Evaluation of the microbial diversity in a horizontal-flow anaerobic immobilized biomass reactor treating linear alkylbenzene sulfonate

Abstract

The purpose of this work was to assess the degradation of linear alkylbenzene sulfonate (LAS) in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. The reactor was filled with polyurethane foam where the sludge from a sanitary sewage treatment was immobilized. The hydraulic detention time (HDT) used in the experiments was of 12 h. The reactor was fed with synthetic substrate (410 mg l(-1) of meat extract, 115 mg l(-1) of starch, 80 mg l(-1) of saccharose, 320 mg l(-1) of sodium bicarbonate and 5 ml l(-1) of salt solution) in the following stages of operation: SI-synthetic substrate, SII-synthetic substrate with 7 mg l(-1) of LAS, SIII-synthetic substrate with 14 mg l(-1) of LAS and SIV-synthetic substrate containing yeast extract (substituting meat extract) and 14 mg l(-1) of LAS, without starch. At the end of the experiment (313 days) a degradation of approximately 35% of LAS was achieved. The higher the concentration of LAS, the greater the amount of foam for its adsorption. This is necessary because the isotherm of LAS adsorption in the foam is linear for the studied concentrations (2 to 50 mg l(-1)). Microscopic analyses of the biofilm revealed diverse microbial morphologies, while Denaturing Gradient Gel Eletrophoresis (DGGE) profiling showed variations in the population of total bacteria and sulphate-reducing bacteria (SRB). The 16S rRNA gene sequencing and phylogenetic analyses revealed that the members of the order Clostridiales were the major components of the bacterial community in the last reactor operation step.

Anaerobic degradation of linear alkylbenzene sulfonate in fluidized bed reactor

“…Oliveira et al (2009) and Duarte et al (2008) obtained removal efficiencies of 28% and 35%, respectively, in a horizontal anaerobic immobilized biomass reactor (HAIB). In a UASB reactor with 4 mg.L -1 of LAS influent, Sanz et al (2003) found removal of 85%.…”

“…In a UASB reactor with 4 mg.L -1 of LAS influent, Sanz et al (2003) found removal of 85%. The efficiencies achieved in the work of Oliveira et al (2009) and Duarte et al (2008), in addition to degradation, consider the LAS removed by adsorption on the support. However, in this work with the fluidized bed reactor, degradation was therefore obtained without the adsorption of LAS onto biomass and sand.…”

“…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 -1 and 4 mg.L -1 , respectively.…”

Las degradation in a fluidized bed reactor and phylogenetic characterization of the biofilm

“…However, for anaerobic systems, information is scarce and has been reported only recently, mainly due to recalcitrance of LAS in those systems. Removal efficiency of about 35% was achieved in horizontal anaerobic fixed bed (Duarte et al, 2008), and 85% in Upflow Anaerobic Sludge Blanket (UASB) reactors (Sanz et al, 2003).…”

“…Recent studies in this area have focused on the use of UASB and fixed bed reactors (Almendariz et al, 2001;Sanz et al, 2003;Duarte et al 2008, Oliveira et al 2009). The microbial communities from biomass present in the reactor were described by 16S rRNA gene analysis.…”