PRIMARYSTUDIESONTHEPURIFICATIONEFFICIENCYOFPHOSPHORUSBYMEANSOFCONSTRUCTEDWETLANDSYSTEM

Twelve sets of macrophyte-planted upflow-downflow constructed wetland systems were set up to treat municipal wastewater.Four of these plots were selected to study their purification efficiency of phosphorus under different hydraulic loading rates.The plots turned to be more stable and showed better purify efficiency of total phosphorus(TP)and inorganic orthophosphate(IP)through the operation.The average removal rates of total phosphorus are more than 40% in winter and 60% in summer.The outflow meets the grade Ⅲ national criteria of surface water(GB 3838 88).The planted plots have better and more stable purify efficiency than the control plot. From average removal efficiency.plot 2 with Zizania latifolia and Acorus tartarinowii was the best one with an average removal rate of TP 65%. But under higher hydraulic loading,plot 4 with Scirpus triqueter and Carex sp. was better than plot 2. The increasing of hydraulic load did not markedly influenced the efficiency of the plots.