Analysis of ammonia-nitrogen removal kinetics by stage in pilot scale vertical flow wetlands treating landfill leachate in series.

This study explored the effect stage number and plant type have on ammonia-nitrogen (NH 3 –N) removal kinetics in a two-stage pilot-scale vertical flow constructed wetland (VFCW) system treating landfill leachate. Half of the VFCW columns were planted with Typha latifolia and the other half Scirpus californicus , and half of the columns were loaded with municipal solid waste landfill leachate (diluted to 1 part leachate to 2 parts total) with the effluent from these columns was collected in two separate barrels. The remaining columns were loaded with the effluent collected from the first columns, creating a two-stage VFCW system with four unique pairs to be tested. The leachate used here experienced no prior pre-treatment, and average influent concentrations of NH 3 –N for the first- and second-stage VFCWs were 508 and 321 mg L−1, respectively— much higher than many other VFCW treatment systems. Some reduction in chemical oxygen demand was observed, as well as generation of nitrate and nitrite, evidence of nitrification. No apparent correlation between aboveground biomass and removal of NH 3 –N was observed. Overall removal efficiency of NH 3 –N through two stages of VFCWs was 53.7% for columns planted with T. latifolia and 58.3% for those planted with S. Californicus. Average NH 3 –N removal efficiencies for the first stage VFCWs were 32.7% and 34.3%, while those in the second stage were 31.3% and 36.5%; no significant difference was observed between the first and second stage, suggesting that stage number does not have a significant effect on the removal efficiency of NH 3 –N in the primary treatment of landfill leachate via VFCWs. However, average mass removal rates of NH 3 –N in the first stage were 166 and 175 mg L−1 d−1; the second stage was significantly lower at 99.4 and 112 mg L−1 d−1, indicating that the first stage removed more pollutants overall. [Display omitted] • Nitrification and denitrification observed throughout entire experiment. • Stage number not found to have a significant impact on NH 3 –N removal. • Higher accumulation of nitrite observed on second day of each loading period. • Results reported as k-values and mass removal rates to better contextualize results. [ABSTRACT FROM AUTHOR]