Analysis of bacterial, fungal and archaeal populations from a municipal wastewater treatment plant developing an innovative aerobic granular sludge process

Mature granules and flocs from aerobic sludge were collected from the wastewater treatment plant (WWTP) treating both municipal and industrial effluents in Haining city China. This plant has been operating under conditions favoring aerobic granular sludge formation, for over 3 years, suggesting that the granules, which stably retained under changing effluent conditions, may contain unique microbial populations. Microbial analysis indicated that the granular sludge was primarily composed of Planctomycetes, Proteobacteria and Bacteroidetes from the bacterial phyla. Interestingly, microbial communities were also observed to be stratified between the structural features of the sludge. For example, Euryarchaeota was found to make up the majority of the archaea found in the granules while Methanosaeta was dominant in the flocs. Additionally, granules were found to contain, 34 phyla and 222 genera of bacteria, 4 phyla and 13 genera of fungi, and 2 phyla and 17 genera of archaea. While flocs contained, 32 phyla and 203 genera of bacteria, 6 phyla and 26 genera of fungi, and 2 phyla and 12 genera of archaea. This biodiversity signifying a preservation of bacterial and archaeal population in granules, and fungal populations in flocs may result from the sedimentary characteristics of the granules. This suggests microbes uniquely associated in the granules are playing a key role in structure formation and stability of the granular ecosystem, which is maintained by the longer sludge retention time.