Assessment of Chromium Tolerance and Removal Using Constructed Wetlands Planted With Emergent Macrophyte (Eleocharis sp.)

DANIELA S. ARÁN; AGUSTIN RIMONDINO; MAGDALENA V. MONFERRAN; CARLOS A. HARGUINTEGUY

Congreso; SETAC Latin America 15th Biennial Meeting; 2023

SETAC Latin America

Industrial development worldwide leads to metal pollution of aquatic ecosystems and water deterioration. Therefore, it is necessary to develop environmentally friendly strategies for treating industrial wastewater. In this study, constructed wetlands planted with Eleocharis sp. were exposed during 30 days to a culture medium with three different levels of chromium contamination (T1: 5 mg L-1; T2: 20 mg L-1; T3: 50 mg L-1) typically found in tanneries, as well as a control treatment. The objectives of this research were to assess the capacity of the wetlands for removing Cr and the physiological response of the macrophyte to metal exposure. At the end of the experiment, the removal efficiency was over 94% for all treatments, but only T1 and T2 achieved Cr values below 1 mg L-1, as established by the guidelines for effluent discharge into surface water bodies of Cordoba, Argentina. The adsorption of Cr in sediments, determined by a sequential chemical extraction, depended on the metal concentration of the culture medium and significantly differedbetween fractions in the order of FIII > FV > FIV > FI + FII. The accumulation of the metal in the FI + FII fraction of sediment was less than 5%, while it was around 75-85% in FIII for all treatments. These results indicate that coprecipitation with Fe is a significant pathway for Cr removal, and in these sediments, Cr is nearly unavailable to aquatic organisms. For this reason, metal accumulation in the plant is likely related to the concentration of Cr in water and in FI and FII of sediments. The accumulation of Cr in the shoots, rhizomes, and roots of the emergent aquatic plant depended on the metal concentration of the culture medium, and in general, there were no significant differences found between different exposure times. The accumulation of metal varied among the macrophyte tissues and was ranked as follows: roots > rhizomes > shoots. Furthermore, aquatic plants exposed to Cr in the constructed wetlands did not exhibit visible damage, and there were no significant differences in the survival of the macrophyte and in the relative growth rate compared to the control treatment. Additionally, the relative growth rate increased in all treatments over time. In conclusion, based on the removal of Cr, the bioavailability of the metal in sediments, and the ability of the macrophyte to tolerate and accumulate Cr, the constructed wetlands could be scaled up to assess its feasibility for real wastewater treatment.