Caitlyn S. Butler

Publication Date

Fall 12-2016


Oxygenic photogranules (OPGs) are compact, spherical, self-immobilizing biofilms in the form of dense aggregates of microorganisms with a predomination of filamentous cyanobacteria cultivated from photoilluminated activated sludge. In this study, aerobic and anaerobic nitrogen transformation processes occurring simultaneously within OPGs, during both successful and unsuccessful cultivations, were examined. Chemical analyses including ammonium, nitrate, and nitrite concentrations at the beginning and periodically during OPG cultivations indicated nitrogen transformations occurring during successful cultivations. Additionally, qPCR studies revealed that successful cultivations supported a greater relative abundance of cyanobacteria, nitrifying, and denitrifying populations during the cultivation period. Dissolved oxygen microprofiles within a successfully cultivated mature OPG exposed to light revealed steep oxygen gradients that provide ecological niches for both nitrification and denitrification processes. Although OPGs have been cultivated from a variety of wastewater sources worldwide, it is unclear what parameters determine the success of granule growth from one cultivation to the next. In this study, preliminary evidence supporting the necessity of a minimal initial nitrogen concentration was discovered