Design configurations affecting flow pattern and solids accumulation in horizontal free water and subsurface flow constructed wetlands

► Clogging development and spatial distribution in constructed wetlands was assessed. ► Organic loading rate is related to the solids accumulated within the wetland. ► The presence of plants entails a decrease of 20% in the hydraulic conductivity. ► Typha angustifolia showed a greater effect on clogging than Phragmites australis. ► Gravel matrix and outlet pipe position greatly influenced water flow paths.