Adopting Emerging PFAS Destruction Technologies: The Orlando SCWO Case Study

Motivation & Goals
The City of Orlando, Florida is a large, fastest growing, progressive, and sustainability minded community. Orlando's Water Reclamation Division of the Public Works Department provides wastewater collection and treatment services to the City's businesses and residents through the Iron Bridge Water Reclamation Facility, a 40 MGD plant, and the Conserv I Water Reclamation Facility, a 7.5 MGD plant. Currently, biosolids from each of the plants are dewatered, stabilized and hauled to land application sites or landfills for disposal. Regulations established by SB 712 restrict this practice during wet weather (when groundwater is within 2 feet of the surface), and landfills are often hesitant to accept biosolids during these periods. This has necessitated on-site dewatering and storage of sludge-a practice the City aims to minimize through the adoption of technologies that can reduce sludge volumes and eliminate reliance on land application.

As a proactive measure, the City is also seeking solutions to address contamination issues, specifically concerning per- and polyfluoroalkyl substances (PFAS), to safeguard water sources potentially impacted by biosolids disposal. After evaluating various management strategies, including composting, incineration, and drying, the City identified supercritical water oxidation (SCWO) as an innovative and cost-effective solution for both biosolids volume reduction and contaminant elimination.

The overarching project goal was to install, commission, and test a SCWO system at the City of Orlando's Iron Bridge Water Reclamation Facility. The measures of success for the project included (1) ensuring the timely preparation of the site and delivery/installation of the SCWO unit, (2) passing functional tests, and (3) continuously processing biosolids that meet volume and organics/PFAS reduction targets.

Methods
The SCWO system used converts organic-rich waste into clean vent gas and liquid effluent composed solely of water, inert inorganics and minerals. During the SCWO process, waste is heated and pressurized above the critical point of water (374°C, 221 bar), allowing it to enter a supercritical state. In this state, organics become highly soluble, facilitating the mineralization of persistent organic compounds like PFAS. The oxidation of organic matter generates energy in the form of heat, which is recycled within the process.

Samples were collected prior to influent wastewater screening, between the end of sludge handling and the SCWO system inlet, at the effluent of the SCWO unit, at the effluent of the plant's wastewater treatment process, and at the air emissions outlet of the SCWO system. At each sampling point, relevant parameters including flowrate, chemical oxygen demand, and PFAS were assessed and used to evaluate the performance. This sampling was conducted at baseline, during system startup, and at regular monthly intervals during system operation.

Results
The City received a grant from the Florida Department of Environmental Protection through the Clean Water State Revolving Fund in February 2024 for upwards of $800,000 (Table 1). After four months of site evaluation and planning, the SCWO provider mobilized the SCWO system to Orlando's Ironbridge facility and completed installation and start-up (including functional tests) within three months. At present, the SCWO system is in its third month of operation and has run multiple types of PFAS wastes including biosolids. Testing is expected to continue through February 2025 at which point an evaluation of whether to demobilize the unit or continue operation will be made (Figure 1). Results from initial PFAS testing reinforce previous research that showcase the ability of SCWO to non-selectively destroy >99% of PFAS analytes (Table 2) of different classes and chain length. Results are repeatable, as shown by data in Table 3 that was collected when treating the same PFAS waste through SCWO the following week.

Significance
This talk will explore the opportunities and challenges of conducting an on-site demonstration of emerging PFAS technologies, using the implementation of SCWO at Orlando's Ironbridge Facility as a case-study. The presentation will highlight key project enablers, including how funding was sourced, to inspire other facilities to support the adoption of emerging PFAS technologies.