Keywords: biomass, forage rice, nitrogen recycling, nitrogen removal, plant uptake, river water, assimilation rate, water pollution, surface flow wetland, Japan, river pollution
Nitrogen removal from polluted river water by surface flow wetland with forage rice (Oryza sativa L. cv. Kusahonami)
To investigate the potential of nitrogen removal and recycling from nutrient polluted river water, a pilot surface flow wetland with forage rice was constructed beside the estuary of the Sannogawa River. The average nitrogen removal rate was 189 mg m−2 d−1 in the constructed wetland. Although the nitrogen assimilation rate by rice plants was only 44 mg m−2 d−1 in the first two months, the rate increased by several times in the last four months. Finally, the nitrogen contained in the rice plants was higher than the total amount of nitrogen removed from influent, suggesting that plant uptake is the major pathway for nitrogen removal of polluted river water.