Compost leachate treatment by a pilot-scale subsurface horizontal flow constructed wetland

Compost leachate contains high concentrations of pollutants (including organic materials and nitrogen compounds) that are seriously harmful to the environment and human health. The main purpose of this study was to remove organic materials and nitrogen compounds from leachate produced in Isfahan composting facility by a sub-surface horizontal flow constructed wetland (CW). Two horizontal flow wetlands with the dimensions of 1.5m × 0.5m × 0.5m, were constructed, one was planted with Vetiver grass (Vetiveria zizanioides), as Vetiver CW and the other one was kept unplanted as control CW. They were operated with a leachate flow rate of 24 L d−1 for over five months. Control and Vetiver CW were capable of removing 21.8% and 74.5% of BOD5, 26.2% and 53.7% of COD, 17.1% and 69.9% of NH3-N, 34.1% and 73.5% of NO3-N and 35% and 73.4% of TN, respectively. This study showed that a sub-surface horizontal flow constructed wetland planted with Vetiver has the potential to be used as a leachate pre-treatment or treatment method to treat highly contaminated composting leachate.