SIGMADAF demonstrates the technical and economic viability of assisted coagulation-flocculation for PFAS removal in industrial wastewater

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The R&D department of the Girona-based company has completed trials on a real civil engineering effluent, achieving an overall removal of 84% of the total PFAS sum, and exceeding 95% with additional polishing using powdered activated carbon.

SIGMADAF, a Spanish manufacturer of wastewater treatment equipment based in Girona, has published the results of a series of physicochemical treatment trials carried out by its laboratory SIGMALAB on a real effluent from contaminated soil washing at a civil engineering site. The aim of the trials was to evaluate the removal of a panel of 17 PFAS microcontaminants and fluorotelomers using an assisted coagulation-flocculation system integrated with dissolved air flotation (DAF).

The trials were conducted by SIGMALAB, the in-house laboratory of AguaSigma — a company specialising in the design, construction and commissioning of wastewater treatment plants within SIGMA Water Group — dedicated to validating treatment processes at laboratory scale. SIGMALAB offers this service to inform the detailed design of an installation, with the aim of ensuring that the proposed solution is technically viable and economically dimensioned before full-scale industrial implementation. Processes that can be tested include coagulation-flocculation with DAF flotation, Filter-Press filtration, activated carbon filtration, hydroxide precipitation, and other bespoke trials, accompanied by in-house analysis of parameters such as COD, suspended solids, nitrogen, phosphorus and turbidity. For analyses requiring official certification, the laboratory collaborates with an external centre accredited by the Spanish National Accreditation Entity (ENAC).

The PFAS removal trial results come at a time of increasing regulatory pressure on emerging contaminants. The recent EU Directive 2024/3019 of the European Parliament and of the Council, concerning urban wastewater treatment, tightens the obligations for removing substances such as PFAS from sanitation and treatment systems, and requires the sector to have effective, scalable and economically viable technological solutions at its disposal.

A real alternative to high-cost technologies

Advanced PFAS removal technologies — granular activated carbon, ion exchange, high-density membranes and advanced redox processes — have well-recognised technical potential, but their installation and operating costs make them unfeasible in many industrial contexts. In this scenario, optimising conventional physicochemical processes such as coagulation-flocculation becomes a strategic priority for the sector.

The key to the process developed by SIGMALAB lies in coagulation assisted by specialised additives: typically medium-to-high charge modified polymers, formulated to promote the formation of stable complexes with the anionic groups of PFAS. The most effective combination identified in the trials incorporated ferric chloride as the base coagulant, a specialised high-cationic-charge PFAS coagulant, and a cationic polyacrylamide flocculant. The resulting flocs — low-density and highly cohesive — are optimal for separation by DAF equipment.

84% overall PFAS removal in the most efficient trial

The most efficient trial achieved an overall removal of 84% of total PFAS microcontaminants, reducing the total concentration from 3,731 µg/L in the original sample to 0.60 µg/L in the clarified effluent. Long-chain compounds — PFOS, PFOA, PFHxS and PFDA — recorded the highest individual removal rates. Short-chain PFAS (PFBA, PFPeA) showed greater resistance to treatment, consistent with existing scientific literature.

The addition of a polishing stage with powdered activated carbon (PAC) or a PFAS-specific adsorbent makes it possible to raise overall removal to above 95%.

A solution adaptable to industrial treatment

The results support assisted coagulation-flocculation, integrated with proprietary DAF systems, as a technically and economically viable solution for the treatment of industrial wastewater containing PFAS. This technology is particularly relevant for sectors such as civil engineering, the chemical industry, the agri-food industry, and any activity generating effluents with these persistent contaminants.

SIGMADAF incorporates the development of this type of process into its R&D activities, aimed at expanding the capabilities of its equipment and solutions in response to the regulatory and environmental challenges facing the water sector.

About SIGMADAF  ·  sigmadafclarifiers.com

About AguaSigma  ·  aguasigma.com