Pollutants degradation performance and microbial community structure of aerobic granular sludge systems using inoculums adapted at mild and low temperature

Three aerobic granular sequencing batch reactors were inoculated using different inocula from Finland, Spain and a mix of both in order to investigate the effect over the degradation performance and the microbial community structure. The Finnish inoculum achieved a faster granulation and a higher depollution performance within the first two month of operation. However, after 90 days of operation, similar physico-chemical values were observed. On the other hand, the Real-time PCR showed that Archaea diminished from inoculum to granular biomass, while Bacteria and Fungi numbers remained stable. All granular biomass massive parallel sequencing studies were similar regardless of the inocula from which they formed, as confirmed by singular value decomposition principal coordinates analysis, expected effect size of OTUs, and β-diversity analyses. Thermoproteaceae, Meganema and a Trischosporonaceae members were the dominant phylotypes for the three domains studied. The analysis of oligotype distribution demonstrated that a fungal oligotype was ubiquitous. The dominant OTUs of Bacteria were correlated with bioreactors performance. The results obtained determined that the microbial community structure of aerobic granular sludge was similar regardless of their inocula, showing that the granulation of biomass is related to several phylotypes. This will be of future importance for the implementation of aerobic granular sludge to full-scale systems.