A review on mechanistic insights into heavy metal removal in constructed wetlands: roles of plants, microbes, and substrates

ABSTRACT

The image shows different sources of HMs from the ecosystem, and its subsequent treatment using CWs incorporating different substrates, microbial communities and macrophytes. The treated water can then be sustainably utilized for agricultural applications, recycling, and reuse.

Heavy metals (HMs) are persistent in nature and cause serious threats to the environment and human health. This generates an urgent need for an efficient and long-term solution. In contrast to the conventional treatment system, constructed wetlands (CWs) are considered a green and cost-effective system to remediate HMs-contaminated wastewater. Their performance is governed by the synergistic interaction of plants, microbes, and substrate/filler, which mediate processes such as phytostabilisation, rhizofiltration, biosorption, bioaccumulation, precipitation, ion exchange, and redox transformations. In this review, we briefly discuss the application of the CWs for HMs-contaminated wastewater treatment. The significance of macrophytes, microbial communities, and substrate has been discussed with a particular emphasis on their interplay in HM removal in CWs. Also, the performance of CWs is discussed by elaborating the underlying removal mechanism for our understanding of HMs removal efficiency. The review covers important aspects to improve the design of CWs for efficient HMs remediation.