Optimization of partial denitrification to maximize nitrite production using glycerol as an external carbon source – impact of influent COD:N ratio Matthew Baideme 1 , Chenghua Long 1 , Luke Plante 2 , Jeffrey Starke 2 , Michael Butkus 2 , and Kartik Chandran 1 1 Earth and Environmental Engineering, Columbia University, 500 West 120 th Street, New York, NY 10027 2 Geography and Environmental Engineering, United States Military Academy, 745 Brewerton Road, West Point, NY 10996 INTRODUCTION: The presence of high concentrations of ammonia (NH3 ) and nitrate (NO3 - ) in industrial waste streams and NH3 in municipal waste streams provides a unique opportunity to harness the capabilities of heterotrophic denitrifying and anaerobic ammonium oxidation (anammox) bacteria. In place of conventional nitrification and denitrification processes, this approach allows for substantial energy and cost savings and needs to be further developed. Thus far, anammox-based wastewater treatment relies on nitritation or partial nitritation to produce nitrite (NO2 - ) for subsequent use as the electron acceptor for anammox bacteria to oxidize NH4 + to dinitrogen (N2 ) gas. Dependent on the waste stream or process characteristics, this approach may be challenging. Herein, we present a novel alternative for NO2 - production from fully nitrified process streams to enable integration into resource-efficient anammox-based biological nutrient removal (BNR) processes (Fig. 1). Critical to this process is the production of NO2 - through partial denitrification (denitratation), or the reduction of NO3 - to NO2 - . Methanol is one of the most widely used external carbon sources for denitrification due to its availability and generally low cost (Lu and Chandran, 2010). With recent increases in methanol prices, several studies have focused on maximizing NO2 - accumulation during denitrification by utilizing different external carbon sources as alternatives (Ge et al., 2012; Du et al., 2016). Additionally, the integration of upstream methanol-fed processes with anammox might be limited by inhibition of anammox bacteria due to methanol (Guven et al., 2005). Glycerol provides a potentially optimal test case as it is similar in cost to methanol, is available as a waste or byproduct (Lu and Chandran, 2010), and has no known inhibitory effects on the anammox process. However, prior to widespread full-scale implementation of glycerol-induced NO2 - production, WEFTEC 2017 WEFTEC 2017 Proceedings Copyright © 2017 Water Environment Federation 1356