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Common way PFAS is disseminated into nature

World-class treatment for PFAS, PFAS-4, PFAS-11, and PFAS-21

Perfluorinated compounds (PFCs)—such as perfluorinated alkyl acids (PFAA), perfluorooctane sulfonate (PFOS) and per- and polyfluoroalkyl (PFAS) substances — are diverse groups of synthetic chemical structures with unique properties: they are thermally stable and have the ability to create smooth surfaces which repel water, oil and dirt. Developed in the 1970’s, these compounds were synthesized in large scale due to their superior utility for various coating applications with water repellent characteristics. This makes PFCs useful components in a wide variety of consumer and industrial products. These products include preservatives, lubricants, paints, foams, non-stick cookware, food packaging, waterproof clothing, fabric stains protectors and firefighting foams. PFAS and PFOS are among the most known compounds, customarily defined as perfluorinated molecules containing eight fluorinated carbon atoms.

One of the most common applications is fire foam, used for effectively extinguishing fires. The widespread global use of these foams, through fire extinguishing exercise fields and such, has caused PFAS and PFOS to trickle down into groundwater aquifers. This has lead to extensive contamination of drinking water with extremely long half-life. The chemical stability of the PFCs causes severe bioaccumulation in plant, animal and human tissues. It is therefore important to apply sustainable treatment solutions in order to prevent contamination and consequently human consumption

In simple terms, PFAS compounds all have stable molecular structures with varying carbon chain lengths, protected by extremely strong carbon-fluorine (C-F) bonds. This gives them their water repellent features. However, they are also soluble due to their single acidic groups or sulfonic groups. Hence, they can freely migrate between water phases and fatty tissues.

Examples of PFAS compounds with varying carbon chains with C-F bonds, making them stable and bioaccumulating.

Emerging pollutants and directives

Large PFAS volumes have been produced since the 1950s, and in recent years, production has shifted more towards short-chain compounds, perfluoroether carboxylic, and sulfonic acids. We can already notice the effects of this shift in our natural water sources. However, these specific compounds represent only a fraction of the PFASs marketed globally. In addition, some production has also been replaced by other highly fluorinated compounds, such as fluorotelomer alcohols that can slowly degrade to PFOA.

PFCs are recognized by an increasingly larger part of the science community as emerging environmental pollutants because of their chemical stability and toxic effects in combination with their ubiquitous occurrence in the environment, biota and humans. The direct exposure pathways to humans are somewhat unclear and general concerns about PFC-polluted water sources have grown dramatically in recent years. Tap water and bottled water are two potential PFC sources, which would partly explain why these compounds occur in human blood.

In 2020, The European parliament issued updated directives on the quality of water intended for human consumption (EU directive 2020/2184). This has lead to local and regional implementation of new permitted PFAS levels, such as 2 ng/L for drinking water in Denmark and 4 ng/L in Belgium and Sweden. The European Food and Safety Authority (EFSA) has stipulated PFAS 4* limits of 4 ng/L which is gradually being applied throughout the EU and other countries. Various limits relating to PFAS 11, PFAS 20, PFAS 21* are also being investigated and implemented.

PFAS in drinking water has been a problem for more than 50 years, now being regulated in the EU and USA

PFAS treatment challenges

In light of the compliance requirements set forth by regulatory bodies all over the world since early 2023, a number of proposed treatment methods have been presented on the market. These methods include, among others, single-stage active media beds, physical separation with foaming agents and various research initiatives focused on advanced small-scale trials. Adsorption processes are generally effective, but require sufficient pre-treatment of the water volumes that contain the PFAS compounds.

It must be understood that PFAS compounds constitute only a fraction of the total amount of dissolved organics and non-organics in water sources, especially in ground water reserves and wastewater collected in ponds. An emerging PFAS hot spot is construction sites where the contaminated groundwater table is exposed during the soil remediation process and the ground preparation work. These processes are performed before new residential housing complexes or buildings are established.

The table below summarizes the most imminent challenges pertaining to sustainable PFAS removal from water bodies that may have pathways to humans, either directly through e.g. drinking water or indirectly through the aquatic flora and fauna that humans consume, such as fish or plant-based food.

Construction sites which expose ground water and may cause PFAS contamination into nearby water bodies

Typical PFAS contaminated water sources, related problem statements and challenges to providing effective treatment

Type of water source	Challenge	General solution
Ground water	PFAS compounds may be present at levels above 500 ng/L. Special methods are required to ensure sufficient treatment results that meet local or regional guidelines. Typical flows are 5-10 m3/h. Depending on the hydrogeological conditions, the salinity levels may be moderate to high. There is likely to be a moderate amount of particles, which puts additional strain on the treatment system.	High PFAS levels can only be reduced to water standard levels below 4 ng/L if the overall removal rate is at least 95%. In order to achieve this, typical filtration steps need to be sized in order to allow for sufficient adsorption rates and retention times, which will require installation redundancy. It would in most cases be necessary to deploy mobile solutions that contain and protect the filtration machinery. If salinity levels are high, membrane filtration would be required as a pre-treatment process in order to separate the salts. PFAS removal would then be achieved through various resins or other sorption beds. In order to maintain high treatment levels, it is recommended to separate particles through sedimentation or sand filtration.
Pond collection from fire drills	High concentrations of suspended solids, heavy metals, other recalcitrant compounds and total organics. In order to maximize PFAS treatment performance and lower the required treatment process footprint, you need to closely consider upstream particle removal systems, treatment of dissolved organics and heavy metal removal. Seasonal treatment needs in secluded areas with limited utilities available that could help sustain a long-term treatment solution. Typical flows are 1-5 m3/h.	This is one of the most common PFAS remediation scenarios and considering multiple pre-treatment steps is a must. In order to combat challenges such as particle high levels with a wide particle size distribution, potential algea growth and biofilm inside process equipment, the final solution is likely to include physical particle separation, particle filtration. biocidal agents, removal of dissolved organics, and finally, targeted PFAS removal. This can be achieved with flocculation, sand filtration, ozonation and adsorption units, carefully sized to fit inside mobile containerized units or other weather-proof containers.
Drinking water bodies	Large volumes must be treated, even though the residual contamination is generally low. A potential drinking water plant extension and intense Front End Engineering Design are required.	These solutions are normally implemented at existing drinking water plants as a retrofit project. They are also implemented at new drinking water plants located in areas where PFAS can be proven to exist in the water sources used for producing drinking water. These water sources are not likely to contain high PFAS levels, although it can vary greatly. Typical concentrations range between 10-100 ng/L, levels that are high enough to necessitate treatment to reach EU and EPA directives. As these processes normally follow existing upstream treatment processes, a solution would normally not include heavy particle separation or salinity reduction measures. The challenge is hydraulic capacity over multi-technology solutions, as with pond collection or ground water treatment. Typical solutions would include active non-pressurized adsorption beds or resins.
Municipal wastewater	Large volumes with moderately complex water matrices. Pre-treatment and functioning biological treatment are both necessary to maximize PFAS removal rates. Generally requires a quartenary treatment step with a plant extension that accommodates the PFAS treatment process.	On some occasions, municipial wastewater treatment plants may encounter elevated PFAS levels in the wastewater, especially if there is natural infiltration in the pump station sewage network or if heavy industries release their effluent into the municipal wastewater management system. In those instances, PFAS removal would be implemented as a quartenary treatment step, following primary, secondary and tertiary treatment steps. PFAS is likely to occur at trace levels, maximum 10 ng/L. As possible treatment solutions, advanced oxidation or adsorption would be viable alternatives to achieve a treatment level of at least 50%. However, particle filtration steps would need to be included in the process in order to protect the PFAS removal step.

Sustainable methods and technologies to treat PFAS

Mellifiq has a proven track record when it comes to supplying effective treatment processes adapted to any PFAS challenge.

Oxidation and Advanced Oxidation Processes (AOP)

Oxidation methods can serve many purposes in complete PFAS removal processes. Oxidation is an excellent pre-treatment choice that reduces generally dissolved organics by means of chemical degradation, prevents biofilm and manages algae, especially in open pond water sources. It can also be used to break down long-chained PFAS compounds into short-chained compounds, making further treatment with resins or adsorption more effective. The general improvement in water quality will also extend media lifetime and lower media saturation by more than 50%.

Mellifiq applies oxidation for such purposes using complete ozonation systems that eliminate any need to use chemicals. Our systems can be delivered as containerized units or as stand-alone turn-key configurations through our Ozonetech RENA Vivo or Tellus lines.

To amplify the PFAS degeneration effects, ozonation processes can be combined with catalytic processes or UV from our Saniray UV-systems to form highly reactive radicals. These are able to penetrate the protective barriers formed by fluoride or bromide bonds which make up a significant portion of all PFAS and PFC substances.

Flocculation to separate particles

Flocculation can play an integral role in a complete PFAS removal process, especially if the water source contains elevated levels of large particles that can significantly disrupt other treatment units. Flocculation is performed by rapidly mixing the process water with specifically selected flocculation chemicals, a process that might also partially remove particle-bound PFAS substances by forming flocs with incoming particles. The formed flocs are then allowed to settle, after which the water can be transferred to other treatment steps.

Mellifiq delivers complete settling systems, our Water Maid AquaFloc sedimentation systems, that can serve as key pieces in PFAS removal processes. Depending on the particle size distribution and flow, AquaFloc units can be configured to employ both active pH control and automatic dosing in order to ensure maximum treatment levels. This way, overall PFAS removal efficiency is improved.

Mobile system for treating PFAS in remote areas consisting of advanced oxidation, particle filtration and adsorption

Mobile solution, including ozonation, used for treating PFAS in groundwater.

Adsorption for capturing low concentrations

As a single-stage method, after particle and dissolved organics treatment steps, adsorption can successfully be used to adsorb PFC chains, both short and long. Short-chained substances generally reduce the need to frequently change media since more of the porous media volume can be used. Due to this, it is recommended to implement an upstream chemical degradation step that uses oxidation. In most cases, the space needed to carry out sufficient treatment is limited, especially for on-site temporary solutions. In addition to considering the proper pre-treatment steps, it is also imperative to choose the most suitable type of active media, which then needs to be adapted to the specific PFAS compounds.

Mellifiq delivers systems with meticulously selected active media beds, ensuring proper iodine adsorption metrics and granule sizes. These systems include Water Maid FlexKarb-C, often with PFAS-1000 active media beds. Such systems, when fully configured, would also include automatic backwashing and pressure monitoring to ensure particle free operation.

Separating particles and dissolved solids

Particle filtration may be useful at various steps in a complete PFAS removal process, depending on the mean particle size in the incoming water flow. It is not recommended to let suspended solids above 10 um enter the advanced treatment units that handle e.g. advanced oxidation or high-rate adsorption steps. Hence, particle separation is recommended and even required for most implementations due to the low, official PFAS limits for effluent. Mellifiq typically employs fine particle sand filtration using our Water Maid FlexKarb-S systems.

If you want to remove particles with a wide size distribution or if all particles below 10 um should be removed, you can make use of customized ultrafiltration systems. In order to reduce salinity levels or high chloride levels, reverse osmosis may be considered in order to protect active adsorption structures in pressurized carbon or media beds. While particle filtration or chloride removal steps do not target PFAS substances directly, they constitute a vital part of a Mellifiq designed treatment process for PFCs and similar pollutants.

Complete contracting and analysis services

In order to properly engineer a solution that targets micropollutants such as PFAS, you require both experience and expertise. The image shows a Mellifiq engineer taking samples so that we can ensure proper treatment levels in a mobile Water Maid membrane filtration system. We like our PFAS levels at zero just as much as we like our zero liquid discharge (ZLD) systems.

We always offer process design, construction, installation and commissioning for small and large-scale PFAS removal projects; we can also accommodate permanent and temporary installations. Our broad range of high-end, integrable treatment units guarantee water discharge levels beyond all customer expectations. Upon request, we offer sampling and analysis services using accredited laboratories and recommend suitable analysis methods based on the water source type.

Containerized membrane filtration to remove micropollutants. An engineer is taking water samples.

Pilot projects

Reducing or eliminating PFCs is a complex task, and to give our clients some peace of mind, we can tailor a pilot project by using Mellifiq’s extensive in-house pilot project platform. After an initial assessment of vital site conditions and discharge levels, we can apply multiple technologies in sequence in order to tailor the most effective removal process for the task at hand.

Using actual water samples, we can simulate the full-scale system, allowing us to scale it and adapt it to almost any flow. We can then determine the required footprint, utilities and the proper process configuration. Results are always verified using third-party laboratories with suitable analysis methods, with the results being summarized in a technical report.

Pilot project system for in-house treatment with various advanced water treatment technologies

*PFAS 21 is the definition of 21 different types of PFAS substances: Perfluorobutane acid (PFBA), perfluoropentane acid (PFPA), perfluorohexane acid (PFHxA), perfluoroheptane acid (PFHpA), perfluorooctane acid (PFOA), perfluorononane acid (PFNA), perfluorodecane (PFDA), perfluoroundecane acid (PFUnDA), perfluoro dodecane acid (PFDoDA), perfluorotridecanoic acid (PFTrDA), perfluorbutane sulfonic acid (PFBS), perfluoropentane sulfonic acid (PFPS), perfluorohexanesulfonic acid (PFHxS), perfluoroheptane sulfonic acid (PFHpS), perfluoroctane sulfonic acid (PFOS), perfluorononane sulfonic acid (PFNS), perfluorodecan sulfonic acid (PFDS), perfluoroundecan sulfonic acid (PFUnDS), perfluorododecane sulfonic acid (PFDoDS), perfluorotridecan sulfonic acid (PFTrDS), F´fluorotelomer sulfonic (6:2 FTS).

PFAS 4 includes: Perfluoroctane sulfonic acid (PFOS), perfluoroctane acid (PFOA), perfluorononane acid (PFNA), perfluorhexane sulfonic acid (PFHxS).