Numerical Simulation and Validation of Constructed Wetlands for Effluent Treatment in eastern China : An Evaluation of MIKE21 in Enhancing Water Purification Efficiency

Abstract

Constructed Wetlands for Effluent treatment (E-CW) play a vital role in the degradation of pollutants, purification of water, and the improvement of freshwater ecosystems. However, conventional designs often lack a methodical approach for quantifying the efficacy of these wetlands, as well as provide feedback on their operational efficiency. In this context, the use of hydrodynamic and water quality simulations facilitates the selection and arrangement of vegetation within these systems, thereby improving their efficiency. The present study utilized the MIKE21 Hydrodynamic (HD) module in conjunction with the ECO-Lab Water Quality (AD) module to perform a numerical simulation of the Yingtai Constructed Wetland for Effluent in Hai'an City. Accordingly, key parameters involved in effective water purification were calibrated and the system's ability to treat effluents from wastewater treatment facilities was assessed. The findings demonstrated significant removal efficiencies for Chemical Oxygen Demand (COD), Total Nitrogen (TN), Total Phosphorus (TP), and ammonia (NH3-N), with average rates of 51.14%, 43.14%, 63.82%, and 54.38%, respectively. In addition, the simulations exhibited a high degree of accuracy, with hydrodynamic predictions deviating by less than 5% and water quality approximations by less than 15%. The quality of the treated water successfully met the standards set for Class IV surface water, in accordance with the relevant environmental regulations. Additionally, the constructed wetland system satisfactorily met the requirements for effluent purification. As observed, the use of numerical simulations can provide valuable guidelines for the future design and functional assessment of wetlands by offering crucial insights that aid in the optimization of purification processes and vegetation selection.