Evaluation of Biodegradability and Biodegradation Kinetics for Anionic, Nonionic, and Amphoteric Surfactants

The biodegradation kinetics of anionic (sodium laureth sulfate – SLES), amphoteric (disodium cocoamphodiacetate – DSCADA), and nonionic surfactants (polyalcohol ethoxylate – PAE) were assessed in this laboratory study. Similar degradation behavior was observed for all surfactants with only a fraction of the parent compound readily biodegradable. Biodegradation, as estimated by COD removal, was initially (i.e., within 24 h) rapid, however only 40–70% of the surfactant molecules were readily biodegradable. Intrinsic kinetic parameters were successfully quantified for the readily biodegradable component of the surfactant. Inhibition was not observed and microbial kinetics of SLES, DSCADA, and PAE degradation fit the Monod model well. Average μ-S curves were generated for each surfactant. Based on these results, complete degradation of the target surfactants using biological waste treatment would be limited.