Effect of Phragmites australis and Typha latifolia on biofiltration of heavy metals from secondary treated effluent

Abstract

The present work deals with a promising approach for the removal of heavy metals from secondary treated wastewater using aquatic plants, which are economic and effective in separating metals from polluted water. Since the conventional sewage treatment processes were inefficient to remove heavy metals from wastewater, batch experiments of Phragmites australis, Typha latifolia and P. australis and T. latifolia grown in association and reference (unplanted) were carried out for 15 days of retention time for the removal of copper (Cu), cadmium (Cd), chromium (Cr), nickel (Ni), iron (Fe), lead (Pb), and zinc (Zn) from the secondary treated effluent. Significantly, higher removal of the heavy metals in planted set than the reference revealed role of plants in their removal (analysis of variance, p \ 0.05). Higher removal of Cr, Fe, and Zn (66.2 ± 3.5, 70.6 ± 1.2, and 71.6 ± 3.9 %) in the combination of the P. australis and T. latifolia than their individual culture suggested synergistic effect of both the plants in the removal of these metals. Positive relationship was observed between retention time and the removal of heavy metals. Mass balance equation has revealed that the loss of heavy metals in wastewater was equivalent to the net accumulation of heavy metals in plant and loss of heavy metals in natural degradation. P. australis showed higher accumulative capacities for Cu, Cd, Cr, Ni, Fe, and Pb than those of T. latifolia. The P. australis and T. latifolia grown in association might be utilized for the heavy metal removal in the tropical environment.

Time plots, trends and seasonal growth/ decay of Cr removal in vertical subsurface flow sewage treatment wetland

“…Cr removal showed a slightly upward trend at low concentration (Cr 1.5 ppm planted or not planted) but a slightly downward trend for medium concentration Cr removal at low Cr influent concentration but Typha performed better at medium and high Cr concentration. [21] also found Typha and Phragmites appropriate for treating wastewater containing Cr.…”

“…Substantial water losses due to high evapotranspiration were considered a major component in the water balance and pollutant removal in constructed wetlands, particularly where treated wastewater are destined for reuse [19,20] . Metal concentrations in plant tissues were more in summer because of the higher evapotranspiration and loss of water led to increase the elemental concentration in the outflow water and other compartments of constructed wetland [21] . Similarly, lower evapotranspiration values and dilution of metal concentration due to precipitation in rainy season resulted in reduced heavy metal uptake by plants in winter [22] .…”

“…Vegetated wetlands were able to remove higher amount of Cr compared to unvegetated one. It was because of additional and cumulative effect amount of metal removed by plants over time [21] . Cr removal showed a slightly upward trend at low concentration (Cr 1.5 ppm planted or not planted) but a slightly downward trend for medium concentration Cr removal at low Cr influent concentration but Typha performed better at medium and high Cr concentration.…”

Removal of selected risk elements from wastewater in a horizontal subsurface flow constructed wetland

“…). Kumari & Tripathi () observed that Phragmites australis showed higher accumulative capacity for Cd than Typha latifolia . Gao et al .…”

“…It can be removed by plant uptake as well (Ladislas et al 2013). Kumari & Tripathi (2015) observed that Phragmites australis showed higher accumulative capacity for Cd than Typha latifolia. Gao et al (2015) obtained the excellent removal efficiency of Cd (91.8%) for microcosmic subsurface vertical flow constructed wetlands planted with Iris sibirica.…”