Sulfate-reducing granular sludge was used for uranium-contaminated wastewater treatment and the responsible microbial community was analyzed. Four feedings, with 6 days for every feeding and 20 mg/L initial uranium, were provided at 27.5 (±2.5) °C. After the four feedings, a uranium removal efficiency of 94% was obtained. Environmental scanning electron microscopy (ESEM) showed that short rod bacteria were the dominant microorganisms in the granular sludge. X-ray energy dispersive spectroscopy (EDS) confirmed the presence of uranium on the granular surface. High-throughput sequencing was carried out for analyzing the bacterial diversity and community structure. The total data set comprised 8,290 high quality sequences, which could be divided into 605 operational taxonomic units (OTUs). The library coverage was 0.96 and the alpha diversity indices of ACE, Chao1, Shannon and Simpson were 2,255.40, 1,346.12, 4.03 and 0.05, respectively. There were 13 bacterial genera present with a ratio of more than 1% of the total 124 genera, among which Desulfovibrio (16.48%), Clostridium IV (9.29%), Bacteroides (3.46%) and Citrobacter (1.41%) were assumed as the functional bacteria, with a cumulative proportion of 30.64% of the total bacterial population. The results provide insights into the bacterial community of sulfate-reducing granular sludge exposed to high concentrations of uranium (20 mg/L).

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