The presence of elevated concentrations of per- and polyfluoroalkyl substances (PFAS) in certain areas of the country has spurred much concern about drinking water quality, but recently attention has begun to extend to wastewater and the relationship between PFAS and biosolids.
“Biosolids are conveyors of PFAS,” explained Lynne Moss, a residuals and odor control practice leader for Black & Veatch. “PFAS compounds that come into water resource recovery facilities can end up in the effluent and in the solids, and then be transported through land application to drinking water supplies.”
The concentrations are generally quite low — in the low parts per billion range — in biosolids that don’t have an industrial contribution, she noted. When there is an industrial discharger, however, like metal platers or manufacturers of coatings and fire retardants, there can be spikes. “That’s where we’ve seen some of those hot spots and concerns about biosolids in particular.”
Given the growing concern about the impacts of PFAS compounds on public health and a lack of science-based federal guidance, localized regulatory activity at the state level is occurring. Moss noted that approaches to addressing PFAS generally fall into three categories.
“In one case, we’ve got the states that are setting either soil or solids screening levels,” she said. Typically, risk assessments will be done but in many cases, she noted, they don’t necessarily reflect the characteristics of the biosolids or the soils. “What you end up with is a limit that may be inappropriately low, not reflective of the practice, or in some cases, levels that are equivalent to background concentrations.”
Another approach, based upon that of industrial pretreatment programs, considers effluent quality. If the concentration is below a certain threshold, no action is required. “However, if the effluent exceeds a certain number then you not only need to find the source in your collection system, you need to control it, monitor your effluent, and monitor your biosolids,” said Moss.
The final approach, which Moss said has great potential for reducing PFAS in biosolids and in the environment in general, is non-municipal source reduction. “What we see is states putting in prohibitions on PFAS,” she said. And, history supports the effectiveness of this approach. “When they quit using two of the most common PFAS — PFOA and PFOS — we found over decades that the concentrations of these persistent chemicals fell dramatically in human blood.”
Part of the challenge with PFAS in biosolids, Moss explained, is that there is not yet an approved measuring approach. There is also little information on exposure effects, although much research is underway. “So, we will be getting those answers — but we don’t have them today and the concern is that, with some of the limits being set, we are in fact getting ahead of the science.”
Moss also cautioned against ignoring the significant benefits associated with biosolids, such as carbon sequestration and improving degraded soils. “These are tangible, measurable benefits against potential or perceived risks,” she said.
As the industry navigates this complex issue, Moss underscored the importance of conducting land application programs in accordance with best practices. “And, if you’re in an area that’s a hot spot for PFAS,” she added, “be aware of what’s happening in your state and understand that regulations can change quickly.” WW