Clogging Zones in Soil Treatment Units – Hydraulic Problems or Natural Filtering Systems?

In conventional domestic soil treatment units, a clogging zone is known to form at the trench-soil interface due to microbial extracellular products and wastewater suspended solids. A clogging zone may cause system failure over time, yet it is also capable of removing contaminants and act as a biological filter. In this work, removal capability of nitrogen – a major contaminant of concern – by the clogging zone was evaluated using a modification of the numerical reactive transport Hydrus-2D. Laboratory experiments were coupled with inverse simulation methods to create a model which describes nitrogen attenuation in mature soil treatment units.