Abstract
National Pollution Discharge Elimination System (NPDES) permits are becoming increasingly stringent for both ammonia and total nitrogen. While traditional nitrification processes are generally reliable, nitrification’s heavy oxygen demand contributes to large electricity budget expenditures. In addition to becoming a detriment to community “wallets,” adverse effects are measured in the environment; electricity production is the second leading source of CO2 emissions globally. Moreover, when total nitrogen removal is required, incomplete denitrification can result in N2O emissions, depending on carbon availability. Research is being conducted at the University of Idaho in the Department of Civil and Environmental Engineering to investigate alternate biological nitrogen removal strategies that can potentially mitigate both concerns. Specifically, a shortcut nitrogen removal mechanism, known as nitritation has been identified as viable process options to offer aeration savings and potentially reduce N2O emissions. Applying aeration control strategies, nitrogen removal mechanisms were studied at a macro and molecular level, with the aim to provide critical insight for process implementation. Sequencing batch reactors (SBRs) aimed at achieving nitritation and nitrification were studied. Nutrients, pH, quantitative polymerase chain reaction (qPCR), real time qPCR, and other metabolic tools were utilized to distinguish between processes and to verify nitrogen removal activity within each SBR. A detailed investigation of structural and functional molecular level differences between nitritation and nitrification was conducted. The aim of these investigations are to provide insight to further specify operational criteria to achieve and sustain nitritation.