Using fundamental hydrogeological equations to monitor the effects of clogging and media consolidation on the hydraulic regime of a vertical subsurface flow treatment system

The design of passive biological filters has evolved and current design practices are predominantly based on flow (either horizontal or vertical) through porous media. To date, no method has been developed to accurately estimate the effective life expectancy of these types of treatment systems, nor have non-intrusive methods to determine the extent of substratum clogging been perfected. This research presents the results of tracer studies on various stages of two hybrid-passive landfill leachate treatment systems: an aerated pretreatment system followed by two different types of vertical-flow through porous media treatment systems. The tracer studies were used to assess changes in the active volumes of the different stages of the leachate treatment systems over a 9-month period. An analytical method, employing the governing equations for flow through porous media, was used to quantify the changes in saturated hydraulic conductivity in the treatment system cells. The results from the analytical method were combined with the results from the tracer study to further the understanding of the flow and mixing within the treatment system cells.

► Two constructed wetlands were analyzed to determine effect of substratum clogging.
► Tracer responses could not quantify the effect of clogging in constructed wetlands.
► A time-lagged flux model was created to quantify changes in hydraulic conductivity.
► Rate of change in hydraulic conductivity decreased with system operation.