Temperature Effects in Anaerobic Biodegradation of Soaps in Anaerobic Screening Tests

Abstract

Abstract Fatty acid salts (soap) are a widely used class of anionic surfactants. The applications are in fabric washing products, fabric conditioners, laundry additives and surface and toilet cleaners. The levels of soap found in the detergents applications ranges from approximately 10–15%. In this work, the percentage of biodegradation of two soaps, Na-laurate and Na-stearate has been determined under anaerobic conditions. The experiments carried out included the analysis of the effect of the temperature on the degradation of the soaps. A bath test system containing municipal digester sludge as a source of anaerobic bacteria, based on the method proposed by the ECETOC, has been applied. Based on the experimental results in the anaerobic ECETOC test, soaps tested (Na-stearate at 20°C, 35°C, 55°C and Na-laurate at 35°C, 55°C) can be regarded as ultimately biodegradable compounds, and it can expected that they are completely biodegraded under anaerobic conditions if time period allows for that. On the other hand, Na-laurate at 55°C in concentrations of 200 and 400 mg C/L was not degradaded at test conditions.