Résumé :
|
To characterize the flow patterns of wastewater through subsurface-flow rock-reed filters, a combination of tracer studies and specific conductance measurements were used. Neither the tracer study nor the specific conductance measurements alone provided the necessary information to understand the flow of wastewater through the system. However, the data taken together indicate that preferential flow occured due to density effects and surface flow. In gravel substrates, dense wastewater flowed beneath the less dense rainwater and influent, rersulting in a decrease in the residence time. Sand-and-gravel substrates, which experienced a great deal of surface flow as a result of clogging, were shown to have very little, if any, flow through the subsurface.
|