Effect of loading rate and planting on treatment of dairy farm wastewaters in constructed wetlands—II. Removal of nitrogen and phosphorus

摘要: The effect of influent loading rate on mass removal nitrogen and phosphorus from dairy parlour wastewaters was compared in four pairs planted (Schoenoplectus validus) unplanted gravel-bed wetlands (each 19 m2). were operated at nominal retention times 7, 5.5, 3 2 days, with outflows sampled fortnightly over a 20 month period. Hydraulic flows monitored to enable calculation the nutrients, plant biomass tissue nutrient levels evaluate uptake. Influent water quality varied markedly during trial period (TN, 10–110; NH4-N, 5–70; TP 8–18 g m−3). As theoretical wastewater increased 7 mean reduction TN 12 41% 48 75% wetlands, respectively, 36% 37 74%, respectively. In annual rates (0.15–1.4 m−2 d−1) (0.13–0.32 d−1), gradually rates. showed marked decline high loadings. Net storage by plants first year monitoring accounted for between 20% greater N 60% P wetlands.