Senehi, Naomi

Naomi Senehi is a speaker at WEFTEC 2026.

Titles from this speaker

Adopting Emerging PFAS Destruction Technologies: The Orlando SCWO Case Study

Abstract

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.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

11:30:00

11:45:00

Session time

10:30:00

12:00:00

SessionThermal Treatment of PFAS in Biosolids

Session locationMcCormick Place, Chicago, Illinois, USA

TopicContaminants of Emerging Concern & Trace Organics

Author(s)

Senehi, Naomi, Viswanathan, Sudhakar, Garb, David

Author(s)N. Senehi1, S. Viswanathan2, D. Garb2

Author affiliation(s)University Of California Irvine1, 374Water Inc.2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825160135

Volume / Issue

Content sourceWEFTEC

Word count11

Description: Application of Supercritical Water Oxidation for Treating Wastes Contaminated with...

Application of Supercritical Water Oxidation for Treating Wastes Contaminated with PFAS, 6PPD-Q, and Other Emerging Pollutants

Abstract

The rapid emergence of contaminants of emerging concern (CECs) in municipal and industrial waste streams has accelerated the need for treatment technologies capable of achieving verifiable destruction across a broad chemical spectrum. Supercritical Water Oxidation (SCWO) has increasingly been positioned within the landscape of 'thermal technologies,' yet is often compared-sometimes inappropriately-to systems that differ fundamentally in chemistry, operating mechanisms, monitoring requirements, and achievable performance. Current technology comparison studies typically fall into two categories: (1) comparisons to broad-treatment thermal technologies capable of addressing many or most CEC classes, and (2) comparisons to highly specialized technologies designed to target only one or a small subset of contaminants. In both cases, economic or performance comparisons often lack the foundational data needed to be meaningful. For technologies in the first bucket, comparisons are limited because regulatory monitoring and verification requirements differ widely across platforms. Many systems do not require, or are not capable of, collecting mass balance data that confirms true destruction rather than transformation or transfer of contaminants. As a result, economic comparisons fail to reflect the cost of achieving verified destruction. For the second bucket-specialized solutions developed in response to accelerated PFAS regulatory pressure-economic analyses are typically framed around PFAS alone. This narrow focus does not account for the longer-term value of a technology capable of treating diverse CECs such as pharmaceuticals, tire-derived contaminants (e.g., 6PPD-q), industrial organics, and complex waste matrices. Consequently, technology selection is often made without considering the operational and financial advantages of broad applicability. This presentation addresses the gap created by these incomplete comparisons by providing new data that illustrates how SCWO performance varies across waste types and CEC classes with only moderate adjustments to system operating parameters. Because SCWO is frequently and incorrectly grouped with incineration and other thermal destruction methods, this work clarifies the fundamental distinctions in reaction environment, destruction mechanisms, emissions profiles, effluent quality, and monitoring requirements. A detailed overview of SCWO's flexibility is presented through data generated from municipal sludges, controlled laboratory studies using spiked CEC solutions, and blended industrial waste streams. Methods: A series of waste matrices were evaluated to assess the performance of SCWO on eliminating various CECs. The contaminants tested include PFAS compounds in wastewater sludge, analytical grade 6PPD-q, and a pharmaceutical waste blend containing various solvents and organic contaminants. Variables examined include alkaline addition, reactor temperature, operating pressure, mixing intensity, and influent water content. Performance was measured using process indicators-pressure drop behavior, temperature stability, CO emissions, metals content in the liquid effluent-and by assessing physical characteristics of the resulting effluent streams. Analytical measurements of contaminant concentrations in the SCWO influent and effluent were used to determine destruction efficiency. Results PFAS in Sludge: Multiple datasets were generated by treating sludges with various concentrations of PFAS (variations on both a diurnal and seasonal level) via SCWO to determine a range of typical PFAS destruction and removal efficiencies (Figure 1). This commercial scale demonstration which showed >98% DRE for every PFAS compound detected in the influent verified the effective treatment of PFAS in biosolids using SCWO. Additionally, valuable insights on run-time and reliability were realized and allowed for optimization of the unit both mechanically and operationally. 6PPD-q: This project was conducted using a bench-scale SCWO system. The main benefits from first conducting this research at bench scale were (1) resource efficiency and (2) cost-effective identification of conditions to be scaled up to commercial SCWO systems. Analytical results showed a reduction from an inlet 6PPD-q concentration of 18 ug/L to non-detect in both of the two effluent grab samples. Considering the method detection limits of 0.64 and 0.58 ng/L (0.00064 and 0.00058 ug/L), a DRE of >99.99% was achieved. Mixed Pharmaceutical Waste: Two variables were tested – the feedstock blend and the SCWO operating temperature and pressure – to determine how versatile the SCWO system is in treating the waste should the blend vary from batch to batch. The results, using COD as a surrogate for all organic constituents, illustrated that the impact of waste blend and/or SCWO operating conditions was marginal. In all instances, >99% removal of COD was achieved, resulting in a SCWO effluent that was in compliance with the existing industrial site. Significance: The ability of SCWO technology to treat a wide range of contaminants with minimal operating adjustments suggests that the benefits of investing in the technology, may outweigh the higher OPEX of SCWO as compared to traditional waste disposal techniques such as landfilling.

This paper was presented at WEFTEC 2026 in New Orleans, Louisiana.

Presentation time

14:30:00

14:45:00

Session time

13:30:00

15:00:00

SessionFighting PFAS With Fire: Advanced Thermal Conversion for Biosolids Management

Session locationErnest N. Morial Convention Center

TopicBiosolids and Residuals, PFAS, Research and Innovation

Author(s)

Senehi, Naomi, Garb, David, Viswanathan, Sudhakar

Author(s)N. Senehi1, D. Garb1, S. Viswanathan1

Author affiliation(s)374Water Inc., 1374Water Inc., 1374Water Inc., 1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2026

DOI10.2175/193864718825160286

Volume / Issue

Content sourceWEFTEC

Word count17

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