A lot of concern has begun to focus on the presence of per- and polyfluoroalkyl substances (PFAS) in water sources that could affect drinking water quality. Discovery and monitoring of PFAS levels has expanded to include wastewater and the subsequent effluent from the treatment process that could potentially lead to biosolids contamination.
PFAS are man-made chemicals that are found in a wide variety of products used by consumers and industries. Many PFAS are resistant to grease, oil, water and heat which made it ideal for applications such as stain- and water-resistant fabrics and carpeting, cleaning products, paints, and fire-fighting foams. Some PFAS are even allowed by the FDA for limited use in cookware, food packaging and processing.
PFAS also have the characteristic of remaining intact in the environment over time which can result in increasing levels of environmental contamination. Blood tests in humans and animals have confirmed the presence of PFAS, but since the science surrounding potential health effects of PFAS is still largely unknown, the bioaccumulation of certain PFAS may cause serious health conditions.
Lynne Moss, a residuals and odor control practice leader for Black & Veatch, believes that biosolids contamination could result from inadequate monitoring of PFAS. She explains that, “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.”
Large concentrations are usually found in industrial dischargers like metal platers or manufacturers of coatings and fire retardants. “That’s where we’ve seen some of those hot spots and increased concerns about biosolids contamination in particular,” Moss says.
Detection of PFAS in biosolids is key for monitoring, however, some concentration limits are not reflective of the characteristics of the biosolids or the soils. Moss says that it may end up with a limit that may be inappropriately low, not reflective of the practice, or in some cases, levels that are equivalent to background concentrations.
Another aspect of investigation is the effluent quality. If concentrations are below a set threshold, then no action is typically done. In situations were the limit is breached, a thorough monitoring of the collection system of the wastewater treatment is done to determine the source of PFAS concentration in either the effluent or the biosolids.
A third approach is to reduce non-municipal sources of PFAS. “What we see are states putting in prohibitions on PFAS. 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,” Moss explains.
The biggest obstacle in addressing high PFAS concentrations and possible biosolids contamination is the lack of an approved measuring approach. There has been very little information on the exposure effects to merit a more concrete standard of measure.
The most prudent approach so far is to maintain best practices for biosolids management. Appropriate land application programs need to be adhered to for minimizing PFAS concentrations in the soil. If you are in an area with high PFAS concentrations, then careful monitoring and appropriate legislation should be enacted to address these issues. The good news is that PFOA and PFOS, the most concerning and most-researched PFAS, have been mostly been banned, lowering potential risk.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.