This research aimed to study the effect of loading rate on the efficiency of constructed wetlands with horizontal subsurface flow (CW-HSSF) to remove pollutants from wastewater. The CW-HSSF were fed with effluent from septic tank under volumetric organic loading rate (OLR V) of 53 to 231 g m-3d-1 of chemical oxygen demand (total-COD) and associated loading rates (LR V) of soluble chemical oxygen demand (soluble COD), total suspended solids (TSS), total nitrogen (total-N) and total phosphorus (total-P). To evaluate the performance of CW-HSSF the same variables were quantified in its effluent. Linear and positive relationship was found between the removal rates of total COD, soluble COD and TSS and the LR V, within the application range, and no negative effects on this variable in removal efficiencies of these pollutants. The removal rate of total-N and total-P did not show, however, tendency to increase with the LR V applied in the CW-HSSF planted with cattail and used in treating sanitary sewage. The loads applied of these nutrients must be considered referential in sizing these systems, if desired to maximize the overall removal of wastewater pollutants.
organic load; wetland systems; biological treatment
