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Clean tech company 374Water has developed a way to leverage properties of water at high temperature and pressure to destroy poly-and perfluoroalkyl substances (PFAS) and other emerging contaminants. Supercritical water oxidation (SCWO) breaks organic material down to its elemental parts, severing carbon bonds.
February 7, 2023
Clean tech company 374Water has developed a way to leverage properties of water at high temperature and pressure to destroy poly-and perfluoroalkyl substances (PFAS) and other emerging contaminants. Supercritical water oxidation (SCWO) breaks organic material down to its elemental parts, severing carbon bonds. While SCWO is not new, the company says its technology, branded as AirSCWO, is differentiated from others in that it can treat any organic material and ultimately generate clean water and clean energy. AirSCWO has been found effective on biosolids, leachate, and industrial manufacturing wastes.
The company that launched in 2018 has so far landed a contract with a California municipality, a Texas-based real estate investment and development firm and will soon run a demo for the U.S. Navy.
Supercritical water oxidation occurs when water reaches 374 Celsius and 221 bar pressure, so the process is like a “pressure cooker on steroids” says Steve McKnight, 374Water Strategy & Government advisor.
In that environment the water acts as a solvent; all organics are oxidized, and the chemical bonds are broken.
Waste is fed into the left side of the unit where oxidation occurs. The effluent comes out on the right side, which is about two-thirds liquid of distilled water quality and one-third brackish water with the minerals settled out.
Heat generated through the process is recovered and used to run the system. And phosphorous in effluent can be made into fertilizer.
The first application under investigation was treatment for biosolids and sludge at wastewater treatment plants. The R&D took place at Duke University in Durham, NC with $6M in funding from the Bill & Melinda Gates Foundation. The technology is a spin out of that research, which was led by Marc Deshusses, a professor at Duke, who went on to become a co-founder of 374Water, where it was finetuned and commercialized, with the systems manufactured by Indiana-based Merrell Brothers, a large biosolids management company.
Today the main focus remains the municipal wastewater industry where emerging contaminants in biosolids are not treated effectively by the existing wastewater infrastructure.
The team is homing in on PFAS, and looking beyond the wastewater sector, seeing a lot of promise as these “forever chemicals” become regulated.
The U.S. Environmental Protection Agency (EPA) has announced a health advisory deeming the amount of PFAS considered safe in the parts per quadrillion. A pending maximum contaminant level is yet to be announced but, once it is, industries watching scrutiny tighten on PFAS believe that utilities and some other operations could become noncompliant overnight.
Now the EPA has proposed designating PFOA and PFOS as hazardous under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), aka Superfund law.
Current and likely future regulations such as these will drive decisions and investments made at the municipal level, with each sector having to address PFAS, McKnight says.
“Now that we can measure these and other micropollutants, we know more about their potential dangers, and SCWO can effectively treat them,” he says, attesting that if the technology can break the fiercely strong carbon-fluorine bond in PFAS and eliminate these compounds it can eliminate any organic contaminant.
Orange County Sanitation District (OC San) in California bought the first commercial-scale unit, slated for deployment in the summer of 2023, to treat biosolids and sludges. The system will initially run 6 wet tons (about 1,600 gallons) a day.
OC San provides wastewater collection, treatment, and recycling for about 2.6 million people within a 479-square-mile area. In 2021-2022 it received an average of 179 million gallons of wastewater a day that’s sent to its treatment plants.
The operation currently converts organic material to gas and kills pathogens in sludge leveraging anaerobic digestion. Solids are pumped to dewatering centrifuges, then hauled off to beneficial land application. But anerobic digestion can’t convert microplastics, PFAS, and other constituents of emerging concern.
“OC San has been following [SCWO] for solids treatment for a number of years. The technology is not new, but 374Water’s approach is simplified and presents an opportunity to convert all complex organic material to more basic and benign compounds like nitrogen, water, carbon dioxide, and mineral salts,” says Rob Thompson, assistant general manager, Orange County Sanitation District.
The agency’s team observed a smaller unit in North Carolina in 2021 and hopes to see it work on a larger scale. If it does, it could potentially change the water and wastewater industry with regard to addressing PFAS, reducing solids processing costs, supporting compliance with air emission requirements for methane and power generation equipment, and increasing energy production, Thompson says.
“The overall objective of this project is to demonstrate continuous processing of municipal wastewater sludge, biosolids, and food slurry while recovering resources [power, nutrients, heat, and reusable water] and simultaneously eliminating emerging contaminants and emerging pathogens. If successful, the 6-ton per day unit can be scaled up to process 30 tons per day,” he says.
EPA’s PFAS Innovative Treatment Team (PITT) has vetted the technology, and 374Water ran its own testing on organic materials from wastewater treatment plants as well as tested landfill leachate.
The effluent streams typically show 99 percent removal for PFAS and other organic contaminants, McKnight says.
Another early customer, Midway, will soon commission the system at a 70-plus-acre, mixed-use development in Texas, where it will treat commercial, industrial, and residential waste at the generation source, bypassing the municipal wastewater treatment plant.
Primary materials to be managed are wastewater, food, and paper.
“This decentralized sustainable solution will work for our mixed-use development because we have enough mass to more effectively deal with our generated wastewater and organic waste on site,” says Brad Freels, chairman and CEO, Midway.
The development has about eight acres of lakes and 25 acres of greenspace that can use the recovered water for irrigation and fertilizer.
In Freels’ eyes, the advantage of this set up to his operation is, “It allows us to continue to be viewed as a leader in our industry, and it provides real community and environmental benefits.”
374Water’s demo for the Navy, funded by the National Defense Center for Energy & Environment (NDCEE), will test efficacy on sorption media and resins from ion exchange, resulting from separating out PFAS. These compounds have been a concern of the Department of Defense (DoD) since their discovery in high concentrations in groundwater under hundreds of military bases, with a large source being aqueous film forming foam used to suppress fires during firefighting training.
No source from the DoD was available for comment, but Howard Teicher, senior director, Government Affairs at 374Water, expressed the startup’s eagerness to work with NDCEE.
“With the DoD citing PFAS investigation and cleanup costs of $1.1B through 2020, and plans to obligate an additional 2.1B after 2022, technologies like AirSCWO will enable the DoD to continue to operate without harming service personnel or the environment," Teicher said in a statement.
Looking ahead, McKnight says the team is thinking about how to fill an anticipated marketplace need for regional destruction centers.
“It might be more effective to ship to regional centers as opposed to deploying on site. Which approach is best depends on the volume of waste and economics of customers. So, we’re looking at both mobile systems and an option where a number of waste streams can be shipped and aggregated for destruction,” he says.
Near-term goals are to deploy the Orange County Sans system; set up for Midway; fulfill the demo project requirements for the Navy; and to target more customers in the municipal wastewater, biosolids, landfill, and industrial spaces.
Freelance writer, Waste360
Arlene Karidis has 30 years’ cumulative experience reporting on health and environmental topics for B2B and consumer publications of a global, national and/or regional reach, including Waste360, Washington Post, The Atlantic, Huffington Post, Baltimore Sun and lifestyle and parenting magazines. In between her assignments, Arlene does yoga, Pilates, takes long walks, and works her body in other ways that won’t bang up her somewhat challenged knees; drinks wine; hangs with her family and other good friends and on really slow weekends, entertains herself watching her cat get happy on catnip and play with new toys.
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