By Michael Bartlett on August 10th, 2023 in PFAS
Currently, it is known that granular activated carbon, ion-exchange resins, high-pressure membrane systems, and the electrochemical advanced oxidation process would be the treatment procedures that may effectively remove PFAS. The best choices between these technologies involve striking a balance among a number of parameters.
Traditional wastewater treatment techniques including coagulation followed by physical separation, aeration, chemical oxidation, UV irradiation, and disinfection are not so effective at getting rid of PFAS, which causes water contamination. For the purpose of eliminating PFAS from source water, common treatment technologies such as granular activated carbon (GAC), ion-exchange resins, reserve osmosis and nanofiltration, and advanced oxidation process are used. Each technique has advantages and disadvantages that should be examined when choosing a treatment method, taking into account the costs, efficiency, stability, long-term performance, and environmental impact.
Since the 1960s, membrane technology has been developed and applied to organic pollutants, suspended particles, and salts from aqueous solutions. It has made great progress in the field of water purification over time. Furthermore, commercial reverse osmosis and nanofiltration membranes have been tested and proven to have high removal efficiencies for PFOS and PFOA.
The key benefits of membrane technology over alternative purification technologies include high rejection efficiency, a high loading flow rate, and the rejection of co-contaminants in PFAS-contaminated waters. Concerns about the use of membrane technologies for PFAS treatment include their relatively high operating costs due to their energy-intensive nature when compared to other technologies such as IX and absorption processes, as well as the production of a waste stream containing PFAS concentrate, which would require further treatment for disposal.
Ion exchange (IX) is a typical purification technique in which target ions from a solution replace exchangeable charged co-ions on the surface of a polymeric resin. When compared to other treatment methods such as filtration, granular activated carbon, or advanced oxidation processes, anionic exchange resins (AER) are a potential method for successfully removing PFAS from various aqueous solutions.
Ion exchange resins work as tiny powerful magnets, attracting and retaining polluted elements as they move through the water system. PFAS ions with negative charges are attracted to positively charged anion exchange resins. Although AER has demonstrated a good removal capacity for various PFAS, it is often more expensive than GAC. Nonetheless, given the poor absorption capabilities of activated carbon and the long equilibrium time for PFAS removal from aqueous environments, the use of IX resins has emerged as a leading strategy.
Activated carbon is a charcoal-like substance to which PFAS adheres effectively and which can be used to remove PFAS from water. Oakdale, Minnesota, introduced an active treatment stage to its water supply in 2006, and not only did the water treatment significantly reduce PFAS levels, but it also resulted in important improvements regarding birth weight and the number of full-term births in that town after the adjustment. Numerous studies have looked at using AC to remove PFAS due to its capacity to remove a diversity of contaminants, including toxic metals and persistent organic compounds.
Granular activated carbon (GAC) which is the most frequently used form, is composed of organic sources with a high carbon content, such as wood, lignite, or coal. The adsorption of organic pollutants is influenced by the size of adsorbent pores. GAC is therefore frequently used to eliminate PFAS from water. When eliminating PFOA or PFOS from water, GAC has an advantage over alternative adsorption methods like ion exchange resin in terms of cost.
Due to its capacity to degrade almost all organic compounds, its use of electricity rather than heat or chemicals to preserve the environment, its ability to deliver quick and efficient results, and its ease of use, electrochemical advanced oxidation processes (EAOP) have grown in popularity and promise as a treatment technology for the removal of organic contaminants, including PFAS.
Despite numerous research investigations in AOP, the technique performance for PFAS removal remains inferior to IX and adsorption procedures. The performance of UV technology, for example, is affected by the turbidity of the feed solutions. When compared to classic adsorption methods, the cost of AOP is less competitive.
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