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Full-Scale Case Study of Aerobic Digestibility of Conventional Activated Sludge versus Nereda© Aerobic Granular Sludge in Colorado’s Mountain West

Authors: Michael Katalinich, James Cochran, Emily Godi, Casey Johnston

Abstract:

The 0.995 MGD water resource reclamation facility (WRRF) in Idaho Springs, Colorado, has operated a dual reactor and full-scale sludge removal aerobic granular sludge (AGS) system since June 2021. Before the AGS system was installed, the existing WRRF had a hydraulic capacity of 0.60 MGD and ran as an SBR system with jet aeration and post-equalization. This included two SBRs with a total volume of over 750,000 gallons operating with anoxic and aerated zones being both mixed and aerated by jets and decanted through stainless-steel decanters. The SBR system always performed well and did not exceed discharge permit limits, but it did not have sufficient treatment capacity for future flows. The facility implemented AquaNereda’s © AGS technology to reduce settling time and improve nutrient removal efficiency, as well as to increase hydraulic and organic load capacity. This study compares the overall aerobic digestibility of AGS waste activated sludge (WAS) versus conventional activated sludge (CAS) from a sequencing batch reactor (SBR). The Idaho Springs WRRF has two 250,000-gallon aerobic digesters set in series equipped with mechanical mixing and coarse-bubble diffusers. A minimum of 38 percent or more volatile suspended solids (VSS) destruction is required to achieve Class B biosolids per EPA Part 503 Biosolids Rule. The design basis was 60-day solids retention time (SRT) at 15 degrees Celsius and approximately 40 percent VSS destruction. Operational data was analyzed before the improvements, during startup, and throughout full-scale operation in order to gauge the operating efficiency and digestibility of the AGS waste and will be presented.

Keywords: AquaNereda, Nereda, AGS, aerobic granular sludge, digester, aerobic digestion, waste activated sludge, activated sludge, WAS, SBR

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