Nashville Metro Water Services (MWS) is embarking on a long journey to upgrade and expand their biosolids handling facilities at the Central Water Reclamation Facility (CWRF). The project is currently in the basis of design development stage, and several evaluations are underway to define the required scope for the upgrades and expansion. All four biosolids treatment processes at the facility including thickening, anaerobic digestion, dewatering, and drying will be expanded in this project to accommodate an increase in loading from 105 DTPD to 205 DTPD, essentially doubling the capacity. Challenges encountered so far include highly variable influent solids loading to the thickening process, lack of expandability of the existing dewatering and drying buildings, flood protection constraints, and a congested site. Additionally, these project constraints make it challenging to provide streamlined operations with two digestion and dryer buildings being required. Thickening operations hold great influence over the site expansion. The existing Dissolved Air Floatation Thickeners (DAFT) are under-performing and cannot be expanded due to limited available adjacent footprint. Alternate thickening technologies, including Suspended Air Floatation (SAF) and thickening centrifuges, with potentially smaller footprints, are being evaluated to replace the DAFT system. For digestion, the recommendation is to install two additional digesters, to have six total digesters, by 2040 to meet the required solids retention time (SRT) and volatile solids loading (VSL) criteria. If the feedstock concentration can be reliably increased to 5.6% total suspended solids (TSS), five digesters would be adequate to process the required solids in year 2040. Dewatering and drying processes are closely linked due to limited cake storage and physical proximity. The existing building cannot accommodate additional equipment, so a new dewatering and drying building is recommended. This facility will house one DDS-100 dryer as part of Phase 1 which offers sufficient capacity and reserve margin for 2040 peak loads. Two new duty centrifuges, plus one spare, will be installed to support the dryer’s maximum throughput. The Biosolids Facility flooded in 2010 during heavy rainfall equating to the flood of record. The tight site, coupled with significant buried infrastructure around the perimeter of the site, makes installing a floodwall extremely challenging. The team is evaluating different options to protect the facilities from flood waters including localized building hardening, protection of new electrical gear, and ‘off-site’ floodwall to keep flood waters at bay. During this presentation, attendees will gain insights into the basis of design for the Nashville Biosolids Facility with a review of the initial site layouts, process flow diagrams and performance criteria for the expansion.