Engineering considerations for AFFF treatment by UV/S-EO. TOC removal. Besides the 10 g L -1 of organic fluorine, AFFF contained heavy amounts of hydrocarbon surfactants. Total organic carbon (TOC) analysis of the 100-fold diluted AFFF found 396 mg L -1 of organic carbon (Fig. ). However, after UV/S treatment, the measured TOC increased to 2005 mg L -1 . Notably, the combustion temperature of the TOC analyzer by default setting (680 °C) cannot thoroughly oxidize all carbons, especially the fluorinated carbons, into CO2. Hence, UV/S treatment converted the "combustion-proof" mixed surfactants into more thermally oxidizable structures. After EO treatment, TOC was drastically reduced to only 13 mg L -1 . Assuming the value of 2005 mg L -1 was similar to or still lower than the actual TOC of the 100-fold diluted AFFF, the TOC removal by EO was ≥99.4%. Because fluorinated carbon that accommodates 100 mg L -1 of organic F as CF2 and CF3 was only a small portion of TOC, we concluded that EO treatment allows very deep mineralization of most hydrocarbon surfactants. Therefore, if organic removal is needed for AFFF treatment at ambient conditions, EO is a highly competitive technology option.