Modeling disinfection by-products: coupling hydraulicand chemical models

There are established chemical models that can predict disinfectant decay and DBPs formation with respect to various water quality parameters and reaction time (water age). While models such as EPANET are powerful tools in hydraulic simulations, they have limited use in simulating water quality, containing only a basic chlorine decay subroutine. This paper presents a study on the use of a link that was developed to couple the external water quality models and the hydraulic model of EPANET 2.The coupled model has been applied to a hypothetical distribution system under steady and non steady conditions. Simulations have taken the form of sensitivity analyses to probe operational strategies such as modified treatment as well as optimized secondary disinfection in order to maintain sufficient chlorine residual at critical points within the distribution system. Simulations have also been performed to compare the relative rates of formation of THMs vs HAAs as well as individual species. Of particular interest is optimization of chlorine dose to minimize residual chlorine under non-steady-state conditions.