Simulation of constructed wetland performance using the advection diffusion equation

Abstract

The advection diffusion equation with variable coefficients was used to predict the performance of a subsurface constructed wetland (SSCW) treatment plant. The effect of evapo-transpiration on the velocity of flow and change of rate of biodegradation kinetics with the length of flow was considered. The differential equation was solved using the Frobenius method. The model was validated on experimental results from a pilot plant in Indian climatic conditions. The data used in this work were obtained from various hydraulic and BOD loadings. Records of biochemical oxygen demand (BOD) concentrations at inlet, outlet and intermediate levels through various stages of the treatment process over eighteen months were used for calibration of the model. The results of the model show that it is an efficient and a robust tool for prediction of the waste-water treatment performance of a constructed wetland.