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HWEA will be the organization of dedicated and knowledgeable professionals
recognized for preserving and enhancing the water environment in the Pacific Island Region.

The Current State of Knowledge, The Current State of Knowledge, Existing Regulations, Industrial Pretreatment and Concerns in POTWS

 By Divyam Goel, University of Utah

Reprinted with permission from the Summer issue of Digested News

The half-lives of many PFAS compounds have been measured to be hours to days The half-lives of many PFAS compounds have been measured to be hours to days in rats and in years in humans.

PFAS is used to describe a broad group of perfluoroalkyl and polyfluoroalkyl chemical substances. Per and polyfluoroalkyl substances (PFAS) are highly fluorinated aliphatic substances that contain one or more carbon atoms on which all hydrogen substituents have been replaced by fluorine atoms. Consequently, they contain the perfluo-roalkyl moiety. PFAS substances have been used since the 1950’s in various capacities due to their resistance properties against oils, water, temperature, chemicals, and heat. Commercial production of PFAS chemicals began over half a century ago. The US is one of the largest producers of PFAS compounds. The per fluorinated or polyfluorinated compounds are anthropogenic in nature and released into the environment due to human and industrial activities. Due to their unique chemical structures and stability, several PFASs have been proven to be bio-accumulative and toxic in many animals, also including humans. Their characteristic carbon backbone surrounded by fluorine atoms makes them one of the most resistant molecules to various degradation processes and, thus, a pain to treat. Due to this unique characteristic, these stubborn chemicals have been used in non-stick cookware, waterproofing treatments, furniture, carpets, waterproof coatings and carboard, mist suppressants in the metal industry, and firefighting foam. PFAS compounds are found worldwide in the environment, wildlife, and humans. The half-lives of many PFAS compounds have been measured to be hours to days in rats and in years in humans. Due to the bio-accumulative nature of most of PFAS compounds, PFAS compounds were added to the “most persistent” chemical list by the United States Protection Agency.  PFAS is used to describe a broad group of perfluoroalkyl and polyfluoroalkyl chemical substances. Per and polyfluoroalkyl substances (PFAS) are highly fluorinated aliphatic substances that contain one or more carbon atoms on which all hydrogen substituents have been replaced by fluorine atoms. Consequently, they contain the perfluo-roalkyl moiety. PFAS substances have been used since the 1950’s in various capacities due to their resistance properties against oils, water, temperature, chemicals, and heat. Commercial production of PFAS chemicals began over half a century ago. The US is one of the largest producers of PFAS compounds. The per fluorinated or polyfluorinated compounds are anthropogenic in nature and released into the environment due to human and industrial activities. Due to their unique chemical structures and stability, several PFASs have been proven to be bio-accumulative and toxic in many animals, also including humans. Their characteristic carbon backbone surrounded by fluorine atoms makes them one of the most resistant molecules to various degradation processes and, thus, a pain to treat. Due to this unique characteristic, these stubborn chemicals have been used in non-stick cookware, waterproofing treatments, furniture, carpets, waterproof coatings and carboard, mist suppressants in the metal industry, and firefighting foam. PFAS compounds are found worldwide in the environment, wildlife, and humans. The half-lives of many PFAS compounds have been measured to be hours to days in rats and in years in humans. Due to the bio-accumulative nature of most of PFAS compounds, PFAS compounds were added to the “most persistent” chemical list by the United States Protection Agency.   Quite recently, the State of Michigan’s Department of Environment, Great Lakes and Energy announced a new set of regulations limiting PFAS contaminants in drinking water. The regulations establish strict Maximum Contaminant Levels (MCLs) on various types of PFAS and the accepted amount in parts per trillion (ppt). For example, PFAS PFNA is permissible at a mere 6 ppt while PFBS is allowed at 420 ppt. The regulations brought a wave of reform as public water supplies in the state have started to modify and evolve their operations to better treat PFAS. The State of Michigan wrote, “MPART agencies like EGLE and MDHHS will assist public water systems to bring their water into compliance over the next several months.” The announcement was released in late July, 2020 (EGLE Media Office, 2020).   

 Sources of PFAS in POTW PFAS can enter the sewage system through a variety of industrial sources that include PFAS manufacturing, fluoropolymer manufacturing, and AFFF manufacturing. PFAS can get into municipal wastewater through a variety of sources including sloughing of the film from non-stick cooking utensils, industrial disposals (plastic manufacturing, textiles and leather industries, surfactants preparation, and even medical applications), landfill seepage and stormwater runoffs (for combined sewer systems). The number one contributing source for PFAS contaminants entering sewage systems is food packaging material.  Due to their widespread use in industries and daily-life products, PFAS have entered the soil and water environments and are now found in microorganisms, plants, various different animals, and humans globally. PFAS are even being found in extreme environments including in the Arctic and Antarctic ecosystems. 

 Concerns about the presence of PFAS in POTWs Exposure to PFAS threatens human health and aquatic habitats when the treated effluent from the wastewater treatment plants is discharged into the environment (WWTPs), and thus, WWTPs act as secondary sources of PFAS (Yiping et al., 2008). While PFAS might be released into the environment during production, usage, or disposal, there are several PFAS precursors, that can be transformed abiotically or biologically into PFASs. Some of the PFAS precursors such as fluorotelomer alcohols can be transformed in the environment and form many intermediate transformation products. The concentrations of these pollutants are typically negligible (μg/L to ng/L) as compared to COD or BOD in wastewater, however, there has been a growing concern on their occurrences as long-term exposure to these substances can be carcinogenic (Wielsøe et al., 2015). Due to persistent and recalcitrant nature of PFAS, most of the PFAS remain unaffected through conventional water treatment processes. As a result, PFAS originating from domestic and industrial sources as well as PFAS originating from their precursor compounds in the treatment train, are typically present in the final effluent in wastewater treatment plants. Hence, established practices towards water sustainability such as recycling and environmental discharges are currently being questioned. The PFAS issue arises in sewage sludge because conventional wastewater and sewage treatment methods cannot efficiently eliminate these recalcitrant compounds from the system. The increase in concentration of some PFAS compounds such as perfluoroalkyl acid (PFAA) in sewage effluents over that in the influent is attributed to the degradation of more complex PFAA precursors during activated sludge treatment For example, wastewater treatment plants could show 9-352 % increase in PFOA concentration in effluents over influents (Schultz et al., 2006). However, PFOS often could exhibit a decrease in concentration in the effluent, attributed to high Kd values causing retention of PFOS in the sludge and lowering final PFOS concentrations in effluents (Yu et al., 2009). Becker et al. (2008) observed a 20-fold increase in PFOA concentrations from influents to effluents, and an additional 10% and 50% PFOA and PFOS, respectively, adsorbed in the sludges. As a result, land application, landfilling and other application of biosolids have been revisited recently in light of the presence of PFAS compounds in biosolids/sewage sludge.  
 Pretreatment of PFAS compounds Because only a small subset (<30) amongst the large set (>5000) of PFAS have been detected and quantified in municipal wastewater and since they are not currently regulated under National Pollution Discharge Elimination system, there are no defined pretreatment methods for PFAS compounds. The carbon-fluorine bond is one of the strongest in chemical bonding. Hence, PFAS compounds are known to be recalcitrant to biodegradation. However, PFAS compounds could be remediated using a variety of abiotic techniques including sorption, immobilisation, stabilisation, filtration, coagulation, separation, chemical oxidation/reduction, thermal decomposition, and UV/photocatalytic degradation. However, most of these techniques have evaluated degradation efficiency of PFAS compounds in terms of removal of parent compound and very few studies included identifying degradation intermediates.  

 Existing regulations and their impacts on industrial users Since 2000, USEPA has taken serious interest in developing strategies to study the presence, fate and transport of long chain PFAS compounds in the environment. EPA intended to implement regulatory actions under the toxic substances control act (TSCA) to address the potential risks from long chain PFAS. In terms of drinking water regulations, there are currently no minimum contaminant limits established for PFAS compounds. However, USEPA initiated the process of MCL for selected PFAS compounds under the regulatory determination process. Consequently, on February 20, 2020, EPA issued preliminary determinations to regulate PFOA and PFOS in drinking water. Nevertheless, EPA has already issued a health advisory for PFOA and PFOS compounds. Under the TSCA act, USEPA has developed three framework rules outlining path forward for future actions but these rules do not require POTWs to operate under any regulatory guidelines. The EPA identified three final Significant New Use Rules (SNURs) and one proposed SNUR that cover 24 of the 40 PFAS chemicals within the scope of this review and require manufacturers to notify the EPA through submission of a Significant New Use Notice (SNUN) at least 90 days before manufacturing, importing, or processing listed chemicals. The EPA does not currently have an approved Clean Water Act analytical method for monitoring PFAS in wastewater discharges. Consequently, state permitting authorities are using the Method 537 drinking water method, or its variations, to establish permit limits or monitoring requirements for NPDES permits as needed.  

 Conclusion Presence, fate and transport of PFAS compounds in different environmental matrixes including in POTWs is still an unknown territory although research is underway. Future directions should focus on degradation intermediates and their toxicity, simple analytical tools for POTWs managers, and training to POTWs personnel about potential health effects of PFAS compounds 

 References Becker, A.M., Gerstmann, S., Frank, H., 2008. Perfluorooctane sulfonate in the sediment of the Roter main river, Bayreuth, Germany. Environ. Pollut. 156, 818–820.  EGLE Media Office. (2020, July 22). Michigan adopts strict PFAS in drinking water standards. Retrieved from Michigan.gov: https://www.michigan.gov/som/0,4669,7-192-47796-534660--,00.html Buck, R., Franklin, J., berger, U., Conder, J., Cousins, I., de Voogt, P., . . . van Leeuwen, S. (2011). Perfluoroalkyl and Polyfluoroalkyl Substances in the Environment: Terminology, Classification, and Origins. Integrated Environmental Assessment and Management , 513-541. EGLE Media Office. (2020, July 22). Michigan adopts strict PFAS in drinking water standards. Retrieved from Michigan.gov: https://www.michigan.gov/som/0,4669,7-192-47796-534660--,00.html Schultz, M.M., Higgins, C.P., Huset, C.A., Luthy, R.G., Barofsky, D.F., Field, J.A., 2006. Fluorochemical mass flows in a municipal wastewater treatment facility. Environ. Sci. Technol. 40, 7350–7357.  Yu, J., Hu, J., Tanaka, S., Fujii, S., 2009. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in sewage treatment plants. Water Res. 43, 2399–2408.

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