PARENT SESSION
3H Analysis, fate, and effects of surfactants in the environment
9:00 AM to 7:00 PM, Monday, 07 May 2001

(M/EH110) Biodegradation of Linear Alkylbenzene Sulfonates (LAS) in anaerobic conditions.

Amils, Ricardo¹, Sanz, José¹, Culubret, Elayne¹, Berna, José², Moreno, Alfonso², Ferrer, Juan², ^{1 2}

ABSTRACT- Linear alkylbenzene sulfonate (LAS) is the most widely used surfactant in all detergent and cleaning products. Aerobic LAS biodegradations is well established, and complete mineralization has been reported. Nevertheless, LAS is considered a non-biodegradable substance in anaerobic environments (Sarrazin et al., Toxicol. Environ. Chem. 1999, 69:487-498). However, presence of sulfophenylcarboxylates (SPC), transient intermediates excreted during degradation of LAS, has been reported by Gonzalez-Mazo et al (Environ. Sci. Technol. 1997, 31:504-510) in anaerobic marine sediments at Cadiz Bay. Moreover, has been recently described that LAS can be used by an anaerobic bacterium as sulphur source (Denger & Cook, J. Appl. Microbiol. 1999, 86:165-168). In this work we report the anaerobic biodegradation of commercial LAS by anaerobic granular sludge (biomass) using UASB reactors. The experimental design consisted of two reactors: R1 feed with a mixture of co-substrates, and R2 without co-substrate. Both reactors were running out for 4 months and total input (influent), output (effluent) and sorbed in the biomass LAS was taken into consideration to calculate the masses balance. It can be concluded that: i) The continuous presence of LAS at working concentration (4-5 ppm) during 3-4 month of exposition did not affected to the anaerobic biomass (EffCOD removing =85-90%). ii) Anaerobic biomass was able to degrade LAS so in presence as in absence of co-substrates. iii) At the end of the experiment, 22% (R1) and 6% (R2) were recovery in the effluent and 13% (R1) and 8% (R2) in the biomass of the total input of LAS. It is mean that 65% (R1) and 86% (R2) of the LAS was biodegraded. iv) Metabolites like-SPCs were detected in the effluent of the reactors. Our results unquestionably evidencing that LAS is primarily biodegraded under methanogenic conditions.

Key words: Alkylbenzenesulfonates, biodegradation, anaerobic, UASB