Abstract: The air emitted from animal manure composting plants is usually rich in many kinds of bacteria which can include human pathogenic bacteria, and can significantly influence the types and abundance of bacteria that are present in different areas of the composting plant usually not assumed to be affected. In this study, air samples from the composting area, packaging area and office area of an animal manure composting plant were collected. Bacterial diversity and community structure in the air samples from the above three areas were compared, and the regional differences in the relative abundance of human pathogenic bacteria were also analyzed. The results show that the distribution of dominant bacteria in the air of composting area, packing area and office area were almost similar to each other, but there were regional differences in the relative abundance of certain dominant bacteria. Generally, the first three dominant bacterial phylum were Firmicutes, Proteobacteria and Actinobacteria, and the dominant bacterial genera were Acinetobacter and Corynebacterium. Both the highest richness and diversity of airborne bacteria were detected in office area. There were significant differences in the airborne bacterial community in the three regions, and the bacterial community structure in the composting area was more similar to that in the packaging area. The bacterial communities in the air of the three regions were significantly different, and the bacterial phyla communities in the composting area and the packaging area were more similar. The proportion of endemic bacterial genera and phylum in the air of office area was the highest. The results of microbiological analysis show that the proportion of common bacterial phyla and genera in the composting area was the highest, to be 85.19% and 85.14%, respectively. There was no significant difference in the structure of human pathogenic bacteria in the air of different regions, and the relative abundance of Acinetobacter was the highest. The relative abundance of two types of human opportunistic pathogens in the air from office area was significantly positively correlated with the same genus in the composting area and the packing area, while there was no significant correlation between the relative abundance of human opportunistic pathogens in the air of the composting area and the packing area. The results of this study can provide basic data for air health risk assessment in different areas of animal manure composting plants.

Key words: composting plant, air bacteria, human pathogenic bacteria, bacterial diversity, community structure