Molecular approach to evaluate bacterial community for H2S treatment in biofilter
Biofilters have emerged as an alternative economic and eco-friendly appeal to treat the odorant emissions from sewage treatment systems. As it is a biological system that depends on a well-established bacterial community to ensure higher treatment efficiencies, the need emerges to deepen the knowledge on structural/functional dynamics and identification of the main microbial genera linked to the treatment of toxic gases, such as Hydrogen sulfide (H2S).  In this way, this work investigated the structural dynamic linked to the functional prediction of the microbial communities present in a biofiltration system. Sampling and analysis were conducted for 720 days covering different climatic seasons and spatial distributions in the filter bed. 16S rRNA metagenomic sequencing Illumina was used to assess the taxonomic profile followed by putative assessment of functional genes. Over physical-chemical results, removal efficiency (RE) of H2S reached 99%. The middle/bottom of packing material played a crucial role in the removal efficiency in the system, where more than 50% of H2S concentration was removed. The microbial community seems to have been more affected by the spacial than the temporal variable. The main bacterial genera found were Acidothermus (higher relative abundance in the bottom layer), Telmatobacter (relative abundance through all verticality of the filter), and Bryobacter (higher relative abundance in the top layer) representing the genera that are possibly involved in the transformation of H2S in the system. The assimilation genes, that showed more identified genes, did not have relative abundance trends (spatial and temporal)  throughout the experiment. The dissimilatory genes identified such as the sat, showed a higher proportion in the bottom layer, while the others showed no trend. Accordingly, genera producing hydrogen sulfide were not identified by the taxonomic classification. These findings may justify the better RE at the bottom of the system, where a higher concentration of H2S was available for microbial groups. Besides, ?we can assume that the functional potential found in the bottom layer and along the verticality of the filter, driven by most assimilatory genes, contributed to the stability of the system. Studies focusing on bacterial behavior and structure in biofiltration systems are still scarce and only with more studies, we can understand the behavioral dynamics. Thus, this study allowed us to understand the dynamics and bacterial metabolism further and to advance the idea that microbial analysis can support changes and hence increase efficiency performance or help in a system dysfunction situation with a focus on expanding the applicability of biofiltration systems for the most varied needs and at the stability of systems used.