Evapotranspiration And Its Influence On Treatment Effect Of Constructed Wetland

Constructed wetland is a waste water treatment system constituted by soil,plant and microorganism. It's an open reactor which necessarily causes evaporation; Plants in the wetland inevitably brings transpiration. But till now, we lack research on characteristic of the plants in constructed wetland.Based on the model of constructed wetland , the treatment experiments on the pre-sedimentation effluent of municipal sewage plant are done. The evapotranspiration of each wetland planted with different plant and the corresponding effluent water quality are determined. The influence of evapotranspiration's diurnal changes and climate changes on constructed wetland's COD,TN,TP removal effect and evapotranspiration between environment factors are analyzed in detail , so as to provide references for further development,design and operation of constructed wetland.Researches show that environment factors have different effect regularity on different plants. In general, the effect of PAR,Cs,Pn is the most and all wetlands plants reach their highest Tr at noon; T capacity of most wetlands accounts for 70~90% of ET, and Luwei's is the most; ET only takes a small percentage of quantity of treated water: the maximum is 5.13% and the minimum is 0.5%. Analysis on ET and the removal effect of wetland shows that removal effect of COD,TN,TP corresponds with ET, and the removal effect of plants is more higher in summer, the reason of which is in summer, the evaporation rate of plant rises, ecology metabolism increases and photosynthesis improves which promote the activity and dissolved oxygen of roots.By virtue of the study on NH4+-N removal system in wetlands, it can be discovered that the amount of volatile nitrogen barely accounts for less than 0.5%, which illustrates that most nitrogen is removed by microorganism and plant's absorption.Finally, experiments demonstrate that ET of wetland has important influence on wetland removal effect, which has guiding significance for plant selection in constructed wetland.