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

Abstract

The present research work aimed at analysing the time series and estimation of seasonal growth/ decay of heavy metals dynamics in the vertical subsurface flow constructed wetlands (VSSFCWs) planted with Typha, Phragmites, Vaccha, Arundo and Vetiver on gravel media. Monthly plant and wastewater samples were collected for 15 months from the VSSF CWs. Plant and water samples were pre-treated in the laboratory, digested using diacid and their heavy metal concentrations were determined using atomic absorption spectrophotometer after filtration. The Main results indicated that the maximum uptakes of metals by plant occurred in summer while the minimum plant uptakes were recorded in winter, regardless of metal concentrations applied and the trends showed a slightly stable profile irrespectively to the level of concentration applied. For the adsorption processes of Cr in the media (gravel) of the constructed wetlands, it appeared that this process was not significantly changing as function of time, except for Cr 1.5 ppm.