Feasibility Study on Using Constructed Wetlands for Remediation of A Highly Polluted Urban River in A Semi-Arid Region of China

Yucong Zheng, Xiaochang Wang, Mawuli Dzakpasu, Yuan Ge, Jiaqing Xiong, Yaqian Zhao



In semi-arid regions, dry climate and insufficient rainfall brings about limited base flow in river channels. For some urban rivers, treated and untreated domestic wastewater and industrial effluent may become the main flow. In order to improve the urban water environment, a large pilot constructed wetland (CW) system was constructed on the bank of an urban river in Xi’an. With a total area about 8000 m2, the pilot CW system was put into operation for two years at an average flow rate of 362 m3/d. The influent water from the urban river contained high concentrations of COD (350.9 ± 29.4 mg/L), BOD5 (125.6 ± 11.4 mg/L), NH3-N (27.2 ± 1.8 mg/L), TN (38.5 ± 1.7 mg/L), and TP (3.9 ± 0.3 mg/L). In the two years of operation, the overall COD, BOD5, NH3-N, TN and TP removals were 74.5%, 94.4%, 57.5%, 56.3% and 69.2%, respectively. Moreover, the removal rates of SS, COD, BOD5 and TP showed linear positive correlations with the inflow loading. Finally, higher removal was achieved as T >15˚C for each of the pollutants, but the influence of water temperature was different for different substances pollutants. The high efficiency of the CW system for the improvement of the inflow water quality from such a highly polluted urban river provided practical evidence of the applicability of the CW technology for protecting urban water environment.