Treatment of reactive azo dye from textile wastewater by burhead (Echinodorus cordifolius L.) in constructed wetland: Effect of molecular size

The potential of burhead (Echinodorus cordifolius L.) for the treatment of textile wastewater has been investigated. Reactive red 2; RR2 [MW=615], reactive red 120; RR120 [MW=1469] and reactive red 141; RR141 [MW=1775] were studied in order to determine the effect of molecular size on the efficiency of dye removal by plants in batch systems of constructed wetlands under soil and soil-free conditions. Dye concentrations, total dissolve solids (TDS), conductivity and pH in the effluents, and the relative growth rates (RGR) of plants were measured. The highest efficiency of dye removal during 7 days under soil-free conditions was RR2 (33.09 molRR2kg-1FW), followed by RR120 (13.35 molRR120kg-1FW) and RR141 (10.57 molRR141kg-1FW), respectively. This suggests that the structure and size of dye molecule strongly affects the efficiency of dye removal by plant. The results from a synthetic wetland experiment found that dye removal was 96 % at 4 days and 6 days under soil and soil-free conditions, respectively. Furthermore, plants were able to decrease TDS (42 %), conductivity (50 %) and pH (from 9.5 to 7.4) within 2 days in the synthetic reactive red141 dye wastewater (SRRW141) under soil-free conditions, thus demonstrating the potential of burhead for textile wastewater treatment.