Study on the River Water Quality Improvement Featuring Deficient Upstream in Flow -- A Case Study of Nanfei River in Hefei City

The largest tributary of Chao Lake located in Hefei City, the Nanfei River, is a river lack of upstream water inflow and receives water mainly from wastewater treatment plant (WWTP) discharge and polluted tributaries. In this study, a mathematical model comprising a hydrodynamic module and a water quality module was developed to simulate water quality improvement schemes. The model was calibrated with the data of local hydrological and water quality monitoring at 18 stations. Using the calibrated model, it was found that even if the discharged water from WWTPs is improved to grade IV (1.5 mg/L for ammonia), the ammonia concentration is still too high for the river to reach a water quality of grade V (2.0 mg/L). Considering water augmentation can only be used as an emergency measure to improve the water quality of the river, priority actions should be taken to reduce the pollution from the tributaries.