A field-scale evaluation of a multi-species water quality and hydraulic model

Drinking water distribution system network models have become a powerful tool in the drinking water industry for simulating both hydraulic and water quality conditions of a water distribution system. This study provides the first comprehensive evaluation of a multi-species chloramine model through the use of field-scale measurements and distribution system network modeling. In particular, this study was focused on evaluating existing, bench-scale water quality models associated with chloramine decay, by-product formation, and nitrification at the field-scale. The hydraulic and multi-species water quality simulations were performed using EPANET-MSX. The results of the field-scale study and modeling assessment were used to identify potential "knowledge gaps" that exist in current advanced water quality models and provide motivation for future improvements associated with distribution system water quality modeling. Results indicated that EPANET-MSX is capable of representing complex water quality dynamics and network hydraulics throughout the distribution system, but further improvements can likely be made to improve the underlying model accuracy. Inconsistencies between modeled and observed results may be attributed to the following factors that were not considered: temporal variability in the influent water quality concentrations, interaction between biological and chemical species (nitrification), reactions between the bulk fluid and pipe wall, and accurate representation of spatial distribution and stochastic consumer demands. These "knowledge gaps" should be considered in future modeling efforts to improved the performance of multi-species water quality modeling. 2010