2D: Understanding PFAS Contaminants in Municipal Biosolids

Polyfluorinated alkyl substances (PFAS) compounds are ubiquitous in our environment and have been associated with adverse effects on human health. They are a significant source of pollution in ecosystems and are often inadvertently released via land application in agriculture, mining reclamation sites, forest soils, or lawns and gardens. Biosolids, or sewage sludge, are a byproduct of wastewater treatment plants. Biosolids are considered a valuable resource because they can improve soil’s water-holding capacity, organic content, and nutrient value. They do, however, contain a wide range of organic and inorganic compounds, including PFAS, that are not removed during conventional wastewater treatment.

A Utah State University study surveyed biosolids generated from a wide range of municipal wastewater treatment plants in northern Utah and central Idaho that served populations ranging from 10,000 to over 600,000 people (Figure 2.D.1). Research revealed that PFAS concentrations are not related to community size nor residential- commercial-industrial make-up. Communities will likely be facing increasingly stringent PFAS biosolids regulations in the future because of the health and environmental risks associated with these substances. Whether biosolids produced by wastewater treatment plants can be beneficially utilized by communities with such regulations in place will depend on how well PFAS can be removed.

At Utah State University’s Utah Water Research Laboratory, studies are underway to evaluate whether composting biosolids at a high temperature with and without a biochar additive will reduce the concentration and/or availability of these elevated levels of PFAS. Developing successful techniques to create safe biosolids will allow users to reap the benefits of this soil amendment without future concerns for human health and environmental harm.