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Item Biocorrosion of copper by Oleidesulfovibrio alaskensis G20 biofilms in static and dynamic environments(Montana State University - Bozeman, College of Engineering, 2024) Keskin, Yagmur; Chairperson, Graduate Committee: Brent M. Peyton; Matthew Fields (co-chair); This is a manuscript style paper that includes co-authored chapters.This study presents a detailed examination of the intricate relationships between Oleidesulfovibrio alaskensis G20 and copper (101), emphasizing three interconnected perspectives: the kinetics of copper toxicity in three distinct media, the impact of surface finishing on microbiologically influenced corrosion (MIC), and the interaction of G20 biofilms and copper in CDC biofilm reactors. Initially, the study concentrates on the kinetic effects of copper toxicity on the growth of G20. The research meticulously quantifies the detrimental impact of different copper (II) concentrations (6, 12, 16, and 24 micron) on bacterial growth kinetics in three media: LS4D balanced (BAL), electron acceptor-limited (EAL), and electron donor-limited (EDL). Using a non-competitive inhibition model, I50 (concentrations of copper causing 50% inhibition of bacterial growth) values were calculated to be 13.1, 13.87, and 11.31 micron for LS4D BAL, EAL, and EDL media, respectively. The second part of the study shifts its focus to the effect of surface finishing on MIC of copper 101 by G20. The biofilm and corrosion pit depths were measured through a series of sophisticated analyses employing 3D optical profilometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX), and X-ray Diffraction Analysis (XRD). The research investigates how different levels of surface roughness, applied through metallographic grinding and polishing, influence corrosion. The findings demonstrate a clear pattern of both uniform and pitting corrosion across all surface finishes. Notably, a statistically significant decrease in corrosion rates was observed when the surface roughness of copper was altered from approximately 13?m to about 0.06?m. Finally, the study explores the interaction between G20 biofilms and copper (101) into CDC reactors to understand biofilm development on copper surfaces and its subsequent impact on copper corrosion in a dynamic environment over periods of 7, 9, and 14 days. The results showed robust biofilm formation through hexose and protein analyses and SEM images displaying progressive increases in SRB cell accumulation over time. Localized pit depths were measured and compared to static conditions, and pits showed only a 20% increase in a dynamic environment. These findings offer an improved understanding of the complex interactions between G20 and MIC of copper.Item Biodegradable composite hydromulches for sustainable organic horticulture(Montana State University - Bozeman, College of Engineering, 2023) Durado, Andrew Dalton; Chairperson, Graduate Committee: Dilpreet S. BajwaIn agriculture, mulch helps retain soil moisture and temperature while preventing weed growth. The most common material used for commercial mulching is low-density polyethylene (LDPE). At the end of the growing season, this plastic is typically buried or burned, causing a negative impact on the environment. This project aims to develop an alternative to LDPE mulch that is acceptable for organic farming and biodegradable. The tested hydromulch (HM) treatments contain a mixture of paper pulp, wood fiber, or hemp hurds combined with a tackifier and water. The tackifiers evaluated were guar gum, psyllium husk, and camelina meal, at various concentrations. These treatments were tested for tensile strength, puncture resistance, rain fastness, density, soil adhesion, porosity, and C:N ratio. The results have shown that samples containing tackifiers outperformed the control that contained no tackifier in the strength tests but not in the rain fastness or soil adhesion tests. Paper was the best fibrous material and guar gum was the top performing tackifier. When tackifier blends were considered, an interaction between two tackifiers occurred resulting in a decrease in strength. Blends containing wood fiber and hemp hurds did not show promising results. The puncture resistance of all mulches significantly decreased at 50% moisture level regardless of tackifier type. Some formulations performed well and could be promising in future field trials. The next step will be to examine these formulations outdoors in large-scale field studies.