Assessing Uncertainties in Mechanistic Modeling of Quality Fluctuations in Drinking Water Distribution Systems

Applying mechanistic water quality analysis models that are proficient at simulating the dynamics of heterotrophic bacteria within distribution pipes is a pragmatic approach to maintaining biological stability during drinking water distribution systems (DWDS) operation. Accurate interpretation of hydrodynamics and the uncertainties associated with the multifaceted exchanges within the distribution pipes is crucial to the reliability of these models' predictions. However, knowledge about most exchanges within DWDS is still inadequate. Therefore, state-of-the-art mechanistic models exist merely as theoretical frameworks to understand the causes and effects of microbiological quality fluctuations in DWDS, and they lack general applicability. Advancing the applicability and reliability of the mechanistic models necessitates adequate consideration of epistemic and aleatory uncertainties. This study developed mechanistic models to realize the degree of complexity that needs to be integrated into the modeling framework to accurately describe the water quality dynamics in a real-world DWDS. Under the test conditions considered, the simplest single-phase models that ignore the complex exchanges associated with the pipe biofilm layers were found to make similar microbiological quality predictions as the relatively complicated two-phase models. The results indicate that the knowledge uncertainty associated with mechanisms concerning heterotrophic bacterial regrowth in the bulk phase and biofilm detachment in the wall phase is critical in controlling the reliability of the mechanistic water quality models.