Nitrogen and phosphorus removal by wetland mesocosms subjected to different hydroperiods |
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Authors: | Max J Busnardo Richard M Gersberg Ren Langis Theresa L Sinicrope Joy B Zedler |
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Institution: | Max J. Busnardo, Richard M. Gersberg, René Langis, Theresa L. Sinicrope,Joy B. Zedler, |
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Abstract: | The effect of hydroperiod on nutrient removal efficiency from simulated wastewater was investigated in replicate wetland mesocosms (area, 2 m2, planted with Scirpus californicus). Alternate draining and flooding of sediments (pulsed discharge) increased nutrient removal efficiency compared to the continuous-flow “control”. Average PO43− removal efficiency was 20–30% higher in wetland mesocosms that drained twice daily compared to the control. Inorganic N removal efficiency was less affected than phosphate removal by hydroperiod variation. At the higher NH4+ loading rate (1.83 g N m−2 day−1), inorganic N removal efficiency was consistently 5–20% higher in pulsed-discharge wetland mesocosms than in the control. At the lower NH4+ loading rate (0.9 g N m −2 day −1), pulsed-discharge hydrology had no effect on inorganic N removal efficiency. Twice-daily drainage exhibited average inorganic N removal efficiencies of 96% (lower N loading rate) and 87% (higher N loading) and average phosphate removal efficiencies of 81% (lower P loading) and 90% (higher P loading). Mass balance data from the continuous-flow treatment revealed that the aquatic macrophyte Scirpus californicus was the most important nutrient sink, assimilating 50% of the NH4+ and PO43− supply. The high plant productivity in the mesocosms (15.6 kg m−2 year−1) occurred under conditions of high light (high edge per mesocosm area) and high root contact with nutrient-rich influent (shallow, sandy substrate) and may overestimate plant uptake in larger wetlands. The addition of a nitrification-inhibitor (N-Serve) indicated that 34% of the NH4+ supply was transformed to NO3− by nitrifying bacteria. |
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