Start-up and Performance Overview of AquaNereda® Aerobic Granular Sludge Technology at Riviera Utilities WWTP at Wolf Creek

The Riviera Utilities Wastewater Treatment Plant at Wolf Creek, located in Foley, Alabama, features North America’s commercial introduction to the AquaNereda® Aerobic Granular Sludge Technology. AquaNereda® is an advanced secondary wastewater treatment process that utilizes the attributes of the granular biomass to provide biological treatment. The aerobic granular sludge (AGS) technology is a batch-based process that creates the proper conditions to develop and maintain aerobic granules: large, dense particles greater than 200 μm in diameter that perform biological nutrient removal (BNR) and display exemplary settleability relative to conventional activated sludge (CAS). The layered microbial community of the granules enable simultaneous nitrification/denitrification and enhanced biological phosphorus removal to occur within the granular biomass. This technology therefore eliminates the need for clarifiers, carrier media, and return sludge pumping stations, as well as selectors or separate compartments for plants looking to achieve BNR. The enhanced settling properties allow the system to operate at a high MLSS in excess of 8 g/L without a loss in aeration efficiency due to the granular nature of the sludge. The AGS process can therefore provide a significant reduction in footprint requirements and energy demand compared to a conventional technology. The AGS process has been implemented successfully for the past 15 years with over 80 wastewater treatment facilities either in operation or under construction worldwide. Introduced to the North American market in 2017, there are now over half a dozen plants operating or under construction in the United States. The first of these installations is the Riviera Utilities Wastewater Treatment Plant (WWTP) at Wolf Creek located in the City of Foley, Alabama. The plant is a municipal treatment facility located near the beaches of the Gulf of Mexico. The discharge point into Wolf Creek eventually flows into Perdido Bay, an Outstanding Florida Waters river and popular destination for water-based recreational activities, which has nitrogen and phosphorus requirements. Not only does Riviera Utilities anticipate similar nutrient limits one day, but a growing population prompted the utility to look into an advanced secondary treatment process to replace the site’s existing oxidation ditches and “future-proof” the facility. The site’s decision to choose the AGS process was prompted by the desire to protect the utility’s rate payers and ensure its investment in their wastewater treatment facility for the next 25 years. Although the site does not have current nutrient limits, the system is designed to achieve effluent TN and TP concentrations of 5.0 mg/L and 1.5 mg/L, respectively. In addition to the AGS WEFTEC 2021 Proceedings process’ ability to provide BNR treatment, the site will be able to significantly increase future treatment capacity within their existing footprint. The AGS system is designed for average and peak flows of 13,250 m3/day (3.5 MGD) and 22,720 m3/day (6.0 MGD, respectively, with room at the site for a future potential average flow of 37,850 m3/day (10 MGD). Expanding the previous 7,570 m3/day (2.0 MGD) oxidation ditch system would have limited the future flow rate to only 13,250 m3/day (3.5 MGD), highlighting the AGS’s significant footprint savings. Riviera Utilities therefore selected the aerobic granular sludge process due to its compact footprint, the system’s inherent capability to meet future nutrient removal requirements, and the anticipated energy savings. Started up in January 2020, the aerobic granular sludge process exceeded expectations with the rapid transfer of flow from the site’s existing treatment system and by meeting effluent limits within one month of start-up. Process optimization during the initial months of operation accelerated granulation and sludge growth rates contributing to continued performance improvements. In addition to an analysis of the start-up and optimization process, the paper provides an in-depth review of the system’s treatment performance and energy use as well as operation during wet weather events in the first year of operation.