Dynamic population changes during a bioaugmented sewage sludge composting process: Improvement of pharmaceutical active compounds degradation and conversion into an organic soil amendment

Bioaugmentation has resulted in an interesting tool to improve the remotion of emerging contaminants through composting technologies in sewage sludge, whose microbial population dynamics might play a critical role during degradation. It was hypothesized that the two-step bioaugmentation-composting technology can guarantee both, an effective addition of specific inoculants and the enhancement of the degradation activity in relation to their application and their interactions with indigenous communities. Following this hypothesis, this study aimed to define the changes of fungal and bacterial populations during microbial bioaugmentation of sewage sludge with two different inoculants (Penicillium oxalicum XD 3.1 and an enriched consortium) and throughout the composting process of the bioaugmented sludge. To do so, microbial DNA was obtained from the natural consortium and from the composite samples (at key stages of the process). The amplicon sequencing of 16S rRNA genes and internal transcribed spacer (ITS) region for bacteria and fungi was then performed using an Illumina Platform. The results highlighted the importance of the inoculation per se plays an important role in determining the success of microbial inoculation during the two-step composting. Thus, correctly addressing the degradation potential as well as the competitive ability of the inoculants to persist alongside native populations by enhancing the abundance, diversity and richness of fungi and bacterial taxa related with degradation processes. Moreover, various physicochemical parameters altered by the bioaugmentation equally explained the microbial diversity changes. Redundancy analyses of β-diversity revealed the asynchronous interaction with all physicochemical parameters that varied according to the composting stage.