EPANET Multispecies Extension to Model Advection-Dispersion-Reaction within Water Distribution System
Shang, F., J. Burkhardt, AND R. Murray. EPANET Multispecies Extension to Model Advection-Dispersion-Reaction within Water Distribution System. 2022 World Environmental & Water Resources Congress, Atlanta, Georgia, June 05 - 08, 2022.
This presentation highlights updates to the EPANET-MSX multispecies extension. These changes are relevant to researchers and users who are interested in modeling complex chemical reactions within water distribution systems. The capabilities of EPANET-MSX may be relevant for anyone interested in disinfectant decay, disinfectant byproduct, advanced chemical fate and transport modeling. Potential users include: utilitity personnel, water distribution system design engineers, and state or local agencies.
EPANET has been used widely to model hydraulics and water quality changes within drinking water distribution systems. One limitation of the EPANET water quality analysis was that it tracks the transport of only one soluble substance. A decade ago, EPA released an extension of EPANET called EPANET-MSX (MultiSpecies eXtension) to model the interactions among multiple species in bulk flow and on pipe walls. In 2020, a major update of EPANET was released with a new water quality routing algorithm that better conserves reactant mass and generates a mass balance report at the end of water quality simulations. This major improvement of the water quality modeling capability is integrated into the EPANET-MSX. All the bulk flow species are now routed topologically from upstream network junctions to the downstream ones, and the topological order is defined by simulated hydraulics and reset whenever a new hydraulic event, such as demand change and pump on/off status switch, happens. A mass balance report is provided for every RATE species of which the reaction kinetics is defined by an ordinary differential equation (ODE). To speed up the multispecies water quality modeling, reaction simulations within the water quality computational elements, i.e. water quality segments as defined in EPANET, are parallelized through OPENMP directives. It was found that up to 60% reduction of computational time can be achieved. A disinfection byproduct model involving multiple reacting species based on literature study was developed with the updated EPANET-MSX. The results are compared with the batch scale results to show its applicability to any water distribution system. The mass balance report provides detailed information about the consumption of disinfectant and generation of the disinfectant byproducts.