Imaging Clogging in a Treatment Wetland Using Time-Domain Induced Polarization

Summary Treatment wetlands are engineered systems for small communities that have been designed to take advantage of the same processes that occur in natural wetlands, the main problem affecting treatment wetlands is the development of clogging wich leads to the exclusion of some subparts of the filter, becoming ineffective for the treatment critically reducing the lifetime of the plant. Time-domain induced polarization is used to image clogging distribution of a gravel filter from a horizontal subsurface flow treatment wetland. Experimental data performed on the laboratory demonstrates the linear relationship between the normalized chargeability and the amount of clogging in the gravel filter because of the substantial increase of the cation exchange capacity caused by clogging coating these grains. Therefore, we were able to convert the normalized chargeability tomograms obtained with the field data into a 3D distribution of the percent clogging. This method allows to identify the zones were the clogging has accumulated through the filter and therefore predict preferential flow paths and dead flow zones. This is an important task to plan preventive measures and anticipate the filter obstruction that may decreases the effectiveness of the wastewater treatment system.