Degradation of contaminants in serially constructed wetlands with macrophyte species from the humid tropics

Abstract

Constructed wetlands (CW) are an efficient, economical and environmentally friendly wastewater treatment technology. In this study, a series CW that operates with a flow between 14 and 30 m3 day-1 of domestic wastewater was evaluated, determining the removal of pollutants and the kinetic behavior. The treatment consists of pretreatment, a free flow constructed wetland (FFCW) with Thalia geniculata, followed by a subsurface flow constructed wetland (SSFCW) with Sagittaria latifolia and a FFCW with Eichhornia crassipes and Pontederia cordata, which were determined in phase starting and stabilizing the variables Temperature, pH, Color, Turbidity, Total Dissolved Solids and Electrical Conductivity. The support medium in the CW presented a particle size of 19±2.36 mm and a porosity of 49.6±3.8. The CWs operated with a hydraulic retention time of 30.74 hours. The global performance constants in the treatment train (kGA) were 2.03 days-1 for COD, 2.03 days-1 for TN and 1.84 days-1 for TP, all these behaviors occurred in a temperature range between 26 and 28 °C. Finally, after one year of operation, the system removed 89.2% of the COD, 87.0% of TN and 84.8% of TP, complying with the discharge criteria of the NOM-001-SEMARNAT-2021 standard and it is known that most of the macrophytes reach their maximum contaminant removal efficiency between two and three years of operation. Sagittaria latifolia, Eichhornia crassipes and Pontederia cordata, are the smallest species presenting a final biomass (moist base) of 73.9 ± 9.2 kg, 42.3 ± 3.7 kg and 73.4 ± 2.3 kg respectively, so they are easier to handle in their production. planting, while Thalia geniculata presented 61.3 ± 8.2 kg. Thalia geniculata shows difficulties in its management as it is easily uprooted due to its size and the action of the wind.