Transforming Midwest Water Supplies: Lessons from Two Reuse Demonstration Pilots

Population growth, increasing water demands for data centers[sup]1[/sup], and the need for more sustainable water practices are prompting the advancement of next-generation water treatment strategies. One of the areas of key growth in water demands is in the Midwest, where non-traditional approaches to augmenting water supply are relatively new. The concept of addressing this need through water reuse has prompted the formation of several new WaterReuse Association chapters, including in Ohio, Illinois, and Kansas. In context of this move toward integrated water supply planning, utilities are exploring advanced water treatment (AWT) technologies for non-potable and potable reuse applications. One promising AWT approach is carbon-based advanced treatment (CBAT), which integrates ozone, biofiltration, and granular activated carbon (GAC) in a multi-barrier process for converting treated wastewater effluent into high-quality reclaimed water. This configuration is an efficient option for addressing a wide spectrum of water quality parameters (nutrients, microorganisms, organic contaminants, and emerging contaminants) for a variety of reuse applications. In fact, while there are still few full-scale installations, some of the most innovative utilities in the US have explored and implemented the CBAT strategy[sup]2,3[/sup]. To demonstrate the versatility of CBAT in the Midwest, where no regulatory framework for water reuse exists, two pilot studies were conducted. The treatment train included coagulation, flocculation, and sedimentation, followed by ozone, biologically activated carbon (BAC) filters, and GAC filters as shown in Figure 1. Each pilot consistently delivered treatment to meet water quality objectives for potable and non-potable reuse. Results from the pilots are now being used to support integrated water resources planning and to inform future regulatory approaches. Water quality from the pilots was analyzed throughout the treatment train, demonstrating how treatment processes can meet various water quality goals. Lessons learned from pilot operations and performance outcomes will be presented in the context of leveraging reuse as an option in a diversified portfolio of water supply alternatives. [b]Pilot Study 1[/b] Pilot-scale CBAT was evaluated for four months at a conventional activated sludge (CAS) wastewater treatment plant (WWTP) with a permitted average design flow of 10 million gallons per day (MGD) and primarily residential inputs to the collection system. Comprehensive water quality monitoring was conducted across the advanced treatment train, including disinfection byproducts (DBPs), DBP precursors, contaminants of emerging concern (CECs), pharmaceuticals and personal care products (PPCPs), and organic and inorganic contaminants. Additional testing included per- and polyfluoroalkyl substances (PFAS), microplastics, nitrogenous DBPs (N-DBPs), and pathogens. Results demonstrated substantial removal of these constituents as exemplified in Figure 2 for total organic carbon (TOC), which shows the consistent trend in TOC reduction across the treatment train. Overall, there was an 85% reduction in TOC to approximately 1.5 mg/L, which is on the order of typical drinking water concentrations. [b]Pilot Study 2[/b] CBAT was also piloted at a major CAS WWTP that receives residential and industrial waste streams and flow from combined sewers. The facility has a permitted average design flow of 114 MGD and a peak hydraulic capacity of 330 MGD. Like Pilot Study 1, comprehensive water quality monitoring was conducted throughout the treatment train. Additional testing included microplastics, toxicity bioassays, pathogen analysis, and bench-scale hollow-fiber nanofiltration. Results showed similar treatment performance, with unique insights for total dissolved solids management using nanofiltration. Figure 3 shows effective treatment of low levels of 1,4-dioxane, a CEC present in the pilot feed, to below the Environmental Protection Agency (EPA) health advisory level of 0.35 µg/L. These pilot efforts have supported the collection of valuable data to validate the effectiveness of CBAT for AWT in the Midwest, with findings informing areas for future research focus at each facility. Performance data from both pilots can be used to support permitting, design, and long-term operations planning for various reuse scenarios. A key benefit of these pilots was the engagement of operators, regulators, and other key stakeholders to familiarize them with water reuse and AWT. There were multiple outreach and public engagement opportunities at each pilot with regular tours of the facility. This provided the opportunity for stakeholders to see the CBAT system in action, facilitating conversations about the merits and application opportunities for AWT alongside governance and regulatory development for reuse in the Midwest. Pilot tours have been important in building trust in technologies that are new to the region during the early stages of reuse initiatives[sup]4[/sup]. This presentation will provide an overview of the regulatory status of reuse in the Midwest and a discussion of why pilot testing AWT technologies is an important factor in building stakeholder support. Data from the pilots will be presented along with a summary of key considerations for advancing reuse in various non-potable and potable applications in the context of emerging water demands in the Midwest.