Effect of climatic conditions, season and wastewater quality on contaminant removal efficiency of two experimental constructed wetlands in different regions of Spain

► Constructed wetlands implemented in different climate regions of Spain were studied. ► TSS, BOD and NH4 mass removal efficiencies were higher in summer (> 90%) than winter (< 80%). ► In summer BOD and NH4 removals were higher in Mediterranean than continental climate. ► Hydraulic conductivity temporal changes were influenced by TSS influent concentration. ► Mass removal rates were mainly season-dependent and less influenced by clogging process.