The time-window – an inadequate criterion for the ready biodegradability assessment of technical surfactants

The attainment of the biodegradation pass-level within a distinct time period (10 days after the end of the lag-phase) is one of the criteria for assessing the ready biodegradability of chemical substances. The time-window as a simple approach for describing biodegradation kinetics is a poor descriptor in the case of mixtures and poorly soluble compounds. Technically used surfactants are a mixture of numerous homologues and isomers and many are composed of two organic moieties which will be degraded sequentially. The associated problems in fulfilling the time-window requirement and the inadequacy of this criterion for the ready biodegradability assessment of surfactants are illustrated and discussed.