Effect of Different Plant Monocultures on Nitrogen Removal Performance in Wetland Microcosms

This study investigated the nitrogen removal performance in wetland microcosms individually planted with different plant monocultures, including emergent, free-floating and submerged plants during ammonia removals, or large- and small-leaf free-floating plants during nitrate removal. For ammonia-dominated wastewater, both emergent (common reed) and free-floating (water hyacinth) plants in wetland microcosms achieved higher total nitrogen removals than a submerged plant (eelgrass) that significantly improved the microbial nitrifying performance. For nitrate-dominated wastewater, efficient nitrate removals in wetland microcosms planted with free-floating plant were achieved by both a full cover of water surface and the concentration of organic oxygen-consuming substances, which resulted in low dissolved oxygen levels and boosted microbial denitrification in wetland microcosms. FWS-CW developers and managers should thus pay close attention to the selection of wetland plant types and optimize their design to achieve optimum nitrogen removal performance.