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 degrees 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/ml. The nitrogen uptake rate by duckweed was found to be 0.62 g-N/(m(2)-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. (C) 2008 Elsevier B.V. All rights reserved.