Constructed wetlands: An approach toward phytoremediation for wastewater treatment

Abstract

Constructed wetlands (CWs) have been used as a proven efficient technology for wastewater treatment since the early 1950s. However, the first full-scale operation was conducted in the late 1960s. CW is an engineered system that utilizes various macrophytes to treat wastewater. It is cost effective, easy to operate, and maintain as compared to other conventional wastewater treatment technologies. It works with the mechanisms of different phytoremediation processes (i.e., phytoextraction, phytostabilization, phytovolatization, phytodegradation) and sedimentation, agglomeration and biodegradation of wastewater. CW can be classified on the basis of vegetation types (submerged, emergent, free-floating, and floating leaved), hydrological properties (free water, surface flow, and subsurface flow). Subsurface flow wetlands can be further classified as vertical or horizontal depending on the flow direction. Hybrid systems such as CWs clubbed with tube settler for hospital wastewater, biochar-based CW for manure wastewater are reported to have better treatment efficiency. However, the performance of CWs depends on several factors like vegetation type, type of wetland, type of wastewater treated, design specification of CWs, substrate used, microbiology of CW, climate and hydrological factors, and so on. Therefore, this chapter mainly focuses on all these aspects to fill the knowledge gaps and gives an insight to future research challenges and opportunities to achieve sustainability in the field of wastewater treatment.