Investigating metal removal potential of aquatic macrophytes at different harvest regimes to maximize remediation of metal contaminated wastewater in constructed wetland

Abstract

In present study, the metal accumulation potential and growth dynamics of two aquatic macrophytes viz. Sagittaria sagittifolia and Colocasia esculenta were investigated at varying harvest time and frequency for maximum metal removal from mixed industrial wastewater employing horizontal flow constructed wetland (CW) technology. Both plant species were harvested five times i.e. 0, 30, 60, 90 and 120 days during experiment. S. sagittifolia attained maximum biomass (216.2 g dw m−1) and growth rate (1.25 g plant−1 day−1) at H3, whilst that of C. esculenta (204.3 g dw m−1 and 1.01 g plant−1 day−1 respectively) at H4. The plant species also differed in their metal uptake capability. With exception of Cr, other heavy metals viz. Zn, Cu and Cd accumulated more in S. sagittifolia than C. esculenta. In general, the metal uptake efficiency of S. sagittifolia was higher than that of C. esculenta, which increased up to H3 in former, whilst up to H4 in latter. The maximum Zn, Cu and Cd removal (115.55, 53.78 and 4.26 g/wetland respectively) was observed by S. sagittifolia in CW1, whilst Cr removal (12.79 g/wetland) by C.esculenta was recorded in CW2. Both plants showed metal tolerance ability in terms of reduced and oxidized glutathione content in their leaves. As such, the optimum harvesting regimes (time and frequency) in sequential manner accumulating maximum metals could enhance the metal removal efficiency of aquatic macrophytes.