Effects of substrate, vegetation and flow on arsenic and zinc removal efficiency and microbial diversity in constructed wetlands

Constructed wetlands (CWs) are considered to be effective for treating industrial wastewater. However, little is known with respect to the bacterial communities within these ecosystems. This study investigated arsenic and zinc removal in twelve mesocosm-scale CWs which differed from each other in substrate, flow and vegetation. Bacterial community diversity and composition of the different mesocosms-scale were compared by analysis of PCR-amplified 16S rRNA clone libraries. The free-water flow wetlands planted with Phragmites australis were the most effective in metal removing. The majority of the bacterial communities were amply dominated by the Proteobacteria phylum and the highest diversity and richness was found in those occupying mesocosms planted with P. australis. Phylogenetic analysis using UniFrac revealed that vegetation and flow influenced the bacterial communities composition and structure. Statistical Canonical Correspondence Analysis showed that the mesocosms planted with P. australis were correlated with bacterial diversity, richness and with arsenic and zinc removal.