Nutrient removal and balance in vertical-flow constructed wetlands planted with different forage macrophytes for domestic wastewater treatment

This study investigated nutrient removal as well as nutrient balance in a vertical flow constructed wetland planted with Andropogongayanus, Chrysopogonzizanioides, Echinochloapyramidalis, Pennisetumpurpureum and Tripsacumlaxum for treating synthetic domestic wastewater. The experiment was conducted under pilot-scale composed of six beds constructed with bricks. Each bed was filled from the bottom to the top with 0.1 m of gravel and 0.6 m of white lagoon sand. Five beds were transplanted wile one unplanted was used as control. On each bed, 80 L of synthetic wastewater were applied (3 times/week) during six months. All plant species improved nutrient removal, but P. purpureum achieved the best TN, NH4+, NO3-, TP and PO43- removal efficiencies around 84.30 %, 84.18 %, 69.32 %, 94.68 % and 97.17 % respectively. Likewise, TP and TN amount decreased in the beds’ sediments from upper surface to the bottom. According to the mass balance approach, plant uptake removed 1.1–15.3% of TN and 1.6–25.3% of TP input while sediment storage contributed to 0.9–49% and 43.9–70.5% of TN and TP removal, respectively. Microbial uptake accounted for 9.3–68.1% and 1.3–20.3% of nitrogen and phosphorus removal, respectively. The results proved that sediment storage and plant uptake were the main phosphorus removal pathways while for nitrogen, plant uptake or sediment storage and microbial mechanisms were the main removal pathways in CWs treating domestic wastewater.