Biodegradation of Two Nonionic Surfactants Used for In Situ Flushing of Oil-Contaminated Soils

Abstract

Abstract Surfactants used for soil in situ flushing are often synthetic monomers of nonionic type. Both ethoxylated sorbitan monoleate and nonyl-phenol have been widely reported because of their washing potential. It is necessary to investigate their aerobic biodegradability at high concentrations found after a soil in situ flushing process. The aim of this work is to show the two nonionic surfactants' biodegradation, when present in water solutions at high concentrations (400 and 800mg/l), using an aerobic consortium obtained from a conventional activated sludge system for treatment of municipal wastewater. It was demonstrated that both TW80 and Surfacpol surfactants were biodegraded (and even partially mineralised) at high concentrations, i.e., 400 and 800mg/l. It is noteworthy that Surfacpol could be biodegraded to a higher extent (about 96%) than TW80 (about 45%) in a period of 168hours. Regarding the mineralization rates, Surfacpol reached mineralization values of about 83%, whereas TW80 reached only a value of about 23%.