An integrated kinetic model for organic and nutrient removal by duckweed-based wastewater treatment (DUBWAT) system

This study was conducted to investigate the efficiency of duckweed (Lemna gibba) in treating a domestic wastewater and to develop an integrated kinetic model for organic and nutrient removal by duckweed-based wastewater treatment (DUBWAT) system. Four pilot-scale DUBWAT units, made of concrete blocks, were operated under ambient conditions (temperatures 30–36 °C), different hydraulic retention times (t), organic loading rates (OLR) and stocking densities (SD). The maximum COD, BOD5, NH3-N, TN and TSS removal efficiencies of 84, 88, 68, 58 and 87%, respectively, were found at optimum operating conditions of t of 10 days, OLR of 50 kgCOD/(ha-d) and SD of 0.5 kg/m2. The nitrogen uptake rate by duckweed was found to be 0.62 g-N/(m2-d). An integrated kinetic model consisting of t, OLR, SD and temperature was developed for the DUBWAT system and validated satisfactorily with data obtained from the literatures.