Simultaneous transport of substrates, disinfectants and microorganisms in water pipes

A mathematical model that accounts for simultaneous transport of substrates, disinfectants and microorganisms has been developed to predict substantial changes in quality of distributed water. The model consists of a set of mass balance equations for organic substances, ammonium nitrogen, oxidized nitrogen, dissolved oxygen, alkalinity, biomass, and disinfectants in the bulk liquid phase and within the biofilm under laminar and turbulent flow conditions. This model is validated by comparing its solutions with the numerical solutions in the literature and then is applied for predicting the behavior of a typical water treatment plant effluent through a distribution pipe. The flow properties and disinfectant consumption rate at the pipe wall play a significant role in the determination of potable water quality in the distribution system.