PARENT SESSION
16 - Oil Pollution & Biodegradation
8:00 AM to 6:30 PM, Monday, 13 May 2002
Exhibition Area

(16-31) Anaerobic Biodegradation of LAS. Effect of Innoculum Source on Biodegradation Rate and Assessment of Individual Homologues Removal.

De Ferrer, Juan¹, Moreno, Alfonso¹, López, Ignacio¹, Berna, José^*,1, ¹ PETRESA - Cepsa Building. Avda. del Partenón, 12 - 5th floor 28042 Madrid - Spain, Madrid, Spain

ABSTRACT- Recent publications (1),(2),(3), have shown considerable removal of LAS under anaerobic conditions when specific analytical methods are used to determine the disappearance of the test substance in screening tests instead of the common biogas pressure determination. Methods such as ECETOC-28 (4), have shown considerable discrepancies when assessing the biodegradation of anionics surfactants and, although negative results based on biogas are recognized as not relevant of actual behaviour in the environment of the test substance, such results are however used in regulatory activities. More recently (5), the metabolites of primary biodegradation of LAS under anaerobic conditions using CSTR (Continuous Stirred Tank Reactors) and UASB(Up Flow Anaerobic Blank Reactors) have been identified (benzene sulfonic acid and benzaldehyde) although the complete pathway has not been yet elucidated. A new and comprehensive study has been carried out using the basic conditions of ECETOC-28 test , while varying the type of innoculum used in the different experiments and assessing in all cases the removal of LAS through specific analysis by HPLC in the liquid and solid phases of the digesters. Anaerobic Sludge from 5 different sewage treatment plants was used as source of Innoculum and removals of LAS from 33.5% up to 70% have been detected at the end of the different experiments. The specific analysis have also been carried out to assess the distributiion of the various LAS homologues, phenyl C10 to phenyl C13, at the end of the tests. In all cases the higher biodegradation removal was observed in the lighter components , phenyl C10 ( 60 - 90%) being the heavier homologues, phenyl C13, those with the lower removals (10 -40%). These results are a new evidence of the LAS biodegradation occurring under anaerobic conditions. References. (1) Sanz J.L. et.al. Proceedings of CESIO World Surfactant Congress, Florence (I) 2000. (2) Prats D.et.al. Proceedings of CESIO World Surfactant Congress. Italy. (3) Berna J.L. Proceedings of CESIO World Surfactant Congress, Italy. (4) ECETOC Test Methods. Brussels (5) Mogensen A. Ph.D. Thesis. DTU (Technical University of Denmark.

Key words: Linear Alkylbenzene Sulfonate, Anaerobic Biodegradation , Removal, Homologues