Microbial diversity and the implications of sulfide levels in an anaerobic reactor used to remove an anionic surfactant from laundry wastewater

The objective of this study was to evaluate the removal of linear alkylbenzene sulfonate (LAS) from commercial laundry wastewater using an expanded granular sludge bed (EGSB) reactor with two specific LAS loading rates (SLLRs), 1.0 and 2.7 mg LAS gVS−1 d−1. The biomass was characterized using denaturing gradient gel electrophoresis (DGGE) and 16S Ion Tag sequencing. Higher LAS removal (92.9%) was observed in association with an SLLR of 1.0 mg LAS gVS−1 d−1 than with an SLLR of 2.7 mg LAS gVS−1 d−1 (58.6%). A relationship between the S−2 concentration in the effluent and the surfactant removal efficiency was observed. This result is indicative of the inhibition of LAS-removing microbiota at S−2 concentrations greater than 20 mg S L−1. By using DGGE, microbial stratification was observed in the reactor in association with granule size, even though the reactor is considered to be a completely mixed regime. The RDP-classifier identified 175 genera, 33 of which were related to LAS degradation.