Modelling Bacterial Biomass in a Non-chlorinated Drinking Water Distribution System

Abstract Water quality can deteriorate as it travels through a drinking water distribution system (DWDS). The DWDS offers reaction surfaces and contact time and, thus, acts as a bioreactor where biofilms develop that influence biomass dynamics. Under normal operational conditions the biofilm is in a steady state and the exchange of biomass between the biofilm and the bulk water phase is in equilibrium. When this equilibrium is disturbed, e.g. by a hydraulic incident, there is a potential of release of biomass from the biofilm leading to higher concentrations of biomass in the drinking water. This could lead to a discolouration event and may have an impact on microbial water quality. The main issue for a water company is to know where in the network the risk of these disturbances of the equilibrium is the largest and what control measures can be taken. The goal of our research is to combine and improve water quality models and a hydraulic network model to determine high and low risk locations in the DWDS with respect to bacterial biomass. As a first result a conceptual model, with parameter values based on internationally published laboratory and in situ measurements in the DWDS, has been developed.