Innovative solutions for wastewater purification and PFAS removal

Activated carbon mobile filters can help WWTPs overcome the above mentioned barriers.

• Greater flexibility vs fixed filters: when relying on fixed units, an increase of production over time will mean buying an extra unit to meet emission limits (e.g., COD). A similar scenario occurs following regulations tightening or contamination variations (e.g., AOX in phytosanitary wastewater). Tapping into a modular system will let plants solve this issue. All it takes is to add more mobile units to handle the extra purification needs. In addition to this, mobile filters can work either as a pre-treatment or polishing step downstream of the WWTP.

• Versatility of activated carbon: besides COD, activated carbon can efficiently remove many other wastewater contaminants. Like, non-ionic surfactants, for instance, that can challenge biological treatments.

• Water reuse: other than promoting drought resilience, reusing wastewater helps companies comply with the EU Water Reuse Regulation. However, before being suitable for reuse, pollutants must be removed from wastewater via an adequate multi-stage treatment. In this regard, activated carbon filtration can be strategically placed prior to reverse osmosis to avoid membrane clogging or on the treatment of the concentrate of this R.O. to remove concentrated pollutants prior to discharge or further reuse.

This case study illustrates DESOTEC’s capacity to deliver fast, effective, and sustainable filtration solutions tailored to client needs in the specialty chemicals sector.

Challenge

A large firm managing multiple waste management projects across France wanted to future-proof its business against upcoming stricter PFAS emission limits. Therefore, they were after a PFAS removal technology to test. Among several options, the company chose DESOTEC’s.

While the customer’s treated water was safe for discharge under current legislation, tests showed a PFAS level (732 µg/l) which is likely to exceed any future emission limit. The client therefore asked DESOTEC for help in lowering PFAS, using the current drinking water limit of 100 ng/l per individual PFAS molecule as its benchmark.

Solution

DESOTEC installed two MOBICON filters in series to treat a flow rate of 60 m³/ hour. The first filter was filled with a carbon grade suitable for removing the bulk of organic compounds in the wastewater, i.e. COD and larger PFAS molecules. Instead, the second unit was filled with a higher grade carbon, from our B-PURE® range, designed for adsorbing even the smallest PFAS molecules such as perfluorobutanoate (PFBA), perfluorobutanesulfonic acid (PFBS) and trifluoroacetate (TFA). This two-filter model preserves the more costly higher grade carbon to treat the smaller PFAS, as a polishing step, thus fostering sustainability and cost-effectiveness.

Results
After the filters went live, tests showed that the treatment was consistently bringing PFAS levels down to below the drinking water limit. The environmental authorities have also tested the water a few times as part of a data collection exercise that will feed into the eventual PFAS treatment framework for France. Their measurements tally with those carried out for the client.

Once a mobile filter is saturated, it is brought back to DESOTEC’s facilities where the spent carbon is safely emptied and treated according to POPs regulations. The measurement of the adsorbed PFAS level is done as per the innovative method described above. This allows us to make an informed decision about the best PFAS treatment option. If the PFAS concentration is below the POPs Regulation limits, the saturated carbon will be subjected to a thermal treatment at DESOTEC facilities, safely and sustainably, making sure PFAS is eliminated below detectable levels. The carbon can then be reactivated for reuse.