Water supplies meeting treatment requirements

Water Treatment & PFAS

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PFAS

 

Lake Superior

Summary

• PFAS are a class of thousands of different persistent chemicals from industry and landfills which can contaminate drinking water sources and cause increased human health risks
• Regulation for maximum contaminant levels of PFAS vary depending on jurisdiction and type
• Drinking water can be treated to remove PFAS with technologies such as granular activated carbon, ion exchange resins, and high-pressure membranes such as reverse osmosis

Where does it come from?

Per-and polyfluoroalkyl substances (PFAS) are a group of environmentally persistent chemicals that have been used for decades in industrial processes and to make consumer products resistant to water and friction.[1] PFAS tend to bioaccumulate in human and animal bodies, leading to increased health risks.[2] PFAS can contaminate both surface and groundwater drinking water sources, often originating from consumer goods legacy contamination, disposal of landfill leachate, and the use of firefighting foam.[2,3] PFAS in manufacturing also creates potential release mechanisms through air emissions, spills, and disposal of wastewater or other wastes all of which can contaminate water sources across surrounding areas.[3]

How is it treated to meet applicable standards?

Maximum contaminant levels (MCL) for PFAS vary between the U.S. and Canada[9], between states, and for different types of PFAS. For example, the MCL ranges between 6-400,000 parts per trillion (ppt) for various PFAS types in the state of Michigan.[8] The U.S. Environmental Protection Agency has announced the release of non-regulatory health advisories for four PFAS. These include 0.004 ppt for PFOA, 0.02 ppt for PFOS, 10 ppt for GenX chemicals, and 2,000 ppt for PFBS.[10]

Drinking water in homes and water treatment facilities can be treated with certain technologies to effectively remove PFAS. These technologies include granular activated carbon, ion exchange resins, and high-pressure membranes such as reverse osmosis.[1] Blending contaminated water with other sources to reduce the contamination level is not considered a treatment but is enacted for some water systems as a cost-effective measure.[4] Proper waste disposal is critical for all the available technologies to ensure that PFAS are not released back into the environment. The cost and method for disposing of reject water and filtration media requires consideration and research regardless of the treatment method used.[4]

Granular Activated Carbon (GAC) has been shown to be a common and more than 90% effective treatment for long-chain PFAS contamination, though the efficiency is based on a number of factors.[4,5] Made from organic materials with high carbon contents, GAC adsorbs pollutants such as PFAS from drinking water.[1] Several base materials are used for GAC and studies show that bituminous-based products demonstrate higher effectiveness for PFAS removal.[4] Case studies have demonstrated the effectiveness of GAC use for treatment plants, ranging in costs from $80,000 to $3 million in facility construction costs.[4,6] Operational costs such as power and inspections, the cost of carbon (estimated at $1.50 per pound), and disposal costs must also be considered.[4] Purolite estimates the cost of their system to be $0.45/1000 gallons of treated water.[7]

GAC can be completely effective for an amount of time dependent on environmental factors and whether the contamination is long or short chain PFAS. GAC adsorbs longer chain PFAS[1] better than shorter chain PFAS, but the media will need to be changed out regularly to maintain effectiveness. GAC media can be disposed of through landfilling or incineration,[4] though incineration requires temperature consideration because this effects the potential creation of byproducts and risk of incomplete incineration. Powdered Activated Carbon (PAC) uses the same material as GAC but with a smaller diameter form, meaning that it is added directly to contaminated water and then removed in a later stage of clarification. PAC is not as economical or effective as GAC when used in this way and the waste must still be disposed of properly. [1,4]

Anion exchange systems involve the use of resins to exchange ions and capture contaminants such as PFAS.[4] Ion exchange systems have been shown to be effective at removing PFAS from drinking water, have capacity for long and short chain PFAS, and have a reduced footprint with a smaller vessel and less media due to the lower contact time requirements. [1,4,5] Costs will vary depending on the type of treatment system and resin;[1] although ion exchange system upstart costs are usually more expensive than GAC, the costs may be less over the project period due to their higher adsorption capacity. Single-use resins are typically less expensive in capital and operating costs than the regenerative resins, which may be regenerated to restore the PFAS removal capacity. Both types create waste which must be managed, and pretreatment of water may be necessary to use ion exchange for PFAS treatment.[4]

Membrane technologies such as reverse osmosis and nanofiltration are a more than 90% effective method to treat PFAS contaminated water, as it removes many pollutants, including shorter chain PFAS.[4] However, the water may require pretreatment for this method to remain effective. [4,5] Reverse osmosis results in the solute being retained on the pressurized side of the membrane, meaning the system will create waste streams of water totaling between 20-25% of the original flow. This rejected water must be managed to reduce chance of further contamination, meaning smaller water volumes are optimal for reverse osmosis such as home use. [1,4] A further limitation is that this process also strips beneficial minerals from drinking water.

Newer PFAS treatment technology is being tested and certified including a group of engineered adsorption media development which have high adsorption capacities such as CETCO’s Fluoro-sorb and Cyclopure’s Dexsorb+.[11]

References

 

  1. EPA, Reducing PFAS in Drinking Water with Treatment Technologies (2018) Accessible online: https://www.epa.gov/sciencematters/reducing-pfas-drinking-water-treatment-technologies
  2. Association of State Drinking Water Administrators, Per- and Polyfluoroalkyl Substances (PFAS) Source Water Protection Guidance Project (2020) Accessible online: https://www.asdwa.org/pfas/
  3. ITRC, History and Use of Per- and Polyfluoroalkyl Substances (PFAS) found in the Environment (2020) Accessible online: https://pfas-1.itrcweb.org/wp-content/uploads/2020/10/history_and_use_508_2020Aug_Final.pdf
  4. Cummings, L., Matarazzo, A., Nelson, N., Sickels, F., Storms, C., Recommendation on Perfluorinated Compound Treatment Options for Drinking Water (2015) Accessible online: https://www.state.nj.us/dep/watersupply/pdf/pfna-pfc-treatment.pdf
  5. ITRC, Treatment Technologies and Methods for Per- and Polyfluoroalkyl Substances (PFAS) (2020) Accessible online: https://pfas-1.itrcweb.org/wp-content/uploads/2020/10/treatment_tech_508_Aug-2020-Final.pdf
  6. EPA Office of Ground Water and Drinking Water, Addressing PFAS in Drinking Water with the Drinking Water State Revolving Fund (2019) Accessible online: https://www.epa.gov/sites/default/files/2019-03/documents/pfas_fact_sheet_and_case_studies_final.pdf
  7. Association of State Drinking Water Administrators, PFAS Treatment Options and Considerations for Drinking Water Utilities (Webinar) (2018) Study by Purolite. Accessible online: https://www.asdwa.org/past-events-webinar-recordings/?mgs_158=pfas&mgi_158=14529/pfas-treatment-options-and-considerations-for-drinking-water-utilities
  8. State of Michigan, Michigan PFAS Action Response Team (2022) Accessible online: https://www.michigan.gov/pfasresponse/drinking-water/mcl
  9. Government of Canada, Guidelines for Canadian Drinking Water Quality – Summary Table (2020). Accessible online: https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/water-quality/guidelines-canadian-drinking-water-quality-summary-table.html 
  10. S. EPA, Drinking Water Health Advisories for PFOA and PFOS (2022). Accessible online: https://www.epa.gov/sdwa/drinking-water-health-advisories-pfoa-and-pfos
  11. Orange County Water District, PFAS Phase I Pilot-Scale Treatment Study Final Report (2021). Accessible online: https://clu-in.org/download/contaminantfocus/pfas/ocwd-pfas-pilot-i_finalreport.pdf