Influences of wall shear stress on bacterial colony formation at pipe joints and elbows in drinking water distribution systems

In drinking water distribution systems (DWDSs), localized flow disturbances induced by pipe joints and elbows lead to variations in shear stress, which can influence bacterial colonization and the subsequent development of biofilms on pipe surfaces. Despite the importance of these dynamics, the effects of microscale hydrodynamic characteristics on bacterial colonization remain inadequately understood, primarily due to the challenges associated with concurrently addressing hydrodynamics and microbiological factors. This study strategically integrates a recirculation pipe testing system with computational fluid dynamic (CFD) simulations to comprehensively investigate the impact of wall shear stress on bacterial colony formation. The results indicate that fluctuations in wall shear stress, resulting from flow disturbances, are correlated with increased bacterial diversity. Within a specific section of the pipe, bacterial communities at the bottom demonstrate a degree of similarity, whereas the highest diversity is observed in samples collected from the mid-sections. Among the bacterial species detected, shear-resistant Caulobacter and metabolically adaptable Aquabacterium emerge as the predominant taxa in environments with highly variable shear stress. To maintain the microbiological safety of water within DWDSs, it is recommended to implement thorough cleaning around pipe connections and to pay particular attention to sediment accumulation at the bottom of the pipelines. Future investigations should incorporate a variety of pipe structural components and different flow regimes to provide a more comprehensive foundation for water quality protection.