Characteristics of fungi formation in urban sewer at different flow conditions: Distribution, metabolism, and...

Fungi are the significant components of the sewer ecology system which can consume substances and exhibit pathogenicity. However, the characteristics of fungi formation and metabolism in the complex sewer environment have not been revealed in depth. In this study, gradient flow conditions were conducted in a pilot sewer and the formation characteristics of fungi were synthetically investigated. The results showed that the low flow rate at 0.1-0.4 m/s led to the loose morphology of biofilms, while the overly loose environment did not allow fungi communities to thrive in sewer. The dense biofilms were found at the middle flow condition (0.4-0.6 m/s), and the fungal communities with degradation functions were exuberant at this condition (such as Tremellales with relative abundance of 6.18% and Talaromyces with relative abundance of 6.51%). In particular, eleven kinds of fungi with known pathogenicity of the sewer biofilm were found in this study, and it is worth noting that the abundance of pathogenic fungi at medium flow rates is significantly higher than that at other flow conditions (higher than 10 %). While, excessive flow shear force (0.8-1.2 m/s) led to biofilm shedding which caused hindering the proper generation of fungi. In summary, the pollutant transformation and pathogenic exposure conducted by fungi communities could affect the sewer management process significantly, and this study could provide research foundation for wastewater quality prediction and management of pathogenic risk in sewer systems.