Heavy metal remediation from municipal waste water using arrowroots (Amaranta arundinacea)

Abstract

Municipal wastewater contains high levels of pollutants since it is a collection of wastes from various sources of human activities. Municipal treatment of such wastewater is usually aimed at lowering the levels of pollutants to permissible amounts before discharge into recipient environment. Several conventional methods are available for treatment of wastewater. However, most of them are costly and not economically feasible due to their secondary environmental impact. Wastewater treatment using natural plants has been considered the most environmentally friendly method. A study has been conducted to establish the metal removal rates from waste water using arrowroots. To establish if arrowroots can tolerate high levels of pollutants under natural conditions,raw arrowroots and raw wastewater were used. Pollutant removal efficiency levels was carried out by setting up a model constructed wetland where arrowroots were planted in raw influent of municipal wastewater and concentration levels of both planted and unplanted influent and effluent determined. Pollutant removal efficiency was compared using the relative treatment efficiency index technique. The results of the metal removal rates in wastewater cultivated with arrowroots were: Fe (68%), Mn (98%), Zn (54%)and Cu (50%) while pollutant removal in wastewater without arrowroots were: Fe (38%), Mn (48%), Zn (9%) and Cu (9%). The percent pollutant removal rate when arrowroots were planted in the effluent from unplanted maturation ponds was: Fe (97%), Mn (97), Zn(48%) and Cu (50%) with relative treatment efficiency of 0.28, 0.34, 0.71, and 0.65, respectively and p < 0.002 at 5% confidence interval. The difference in percent removal showed that more metal ions could be removed both from the raw sewage and final effluent when cultivated with arrowroots than in uncultivated maturation ponds, suggesting that arrowroots can be of significant benefit as a tertiary wastewater treatment alternative.