Remediation of polluted river water by floating treatment wetlands

In this study, the potential of floating treatment wetlands (FTWs), inoculated with selected bacteria, to ameliorate polluted river water was evaluated. Floating cells were prepared by vegetating plants, Typha domingensis and Leptochloa fusca, on a floating mat. The plants were inoculated with three different pollutant-degrading rhizospheric and endophytic bacterial strains. Significantly greater decrease in chemical oxygen demand (COD), biochemical oxygen demand (BOD5) and total organic carbon (TOC) was observed in inoculated FTWs than in the wetlands without bacterial inoculation. However, a slight decrease in pH and EC was seen in most of the treatments. The total nitrogen (TN), nitrate and total phosphorus (TP) contents decreased to 1.77 mg/L, 0.80 mg/L and 0.60 mg/L, respectively. Additionally, the concentration of iron (Fe), nickel (Ni), manganese (Mn), lead (Pb), and chromium (Cr) in the water lowered to 0.41, 0.16, 0.10, 0.25, and 0.08 mg/L, respectively. Overall the performance of T. domingensis was significantly better than L. fusca. The treated effluents meet the water quality guidelines for irrigation and aquatic life. This study revealed that FTWs supplemented with selective bacteria are a promising approach for the restoration and management of polluted river water.