Pfas Activated Carbon Filter
Salomon Thoj
If you have concerns about your health, you can take steps to reduce your potential exposure to PFAS. Filters containing activated carbon or reverse osmosis membranes have been shown to be effective at removing PFAS from water supplies. All water treatment units require regular maintenance to work properly. Water treatment units that are not properly maintained will lose their effectiveness over time.
Other types of common water treatment systems, such as water softeners or iron filtration systems, are not likely to remove PFAS. Boiling water will not remove PFAS. While many homes have whole-house water softening or iron filtration systems, sampling data indicate that those systems do NOT remove PFAS.
There are both point-of-use (water is treated at one faucet or location) and point-of-entry (all the water in your home is treated) treatment options to reduce PFAS in drinking water. Point-of-use treatment tends to be more economical than point-of-entry. The following treatment options are effective at removing PFAS from drinking water when the unit is properly installed and maintained
Industrial Environmental Professionals
Calgon Carbon has developed many effective solutions and strategies for PFAS remediation issues for companies of all sizes. Learn more about how we can develop a customized option for your operation.
Products & Systems Tailored for Your Need
Our products and engineered systems are found in water treatment facilities and industrial applications across the U.S. and beyond. These products and services, combined with expert and on-site support, allow our customers to be confident knowing their water is being treated effectively for PFAS.
Calgon Carbon has offered the proven treatment solution for PFAS removal in both drinking water and remediation applications for over 15 years with our FILTRASORB granular activated carbon (GAC) and Equipment product lines. Calgon Carbon provides a complete solution including activated carbon, equipment, on-site installation and exchange services, reactivation, and financing.
CCC FILTRASORB can remove typical levels of PFOA and PFOS to non-detect levels. Our studies show that reagglomerated, coal-based GAC performs significantly better than coconut for PFOA and PFOS removal. Even if local regulations require lower PFAS concentrations than the EPA health advisory, GAC is an effective solution.
Laboratory tests and column tests were carried out in a waterwoks to investigate the removal of short- and long-chain PFAS using activated carbon filtration and ion exchange treatment. For all adsorbents, the sorption affinity of short-chain per- and polyfluoroalkyl carboxylic acids (PFCA) was significantly lower than that of long-chain PFAS or short-chain per- and polyfluoroalkyl sulfonic acids (PFSA). In the PFAS-polluted groundwater matrix, the short-chain PFCA PFBA and PFPeA could only be sufficiently removed with activated carbon over short run times of 6000 and 11,000 bed volumes (BV), respectively. Longer PFCA with a chain length of C6 or more were removed over longer run times.
The removal of short-chain PFCA using ion exchange media could also only be achieved over relatively short run times of 5000 BV for PFBA, 10,000BV for PFPeA and 18,000 BV for PFHxA. These are sometimes significantly longer than those of activated carbon. Due to the higher material costs for ion exchange media, there are nevertheless no lower operating costs when the ion exchangers are used in single-use mode. However, ion exchangers can be regenerated and then reused which can result in economic advantages compared to activated carbon filtration. However, for the extensive regeneration, especially for the elution of the long-chain PFAS, the additional use of ethanol is needed in the process. In contrast, the short-chain PFBA and PFPeA can be extracted without organic solvent from a weakly basic ion exchanger.
The group of per- and polyfluoroalkyl substances (PFAS) is a large family of anthropogenic substances. They consist in part of aliphatic, acyclic hydrocarbons in which many (poly) or all (per) of the hydrogen atoms have been replaced by fluorine atoms (Buck et al. [3]). These carbon chains are connected to different functional groups. Due to their hydrophilic and hydrophobic properties, PFAS are as well oil and water repellent. PFAS show a high stability to thermal, biological and chemical processes. Thus, they have been used in a wide range of industrial and household products over several decades. One main application is their use in aqueous film forming foams (AFFF).
The group of PFAS can be subdivided into per- and polyfluoroalkyl carboxylic acids (PFCA) and per- and polyfluoroalkyl sulfonic acids (PFSA). In addition to these two subgroups, a broad variety of PFAS exist with different chemical structures at the non-fluorinated part of the molecules (Buck et al. [3]). Single perfluorinated substances, like perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), have been well researched and are regulated due to their extreme resistance to degradation and their bioaccumulation potential. Owing to their very high toxicity to humans, the use of PFOS has been forbidden in the EU to a large extend since 2006 (EC [7]), based on agreements in the Stockholm Convention. The use of PFOA is also strongly restricted and in 2019 the use of firefighting foams containing PFOA has also been banned in the EU (Stockholm Convention [28]). Since over 150 countries across all inhabited continents have ratified the Stockholm Convention, the use of designated PFAS is virtually banned worldwide (Brennan et al. [2]).
Consequently, alternative PFAS are now used in many applications. These PFAS have either shorter-chain lengths or are only partly fluorinated compounds (such as the fluorotelomers) [1, 24, 26]. The non-fluorinated part of the fluorotelomers with shorter-chain lengths might be degraded microbially in the environment leading to the formation of PFCA or PFSA (Pancras et al. [21]). Short-chain PFAS are defined to have five or less carbon atoms in the case of PFSA and to have seven or less carbon atoms in the case of PFCA ([3], OECD [20]).
In general, short-chain PFAS are less toxic than long-chain PFAS; however, the short-chain PFAS have been found to be more mobile in groundwater and able to move more rapidly in the case of soil contamination [33]. This is apparent by comparing the drinking water guidance values set from the German Environmental Protection Agency for the C4 compound PFBA (perfluorobutanoic acid) of 10 g/L and for the C8 compound PFOS of 0.1 g/L (UBA [34]). Nevertheless, short-chain perfluoroheptanoic acid (PFHpA) has a health-oriented guidance value of 0.3 g/L and thus exhibits a comparable toxicity like PFOS. In addition, the EC Drinking Water Directive 2020/2184 includes a drinking water limit value of 0.1 g/L for the sum of 20 PFAS (C4 to C13 of PFCA and PFSA) (EU [8]).
Most cases of PFAS contamination of groundwater have resulted from firefighting operations using aqueous film forming foams near airports. These contaminations are often characterised by the occurrence of long-chain PFAS, like PFOS, PFHxS and PFOA. More recent groundwater contaminations are often characterised by contributions from short-chain PFAS, such as PFBA, PFPeA (perfluoropentanoic acid) or PFHxA (perfluorohexanoic acid) [12, 25, 38].
Adsorption onto granular activated carbon (GAC) is a field-proven technology for the removal of long-chain PFAS, like PFOS and PFOA, from contaminated water [14, 27]. Due to the raising concerns of emerging short-chain PFAS, new treatment technologies have recently been developed, investigated and evaluated.
Sustainable PFAS treatment technologies ensure a destruction of the substance until full degradation and mineralisation has occurred. Nevertheless, due to the very high electronegativity of fluorine and the very stable chemical bond between carbon and fluorine, destruction technologies for PFAS are very energy intensive. PFAS destruction has been investigated for electrochemical degradation, sonochemistry, plasma destruction, oxidation processes, UV radiation and incineration [15, 22, 30, 32, 35, 37]. In the case of drinking water treatment and of certain contaminant site remediation, PFAS concentrations can be rather low, and thus, these technologies are not very attractive from an economical perspective.
The operation time of adsorptive media can be increased by applying a flocculation step with PFAS-specific coagulation compounds prior to adsorption to decrease the PFAS concentration in the adsorbent feed or to reduce, e.g. the concentration of natural organic substances, which compete for adsorption sites. One example of this approach is the PerfluorAd technology [4].
In this paper, PFAS removal from water by activated carbon adsorption and both strong base (SBA) and weak base anion exchangers (WBA) is investigated. Results are evaluated related to capacities and operating times for both long-chain and short-chain PFAS. The influence of operating parameters, such as carbon bed depth on PFAS breakthrough, is discussed. Methods for resin regeneration are shown and resulting separation factors, which indicate the volume of PFAS containing water related to the initial volume of water, are determined.
For the batch experiments, demineralized water or tap water was used and for the field column experiments, PFAS-contaminated groundwater was used. Concentrations of relevant parameters are listed in Table 3.
IEX were pre-treated with 1 M hydrochloric acid and 1 M caustic soda to remove impurities and monomers prior to batch experiments [25]. IEX samples were taken after centrifuging at 1300 g for a time of 20 min to strip off adhering water and convert the material to a comparable state.
GAC was dried and pulverised. Sorption equilibria of PFAS on GAC were determined by equilibrating a series of activated carbon quantities between 0.5 and 150 mg with 1 L of the initial solution. The contact time was 24 h when a constant concentration was achieved. The initial solution was demineralized water spiked with four PFAS (PFBA, PFPeA, PFHxA, PFOA) at an initial concentration of 6 g/L each.
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