Biosolids

Public clean water utilities generate biosolids everyday as they treat the nation’s wastewater, but are limited to only three primary management methods for the tons of biosolids created – land application, land disposal (landfilling) and thermal treatment/incineration via sewage sludge incinerators (SSI). For decades, EPA has supported the public clean water community by developing and updating as necessary regulations pursuant to the Clean Water Act (CWA) to ensure that these biosolids are managed – regardless of which method the community chooses – in a safe, responsible manner.

Municipally derived biosolids have been subject to stringent federal regulatory requirements under 40 CFR Part 503 since the early 1990s. NACWA and its members work to ensure that the Part 503 regulations reflect the latest scientific information, and that EPA remains committed to helping communities preserve a range of management options for biosolids.

Preserving Options for Biosolids Management

Biosolids are nutrient-rich materials that can improve and maintain productive soils, and close to 70% of utilities manage their biosolids through land application, making it the most common management method. The practice of biosolids land application, however, has not escaped scrutiny. While studies over the past 30 years have consistently shown that land application of biosolids, done in accordance with the Part 503 regulations, is protective of public health and the environment, the practice still has its critics. NACWA and its members work with state and federal policymakers to make sure that decisions regarding land application are based on the latest data and risk information to ensure this practice remains as a viable management option.  Many choose to manage their biosolids through disposal in landfills, the second most common management method. Utilities also rely on landfills when their other biosolids management options are not available. Clean water utilities are increasingly facing challenges with this management option as capacity in landfills dwindles, new rules prohibiting landfilling of organic materials and stability arise, and transportation and other costs grow. Each of these issues weigh heavily on utilities, but landfills must remain a viable option for utilities into the future.

Thermal treatment in SSIs is the third major management practice, which reduces the volume of the biosolids, resulting in an ash that is usually landfilled. This practice is the most heavily regulated option with rules under the CWA governing the practice as well as stringent Clean Air Act Maximum Achievable Control Technology (MACT) standards. The complexity and stringency of these air emission requirements, combined with the cost to upgrade existing SSIs, have led many utilities to shutter their SSI units. Despite the sometimes negative image SSIs have with the public and regulators, incineration is a vital management option, particularly in parts of the country where land application and landfilling are not viable or are cost prohibitive. NACWA works to inform EPA efforts to develop and update requirements for SSIs.

Future Challenges

These few options demonstrate the limited management capacity available in the US for the tons of biosolids generated daily by wastewater treatment plants. These management options are narrowing in some areas of the country due to increased public health and environmental concerns over the mere presence of certain chemical contaminants, like per- and polyfluoroalkyl substances (PFAS).

Municipal clean water utilities are passive receivers of a variety of chemicals - meaning these chemicals de facto enter the wastewater treatment process through upstream industrial and domestic (i.e., household) sources that arrive in the raw influent. As a result, municipal biosolids may contain low concentrations of certain pollutants. Regulators and the public must not rush to judgement on the presence of these pollutants and allow the risk assessment and regulatory review processes to work as intended.

NACWA and its members will continue to advocate for the use of all three of these primary biosolids management pathways and explore the practicality of newer technologies and management options that are being researched now. Even the loss of one method would have catastrophic consequences on the clean water community. 

Continued Research and Study Key to Sustainable Management

Similar to the work EPA conducted in the late 1990s and early 2000s for dioxins and furans, EPA must continue its work on assessing the risk posed by chemicals found in biosolids. Analytical methods must be updated on a regular basis and additional data collection, including collecting samples and completing comprehensive risk assessment based on updated toxicity analyses are needed to ensure the biosolids program remains protective of human health and the environment.

Over the next several years, NACWA will be engaging with EPA on its risk assessment efforts, including to address PFAS concerns, and its chemical screening tool to “screen” new chemicals for further review. NACWA looks forward to engaging with the Agency as it seeks Science Advisory Board (SAB) review of its work and evaluates the potential need for changes to Part 503.  

Additional Resources