Removal of fluorinated surfactants by reverse osmosis – Role of surfactants in membrane fouling

The current treatment for firefighting waters containing fluorinated surfactants is incineration. A process for purifying firefighting water was proposed in a previous paper: electrocoagulation and filtration followed by reverse osmosis. Here the objective was to demonstrate the efficiency of reverse osmosis to reduce the fluorinated surfactant concentration from 30 to 0.1 mg L−1 at large scale and over several days. A polyamide thin film membrane was selected. Retention rate, obtained at laboratory and industrial scale for fluorinated surfactant (RR=0.994–0.999), was sufficient to reach the limit concentration in permeate defined in the project. Permeability (0.5 L h−1 m−2 bar−1) and retention rates were stable for several days. The flux decline observed was governed by the accumulation of surfactants. The fouling due to adsorption of the surfactant mixture was successfully described by a combination of the resistance-in-series and Langmuir adsorption models.