Redefining FAT in Potable Reuse: The Skinny on CBAT

For many years, reverse osmosis (RO)-based advanced treatment (RBAT) using membrane filtration, RO, and UV advanced oxidation process has been an established standard for treating municipal wastewater effluent to drinking water standards for potable reuse. However, most inland water service providers and others with limitations on RO concentrate disposal will require alternative potable reuse approaches. Building upon the success of the full-scale facility in Windhoek, Namibia, nearly half a dozen years ago, the City of Altamonte Springs' pureALTA project piloted the first carbon-based advanced treatment (CBAT) train for direct potable reuse using ozonation, biological activated carbon filtration (O3/BAC), UF, granular activated carbon (GAC) adsorption, and UV disinfection. This award-winning project offered a market-changing innovative solution to inland utilities looking for sustainable approaches to water augmentation. The yearlong pilot demonstrated the use of several process control measures for optimized performance, such as ozone dose control based on influent total organic carbon (TOC) and nitrite concentration, empty bed contact time in the BAC filter for maximum TOC removal, and analysis of simultaneous removal of TOC and per- and polyfluoroalkyl substances (PFAS) in the GAC adsorber. Challenge testing using non-pathogenic surrogate organisms confirmed log removal values for Cryptosporidium, Giardia, and enterovirus at 10.6-log, 10.6-log, and 12.7-log, respectively, far exceeding the site-specific goals of 3.9-log, 4.2-log, and 11.2-log, respectively. This permanent demonstration facility has also been leveraged for public education and has hosted multiple tours for other water purveyors interested in similar solutions, and the presentation will highlight the cascading effect of the City's bold vision. Similar projects are developing across the US: The City of South Jordan in Utah, and inland utility, is currently piloting a similar treatment train for DPR downstream of membrane bioreactors (MBRs) and working with state regulators to pave the path for potable reuse in Utah. Colorado Springs Utilities' PureWater Colorado Mobile Demonstration Project, a traveling DPR demonstration system, meets stringent drinking water regulations and provided valuable data to the Colorado Department of Public Health and Environment in developing DPR rules for the State. Hampton Roads Sanitation District's SWIFT project in Virginia aims at performing managed aquifer recharge for eliminating effluent discharge to the Chesapeake Bay and mitigating saltwater intrusion, and is advancing the design and construction of full-scale CBAT for over 100 mgd of managed aquifer recharge. Clay County Utility Authority (CCUA) in Northeast Florida is exploring CBAT for indirect potable reuse with groundwater injection at Project Quench to meet future water demands in this growing part of the State, and is constructing a permanent demonstration facility. Polk County Utilities' (PCU) One Water Polk project is exploring CBAT for DPR in their northwest region which has limited groundwater supply. This project is testing the need for pre-treatment for enhanced TOC removal within a CBAT train using enhanced coagulation, and their permanent demonstration facility is currently in operation. The knowledge base generated by comparing the technical and implementation experiences of these projects can be used to inform a robust foundation for wide-spread adoption of CBAT. This presentation will offer highlights for each project, compare technical similarities and differences, and discuss lessons learned in CBAT application for potable reuse. Attendees will learn about the alternatives available to RBAT if brine management is not feasible for their service area, giving them the tools needed to evaluate the feasibility of implementing potable reuse schemes for addressing future water supply challenges.