Nutrient Symposium 2017, June 11-14, Fort Lauderdale, FL, USA Implementation of an External Selector to Improve the Stability and Nutrient Removal of Aerobic Granular Sludge with Low-Strength Municipal Wastewater Rasha Faraj, Belinda Sturm, Theresa Amante and Mariela Mosquera Department of Civil, Environmental and Architectural Engineering, The University of Kansas, 1530 West 15 th Street., Lawrence, KS 66045, USA Abstract: Low-strength wastewater with high fractions of particulate matter can be a challenge for the applicability of aerobic granular sludge technology in the United States. Development of filamentous growth takes place at low readily biodegradable substrate concentrations. This can affect the structure and settleability characteristics of aerobic granular sludge. In this project, selective wasting of flocs and fine particles was implemented to retain fast-settling and dense granules, which eventually lead to improved treatment performance. The selective wasting was achieved by sieving sludge through 0.2 mm opening screens. A 70-L aerobic granular reactor (AGR) was operated at the Lawrence Wastewater Treatment Plant in sequencing batch reactor regime. The findings of this work revealed that applying selective wasting successfully stabilized granular sludge and nitrification. The results showed that the application of short settling times to form aerobic granular sludge resulted in elevated ESS and the low-strength wastewater with a large fraction of particulate COD selected for filamentous granule structures and fines; that entrained granules and caused short SRTs. Selective wasting external to the settling time and effluent washout provided a mechanism to remove slow-settling particles and retain dense structures. Keywords: Aerobic granular technology, low-strength municipal wastewater and external selector. Introduction: Aerobic granular sludge technology has become a promising technology to maximize nutrient removal and treatment capacity for industrial and municipal wastewater. This wastewater treatment application has successfully been implemented for full-scale under the product name of Nereda. However, relatively high -strength wastewater was applied at previous operations (880 mg COD/L for Epe, the Netherlands and 506 mg COD/L for Garmerwolde, the Netherlands) (Pronk et al., 2015). Moreover, past studies have focused on implementing this treatment for wastewater with high substrate concentration (Adav, Lee, Show, & Tay, 2008; Bassin, Kleerebezem, Dezotti, & van Loosdrecht, 2012). Within the United States, municipal wastewater is typically low strength with a predominantly particulate substrate, which is challenging for aerobic granule formation. WEF Nutrient Symposium 2017 Copyright© 2017 by the Water Environment Federation 461