Comparison of four aquatic plant treatment systems for nutrient removal from eutrophied water

Nutrient removal behaviors of four aquatic plant treatment systems (Oenanthe javanica, Iris pseudacorus L., Canna lily, and Potamogeton crispus) were systematically examined and compared. The kinetics of nutrient uptake were conducted with the standard depletion method. All four aquatic species exhibited a strong preference of ammonium nitrogen (NH4+-N) over nitrate nitrogen (NO3−-N) and nitrite nitrogen (NO2−-N). Main pathways of nutrient removal in the aquatic plant treatment system were examined in details. It was estimated that direct assimilation by plants accounted for 28.2–34.5% of N reduction and 25.2–33.4% of P reduction while substrate absorption accounted for 7.2–25.5% of N reduction and 7.3–25.0% of P reduction. The activity of urease and phosphatase in the substrates could indicate the aquatic plant treatment system’s capability for reducing TN and soluble P load.