Nitrogen removal in a subsurface flow constructed wetland planted with Heliconia psittacorum.

In order to investigate the influence of the plants and hydraulic loading on nitrogen removal in constructed wetlands built with horizontal sub-surface flow (HFSS, abbreviation in Spanish) for domestic wastewater treatment, twelve laboratory-scale (microcosm) HFSS were constructed using gravel substrate. Six of these were planted with Heliconia psittacorum and six were not (controls). The planted and unplanted wetlands were exposed to hydraulic load rates of 0.02 m3 d-1 and 0.05 m3 d-1, respectively (corresponding to hydraulic retention times of 2.5 days and 1.0 day, respectively). The experimental results showed better performance in the removal of NH3, NO3- and DQO for treatments exposed to the smaller hydraulic loading (0.02 m3 d-1), reaching rates of removal of 56.7, -24.0 and 69.8%, respectively; low hydraulic loading (0.05 m3 d-1) efficiencies were 33.6, -3.4 and 53.6% respectively. Although the rate of nitrogen assimilation, in weight (g N / Kg plant), by Heliconia psittacorum under hydraulic loading of 0.05 m3 d-1 was only 0.2%, a significant effect of Heliconia was observed on nitrogen removal in planted microcosms.