Early succession of biofilm bacterial communities in newly built drinking water pipelines via multi-area analysis

Biofilms inhabiting pipeline walls are critical to drinking water quality and safety. With massive pipeline replacement underway, however, biofilm formation process in newly built pipes and its effects on water quality are unclear. Moreover, differences and connections between biofilms in newly built and old pipes are unknown. In this study, early succession (<= 120 days) of biofilm bacterial communities (abundance and diversity) in upper, middle and bottom areas of a newly built cement-lined ductile iron pipeline were evaluated using improved PropellaT biofilm reactor and multi-area analysis. A comparison with old pipelines (grey cast iron, 10 years) was performed. In the newly built pipeline, the abundance of biofilm bacteria did not change significantly between 40 and 80 days, but increased significantly between 80 and 120 days. The biofilm bacterial abundance (per unit area) in the bottom area was always higher than that in the upper and middle areas. Based on alpha diversity index and PCoA results, biofilm bacterial community richness, diversity and composition did not change significantly during the 120-day operation. Besides, biofilm shedding from the walls of newly built pipeline significantly increased bacterial abundance in the outlet water. Opportunistic pathogen-containing genera, such as Burkholderia, Acinetobacter and Legionella, were identified in both water and biofilm samples from newly built pipelines. The comparison between new and old pipelines suggested a higher bacterial abundance per unit area at the middle and bottom areas in old pipelines. Moreover, the bacterial community composition of biofilms in old pipelines was similar to that of newly built pipelines. These results contribute to accurate prediction and management of biofilm microbial communities in drinking water pipelines, ensuring the biosafety of drinking water.

Automated summary

Biofilms on pipeline walls are crucial for drinking water quality and safety. The process of biofilm formation in newly built pipes and its impact on water quality are poorly understood, as are the differences and connections between biofilms in new and old pipes. This study examined the early succession of biofilm bacterial communities in a newly built cement-lined ductile iron pipeline and compared them with those in old pipelines. The results provide insights into the accurate prediction and management of biofilm microbial communities in drinking water pipelines and ensuring the biosafety of water.