While EPA’s risk model simulations and estimates could inform risk management decisions, the agency recognizes the limits of this largely prospective evaluation. Scenarios marked with unacceptable risk in the assessment are not necessarily expected to pose actual risks to human health. This is because actual risks depend on PFAS concentrations in biosolids, the number and extent of applications, environmental and geological conditions, the type of farming, the proximity of applied biosolids to surface water and groundwater, and the extent of reliance on self-raised crops and livestock.
What’s more, since PFAS are ubiquitous and can be found in soil and rain at ppb levels, it may be challenging to tell biosolids impacts apart from ambient background and other anthropogenic inputs. Thus, the evaluation of any likely risks resulting from biosolid application better lends itself to a site-specific rather than a global risk management approach.
Are Biosolids Suitable for My Land?
It depends. If applied to non-food growing areas, the potential risks are lower than if applied to pastures, crops, and gardens intended for livestock grazing and human consumption. The latter use requires extra vigilance according to EPA’s risk evaluation.
Following recommended PFAS limits, such as those published by Connecticut, Maine, and the University of Maine, for example, can help mitigate the risks of land application.
A detailed, site-specific risk assessment encompassing comprehensive chemical testing of biosolid sources, application rates, past application history, baseline conditions/background, groundwater depth, and crop type would provide the highest measure of protection. Desktop risk assessments rely on existing environmental risk assessment methodologies and conservative assumptions published by state and federal agencies. Such assessments can be completed with a relatively modest level of effort.
What to Do with PFAS-Tainted Biosolids?
Options are limited for the disposal and management of biosolids that exceed permissible PFAS limits. Hazardous waste landfilling and incineration are available, though the former can be expensive, and the latter needs to ensure complete PFAS destruction to not create an air pollution problem.
This is why many agencies are looking into source identification and reduction as the best management practice—preventing PFAS from getting into WWTPs in the first place rather than devising technologies to treat biosolids for PFAS after the fact. However, with current technology, it is practically impossible to prevent PFAS from entering WWTPs.
In terms of possible risk reduction, EPA suggests the following:
- Industrial pre-treatment
- Application to areas away from fishable waters, shallow groundwater/recharge zones, and grazing and crop lands
- Using synthetic-lined landfills for sludge disposal
- Only sending biosolids to performance-tested incinerators
Soon, there may be commercially available PFAS destruction and isolation technologies specifically developed for sewage sludge. Stay tuned.
EPA expects to publish a final risk assessment after completing a 60-day public comment period and revising the draft risk assessment accordingly. Once finalized, the risk assessment will provide information on risk from use or disposal of sewage sludge and will inform EPA’s potential future regulatory actions under the Clean Water Act. To manage risks, EPA may develop biosolids numerical limits and impose performance/equipment standards and/or best management practices that consider economic costs and treatment feasibility.
We will continue to monitor this development and keep you updated. Please be on the lookout for additional articles on this topic. Meanwhile, if you have PFAS-related questions, concerns, or challenges, drop your information into our contact form and we’ll schedule time to discuss how you can prepare for and manage PFAS regulations.
