Spatial Distribution Behavior of Basic Pollutants in A Subsurface-Flow Wetland with Thalia Geniculata

Constructed wetland is a technically feasible, economically viable and environmentally sustainable natural technology that contributes at reducing greenhouse gases in the wastewater treatment. In this context, a pilot-scale subsurface horizontal-flow constructed wetland (HF-CW) was evaluated by using Thalia geniculata as native vegetation. The reactor operated with an average flow rate of 204 ± 66 L/ day of wastewater, with gravel support medium diameter of 2.8 ± 0.8 cm, porosity of n = 56.3 ± 3.5 and density of 1,666.7 ± 119.3 kg/m3, with 4.2 days as a hydraulic retention time. The HF-CW weighs approximately 2,600 kg, considering 1,108 kg of gravel, 850 kg of water and the weight of the container (carbon steel). The kinetic behavior was observed to be first order with k = −0.43 days−1, favoring the efficiency of biological oxygen demand removal up to 90%. During the experiments, it was shown that the bacterial biomass attached to the support material decreased its concentration from influent to effluent (33,000 to 2,000 mg/kg, mg of fixed biomass attached to each kg of gravel). For the electrical con- ductivity, color and turbidity, values were found to decrease in the order of 7.2 ± 4.8%, 86.7 ± 6.8% and 90.3 ± 5.8%, respectively. From the current experimental results, it was demonstrated that constructed wetlands, involving native species as vegetation, are highly efficient for the removal of basic pollutants.