Mineralization of surfactants in anaerobic sediments of a laundromat wastewater pond

Abstract

The mineralization of 14C-labeled linear alkylbenzene sulfonate (LAS), stearyltrimethylammonium chloride (STAC) and linear alcohol ethoxylate (LAE) was examined in the anaerobic sediments of a laundromat wastewater pond and a pristine control pond. The microbial communities in sediments of the wastewater pond had been exposed to high levels of surfactants for over 25 years. Mineralization was determined by measuring the evolution of 14CO 2 and 14CH 4 from the 14C-test substances. [ 14C]Glucose and [ 14C]benzoic acid served as positive controls. LAS and STAC were not mineralized in sediments from either pond: LAE, glucose and benzoic acid were mineralized in both ponds. LAE mineralization was most rapid in sediment from the margin of the wastewater pond, while glucose and benzoic acid mineralization was most rapid in the control pond. With sediment from the center of the wastewater pond, mineralization of LAE, glucose and benzoic acid was preceded by a substantial lag. An experiment with specific metabolic inhibitors suggested that both methanogenic and sulfate reducing bacteria may play a role in LAE mineralization. In summary, this work demonstrates that LAE degrades anaerobically in sediments and indicates that extended acclimation does not relieve the need for molecular oxygen in LAS and STAC mineralization.