Exploring the contribution of plant species in the performance of constructed wetlands for domestic wastewater treatment

The selection of plants in constructed wetlands (CWs) is challenging due to limited understanding of their actual role in the organics and nutrient removal processes. This review is aimed to facilitate this process by analyzing the secondary data of 82 vertical flow constructed wetlands (VFCWs) involving seven plant species. Comparisons regarding system performance were made following appropriate data normalizations taking into account the differences in volumetric loadings instead of areal loadings. Possible relationships between macrophyte performance and their physiological characteristics and the associated microbial communities are also analyzed. The review suggests that the indirect role of macrophytes in CWs may far exceed their direct role in nutrient removal. This indirect effect is exerted through the influence of plant species on the rhizospheric microbial communities. Thus, this review underscores the requirement of more extensive studies on different plant species under controlled environments specifically for field-scale CWs.