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Common way PFAS is disseminated into nature
PFAS-borttagning 

What are PFAS and related forever chemicals?

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, such as thermal stability and 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 utlity for various coating applications with water repellent characteristics. This makes PFCs useful components in a wide variety of consumer and industrial products, including 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 application is fire foam which has been used to quench fire effectively. The wide spread use of these foams globally through fire extinguishing exercise fields has caused PFAS and PFOS to trickle into groundwater aquifers. This has lead to extensive contamination of drinking water with extremely long half-life. The chemical stability causes severe bioaccumulation in plant, animal and human tissues. It is therefore important to prevent the consumption of PFAS and apply sustainable treatment solutions to prevent contamination and human consumption.

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

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

Emerging pollutants and directives

PFC har producerats i stora volymer sedan 1950-talet och under senare år har produktionen skiftat mer mot kortkedjiga föreningar och perfluoroeter-karboxyl- och sulfonsyror, vilket redan har märkts i våra vattenmiljöer. Dessa specifika föreningar utgör dock endast en bråkdel av de PFAS som säljs globalt. En del produktion har också ersatts av andra starkt fluorerade föreningar som fluorotelomeralkoholer som långsamt kan brytas ned till PFOA.

PFC:er erkänns nu av en allt större del av det vetenskapliga samfundet som en växande miljöförorening på grund av deras kemiska stabilitet och toxiska effekter i kombination med deras höga förekomst i miljön, biota och människor. De direkta exponeringsvägarna av dessa kemikalier för människor är något oklara och oron för PFC-förorenade vattenkällor har ökat dramatiskt de senaste åren hos allmänheten. Kranvatten och flaskvatten är två potentiella källor till PFC, vilket delvis förklarar varför de finns i människans blod.

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 PFAS removal down to levels of 2 ng/L for drinking water in Denmark and 4 ng/L in Belgium and Sweden. European Food and Safety Authority (EFSA) stipulates PFAS 4* limits of 4 ng/L which is being applied gradually in the EU and other countries. Various limits pertaining to PFAS 11, PFAS 20, PFAS 21* are 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 recent compliance requirements set forth by regulatory bodies globally since early 2023, a number of proposed treatment methods have been presented on the market, among others single-stage active media beds, physical separation with foaming agents and various research initiatives focused on advanced small-scale trials. Adsorption process are generally effective, but require sufficient pre-treatment of water volumes in which PFAS compounds are present.

It must be understood that PFAS compounds constitute only a fraction of the total amount of dissolved organics and non-organics, 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 soil remidiation or ground preparation work before establishing new a new residential housing complex or buildings.

The table below summarizes the most imminent challenges pertaining to sustainable PFAS removal from water bodies that may exhibit a direct or indirect pathway into human consumption, or into the aquatic flora and fauna with subject to human consumption, such as fish or plant based foods.

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

Typical water sources of PFAS contamination and related problem statements and challenges of effective treatment

 

Type of water source Utmaning General solution
Ground water PFAS levels may be present above 500 ng/L. Requires special methods to ensure sufficient treatment levels to below local or regional guidelines. Typical flows are 5-10 m3/h. Depending on the hydrogeological conditions may cause moderate to high salinity levels. Moderate particle content is likely to occur which puts additional strain on the treatment system. High PFAS levels can only be treated to below drinking water standards below 4 ng/L with an overall removal rate of 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 to contain and protect filtration mechinery.

If salinity levels are high, separation of these would require membrane filtration as a pre-treatment process. PFAS removal would then be achived through various resins or other sorption beds. Particle separation by sedimentation or sand filtration is recommended to sustain the high treatment levels.

Pond collection from fire drills High concentrations of suspended solids, heavy metals and other recalcitrant compounds and total organics. This requires additional attention to upstream particle removal systems, treatment of dissolved organics and heavy metal removal in order to maximize PFAS treatment performance and lower the required treatment process footprint. S

easonal treatment needs in secluded areas with limited utilities available to sustain a long-term treatment solution. Typical flows are 1-5 m3/h.

This is one of the most common PFAS remediation scenarios and absolute attention to multiple pre-treatment steps is a must. In order to combat high levels of particles with a wide particle size distribution, potential algea growth and biofilm inside process equipment, the solution is likely to require physical particle separation, particle filtration. biocidal agents, 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 and/or weather protection.
Drinking water bodies Large volumes must be treated, even though residual contamination is generally low. Requires potential drinking water plant extension and intense Front End Engineering Design. These solutions are normally implemented at existing drinking water plants as a retrofit project, or in new drinking water plants in areas where PFAS can be proven to exist in the water sources from which drinking water is produced. These solutions are not likely to contain high levels of PFAS, although it can vary greatly. Typical concentrations vary in the range of 10-100 ng/L, enough to necessitate treatment to reach EU and EPA directives.

As these processes normally follow upstream treatment which already exist in the plant, a solution would normally not comprise heavy particle separation or salinity reduction measures. The challenge is hydrualic 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 matrix, where both pre-treatment and functioning biological treatment is necessary to maximize PFAS removal rates. Generally requires a quartenary treatment steps with plant extension to accommodate PFAS treatment process. On some occations, municipial wastewater treatment plants may encounter elevated levels of PFAS, especially if there is natural infiltration in the pump station sewage network or if heavy industries are releasing their effluent into the municipal wastewater management system. PFAS removal in those instances would be implemented as a quartenary treatment step, following primary, secondary and tertiary treatment. PFAS levels are likely to occur in trace levels at maximum 10 ng/L.

In order to treat it, advanced oxidation or adsorption would be viable alternatives to achieve at least 50% treatment levels. However, particle filtration steps as part of the process would be required in order to protect the PFAS removal step.

Sustainable methods and technologies to treat PFAS

Mellifiq has a proven track record for the supply of effective treatment processes adapted to any PFAS challenge.

Oxidation and Advanced Oxidation Processes (AOP)

Oxidation methods may serve many purposes in designing a complete process for PFAS removal. It is an excellent choice for pre-treatment to reduce generally dissolved organics by means of chemical degradation, prevent biofilm and manage algae, especially in open pond water sources. It can also be used to break down long-chained PFAS into short-chain, making further treatment with resins or adsorption more effective. The general improvement in water quality on total organics will also extend the life time and lower media saturation by more than 50%.

Mellifiq applies oxidation for such purposes with complete ozonation systems to eliminate the need for chemicals. Such systems can be delivered as containerized units or stand-alone turn-key configurations through or Ozonetech RENA Vivo eller Tellus lines.

To amplify the the PFAS degeneration effects, ozonation can be combined with catalytic processes or UV from our Saniray UV-systems to form highly reactive radicals which 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 may play an integral role in a complete PFAS removal process, especially if the water source contains elevated levels of large particles, which will interfer signficantly with other treatment units. Flocculation is performed by implementing rapid mixing of process water with especially selected flocculation chemicals, and may also partially remove particle-bound PFAS substances by forming flocs with incoming particles. Flocs are then allowed to settle, leaving a clear phase which can be fed to further treatment.

Mellifiq delivers complete settling systems to used as a key piece for PFAS removal with Water Maid AquaFloc sedimentation systems. Depending on the particle size distribution and flow, AquaFloc units can be configured with both active pH control and automatic dosing to ensure maximum treatment levels, thereby increasing the overall PFAS removal efficiency.

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

Mobile solution including ozonation for PFAS treatment from groundwater.

Adsorption for capturing low concentrations

As a single-stage method, with already pre-treated particle and dissolved organics free water phase, adsorption can successfully be used to adsorb PFC chains, both short and long. Short-chained substances will generally enable less frequent media exchange due to increased use of porous media volumes. It is for that reason recommended to implement upstream chemical degradation with oxidation. For most cases, the available footprint to carry out sufficient treatment is limited, especially for on-site temporary solutions. Along with proper pre-treatment, it is imperative to consider the type of active media, which 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. The proper configuration of such systems would include automatic backwashing and pressure monitoring to ensure particle free operation.

Particle and dissolved solids separation

Particle filtration may be useful at various steps in a complete PFAS removal process, depending on the mean particle size which enters the treatment train from the water source. It is not recommended that suspended solids above 10 um enter the advanced treatment units, such as advanced oxidation or high rate adsorption. Hence, particle separation is recommended and even required for most implementation due to the low allowable PFAS effluent limits. Mellifiq typically employs fine particle sand filtration from our Water Maid FlexKarb-S systems.

For removing particles with a wide size distribution or if the occurance of particle sizes below 10 um should be removed, customer ultrafiltration systems may be used. In order to remove salinity or high levels of chlorides, reverse osmosis may be considered in order to protect active adsorption structures in pressurized carbon or media beds. While, particle filtration steps or chloride removal does 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

A properly engineered solution for micropollutants including PFAS requires experience and expertise. The image shows Mellifiq engineers taking samples to ensure proper treatment levels in a mobile Water Maid membrane filtration system targeted at zero PFAS levels for zero liquid discharge (ZLD).

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

Containerized membrane filtration to remove micropollutants

Pilotprojekt

Reducing or eliminating PFCs is a complex task, and in order to instill peace-of-mind with our clients, we can tailor a pilot project utilizing Mellifiq’s extensive in-house pilot project platform. Upon initial assessment of vital site conditions and discharge levels, multiple technologies can be applied in sequence to tailor the most effective removal process for the task at hand.

Using actual water samples, the full scale system can be similated with a hands-on approach, allowing for scaling to almost any flow in order to determine required footprint, utilities and process configuration. Results are always verified using third-party laboratories with suitable analysis methods and are 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), Perfluortridekansyra (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), Fluorotelomer sulfonic (6:2 FTS).

PFAS 4 includes: Perfluoroctane sulfonic acid (PFOS), Perfluoroctane acid (PFOA), Perfluorononane acid (PFNA), Perfluorhexane sulfonic acid (PFHxS).

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