Addressing the Growing Challenges of Biosolids Management: How 374Water’s AirSCWO Provides a Sustainable Solution

Wastewater treatment is essential to everyday life, but managing the byproducts presents significant challenges to municipalities. One of these byproducts is biosolids - nutrient-rich organic materials left over after treating sewage sludge. While biosolids can be beneficial when treated and reused appropriately, it can also pose environmental and health risks due to contaminants such as heavy metals, pathogens, pharmaceuticals, and harmful chemicals like PFAS (per- and polyfluoroalkyl substances). Traditionally, biosolids have been land-applied as fertilizer, disposed of in landfills, or incinerated, but these practices are under increasing scrutiny due to concerns about environmental contamination and potential human health impacts. As states and municipalities reevaluate these methods, the need for sustainable and effective alternatives is becoming more urgent.

374Water's AirSCWO system is an excellent solution for sludge management due to its ability to efficiently destroy or reduce waste volume while minimizing environmental impact. The process transforms sludge into clean water and non-toxic byproducts which do not require further management, eliminating the need for further treatment or disposal of harmful residues. AirSCWO operates with low energy consumption and requires minimal operational maintenance, making it a cost-effective and sustainable option for managing biosolids. Its scalability and versatility make it suitable for a wide range of waste treatment facilities, providing an efficient and environmentally friendly alternative to traditional sludge management practices.

Approaching biosolids management from a new paradigm has widespread impacts on the economy and the perception of government by rate payers. Ultimately, sticking to traditional biosolids management approaches, such as land application, landfilling, and incineration, are increasingly becoming economically inefficient, which burdens ratepayers and local economies. Costs associated with environmental remediation (contamination of soil and water and air pollution) and the healthcare costs incurred by exposure to environmental contaminants are increasingly on the shoulders of local governments. In addition, these issues foster tension and mistrust between ratepayers and the government. The financial burden of these outdated methods falls on ratepayers through higher utility bills and taxes, diverting funds from more innovative and environmentally responsible alternatives, such as resource recovery and nutrient recycling. Moving away from these traditional approaches toward more sustainable waste destruction solutions would drive long-term economic benefits, reduce environmental liabilities, and lower costs for the public.

Biosolids in the U.S.: A Growing Challenge with the Decline of Traditional Waste Treatment/Disposal Methods

According to the U.S. Environmental Protection Agency (EPA), in 2022 approximately 7 million dry tons of biosolids were generated by wastewater treatment plants in the U.S. Biosolids management practices are primarily distributed as follows: 56.0% are land applied, 27.0% are landfilled, 16.0% are incinerated, and 1.0% are managed through other methods. The majority of biosolids are managed through land application, a practice that carries significant risks due to concerns over PFAS and other contamination in the environment.

Source: US EPA

Each traditional disposal method faces significant challenges in today's evolving regulatory and environmental landscape.

• Land application: Land application of biosolids as fertilizer and for nutrient recycling has been practiced and supported by the federal government since 1993, with the publication of the 40 CFR Part 503 Standards for the Use or Disposal of Sewage Sludge. However, the presence of contaminants like PFAS, pharmaceuticals, plastics, and heavy metals raises serious questions/concerns about the safety of this practice, especially when applied to agricultural land where crops are grown for human consumption. In fact, studies have found that these contaminants can seep into groundwater, accumulate in soil, and enter the food chain. Sewage sludge disposal through land application accounts for approximately 56% of the total volume of biosolids disposed of in the US in 2022.
• Landfilling:Landfilling biosolids is a growing issue in the U.S. due to limited capacity, rising costs, PFAS contamination concerns, and regulatory restrictions. Landfilling biosolids has become an increasingly costly and difficult disposal method for biosolids due to concerns over liability from leachate contamination and greenhouse gas emissions. Biosolids decompose in landfills, releasing methane, a potent greenhouse gas through fugitive emissions. Additionally, if biosolids have elevated levels of contaminants such as metals and PFAS, concerns about contamination of the landfill leachate arise. Landfill leachate is another major issue for landfill operators because it contains a complex mixture of hazardous chemicals, including heavy metals, organic compounds, and pollutants, which can contaminate surrounding soil and groundwater if not responsibly managed. For the time being, this disposal method is still widely used as approximately 27% of the total volume of biosolids in the US in 2022.
• Incineration: Incinerating biosolids is a costly process due to its high energy cost. In the future, this practice may increase in price both due to litigation and new air pollution control device requirements as concerns are being raised over the emission of incomplete combustion products and contaminants such as PFAS. While incineration reduces waste volume, the ash produced still requires disposal, often in landfills, and may also release harmful contaminants into the landfill leachate. While incineration is still one of the most common disposal methods, it accounts for a smaller share of the biosolids volume with approximately 16% of the total volume of biosolids in the US in 2022.

State and Federal Regulations: The Impact on Humans, Farm Animals, Agricultural Products, and Water

The land application of biosolids has become a focal point in discussions about environmental and public health due to its potential risks to humans, farm animals, agricultural products, and water systems. High-profile incidents, including contamination in farm products such as milk and beef, have highlighted the risks associated with biosolids application, particularly when originating from industrially impacted wastewater. For example, PFAS contamination in biosolids has been linked to the bioaccumulation of these chemicals in farm animals and subsequent entry into the food chain. This has raised alarms over potential human exposure through consumption of contaminated food products and drinking water sourced from contaminated aquifers.

In Maine, farmers began to find elevated levels of PFAS in their milk and meat production in 2016. Initially, a third-generation dairy farmer discovered cows were exposed to PFAS-contaminated soil from industrial impacted biosolids that had been spread on his fields as fertilizer decades earlier. Many other dairy and meat farms in the state then yielded the same result, rendering the animal products unsafe for consumption and forcing the farmers to halt their milk and meat production. This incident raised alarms about the potential for contaminants to enter the food supply through biosolid application and prompted a statewide examination of biosolids usage. In 2022, Maine enacted a ban on land application and sale of biosolids containing detectable levels of PFAS, becoming one of the first states to take direct and proactive action against the potential environmental and health hazards posed by biosolid use on agricultural land.

Other states are following Maine's lead and enacting policies to either limit or ban the land application of biosolids, to protect both the environment and human health.

In October 2024, Connecticutbecame the second state to fully ban the land application of biosolids. PFAS-containing biosolids or wastewater sludge are prohibited from being used or sold in the state.

In January 2024, Michigan updated its requirements for PFAS testing in biosolids before they can be applied to land. If contaminants exceed certain safety thresholds, biosolids are disqualified from land application, increasing pressure on municipalities to adopt alternative treatment methods, such as AirSCWO, to manage these biosolids effectively. Some large cities are shipping their biosolids to Canada for disposal due to limited in-state management options and stringent local regulations. This practice is driven by the lack of cost-effective and comprehensive solutions, leading municipalities to rely on out-of-state solutions, despite the logistical and environmental challenges associated with transporting biosolids across borders.

In Texas , concerns over PFAS contamination from biosolids have escalated following reports of livestock deaths in Johnson County where ranchers linked the deaths of cattle and other animals to biosolids-based fertilizers containing PFAS "forever chemicals." These incidents have sparked lawsuits against biosolid producers and wastewater treatment companies, with claims that they knowingly distributed contaminated fertilizer without adequate warnings. Despite these legal actions, Texas does not currently require PFAS testing for biosolids before land application, leaving farmers and ecosystems vulnerable. Lawsuits are currently (2024) underway by individuals, such as those in Johnson County, which may pave the way for preventing further contamination and protect agricultural livelihoods.

In Indiana , biosolids management has also come under scrutiny as the state deals with PFAS contamination. While there are currently no state-level regulations specifically addressing PFAS in biosolids, environmental advocacy groups and communities have raised alarms about the potential risks. A 2024 lawsuit was launched by Attorney General Todd Rokita against 22 companies, including 3M and DuPont, for allegedly concealing the dangers of PFAS in their products. The lawsuit seeks damages for cleanup and remediation, highlighting the widespread environmental and health risks posed by PFAS chemicals.

In Florida , the state has been increasingly criticized for its biosolid disposal practices due to their impact on water quality. In response to the nutrient pollution caused by these practices, Florida introduced new biosolids regulations in 2020, as outlined in House Bill HB 1405, and updated them in 2021. These regulations impose stricter limits on the land application of biosolids, previously a primary disposal method, and enhanced monitoring to prevent harmful algal blooms. Consequently, many Florida municipalities now face the challenge of transporting biosolid waste long distances to out-of-state landfills, significantly increasing their disposal costs. With landfills gradually refusing biosolids and tipping fees rising, the urgency for alternative sludge management solutions has intensified, creating a perfect storm in the Florida regulatory landscape.

In California, the majority (~60% by mass) of biosolids are land applied with restrictions and bans applying on a county wide basis. As of 2022 over half of the counties in CA have restrictions on land application: three counties ban biosolids land application completely, six counties ban Class B biosolids land application, and 28 counties land apply according to conditional use permits. Although land application is currently the most common management method in CA, several contracted biosolids management partners are facing PFAS litigation challenges that jeopardize the long-term viability of this practice. CA faces additional challenges imposed by the enactment of SB 1383 in September 2016, which mandates 75% diversion of organics (including biosolids) by 2025. This calls for a revised management strategy for biosolids that are currently being landfilled and used as alternative daily cover (~15% by mass of all biosolids produced).

At the national level, regulations for PFAS in drinking water were promulgated by the EPA in 2024. Biosolids are currently under the pre-regulation risk assessment phase. However, according to the EPA's strategic roadmap, the biosolids risk assessment will be published by the end of 2024.

Exploring Sustainable Solutions: How 374Water's AirSCWO Technology Can Help Address these Issues

As states tighten regulations on biosolid disposal, restrict land application, reduce reliance on landfilling, and approach incineration with caution, the demand for sustainable solutions such as AirSCWO becomes increasingly evident.

374Water's AirSCWO technology is a promising solution to convert wastewater sludges and biosolids into contaminant-free water and minerals. AirSCWO effectively destroys organic material, including wastewater solids and any PFAS entrapped within them, by harnessing the power of supercritical water oxidation (SCWO). SCWO is a physical-thermal process powered by water above its critical point (374 degrees Celsius and 221 bar) and air that yields a highly effective oxidation reaction, which indiscriminately eliminates nearly 100% of organic contaminants (e.g., PFAS, microplastics, pharmaceuticals, etc.) including the sludge.

374Water's AirSCWO technology has several notable advantages:

1. Complete Destruction of Contaminants: AirSCWO mineralizes harmful contaminants, including PFAS, pathogens, pharmaceuticals, and plastics. The process effectively breaks down these compounds at a molecular level, leaving behind clean water and inert minerals that can be repurposed or disposed of safely.
2. Reduces Waste Volume Significantly: AirSCWO reduces biosolid waste volume, turning it into a fraction of its original mass. The remaining minerals are safe for reuse or disposal, reducing landfill usage and disposal costs.
3. Energy Efficiency and Heat Recovery: The AirSCWO process is energy-efficient, generating heat that can be recovered and reused to support other energy needs. This makes the technology not only environmentally sound but also cost-effective for municipalities and industries.
4. Eliminates Need for Land Application, Landfilling, and Incineration: By safely processing biosolids into clean water, minerals, and recoverable heat, AirSCWO eliminates the need for land application, landfilling, and incineration. This helps prevent contamination of soil and water, avoids air emissions issues, and reduces costs and liability.

374Water's AirSCWO system is making significant strides in biosolids management and destruction, starting with its first installation at the Iron Bridge Water Reclamation Facility in Orlando, Florida. Beyond Florida, 374Water is collaborating with Orange County Sanitation District in California to expand the use of AirSCWO, aiming to improve waste treatment nationwide. In addition, 374Water recently launched its Waste Destruction-as-a-Service (DaaS) offering to greatly reduce the capital and operating cost burden associated with the management and destruction of biosolids and other waste streams.

374Water's AirSCWO system is a highly effective solution for sludge management due to its ability to drastically reduce waste volume, eliminate harmful byproducts, reduce greenhouse gas production, and operate with low energy consumption. This advanced technology provides an efficient, scalable solution for treating and mineralizing biosolids, addressing key regulatory goals related to PFAS contamination and broader waste management challenges. Finally, 374Water's AirSCWO system is a versatile and sustainable choice for waste facilities across the United States and the rest of the world.

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