Primary biodegradation kinetics of linear alkylbenzene sulphonates in estuarine waters

Abstract

Primary biodegradation kinetics of a typical commercial mixture of linear alkylbenzene sulphonates (LAS), containing alkyl homologues in the range of C 10 to C 13, has been investigated using three mixed bacterial cultures. Two of the cultures originated from the Krka River Estuary (freshwater layer and saline layer) while the third one originated from the adjacent coastal waters. Determination of the remaining LAS during the biodegradation experiments was performed using reversed-phase high-performance liquid chromatography (HPLC) which allowed specific determinations of individual homologues and/or isomers. Results obtained under static conditions (die-away method) have shown that the biodegradation rate depended strongly upon the origin of the bacterial culture, the temperature condition, and the structure of alkylbenzene moiety. The mixed bacterial culture originating from the freshwater layer of the estuary revealed a significantly greater ability to degrade LAS than that from the underlying saline water layer or from the reference marine station. The biodegradation rate was significantly higher in summer (23°C) than in winter (14°C) temperature conditions. When comparing biodegradation rates of the individual homologues, the highest rate was observed for those with the longest alkyl chain. For different isomers of the same homologue, it has been noticed that biodegradation rate increased with increasing distance of the sulphophenyl group from the terminal methyl group.