A (Nearly) Full Public Reuse Regional Utility Evaluates Potable Reuse as an Alternative Water Supply

Clay County Utility Authority (CCUA), serving the greater Clay County area in Northeast Florida, is a substantial water and wastewater service provider catering to 55,000 customers. The County is growing rapidly and is expected to double in population in the next 20-25 years. CCUA operates 7 Water Reclamation Facilities, five of which produce public access reclaimed water, and 22 water treatment plants. CCUA is situated in a region with limited groundwater resources. In response to the growing need to allocate water resources efficiently and limit groundwater withdrawals from the Floridan aquifer, the primary source of water supply, CCUA has embarked on a PAR optimization program while concurrently investigating alternative water supply (AWS) solutions such as potable reuse. Currently operating at 70% water reuse (non-potable reuse, known as public access reuse or PAR), CCUA is committed to achieving 100% PAR by 2030, and is evaluating potable reuse as an alternative water supply to expand the water portfolio. CCUA's potable reuse project is called 'Project Quench,' which uses reclaimed water (tertiary treated filtered and disinfected wastewater effluent) as source water for treating to drinking water standards. While there are other water sources in the area, such as surface water from the ocean, the St. Johns River and Black Creek, and stormwater, reclaimed water remains the most reliable from a quality and quantity perspective. Potable reuse takes careful early planning and piloting to demonstrate the feasibility of treatment techniques and multi-barrier treatment. With this goal, CCUA has completed several steps in the long-range planning efforts for potable reuse:

*Source Water Characterization: A comprehensive water quality sampling program was conducted at several of CCUA's interconnected treatment plants producing reclaimed water, which allowed an understanding of the quality and composition of available sources to ascertain their suitability as an AWS. Sampling was conducted for several regulated and unregulated contaminants, such as perfluoroalkyl substances and chemicals of emerging concern and pathogens. Data suggested that the Mid-Clay Water Reclamation Facility's reclaimed water was best suited for potable reuse from two perspectives: (i) proximity to areas of growth/development and the anticipated increase in water demand in the near future, and (ii) quality of reclaimed water due to lack of industrial wastewater contribution in the collection system and superior wastewater treatment. Reclaimed water quality at this facility averaged (n=4) at 2.5 mg/L total organic carbon (TOC), 350 mg/L total dissolved solids (TDS), 6.6 ng/L perfluorooctanoic acid (PFOA), 2.2 ng/L perfluorooctanesulfonic acid (PFOS), and 1.8 mg/L total nitrogen. Figure 1

*Selection of Treatment Train: Several factors were considered in the process of selecting the optimal treatment barriers for potable reuse at CCUA. These factors included the efficiency of treatment in removing pathogens and chemicals, associated treatment residuals handling, operational complexity, ability to permit a potential future facility, and cost considerations. Two primary treatment types were compared: reverse osmosis-based advanced treatment (RBAT) and carbon-based advanced treatment (CBAT). The selected processes to treat reclaimed water to drinking water standards include ozonation, biologically activated carbon (BAC) filtration, ultrafiltration (UF), granular activated carbon GAC) adsorption, UV disinfection, and chlorine disinfection. The table below shows the results of the different factors considered during process selection. Figure 2 Figure 3

*Design/ Construction, Test Plan, and Commissioning: Potable reuse project planning involves the development of a comprehensive roadmap encompassing design, construction, meticulous testing protocols, and commissioning stages for the potable reuse system. A 20 gallons per minute (gpm) demonstration pilot is currently under construction at the Mid-Clay Water Reclamation Facility site. Construction completion, facility startup, and commissioning will occur in the first quarter of 2024. Figure 4 Public Outreach A key component of potable reuse projects is the early engagement of internal and external stakeholders with clear and consistent messaging. During the facility's construction phase, CCUA developed several public engagement products, including a project website, handouts and brochures, a PowerPoint presentation slide deck, infographics for the pilot facility building, school and classroom resources, and a project video. Having a uniform theme for Project Quench and using clear, consistent, and correct messaging set CCUA up for success in communicating project details, its current investigative stage, and its future. Figure 5 The demonstration facility/evaluation of potable reuse is one element of CCUA's One-Water water supply planning approach. This abstract and presentation will encapsulate Project Quench's stages of comprehensive evaluation, outlining CCUA's vision to leverage reclaimed water as a superior AWS while navigating the complexities of water source integration and quality assurance.