Assessment of Corn Husk Biochar-Amended Coix lacryma-jobi-planted Constructed Wetland for Sustainable Jabi Lake Water Treatment

The high demand for potable water and the unavailability of functional treatment facilities at Jabi Lake, with its toxic heavy metal and nutrient-contaminated water, necessitated the development of sustainable, environmentally friendly remediation technology to improve its quality. A corn-husk-biochar-modified Coix lacryma-jobi planted batch-flow-constructed wetland was developed to treat Jabi Lake water samples to reduce the heavy metals (Zn, Pb, Fe), nutrients (N, P, K) and other physico-chemical parameter concentrations. The Jabi Lake water characterization was done using standard procedures, with determination of concentrations of heavy metals using an Atomic Absorption Spectrophotometer (AAS). Three composite samples were taken from each of the four substrate types, which were made of sharpsand only (SSS-only), Quarry dust only (QD-only), biochar with sharpsand (A-SS) and biochar with Quarry dust (A-QD) under HRT-3 and 5. Sampling was replicated thrice, making a total of 72 samples. Water samples were tested before and after treatment in the constructed wetlands (CWs) for the same parameters previously tested. Corn husk was charred in a fabricated kiln and characterized before its application in the CWs. The biochar exhibited improved microporosity, which enhanced its sequestration capacity. The highest removal efficiencies (REs) obtained were COD (88.99%, SS-only); BOD(93.49%, QD-only); DO (23.21%, A-QD); TN (54.34%, A-SS); EC (65.91%, A-QD); TDS (83.84%, A-SS); TSS (77.27%, SS-only); colour (78.74%, SS-only); HCO3− (75.00%, A-SS); Zn (49.73%, A-QD); Pb (75.40%, SS-only); Fe (81.63%, QD-only), all under HRT-5. This indicates that Jabi Lake raw water can be phytoremediated using corn-husk-biochar-amended Coix lacryma-jobi-planted CWs, commonly found at the study site. Graphic abstract