The impacts of demand variability on distribution system water quality

A stochastic water demand generator (PRPsym) and a distribution system network solver (EPANET) were linked to analyze the impact of demand variability on water quality simulations at three temporal demand aggregations (1-hour, 10-minute, and 1-minute). The water quality simulation was modeled as a short-duration conservative chemical injection. Results showed that decreasing temporal demand aggregation increased chemical concentration variability and, in some cases, changed the underlying transport characteristics. The results were also interpreted within a risk assessment framework assuming a toxic chemical species, which illustrated that the impacts of temporal demand aggregation were more evident for nodes where the underlying hydraulic path had been altered. These underlying changes in hydraulic transport were typically observed at the edges of the system rather than main trunk lines, which suggest that there may be portions of a distribution system where typical deterministic modeling assumptions may not adequately represent localized water quality conditions.