Plant species richness and hydraulic retention time (HRT) are two important variables in mediating pollutant
removals of constructed wetlands, but their collective effects have not been clear. Pollutant removals
in vertical flow mesocosms were investigated using both plant species richness and HRT as fixed factors.
Both BOD5 and COD removals were enhanced by the longer HRT and the significant species richness
×HRT
interaction, as shown by two-way ANOVA. Differently, the removals of the NH4–N, NO3–N and phosphate
were improved by the species richness, HRT, and the species richness
×HRT interaction. The present
findings highlight the importance of the interaction between the plant species richness and the HRT in
improving the pollutant removals in vertical flow constructed wetlands