Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7q. Managing PFAS at Publicly-Owned Treatment Works (POTWs)

Formatted Title:

Cost of Removing PFAS from WRRF Effluent and Biosolids

Background/Objectives:

The accumulation and persistence of per- and poly-fluoroalkyl substances (PFAS) in the environment presents an ongoing challenge. Municipal water resource recovery facilities (WRRFs) reflect a central collection point where PFAS from industrial, municipal, and commercial sources are combined before being discharged into the environment via treated effluent and biosolids.

PFAS in WRRF effluent and biosolids are beginning to be scrutinized and regulated, as demonstrated by recent implementation of WRRF effluent permit limits for PFAS in Michigan and a ban on land application of biosolids in Maine. Even with management of upstream sources (e.g., through industrial pretreatment agreements or by reducing PFAS in consumer products), PFAS are expected to persist in WRRF effluent and biosolids) into the foreseeable future. However, limited work has been completed to characterize the economic impacts of treating PFAS in WRRF effluent and biosolids.

The objective of this project was to provide conceptual understanding and costs for currently available approaches to manage and destroy PFAS down to below analytical reporting limits in municipal WRRF effluent and biosolids. These costs can help establish a framework for legislators and facility managers to plan for potential capital and operational costs associated with removing PFAS from WRRF effluent and biosolids, should it be required in the future.

PFAS management has increasingly focused on the final fate and destruction of PFAS to avoid potential re-release to the environment. This study aims to develop PFAS management strategies that destroy targeted PFAS, ideally to non-fluorinated end-products. As such, management options that return PFAS to wastewater treatment plants, landfills, or other temporary reservoirs were not considered.

PFAS guidelines for human and environmental health are rapidly evolving, and toxicity thresholds vary by compound. Treatment targets for this study were set to match the order of magnitude of current analytical reporting limits (approximately 5 nanograms per liter or 5 nanograms per gram), to reflect the target of full PFAS removal and destruction from targeted waste streams. While some laboratories are achieving lower reporting limits, differences within about one order of magnitude would not necessarily affect technology selection for this study. We recognize that targeting analytical reporting limits is aggressive, especially for short-chain PFAS with limited regulatory guidance, and that many beneficial projects may target mass removal of several PFAS or long-chain PFAS instead of specific target compounds. However, evolving regulations and lack of health risk data make it challenging to select appropriate alternate thresholds for many PFAS.

Approach/Activities:

Preliminary designs and cost estimates were developed for multiple size facilities to address an assumed design basis established for WRRF effluent and biosolids quality based on available literature and project experience.

Preliminary design of major equipment as well as equipment cost estimates were developed based on input from vendors as well as relevant project experience. Class 5 capital cost estimates with an uncertainty range of -30%/+50% were developed into cost curves spanning multiple orders of magnitude of facility sizing. Operation and maintenance costs also relied on vendor input and relevant project experience as well as current industry rates for labor, electrical, sorption media, transportation, and disposal.

Results/Lessons Learned:

The costs associated with removing and destroying PFAS from a 10 million gallons per day (MGD) WRRF’s effluent to below analytical detection limits are estimated to be approximately $110 million in capital costs (in US dollars) and $8.7 million in annual operating costs. Where a facility falls in this range will depend on site-specific design and operational decisions related to existing infrastructure, space availability, current treated water quality, operational preferences, PFAS treatment targets, and PFAS treatment reliability requirements. The presentation will include cost curves developed for WRRF effluent treatment between 0.1 and 10 MGD and WRRF biosolids treatment between 1 and 10 dry tons per day (dtpd). Costs are in the millions, even for facilities as small as 0.1 MGD. When these costs are applied to rate payers in Minnesota as an example, the cost per household is estimated to increase by a factor between 2 and 210. The resulting economic burden to utilities and rate payers as well as potential funding avenues should be considered before implementing PFAS discharge regulations.

Removal and destruction of PFAS from either WRRF effluent or biosolids is expected to cost between $0.5 million to $10 million per pound of PFAS removed over a 20-year operating period. These costs will vary depending on facility size, biosolids production rates, and the concentration and speciation of PFAS reporting to biosolids and effluent at each facility. Lower costs per mass of PFAS are likely achievable upstream at industrial facilities and landfills, due to the higher concentration of PFAS in those discharges.

Continued research and technology development is needed, especially into separation technologies that effectively remove short-chain PFAS from the water phase and destruction technologies that operate at low temperatures or recover heat for improved energy efficiency.

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Scott Kyser