Use of tropical macrophytes in wastewater treatment

Objective: To evaluate the adaptation process of ornamental tropical macrophytes irrigated with wastewater, through physiological measurements before and after planting in a tropical constructed wetland (CW).
Design/Methodology/Approach: Three fractions were evaluated with 50%, 75%, and 100% wastewater and natural water (blank) in 0.5 × 2.0 m fiberglass containers. The following species were placed in the containers during 40 days: Strelitzia reginae, Alpinia purpurata, Canna indica, Xanthosoma robustum, Cyperus papyrus, Pistia stratiotes, Spathiphyllum wallisii, Ruellia brittoniana, Pasto pennisetum, Solenostemon scutellarioides, Iresine herbstii, Lantana camara, Duranta eracta golden, and Asparagus densiflorus. Subsequently, the individuals —including Heliconia psittacorum and Iris germanica— were planted and evaluated in a CW after the adaptation period, in order to replace the macrophyte lost during the said period. The following physiological variables were measured: survival percentage, stem thickness, number of flowers, chlorophyll index, and biomass (as a growth variable).
Results: During the first stage (containers), only 11 out of the 14 initial species survived (78.5%), which allowed us to establish which plants had the highest survival capacity in high concentrations of pollutants. These results determined the priority with which these would be planted in the CW.
Study Limitations/Implications: Significant physiological differences were observed (p ≤ 0.005) in all CW species. Canna indica, Xanthosoma robustum, Ruellia brittoniana, Alpinia purpurata, Cyperus papyrus, and Heliconia psittacorum recorded better adaptation.
Findings/Conclusions: The macrophytes studied show great adaptation as phytoremediative plants in tropical CW systems; however, their physiological development is different.