Anaerobic degradation of alcohol ethoxylates and polyethylene glycols in marine sediments

This research is focused on alcohol polyethoxylates (AEOs), nonionic surfactants used in a wide variety of products such as household cleaners and detergents. Our main objective in this work was to study the anaerobic degradation of these compounds and their main aerobic degradation products and precursors (polyethylene glycols, PEGs, which are also used for many other applications) in marine sediments, providing the first data available on this topic. First, we observed that average AEO sediment-water partition coefficients (K-d) increased towards those homologs having longer alkyl chains (from 257 L/kg for C-12 to 5772 L/kg for C-18), which were less susceptible to undergo biodegradation. Overall, AEO and PEG removal percentages reached up to 99.7 and 93%, respectively, after 169 days of incubation using anaerobic conditions in sediments ([O-2] = 0 ppm, E-h = -170 to -380 mV and T = 30 degrees C). Average half-life was estimated to be in a range from 10 to 15 days for AEO homologs (C(12)AEO(8)-C(18)AEO(8)), and 18 days for PEGEO(8). Methanogenic activity proved to be intense during the experiment, confirming the occurrence of anaerobic conditions. This is the first study showing that AEOs and PEGs can be degraded in absence of oxygen in marine sediments, so this new information should be taken into account for future environmental risk assessments on these chemicals. (C) 2015 Elsevier B.V. All rights reserved.