Treatment of commercial surfactants with chemical and photochemical advanced oxidation processes

Surfactants are among the most abundant, man-made organic pollutants with a high potential to enter the environment through the discharge of domestic and industrial wastewater as well as sewage sludge. Due to their amphiphilic structure, they not only are present in natural waters at concentrations varying between nondetectable to several μg/L’s, but also tend to significantly sorb onto sewage sludge, ultimately bioaccumulating in soil sediments of receiving water bodies. According to extensive biodegradability and ecotoxicological studies, most surfactants are readily biodegradable regarding the parent compound; however complete oxidation is usually achieved neither in engineered treatment systems nor in the natural environment. In addition, acute toxicity data reveal that most surfactants are fairly toxic toward aquatic as well as terrestrial organisms. Considering these facts, treatment with alternative, advanced oxidation processes (AOPs) could be a promising option to alleviate the problem of uncontrolled bioaccumulation and biodegradation of surfactants in the environment. The present work reviews the application of chemical and photochemical AOPs for the detoxification and mineralization of commercial surfactant formulations. Special emphasis has been given to the main limitations of advanced oxidative treatment applications, namely toxicity of advanced oxidation intermediates/end products.