Abstract:
The aim of this study was to get an understanding of the transport of
contaminants in a water distribution system, using the Model EPANET, in order
to meet water quality regulations and customer expectations.
For the application of the model a rural water supply system , having two
probable water sources, an elevated tank, three schools and a hospital was
selected. The transport of a conservative substance introduced at source, within
the system was analysed by varying the hydraulic and water quality parameters
for a predetermined demand pattern. The model was also used to design an
effective operating program in a two-source distribution system in which
pumping schedules were changed to get the contaminant levels below the
maximum permissible values. Another application that was studied was the
travel of a contaminant introduced at a point in the distribution system other than
the source. Here, the study was confined to the behaviour of a conservative
trace introduced at the hospital node. Finally, the behaviour of a non
conservative substance entering the system at source was studied. Here the
substance considered was residual chlorine, and the decay of the residual
chlorine introduced at the source with time and distance was studied. This is
helpful in determining the lowest residual chiorine levels in the system, which h,
a useful parameter in maintaining a safe water supply.
It was revealed that, under-average demand conditions, time, of travel of ?
contaminant to any point within the distribution system is the same irrespective
of the contaminant concentration, and also it was observed that, if the
contaminant is removed promptly the maximum concentration appearing at the
nodes in the distribution system can be reduced to a great extent. Thus it was
concluded that close monitoring of the source is extremely important in
protecting the water supply from contamination.
