Influence of hydraulic retention time variation on purification effects of two different constructed wetlands
水力停留时间变化对2种人工湿地净化效果的影响

Based on the pilot-scale field experiment of constructed wetland on the riverside of Xinyi River,the relationship between hydraulic retention time variation and purification effect of two different constructed wetlands was studied.It is showed that hydraulic retention time variation significantly influenced purification effect of subsurface flow constructed wetland (SSFW) and vertical flow constructed wetland (VFW).With the variation of hydraulic retention time,potassium permanganate index (CODMn) and ammonia nitrogen (NH4+-N) removal effect increased,and then declined.The purification effect of VFW was better and more stable than SSFW.For both wetlands,the best retention time for CODMn and NH4+-N removal effect appeared about 2 d.The removal rates were 93.1% and 87.7%,respectively.However,for SSFW,the best hydraulic retention time of CODMn removal was about 2 d,and the removal rate was 92.3%.The best retention time for NH4+-N removal was about 2.5 d,the removal rate was 81.5% accordingly.SSFW and VFW are both suitable for Xinyi River pollution treatment;the best hydraulic retention time of both wetlands can be set as 2 d.