Senehi, Naomi

Naomi Senehi is with 374Water, based in North Carolina.

Titles from this speaker

Description: SCWO for Orlando: A Case Study on Commissioning Supercritical Water Oxidation for...

SCWO for Orlando: A Case Study on Commissioning Supercritical Water Oxidation for the Treatment of Biosolids to Eliminate PFAS and Reduce Reliance on Biosolids Land Application

Abstract

The City of Orlando, Florida is home to 312,000 people and is one of the fastest growing cities in the U.S. The City is recognized as a progressive, sustainability minded community and has a Water Reclamation Division of the Public Works Department that provides wastewater collection and treatment services to the City's businesses and residents. The Water Reclamation System has historically been divided into the easterly and westerly subsystems. The easterly subsystem is served by the Iron Bridge Water Reclamation Facility, a 40 million gallon per day ('MGD') plant, and the Conserv I Water Reclamation Facility, a 7.5 MGD plant. The westerly subsystem is served by the Conserv II Water Reclamation Facility, a 25 MGD plant. Currently, biosolids from each of the plants are dewatered, stabilized and hauled to land application sites or landfills for disposal. Due to concerns of nutrient contamination of both surface and groundwaters, regulations established by SB 712 restrict this practice during wet weather. Presently, biosolids cannot be applied to land when groundwater is within 2 feet of the surface, and landfills are often hesitant to accept biosolids during these periods. Considering Florida's seasonal pattern of thunderstorm activity and exposure to tropical weather, this happens with regularity, necessitating 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 biosolid 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. With support from the Bipartisan Infrastructure Law emerging contaminant funding, the City received a grant from the Florida Department of Environmental Protection (FDEP) through the Clean Water State Revolving Fund to pilot test a SCWO system capable of processing 6 wet tons of biosolids per day developed by the technology provider 374Water. If the pilot test proves to be successful, FDEP has committed to provide an additional grant to the City for the purchase and installation of a 30 ton per day unit at the City's Conserv I plant. SCWO is a waste treatment technique that 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 compounds like PFAS. The oxidation of organic matter generates energy in the form of heat, which is recycled within the process. The outcome is a treatment technology that transforms biosolids into a contaminant-free, mineral-rich effluent and clean vent gas. 374Water's AirSCWO system utilizes ambient air to supply oxygen, enhancing oxidation efficiency while reducing costs and risks associated with the handling of compressed gases such as pure oxygen or hydrogen peroxide. Its innovative reactor design promotes high velocity to prevent clogging, enhances corrosion protection, and allows for a more compact system. Additionally, the modular, containerized design fits within a 40-foot shipping container, ensuring safety and ease of transport and installation. Pilot-scale demonstrations and numerous lab-scale studies have confirmed AirSCWO's capability to eliminate emerging contaminants like PFAS with over 99.9% efficiency, generating no harmful by-products in the liquid effluent or vent gas. These advancements provide confidence that 374Water's technology is well-suited to meet the biosolids management goals of Orlando's Iron Bridge Water Reclamation Facility. The overarching project goal was to install, commission, and test one of 374Water's AirSCWO 6 units 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 AirSCWO 6 unit, (2) passing functional tests, and (3) continuously processing biosolids that meet volume and organics/PFAS reduction targets. To do so, samples were collected prior to influent wastewater screening, between the end of sludge handling and the AirSCWO 6 inlet, at the effluent of the AirSCWO 6 unit, and at the effluent of the wastewater treatment process (see Figure 1). At each sampling point, relevant parameters including flowrate, chemical oxygen demand, and PFAS (via EPA Method 1633) were assessed and used to evaluate the performance. The extensive sampling plan (Table 1) included baseline testing, system startup testing, and monthly testing. This presentation will explore the opportunities and challenges of conducting an on-site demonstration of an emerging technology, using the implementation of 374Water's AirSCWO 6 at the City of Orlando's Iron Bridge Water Reclamation Facility as a case-study. The discussion will outline the project's background, the City's motivations and planning processes, as well as expectations, risk analysis/mitigation strategies, timelines, and budgeting. 374Water will provide updates on progress toward meeting project goals, address past, present, and upcoming risks, and offer insights on navigating flexible timelines to ensure the successful commercialization of new technologies.

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerSenehi, Naomi

Presentation time

10:15:00

10:35:00

Session time

10:15:00

11:45:00

SessionAdvanced Thermal Processes for Sustainable Biosolids Management: Case Studies and Innovations

Session number25

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicBiosolids treatment, business case evaluation, Hydrothermal Liquefaction, Innovative Technology, PFAS/Emerging Contaminants, Sludge treatment