Initial Simulation Study Of Laboratory Scale Subsurface Flow Constructed Wetland Based On CWM1

The technology of wastewater treatment for constructed wetlands(CWs) has remarkable superiority of small investment, simple operating maintenance. However, the understanding of the mechanism of pollutant removal and degradation remains uncomprehensive. With the dramatic development in computer technology, employing models to carry out the simulation on pollutant degradation has become an effective way for understanding the complicated reaction mechanism. Studying on the laboratory scale CWs with vertical flow(VFCW) and horizontal flow(HFCW) and applying CWM1 model to carry out numerical simulation research in this paper, the research contents and conclusions are as follows.First of all, the existing VFCW and HFCW were repaired in our research group, and aritificially prepared and simulated domestic sewage for trial operation. The VFCW operated under the condition of 120 L/d inflow, 187.5 mm/d hydraulic loadings, batch influent with water inlet velocity at 6.25 mm/min, and water distribution.By monitoring the water quality index of influent and effluent, we obtained the removal rates for COD, +4NH-N,TP, and respectively were 72.34%, 51.96%, 65.80% and 38.52%. While the HFCW operated under the condition of 120 L/d inflow, 197.5 mm/d hydraulic loadings with continuous influent for 24 hours and design of influent and effluent quality as in the above case. The removal rates separately were 65.10%, 42.97%, 68.92% and 46.17%. And the obtained data was the basic data of model simulation.Next, by analyzing and discussing the mechanism of CWM1 and using the assay method of ASM parameters, a reletively complete estimating method for the parameter and component of model CWM1 are summarized to provide the initial values for model simulation as accurate as possible. And the related measured results are as follows: YH, YA, bH, bA, Hμ and Aμ separately were 0.683 gCODBM/gCODSF, 0.24mgCOD/mgN, 0.3091 d-, 0.2 d-, 5.7441 d- and 0.88 d-; the conversion rates of COD components SF, SA, SI, XS and XI separately were 10.53%, 2.12%, 6.31%, 68.99% and 12.05%.Last but not the least, by respectively set the initial values of finite element mesh, thesoil hydraulic parameters, transport parameters, adsorption parameters, influent and effluent concentration. Identical simulation values of degradation trend in pollutant substance with the measured values based on CWM1 are basically obtained.