Pilot-scale study on advanced treatment of tail water of urban sewage treatment plant by constructed wetlands with different plants

Abstract

In order to meet stringent water quality standards, the tail water of the local wastewater treatment plant has been treated by constructed wetlands with different plants. Five pilot-scale constructed wetlands were investigated for the advanced treatment of the tail water of wastewater treatment plant, they had the same size, and were operated with a tidal flow, while they were planted with different plants to compare their treatment effects. After one year's experiment, the results showed that the all indexes of effluent from five constructed wetlands could meet the improved requirements. Among them, the constructed wetland planted with Phragmites communis had the highest average removal rates of chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen (TN), which were 24.01%, 68.15%, and 92.70%, respectively. The constructed wetland planted with Cyperus alternifolius had the highest average removal rate of total phosphorus (TP), which was 71.68%. In the contrast experiment of the performance in different seasons, in the spring, the constructed wetland planted with Phragmites communis had the best removal effect on COD, ammonia nitrogen and TN, the average removal rates were 52.51%, 76.06% and 92.04%, respectively, and the constructed wetland planted with Canna indica had the best removal effect on TP, the average removal rate was 66.72%. In the summer, the constructed wetland respectively planted with Phalaris arundinacea, Acorus calamus, Cyperus alternifolius and Phragmites communis had the best removal effect on COD, ammonia nitrogen, TP and TN, the average removal rates were 15.83%, 78.11%, 67.30% and 91.73%, respectively. In the autumn, the constructed wetland respectively planted with Phragmites communis, Phalaris arundinacea, Cyperus alternifolius and Canna indica had the best removal effect on COD, ammonia nitrogen, TP and TN, respectively, the average removal rates were 12.19%, 58.82%, 83.16% and 94.01%, respectively. In the winter, the constructed wetland planted with Phalaris arundinacea had the best removal effect on COD, the average removal rate was 33.39%, the constructed wetland planted with Canna indica had the best removal effect on ammonia nitrogen and TP, the average removal rates were 76.33% and 79.43%, respectively, and the constructed wetland planted with Phragmites communis had the best removal effect on TN, the average removal rate was 94.97%. It will be of significance to the practical engineering in the future.