Identification of the bacterial community of a pilot-scale thermophilic aerobic bioreactor treating sewage sludge

The goal of this study was to investigate the bacterial community associated with a pilot-scale thermophilic aerobic digestion (TAD) reactor treating sewage sludge. The digestion system removed up to approximately 30% of volatile solids (VS); VS and total solids (TS) decreased from 38.4 to 26.9 g/L and from 51.2 to 43.8 g/L, respectively, and the ratio of VS/TS declined from 75.4% to 62.8%. Coincident with the thermal reduction of sludge, 16S rRNA clone library data showed that a significant shift occurred in the bacterial community composition with the selection of the Firmicutes and Deinococcus-Thermus families as well as a marked decrease in the relative abundance of a large part of bacterial taxa such as Proteobacteria. A unique bacterial community in the TAD reactor developed resulting from specific environmental pressures such as thermal stress. A predominance of thermophilic bacteria belonging to Bacillus sp., Geobacillus sp., Thermaerobacter sp. and Thermus thermophilus sp. suggest their putative roles for potentially high thermophilic degradation of sewage sludge. (C) 2014 Elsevier Ltd. All rights reserved.