Floating treatment wetlands (FTW) at microcosm scale for the removal of Cr(III) and Cr(VI)

MONTAÑEZ, F.; NOCETTI, E.; MUFARREGE, M.M.; MAINE, M.A.; DI LUCA, G.A.; HADAD, H.R.

Viena

Simposio; 9th International Symposium on Wetland Pollutant Dynamics and Control, WETPOL 2021; 2021

University of Natural Resources and Life Sciences, Vienna (BOKU)

The aim of this work was to evaluate the removal of Cr(III) and Cr(VI) by Floating TreatmentWetlands (FTW) at microcosm scale. Wetlands were planted with Typha domingensis. The metaldistribution in the system water-plants-bottom sediment was also studied. The FTW were designedand constructed in such a way that the roots and rhizomes remain submerged in the water whilethe aerial parts emerge. The treatments were 5 and 10ppm of Cr(III) and 5 and 10ppm of C(VI).Controls without FTW and without Cr addition were installed.T. domingensis plants, sediment and water were collected from an unpolluted pond from theParaná River floodplain near Santa Fe City, Argentina. Plastic reactors (70 L) were installedoutdoors under a semi-transparent plastic roof. All reactors contained 4 Kg of sediment. In thereactors, this sediment mass generates a layer of 3-4 cm depth. The experiment lasted 45 daysand it was performed in triplicate. Conductivity, pH, dissolved oxygen (DO), Cr(VI) an total Cr weremeasured periodically in water in all treatments. Sediment and plants were sampled at thebeginning and the end of the experiment. Plants were separated into roots, rhizomes and leaves.In the sediment, pH, Eh and organic loss on ignition (%OM) were measured in all treatments. TotalCr concentrations in plant tissues and sediment were determined. Besides, Cr fractionations insediments were performed.Both Cr species were efficiently removed from water in all treatments (> 80%). The highestremovals were obtained in the FTW treatments, suggesting that T. domingensis is directly involvedin metal removal. Cr(III) removal was faster than Cr(VI) removal, probably due Cr(III) can be takenup by plant roots without energy cost , sorbed by the root cell walls or precipitated in the bottomsediment.Cr concentration in sediments increased in all treatments, being significantly higher in Controlswithout FTW. Cr was mainly accumulated in the fraction bound to organic matter in all treatments.At the end of the experiment, Cr concentration in tissues of T. domingensis were significantly higherthan the obtained at the beginning of the experiment. In all treatments, roots showed the highestCr concentration, while the lowest concentration was measured in leaves. Since this macrophytedid not translocate the metal to the aerial parts, its pruning in winter will not affect the removalcapacity of the system. In addition, the presence of FTW minimized algal formation, which wouldallow the biota further develop in aquatic systems.The obtained results demonstrated the ability of FTW planted with T. domingensis to remove Cr(III)and Cr(VI) from water. The use of FTW planted with T. domingensis is a promising tool to remediatewater bodies contaminated with Cr.