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Diaz, Maria EugeniaA Modeling Approach towards Understanding Solid-Solution Interactions of Metals in Biosolids
Doctor of Philosophy in Engineering, University of Toledo, 2010, Chemical Engineering

Biosolids are the solid byproduct resulting from the treatment of domestic sewage in a treatment facility. Biosolids contain large amounts of nutrients such as C and N making them an excellent fertilizer; however, they also contain trace amounts of heavy metals that can leach to the ground limiting their application rate. The leaching process of heavy metals from biosolids is dictated by the physical properties of the soil and by the solid/liquid partitioning of the metals. Biosolids contain multiple sorptive surfaces such as organic matter, iron, aluminum and manganese oxides, silicates and carbonates. To accurately predict leaching of metals from biosolids, the interaction of metals with these surfaces need to be considered. Beforehand, models have been developed to simulate the interactions of metals with individual sorptive surfaces such as hydrous ferric oxides and manganese oxides. The goal of this research was to develop a multisurface geochemical modeling approach to predict the release of As, Cd, Cr, Cu, Mo, Ni, Pb and Zn from biosolids and to determine the affinity of heavy metals for the different sorptive sites present in biosolids. First, pH dependent leaching and isotherm experiments were conducted on biosolids. A multisurface approach was implemented using the NICA-Donnan model to incorporate organic matter (OM) as a sorbent. The generalized two layer model was used to incorporate iron, aluminum and manganese oxides. Selective chemical extractions were conducted to determine the concentration of available surface sites. The multisurface geochemical model required a large number of laboratory measured input values that demanded extensive laboratory analysis and had an associated uncertainty for which there was little knowledge on its impact to the uncertainty of the output. A sampling based global sensitivity analysis was used to relate model output variability and uncertainty with the uncertainty of the input.

The leaching pattern of the heavy metals showed strong pH dependence, similar to other waste materials. Overall, the model accurately predicted the release of metals over the pH range and the isotherms. The percentage of active dissolved organic matter (DOM) necessary to successfully model the leaching of metals under acidic conditions was significantly lower than under basic conditions; nevertheless, in the solution phase Cd, Cr, Cu, Ni, Pb and Zn complexes with DOM were predominant for the entire pH range. Organic matter (OM) was the predominant sorptive site in the matrix, however simulations of a case scenario in which OM was completely removed showed that biosolids still retained a large sorption capacity. The sensitivity analysis showed that the dissolved concentration of metals was not sensitive to variations of the input concentrations of: SO4-2, Na+1, NO3-1, Cl-1, Mg+2, K+1, F-1 and H4SiO4. In other words, the dissolved metal concentrations were not affected by the presence of SO4-2, Na+1, NO3-1, Cl-1, Mg+2, K+1, F-1 and H4SiO4. The dissolved metal concentrations leached from biosolids were sensitive to total metal concentrations, total sorptive sites available, and DOC, PO4-3, Al+3, Mn+2, and Fe+3 concentrations. The model uncertainty and sensitivity to the different input values varied with pH. Additionally, each metal input was only relevant for its own output suggesting that in these circumstances there was no competition effect among metals. The uncertainty of the output varied between 5 to 8 orders of magnitude depending on the metal.

Committee:

Defne Apul, PhD (Advisor); Isabel Escobar, PhD (Committee Member); Dong-Shik Kim, PhD (Committee Member); G. Glen Lipscomb, PhD (Committee Member); Jon Petter Gustafsson, PhD (Committee Member)

Subjects:

Environmental Engineering; Environmental Science

Keywords:

Biosolids; geochemical modeling; sensitivity analysis

Lees, Michael ECorrosion of Brass Meters in Drinking Water: The Influence of Alloy Composition and Water Chemistry on Metal Release and Corrosion Scale
MS, University of Cincinnati, 2017, Arts and Sciences: Geology
Brass plumbing components including meters, fittings and valves are used extensively in drinking water distribution systems. Until recently, most in-line brass components contained toxic lead, many of which are still presently in use. Corrosion of brass components leads to the release of metals to drinking water. The primary factors of brass corrosion in drinking water are temperature, alloy composition and water chemistry. In this thesis, a combination of mathematical modeling, analytical techniques and geochemical modeling were used to better understand what causes corrosion in brass components. A comprehensive model for the release of copper, lead and zinc from brass water meters has been developed. This model provides a framework to evaluate how meter parameters, such as alloy composition and age, influence metal leaching from brass components. When considering brass composition, zinc concentration within the alloy is shown to be the primary factor in copper and zinc release. Brasses with greater than 8 – 9% zinc exhibit more rapid corrosion when compared to brasses with less than 8% zinc. Age was found to have more influence over lead release than alloy composition, with newer meters releasing significantly higher concentrations of lead versus older meters. In addition to the oxidation of metallic surfaces, corrosion scale formation and dissolution also have a significant impact upon metal concentrations within drinking water. Optical microscopy, X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), were used to characterize the morphology and mineralogy of corrosion scale in two sets of residential water meters. The meters, which were in service for up to 40 years, came from two locations with contrasting water chemistries; Seattle, with relatively low alkalinity, hardness and total dissolved solids (TDS), and Cincinnati, which has moderate alkalinity, hardness and TDS. Results showed the copper minerals cuprite and malachite, to be most abundant within the corrosion scale from both sources. Lead minerals were much more prevalent within the Cincinnati meters, as were carbonates (both Cu & Pb). In general, the Cincinnati meters contained more substantial and consistent scale coverage whereas coverage on the Seattle meters was patchier and more localized. Real world use of drinking water systems cycle between flow and periods of stagnation, where water sits quiescently within the system. During stagnation, changes in water chemistry can include metal concentration, solution pH, and oxidation reduction (redox) potential. PHREEQC was utilized to calculate the saturation index (SI) of metallic species with changing water chemistry. The SI values were used to evaluate whether a given mineral will dissolve or precipitate from water during stagnation. These values were compared to the mineralogy identified in the meters to better understand the mechanism of scale development. Changes in redox potential had the most significant effect upon SI values. Minerals present within the scale were found to form under distinctly different conditions suggesting that dissolution and precipitation rates must also be considered.

Committee:

Warren Huff, Ph.D. (Committee Chair); Andrew Czaja, Ph.D. (Committee Member); J Barry Maynard, Ph.D. (Committee Member)

Subjects:

Geochemistry

Keywords:

brass corrosion;corrosion in drinking water;lead leaching;corrosion scale mineralogy;geochemical modeling;water chemistry

Zerai, BiniamCO2 Sequestration in Saline Aquifer: Geochemical Modeling, Reactive Transport Simulation and Single-phase Flow Experiment
Doctor of Philosophy, Case Western Reserve University, 2006, Geological Sciences

Storage of CO2 in saline aquifers is one way to limit the buildup of greenhouse gases in the atmosphere. Large-scale injection of CO2 into saline aquifers will induce a variety of coupled physical and chemical processes including multiphase fluid flow, solute transport, and chemical reactions between fluids and formation minerals. These issues were addressed using CO2 solubility modeling, simulation using geochemical reaction, 1-D reactive transport and Particle Image Velocimetry (PIV).

Comparison of CO2 solubility model against experimental data suggest that Duan and Sun (2003) CO2 solubility model (DS-CSM) accurately modeled solubility of CO2 in brine for range of temperatures, pressures and salinities. Modeling under equilibrium, path-of-reaction and kinetic rate using a reactor type Geochemists Workbench demonstrate that dissolution of albite, K-feldspar, and glauconite, and the precipitation of dawsonite and siderite are very important for mineral trapping of CO2.

A 1-D reactive transport was developed based on CO2 solubility model that take in to account the high salinity of Rose Run brine and a module that calculates the equilibrium constants based on temperature and pressure. The results indicate that the extent of sequestration through solubility and mineral trapping is sensitive to the choice of CO2 solubility model and the fugacity of CO2. Reactive transport modeling underscores in the long-run siderite and dawsonite minerals are important sink in trapping CO2 in the Rose Run Sandstone but over a short time-scale the hydrodynamic trapping plays a crucial role. The calculated storage capacity using DS-CSM suggest that for the first 100 years, 90 percent of the injected CO2 trapped as free CO2 whereas 6 percent are trapped in dissolve form and the rest sequestered in minerals.

Micro-scale single-phase flow through a network model of porous rock was investigated using experimental and numerical analysis. PIV with refractive index matching was developed to map velocity of pore-scale fluid flow through acrylic two-dimensional network without chemical reaction. Experimentally determined velocity vectors for single-phase flow through pore bodies and adjoining throats as well as for the outlet of the flow cell were compared with numerical simulations of flow through the cell using FLUENT computer code.

Committee:

Beverly Saylor (Advisor)

Keywords:

CO2 sequestration; Reactive transport simulation; Rose Run Sandstone; Geochemical modeling; Particle Image Velocimetry

Goetz, Elaine R.Sustainable Treatments of Acid Mine Drainage
Doctor of Philosophy (PhD), Ohio University, 2015, Civil Engineering (Engineering and Technology)
Acid mine drainage (AMD) is a significant concern in southeastern Ohio. Streams impaired by AMD are ecologically damaged, affect quality of life for area residents, and are expensive to remediate. Two treatment processes that appear promising for sustainably remediating AMD are steel slag leach beds (SLBs) and electrolysis with product recovery. A unique sustainability attribute of SLBs is the use of waste steel slag as an alkalinity source. For electrolysis, product recovery can offset costs of treating the AMD. An evaluation of the performance of twelve SLBs in southeastern Ohio demonstrated that SLBs did not meet targets for alkaline loadings to AMD-affected waterways. Alkalinity production decreased rapidly over SLB operation in a predictable mathematical relationship, and was further impeded by accumulation of calcite-like solids within the SLBs. Recommendations were made for design and operating changes to improve loadings. The effects of influent CO2 were investigated further using geochemical modeling and XRD analyses. A simple model for molar Ca dissolution potential was combined with PHREEQC Interactive geochemical modeling for individual SLBs to successfully predict most aspects of SLB effluent conditions, including calcite presence both inside and at the effluent to SLBs. XRD analyses also confirmed the presence of calcite at the effluent to SLBs. An electrolysis treatment system was designed, constructed, and operated with AMD from local seeps. The system was effective at neutralizing acidity and removing iron (98%), aluminum (89%), and manganese (56%) metals from high-Fe-concentration AMD from the Truetown site near Chauncey, Ohio. Treatment sludge was dried, ground, and used as pigment for paint by John Sabraw, Ohio University Professor of Art. Limited data indicates that the net cost of electrolysis treatment is high for AMD treatment systems, but may decrease with process optimization. Using multi criteria decision analysis (MCDA), four treatment systems were ranked for sustainability. Stakeholders ranked limestone leach beds most sustainable compared to electrolysis (p=0.238), SLBs (p<0.05), and lime dosers (p<0.05). The analysis determined rankings using forced equal weighting for economic, environmental, and social pillars of sustainability. Sensitivity analyses verify the importance of equal weighting: rankings of treatment systems vary as weightings vary.

Committee:

R. Guy Riefler, PhD (Advisor); Natalie Kruse Daniels, PhD (Committee Member); Ben Stuart, PhD (Committee Member); Eung-Seok Lee, PhD (Committee Member); Aaron Jennings, PhD (Committee Member); Gayle Mitchell, PhD (Committee Member)

Subjects:

Civil Engineering; Environmental Engineering; Sustainability

Keywords:

Acid mine drainage; AMD; steel slag leach beds; electrolysis; pigment recovery; sustainability assessment; multi-criteria decision analysis; PHREEQC; geochemical modeling

Schleich, Katharine L.Geochemical Modeling of Processes Affecting Water and Sediment Chemistry and their Relationship to Biological Recovery in an Acid Mine Drainage Remediated Stream
Master of Science (MS), Ohio University, 2014, Geological Sciences (Arts and Sciences)
The Hewett Fork watershed in Southeastern Ohio is impacted by AMD from the AS-14 mine complex in Carbondale, Ohio. In attempts to remediate the stream, the water is being treated with continuous alkaline input from a calcium oxide doser. While the section of watershed furthest downstream from the doser is showing signs of recovery, the water chemistry and aquatic life near the doser are still impacted. The objectives of this study are to evaluate the alkalinity and acidity budgets of the main stem of the stream and examine and model the chemistry of main stem and the tributaries of Hewett Fork. By examining the inputs of tributaries into the main stem, the project aims to understand processes occurring during remediation throughout the entire stream system. Chemical analysis of water and sediment samples, XRD identification of minerals, and geochemical modeling using the PHREEQCI program have been applied to understand the chemical processes happening in the Hewett Fork watershed. Results show that the minerals ferrihydrite, goethite, calcite, diaspore, gibbsite, and gypsum form when the acidic waters mix with CaO in equilibrium with CO2 and O2 in the air, transferring the contaminants from the water to the sediments. While these processes contribute to improvements in water chemistry, the precipitation and deposition of metals inhibits biological recovery downstream of the doser. When examining the recovery of an acid mine drainage remediated stream, the inputs of contaminants, the transport of sediments, and the complex reactions between the water and sediments need to be considered together to understand how the variations in stream chemistry affect the biology of the stream.

Committee:

Dina Lopez (Advisor); Natalie Kruse (Committee Member); Elizabeth Gierlowski-Kordesch (Committee Member)

Subjects:

Environmental Geology; Geochemistry

Keywords:

acid mine drainage; AMD; Hewett Fork; remediation; geochemical modeling; PHREEQCI; sediment mineralogy