Phosphorus uptake by macrophyte plants in monocultures and polycultures in constructed wetlands for wastewater treatment

Phosphorus uptake by common and ornamental plants was studied in pilot-scale horizontal subsurface flow (HSSF) constructed wetlands (CWs) with monocultures and polycultures. Three HSSF CWs were planted with monocultures of Phragmites australis (HSSF-Phr), Schoenoplectus californicus (HSSF-Sch) and Cyperus papyrus (HSSF-Cyp), and one polyculture was planted with C. papyrus and Zantedeschia aethiopica (HSSF-Cyp/Zant). During the experimental period, removal efficiency, growth characteristics, biomass production and phosphorus uptake were evaluated in the cold season (fall/winter) and warm season (spring/summer). In general, the cold season showed better performance with an order of HSSF-Cyp/Zant > HSSF-Cyp > HSSF-Sch > HSSF-Phr in the evaluated parameters. The removal efficiencies were 33%, 27%, 23% and 12%, respectively. The biomass pro-duction and density of the HSSF treatments ranged from 1.5 to 5.4 kg dry weight (DW)/m(2), and 435 to 1298 individuals/m(2) with higher values for HSSF-Sch. The tissue phosphorus content was 5 to 20% higher below-ground in all plants, including ornamentals. Phosphorus uptake was higher for polyculture (HSSF-Cyp/Zant) and monoculture (HSSF-Cyp) planted with ornamentals, with a mean of 30 g P/m(2). Also, the polyculture was not affected by the seasons, reaching up to 27% phosphorus uptake by the plants. According to our results, the ornamental species of the polyculture contribute to the phosphorus uptake.