Análise da comunidade microbiana em sistema de tratamento de biogás com elevadas concentrações de sulfeto

Abstract

Vinasse is the residue of the first distillation during the ethanol production and when treated by anaerobic digestion, produces a biogas with high concentrations of H2S, a toxic gas which may lead to corrosion of biogas utilization structures. For energetic purposes, biogas should therefore be desulfurized. In this work, a system in pilot scale was studied, which integrates physical, chemical and biological principles for the removal of H2S contained in the biogas derived from methanation of vinasse. The system is located in the city of Belo Monte (MG). Since the biological sulfide oxidation reactions are an important part of the process, changes in the microbial community, both adhered to the support medium and dispersed in the liquid phase, in response to changes in volumetric loading of H2S, which ranged from 2 to 19 kgH2S.m-3.d-1, were investigated. Techniques of DGGE and next-generation sequencing in Miseq platform were used. The physical and chemical parameters were monitored on site. The desulfurization system showed H2S high removal efficiency (above 99%) and biological analysis revealed that the bacterial community is complex and remained fairly constant throughout the experiment. Some differences were observed between the recirculating liquid and attached biomass samples, indicating that, despite the contact between the liquid and the biofilm, there may be specific groups for each site. Most of the sequences were classified as Firmicutes (52.4%) and Proteobacteria (14.2%), corresponding to 66.6% of the total. To a lesser extent, Bacteroidetes (7.5%), Synergistetes (4.4%) and Chloroflexi (4.3%) phyla were found. The relative abundance of taxa of sulfide-oxidizing bacteria was low, however, other groups involved in the oxidation of sulfide could be among unidentified sequences. In addition, there were no OTUs related to the main groups of green and purple sulfur bacteria. Statistical analysis indicate that the COD and dissolved oxygen can be very important parameters in the stability and shock resistance of the system.