Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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Quagga Mussels (Dreissena bugensis) are an invasive species of mollusk that have established themselves within the Colorado River system of Arizona since 2007. However, despite close proximity and frequent travel by recreational boaters between reservoirs, they have not yet infested the Salt River or Verde River systems. Laboratory experimentation was done to test the survival rate of adult D. bugensis specimens in waters collected from Bartlett Lake (Verde River), Saguaro Lake (Salt River), and Salt River Project (SRP) canals (Salt River/Verde River/Colorado River blend) as well as Central Arizona Project (CAP) canals with the addition of turbidity to simulate high runoff storm events. Under each condition, adult survival for a time period of 21 days exceeded 98%, ruling out water chemistry or turbidity as a factor. Spawning was investigated using mussels collected from Lake Pleasant in August 2015. In 4 trials of serotonin dosage between 0.5 – 1.0 mMol, spawning was not successful. Calanoid copepod predation was also investigated by field sampling at Lake Pleasant, Saguaro Lake, and Bartlett Lake during September 2015. Calanoid copepods were identified in Lake Pleasant at a density of 104.22 individuals per cubic meter at a depth of 2 meters and 9.75 individuals per cubic meter at the surface. Calanoid copepods were not found in Bartlett Lake or Saguaro Lake, ruling out copepod predation as a factor. Finally, dissolved oxygen and temperature trends were analyzed in each reservoir. While temperature profiles are similar throughout the year, seasonal drops in dissolved oxygen below survivable concentrations for D. bugensis has been observed in both Saguaro Lake and Bartlett Lake but not Lake Pleasant, representing the most plausible explanation for no observed infestation.
ContributorsSokolowski, Matthew (Author) / Fox, Peter (Thesis advisor) / Abbaszadegan, Morteza (Thesis advisor) / Alum, Absar (Committee member) / Arizona State University (Publisher)
Created2015
Description
Factors affecting biofilm development, specifically the materials of the pipe, were investigated. Two laboratory scale bioreactor systems were constructed to study biofilm formations: a pipe loop bioreactor with continuous flow at 10.1 liters per minute (LPM), and a tank bioreactor under stagnant conditions with a minimal flow of 0.0095 LPM. The continuous flow bioreactors were constructed using cross-linked polyethylene (PEX), copper, and galvanized steel pipes. The tank bioreactors consisted of glass chambers containing coupons made from the pipe materials, as well as glass microscope slides. Municipality tap water was used in the experimentation, with no nutrients added. Legionella pneumophila was spiked into all the pipe loop bioreactors, and only in one tank bioreactor. Detection of heterotrophic bacteria, coliforms and Legionella using tryptic soy agar (TSA), Brilliance, and buffered yeast charcoal extract (BYCE), respectively. Over ten weeks, biofilms were developed on PEX, copper, and steel, in the pipe loop bioreactors and the tank bioreactors. Heterotrophic bacteria were detected in all systems; however, no coliforms were detected, and Legionella pneumophila was only detected on a coupon in the copper pipe loop bioreactor, as measured by bacterial concentration on test materials. In the tank bioreactors, biofilms developed the most rapidly on PEX, followed by galvanized steel, and finally copper. Out of the four materials, copper had the lowest bacterial growth, which can be ascribed to the bactericidal impact of copper ions on the bacterial cells attaching to the copper surface. After biofilm aging, higher bacterial colonization on copper and accumulation of dead bacterial layer on the surface may act as a protective barrier against copper ions. Bacterial densities in the biofilm reached a high concentration of 1.40 x 105 CFU/cm2 on the PEX pipe loop bioreactor, and 1.05 x 104 CFU/cm2in the PEX coupon in the tank bioreactors. Comparing the turbulent conditions in the pipe loop bioreactors to the stagnant conditions in the tank bioreactor, showed that biofilms formed more rapidly under stagnant conditions, but in larger quantities under turbulent conditions.
ContributorsGreenberg, Samuel Gabe (Author) / Abbaszadegan, Morteza (Thesis advisor) / Alum, Absar (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2021