Plants for constructed wetland treatment systems — A comparison of the growth and nutrient uptake of eight emergent species

Abstract

Allocation of above and below-ground growth and nutrient uptake, and pollutant removal were compared for Schoenoplectus validus, Phragmites australis, Glyceria maxima, Baumea articulata, Bolboschoenus fluviatilis, Cyperus involucratus, Juncus effusus and Zizania latifolia. Plants were grown in triplicate 0.238 m 2 × 0.6 m deep gravel-bed wetland mosocosms fed with dairy farm wastewaters pre-treated in an anaerobic lagoon. After 124 days, mean species total biomass ranged from 0.3 to 7.4 kg m −2, with above-below-ground ratios between 0.35 and 3.35. Growth of Baumea and Juncus was relatively poor. Zizania and Glyceria showed the highest above-ground biomass values, ranging between 3 and 4 kg m −2. Above-ground tissue concentrations of nitrogen (N) and phosphorus (P) ranged from 15 to 32 and 1.3 to 3.4 mg g −1, respectively. Maximum plant accumulations of 135 g N m −2 and 18.5 g P m −2 accounted for around 30% of the levels supplied in wastewaters. Mean removals of 76–88% of suspended solids, 77–91% of biochemical oxygen demand, and 79–93% of total P were recorded for the established mesocosms irrespective of plant species. Mean removal of total N ranged from 65 to 92%, showing a significant positive linear correlation with plant biomass. Comparisons are made with information from other studies on establishment rate, productivity, nutrient uptake, potential for root-zone aeration and general life history traits in constructed wetlands.