The objective of this study was to demonstrate a real-time chlorine decay with enhancement of simulation program (EPANET 2.0) developed for drinking water supply networks. Periodically samples, two runs/week at various time intervals, were tested at (20) locations in water distribution system of Mosul University and analyzed in site with chlorinator instrument. First the system hydraulic model (EPANET) was used with the entire pipe and junction data which was obtained from university’s records, while chlorine decay coefficients (both bulk and wall) were used from previous literatures and some model runs. A value of the bulk decay coefficient of (-1.0 d-1) was chosen, as for the wall decay coefficient, it was set to zero.
The study demonstrated that most of the highly water consumption nodes have a residual chlorine concentration within (0.25 -1.2) mg/l. Moreover, the simulation program shows that from (12 – 5 A.M) chlorine concentration has nil values .However, due to the lack of maintenance works in both storage tank and piping network, about 93% of the reaction rates of the chlorine were happened in, so it is recommended to add an adequate dosing of chlorine with appropriate mixing in the high elevated tank.

KEYWORDS: simulation, chlorine decay, water quality, distribution networks, EPANET