Effect of hydrodynamic conditions on the water quality in urban landscape water

Abstract

In this study, a 2D hydrodynamic and water quality model was built based on MIKE 21 to investigate the relationship between hydrodynamic condition and water quality, and then applied in an urban landscape lake in Tianjin, China. Moreover, an engineering experiment was carried out to confirm the comprehensive degradation coefficients of chemical oxygen demand (COD), total phosphorus (TP), nitrogen ammonia (NH4 -N), and total nitrogen (TN) (0.014 d-1, 0.024 d-1, 0.019 d-1, and 0.005 d-1, respective). Circulation system was the main force that expedited water changes and pollutant movement, increased the lake average water speed from 0.003 m/s to 0.008 m/s, and could effectively reduce the COD, NH4 -N and TN concentration nearly by 35, 32, and 5%. The high concentrations nitrogen and phosphorus in the reclaimed water would accelerate the deterioration of water quality, and the concentrations of TP, NH4 -N, and TN in the lake increased from 0.080 mg/L, 0.53 mg/L, and 1.53 mg/L to 0.090-0.096 mg/L, 0.71-0.81 mg/L, and 1.89-2.08 mg/L, respectively. The circulation system could slow the water quality deterioration but cannot eliminate the eutrophication risk. Improving the hydrodynamic conditions was proposed for enhancing water quality in urban landscape lakes.