Ecosystems & Environment: Biosolids
In the United States, about 60% of biosolids, the solid residues produced by wastewater treatment, are applied to land as an agricultural amendment. The biosolids supplement the nitrogen and phosphorous as well as the organic carbon in the soil and help crops grow. Many believe that biosolids application is a beneficial use of this material. In 1993 under the Clean Water Act, the U.S. Environmental Protection Agency (EPA) issued regulations governing land application of sewage sludge (biosolids), commonly referred to as the Part 503 Rule. In the Part 503 Rule, biosolids are defined as sewage sludge that has been treated to meet federal and state regulations for land application. In the years since the regulations were issued, wastewater treatment technologies and practices have changed and public concerns about the land application of biosolids have grown. In 2002, the National Research Council of the National Academy of Science issued a report entitled: "Biosolids Applied to Land: Advancing Standards and Practices” (NRC, 2002). The report noted that no scientific evidence documented that the Part 503 Rule had failed to protect public health and recommended additional scientific work to reduce uncertainties about the potential for adverse human health effects from exposure to biosolids. In 2009, EPA released a report measuring some chemicals present in biosolids. The chemicals measured include metals, steroids and hormones, pharmaceuticals, and semivolatile or polycyclic aromatic hydrocarbons. Endocrine disrupting effects have been observed for some of these chemicals. Spurred in part by the NRC report and the data available about chemicals present in biosolids, EPA researchers have started to fill the knowledge gaps.
EPA researchers are working to address some of these uncertainties by evaluating whether chemicals in biosolids degrade when biosolids are applied to agricultural soils or if the chemicals persist. The biosolids are treated using methods similar to those commonly used in sewage-treatment plants, and then spread on fields using conventional methods - such as a manure spreader which distributes the material. After application of the biosolids, EPA researchers are taking samples to determine the persistence of chemicals, including endocrine disrupting chemicals.
Results and Impact
One recent study examined fields in North Carolina after a Fall application of biosolids and tested for the presence of nonyl- and octylphenols. These chemicals are commonly used in industrial detergents and if exposed to high concentrations of these chemicals fish have shown developmental and reproductive effects in some studies. EPA researchers found that these chemicals were present in the soil after application and did not degrade after 98 days when the study concluded. It is unclear whether these concentrations of nonyl- and octylphenols in the soil might be a potential risk to people or the environment, or whether they enter food or water. The studies were not designed to assess these questions. EPA researchers are now conducting follow-up studies in a different geographic location in the Spring to determine whether persistence is affected by weather, soil, and local conditions. They also will be assessing fields over a longer time period and expanding the chemicals measured
Results from these studies will provide research that will be used to help inform regulatory and policy decisions to better protect human health and the environment. Using research results, EPA will better understand the impacts of using biosolids, will be able to use the research to provide guidance on safer ways (time and mechanisms) to apply biosolids and could develop innovative solutions to reduce the concentrations of these endocrine disrupting chemicals in biosolids.