Environmental impacts of oil spills affecting urban sewage networks can be eliminated
if timely intervention is taken. Design of such actions requires the knowledge of
transport of surface pollutants in open channels. In this study we investigated travel
time and dispersion by means of tracer experiments in sewage networks and in a creek.
Travel time of surface tracers has been found to be significantly shorter than that
of the bulk flow tracer. The ratio of travel times of bulk flow tracer and surface
tracers agreed with known correlations obtained for rivers. An increasing tendency
of the ratio of travel times has been observed for increasing bulk flow velocity.
A segment-wise dispersion model was implemented in the existing hydraulic model of
the sewer system. Simulation results were compared with experimental observations.
Dispersion rate of the bulk flow tracer has been found to obey Taylor’s mixing theory
for long channels and was more intensive than that of surface tracers in community
sewage channels.
