Elimination des métaux lourds présents dans les eaux usées par les macrophytes et l’étude de l’accumulation de ces métaux au niveau des organes de ces plantes

Abstract

The discharge of wastewater into the natural environment presents a worrying problem, inducing the spread of chemical elements such as nitrogen and phosphorus, which pose a problem of eutrophication, and heavy metals, which pose a problem of ecotoxicity due to their non-biodegradable nature. The present study aims to highlight the potentialities of planted filters with four species of macrophytes (Arundo donax, Phragmites australis, Typha latifolia and Cyperus papyrus), assessing their abilities to remove contaminants from wastewater; also, calculating the bioaccumulation (BAF) and translocation (TF) factors. The methodology consists of filling out the filters with raw wastewater of urban and industrial origins, then recovering filtered water to assess the rate of contaminants removal according to fixed residence time. After 15 days of residence time, macrophytes have shown a significant removal ability of ammonium (98.7%), nitrites (97.2%) and phosphorus (97.9%) from urban wastewater in addition to heavy metals (Lead with 97.5%, Zinc with 94.7%, Copper with 94.7% and Iron with 96.5%) loaded in industrial wastewater. ANOVA statistical analysis revealed a high significant effect of residence time on the heavy metals’ removal. Calculated BAF and TF had confirmed the accumulation and the mobility of heavy metals in different plants organs (roots, stems and leaves). Among four studied species, recorded values of BAF>1 allowed the consideration of hyper accumulator plants that are Arundo donax and Typha latifolia for Pb, Cu and Fe, Phragmites australis for Fe and Cyperus papyrus for Zn and Fe. Chi-square test for BAF revealed that heavy metals repartition was homogenous among different plants parts. For the studied metals, the higher TF values indicate a good mobility of a metal in different plants organs; Pb, Cu and Fe present a good mobility in Phragmites australis and Fe in Typha latifolia. Obtained results confirm the efficiency of phytoremediation technology using macrophytes to treat wastewater in Biskra region (Algeria). This purification process serves as a natural, economic and ecological green technology for the wastewater treatment in particular and the environment decontamination and preservation in general.