Comparative Treatment Performance Between Duckweeds-Based andConstructed Wetland Systems

摘要

This study was conducted to compare treatment performance of duckweeds-based wastewater treatment (DUBWAT) system and free-water-surface constructed wetland (FWS CW) system. The four DUB WAT units were operated at different hydraulic retention times (HRT), organic loading rates (OLR) and stocking densities (SD) at ambient temperature of 30-36 ℃. Secondary data of FWS CW, operating under similar environmental conditions with different HRT and OLR, were taken for comparison a domestic wastewater treatment performance. The first-order kinetic coefficients at 20 ℃ (k_(20)) of COD, BOD_5, NH_3-N and TN removal in the DUBWAT system were found to be 0.085, 0.087, 0.046 and 0.035 d~(-1), respectively. In the DUB WAT system, maximum COD, BOD_5, NH_3-N, and TN removal rates of 4.6 gCOD/(m~2-d), 2.8 gBOD_5/(m~2-d), 0.85 gNH_3-N/(m~2-d), and 0.9 gTN/(m~2-d), respectively were found at the optimum operating conditions of HRT of 10 days, OLR of 50 kgCOD/(ha-d) and SD of 0.5 kg/m~2. Whereas in the FWS CW system, the maximum COD, BOD_5, and TN removal rates of 10.85 gCOD/(m~2-d), 3.15 gBOD_5/(m~2-d), and 3.67 gTN/(m~2-d), respectively were found at optimum operating conditions of HRT of 7 days and OLR of 84 kgCOD/(ha-d). The nitrogen (N) uptake rate by the duckweeds was found to be 0.62 gTN/(m~2-d).