Response of Typha domingensis during an accidental discharge of high Cr(VI) concentration in a full-scale treatment wetland

Abstract

This work assesses the Cr accumulation and tolerance of Typha domingensis after an accidental discharge of wastewater that produced a concentration of Cr(VI) of approximately 120 mg L−1 in a free-water surface wetland. The wetland was constructed for the final wastewater treatment of a metallurgical manufacturing plant. It is 7 m wide, 20 m long, and waterproofed with a geomembrane. A 1.5 m soil layer was placed on top of the geomembrane. Water, plants, and sediment were sampled before and after an accidental discharge. The root anatomical measurements of the plants from the treatment wetland were compared with those of plants from an uncontaminated wetland (control). Roots and dead leaves from the inlet plants showed the highest Cr concentrations after the accidental discharge (12.4 and 11.6 mg g−1, respectively). SEM-EDX mapping determined that Cr was accumulated in root epidermis. Cr accumulation in plant detritus, plant roots, and sediment were the mechanisms for Cr removal. Plants accumulated Cr in belowground tissues demonstrating their potential for phytostabilization. T. domingensis was capable of modifying its morphology to respond to high Cr concentrations. This macrophyte is a suitable species for wetlands constructed for the treatment of a wastewater with high Cr(VI) concentration. The studied system was capable of minimizing the impact and preserving the environment.