I am looking for a way to determine how long it takes effluent from different points on a network, which counts tens of kilometers of pipe, to reach the treatment plant.
So far I haven't been seduced by modeling or large-scale instrumentation, but would be interested in a device or system that could be installed in the network and monitored.
When you are setting up a new wastewater treatment network, the minimum slope is 3 mm/m or, in terms of speed, you calculate a minimum of 0.6 m/s. It is a baseline for estimating wastewater travel time.
A geolocatable tracking buoy or tag would help you fine-tune the calculation.