Nitrogen management in reservoir catchments through constructed wetland systems

In this study, nitrogen removal was investigated in pilot-scale subsurface flow (SSF) and in free water surface flow (FWS) constructed wetlands installed in the campus of TUBITAK-Marmara Research Center, Gebze, near Istanbul, Turkey. The main purposes of this study are to apply constructed wetlands for the protection of water reservoirs and to reuse wastewater. Experiments were carried out at continuous flow reactors. The effects of the type of plants on the removal were investigated by using emergent (Canna, Cyperus, Typhia spp., Phragmites spp., Juncus, Poaceae, Paspalum and Iris.), submerged (Elodea, Egeria) and floating (Pistia, Salvina and Lemna) marsh plants at different conditions. During the study period HLRs were 30, 50, 70, 80 and 120 L m² d⁻¹ respectively. The average annual NH₄-N, NO₃-N, organic N and TN treatment efficiencies in SSF and FWS wetlands are 81% and 68%, 37% and 49%, 75% and 68%, 47% and 53%, respectively. Nitrification, denitrification and ammonification rate constant (k₂₀) values in SSF and FWS systems have been found as 0.898 d⁻¹ and 0.541 d⁻¹, 0.488 d⁻¹ and 0.502 d⁻¹, 0.986 d⁻¹ and 0.908 respectively. Two types of the models (first-order plug flow and multiple regression) were tried to estimate the system performances