Effect of feeding strategy on the performance of a pilot scale vertical flow wetland for the treatment of landfill leachate.

Landfill leachate is one of the most challenging types of wastewater to treat using constructed wetlands. The objective of this study was to evaluate the effect of two feeding strategies on the treatment efficiency of a landfill leachate using vertical flow wetlands (VFWs) planted with Typha domingensis or Canna indica. The tolerance of these macrophytes to the leachate was also evaluated. Coarse sand and light expanded clay aggregates (LECA) were used as substrates. Two feeding strategies (FS) were applied: FSA = 1 pulse per day of 0.21 m pulse-1, FSB = 3 pulses per day of 0.07 m pulse-1. VFWs planted with T. domingensis presented removal efficiencies of 34/74% (NH4+) and 16/48% (TN) for FSA/FSB, respectively. VFWs planted with C. indica presented removal efficiencies of 27/72% (NH4+) and 18/46% (TN) for FSA/FSB, respectively. NH4+ and total nitrogen (TN) removal efficiencies were significantly higher in FSB than in FSA, but there were no significant differences between macrophyte species. COD removal showed no significant differences between FSs or between macrophyte species. T. domingensis and C. indica demonstrated to be tolerant to the leachate studied. VFWs planted with T. domingensis or C. indica are suitable to treat diluted landfill leachate with high ammonium concentrations using a feeding strategy of pulses. However, an anaerobic stage may be added after the VFW to get higher TN and COD removal.