Optimization of organic matter degradation kinetics and nutrient removal on artificial wetlands using Eichhornia...

This study describes the optimization of the wastewater treatment process through the use of a free water surface flow constructed wetland with floating macrophytes at the laboratory level (20 L). A factorial design 2³ was used in order to find the best operation conditions of the wastewater treatment process. The performance of macrophytes Eichhornia crassipes and Typha domingensis was investigated by operating the wetland system at hydraulic retention times of 2 and 4 days. The results showed an optimum operational condition that removed 92.39% of initial organic load (measured as COD). The nutrient removal efficiency of the constructed wetland was 99.28% for total nitrogen and 87.78% for phosphorus. The best operating condition includes the use of E. crassipes, with 4 days of hydraulic retention and the use of gravel as a filter. According to this, organic matter degradation kinetics was studied by the comparison of three kinetic models: first-order model, Stover-Kincannon model and Grau-second-order model. Stover-Kincannon and Grau kinetics models were more appropriate to represent the organic matter degradation kinetics in constructed wetland, with a determination coefficient of 0.9997. Based on the kinetic removal results, the process showed a maximum rate of organic load removal of 2500 mg/L d.