Biodegradation of fatty alcohol ethoxylates in the continuous flow activated sludge test

Biodegradation of two fatty alcohol ethoxylates: surfactant C12E10 (C12 with an average 10 oxyethylene subunits (EO)) and Marlipal 1618/25 (C16–18 with an average 25 EO) were tested under the continuous flow activated sludge conditions of the classical Husmann plant and a plant having a denitrifying chamber. Primary biodegradation and concentration of metabolites: free fatty alcohol (FFA) and poly(ethylene glycols) (PEG) were measured. PEG were divided into two fractions: short-chained (1–3 EO) and long-chained PEG (>3 EO). Tensammetric methods were used for analysis. High primary biodegradation was found (96.8±0.5% for surfactant C12E10 (C12E10) and 99.6±0.1% for Marlipal 1618/25 (Marlipal)), though with a high concentration of metabolites: FFA and PEG. FFA concentration corresponded to 30–100% of theoretically predicted concentration (presuming central fission) and dependent on the chemical structure of surfactant and type of plant used for testing. Total PEG concentration was about 20% of that predicted on the basis of central fission, while the ratio of short-chained PEG in the total PEG varied from 20 to 70% and depended on the chemical structure of surfactant and type of plant used for testing.