Modeling Framework for Pathogen Dynamics in Water Distribution System Biofilms

Abstract Submission: The behaviour of pathogens within biofilms in water distribution systems remains poorly understood due to difficulties with in situ measurement of microbes and the complexities of physical, chemical and microbial reactions. While advances have been made in modeling general biofilm growth dynamics, the interaction of pathogens is typically not included in such efforts and field verification of these models has been minimal. This presentation will discuss the development of a novel modeling framework for pathogen dynamics in biofilms to better understand the risks to public health. The framework consists of several individual modelling components brought together to support quantitative microbial risk assessment (QMRA). First, incorporating the Neutral Community Model that has previously been applied to predict taxa abundance in biofilms for wastewater treatment, a Two-Phase Model (TPM) of pathogen attachment to and growth within biofilms under varying hydraulic conditions and disinfectant residual concentrations is being developed. The resulting stochastic prediction of pathogen content in biofilms is then linked to an adapted version of the Variable Condition Discolouration Model (VCDM) to predict mobilization of pathogens from different biofilm layers under various hydraulic conditions. Finally, the mobilized pathogen concentrations are then linked to water distribution system network models to simulate fate and transport. The models within the framework will be calibrated using robust experimental data from annular reactors and full-scale pipe loops, ultimately to provide health risk estimation from pathogens within biofilms for a number of contamination scenarios.

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