Nitrogen and phosphorus removal efficiency of three helophytes in constructed surface flow wetlands for urban wastewater treatment

Abstract

Nutrient absorption is a function, among others, aimed at macrophytes for wastewater treatment. In this work, Typha angustifolia, Phragmites australis, and Sparganium erectum were multi-annually compared in secondary and tertiary treatment of urban wastewater under Mediterranean climate. Phragmites shows higher growth in height and density during the vegetative period of 1.83-2.09 cm. d-1 and 29-49 times the planting density, respectively. Aerial biomass records 52.2-54.3, 38.1-41.0, and 19.4 t dw. ha-1 in Phragmites, Typha, and Sparganium in the same order. The underground biomass fluctuates depending on the rooting vigour from 1.45 t dw. ha-1 for Sparganium to 44.49 t dw. ha-1 for Phragmites in tertiary treatment. Nitrogen and phosphorus aerial mineralomasses are more important in Phragmites (787 kg N. ha-1) and Typha (107 kg P. ha-1) in secondary treatment. Phragmites is, by far, the most cumulative of N and P in its underground part. The N and P retention by the vegetated mesocosms apparently has overall relationship with N-NH4 + and P-PO4 3-. Compared to mesocosm input, Phragmites assimilates one's maximum of 6.39% N in its aerial tissues and 7.86% P in the underground ones, whereas Typha records maxima of 14.8% N and 33.6% P in its aerial part with respect to corresponding mesocosm removal.