Anaerobic degradation of linear alkylbenzene sulfonate in fluidized bed reactor

Abstract

Abstract - An anaerobic fluidized bed reactor was used to assess the degradation of the surfactant linear alkylbenzene sulfonate (LAS). The reactor was inoculated with sludge from an UASB reactor treating swine wastewater and was fed with a synthetic substrate supplemented with LAS. Sand was used as support material for biomass immobilization. The reactor was kept in a controlled temperature chamber (30±1 oC) and operated with a hydraulic retention time (HRT) of 18 h. The LAS concentration was gradually increased from 8.2±1.3 to 45.8±5.4 mg.L -1 . The COD removal was 91%, on average, when the influent COD was 645±49 mg.L -1 . The results obtained by chromatographic analysis showed that the reactor removed 93% of the LAS after 270 days of operation. Keywords : Sand; Biodegradation; LAS; HPLC; Surfactant. INTRODUCTION Linear alkylbenzene sulfonate (LAS) is a surfactant used worldwide in detergent production and is present in domestic and industrial wastewaters. Its presence in wastewater treatment plants may result in some problems, such as foaming and inhibition of microorganisms that degrade organic matter, implying a decrease in treatment efficiency. LAS degradation has been widely studied in aerobic systems, in which removal efficiencies of up to 97% have been achieved (Brunner et al., 1988). However, in anaerobic systems, studies are recent, since LAS has been reported to be recalcitrant under these conditions. Removal of 35% has been achieved in a horizontal anaerobic immobilized biomass reactor (Duarte et al., 2008) and 85% in an UASB reactor (Sanz et al., 2003) for concentrations of 14 mg.L