Efficiency of a subsurface flow constructed wetland in pretreating a micro-polluted drinking water source

Taking the Yuqing Lake Reservoir in Jinan as an example,a horizontal flow constructed wetland system was used to pretreat the micro-polluted raw water from the Yellow River after sedimentation. The pollutant removal efficiency in the wetland treatment system was studied. According to analysis of the experimental data,a first order kinetic simulation equation of chemical oxygen demand (COD),total nitrogen (TN) and total phosphorus (TP) were established in the subsurface flow constructed wetland. The results of the pretreatment experiment showed that the average removal efficiencies of COD,TP,TN and NH+4-N were 49.89%,50.44%,53.41% and 48.45%,respectively in the horizontal flow constructed wetland system. Purifying pollutants by the subsurface flow wetland is a combined action of physical,chemical,and biological processes. According to the longitudinal variation of pollutant concentration in the constructed wetland and different heights,it can be clearly observed that the pollutant removal efficiencies in the constructed wetland system declined along the water flow direction,and most of the pollutants were removed in the front of the constructed wetland system. Furthermore,the top of the subsurface constructed wetland system had a better treatment effect.