An evaluation of the waste water treatment performance of constructed wetlands with <i>Canna indica</i> and <i>Colocasia esculenta</i> macrophytes

Water scarcity and pollution are major environmental problems in developing countries. To tackle these issues, it is crucial to develop sustainable and innovative waste water treatment methods. Constructed wetlands (CW) are efficient and eco-friendly waste water treatment systems, valued for their low cost, energy efficiency, and easy maintenance. The current study aimed to evaluate the potential of <i>Canna indica</i> and <i>Colocasia esculenta</i> plant species, along with Styrofoam and crushed plastic as amendments to filtration media (large gravel, small gravel, loamy soil, and sand), in treating waste water. We constructed four wetland units, each with four treatments, and monitored their performance by measuring pH, electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), biological oxygen demand (BOD), chemical oxygen demand (COD), nitrate nitrogen (NO₃-N), phosphate (PO₄^3-), lead (Pb), cadmium (Cd), and <i>Escherichia coli</i> (<i>E. coli</i>). The pH of waste water in treatment T4 (filtration media with crushed plastic and styrofoam planted with <i>C. indica</i> and <i>C. esculenta</i>) of Unit 4 reached 8.1, which was the highest observed and played a key role in breaking down organic substances in the waste water. Results showed that unit 4 led to the best improvement in plant growth. T4 treatment of unit 4 produced the highest root fresh biomass (197 g for Ci and 1126 g for Ce) and shoot fresh biomass (607 g for Ci and 458 g for Ce). The increased root volume of both plant species provided microbial films and helped to reduce BOD by 92.7% and COD by 83.1%. T4 treatment of unit 4 turned out to be the most effective, achieving significant reductions in various waste water quality parameters. For instance, levels of NO₃-N dropped by 100%, PO₄^3- by 77%, EC by 77%, TDS by 92%, TSS by 50%, Pb by 77%, Cd by 100%, and <i>E. coli</i> by 99.1%. These findings confirm that our developed CWs are an effective, economical, and environment friendly solution for waste water treatment, particularly in developing countries facing water scarcity.