This article investigates trihalomethanes
(THMs) production and simulates water age in Assiut
drinking water system using WaterCAD software. Prechlorinated
water samples were collected from Nazlet
Abdellah water treatment plant and post-disinfected with
chlorine/chloramines with different chlorine-to-nitrogen
ratios (Cl2/N). Experiments have examined varying residence
times, ratios of Cl2/N, pH conditions, and storage
containers’ type on THMs formation. The results showed
that as the residence time increased, THMs concentrations
increased. Water age in Assiut drinking water distribution
network reaches more than 10 h. Using chloramines
instead of free chlorine for post-disinfection resulted in
lowering THMs concentrations to 58.9 % after 48 h of
disinfection. Ratios of Cl2/N (2:1–6:1) were comparable
and effective on lowering THMs concentrations, and the
most effective ratio was 4:1. Also, as the pH increased, the
THMs increased. The measured THMs concentrations in
chloraminated water stored in glass and plastic bottles were
approximately the same.