A review of Heavy Metal Removal Mechanisms in wetlands

1 * All correspondence ABSRACT Heavy metals are released into the environment from a wide range of natural and anthropogenic sources. The rate of influx of these heavy metals into the environment exceeds their removal by natural processes. Therefore there is attendance of heavy metals accumulating in the environment. Aquatic ecosystems are normally at the receiving end and usually, with wetlands as intermediaries. The conventional clean up technologies used in the prevention of heavy metal pollution are either inadequate or too expensive for some countries. In the past decades, therefore, research efforts has been directed towards wetlands as an alternative low cost means of removing heavy metals from domestic, commercial, mining and industrial discharge of wastewater. This paper is a comprehensive review of over 200 literature sources. It discusses the potential for heavy metal removal mechanisms by wetlands through reactions involving sedimentation, flocculation, absorption, co-precipitation, cation and anion exchange, complexation, precipitation, oxidation/reduction, microbiological activity and plant uptake.