DuPont Presents at 5th International Foam Conference
Representatives from DuPont Chemicals & Fluoroproducts attended the 5th International Foam Conference at the Reebok Stadium, Bolton, UK, 18-19th March 2013 to present a paper entitled “Water treatment after firefighting foam uses: Implementation at commercial scale.” The conference was designed to appeal to a broad range of delegates from the chemical, oil and gas industries, municipal and airport fire brigades, foam equipment manufacturers, fire industry consultants and academic researchers.
Fluorotelomer-based surfactants have been produced and used since the 1970s due to their unique chemical-physical properties. Specifically, they have unique surface-tension lowering capability in aqueous systems at low concentrations, e.g., 100s of ppm. Compared to hydrocarbon surfactants, fluorotelomer-based surfactants have a lower critical micelle concentration. The surface tension of water is reduced from 72 to 16 mN.m-1 at 25 °C, whereas classical surfactants lead only to 30 mN.m-1. These specific properties make them highly suitable for many industrial processes which require low surface energy solutions, such as aqueous firefighting foam (AFFF).
Extinguishments of large scale solvent fires produce large amounts of water that may contain various fluorinated surfactants, depending on the type of firefighting foam used. Due to their chemical nature, fluorinated parts of fluorinated compounds are highly resistant to biochemical and advanced oxidation processes. Therefore, the current treatment for the degradation of fluorinated surfactant from water used in fire extinguishing is high temperature incineration of the water in halogen-resistant incinerators. The lecture at the Reebok Conference proposes a process for purifying firefighting water containing fluorinated surfactants, combining electrocoagulation with reverse osmosis.
In conjunction with a brief summary of the technical effectiveness of this approach, a cost analysis was presented in comparison with the incineration cost and the adsorption alternative (activated carbon option). Finally, several examples of existing equipment were presented that illustrate the feasibility of such treating units.