Performance evaluation and numerical simulation of vertical subsurface flow constructed wetlands in wastewater treatment

Constructed wetlands are extensively employed to treat wastewater in many countries and are an eco-friendly and low-cost wastewater treatment technique. In this study, the performance of an intermittently operated vertical subsurface flow constructed wetland planted with Amaranthus dubius and the effect of adding oyster shells as a substrate layer in the wetland on its performance were investigated. Major quality parameters such as phosphates, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, Total Organic Carbon and COD in the effluent and influent were monitored and compared. The concentration of these quality parameters was determined by the colorimetric method in the laboratory using a UV-Visible spectrophotometer. The results indicated that the planted vertical subsurface flow constructed wetlands achieved efficient removal of ammonia nitrogen from the wastewater and were effective for nitrification. The addition of oyster shells in the substrate enhanced the total nitrogen removal from the wastewater. The ability of the HYDRUS CW2D model in simulating reactive transport through a vertical subsurface flow constructed wetland was also investigated. A good match between the measured and simulated parameters could be achieved after adjusting certain constructed wetland parameters in the HYDRUS CW2D model. Model validation was performed based on a quantitative statistic known as the ratio of root mean square error (RMSE) to the standard deviation of the observed data - . The value for ammonia nitrogen and nitrate nitrogen was less than 0.70, which is satisfactory.