Nutrient recovery by seven aquatic garden plants in a laboratory-scale subsurface-constructed wetland

Abstract

Commercial nurseries use large amounts of water and nutrients to produce container-grown plants. The large volume of runoff containing nitrogen (N) and phosphorus (P) that leaves nurseries can contaminate surface and groundwater. Subsurface flow-constructed wetlands have been shown to effectively treat agricultural, industrial, and residential wastewater and to be well-suited for growers with limited production space. We investigated the possibility of using commercially available aquatic garden plants in subsurface-constructed wetlands to remove nutrients in a laboratory scale, gravel-based system. Seven popular aquatic garden plants received N and P from Hoagland's nutrient solution every 2 days for 8 weeks. These rates (0.39 to 36.81 mg·L-1 of N and 0.07 to 6.77 mg·L-1 P, respectively) encompassed low to high rates of nutrients found at various points between the discharge and inflow points of other constructed wetland systems currently in use at commercial nurseries. Plant biomass, nutrient recovery, and tissue nutrient concentration and content were measured. Whole plant dry weight positively correlated with total N and P supplied. Louisiana Iris hybrid 'Full Eclipse', Canna X generalis Bailey (pro sp.) 'Bengal Tiger', Canna X generalis Bailey (pro sp.) 'Yellow King Humbert', Colocasia esculenta (L.) Schott 'Illustris', Peltandra virginica (L.) Schott, and Pontederia cordata L. 'Singapore Pink' had the greatest N recovery rates. The P recovery rates were similar for the cannas, Colocasia esculenta 'Illustris', Louisiana Iris 'Full Eclipse', Pe. virginica, and Po. cordata 'Singapore Pink'. The potential exists for creating a sustainable nursery and greenhouse production system that incorporates a subsurface-constructed wetland planted with marketable horticultural crops that provide remediation and revenue.