374Water Advances the Solution to the World's Growing Biosolids Problem with Successful Factory Acceptance Test for Orange County Sanitation District

374Water breaks barriers with biosolids duration run, and opens a commercial frontier beyond land application, incineration, and landfill disposal.

MORRISVILLE, NC / ACCESS Newswire / June 2, 2026 / 374Water Inc. (NASDAQ:SCWO) ("374Water" or the "Company"), a leading cleantech and environmental services company developing supercritical water oxidation technology for the destruction of organic waste streams, today announced the successful completion of the Factory Acceptance Test ("FAT") for its AirSCWO system as part of its delivery and deployment milestones for Orange County Sanitation District ("OC San").

The FAT completion is a critical milestone activating the next phase of a project that positions OC San and 374Water to deliver a potential solution for the permanent destruction of biosolids contaminated with PFAS ("forever chemicals"), pharmaceuticals, microplastics, and other recalcitrant compounds by converting waste into water, benign minerals, and clean energy.

The Company and OC San have planned for deployment of the system and team in October of this year.

"OC San is excited to see the progress made by 374Water in developing the AirSCWO system. We look forward to receiving the unit and partnering with 374Water to demonstrate the industrial readiness of supercritical water oxidation for the destruction of sewage solids," said Rob Thompson, General Manager of the Orange County Sanitation District.

Development Update

This milestone reflects over three years of focused engineering, collaboration, and continuous improvement by 374Water and OC San.

Throughout the development process, both organizations remained committed to delivering the most advanced, reliable, and scalable biosolids destruction solution possible.

Each design and operational enhancement has aimed to improve:

• Reliability & operability

• Volume throughput and scale

• System durability under demanding conditions

The result is an AirSCWO™ system engineered to meet the real-world demands of large-scale wastewater treatment. 374Water's patented AirSCWO design and technology has already demonstrated its ability to destroy PFAS, pharmaceuticals, microplastics, and other recalcitrant compounds, and can now achieve industry-leading runtime and throughput for biosolids and slurries to unlock enormous value creation in expansive markets and applications.

"This successful operational and technological advancement represents not only a significant project milestone required for deployment to OC San, but an industry breakthrough," said Brad Meyers, Chief Operations Officer of 374Water. "This has been a multi-year journey focused on getting the system right. At every step, we made the deliberate decision-together with OC San-to continue improving the technology so that what we deliver is not just functional, but best-in-class."

Wastewater facilities from Florida to California to Minnesota are facing mounting obstacles to business as usual. The disposal of biosolids is being restricted due to human health concerns. Maine has banned land application all together; municipalities in Florida are limited largely to landfilling due to elevated water tables and loss of suitable agricultural lands; and some districts in California often transport solids hundreds of miles to neighboring States; while many other States and management agencies consider additional restrictions.

With 97% reduction in solids and 99.99%+ destruction of PFAS, together with commercial throughput and industrial validation, this achievement showcases 374Water's potential to address many of the challenges facing the nation's 16,000 wastewater treatment facilities.

Advancing the OC San Partnership

The Company is now coordinating with OC San and contracted partners to finalize required permits to operate our AirSCWO system at the OC San site, in California. 374Water expects to provide updated timing for shipment and startup once permitting and site-readiness milestones are further advanced. This achievement unlocks the ability to progress towards successive milestones and the remaining $3M on the contract as milestones are achieved.

OC San processes over 180 million gallons of wastewater daily, serving more than 2.6 million people across Orange County, California. The agency currently transports over 525 wet tons of Class B biosolids to sites in California and Arizona for agricultural reuse and disposal every day - a practice facing increasing regulatory and environmental pressure.

374Water's AirSCWO system is intended to provide a potential alternative to offsite biosolids transport and disposal. The Company expects field performance, operating reliability, and economics to be key factors in evaluating broader commercial use of the technology.

Technology Validation Drives Commercial Momentum

The OC San deployment represents an important demonstration of AirSCWO technology for municipal biosolids destruction applications. With over 16,000 wastewater treatment facilities across the United States facing mounting pressure to transition away from land application, incineration, and landfill disposal, 374Water believes this milestone demonstrates the technology's readiness to serve a rapidly expanding addressable market.

About 374Water

374Water Inc. (NASDAQ: SCWO) is a cleantech and environmental services company developing supercritical water oxidation technology for the destruction of organic waste streams within the industrial, municipal, and federal markets. 374Water's AirSCWO technology is designed to efficiently destroy and mineralize a broad spectrum of nonhazardous and hazardous organic wastes, producing safe dischargeable water streams, safe mineral effluent, safe vent gas, and recoverable heat energy. 374Water's AirSCWO technology has the potential to assist its customers to meet discharge requirements, reduce or eliminate disposal costs, remove bottlenecks, and reduce litigation and other risks. 374Water continues to be a leader in innovative waste treatment solutions, dedicated to creating a greener future and eradicating harmful pollutants. Learn more by visiting www.374water.com and follow us on LinkedIn.

Forward-Looking Statements

Certain statements in this communication are "forward-looking statements" within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995, as amended. Words such as "anticipate," "believe," "confidence," "could," "design," "estimate," "expect," "intend," "may," "plan," "predict," "project," "potential," or other comparable terminology are intended to identify forward-looking statements. 374Water has based these forward-looking statements on its current expectations, assumptions, estimates, beliefs, and projections. While 374Water believes these expectations, assumptions, estimates, and projections are reasonable, such forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which involve factors or circumstances that are beyond the 374Water's control. These forward-looking statements are subject to risks and uncertainties, including those discussed under "Risk Factors" in 374Water's Form 10-K for the year ended December 31, 2025, and in 374Water's subsequent filings and reports with the SEC. The forward-looking statements herein are made only as of the date they were first issued, and unless otherwise required by laws, 374Water disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events, or otherwise.

Investor Relations Contact

Belton Copp
Vice President
Direct: 401-419-1545
Belton.Copp@374water.com
www.374Water.com

SOURCE: 374Water Inc.