rich frozen soils were studied in relation to their cryostructure. The CRREL permafrost tunnel was the primary source of the studied ice-rich soils. Mapping of the permafrost geology of the main adit of the CRREL permafrost tunnel was performed and reinterpreted in the context of a cryofacial approach. The cryofacial approach in based on the concept that cryostructure is dependent on how a soil was deposited and subsequently frozen. Three main soil cryostructures were determined to represent the main aspects of the permafrost geology. Soils with micro-lenticular cryostructure represent the original ice-rich syngenetic permafrost formed during the Pleistocene. Reworked sediment due to fluvial-thermal erosion resulted in soils with massive cryostructure and soils with reticulate-chaotic cryostructure. Ice bodies within the tunnel include syngenetic wedge ice and secondary thermokarst cave ice deposits. A testing program for determining the time dependent mechanical properties, including the creep and long term strength characteristics of permafrost in relation to soil cryostructure, was performed. Undisturbed frozen soils include silty soil containing micro-lenticular, reticulate-chaotic, and massive cryostructure. Remolded silt from the tunnel was used to create artificial samples with massive cryostructure for comparison to the undisturbed frozen soils. In addition to frozen silt, undisturbed ice facies were tested. These included syngenetic wedge ice, Matanuska basal glacial ice, and Matanuska glacial ice. Testing methods include uniaxial constant stress creep (CSC) tests and uniaxial relaxation tests. It was shown that soil cryostructure and ice facies influences the creep and long term strength properties of frozen soils. It was shown that remolded soils provide non-conservative creep and long term strength estimates when extrapolated to undisturbed frozen soils. Minimum strain rate flow laws show that at low stresses, undisturbed soils creep at a faster rate than remolded soils. At high stresses, frozen soils creep at a faster rate than ice. It was also shown that the unfrozen water content influences the mechanical properties of frozen soils and that the unfrozen water content is influenced by soil cryostructure. Through cryostructure, the permafrost geology is related to the time dependent mechanical properties of frozen soils.
    • Using Geophysical Constraints To Determine Groundwater Travel Times, Seafloor Arrival Locations, And Saltwater Concentrations For Transition Zone Depths At Underground Nuclear Detonations On Amchitka Island

      Wagner, Anna M.; Barnes, David (2007)
      There is a great amount of radioactive material in the subsurface of Amchitka Island as a result from underground nuclear testing performed between 1965 and 1971. It is unknown how long it will take for the radionuclides to travel to the seafloor and the marine environment or where possible seepage zones will occur. The contaminant transport is greatly affected by the location of the transition zone (TZ) and the effective porosity, which were both determined by magnetotellurics (MT) in 2004. The hypothesis of this study was as follows: the groundwater travel times and seafloor arrival locations, can be estimated through groundwater modeling, with the location of the transition zone being estimated by magnetotellurics. An additional hypothesis is as follows: saltwater concentration for a TZ and the general subsurface characteristics can be quantified with groundwater modeling, using geophysical constraints in combination with saltwater and hydraulic head measurements. The groundwater travel times were estimated with groundwater modeling using the transition zone location as determined by MT. Shortest groundwater travel times are 1,200 and 2,100 years, at Long Shot and Cannikin respectively. At Long Shot, a decreased groundwater travel time of up to 55% could be seen when an enhanced hydraulic conductivity was included at the location of an assumed andesite sill layer. The seafloor arrival locations can be up to 1,000 and 2,100 m offshore at Long Shot and Cannikin respectively but will most likely occur closer to shore. This study was also successful at establishing the general characteristics of the subsurface by using geophysical constraints in combination with saltwater and hydraulic head measurements. The subsurface at Long Shot is isotropic or has mild anisotropy ratio of 1:2, which confirms the study by Fenske (1972). As represented in this study, this method has been shown to be valuable in determining the saltwater concentration of the TZ as determined by MT and can thus be used in further studies of islands and coastal areas.
    • Experimental Study Of Adsorbed Cation Effects On The Frost Susceptibility Of Natural Soils

      Darrow, Margaret Marie; Huang, Scott; Shur, Yuri (2007)
      Frost heaving is ubiquitous throughout cold regions, causing damage to building foundations, roads, airfields, railways, utilities, and pipelines. Out of the voluminous body of research conducted over the last 80 years, few studies investigated the mineral surface effects on frost heaving. These previous studies were conducted nearly 50 years ago with rudimentary equipment and on homogeneous and artificial soils that have limited applicability to actual field conditions. The purpose of the research presented here is to investigate the adsorbed cation effects on the frost susceptibility of natural soils through experimental testing. A comprehensive suite of laboratory experiments was conducted on five natural heterogeneous soils, including the preparation of divalent and monovalent cation-treated samples. Experimental testing included measurements of engineering index properties, chemical properties, clay content and mineralogy, soil-moisture characteristic curves, unfrozen water content, zeta potential, and frost heave testing. Frost heave tests were conducted using a state-of-the-art laboratory system that demonstrates high repeatability. Soil-moisture characteristic---soil freezing characteristic (SMC-SFC) relations were developed for the five natural soils over an unprecedented range of measurements and using a new approach, which can be related to the Clausius-Clapeyron equation. The SMC-SFC relations yield a new variable, eta, which describes the water retention properties of soil at increasing matric potentials and decreasing temperatures. The five untreated soils demonstrated significantly different frost heave ratios, ranging from 0.7 percent to 49.2 percent. Statistical analysis indicates that the frost susceptibility of the five untreated soils is most dependent on adsorbed cations, eta, amount of microaggregates smaller than 2 mum, and clay content. For the entire body of untreated and cation-treated samples, statistical analysis indicates that the frost susceptibility is most dependent on adsorbed cations, unfrozen water content, and amount of smectite, kaolinite, and chlorite present in the soil. The results from each cation treatment indicate that the frost susceptibility of (1) Ca2+-saturated soil is most dependent on zeta potential and unfrozen water content; (2) Mg2+-saturated soil is most dependent on zeta potential and amount of chlorite; and (3) Na +-saturated soil is most dependent on zeta potential, unfrozen water content, and amount of chlorite.
    • Dynamic Modeling Of The Hydrologic Processes In Areas Of Discontinuous Permafrost

      Bolton, William Robert; Hinzman, Larry (2006)
      The overarching hypothesis of this dissertation is "in the sub-arctic environment, the presence or absence of permafrost is dominant influence on hydrologic processes." The presence or absence of permafrost is the defining hydrologic characteristic in the sub-arctic environment. Discontinuous permafrost introduces very distinct changes in soil hydraulic properties, which introduce sharp discontinuities in hydrologic processes and ecosystem characteristics. Hydraulic properties vary over short and long time scales as the active layer thaws over the course of a summer or with changes in permafrost extent. The influence of permafrost distribution, active layer thaw depth, and wildfire on the soil moisture regime and stream flow were explored through a combination of field-based observations and computer simulations. Ice-rich conditions at the permafrost table do not allow significant percolation of surface waters, which result in saturated soils near the ground surface and limited subsurface storage capacity, compared to well-drained non-permafrost sites. The removal of vegetation by wildfire results in short-term (<10 years) increases in moisture content through reduced evapotranspiration. Long-term (>10 years) drying of soils in moderate to severe wildfire sites is the result of an increased active layer depth and storage capacity. A spatially-distributed, process-based hydrologic model, TopoFlow, was modified to allow spatial and temporal variation in the hydraulic conductivity and porosity of soils. By continual variation of the hydraulic conductivity (proxy for permafrost distribution and active layer thaw depth) and porosity (proxy for storage capacity), the dynamic soil properties found in the sub-arctic environment are adequately represented. The sensitivity of TopoFlow to changes in permafrost condition, vegetation regime, and evapotranspiration is analyzed. The net result of the field observations and computer simulations conducted in this research suggest the presence or absence of permafrost is the dominant influence on soil moisture dynamics and has an important, but secondary role in the stream flow processes.
    • The Physical Dynamics Of Patterned Ground In The Northern Foothills Of The Brooks Range, Alaska

      Overduin, Pier Paul; Kane, Douglas L. (2005)
      Periglacial landforms, called patterned ground, change the vegetation, microtopography and organic content of the surface soil horizons. Because they are uniquely products of the periglacial environment, changes in that environment affect their distribution and activity. As surface features, they mitigate heat and mass transfer processes between the land and atmosphere. For environmental change detection, the state of the soil and active layer must be monitored across temporal and spatial scales that include these features. It is suggested here that changes in the state of the active layer due to the abrupt spatial changes in surface soil character lead to changes in the distribution of soil components, soil bulk thermal properties and the thermal and hydrological fluxes result. The determination of soil volumetric moisture content using the relative dielectric permittivity of the soil is extended to include live and dead low-density feathermoss. High temporal resolution monitoring of the thermal conductivity of mineral and organic soil horizons over multiple annual cycles is introduced, along with a new method for analyzing the results of transient heat pulse sensor measurements. These results are applied to studies of frost boils and soil stripes in the northern foothills of the Brooks Range in Alaska. Active layer ice dynamics determine the thermal properties of the frozen soil in the frost boil pedon. Annual heaving and subsiding of the ground surface reflects these changes in ice content and can be used to estimate active layer ice content as a function of depth. These estimates correlate with bulk soil thermal diffusivity, inferred as a function of depth from temperature data. Differences in soil thermal diffusivity determine thaw depth differences between frost boil and tundra, and between wet and dry soil stripes. For the latter, deeper subsurface flow through the high organic content wet stripes is delayed until mid-summer; when it does occur, it has a large component normal to the hillslope as a consequence of differential heave. Dynamics in these periglacial landforms can be identified from surface features, highlighting the potential for scaling up their net effect using remote sensing techniques.
    • Improved Membrane Filtration For Water And Wastewater Using Air Sparging And Backflushing

      Psoch, Christian (2005)
      The goal of this research was to investigate methods and techniques that enhance mass transfer through the membranes. Two general types of fluids were investigated: synthetic wastewater treated in a membrane bioreactor (MBR) and natural and simulated river water. For both fluids, a wide range of solid concentrations (up to 18 g/L) were tested. The membranes investigated were all tubular modules at pilot scale between 0.75 and 1.20 m length, with tubular diameters of 5.5--6.3 mm, 0.2 mum pore size, and membrane surface areas of 0.036--0.1 m2. For flux enhancement, two techniques were applied: air sparging (AS), and backflushing (BF). Both techniques were compared with the sponge ball cleaning method. The experimental temperature ranged between 10 and 30�C, cross-flow velocities (CFV) ranged between 0.5 and 5.2 m/s, and transmembrane pressure (TMP) ranged between 30 and 350 kPa. Research results showed, that AS was able to enhance the conventional flux over weeks to months up to factor of 4.5 for river water and a factor of 3 for wastewater. At modest CFV of 1.5--2 m/s, AS was as successful as BF. If higher CFV (up to 5.2 m/s) were supplied for BF, this technique could enhance the wastewater flux by factor 4.5. The supply of AS and BF combined was superior to the single application even at moderate CFV. The major finding of this research was that cake thickness on the membrane surface was decreased by AS, contrary to research by other authors. AS can be used as substitute aeration in MBRs, without impairing the degradation performance. The combination of AS and BF generated the least filter cake, but the lowest fouling was observed for AS. An empirical equation was proposed to calculate the viscosity in a sidestream MBR depending on reactor temperature and mixed liquor suspended solids (MLSS).
    • Behavior Of Granular Materials Under Cyclic And Repeated Loading

      Minassian, George H.; Raad, Lutfi (2003)
      Granular layers are essential contributors to the structural integrity of the pavement system, their premature deformation radically decrease support of the asphalt concrete surface layer, thus leading to the early deterioration of the overall pavement structure. This research was conducted to better understand the behavior of granular materials when subjected to the complex nature of traffic loading. Long-term triaxial tests were conducted on typical Alaskan base course material using both repeated as well as cyclic loading to also account for the shear reversal effects induced by wheel load. Results show that the shear reversal component of the traffic loads, which have been ignored so far, induces considerable damage to the granular layers. Models were presented to predict the different soil moduli while also accounting the effect of strain hardening or densification due to the repetitive nature of the loads applied. Moreover, a simple yet powerful model was presented to predict accumulated permanent strains as function of the stress state, number of load repetitions and the strength level applied. The results obtained in this study also show a clear indication of the existence of given stress level limit beyond which incremental collapse of the system takes place. Furthermore, regions of instability of granular layers subjected to dynamic loading have been defined using a simple response parameter and monotonic shear strength of the soil. An effort was made to explain the instability zones identified in this research by the shakedown theory.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office.
    • Seasonal Effects Of Frozen Soil On The Stiffness Of Bridge Piles

      Horazdovsky, Jacob E.; Hulsey, J. Leroy (2010)
      In the northern regions, the upper layer of soil is frozen throughout winter months. Soil stiffness can be expected to increase several orders of magnitude as it changes from thawed to frozen. Thus, pile foundation systems embedded in frozen soils are considerably stiffer during winter months when subjected to lateral loads. This thesis explores and quantifies stiffness change for 16 inch diameter steel jacketed, reinforced concrete pilings in seasonally frozen silt. Two test piles were driven 20 feet into silty soil at a site approximately 1.5 miles from Fairbanks, Alaska. Three quasi-static lateral load cyclic tests were conducted on the piles throughout the year; one in September when the soil was thawed, the other two in January and March with frost depths of 4.5 and 7.5 feet respectively. Soil temperatures ranged from thawed to -18 degrees C. The shear demand on the piles increased by over 400 percent. Depth to fixity changed from approximately 6 pile diameters (thawed) to less then 0.75 pile diameters (frozen).
    • Winter Precipitation Depths Across The North Slope Of Alaska Simulated From The Weather Research And Forcasting Model And Snowtran-3D

      Byam, Sarah Jean; Cherry, Jessica E.; Toniolo, Horacio; Kane, Douglas (2012)
      Accurately predicting snow distribution and blowing snow conditions in the Arctic is critical to the design of ice road construction and maintenance as well as for predicting water supplies and runoff during snowmelt, estimating the cost of snow removal, and forecasting tundra travel conditions. A current atmospheric model used by both the operational weather prediction and research communities is the Weather Research and Forecasting model. However, the built-in snow schemes in the model neglect redistribution of snow via wind, one of the key processes in snow pack evolution. This study will involve three parts: (1) diagnostic of the differences in the current snow schemes of the model, (2) evaluation of the model's snow schemes as compared to observational data, and (3) asynchronous coupling of the SnowTran-3D to model predictions using a simple algorithm. The approach provides a simple method for the prediction of snow distribution, improving the realism of current snow distribution models, and will be easily employable for both operational and research applications.
    • Initial Permafrost Engineering Research In Alaska

      Cysewski, Margaret Hope; Shur, Yuri (2013)
      Past permafrost engineering research and projects can aid modern permafrost engineering. The knowledge base of lessons learned among engineers is important, especially between generations of engineers, so history does not repeat itself Uncovering the history of permafrost engineering, and its compilation, summarization, and analysis, is beneficial for the Alaskan engineering community. This master's thesis is devoted to the early years of permafrost engineering in Alaska with projects carried out from the Gold Rush era to shortly after WWII. The projects include: thawing technology developed by gold miners, Alaska Highway road design and construction with its influence, and early comprehensive research by the Permafrost Division of the U.S. Army Corps of Engineers' St. Paul District, particularly the development of the test site, the Fairbanks Research Area, along Farmers Loop Road. Each of these projects has been successfully adapted to modern practices, laying the foundation of permafrost engineering.
    • Stochastic Analysis Of Response Functions Of Nitrogen In Stream Water

      Park, Hyun Ae; Tumeo, Mark A. (1992)
      In the present study, a stochastic model of nitrogen in streams is created using a new mathematical technique, Probability Density Function/Moment technique (PDF/M). The model is based on a set of four highly non-linear second order equations for nitrogen species in streams (NH$\sb3,$ NO$\sb2,$ NO$\sb3,$ and organic-N). The purpose of the PDF/M technique is to include occurrence of natural variability. The first step is to separate the stochastic terms from the non-stochastic terms and solve the resulting set of equations simultaneously. The moments of the output variables then are obtained using expectation mathematics. The moments are used in a solution of the Fokker-Planck equation to produce an analytical solution for the probability density functions of the dependent variables. Comparison of the present study to the results of the Monte Carlo method showed the application of PDF/M technique to nitrogen cycle simulation valid. <p>
    • A Mechanical Evaluation Of Alaskan White Spruce

      Syta, Dean Edward; Curtis, Kevin; Gasbarro, Tony; Raad, Luffi (1993)
      This project serves to demonstrate the usefulness of Alaskan White Spruce as a construction material. This is done through the development of allowable strength values for design purposes. Such values allow engineers to design structures using Alaskan White Spruce, increasing the usefulness of the wood species.<p> The mechanical properties of Alaskan White Spruce are investigated. Summaries of the mechanical properties and of subsequently developed allowable structural design values are given. Included are discussions of the Alaskan White Spruce species, general wood behavior, mechanical testing of wood, statistical data analysis, and allowable property development. Results are compared against the work of other researchers. Appendices of test data are given.<p> Test results and subsequent data analysis indicate Alaskan White Spruce possesses strength similar to Douglas-Fir/Larch lumber and higher strength than Spruce/Pine/Fir type lumbers. This indicates that Alaskan White Spruce may have considerable worth as a construction material. <p>
    • Structural health monitoring of Klehini River bridge

      Xiao, Feng (2012-08)
      The objective of the research is to improve the safety of bridge structures in the state of Alaska through implementation of innovative structural health monitoring (SHM) technologies. The idea is to evaluate structural integrity and serviceability, and to provide reliable information for changing structural response, etc. of monitored bridges. Based on the finite element model's moving load analysis, modal analysis results and field inspection, this study was used to establish a bridge SHM system for a particular bridge including a preferred sensor layout, system integrator and instrumentation suitable for Alaska's remote locations with harsh weather. A variety of sensors were proposed to measure and monitor structural and environmental conditions to assist in the evaluation of the performance of the Klehini River Bridge. This system is able to provide more reliable information on the real structural health condition. It can be used to improve safe performance of this bridge. As a new safety and management tool, this SHM system will complement traditional bridge inspection methods. Implementation of an effective monitoring system will likely result in a reduction in inspection manpower, early detection of deterioration/damage, development of optimum inspection cycle and repair schedules before deterioration/damage grows to a condition where major repairs are required.