Removal of Nitrogen and Phosphorus from Effluent of a Secondary Wastewater Treatment Plant Using a Pond-Marsh Wetland System.

constructed wetland composed of a pond- and a marsh-type wetland was employed to remove nitrogen (N) and phosphorus (P) from effluent of a secondary wastewater treatment plant in Korea. Nutrient concentrations in inflow water and outflow water were monitored around 50 times over a 1-year period. To simulate N and P dynamics in a pond- and a marsh-type wetland, mesocosm experiments were conducted. In the field monitoring, ammonium (NH) decreased from 4.6 to 1.7 mg L, nitrate (NO) decreased from 6.8 to 5.3 mg L, total N (TN) decreased from 14.6 to 10.1 mg L, and total P (TP) decreased from 1.6 to 1.1 mg L. Average removal efficiencies (loading basis) for NO, NH, TN, and TP were over 70%. Of the environmental variables we considered, water temperature exhibited significant positive correlations with removal rates for the nutrients except for NH. Results from mesocosm experiments indicated that NH was removed similarly in both pond- and marsh-type mesocosms within 1 day, but that NO was removed more efficiently in marsh-type mesocosms, which required a longer retention time (2-4 days). Phosphorus was significantly removed similarly in both pond- and marsh-type mesocosms within 1 day. Based on the results, we infer that wetland system composed of a pond- and a marsh-type wetland consecutively can enhance nutrient removal efficiency compared with mono-type wetland. The reason is that removal of NH and P can be maximized in the pond while NO requiring longer retention time can be removed through both pond and marsh. Overall results of this study suggest that a constructed wetland composed of a pond- and a marsh-type wetland is highly effective for the removal of N and P from effluents of a secondary wastewater treatment plant. [ABSTRACT FROM AUTHOR]