Structure and Succession of Bacterial Communities of the Granular Sludge during the Initial Stage of the Simultaneous Denitrification and Methanogenesis Process

Abstract

Batch experiment at COD/NO3 −-N ratio of 8.0 was conducted to investigate the initial performance of the simultaneous denitrification and methanogenesis (SDM) process and corresponding granular sludge (SDMGS). The results showed a high level of inhibition of methanogenesis activity with nitrate addition, and the particle size, settling performance, and morphologies of the SDMGS were also different from conventional methanogenesis granular sludge. The structure and succession of bacterial communities of the granular sludge during the initial stage of the SDM process were determined using the high-throughput sequencing method. Sequence analysis indicated that diversity of bacterial communities was significantly decreased due to nitrate addition. Proteobacteria, Bacteroidetes, Firmicutes, and Spirochaetes were identified to be the dominant bacterial communities (96.06%) of the SDMGS samples, and microbes associated with anaerobic fermentation were reorganized. Alpha-, Beta- and Gamma-proteobacteria, and Bacteroides might be the sources of denitrificans. Lastly, species associated with animal and human infections, such as Enterobacteriaceae, Bacteroides, and other common human enteric pathogens, were found to be recovered during the initial stage. Short-term assessment of bacterial communities of the SDMGS would strengthen understandings of the effects of nitrate contamination in water bodies and provide vital guidance for operation of nitrate-containing wastewater treatment.