Effects of temperature on purification of polluted river water by VFW-DP systems

The combined process of vertical flow constructed wetland-detention pond (VFW-DP) was constructed to treat simulated contaminated river water. The effect of temperature on COD_Cr and nutrient removal and influent modes were investigated. The results indicated that the combined process of VFW-DP can effectively remove COD_Cr, NH_4^+-N and TP, and the average removal rate of COD_Cr, NH_4^+-N and TP are higher than 47.9%, 60.0% and 27.5%, respectively. At initial operating stage (medium temperature period), the removal rate of downward vertical flow constructed wetland-detention pond (DVFW-DP) for COD_Cr, NH_4^+-N and TP are 61.7%, 77.1% and 19.9%, respectively, and the removal rate of upward vertical flow constructed wetland-detention pond (UVFW-DP) are 29.5%, 53.5% and 35.9%, respectively, thus the down-flow influent mode is more beneficial to removal pollutants. Temperature can significantly affect the removal of pollutants; at high temperature period, the effect of pollutants removal is significantly better than that at medium temperature and low temperature period.