Nitrogen and Phosphorus Removal from Wastewater by Useful Plants and the Effect of Shading on the Removal Efficiency

Nitrogen and phosphorus removal from wastewater by a ditch planted with several plants, including terrestrial species, was studied. The effects on the removal rate by shading were also examined. Papyrus, marigold, reed, peppermint, sorghum, impatiens, and kenaf were tested. All plants were effective for removing nitrogen and phosphorus from the wastewater, which contained 2.5 mgL-1 nitrogen and 0.5 mgL-1 phosphorus. The ditch planted with papyrus, kenaf and sorghum removed 70-90% of nitrogen and phosphorus loaded. The nitrogen and phosphorus removal rate of the ditch planted with papyrus, kenaf, and sorghum was 1.17, 1.07, 0.80 gm-2d-1, and 0.21, 0.16, 0.12 gm-2d-1, respectively. Removal rates fluctuated with the change in solar radiation. During the shading treatment, the removal rate decreased, but it recovered soon after the treatment ended.